Electrochemical sulfur-carbon integrated trapping and grading regeneration method and device

Abstract

According to the electrochemical sulfur-carbon integrated trapping and grading regeneration method and device, energy is supplied through an external power source, an absorbent is promoted to be reduced and converted into Lewis base, and the Lewis base has the capacity of trapping H2S and CO2; meanwhile, due to the fact that the absorbent follows different mechanisms to capture H2S and CO2, and the potential of H2S released by reducing state substances of the absorbent is higher than the potential of CO2 released, on the basis, pure H2S and CO2 are desorbed in a step-by-step oxidation and grading mode through potential difference, and a continuous system which is easy to implement and free of secondary pollution is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemistry, and particularly relates to an electrochemistry integrated sulfur-carbon capture and hierarchical regeneration method and device. Background Art

[0002] In chemical processes, the purification of natural gas, oilfield gas, refinery gas and coal-based syngas all have the problem of removing acidic gases. The existence of these acidic gases will cause serious corrosion to equipment and pipelines, posing major safety hazards, and acidic gases will also pollute the environment; for example, CO2 is one of the typical greenhouse gases, H2S is a gas with strong toxicity, and in addition, hydrogen sulfide is also an important raw material for preparing sulfur in the Claus desulfurization process. Therefore, the integrated capture and removal of acidic gases remains an important research direction in the chemical industry.

[0003] The current traditional technologies for capturing and removing acidic gases (H2S and CO2) are as follows:

[0004] First, the alkanolamine method in chemical absorption uses an alkaline solvent to react with acidic gases to form unstable salts, and then the solvent is recovered by heating and desorbing.

[0005] Second, in physical absorption, solvents such as methanol and polyethylene glycol dimethyl ether are used to physically dissolve and absorb acidic gases, and then desorption is carried out by reducing pressure or heating.

[0006] Third, the adsorption method uses activated carbon, molecular sieves, etc. to adsorb and separate acidic gases, and then desorption is carried out by heating or reducing pressure.

[0007] Although the above methods are widely used, they also have some drawbacks, such as high energy consumption, high cost, equipment corrosion, efficiency decline, etc. Moreover, the existing process regenerates and desorbs a mixture of H2S and CO2. If the CO2 content in the mixture is too high and the H2S content is too low, it will affect the working conditions of the subsequent Claus desulfurization process. In addition, the CO2 captured and regenerated previously will re-enter the Claus desulfurization process tail gas and secondary decarbonization is required. Therefore, it is necessary to develop an efficient and economical method for removing and separating H2S and CO2 in acidic gases.

[0008] Electrochemical technology has significant advantages in capturing and separating CO2, with advantages such as high efficiency, environmental protection, flexibility and low energy consumption. However, there is no relevant research on H2S capture and separation, and there is also no relevant research on electrochemically capturing and separating H2S and CO2 in acidic gases containing both H2S and CO2.

[0009] Based on this, there is an urgent need for a device and method that can achieve the integrated capture and hierarchical removal of acidic gases H2S and CO2 to achieve low cost, high efficiency and no secondary pollution. Summary of the Invention

[0010] In order to achieve the integrated capture and separation of H2S and CO2, one of the objectives of the present invention is to provide an electrochemical integrated sulfur and carbon capture and hierarchical regeneration method.

[0011] The technical solution of the present invention to solve the above technical problems is as follows: An electrochemical integrated sulfur and carbon capture and hierarchical regeneration method includes the following steps:

[0012] Desulfurization and decarbonization of the raw material gas: The raw material gas containing H2S and / or CO2 is introduced into the electrolyte solution containing the reduced state substance of the absorbent, and after absorbing H2S and / or CO2, an electrolyte solution containing acidic gas is obtained;

[0013] First electrolysis: The electrolyte solution containing acidic gas is electrolyzed in the CO2 regeneration electrolytic cell, so that a first gas-liquid mixture of CO2 and the electrolyte solution is formed in the anode chamber of the electrolytic cell, and the first gas-liquid mixture is separated to obtain a first electrolyte solution and CO2 gas;

[0014] Second electrolysis: The first electrolyte solution is electrolyzed in the H2S regeneration electrolytic cell, so that a second gas-liquid mixture of H2S and the electrolyte solution is formed in the anode chamber of the electrolytic cell, and the second gas-liquid mixture is separated to obtain a second electrolyte solution and H2S gas; Both the first electrolyte solution and the second electrolyte solution contain the absorbent, and the voltage of the second electrolysis is higher than that of the first electrolysis;

[0015] Reduction of the absorbent: The second electrolyte solution is introduced into the cathode chamber of the electrolytic cells used in the first electrolysis and the second electrolysis, and the absorbent is reduced in the cathode chamber to obtain an electrolyte solution containing the reduced state substance of the absorbent, and it is reused for the desulfurization and decarbonization step of the raw material gas.

[0016] On the basis of the above technical solution, the present invention can also be improved as follows:

[0017] Further, the electrolyte solution also includes an organic solvent and an electrolyte supporting salt, and each 1 L of the organic solvent contains 10-100 mmol of the absorbent and 0.5-4 mol / L of the electrolyte supporting salt.

[0018] Further, the absorbent is any one of phenazine, pyridine, azobenzene, p-benzoquinone, anthraquinone, disulfide and its derivatives.

[0019] Further, the electrolyte supporting salt is any one of tetrapropylammonium hexafluorophosphate, tetrabutylammonium perchlorate, tetraethylammonium hexafluorophosphate, tetraethylammonium perchlorate, lithium hexafluorophosphate and tetraethylammonium tetrafluoroborate.

[0020] Further, the organic solvent is any one of dimethyl sulfoxide, N,N-dimethylformamide, acetonitrile, N-methylpyrrolidone, tetrahydrofuran and dichloromethane.

[0021] Furthermore, the flow rate of the raw material gas is 20 - 60 sccm;

[0022] The conditions for the first electrolysis and the second electrolysis are: normal temperature and constant current; the voltage of the first electrolysis is 0.5 - 1 V lower than that of the second electrolysis, and the voltage of the second electrolysis is 1.5 - 3 V.

[0023] The second object of the present invention is to provide a device for the electrochemical sulfur-carbon integrated capture and fractional regeneration method in the first object, including:

[0024] An acid gas absorption tank for placing an electrolyte containing a reduced state substance of an absorbent;

[0025] A CO2 separation unit: including a CO2 regeneration electrolytic cell, a diaphragm located inside the CO2 regeneration electrolytic cell and separating the CO2 regeneration electrolytic cell into an anode chamber and a cathode chamber, an anode and a cathode respectively located in the anode chamber and the cathode chamber, and a CO2 separation tank connected to the anode chamber of the CO2 regeneration electrolytic cell, and the anode chamber of the CO2 regeneration electrolytic cell is connected to the acid gas absorption tank;

[0026] An H2S separation unit: including an H2S regeneration electrolytic cell, a diaphragm located inside the H2S regeneration electrolytic cell and separating the H2S regeneration electrolytic cell into an anode chamber and a cathode chamber, an anode and a cathode respectively located in the anode chamber and the cathode chamber, and an H2S separation tank connected to the anode chamber of the H2S regeneration electrolytic cell, and the anode chamber of the H2S regeneration electrolytic cell is connected to the CO2 separation tank;

[0027] Wherein, the H2S separation tank is connected to both the cathode chamber of the H2S regeneration electrolytic cell and the cathode chamber of the CO2 regeneration electrolytic cell, and the acid gas absorption tank is connected to both the cathode chamber of the H2S regeneration electrolytic cell and the cathode chamber of the CO2 regeneration electrolytic cell.

[0028] Furthermore, air outlets are provided at the tops of the acid gas absorption tank, the CO2 separation tank and the H2S separation tank.

[0029] Furthermore, both the anode and the cathode are made of carbon cloth, carbon felt, carbon fiber or graphite plate.

[0030] Furthermore, the diaphragm is an ion exchange membrane.

[0031] The present invention has the following beneficial effects:

[0032] 1. The present invention is powered by an external power supply, which promotes the reduction of the absorbent to transform it into a Lewis base, enabling it to have the ability to capture H2S and CO2; at the same time, since the binding ability of the reduced state substance of the absorbent with H2S is stronger than its binding ability with CO2, based on this, the present invention stepwise oxidizes and fractionally removes pure H2S and CO2 through potential differences, realizing a continuous system that is easy to implement and has no secondary pollution.

[0033] 2. The present invention features high-efficiency separation and low energy consumption: The electrochemical technology can achieve highly selective separation of H2S and CO2 by regulating the potential; the operation process is usually carried out at normal temperature and pressure without high temperature or high pressure, resulting in low energy consumption.

[0034] In addition, the present invention also has good flexibility and can be modularized: Specifically, the electrochemical system can flexibly adjust the operating parameters to adapt to different concentrations of H2S and CO2; it can be designed in a modular form later, which is convenient for expansion and integration into existing acid gas treatment facilities.

[0035] 3. The present invention also has simple equipment and low maintenance costs: Specifically, the electrochemical system usually does not require complex equipment, and the electrochemical process has low corrosiveness to the equipment, reducing maintenance costs and equipment losses. Moreover, the present invention is also convenient for resource utilization. The H2S and CO2 in the present invention can be completely separated, and H2S and CO2 can be further converted into high-value-added products. Description of the Drawings

[0036] Figure 1 It is the schematic diagram of the electrochemical sulfur-carbon integrated capture and staged regeneration method of the invention;

[0037] Figure 2 It is the device diagram of the electrochemical sulfur-carbon integrated capture and staged regeneration of the present invention;

[0038] Figure 3 It is the cyclic voltammogram under the conditions of N2, H2S and CO2. Detailed Embodiments

[0039] The following will describe the electrochemical sulfur-carbon integrated capture and staged regeneration method and device in the present application in combination with embodiments. However, the present application can be exemplified in many different forms and should not be construed as limited to the specific embodiments described herein. More precisely, the purpose of providing these embodiments is to make the present application thorough and complete, and to fully convey the scope of the present application to those skilled in the art.

[0040] Based on the Lewis acid-base theory, the present invention selects an absorbent that can be reduced to a Lewis base to capture H2S and CO2, and designs an integrated capture and staged regeneration method and device for H2S and CO2 according to the different binding strengths of H2S and CO2 with the reduced Lewis base.

[0041] An embodiment of the first aspect of the present invention provides an electrochemical sulfur-carbon integrated capture and staged regeneration method, including the following steps:

[0042] Raw gas desulfurization and decarbonization: Feed the raw gas containing H2S and / or CO2 into the electrolytic solution containing the reduced form of the absorbent, absorb H2S and / or CO2, and obtain the electrolytic solution containing acid gas;

[0043] First electrolysis: Electrolyze the electrolytic solution containing acid gas in the CO2 regeneration electrolytic cell, so as to form a first gas-liquid mixture of CO2 and the electrolytic solution in the anode chamber of the electrolytic cell, separate the first gas-liquid mixture to obtain the first electrolytic solution and CO2 gas;

[0044] Second electrolysis: Electrolyze the first electrolytic solution in the H2S regeneration electrolytic cell, so as to form a second gas-liquid mixture of H2S and the electrolytic solution in the anode chamber of the electrolytic cell, separate the second gas-liquid mixture to obtain the second electrolytic solution and H2S gas; Both the first electrolytic solution and the second electrolytic solution contain the absorbent, and the voltage of the second electrolysis is higher than that of the first electrolysis;

[0045] Absorbent reduction: Feed the second electrolytic solution into the cathode chamber of the electrolytic cells used in the first electrolysis and the second electrolysis, the absorbent is reduced in the cathode chamber to obtain the electrolytic solution containing the reduced form of the absorbent, and reuse it in the raw gas desulfurization and decarbonization step.

[0046] In this embodiment, energy is supplied by an external power source. The absorbent is reduced to transform into a Lewis base, while both H2S and CO2 are Lewis acids. Therefore, H2S and CO2 can be trapped by the reduced form of the absorbent (i.e., the substance after the absorbent is reduced). At the same time, since the reduced absorbent (in the subsequent description of this patent, "A" represents the absorbent, and "A - " represents the reduced absorbent, that is, the reduced form of the absorbent) has a stronger binding ability with H2S than with CO2. Therefore, in this embodiment, CO2 is desorbed at a lower potential first, and then H2S is desorbed at a higher potential. Furthermore, pure H2S and CO2 are desorbed step by step through potential difference and stepwise oxidation, realizing a continuous system without secondary pollution.

[0047] The chemical reactions involved in this embodiment are as follows:

[0048] The electrochemical reaction occurring in the cathode chamber is as follows:

[0049] A + e - → A - (Equation 1)

[0050] The reactions occurring in the H2S and CO2 absorption tanks are as follows:

[0051] A - + H2S → A-H2S (Equation 2)

[0052] A -+CO2 → A-CO2 (Equation 3)

[0053] The electrochemical reactions occurring in the anodic chamber are as follows:

[0054] A-H2S - e - → A + H2S (Equation 4)

[0055] A-CO2 - e - → A + CO2 (Equation 5).

[0056] In this embodiment, the specific implementation is as follows: First, the raw gas containing H2S and / or CO2 is introduced into the electrolyte solution containing the reduced-state substance of the absorbent. The reduced-state substance of the absorbent combines with H2S and / or CO2 to carry out the reaction shown in Equation 2 or Equation 3. Then, the electrolyte solution that has absorbed H2S and / or CO2 is input into the anodic chamber of the CO2 regeneration electrolytic cell and undergoes an oxidation reaction at a low potential to desorb CO2, and the reaction shown in Equation 5 occurs, thereby generating a first gas-liquid mixture. After the first gas-liquid mixture is output from the anodic chamber of the CO2 regeneration electrolytic cell, CO2 separation is achieved by reducing the gas-liquid mixture flow rate and the fact that the liquid phase density is greater than the gas phase. The electrolyte solution after desorbing CO2 enters the anodic chamber of the H2S regeneration electrolytic cell and undergoes an oxidation reaction at a high potential to desorb H2S, and the reaction shown in Equation 4 occurs, thereby generating a second gas-liquid mixture. After the second gas-liquid mixture is output from the anodic chamber of the H2S regeneration electrolytic cell, H2S separation is also achieved by reducing the gas-liquid mixture flow rate and the fact that the liquid phase density is greater than the gas phase. The electrolyte solution after desorbing H2S is recycled back to the cathodic chamber of the CO2 regeneration electrolytic cell and the cathodic chamber of the H2S regeneration electrolytic cell, enters the reaction shown in Equation 1, undergoes a reduction reaction to obtain the electrolyte solution containing the reduced-state substance of the absorbent, and this electrolyte solution is reused to absorb H2S and / or CO2 in the raw gas, realizing the internal circulation flow of the electrolyte solution in the device and continuous operation.

[0057] In addition, in order to further verify that the method in the present invention can achieve the stepwise desorption of H2S and CO2 at different potentials, the present invention also carried out cyclic voltammetry tests, and the results are as Figure 3 shown. This test is as follows: 0.1 mol / L tetrabutylammonium hexafluorophosphate (TBAPF6) is used as the supporting electrolyte, and the absorption solvent is dimethyl sulfoxide (DMSO) containing 10 mmol / L phenazine. It can be seen from Figure 3 that in the CO2-saturated solvent, phenazine has peaks at -1.65 and -0.78 V vs. Fc +Redox peaks appeared at the potential positions of / Fc, corresponding to the association process of the reduced phenazine with CO2 and the oxidation and release process of the associated CO2, respectively. In the solvent saturated with H2S, phenazine also showed reversible redox peaks, indicating that it can achieve the reversible absorption and desorption of H2S. When the association compounds formed by CO2 and H2S with phenazine are oxidized and released again, there is a significant potential difference, which means that the stepwise desorption of CO2 and H2S can be achieved by regulating the applied oxidation potential.

[0058] Preferably, the raw gas in this embodiment can be natural gas, oilfield gas, refinery gas or coal-based syngas rich in H2S and CO2; of course, in practice, it can also be other gases rich in H2S and CO2.

[0059] In addition, in some embodiments, the electrolyte solution further includes an organic solvent and an electrolyte supporting salt, and each 1 L of the organic solvent contains 10-100 mmol of the absorbent and 0.5-4 mol / L of the electrolyte supporting salt.

[0060] In addition, in some embodiments, the absorbent is any one of phenazine, pyridine, azobenzene, p-benzoquinone, anthraquinone, disulfide and its derivatives.

[0061] In addition, in some embodiments, the electrolyte supporting salt is any one of tetrapropylammonium hexafluorophosphate, tetrabutylammonium perchlorate, tetraethylammonium hexafluorophosphate, tetraethylammonium perchlorate, lithium hexafluorophosphate and tetraethylammonium tetrafluoroborate.

[0062] In addition, in some embodiments, the organic solvent is any one of dimethyl sulfoxide, N,N-dimethylformamide, acetonitrile, N-methylpyrrolidone, tetrahydrofuran and dichloromethane.

[0063] In addition, in some embodiments, the flow rate of the raw gas is 20-60 sccm; at this flow rate, it is beneficial for the electrolyte solution containing the reduced substance of the absorbent to fully absorb H2S and / or CO2 in the raw gas. The conditions for the first electrolysis and the second electrolysis are: normal temperature, constant current; the voltage of the first electrolysis is 0.5-1 V lower than that of the second electrolysis, and the voltage of the second electrolysis is 1.5-3 V.

[0064] An embodiment of the second aspect of the present invention provides a device for the electrochemical sulfur-carbon integrated capture and fractional regeneration method in the embodiment of the first aspect, as Figure 2 shown, the device includes an acid gas absorption tank, a CO2 separation unit and an H2S separation unit.

[0065] Specifically, the acid gas absorption tank is used to place the electrolyte containing the reduced-state substance of the absorbent, so as to absorb H2S and / or CO2 in the raw material gas. In addition, a discharge port for the purified raw material gas is provided at the top of the acid gas absorption tank, and a liquid discharge port is provided at the bottom, facilitating the electrolyte that has absorbed H2S and / or CO2 to enter the CO2 separation unit (not shown in the drawings).

[0066] As Figure 2 shown, the CO2 separation unit includes a CO2 regeneration electrolytic cell, a diaphragm, a cathode, an anode, and a CO2 separation tank. Among them, the diaphragm divides the CO2 regeneration electrolytic cell into an anode chamber and a cathode chamber. The anode chamber of the CO2 regeneration electrolytic cell is connected to the acid gas absorption tank. In this embodiment, the anode chamber of the CO2 regeneration electrolytic cell and the acid gas absorption tank are mainly connected by a pipeline, and then a pump is added to the pipeline to pump the electrolyte in the acid gas absorption tank into the anode chamber; preferably, the diaphragm in this embodiment is an ion exchange membrane. In addition, the anode and the cathode are respectively located in the anode chamber and the cathode chamber. Preferably, both the anode and the cathode in this embodiment are made of carbon cloth, carbon felt, carbon fiber, or graphite plate. In addition, the CO2 separation tank in this embodiment is connected to the anode chamber of the CO2 regeneration electrolytic cell. In this embodiment, under the action of an external power source, the reaction shown in Equation 5 occurs in the anode chamber of the CO2 regeneration electrolytic cell. Therefore, the electrolyte in the anode chamber contains a gas-liquid mixture of CO2 gas, absorbent (A), and A-H2S (the substance obtained by adsorbing H2S after the absorbent is reduced); while the reaction shown in Equation 1 occurs in the cathode chamber of the CO2 regeneration electrolytic cell, and the absorbent is reduced to form the reduced-state substance of the absorbent and exhibits the characteristics of a Lewis base.

[0067] In addition, an air outlet is provided at the top of the CO2 separation tank in this embodiment, and a liquid discharge port is provided at the bottom (not shown in the drawings). In this embodiment, the electrolyte after electrolysis in the anode chamber of the CO2 regeneration electrolytic cell is introduced into the CO2 separation tank. After the gas-liquid mixture enters the separation tank, the liquid phase flows out from the bottom liquid discharge port, and CO2 is discharged from the top air outlet, thereby realizing the purification of CO2, and the absorbent (A) and A-H2S are pumped from the CO2 separation tank into the H2S separation unit. In this embodiment, the CO2 purification principle is: after the gas-liquid mixture enters the separation tank, due to the reduction in flow rate and the fact that the liquid phase density is greater than the gas phase density, the liquid phase sinks to the bottom of the CO2 separation tank under the action of gravity, thereby realizing gas-liquid separation and finally realizing the purification of CO2.

[0068] As Figure 2As shown in the figure, the H2S separation unit in this embodiment includes an H2S regeneration electrolytic cell, a diaphragm, a cathode, an anode, and an H2S separation tank. Among them, the diaphragm divides the H2S regeneration electrolytic cell into an anode chamber and a cathode chamber. The anode chamber of the H2S regeneration electrolytic cell is connected to the CO2 separation tank. In this embodiment, the anode chamber of the H2S regeneration electrolytic cell and the CO2 separation tank are mainly connected by a pipeline, and then a pump is added to pump the electrolyte in the CO2 separation tank into the anode chamber; preferably, the diaphragm in this embodiment is an ion exchange membrane. In addition, the anode and the cathode are respectively located in the anode chamber and the cathode chamber. Preferably, both the anode and the cathode in this embodiment are made of carbon cloth, carbon felt, carbon fiber or graphite plate. In addition, the H2S separation tank in this embodiment is connected to the anode chamber of the H2S regeneration electrolytic cell. In this embodiment, under the action of an external power supply, the reaction shown in Equation 4 occurs in the anode chamber of the H2S regeneration electrolytic cell. Therefore, the electrolyte in the anode chamber is a gas-liquid mixture containing H2S gas and absorbent (A); while the reaction shown in Equation 1 occurs in the cathode of the H2S regeneration electrolytic cell, and the absorbent is reduced to form a reduced state of the absorbent and exhibits the characteristics of a Lewis base.

[0069] In addition, the top of the H2S separation tank in this embodiment is provided with an air outlet, and the bottom is provided with a liquid discharge port (not shown in the figure). In this embodiment, the electrolyte after electrolysis in the anode chamber of the H2S regeneration electrolytic cell is introduced into the H2S separation tank. After the gas-liquid mixture in the electrolyte enters the separation tank, the liquid phase flows out from the bottom liquid discharge port, and H2S will be discharged from the top air outlet, thereby realizing the purification of H2S. Only the electrolyte containing absorbent (A) remains in the H2S separation tank. The principle of realizing the purification of H2S in this embodiment is the same as that of CO2 purification.

[0070] In addition, in this embodiment, the H2S separation tank is connected to both the cathode chamber of the H2S regeneration electrolytic cell and the cathode chamber of the CO2 regeneration electrolytic cell. The connection is mainly through a pipeline, and according to Figure 2 As shown, a pump is provided on the pipeline for connecting the H2S separation tank to the cathode chamber of the H2S regeneration electrolytic cell and the cathode chamber of the CO2 regeneration electrolytic cell. In addition, it can also be seen from Figure 2 that the acid gas absorption tank is connected to both the cathode chamber of the H2S regeneration electrolytic cell and the cathode chamber of the CO2 regeneration electrolytic cell. Therefore, in this embodiment, the electrolyte in the H2S separation tank is respectively pumped into the cathode chamber of the H2S regeneration electrolytic cell and the cathode chamber of the CO2 regeneration electrolytic cell by a pump, and the reaction shown in Equation 1 occurs to reduce A to form A - , obtaining an electrolyte containing A - , and at the same time inputting the electrolyte into the acid gas absorption tank to be reused for absorbing H2S and CO2 in the raw material gas.

[0071] Embodiment

[0072] Embodiment 1

[0073] This embodiment adopts the above-mentioned Figure 2 device for integrated electrochemical sulfur and carbon capture and staged regeneration to carry out the integrated electrochemical sulfur and carbon capture and staged regeneration method, and this method includes the following steps:

[0074] Step 1: Pour 50 mL of electrolyte solution (the electrolyte solution is composed of phenazine (PhN), TBAPF6 (tetrapropylammonium hexafluorophosphate) and dimethyl sulfoxide, and their concentrations are 10 mmol / L and 4000 mmol / L respectively) into the CO2 regeneration electrolytic cell and the H2S regeneration electrolytic cell respectively. Turn on the power supply to electrolyze the CO2 regeneration electrolytic cell and the H2S regeneration electrolytic cell. The reaction shown in Equation 1 occurs in the cathode chambers of the CO2 regeneration electrolytic cell and the H2S regeneration electrolytic cell, and the absorbent PhN is reduced to the Lewis base PhN - (as Figure 1 shown); at the same time, drive the pump to make the electrolyte solution circulate through the acid gas absorption tank, the CO2 regeneration electrolytic cell, the CO2 separation tank, the H2S regeneration electrolytic cell and the H2S separation tank; among them, the electrolysis conditions of the CO2 regeneration electrolytic cell and the H2S regeneration electrolytic cell are: at 25 °C and constant current electrolysis; a voltage of 1 V is applied to the CO2 regeneration electrolytic cell, and a voltage of 2 V is applied to the H2S regeneration electrolytic cell;

[0075] Step 2: Then introduce simulated natural gas (10% CO2, 10% H2S, 80% CH4) into the acid gas absorption tank at a flow rate of 20 mL / min. The PhN in the electrolyte solution - absorbs H2S and CO2 in the natural gas to form PhN-H2S and PhN-CO2 (as Figure 1As shown, the remaining unabsorbed gas enters the infrared analyzer through the gas outlet at the top of the acid gas absorption tank for detection; the electrolyte containing PhN-H2S and PhN-CO2 is pumped into the anode chamber of the CO2 regeneration electrolytic cell. In the anode chamber, an electrolytic reaction occurs to produce an electrolyte of a gas-liquid mixture of PhN-H2S, PhN, and CO2. This electrolyte flows from the anode chamber of the CO2 regeneration electrolytic cell into the CO2 separation tank for gas-liquid separation. The separated CO2 enters the infrared analyzer through the gas outlet on the CO2 separation tank for detection. The remaining electrolyte (containing PhN-H2S and PhN) is pumped into the anode chamber of the H2S regeneration electrolytic cell. In the anode chamber of the H2S regeneration electrolytic cell, an electrolytic reaction occurs to produce an electrolyte of a gas-liquid mixture of PhN and H2S. This gas-liquid mixed electrolyte flows into the H2S separation tank for separation. The separated H2S gas enters the infrared analyzer through the top gas outlet of the H2S separation tank for detection. The electrolyte in the H2S separation tank after separation is then pumped into the cathode chambers of the CO2 regeneration electrolytic cell and the H2S regeneration electrolytic cell to carry out the reaction of Formula 1, obtaining an electrolyte containing the reduced state substance of the absorbent. This final electrolyte is sent back to the acid gas absorption tank to re-absorb H2S and CO2.

[0076] Test analysis:

[0077] Through detection by the infrared analyzer, the CO2 concentration in the purified raw gas discharged from the acid gas absorption tank is 0.1%, the H2S concentration is 0.1%, the CO2 concentration discharged from the CO2 separation tank is 98%, and the H2S concentration discharged from the H2S separation tank is 96%.

[0078] Example 2

[0079] This example is the same as Example 1, except that the raw gas entering the acid gas absorption tank is simulated coal-to-synthesis gas (15% CO2, 0.5% H2S, 84.5% CO and H2).

[0080] Through detection by the infrared analyzer, the CO2 concentration in the purified raw gas discharged from the acid gas absorption tank is 0.15%, the H2S concentration is 0.005%, the CO2 concentration discharged from the CO2 separation tank is 99%, and the H2S concentration discharged from the H2S separation tank is 97%.

[0081] Example 3

[0082] This example is the same as Example 1, except that the electrolyte consists of phenazine (PhN), TBAPF6 (tetrapropylammonium hexafluorophosphate), and dimethyl sulfoxide, with concentrations of 50 mmol / L, 2000 mmol / L, respectively.

[0083] The electrolysis conditions of the CO2 regeneration electrolytic cell and the H2S regeneration electrolytic cell are as follows: at 25 °C with constant current electrolysis; a voltage of 1 V is applied to the CO2 regeneration electrolytic cell, and a voltage of 1.5 V is applied to the H2S regeneration electrolytic cell.

[0084] The simulated natural gas (10% CO2, 10% H2S, 80% CH4) is introduced into the acid gas absorption tank at a flow rate of 40 mL / min.

[0085] Through the detection by an infrared analyzer, the CO2 concentration in the purified raw gas discharged from the acid gas absorption tank is 0.4%, the H2S concentration is 0.3%, the CO2 concentration discharged from the CO2 separation tank is 98%, and the H2S concentration discharged from the H2S separation tank is 99%.

[0086] Example 4

[0087] This example is the same as Example 1, except that the electrolyte is composed of phenazine (PhN), TBAPF6 (tetrapropylammonium hexafluorophosphate) and dimethyl sulfoxide, and their concentrations are 100 mmol / L and 1000 mmol / L respectively.

[0088] The electrolysis conditions of the CO2 regeneration electrolytic cell and the H2S regeneration electrolytic cell are as follows: at 25 °C with constant current electrolysis; a voltage of 0.8 V is applied to the CO2 regeneration electrolytic cell, and a voltage of 1.5 V is applied to the H2S regeneration electrolytic cell.

[0089] The simulated natural gas (10% CO2, 10% H2S, 80% CH4) is introduced into the acid gas absorption tank at a flow rate of 60 mL / min.

[0090] Through the detection by an infrared analyzer, the CO2 concentration in the purified raw gas discharged from the acid gas absorption tank is 1%, the H2S concentration is 0.8%, the CO2 concentration discharged from the CO2 separation tank is 99%, and the H2S concentration discharged from the H2S separation tank is 95%.

[0091] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An electrochemical sulfur-carbon integrated capture and graded regeneration method, characterized in that: The following steps are involved: Desulfurization and decarbonization of raw gas: the raw gas containing H2S and / or CO2 is introduced into the electrolyte containing the reducing substance of the absorbent, and the H2S and / or CO2 are absorbed to obtain the electrolyte containing acidic gas; First electrolysis: electrolyzing the acidic gas-containing electrolyte in a CO2 regeneration electrolytic cell, thereby forming a first gas-liquid mixture of CO2 and electrolyte in the anode chamber of the electrolytic cell, and separating the first gas-liquid mixture to obtain a first electrolyte and CO2 gas; Second electrolysis: electrolyzing the first electrolyte in the H2S regeneration electrolytic cell, thereby forming a second gas-liquid mixture of H2S and electrolyte in the anode chamber of the electrolytic cell, and separating the second gas-liquid mixture to obtain a second electrolyte and H2S gas; the first electrolyte and the second electrolyte both contain an absorbent, and the voltage of the second electrolysis is higher than the voltage of the first electrolysis; Absorbent reduction: The second electrolyte is introduced into the cathode chamber of the electrolytic cell used for the first electrolysis and the second electrolysis, and the absorbent is reduced in the cathode chamber to obtain an electrolyte containing the reduced state of the absorbent, which is reused in the raw gas desulfurization and decarbonization steps.

2. The method according to claim 1, characterized in that The electrolyte also includes an organic solvent and an electrolyte supporting salt, and each 1L of the organic solvent contains 10-100 mmol of absorbent and 0.5-4 mol / L of electrolyte supporting salt.

3. The method according to claim 2, characterized in that The absorbent is any one of phenazine, pyridine, azobenzene, p-benzoquinone, anthraquinone, disulfide and derivatives thereof.

4. The method according to claim 2, characterized in that: The electrolyte supporting salt is any one of tetrapropylammonium hexafluorophosphate, tetrabutylammonium perchlorate, tetraethylammonium hexafluorophosphate, tetraethylammonium perchlorate, lithium hexafluorophosphate and tetraethylammonium tetrafluoroborate.

5. The method according to claim 2, characterized in that: The organic solvent is any one of dimethyl sulfoxide, N,N-dimethylformamide, acetonitrile, N-methylpyrrolidone, tetrahydrofuran and dichloromethane.

6. The method according to any one of claims 1 to 5, characterized in that The flow rate of the raw gas is 20-60 sccm; The conditions for the first electrolysis and the second electrolysis are: room temperature and constant current; the voltage of the first electrolysis is 0.5-1V lower than the voltage of the second electrolysis, and the voltage of the second electrolysis is 1.5-3V.

7. A device suitable for the electrochemical sulfur-carbon integrated capture and graded regeneration method according to any one of claims 1 to 6, characterized in that: include: Acid gas absorption tank, used to place electrolyte containing reduced state substances of absorbent; A CO2 separation unit comprises a CO2 regeneration electrolytic cell, a diaphragm located inside the CO2 regeneration electrolytic cell and separating the CO2 regeneration electrolytic cell into an anode chamber and a cathode chamber, an anode and a cathode located in the anode chamber and the cathode chamber, respectively, and a CO2 separation tank connected to the anode chamber of the CO2 regeneration electrolytic cell, wherein the anode chamber of the CO2 regeneration electrolytic cell is connected to the acid gas absorption tank; The H2S separation unit comprises an H2S regeneration electrolytic cell, a diaphragm located inside the H2S regeneration electrolytic cell and separating the H2S regeneration electrolytic cell into an anode chamber and a cathode chamber, an anode and a cathode located in the anode chamber and the cathode chamber, respectively, and an H2S separation tank connected to the anode chamber of the H2S regeneration electrolytic cell, wherein the anode chamber of the H2S regeneration electrolytic cell is connected to the CO2 separation tank; Among them, the H2S separation tank is connected to the cathode chamber of the H2S regeneration electrolytic cell and the cathode chamber of the CO2 regeneration electrolytic cell, and the acid gas absorption tank is connected to the cathode chamber of the H2S regeneration electrolytic cell and the cathode chamber of the CO2 regeneration electrolytic cell.

8. The device according to claim 7, characterized in that The tops of the acid gas absorption tank, the CO2 separation tank and the H2S separation tank are all provided with gas outlets.

9. The device according to claim 7, characterized in that The anode and cathode are both made of carbon cloth, carbon felt, carbon fiber or graphite plate.

10. The device according to claim 7, characterized in that The diaphragm is an ion exchange membrane.

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