Systems and related methods for producing solid carbon from CO2

Abstract

A system (100) for producing solid carbon (C) from carbon dioxide (CO), for example, from captured CO from a power plant. The system includes a methanation unit (110) fluidly coupled to a carbon capture system and configured to receive carbon dioxide (CO) and perform methanation of the carbon dioxide (CO) to produce at least methane (CH) and heat, and a pyrolysis unit (120) configured to receive methane (CH) and heat and perform pyrolysis of the methane (CH) to produce hydrogen (H) and solid carbon (C), the methanation unit (110) and the pyrolysis unit (120) being thermally and fluidly coupled such that at least gaseous hydrogen (H) is provided from the pyrolysis unit (120) to the methane production unit (110) and heat is provided from the methane production unit (110) to the pyrolysis unit (120).

Description

[Technical Field]

[0001] The subject matter disclosed herein relates to systems and related methods for producing solid carbon from CO2. [Background technology]

[0002] To achieve the ambitions of the Paris Agreement and limit future temperature rise to 1.5°C, efforts to reduce emissions are increasing, as is the development of technologies to remove carbon dioxide (CO2) from the atmosphere, known as carbon capture (CC) and carbon capture and storage (CCS). Generally, carbon dioxide (CO2) can be captured pre- or post-combustion. In particular, CO2 is removed post-combustion after burning fossil fuels (CO2 is captured or "scrubbed" from exhaust or "flue" gases). Typically, CO2 is captured at the source, such as power plants, natural gas processing facilities, and industrial processes (although capture from the open air is also possible).

[0003] CCS involves capturing carbon dioxide (CO2) at the emission source, transporting the captured CO2, and then sequestering it in a suitable deep underground location. However, these locations are not generally available.

[0004] After capture, CO2 must be transported to a suitable storage location. Pumping CO2 through pipelines is a well-known and reliable technology. However, pipeline safety is a critical aspect, especially in populated or seismically active areas. Furthermore, pumping CO2 through pipelines increases the CO2 pressure, requiring CO2 compression stations for transport, and CO2 interacting with water vapor can cause pipeline corrosion. Finally, gaseous CO2 can be used, for example, to perform enhanced oil recovery (EOR), or it can be converted to a high-pressure liquid form known as "supercritical CO2" and injected directly into sedimentary rocks for storage. Therefore, capturing CO2 and using / storing the captured CO2 requires a lot of energy.

[0005] It would be desirable to have a system that allows for more convenient transportation and storage of CO after capture, and in particular, a system with a carbon capture system that does not require CO compression and / or CO liquefaction to achieve CO storage (i.e., does not require energy-intensive CO conversion). Summary of the Invention

[0006] According to one aspect, the subject matter disclosed herein relates to a system for producing solid carbon C from carbon dioxide CO, for example, from CO captured from power plant flue gas or other CO source.

[0007] The system comprises a methanation unit fluidly coupled to the carbon capture system and configured to receive carbon dioxide CO2 and perform methanation of the 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 the methane CH4 to produce hydrogen H2 and solid carbon C, wherein the methanation unit and pyrolysis unit are thermally and fluidly coupled such that at least gaseous hydrogen H2 is provided from the pyrolysis unit to the methanation unit and heat is provided from the methane generation unit to the pyrolysis unit.

[0008] According to another aspect, the subject matter disclosed herein relates to a method for producing solid carbon (C) from carbon dioxide (CO), the method including: performing pyrolysis of methane (CH) in a pyrolysis unit to produce hydrogen (H) and solid carbon (C); and performing methanation of carbon dioxide (CO) in a methanation unit to produce at least methane (CH) and heat. The heat produced by the methanation is used for the pyrolysis of methane (CH), and the hydrogen (H) produced by the pyrolysis is used for the methanation of carbon dioxide (CO). [Brief explanation of the drawings]

[0009] A more complete understanding of the disclosed embodiments of this invention and many of the attendant advantages thereof will be readily obtained as the same become better understood by reference to the following detailed description when considered in connection with the accompanying drawings. [Figure 1] FIG. 1 shows a schematic diagram of a first embodiment of an innovative system for producing solid carbon C from carbon dioxide CO. [Figure 2] 2 shows a more detailed view of the methane production unit of FIG. 1. [Figure 3] 2 shows a more detailed view of the pyrolysis unit of FIG. 1. [Figure 4] FIG. 1 shows a schematic diagram of a second embodiment of an innovative system for producing solid carbon C from carbon dioxide CO. [Figure 5]1 shows a flow chart of one embodiment of a method for producing solid carbon C from carbon dioxide CO2. DETAILED DESCRIPTION OF THE INVENTION

[0010] According to one aspect, the subject matter disclosed herein relates to an innovative alternative for implementing CCS by eliminating the energy-intensive processes and infrastructure required for carbon dioxide compression, storage, and transportation. This is accomplished by utilizing pyrolysis and methanation processes to produce solid carbon from captured CO2. The solid carbon is produced from methane via a pyrolysis process, which also produces hydrogen as a product. Note that the pyrolysis process is an endothermic process and therefore requires heat to carry out the reaction. The heat is provided by the methanation process, which is an exothermic process and therefore generates heat during the reaction. The methanation process produces methane starting from carbon dioxide and hydrogen, which are supplied by a carbon capture system and a pyrolysis process, respectively. Advantageously, the methane produced by the methanation process can be recycled to the pyrolysis process to carry out the thermal decomposition of methane and / or to generate additional heat for the pyrolysis process by burning it.

[0011] Reference will now be made in detail to embodiments of the present disclosure, examples of which are illustrated in the drawings. The examples and drawings are provided as explanations of the present disclosure and should not be construed as limiting the disclosure. Indeed, it will be apparent to those skilled in the art that various modifications and variations can be made to the present disclosure without departing from the scope or spirit of the present disclosure. In the following description, like reference numerals are used in the illustrative figures of the embodiments to indicate elements that perform the same or similar functions. Moreover, for clarity of illustration, some reference numerals may not be repeated in all figures.

[0012] FIG. 1 shows a simplified diagram of a first embodiment of an innovative system for producing solid carbon (=C) from carbon dioxide (=C0), hereinafter referred to as "system 100." With non-limiting reference to FIG. 1, system 100 comprises a methane production unit 110 and a pyrolysis unit 120, which are thermally and fluidly coupled to each other, as better described below. System 100 may be advantageously located downstream of a power plant, particularly downstream of a process / plant that produces flue gases containing C0. More advantageously, system 100 may be located downstream of a carbon capture system of a power plant, particularly fluidly coupled to the carbon capture system, to receive captured C0 from the carbon capture system. It should be noted that several methods and systems are known for capturing C0 from flue gases, in order to separate the C0 and release the C0-free flue gases to the atmosphere. For purposes of this disclosure, any known carbon capture system may be used to separate the gaseous carbon dioxide C0 stream and produce solid carbon C therefrom.

[0013] The methanation unit 110 is configured to receive at least gaseous carbon dioxide CO2 and perform methanation of the carbon dioxide CO2 to produce at least gaseous methane CH4 and heat Q. In fact, the methanation reaction of carbon dioxide CO2 is CO2 + 4H2 ⇔ CH4 + 2H2O is an exothermic reaction and is therefore known to generate heat (=Q) when carried out.

[0014] In particular, and without limitation, with reference to Figure 2, the methane production unit 110 comprises a pre-treatment unit 130 configured to receive gaseous carbon dioxide at a second inlet 111. Advantageously, the second inlet 111 is fluidly coupled to a carbon capture system such that the carbon capture system can supply gaseous carbon dioxide to the pre-treatment unit 130. The pre-treatment unit 130 further comprises a first inlet 113, as better explained below, and is configured to receive gaseous hydrogen H2 from the pyrolysis unit 120. Advantageously, the pre-treatment unit 130 - carbon dioxide and / or hydrogen purification, - compression of carbon dioxide and / or hydrogen, - configured to mix carbon dioxide and hydrogen;

[0015] Advantageously, carbon dioxide and hydrogen may be mixed with one another according to the stoichiometric ratio required for the methanogenesis reaction.

[0016] 2, the methane production unit 110 further comprises a reactor unit 140 fluidly coupled to the pretreatment unit 130. In particular, the reactor unit 140 has a main inlet 141 configured to receive the carbon dioxide and hydrogen streams from the pretreatment unit 130. Advantageously, the carbon dioxide and / or hydrogen are pre-compressed to meet the inlet pressure requirements of the reactor unit 140. The reactor unit 140 further comprises a catalyst and is configured to carry out a methanation reaction of carbon dioxide CO2. In other words, in the reactor unit 140, the methanation reaction occurs between CO2 and H2 in the presence of the catalyst to produce, among other things, methane CH4 and possibly other reaction by-products.

[0017] As already mentioned, the methanation reaction of carbon dioxide is an exothermic reaction. Therefore, heat Q is generated in the reactor unit 140. Referring non-limitingly to FIG. 1 , the heat Q generated by the methanation unit 110 through the methanation of carbon dioxide CO is provided to the thermal decomposition unit 120 and used to carry out the thermal decomposition of methane CH. Advantageously, water HO is supplied to the reactor unit 140 from the secondary inlet 115 to remove the heat Q, thereby producing hot water and / or steam HO / S supplied by the second outlet 114 of the reactor unit 140. Advantageously, as will become clear below, the hot water and / or steam HO / S from the second outlet 114 is supplied to the thermal decomposition unit 120.

[0018] 2, the methane production unit 110 further comprises a post-treatment unit 150 fluidly coupled to the reactor unit 140. In particular, the post-treatment unit 150 has a main inlet 151 configured to receive methane CH and by-products from the reactor unit 140. The post-treatment unit is configured to perform separation between the methane CH and the by-products. In particular, the post-treatment unit 150 has a first outlet 112 configured to supply methane CH, in particular gaseous methane CH, and a second main outlet 116 configured to discharge by-products such as unreacted CO / H and / or HO. For example, the post-treatment unit 150 can be a distillation column, an adsorption column, or a separation unit.

[0019] According to a first embodiment shown in Figure 1, the pyrolysis unit 120 is configured to receive gaseous methane CH4 and heat Q and perform pyrolysis of the methane to produce gaseous hydrogen H2 and solid carbon C. The pyrolysis reaction of methane is CH4⇔2H2+C and is an endothermic reaction and therefore requires heat (=Q) to carry out.

[0020] As mentioned above, the hot water and / or steam HO / S produced in the methane generation unit 110 is supplied to the thermal decomposition unit 120. In other words, at least a portion (and advantageously all) of the heat Q required to perform the thermal decomposition of methane is provided by the methane generation unit 110 in the form of hot water and / or steam HO / S. As better explained with reference to Figure 4, according to a second embodiment, at least another portion of the heat Q required to perform the thermal decomposition of methane is provided by the methane generation unit 210 in the form of methane CH4, which is combusted in the thermal decomposition unit 220 to generate additional heat Qi (see, for example, Figure 3). Advantageously, all of the heat Q required to perform the thermal decomposition of methane is provided by the methane generation unit 110 in the form of both hot water and / or steam HO / S and combusted methane CH4. It should be noted that elements 210, 211, 212, 213, 214, 220, 221, 222, and 224 in FIG. 4 may be identical to or similar to elements 110 (methane production 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, respectively, and may perform the same or similar functions.

[0021] In particular, and without limitation, referring to FIG. 3, the thermal decomposition unit 120 comprises a pre-treatment unit 160 configured to receive gaseous methane CH4 at a first inlet 121. It should be noted that the first inlet 121 may be fluidly coupled to a methane pipeline. It should be noted that the gaseous methane CH4 from the methane pipeline may be used to perform the thermal decomposition of the methane CH4 and / or may be combusted to generate additional heat Qi in the thermal decomposition unit 120, in particular to perform the thermal decomposition reaction. Advantageously, according to the embodiment shown in FIG. 4, the pre-treatment 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 methane production unit 210 (in particular, the first outlet 212 of the post-treatment unit 150 of the methane production unit 210) and configured to receive methane CH4, in particular gaseous methane CH4, produced by the methane production unit 210. It should be noted that the gaseous methane CH4 from the methane production unit 210 may be used to perform pyrolysis of the methane CH4 and / or may be combusted to generate additional heat Qi in the pyrolysis unit 220, particularly to perform the pyrolysis reaction.

[0022] Advantageously, the pre-processing unit 160 comprises - Purification of gaseous methane CH4, - configured to preheat gaseous methane CH4;

[0023] In particular, the pre-treatment unit 160 has a second inlet 123 fluidly coupled to the second outlet 114 of the reactor unit 140 to receive hot water and / or steam HO / S and pre-heat the gaseous methane CH. Advantageously, the pre-treatment unit 160 is configured to transfer heat from the hot water and / or steam HO / S to the gaseous methane CH, thus providing heated gaseous methane CH from the first outlet 162 and cold water from the second outlet 126.

[0024] 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 for carrying out the pyrolysis reaction (see the large arrow in FIG. 3). Advantageously, both the pyrolysis reactor 170 and the burner unit 180 are fluidly coupled to the pretreatment unit 160. In particular, the heated gaseous methane CH4 supplied by the first outlet 162 of the pretreatment unit 160 is advantageously divided between the pyrolysis reactor 170 and the burner unit 180. 3, burner unit 180 has a first inlet 181 configured to receive a portion of the heated gaseous methane CH4 from pretreatment unit 160 to be used as fuel, and a second inlet 182 configured to receive an oxidant, e.g., air, and is configured to generate additional heat Qi by combusting the heated gaseous methane CH4 and the oxidant. Advantageously, as will become apparent below, burner unit 180 may further have a third inlet 183 configured to receive any unused gaseous methane CH4, preferably unused heated gaseous methane CH4, to be used as fuel in burner unit 180.

[0025] 3, the pyrolysis reactor 170 has a first inlet 171 configured to receive a portion of the heated gaseous methane CH4 from the pretreatment unit 160 and to carry out the thermal decomposition of the methane according to the aforementioned thermal decomposition reaction. In other words, in the pyrolysis reactor 170, the heat Q provided by the methane production unit 110 and, optionally, additional heat Qi provided by the burner unit 180 cause the thermal decomposition reaction of the methane CH4 to occur, producing, among other things, hydrogen H2 and solid carbon C at an outlet 172 of the pyrolysis reactor 170. However, it should be noted that some of the gaseous methane CH4 may be unused (i.e., unreacted) and supplied to the outlet 172 together with the hydrogen H2 and solid carbon C.

[0026] 3, the pyrolysis unit 120 further comprises a post-treatment unit 190 fluidly coupled to the pyrolysis reactor 170. In particular, the post-treatment unit 170 has a main inlet 191 fluidly coupled to the outlet 172 and configured to receive hydrogen H and solid carbon C and, optionally, unused methane CH from the pyrolysis reactor 170. In particular, the post-treatment unit 190 has a first outlet 122 fluidly coupled to the first inlet 113 and configured to supply gaseous hydrogen H to the methanation unit 110, and a second outlet 124 configured to supply solid carbon C. For example, the post-treatment unit 190 can be a separation unit such as a cyclone separator or an adsorption vessel performing PSA (= Pressure Swing Adsorption).

[0027] Advantageously, post-treatment unit 190 is further configured to separate unused gaseous methane CH4 from hydrogen H2 and solid carbon C. In particular, post-treatment unit 190 has a third outlet 192 fluidly coupled to third inlet 183 of burner unit 180 and configured to supply unused gaseous methane CH4 to be used as fuel in burner unit 180. Further advantageously, unused gaseous methane CH4 from post-treatment unit 190 can be heated before being supplied to burner unit 180. In particular, pyrolysis unit 190 can further comprise a heat exchanger 175 disposed downstream of outlet 172 of pyrolysis reactor 170 and fluidly coupled to outlet 172 and the third outlet 192 of post-treatment unit 190. Advantageously, the heat exchanger 175 is configured to transfer heat from the streams of hydrogen H2, solid carbon C, and possibly unused methane CH4 supplied at the outlet 172 to unused gaseous methane CH4 provided at the third inlet 183.

[0028] According to another aspect, the subject matter disclosed herein relates to a method 300 for producing solid carbon (C) from gaseous carbon dioxide (CO), particularly from gaseous carbon dioxide (CO) captured by a carbon capture system. With non-limiting reference to FIG. 5, the method 300 includes: - a step 320 of methanation of carbon dioxide CO2 in the methanation units 110 and 210 to produce at least gaseous methane CH4 and heat Q; - carrying out a step 310 of pyrolysis of methane CH4 in pyrolysis units 120 and 220 to produce gaseous hydrogen H2 and solid carbon C.

[0029] According to method 300, the heat Q generated in step 320 is used to perform thermal decomposition of methane CH4 in step 310, and the gaseous hydrogen generated in step 310 is used to perform methanation of carbon dioxide CO2 in step 320. According to one possibility, the methane CH4 used to perform thermal decomposition of methane CH4 (310) can be supplied by a methane pipeline. According to another possibility, method 300 can further include step 330 of supplying the gaseous methane CH4 generated through the methanation of carbon dioxide CO2 in step 320 to the thermal decomposition unit 220. In particular, the gaseous methane CH4 supplied to the thermal decomposition unit 220 is used to perform thermal decomposition of methane CH4 (310) and / or combusted in the thermal decomposition unit 220 to generate additional heat Qi. In other words, at least a portion (possibly all) of the methane CH4 supplied to the thermal decomposition unit 220 is generated in step 310. In particular, gaseous methane CH4 supplied to the pyrolysis unit (which may be supplied by a methane pipeline and / or by a methane production unit) may be used to carry out the pyrolysis of methane CH4 (310) and / or may be combusted to generate additional heat Qi in the pyrolysis unit, in particular to carry out the pyrolysis reaction.

Claims

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

2. 2. The system of claim 1, wherein the pyrolysis unit has a first outlet configured to supply gaseous hydrogen, and the methane production unit has a first inlet configured to receive gaseous hydrogen, and the first outlet and the first inlet are fluidly coupled.

3. 2. 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. 2. The system (100, 200) of claim 1, wherein the methane production unit (110, 210) has a second inlet (111, 211) configured to receive gaseous carbon dioxide (CO2) from the carbon capture system.

5. 2. 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, the gaseous methane (CH4) from the methane pipeline being used to perform pyrolysis of methane (CH4) and / or being combusted in the pyrolysis unit (120, 220) to generate additional heat (Qi).

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

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

8. 2. The system of claim 1, wherein the methane generation unit has a first outlet configured to supply gaseous methane, the thermal decomposition unit has a second inlet configured to receive the gaseous methane, the first outlet and the second inlet are fluidly coupled, a portion of the gaseous methane from the methane generation unit is used to perform thermal decomposition of methane, and a portion of the gaseous methane from the methane generation unit is combusted in the thermal decomposition unit to generate additional heat.

9. A method (300) for producing solid carbon (C) from gaseous carbon dioxide (CO2), the method comprising: - methanation (320) of carbon dioxide (CO2) in a methane production unit (110, 210) to produce at least gaseous methane (CH4) and heat (Q); - carrying out the pyrolysis of methane (CH4) in a pyrolysis unit (120, 220) (310) to produce gaseous hydrogen (H2) and solid carbon (C), The heat (Q) generated by methane production is used to thermally decompose methane (CH4), The method (300) uses the gaseous hydrogen (H2) produced by pyrolysis to methanate carbon dioxide (CO2).

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

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

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

13. 11. The method (300) of claim 10, wherein a portion of the gaseous methane (CH4) supplied to the thermal decomposition unit (220) is used to perform thermal decomposition (310) of methane (CH4), and a portion of the gaseous methane (CH4) supplied to the thermal decomposition unit (220) is combusted in the thermal decomposition unit (220) to generate additional heat (Qi).

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