Deep desulfurization system for preparing methanol from coke oven gas and use method

Abstract

The invention relates to the technical field of gas treatment, and discloses a deep desulfurization system for preparing methanol from coke oven gas and a use method.The deep desulfurization system comprises a photoelectrocatalysis desulfurization module, a nano molecular sieve adsorption module and a regeneration module which are sequentially arranged in the movement direction of the coke oven gas; the photoelectrocatalytic desulfurization module is composed of a reaction tower, a photoanode, a photocathode and an electrolyte, the material of the photoanode is a TiO2-ZrO2 heterojunction nanotube array, the material of the photocathode is a NiFe-LDH / carbon felt composite electrode, and the electrolyte adopts an ionic liquid [BMIM] [BF4] coupled Fe < 3 + > / EDTA redox medium; through integration of a photoelectric coupling technology and a deep desulfurization system, efficient desulfurization, pollutant removal, prolonging of the service life of equipment, prolonging of the service life of a methanol synthesis catalyst and maximization of environmental protection benefits in the process of preparing methanol from coke oven gas are realized; sulfide oxidation / hydrogenation reaction kinetics is improved, and energy consumption is reduced.

Description

Technical Field

[0001] This invention relates to the field of gas treatment technology, specifically to a deep desulfurization system for producing methanol from coke oven gas and its application method. Background Technology

[0002] Sulfides in coke oven gas exist in both inorganic and organic forms and are present in high concentrations. Without thorough desulfurization, these sulfides can poison methanol synthesis catalysts, leading to catalyst deactivation and affecting methanol yield and quality, such as copper-based catalysts. Furthermore, sulfide emissions can cause environmental pollution; therefore, the total sulfur content must be reduced to below 0.1 ppm.

[0003] The current desulfurization process for methanol production from coke oven gas faces numerous technical challenges: the process is complex and energy-intensive, requiring the use of multiple desulfurization systems, such as pre-desulfurization, hydrogenation conversion, medium-temperature desulfurization, and ambient-temperature desulfurization, which are cumbersome to operate and consume a lot of power.

[0004] Insufficient performance of catalysts and desulfurizers; iron-molybdenum catalysts are prone to poisoning and deactivation; ZnO desulfurizers have low efficiency in removing residual organic sulfur and are difficult to regenerate, resulting in total sulfur levels that are difficult to meet standards.

[0005] The treatment and resource utilization of by-products are prominent challenges. The sulfide by-products produced by wet desulfurization are prone to causing equipment corrosion, the sulfur recovery rate is low and the quality is poor, and the resource utilization rate is insufficient.

[0006] Furthermore, equipment corrosion and operational risks are significant, and high-temperature, high-pressure operation easily leads to packing blockage, while the high requirements for raw gas pretreatment further exacerbate the system's complexity. These technical challenges restrict the economic efficiency and environmental compliance of desulfurization processes, necessitating breakthroughs in process optimization and the development of novel desulfurization materials to achieve technological upgrades. Summary of the Invention

[0007] The purpose of this invention is to provide a deep desulfurization system and method for producing methanol from coke oven gas, which solves the technical problems of low desulfurization efficiency, high operating cost and difficulty in regenerating desulfurizing agents in the current process, thereby improving the lifespan of methanol synthesis catalysts and increasing methanol yield and quality, thus solving the problems mentioned in the background art.

[0008] To achieve the above objectives, the present invention provides the following technical solution: A deep desulfurization system for methanol production from coke oven gas includes a photoelectrocatalytic desulfurization module, a nano-molecular sieve adsorption module, and a regeneration module arranged sequentially according to the direction of coke oven gas movement. The photoelectrocatalytic desulfurization module consists of a reaction tower, a photoanode, a photocathode, and an electrolyte. The photoanode material is a TiO2-ZrO2 heterojunction nanotube array, the photocathode material is a NiFe-LDH / carbon felt composite electrode, and the electrolyte is an ionic liquid [BMIM][BF4] coupled with Fe.3+ / EDTA redox medium; The nano-molecular sieve adsorption module uses NaX molecular sieve, with sulfur capacity increased to 30 mg / g. The regeneration module has a microwave unit and a gas supply unit, with the gas supplied by the gas supply unit being nitrogen.

[0009] As a further aspect of the present invention: the microwave unit is specifically a 2.45GHz microwave generator with a penetration depth of 1.5m.

[0010] As a further aspect of the present invention: the gas delivered by the gas delivery unit is replacement low-pressure nitrogen, 200-250°C nitrogen, and purging nitrogen.

[0011] As a further aspect of the present invention: the TiO2-ZrO2 heterojunction nanotube array in the photoanode is modified with ZrO2 quantum dots to extend the photoresponse range to 450nm.

[0012] As a further embodiment of the present invention: Pt nanoparticles are loaded on the surface of the NiFe-LDH / carbon felt composite electrode in the photocathode.

[0013] As a further embodiment of the present invention: the reaction tower is composed of a 316L stainless steel shell and a polytetrafluoroethylene lining.

[0014] As a further embodiment of the present invention: a honeycomb-shaped flow guide plate is provided inside the reaction tower.

[0015] As a further embodiment of the present invention: the nanomolecular sieve adsorption module has three towers, which respectively realize adsorption, regeneration and static standby.

[0016] As a further aspect of the present invention: S1: Before starting, the TiO2-ZrO2 heterojunction photoanode is pre-irradiated with ultraviolet light for 30 minutes to activate the photoanode; S2: Injection of ionic liquid [BMIM][BF4] with 0.1 mol / L Fe 3+ / EDTA mixed solution, maintained at pH=8.5-9.5, conductivity>10mS / cm; S3: Turn on the xenon lamp. The photoanode absorbs photons to excite electron-hole pairs, while a bias voltage of 1.2-1.5V is applied to drive charge separation. S4: Coke oven gas enters from the bottom of the tower at a flow rate of 0.5-1.5 m / s and comes into countercurrent contact with the electrolyte sprayed from the top. The honeycomb guide plate design ensures that the gas residence time is >60 seconds, ensuring that the sulfides are fully diffused to the catalyst surface, and desulfurized coke oven gas is obtained after the reaction. S5: Coke oven gas enters from the top of the nano-molecular sieve adsorption module tower, and the airflow is evenly distributed through a buffer mesh plate with a pore size of 0.5-1mm to reduce the scouring speed of NaX molecular sieve. S6: At airspeeds of 1800-3000 h -1 The remaining hydrogen sulfide and carbonyl sulfide are adsorbed by NaX molecular sieve to obtain coke oven gas with a sulfur content ≤0.05ppm, which is then introduced into the subsequent methanol synthesis unit. S7: The regeneration module monitors the outlet sulfur concentration in real time through a laser gas analyzer, and triggers a switching signal when the concentration exceeds the standard. S8: Introduce low-pressure nitrogen gas with a purity >99.99% to replace the residual coal gas; S9: Activate the 2.45GHz microwave generator, penetrate to a depth of 1.5m, selectively heat sulfides, and achieve a final sulfur desorption rate >98%; S10: Hot nitrogen gas at 200-250℃ carries desorbed sulfides into the sulfur recovery system; S11: Finally, the gas is purged in reverse with nitrogen at 80% of the adsorption gas volume, cooled to below 20°C, and the purified gas from the other adsorption tower is introduced into the regeneration tower and slowly pressurized to 0.3-0.5MPa. S12: Keep it still for 2 hours to balance the temperature and pressure gradient inside the tower and ensure that the adsorbent recovers its activity.

[0017] Compared with the prior art, the beneficial effects of the present invention are: This invention integrates photoelectric coupling technology with a deep desulfurization system to achieve highly efficient desulfurization, pollutant removal, extended equipment lifespan, improved methanol synthesis catalyst lifespan, and maximized environmental benefits in the coke oven gas-to-methanol process, providing key technological support for the green and low-carbon transformation of the coal chemical industry. The photocatalytic desulfurization module enhances the kinetics of sulfide oxidation / hydrogenation reactions and reduces energy consumption through the synergistic effect of light excitation and electric field drive. Combined with a nano-molecular sieve adsorption module, the sulfur content can be reduced to ≤0.05ppm, while the nano-molecular sieve adsorbent can be regenerated to achieve adsorption performance regeneration.

[0018] In this invention, a photoelectrocatalytic desulfurization module is constructed using band structure engineering. ZrO2 quantum dot modification reduces the TiO2 conduction band potential from -0.5V to -0.8V, enhancing electron reduction capability. The photoanode and cathode are arranged in an interdigitated pattern, increasing light utilization by 40%.

[0019] This invention employs nano-sized NaX molecular sieves in both the nano-molecular sieve adsorption and regeneration modules, shortening the diffusion path and increasing the sulfur capacity to 30 mg / g. Simultaneously, it utilizes 2.45 GHz microwave selective heating of the sulfide, reducing the regeneration temperature to 250°C, lowering energy consumption to 8-9 kWh / kg S, and achieving a sulfur desorption rate >98%. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 A system block diagram for deep desulfurization of methanol production from coke oven gas; Detailed Implementation

[0022] The technical solution of the present invention will be described in detail and comprehensively below with reference to specific embodiments. However, those skilled in the art should understand that the following embodiments are only some specific implementations of the present invention and do not cover all implementation scenarios of the present invention. Their core purpose is to provide an exemplary explanation of the technical concept of the present invention, rather than to limit the scope of protection of the present invention. Based on the embodiments disclosed in the present invention, all other embodiments that can be deduced by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] The coke oven gas used in this method is taken from the purification section of a coke oven gas to methanol plant, and its specific composition is shown in Table 1 below.

[0024] Table 1. Composition of the raw material gas <![CDATA[H2]]> <![CDATA[N2]]> CO <![CDATA[CO2]]> <![CDATA[CH4]]> <![CDATA[H2S]]> Organic sulfur mol% mol% mol% mol% mol% ppm ppm 65 4.5 5.5 2 23 150 140 Example 1:

[0025] Step 1: Before starting, pre-irradiate the TiO2-ZrO2 heterojunction photoanode with ultraviolet light for 30 minutes to activate the photoanode; Step 2: Inject ionic liquid [BMIM][BF4] with 0.1 mol / L Fe 3+ / EDTA mixed solution, maintained at pH=8.5-9.5, conductivity>10mS / cm; Step 3: Turn on the xenon lamp. The photoanode absorbs photons and excites electron-hole pairs. Simultaneously, a bias voltage of 1.2-1.5V is applied to drive charge separation. Ultraviolet / visible light excites the TiO2-ZrO2 heterojunction photoanode, generating electrons (e... - )-hole (h + Yes, external bias drives e - Migration towards the cathode, h + Accumulated on the photoanode surface, inhibiting recombination. Holes (h + The free radicals •OH oxidize organic sulfur (such as thiophene, COS) to sulfur. 0 or SO4 2-The cathode (NiFe-LDH / carbon felt) drives the decomposition of hydrogen sulfide to generate elemental sulfur and high-purity hydrogen. Step 4: Coke oven gas enters from the bottom of the tower at a flow rate of 0.5-1.5 m / s and comes into countercurrent contact with the electrolyte sprayed from the top. The honeycomb guide plate design ensures that the gas residence time is >60 seconds, ensuring that the sulfides are fully diffused to the catalyst surface. After the reaction, desulfurized coke oven gas is obtained, and samples are taken for analysis.

[0026] Step 5: Desulfurized coke oven gas enters from the top of the nano-molecular sieve adsorption module. The gas is evenly distributed through a buffer mesh plate with pore sizes of 0.5-1 mm, reducing the scouring velocity of the NaX molecular sieve. The NaX molecular sieve achieves physical adsorption of methane through its 10 Å pore structure. Methane molecules preferentially interact with oxygen atoms on the pore surface through van der Waals forces and electrostatic interactions. The adsorption process conforms to a pseudo-second-order kinetic model. By shrinking the micron-sized NaX molecular sieve to the nanoscale, mesopores are formed, shortening the diffusion path and increasing the sulfur capacity to 30 mg / g.

[0027] Step Six: At an airspeed of 2000 h -1 The residual hydrogen sulfide and carbonyl sulfide were adsorbed by NaX molecular sieve, and samples of the deeply desulfurized coke oven gas were taken for analysis.

[0028] Comparative Example 1: Step 1: Before starting, pre-irradiate the TiO2 photoanode with ultraviolet light for 30 minutes to activate the photoanode; Step 2: Inject ionic liquid [BMIM][BF4] with 0.1 mol / L Fe 3+ / EDTA mixed solution, maintained at pH=8.5-9.5, conductivity>10mS / cm; Step 3: Turn on the xenon lamp. The photoanode absorbs photons to excite electron-hole pairs, while a bias voltage of 1.2-1.5V is applied to drive charge separation. Step 4: Coke oven gas enters from the bottom of the tower at a flow rate of 0.5-1.5 m / s and comes into countercurrent contact with the electrolyte sprayed from the top. The honeycomb guide plate design ensures that the gas residence time is >60 seconds, ensuring that the sulfides are fully diffused to the catalyst surface. After the reaction, desulfurized coke oven gas is obtained, and samples are taken for analysis.

[0029] Step 5: The desulfurized coke oven gas enters from the top of the nano-molecular sieve adsorption module tower, and the airflow is evenly distributed through the buffer mesh plate with a pore size of 0.5-1mm to reduce the scouring speed of the NaX molecular sieve.

[0030] Step Six: At an airspeed of 2000 h -1 Under these conditions, residual hydrogen sulfide and carbonyl sulfide are adsorbed through NaX molecular sieves, and samples of deeply desulfurized coke oven gas are taken for analysis.

[0031] Comparative Example 2 Step 1: Before starting, pre-irradiate the TiO2-ZrO2 heterojunction photoanode with ultraviolet light for 30 minutes to activate the photoanode; Step 2: Inject ionic liquid [BMIM][BF4] with 0.1 mol / L Fe 3+ / EDTA mixed solution, maintained at pH=8.5-9.5, conductivity>10mS / cm; Step 3: Turn on the xenon lamp. The photoanode absorbs photons to excite electron-hole pairs, while a bias voltage of 1.2-1.5V is applied to drive charge separation. Step 4: Coke oven gas enters from the bottom of the tower at a flow rate of 0.5-1.5 m / s and comes into countercurrent contact with the electrolyte sprayed from the top. The honeycomb guide plate design ensures that the gas residence time is >60 seconds, ensuring that the sulfides are fully diffused to the catalyst surface. After the reaction, desulfurized coke oven gas is obtained, and samples are taken for analysis.

[0032] Step 5: The desulfurized coke oven gas enters the adsorption module, and the adsorption tower is filled with non-nano-sized NaX molecular sieves. The desulfurized coke oven gas is evenly distributed through a buffer mesh plate with a pore size of 0.5-1mm to reduce the scouring velocity of the NaX molecular sieves.

[0033] Step Six: At an airspeed of 2000 h -1 Under these conditions, residual hydrogen sulfide and carbonyl sulfide are adsorbed through NaX molecular sieves, and samples of deeply desulfurized coke oven gas are taken for analysis.

[0034] The desulfurization effect in Example 1 and Comparative Examples 1-2 was tested, and the test results are shown in Table 2.

[0035] Table 2. Hydrogen sulfide and organic sulfur content in desulfurized coke oven gas

[0036] Analyzing the data in Table 1, the hydrogen sulfide removal rate of the coke oven gas at the outlet of the photoelectrocatalytic reaction module in Example 1 was 90.67%, and the organic sulfur removal rate was 92.86%. In contrast, the hydrogen sulfide removal rate of the coke oven gas at the outlet of the electrocatalytic reaction module in Comparative Example 1 was only 78.00%, and the organic sulfur removal rate was only 71.42%. This indicates that the TiO2 photoanode, after being modified with ZrO2 quantum dots to form a TiO2-ZrO2 heterojunction, can broaden the photoresponse range and improve the desulfurization efficiency. The hydrogen sulfide and organic sulfur removal rates of the coke oven gas at the outlet of the photoelectrocatalytic reaction module in Comparative Example 2 were basically consistent with those in Example 1, but the hydrogen sulfide and organic sulfur content in the coke oven gas of the adsorption module was significantly higher than in Example 1. This indicates that the nano-sized NaX molecular sieve, with its high specific surface area and fast mass transfer rate, has a higher removal rate of hydrogen sulfide and organic sulfur in coke oven gas.

[0037] Additional notes: The specific operation steps of the regeneration module are as follows: Step 1: Monitor the outlet sulfur concentration in real time using a laser gas analyzer, and trigger a switching signal when the concentration exceeds the standard; Step 2: Introduce low-pressure nitrogen (purity > 99.99%) to replace the residual coal gas; Step 3: Activate the 2.45GHz microwave generator, with a penetration depth of 1.5m, to selectively heat sulfides and achieve a sulfur desorption rate >98%; Step 4: Hot nitrogen gas (200-250℃) carries the desorbed sulfides into the sulfur recovery system; Step 5: Use nitrogen to purge in reverse at 80% of the adsorption gas volume, cool to below 20°C, introduce the purified gas from another adsorption tower into the regeneration tower, and slowly increase the pressure to 0.3-0.5 MPa; Step 6: Let it stand for 2 hours to balance the temperature and pressure gradient inside the tower and ensure that the adsorbent regains its activity.

Claims

1. A deep desulfurization system for methanol production from coke oven gas, characterized in that: It includes a photoelectrocatalytic desulfurization module, a nano-molecular sieve adsorption module, and a regeneration module arranged sequentially according to the direction of coke oven gas movement; The photoelectrocatalytic desulfurization module consists of a reaction tower, a photoanode, a photocathode, and an electrolyte. The photoanode material is a TiO2-ZrO2 heterojunction nanotube array, the photocathode material is a NiFe-LDH / carbon felt composite electrode, and the electrolyte is an ionic liquid [BMIM][BF4] coupled with Fe. 3+ / EDTA redox medium; The nano-molecular sieve adsorption module uses NaX molecular sieve, with sulfur capacity increased to 30 mg / g. The regeneration module has a microwave unit and a gas supply unit, with the gas supplied by the gas supply unit being nitrogen.

2. The deep desulfurization system for methanol production from coke oven gas according to claim 1, characterized in that: The microwave unit is specifically a 2.45GHz microwave generator with a penetration depth of 1.5m.

3. The deep desulfurization system for methanol production from coke oven gas according to claim 2, characterized in that: The gas delivered by the gas delivery unit is replacement low-pressure nitrogen, 200-250℃ nitrogen, and purging nitrogen.

4. The deep desulfurization system for methanol production from coke oven gas according to claim 1, characterized in that: The TiO2-ZrO2 heterojunction nanotube array in the photoanode is modified with ZrO2 quantum dots to extend the photoresponse range to 450 nm.

5. The deep desulfurization system for methanol production from coke oven gas according to claim 1, characterized in that: The photocathode contains Pt nanoparticles loaded on the surface of the NiFe-LDH / carbon felt composite electrode.

6. The deep desulfurization system for methanol production from coke oven gas according to claim 1, characterized in that: The reaction tower consists of a 316L stainless steel shell and a polytetrafluoroethylene lining.

7. The deep desulfurization system for methanol production from coke oven gas according to claim 1, characterized in that: The reaction tower is equipped with a honeycomb-shaped flow guide plate.

8. The deep desulfurization system for methanol production from coke oven gas according to claim 1, characterized in that: The nanomolecular sieve adsorption module has three towers, which are used for adsorption, regeneration, and static standby, respectively.

9. A method of using a deep desulfurization system for methanol production from coke oven gas according to any one of claims 1-8, characterized in that: include: S1: Before starting, the TiO2-ZrO2 heterojunction photoanode is pre-irradiated with ultraviolet light for 30 minutes to activate the photoanode; S2: Injection of ionic liquid [BMIM][BF4] with 0.1 mol / L Fe 3+ / EDTA mixed solution, maintained at pH=8.5-9.5, conductivity>10mS / cm; S3: Turn on the xenon lamp. The photoanode absorbs photons to excite electron-hole pairs, while a bias voltage of 1.2-1.5V is applied to drive charge separation. S4: Coke oven gas enters from the bottom of the tower at a flow rate of 0.5-1.5 m / s and comes into countercurrent contact with the electrolyte sprayed from the top. The honeycomb guide plate design ensures that the gas residence time is >60 seconds, ensuring that the sulfides are fully diffused to the catalyst surface, and desulfurized coke oven gas is obtained after the reaction. S5: Coke oven gas enters from the top of the nano-molecular sieve adsorption module tower, and the airflow is evenly distributed through a buffer mesh plate with a pore size of 0.5-1mm to reduce the scouring speed of NaX molecular sieve. S6: At airspeeds of 1800-3000 h -1 The remaining hydrogen sulfide and carbonyl sulfide are adsorbed by NaX molecular sieve to obtain coke oven gas with a sulfur content ≤0.05ppm, which is then introduced into the subsequent methanol synthesis unit. S7: The regeneration module monitors the outlet sulfur concentration in real time through a laser gas analyzer, and triggers a switching signal when the concentration exceeds the standard. S8: Introduce low-pressure nitrogen gas with a purity >99.99% to replace the residual coal gas; S9: Activate the 2.45GHz microwave generator, penetrate to a depth of 1.5m, selectively heat sulfides, and achieve a final sulfur desorption rate >98%; S10: Hot nitrogen gas at 200-250℃ carries desorbed sulfides into the sulfur recovery system; S11: Finally, the gas is purged in reverse with nitrogen at 80% of the adsorption gas volume, cooled to below 20°C, and the purified gas from the other adsorption tower is introduced into the regeneration tower and slowly pressurized to 0.3-0.5MPa. S12: Keep it still for 2 hours to balance the temperature and pressure gradient inside the tower and ensure that the adsorbent recovers its activity.

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