SYSTEM AND METHOD FOR REMOVAL OF CARBON FROM CARBON DIOXIDE

Abstract

Disclosed is a system and method related to removal of carbon from carbon dioxide via the use of plasma arc heating techniques. The method involves generating C atoms and H atoms from C.sub.xH.sub.y. The method involves generating graphite and H.sub.2 from the C atoms and H atoms, and extracting the graphite. The method involves quenching the H.sub.2 with C.sub.xH.sub.y. The method involves receiving, at a generator, the quenched the H.sub.2 and C.sub.xH.sub.y and generating electricity. The method involves generating a concentrated stream of H.sub.2 from the quenched H.sub.2 and C.sub.xH.sub.y. The method involves receiving CO.sub.2 and the concentrated stream of H.sub.2 and generating C, O, and H atoms. The method involves receiving the C, O, and H atoms and generating graphite, wherein the graphite is extracted. In the hydrocarbon C.sub.xH.sub.y: x is an integer 1, 2, 3, . . . , and y=2x+2.

Claims

1-9. (canceled)

10. A method for removal of carbon from carbon dioxide, the method comprising: (a) generating C atoms and H atoms from CH.sub.4; (b) generating graphite and H.sub.2 from the C atoms and H atoms, and extracting the graphite; (c) quenching the H.sub.2 with CH.sub.4 and heavier weight hydrocarbons; (d) receiving, at a generator, the quenched the H.sub.2, CH.sub.4 and heavier weight hydrocarbons and generating electricity; (e) generating a concentrated stream of H.sub.2 from the quenched H.sub.2, CH.sub.4 and heavier weight hydrocarbons; (f) receiving CO.sub.2 and the concentrated stream of H.sub.2 and generating C, O, and H atoms; and (g) receiving the C, O, and H atoms and generating graphite, wherein the graphite is extracted.

11-19. (canceled)

20. A method for removal of carbon from carbon dioxide, the method comprising: (a) generating C atoms and H atoms from C.sub.xH.sub.y; (b) generating graphite and H.sub.2 from the C atoms and H atoms, and extracting the graphite; (c) quenching the H.sub.2 with C.sub.xH.sub.y and heavier weight hydrocarbons; (d) receiving, at a generator, the quenched H.sub.2, C.sub.xH.sub.y and heavier weight hydrocarbons and generating electricity; (e) generating a concentrated stream of H.sub.2 from the quenched H.sub.2, C.sub.xH.sub.y and heavier weight hydrocarbons; (f) receiving CO.sub.2 and the concentrated stream of H.sub.2 and generating C, O, and H atoms; and (g) receiving the C, O, and H atoms and generating graphite, wherein the graphite is extracted, wherein in the hydrocarbon C.sub.xH.sub.y: x is an integer 1, 2, 3, . . . , and y=2x+2.

21. The method of claim 10, wherein step (a) comprises passing the CH.sub.4 through an arc column whose temperature is above 5,000° C. to generate the C and H atoms.

22. The method of claim 10, further comprising cooling, after step (c) the quenched H.sub.2, CH.sub.4 and heavier weight hydrocarbons.

23. The method of claim 10, wherein the electricity in step (d) is used by a plasma arc heating in step (a) to generate the C atoms and H atoms from CH.sub.4.

24. The method of claim 10, wherein in addition to the concentrated stream of H.sub.2, a concentrated stream of acetylene is also generated at step (e) from the quenched H.sub.2, CH.sub.4 and heavier weight hydrocarbons.

25. The method of claim 10, wherein in addition to the graphite, a steam H2O stream is also generated at step (g) from the C, O and H atoms.

26. The method of claim 20, wherein step (a) comprises passing the C.sub.xH.sub.y through an arc column whose temperature is above 5,000° C. to generate the C and H atoms.

27. The method of claim 20, further comprising cooling, after step (c) the quenched H.sub.2, C.sub.xH.sub.y and heavier weight hydrocarbons.

28. The method of claim 20, wherein the electricity in step (d) is used by a plasma arc heating in step (a) to generate the C atoms and H atoms from C.sub.xH.sub.y.

29. The method of claim 20, wherein in addition to the concentrated stream of H.sub.2, a concentrated stream of acetylene is also generated at step (e) from the quenched H.sub.2, C.sub.xH.sub.y and heavier weight hydrocarbons.

30. The method of claim 20, wherein in addition to the graphite, a steam H.sub.2O stream is also generated at step (g) from the C, O and H atoms.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIGS. 1 and 2 are schematic flow diagrams of particular examples of stages of a treatment system; and

[0040] FIG. 3 is a schematic flow diagram of an example plasma reactor for converting CO.sub.2 from power plant emissions to graphite, in conjunction with elements such as those of FIGS. 1-2.

DETAILED DESCRIPTION

[0041] FIGS. 1, 2 and 3 will be individually discussed but first their relation to each other in an example multi-step reactor system will be described.

[0042] It will be seen in FIGS. 1, 2 and 3 that carbon dioxide CO.sub.2 can be converted to graphite and water by using natural gas CH.sub.4. It will also be appreciated how an abundantly available fossil fuel can be beneficially utilized without adding greenhouse gas to the Earth's atmosphere. The examples being presented are illustrative of systems that may be chosen not merely for good technical performance but also for reasons relating to economic factors, such as initial capital cost and operating cost, as well as convenience factors, such as space requirements and portability.

[0043] Each of the FIGS. 1-3, merely by way of further example and without limitation, may include legends including numerical values (all of which are merely representative approximations and are not necessarily exact technical values and/or calculations). Further these legends are not necessarily the only suitable values that represent the nature and characteristics of materials as applied to, affected by, and resulting from the operations of the example system. Not all such legends will be repeated in this text although all form a part of this disclosure and are believed understandable to persons of ordinary skill in thermal processes; such data are sometimes referred to as heat and material balances.

[0044] Referring to FIG. 1, it shows an exemplary first stage 800 of an exemplary carbon sequestration process. In this first stage 800, the main process activity is extraction of hydrogen, H.sub.2 from natural gas, CH.sub.4. The CH.sub.4 at an inlet 1, is fed in to the primary plasma arc heater 2, also known as plasma torch. The primary plasma arc heater 2 is supplied with electricity from the grid at 70. Inside the plasma arc heater 2, the CH.sub.4 is passed through an arc column whose temperature is above 5,000° C. At these temperatures, the bonds between carbon atoms and hydrogen atoms are broken. The mixture 3 of carbon atoms and H.sub.2 atoms is fed in to pyrolysis reactor 4. In the pyrolysis reactor 4, these atoms combine to form predominantly H.sub.2 and graphite molecules and to a lesser extent other molecules of heavier molecular weight hydrocarbons like acetylene C.sub.2H.sub.2, ethylene C.sub.2H.sub.4, etc. The graphite is removed from the pyrolysis reactor 4 at outlet 32. The hot gases at outlet 13 of the pyrolysis reactor 4 are first quenched by stream of recycled heavier molecular weight hydrocarbons at 50 in a gas mixer 60 and then are further cooled in a steam generator 5. The steam generator 5 can be series of heat exchangers that reduce the temperature of the hot gases at 61 to a temperature at outlet 6 which is suitable to enter hydrogen separator 7. The hydrogen separator 7 can be series of separators, each capable of removing a particular molecule or group of molecules as mentioned above. The hydrogen separator's 7 primary function is to remove a concentrated stream of H.sub.2 from other heavier molecular weight gases generated in the pyrolysis reactor 4. A first series of separators of the hydrogen separator 7 separates CH.sub.4 to form a concentrated stream of CH.sub.4 at outlet stream 9. A second series of separators of the hydrogen separator 7 generates a stream 10 of all remaining heavier molecular weight hydrocarbon gases. The concentrated stream of H.sub.2 exits the hydrogen separator 7 at outlet 8.

[0045] The concentrated stream of recycled heavier molecular weight hydrocarbons at 10 is split in to two streams. One stream of recycled heavier molecular weight hydrocarbons at 51 is recycled to the primary plasma arc heater 2 where it is cracked along with the CH.sub.4 feed. The second stream of recycled heavier molecular weight hydrocarbons at 50 is used to quench the hot gas stream 13 exiting the pyrolysis reactor 4 in a gas mixer 60. The quenching results in rapid cooling of the hot gas to temperature level that can be handled by conventional components of steam generator system 5. The stream 9 containing CH.sub.4 is recycled through a secondary plasma arc heater 11. The secondary plasma arc heater 11 is supplied with electricity from the grid at 71. Unlike the primary plasma arc heater 2, the secondary plasma arc heater 11 is operated with different parameters of arc power and energy density, which is needed to crack concentrated stream of CH.sub.4. Inside the secondary plasma arc heater 11, the concentrated stream of CH.sub.4 is passed through an arc column whose temperature is above 5,000° C. At these temperatures, the bonds between carbon atoms and hydrogen atoms are broken. The mixture 12 of carbon atoms and H.sub.2 atoms is fed in to pyrolysis reactor 4.

[0046] One of the series of separators in the hydrogen separator 7 can be used to separate acetylene via feed 33, which is valuable fuel.

[0047] In addition, a portion of the H.sub.2 at 8 can also be recycled to assist in quenching the hot gas stream 13 in the gas mixer 60.

[0048] The steam generator 5 includes conventional components of a steam generator system that is used to recover heat from the hot gas stream 61 and generate high pressure steam 14 for power generation in a steam turbine 15 which is connected directly at 19 to a generator 20 to produce electricity at 21. The low pressure steam at 16 is condensed to water by steam condenser 17 which is recirculated to the steam generator 5 at 18. This electricity 21 is used to operate the primary plasma arc heater 2 whereby the amount of electricity 70 needed from the utility grid system, is reduced.

[0049] In addition, a portion of electricity 21 can also be provided to secondary plasma arc heater 11 to reduce the amount electricity needed from the utility grid system.

[0050] Referring to FIG. 2, it shows an exemplary second stage 900 of the exemplary carbon sequestration process. In this second stage 900, the main process activity is conversion of CO.sub.2 to graphite and water by use of hydrogen, H.sub.2 generated from the natural gas, CH.sub.4 in the first stage 800 described above. The CO.sub.2 at an inlet 22, is fed in to the plasma arc heater 130 along with H.sub.2 at inlet 23, which is generated from the natural gas, CH.sub.4 in first stage. The H.sub.2 entering at inlet 23 is the H.sub.2 exiting the hydrogen separator 7 at outlet 8. Inside the plasma arc heater 130, a mixture of H.sub.2 and CO.sub.2 is passed through an arc column whose temperature is above 5,000° C. At these temperatures, the bonds between carbon, oxygen and hydrogen atoms are broken. The mixture 25 of carbon, oxygen and H.sub.2 atoms is fed in to CO.sub.2 converter reactor 140. In converter reactor 140, these atoms combine to form steam H.sub.2O and graphite molecules. The graphite is removed from the converter reactor 140 at outlet 28. The hot gases containing unreacted hydrogen H.sub.2, unreacted CO.sub.2 and steam H.sub.2O at outlet 29 are quenched by stream of recycled unreacted hydrogen H.sub.2 and unreacted CO.sub.2 at 43 in a gas mixer 80. The quenching results in rapid cooling of the hot gas to temperature level that can be handled by conventional components of steam generator system 90. The steam generator 90 can be series of heat exchangers that reduce the temperature of the hot gases at 30 to a temperature at outlet 31 which is suitable to condense the steam H.sub.2O into water H.sub.2O before entering water separator 40, also known conventionally as knock out pot 40. The knock out pot's 40 primary function is to separate unreacted hydrogen H.sub.2 and unreacted CO.sub.2 from steam generated in the CO.sub.2 converter reactor 140. The water exits the water separator 40 at outlet 41.

[0051] The unreacted hydrogen H.sub.2 and unreacted CO.sub.2 stream at 42 is split in to two streams. One stream of unreacted hydrogen H.sub.2 and unreacted CO.sub.2 at 44 is recycled to the plasma arc heater 130 where it is reheated to be cracked along with the CO.sub.2 feed at 22. The second stream of unreacted hydrogen H.sub.2 and unreacted CO.sub.2 at 43 is used to quench the hot gas stream 29 exiting the converter reactor 140 in a gas mixer 80. The quenching results is rapid cooling of the hot gas to a temperature level that can be handled by conventional components of steam generator system 90.

[0052] The steam generator 90 includes conventional components of a steam generator system that is used to recover heat from the hot gas stream 30 and generate high pressure steam 114 for power generation in a steam turbine 100 which is connected directly at 119 to a generator 120 to produce electricity at 121. This electricity 121 is used to operate the plasma arc heater 130 whereby the amount of electricity 122 needed from the utility grid system, is reduced. The low pressure steam at 116 is condensed to water by steam condenser 117 which is recirculated to the steam generator 90 at 118.

[0053] Referring to FIG. 3, it shows an exemplary system 1000 in which carbon dioxide CO.sub.2 at inlet 200 which has been sequestered from the emissions of a 1000 MW power plant or similar system utilized to generate electricity from fossil fuels, is fed to the plant 100 utilizing systems and processes described in current invention. The CO.sub.2 sequestration system is commercially available and is described in published literature and will not be described herein other than its known use to capture and concentrate CO.sub.2 from power plant emissions. The natural gas CH.sub.4 at inlet 300 and electricity from the utility grid at inlet 400 are the other input streams to the plant 100. The graphite at outlet 500 and water at outlet 600 are produced by the plant 100.

[0054] In an exemplary embodiment, the system includes a first stage 800 (FIG. 1) configured to generate a H.sub.2 stream from a CH.sub.4 stream. The generated H.sub.2 stream is fed to a second stage 900 (FIG. 2), along with a CO.sub.2 stream (e.g., a CO.sub.2 stream that is sequestered from a power plant, for example). Both the first stage 800 and second stage 900 generate graphite as an output.

[0055] The first stage 800 includes a first stage primary plasma arc heater 2 in connection with a pyrolysis reactor 4 via feed 3. CH.sub.4 is fed into the primary plasma arc heater 2 via feed line 1. Any of the plasma arc heaters disclosed herein can be a furnace configured to use plasma flow to transfer heat to a substance. Any of the plasma arc heaters disclosed herein can be configured to obtain electrical power from an electrical power grid or external electrical power source 70, as its main source of electrical power. The plasma flow can be generated via one or more plasma torches. Typically, the plasma torch includes housing, axial tubing, nozzle, electrodes, etc., for feeding a plasma-forming gas (e.g., air, nitrogen or argon). For cracking of CH.sub.4, a non-transferred arc is used such that the arc produced during its operation stays inside the plasma torch. The CH.sub.4 and other gases are fed in a manner so that a predominant amount of gases fed to the plasma torch are made to go through the plasma arc column in order to facilitate cracking of the gas molecules in to their constituent atoms. In the case of the primary plasma arc heater 2, heat is generated and transferred to CH.sub.4 as the CH.sub.4 passes through an arc column of the plasma arc heater 2. The CH.sub.4, while passing through the arc column, is subjected to temperatures 5,000° C. or greater so that the bonds between carbon atoms and hydrogen atoms are broken. Typically, the energy density of the plasma arc column is in the range of 100-400 kilowatts for a flow of one kilogram of CH.sub.4. Temperatures of 5,000° C. or greater are required to crack CH.sub.4, and thus it is contemplated for the temperature within the arc column to be within a range from 5,000° C. to 10,000° C. This will require the primary plasma arc heater 2 to generate plasma gas within a range from 1,500° C. to 5,000° C. In a preferred embodiment, the primary plasma arc heater 2 generates plasma gas within a range from 3,000° C. to 5,000° C. The result is a mixture comprising C atoms and H atoms. This C atom and H atom mixture is fed to the pyrolysis reactor 4.

[0056] The pyrolysis reactor 4 can be a device configured to decompose organic material at elevated temperatures. This is typically done by subjecting the organic material to elevated temperature in an inert atmosphere (e.g., in the absence of an oxidizer). In this case, the a reaction vessel which is part of the pyrolysis reactor 4 maintains the C atom and H atom mixture to elevated temperatures in the range of 3,000° C. to 5,000° C. in the absence of oxygen for sufficient time in the range of 30-120 seconds. The pyrolysis causes C atoms to combine with C atoms to form graphite molecules, and H atoms to combine with H atoms to form H.sub.2. The pyrolysis also forms other hydrocarbon molecules, such as acetylene C.sub.2H.sub.2, ethylene C.sub.2H.sub.4, etc. The mixture of graphite molecules, H.sub.2, and other hydrocarbon molecules is fed to a chemical separator which is part of the pyrolysis reactor 4. Conventional chemical separation methods (e.g., vortex separator, gravity separator, etc.) can be used to separate the graphite molecules from the H.sub.2 and other hydrocarbon molecules to produce a graphite stream. The graphite stream can be removed from the system at outlet 32, leaving a mixture of hot gasses (e.g., H.sub.2 and other hydrocarbon molecules) in the system.

[0057] The pyrolysis reactor 4 is in connection with a first stage mixer 60 via feed 13. The mixture of hot gasses (e.g., H.sub.2 and other hydrocarbon molecules) exists the pyrolysis reactor 4 and is directed via feed 13 to a first stage mixer 60. The hot gases at feed 13 are quenched from approximately 3,500° C. to 1,500° C. by a stream of recycled heavier molecular weight hydrocarbons 10 at 50 in the first stage mixer 60. The purpose of quenching the hot gases is to rapidly cool the hot gases to a temperature level that can be handled by conventional components of a steam generator 5. For instance, the mixer 60 can be configured as a quench mixer to effectively and efficiently mix the hot gases with the stream of recycled heavier molecular weight hydrocarbons using vortex cooling. This stream of recycled heavier molecular weight hydrocarbons at 50 comes from a downstream operation via a hydrogen separator 7, which will be discussed in detail later. The quenched hot gases and the recycled heavier molecular weight hydrocarbons exit the first stage mixer 60 and are fed into a steam generator 5 via feed 61—e.g., the first mixer 60 is in connection with a first steam generator 5 via inlet 61. The steam generator 5 includes a series of heat exchangers configured to reduce the temperature of the hot gases and recycled heavier molecular weight hydrocarbons to a temperature in the range of 100° C. to 300° C. at outlet 6 which is suitable to enter a hydrogen separator 7. The heat exchangers transfer heat from the hot gases and recycled heavier molecular weight hydrocarbons to water to generate steam, which is transferred via feed 14 to a steam turbine 15.

[0058] The first stage steam turbine 15 is in connection with a first stage steam condenser 17 via feed 16. The first stage steam condenser 17 is in connection with the first stage steam generator 5 via a feedback feed 18 so as to circulate the condensed/cooled water back to the first stage steam generator 5 for generating more steam when more heat is supplied to the steam generator 5. The first stage steam turbine 15 is also in connection with a first stage generator 20 at 19. For instance, the first stage steam turbine 15 can include a rotating turbine shaft that rotates due to the steam being supplied to it. The first stage generator 20 can be an electrical generator configured to generate electrical power from the rotating turbine shaft of the first stage steam turbine 15. The first stage generator 20 is in electrical connection with the first plasma arc heater 2 to supply electrical power thereto via connection 21. This electrical power can supplement electrical power being supplied to the first plasma arc heater 2 via an electrical power grid or external electrical power source 70. Typically, the steam generator system produces high pressure steam at pressures in the range of 100-500 atmospheres which is sent through the steam turbine generator combination system to produce electricity. The steam exiting the first stage steam turbine 15 is at low pressure in the range of few mm of Hg to few atmospheres depending on the design of the steam turbine. The electricity generated by the steam turbine generator set could be in the range of 10 MW to 500 MW.

[0059] The first stage steam generator 5 is also in connection with a hydrogen separator 7 via feed 6. The hot gases consisting of H.sub.2, unreacted CH.sub.4 and heavier molecular weight hydrocarbons from the first stage steam generator 5 are fed to the hydrogen separator 7 via feed 6, wherein the hydrogen separator 7 generates a H.sub.2 stream to be fed into the second stage 900. Conventional chemical separation methods, e.g., molecular sieves, etc., can be used to separate out the H.sub.2 gas from the unreacted CH.sub.4 and recycled heavier molecular weight hydrocarbons stream to produce the H.sub.2 stream that will be feed into the second stage 900. It is contemplated for the hydrogen separator 7 to include a series of separators, each separator capable of removing a particular molecule or group of molecules. For example, a first separator of the hydrogen separator 7 can separate unreacted CH.sub.4 to form a concentrated stream of CH.sub.4. This concentrated stream of CH.sub.4 can be directed to outlet stream 9. A second separator of the hydrogen separator 7 can separate all remaining heavier molecular weight hydrocarbon gases to form stream 10. The gasses passing through the first (removing CH.sub.4) and second (removing the heavier molecular weight hydrocarbon gases) separators leave a concentrated H.sub.2 stream, which is directed to outlet 8 and into the second stage 900. It should be noted that more or less separators can be used for the hydrogen separator 7.

[0060] The hydrogen separator 7 is also in connection with the primary plasma arc heater 2 via feed 10, which will use the concentrated stream of recycled heavier molecular weight hydrocarbons 51 produced by the hydrogen separator 7—this concentrated stream of recycled heavier molecular weight hydrocarbons 51 is combined with the CH.sub.4 being introduced into the primary plasma arc heater 2 via feed 1. It is contemplated for the CH.sub.4 being introduced into the primary plasma arc heater 2 via feed 1 to enter the primary plasma arc heater 2 through a first port and be used generate plasma heat gas for the primary plasma arc heater 2. The recycled heavier molecular weight hydrocarbons 51 introduced into the primary plasma arc heater 2 via feed 10 enter the primary plasma arc heater 2 through a second port and are not used to generate plasma heat gas for the primary plasma arc heater 2. Feed 10 also has a connection to the first mixer 60 via feed 50, which will also use the concentrated stream of recycled heavier molecular weight hydrocarbons produced by the hydrogen separator 7 to quench the hot gases. The hydrogen separator 7 is also in connection with a secondary plasma arc heater 11 via feed 9, which will use recycled unreacted CH.sub.4 of stream 9—the secondary plasma arc heater 11 will crack unreacted CH.sub.4 to generate C atoms and H.sub.2 atoms, which are fed into the pyrolysis reactor 4 along with the C atoms and H.sub.2 atoms from the primary plasma arc heater 2. The recycled unreacted CH.sub.4 of stream 9 is used to generate plasma heat gas for the secondary plasma arc heater 11. Again, temperatures of 5,000° C. or greater are required to crack CH.sub.4, and thus it is contemplated for the temperature within the arc column to be within a range from 5,000° C. to 10,000° C. This will require the secondary plasma arc heater 11 to generate plasma gas within a range from 1,500° C. to 5,000° C. In a preferred embodiment, the secondary plasma arc heater 11 generates plasma gas within a range from 3,000° C. to 5,000° C.

[0061] An exemplary process for the first stage 800 is as follows. CH.sub.4 is fed into a first stage primary plasma arc heater 2 via feed 1, wherein the CH.sub.4 is subjected to a 5,000° C. environment via an arc column of the primary plasma arc heater 2. During this process, bonds between C atoms and H atoms are broken. A stream of C atoms and H atoms is fed in to pyrolysis reactor 4 via feed 3, wherein H atoms combine with H atoms and C atoms combine with C atoms to form predominantly H.sub.2 and graphite molecules. Graphite is removed from the pyrolysis reactor 4 at outlet feed 32. Hot H.sub.2 gas is fed into the first stage mixer 60 via feed 13. A stream of recycled heavier molecular weight hydrocarbons via feed 50 is introduced into the first stage mixer 60 to quench the H.sub.2 gas at the first stage mixer 60. The quenched H.sub.2 gas, quenched unreacted CH.sub.4 and quenched recycled heavier molecular weight hydrocarbons gas are fed into a first stage steam generator 5 via feed 61, wherein the quenched H.sub.2 gas, quenched unreacted CH.sub.4 and quenched recycled heavier molecular weight hydrocarbons gas are further cooled. The cooling of the quenched H.sub.2 gas, quenched unreacted CH.sub.4 and quenched recycled heavier molecular weight hydrocarbons gas in the first stage steam generator 5, along with the first generator 20, is used to generate electricity. The electricity is transmitted to the primary plasma arc heater 2 via connection 21. The cooled H.sub.2 gas, unreacted CH.sub.4 and recycled heavier molecular weight hydrocarbons gas from the first steam generator 5 is fed to the hydrogen separator 7 via feed 6, wherein a concentrated stream of H.sub.2 is removed from other heavier molecular weight gases generated in the pyrolysis reactor 4.

[0062] It is contemplated for the hydrogen separator 7 to include a series of separators, each separator capable of removing a particular molecule or group of molecules. For example, a first separator of the hydrogen separator 7 can separate unreacted CH.sub.4 to form a concentrated stream of CH.sub.4. This concentrated stream of CH.sub.4 can be directed to outlet stream 9. A second separator of the hydrogen separator 7 can separate all remaining heavier molecular weight hydrocarbon gases to form stream 10. The gasses passing through the first (removing CH.sub.4) and second (removing the heavier molecular weight hydrocarbon gases) separators leave a concentrated H.sub.2 stream, which is directed to outlet 8 and into the second stage 900. It should be noted that more or less separators can be used for the hydrogen separator 7.

[0063] The hydrogen separator 7 is also in connection with the primary plasma arc heater 2 via feed 10, which will use the concentrated stream of recycled heavier molecular weight hydrocarbons produced by the hydrogen separator 7—this concentrated stream of recycled heavier molecular weight hydrocarbons is combined with the CH.sub.4 being introduced into the primary plasma arc heater 2 via feed 1. Feed 10 also has a connection to the first mixer 60 via feed 50, which will also use the concentrated stream of recycled heavier molecular weight hydrocarbons produced by the hydrogen separator 7 to quench the hot gases. The hydrogen separator 7 is also in connection with a secondary plasma arc heater 11 via feed 9, which will use recycled unreacted CH.sub.4 of stream 9—the secondary plasma arc heater 11 will crack unreacted CH.sub.4 to generate C atoms and H.sub.2 atoms, which are fed into the pyrolysis reactor 4 along with the C atoms and H.sub.2 atoms from the primary plasma arc heater 2 via feed 12.

[0064] The second stage 900 includes a third plasma arc heater 130. The H.sub.2 stream generated from the hydrogen separator 7 of the first stage 800 enters the third plasma arc heater 130 via feed 23. A stream of CO.sub.2 that has been sequestered or captured from an energy intensive operation, such as a 1,000 MW power plant, is also introduced into the third plasma arc heater 130 via feed 22. The third plasma arc heater 130 subjects the H.sub.2 and CO.sub.2 gas mixture 3 to temperatures of 5,000° C. or greater. At these temperatures, the bonds between carbon, oxygen and hydrogen atoms are broken. The third plasma arc heater 130 is in connection with a CO.sub.2 converter 140 via feed 25, wherein the mixture 3 of carbon, oxygen and H.sub.2 atoms is fed into the CO.sub.2 converter reactor 140. The CO.sub.2 converter 140 combines the of carbon, oxygen and H.sub.2 atoms to form a steam H.sub.2O stream and a graphite stream. The steam H.sub.2O stream and any unreacted hydrogen H.sub.2 and unreacted CO.sub.2 exit the CO.sub.2 converter reactor 140 and enter the second stage mixer 80 via feed 29. The graphite stream exits the system as an output at outlet feed 28. Again, conventional chemical separation methods can be used to separate the graphite molecules from the H.sub.2/steam H.sub.2O stream.

[0065] The CO.sub.2 converter 140 is in connection with a second stage mixer 80 via feed 29. The second stage mixer 80 is in connection with a second steam generator 90 via feed 30. The second stage steam generator 90 is in connection with a second stage steam turbine 100 via feed 114. The second stage steam turbine 100 is in connection with a second stage steam condenser 117 via feed 116. The second stage steam condenser 117 is in connection with the second stage steam generator 90 via a feedback feed 118. The second stage steam turbine 100 is also in connection with a second stage generator 120 via feed 119. The second stage generator 120 is in electrical connection with the third plasma arc heater 130 to supply electrical power thereto via connection 121. This electrical power can supplement electrical power being supplied to the third plasma arc heater 140 via an electrical power grid or external electrical power source 122. The second stage steam generator 90 is also in connection with a water separator 40 via feed 31. The water separator 40 separates unreacted hydrogen H.sub.2 and unreacted CO.sub.2 from steam generated in the CO.sub.2 converter reactor 140. The water exits the water separator 40 at outlet 41. The unreacted hydrogen H.sub.2 and unreacted CO.sub.2 stream at 42 from the water separator 40 is split in to two streams. One stream of unreacted hydrogen H.sub.2 and unreacted CO.sub.2 at 44 is recycled to the third plasma arc heater 130 where it is reheated to be cracked along with the CO.sub.2 feed at 22. The second stream of unreacted hydrogen H.sub.2 and unreacted CO.sub.2 at 43 has a connection to the second stage mixer 80.

[0066] It is contemplated for the CO.sub.2 being introduced into the third plasma arc heater 130 via feed 22 to enter the third plasma arc heater 130 through a first port and be used generate plasma heat gas for the third plasma arc heater 130. The H.sub.2 stream via feed 23 and the unreacted hydrogen H.sub.2 and unreacted CO.sub.2 via feed 22 introduced into the third plasma arc heater 130 enter the third plasma arc heater 130 through second and third ports, respectively, and are not used to generate plasma heat gas for the third plasma arc heater 130. Temperatures of 5,000° C. or greater are required to crack H.sub.2 and CO.sub.2, and thus it is contemplated for the temperature within the arc column to be within a range from 5,000° C. to 10,000° C. This will require the third plasma arc heater 130 to generate plasma gas within a range from 1,500° C. to 5,000° C. In a preferred embodiment, the third plasma arc heater 130 generates plasma gas within a range from 3,000° C. to 5,000° C.

[0067] An exemplary process for the second stage 900 is as follows. The H.sub.2 stream generated from the hydrogen separator 7 of the first stage 800 enters the third plasma arc heater 130 via feed 23. A stream of CO.sub.2 is also introduced into the third plasma arc heater 130 via feed 22. The stream of H.sub.2 and CO.sub.2 is subjected to a 5,000° C. environment via an arc column of the third plasma arc heater 130, wherein the bonds between carbon, oxygen, and hydrogen atoms are broken. The mixture of carbon, oxygen, and hydrogen atoms is fed into the CO.sub.2 converter reactor 140 via feed 25, wherein graphite is removed from the CO.sub.2 converter reactor 140 at feed 28. Hot gases comprising unreacted hydrogen H.sub.2, unreacted CO.sub.2 and H.sub.2O steam exit the CO.sub.2 converter reactor 140 and enter the second stage mixer 80 via feed 29, wherein the stream of unreacted hydrogen H.sub.2, unreacted CO.sub.2 and H.sub.2O steam is quenched by recycled unreacted hydrogen H.sub.2 and unreacted CO.sub.2 fed into the mixer 80 via feed 43. The quenched unreacted hydrogen H.sub.2 and quenched unreacted CO.sub.2 and quenched H.sub.2O stream is fed into the second stage steam generator 90 (which may comprise a series of heat exchangers) to be further cooled, wherein the H.sub.2O steam condenses to water. The cooling of the quenched unreacted hydrogen H.sub.2 and unreacted CO.sub.2 and quenched H.sub.2O stream is used to generate electricity that is transmitted to the third plasma arc heater 130 via connection 121. The cooled unreacted hydrogen H.sub.2, unreacted CO.sub.2 and water H.sub.2O stream is fed into the water separator 40 via feed 31, wherein water is condensed and is separated out at 41. The concentrated stream of unreacted hydrogen H.sub.2 and unreacted CO.sub.2 is split into two streams. A first concentrated stream of unreacted hydrogen H.sub.2 and unreacted CO.sub.2 is recycled (directed to) to the third plasma arc heater 130 via feed 44 where it is reheated to be cracked along with CO.sub.2 being introduced via feed 22. The second stream of unreacted hydrogen H.sub.2 and unreacted CO.sub.2 is directed via feed 43 into the second stage mixer 80 to quench the hot gas stream entering the second stage mixer 80.

[0068] The system described and illustrated herein has two plasma arc heaters 2, 11 in the first stage 800 and one plasma arc heater 130 in the second stage 900. The plasma arc heaters are used to crack streams of gas flowing through the system, the cracked gas then being supplied to the pyrolysis reactor 4 or CO.sub.2 converter 140. It is understood that any number of plasma arc heaters can be used to crack gas streams to meet desired design criteria. For instance, it may be desirable to use more than two or less than two plasma arc heaters in the first stage 800 to obtain a desired operating efficiency for the system.

[0069] FIG. 3 illustrates an exemplary system 1000 in which an embodiment of the invention can be applied. An embodiment of the inventive system is referred to as a plant 100 and is placed in connection with a power plant that generates CO.sub.2 emissions. CO.sub.2 emissions from the power plant are sequestered and fed into the plant 100 via feed 200—e.g., this gas is fed into the third plasma arc heater 130 of the second stage 900. CH.sub.4 is fed into the plant 100 via feed 300—e.g., this gas is fed into the primary plasma arc heater 2 of the first stage 800. Electrical power is provided to various components (e.g., plasma arc heaters 2, 11, 130) of the plant 100 via line 400. The plant 100 is operated in accordance with the process steps described herein to generate a graphite stream 500 and a water stream 600. The graphite stream 500 comprises the graphite exiting the first stage 800 at outlet 32 and the graphite exiting the second stage 900 at outlet 28. The water stream 600 comprises the water exiting the second stage 900 at outlet 41.

[0070] It is therefore seen that systems and processes in accordance with the present invention can make use of known and available components, such as plasma arc heaters 2, 11, 130 for converting carbon dioxide in to graphite and water by utilizing hydrogen generated from natural gas, in particular innovative ways to minimize greenhouse gas, with insight as to both the capital cost and the operating cost. A need for such cost-effective treatment of carbon dioxide has been heightened by climate change that has been caused by temperature rise of Earth's atmosphere.

[0071] In general summary, but without limitation, the present invention can be characterized in the following ways, for example:

[0072] A system, and a corresponding method, in which carbon dioxide is converted to graphite and water in a reactor which is supplied with hydrogen produced from natural gas. The system additionally has heat recovery feature such that the energy requirement of the system is optimized. The heat recovery system produces high pressure steam which is utilized in a turbine generator system to produce electricity which reduces the amount of total electricity required from the grid. The system additionally has resource recovery features such that conversion of carbon dioxide results in production of graphite, an industrially widely used resource and water, a scare resource in most regions of world. Also, or alternatively, such a system may be used to generate hydrogen for general use in the world economy.

[0073] It will be apparent to those skilled in the art that numerous modifications and variations of the described examples and embodiments are possible in light of the above teachings of the disclosure. The disclosed examples and embodiments are presented for purposes of illustration only. Other alternate embodiments may include some or all of the features disclosed herein. Therefore, it is the intent to cover all such modifications and alternate embodiments as may come within the true scope of this invention, which is to be given the full breadth thereof. Additionally, the disclosure of a range of values is a disclosure of every numerical value within that range, including the end points.