Plasma system for converting carbon dioxide to carbon monoxide

Abstract

A system and method for plasma discharge induced reduction of CO2 to CO in the presence of a predetermined amount of a reducing agent (i.e. Methane or hydrogen) is provided.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 412,403, filed on October 1, 2022, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] The present invention generally relates to converting carbon dioxide (CO2) into carbon monoxide (CO). More particularly, the present invention relates to a system for converting carbon dioxide (CO2) into carbon monoxide (CO) within a predetermined conversion range. Background Art

[0004] Developing effective CO2 utilization technology is a key condition for the transformation to the reality of green CO2-free industry. The problem is not only to make energy generation a completely green process, but also to make all other industrial processes (agriculture, metallurgy, cement production, etc.) CO2-free. Only by fully utilizing the CO2 produced in the industrial process can the task be solved, rather than underground CO2 storage, which is only a temporary solution. Ideally, CO2 should be utilized to produce some valuable products that actually have unlimited markets and are comparable to the generation scale of huge CO2 in the industrial process. Such a product is carbon monoxide or CO. CO is a precursor to many chemical processes, which can be used to make medicines, flavors, fuels, plastics and many other valuable products. Therefore, although from an environmental point of view, generating CO2 is considered to be an undesirable waste product, CO is actually a useful chemical component in many chemical processes.

[0005] Efficient technologies for converting CO2 to CO could also have new applications, which could solve the global problem of hydrogen production and transportation.

[0006] For CO2 decomposition, there are several known processes for converting CO2 to CO that use plasma to stimulate the reaction. One plasma process is called "methane dry reforming," which uses a 50% / 50% mixture of CO2 and methane by volume:

[0007] (1) CH4 + CO2 = 2H2 + 2CO

[0008] In this process, CO can be produced as a reaction product. A large amount of methane is converted into hydrogen together with the utilization of CO 2 . A disadvantage of this process is that complex techniques are required to separate the reaction products from each other and from the residual starting reagents. Figure 1A simplified gas separation flow diagram of the process is presented, showing a plasma reactor 104 supplied with a power source 102. The plasma reactor 104 receives two inputs—50% methane and 50% CO2. The output of the plasma reactor 104 is fed to a first gas separation stage 108 via a compressor 106. The first gas separation stage 108 produces four outputs—H2 and CO2, and methane and CO. The H2 and CO2 are fed to a second gas separation stage 112 via a compressor 110, and the methane and CO are fed to a third gas separation stage 114. The CO is then removed as a useful product, and the other components are fed back to the plasma reactor.

[0009] Real gas separation systems are much more complex and have many stages to ensure product purity. Each stage requires additional energy to pressurize the gas, which increases the energy cost of the final product.

[0010] The process of directly decomposing CO2 by plasma is also known, as shown in the following reaction:

[0011] (2) CO2 = CO + 1 / 2O2 The process also requires the separation of CO and oxygen from each other and from the residual CO2, which should be returned to the reactor input for further processing. The separation of CO2, which can be carried out by membranes, TSA (temperature swing adsorption) technology or PSA (pressure swing adsorption) technology, produces an explosive and flammable mixture of CO and oxygen, which is dangerous for further processing. Another problem with this process is the residual oxygen in the CO2 reflux returned to the reactor. This residual oxygen is inevitably present in the recycled CO2 stream and increases the energy cost of CO production by stimulating the reverse reaction of CO oxidation. Figure 2 A simplified gas separation flow diagram of the process is presented, in which the same components have Figure 1 The same reference numerals are used as in , with the addition of a compressor 106 for a mixture of CO and oxygen.

[0012] Real gas separation systems are much more complex than the simple diagram shown, but all gas separation solutions maintain these issues. Summary of the Invention

[0013] In one aspect of the present invention, a system for generating carbon monoxide (CO) from carbon dioxide (CO2) is provided, the system comprising: a plasma reactor; a CO2 source connected to a first valve fluid; a reducing agent source connected to a second valve fluid; wherein the first valve and the second valve are controlled to provide a mixture of CO2 and the reducing agent in a predetermined molar ratio to the plasma reactor, and wherein the reducing agent is selected from hydrogen (H2) and methane (CH4), and wherein: the predetermined molar ratio between CO2 and CH4 is at least 3:1; the predetermined molar ratio between CO2 and H2 is at least 1:1; a compressor connected to the outlet fluid of the plasma reactor; a water separator connected to the outlet fluid of the compressor; and a gas separation membrane (GSM) connected to the outlet fluid of the water separator, including a CO outlet and a CO2 outlet.

[0014] In one embodiment, the molar ratio is calculated based on normal flow rates.

[0015] In one embodiment, the system further includes: a first flow meter for measuring a first flow rate of CO2; a second flow meter for measuring a second flow rate of the reductant; and a controller configured to control the first valve and the second valve based on measurements received from the first flow meter and the second flow meter.

[0016] In one embodiment, the system further includes a gas composition analyzer fluidly connected between the outlet of the water separator and the inlet of the GSM, and wherein the controller is further configured to control the first valve and the second valve based on the conversion rate of CO2 determined by the gas composition analyzer.

[0017] In one embodiment, the controller is further configured to: set a desired conversion rate; and adjust the first valve and the second valve until the desired conversion rate is detected by the gas composition analyzer.

[0018] In one embodiment, the desired conversion is less than 65% measured under normal conditions.

[0019] In one embodiment, the desired conversion is between about 30% and about 55%.

[0020] In one embodiment, the system further comprises a recycling blower fluidly connected between the CO 2 outlet of the GSM and the inlet of the plasma generator, and wherein the controller is further configured to control the first valve and the second valve based also on the flow rate of the recycled CO 2 .

[0021] In one embodiment, the gas at the CO outlet has a chemical purity of at least 99%, and wherein the gas has no more than 1% v / v of O2, H2, or both.

[0022] In one embodiment, the pressure of the mixture is 5% to 20% higher than the pressure at the plasma reactor.

[0023] In one embodiment, the controller is further configured to control power provided to the plasma generator.

[0024] In one embodiment, the power is controlled to provide the desired conversion rate.

[0025] On the other hand, a method for generating carbon monoxide (CO) from carbon dioxide (CO2) is provided, comprising: providing CO2 from a CO2 source to a plasma reactor at a first flow rate; providing a reducing agent from a reducing agent source to the plasma reactor at a second flow rate to obtain a mixture of the CO2 and the reducing agent in a predetermined molar ratio, wherein the reducing agent is selected from hydrogen (H2) and methane (CH4), and wherein: the predetermined molar ratio between CO2 and CH4 is at least 3:1; or the predetermined molar ratio between CO2 and H2 is at least 1:1; wherein the providing is carried out while generating an electrical discharge in the plasma reactor to produce gaseous products including CO, residual CO2 and water; separating water from the gaseous products to obtain CO and residual CO2; and separating CO from the residual CO2.

[0026] In one embodiment, the method further includes determining a conversion of the gaseous product and controlling the first flow rate and the second flow rate to achieve a desired conversion.

[0027] In another aspect, a system for generating carbon monoxide (CO) from carbon dioxide (CO2) is provided, the system comprising:

[0028] a plasma reactor configured to receive a mixture of carbon dioxide (CO2) and methane (CH4) and to produce a mixture including water and CO;

[0029] a compressor configured to receive and compress the mixture of water and CO from the plasma reactor and to output the compressed mixture of liquid water and CO;

[0030] a water separator configured to receive the compressed mixture and to remove liquid water from the compressed mixture; and

[0031] A gas separation membrane is configured to receive the compressed mixture after water removal and to separate the CO from any residual carbon dioxide and to feed the residual carbon dioxide back to the plasma reactor.

[0032] In one embodiment, the mixture of carbon dioxide and methane has a volume ratio of methane to carbon dioxide of up to 1:3.

[0033] In one embodiment, the methane supplied to the system is fully converted.

[0034] In one embodiment, the plasma reactor is an arc plasmatron.

[0035] In one embodiment, the plasma reactor is a gliding arc plasmatron.

[0036] In one embodiment, the plasma reactor is an RF plasma generator.

[0037] In one embodiment, the plasma reactor is a nanosecond pulsed plasma reactor.

[0038] In one embodiment, the plasma reactor is a microwave plasma reactor.

[0039] In one embodiment, the plasma reactor includes a circulation blower to ensure movement of gaseous components through the plasma reactor.

[0040] In one embodiment, the CO is liquefied and transported by sea for subsequent generation of hydrogen from water via a shift reaction of the CO with water.

[0041] In another aspect, there is provided a method for generating carbon monoxide (CO) from carbon dioxide (CO 2 ), the method comprising:

[0042] feeding a mixture of carbon dioxide and methane into a plasma reactor;

[0043] activating a plasma reactor to generate a mixture including gaseous water and CO;

[0044] Compressing a mixture of water and carbon dioxide to liquefy the water;

[0045] removing liquid water from the compressed mixture;

[0046] separating the CO2 form from residual carbon dioxide in the compressed mixture; and

[0047] The residual carbon dioxide is fed back to the plasma reactor.

[0048] In one embodiment, the mixture of carbon dioxide and methane has a volume ratio of methane to carbon dioxide of up to 1:3.

[0049] In one embodiment, the methane supplied to the system is fully converted.

[0050] In one embodiment, the plasma reactor is an arc plasma generator.

[0051] In one embodiment, the plasma reactor is a gliding arc plasma generator.

[0052] In one embodiment, the plasma reactor is an RF plasma generator.

[0053] In one embodiment, the plasma reactor is a nanosecond pulsed plasma reactor.

[0054] In one embodiment, the plasma reactor is a microwave plasma reactor.

[0055] In one embodiment, the plasma reactor includes a circulation blower to ensure movement of gaseous components through the plasma reactor.

[0056] In one embodiment, the CO is liquefied and transported by sea for subsequent generation of hydrogen from water via a shift reaction of the CO with water. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. However, the invention, both as to its organization and method of operation, together with objects, features, and advantages thereof, may be best understood by reference to the following detailed description when read in connection with the accompanying drawings, in which:

[0058] Figure 1 A simplified gas separation flow diagram illustrating a conventional dry reforming process for CO generation;

[0059] Figure 2 A simplified gas separation flow diagram illustrating the production of CO by a CO2 plasma dissociation process is shown;

[0060] Figure 3A is a block diagram depicting a system for generating CO from CO2 according to some embodiments of the present invention;

[0061] Figure 3B is a flow chart of a method for generating CO from CO2 according to some embodiments of the present invention;

[0062] Figure 4 describes the use of technology for hydrogen generation and marine transport according to some embodiments of the present invention; and

[0063] Figure 5 It is shown how CO2 can be used in a recycling process for hydrogen generation and marine transport according to some embodiments of the present invention.

[0064] It will be understood that for simplicity and clarity of illustration, the elements shown in the figures are not necessarily drawn to scale. For example, the dimensions of some elements may be exaggerated relative to other elements for clarity. Furthermore, where deemed appropriate, reference numerals may be repeated between the figures to indicate corresponding or similar elements. DETAILED DESCRIPTION

[0065] Those skilled in the art will recognize that the present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The above embodiments are therefore to be considered in all respects as illustrative rather than restrictive of the invention described herein. The scope of the invention is therefore indicated by the appended claims rather than by the foregoing description, and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

[0066] All plasma processes for producing CO by CO2 conversion need to be combined with gas separation technology to separate the products / impurities (sand) to recycle the initial reagents. An efficient process for converting CO2 to CO should meet the following requirements:

[0067] 1. Efficient plasma generation and separation of CO from other products and residual CO2, which should be returned to the reactor input.

[0068] 2. Scalability of the system to any necessary capacity of a specific chemical plant consuming CO. Preferably, in order to avoid expensive and dangerous CO transportation, the system should be installed next to the chemical plant consuming CO and supply it with the necessary capacity.

[0069] It is therefore an object of the present invention to provide an efficient method and system for the plasma chemical conversion of CO2 to CO. Plasma chemical conversion of pure CO2 to CO and oxygen is inefficient because the resulting mixture of CO and oxygen is a flammable mixture. Thus, after only about 20% of the CO2 is converted, the resulting mixture will spontaneously ignite, and further conversion will be impossible.

[0070] As a solution to the problem of CO conversion limitations and the increased energy cost of CO generation near the ignition limit of the mixture, the inventors have added that a reducing agent (e.g., methane) can be used in the CO stream. Alternatively, hydrogen can also be used as a reducing agent. The term "CO conversion" is well known to those skilled in the art and refers to the molar ratio of the resulting CO (after the plasma chemical reaction) relative to the initial amount of CO fed to the plasma reactor.

[0071] The admixture of methane effectively neutralizes atomic oxygen through the methane oxidation reaction, which further increases the yield of CO. The final integrated reaction of the process can be presented as:

[0072] (3) 3 CO2 + CH4 = 4CO + 2H2O

[0073] The present inventors have found that for a completely stoichiometric reaction with zero oxygen output concentration, one methane molecule is required for every four CO molecules produced or every three CO2 molecules converted, but that even smaller ratios of methane admixture can significantly improve the energy cost of CO production, since the CO energy cost has a strong dependence on the oxygen concentration close to the ignition limit of the mixture. In this case, some residual oxygen concentration will remain in the gaseous products. A stoichiometric reaction or stoichiometric ratio is essential because the separation of methane / CO mixtures is very cumbersome with respect to oxygen consumption. Therefore, in order to optimize the overall process of CO2 to CO conversion, a complete (stoichiometric) reaction of methane is required, so that all the methane fed to the plasma reactor is oxidized. This is also true when using hydrogen as a reducing agent, however, the stoichiometric ratio between H2 and CO2 is 1:1.

[0074] Thus, the present invention, in some embodiments thereof, is based on the surprising discovery that limiting the CO conversion rate to a maximum of about 65%, or a maximum of about 60%, results in a significant improvement in the cost-effectiveness of the claimed process (i.e., the conversion of CO to CO). Furthermore, the inventors have discovered that maintaining the amount of reducing agent fed to the plasma reactor within the limits of stoichiometric conversion (not exceeding the stoichiometric ratio such that the generated oxygen completely reacts with the reducing agent and the resulting gaseous products are substantially free of unreacted reducing agent) is essential for optimal cost-effectiveness of the CO conversion process disclosed herein.

[0075] Now refer to Figure 3A , which is a block diagram depicting a system for generating CO from CO2 according to some embodiments of the present invention. System 200 may include a plasma reactor 210 powered by a power supply 215. Plasma reactor 210 may be fed with gas from a CO2 source 220 and a reducing agent source 230, for example, via inlet 212. Figure 3A As schematically illustrated in FIG, thick lines indicate fluid connections between components, while thin lines are communication / electrical connections between components.

[0076] The plasma reactor 210 (also referred to as a plasma generator, plasma generator, etc.) is any reactor configured to induce an electrical discharge in a gas. For example, the plasma reactor 210 can be selected from an arc plasma generator, a gliding arc plasma generator, an RF plasma generator, a nanosecond pulsed plasma reactor, a microwave plasma reactor, and the like. In a non-limiting example, the gas pressure within the reactor 210 can be between 1.05 and 10 atm, such as, for example, 1.2 atm, 1.5 atm, 2 atm, 2.5 atm, 5 atm, 7 atm, 10 atm, and any values therebetween. In some embodiments, the power supply 215 can provide between 5 and 100 kW, such as, for example, 10 kW, 15 kW, 20 kW, 25 kW, 30 kW, 50 kW, 75 kW, 95 kW, and any values therebetween. In some embodiments, the power supply 215 can be controlled by a controller, such as, for example, the controller 270 discussed below.

[0077] In some embodiments, CO2 from CO2 source 220 and reducing agent from reducing agent source 230 can be continuously provided to reactor 210 to be treated by plasma. Thus, gaseous products of the reaction can continuously exit outlet 217 of reactor 210. In some embodiments, the gaseous products can include CO, residual reducing agent, residual CO2, and water.

[0078] The term "reducing agent" encompasses gases that are capable of reducing oxygen to water via a plasma-assisted reaction.

[0079] In some embodiments, the CO2 source 220 is fluidically connected to a first valve 225 for controlling the flow of CO2. The CO2 source 220 can be a pressurized tank, a pipe, etc. In some embodiments, the first valve 225 can be fluidically connected to a first flow meter 222 for measuring the flow of CO2. In some embodiments, the CO2 flow rate is between 2 and 10 m 3 / hour, for example, measured under normal conditions (eg, at 1 atm. and 25° C.) One skilled in the art will appreciate that when different pressures or temperatures are used, the gas equations can be used to convert the ranges.

[0080] In some embodiments, the reductant source 230 is fluidly connected to the second valve 235 and can be a pressurized tank, a pipe, etc. In some embodiments, the second valve 235 can be fluidly connected to a second flow meter 232 for measuring the flow of the reductant. In some embodiments, the reductant is selected from hydrogen (H2) and methane (CH4).

[0081] In some embodiments, the first valve 225 and the second valve 235 are controlled to provide a mixture of CO2 and the reducing agent at a predetermined molar ratio to the plasma reactor 210. In some embodiments, the predetermined molar ratio between CO2 and the reducing agent corresponds to a ratio equal to or less than a stoichiometric ratio, as disclosed herein.

[0082] In some embodiments, the predetermined molar ratio between CO2 and CH4 is at least 3:1, e.g., 3.2:1, 3.5:1, 3.8:1, 4:1, 4.5:1, 5:1, 8:1, 10:1, and any value therebetween. In some embodiments, the predetermined molar ratio between CO2 and CH4 is between 3:1 and 30:1, between 3:1 and 20:1, between 3:1 and 10:1, between 3:1 and 6:1, including any ranges therebetween.

[0083] In some embodiments, the predetermined molar ratio between CO2 and H2 is at least 1:1, e.g., at least 1.5:1, 2:1, 2.5:1, 3:1, and any value therebetween. In some embodiments, the predetermined molar ratio between CO2 and H2 is between 1:1 and 15:1, between 1:1 and 10:1, between 1:1 and 8:1, between 1:1 and 6:1, between 1:1 and 4:1, between 1:1 and 3:1, between 1:1 and 2:1, including any ranges therebetween. In some embodiments, the molar ratio is calculated based on normal flow rate.

[0084] In some embodiments, the first valve 225 and the second valve 235 can be controlled by a controller, such as the controller 270 discussed below.

[0085] In some embodiments, the system 200 can further include a first pressure sensor 218 that measures the pressure of the mixture of CO2 and the reducing agent provided to the inlet 212. In some embodiments, the pressure of the mixture is 5% to 20% higher than the pressure at the plasma reactor, such as 5%, 7%, 10%, 15%, and any value therebetween.

[0086] In some embodiments, the system 200 can further include a compressor 240 fluidly connected to the outlet 217 of the plasma reactor 210. The compressor 240 compresses the gaseous products of the reaction occurring within the reactor 210. In some embodiments, a second pressure sensor 245 can be connected to the outlet of the compressor 240 for measuring the pressure of the gaseous products.

[0087] In some embodiments, the system 200 can further include a water separator 250 fluidly connected to the outlet of the compressor 240. The water separator 250 can separate water from the compressed mixture. The water separator 240 can include a cooler and a liquid water filter. As shown, water can be extracted from the water separator 250.

[0088] In some embodiments, the system 200 may further include a gas separation membrane (GSM) 260 fluidly connected to the outlet 257 of the water separator 250. The GSM 260 may include a CO outlet 263 and a CO2 outlet 262. The GSM may be any membrane configured to separate CO and CO2. In a non-limiting example, the GSM 260 may include a polysulfone gas separation hollow fiber membrane.

[0089] In some embodiments, the GSM 260 can separate CO and CO2 to provide a gas product having a CO2 concentration of no more than 5%, no more than 2%, no more than 1%, no more than 0.1%, or no more than 0.01% based on the total volume of the gas product at the CO outlet 263. In some embodiments, the CO gas product at the CO outlet 263 is characterized by a chemical purity (by volume) of at least 99%, such as at least 99.1%, at least 99.4%, at least 99.6%, at least 99.7%, at least 99.8%, at least 99.9%, at least 99.99% or more. In some embodiments, the CO gas product at the CO outlet 263 is characterized by a concentration of at least one of oxygen, CO2, and a reducing agent of no more than 1%, no more than 0.1%, or between 10 ppm and 1%, between 10 ppm and 0.1%, including any ranges therebetween.

[0090] GSM 260 can separate CO and CO2, thereby providing a gas product having a chemical purity of at least 99% v / v CO, for example, at least 99.1% CO, at least 99.4% CO, at least 99.6% CO, at least 99.7% CO, at least 99.8% CO, or higher, at CO outlet 263. In some embodiments, CO outlet 263 can be fluidly connected to a CO valve 265 and a CO flow meter 267 for controlling the flow of CO. In some embodiments, the CO gas has no more than 1% v / v of O2, H2, or both. In some embodiments, the CO gas after GSM 260 has trace amounts of at least one of the following: CO2, O2, or H2.

[0091] In some embodiments, the gaseous product at outlet 217 is characterized by a volume concentration of oxygen and reducing agent of no more than 5%, no more than 4%, no more than 3%, no more than 2%, no more than 1%, no more than 0.5%, no more than 0.1%, including any ranges therebetween.

[0092] In some embodiments, the system 200 may further include a controller 270 for controlling various aspects, parameters, and components of the system 200. The controller 270 may include a processor 272, which may be any known processing unit (e.g., a chip) or a processing service (e.g., in a cloud service). The processor 272 may execute code instructions stored in the memory 274, such as instructions for controlling CO generation using the system 200.

[0093] For example, the controller 270 may receive flow measurements from the first flow meter 222 and the second flow meter 232 and may control the first valve 225 and the second valve 235 based on the measurements received from the first flow meter 222 and the second flow meter 232 .

[0094] In another example, the controller 270 can set a desired conversion rate between CO and CO2 (as a product of the reaction in the reactor 210) and can control the first valve 225 and the second valve 235 to provide a molar ratio between CO2 and the reducing agent that will produce the desired conversion rate. In a non-limiting example, the desired conversion rate measured under normal conditions is less than 65%, for example, between about 30% and about 55%, between about 10% and about 67%, between about 10% and about 65%, between about 10% and about 62%, between about 10% and about 60%, between about 20% and about 55%, between about 30% and about 55%, including any range therebetween. It will be understood by those skilled in the art that these are relatively low conversion rates, which the inventors have found to be surprisingly beneficial for producing high purity CO at low energy costs. For example, the inventors surprisingly found that the production cost at a conversion rate of 70% is much higher than at a conversion rate of about 50% (see #2 and #4 in the Examples section). This contradicts the prior art knowledge that the conversion rate should be as high as possible.

[0095] In yet another example, the controller 270 can be further configured to control the power provided to the plasma reactor 210, such as by controlling the power supply 215. In some embodiments, the power can be controlled / regulated to provide a desired conversion rate.

[0096] Thus, in some embodiments, the controller 270 can control one or more of the following parameters and components to cause the plasma reactor 210 to produce CO at a desired conversion rate. In some embodiments, the parameters and components are a first flow rate of CO controlled by the first valve 225; a second flow rate of the reducing agent controlled by the second valve 235; and power provided to the plasma reactor 210 from the power supply 215.

[0097] In some embodiments, the system 200 may further include a gas composition analyzer 255 fluidly connected between the outlet 257 of the water separator 250 and the inlet of the GSM 260. For example, the gas composition analyzer 255 may be a spectroscopic gas analyzer, such as an infrared gas analyzer. In some embodiments, the controller 270 may control the first valve 225 and the second valve 235 based on the conversion rate detected by the gas composition analyzer 255, for example, until a desired conversion rate is detected. In some embodiments, the controller 270 may continuously monitor the conversion rate to maintain the desired conversion rate throughout the conversion process.

[0098] In some embodiments, the system 200 can further include a recirculation blower 280 fluidly connected between the CO2 outlet 262 of the GSM 260 and the inlet 212 of the plasma generator 210. In some embodiments, the controller 270 is further configured to control the first valve 225 and the second valve 235 based on the flow rate of the recycled CO2.

[0099] Now refer to Figure 3B , which is a flow chart of a method for generating carbon monoxide (CO) from carbon dioxide (CO2) according to some embodiments of the present invention. For example, under the supervision and control of controller 270 or any other suitable controller, system 200 can be used to perform Figure 3B method.

[0100] In step 310, the method may include providing CO2 at a first flow rate from a CO2 source. For example, CO2 may be provided at a flow rate of 2 to 10 m 3 A first flow rate of between 100 Å and 100 Å / hour is provided from CO 2 source 220 .

[0101] In step 320, the method may include providing the reducing agent from the reducing agent source at a second flow rate. For example, the reducing agent may be provided at a flow rate of 1 to 5 m 3 A second flow rate of between 100 Å and 100 Å per hour is provided from the reducing agent 230. In some embodiments, the method may include performing steps 310 and 320 simultaneously or subsequently.

[0102] In step 330, the method may include mixing CO2 and the reducing agent in a predetermined molar ratio. In some embodiments, the mixing (step 330) is performed in a mixing chamber. In some embodiments, the mixing (step 330) is performed in a gas feed pipe. In some embodiments, each gas is fed to the plasma reactor separately, and the mixing (step 330) is performed inside the plasma reactor to obtain a mixture of CO2 and the reducing agent. The plasma reactor can be equipped with a mixer (blower or fan) that increases the mixing rate. The skilled person will understand that the diffusion rate of the two gases fed to the plasma reactor (typically operated at a temperature between 100 and 300°C or between 100 and 200°C) can be sufficient for proper mixing.

[0103] In some embodiments, the predetermined molar ratio refers to the molar ratio of CO2 to the reducing agent in the mixture, as disclosed above. In some embodiments, the predetermined molar ratio is at most a stoichiometric ratio (i.e., the amount of reducing agent in the mixture and / or relative to the CO2 fed to the reactor does not exceed the stoichiometric ratio). In some embodiments, the reducing agent is selected from hydrogen (H2) and methane (CH4). In some embodiments, the predetermined molar ratio between CO2 and CH4 is at least 3:1, or the predetermined molar ratio between CO2 and H2 is at least 1:1, i.e., the amount of CH4 or H2 does not exceed the stoichiometric ratio of each reducing agent, respectively.

[0104] In step 340, the method may include feeding the mixture into a plasma reactor while generating an electrical discharge in the plasma reactor to produce a gaseous product comprising CO, a reducing agent, residual CO2, and water. For example, the mixture may be continuously fed into the plasma reactor 210 while the reactor is operating and generating an electrical discharge, thereby producing a gaseous product comprising CO, residual CO2, and no more than 1% v / v of the reducing agent, O2, H2, or either of the two. Alternatively, the mixture may be generated inside the reactor (in situ), wherein each of the gases is fed to the reactor separately. Step 340 may result in the formation of a gaseous product comprising CO, residual CO2, and water. The amount of reducing agent, O2, or both in the gaseous product after step 340 does not exceed 1% v / v, or does not exceed 0.1% v / v.

[0105] The method may include separating water from the additional gas of the gaseous product at step 350. For example, the gaseous product may be introduced into a water separator 250 to extract water from the gaseous product to obtain a dry gaseous product.

[0106] In step 360, the method may include separating CO from residual CO2. For example, the dry gaseous product may be introduced into GSM 260 to be separated into CO and residual CO2. In some embodiments, CO having a purity of at least 99% after GSM 260 may exit via outlet 263, and residual CO2 may exit via outlet 262. In some embodiments, the gas containing residual CO2 exiting via outlet 262 may further include residual CO.

[0107] In some embodiments, the method may further include recycling and re-feeding residual CO2 into the mixture. For example, before the mixture of CO2 and reducing agent is fed into the plasma reactor 210, the residual CO2 may be fed and mixed with the mixture.

[0108] In some embodiments, the method may further include determining the conversion rate after step 340 (e.g., by analyzing the gaseous products using a gas composition analyzer and calculating the molar ratio between CO and CO2, and thereby determining the conversion rate), and controlling (i) the first flow rate and the second flow rate (while maintaining a predetermined molar ratio between CO2 and the reducing agent in the mixture), and / or (ii) the power, to obtain a desired conversion rate, wherein the desired conversion rate is as described herein.

[0109] Therefore, the technology can be used not only for CO2 utilization and CO generation, but also for hydrogen generation and CO transport by sea, as can be Figure 4 In some embodiments, CO generated from CO2 can be liquefied and transported under similar conditions and using similar technologies as liquefied natural gas transportation. Compared with hydrogen liquefaction and transportation, CO liquefaction and liquid CO transportation are much easier and safer.

[0110] In some embodiments, the CO2 may be transported back to a Figure 5 shown.

[0111] As will be well understood by one of ordinary skill in the art, all of the processes accompanying the described technology for plasma CO generation from CO2 for use in hydrogen transport are well known industrial processes implemented in the state of the art.

[0112] Working Examples

[0113] Example #1

[0114] The following is a non-limiting example of a method for producing CO from CO2 and CH4 using system 200. 3 / hour normal flow rate to provide CO2 and 2.31m 3CH4 was provided at a normal flow rate of 1.05 to 1.2 atm before the mixture entered the inlet 212. The mixture was fed into the plasma reactor 210 which was supplied with 19 kW of power by the power supply 215.

[0115] The gaseous products leave the outlet 217 to be compressed to a pressure of 1 bar by the compressor 240 and further separated from the water in the water separator 250. The process produces 3.7 liters / hour of water.

[0116] After water separation, at 17.1m 3 At a normal flow rate of 1 t / h, the gas contains 59.6 mol % CO and 40.4 mol % CO2.

[0117] The gas is then fed to the GSM 260 and separated into CO with a purity of 99.8% and a normal flow rate of 9.2 m 3 / hour; and a gas containing 88.4 mol % CO2 and 11.6 mol % CO, and a normal flow rate of 7.8m 3 / Hour.

[0118] Example #2

[0119] The system includes a plasma reactor based on a DC plasma generator, which consumes 1.9 kW of power. The plasma reactor is equipped with a circulating blower to provide 5 m³ of air for normal plasma generator operation and a gas flow cooler. 3 / hour of air flow. The reactor is passed through 1m 3 / hour of fresh CO2 from a gas cylinder. Inside the plasma reactor, CO2 showed 12% decomposition into CO and O2. After blending 10% of methane into the CO2 stream, the CO output concentration increased by up to 35%.

[0120] Example #3

[0121] The system includes a plasma reactor based on a pulsed plasma generator, which consumes 1.5 kW of power. The plasma reactor is equipped with a circulating blower to provide 15 m³ of air for normal plasma generator operation and a gas flow cooler. 3 / hour of gas flow. The reactor feed has 1m 3 / hour of fresh CO2 from a gas cylinder. In the plasma reactor, CO2 showed 14% decomposition into CO and O2. After blending 10% of methane into the CO2 stream, the CO output concentration increased by up to 38%.

[0122] Example #4

[0123] The system consists of a plasma reactor based on pulsed nanosecond hot discharge in a gas stream, which consumes 2.5 kW of power. The plasma reactor is equipped with a circulating blower that provides 20 m³ of heat for normal reactor operation and a gas stream heat exchanger. 3 / hour of air flow. The system is passed through a 1.5m 3 / hour of fresh CO2 and 0.5m 3 / hour of methane to feed. In the plasma reactor, 30% of the CO2 is decomposed into CO and O2, and the oxygen oxidizes the methane into water and CO. The compressor takes a flow from the plasma reactor output that is sufficient to balance the constant pressure in the plasma generator cycle and pressurizes it to 1 bar. After the compressor, the gas flow enters a cooler to condense water and a water separator, and then enters a gas separation membrane system that separates the residual CO2 from the product gas CO. The CO2 flow is returned to the reactor input. Finally, at the system output, 2m 3 / hour of pure CO flow. The membrane is a polysulfone gas separation hollow fiber membrane. The total energy cost of CO production is per 1m 3 The CO is about 2.8kW*hour.

[0124] Additional Examples to illustrate optimal CO2 conversion:

[0125] The system consists of a plasma reactor based on a pulsed nanosecond thermal discharge in a gas flow, wherein the power consumption is 19 kW, which is the same for all examples. The plasma reactor is equipped with a circulation blower to provide 400 m3 / h of gas flow for normal reactor operation and gas flow cooling.

[0126] #1

[0127]

[0128] #2

[0129]

[0130] #3

[0131]

[0132] #4

[0133]

[0134] The inventors inferred from the above examples (entries 1-4) that the optimal conversion of CO should be below 70%, such as about 50%. Increasing the conversion above 60% or above 65% results in increased plasma energy costs, making the entire process unfeasible.

[0135] Unless explicitly stated, the method embodiments described herein are not limited to a particular order or sequence. In addition, all schemes described herein are intended to be examples only, and other or different schemes may be used. In addition, some of the described method embodiments or elements thereof may occur or be performed at the same time.

[0136] Although certain features of the present invention have been illustrated and described herein, many modifications, substitutions, changes and equivalents may be made by those skilled in the art. Therefore, it should be understood that the appended claims are intended to cover all such modifications and changes that fall within the true spirit of the invention.

[0137] Various embodiments have been presented. Of course, each of these embodiments may include features of the other embodiments presented, and embodiments not specifically described may include various features described herein.

Claims

1. A system for generating carbon monoxide (CO) from carbon dioxide (CO2), the system comprising: plasma reactor; a CO2 source in fluid connection with the first valve; a reducing agent source fluidly connected to the second valve; wherein the first valve and the second valve are controlled to provide a mixture of CO2 and the reducing agent in a predetermined molar ratio to the plasma reactor, And wherein, the reducing agent is selected from hydrogen (H2) and methane (CH4), and wherein: said predetermined molar ratio between CO2 and CH4 is at least 3:1; said predetermined molar ratio between CO2 and H2 is at least 1:1; a compressor fluidly connected to an outlet of the plasma reactor; a water separator fluidly connected to an outlet of the compressor; and A gas separation membrane (GSM) is fluidically connected to the outlet of the water separator and includes a CO outlet and a CO2 outlet.

2. The system according to claim 1, wherein: The molar ratios are calculated based on normal flow rates.

3. The system according to claim 1 or claim 2, further comprising: a first flow meter, configured to measure a first flow rate of the CO2; a second flow meter, for measuring a second flow of the reducing agent; as well as The controller is configured as follows: The first valve and the second valve are controlled based on measurements received from the first flow meter and the second flow meter.

4. The system according to claim 3, further comprising: a gas composition analyzer fluidly connected between the outlet of the water separator and the inlet of the GSM, And wherein the controller is further configured to control the first valve and the second valve based on the conversion rate of CO2 determined by the gas composition analyzer.

5. The system according to claim 3, wherein: The controller is further configured to: Set a desired conversion rate; and The first valve and the second valve are adjusted until the desired conversion rate is detected by the gas composition analyzer.

6. The system according to claim 5, wherein: The desired conversion measured under normal conditions is less than 65%.

7. The system according to claim 5, wherein: The desired conversion is between about 30% and about 55%.

8. The system of any one of claims 2 to 5, further comprising a recirculation blower fluidly connected between the CO2 outlet of the GSM and the inlet of the plasma generator, and wherein the controller is further configured to control the first valve and the second valve also based on the flow rate of recycled CO2.

9. The system according to any one of claims 1 to 8, wherein: The gas at the CO outlet has a chemical purity of at least 99%, and wherein the gas has no more than 1% v / v of O2, H2, or both.

10. The system according to any one of claims 1 to 9, wherein: The pressure of the mixture is 5% to 20% higher than the pressure at the plasma reactor.

11. The system according to any one of claims 2 to 10, wherein: The controller is further configured to control power provided to the plasma generator.

12. The system according to claim 11, wherein The power is controlled to provide the desired conversion rate.

13. A method for producing carbon monoxide (CO) from carbon dioxide (CO2), comprising: providing CO2 from a CO2 source to the plasma reactor at a first flow rate; providing a reducing agent from a reducing agent source to the plasma reactor at a second flow rate to obtain a mixture of the CO2 and the reducing agent in a predetermined molar ratio, wherein the reducing agent is selected from hydrogen (H2) and methane (CH4), and wherein: The predetermined molar ratio between CO2 and CH4 is at least 3:1; or said predetermined molar ratio between CO2 and H2 is at least 1:1; wherein said providing is performed while generating an electric discharge in said plasma reactor for producing gaseous products comprising CO, residual CO2 and water; Separating the water from the gaseous product to obtain CO and residual CO2; and The CO is separated from the residual CO2.

14. The method according to claim 13, further comprising: The residual CO2 is recycled and fed back into the mixture.

15. The method according to claim 13 or claim 14, wherein: The first flow rate is between 2 and 10 m 3 / hours.

16. The method according to any one of claims 13 to 15, wherein The second flow rate is between 1 and 5 m 3 / hours.

17. The method according to any one of claims 13 to 16, wherein The gaseous product has no more than 1% v / v of any of the following: the reducing agent, O2, H2, or both.

18. The method of any one of claims 13 to 17, further comprising determining a conversion of the gaseous product and controlling the first flow rate and the second flow rate to obtain a desired conversion.

19. The method according to claim 18, wherein The conversion rate was determined by a gas composition analyzer.

20. The system according to claim 18 or 19, wherein: The desired conversion measured under normal conditions is less than 65%.

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