Patent Application
20240279480
This invention relates to methods and apparatus for recovering and reusing components of tail gas and flue gas produced in carbon black production and tail gas combustion processes.
Carbonaceous fuels and other organic material are combusted in a wide variety of industrial processes. Furnace reactors, combustion engines, combustion chambers, boilers, furnaces, heaters, hot gas generators, burners, waste incinerators, and the like, are used to combust carbonaceous fuels. This combustion equipment may be used to make energy, incinerate waste and byproduct materials, or both. During a typical combustion process within a furnace or boiler, for example, a hydrocarbon feedstock or fuel is combusted in the presence of oxygen or other oxidizing gas, and a flow of a combustion exhaust gas is produced. In some industries, such as in carbon black production, refinery operations, or petrochemical operations, exhaust gases generated in primary process units are conveyed to heaters or boilers for energy production or heat recovery. These operations can generate emissions, which can be subject to any applicable air quality controls or requirements.
A furnace carbon black producing process, for example, typically employs a furnace reactor having a burner or combustion chamber followed by a reactor. A combustion fuel feed stream, typically a hydrocarbon gas stream such as natural gas, or the like, is combusted in the burner portion along with an oxidant feed gas stream such as air, oxygen, or oxygen enriched air to produce hot combustion gases which pass then to the reactor portion of the furnace. In the reactor, hydrocarbon feedstock is exposed to the hot combustion gases. Part of the feedstock is burned, while the rest is decomposed to form carbon black, hydrogen, carbon monoxide, and other gaseous products. The reaction products typically are quenched with water, and the resulting product stream, a mixture of carbon black and tail gas, is cooled, conveyed to a bag collector or other filter system, whereupon the carbon black content is separated from the tail gas. The recovered carbon black typically is finished to a marketable product, such as, for example, by pulverizing and wet pelletizing. Water from the pelletizing typically is driven off with a dryer, which may be gas-fired, oil-fired, process-gas fired such as with tail gas, or combinations of these. The dried pellets can then be conveyed from the dryer to bulk storage or other handling. The dryer also can generate gaseous emissions. The principal source of emissions in the carbon black furnace process typically is from the tail gas. Other than direct venting, tail gas emissions have been discharged using flares. The tail gas can contain combustible gas components. This tail gas may be advantageously combusted to generate heat for a dryer as described above or for other uses. Following combustion, the resulting flue gas typically may include carbon dioxide, water, nitrogen, oxygen, and other species. The carbon dioxide may be separated from the flue gas and sequestered to reduce greenhouse gas emissions. However, it is desirable to make more efficient use of various gas species present in the tail gas and flue gas. Moreover, it is desirable to increase the concentration of carbon dioxide in the flue gas to improve the efficiency of greenhouse gas separation processes prior to any discharge of the flue gas.
In one aspect, a method to produce carbon black comprises, in a carbon black reactor comprising a combustion zone, at least one feedstock injection zone downstream of the combustion zone, and at least one reaction zone downstream of the first feedstock injection zone, converting in the reaction zone(s) a hydrocarbon feedstock to carbon black in the presence of combustion gases generated in the combustion zone by burning a fuel in an oxidation gas mixture comprising 20-85 vol % carbon dioxide, 15-80 vol % oxygen, at most 30 vol % water, and at most 35 vol % nitrogen, to form a first product stream comprising carbon black, carbon dioxide, carbon monoxide, water vapor, and hydrogen, wherein the fuel is a portion of the hydrocarbon feedstock or a separate fuel source and wherein at least a portion of the hydrocarbon feedstock is contacted with the combustion gases in the at least one feedstock injection zone. The method further includes adding water to the first product stream to at least partially halt the conversion and form a second product stream comprising carbon black, carbon dioxide, carbon monoxide, hydrogen, and water vapor, removing the carbon black from the second product stream to form a tail gas, decreasing the carbon monoxide and hydrogen content in at least a portion of the tail gas to produce a flue gas, decreasing the carbon monoxide and hydrogen content in at least a portion of the tail gas to produce a flue gas comprising at most 40 vol % nitrogen, and directing at least a first portion of the flue gas to at least one of the combustion zone, the at least one feedstock injection zone, and the at least one reaction zone.
The first product stream may further include sulfur-containing species, and removing water may further include removing at least a portion of the sulfur-containing species from the first portion of the flue gas, a second portion of the flue gas, or both. Decreasing may include combusting the tail gas, separating and recovering at least a portion of the hydrogen from the tail gas, or both. The first product stream and second product stream may each contain carbon monoxide, and decreasing may further include combusting the tail gas following separating and recovering. The method may further include removing water from the tail gas prior to removing hydrogen. The method may further include directing at least a portion of the tail gas to the combustion zone. The method may further include removing water from the tail gas prior to directing at least a portion of the tail gas, and the removed water may be directed for use in step (b).
The method may further include combining the first portion of the flue gas with an oxidation reagent prior to directing, wherein the oxidation gas mixture comprises the combined first portion of the flue gas and oxidation reagent, and the combined first portion of the flue gas and oxidation reagent may be directed to the combustion zone, the reaction zone, or both. The method may further include heating the first portion of the flue gas before combining. The method may further include heating the combined first portion of the flue gas and the oxidation reagent. The method may further include heating the first portion of the flue gas prior to directing. The method may further include combining the first portion of the flue gas with the hydrocarbon feedstock prior to directing, wherein the combined flue gas and hydrocarbon feedstock are directed to the at least one feedstock injection zone. The method may further include heating the combined first portion of the flue gas and hydrocarbon feedstock. The method may further include heating the first portion of the flue gas to form a hot flue gas and combining the hot flue gas with the hydrocarbon feedstock prior to directing. The method may further include heating the first portion of the flue gas with an energy source selected from a microwave, a plasma, and a resistive heating element.
The method may further include removing water from the first portion of the flue gas to produce a dewatered flue gas comprising at most 35 vol % water, and the removed water may be directed for use in step (b). The method may further include pelletizing at least a portion of the carbon black by combining the portion with a liquid, forming carbon black beads, and drying the carbon black beads to reduce the water content to at most 1 wt %, wherein drying comprises heating the dewatered flue gas and contacting carbon black beads with the heated dewatered flue gas. The method may further include diverting a portion of the dewatered flue gas and removing at least a portion of the carbon dioxide from the diverted dewatered flue gas. The method may further include either or both of condensing and storing the carbon dioxide removed from the diverted dewatered flue gas.
Where the flue gas is dewatered, the method may further include providing the oxidizing gas by allowing liquid oxygen to evaporate, wherein the method further comprises transferring thermal energy from the dewatered flue gas to the liquid oxygen. Removing the carbon black may include passing the second product stream through a filter that separates the second product stream into carbon black and tail gas, wherein the method further comprises using the dewatered flue gas to purge solid particulates from the filter. Removing the carbon black may include passing the second product stream through a cyclone separator, and the method may further include employing a portion of the dewatered flue gas to separate the tail gas and the carbon black in the cyclone separator. The method may further include compressing at least a portion of the dewatered flue gas, and removing the carbon black may further include passing the second product stream through a filter, and optionally using the compressed dewatered flue gas to clean the filter. Decreasing may include combusting the tail gas in a burner, and the method may further include using the compressed dewatered flue gas to clean the burner.
Adding water may further include adding at least a portion of the first portion of the flue gas to the first product stream to halt the conversion.
In another aspect, carbon black is formed using any combination or subcombination of the method steps outlined above.
In another aspect, an apparatus for producing carbon black includes a carbon black reactor including a combustion zone for combusting an oxidation gas mixture and a fuel to generate a heated gas stream, a first feedstock injection zone for injecting a hydrocarbon feedstock into the heated gas stream to form a product stream, a first reaction zone in which carbon black is formed in the product stream, a first quench injector, and a first quench zone in which the carbon black is at least partially quenched with quench fluid injected from the first quench injector into the product stream. The apparatus further includes a separator in fluidic communication with the first quench zone in which the carbon black is separated from the product stream to form a tail gas, a thermal oxidizer configured to combust the tail gas with additional oxidation gas to form a hot flue gas, and a first flue gas heat exchanger that removes thermal energy from the hot flue gas to form a cooled flue gas The outlet is in fluidic communication with and upstream of at least one of the combustion zone, the first feedstock injection zone, and the first reaction zone.
The apparatus may further include a scrubber cooler including a sulfur-species scrubber and a water condenser. The scrubber cooler is to remove sulfur-containing species and water from at least a portion of the cooled flue gas, thereby producing dewatered flue gas, and includes an outlet through which the dewatered flue gas is discharged. The outlet of the scrubber cooler may further be in fluidic communication with a heater. The apparatus may further include a carbon black pelletizer configured to receive at least a portion of the heated dewatered flue gas, which then dries carbon black pellets formed in the pelletizer. The separator may include a bag filter, and the apparatus may be operable to direct at least a portion of the dewatered flue gas to periodically purge particulate solids from the bag filter. The apparatus may further include a carbon capture system operable to remove at least a portion of carbon dioxide present in the dewatered flue gas.
The heat exchanger may be a boiler in which thermal energy from the hot flue gas is transferred to water. The apparatus may further include a compressor configured to receive the flue gas from the outlet and discharge compressed flue gas. The apparatus may be configured to direct at least a portion of the tail gas to the combustion zone. The apparatus may further include a condenser upstream of the combustion zone configured to remove water from the tail gas. The apparatus may further include a hydrogen removal device upstream of the combustion zone configured to remove hydrogen from the tail gas. The apparatus may further include a second quench injector and a second quench zone in which the at least partially quenched carbon black is further quenched with quench fluid injected from the second quench injector into the product stream.
The apparatus may further include a heater disposed between the outlet and the at least one of the combustion zone and the first reaction zone to heat at least a portion of the flue gas. The heater includes a microwave source, a plasma source, or a resistive heating element. The apparatus may further include a heat exchanger to receive the product stream from the first quench zone, wherein the heat exchanger is operable to exchange heat of the product stream with at least a portion of the flue gas to heat the portion of the flue gas to a temperature from 400 to 950° C.
The apparatus may be configured to combine at least a portion of the flue gas with the additional oxidation gas and direct the combined flue gas and additional oxidation gas to the thermal oxidizer. The combustion zone, the first reaction zone, or both, may be configured to receive the oxidation gas mixture, which in turn comprises a mixture of the portion of the mass of the cooled flue gas and an oxidation reagent. That is, a portion of the cooled flue gas may be further processed, for example, by removal of sulfur and/or containing species, removal of water vapor, heating, compression, or more than one of these, and the processed portion of the cooled flue gas is then combined with the oxidation reagent.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the present invention, as claimed.
The invention is described with reference to the several figures of the drawing, in which,
In one embodiment, a method to produce carbon black includes, in a carbon black reactor having a combustion zone, at least one feedstock injection zone downstream of the combustion zone, and at least one reaction zone downstream of the first feedstock injection zone, converting in the reaction zone(s) a hydrocarbon feedstock to carbon black in the presence of combustion gases generated in the combustion zone by burning a fuel in an oxidation gas mixture comprising 20-85 vol % carbon dioxide, 15-80 vol % oxygen, at most 30 vol % water, and at most 35 vol % nitrogen to form a first product stream comprising carbon black, carbon dioxide, carbon monoxide, hydrogen, and water vapor, wherein the fuel is a portion of the hydrocarbon feedstock or a separate fuel source, e.g. burner fuel 24. Water is added to the first product stream to substantially halt the conversion and form a second product stream comprising carbon black, carbon dioxide, carbon monoxide, hydrogen, and water vapor. Carbon black is removed from the second product stream to form a tail gas, which is processed to oxidize and optionally remove oxidizable species such as carbon monoxide and hydrogen to produce a flue gas comprising at most 40 vol % nitrogen, and at least a portion of the flue gas is directed to the at least one of the combustion zone, the at least one feedstock injection zone, and the at least one reaction zone. The flue gas may optionally be processed to reduce the concentration of SOx, NOx, and water vapor to produce a dewatered flue gas.
The methods and apparatus of the various embodiments and implementations can be used to modify any furnace carbon black reactor known to those of skill in the art. For example, these methods and apparatus may be used to modify furnace carbon black reactors such as those described in U.S. Pat. Nos. 3,922,335; 4,383,973; 5,190,739; 5,877,250; 5,904,762; 6,153,684; 6,156,837; 6,403,695; 6,485,693; 7,829,057; 8,871,173; and 10,829,642, the entire contents of all of which are incorporated by reference. In an exemplary embodiment shown in
Carbon black yielding feedstock may be introduced into feedstock injection zone 14 radially, axially or both. Carbon black yielding feedstock is typically heated prior to introduction. As shown in
Optionally, and as shown in
Among the fuels suitable for use in reacting with the oxidation gas mixture in combustion zone 12 to generate the hot combustion gas stream are included any readily combustible gas, vapor, and/or liquid stream such as natural gas, coal gas, biomass gas, biomass liquid, liquid fuel generated from a chemical process byproduct stream, hydrogen, carbon monoxide, methane, acetylene, alcohols, kerosene, or any gas having a lower heating value (LHV) greater than 2 MJ/Nm3. Combinations of these may also be employed. It is generally preferred, however, to utilize fuels having a high content of carbon-containing components, and, in particular, hydrocarbons. For example, any of the carbon black-yielding feedstocks listed below may also be employed as a burner fuel 24. The burner fuel 24 may be injected into combustion zone 12 at any temperature from its ambient temperature (i.e., without any heating or cooling) to 800° C. To facilitate the generation of hot combustion gases, oxidation reagent 26, the oxidation gas mixture comprising oxidation reagent 26, or other components of the oxidation gas mixture may be preheated before or after mixing, for example, to a temperature from 400-950° C. For example, in
The carbon black-yielding feedstock that can be employed with the present invention can include any hydrocarbon gas, liquid or oil feedstocks useful for carbon black production. Suitable liquid feedstocks include, for example, unsaturated hydrocarbons, saturated hydrocarbons, olefins, aromatics, and other hydrocarbons such as biomass-derived liquids, decant oil, coal tar derived liquids, asphaltene containing oils, kerosenes, naphthalenes, terpenes, ethylene tars, cracker residues, oils produced from recycled materials, or any combinations thereof. In general, any hydrocarbon-containing liquid with at least 60 wt % carbon content may be employed. Suitable gaseous feedstocks include, for example, natural gas, methane, ethylene, acetylene, and other C4-C6 hydrocarbon gases. Any of these feedstocks may be processed using techniques known to those of skill in the art to remove sulfur or other undesirable species prior to use. The carbon black-yielding feedstock 28 may be injected into feedstock injection zone 14 or subsequent injection zone(s) as discussed above at any temperature from its ambient temperature (i.e., without any heating or cooling) to 500° C. for liquid feedstocks or to 900° C. for gaseous feedstocks.
Also, any of the feedstocks for the described process schemes and methods can contain additional materials or compositions which are commonly used to make conventional carbon black. The method of the present invention can further include introducing at least one substance that is or that contains at least one Group IA and/or Group IIA element (or ion thereof) of the Periodic Table. The substance containing at least one Group IA and/or Group IIA element (or ion thereof) contains at least one alkali metal or alkaline earth metal. Examples include lithium, sodium, potassium, rubidium, cesium, francium, calcium, barium, strontium, or radium, or combinations thereof. Any mixtures of one or more of these components can be present in the substance. The substance can be a solid, solution, dispersion, gas, or any combinations thereof. More than one substance having the same or different Group IA and/or Group IIA metal (or ion thereof) can be used. If multiple substances are used, the substances can be added together, separately, sequentially, or in different reaction locations. For purposes of the present invention, the substance can be the metal (or metal ion) itself, a compound containing one or more of these elements, including a salt containing one or more of these elements, and the like. The substance can be capable of introducing a metal or metal ion into the reaction that is ongoing to form the carbon black product. For purposes of the present invention, the substance containing at least one Group IA and/or IIA metal (or ion thereof), if used, can be introduced at any point in the reactor, for example, prior to the complete quenching. The amount of the Group IA and/or Group IIA metal (or ion thereof) containing substance, if used, can be any amount as long as a carbon black product can be formed. The substance can be added in the same manner that a carbon black yielding feedstock is introduced. The substance can be added as a gas, liquid, or solid, or any combination thereof. The substance can be added at one point or several points and can be added as a single stream or a plurality of streams. The substance can be mixed in with the feedstock, fuel, and/or oxidant prior to or during their introduction.
In addition to carbon black, the product stream contains carbon dioxide, carbon monoxide, hydrogen, and water vapor. Water vapor is present before quenching and the product stream becomes more humid as a result of the quench. In addition, the product stream may include some nitrogen, acetylene, SOx, NOx, and other species that are typically generated during furnace carbon black production processes. Following quenching, the product stream containing hot carbon black can be passed through one or more heat exchangers, for example, through heat exchanger 30. The use of the heat extracted thereby is discussed in more detail below. As shown in
After the product stream is quenched, it passes downstream into any conventional separating and cooling steps whereby the carbon black is recovered, denoted in
Carbon black 37 may be any conventional carbon black. For example, carbon black 37 may be any of the N-series carbon blacks in accordance with ASTM D-1765, for example, an N100, N200, N300, N500, N600, N700, N800, or N900 series carbon black. More particular examples of ASTM N-series carbon blacks include N110, N121, N134, N 220, N231, N234, N299, N326, N330, N339, N347, N351, N358, N375, N550, N660, N683, N762, N765, N774, or N990 carbon blacks. Alternatively or in addition, carbon blacks produced according to the embodiments provided herein may have a structure, as given by the oil adsorption number for the carbon black, (OAN, ASTM D-6556) from 30 to 450 mL/100 g, for example, 30 to 100 mL/100 g, from 100 mL/100 g to 200 mL/100 g, from 200 mL/100 g to 300 mL/100 g, or from 300 mL/100 g to 450 mL/100 g. Alternatively or in addition, and in combination with any of the structure values provided above, the carbon black may have a surface area (BET surface area, ASTM D-2414) from 5 to 1800 m2/g, for example, from 8 m2/g to 150 m2/g, from 150 m2/g to 350 m2/g, from 350 m2/g to 600 m2/g, from 600 m2/g to 900 m2/g, from 900 m2/g to 1300, or from 1300 m2/g to 1800 m2/g. The carbon black may be used in any end-use application in which carbon black is exploited, for example, as a pigment, reinforcing agent, filler, and/or thermal and/or electrical conductor and be useful in elastomers, plastics, polymers, toners, inks, batteries, adhesives, coatings, and the like.
In the embodiment shown in
While oxidation reagent 26 and oxidation reagent 26A may include air, the oxidation reagent preferably does not include substantial amounts of nitrogen such as are found in air. For example, oxidation reagent 26 and/or oxidation reagent 26A may comprise 80-100% oxygen by volume, for example 90-100 vol % oxygen. Such oxygen may be compressed oxygen or more preferably liquified oxygen which has been allowed to evaporate. Alternatively or in addition, oxidation reagent 26 and/or oxidation reagent 26A may be produced from air or other gases using pressure swing adsorption or other methods known to those of skill in the art such as cryogenic air separation processes to increase the oxygen gas concentration. Such processes may leave small amounts of nitrogen, argon, or other gases in oxidation reagent 26 and/or oxidation reagent 26A. In some embodiments, oxidation reagent 26 comprises up to 40 vol % nitrogen, for example, 2 vol %-30 vol %, 3 vol %-20 vol %, or 5 vol %-10 vol % nitrogen. The less nitrogen employed in the oxidation reagent 26 and/or oxidation reagent 26A, the more concentrated the resulting dewatered flue gas 48 will be in carbon dioxide. Recycling the flue gas through the furnace carbon black reactor 10 can partially or completely obviate the use of air or other externally provided gases as a diluent for oxidation reagent 26 and/or oxidation reagent 26A, e.g., as a part of the oxidation gas mixture, further reducing the use of nitrogen in the system.
The oxidation reagent 26 employed in carbon black reactor 10 may be different than the oxidation reagent used in the downstream processes to process tail gas 38. For example, an alternative oxidation reagent 26A, which may be air or pressurized air, may be used to supply thermal oxidizer 40 (see
Alternatively or in addition, additional carbon dioxide from a separate source may be directed into combustion zone 12 and/or reaction zone 16. For example, carbon dioxide 108 may be combined with oxidation reagent 26 (
In an alternative embodiment, tail gas 38 may be directed to several parallel processes in which tail gas 38 is processed and the energy therein exploited. As shown in
The scrubbed flue gas 46A emerging from scrubber 47, which may have any water vapor content resulting from the previous unit processes, e.g., 40-50 vol %, is then dewatered in gas dryer 49. Gas dryer 49 may employ apparatus known to those of skill in the art for dewatering gases, including both direct and indirect methods. Direct methods include use of cooling water to contact scrubbed flue gas 46A in a cooling scrubber or in a venturi mixer and scrub tank. Alternatively, a cooling reagent such as water, ammonia, glycol, etc., may be used to dewater the scrubbed flue gas 46A in a heat exchanger, with the cooling reagent recycled through a condenser to remove the heat transferred from the scrubbed flue gas 46A. The cooled water 50 may be discharged as wastewater 51 and/or recycled for use as at least a portion of process water 22. As shown in
Dewatered flue gas 48 may be employed in several unit processes in the furnace carbon black reactor 10 and the downstream processing of the resulting carbon black and other by-products. For example, it may form part of the oxidation gas mixture in which burner fuel 24 is combusted in combustion zone 12. As shown in
Alternatively or in addition, dewatered flue gas 48 may be combined with oxidation reagent 26 and the resulting oxidation gas mixture heated prior to introduction into combustion zone 12, reaction zone 16, or subsequent reaction zone(s) as described above. As shown in
The compressed dewatered flue gas 57 may be used to support any process in furnace carbon black reactor 10 or the associated downstream processes shown in the various figures that require compressed gas. For example, the compressed dewatered flue gas 57 may be used to cool sight glasses or a pilot burner in carbon black reactor 10. Alternatively or in addition, it may be used to blow soot off of boiler 44 and/or thermal oxidizer 40. The compressed dewatered flue gas 57 may be used to blow soot off an SCR catalyst in scrubber 47. The increased carbon dioxide concentration also allows dewatered flue gas 48, preferably following compression to compressed dewatered flue gas 57, to be used as a process gas for cleaning separator 36 (
Alternatively or in addition, the dewatered flue gas 48 may be used to further process the carbon black. Carbon black is frequently compressed into pellets to reduce dusting and ease handling. To improve the handling characteristics of the relatively fluffy carbon black, it is frequently agglomerated by various mechanical processes to produce pellets, either in the dry state or with the aid of a liquid pelletizing aid. Generally the carbon black particles are held together by weak forces. Processes for pelletizing carbon blacks to produce carbon black pellets are known in the art. For example, U.S. Pat. No. 2,065,371 to Glaxner describes a wet pelletization process whereby the fluffy carbon black and a liquid such as water are combined and agitated until generally spherical carbon black beads are formed. Typical carbon black pellets are about a millimeter in size. In addition to water, a wide variety of binder additives are known to be useful in the wet pelletization process to further improve the pellet handling characteristics of the fluffy carbon blacks. Such additives include but are not limited to hygroscopic organic liquids such as ethylene glycol, carbohydrates (e.g., sugar, molasses, soluble starches, saccharides, lignin derivatives), rosin, sulfonate and sulfate anionic surfactants, fatty amine ethoxylate nonionic surfactants, sodium ligno sulfonates, silanes, sucrose, alkyl succinimides, alkylated succinic esters, and polyethylene oxide-co-polydimethyl siloxane surfactants. The beads are then dried to reduce the water content to at most 1% to form carbon black pellets. The dewatered flue gas 48 may be heated and used to dry the carbon black pellets through direct contact in the dryer. Dewatered flue gas 48 may be heated in heat exchanger 30 or using alternative heating methods as described below. For example, in
The enhanced carbon dioxide concentration of dewatered flue gas 48 provides several advantages for the operation of furnace carbon black reactor 10 and downstream processes for collecting carbon black and other byproducts. In one embodiment, at least a portion of dewatered flue gas 48 may be diverted to a carbon capture system, e.g. carbon capture system 52. The increased partial pressure of carbon dioxide in dewatered flue gas 48 can improve the efficiency of carbon capture system 52. Carbon capture system 52 may include any carbon dioxide separation, utilization, sequestration and/or storage system known to those of skill in the art, for example, a physical adsorption based process (for example, using activated carbon, methanol, glycol, or other solvents that can engage in van der Waals interactions with carbon dioxide), a chemical absorption process (for example, employing an amine-based solvent, inorganic alkaline solutions such as potassium carbonate or sodium carbonate, or other chemicals that can form a weak chemical bond with carbon dioxide and be easily regenerated), and/or a membrane separation process (for example, using ceramic or zeolite membranes). Physical adsorption processes include but are not limited to thermal swing adsorption, pressure swing adsorption, and partial pressure swing adsorption. Carbon dioxide separation may also include drying processes, for example, by using a chiller, pressure swing adsorption, or other suitable process to remove water and then condensing carbon dioxide while removing lower boiling point gases such as oxygen and argon. Carbon dioxide separation processes may also remove oxygen, for example, excess oxygen that was not consumed in thermal oxidizer 40. Following separation, carbon dioxide 90 (
Alternatively or in addition, at least a portion of cooled flue gas 46 may be diverted and blended with dewatered flue gas 48 before the combined flue gas stream is used in the various combustion processes described herein. For example, in
As for dewatered flue gas 48, flue gas mixture 118 may be compressed to achieve a desired pressure. For example, in
Alternatively or in addition, the dewatered flue gas 48 or flue gas mixture 118 may be used as an atomizing gas for the injection of carbon black yielding feedstock in feedstock injection zone 14 or subsequent feedstock injection zone(s) as described above (
Alternatively or in addition, the enhanced carbon dioxide content of dewatered flue gas 48 and/or flue gas mixture 118 enables additional techniques for heating the dewatered flue gas 48 and/or flue gas mixture 118 as desired, for example, prior to injection into combustion zone 12 or reaction zone 16, prior to mixing with oxidation reagent 26, or prior to use as an atomizing gas for carbon black yielding feedstock 28. This can reduce or eliminate the need for combustion techniques to heat carbon black yielding feedstock 28 or oxidation reagent 26. Because of the low hydrocarbon and limited oxidizing content of dewatered flue gas 48 and flue gas mixture 118, they can be heated not only by combustion methods but also by electrically powered methods such as resistive heating elements, microwaves, or a thermal plasma, e.g., a direct arc plasma. For example, dewatered flue gas 48 and flue gas mixture 118, with or without compression, may be directly heated with an electrically powered heating element that can supply energy at elevated temperature. Preferably, the heating element is fabricated form a corrosion- and high temperature-resistant material such as zirconia, molybdenum carbide, silicon carbide, and other such materials known to those of skill in the art. Likewise, microwaves or an electric current could be passed through dewatered flue gas 48 or flue gas mixture 118. The electric current creates a plasma; microwave heating may also create a plasma depending on the microwave energy.
Moreover, the use of dewatered flue gas 48 or flue gas mixture 118 as a carrier gas or as part of the oxidation gas mixture potentially reduces the amount of gas delivered to the combustion zone 12 in proportion to the desired amount of oxygen. While air is only about 21% oxygen by volume, a synthetic gas prepared with dewatered flue gas 48 or flue gas mixture 118, with or without compression and/or heating, and purified (e.g., compressed or liquified/evaporated) oxygen can have an arbitrary proportion of oxygen, reducing the total amount of gas needed and essentially concentrating the carbon black content of the product stream. The reduced amount of gas employed to carry the carbon black product can increase the reactor throughput by allowing more carbon black to be produced for a given volume of the product stream. Moreover, the enhanced carbon dioxide content of dewatered flue gas 48 or flue gas mixture 118 in comparison to air may increase the amount of carbon black that can be produced from a given amount of carbon black yielding feedstock (yield efficiency).
The oxidation gas mixture in which burner fuel 24 is combusted may include 20-85 vol % carbon dioxide, 15-80 vol % oxygen, at most 30 vol % water vapor, and at most 35 vol % nitrogen. Small amounts of other materials, such as argon, NOx, SOx, CO, and other components commonly found in compressed oxygen, compressed nitrogen, flue gases, and air may also be present. For example, the oxidation gas mixture can include 30-80 vol %, 40-75 vol %, 45-70 vol %, or 50-60 vol % carbon dioxide. Alternatively or in addition, the oxidation gas mixture can include 20-70 vol % or 25-60 vol % or 30-50 vol % oxygen. Alternatively or in addition, the oxidation gas mixture can include 0.1-20 vol %, 0.5-15 vol %, 1-10 vol %, or 2-5 vol % water. Alternatively or in addition, the oxidation gas mixture can include 2 vol %-35 vol % nitrogen, 4 vol %-25 vol % nitrogen, 5 vol %-15 vol %, or up to 10 vol % nitrogen.
Where at least a portion of cooled flue gas 46 is recycled, dewatered flue gas 48 need not be recycled to furnace carbon black reactor 10. Rather, dewatered flue gas 48 may be directed to carbon capture system 52, with a portion optionally diverted for use as a process gas (
The use of a low-nitrogen oxidation gas mixture also enables more beneficial use of the tail gas 38. For example, the reduced concentration of nitrogen also increases the proportion of hydrogen in the tail gas 38. Alternatively or in addition, at least a portion of tail gas 38 may be dewatered in tail gas processor 100 (
Hydrogen can be optionally removed from the tail gas in tail gas processor 100 before or after dewatering using any method known to those of skill in the art, including hydrogen permeable membranes, pressure swing adsorption, and other swing methods. The resulting hydrogen 104 may be recycled for various uses including as rocket fuel, in fuel cells to generate electricity (for example, for zero-emissions vehicles), in hydrodesulfurization processes for fossil fuels, in the Haber-Bosch process for producing ammonia, as a reducing agent to recover metals such as tungsten and copper from various ores, and to hydrogenate oils and fats for use in food, to produce chemicals such as methanol and hydrogen peroxide, and in other industrial processes. Following dewatering and optional hydrogen removal, the processed tail gas 106 may be combusted, e.g., in a device similar to tail gas burner 60, firing box 68, or thermal oxidizer 40. In embodiments where hydrogen is removed from the tail gas 38, the primary combustible gas in the processed tail gas 106 will be carbon monoxide, further reducing the amount of oxidant, e.g., oxidation reagent 26A, required to combust the tail gas.
Alternatively or in addition, the increased concentration of hydrogen and carbon monoxide in tail gas 38 in comparison to a tail gas generated with the use of air in carbon black reactor 10 makes the tail gas 38, following dewatering, especially suitable for reuse as at least a portion of burner fuel 24 (
Alternatively or in addition, at least a portion of the tail gas 38 may be pressurized. Equipment using compressed tail gas can be operated at higher pressures or can be smaller, or both, since the volume of tail gas is less. For example, use of compressed tail gas from compressor 112 (
Two typical carbon black product grades production processes were simulated based on empirical furnace operation parameters, carbon black product yield correlations etc. The two types of CB grade simulated include a Semi-reinforced grade of ASTM N-500 and 600 series carbon blacks (low surface area, or LS carbon black) and reinforced grade of ASTM N-100 to 300 series carbon blacks (high surface area, or HS carbon black).
For all the production process simulated, similar feedstock and natural gas fuel are used. Their characteristics can be represented in Table 1 and Table 2 respectively.
In this example, the carbon black product is produced using a furnace carbon black reactor 10 shown in
Table 3 summarizes the key process parameters for LS grade carbon black production following this process.
In this comparative example, there will be 49,429 Nm3/h of dewatered flue gas 148 to be processed in the CO2 capturing unit. This gas stream contains 8.06 vol. % of CO2 (Table 4).
In this example, the carbon black product is produced using a furnace carbon reactor 10 having a similar configuration to that employed in Comparative Example 1 but employing flue gas recycling as shown in
The resulting tail gas 38 is also combusted with the oxidation reagent 26A of oxygen (97 vol. % of O2 and 3 vol. % N2) mixed with dewatered flue gas 48B to target a desired flame temperature and level of excess oxygen concentration in the hot flue gas 42 and generate about 28.6 MW of thermal energy. Similar to Comparative Example 1, hot flue gas 42 from combustion of tail gas 38 will be cooled in boiler 44 to generate steam 45. After removing NOx and SOx to the desired permit level, the scrubbed flue gas 46A is dewatered at 40° C. (cooling duty for dewatering ˜19.9 MW). A slip stream of the resulting dewatered flue gas 48 is partially (48A) recycled back to mix with oxygen to form the oxidation gas mixture and preheated in heat exchanger 30 to the desired temperature before entering into the burner. Stream 48B is a slip stream of the dewatered flue gas 48, which is recycled back to mix with oxidation reagent 26A to be used as oxidant for thermal oxidizer 40. The balance of the dewatered flue gas 48 is sent to the CO2 capturing unit 52 for CO2 removal. The key parameters for this example are summarized in Table 5 below.
In this example, there will be 4,697 Nm3/h of dewatered flue gas that needs to be processes in the CO2 capturing unit. This gas stream contains 84.86 vol. % of CO2 (Table 6).
In this Comparative Example 3, high surface area grade carbon black is produced using a conventional recipe as described in Example 1 but with a quench length of about 1-10 m. The carbon black product processing, tail gas combustion, energy recovery and flue gas treatment generally follow the same protocol as shown in Example 1. The key process parameters for this Example are summarized in Table 7 below. Combustion of tail gas 138 results in about 36.9 MW of thermal energy, and a cooling duty of about 25.6 MW is required to dewater the scrubbed flue gas 146A.
In this comparative example, there will be 60,588 Nm3/h of dewatered flue gas to be processed in the CO2 capturing unit. This gas stream contains 10.18 vol. % of CO2 (Table 8).
In this Example 4, high surface area grade carbon black is produced using a process similar to that described in Example 2 but with a quench length of 1-10 m. The carbon black product processing, tail gas combustion, energy recovery and flue gas treatment generally follow the same protocol as shown in Example 2. The key process parameters for this Example are summarized in Table 9 below. Combustion of tail gas 38 results in about 39.3 MW of thermal energy, and a cooling duty of about 27.1 MW is required to dewater the scrubbed flue gas 46A.
In this example, there will be 7,410 Nm3/h of dewatered flue gas to be processed in the CO2 capturing unit. This gas stream contains 85.08 vol. % of CO2 (Table 10).
In this Example 5, high surface area grade carbon black is produced using the same apparatus as in Example 4. Instead of pure oxygen, oxygen enriched air (containing 40 vol % O2 and 60 vol % N2) is used as the oxidation reagent 26A in thermal oxidizer 40. The oxidation reagent 26 contains 3 vol % N2 and 97 vol % O2. The carbon black product processing, tail gas combustion, energy recovery and flue gas treatment generally follow the same protocol as shown in Example 2. The key process parameters for this Example are summarized in Table 11 below. Combustion of tail gas 38 results in about 39 MW of thermal energy, and a cooling duty of about 29 MW is required to dewater the scrubbed flue gas 46A.
In this Example 6, high surface area grade carbon black is produced using the same apparatus as in Example 4. A similar composition for oxidation reagent 26 and oxidation reagent 26A (3 vol % N2 and 97 vol % O2) is used in this example as in Example 4. This Example demonstrates the impact of higher moisture content in the dewatered flue gas 48 dewatered at 55° C. The key process parameters for this Example are summarized in Table 13 below. Combustion of tail gas 38 results in about 41 MW of thermal energy, and a cooling duty of about 29 MW is required to dewater the scrubbed flue gas 46A.
In this Example 7, low surface area grade carbon black is produced using the same apparatus as in Example 2. Instead of pure oxygen, air is used as the oxidation reagent 26. Oxidation reagent 26A contains 3 vol % N2 and 97 vol % O2. The carbon black product processing, tail gas combustion, energy recovery and flue gas treatment generally follow the same protocol as shown in Example 2. The key process parameters for this Example are summarized in Table 15 below. Combustion of tail gas 38 results in about 28 MW of thermal energy, and a cooling duty of about 19 MW is required to dewater the scrubbed flue gas 46A.
The foregoing description of preferred embodiments of the present invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Modifications and variations are possible in light of the above teachings, or may be acquired from practice of the invention. One of skill in the art will recognize that a wide variety of alternative system configurations are provided by the various embodiments described herein and depicted schematically in the figures. It is expected that the skilled artisan will be able to, with the benefit of the present disclosure, easily adjust the configuration and process parameters for desired operation of a furnace carbon black reactor according to the various embodiments of the invention. The embodiments were chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2022/034713 | 6/23/2022 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63214497 | Jun 2021 | US | |
| 63240062 | Sep 2021 | US |
