EP4665678A1

EP4665678A1 - System for producing solid carbon from co2 and relative method

Info

Publication number: EP4665678A1
Application number: EP24711784.9A
Authority: EP
Inventors: Manjush GANIGER; Maneesh PANDEY
Original assignee: Nuovo Pignone Technologie SRL
Current assignee: Nuovo Pignone Technologie SRL
Priority date: 2023-03-08
Filing date: 2024-03-04
Publication date: 2025-12-24
Also published as: WO2024183956A1; MX2025010328A; AU2024231661A1; JP2026507224A; KR20250156797A; CN120835864A; IT202300004302A1

Abstract

System (100) for producing solid carbon C from carbon dioxide CO2, for example from CO2 captured from a power plant. The system comprises a methanation unit (110) fluidly coupled to a carbon capture system and configured to receive carbon dioxide CO2 and perform methanation of carbon dioxide CO2 to produce at least methane CH4 and heat, and a pyrolysis unit (120) configured to receive methane CH4 and heat, and perform pyrolysis of methane CH4 to produce hydrogen H2 and solid carbon C, in which the methanation unit (110) and the pyrolysis unit (120) are thermally and fluidly coupled so that at least gaseous hydrogen H2 is supplied from the pyrolysis unit (120) to the methanation unit (110) and heat is provided from the methanation unit (110) to the pyrolysis unit (120).

Description

TITLE

System for producing solid carbon from CO2 and relative method

DESCRIPTION

TECHNICAL FIELD

[0001] The subject-matter disclosed herein relates to a system for producing solid carbon from CO2 and relative method.

B ACKGROUND ART

[0002] In order to achieve the ambitions of the Paris Agreement and limit future temperature increases to 1.5 °C, the efforts to reduce emissions is increased, as well as the development of technologies to remove carbon dioxide (CO2) from the atmosphere, known as Carbon Capture (=CC) and Carbon Capture and Storage (=CCS). In general, carbon dioxide (CO2) may be captured pre-combustion or post-combustion. In particular, CO2 is removed in post-combustion after burning the fossil fuel (CO2 is captured or “scrubbed” from the exhaust or “flue” gases). Typically, CO2 is captured at emission sources, such as power plants, natural gas processing facilities and industrial processes (however, capture from the open atmosphere is also possible).

[0003] CCS involves capturing carbon dioxide (CO2) at emission sources, transporting captured CO2 and then sequestrating it in a suitable deep, underground location; however, these locations are not commonly available.

After capture, CO2 must be transported to suitable storage sites. Pumping CO2 through pipelines is a well-known and reliable technology. However, pipeline safety is a critical aspect, particularly in heavily populated areas or areas of high earthquake activity. Moreover, pumping CO2 through pipelines requires C02 compression stations in order to increase CO2 pressure and perform CO2 transport and CO2 interacting with water vapor may also cause pipeline corrosion. Finally, gaseous CO2 may be used for example to perform Enhanced Oil Recovery (=EOR) or may be converted into a high pressure, liquid-like form known as “supercritical CO2” and injected directly into sedimentary rocks for storing it. Therefore, capturing and using/ storing captured CO2 requires a lot of energy.

[0004] It would be desired to have a system which allows a more convenient transporting and storage of CO2 after CO2 capture. In particular, it would be desired to have a system provided with a carbon capture system which does not require CO2 compression and/or CO2 liquefaction to perform CO2 storage (i.e. does not require energy intensive CO2 transformations).

SUMMARY

[0005] According to an aspect, the subject-matter disclosed herein relates to a system for producing solid carbon C from carbon dioxide CO2, for example from CO2 captured from exhaust gases of a power plant or other CO2 sources. The system comprises a methanation unit fluidly coupled to a carbon capture system and configured to receive carbon dioxide CO2 to perform methanation of carbon dioxide CO2 to produce at least methane CH4 and heat, and a pyrolysis unit configured to receive methane CH4 and heat, and perform pyrolysis of methane CH4 to produce hydrogen H2 and solid carbon C, in which the methanation unit and the pyrolysis unit are thermally and fluidly coupled so that at least gaseous hydrogen H2 is supplied from the pyrolysis unit to the methanation unit and heat is provided from the methanation unit to the pyrolysis unit.

[0006] According to another aspect, the subject-matter disclosed herein relates to a method for producing solid carbon C from carbon dioxide CO2 comprising the steps of performing pyrolysis of methane CH4 in a pyrolysis unit to produce hydrogen H2 and solid carbon C and performing methanation of carbon dioxide CO2 in a methanation unit to produce at least methane CH4 and heat. The heat produced through methanation is used to perform pyrolysis of methane CH4 and the hydrogen H2 produced through pyrolysis is used to perform methanation of carbon dioxide CO2.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] A more complete appreciation of the disclosed embodiments of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

Fig. 1 shows a schematic diagram of a first embodiment of an innovative system for generating solid carbon C from carbon dioxide CO2,

Fig. 2 shows a more detailed di agram of the methanation unit of Fig. 1,

Fig. 3 shows a more detailed diagram of the pyrolysis unit of Fig. 1,

Fig. 4 shows a schematic diagram of a second embodiment of an innovative system for generating solid carbon C from carbon dioxide CO2,

Fig. 5 shows a flow chart of an embodiment of a method for producing solid carbon C from carbon dioxide CO2.

DETAILED DESCRIPTION OF EMBODIMENTS

[0008] According to an aspect, the subject-matter disclosed herein relates to an innovative alternative to perform CCS by eliminating the energy intensive processes and infrastructures needed for carbon dioxide compression, storage and transport. This is reached by producing solid carbon from captured CO2 exploiting a pyrolysis and a methanation processes. The solid carbon is produced from methane through a pyrolysis process, which also produces hydrogen as product. It is to be noted that the pyrolysis process is an endothermic process, therefore requiring heat to carry out the reaction. The heat is provided by a methanation process which is an exothermic process, therefore generating heat during the reaction. The methanation process produces methane starting from carbon dioxide and hydrogen, which are supplied respectively by a carbon capture system and the pyrolysis process. Advantageously, the methane produced by the methanation process may be recirculated to the pyrolysis process in order to perform pyrolysis of methane and/or to produce additional heat for the pyrolysis process by burning it.

[0009] Reference now will be made in detail to embodiments of the disclosure, examples of which are illustrated in the drawings. The examples and drawing figures are provided by way of explanation of the disclosure and should not be construed as a limitation of the disclosure. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the scope or spirit of the disclosure. In the following description, similar reference numerals are used for the illustration of figures of the embodiments to indicate elements performing the same or similar functions. Moreover, for clarity of illustration, some references may be not repeated in all the figures.

[0010] In Fig. 1 is shown a simplified diagram a first embodiment of an innovative system for generating solid carbon (=C) from carbon dioxide (=CO2), referred in the following as “system 100”. With non-limiting reference to Fig. 1, the system 100 comprises a methanation unit 110 and a pyrolysis unit 120 which are thermally and fluidly coupled to each other, as it will be better described below. The system 100 may be advantageously arranged downstream a power plant, in particular downstream of a process/plant which produces exhaust gases comprising CO2; more advantageously, the system 100 may be arranged downstream a carbon capture system of the power plant, in particular being fluidly coupled to the carbon capture system, in order to receive captured CO2 from the carbon capture system. It is to be noted that there are known several methods and system to perform CO2 capture from exhausted gases in order to separate CO2 and discharge CO2-free exhaust gases in atmosphere. According to the scope of the present disclosure, any known carbon capture system may be used in order to separate a gaseous carbon dioxide CO2 stream from which solid carbon C may be produced.

[0011] The methanation unit 110 is configured to receive at least gaseous carbon dioxide CO2 and perform methanation of carbon dioxide CO2 to produce at least gaseous methane CH4 and heat Q. In fact, it is known that the methanation reaction of carbon dioxide CO2 is

CO₂ + 4H₂ CH₄ + 2H₂O and is an exothermic reaction, therefore generating heat (=Q) when carried out.

[0012] In particular, with non-limiting reference to Fig. 2 the methanation unit 110 comprises a pre-processing unit 130 configured to receive gaseous carbon dioxide at a second inlet 111. Advantageously, the second inlet 111 is fluidly coupled to the carbon capture system so that the carbon capture system may supply gaseous carbon dioxide to the pre-processing unit 130. The preprocessing unit 130 further comprises a first inlet 113 and configured to receive gaseous hydrogen H2 from the pyrolysis unit 120, as it will be better described in the following. Advantageously, the pre-processing unit 130 is configured to perform: purification of carbon dioxide and/or hydrogen; compression of carbon dioxide and/or hydrogen; mixing of carbon dioxide and hydrogen. Advantageously, carbon dioxide and hydrogen may be mixed with each other according to the required stoichiometric ratio for the methanation reaction.

[0013] With non-limiting reference to Fig. 2, the methanation unit 110 further comprises a reactor unit 140 fluidly coupled to the pre-processing unit 130; in particular, the reactor unit 140 has a main inlet 141 configured to receive a stream of carbon dioxide and hydrogen from the pre-processing unit 130. Advantageously, carbon dioxide and/or hydrogen are previously compressed to meet inlet pressure conditions for the reactor unit 140. The reactor unit 140 further comprises a catalyst and is configured to perform methanation reaction of carbon dioxide CO2; in other words, in the reactor unit 140 methanation reaction occurs between the CO2 and H2 in the presence of catalyst, in particular to produce methane CH4 and possibly other reaction by-products.

[0014] As already described before, the methanation reaction of carbon dioxide is an exothermic reaction; therefore, heat Q is generated in the reactor unit 140. With non-limiting reference to Fig. 1, the heat Q produced by the methanation unit 110 through methanation of carbon dioxide CO2 is provided to the pyrolysis unit 120 and used to perform pyrolysis of methane CH4. Advantageously, water H2O is supplied to the reactor unit 140 from a secondary inlet 115 to take away the heat Q, thereby producing hot water and/or steam H2O/S supplied by a second outlet 114 of the reactor unit 140. Advantageously, as it will be apparent from the following, hot water and/or steam H2O/S from the second outlet 114 is supplied to the pyrolysis unit 120.

[0015] With non-limiting reference to Fig. 2, the methanation unit 110 further comprises a post-processing unit 150 fluidly coupled to the reactor unit 140; in particular, the post-processing unit 150 has a main inlet 151 configured to receive methane CH4 and by-products from the reactor unit 140. The postprocessing unit is configured to perform separation between methane CH4 and by-products. In particular, the post-processing unit 150 has a first outlet 112 configured to supply methane CH4, in particular gaseous methane CH4, and a second main outlet 116 configured to discharge by-products like unreacted CO2/H2 and/or H2O. For example, the post-processing unit 150 may be a distillation column or adsorption column or separation unit.

[0016] According to the first embodiment shown in Fig. 1, the pyrolysis unit 120 is configured to receive gaseous methane CH4 and heat Q and perform pyrolysis of methane to produce gaseous hydrogen H2 and solid carbon C. It is known that the pyrolysis reaction of methane is

CW₄ 2H₂ + C and is an endothermic reaction, therefore requiring heat (=Q) to be carried out.

[0017] As described above, the hot water and/or steam H2O/S produced in the methanation unit 110 is supplied to the pyrolysis unit 120; in other words, at least part of the heat Q (advantageously all the heat Q) needed to perform pyrolysis of methane is provided by the methanation unit 110 in the form of hot water and/or steam H2O/S. As it will be better described with the aid of Fig. 4, according to a second embodiment at least another part of the heat Q needed to perform pyrolysis of methane is provided by the methanation unit 210 in the form of methane CH4 to be burned in the pyrolysis unit 220 to generate additional heat Qi (see for example Fig. 3). Advantageously, all the heat Q needed to perform pyrolysis of methane is provided by the methanation unit 110 both in the form of hot water and/or steam H2O/S and methane CH4 to be burned. It is to be noted that elements 210, 211, 212, 213, 214, 220, 221, 222 and 224 in Fig. 4 may be identical or similar respectively to elements 110 (methanation unit), 111 (second inlet), 112 (first outlet), 113 (first inlet), 114 (second outlet), 120 (pyrolysis unit), 121 (first inlet), 122 (first outlet) and 224 (second outlet) in Fig. 1 and perform the same or similar functions.

[0018] In particular, with non-limiting reference to Fig. 3, the pyrolysis unit 120 comprises a pre-processing unit 160 configured to receive gaseous methane CH4 at a first inlet 121. It is to be noted that the first inlet 121 may be fluidly coupled to a methane pipeline. It is to be noted that gaseous methane CH4 from the methane pipeline may be used to perform pyrolysis of methane CH4 and/or may be burned to produce additional heat Qi in the pyrolysis unit 120, in particular to carry out pyrolysis reaction. Advantageously, according to the embodiment shown in Fig. 4, the pre-processing unit may further comprise a second inlet 223 configured to receive gaseous methane CH4; in particular, the second inlet 223 may be fluidly coupled to the methanation unit 210 (in particular to the first outlet 212 of the post-processing unit 150 of the methanation unit 210) and may be configured to receive methane CH4, in particular gaseous methane CH4, produced by the methanation unit 210. It is to be noted that gaseous methane CH4 from the methanation unit 210 may be used to perform pyrolysis of methane CH4 and/or may be burned to produce additional heat Qi in the pyrolysis unit 220, in particular to carry out pyrolysis reaction.

[0019] Advantageously, the pre-processing unit 160 is configured to perform: purification of gaseous methane CH4; pre-heating of the gaseous methane CH4.

In particular, the pre-processing unit 160 has a second inlet 123 fluidly coupled to the second outlet 114 of the reactor unit 140 so to receive hot water and/or steam H2O/S and perform pre-heating of gaseous methane CH4. Advantageously, the pre-processing unit 160 is configured to transfer heat from the hot water and/or steam H2O/S to the gaseous methane CH4 and therefore supplying heated gaseous methane CH4 from a first outlet 162 and cold water from a second outlet 126.

[0020] With non-limiting reference to Fig. 3, the pyrolysis unit 120 further comprises a pyrolysis reactor 170 and a burner unit 180 thermally coupled to each other; in particular, the burner unit 180 is configured to provide additional heat Qi to the pyrolysis reactor (see the big arrow in Fig. 3) in order to perform pyrolysis reaction. Advantageously, both the pyrolysis reactor 170 and the burner unit 180 are fluidly coupled to the pre-processing unit 160; in particular, the heated gaseous methane CH4 supplied by the first outlet 162 of the preprocessing unit 160 is advantageously split between the pyrolysis reactor 170 and the burner unit 180. With non-limiting reference to Fig. 3, the burner unit 180 has a first inlet 181, configured to receive fraction of the heated gaseous methane CH4 from the pre-processing unit 160 to be used as fuel, and a second inlet 182, configured to receive an oxidant, for example air, and is configured to generate additional heat Qi by burning the heated gaseous methane CH4 and the oxidant. Advantageously, as it will be apparent from the following, the burner unit 180 may further have a third inlet 183 configured to receive any unutilized gaseous methane CH4, preferably unutilized heated gaseous methane CH4, to be used as fuel in the burner unit 180.

[0021] With non-limiting reference to Fig. 3, the pyrolysis reactor 170 has a first inlet 171, configured to receive fraction of the heated gaseous methane CH4 from the pre-processing unit 160 to perform pyrolysis of methane according to the pyrolysis reaction previously described; in other words, in the pyrolysis reactor 170 pyrolysis reaction of methane CH4 occurs thanks to the heat Q provided by the methanation unit 110 and possibly to the additional heat Qi provided by the burner unit 180, in particular to produce hydrogen H2 and solid carbon C at an outlet 172 of the pyrolysis reactor 170. However, it is to be noted that some gaseous methane CH4 may be unutilized (i.e. unreacted) and be supplied together with the hydrogen H2 and solid carbon C at the outlet 172.

[0022] With non-limiting reference to Fig. 3, the pyrolysis unit 120 further comprises a post-processing unit 190 fluidly coupled to the pyrolysis reactor 170; in particular, the post-processing unit 170 has a main inlet 191 fluidly coupled to the outlet 172 and configured to receive hydrogen H2 and solid carbon C and possibly unutilized methane CH4 from the pyrolysis reactor 170. In particular, the post-processing unit 190 has a first outlet 122 fluidly coupled to the first inlet 113 and configured to supply gaseous hydrogen H2 to the methanation unit 110, and a second outlet 124 configured to supply solid carbon C. For example, the post-processing unit 190 may be a separation unit like cyclone separators or adsorbent vessels performing PSA (=Pressure Swing Adsorption).

[0023] Advantageously, the post-processing unit 190 is further configured to separate any unutilized gaseous methane CH4 from the hydrogen H2 and the solid carbon C. In particular, the post-processing unit 190 has a third outlet 192 fluidly coupled to the third inlet 183 of the burner unit 180 and configured to supply unutilized gaseous methane CH4 to be used as fuel in the burner unit 180. Even more advantageously, the unutilized gaseous methane CH4 from post-processing unit 190 may be heated before being supplied to the burner unit 180. In particular, the pyrolysis unit 190 may further comprise a heat exchanger 175 arranged downstream the outlet 172 of the pyrolysis reactor 170 and fluidly coupled to the outlet 172 and the third outlet 192 of the postprocessing unit 190. Advantageously, the heat exchanger 175 is configured to transfer heat from the flow of hydrogen H2, solid carbon C and possibly unutilized methane CH4 supplied at the outlet 172 to the unutilized gaseous methane CH4 provided at the third inlet 183.

[0024] According to another aspect, the subject-matter disclosed herein relates to a method 300 for producing solid carbon C from gaseous carbon dioxide CO2, in particular from gaseous carbon dioxide captured CO2 by a carbon capture system. With non-limiting reference to Fig. 5, the method 300 comprises the steps of: performing 320 methanation of carbon dioxide CO2 in a methanation unit 110 e 210 to produce at least gaseous methane CH4 and heat Q, and performing 310 pyrolysis of methane CH4 in a pyrolysis unit 120 and 220 to produce gaseous hydrogen H2 and solid carbon C.

According to the method 300, the heat Q produced at step 320 is used to perform pyrolysis of methane CH4 in step 310 and the gaseous hydrogen produced at step 310 is used to perform methanation of carbon dioxide CO2 in step 320. According to a possibility, the methane CH4 used to perform 310 pyrolysis of methane CH4 may be supplied by a methane pipeline. According to another possibility, the method 300 may further comprise the step of supplying 330 gaseous methane CH4 produced through methanation of carbon dioxide CO2 at step 320 to the pyrolysis unit 220. In particular, the gaseous methane CH4 supplied to the pyrolysis unit 220 is used to perform 310 pyrolysis of methane CH4 and/or is burned to produce additional heat Qi in the pyrolysis unit 220; in other words, at least part (possibly all) of the methane CH4 supplied to the pyrolysis unit 220 is produced in step 310. In particular, the gaseous methane CH4 supplied to the pyrolysis unit (which may be supplied by the methane pipeline and/or by the methanation unit) may be used to perform 310 pyrolysis of methane CH4 and/or may be burned to produce additional heat Qi in the pyrolysis unit, in particular to carry out pyrolysis reaction.

Claims

1. System (100, 200) for producing solid carbon (C) from gaseous carbon dioxide (CO2), the system (100, 200) comprising: a methanation unit (110, 210) configured to receive at least gaseous carbon dioxide (CO2) and perform methanation of carbon dioxide (CO2) to produce at least gaseous methane (CH4) and heat (Q); and a pyrolysis unit (120, 220) configured to receive gaseous methane (CH4) and heat (Q) and perform pyrolysis of methane (CH4) to produce gaseous hydrogen (H2) and solid carbon (C), wherein the methanation unit (110, 210) is fluidly coupled to a carbon capture system, wherein the methanation unit (110, 210) and the pyrolysis unit (120, 220) are fluidly coupled so that at least gaseous hydrogen (H2) is supplied to the methanation unit (110, 210), wherein the methanation unit (110, 210) and the pyrolysis unit (120, 220) are thermally coupled so that heat (Q) is provided to the pyrolysis unit (110, 210).

2. The system (100, 200) of claim 1, wherein the pyrolysis unit (120, 220) has a first outlet (122, 222) configured to supply gaseous hydrogen (H2), wherein the methanation unit (110, 210) has a first inlet (113, 213) configured to receive gaseous hydrogen (H2), wherein the first outlet (122, 222) and the first inlet (113, 213) are fluidly coupled.

3. The system (100, 200) of claim 1, wherein the heat (Q) produced by the methanation unit (110, 210) through methanation of carbon dioxide (CO2) is received by the pyrolysis unit (110, 210) and used to perform pyrolysis of methane (CH4).

4. The system (100, 200) of claim 1, wherein the methanation unit (110, 210) has a second inlet (111, 211) configured to receive gaseous carbon dioxide (CO2) from the carbon capture system.

5. The system (100, 200) of claim 1, wherein the pyrolysis unit (120, 220) has a first inlet (121, 221) configured to receive gaseous methane (CH4) from a methane pipeline, wherein gaseous methane (CH4) from the methane pipeline is used to perform pyrolysis of methane (CH4) and/or is burned to produce additional heat (Qi) in the pyrolysis unit (120, 220).

6. The system (200) of claim 1, wherein the methanation unit (210) has a first outlet (212) configured to supply gaseous methane (CH4), wherein the pyrolysis unit (220) has a second inlet (223) configured to receive gaseous methane (CH4), wherein the first outlet (212) and the second inlet (223) are fluidly coupled, wherein the gaseous methane (CH4) from the methanation unit (210) is used to perform pyrolysis of methane (CH4).

7. The system (200) of claim 1, wherein the methanation unit (210) has a first outlet (212) configured to supply gaseous methane (CH4), wherein the pyrolysis unit (220) has a second inlet (223) configured to receive gaseous methane (CH4), wherein the first outlet (212) and the second inlet (223) are fluidly coupled, wherein the gaseous methane (CH4) from the methanation unit (210) is burned to produce additional heat (Qi) in the pyrolysis unit (220).

8. The system (200) of claim 1, wherein the methanation unit (210) has a first outlet (212) configured to supply gaseous methane (CH4), wherein the pyrolysis unit (220) has a second inlet (223) configured to receive gaseous methane (CH4), wherein the first outlet (212) and the second inlet (223) are fluidly coupled, wherein part of the gaseous methane (CH4) from the methanation unit (210) is used to perform pyrolysis of methane (CH4) and part of the gaseous methane (CH4) from the methanation unit (210) is burned to produce additional heat (Qi) in the pyrolysis unit (220).

9. Method (300) for producing solid carbon (C) from gaseous carbon dioxide (CO2), the method comprising the steps of: performing (320) methanation of carbon dioxide (CO2) in a methanation unit (110, 210) to produce at least gaseous methane (CH4) and heat (Q), performing (310) pyrolysis of methane (CH4) in a pyrolysis unit (120, 220) to produce gaseous hydrogen (H2) and solid carbon (C), wherein the heat (Q) produced through methanation is used to perform pyrolysis of methane (CH4), wherein the gaseous hydrogen (H2) produced through pyrolysis is used to perform methanation of carbon dioxide (CO2).

10. The method (300) of claim 9, further comprising the step of supplying (330) gaseous methane (CH4) produced through methanation of carbon dioxide (CO2) to the pyrolysis unit (220).

11. The method (300) of claim 10, wherein the gaseous methane (CH4) supplied to the pyrolysis unit (220) is used to perform (310) pyrolysis of methane (CH4).

12. The method (300) of claim 10, wherein the gaseous methane (CH4) supplied to the pyrolysis unit (220) is burned to produce additional heat (Qi) in the pyrolysis unit (220).

13. The method (300) of claim 10, wherein part of the gaseous methane (CH4) supplied to the pyrolysis unit (220) is used to perform (310) pyrolysis of methane (CH4) and part of the gaseous methane (CH4) supplied to the pyrolysis unit (220) is burned to produce additional heat (Qi) in the pyrolysis unit (220).