PROCESS FOR USING SEQUESTERED CARBON DIOXIDE IN FUELS AND CHEMICALS

Abstract

A process to optimize carbon from carbon dioxide in synthesis gas used to produce synthetic chemicals and fuels. The process involves using captured carbon dioxide from any source and controlling its reformation with gaseous hydrocarbons to produce a synthesis gas with a specific carbon monoxide to hydrogen ratio suitable for selected intermediate and end products. The carbon from carbon dioxide displaces fossil carbon and lowers the carbon intensity of the products. The process uses any hydrocarbon gas, fossil or renewable, and may utilize steam to optimize the synthesis gas composition. The invention also includes recycling gases and the generation of heat, steam and electrical power for the reformer and other equipment, significantly reducing the carbon footprint of the plant.

Claims

1. A process to produce a synthesis gas comprising at least carbon from carbon dioxide: a. extracting and collecting gases containing at least carbon dioxide from a source; b. cleaning the gases containing at least carbon dioxide of impurities if required in downstream process operations; c. pressuring the gases containing at least carbon dioxide and feeding to a heated pressurized catalytic reactor; d. cleaning a gas stream containing at least gaseous hydrocarbons of impurities if required in downstream process operations; e. pressurizing the gas stream containing at least gaseous hydrocarbons if required and feeding to the heated pressurized catalytic reactor; f. adding a calculated volume of steam to the reactor such as to promote the reactions to produce a synthesis gas containing at least carbon monoxide and hydrogen in a ratio which favors the production of an end product; g. feeding the formed synthesis gas containing at least the desired ratio of carbon monoxide to hydrogen to a reactor or series of reactors to produce an end product comprising at least carbon from the input carbon dioxide.

2. A process to produce a synthesis gas comprising at least carbon from carbon dioxide as in claim 1 where the input gases containing at least carbon dioxide have been captured from flue gas emitted by a process which uses biomass, fossil fuel or flare gas;

3. A process to produce a synthesis gas comprising at least carbon from carbon dioxide as in claim 1 where the gases containing at least carbon dioxide are produced by anaerobic digestion or fermentation;

4. A process to produce a synthesis gas comprising at least carbon from carbon dioxide as in claim 1 where the gases containing at least carbon dioxide are captured from a synthesis process;

5. A process to produce a synthesis gas comprising at least carbon from carbon dioxide as in claim 1 where the gases containing at least carbon dioxide or gaseous hydrocarbons are recycled from any step in the process;

6. A process to produce a synthesis gas comprising at least carbon from carbon dioxide as in claim 1 where the gases containing at least gaseous hydrocarbons are provided directly from a gas well or from a pipeline;

7. A process to produce a synthesis gas comprising at least carbon from carbon dioxide as in claim 1 where the gases containing at least gaseous hydrocarbons are contained in the emissions from anaerobic digestion or fermentation.

8. A process to produce a synthesis gas comprising at least carbon from carbon dioxide as in claim 1 where the gases containing at least gaseous hydrocarbons is synthetic natural gas produced from biomass or coal.

9. A process to produce a synthesis gas comprising at least carbon from carbon dioxide as in claim 1 where the optimum carbon monoxide to hydrogen ratio of 0.5-3.0 for step g is achieved from the controlled volume of carbon dioxide relative to the carbon composition of the gaseous hydrocarbons and the volume of steam required to eliminate coking and maintain reaction kinetic equilibrium.

10. A process to produce a synthesis gas comprising at least carbon from carbon dioxide as in claim 1 whereas the reactor in step c. operates at a temperature range of 800° C. to 1000° C. and preferably at 875° C. and a pressure of 0.1-5 MPa, preferably at 0.1 MPa.

11. A process to produce a synthesis gas comprising at least carbon from carbon dioxide as in claim 1 whereas steam is fed into the reactor at a temperature range of 210° C. to 225° C. and preferably 215° C. and at a pressure of 1.5 MPa to 2.0 MPa and preferably at 1.9 MPa.

12. A process to produce a synthesis gas comprising at least carbon from carbon dioxide as in claim 1 step g where the first reactor produces methanol or a mixture of methanol and dimethyl ether comprising at least carbon from carbon dioxide and the second reactor produces gasoline-range hydrocarbons comprising at least carbon from carbon dioxide.

13. A process to produce a synthesis gas comprising at least carbon from carbon dioxide as in claim 1 step g where the first reactor produces a mixture of methanol and dimethyl ether comprising at least carbon from carbon dioxide which is separated into methanol and dimethyl ether, the methanol is converted in a second reactor to olefins, and the dimethyl ether is converted in a third reactor into hydrocarbons and aromatics and the olefins, hydrocarbons and aromatics are blended into jet fuel comprising at least carbon from carbon dioxide.

14. A process to produce a synthesis gas comprising at least carbon from carbon dioxide as in claim 1 step g where the first reactor produces methanol or a mixture of methanol and dimethyl ether, comprising at least carbon from carbon dioxide and the next reactions are chosen to produce at least acetic acid and its derivatives comprising at least carbon from carbon dioxide.

15. A process to produce gasoline-range hydrocarbons comprising at least carbon from carbon dioxide as in claims 12, 13 and 14 where the unconverted gases from the chemical reactors is recycled back to the reformer.

16. A process to produce gasoline-range hydrocarbons comprising at least carbon from carbon dioxide as in claims 12, 13, and 14 where the heat from the reactors is captured to produce steam and electricity for use in the reformer and process equipment.

17. A process to produce a synthesis gas comprising at least carbon from carbon dioxide as in claim 1 where step f is not required and where as in step g the first reactor produces dimethyl ether comprising at least carbon from carbon dioxide and the second reactor produces gasoline-range hydrocarbons comprising at least carbon from carbon dioxide.

18. A process to produce a synthesis gas comprising at least carbon from carbon dioxide as in claim 1 where as in step g. there is only one reactor which is a Fischer-Tropsch reactor.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0034] FIG. 1 is a description of the main feature of the instant invention, the creation of synthesis gas comprising substituted fossil carbon using carbon dioxide as a feedstock.

[0035] FIG. 2 is the preferred embodiment of a process to produce methanol and gasoline-range hydrocarbons from substituted-carbon synthesis gas, with internal energy generated and employed to reduce the external energy requirement.

[0036] FIG. 3 is an embodiment of a process to produce dimethyl ether and gasoline-range hydrocarbons from substituted-carbon synthesis gas, with internal energy generated and employed to reduce the external energy requirement.

MODES FOR CARRYING OUT THE INVENTION

[0037] FIG. 1 at 10: Carbon dioxide at 1 is collected for the process. The source of the carbon dioxide determines the method by which it is collected. By way of example, flue gases containing carbon dioxide can be partially diverted into a collection system using state-of-the-art methods. Methods could include, but are not limited to, suctioning the flue gases and stripping them of the carbon dioxide using solvents, which may contain enzymes; forcing the flue gases through molecular sieves and collection of the filtered carbon dioxide; passing the flue gases over electrodes to attract and trap the carbon dioxide; or other methods which may become apparent. The captured carbon dioxide is then cleaned and compressed 2 to remove all contaminants which would poison the catalysts in the downstream reactions, and to meet the specifications required in the reforming reactor. Once cleaned and compressed, which will be specific to the carbon dioxide source, the cleaned, compressed carbon dioxide is then sent to storage 3 and maintained at the pressure required in the reformer. Storage is required if the supply of carbon dioxide is not continuous, or if the rate of collection does not match the rate at which the reformer operates. By way of example, no storage would be required if the carbon dioxide is acquired from a pipeline which provides a continuous supply. On the other hand, collection from flue gas may not acquire a consistent volume of carbon dioxide, and storage may therefore be required. The compressed, clean, carbon dioxide 3 is then fed into the Reformer 4 at a consistent measured rate and volume which maintains reaction equilibrium in the reformer, and which is in turn dependent upon the chemical composition of the gaseous hydrocarbon co-feedstock.

[0038] Gaseous hydrocarbons 5 are acquired. The gas or gases could include any or all of methane (CH.sub.4), ethane (C.sub.2H.sub.6), propane (C.sub.3H.sub.8), butanes (C.sub.4H.sub.10), pentanes (C.sub.5H.sub.12), hexane (C.sub.6H.sub.14), heptane (C.sub.7H.sub.16), octane (C.sub.8H.sub.18), ethylene (C.sub.2H.sub.4), propylene (C.sub.3H.sub.6), and higher molecular weight hydrocarbons, nitrogen (N.sub.2), hydrogen (H.sub.2), carbon dioxide (CO.sub.2), water (H.sub.2O). and sulphur (SOX), trace rare gases such as argon (Ar), helium (He), neon (Ne), Xenon (Xe). The composition of the gaseous hydrocarbon stream will depend on its source. By way of examples, if the gaseous hydrocarbons are acquired from sources such as a pipeline or is synthetic (renewable) natural gas, it is generally almost pure methane and has been cleaned of contaminants. If acquired from other sources such as anaerobic digestion, natural gas wellhead, or a natural gas pipeline prior to cleaning, the gases must be then cleaned of all contaminants 6 which would poison the catalyst used in the reforming step which follows. This would include the removal of sulphur, which is particularly poisonous to catalysts. The cleaned gaseous hydrocarbons must then be compressed 6 to the pressure required by the Reformer 4. By way of example, compression may not be required for pipelined natural gas, which is already pressurized. In this case the gases are fed directly into the Reformer. In other cases, extensive cleaning of contaminants may be required, and one skilled in the art would select the appropriate methods to accomplish this.

[0039] A measured volume of the cleaned and compressed gaseous hydrocarbons 6 is fed continuously into the Reformer 4. The Reformer is a pressurized vessel with a catalyst and an external heat source 9. Steam 7 which has been pressurized to match the pressure required by the Reformer is measured by a metering valve 8 and sent to the Reformer 4. The volume of steam provided is selected to provide the optimum oxygen and hydrogen reagents to the chemical reactions which take place within the Reformer. The chemical reactions which take place are a combination of the typical reactions occurring in a steam methane reformer and reactions which involve methane and carbon dioxide in what is termed “dry reforming”. It will be apparent to those skilled in the art that the chemical composition of the gaseous hydrocarbons will dictate the volume of steam required to produce carbon monoxide from the carbon present. In illustration, if methane is present, the general equations for the reactions are:

CH.sub.4+H.sub.2OCO+3H.sub.2  Eq.3

CO+H.sub.2OCO.sub.2+H.sub.2  Eq.4

If, by way of example, propane is present, the general equations for the reactions are:

C.sub.3H.sub.8+3H.sub.2O3CO+5H.sub.2  Eq.3

3CO+3H.sub.2O3CO.sub.2+3H.sub.2  Eq.4

It is evident that more steam must be added to provide for the reactions gaseous hydrocarbons other than methane are present in the input gases.

[0040] It will also be apparent to those skilled in the art that the volume of carbon dioxide 3 will be injected to provide equilibrium to the reactions without exceeding the optimum requirement in the first reactor 11.

[0041] The synthesis gas 10 produced in the Reformer contains carbon which is donated from the carbon dioxide as well as carbon from the gaseous hydrocarbon. This creates a synthesis gas which has a substituted fossil carbon, regardless of whether or not steam is added to the Reformer to produce the synthesis gas. The synthesis gas is then sent to the first reactor 11 to create a product 12 which may optionally be used to create further products 13.

[0042] It will be appreciated by those skilled in the art that there are a number of variables which may affect the actual application of the instant invention For this reason, it is necessary to analyze the composition of the input gaseous hydrocarbons and calculate the required volumes of steam and carbon dioxide to provide the optimum synthesis gas ratio for downstream reactions.

[0043] FIG. 2 at 20: In one embodiment gasoline-range hydrocarbons are produced through a methanol intermediate. Synthesis gas 23 is produced as in FIG. 1 by reacting a specific volume of cleaned, compressed carbon dioxide 20 with a specific volume of cleaned, compressed gaseous hydrocarbons 21, in the presence of a measured volume 34 of steam 33 in a heated, pressurized reformer 22 with a catalyst. The synthesis gas 23 produced comprises at least carbon monoxide, hydrogen and carbon dioxide, which, in this embodiment, provides an H.sub.2:CO ratio of 2.05=(H.sub.2+CO)/(CO.sub.2+CO) suitable for the first reaction, which is the conversion of the synthesis gas into methanol in a methanol reactor 24.

[0044] It will be appreciated by those skilled in the art that there are a number of variables which may affect the actual application of the instant invention For this reason, it is necessary to analyze the composition of the input gaseous hydrocarbons and calculate the required volumes of steam and carbon dioxide to provide the optimum synthesis gas ratio for downstream reactions. 2. The volumes of carbon dioxide 20 fed to the Reformer 22 is adjusted according to the composition of the two recycle streams 25. 27 from the methanol reactor 24 and the gasoline reactor 26. Accordingly, the volume of steam required will also be adjusted through the metering valve 34 to maintain the inputs to the Reformer to achieve the 2.05 ratio. It will be evident to those skilled in the art that steady-state operations will be achieved through the use of process controls coupled with the results of on-stream sampling of the recycle gases, which enable the balancing of all inputs to the Reformer.

[0045] The synthesis gas enters the methanol reactor 24, a pressurized, thermally-controlled vessel containing a catalyst, where in an exothermic reaction it is converted to at least methanol. At least methanol is sent to the gasoline reactor 26, while the unreacted gases, which may contain at least CO, H.sub.2, and CO.sub.2, are recycled 25 back to the Reformer 22. The gasoline reactor 26 is a pressurized, thermally-controlled vessel containing a catalyst, which in exothermic reactions converts the at least methanol into at least gasoline-range hydrocarbons, at least light gaseous hydrocarbons, and water. The at least hydrocarbon gases 27 are recycled back to the Reformer 22 to be reprocessed. The gasoline-range hydrocarbons are sent to a separator 30 and separated 31 from water created during the reaction, and sent to storage. Separated water 32 is sent to a boiler 33. The boiler is heated using waste heat 34 provided by the methanol reactor 24 and the gasoline reactor 26, both of which are highly exothermic and from which the excess heat must be continually removed to protect their respective catalysts from sintering. A portion of the steam 35 created by the boiler 33 is then sent through the metering valve 36 to heat the Reformer. The unused portion of the steam is used in a turbine 37 to generate electrical power 38, which then may be used internally to power process equipment.

[0046] It will be evident to those skilled in the art that this embodiment can be implemented using different methanol or gasoline reactors, which will require specific inputs to achieve their products. The production of synthesis gas appropriate to these reactions will be achieved through the mechanism described herein to optimize the process with each reactor used.

[0047] FIG. 3 at 30: In another embodiment gasoline-range hydrocarbons are produced through a dimethyl ether intermediate. Synthesis gas 43 is produced as in FIG. 1 by reacting a specific volume of cleaned, compressed carbon dioxide 40 with a specific volume of cleaned, compressed gaseous hydrocarbons 41 in a heated, pressurized reformer 42 with a catalyst. The synthesis gas 43 produced comprises at least carbon monoxide, hydrogen and carbon dioxide, which, in this embodiment, provides an H.sub.2:CO ratio of 1:1.1=(H.sub.2+CO)/(CO.sub.2+CO) suitable for the first reaction, which is the conversion of the synthesis gas into dimethyl ether. The volumes of carbon dioxide 40 fed to the Reformer 42 is adjusted according to the composition of the two recycle streams 45, 47 from the dimethyl ether reactor 44 and the gasoline reactor 46. It will be evident to those skilled in the art that steady-state operations will be achieved through the use of process controls coupled with the results of on-stream sampling of the recycle gases, which enable the balancing of all inputs to the Reformer.

[0048] The synthesis gas enters the dimethyl ether reactor 44, a pressurized, thermally-controlled vessel containing a catalyst, where in an exothermic reaction it is converted to at least dimethyl ether. At least dimethyl ether is sent to the gasoline reactor 46, while the unreacted gases, which may contain at least CO, H.sub.2, and CO.sub.2, are recycled 45 back to the Reformer 42. The gasoline reactor 46 is a pressurized, thermally-controlled vessel containing a catalyst, which in exothermic reactions converts the at least dimethyl ether into at least gasoline-range hydrocarbons, at least light gaseous hydrocarbons, and water. The at least light gaseous hydrocarbons 47 are recycled back to the Reformer 42 to be reprocessed. The gasoline-range hydrocarbons and water formed in the reaction are sent to a separator 48 and separated from the water It will be appreciated by those skilled in the art that there are a number of variables which may affect the actual application of the instant invention For this reason, it is necessary to analyze the composition of the input gaseous hydrocarbons and calculate the required volumes of steam and carbon dioxide to provide the optimum synthesis gas ratio for downstream reactions 49, and sent to storage. Water 50 is sent to a boiler 51. The boiler is heated using waste heat 53 provided 52, 57 by the dimethyl ether reactor 44 and the gasoline reactor 46, both of which are highly exothermic and from which the excess heat must be continually removed to protect their respective catalysts from sintering. The steam 54 is used in a turbine 55 to generate electrical power 56, which then may be used internally to power the pumps and other components of the process equipment. If the Reformer 42 is found to coke from excess carbon deposition formed during the synthesis gas reactions, then steam 58 can be used to produce additional carbon monoxide. This will affect the synthesis gas composition, which will then require adjustment through the mechanisms described herein.

[0049] It will be evident to those skilled in the art that this embodiment can be implemented using different dimethyl ether or gasoline reactors, which will require specific inputs to achieve their products. The production of synthesis gas appropriate to these reactions will be achieved through the mechanism described to optimize the process with those variations.

[0050] It will be evident to those skilled in the art that there are many variations of the instant process which will accomplish the technical goals of utilizing carbon dioxide as a feedstock together with gaseous hydrocarbons and reforming them into a synthesis gas suitable for downstream reactions. It will be evident that the adjustment of the input ratios to the reformer will allow a variation in the composition of the synthesis gas, and therefore allow for the production of many end products. Because almost all chemical reactions will be exothermic, the principles described herein will be applicable to each embodiment utilized, and produced water, if any, will be able to be used to produce steam for generating electrical power and for modulating the reactions in the reformer.

[0051] In the instant invention, the use of steam or electrical power from a host facility, which may supply the carbon dioxide and/or the gaseous hydrocarbons, will also enable a similar opportunity to shrink the carbon footprint of the plant. The use of host energy is therefore included by reference in the description herein.

INDUSTRIAL APPLICABILITY

[0052] The instant invention has valuable industrial applicability to any process which is emitting carbon dioxide to the atmosphere and desires to reduce them. Capture of all or part of the carbon dioxide is beneficial by reducing the atmospheric carbon pool, and the interim sequestration of that carbon in a chemical or fuel successfully displaces carbon from a fossil source. Overall reduction of fossil carbon in products is a transition to the time when a permanent and more extensive solution can be found. There are a vast number of industrial production facilities globally which could provide carbon dioxide. The volumes which could be sequestered in consumable products is incalculable. In addition, the use of recycling and generation of internal process energy reduces the carbon footprint of the facility, which provides a means by which emitters can diversity their operations and participate in rewarding and environmentally beneficial processes.

[0053] The instant invention also has carbon-saving applicability to established plants which may be generating excess steam or energy in their facility. The bolt-on ability of the instant invention to an existing facility which is not only emitting volumes of carbon dioxide, but also has excess energy and steam, provides a means by which those facilities can shrink their own carbon footprint. This ability in the very near future may mean the difference between maintaining operations or being forced to close.