Patent Application
20170267538
Among human activities, CO2 emissions from electricity generation and industry make up 65% of global greenhouse gas emissions. Considering the world's growing energy demand and continued dependence on fossil fuels, there is an unprecedented need to develop technologies to significantly reduce CO2 emissions.
One promising means of reducing CO2 emissions is post-combustion CO2 capture and utilization (CCU), which transforms low concentrations of CO2 in emissions into high purity CO2 for utilization or disposal. However, implementation of these technologies, such as the chilled ammonia and monoethanolamine (MEA) carbon capture processes, has been limited to pilot plants due to enormous operating costs. The most effective current processes require high temperature heat, generally supplied by steam diverted from power generation, increasing electricity costs by over 70% in some cases. High temperature heat constitutes >80% of the energy consumption in current carbon capture processes and is the costliest component of CO2 capture. A significantly lower operating and capital cost CO2 capture system is necessary to make CCU an effective means of reducing CO2 emissions.
Pure CO2 is a valuable product with 80 Mt per year commercial market. Due to the cost prohibitive nature of current CO2 capture systems, over 80 percent of the demand for pure CO2 is supplied by the unsustainable drilling of CO2 source fields, which contain CO2 that has been sequestered for millions of years. An effective system that captures CO2 from flue gas below market prices would at least partially displace the pure CO2 production from these unsustainable and counterproductive sources.
Advantageously, the present invention pertains to a new highly efficient, low energy, and low cost system and methods to capture CO2 from one or more CO2 containing gas mixtures. CO2 is absorbed from a gas mix containing CO2, such as flue gas, by a CO2-lean solution comprising one or more CO2 absorbents. Then a soluble substance is added to the resulting CO2 rich solution, eliciting the desorption of gaseous carbon dioxide. The resultant solution following the aforementioned CO2 desorption is separated into the soluble substance and the CO2-lean absorption solution. The CO2-lean absorption solution is transferred to the absorption step and the soluble substance is transferred to the CO2 desorption step, making the process regenerable. The soluble substance and the CO2-lean absorption solution recovery is characterized by one or more or a combination of the following:
In one embodiment the invention pertains to an integrated process for capturing CO2. The process comprises desorbing gaseous CO2 from a CO2 containing aqueous solution comprising carbonate, bicarbonate, sesquicarbonate, carbamate, or a mixture thereof. The desorbing of gaseous CO2 is conducted in the presence of a suitable water soluble substance.
In another embodiment the invention pertains to an integrated process for capturing CO2. The process comprises capturing CO2 to form a CO2 containing solution comprising carbonate, bicarbonate, sesquicarbonate, carbamate, or a mixture thereof. Gaseous CO2 is desorbed from the CO2 containing solution comprising carbonate, bicarbonate, sesquicarbonate, carbamate, or a mixture thereof. The desorbing of gaseous CO2 is conducted in the presence of a suitable soluble substance. The soluble substance is at least partially recovered by employing (1) a membrane with a molecular weight cutoff of greater than about 80 daltons or (2) distillation or (3) a combination thereof.
The soluble substance may comprise water, organic solvent, siloxanes, ionic liquids, water soluble polymer, soluble polymer, glycol, polyethylene glycol, polypropylene glycol, ethers, glycol ethers, glycol ether esters, triglyme, polyethylene glycols of multiple geometries, including, branched polyethylene glycols, star polyethylene glycols, comb polyethylene glycols, methoxypolyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic Acid, diol polymers, 1,2 propanediol, 1,2 ethanediol, 1,3 propanediol, cellulose ethers, methylcellulose, cellosize, carboxymethylcellulose, hydroxyethylcellulose, sugar alcohol, sugars, alcohols, ketones, aldehydes, esters, organosilicon compounds, halogenated solvents, non-volatile solvents, a substance with a vapor pressure less than 0.01 atm at 20° C., soluble substances with a molecular weight greater than 80 daltons, volatile organic solvents, soluble substances with a molecular weight less than 600 daltons, soluble substances with a molecular weight less than 200 daltons, dimethoxymethane, acetone, acetaldehyde, methanol, dimethyl ether, THF, ethanol, isopropanol, propanal, methyl formate, azeotropes, alcohols, ketones, aldehydes, esters, organosilicon compounds, halogenated solvents, a substance with a vapor pressure greater than than 0.01 atm at 20° C., or a mixture thereof.
The instant invention generally pertains to an integrated process for capturing CO2. The process comprises desorbing gaseous CO2 from a CO2 containing solution comprising carbonate, bicarbonate, sesquicarbonate, carbamate, or a mixture thereof. The desorbing of gaseous CO2 is usually conducted in the presence of a suitable soluble substance.
The CO2 containing solution may be formed in any convenient manner. Generally, any solution capable of dissolving CO2 in desirable amounts may be employed. The components and amounts of such solutions may vary depending upon factors such as, for example, the amount of CO2 to be dissolved, the source and state of CO2 and any impurities therewith, the specific desorbing steps, any subsequent processing steps, and other factors.
Typically, the CO2 containing solution may be derived from or comprise a CO2 absorbent that is capable of capturing CO2 from the desired source at the desired parameters. Such absorbents may vary widely depending upon the source and desired characteristics of the CO2 containing solution to be formed. Typically the CO2 absorbent may comprise, for example, water, ammonia, ammonium, amine, azine, amino ethyl ethanol amine, 2-amino-2-methylpropan-1-ol (AMP), MDEA, MEA, primary amine, secondary amine, tertiary amine, low molecular weight primary or secondary amine, metal-amine complex, metal-ammonia complex, metal-ammonium complex, sterically hindered amine, imines, azines, piperazine, alkali metal, lithium, sodium, potassium, rubidium, caesium, alkaline earth metal, calcium, magnesium, ionic liquid, thermally switchable compounds, CO2 switchable compounds, enzymes, metal-organic frameworks, quaternary ammonium, quaternary ammonium cations, quaternary ammonium cations embedded in polymer, or mixtures thereof.
The amounts of CO2 to be captured from the source will vary. Typically, it is desired to capture at least about any of the following percentages (%) from the total CO2 in the source: 40, or 50, or 60, or 70, or 80, or 90, or substantially 100.
The CO2 may be captured from any convenient source using any convenient manner. If desired, the CO2 source may be treated, e.g., scrubbed, before being subjected to the absorbent and/or forming the CO2 containing solution. Such treating methods may be particularly advantageous if the source has impurities that may deleteriously affect subsequent processing steps, e.g., recovery steps employing a membrane or distillation. Such impurities include, but are not limited to, NOx, SOx, oils, particulate matter, heavy metals, and heavy compounds, etc. Conventional treating methods may be employed for this purpose.
If desired, the CO2 source may be left untreated or only partially treated before being subjected to the absorbent and/or forming the CO2 containing solution. Such an instance may be particularly advantageous if the source does not have impurities or has impurities which are benign or have ameliorable affects. Such an example may include a CO2 source containing NOx or SOx, which may be subjected to a CO2 absorbent comprising of aqueous ammonia. The NOx or SOx may react with said ammonia, forming salable products, such as ammonium nitrate, ammonium sulfate, ammonium sulfite, ammonium bisulfite, ammonium metabisulfite or ammonium nitrite. Said salable byproducts may be removed by any convenient manner, including, but not limited to, ion exchange, ion exchange membrane, electrodialysis, or removal or replacement of the absorbent and/or CO2 containing solution.
Convenient sources from which to capture CO2 for the CO2 containing solution include sources selected from the group consisting of flue gas; combustion emissions; manufacturing emissions; refining emissions or a combination thereof. Such sources may include, for example, from combustion of one or more hydrocarbons; emissions from the combustion of natural gas, coal, oil, petcoke, gasoline, diesel, biofuel, or municipal waste; emissions from waste water treatment gases, or landfill gases, from air, from metal production/refining, from the production of Iron, Steel, Aluminum or Zinc, from cement production, from quicklime production, from Glass production, oil and gas refineries, steam reforming, hydrogen production, HVAC, refrigeration, transportation vehicles (ships, boats, cars, buses, trains, trucks, airplanes), natural gas, biogas, alcohol fermentation, volcanic activity, decomposing leaves/biomass, septic tank, respiration, manufacturing facilities, fertilizer production, geothermal wells, and combinations thereof.
Once the CO2 is captured the CO2 containing solution may typically comprise carbonate, bicarbonate, sesquicarbonate, carbamate, or a mixture thereof. Of course, the solution may also comprise suitable cations such as ammonium and other species such as described above that may remain from any CO2 absorbent. Generally, the CO2 containing solution may be aqueous, but, of course, it may take other forms as well depending upon the embodiment employed.
The desorbing of gaseous CO2 may be conducted in any convenient manner. Such manner will vary depending upon the specific amount, composition, and nature of the CO2 containing solution. Typically, the desorbing is conducted in the presence of a suitable soluble substance, for example, water soluble substance. Useful substances and potentially useful concentrations vary depending upon the reactants, amounts, and desired outcomes. The specific manner of combining the suitable soluble substance and CO2 containing solution is not particularly critical in most instances. That is, the suitable soluble substance may be added to the CO2 containing solution, the CO2 containing solution may be added to the suitable soluble substance, or one or the other could even be formed in situ or combined in some other manner.
The amounts of CO2 to be desorbed will vary. Typically, it is desired to desorb at least about any of the following percentages (%) from the total CO2 in the source: 40, or 50, or 60, or 70, or 80, or 90, or substantially 100%.
The soluble substance employed may vary depending upon, for example, whether it is to be at least partially recovered, and, if so, in what manner. By “at least partially recovered” it is meant from at least about 50%, or at least about 60%, or at least about 70%, or at least about 80%, or at least about 90%, or at least about 95%, or at least about 99% up to nearly 100% of the soluble solvent is recovered for re-use in the process or something else.
The manner of at least partially recovering the soluble substance is not particularly critical and will vary depending upon such factors as the specific composition, the desired outcome, and equipment available. For example, the separation mechanism used for at least partially recovering the soluble substance may include one or more or a combination of the following: membrane, reverse osmosis, hot reverse osmosis, nanofiltration, organic solvent nanofiltration, hot nanofiltration, ultrafiltration, hot ultrafiltration, microfiltration, filtration, distillation, membrane distillation, multi-effect distillation, mechanical vapor compression distillation, binary distillation, azeotrope distillation, hybrid separation devices, flash distillation, multistage flash distillation, extractive distillation, switchable solvent, ‘salting-out,’ or centrifuge, or combinations thereof.
In one embodiment the soluble substance may be at least partially recovered by employing a membrane that is, for example, capable of at least partially rejecting said soluble substance while allowing substantial passage of CO2 containing aqueous solution or vice versa. “CO2 containing solution” or “CO2 containing aqueous solution” simply refers to the subsequently obtained solution after desorbing of CO2. Thus, CO2 containing aqueous solution or CO2 containing solution may have various amounts of CO2 or even no CO2 depending upon the amount of CO2 desorbed in the desorbing step. This subsequently obtained solution typically comprises the solution components less any CO2 desorbed while any soluble substance is at least partially recovered by virtue of being rejected by the membrane. In such embodiments the soluble substance may comprise, for example, water, organic solvent, water soluble polymer, soluble polymer, glycol, polyethylene glycol, polypropylene glycol, ethers, glycol ethers, glycol ether esters, triglyme, polyethylene glycols of multiple geometries, including, branched polyethylene glycols, star polyethylene glycols, comb polyethylene glycols, methoxypolyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic Acid, diol polymers, 1,2 propanediol, 1,2 ethanediol, 1,3 propanediol, cellulose ethers, methylcellulose, cellosize, carboxymethylcellulose, hydroxyethylcellulose, sugar alcohol, sugars, alcohols, ketones, aldehydes, esters, organosilicon compounds, halogenated solvents, non-volatile solvents, a substance with a vapor pressure less than 0.01 atm at 20° C., soluble substances with a molecular weight greater than 80 daltons, or mixtures thereof.
Useful membranes for at least partial recovery may include, for example, any membrane capable of at least partially rejecting said soluble substance while allowing substantial passage of CO2 containing aqueous solution or vice versa. Such membranes may comprise a membrane selected from the group consisting of Reverse Osmosis, Nanofiltration, Organic Solvent Nanofiltration, Ultrafiltration, Microfiltration, and Filtration membranes. In some embodiments the membrane may have a molecular weight cutoff of greater than about 80 daltons. That is, the membrane allows passage of a substantial or majority amount of components with a molecular weight of less than about 80 daltons while rejecting a substantial or majority amount of components with a molecular weight of greater than about 80 daltons up to about 600 daltons. In the art, another definition of molecular weight cut-off may refer to the lowest molecular weight solute (in daltons) in which 90% of the solute is retained by the membrane, or the molecular weight of the molecule that is 90% retained by the membrane. Membranes with a molecular weight cutoff of less than 1,000 daltons, or less than 10,000 daltons, or less than 50,000 daltons, or less than 100,000 daltons, or less than 200,000 daltons, or less than 500,000 daltons, or less than 1,000,000 daltons may also be useful depending upon the circumstances and components employed.
The membrane may be comprised of any useful material and such useful material may vary depending upon the components to be separated, their molecular weight, viscosity, and/or other properties. Useful membranes may include, for example, membranes comprised of a material selected from a thin film composite; a polyamide; a cellulose acetate; a ceramic membrane; other materials and combinations thereof.
Generally, it may be preferred to select membranes, substances, and conditions such that any at least partial recovery step(s) involving one or more membranes may be conducted at a temperature of less than or equal to about 50, or less than or equal to 40, or less than or equal to about 35, or less than or equal to about 30° C. In other specific embodiments the at least partial recovery step(s) temperature may be at a temperature of from about 18° C. to about 32° C. Similarly, the pressure employed during any at least partial recovery may be any convenient pressure, e.g., elevated, reduced, or substantially atmospheric. For example, the step(s) may be conducted at a pressure of from about 0.75 to about 1.25 atmospheres. In another embodiment the at least partial recovery conditions employing one or more membranes are substantially room temperature and pressure.
In another embodiment the at least partially recovering said soluble substance may be accomplished by distillation or some equivalent thereof. In such embodiments the soluble substance may comprise, for example, one or more or a combination of the following: volatile organic solvents, soluble substances with a molecular weight less than 600 daltons, soluble substances with a molecular weight less than 200 daltons, dimethoxymethane, acetone, acetaldehyde, methanol, dimethyl ether, THF, ethanol, isopropanol, propanal, methyl formate, azeotropes, alcohols, ketones, aldehydes, esters, organosilicon compounds, halogenated solvents, a substance with a vapor pressure greater than 0.01 atm at 20° C., or a mixture thereof.
The integrated process wherein CO2 volatilizes may occur in the presence of a low CO2 partial pressure gas, in the presence of air, with the application of heat, or a combination thereof.
If distillation is to be employed then often the distillation of the substance to be at least partially received depends upon the components and may occur at a temperature of less than about 110° C., or less than about 100° C., or less than about 90° C., or less than about 80° C., or less than about 70° C., or less than about 60° C., or less than about 50° C., or less than about 40° C., or less than about 30° C.
In some embodiments the soluble substance may comprise a thermally switchable substance, a CO2 switchable substance, or a non-ionic carbon containing compound. A switchable substance is one which substantially separates from other materials depending upon, for example, a property or other ingredients of a combined composition. That is, a thermally switchable substance may precipitate from a given solution when subjected to temperatures above or below a certain threshold, e.g., cloud point. Useful thermally switchable substances may include, for example, those that substantially precipitate, separate, or have a cloud point at or above 30, or 40, or 50, or 60, or 70, or 80, or 90, or 100, or 110° C.
The integrated process may be conducted with a CO2-switchable substance as the soluble substance. Such substances may precipitate or separate depending upon the amount of CO2 dissolved in the solution. That is, a CO2-switchable substance may be soluble in solutions such as aqueous solutions when sufficient CO2 is dissolved but separate and become insoluble upon release of sufficient gaseous CO2. For example, the switchable solvent may be hydrophobic upon volatilization of substantial amounts, e.g., a majority, of dissolved CO2.
The concentration of the soluble substance(s) and any CO2 absorbent employed in the integrated process may vary depending upon the substance, other substances, and desired results. Typically, each may have a concentration of from about 1M to about 18M. That is, the concentration of each may be independent or dependent of the other and be, for example, greater or less than 1M, or less than 2M, or less than 3M, or less than 4M, or less than 5M, or less than 6M or less than 10M up to as high as 18M.
The specific desorbing conditions may vary depending upon the amount of CO2 present, the soluble substance employed and its concentration, the absorbent precursor or residual, if any, and its concentration, the presence and type of any impurities, the desired partial recovery steps, if any, and other factors. Generally, it may be preferred to select substances and conditions such that the desorbing step may be conducted at a temperature of less than or equal to about 50, or less than or equal to 40, or less than or equal to about 35, or less than or equal to about 30° C. In other embodiments the desorbing temperature may be at a temperature of from about 18° C. to about 32° C. Similarly, the pressure employed may be any convenient pressure. For example, the CO2 may be desorbed at a pressure of from about 0.75 to about 1.25 atmospheres. In another embodiment the desorbing conditions are substantially room temperature and pressure.
The integrated process of the present invention may involve further comprising making additional useful compounds from the solution, CO2, or both. That is, further processing steps may comprise producing ammonium carbamate, urea, or a derivative thereof.
1) Absorption (stage 1): Flue gas enters one or more absorption columns and carbon dioxide is absorbed in a CO2-lean aqueous CO2 absorbent-carbon dioxide solution, forming a CO2-rich aqueous solution. Any remaining inert gases from the flue gas, such as N2, O2, Ar, low concentrations of CO2, may be released from the absorption column and may undergo further treatment. The CO2-rich solution created in the absorption stage can be transferred to the CO2 desorption stage (stage 2).
2) CO2 Desorption (stage 2): A soluble substance, such as an organic solvent or water soluble polymer as described above, is added and mixed with the CO2-rich solution under, for example, room temperature and pressure conditions. CO2(g) is desorbed from the solution and may undergo compression or other treatment prior to utilization or conversion. After CO2 desorption, the CO2-lean solution comprising the soluble substance can be transferred to soluble substance and CO2 absorption solution recovery stage (stage 3).
3) Soluble Substance and CO2 Absorbing Solution Recovery (stage 3): The CO2-lean solution containing the soluble substance is separated into the CO2-lean absorption solution and the soluble substance using one or more separation mechanisms or devices. The CO2-lean absorption solution can be circulated to stage 1 and the soluble substance can be circulated to stage 2. Stage 3 allows the integrated process to be as regenerable as desired.
Carbon dioxide absorption with examples employing aqueous ammonia or amine species solutions involve absorbing CO2 from CO2(g) containing gas streams in a lean solution to create a rich solution. The lean solution may have a CO2 loading comprising between 0.2-0.67 and the rich solution may have a CO2 loading comprising between 0.45-1. The molar ratio may differ depending on the embodiment and CO2 absorbent or absorbents employed. Greater CO2 loading in the CO2 rich solution may be achieved by, including, but not limited to, changing the temperature, increasing pressure, increasing CO2 partial-pressure, increasing contact time, increasing residence time, increasing packing surface area, and/or the addition of a catalyst that accelerates CO2 absorption.
The absorption tower may be chilled to reduce absorbent volatilization, such as ‘ammonia-slip’ or the volatilization of other components of the absorption media. Absorbent volatilization may also be reduced by operating the absorption solutions at a greater CO2 loading, although this may result in lower absorption rates and CO2 absorption capacity. CO2 loading may be optimized to maximize reaction kinetics and solution capacity. The absorption column may absorb less than or equal to any of the following: 5%, or 10% or 20%, or 30%, or 40%, or 50%, or 60%, or 70%, or 80% or 90%, or 99%, or 99.9%, or 100% of the CO2 from the CO2 containing gas stream.
The absorption stage may include any absorption setup known in the art and may be composed of one or more absorption columns or vessels or other devices. The absorption column may include, but is not limited to, continuous absorption, continuous stirred absorption, batch column, packed column, plate column, hybrid absorption processes and other absorption processes known in the art. The absorption column or absorption solution may be chilled, wherein cooling may be conducted via any means including, but not limited to, ambient source, water bodies, cooling tower, industrial evaporative chiller and other chilling or cooling processes known in the art. It may be desirable for the CO2 concentration in the CO2 lean solution to be less than the CO2 concentration in the CO2 rich solution. A CO2(g) containing gas stream, including but not limited to flue gas, synthesis gas, steam-reforming gas, methane reforming gas, hydrogen production gases, air, concentrated, membrane concentrated gas stream, membrane concentrated flue gas, upstaged air (as would be created from the moisture swing CO2 upstaging processes described by Klaus Lackner http://pubs.acs.org/doi/abs/10.1021/es201180v, incorporated herein by reference), biogas, landfill gas, or anaerobic digester gas. The CO2 containing gas stream may be treated, used as an enthalpy, heat or cold source, or otherwise used prior to the absorption stage.
The remaining gas stream after at least a portion of the CO2(g) is absorbed, or ‘inert gases’ may undergo further treatment or utilization, including but not limited to, thermal exchange with incoming CO2 lean solution, water wash to remove trace gases, such as ammonia or organic solvent, removal process for trace gases, additional CO2 scrubbing method, including, but not limited to, amines, solid sorbent, SELEXOL, UCARSOL, membrane or strong base, separation, purification, or use of constituents, such as hydrogen, carbon monoxide, nitrogen, oxygen and/or argon.
Additionally, the remaining gas stream following the absorption column, such as the ‘inert gases,’ which may contain a lower concentration of CO2 than the entering CO2 containing gas stream, may be advantageously used in a CO2 conversion process that benefits from a relatively lower concentration of CO2, such as biological processes and certain cement production processes. For example, cement production processes that use CO2 as a reagent, the oxide or silicate or calcium oxide or calcium silicate or magnesium oxide or magnesium silicate containing reactants may initially require only low CO2 concentrations due to the highly exothermic nature of the reaction to form carbonates. As a significant portion of the reagents react with the CO2, such as a conversion yield of greater than any of the following: 0.01%, or 1%, or 5%, 10%, or 20%, or 30%, or 40% or 50%, or 60%, or 70%, or 80%, or 90%, or 95% conversion, the unreacted reagents require an increasingly greater concentration of CO2. This higher purity CO2 may be supplied by the integrated CO2 capture process.
Additionally, the absorption column may absorb a smaller percentage of the CO2 in the CO2 containing gas stream, such as less than any of the following: 20%, or 30%, or 40% or 50% or 60%, or 70%, or 80%, or 90%, or 99%. This may further reduce energy requirements, including due to the ability for the CO2 lean and rich solutions to a higher CO2 loading. The substance addition CO2 desorption stage may work more efficiently when the CO2-rich and CO2-lean solutions are at a relatively higher CO2-loading. This may also may reduce capital costs by decreasing the require dimensions of the absorption column.
The CO2-rich solution may exit the absorption column and may be transferred to Step 2. It may be advantageous to heat exchange this CO2-rich solution with the CO2-lean solution entering the absorption column. This may include a countercurrent heat exchange, resulting in a cooler/pre-cooled CO2 lean stream and a warmer/pre-heated CO2 rich stream.
Prior to entering the CO2 absorption column, the CO2 containing gas stream may, if advantageous, be treated, via methods, including but not limited to, chilling and removal of contaminants, such as hydrogen sulfide, NOx, SOx, particulates and metals. The gas stream may be further concentrated with a gas membrane CO2 concentrator or moisture-swing CO2 concentrator. The entering gas stream may be used as an energy source to supplement energy requirements, including, but not limited to, heating or cooling in the integrated process or components of connecting infrastructure, such as piping. This gas stream may be thermally exchanged by means including, but not limited to, a heat exchanger or direct contacting.
Absorption Solution: The absorption solution includes any aqueous or non-aqueous solution which absorbs CO2. CO2 absorbents include, but are not limited to, one or more or a combination of the following: water, ammonia, ammonium amine, primary amine, secondary amine, tertiary amine, methylamine (MEA), methylethanolamine, aminoethylethanolamine, azine, imine, strong base, hydroxide, sodium hydroxide, potassium hydroxide, sodium oxide, potassium oxide, organic solvent, commercial CO2 capture absorbents, quaternary ammonium compound, Selexol, Rectisol, KS-1, UCARSOL, metal-organic framework, solid adsorbent, high surface area compounds, activated carbon, zeolites, carbon nanotubes, graphene, graphene oxide, amine, amino ethyl ethanol amine, 2-Amino-2-methylpropan-1-ol (AMP), MDEA, MEA, primary amine, secondary amine, or tertiary amine, low molecular weight primary or secondary amine, metal-ammine complex, metal-ammonia complex, metal-ammonium complex, sterically hindered amine, imines, azines, piperazine, amine functionalized polymers, alkali metal, lithium, sodium, potassium, rubidium, caesium, alkaline earth metal, calcium, magnesium, cations, ionic liquid, CO2 switchable solvents, CO2 switchable surfactants carbonate, polymer containing amine functional groups, poler containing CO2 reactive functional groups, enzymes, metal-organic frameworks, glycolamine, diglycolamine, quaternary ammonia or quaternary ammonium cations, or quaternary ammonium cations embedded in polymer, or mixtures thereof. CO2 may be present in solution as one or more species throughout the integrated process, including, but not limited to, one or more or a combination of the following: bicarbonate, carbonate, carbamate, sesquicarbonate, free CO2, or dissolved CO2.
Additionally, the absorption solution may contain a desorption, absorption, or adsorption rate promoter, including, but not limited to, piperazine, diethanolamine, diglycolamine, and diisopropanolamine. Rate promoters may be used to, including, but not limited to, influence one or more of the following: CO2 absorption, CO2 desorption, soluble substance regeneration or reaction kinetics.
The CO2 loading of the CO2-lean solution may be dependent on the amount of CO2 desorbed during the substance addition CO2 desorption and the regeneration stages. Therefore, CO2 loading of CO2-lean solution may be adjusted through, including, but not limited to, changing one or more or a combination of the following: residence time, added substance type or types, soluble substance concentration in the mixed CO2 desorption solution, concentration of the soluble substance in the added substance solution, temperature, application of heating or cooling, CO2 loading in the CO2 rich solution, pressure, or CO2 loading in the in the added substance solution.
Small concentrations of soluble substance may persist or be present in the CO2 absorption solution. Low concentrations of soluble substances, such as organic solvents, may reduce ammonia slip or other CO2 absorbent volatilization in the absorption column and reduce energy consumption during regeneration. Additionally, low concentrations of soluble substances, such as organic solvents, may increase CO2 uptake and inhibit unintended CO2 volatilization. The maximum said low concentration is dependent on the type of substance and includes, but is not limited to, vol/vol % concentrations of less than any of the following: 0.001%, or 0.1%, or 0.5%, or 1%, or 1.5%, or 2%, or 2.5%, or 3%, or 3.5%, or 4%, or 4.5%, or 5%, or 5.5%, or 6%, or 6.5%, or 7%, or 7.5%, or 8%, or 8.5%, or 9%, or 9.5%, or 10%, or 10.5%, or 11%, or 11.5%, or 12%, or 12.5%, or 13%, or 13.5%, or 14%, or 14.5%, or 15%.
Carbon Dioxide Sources: Any process or resource producing or containing carbon dioxide. Examples of CO2 sources include, but are not limited to, the following: Power Plant (Natural gas, coal, oil, petcoke, biofuel, municipal waste), Waste Water Treatment, Landfill gas, Air, Metal production/refining (such as Iron, Steel, Aluminum, etc.), Glass production, Oil refineries, HVAC, Transportation vehicles (ships, boats, cars, buses, trains, trucks, airplanes), Natural Gas, Biogas, Alcohol fermentation, Volcanic Activity, Decomposing leaves/biomass, Septic tank, Respiration, Manufacturing facilities, Fertilizer production, or Geothermal processes where CO2(g) releases from a well or wells.
Non-Aqueous Embodiment: The integrated process may be aqueous or non-aqueous. A non-aqueous process may use a non-aqueous solution media as part of the CO2 containing solution. Media include, for example, polar organic solvents, including, but not limited to, ethylene carbonate, propylene carbonate, ethylene glycol, propylene glycol, DMSO, water and acetonitrile or inorganic solvents, such as liquid ammonia or liquid amines and mixtures thereof. The non-aqueous system may use a solution media containing of one or more CO2 absorbents, such as ammonia, ammonium, amines or amine functionalized polymers.
CO2 Absorbent Concentration: CO2 absorbents may be at a wide range of concentrations. The absorbent concentration may be as a low as 0.000001 M or as great as pure absorbent. In molarity terms, the concentration of the CO2 absorbent may be as low as 0.00001M or less than any of the following: 0.01 M, or 0.05M, or 0.1M, or 0.3M, or 0.5M, or 0.8 M, or 1M, or 1.3M, or 1.5M, or 1.8M, or 2M, or 2.3M, or 2.5M, or 2.8M, or 3M, or 3.3M, or 3.5M, or 3.8M, or 4M, or 5M, or 6M, or 7M, or 8M, or 9M, or 10M, or 12M, or 15M, or 18M, or even pure absorbent.
In volume/volume % terms, the CO2 absorbent concentration range may be as low as 0.0001% to as great as 99.99999%. The concentration of the CO2 absorbent may be as low as 0.001%, or any of the following: 0.01%, or less than 0.1%, or 0.5%, or 1%, or 1.5% or 2%, or 2.5%, or 3%, or 3.5%, or 4%, or 4.5% or 5%, or 5.5%, or 6%, or 6.5%, or 7%, or 7.5%, or 8%, or 8.5%, or 9%, or 9.5%, or 10%, or 10.5%, or 11%, or 11.5%, or 12%, or 12.5%, or 13%, or 13.5%, or 14%, or 14.5%, or 15%, or 15.5%, or 16%, or 16.5%, or 17%, or 17.5% or 18%, or 18.5%, or 19%, or 19.5%, or 20%, or 20.5%, or 21%, or 21.5%, or 22%, or 22.5%, or 23%, or 23.5% or 24%, or 24.5%, or 25%, or 25.5%, or 26%, or 26.5%, or 27%, or 27.5%, or 28%, or 28.5%, or 29%, or 29.5%, or 30%, or 31%, or 32%, or 33%, or 34%, or 35%, or 36%, or 37%, or 38%, or 39%, or 40%, or 41%, or 42%, or 43%, or 44%, or 45%, or 46%, or 47%, or 48%, or 49%, or 50%, or 51%, or 52%, or 53%, or 54%, or 55%, or 56%, or 57%, or 58%, or 59%, or 60%, or 61%, or 62%, or 63%, or 64%, or 65%, or 66%, or 67%, or 68%, or 69%, or 70%, or 71%, or 72%, or 73%, or 74%, or 75%, or 76%, or 77%, or 78%, or 79%, or 80%, or 81%, or 82%, or 83%, or 84%, or 85%, or 86%, or 87%, or 88%, or 89%, or 90%, or 90.5%, or 91%, or 91.5%, or 92%, or 92.5%, or 93%, or 93.5%, or 94%, or 94.5%, or 95%, or 95.5%, or 96%, or 96.5%, or 97%, or 97.5%, or 98%, or 98.5%, or 99%, or 99.5%, or 99.9%, or less than or equal to 100%.
The specific absorbent: CO2 species molar ratios in the CO2 rich and CO2 lean solutions may be from as great as pure absorbent to as low as pure CO2. It may be desirable for the CO2 rich solution to comprise a greater molar ratio of absorbent:CO2 species than the CO2 lean solution. The CO2 rich solution absorbent:CO2 species molar ratios, include but are not limited to, less than 2:1, or less than 10:1 or any of the following: 8:1, or 6:1, or 4:1, or 2:1, or 1.9:1, or 1.85:1, or 1.8:1, or 1.75:1, or 1.7:1, or 1.65:1, 1.6:1, or 1.55:1, or 1.5:1, or 1.45:1, or 1.4:1, or 1.35:1, or 1.3:1, or 1.25:1, or 1.2:1, or 1.15:1, or 1.1:1, or 1.05:1 or 1:1, or 0.95:1, or 0.9:1. The CO2 lean solution absorbent: CO2 species molar ratios, include but are not limited to, greater than 1.5:1, or greater than any of the following: 100:1, or 50:1, or 10:1, or 8:1, or 6:1, or 4:1, or 2:1, or 1.95:1, or 1.9:1, or 1.85:1, or 1.8:1, or 1.75:1, or 1.7:1, or 1.65:1, 1.6:1, or 1.55:1, or 1.5:1, or 1.45:1, or 1.4:1, or 1.35:1, or 1.3:1, or 1.25:1, or 1.2:1, or 1.15:1, or 1.1:1, or 1.05:1 or 1:1, or 0.95:1, or 0.9:1.
The CO2 rich solution enters the CO2 desorption setup. The CO2 rich solution may be a liquid solution or a liquid-solid slurry. In this step, a soluble substance and/or soluble substance containing solution is added to a CO2 rich aqueous solution and CO2(g) is subsequently desorbed, while the CO2 absorbent, such as ammonia or an amine or other absorbents known in the art, predominantly remain in solution, such as less than 2% or less than any of the following: or 1%, or 0.5%, or 0.1% absorbent volatilization. The CO2 desorption mechanism, may include, but is not limited to, the soluble substance interfering with the interactions between CO2 species' and the CO2 absorbent or CO2 absorbents. Said interferences may include, but are not limited to, one or more or a combination of the following: reducing of solution dielectric constant, decrease in CO2 species solubility, decrease in absorbent solubility, decrease in absorbent-CO2 species compound solubility, decrease in absorbent-CO2 species salt solubility, weakening of hydration shells surrounding dissolved CO2 species, weakening of hydration shells surrounding CO2 absorbent, weakening of hydration shells in absorbent-CO2 species compound, weakening of hydration shells absorbent-CO2 species salt, formation of a trimer, formation of an adduct, formation of a complex, formation of a complex ion, formation of a zwitterion, reaction with CO2 absorbent, reversible reaction with CO2 absorbent, reaction with CO2 species, or reversible reaction with CO2 species.
It may be desirable for the interaction of the soluble substance with the CO2 absorbent-carbon dioxide salt to not involve a metathesis reaction or a single displacement reaction. It may be desirable for no chemical reaction to occur between the soluble substance and the CO2 absorbent. It may be desirable for the CO2 desorption to be entirely due to changes in solution media properties, such as changes in solution dielectric constant, changes in solution polarity, and changes in hydration shell stability.
The soluble substance may be preheated or cooled before injection into the mixing apparatus. The mixing apparatuses and methods include, but are not limited to, batch mixers, continuous stirred-tank reactors, CSTRs, distillation column, packed column, electrospray, spray column, countercurrent spray column, and/or other apparatuses and/or methods. The apparatus may be heated using waste heat or other heat source for, including, but not limited to, promoting CO2 desorption, reducing viscosity and/or increasing the rate of solvent mixing.
The CO2 may pressurize, by any means, including but not limited to, closing and opening a release valve to allow the system to pressurize, utilizing a smaller gas release valve, temperature change, or using external compression. In the case where the CO2(g) is desorbed at a pressure greater than atmospheric pressure, less energy may be required for compression of this CO2(g), if compression is desired. The exiting gas stream may contain predominantly CO2. At least a portion of this desorbed CO2 may be used for, including, but not limited to, one or more or a combination of the following: enhanced oil recovery, methanol production, syngas production, fuel production, urea production, fertilizer production, carbonate, bicarbonate production, carbamate production, beverage production, greenhouse, agricultural applications, welding gas, turbine working fluid, laser gas, food production, inert gas, cement production, CO2 conversion processes, and other existing and future applications. This gas stream may be further treated by, including, but not limited to, water wash down, aqueous wash down, non-aqueous wash down, changes in pressure, changes in temperature, compression, vacuum, and an additional carbon capture process. Additives may be added to this gas stream prior, during or after treatment or in the absence of treatment. These additives include, but are not limited to, ammonia, electricity, light, hydrogen, amine, oxygen, methane, methanol, carbon monoxide, hydrogen sulfide, haloalkanes, chlormethane, dimethylether, hydrogen cynide, sulfur, acid or acid gas, hydroxide, oxide, carbonate, carbamate, and bicarbonate.
Maintaining CO2(g) in Headspace: Measures may be taken to ensure the gas stream or headspace contains a high concentration of CO2(g), especially during the first instance of use or after construction. This may be achieved by, including, but not limited to, purging the CO2(g) generation vessel with pure CO2(g) before the first run of the process. Self-purging may also be employed by using the CO2(g) desorbed during solvent addition in initial runs to displace or dilute the other gases present in the vessel.
Added Solvent: The added soluble substance may include, but is not limited to, one or more or a combination of the following: organic solvents, concentrated soluble substance solutions, water soluble polymers, combinations of soluble substances, solvent mixtures, emulsions, pure substance, pure solvent, aqueous solvent, surfactant containing solvents, zwitterions, solids, soluble solids, gases, liquid-solid mixtures, soluble gases, aerosols, suspended solids, solid-gas mixtures, super critical fluids, and fluid mixtures.
Precipitate during Solvent Addition CO2 Desorption: When a soluble substance is added to a CO2 rich solution, such as 2M aqueous ammonium bicarbonate, in addition to the desorption of CO2(g), a portion of the CO2 containing salt may precipitate as a solid. This precipitate may dissolve back into solution, including, but not limited to, as CO2(g) desorption occurs. This may be due to ammonium carbonate or carbamate (NH3:CO2 of 2:1) being more soluble than ammonium bicarbonate (NH3:CO2 of 1:1) in the water-soluble substance solution. In some embodiments there is no substantial precipitate formed.
Application of Heating or Cooling: Heating or cooling may be incorporated throughout the integrated process. For example, heating or cooling may be beneficial during CO2 desorption to increase CO2(g) yield and soluble substance solubility. Polyethylene glycols (PEGs) and polypropylene glycols (PPGs), for example, have higher Gibbs free energy of mixing and osmotic pressure at lower temperatures. Cooling may enhance CO2(g) desorption, including, but not limited to, due to the greater Gibbs free energy of mixing and osmotic pressure of PEGs and PPGs at cooler temperatures and the decreased solubility of the CO2 containing salts, such as ammonium bicarbonate or carbonate, at lower temperatures. Heating may enhance CO2(g) desorption, including, but not limited to, due to greater reaction kinetics and lower CO2 species solubility.
The soluble substance may be added to the CO2 rich solution as a concentrated aqueous or non-aqueous solution or in a pure form. Said concentrated solution of the soluble substance may contain a vol/vol % concentration of soluble substance as low as 0.0001% to as great as 99.99999%. Vol/vol % concentrations of the soluble substance or concentrated soluble substance solution may be practically greater than any of the following: 1%, or 5%, or 10%, or 11%, or 12%, or 13%, or 14%, 15%, or 16%, or 17%, or 18%, or 19%, or 20%, or 21%, or 22%, or 23%, or 24%, or 25%, or 26%, or 27%, or 28%, or 29%, or 30%, or 31%, or 32%, or 33%, or 34%, or 35%, or 36%, or 37%, or 38%, or 39%, or 40%, or 41%, or 42%, or 43%, or 44%, or 45%, or 46%, or 47%, or 48%, or 49%, or 50%, or 51%, or 52%, or 53%, or 54%, or 55%, or 56%, or 57%, or 58%, or 59%, or 60%, or 65%, or 70%, or 75%, or 80%, or 85%, or 90%, or 95%, or less than or equal to 100%.
The resulting concentration of the soluble substance in the CO2 desorption/mixing step may be a vol/vol % concentration of soluble substance as low as 0.0001% to as great as 99.99999%. Vol/vol % concentrations of the soluble substance in the CO2 desorption/mixing step or resulting mixed solution may be practically greater than any of the following: 0.1%, or 1%, or 2%, or 3%, or 4%, or 5%, or 5.5%, or 6%, or 6.5%, or 7%, or 7.5%, or 8%, or 8.5%, or 9%, or 9.5%, or 10%, or 10.5%, or 11%, or 11.5%, or 12%, or 12.5%, or 13%, or 13.5%, or 14%, or 14.5%, or 15%, or 15.5%, or 16%, or 16.5%, or 17%, or 17.5% or 18%, or 18.5%, or 19%, or 19.5%, or 20%, or 20.5%, or 21%, or 21.5%, or 22%, or 22.5%, or 23%, or 23.5% or 24%, or 24.5%, or 25%, or 25.5%, or 26%, or 26.5%, or 27%, or 27.5%, or 28%, or 28.5%, or 29%, or 29.5%, or 30%, or 31%, or 32%, or 33%, or 34%, or 35%, or 36%, or 37%, or 38%, or 39%, or 40%, or 41%, or 42%, or 43%, or 44%, or 45%, or 46%, or 47%, or 48%, or 49%, or 50%, or 51%, or 52%, or 53%, or 54%, or 55%, or 56%, or 57%, or 58%, or 59%, or 60%, or 65%, or 70%, or 75%, or 80%, or 85%, or 90%, or 95%, or less than 99%.
The maximum solubility of the soluble substance in the CO2 desorption/mixing step may be a vol/vol % concentration of soluble substance as low as insoluble to as great as completely miscible. Vol/vol % solubility of the soluble substance may be practically greater than any of the following: 0.001%, 0.01%, 0.1%, or 1%, or 2%, or 3%, or 4%, or 5%, or 6%, or 7%, or 8%, or 9%, or 10%, or 11%, or 12%, or 13%, or 14%, or 15%, or 16%, or 17%, or 18%, or 19%, or 20%, or 21%, or 22%, or 23%, or 24%, or 25%, or 26%, or 27%, or 28%, or 29%, or 30%, or 31%, or 32%, or 33%, or 34%, or 35%, or 36%, or 37%, or 38%, or 39%, or 40%, or 41%, or 42%, or 43%, or 44%, or 45%, or 46%, or 47%, or 48%, or 49%, or 50%, or 51%, or 52%, or 53%, or 54%, or 55%, or 56%, or 57%, or 58%, or 59%, or 60%, or 61%, or 62%, or 63%, or 64%, or 65%, or 66%, or 67%, or 68%, or 69%, or 70%, or 71%, or 72%, or 73%, or 74%, or 75%, or 76%, or 77%, or 78%, or 79%, or 80%, or 81%, or 82%, or 83%, or 84%, or 85%, or 86%, or 87%, or 88%, or 89%, or 90%, or 90.5%, or 91%, or 91.5%, or 92%, or 92.5%, or 93%, or 93.5%, or 94%, or 94.5%, or 95%, or 95.5%, or 96%, or 96.5%, or 97%, or 97.5%, or 98%, or 98.5%, or 99%, or 99.5%, or 99.9%, or 100%, or completely miscible.
Purity of CO2 Desorbed: The purity of CO2 may desirably by greater than 90%. The CO2 concentration range may be as low as 0.0001% to as great as 99.99999%. The purity or concentration of the desorbed CO2 may be as low as any of the following: 0.1% or greater than 0.1%, or 1%, or 2%, or 3%, or 4%, or 5%, or 6%, or 7%, or 8%, or 9%, or 10%, or 11%, or 12%, or 13%, or 14%, or 15%, or 16%, or 17%, or 18%, or 19%, or 20%, or 21%, or 22%, or 23%, or 24%, or 25%, or 26%, or 27%, or 28%, or 29%, or 30%, or 31%, or 32%, or 33%, or 34%, or 35%, or 36%, or 37%, or 38%, or 39%, or 40%, or 41%, or 42%, or 43%, or 44%, or 45%, or 46%, or 47%, or 48%, or 49%, or 50%, or 51%, or 52%, or 53%, or 54%, or 55%, or 56%, or 57%, or 58%, or 59%, or 60%, or 61%, or 62%, or 63%, or 64%, or 65%, or 66%, or 67%, or 68%, or 69%, or 70%, or 71%, or 72%, or 73%, or 74%, or 75%, or 76%, or 77%, or 78%, or 79%, or 80%, or 81%, or 82%, or 83%, or 84%, or 85%, or 86%, or 87%, or 88%, or 89%, or 90%, or 90.5%, or 91%, or 91.5%, or 92%, or 92.5%, or 93%, or 93.5%, or 94%, or 94.5%, or 95%, or 95.5%, or 96%, or 96.5%, or 97%, or 97.5%, or 98%, or 98.5%, or 99%, or 99.5%, or 99.9%, or less than or equal to 100%.
Partial Pressure of CO2 Desorbed: The partial pressure of CO2 may be greater than 0.5 atm or 1 atm. The CO2 partial pressure range may be as low as 0.001 atm to as great as 100,000 atm, liquid CO2, supercritical CO2, or solid CO2. The partial pressure of CO2 may be as low as any of the following: 0.001 atm, or 0.01 atm, or greater than or less than 0.05 atm, or 0.1 atm, or 0.2 atm, or 0.3 atm, or 0.4 atm, or 0.5 atm or 0.6 atm, or 0.7 atm, or 0.8 atm, or 0.9 atm, or 1 atm, or 1.1 atm, or 1.2 atm, or 1.3 atm, or 1.4 atm, or 1.5 atm, or 1.6 atm, or 1.7 atm, or 1.8 atm, or 1.9 atm, or 2 atm, or 2.1 atm, or 2.2 atm, or 2.3 atm, or 2.4 atm, or 2.5 atm, or 2.6 atm, or 2.7 atm, or 2.8 atm, or 2.9 atm, or 3 atm, or 3.5 atm, or 4 atm, or 4.5 atm, or 5 atm, or 5.5 atm, or 6 atm, or 6.5 atm, or 7 atm, or 7.5 atm, or 8 atm, or 8.5 atm, or 9 atm, or 9.5 atm, or 10 atm, or 12 atm, or 15 atm, or 18 atm, or 20 atm, or 22 atm, or 25 atm, or 28 atm, or 30 atm, or 40 atm, or 50 atm, or 60 atm, or 75 atm, or 100 atm, or 150 atm, or 200 atm, or 500 atm, or 1,000 atm, or 10,000 atm, or 100,000 atm, or less than 1,000,000 atm.
The purity or concentration of the desorbed CO2 or final CO2 produced may be dependent on the application. The setup may contain other gases than CO2(g). The other gas or gases present in with this CO2 may be dependent on the application. For example, if the CO2 will be mixed with hydrogen (such as at about a 2:1 or 3:1 ratio) to produce CO2 derived chemicals, hydrogen may be added as a headspace gas during CO2 desorption. This example may reduce CO2 capture energy requirements, including, but not limited to, due to the requirement of a lower partial pressure of CO2(g) desorbed and lower final solvent concentration required.
In this stage, the substance or substances may be recovered via one or more separation mechanisms. This stage involves separating the solution produced by the CO2 desorption stage into two main streams: 1) the CO2-lean absorption solution; 2) the soluble substance. The absorption solution is recycled back to the CO2 absorption stage and the soluble substance is recycled back to the substance CO2 desorption stage.
The separation devices and mechanisms employed are dependent on the type or types of added substances. Separation devices and mechanisms include, but are not limited to, one or more or a combination of the following: semi-permeable membrane, nanofiltration, organic solvent nanofiltration, reverse osmosis, ultrafiltration, microfiltration, hot nanofiltration, hot ultrafiltration, distillation, membrane distillation, flash distillation, multi-effect distillation, mechanical vapor compression distillation, switchable solvent, hybrid systems, thermally switchable solvent, centrifuge, or filter or combinations thereof.
Specific recovery methods or separation devices and mechanisms and combinations thereof are further described herein.
Nonvolatile Solvent Addition with Membrane Recovery
Example embodiments include, but are not limited to,
1) Absorption: Gas containing CO2 enters the absorption column and CO2 is absorbed in a CO2-lean aqueous absorbent-carbon dioxide solution, forming a CO2-rich aqueous absorbent-solution. The remaining inert gases from the flue gas (N2, O2, Ar, low concentrations of CO2) are released from the absorption column. The CO2 rich solution created is transferred to stage 2.
2) CO2 Desorption: A concentrated soluble substance solution or ‘concentrate’, such as 30% PEG, 70% CO2 lean aqueous ammonia-carbon dioxide, is added and mixed with the CO2 rich solution at a preset vol/vol % ratio under room temperature and pressure conditions. CO2(g) is desorbed from the CO2 rich solution and may undergo compression or other treatment prior to utilization. The CO2-lean mixed solution containing the added substance, is transferred to stage 3.
3) Soluble Substance and Absorption Solution Regeneration via Nanofiltration: The CO2-lean solution containing the soluble substance, such as Polyethylene Glycol (PEG) or Polypropylene Glycol (PPG), is fed into a nanofiltration membrane module and pressurized using a pump. The nanofiltration membrane rejects the dissolved soluble substance while allowing water, the CO2 absorbent or absorbents (such as ammonia or amine) and carbon dioxide to pass. Two aqueous streams are generated: 1) a ‘concentrate’ stream (30% PEG(1) in diagram), which contains a high concentration of the soluble substance, such as PEG or PPG; 2) a ‘permeate’ stream (CO2 lean in diagram) which contains less, minimal concentrations, or none of the added substance, such as PEG or PPG. Additional CO2 may be desorbed from the ‘concentrate’ side and may be used as additional captured CO2 (not shown in diagram). The ‘concentrate’ stream is transferred to stage 2 (CO2 desorption) and the ‘permeate’ stream is transferred to stage 1 (flue gas CO2 absorption).
Advantages, include, but are not limited to:
Description: The embodiment is composed of three main steps: 1) The addition/contacting of a gas containing CO2 to convert aqueous ammonia, ammonium or amine containing CO2 lean solution to a CO2 rich solution. The remaining inert gases may undergo further purification, treatment or compression; 2) The addition of a large molecular weight (MW) water soluble substance or substances to the CO2 rich solution to desorb CO2(g), creating a CO2 lean solution+added substance+CO2(g). This CO2(g) stream may undergo further purification, treatment or compression; 3) The recovery of the added substance or substances using a separation mechanism. The CO2 lean aqueous soluble substance-CO2 absorbent-carbon dioxide solution formed in the second stage is fed into a membrane module and may be separated using pressurization. The separation mechanism may include, but is not limited to, one or more or combination of the following: microfiltration, ultrafiltration, nanofiltration organic solvent nanofiltration and reverse osmosis. The membrane rejects the organic solvent or soluble substance, while allowing the CO2 lean aqueous ammonia-carbon dioxide salt to pass through the membrane. The solution that passes through the membrane, or the permeate stream, is then transferred to the CO2 absorption column. The solution rejected by the membrane, which contains a higher concentration of the soluble substance, is recycled to the CO2 desorption stage as the soluble substance containing solution.
The type of membrane or filter employed may be dictated by the molecular weight of the soluble substance added, which may be advantageously larger than the molecular weight cut-off of the membrane. The molecular weight cut-off of the membrane or filter may be sufficiently large to allow aqueous ammonia-carbon dioxide species to pass though or to be minimally rejected. The power source of the pump is not of particular importance, however it may be powered by electricity, pressure exchanger, turbocharger, hydraulic pressure, heat, pressure retarded osmosis, or forward osmosis.
Following the membrane or filter based separation, energy can be recovered by both or either the permeate (the absorption solution) and the concentrate (the soluble substance containing solution). These energy recovery devices are known in the art and include, but are not limited to, pressure exchangers and turbochargers.
The embodiment may be heated or cooled where advantageous. For example, the solvent addition and mixing step may be heated or cooled for various purposes, including, but not limited to, increasing CO2(g) yield, decreasing timeframe of CO2(g) generation, increasing solvent solubility, reducing energy consumption in the membrane or filtration module or a combination thereof. Energy consumption in the membrane or filtration module may be reduced from solution or module heating due to, but not limited to, the one or more of the following: 1) reduction of osmotic pressure (which decreases with increasing temperature in PEGs, PPGs and other water soluble polymers), reduction in concentration polarization, reduction in viscosity and change in solubility. Any portion of the process may be heated or cooled. Heat sources may include, but are not limited to, waste heat, power plant waste heat, steam, heat, pump or compressor waste heat, industrial process waste heat, steel waste heat, metal refining and production waste heat, paper mill waste heat, cement production waste heat, calcination waste heat, factory waste heat, petroleum refining waste heat, solar heat, solar pond, air conditioner waste heat, combustion heat, geothermal heat, ocean or water body thermal heat, stored heat, and CO2(g) absorption solution heat. Temperatures of heating or cooling for any of the embodiments disclosed include, but are not limited to, less than any of the following: −20° C., or −10° C., or 0° C., or 10° C., or 20° C., or 25° C., or 30° C., or 35° C., or 40° C., or 41.5° C., or 41.5° C., or 41.5° C.-60° C., or 45° C., or 50° C., or 55° C., or 60° C., or 60-100° C., or 110° C., or 150° C. For example, power plant condenser waste heat is generally abundant at ˜41.5° C. and may be employed. Relatively lower molecular weight solvents may be employed if advantageous, including, but not limited to, polyethylene glycols 150-2000, polypropylene glycols 425-4000 and glycol ethers, such as triglyme. Although relatively lower molecular weight solvents or soluble substances, such as polyethylene glycols 150-2000, may have a higher osmotic pressure for a given volume/volume % concentration, these may be advantageous due to including, but not limited to, one or more of the following: 1) exhibit lower viscosity, 2) higher solubility, 3) less prone to degradation, 4) less expensive, 5) lower concentration polarization, 6) higher mole fraction per given vol/vol %, 7) greater Gibbs free energy of mixing and 8) greater influence on dielectric constant. Relatively larger molecular weight solvents may be advantageous due to one or more of the following: 1) lower osmotic pressure, 2) greater reduction of osmotic pressure with heat, 3) allow for the use of a larger pore size membrane or filter, 4) allow for the use of a higher permeability membrane, 4) may possess an LCST or UCST phase change with temperature and 5) may decrease in solubility with changes in temperature. The process may be constructed for large scale, stationary CO2 capture.
The process may also be constructed and transported in smaller scale modules or as a unit, such as in shipping containers and transported and used in other locations. This may facilitate the ability to capture carbon dioxide in remote locations, in applications including, but not limited to, oil and gas production, cement production, mining and air CO2 capture. The process may also be constructed as a stationary process.
The added concentrate, which may be a solution with a high concentration of the large molecular weight soluble substance, may comprise one or more or a combination of the following: a solid, a liquid, an aqueous solution containing the recovered substance, an aqueous solution containing the recovered solvent and CO2 absorption species, an aqueous solution containing the recovered solvent and CO2 absorption species and CO2 species or a combination thereof.
Application of Heating or Cooling: Heating prior or during membrane recovery may reduce energy consumption due to, including, but not limited to, lower osmotic pressure and lower concentration polarization. Chilling may be useful in the absorption column to reduce ammonia slip.
If the solution is mildly heated, the energy required to separate water soluble polymers, hydrogels and other substances separable via a membrane may be reduced for reasons, including but not limited to, 1) lower concentration polarization; 2) lower viscosity; 3) lower osmotic pressures at higher temperatures in aqueous solutions. CO2(g) may be desorbed during Step 3 with or without heating. This CO2(g) and other CO2(g) desorbed at or between stages 1, 2 or 3 of this process may undergo the same use or treatment as the CO2(g) desorbed from the desorption stage (stage 2), including use as captured CO2(g). CO2(g) may be desorbed due to, including, but not limited to, one or more or a combination of the following: increase in soluble substance concentration, a further decrease in the dielectric constant in the solution, weakening of the hydration shells solvating the aqueous ammonia (or other CO2 absorbent molecule or molecule combination)-carbon dioxide compound, or changes in temperature or pressure. The pressure of the CO2(g) generated may supplement the pressurization energy requirements of the pump or other pressurization method.
The regeneration portion of this embodiment may employ, including, but not limited to one, or more or a combination of the following: reverse osmosis, nanofiltration, organic solvent nanofiltration, ultrafiltration, microfiltration or switchable solvent.
The embodiment may employ a reverse osmosis membrane with a low molecular weight cut-off, including but not limited to, less than any of the following: 250 da, or 200 da, or 150 da, or 125 da, or 100 da, or 95 da, or 90 da, or 85 da, or 80 da, or 75 da, or less than the hydration radius of ammonium bicarbonate. For example, this embodiment may employ aqueous ammonia as the CO2 absorbent. In this instance, it may be advantageous for the NH3:CO2 molar ratio of the aqueous ammonia-carbon dioxide in the solution produced by the desorption stage to be greater than 1.5:1 or the pH to be greater than about 8.5. Ionic aqueous ammonia (or ammonium)-carbon dioxide species may become free dissolved ammonia or carbon dioxide under these conditions. The hydration radius of free ammonia or carbon dioxide is significantly smaller than the hydration radius of ionic species of ammonia (ammonium) and carbon dioxide (bicarbonate or carbonate or carbamate). Thus, under these conditions, the ammonia-carbon dioxide may more freely pass through a relatively small molecular weight cut-off reverse osmosis or forward osmosis membrane. This may allow for the use of lower molecular weight added substances, such as ethylene glycol, ethylene carbonate, propylene glycol, propylene carbonate, and polyethylene glycol (PEG) 200, which may be advantageous due to, including, but not limited to, one or more or a combination of the following: greater solubility, lower viscosity, lower cost, exhibit a greater Gibbs free energy of mixing, exhibit a greater influence on solution dielectric constant, less prone to degradation, and exhibit less concentration polarization during membrane solvent recovery. Additionally, it may allow for appreciably complete recovery or removal of the added solvent, including when a relatively larger molecular substance is employed.
Multicomponent separation devices or multistage separation devices may be employed. Said device or devices may include, but are not limited to, one or more or a combination of the following: binary distillation, azeotrope distillation, membrane distillation, mechanical vapor compression, hybrid systems, flash distillation, multistage flash distillation, multieffect distillation, extractive distillation, switchable solvent, reverse osmosis, nanofiltration, organic solvent nanofiltration, ultrafiltration, and microfiltration. For example, such a hybrid system may involve at least partially recovering the soluble substance using nanofiltration and then further concentrating the soluble substance using membrane distillation.
Another example of such a hybrid system may be a process wherein a switchable solvent ‘switches’ out of solution due to the presence of a stimulant, such as a change in temperature, then nanofiltration is employed to further concentrate the switchable solvent or remove remaining switchable solvent in the CO2 lean solution. The switchable solvent or other substance dissolved in solution may be further recovered or concentrated or even removed from the one or more layers or separate solutions that are formed.
Applied Pressure or Osmotic Pressure of Solution: The osmotic pressure range of the resulting water soluble substance solution may be as low as 0.001 atm to as great as 1,000,000 atm. The osmotic pressure may be as low as less than any of the following: 0.001 atm, or 0.01 atm, or greater than or less than 0.05 atm, or 0.1 atm, or 0.2 atm, or 0.3 atm, or 0.4 atm, or 0.5 atm or 0.6 atm, or 0.7 atm, or 0.8 atm, or 0.9 atm, or 1 atm, or 1.1 atm, or 1.2 atm, or 1.3 atm, or 1.4 atm, or 1.5 atm, or 1.6 atm, or 1.7 atm, or 1.8 atm, or 1.9 atm, or 2 atm, or 2.1 atm, or 2.2 atm, or 2.3 atm, or 2.4 atm, or 2.5 atm, or 2.6 atm, or 2.7 atm, or 2.8 atm, or 2.9 atm, or 3 atm, or 3.5 atm, or 4 atm, or 4.5 atm, or 5 atm, or 5.5 atm, or 6 atm, or 6.5 atm, or 7 atm, or 7.5 atm, or 8 atm, or 8.5 atm, or 9 atm, or 9.5 atm, or 10 atm, or 12 atm, or 15 atm, or 18 atm, or 20 atm, or 22 atm, or 25 atm, or 28 atm, or 30 atm, or 35 atm, or 40 atm, or 45 atm, or 50 atm, or 55 atm, or 60 atm, or 65 atm, or 70 atm, or 75 atm, or 80 atm, or 85 atm, or 90 atm, or 95 atm, or 100 atm, or 150 atm, or 200 atm, or 500 atm, or 1,000 atm, or 10,000 atm, or 100,000 atm, or less than 1,000,000 atm, or pure solvent.
Organic Solvent and CO2 Lean Absorbing Solution Recovery:
This embodiment employs a nanofiltration membrane with a pore size sufficiently small to reject the large molecular weight organic solvent and sufficiently large to allow aqueous ammonia-carbon dioxide salts to pass through the membrane. An effective membrane for this process may have molecular weight cutoff of above 200 Daltons to allow hydrated ammonia or amine and carbon dioxide to pass through the membrane and below the molecular weight of the organic solvent or soluble substance, such as PEG 600.
Energy for separation is supplied by pressurization, which may be accomplished using electricity and pumps used in commercial reverse osmosis desalination and nanofiltration process. Energy requirements in commercial aqueous membrane-based separation processes can approach the minimum thermodynamic energy requirement, exponentially improving the efficiency of CO2 capture. Embodiments may include:
Embodiment Tested: (1) CO2 is absorbed in the CO2 lean aqueous ammonia in the absorption column, forming CO2 rich aqueous ammonia; (2) PEG concentrate is added and mixed with the CO2 rich aqueous ammonia, desorbing CO2 and forming a CO2 lean solution; (3) PEG concentrate and CO2 lean aqueous ammonia are separated using nanofiltration and recycled. Nanofiltration membranes reject PEG, while ammonia, water and carbon dioxide species pass through the membranes.
CO2 Desorption Experiments: The CO2 desorption stage of this embodiment involves adding the substance, such as a concentrated aqueous PEG solution, to the CO2 rich aqueous CO2 absorbent-carbon dioxide solution, such as ammonia-carbon dioxide, from the absorption column. Pure CO2(g) is desorbed at room temperature and pressure (RTP) conditions.
The following shows data from experiments assessing the desorption rate and total yield of pure CO2(g) in relation to final PEG concentration and ammonium bicarbonate concentration. Pure PEG 600 was injected and mixed at a consistent mixing rate. The CO2 desorption trials were conducted at room temperature and atmospheric pressure.
The graph at
30 mL=30 mL PEG+100 mL 2M NH4HCO3(aq)=˜23% PEG
10 mL=10 mL PEG+100 mL 2M NH4HCO3(aq)=9.09% PEG
7 mL=7 mL PEG+100 mL 2M NH4HCO3(aq)=6.54% PEG
6 mL=6 mL PEG+100 mL 2M NH4HCO3(aq)=5.66% PEG
5 mL=5 mL PEG+100 mL 2M NH4HCO3(aq)=4.76% PEG
The graph at
While not wishing to be bound by any particular theory it may be concluded:
Optimization may involve, including, but not limited to, changing mixing rate, soluble substance type, soluble substance concentration, CO2 absorbent solution, CO2 absorbent concentration, CO2 absorbent combination and temperature. Optimization of solvent type may involve determining the most effective molecular weights and molecular structures of each soluble substance type and making most effective use of each soluble substances' properties. For example, the osmotic pressure of aqueous propylene glycols (PPGs) decrease significantly with temperature, even becoming thermally switchable at higher temperatures. For example, the osmotic pressure of a 50% PPG 425 vol/vol solution is ˜75% less at 40° C. than 20° C. (pg. 38, http://projekter.aau.dk/projekter/files/17652274/Investigation_of_Polypropylene_Glycol_425_as_a_Draw_Solution_for_Forward_Osmosis.pdf, incorporated herein by reference). An example of making optimal use of this property may involve preheating the solution produced in the CO2 desorption mixer prior to the nanofiltration soluble substance recovery stage. This may reduce regeneration energy requirements by reducing osmotic pressure, viscosity and concentration polarization.
These experiments use 2M concentration ammonium bicarbonate, which is near the ammonium bicarbonate solubility limit of 2.7M at 20° C. Higher concentrations than 2.7M may be employed, even at temperatures below 20° C., as the process may function properly under conditions where the CO2 rich or CO2 lean streams comprise of solids or contain solids or comprise a solid-liquid slurry.
Solid precipitation and dissolution may occur throughout the process, including, but not limited to, due to changes in soluble substance concentration, CO2 loading, and temperature. For example, precipitate may form in the absorption column, such as due to the increase in CO2 concentration. The precipitate may dissolve back into solution during the CO2 desorption or soluble substance regeneration stages, due to, including, but not limited to, a decrease in CO2 concentration, increases in temperature, and recovery of at least a portion of the soluble substance.
Prior to the regeneration stage, such as nanofiltration soluble substance recovery or distillation soluble substance recovery, a separation device, such as a filter, may be employed, for purposes, including but limited to, preventing the buildup of solids in the substance regeneration component.
Solubility of ammonium bicarbonate increases with temperature until it begins to decompose at 40° C.-60° C. Thus, higher concentrations than 2.7M (the solubility limit of ammonium bicarbonate in water at 20° C.) may be still contain no solids, including, but not limited to, if the temperature is raised. In this instance, ammonium bicarbonate, carbonate or sesquicarbonate precipitate may form in the absorption column, including, but not limited to, because the absorption column may operate at near or below room temperature to prevent ammonia slip. Maximizing concentration may be useful as it may, including, but not limited to, increase the CO2 absorption-desorption capacity.
Nanofiltration PEG 600 Energy Requirement Calculations: This stage employs nanofiltration membranes with a pore size sufficiently small to reject the large molecular weight organic solvent, such as polyethylene glycol, or other soluble substance and sufficiently large to allow aqueous ammonia-carbon dioxide salts, or other CO2 absorbent-CO2 species, to pass through the membrane. An effective membrane for this process may have a molecular weight cutoff of above 200 Daltons to allow hydrated ammonia and carbon dioxide to pass through the membrane and below the molecular weight of the organic solvent (e.g. PEG 600).
Aqueous PEGs are commonly employed to evaluate the molecular weight cutoff of standard reverse osmosis and nanofiltration membranes. PEG is nontoxic and inert, and may pose little threat of degradation, fouling or other unintended interaction with nanofiltration membranes. The process may use standard industrial nanofiltration membrane modules and setups known in the art.
Energy for separation may be supplied by pressurization, which may be accomplished using electricity and pumps used in commercial reverse osmosis desalination and nanofiltration processes known in the art. Energy requirements in commercial aqueous membrane-based separation processes may approach the minimum thermodynamic energy requirement, exponentially improving the efficiency of CO2 capture.
Below is the modelled energy consumption of the process and estimated the CO2 generated from a 9.09% v/v concentration solution of PEG 600 in a CO2 rich aqueous ammonia-carbon dioxide solution. 9.09% v/v was a sufficient concentration of PEG 600 to convert 25% of aqueous CO2 into pure CO2(g) over a 30-minute period. The energy consumption per kg of CO2 captured is slightly greater than the thermodynamic limit for flue gas capture (172 kJ/kg CO2) and over 96% less energy than the chilled ammonia process.
The nanofiltration setup may be designed based on optimized solution flow rates and PEG concentration in the ‘PEG-concentrate’ added solution and the mixed solution. These parameters may be determined based on the absorption column and CO2 desorption stages.
Generally desirable properties: There are a wide range of substances capable of being added to an aqueous solution containing ammonia, ammonium, amine or bicarbonate, carbonate or carbamate species that would desorb CO2 can be subsequently recovered using membrane or filter based processes (e.g. Microfiltration, Ultrafiltration, Nanofiltration, Reverse Osmosis). The following is a list of potentially desirable properties for these added substances. Desired substances may include one or more of the following, although the properties are not limited to those described herein and added substances may or may not exhibit any of these properties.
Solvents that meet the properties thereof include, but are not limited to, a wide range of glycols (such as polyethylene glycols [PEG] and polypropylene glycols [PPG]).
Solvent Addition with Distillation Recovery
Embodiments described include the embodiment shown in
Brief Description: The system is composed of three main steps: 1) Gas containing CO2 enters the absorption column and CO2 is absorbed in a CO2-lean aqueous absorbent-carbon dioxide solution, forming a CO2-rich aqueous absorbent-carbon dioxide solution. The remaining inert gases from the flue gas (N2, O2, Ar, low concentrations of CO2) are released from the absorption column. 2) The addition of a water-soluble solvent to a CO2 rich solution, resulting in the formation of gaseous CO2(g) and a CO2-lean solution. The gaseous CO2(g) may undergo further purification or treatment to remove solvent, water vapors, or traces of absorbent vapor, which may be recycled in the process; 3) The distillation and condensation of the low boiling point solvent from the remaining CO2 lean solution, which may include using ultra low grade heat (less than any of the following: ˜42° C., or 60° C., or 80° C., or 100° C.). The CO2 lean solution, which now contains an appreciably lower concentration of organic solvent, is circulated to the absorption column, while the condensed organic solvent is circulated to the substance addition desorption stage.
In instances where the solvent used has a higher boiling point than the temperature of the waste heat, distillation may be conducted by exploiting the high vapor pressure of the solvent via one or more or a combination of the following: multi-effect distillation, membrane distillation, a lower temperature condenser, vapor compression, or mechanical vapor compression distillation. The CO2-lean solution, after the recovery of the solvent, may be recycled to the first step of the process.
1) Absorption:
Dilute CO2 in flue gas is absorbed in a CO2 lean aqueous ammonia-carbon dioxide solution forming a CO2 rich aqueous ammonia-carbon dioxide solution. The CO2(g) lean aqueous ammonia-carbon dioxide solution may be composed of predominantly aqueous ammonium carbonate and ammonium carbamate at an NH3:CO2 molar ratio that may be greater than 1.5:1 and may be near 2:1. CO2(g) is absorbed in the CO2 lean aqueous ammonia to form aqueous ammonium bicarbonate at an NH3:CO2 molar ratio, such as less than 1.5:1 and near 1:1. Dilute CO2(g) is absorbed in a CO2 lean aqueous ammonia-carbon dioxide solution according to the following chemical reaction:
(NH4)2CO3(aq)+H2O(aq)+CO2(dilute gas)→2NH4HCO3(aq)
CO2 is desorbed by adding one or more water soluble, low cost organic solvents under moderate conditions to the CO2 rich aqueous ammonia-carbon dioxide solution, such as room temperature and pressure conditions. In the case of the low-grade waste heat powered CO2 capture process, a low boiling point organic solvent, such as acetone, dimethoxymethane, acetaldehyde, methyl formate, or dimethyl ether is employed. CO2(g) is desorbed under substantially room temperature and pressure (RTP) conditions according to the following chemical reaction:
2NH4HCO3(aq)+Organic Solvent(l)→(NH4)2CO3(aq)+CO2(g)+H2O(aq)+Organic Solvent(aq)
CO2(g) is desorbed from solution due to the organic solvent reducing the solution dielectric constant. It may be theorized that aqueous ammonia catalyzes and fosters the hydration of CO2 into carbonic acid, thus enabling CO2 to dissolve at a significantly greater concentration than it would without the presence of ammonia. The addition of an organic solvent may weaken the aqueous ammonia catalyzed hydration shells surrounding the dissolved CO2 due to reduction of the solution dielectric constant, thus prompting the generation of CO2(g) owing to the significantly lower solubility of aqueous phase CO2 when uncatalyzed by ammonia. Significant pure CO2(g) yields were achieved under room temperature and pressure conditions in a relatively short timeframe.
3) CO2 Lean Absorbing Solution and Organic Solvent Recovery:
The CO2 lean aqueous ammonia-carbon dioxide-organic solvent solution created in stage 2 is separated into pure organic solvent and an aqueous CO2 lean ammonia-carbon dioxide solution using low temperature distillation. The CO2 lean absorbent-carbon dioxide salt may predominantly remain in the aqueous solution during distillation, such as with absorbent volatilization of less than any of the following: 10%, or 5%, or 2%, or 1%, or 0.5%, or 0.1%, or 0.01%, while the organic solvent is volatized and condensed. The CO2 lean absorbing solution and organic solvent are recovered according to the following:
(NH4)2CO3(aq)+Organic Solvent(aq)+Low Grade Heat→(NH4)2CO3(aq)+Organic Solvent(g)
Organic Solvent(g)+Condenser→Organic Solvent(l)
In this embodiment, it may be desirable for ammonia-carbon dioxide decomposition to be minimized.
CO2 desorption or absorbent-CO2 salt decomposition, unintended or intended, may occur during this stage. Desorbed CO2 may be separated from the organic solvent vapor and treated similarly to the captured CO2 produced in the desorption or mixing step. In the instance where the CO2 absorbent exhibits volatility, such as in the case of ammonia, the CO2 absorbent may be recycled, including, but not limited to, by dissolving in the added organic solvent or other added substance in the CO2 desorption step.
Additional Details:
For the embodiment shown in
Solvents that typically do not react with ammonia include those in the categories of Ethers and low molecular weight Alcohols. These substances rarely form unfavorable reactions with ammonia.
According to http://pubs.acs.org/doi/abs/10.1021/es5060989, incorporated herein by reference, 96% of power plant waste heat energy is at or below a temperature of 41.5° C. The remaining 4% is the higher temperature heat of the exhaust gas stream(s). Present carbon capture systems use higher temperatures (usually 110° C.-130° C.) and higher pressures (2-136 atm) and, therefore, cannot be solely powered by waste heat. Instead, these processes divert steam away from power generation and use it to power carbon capture. The process described herein may be capable of using abundant low temperature waste heat to capture carbon dioxide, allowing for the capture of carbon dioxide without appreciably impacting power plant efficiency.
In this embodiment, the solvent may be distilled at or below 85° C. without appreciable volatilization of ammonia from solution at atmospheric pressure. In the instance where CO2(g) or NH3(g) are released from solution, these may re-dissolve in solution when the solvent is recycled. In the instance described thereof, CO2(g) may be released in significant excess to NH3(g), and may be removed as captured CO2(g).
Raoult's law may be useful for the solvent distillation step of this embodiment. Raoult's Law describes the relationship between the mole fraction of a liquid in solution and the liquid's vapor pressure (ex. Mole fraction*Partial pressure of liquid at temperature=Partial pressure in system). In accordance with Raoult's Law, traces of added solvent may continue to remain in the CO2 absorption solution. In an instance where traces of solvent have an influence on system performance, the timeframe of distillation may need to be lengthened. Distillation may be optimized to minimize energy demand, while achieving optimal solvent concentrations in the CO2 absorber and CO2 desorber.
Summary:
In these experiments, high purity CO2 is generated through the addition of an organic solvent—such as acetone, dimethoxymethane, or acetaldehyde—to CO2 rich, aqueous ammonia-carbon dioxide solution under room temperature and pressure conditions. The organic solvent and CO2 absorbing solution are then regenerated using low temperature heat. When acetone, dimethoxymethane, or acetaldehyde were added at 16.7% (v/v) to 2 M aqueous ammonium bicarbonate, 39.8%, 48.6%, and 86.5%, respectively, of the aqueous CO2 species transformed into high purity CO2 gas over 3 hours. Thermal energy and temperature requirements to recover acetaldehyde and the CO2 absorbing solution were 1.39 MJ per kilogram of CO2 generated and 68° C., respectively, 75% less energy and 53° C. lower temperature than a pilot chilled ammonia process. These findings exhibit the promise of economically viable carbon capture powered entirely by abundant low temperature waste heat.
This embodiment generates high purity CO2 via the addition of a water soluble organic solvent to a CO2 rich aqueous ammonia-carbon dioxide solution, such as would be generated from the absorption of flue gas CO2 in aqueous ammonia. The organic solvent is subsequently distilled using low temperature heat, resulting in recovery of the solvent and remaining CO2 lean aqueous ammonia-carbon dioxide solution. Pure CO2 is desorbed under room temperature pressure (RTP) conditions and employs only low cost, abundant reagents. The results demonstrate that this embodiment is capable of converting CO2 in flue gas into high purity CO2 with significantly lower temperature and energy requirements than current technologies.
Materials and Methods:
Measurements were acquired using a gas flow setup with on-line mass spectrometry. An Omega mass flow controller was used to control the flow rate of the carrier gas (ultra-high purity helium, 50 mL/min). The outlet line was heated to prevent solvent condensation. For each experiment, an appropriate amount of ammonium bicarbonate (>99.5%, Sigma Aldrich) was dissolved in deionized (DI) water to form 100 mL of total solution at a desired molarity (1.0, 1.5 M, or 2.0 M). A 250 mL glass media bottle containing the solution was attached to a three-port cap containing helium carrier gas inflow port, gas mixture outlet port, and organic solvent injection port. Helium gas was flowed into the headspace at 50 mL/min until no traces of air gases (N2, O2, and Ar) were present and the flow stabilized. Stirring was applied at a consistent mixing rate for all trials. An appropriate amount of organic solvent-acetaldehyde (≧99.5%, Sigma Aldrich), acetone (≧99.5%, Fisher Scientific), or dimethoxymethane (99%, Sigma Aldrich)—was injected. These solvents were selected based on their high solubility in water, low molar mass, low toxicity, high volatility relative to water, and lack of irreversible reactivity with ammonia or CO2. A needle valve connected to a vacuum chamber with an SRS 100 residual gas analyzer was used to sample the outlet gas and obtain the CO2 partial pressure. CO2 partial pressures were converted to molar flow rates using a calibration curve derived from previous measurements of mass flow controlled ultrahigh purity CO2 and by normalizing the signal intensity to the helium carrier gas. Integration of CO2 flow rates over one hour yielded the values for total pure CO2 generation.
Total CO2 generation was determined by extrapolating results from 1 hour experiments with an ExpConvExp fitting function using the Multi-peak Fit package in Igor Pro (WaveMetrics Inc.). During long timeframe experiments with 20 mL of organic solvent added, CO2 generation tapered off after a three-hour period. Correspondingly, CO2 generation from 1 hour experiments were extrapolated to three hours. Three-hour extrapolations deviated less than 12.5% from experimental results.
Modeling Organic Solvent Distillation:
The heat duty and temperature requirements for the recovery of acetaldehyde, acetone, or dimethoxymethane from their respective aqueous solutions were determined using an industrial process modeling software (Aspen HYSYS) with the UNIQUAC fluid package. The simulation used a 1.5 m diameter distillation column with 10 sieve trays and a 0.1 m3 reboiler and condenser. The feed stream flow rate was 1 m3 solution per hour and contained the optimal organic solvent mole fraction (xf) to generate pure CO2 (0.0467 for acetone, 0.0393 for dimethoxymethane, and 0.0599 for acetaldehyde) in water. According to vapor—liquid equilibrium studies, only slight traces of NH3 and CO2 vaporize at the low temperatures employed. The simulated distillation column was at a scale sufficient for 0.43-1.83 tons CO2 captured per day, or a similar scale to the referenced current process pilot plants, 1.7 and 4.0 tons of CO2 per day for chilled ammonia and MEA, respectively. The optimal organic solvent mole fraction was experimentally determined by adding the organic solvent at RTP conditions to a 100 mL 2 M aqueous ammonium bicarbonate solution until the injection of additional organic solvent had no discernable influence on CO2 generation. The feed solution was distilled to the operational organic solvent mole fraction (xb) in the regenerated solution (0.0216 for acetone, 0.0181 for dimethoxymethane, and 0.0279 for acetaldehyde). The operational organic solvent mole fraction was experimentally determined by adding small amounts of organic solvent at RTP conditions to a 100 mL 2 M aqueous ammonium bicarbonate solution until the injection of additional organic solvent resulted in CO2 generation (
System Overview: This embodiment is composed of three steps: (1) flue gas CO2 absorption in CO2 lean aqueous ammonia solution, (2) pure CO2 generation through mixing in an organic solvent, and (3) recovery of organic solvent via low-temperature distillation.
In the first stage, the CO2 absorption column, CO2 in flue gas is absorbed by a CO2 lean aqueous ammonia-carbon dioxide solution (NH3:CO2 molar ratio >1.5), forming a CO2 rich solution (NH3:CO2 molar ratio ˜1). The remaining gases after the CO2 is absorbed are released from the absorption column (‘Inert Gases’ in
In the second stage, the solvent mixer, the CO2 rich ammonia-carbon dioxide solution from the CO2 absorption column is mixed with an organic solvent (acetone, acetaldehyde, or dimethoxymethane) under mild temperatures and pressures, such as RTP conditions, generating high purity CO2. The solution becomes CO2 lean as pure CO2 is generated.
In the last stage, the solvent distillation column, the solution formed in the solvent mixer enters a distillation column, where the organic solvent is distilled from the CO2 lean aqueous solution. The aqueous solution is recirculated to the CO2 absorption column and the organic solvent is recirculated to the solvent mixer.
CO2 Desorption Mechanism: CO2 was desorbed by adding acetone, dimethoxymethane (DMM), or acetaldehyde to aqueous ammonium bicarbonate solutions under RTP conditions. The graph (
Reports on desalination processes suggest organic solvents precipitate dissolved salts by reducing the dielectric constant (∈r) of an aqueous solution. Specifically, a reduction in dielectric constant from organic solvent addition weakens the hydration shells surrounding the solvated ions and increases ion association due to the coulombic attraction between oppositely charged ions, thereby triggering salt precipitation. In this study, an organic solvent was added to generate CO2(g) rather than a solid precipitate. According to studies on the CO2 absorbing mechanism in aqueous ammonia, aqueous ammonia performs multiple roles as a reactant, catalyst, base, and product controller, thus enabling aqueous phase CO2 to dissolve at a significantly greater concentration than it would without the presence of ammonia. The addition of an organic solvent may weaken the hydration shells surrounding the dissolved CO2 due to reduction of the solution dielectric constant, thus prompting the generation of CO2(g) owing to the significantly lower solubility of aqueous phase CO2 when its interaction with ammonia is inhibited. DMM's greater CO2 desorption may be attributed to its significantly lower dielectric constant (DMM ∈r=2.6; acetone ∈r=20.7), as DMM requires a lower solvent mole fraction than acetone to decrease the solution dielectric constant by the same magnitude.
Acetaldehyde desorbed more CO2 than both DMM and acetone, despite having a greater dielectric constant (acetaldehyde ∈r=21.7) because it possessed a greater solvent mole fraction and a reversible reaction with ammonia species. Acetaldehyde reacts with ammonia under anhydrous conditions to form a trimer. Under aqueous conditions, the acetaldehyde-ammonia trimer is stable at pH above 10, forms the acetaldehyde-ammonia adduct ion at a pH less than 10 and greater than 7, and reversibly dissociates into acetaldehyde and free ammonia at a pH below 7. The aqueous acetaldehyde-ammonia adduct ion, which forms at the pH of aqueous ammonia-carbon dioxide solutions (CO2 rich pH ˜8; CO2 lean pH ˜9), decomposes into acetaldehyde vapor and aqueous ammonia upon the volatilization of acetaldehyde. Correspondingly, acetaldehyde desorbed more CO2 than DMM and acetone and was effectively recovered from the aqueous ammonia-carbon dioxide solution during low temperature distillation.
Negligible CO2 generation occurs at low solvent concentrations. At 5 mL of organic solvent added to 100 mL of 2 M ammonium bicarbonate, the amount of CO2 desorbed was 8% less than the no solvent case. This is consistent with a previous study that investigated the use of low concentrations of water soluble organic solvents to prevent the release of ammonia from solution. Specifically, it was found that low concentrations of organic solvents did not influence the rate of CO2 absorption and desorption.
At high ammonium bicarbonate and solvent concentrations, a plateau in CO2 generation occurred, as shown in
The CO2 desorbed from 2 M ammonium bicarbonate solutions at RTP conditions with 30 mL added solvent was 2% and 8% less than 20 mL added solvent for acetone and DMM, respectively, and was accompanied by the immediate formation of solid precipitate. At lower ammonium bicarbonate concentrations (1 M), CO2 generation increased with higher solvent volumes (20-30 mL) and no precipitate formed. These phenomena may be attributed to an equilibrium between the formation of CO2 gas and solid precipitate, which shifted toward solid precipitate at higher ammonium bicarbonate and solvent concentrations.
Energy Consumption: The reboiler and condenser heat duties were determined with Aspen HYSYS using the xf and xb organic solvent mole fraction values for each organic solvent in 2 M ammonium bicarbonate. The simulated feed solution contained the xf organic solvent mole fraction and was distilled to form an outlet stream with the xb organic solvent mole fraction. The simulated condenser was cooled using a 20° C. water stream. Acetaldehyde reboiler heat duty was 70% less than DMM and 64% less than acetone due to acetaldehyde possessing a lower boiling point (20.2° C.) and greater xf solvent mole fraction.
The reboiler energy and temperature requirements of this embodiment were compared with present CO2 capture processes, the chilled ammonia and MEA processes. Present CO2 capture processes use energy intensive thermal desorption with costly high temperature heat (>120° C.) to generate pure CO2. This embodiment requires no heat input during CO2 desorption, instead, desorbing pure CO2 under room temperature pressure (RTP) conditions through the addition of an organic solvent. The organic solvent is subsequently distilled using abundant low temperature waste heat, resulting in recovery of the solvent and remaining aqueous ammonia-carbon dioxide solution. The energy requirement was calculated by dividing the energy to distill the organic solvent (16.7% v/v) added to 2M aqueous ammonium bicarbonate solution by the mass of pure CO2 generated.
As shown in
In this embodiment, aqueous ammonia-carbon dioxide salt decomposition may occur under substantially room temperature and pressure (RTP) conditions using the addition of a water soluble organic solvent to a CO2 rich aqueous ammonia-carbon dioxide solution (stage 2). Other than mechanical mixing, it may be advantageous for minimal energy to be added during the desorption stage of this embodiment.
Thermal energy is consumed in this during the recovery of the organic solvent from the CO2 lean aqueous ammonia solution via distillation. Minimal ammonia-carbon dioxide salt decomposition may be intended to occur during this stage. Due to the low temperatures employed and high NH3:CO2 molar ratio of the solution, only slight traces of NH3 vaporize in the distillation column, according to vapor-liquid equilibrium studies. Thus, negligible heat energy may be expended on incidental thermal decomposition of the aqueous ammonia-carbon dioxide salt. Therefore, carbamate decomposition may be negligible in the distillation step.
The energy consumed in the distillation section of this embodiment may be dependent on the relative volatility of the organic solvent to the aqueous solution and the enthalpy of vaporization of the organic solvent. Water soluble solvents with low boiling points, such as acetaldehyde, require significantly lower temperature heat in the distillation and less reflux. Additionally, at these lower temperatures, less water is vaporized, further reducing energy consumption.
Switchable Solvent Addition with Various Recovery Methods
The embodiment uses the addition of a soluble substance or substances to a solution containing CO2 absorbent—carbon dioxide species, such as ammonia, ammonium, amine, bicarbonate, carbonate, carbon dioxide or carbamate species, to trigger the release of carbon dioxide gas from solution. The added substance recovered from solution via a change in one or more or a combination of system conditions, including, but not limited to, changes in temperature, light, pressure, magnetic field, kinetic energy or a change in the presence of one or more compounds, such as changes in humidity or carbon dioxide concentration. The added substance can be separated and recovered by one or more techniques, including, but not limited to, filtration, centrifuge, decanting, distillation and membrane based process, such as nanofiltration, organic solvent nanofiltration, reverse osmosis, ultrafiltration, membrane distillation, and other membrane based separation devices described herein.
The embodiment may be composed of three main steps: 1) The absorption of CO2 in a CO2 lean solution, resulting in the formation of a CO2 rich solution; 2) The addition of a water-soluble substance or substances to decompose the CO2 rich solution to a CO2 lean solution+CO2(g). This CO2 gas stream may undergo further purification or treatment to remove water vapor or traces of ammonia or other substances, which may be recycled in the process; 3) The recovery of the added substance or substances using one or more or a combination of changes in system conditions, which may be followed by or integrated with a physical separation mechanism. Changes in system conditions include, but are not limited to changes in temperature, light, pressure, magnetic field, kinetic energy, favorable reaction or a change in the presence of one or more compounds, such changes in the concentration of water vapor or humidity or changes in the presence or headspace concentration of CO2. The added substance may be physically separated and recovered by one or more techniques, including, but not limited to, filtration, centrifuge, decanting, distillation, magnetism, and/or membrane based process, such as reverse osmosis, forward osmosis, electrodialysis, nanofiltration, organic solvent nanofiltration ultrafiltration, membrane distillation, integrated electric-field nanofiltration, hot nanofiltration, or hot ultrafiltration. The CO2 lean solution, after the recovery of the added substance or substances may be recycled to the first step of the process. The recovered substance or substances may be recycled to the second step of the process.
The embodiments described below include those shown in
Description (such as
Description of
Overall desirable properties: It has been discovered that there are a wide range of substances capable of being added to an aqueous solution containing a CO2 absorbent and carbon dioxide to prompt the desorption of gaseous CO2 desorption. The following is a list of potentially desirable properties for these added substances. Desired properties may include one or more of the following, although the properties are not limited to those described and added substances may or may not exhibit any up to all of these properties.
Many of these desired properties overlap with those for recoverable forward osmosis draw solutes. Added substance examples and types may include, but are not limited to, recoverable forward osmosis draw solutes, including those described in the review paper http://www.sciencedirect.com/science/article/pii/S2214714414001202, incorporated herein by reference.
The embodiments described below include those shown in
Polypropylene glycol 425 is thermally switchable (http://projekter.aau.dk/projekter/files/17652274/Investigation_of_Polypropylene_Glycol_425_a s_a_DrawSolution_for_Forward_Osmosis.pdf which is incorporated herein by reference).
An example of non-toxic, inexpensive thermally switchable substances includes random or sequential copolymers of low molecular weight diols such as 1,2 propanediol, 1,2 ethanediol, and/or 1,3 propanediol. These switchable substances have a cloud point temperature of between 40° C. to 90° C. and a molecular weight high enough to allow for further separation of the substance using nanofiltration. These solutes are used in forward osmosis for desalination. These thermally switchable substances, and other thermally switchable substances, are further described in https://www.google.com/patents/US20120267308, incorporated herein by reference.
Thermally responsive compounds include, but are not limited to, Lower Critical Solution Temperature (LCST) and Upper Critical Solution Temperature (UCST) compounds, thermosensitive magnetic nanoparticles, thermally responsive polyelectrolytes and thermally responsive ionic liquids.
LCST compounds are soluble or have a higher solubility below a certain threshold temperature, the lower critical solution temperature. For example, thermosensitive poly(N-isopropylacrylamide) (PNIPAM) hydrogels can absorb water below the volume phase transition temperature (VPTT, ˜32C) and expel water at temperatures above the VPTT. Other examples of these hydrogel substances include polyacrylamide (PAM), PNIPAM, and poly(Nisopropylacrylamide-co-acrylic acid) and sodium (P(NIPAM-co-SA)). Non-hydrogel LCST compounds include, but are not limited to, Methylcellulose and triethylamine.
Substances may also exhibit a UCST, a temperature which the solution must be above to exhibit more solubility. Many water soluble, non-ionic compounds exhibit both an LCST and a UCST, such as the nicotine-water system.
Examples of thermosensitive magnetic nanoparticles include, but are not limited to those described in the following article http://pubs.rsc.org/en/content/articlelanding/2011/cc/c1cc13944d#!divAbstract which is incorporated herein by reference. These nanoparticles are typically hydrophilic and are coated with various functional groups to allow them to generate osmotic pressure in solution.
Thermally responsive ionic liquids include, but are not limited to those described in the following article http://pubs.rsc.org/en/Content/ArticleLanding/2015/EW/c4ew00073k#!divAbstract which is incorporated herein by reference.
Light based solubility change or other form of recovery have been investigated in forward osmosis applications. These include, but are not limited to, P(NIPAM-co-SA) hydrogels with light-absorbing carbon particles.
Substances showing magnetic field based change in solubility or other form of recovery via changes in magnetic field may be useful. These include, but are not limited to, magnetic nanoparticles with added functional groups (such as those described in http://pubs.acs.org/doi/abs/10.1021/ie100438x, incorporated herein by reference), and magnetic or inductive heating of nanoparticles in solution.
Substances that change solubility or other recovery method due to pressure or a combination of pressure and temperature may also be useful. These include, but are not limited to, PSA, polyacrylamide (PAM), PNIPAM, and poly(Nisopropylacrylamide-co-acrylic acid sodium (P(NIPAM-co-SA)) hydrogels.
Changes in solution kinetic energy can act as a stimulus to change or promote a change in the solubility or other form of recovery of an added substance. Kinetic energy can be of various forms, including, but not limited to, mixing and sonication. Ultrasonic sonication may either increase or decrease solubility and to promote precipitation and crystal nucleation. Ultrasonic sonication may be used to increase the rate of CO2 desorption.
Mixing may be employed for, including, but not limited to, facilitating the dissolution of the added substance and increase the rate of CO2 gas desorption.
The general substance embodiment may not involve the added substance chemically reacting with the CO2 absorbent or CO2 species. However, if the substance does react with CO2, the following may be some favorable properties for these reactions:
Properties of a favorable reaction include, but are not limited to one or more or a combination of the following:
An example of a potentially favorable reversible reaction includes the formation of reversible ammonia-metal complexes. These complexes may reduce the affinity of ammonia to the carbon dioxide in solution, resulting in a release or a low temperature release of carbon dioxide from solution.
In some favorable reactions, the reagents may function as catalysts. Instances may also exist where the favorable reaction does not involve reversibility. In the instance where the reaction is irreversible, it may be advantageous for one or more byproducts to have a value-added application, such as use in forward osmosis desalination or fertilization.
Preventing Unfavorable Reaction with Ammonia or Carbon Dioxide Species:
Some substances with favorable properties, may react or interact with ammonia and or carbon dioxide species in potentially unfavorable ways within the process unless additional measures are taken. Substances that have a greater likelihood of reaction with ammonia or ammonium salts include those with Amine, Amide, Ketone, Aldehyde, Ester, or Carboxylic Acid functional groups. If substances on their own react with the ammonia or carbon dioxide species in potentially unfavorable ways, it may be advantageous for the reaction to be slow or the reaction may be inhibited with the addition of another substance or a change in system conditions.
Embodiment with at Least Partial Thermal Decomposition
The addition or presence of a water-soluble substance, such as an organic solvent, to a CO2 rich aqueous ammonia-carbon dioxide solution may generally initiate and foster CO2 desorption independently of temperature. However, heat, including heat above the decomposition temperature of the absorbent—carbon dioxide, may be applied to the CO2 desorption and substance regeneration stages. This may, include, but not be limited to, increase CO2 desorption rate, increase solution capacity, reduce CO2 loading, improve the properties of the CO2 absorption solution to maximize CO2 uptake, improve the properties of the CO2 absorption solution to maximize the rate of CO2 uptake, help overcome enthalpy of desorption or overcome activation energy, which may be especially useful for CO2 absorbents with high enthalpies of reaction relative to ammonia. The presence of the soluble substance, such as PEG or PPG, may reduce the temperature and energy requirements of CO2 desorption during thermal desorption in comparison to existing ammonia or amine thermal desorption processes.
A water soluble substance is added at a moderate or cool temperature, such as at room temperature, in the CO2 desorption stage and gaseous CO2 is desorbed. After at least a significant portion, such as less than any of the following: 5%, or 10%, or 15%, or 20%, or 25%, or 30%, or 35%, or 40%, or 45%, or 50% of the CO2 in solution, is desorbed, heat may be applied to the mixed desorption solution in a separate or the same reactor or reactors. It may also be desirable for heat to be applied when the CO2 desorption rate due to the presence of the soluble substance has appreciably subsided, such as the CO2 desorption rate subsiding to less than any of the following: 95%, or 90%, or 75%, or 60%, or 50% or 40%, or 30%, or 20%, or 10% of the maximum CO2 desorption rate after soluble substance injection. The application of heat may enhance CO2(g) desorption. The temperature and energy requirements for thermal desorption may be significantly less than conventional thermal desorption processes due to the presence of the water-soluble substance. It may be desirable for the added substance in this example to be non-volatile, such as a vapor pressure at 20° C. at less than 0.1 atm, or any of the following: 0.05 atm, or 0.03 atm, or 0.01 atm, or 0.001 atm, or 0.0001 atm, and minimally prone to thermal degradation. Such substances, include, but are not limited to, PEG and PPG. This embodiment may allow for significant reductions in energy requirements for CO2 capture, while allowing for, including, but not limited to, one or more or a combination of the following: greater CO2 desorption rates, greater CO2 solution capacity, lower precipitate formation, lower CO2 loading in the CO2 lean solution, and greater CO2 uptake in the CO2 absorption column.
The water-soluble substance is added to the CO2-rich solution in the CO2 desorption stage and heat is applied to the solution during most the CO2 desorption timeframe. Depending on the concentration of the added substance, the rate and temperature of heat input, residence time, the rate of mixing and other factors, the initial CO2 desorption may be primarily due to the influence of the soluble substance. During this initial timeframe, the heat may, include, but not be limited to, increase the rate of CO2 desorption or facilitate CO2 desorption. Depending on many factors, the influence of heat application on CO2 desorption may increase over time and the influence of the added substance may subside. It may be desirable for the added substance in this example to be relatively non-volatile and not prone to substantial thermal degradation. Such substances, include, but are not limited to, PEGs and PPGs.
In embodiments where the added substance is recovered using heat, such as embodiments with various forms of distillation or switchable solvent, or where heat is applied during soluble substance recovery, such as may be the case in membrane-based recovery embodiments, CO2(g) may be desorbed. This CO2 desorption may be in part due to thermal decomposition. This CO2 may be recovered and utilized in a similar manner to the CO2 desorption during the CO2 desorption stage.
Soluble Substance Addition Carbon Capture with ‘Salting-Out’ Solvent Recovery
The embodiments described below include those shown in
In this embodiment, following soluble substance addition, CO2(g) is generated until the NH3:CO2 molar ratio in the aqueous solution is sufficient to prompt ‘salting-out’ or the formation of a multi-layer solution. This NH3:CO2 molar ratio may be greater than 1.5:1. The presence of aqueous ammonium carbamate species may facilitate the formation of a two layer solution. After the formation of the two or more-layer solution, the layer with a lower concentration of large molecular weight solvent is fed into a separation mechanism, which includes those described in
The embodiments described below include those shown in
This embodiment is composed of three main steps: 1) The contacting of a gas containing CO2 to convert a CO2 lean solution to a CO2 rich solution. The remaining inert gases may undergo further purification, treatment or compression; 2) The addition of low boiling point soluble substance or substances, such as dimethyl ether, to the CO2 rich solution to generate CO2(g), creating a CO2 lean solution+added substance+CO2(g). The substance may be added in the gas phase, liquid phase or a combination of gas and liquid phases. This CO2(g) stream may undergo further purification, treatment or compression. Any remaining or residual solvent vapor in the CO2(g) stream may be separated and recovered; 3) The recovery of the added substance or substances using ultra-low temperature distillation. Heat or enthalpy sources include, but are not limited to, ultra-low temperature waste heat sources, ambient temperature enthalpy sources, and chilling fluids. The process may replace or greatly minimize the need for evaporative cooling towers, as the distillation column can cool the condenser fluids in an open or closed loop. Higher temperature heat may be used if desired. The process may be conducted without a vapor compressor and may condense the solvent with lower temperatures or only condense a portion of the pure solvent to the liquid phase before solvent addition. The process may be conducted under a higher pressure, allowing for the solvent to condense under more moderate conditions without a compressor. With a vapor compressor or mechanical vapor compression distillation, the solvent may condense at a greater temperature and residual solvent vapors may be easier to recover. Heat may be recovered or removed during to solvent vapor condensation or compression. The CO2(g) may need to be separated from the low boiling point solvent vapor during CO2 desorption. This may involve various treatment methods, including, but not limited, water wash-down, condenser, compression or other systems and methods described herein.
In another embodiment,
Generally desirable ultra-low boiling point substances: Desired substances may include one or more of the following, although the properties are not limited to those described and added substances may or may not exhibit any of these properties.
An example solvent that meets this criteria is dimethyl ether. Dimethyl ether exhibits high solubility in water, even above its boiling point, is essentially non-toxic and is a low cost, commodity chemical. Dimethyl Ether may be sufficiently soluble in water for this application under moderate conditions (see graph below). Based on its molar mass and dielectric constant, the process may require a mole fraction of 0.04-0.06 to prompt CO2 desorption, which may be achieved under moderate conditions (http://www.pet.hw.ac.uk/icgh7/papers/icgh2011Final00008.pdf, incorporated herein by reference).
In another embodiment, the solvent distillation is used for chilling an external medium. This may include, but is not limited to, cooling condenser fluid from power generation, HVAC systems, ice skating rinks, datacenters, manufacturing, industrial processes, solar thermal or photovoltaic and mining and natural resource extraction. Natural heat sinks may also be used as enthalpy or heat sources including, but not limited to, water bodies, air, geothermal sources, and solar thermal sources.
Substance is added to a CO2 adsorbent, such as quaternary ammonium cation containing material, to desorb CO2.
In the case of adsorbents, the adsorbents may exhibit any range of surface areas or surface morphologies.
General Conditions and System Technicalities Regarding Systems and Methods of the Integrated Process:
Soluble Substances Lists:
Water soluble substances may include, but are not limited to, the substances detailed below:
Overview of substances: Aqueous solution, Water soluble polymer, Soluble polymer, Glycol Polyethylene Glycol, Polypropylene Glycol Ethers, Glycol Ethers, Glycol ether esters, Triglyme. Polyethylene Glycols of multiple geometries, Methoxypolyethylene Glycol, Polyvinyl Alcohol Polyvinylpyrrolidone, Polyacrylic Acid, Diol polymers, 1,2 propanediol, 1,2 ethanediol, 1,3 propanediol, Cellulose Ethers, Methylcellulose, Cellosize, Carboxymethylcellulose, Hydroxyethylcellulose, Sugar Alcohol, Sugars, Alcohols Ketones, Aldehydes, Esters, Organosilicon compounds, Halogenated solvents
Substance Details for embodiments, including, but not limited to, one or more or a combination of the following:
Azeotrope Sources, the following are incorporated herein as references:
Note: amines and other CO2 reactive compounds may be employed, however, it may be desirable for the amines to not react with the CO2 absorbent-CO2, such as in a metathesis reaction.
The instant application claims priority to U.S. Ser. No. 62/290,519 filed Feb. 3, 2016. This application is related to U.S. Ser. No. 14/826,771 filed Aug. 14, 2015 which claims priority to U.S. Ser. Nos. 62/106,822 filed Jan. 23, 2015 and 62/090,272 filed Dec. 10, 2014 and 62/159,481 filed May 11, 2015. This application is also related to PCT/US2015/064669 filed Dec. 9, 2015 claiming priority to U.S. Ser. No. 14/826,771 filed Aug. 14, 2015 which claims priority to U.S. Ser. Nos. 62/106,822 filed Jan. 23, 2015 and 62/090,272 filed Dec. 10, 2014 and 62/159,481 filed May 11, 2015. All of the aforementioned applications are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 62290519 | Feb 2016 | US | |
| 62375471 | Aug 2016 | US | |
| 62106822 | Jan 2015 | US | |
| 62090272 | Dec 2014 | US | |
| 62159481 | May 2015 | US | |
| 62309666 | Mar 2016 | US | |
| 62325620 | Apr 2016 | US | |
| 62363445 | Jul 2016 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14826771 | Aug 2015 | US |
| Child | PCT/US2015/064669 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14826771 | Aug 2015 | US |
| Child | 15424218 | US | |
| Parent | PCT/US2015/064669 | Dec 2015 | US |
| Child | 14826771 | US |
