SYSTEM AND METHOD FOR UTILIZING RENEWABLE ELECTRICITY BY METHANOL SYNTHESIS VIA PLASMA-CATALYSIS CARBON DIOXIDE HYDROGENATION

Abstract

A system and method for utilizing renewable electricity by methanol synthesis via plasma-catalysis CO.sub.2 hydrogenation. Hydrogen produced via water electrolysis and CO.sub.2 captured from industrial processes undergo a reverse water-gas shift reaction, driven efficiently by an atmospheric-pressure plasma jet, yielding a CO/CO.sub.2/H.sub.2 mixed product. This mixture is subsequently pressurized in multi-stage pressurization after passing a buffer storage tank to further efficiently synthesize green methanol in the plasma jet reactor. The present disclosure employs a two-stage methanol synthesis process that powered by renewable electricity: plasma-based CO.sub.2 pre-conversion followed by CO/CO.sub.2 catalytic hydrogenation. This approach addresses the issues of catalyst deactivation and high reaction temperatures associated with traditional thermocatalytic reverse water-gas shift reactions, while overcoming the thermodynamic limitations of direct CO.sub.2 hydrogenation. The plasma jet reactor exhibits high energy efficiency, with rapid start-up and shutdown capabilities, and can operate directly using fluctuating renewable energy.

Claims

1. A system for utilizing renewable electricity by methanol synthesis via plasma-catalysis CO.sub.2 hydrogenation, comprising: a feed system configured to provide H.sub.2 and CO.sub.2 for a plasma jet reactor; a plasma jet reaction tower configured to pre-activate and convert CO.sub.2 using plasma jet to allow CO.sub.2 and H.sub.2 undergo reverse water-gas shift reaction, and produce a CO/CO.sub.2/H.sub.2 mixed intermediate product at atmospheric pressure and low temperature; a storage and pressurization system comprising a mixed intermediate product storage tank and a multi-stage pressurization system and configured to store and pressurize the CO/CO.sub.2/H.sub.2 mixed intermediate product produced by the plasma jet reactor to achieve decoupling of the plasma jet reactor and a methanol synthesis reactor; the methanol synthesis reactor configured to catalytically synthesize methanol from the CO/CO.sub.2/H.sub.2 mixed intermediate product conveyed by the storage and pressurization system; a power source configured to supply renewable electricity to the plasma jet reactor, the methanol synthesis reactor and the feed system; and a purification treatment system configured to separate methanol from remaining reaction gas and purify the methanol.

2. The system according to claim 1, wherein the feed system comprises a water electrolysis hydrogen production reactor, a H.sub.2 storage tank, a CO.sub.2 storage tank, a water pump, a first flow controller and a heat exchanger, and wherein the water pump, the first flow controller and the heat exchanger are configured to convey H.sub.2O to the water electrolysis hydrogen production reactor and control flow, and the water electrolysis hydrogen production reactor is connected to the H.sub.2 storage tank.

3. The system according to claim 2, wherein each output of the H.sub.2 storage tank, the CO.sub.2 storage tank and the mixed intermediate product storage tank is provided with a check valve, a flow controller and a centrifugal pump.

4. The system according to claim 1, wherein a top of the plasma jet reaction tower is provided with a gas collecting unit that directs the mixed intermediate product to the mixed intermediate product storage tank, a bottom of the plasma jet reaction tower is provided with a liquid collecting pipeline, three plasma jet reaction groups are evenly provided at a same side of a tower body of the plasma jet reaction tower in a vertical staggered mode, and each plasma jet reaction group comprises six plasma jet reactors symmetrically arranged in a hexagonal array and fixed to a disk-shaped base; and three sight glasses are correspondingly provided at another side of the tower body of the plasma jet reaction tower and configured to observe a reaction process, and temperature and pressure sensors are provided at a wall surface of the plasma jet reaction tower.

5. The system according to claim 4, wherein the plasma jet reactor comprises: the base; an outer electrode fixed to the base and is a hollow sleeve electrode with a tapered outlet at an upper portion; an inner electrode, conical in shape, arranged at a lower-mid part of a hollow structure of the outer electrode, and integrally formed by a lower cylinder and an upper cone frustum, and a bottom of the inner electrode is fixed to the base and connected to a high voltage end of a plasma power source via an electrode lead penetrating through the base; an outer wall of the inner electrode is parallel to an inner wall of the outer electrode; and a H.sub.2/CO.sub.2 inlet formed in a wall surface of the outer electrode and provided at a bottom of the plasma jet reactor and tangentially introduced from the bottom of the plasma jet reactor to form a swirling rising flow in a gap between the inner electrode and the outer electrode, to drive an arc between the inner and outer electrodes to rise rotationally, and plasma is ejected in a jet form under the action of the tapered outlet; and the outer and inner electrodes are connected to a frequency-adjustable high voltage alternating current (AC) power source.

6. The system according to claim 1, wherein the methanol synthesis reactor is provided with a CO/CO.sub.2 hydrogenation methanol synthesis reaction unit and a crude methanol outlet, CO/CO.sub.2 and H.sub.2 are selectively converted into crude methanol over copper-based composite nanocatalyst, the crude methanol is purified through the purification system, thereby realizing efficient chemical energy storage of power/valley electricity and collaborative conversion of greenhouse gas CO.sub.2.

7. The system according to claim 1, wherein the multi-stage pressurization system comprises a booster pump, a buffer tank, a back pressure valve and a real-time pressure monitoring system.

8. The system according to claim 1, wherein the purification treatment system further comprises a reheater, a gas-liquid desuperheater, a flash tank, a methanol rectification tower and a methanol storage tank connected to one another in sequence, and wherein a liquid channel of the flash tank is directly connected to the methanol rectification tower, and a gas channel of the flash tank is connected to the methanol synthesis reactor and the methanol rectification tower.

9. The system according to claim 1, wherein the power source comprises a water electrolysis hydrogen production power source, a plasma jet reactor power source and a multi-stage pressurization system power source configured to supply power to a water electrolysis hydrogen production reactor, the plasma jet reactor and the multi-stage pressurization system, respectively, all powered by off-grid renewable energy.

10. A method for utilizing renewable electricity by methanol synthesis via plasma-catalysis CO.sub.2 hydrogenation using the system according to claim 1, comprising: step 1, activating a power source to perform water electrolysis hydrogen production, and directly introducing produced hydrogen into a H.sub.2 storage tank for storage; step 2, opening a CO.sub.2 storage tank and the H.sub.2 storage tank, mixing CO.sub.2 and H.sub.2 according to a specific ratio and introducing the CO.sub.2 and H.sub.2 into the plasma jet reactor, forming a swirling flow inside the plasma jet reactor, activating the power source to form an arc between inner and outer electrodes to rise rotationally, ejecting plasma jet under an action of a tapered outlet, adjusting power and gas flow of the plasma jet reactor for optimal performance, and conducting real-time temperature monitoring; and performing pre-activation conversion on CO.sub.2, and reacting as follows:
CO.sub.2+H.sub.2CO+H.sub.2O, step 3, introducing mixed CO, CO.sub.2 and H.sub.2 gas into the mixed gas intermediate storage tank for storage, as the mixed CO, CO.sub.2 and H.sub.2 gas produced by the reaction rising after passing an air distributor, and letting water flow out from a lower liquid collecting pipeline; step 4, pressurizing, by a multi-stage pressurization system, the mixed CO, CO.sub.2 and H.sub.2 gas in the mixed intermediate product storage tank to 3 MPa-5 MPa, and introducing the mixed intermediate product from the mixed intermediate product storage tank into the methanol synthesis reactor to synthesize methanol under the action of a catalyst; and step 5, cooling, by a heat exchanger and a gas-liquid desuperheater, a gas-liquid mixture of the methanol produced after reaction in the methanol synthesis reactor and unreacted gas sequentially, performing gas-liquid separation on the cooled gas-liquid mixture using a flash tank, purifying, by a methanol rectification tower, separated liquid methanol, sending the purified liquid methanol to a methanol storage tank, passing separated gas through a separator, collecting and uniformly treating a part of the separated gas, and returning another part of the separated gas to the methanol synthesis reactor for further reaction.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0037] FIG. 1 is a flow chart of a method of the present disclosure.

[0038] FIG. 2 is a structural diagram of a system of the present disclosure.

[0039] FIG. 3 is a structural diagram of a plasma jet reactor.

[0040] FIG. 4 is a schematic diagram of a multi-stage pressurization system.

[0041] In the figures: 1, water pump; 2, first flow controller; 3, heat exchanger; 4, power source; 5, water electrolysis hydrogen production reactor; 6, H.sub.2 storage tank; 7, first check valve; 8, second flow controller; 9, first centrifugal pump; 10, CO.sub.2 storage tank; 11, second check valve; 12, third flow controller; 13, second centrifugal pump; 14, liquid collecting pipeline; 15, plasma jet reactor; 16, sight glass; 17, temperature and pressure sensors; 18, disk-shaped base; 19, gas inlet; 20, plasma jet reaction tower; 21, mixed gas intermediate storage tank; 22, third check valve; 23, fourth flow controller; 24, third centrifugal pump; 25, multi-stage pressurization system; 26, catalyst; 27, methanol synthesis reactor; 28, gas-liquid desuperheater; 29, flash tank; 30, separator; 31, methanol rectification tower; 32, methanol storage tank; 2-1, outer electrode; 2-2, inner electrode; 2-3, base; 3-1, first inlet; 3-2, gas-liquid separator; 3-3, cooling pump; 3-4, needle valve; 3-5, drying pipe; 3-6, first three-way valve; 3-7, second inlet; 3-8, second three-way valve; 3-9, first buffer tank; 3-10, diaphragm pump; 3-11, second buffer tank; 3-12, first booster pump; 3-13, first micrometering valve; 3-14, first back pressure valve; 3-15, third buffer tank; 3-16, pressure stabilizing valve; 3-17, fourth buffer tank; 3-18, second booster pump; 3-19, second micrometering valve; 3-20, second back pressure valve; and 3-21, fifth buffer tank.

DESCRIPTION OF EMBODIMENTS

[0042] The detailed description of the present disclosure is further described in detail below in combination with the accompanying drawings.

[0043] As shown in FIG. 1 and FIG. 2, an embodiment of the present disclosure provides system for utilizing renewable electricity by methanol synthesis via plasma-catalysis CO.sub.2 hydrogenation, and the system includes reactors, a feed system, a storage and pressurization system, a power source and a purification treatment system.

[0044] The reactors include a water electrolysis hydrogen production reactor 5, a plasma jet reactor 15 and a methanol synthesis reactor 27, and all the reactors are equipped with temperature monitoring devices.

[0045] The water electrolysis hydrogen production reactor 5 is a solid oxide electrolytic cell (SOEC) reaction chamber, with a working temperature of 600 C. to 1000 C., and a main structure includes a cathode, an anode and an electrolyte layer. The cathode uses Ni/YSZ porous metal ceramic, the anode is a rare-earth-element containing perovskite (ABO.sub.3) oxide, and the electrolyte layer is an oxygen ion conductor (YSZ or ScSZ, etc.).

[0046] In the water electrolysis hydrogen production reactor 5, H.sub.2 is introduced through a hydrogen outlet pipe into a storage tank to be stored, the storage tank is connected with a first check valve 7, a second flow controller 8 and a first centrifugal pump 9 in sequence, and oxygen is discharged by an oxygen outlet pipe.

[0047] As shown in FIG. 3, the plasma jet reactor 15 includes a high voltage electrode and a grounding electrode, a plasma discharge is formed, and a plasma jet reaction tower 20 is connected with a mixed gas intermediate storage tank 21 which is used for storing mixed gas produced after plasma CO.sub.2 pre-activation conversion; and the plasma jet reactor includes an outer electrode 2-1, an inner electrode 2-2, a CO.sub.2/H.sub.2 air inlet and a base 2-3.

[0048] The outer electrode and the inner electrode are connected to a frequency-adjustable high voltage alternating current power source with frequency of 5 to 40 kHz, a maximum output voltage of 20 kV and maximum power of 1 kW.

[0049] The outer electrode, fixed to an insulating base, is a hollow sleeve electrode with a tapered outlet at an upper portion.

[0050] The inner electrode, conical in shape, is positioned at the lower-mid part of the hollow structure of the outer electrode, and integrally formed by a lower cylinder and an upper cone frustum. The inner electrode is fixed to the base and connected to a high voltage plasma power source via an electrode lead penetrating through the base; an outer wall of the inner electrode is parallel to an inner wall of the outer electrode.

[0051] The H.sub.2/CO.sub.2 inlet is located at the bottom of the plasma jet reactor, and is tangentially introduced from the bottom to form a swirling rising flow in a gap between the inner and outer electrodes, so as to drive an arc between the inner and outer electrodes to rise rotationally, and plasma is ejected in a jet form under the action of a tapered outlet.

[0052] Further, the plasma jet reactors 15 are distributed and fixed on a disk-shaped base 18 in a symmetric array to form a reaction group, three reaction groups are evenly distributed on the same side of the plasma jet reaction tower 20 in a vertical staggered mode, three sight glasses 16 are correspondingly distributed on the other side and configured to observe a reaction process, a gas collecting unit is located at the top of the reaction tower, and liquid flows out from a bottom liquid collecting pipeline 14. Temperature and pressure sensors 17 are mounted on a wall surface of the reaction tower to monitor a state of the reaction system in real time.

[0053] The feed system is connected with a flow control device, and the feed system includes a vapor feed system and a CO.sub.2 feed system.

[0054] Further, a water pump is configured to supply water to a vapor producing device, and produced vapor enters the water electrolysis hydrogen production reactor through a vapor inlet valve and a vapor inlet pipe. The vapor feed system includes the water pump 1, the vapor producing device (heat exchanger 3) and a first flow controller 2. The water pump is connected with the heat exchanger through the first flow controller and supplies water, the heat exchanger achieves heat exchange between a product methanol and a reactant water, water is heated while methanol is cooled, and the produced vapor enters the water electrolysis hydrogen production reactor 5 through the vapor inlet valve and the vapor inlet pipe.

[0055] The CO.sub.2 feed system is configured to feed a reactant CO.sub.2, after being mixed with H.sub.2, the CO.sub.2 is introduced into the plasma jet reactor 15 from a gas inlet 19 to feed CO.sub.2. In the present embodiment, the CO.sub.2 feed system includes a CO.sub.2 storage tank 10, a second check valve 11, a third flow controller 12 and a second centrifugal pump 13.

[0056] The CO.sub.2 storage tank is configured to store CO.sub.2, and the second check valve, the third flow controller and the second centrifugal pump are connected with one another to be used for controlling the flow of CO.sub.2.

[0057] The power source includes a water electrolysis hydrogen production power source 4, a plasma jet reactor power source and a multi-stage pressurization system power source, all powered by off-grid renewable energy (such as photovoltaic power and wind power).

[0058] The water electrolysis hydrogen production power source is configured to supply renewable electricity to drive the electrochemical hydrogen evolution reaction in the water electrolysis hydrogen production reactor 5, finally completing the production of methanol under atmospheric pressure with the plasma jet reactor as the core. The water electrolysis hydrogen production power source is a direct current device. One end of a negative electrode line is connected with a hydrogen evolution pole of the water electrolysis hydrogen production reactor, and the other end is connected with a negative electrode of the direct current power source; and one end of a positive electrode line is connected with an oxygen evolution pole of the water electrolysis hydrogen production reactor, and the other end is connected with a positive electrode of the direct current power source.

[0059] The multi-stage pressurization system power source is configured to supply power to a booster pump, an electromagnetic valve and the like in a multi-stage pressurization system 25.

[0060] The storage and pressurization system is configured to store and pressurize the CO/CO.sub.2/H.sub.2 mixed gas produced by the plasma jet reactor. The storage and pressurization system includes a mixed gas intermediate storage tank 21, a third check valve 22, a fourth flow controller 23, a third centrifugal pump 24 and the multi-stage pressurization system 25.

[0061] A pressurization flow chart of the multi-stage pressurization system is as shown in FIG. 4, gas enters a gas-liquid separator 3-2 after being introduced from a first inlet 3-1, separated liquid is discharged by a needle valve 3-4, and the gas is subjected to multi-stage pressurization after moisture is desorbed through a drying pipe 3-5; the gas passes a diaphragm pump 3-10 and enters a second buffer tank 3-11 from a first buffer tank 3-9 to complete front-stage pressurization; gas in the second buffer tank 3-11 is pressurized through a first booster pump 3-12 and enters a third buffer tank 3-15, if a pressure of the third buffer tank 3-15 is higher than a designated pressure, the pressure may be relieved to the second buffer tank through a first back pressure valve 3-14, the second buffer tank 3-11 and the third buffer tank 3-15 achieve parallel pressurization together with the booster pump and the back pressure valve, a fourth buffer tank 3-17 and a fifth buffer tank 3-21 further perform parallel pressurization, and the four buffer tanks complete rear-stage secondary pressurization together; and if a pressure of the first buffer tank 3-9 is too low, gas may be supplemented through a second inlet 3-7, and if a pressure of the first buffer tank 3-9 is too high, gas may be discharged through a first three-way valve 3-6.

[0062] The purification treatment system is configured to separate methanol from the remaining reaction gas and purify the methanol product. A gas-liquid mixture produced after reaction in the methanol synthesis reactor is cooled through the heat exchanger 3 and a gas-liquid desuperheater 28 in sequence, gas-liquid separation is performed on the cooled gas-liquid mixture in a flash tank 29, separated liquid methanol is purified through a methanol rectification tower 31 and then stored in a methanol storage tank 32, gas separated by the flash tank and gas separated by the rectification tower pass through a separator 30, then part of the gas is collected and then treated uniformly, and the other part of the gas is returned to the methanol synthesis reactor 27 for further reaction.

[0063] In the present disclosure, two key reactions-plasma CO.sub.2 pre-activation/conversion and catalytic methanol synthesis-occur in two independent and isolated reaction chambers. Unlike traditional methanol synthesis methods, which rely on the direct thermocatalytic conversion of CO.sub.2, this method, utilizing plasma-catalysis CO.sub.2 hydrogenation, allows for these reactions to occur in separate reactors under different conditions. This separation enables the optimization of each step independently to achieve the best overall performance of the system. The inclusion of an intermediate storage system decouples the methanol synthesis reactor from the plasma jet reactor, ensuring that the methanol synthesis process remains unaffected by fluctuations in the plasma jet reactor. Meanwhile, CO.sub.2 is partially converted to CO by adopting plasma technology. This process eliminates the need for a catalyst, thereby addressing issues of catalyst deactivation and high reaction temperatures associated with traditional thermocatalytic reverse water-gas shift reactions. Furthermore, the system allows for the adjustment of product component ratios by regulating gas flow, power, and other parameters, enabling more efficient catalytic synthesis of methanol from the CO/CO.sub.2/H.sub.2 mixed gas, which significantly enhances the overall process efficiency.

[0064] An embodiment of the present disclosure provides a method for utilizing renewable electricity by methanol synthesis via plasma-catalysis CO.sub.2 hydrogenation, and the method includes the following steps:

[0065] 1, The power source 4 is activated to perform water electrolysis hydrogen production, and produced hydrogen is directly introduced into the H.sub.2 storage tank 6 for storage.

[0066] 2, The CO.sub.2 storage tank 10 and the H.sub.2 storage tank 6 are opened, the gases are mixed in a specific ratio of 1:3 and introduced them into the plasma jet reactor 15, a swirling flow is formed inside the reactor, the power source is activated to form an arc between the inner and outer electrodes which then rises rotationally, plasma jet is ejected under the action of a tapered outlet. The reactor's power and gas flow are adjusted for optimal performance, within a range of 50 to 300 W and a range of 1 to 10 L/min, respectively, while real-time temperature monitoring is conducted. CO.sub.2 undergoes pre-activation and the following reaction occurs:

CO.sub.2+H.sub.2CO+H.sub.2O.

[0067] 3, The mixed gas produced after the reaction rises after passing an air distributor, and is introduced into a mixed gas intermediate storage tank 21 to be stored. Water flows out from a lower liquid collecting pipeline.

[0068] 4, After being pressurized to 3-5 MPa through a multi-stage pressurization system, gas in the mixed gas intermediate storage tank 21 is introduced into the methanol synthesis reactor 27 to synthesize methanol over a catalyst. The specific pressurization data are as follows:

TABLE-US-00001 First-stage Second-stage Third-stage Initial pressure pressurization pressurization pressurization 0.1 MPa 0.5 MPa 3 MPa 10 MPa

[0069] 5, A gas-liquid mixture of the methanol produced after reaction in the methanol synthesis reactor 27 and unreacted gas is cooled through a heat exchanger 3 and a gas-liquid desuperheater 28 in sequence, gas-liquid separation is performed on the cooled gas-liquid mixture by using a flash tank 29, separated liquid methanol is purified through a methanol rectification tower 31 and then sent to a methanol storage tank 32, a pressure in the methanol rectification tower 31 is controlled to be 0.15 MPa, separated gas passes through a separator 30, then part of the gas is collected and then treated uniformly, and the other part of the gas is returned to the methanol synthesis reactor 27 for further reaction.

[0070] The above description is only a preferred implementation of the present disclosure, and although the present disclosure has been disclosed as above through preferred embodiments, it is not intended to limit the present disclosure. Any person skilled in the art may use the method and technical content disclosed above to make many possible changes and modifications to the technical solution of the present disclosure, or modify it into equivalent embodiments with equivalent changes, without departing from the scope of the technical solution of the present disclosure. Therefore, any simple amendments, equivalent changes, and modifications made to the above embodiments in accordance with the technical essence of the present disclosure that do not depart from the content of the technical solution of the present disclosure still fall within the scope of protection of the technical solution of the present disclosure.