Patent Application
20090028767
This invention relates generally to utilizing halogen-containing compounds for energy production. More specifically, the invention relates to utilizing bromine-containing compounds in systems for energy generation, energy storage, hydrogen production, pollutant capture and removal, and waste treatment.
Research in halogenation (e.g., bromination) processes are motivated by the need to produce fuels from biomass, advances in hydrogen bromide electrolysis, the continued rise of gas and oil prices, growing need for energy storage to encourage adoption of renewable energy and increased concern over regulated and unregulated pollutants. Prior work is described regarding bromination of carbonaceous material, the capture and conversion of regulated and unregulated pollutants, hydrogen production, electrical energy storage and the production of liquid fuels.
Reserves of oil and natural gas are rapidly being depleted, causing economic hardship, while growing concern for carbon dioxide and other greenhouse gas emissions are prompting the adoption of carbon-neutral technologies for energy needs. Hydrogen (H2) can potentially serve as fuel for the world's energy requirements if it could be manufactured economically and in an environmentally friendly manner. Hydrogen has a variety of uses, such as, for example, hydrocracking, upgrading, and removing sulfur from crude oil in refineries, the production of ammonia for fertilizer, and for use in explosives, food processing, welding, and semiconductors. A hydrogen economy would use hydrogen as a fuel and chemical feedstock, thus reducing the world's dependence on oil and natural gas (methane, CH4).
The principal source of hydrogen in the United States is steam-hydrocarbon reforming, which uses a fossil fuel to create hydrogen and carbon monoxide, which is then oxidized by steam (H2O) to yield carbon dioxide and more hydrogen. This process is complex and requires catalysts. Additionally, due to the requirement for high operating temperatures and pressures, expensive equipment is required for steam-hydrocarbon reforming. Furthermore the hydrogen-rich product gas stream requires additional steps to purify the hydrogen and remove contaminants, such as sulfur species, adding to processing costs. An alternative to steam-hydrocarbon reforming is the electrolysis of water to produce hydrogen: 2H2O→2H2+O2. The theoretical decomposition voltage (half cell potential) of water is 1.23 volts (V), but in actual practice, the half-cell potential for water is 1.7 volts, while at typical operating current densities over 2 volts are required. Water must be purified before electrolysis and direct current (DC) must be used for the electrolytic process. Because electricity is typically available in the form of alternating current (AC), an ac-to-dc converter is required, which leads to increased processing costs and energy losses. These factors contribute to making water electrolysis more expensive (and impractical) than steam-hydrocarbon reforming.
The combustion of carbonaceous matter with bromine and water to form hydrogen bromide (HBr) and carbon dioxide (CO2) is exothermic, releasing a large amount of energy (heat), which may be used to generate steam (or another working fluid) for the production of electricity. Hydrogen bromide (HBr) may be electrolyzed or reacted with a metal bed to produce hydrogen. High pressure carbon dioxide formed during combustion with bromine (Br2) or another halogen-containing chemical and water may be expanded through a turbine to produce electricity, or combined with hydrogen to make methanol, ethanol, or other liquid fuels.
The combustion of carbonaceous matter with oxygen has been exploited for centuries, and some well-known material heat of combustion, specific reactions and reaction enthalpies are as follows:
Cellulose(Wood)Oxidation: ΔcH=6,900Btu/lb (1)
C6H10O5(s)+7O2(g)→5H2O(g)+7CO2(g) ΔH°=−2,610kJ/mol (2)
Coal(Lignite-Bituminous)Oxidation: ΔcH=8-13,500Btu/lb (3)
C135H96O9NS+157½O2→48H2O+135CO2+SO2+NO2 (4)
Carbon(Charcoal)Oxidation: ΔcH=14,100Btu/lb (5)
C(s)+O2(g)→CO2(g) ΔH°=−394kJ/mol (6)
Methane Oxidation: ΔcH=21,600Btu/lb (7)
CH4(g)+2O2(g)→CO2(g)+2H2O(g) ΔH°=−802kJ/mol (8)
Hydrogen is produced through the partial oxidation of carbon (and other hydrocarbons) to carbon monoxide followed by its reaction with steam:
C(s)+½O2(g)→CO(g) ΔH°=−111kJ/mol; ΔcH=4,000Btu/lb (9)
CO(g)+H2O(g)→H2(g)+CO2(g) ΔH°=−41kJ/mol; ΔcH=630Btu/lb (10)
It has been proposed that large quantities of hydrogen can be produced from electrolysis of water:
H2O(l)→H2(g)+½O2(g) ΔH°=286kJ/mol (11)
Similar to oxidation, the bromination of carbonaceous material with water as a co-reactant is an exothermic reaction, creating an opportunity to convert the released energy into work. These reactions can produce high temperature and high pressure CO2, which may be expanded through a turbine to produce additional work, and hydrogen bromide (HBr), which may be dissociated through a variety of processes to recover bromine for recycling and hydrogen production. The hydrogen-bromine bond of HBr is considerably weaker than the highly stable hydrogen-oxygen bonds of water. The exothermic nature of the reactions reduces the energy requirements for the production of hydrogen to only that required for electrolytic, catalytic, or thermal dissociation of hydrogen bromide. Several sample bromination reactions are shown in the equations below (‘az’ designates a 47.5 wt % HBr solution):
Cellulose Bromination:yields 2moles H2 per mole Carbon ΔcH=5,400Btu/lb (12)
C6H10O5(s)+7H2O(l)+12Br2(l)→24HBr(az)+6CO2(g) ΔH°=−2038kJ/mol (13)
Coal Bromination:yields 2.3moles H2 per mole Carbon ΔcH=6-10,500Btu/lb (14)
C135H96O9NS+265H2O+312Br2→624HBr+135CO2+H2SO4+ 1/2N2 (15)
Carbon(charcoal)Bromination:yields 2moles H2 per mole C ΔcH=11,000Btu/lb (16)
C(s)+2H2O(l)+2Br2(l)→4HBr(az)+CO2(g) ΔH°=−308kJ/mol (17)
The bromination of carbonaceous compounds with water to produce hydrogen bromide and carbon dioxide has been demonstrated by several groups. Table 1 summarizes these results.
In 1983 Rockwell International published an informative study on the bromination of coal (bituminous and lignite), biomass (Douglas fir, sugar cane, water hyacinth, and kelp), and milorganite (sewage sludge) in the presence of water. HBr yields at different temperatures and reaction times were determined. The HBr yield is the amount of HBr produced divided by the total amount of HBr that could be produced based on the amount of hydrogen in the sample (i.e., yieldactual/yieldtheoretical). The carbonaceous material water and bromine were placed in a glass ampoule, sealed, and heated at predetermined temperatures and times, as indicated in Tables 2, 3 and 4. Small amounts of reactants were used in these experiments, on the order of 0.1 grams carbonaceous material, 1 gram water, and 1 gram bromine. After the reaction, the un-reacted bromine was boiled off and the HBr concentration was determined by titration with NaOH.
The data suggests that bromine readily reacts with coal, biomass, and milorganite at elevated temperatures. It was found that many materials would form an initial amount of HBr very rapidly, but that higher temperatures were needed to get complete conversion of the hydrogen feedstock. This refractory fraction was resistant to bromination and required higher reaction temperatures. At 250° C. 80% of the coal reacted, while at 300° C. nearly all the coal was consumed. The Rockwell study suggested that there would be a higher temperature at which 100% of the biomass and milorganite would be converted. However, the researchers did not investigate this process beyond 250° C. and 300° C. respectively.
Some of the bromine used reacted with ash in the carbonaceous material to form soluble and insoluble bromide compounds. Bromine may be recovered from these compounds by reacting with 5% by weight sulfuric acid to form metal sulfates and additional HBr. The metals may then be recovered as hydroxides after neutralization with lime. These two steps reduce the amount of ‘lost’ bromine from 0.26%-0.63% to roughly 0.001% per bromination reaction.
Coal-fired power plants (also “coal power plants” herein) are responsible for 67% of sulfur oxide (SOx), 22% of nitrogen oxide (NOx) and 41% of mercury (Hg) emissions in the U.S., according to Pollution on the Rise. Local Trends in Power-plant Pollution, Penn Environment Research and Policy Center, January 2005, which is entirely incorporated by reference herein. Hazardous Air Pollutants (HAP) are also emitted by coal power plants. The amount of SOx and NOx emitted from coal power plants, chemical operations and manufacturing facilities is limited by environmental air discharge permits issued by local, state, federal and/or regulatory agencies worldwide. The limits for these emissions are being reduced. The Clean Air Act's acid rain program imposes limits on SO2 emissions, and the Clean Air Interstate Rules and Clean Air Mercury Rules (and any future legislation) can impose limits on NOx and Hg emissions, while imposing further limits on SO2 emissions. Accordingly, a process to remove these chemicals efficiently and economically is needed.
The deleterious effects of these pollutants include the formation of ground level ozone and acid rain, which is an aqueous solution of sulfuric acid (H2SO4). Acid rain poses several problems, such as acidifying bodies of water and damaging forests. These emissions also contribute to respiratory problems, reduced atmospheric visibility, and the corrosion of materials.
Coal used in coal-fired power plants contains a considerable amount of sulfur, which is oxidized to SOx (also referred to as ‘sulfur oxide’ which includes, e.g., SO2 and SO3) during combustion. Conventional methods for removing sulfur oxides include the use of wet alkaline scrubbers to convert SO2 into SO3, followed by absorbing the SO3 into a water solution to form sulfuric acid, which is then reacted with an alkaline agent, such as lime or limestone, to form gypsum, (CaSO4). This process, used in about 95% of the flue gas desulfurization (FGD) systems in the United States, requires a consumable reagent and produces a waste product that must be dried and disposed of in an environmentally-friendly fashion. While conventional scrubbers achieve removal efficiencies in excess of 90%, the quantity of SOx emitted is still considerable, necessitating a need for improvements in SOx removal techniques.
The European Research Centre developed and patented a process for controlling sulfur dioxide power-plant emissions through the following reaction (‘aq’ designates a 1 M (mole/liter) solution, and should not be taken as the exact condition used, but as an example condition):
SO2(g)+Br2(aq)+2H2O(l)→H2SO4(aq)+2HBr(aq) (18)
ΔH°=−281kJ/mole ΔG°=−182kJ/mole (19)
U.S. Pat. No. 4,668,490, which is entirely incorporated by reference herein, teaches a method of reacting SO2 with bromine per reaction (18) above to form sulfuric acid (H2SO4) and hydrobromic acid (HBr); the regeneration of bromine and production of hydrogen from the latters electrolysis; and a method for concentrating the sulfuric acid to a saleable product. U.S. Pat. No. 5,674,464, which is entirely incorporated by reference herein, teaches a method of regenerating bromine catalytically from the reaction of hydrogen bromide with oxygen over a catalyst.
The NOx in waste gas streams is typically composed of NO, NO2, N2O3, N2O4 and N2O5 and may include N2O, HNO2 and HNO3. Most of these can be easily removed through conventional alkaline wet scrubbers with the exception of NO. To remove NO it must be oxidized to NO2 prior to removal by conventional scrubbing.
The typical method of removing NO is by Selective Catalytic Reduction (SCR) or Selective Noncatalytic Reduction (SNCR). The former uses a catalyst, such as vanadium pentoxide, to oxidize NO to NO2, while the latter does not use a catalyst. In both case ammonia (NH3) is added to the flue gas to react with the NOx (e.g., NO, NO2) species. SCR and SNCR reactions include the following:
3NO2(g)+4NH3g)→7/2N2(g)+6H2O(g) ΔH°=−1367kJ/mol (20)
3NO(g)+2NH3(g)→5/2N2(g)+3H2O(g) ΔH°=−904kJ/mol (21)
NO(g)+½O2(g)→NO2(g) ΔH°=−57kJ/mol (22)
U.S. Pat. No. 5,328,673, which is entirely incorporated by reference herein, teaches using an aqueous solution of hydrochloric acid to oxidize NOx and SOx pollutants. The pollutants are converted to acids and then neutralized prior to disposal. The process consumes its reagent and does not produce any saleable products. U.S. Pat. No. 4,619,608, which is entirely incorporated herein by reference, teaches using chlorine to oxidize NOx, SOx and H2S pollutants to facilitate the removal of their oxidized forms through water absorption.
The Clean Air Act has set a pollution threshold for Mercury emissions, which is regulated by the United States Environmental Protection Agency (EPA). Coal-fired power plants account for a significant fraction of total mercury emissions. This emitted mercury is found in a variety of forms, including elemental mercury and oxidized mercury compounds. Highly soluble mercury compounds may be removed in a wet scrubber; however insoluble mercury compounds, such as elemental mercury, are difficult to remove via conventional removal methods. Therefore, it is desirable to oxidize the elemental mercury to a form that may be more readily captured.
U.S. Pat. No. 5,900,042 (“'042 patent”), which is entirely incorporated by reference herein, teaches reacting elemental mercury with aqueous solutions of chlorine, bromine, iodine and hydrochloric acid. The '042 patent teaches the oxidation of mercury and its subsequent absorption by water in the presence of NOx and/or SOx.
The Clean Air Act designates numerous substances as Hazardous Air Pollutants (HAPs). These pollutants can lead to health issues. The standard method for their removal is to capture using, e.g., electrostatic precipitators and bag filters as used for particulate matter removal. However, these methods can be costly. There is a need for new technologies capable of capturing these pollutants.
Particulate matter (PM) includes small particles of carbon, silca, alumina and other species created or formed in the combustion of coal. PM is formed from the melting of coal constituents in a coal-fired boiler and their condensation in the flue gas stream into very fine particles that are small enough to behave as gases. Much PM is removed as fly-ash using existing removal technologies, such as filter bag houses and electrostatic precipitators, but significant quantities are still released to the environment. Particulate matter is responsible for respiratory illness. Regulations currently limit the emission of particulate matter into the environment.
H2S is an odorous and corrosive (environmental) pollutant with toxicity worse than hydrogen cyanide (HCN). It is commonly found in natural gas, and is made at oil refineries and waste treatment facilities. In 1996 more than 5 million tons of H2S waste was generated through hydro-desulphurization to remove sulfur compounds from crude oil, according to T-Raissi, A. Technoeconomic Analysis of Area II Hydrogen Production—Part 1, in Proceedings of the 2001 DOE Hydrogen Program Review, DE-FC36-00GO10603, 2001.
H2S deactivates industrial catalysts, is corrosive to metal piping and damages gas engines, and therefore must be eliminated from many industrial processes, or removed from biogas before it is used or sold. Presently H2S is removed by chemical absorption with an iron oxide sponge or an amine solution. The resulting H2S laden product is then heated to high temperatures to release the H2S under controlled conditions for processing in sulfur producing plants that use the modified-Claus process (see below). A third of the sulfide gas stream is oxidized by air or oxygen to form sulfur dioxide. This stream is mixed with the remaining two-thirds of the sulfide stream over a catalyst to produce sulfur via the Claus reaction:
2H2S(g)+SO2(g)→3S(s)+2H2O(g) ΔH°=−145kJ/mole ΔG°=−90kJ/mol (23)
Sulfur is not very valuable and is typically burned to produce more useful sulfuric acid. Moreover, modified-Claus plants are expensive to operate and typically treat only 98% of the sulfide gases, requiring a tail gas unit to remove the remaining sulfide gases. The above-mentioned processes are not particularly attractive when considering the capital cost, energy consumption, plant footprint requirements, and manpower, operating and maintenance costs.
Other methods for removing hydrogen sulfide include absorption on activated carbon and scrubbing processes using a caustic soda solution. These methods are expensive and can produce considerable waste water, requiring further treatment and disposal.
Hydrogen Production from HBr
Once an aqueous HBr solution, preferably an azeotrope or more concentrated solution, is produced, it may be electrolyzed using commercially available electrolysis cells to produce hydrogen and bromine. Such cells are extensively used by the chlor-alkali industry. The regenerated bromine may be used for continuing the bromination processes described herein. Compared to the theoretical energy for the electrolysis of water at +287kJ/mol H2 (eq 11), actual HBr electrolysis requires less energy as shown:
Electrolysis: 2HBr(aq,azeotrope)→H2(g)+Br2(aq) ΔH°=+217kJ/mol H2 (24)
Referring to equations 12-17, which show the bromination of cellulose and carbon, it is evident the energy required to produce hydrogen can be significantly reduced if a carbon feedstock is utilized.
Overall: C6H10O5(s)+7H2O(l)→12H2(g)+6CO2(g) ΔH°=+50kJ/mol H2 (25)
Overall: C6H10O5(s)+7H2O(g)→12H2(g)+6CO2(g) ΔH°=+24kJ/mol H2 (26)
Overall: C(s)+2H2O(l)→2H2(g)+CO2(g) ΔH°=+89kJ/mol H2 (27)
Overall: C(s)+2H2O(g)→2H2(g)+CO2(g) ΔH°=+45kJ/mol H2 (28)
The HBr produced may be in different forms. The reaction thermodynamics are shown for alternative initial HBr and final product states, ‘aq’ designates a 1 M (mole/liter) solution.
Electrolysis: 2HBr(aq)→H2(g)+Br2(l) ΔH°=+243kJ/mol H2 (29)
Electrolysis: 2HBr(aq)→H2(g)+Br2(aq) ΔH°=+240kJ/mol H2 (30)
A second option for splitting HBr involves gas-phase electrolysis. HBr boils at −66.8° C., but is very soluble in water. It forms an azeotrope with water at a concentration of about 47.5%, the boiling point of which is about 126° C. Present proton exchange membrane (PEM) cells can operate at temperatures up to 200° C., making gas-phase electrolysis an option for reducing the energy required to split HBr by 50%. The reaction thermodynamics are described in the equations below for gas (g), liquid (l) or aqueous (aq, 1 M) phase products:
Electrolysis: 2HBr(g)→H2(g)+Br2(g) ΔH=+104kJ/mol H2 (31)
Electrolysis: 2HBr(g)→H2(g)+Br2(l) ΔH=+73kJ/mol H2 (32)
Electrolysis: 2HBr(g)→H2(g)+Br2(aq) ΔH=+70kJ/mol H2 (33)
A third option for splitting HBr involves reaction with a copper packed bed (hereinafter “bed”), a silver bed, or a bed comprising another metal. In this process, bromine reacts with the metal, releasing hydrogen, which is typically captured. Upon the completion of the reaction, the bed is heated to thermally dissociate the bromine from the metal for further bromination. The thermodynamics of such reactions are shown in the equations below for copper and silver beds:
Copper bed: HBr(g)+Cu(s)→CuBr(s)+½H2(g) ΔH=−68kJ/mol H2 (34)
CuBr(s)→Cu(s)+½Br2(g) ΔH=+120kJ/mol H2 (35)
Silver bed: HBr(g)+Ag(s)→AgBr(s)+½H2(g) ΔH=−64kJ/mol H2 (36)
AgBr(s)=Ag(s)→½Br2(g) ΔH=+116kJ/mol H2 (37)
The hydrogen produced from hydrogen bromide may be reacted with oxygen in air to release more energy than needed to create the hydrogen:
H2(g)+½O2(g)→H2O(g) ΔH=−242kJ/mol H2 (38)
H2(g)+½O2(g)→H2O(l) ΔH=−286kJ/mol H2 (39)
Energy Storage with Reversible Fuel Cells
Hydrogen bromide proton exchange membrane electrolyzers have been produced, which can operate as fuel cells to produce electricity through the reaction of hydrogen with bromine, oxygen or another oxidizer. Cells utilizing hydrogen and chlorine were the first fuel cells operated due to greatly augmented reaction rates when compared to hydrogen and oxygen. The ability to use a reversible fuel cell with hydrogen and bromine allows the electrolyzer to regenerate bromine from hydrogen bromide, which can be operated as a fuel cell to generate electricity from the reaction of hydrogen with an oxidizer. This is important when the time value of electricity is considered which favors electrical consumption during off-peak night periods, and electricity generation during on-peak daytime periods. U.S. Pat. No. 5,219,671, which is entirely incorporated herein by reference, discloses the use of reversible hydrogen-halogen fuel cells for energy storage.
The reaction between hydrogen and a halogen is known to be very efficient, allowing hydrogen and the halogen to be reacted to produce a hydrogen halide and electricity, and then decomposed with electricity to regenerate hydrogen and halogen with close to theoretical energy. Round trip electric-to-electric efficiencies of 80% have been demonstrated at high current densities exceeding 3 kA/m2.
Due to the difficulty in transporting and storing gaseous hydrogen, and the absence of infrastructure and significant demand for hydrogen as a vehicle-fuel, hydrogen is reacted with co-produced carbon dioxide to produce methanol. This methanol may then be hydrated in the presence of sulfuric acid to produce ethanol, which may be burned in existing flex-fuel vehicles or blended with regular gasoline for existing gasoline-fuelled vehicles. The reactions for these steps are exothermic and are shown in the equations below:
Methanol Synthesis: CO2(g)+3H2(g)→CH3OH(g)+H2O(g) ΔH=−38kJ/mole (40)
Ethanol Synthesis: 2CH3OH(l)→CH3CH2OH(l)+H2O(l) ΔH=−86kJ/mole (41)
Six moles of hydrogen are required for each mole of ethanol produced. All of the steps proposed are exothermic, with the exception of dissociating hydrogen from HBr. Table 5 (below) shows the chemicals required and made from one pound of carbonaceous starting species.
1lb Cellulose+0.778lbs H2O→0.148lbs H2+1.63lbs CO2 (42)
or→0.790lbs Methanol+0.543lbs CO2+0.444lb H2O (43)
or→0.568lbs Ethanol+0.543lbs CO2+0.667lb H2O (44)
1lb Coal+2.50lbs H2O→0.327lbs H2+3.117lbs CO2 (45)
or→1.746lbs Methanol+0.72lbs CO2+1.041lb H2O (46)
or→1.255lbs Ethanol+0.72lbs CO2+1.532lb H2O (47)
1lb C+3.00lbs H2O→0.333lbs H2+3.667lbs CO2 (48)
or→1.78lbs Methanol+1.22lbs CO2+1.00lb (49)
or→1.28lbs Ethanol+1.22lbs CO2+1.50lb H2O (50)
Tables 6 and 7 detail the mass balances of the reactions discussed herein. Table 6 shows the amount of hydrogen, methanol, and ethanol that can be made from each pound of reacting species (“species”) and the pounds of reacting species required to make a gallon of methanol and ethanol.
Table 7 shows the amount of carbon dioxide emitted per pound of hydrogen, methanol, and ethanol, the fraction of hydrogen that comes from the water co-reactant, and the percentage of carbon dioxide reused from the bromination step to make methanol and ethanol.
Table 8 shows the amount of water required and carbon dioxide produced in the first bromination reaction, and the amount of carbon dioxide not used and water produced in the methanol/ethanol synthesis reactions. All production numbers are indicated per pound of reacting species.
Accordingly, there is a need in the art for efficient energy production processes as well as chemical processes that can utilize biomass, methane, sewage, nitrogen, sulfur and phosphorus pollutants, as well as other waste material, to generate energy, while reducing the energy needed to make useable fuels, such as, e.g., hydrogen (H2), methanol (CH3OH), ethanol (C2H5OH), other alcohols, hydrocarbons (including high molecular weight hydrocarbons and aromatic compounds), aldehydes, ketones, ammonia (NH3) and urea. Additionally, there is a need for processes to capture and treat pollutants, such as, e.g., mercury, lead and other metals, and nitrogen oxide (NOx) and sulfur-containing species (e.g., elemental sulfur, SO2, H2SO4).
The invention provides systems, apparatuses, devices and methods for reacting a halogen-containing chemical with a reactant to produce energy. Such systems may include one or more reaction modules (also “reactors” herein) configured for reacting a carbon-containing, a sulfur-containing, and/or nitrogen-containing chemical with a first halogen-containing chemical to produce a second halogen-containing chemical, which can be dissociated to produce the first halogen-containing chemical. In some embodiments, the second halogen-containing chemical can be dissociated in an electrolyzer, such as an electrolyzer as part of a reversible fuel cell.
An aspect of the invention provides methods for generating energy and/or fuel from the halogenation of a carbon-containing material. In an embodiment of the invention, a method comprises supplying the carbon-containing material and a first halogen-containing chemical to a reactor. The carbon-containing material and the halogen-containing chemical are reacted in the reactor to form a second halogen-containing chemical and carbon dioxide. The second halogen-containing chemical is dissociated (e.g., electrolyzed) to form the first halogen-containing chemical and hydrogen gas (H2). In an embodiment of the invention, the second halogen-containing chemical is dissociated into the first halogen-containing chemical and H2 in the reactor. In such a case, the reactor may be configured for halogenation and electrolysis. In another embodiment of the invention, the first halogen-containing chemical is Br2 and the second halogen-containing chemical is HBr. In another embodiment of the invention, any carbon dioxide formed during reaction is directed to a prime mover (e.g., turbine) to generate electricity. In yet another embodiment of the invention, a sulfur-containing chemical is supplied to the reactor. In an embodiment of the invention, the sulfur-containing chemical can include one or more of H2S, elemental sulfur, SO2, SO3 and sulfuric acid. The sulfur-containing chemical can react with the first halogen-containing chemical to yield the second halogen-containing chemical.
Another embodiment of the invention provides a method for brominating a carbon-containing material. The method comprises supplying a carbon-containing material, Br2 and H2O to a reaction module; reacting the carbon-containing material, Br2 and H2O in the reaction module (or reactor) to form HBr and CO2; and dissociating (e.g., electrolyzing) HBr into H2 and Br2. In an embodiment of the invention, the carbon-containing chemical, Br2 and H2O are reacted at a temperature between about 1° C. and about 500° C., or between about 100° C. and about 400° C., or between about 200° C. and about 350° C. In another embodiment of the invention, the carbon-containing chemical, Br2 and H2O are reacted at a pressure between about 1 atm and about 500 atm, or between about 15 atm and about 400 atm, or between about 150 atm and 300 atm, or between about 1 atm and 15 atm. Yet another embodiment of the invention provides a method for cleaning a contaminated gas stream. The method comprises providing a contaminant in a reactor; providing a first halogen-containing chemical in the reactor; reacting the contaminant with the first halogen-containing chemical to form a second halogen-containing chemical; and dissociating the second halogen-containing chemical to form the first halogen-containing chemical and hydrogen (H2). In an embodiment of the invention, the second halogen-containing chemical is dissociated in the reactor. In another embodiment of the invention, the first halogen-containing chemical is selected from F2, Cl2, Br2 and I2 gases. In yet another embodiment of the invention, the second halogen-containing chemical is selected from HF, HCl, HBr and HI. In still another embodiment of the invention, the contaminant includes one or more of a carbon-containing chemical, elemental sulfur, H2S, SO2, SO3, NO, NO2, N2O and ash.
Another aspect of the invention provides reactors, such as halogenation reactors, reversible fuel cells, fuel cells and combined (or dual) halogenation and electrolysis reactors. In an embodiment of the invention, a halogenation reactor comprises a first module configured for reacting a carbon-containing material and a first halogen-containing chemical to form a second halogen-containing chemical. The halogenation reactor further comprises a second module configured for dissociating the second halogen-containing chemical into the first halogen-containing chemical and hydrogen gas (H2). In an embodiment of the invention, the halogenation reactor can be a fuel cell. In another embodiment of the invention, the halogenation reactor can be a reversible fuel cell. In yet another embodiment of the invention, the halogenation reactor further comprises a proton exchange membrane for separating protons from ionic fragments of the second halogen-containing chemical. In still another embodiment of the invention, the first module and the second module can be the same module. In such a case, reaction between the carbon-containing material and the first halogen-containing chemical, and dissociation of the second halogen-containing chemical can take place in the same reactor or reaction vessel. In still another embodiment of the invention, the second module is configured for reacting H2(g) with O2(g) to form water. In still another embodiment of the invention, the second module is configured for reacting H2(g) with the first halogen-containing chemical to form the second halogen-containing chemical.
Another embodiment of the invention provides an energy production system, comprising a reversible fuel cell configured for reacting a carbon-containing material and a first halogen-containing chemical to form a second halogen-containing chemical and carbon dioxide. The reversible fuel cell is further configured for dissociating the first halogen-containing chemical into the second halogen-containing chemical and hydrogen gas (H2). The system further comprises a primer mover for generating energy from one or both of H2(g) and CO2(g).
In preferable embodiments of the invention, processes and systems of components provide chemicals and energy from waste or non-waste feedstock. Different implementations of the processes of preferable embodiments of the invention are capable of reacting a variety of carbon, nitrogen, sulfur and phosphorus-containing chemicals or materials to produce electricity and a range of chemicals, including hydrogen, water, carbon dioxide, ammonia, methanol, ethanol, sulfuric acid, nitric acid, phosphoric acid and halogen-containing acids (e.g., HBr, HCl, HI, HF), as well as ammonium and metal sulfates, nitrates and phosphates. Reactants (also “feedstock compounds” herein) of particular interest include, without limitation, carbon, cellulose, biomass, coal, petroleum coke, carbon monoxide, carbon dioxide, nitrogen oxide, nitrogen dioxide, nitrates, sulfur, sulfur dioxide, sulfur trioxide, hydrogen sulfide, sulfates, phosphorus and nitrogen compounds, as well as biowaste, such as sewage, manure and crop residues. Feedstock (or waste) streams can contain one or more metals, biological and chemical contaminants, including mercury, arsenic, lead, cadmium, tellurium, cadmium tellurium, hormones, pharmaceuticals, pesticides, herbicides, and other organic and inorganic contaminants, some of which may be classified as hazardous air pollutants. Methods and processes of preferable embodiments of the invention can capture, react with, and/or break down these contaminates to provide an environmentally friendly ash having, e.g., inert and/or un-reacted compounds, that may be recycled or disposed.
Other goals and advantages of the invention will be further appreciated and understood when considered in conjunction with the following description and accompanying drawings. While the following description may contain specific details describing particular embodiments of the invention, this should not be construed as limitations to the scope of the invention but rather as an exemplification of preferable embodiments of the invention. For each aspect of the invention, many variations are possible as suggested herein that are known to those of ordinary skill in the art. A variety of changes and modifications can be made within the scope of the invention without departing from the spirit thereof.
All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference.
The features and advantages of the invention may be further explained by reference to the following detailed description and accompanying drawings that sets forth illustrative embodiments of the invention.
While various embodiments of the invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention.
Methods, processes, devices, structures, apparatuses and systems of aspects and embodiments of the invention can overcome various problems and limitations associated with prior art systems and methods. In some embodiments of the invention, methods and apparatuses for the treatment of waste material to produce useful products are provided. In other embodiments, methods and apparatuses for the treatment of waste material and the creation of high-pressure gas to operate a prime mover (e.g., turbine, motor, turbine and generator combination, compressor) are provided. In still other embodiments, methods and apparatuses for integrating the ability to store energy and providing peaking power are provided. It will be appreciated that several types of modules can be utilized to process various reactants and products.
In embodiments of the invention, the bromination of carbon-containing material, such as, e.g., carbonaceous material or biomass, provides for meeting domestic energy requirements, thus reducing the need for oil and natural gas, and reducing pollution. The basic methods and processes of preferable embodiments of the invention have several advantages over prior art methods and processes, which include, without limitation:
In embodiments of the invention, providing a first halogen-containing chemical, a carbon-containing chemical and water to a reactor (e.g., halogenation reactor and electrolyzer combined in a single reactor) can yield CO2 and a second halogen-containing chemical. CO2 can be directed through a prime mover (e.g., turbine) to generate energy or used in liquid fuel synthesis. The second halogen-containing chemical can be decomposed into hydrogen and the first halogen-containing chemical, which can be recycled into the reactor.
In other embodiments of the invention, providing a first sulfur-containing chemical (e.g., elemental sulfur, SO2) and a first halogen-containing chemical (e.g., Br2) to a reactor can yield a second halogen-containing chemical (HBr) and a second sulfur-containing chemical (e.g., elemental sulfur, H2SO4). By providing the sulfur-containing chemical at high pressure to a pressurized reactor, the size of the equipment can be reduced, leading to savings in equipment and process costs.
Various processes of embodiments of the invention separate bromine (Br2) and HBr. Liquid bromine with the highest density can be concentrated at the bottom of a pressurized column or reactor, followed by a bromine-HBr aqueous solution at the top. Sulfur-containing gases are soluble and react exothermically with the elemental bromine liquid at the bottom and with the bromine-water solution forming HBr, sulfur and/or sulfuric acid. The process produces considerable thermal energy in the production of the by-products and the enthalpy of dissolution of HBr. In an embodiment of the invention, a pressurized carbon-containing gas (e.g., methane) is insoluble in the liquid column and its bubbling passage up through the column “carries” the sulfur-containing byproduct and aqueous HBr up to the top of the column via the turbulence of an insoluble gas rising and expanding in a liquid column. A glass frit or other porous device separating the pressurized gasses at the bottom from the pressurized liquid produces a very small bubble stream which allows for more intimate mixing and increased reaction rates.
In an embodiment of the invention, heat from the reactions can be removed with a spiral heat exchanger centrally located within a reactor or reaction column, which also aids in generating turbulence with the insoluble carbon-containing carrier gas. The heat is used to concentrate a portion of the dilute aqueous HBr solution which has been removed from the column for electrolysis into hydrogen and bromine, with the bromine-water solution re-introduced low into the pressurized column. In another embodiment of the invention, process heat is used to produce gaseous HBr for gas-phase electrolysis.
In an embodiment of the invention, to facilitate electrolysis of a halogen-containing chemical, acentral spiral heat exchanger can be used as the anode and the wall of column as the cathode, with solid particulates suspended in the electrolyte behaving as a “slurry” electrode. See U.S. Pat. No. 4,239,607, which is entirely incorporated herein by reference.
Reaction columns (or reactors, reaction vessels) and heat-exchangers can be formed of Hexyloy® SG silicon carbide, an electrically conductive analog of sintered silicon carbide. Alternatively, reactors can be coated with an electrically conductive glass material containing oxides of titanium (i.e., TiOx). See U.S. Pat. No. 2,933,458, which is entirely incorporated herein by reference.
In an embodiment of the invention, a carbon-containing material, a sulfur-containing chemical and a first halogen-containing chemical are provided in the same reactor. This enables simultaneous bromination and ash-treatment, thereby ensuring that all or essentially all of the first halogen-containing chemical (e.g., Br2) is converted to a second halogen-containing chemical (e.g., HBr). In a preferable embodiment of the invention, slurry electrodes in an agitated single reactor (or electrolyzer) tank configuration can be used.
In another embodiment of the invention, a first halogen-containing chemical can be photolyzed to a second halogen-containing chemical to get higher yields at lower temperatures and pressures. In such a case, concentrated solar or laser energy can be provided using a quartz port in a reactor to photolyze the first halogen-containing chemical (e.g., HBr) to the second halogen-containing chemical (e.g., Br2). In an embodiment, the electrolyte can be seeded with one or more Group VIII transitional metals. See U.S. Pat. No. 5,219,671, which is entirely incorporated herein by reference.
“Halogen-containing species” (also “halogen-containing compound”, “halogen-containing chemical” and “halogen-containing material” herein) refers to any chemical species comprising one or more halogen atoms (e.g., F, Cl, Br, I). A halogen-containing species may be a chemical species selected from bromine (Br2), fluorine (F2), chlorine (Cl2), iodine (I2), hydrogen flouride (HF), hydrogen chloride (HCl) and hydrogen iodide (HI). In some embodiments, a halogen-containing chemical may be a halogen-containing acid, such as, e.g., HF, HCl, HBr or HI. A halogen-containing compound can exist in any state, such as gaseous and/or liquid (or aqueous) states. While various embodiments of the invention make use of bromine (Br2) and hydrobromic acid (HBr), it will be appreciated that other halogen-containing compounds, such as, e.g., Cl2 and HCl or I2 and HI, may be used in place of Br2 and HBr.
“Sulfur-containing species” (also “sulfur-containing chemical” and “sulfur-containing material” herein) refers to any chemical species comprising one or more sulfur atoms. A sulfur-containing species may be a chemical species (or a chemical compound) selected from elemental sulfur (S), H2S, HDS, D2S, sulfur oxide (SOx, such as, e.g., SO, SO2, SO3), sulfurous acid (H2SO3) and sulfuric acid (H2SO4). A sulfur-containing species can exist in any form, such as solid, liquid, or gaseous (vapor) form. The skilled artisan will understand that various sulfur-containing species can exist in aqueous form. For example, sulfuric acid can exist in aqueous form.
“Carbon-containing species” (also “carbon species”, “carbon-containing chemical,” “carbon-containing matter” and “carbon-containing material” herein) refers to any chemical species comprising one or more carbon atoms. In embodiments of the invention, a carbon-containing species can be selected from a carbon-rich (carbonaceous) compound, coal, biomass, sewage, lignite, cellulose, animal manure, municipal solid waste, pulp, paper products, food waste, milorganite, alkanes (e.g., CH4), alkenes (e.g., C2H4), alkynes (e.g., C2H2), aromatics (e.g., C6H6), alcohols (e.g., CH3OH, CH3CH2OH), aldehydes and ketones. In some embodiments of the invention, biomass may be a carbon-containing species. A carbon-containing species can react to form other carbon-containing species.
“Nitrogen-containing species” (also “nitrogen-containing chemical” and “nitrogen-containing material” herein) refers to any species comprising one or more nitrogen atoms. A nitrogen-containing species may be N2 or NOx (e.g., NO, NO2, N2O3, N2O4, N2O5, N2O, HNO2 and HNO3). A nitrogen-containing species can react to form other nitrogen-containing species.
“Phosphorous-containing species” (also “phosphorous-containing chemical” or “phosphorous-containing material” herein) refers to any species comprising one or more phosphorous atoms. A phosphorous-containing species can be phosphoric acid, or a compound comprising phosphate or organophosphorus. A phosphorous-containing species can react to form other phosphorous-containing species.
Processes of embodiments of the invention can yield various sulfur-containing species as products (or by-products). In some embodiments, sulfuric acid (H2SO4) is a product. In some applications, sulfuric acid may need to be added to the reactants. This can be achieved by adding a sulfur-containing species (e.g., S, SO2) to a reactor. In other embodiments, elemental sulfur is a product. In still other embodiments, a sulfur oxide (SOx) is a product.
It will be appreciated that nitrogen-containing species, phosphorous-containing species, carbon-containing species, sulfur-containing species and halogen-containing species are not mutually exclusive. That is, a carbon-containing species can include one or more sulfur atoms.
In various embodiments, during reaction hydrogen halide, such as, e.g., hydrogen bromide (HBr) or hydrogen chloride (HCl), can be formed. Metal bromides can result from reaction with non-nitrogen, sulfur, carbon and phosphorus compounds.
Hydrogen Production from Carbon-Containing Waste
In an aspect of the invention, performing a bromination reaction at higher temperature can accelerate the burning (or combustion) of carbon-containing material with bromine. This enhances the generation of steam and other gases, increases the final HBr concentration, and decreases the energy required to produce hydrogen and regenerate bromine.
In an embodiment of the invention, a carbon-containing chemical (e.g., cellulose), Br2 and H2O can be reacted at a temperature between about 1° C. and about 500° C., or between about 100° C. and about 400° C., or between about 200° C. and about 350° C. The carbon-containing chemical, Br2 and H2O can be reacted at a pressure between about 1 atm and about 500 atm, or between about 15 atm and about 400 atm, or between about 150 atm and 300 atm, or between about 1 atm and 15 atm.
In another embodiment of the invention, the HBr solution is electrolyzed at high temperature to regenerate bromine and produce hydrogen using less energy than HBr electrolysis at room temperature and other prior art methods. The electrolysis of HBr benefits greatly with increased temperature.
In another embodiment of the invention, if the reactor and electrolyzer are operated at high pressure, hydrogen produced at a high pressure does not need to be compressed as much (or at all) before further use (e.g., sale, storage, or consumption). Delivering hydrogen at 200 atm (about 3000 psi) saves 2½kWhr per kilogram of hydrogen.
In another embodiment of the invention, CO2 and/or other gases (N2, HBr, H2O) generated in the reactor may be expanded through a prime mover (e.g., a turbine, motor, turbine and generator, compressor, or an equivalent) to produce power.
In another aspect of the invention, reactors (also “reaction vessels” or “chambers” herein) configured for halogenation and electrolysis are provided. Reactors of embodiments of the invention can be configured for bromination, iodization, chlorination or fluoridation of one or more carbon-containing species. In preferable embodiments of the invention, a first halogen-containing chemical, a carbon-containing material and water are added to the reactor. The carbon-containing material may include certain quantity of a sulfur-containing chemical, such as, e.g., elemental sulfur, SO2 or H2SO4. In some embodiments of the invention, a sulfur-containing chemical (e.g., elemental sulfur or sulfuric acid) can be added to the reactor. The first halogen-containing chemical is disassociated into a second halogen-containing chemical and hydrogen gas, which are removed from the reactor. In an embodiment of the invention, the first halogen-containing chemical is electrolyzed into the second halogen-containing chemical and hydrogen gas. The second halogen-containing chemical reacts with the carbon-containing material to yield, among other things, carbon dioxide, water and a third halogen-containing chemical. In an embodiment of the invention, the third halogen-containing chemical is equivalent to the first halogen-containing chemical. In a preferable embodiment of the invention, the first halogen-containing chemical is HBr, the second halogen-containing chemical is Br2 and the third halogen-containing chemical is HBr.
In an embodiment of the invention, a mixture of reactants, including a carbon-containing material, HBr, water and a sulfur-containing chemical, is added to the reactor. HBr is disassociated into H2 and Br2. Br2 reacts with the carbon-containing material to yield water, CO2 and HBr. CO2 released during reaction can be directed through a prime mover (e.g., turbine) to generate energy. HBr is recovered via one or more vapor phase recovery apparatuses, such as, e.g. one or more scrubbers.
With reference to
The reactor can be a dual or combined halogenation reactor and electrolyzer. In an embodiment of the invention, the reactor 70 can be a fuel cell. In another embodiment of the invention, the reactor 70 can be a reversible fuel cell.
With continued reference to
In a preferable embodiment of the invention, in the reactor 70 hydrobromic acid (HBr) is decomposed (or dissociated) into ionic fragments (e.g., H+ and Br−), which combine to form bromine (Br2) and hydrogen (H2). In an embodiment of the invention, Br2 and H2 are in gaseous (or vapor) form. While a PEM 75 is used in the reactor 70, the decomposition and/or separation of ionic fragments of HBr may be facilitated using other means, such as, e.g., a metal bed or ceramic membrane.
With continued reference to
With continued reference to
With reference to
In another aspect of the invention, an energy production system comprises a reactor configured for reacting a carbon-containing material and a first halogen-containing chemical to form a second halogen-containing chemical and carbon dioxide. In some embodiments, the reactor is further configured for dissociating the first halogen-containing chemical into the second halogen-containing chemical and hydrogen gas (H2). In embodiments of the invention, the reactor is a combination of a halogenation reactor and electrolyzer. In some cases the reactor can be reversible fuel cell. The energy production system can further comprise a primer mover for generating energy from one or both of H2 and CO2.
In some embodiments of the invention, the energy production system can include a computer system (such as the computer system 93 of
With continued reference to
With continued reference to
With reference to
While the systems of
In some embodiments, hydrogen can be reacted with a halogen-containing chemical (e.g., Br2, Cl2, I2), oxygen or air in a fuel cell to generate electrical power. In an embodiment of the invention, the same system or reactor that electrolyzes hydrogen bromide to produce hydrogen may be designed to react the hydrogen with oxygen to produce electricity, possibly more electricity than required for the hydrogen's generation from hydrogen bromide.
With reference to
With continued reference to
An electrolyzer may include a stack of alternating plates to provide for the control of reactant and product flows, current collection and distribution, cation and/or anion exchange membranes, and insulation.
With continued reference to
The reversible fuel cell 130 of
All reactors (e.g., reversible fuels cells, electrolyzers, fuel cells) described above may contain a variety of catalyst materials (e.g., platinum, ruthenium, rhodium, palladium, osmium, iridium, gold, silver, nickel, copper and other rare earth elements and combinations thereof) with compositions ranging from several nanograms/m3 to pure catalyst material. The structural supports may be made up of a range of materials, including, e.g., carbon, graphite, plastics, metals, inorganic and organic materials. In an embodiment of the invention, a reversible fuel cell apparatus comprises a plastic structure flow control for promoting the flow of one or more reactants (e.g., HBr or H2 and O2/Br2), a graphite carbon Toray paper as the anode material, and a catalyst-doped graphite carbon Toray paper as the cathode material.
With continued reference to
In some embodiments of the invention, methods for removing a nitrogen-containing chemical, such as, e.g., NOx (e.g., NO, NO2, N2O3, N2O4, N2O5, N2O, HNO2 and HNO3), from exhaust waste gas streams and, more specifically, coal-fired power plant flue gases, are provided. In an embodiment of the invention, a process chemically similar to the ISPRA Mark 13a process for controlling sulfur dioxide power plant emissions is provided, wherein:
SO2(g)+Br2(l)+2H2O(l)→H2SO4(l)+2HBr(aq) (51)
ΔH°=−188kJ/mole ΔG°=−123kJ/mole (52)
SO2(g)+Br2(aq)+2H2O(l)→H2SO4(aq)+2HBr(aq) (53)
ΔH°=−281kJ/mole ΔG°=−182kJ/mole (54)
Nitrogen oxide species are reacted with a solution of bromine and water to form nitric and hydrobromic acid:
NO(g)+1.5Br2(aq)+2H2O(l)→HNO3(aq)+3HBr(aq) (55)
ΔH°=−88kJ/mole ΔG°=−43kJ/mole (56)
NO2(g)+½Br2(aq)+H2O(l)→HNO3(aq)+HBr(aq) (57)
ΔH°=−75kJ/mole ΔG°=−32kJ/mole (58)
N2O(g)+4Br2(aq)+5H2O(l)→2HNO3(aq)+8HBr(aq) (59)
ΔH°=−29kJ/mole ΔG°=12kJ/mole (60)
N2O3(g)+2Br2(aq)+3H2O(l)→2HNO3(aq)+4HBr(aq) (61)
ΔH°=−29kJ/mole ΔG°=12kJ/mole (62)
N2O4(g)+Br2(aq)+2H2O(l)→2HNO3(aq)+2HBr(aq) (63)
ΔH°=−29kJ/mole ΔG°=12kJ/mole (64)
N2O5(g)+H2O(l)→2HNO3(aq) (65)
ΔH°=−29kJ/mole ΔG°=12kJ/mole (66)
The following reactions are also relevant to the reduction (or oxidation of species comprising NO and NO2.
NO(g)+½Br2(aq)+H2O(l)→HNO2(aq)+HBr(aq) (67)
ΔH°=exothermic (68)
HNO2(aq)+½O2(g)→HNO3(aq) (69)
ΔH°=exothermic (70)
HNO2(aq)+Br2(aq)→BrNO2(aq)+HBr(aq) (71)
ΔH°=exothermic (72)
BrNO2(aq)+H2O(l)→HNO3(aq)+HBr(aq) (73)
ΔH°=exothermic (74)
HNO2(aq)+Br2(aq)+H2O(l)→HNO3(aq)+2HBr(aq) (75)
ΔH°=exothermic (76)
With reference to reaction (67), bromine oxidizes nitrogen oxide (NO) to nitric acid (HNO2) and HBr in a thermodynamically favorable (exothermic) reaction. HBr formed during reaction is directed to an electrolyzer (also “electrolysis cell” here), where the HBr is electrolyzed to produce H2 and bromine (Br2), which can be recycled to react with NO per reaction (67) above:
2HBr(aq)→H2(g)+Br2(aq) ΔH°=240kJ/mole ΔG°=212kJ/mole (77)
HBr may also be reacted in an alternate process, such as, e.g., reacted with a metal bed (or catalytic bed) to obtain hydrogen, or burned with oxygen to recover bromine.
A portion of the spent scrubbing solution can be continually removed, and its nitric acid content can be concentrated and stored. Both hydrogen (H2) and nitric acid may be sold, consumed internally, or used to make other chemical products, including alternative liquid fuels, which can be used to generate electricity in an environmentally friendly fashion. If reacted with oxygen, hydrogen releases more energy than needed to electrolyze HBr:
H2(g)+½O2(g)→H2O(g) ΔH°=−242kJ/mole ΔG°=−229kJ/mole (78)
Not only are emissions of the polluting oxides of nitrogen controlled, but renewable hydrogen is produced from their conversion to marketable nitric acid.
In some embodiments of the invention, the NOx reactants can be converted to molecular nitrogen. This conversion may be dependent on reaction conditions, such as, e.g., temperature and pressure.
In some embodiments of the invention, methods for removing mercury from exhaust waste gas streams, such as from coal-fired power plant (also “coal power plant” herein) flue gas streams, are provided. In an embodiment of the invention, a process captures mercury and mercuric oxide emissions, and converts them into mercuric bromide via exothermic reactions, as shown in Table 9:
Mercuric bromide salt can precipitate out of solution or react with sulfuric acid in solution to form mercuric sulfate, which can precipitate out of solution or filtered out of solution. The relatively small amount of precipitate (about 115 lbs/year Hg equivalent from a 300 MW coal plant) can be collected in a reactor, pre-concentrator or final concentrator, or any other device configured for precipitate removal (or capture), and be disposed of or treated to regenerate elemental mercury.
In some embodiments of the invention, methods for removing HAPs from exhaust waste gas streams, such as from coal-fired power plant flue gas streams, are provided. In an embodiment of the invention, an aqueous solution of bromine is used to capture Hazardous Air Pollutants (HAPs). The strong oxidizing properties of bromine can facilitate the capture of HAPs. Table 10 provides reactions between some HAPs and an aqueous bromine solution:
In an embodiment of the invention, most of the bromide salts formed can precipitate out of solution or react with sulfuric acid in solution to form sulfates, which can precipitate out of solution in the reactor where they can be collected with the mercuric bromide or mercuric sulfate for disposal or treatment. Following reaction, some HAP species may remain in solution as a soluble ash; these compounds may be removed with sulfuric acid, which is already in solution from the SOx control reaction discussed above, or can be added to form metal sulfates. These sulfate compounds can precipitate out of solution in the reactor, or can be removed with lime by forming metal hydroxides. Filters, centrifuges and boilers may be used to separate hydroxide, bromide and sulfate species.
It will be appreciated that the reactions and processed discussed above can be applied to other HAPs not mentioned. It will be appreciated that there may be other feasible reactions with bromine to capture and react with the HAPs, sometimes with the aid of water. Hazardous air pollutants bromine can react or interact with include, without limitation: Acetaldehyde, Acetamide, Acetonitrile, Acetophenone, 2-Acetylaminofluorene, Acrolein, Acrylamide, Acrylic acid, Acrylonitrile, Allyl chloride, 4-Aminobiphenyl, Aniline, o-Anisidine, Asbestos, Benzene, Benzidine, Benzotrichloride, Benzyl chloride, Biphenyl, 3,3-Dimethoxybenzidinem Bis(chloromethyl)ether, Bromoform, 1,3-Butadiene, Calcium cyanamide, Caprolactam, Captan, Carbaryl, Carbon disulfide, Carbon tetrachloride, Carbonyl sulfide, Catechol, Chloramben, Chlordane, Chlorine, Chloroacetic acid, 2-Chloroacetophenone, Chlorobenzene, Chlorobenzilate, Chloroform, Chloromethyl methyl ether, Chloroprene, Cresols/Cresylic acid, o-Cresol, m-Cresol, p-Cresol, Cumene, 2,4-D, salts and esters, DDE, Diazomethane, Dibenzofurans, 1,2-Dibromo-3-chloropropane, Dibutylphthalate, 1,4-Dichlorobenzene(p), 3,3-Dichlorobenzidene, Dichloroethyl ether, 1,3-Dichloropropene, Dichlorvos, Diethanolamine, N,N-Dimethylaniline, Diethyl sulfate, Naphthalene, Bis(2-ethylhexyl)phthalate (DEHP), Dimethyl aminoazobenzene, 3,3′-Dimethyl benzidine, Dimethyl carbamoyl chloride, Dimethyl formamide, 1,1-Dimethyl hydrazine, Dimethyl phthalate, Dimethyl sulfate, 4,6-Dinitro-o-cresol, and salts 2,4-Dinitrophenol, 2,4-Dinitrotoluene, 1,4-Dioxane (1,4-Diethyleneoxide), 1,2-Diphenylhydrazine, Epichlorohydrin (1-Chloro-2,3-epoxypropane), 1,2-Epoxybutane, Ethyl acrylate, Ethyl benzenz, Ethyl carbamate (Urethane), Ethyl chloride (Chloroethane), Ethylene dibromide (Dibromoethane), Ethylene dichloride (1,2-Dichloroethane), Ethylene glycol, Ethylene imine (Aziridine), Ethylene oxide, Ethylene thiourea, Ethylidene dichloride (1,1-Dichloroethane), Formaldehyde, Heptachlor, Hexachlorobenzene, Hexachlorobutadiene, Hexachlorocyclopentadiene, Hexachloroethane, Hexamethylene-1,6-diisocyanate, Hexamethylphosphoramide, Hexane, Hydrazine, Hydrochloric acid, Hydrogen fluoride (Hydrofluoric acid), Hydrogen sulfide (See Modification), Hydroquinone, Isophorone, Lindane (all isomers), Maleic anhydride, Methanol, Methoxychlor, Methyl bromide (Bromomethane), Methyl chloride (Chloromethane), Methyl chloroform (1,1,1-Trichloroethane), Methyl ethyl ketone (2-Butanone), Methyl hydrazine, Methyl iodide (Iodomethane), Methyl isobutyl ketone (Hexone), Methyl isocyanate, Methyl methacrylate, Methyl tert butyl ether, 4,4-Methylene bis(2-chloroaniline), Methylene chloride (Dichloromethane), Methylene diphenyl diisocyanate (MDI), 4,4-Methylenedianiline, Nitrobenzene, 4-Nitrobiphenyl, 4-Nitrophenol, 2-Nitropropane, N-Nitroso-N-methylurea, N-Nitrosodimethylamine, N-Nitrosomorpholine, Parathion, Pentachloronitrobenzene (Quintobenzene), Pentachlorophenol, Phenol, p-Phenylenediamine, Phosgene, Phosphine, Phosphorus, Phthalic anhydride, Polychlorinated biphenyls (Aroclors), 1,3-Propane sultone, beta-Propiolactone, Propionaldehyde, Propoxur (Baygon), Propylene dichloride (1,2-Dichloropropane), Propylene oxide, 1,2-Propylenimine(2-Methyl aziridine), Quinoline, Quinone, Styrene, Styrene oxide, 2,3,7,8-Tetrachlorodibenzo-p-dioxin, 1,1,2,2-Tetrachloroethane, Tetrachloroethylene (Perchloroethylene), Titanium tetrachloride, Toluene, 2,4-Toluene diamine, 2,4-Toluene diisocyanate, o-Toluidine, Toxaphene (chlorinated camphene), 1,2,4-Trichlorobenzene, 1,1,2-Trichloroethane, Trichloroethylene, 2,4,5-Trichlorophenol, 2,4,6-Trichlorophenol, Triethylamine, Trifluralin, 2,2,4-Trimethylpentane, Vinyl acetate, Vinyl bromide, Vinyl chloride, Vinylidene chloride (1,1-Dichloroethylene), Xylenes (isomers and mixture), o-Xylenes, m-Xylenes, p-Xylenes, Coke Oven Emissions, Cyanide Compounds1, Glycol ethers2, Fine mineral fibers3, Polycylic Organic Matter4 and Radionuclides (including radon)5.
In other embodiments of the invention, methods for removing PM from exhaust waste gas streams, such as from coal-fired power plant flue gas streams, are provided. Particulate matter includes, without limitation, particles of carbon, silica and alumina having various particle sizes (or diameters), such as, e.g., on the order of several nanometers or micrometers (“microns”). In some cases, these particles may be sufficiently small to behave as gases. In an embodiment of the invention, an aqueous, preferably dilute bromine water solution can be contacted with flue gas to capture particulate emissions. The contacted solution may contain nitric acid, sulfuric acid, hydrobromic acid (HBr) and other chemical species. The particulate matter may be captured using a scrubber. The scrubbing solution can be an all-fluid mixture, which allows it to be pumped and sprayed through smaller diameter nozzles. This results in smaller drop sizes, which increases the surface area (or contact area) of spray for a given recirculation volume and increases the likelihood of contacting PM in the flue gas. Conventional emission control processes utilize slurries of solids in water, which require a larger minimum spray nozzle size to avoid clogging, and are therefore unable to remove significant particulate matter.
In
In other embodiments of the invention, methods for removing H2S from gas streams, such as sour well-head gas, refinery waste streams, anaerobic digesters, coal-bed methane, and coal-fired power plant flue gas streams as found in coal gasification plants, are provided. In an embodiment of the invention, hydrogen sulfide species are reacted with a solution of bromine and water to form sulfuric acid (H2SO4) and hydrobromic acid (HBr):
H2S(g)+4Br2(l)+4H2O(l)→H2SO4(l)+8HBr(aq) (79)
ΔH°=−622kJ/mole ΔG°=−540kJ/mole (80)
H2S(g)+4Br2(aq)+4H2O(l)→H2SO4(aq)+8HBr(aq) (81)
ΔH°=−707kJ/mole ΔG°=−610kJ/mole (82)
Bromine oxidizes the sulfide species to sulfuric acid and forms hydrogen bromide (HBr). Reactions (79) and (81) are exothermic. HBr can then be directed to an electrolysis cell (e.g., a reversible fuel cell), where the HBr is electrolyzed to produce hydrogen (H2) and bromine (Br2), which can be recycled to react with H2S per reactions (79) and (81) above. One mole of H2S can yield one mole of H2 and one mole of H2SO4.
H2S(g)+4H2O(l)→H2SO4(aq)+4H2(g) (83)
In this process, 8 pounds (“lb”) of hydrogen and 103 lb of sulfuric acid can be produced for every 32 lb of sulfur removed in H2S. A portion of the spent scrubbing solution can be continually removed and its sulfuric acid content can be concentrated and stored. Both the hydrogen, which is renewable since it is produced from water, and the sulfuric acid, may be sold, consumed internally, or used to make other chemical products, including alternative liquid-fuels.
In another embodiment of the invention, methane can react with bromine and water in the following exothermic reaction:
CH4(g)+4Br2(aq)+2H2O(l)→CO2(g)+8HBr(aq) (84)
ΔH°=−709kJ/mole ΔG°=−716kJ/mole (85)
Methane's limited solubility allows it to pass through a dilute bromine-water solution without reacting with any of the species in solution as long as the temperature is kept between about 50° C. and about 400° C. H2S is about a hundred times more soluble than methane; it reacts at lower temperatures. The reaction yield can be a function of temperature. A scrubbing apparatus may be used to increase the gas/liquid contact and accelerate the processes described above.
In another embodiment of the invention, hydrogen sulfide is reacted with bromine (Br2), e.g., over a catalyst material (or catalyst bed) or under conditions suitable for sulfuric acid production (see above), to yield sulfur and hydrogen bromide:
H2S(g)+Br2(l)→S(s)+2HBr(g) (86)
ΔH°=−12.5kJ/mole ΔG°=−9.9kJ/mole (87)
H2S(g)+Br2(aq)→S(s)+2HBr(aq) (88)
ΔH°=−53.1kJ/mole ΔG°=−34kJ/mole (89)
In other embodiments of the invention, methods for removing a phosphorous-containing chemical, such as, e.g., phosphate, phosphorus, or organophosphorus compounds, from sewage plant and agricultural waste streams, are provided. In an embodiment of the invention, phosphorus is converted to phosphoric acid, which can be removed and used in, e.g., fertilizer. Exemplary exothermic reactions are as follows, wherein ‘R’ denotes a side group, such as, e.g., carbon:
P+2.5Br2+4H2O→H3PO45HBr ΔG°=−34kJ/mole (90)
POR3+1.5Br2+3H2O→H3PO4+3HBr+3R ΔG°=−34kJ/mole (91)
PO2R2+0.5Br2+2H2O→H3PO4+HBr+2R ΔG°=−34kJ/mole (92)
HPO3R+H2O→H3PO4+R(in the presence of halogen) ΔG°=−34kJ/mole (93)
In the reaction above, R may form a different compound during reaction. In some cases, R forms a different compound through reaction with water. For cases in which R is carbon, carbon is oxidized to carbon dioxide, as presented in other embodiments. It will be appreciated that the abovementioned reactions can occur in the liquid (e.g., aqueous solution) or gas phase.
In some embodiments of the invention, phosphorus is converted into other soluble or insoluble compounds, which may be incorporated into unreacted ash or converted into fertilizer.
In another aspect of the invention, devices, apparatuses and systems for removing waste gas are provided.
With reference to
With continued reference to
With reference to
In an embodiment of the invention, the reactor 182 can be a co-current enclosed spray tower. The spraying liquid is an aqueous solution, containing about 15% HBr and about 1% bromine at a temperature of about 65° C. The bromine forms a complex with HBr, which makes it significantly less volatile before reaction. The liquid produced in the reactor 182, a bromine-free aqueous solution of about 10% sulfuric (H2SO4), 10% nitric (HNO3) and 20% hydrobromic (HBr) acids, is sent to the pre-concentrator 181 via a condenser 184, where it is heated by incoming flue gas to evaporate the HBr vapors and most of the water. The pre-concentrator is a counter-current spray tower that outputs a solution of about 70% H2SO4 and HNO3 to the final concentrator 180. In an embodiment of the invention, design temperatures are about 200° C. at the gas inlet to the pre-concentrator 181 and about 120° C. at the gas outlet of the pre-concentrator 181. The liquid leaving the pre-concentrator 181, a solution of about 70% H2SO4 and HNO3, undergoes a final concentration step in the final concentrator 180, where about 93% sulfuric and 62% nitric acid solutions are produced. The final concentrator 180 can be a relatively small counter-current evaporator (or distillation) column where hot flue gases provide the necessary heat to concentrate and distill the H2SO4 and HNO3. In an embodiment of the invention, the hot flue gases directed into the final concentrator 180 are at a temperature between about 100° C. and 500° C., or between about 200° C. and 400° C., or between about 250° C. and 350° C. In the illustrated embodiment of
With continued reference to
The HBr and water vapors boiled off in the pre-concentrator 181 are condensed into aqueous HBr in the condenser 184 and sent to the electrolyzer 186, which may include a stack of proton exchange membrane cells. The concentrated HBr electrolyte is split into hydrogen gas at a cathode and aqueous bromine at an anode of the electrolyzer 186. Process parameters, such as electrolyte flow and current density, are adjusted to control the quantity and concentration of bromine solution required for optimum emission control. In a preferable embodiment of the invention, the solution exiting the electrolyzer 186 is mixed with part of a final solution from the scrubber 183 to form dilute HBr and 1% (by weight) bromine oxidizing spray solution, which is directed into the reactor 182.
With continued reference to
Integrating the Pre-Concentrator, Reactor and/or Scrubber into One Device
With reference to
With continued reference to
As an alternative, the spray nozzles and scrubber section 194 can be replaced with a scrubber that operates to form a froth zone of turbulent and intimate mixing between the flue gas and a scrubbing solution. Such intimate mixing increases the rate of reaction, the surface area of interaction and can serve to quench an incoming hot gas stream. Multiple sections (or stages) may be used in order to transition from a reactor to the scrubber so that both steps can be accomplished in the same vessel. The spray nozzle can have a large bore with less pressure drop than traditional small-bore spray nozzles.
With reference to
With continued reference to
In another aspect of the invention, a system 500 for brominating reactants is provided. With reference to
It will be appreciated that in the illustrated embodiment of
In another aspect of the invention, methods for brominating reactants are provided. In embodiments of the invention, methods are provided for using a first halogen-containing chemical (e.g., Br2) to halogenate (e.g., brominates, chlorinate) a contaminant, such as a carbon-containing chemical, H2S, PM or a HAP, to form a second halogen-containing chemical (e.g., HBr).
With reference to
With reference to
In an embodiment of the invention, electrolytic hydrogen generated from the processes described above may be used for generator cooling; hydrogen-enriched combustion to reduce nitrogen oxide emissions from natural gas combustion; the reduction of carbon monoxide or carbon dioxide to produce methanol and other higher carbon fuels (e.g., ethanol, propanol); and reaction with bromine, oxygen, or air in a fuel cell to generate electricity.
In some embodiments of the invention, hydrogen can be used to cool power plants. Its high heat capacity and low viscosity increases a generator's capacity by efficiently removing excess heat and reducing rotor windage losses. The processes described above produce high purity (i.e., electrolytic grade) hydrogen. A 4% increase in hydrogen purity allows an 800 MW generator to generate about 24 MW of additional electricity without any additional fuel requirement.
If an energy storage/black-start capability is desired, a reversible HBr stack (fuel cell) may be used in place of a dedicated electrolyzer, thereby enabling the production of electricity from the reaction of hydrogen with bromine (Br2) or oxygen (O2). For gas-fired boilers and turbines, hydrogen may be used to improve lean combustion stability limits and reduce the production of NOx. Natural gas enriched with 1% hydrogen can reduce NOx emissions by about 15%; translating to 0.8 kg reduction in NOx emissions for every kilogram of hydrogen. A 5% hydrogen/natural gas blend can reduce NOx by over 50%.
In addition, hydrogen may be combined with a plant's carbon dioxide emissions to produce methanol (CH3OH), or with nitrogen to produce ammonia (NH3), which may be used with selective catalytic reduction (SCR) or combined with CO2 to produce urea, which can be used to reduce NOx in exhaust emissions. Ammonia can also be reacted with sulfuric acid (a by-product of certain reactions; see above for examples) to produce ammonium sulfate.
Sulfuric and nitric acids are prominent chemical commodities consumed globally. The yearly U.S. production of sulfuric acid and nitric acid are greater than 48 and 11 million tons, respectively. Some power plants may not have a convenient market for the acid by-products. In these cases, according to methods of preferable embodiments of the invention, the acid may be reacted with scrap iron or aluminum to produce ferrous sulfate or aluminum sulfate/nitrate, in addition to hydrogen. This reaction advantageously doubles the production of hydrogen and is cost effective because electrolysis (which is energy-intensive) is not used to generate hydrogen.
In other cases the sulfuric acid may be decomposed into sulfur dioxide (SO2), water and oxygen. The purpose of such a process will be to convert the relatively inexpensive sulfuric acid into much more valuable sulfur dioxide, which could be used for alternative sulfur chemistries. These chemistries are understood and can be used in the pulp and paper, water treatment, tanning, food processing and other industries. Nitric acid may also be thermally decomposed for making other compounds or disposing of the acid.
It should be understood from the foregoing that, while particular implementations have been illustrated and described, various modifications can be made thereto and are contemplated herein. It is also not intended that the invention be limited by the specific examples provided within the specification. While the invention has been described with reference to the aforementioned specification, the descriptions and illustrations of embodiments of the invention herein are not meant to be construed in a limiting sense. Furthermore, it shall be understood that all aspects of the invention are not limited to the specific depictions, configurations or relative proportions set forth herein which depend upon a variety of conditions and variables.
Various alternatives and modifications in form and detail of the embodiments of the invention will be apparent to a person skilled in the art. It is therefore contemplated that the invention shall also cover any such alternatives, modifications, variations and equivalents. For example, while certain embodiments provide methods and apparatuses for the using of HBr and Br2, it will be appreciated that other halogen-containing species may be used. In some cases HCl and Cl2 may be used instead of HBr and Br2, respectively; or HF and F2 may be used instead of HBr and Br2, respectively; or HI and I2 may be used instead of (or in place of) HBr and Br2, respectively. As an example, a chlorine-containing compound (e.g., Cl2) can be used in the process flow of
This application claims the benefit of priority to U.S. Provisional Application No. 60/949,994, filed Jul. 16, 2007 and entitled “WASTE TREATMENT AND ENERGY PRODUCTION UTILIZATION HALOGENATION PROCESSES,” which is entirely incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| 60949994 | Jul 2007 | US |
