Process for the production of sulphur from sulphur dioxide

Abstract

This invention belongs to the field of sulfur preparation technology, specifically relating to a process for producing sulfur from sulfur dioxide. Through one or more reaction devices, at a temperature of 160-320°C, hydrogen gas introduced by a hydrogen gas stream selectively reduces SO2 introduced by a sulfur dioxide gas stream to elemental sulfur. Each reaction device includes one or more selective reduction reactors connected in series, and each selective reduction reactor contains one or more catalyst beds, each catalyst bed being filled with a selective reduction catalyst. The process of this invention is relatively simple, has a short flow rate, and high efficiency. The product other than sulfur is water or primarily water, showing promising application prospects.

Description

Technical Field

[0001] This invention belongs to the field of sulfur preparation technology, specifically relating to a process for producing sulfur from sulfur dioxide. Background Technology

[0002] For many industries, such as various non-ferrous metal smelting enterprises, capturing most of the sulfur dioxide in the exhaust gas and converting the captured sulfur dioxide into sulfur that is easy to store, sell and transport is a reasonable choice.

[0003] Chinese patent CN103303872A discloses a method for recovering sulfur dioxide from flue gas and producing sulfur. In this method, coal gas containing 11-15% H2, 24-30% CO, and water vapor undergoes a shift reaction. The pure sulfur dioxide stream extracted from the flue gas is divided into two streams. One stream, accounting for 70-80% of the total, is mixed with the outlet stream (H2 content above 30%) of the coal gas shift reactor and fed into a reduction reactor, where sulfur dioxide is reduced to elemental sulfur and hydrogen sulfide. The outlet stream of the reduction reactor is cooled and liquid sulfur is separated by a first-stage sulfur condenser. The non-condensable stream from the first-stage sulfur condenser is mixed with the other stream of pure sulfur dioxide (i.e., the remaining 20-30% flow rate) and fed into a Claus reactor. The outlet stream of the Claus reactor is cooled and liquid sulfur is separated by a second-stage sulfur condenser. The non-condensable tail gas is sent to a boiler for combustion. SO2 in the boiler flue gas is recovered, and pure sulfur dioxide is extracted and reused in the sulfur production process. This method is technically flawed and has not yet been reported for industrial application. Summary of the Invention

[0004] The purpose of this invention is to provide a process for producing sulfur from sulfur dioxide. The process is relatively simple, has a short flow, and is highly efficient. The product other than sulfur is water or mainly water, which has certain application prospects.

[0005] The process for producing sulfur from sulfur dioxide described in this invention involves one or more reaction devices at a temperature of 160-320°C, using hydrogen gas introduced by a hydrogen gas stream to selectively reduce SO2 introduced by the sulfur dioxide gas stream to elemental sulfur. Each reaction device is equipped with one or more selective reduction reactors connected in series. The first-stage selective reduction reactor is sequentially connected to a heater A and a gas flow mixer A. The final-stage selective reduction reactor is sequentially connected to an elemental sulfur condenser A and a water condenser. The gas flow outlet of the water condenser is connected to a pressurized blower. The liquid sulfur discharged from the elemental sulfur condenser A is buffered in a liquid sulfur pool or liquid sulfur tank. The condensate discharged from the condenser is buffered in a condensate pool or tank; each selective reduction reactor is equipped with one or more catalyst beds, each filled with selective reduction catalyst; in the reaction of each reactor, the total volumetric flow rate of H2 is 1.9-2.2 times the total volumetric flow rate of SO2; the reaction exhaust gas is cooled in stages by elemental sulfur condenser A and water condenser, and liquid sulfur and condensate are separated; more than 95% of the gas flow from the pressurized blower outlet is used as circulating gas to each reactor, and the remaining flow is treated as reaction tail gas and discharged after purification.

[0006] The selective reduction reactor is a fixed-bed catalytic reactor.

[0007] The selective reduction reactor is an internally cooled reactor with controllable maximum catalyst bed temperature, and can adopt either radial or axial reaction structures.

[0008] When the reaction apparatus is equipped with multiple selective reduction reactors connected in series, and each selective reduction reactor has a catalyst bed, the internally cooled reactor is a self-limiting temperature reactor with a vertical water-cooled jacket structure, and its upper limit temperature of the catalyst bed is easily controlled. A characteristic of this reaction is its large exothermic reaction and adiabatic temperature rise. Under gas flow conditions of 160-320℃, the adiabatic temperature rise for the reaction of 1v% SO2 with 2v% H2 to produce elemental sulfur and 2v% water vapor is above 40℃. The internally cooled reactor generally removes heat through the vaporization of liquid water in the tubes; adjusting the pressure of the produced steam controls the maximum temperature of the catalyst bed. It is widely used in methanol synthesis, sulfur conversion, and other processes. The specific structure, application method, and effects of the self-limiting temperature reactor with the vertical water-cooled jacket structure are described in CN106629625A.

[0009] In the inlet gas stream of each catalyst bed, the volume content of SO2 and H2 is controlled to be: 6v%≤(C SO2 +0.5C H2The H2 content should be ≤15v% to achieve a balance between the stability of the reaction process, the reliability of bed temperature control, reactor cost, and catalyst lifetime. It is generally believed that when the H2 content in the inlet gas stream of the catalyst bed is ≤12v%, the active component of the catalyst can maintain a highly active sulfided state (i.e., avoid irreversible reduction of the sulfided active component).

[0010] In the inlet gas stream of elemental sulfur condenser A, the elemental sulfur content (S2) is 10-15 v, and the upper limit of water vapor content is 60 v, to achieve higher single-pass reaction efficiency and lower heating and cooling costs per unit sulfur yield; the gas hourly space velocity in each catalyst bed is 500-5000 h⁻¹. -1 .

[0011] When each reaction unit is equipped with a selective reduction reactor, multiple catalyst beds are arranged in series within the selective reduction reactor along the overall airflow direction. An airflow mixing structure, composed of a mixing space and mixing components, is provided between the catalyst beds and supplemented with airflow. The inlet airflow conditions for the first catalyst bed include: temperature 160-220℃, water vapor content 15-40% vol%, and SO2 content 5-12% vol%. The airflow mixing structure between the catalyst beds mixes the exhaust airflow from the previous catalyst bed with the supplemented airflow to a temperature of 160-250℃ before entering the next catalyst bed. The supplemented airflow is a mixture of at least two of the following: sulfur dioxide airflow, hydrogen airflow, or circulating airflow.

[0012] When multiple selective reduction reactors are connected in series in each reaction unit, a gas flow mixer B is installed in the connecting pipeline between the selective reduction reactors. The outlet gas flow of the previous selective reduction reactor is combined with the feed gas flow, and then mixed by the gas flow mixer B to reach a temperature of 180-250°C before entering the next selective reduction reactor. The feed gas flow is a mixture of at least two of the following: sulfur dioxide gas flow, hydrogen gas flow, or circulating gas flow.

[0013] The sulfur dioxide gas stream is supplied by the Cansolv process or its modified process unit, with an SO2 content ≥99.5v on a dry basis; the hydrogen gas stream has an H2 content ≥98v and a CO content ≤0.5v; the hydrogen gas stream is generally obtained from raw materials such as coal, natural gas or methanol, and is finally separated by a pressure swing adsorption (PSA) unit. The main impurity components are N2 and / or CO, in order to control the COS generation concentration during the reaction process and reduce the purification cost of the reaction tail gas.

[0014] The temperature of the gas flow at the outlet of elemental sulfur condenser A is 140-160℃, while the temperatures of the sulfur dioxide gas flow and the water condenser outlet gas flow are both controlled at 60-75℃.

[0015] In the reaction apparatus, each catalyst bed is preferably heated to a maximum temperature of 290-310°C to obtain a higher reaction rate and a higher bed space velocity, thus achieving a proper balance between process economy and catalyst lifetime. The selective reduction catalyst exhibits excellent high-temperature resistance and high-content steam resistance under reaction conditions below 320°C and other conditions.

[0016] When the total flow rate of sulfur dioxide gas treated by the process of this invention is very large, i.e., the equipment scale is large and the hydrogen gas used contains CO, the combined flow rate of the tail gas from each reaction unit will also be large. It can be first treated by a smaller tail gas treatment reactor, and then treated by oxidation adsorption desulfurization to meet emission standards, thereby improving the overall operational flexibility of the selective reduction reactor and the overall economic efficiency of the process. At this time, the volume content of SO2 and H2S in the water condenser outlet gas is controlled to be: 1.5v%≤(C SO2 +C H2S The sulfur content in the gas stream is ≤3v%; the tail gas stream first passes through heater B and tail gas treatment reactor. Under conditions where the elemental sulfur content and bed temperature in the gas stream are both low (compared to the selective reduction reactor), the gas stream composition is controlled to have H2S content ≤0.5v% and SO2 content ≤0.15v%, and is less than 35% of the H2S content. The gas stream is then cooled to 140-150℃ by elemental sulfur condenser B and liquid sulfur is separated. It is then cooled to 20-60℃ by cryogenic cooler and condensate is separated. After that, it is treated by oxidation adsorption desulfurization method. The tail gas treatment reactor is filled with the selective reduction catalyst, and the gas stream inlet temperature is 170-180℃. The liquid sulfur separated by elemental sulfur condenser B enters the liquid sulfur pool or liquid sulfur tank, and the condensate separated by cryogenic cooler enters the condensate pool or condensate tank. The aforementioned oxidative adsorption desulfurization method specifically involves using two or more oxidative adsorption desulfurization towers, which can be connected in series or parallel, to desulfurize the outlet airflow of the cryogenic cooler. An appropriate amount of air is first introduced and mixed before entering the oxidative adsorption desulfurization towers. The oxidative adsorption desulfurization towers can be filled with catalytic oxidative adsorption desulfurizing agents prepared by modifying activated carbon, such as catalytic oxidative adsorption desulfurizing agents prepared by modifying macroporous activated carbon with one or more oxide components selected from Fe, Mn, Cu, or Zn. Preferably, a thermally regenerable catalytic oxidative adsorption desulfurizing agent is used, and more preferably, a catalytic oxidative adsorption desulfurizing agent with COS hydrolysis removal capability is employed. The Z979G activated carbon modified desulfurizing agent produced by Shandong Xunda Chemical Group Co., Ltd. is particularly suitable, possessing a sulfur capacity of ≥20wt% or even ≥30wt% and an H2S removal accuracy of ≤0.5ug / L, as well as COS hydrolysis removal capability and a COS removal accuracy of ≤1ug / L. Furthermore, the desulfurization performance can be essentially restored by thermally regenerating and blowing away deposited sulfur and adsorbed sulfides.

[0017] A gas stream (pressurized by a compressor) obtained from the purification of the reaction tail gas and / or a supplementary dilution gas stream is introduced into the liquid sulfur pool or liquid sulfur tank to remove the hydrogen polysulfides and hydrogen sulfide contained in the buffer liquid sulfur into H2S, thereby purifying the liquid sulfur. The supplementary dilution gas stream is a nitrogen stream with an N2 content ≥99% vol%. The resulting H2S-containing gas stream C is used at the inlet of the gas stream mixer A. The purified liquid sulfur obtained from the liquid sulfur pool or liquid sulfur tank, after removing H2S, can be further processed into a powder product for storage and transportation, or it can be directly transported in liquid sulfur form.

[0018] The main impurity component in the nitrogen gas stream is O2, which reacts with H2 to generate water vapor during the reaction process. Since the exhaust flow rate of the tail gas stream is relatively small (relative to the flow rate of the sulfur dioxide gas stream or hydrogen gas stream), the amount of nitrogen gas used is small and can contain O2.

[0019] Sulfur foam collected from the surface of the water in the condensate pool or tank is sent to a sulfur melter to recover liquid sulfur at 150-160°C, which is then returned to the liquid sulfur pool or tank. H2S and SO2 contained in the process gas flow react in the water condenser to generate a small amount of elemental sulfur, which enters the condensate pool or tank with the condensate and floats on the water surface as sulfur foam. Dissolved H2S and SO2 in the condensate also react to generate elemental sulfur, which rises to the surface and joins the sulfur foam.

[0020] The number of reaction devices can be determined based on the total flow rate of the sulfur dioxide gas stream.

[0021] The SO2 and H2 content in the reaction gas streams of each reaction unit, as well as the reaction effect, are controlled by adjusting the flow ratios of sulfur dioxide gas stream, hydrogen gas stream, circulating gas stream, and supplementary dilution gas stream, as well as the flow ratios at each specific inlet location and the temperature conditions of the catalyst bed.

[0022] The selective reduction catalyst and its preparation method used in this invention are the same as those in the prior application CN202512027394.0 (Selective reduction catalyst for producing sulfur from sulfur dioxide and its application method).

[0023] The selective reduction catalyst contains 1-2 wt% cobalt (based on CoO), 4-10 wt% molybdenum (based on MoO3), and 2-4 wt% zinc (based on ZnO), with TiO2-Al2O3 as the support; it is prepared through the following steps:

[0024] (A) The dry powder of metatitanic acid was calcined at 550-570℃ for 3-5 hours to obtain TiO2 powder; the dry powder of boehmite was calcined at 750-800℃ for 3-5 hours to obtain Al2O3 powder; the obtained TiO2 powder and Al2O3 powder were mixed and ball-milled in a ball mill to obtain TiO2-Al2O3 mixed powder;

[0025] (B) In a kneader, add metatitanic acid powder and pseudoboehmite powder, mix evenly to obtain powder; spray acetic acid aqueous solution into the powder through an atomizing nozzle, continue mixing after the acetic acid aqueous solution is added, stop mixing and cover and seal; then add zinc compound powder, TiO2-Al2O3 mixed powder from step (A) and organic pore-forming agent powder, mix evenly, spray water through an atomizing nozzle, knead until the material is uniform, then discharge, extrude, granulate, dry, and calcine under air conditions to obtain a TiO2-Al2O3 carrier containing ZnO;

[0026] (C) In the spray drum, the TiO2-Al2O3 support containing ZnO obtained in step (B) is added, and the cobalt-molybdenum ammonia solution is sprayed into it through the atomizing nozzle. After the cobalt-molybdenum ammonia solution is sprayed, it is placed in a sealed container for homogenization treatment, then discharged, dried, and calcined to obtain a selective reduction catalyst for the production of sulfur from sulfur dioxide.

[0027] In step (A), the weight ratio of TiO2 powder to Al2O3 powder is 1:(2-3), the fineness of both metatitanic acid dry powder and pseudoboehmite dry powder is -600 mesh, and the fineness of TiO2-Al2O3 mixed powder is -200 mesh.

[0028] In step (B), the concentration of the acetic acid aqueous solution is 18-30 wt%, and the weight ratio of pseudoboehmite dry powder to acetic acid aqueous solution is 1:(0.5-0.8); the mixing time is 40-60 min, and the standing time is 15-20 h; the calcination temperature is 450-480℃, and the calcination time is 2-4 h; the zinc compound dry powder is zinc hydroxide dry powder or basic zinc carbonate dry powder; the organic pore-forming agent powder is made by mixing guar gum powder and polyacrylamide in a weight ratio of 1:(2-4), and the molecular weight of polyacrylamide is 10 million-20 million; the organic pore-forming agent powder is burned off during the calcination process at 450-480℃ and in air.

[0029] In step (B), the weight ratio of the total amount of water contained in the metatitanic acid powder, pseudoboehmite powder, zinc compound powder, TiO2-Al2O3 mixed powder, organic pore-forming agent powder, and acetic acid aqueous solution, plus the injected water, is (20-30):(15-25):(2-5):(45-65):(2-4):(95-140), where the metatitanic acid powder is calculated as TiO2, the pseudoboehmite powder as Al2O3, and the zinc compound powder as... The dry powder is calculated as ZnO; the fineness of the metatitanic acid dry powder and the pseudoboehmite dry powder is -600 mesh, and the fineness of the zinc compound dry powder is -200 mesh (which can be observed through an optical microscope) to obtain uniform mixing; the shape of the ZnO-containing TiO2-Al2O3 support is one of cylindrical, clover-shaped or tetraclover-shaped, and the equivalent external dimensions of the ZnO-containing TiO2-Al2O3 support are Φ(2.5-4)×(3-8)mm.

[0030] In step (B), an aqueous acetic acid solution was sprayed into the metatitanic acid powder and the pseudoboehmite powder to generate aluminum glue, which serves as the main adhesive component of the carrier. Since the amount of aqueous acetic acid solution used was small, the powder had good fluidity during the mixing process and could be basically mixed with other powders added later.

[0031] The parameters of the metatitanic acid powder in both steps (A) and (B) are: SO4 2- With a content ≤0.5%, after calcination at 450℃, it has a purity ≥130m 2 The specific surface area is ≥0.25 mL / g and the pore volume is ≥0.25 mL / g; metatitanic acid dry powder is prepared by the following method: using SO4 2- Using industrial metatitanic acid produced by the sulfuric acid process with a content of 1.5-5 wt% (on a dry basis) and an average particle size (outer diameter, the same below) ≤1 μm as raw material, the mixture is pulped with a washing solution containing 1-3 wt% ammonia for 3-10 hours. The pulp is filtered, washed with water, dried, and pulverized to obtain metatitanic acid dry powder. In steps (A) and (B), the pseudoboehmite dry powder is calcined at 450℃ and has a particle size of 300-350 μm. 2 The specific surface area is 0.75-0.9 mL / g and the pore volume is 0.75-0.9 mL / g. Among the indicators of the metatitanic acid powder and pseudoboehmite powder, the specific surface area and pore volume were determined by low-temperature nitrogen adsorption method.

[0032] In step (C), the amount of cobalt-molybdenum ammonia solution added is 95-100% of the saturated water absorption volume of the ZnO-containing TiO2-Al2O3 support; the cobalt-molybdenum ammonia solution is prepared from raw materials, including ammonium molybdate, cobalt nitrate and ammonia, wherein the ammonium molybdate is heptamolybdate or tetramolybdate, the concentration of ammonia is 15-20 wt%, the concentration of ammonium molybdate in the cobalt-molybdenum ammonia solution is 143-316 g / L, and the concentration of cobalt nitrate in the cobalt-molybdenum ammonia solution is 78-166 g / L.

[0033] The raw materials also include ethylenediamine. The concentration of ethylenediamine in the cobalt-molybdenum ammonia solution is 6-10 g / L. Ethylenediamine is added to the cobalt-molybdenum ammonia solution to improve the distribution of cobalt and molybdenum.

[0034] In step (C), after the cobalt-molybdenum ammonia solution is sprayed in, zinc oxide is dissolved by the ammonia and forms uniformly distributed and highly dispersed ZnO during the subsequent drying and calcination processes. ZnO is intercalated with highly dispersed MoO3 and CoO. The stability of the ZnO sulfide products in the selective reduction catalyst is much higher than that of the MoO3 and CoO sulfide products, which modifies the inner surface of the TiO2-Al2O3 support and improves the dispersion state of MoO3, CoO and their sulfide products as well as their binding state with the support components. Thus, without reducing the catalyst's wide-temperature reaction effect, the stability of the catalyst's reaction performance under high water vapor content conditions is significantly improved.

[0035] In step (C), the homogenization time is 10-15 h, the calcination temperature is 450-480 ℃, and the calcination time is 2-4 h.

[0036] Selective reduction catalysts exhibit good heat resistance, water vapor resistance, and wide-temperature reaction performance during the reaction process.

[0037] The beneficial effects of this invention are as follows:

[0038] In this invention, SO2 is selectively reduced to elemental sulfur using H2. The reaction is relatively simple, the process is short, and the efficiency is high. The product other than sulfur is water or almost water. When using high-purity hydrogen, almost no tail gas is generated. When using hydrogen with a purity of 98% or higher, the amount of tail gas generated is also very small, and the burden of tail gas purification is light. The selective reduction catalyst used has relatively stable and high reaction performance under conditions of a low inlet gas flow temperature of 160-180℃, a water vapor content of up to 60v%, and a maximum bed temperature of 280-320℃. It can convert up to 10-25v% SO2 in a single pass to generate elemental sulfur. This process is economically competitive and has certain application prospects.

[0039] (1) The selective reduction catalyst used in the process of this invention has Claus activity. The H2S generated in the catalyst bed and the H2S contained in the circulating gas after the single-pass reaction and the separation of elemental sulfur and condensate by two-step condenser will continue to react with SO2 in the circulating reaction to be converted into elemental sulfur. Therefore, the H2S content in the reaction gas and the circulating gas will be limited to, for example, below 1v%. At the same time, the generation of H2S does not consume much H2 (when using high-purity hydrogen) or only consumes a small amount of H2 (when using, for example, 98v% hydrogen, a small amount of impurity components need to be discharged to maintain a reasonable composition of the circulating gas and the reaction gas in the catalyst bed).

[0040] (2) The selective reduction catalyst used in the process of the present invention also has the activity of reducing SO2 to elemental sulfur with CO (generating elemental sulfur and CO2) and COS hydrolysis activity (generating H2S and CO2). If necessary, hydrogen containing a small amount of CO, such as less than 0.5v%, or a synthesis gas containing CO and H2 can be added as a supplement. CO can be utilized to a high extent, and the CO content in the circulating gas will be limited to less than 0.1v%. The CO will generate a small amount of COS with elemental sulfur, but because the catalyst has COS hydrolysis activity (especially when the bed temperature is 280-320℃), the COS content in the circulating gas will be limited to less than 0.005v% or even 0.002v%.

[0041] (3) In step (A), the metatitanic acid powder is calcined at 550-570℃ to obtain TiO2, and the pseudoboehmite powder is calcined at 750-800℃ to obtain Al2O3; in step (B), the metatitanic acid powder, pseudoboehmite powder and their acetic acid gel are calcined at 450-480℃ to obtain TiO2 and Al2O3; the TiO2 and Al2O3 obtained by step (A) and the TiO2 and Al2O3 obtained by step (B) have different surface properties; the CoO and MoO3 introduced in step (C) are distributed in the pores and on the surface of TiO2 and Al2O3 particles. Among them, the CoO and MoO3 (sulfided state) distributed on the inner and outer surfaces of the TiO2 and Al2O3 particles obtained in step (A) have stable reactivity under higher temperature conditions, and the CoO and MoO3 (sulfided state) distributed on the inner and outer surfaces of the TiO2 and Al2O3 particles obtained in step (B) have stable reactivity under lower temperature conditions. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the process for producing sulfur from sulfur dioxide in Example 1.

[0043] Figure 2 This is a schematic diagram of the structure of the sulfur recovery catalyst evaluation device used in Example 1;

[0044] In the diagram: 1. Tubular stainless steel reactor; 2. Two-stage electric heating furnace; 3. Sulfur collection cylinder; 4. First-stage catalyst loading and unloading pipe; 5. Thermocouple sheath; 6. Second-stage make-up gas pipe; 7. N2 inlet pipe; 8. First H2 inlet pipe; 9. SO2 inlet pipe; 10. First gas mixer; 11. Storage bottle; 12. Horizontal flow pump; 13. Vaporizer; 14. Refrigerator; 15. Water vapor condenser separator; 16. Dryer; 17. First gas chromatograph; 18. First desulfurization tank; 19. Inlet pipe; 20. CO inlet pipe; 21. H2S inlet pipe; 22. Second gas chromatograph; 23. Second H2 inlet pipe; 24. Second gas mixer; 25. Second desulfurization tank. Detailed Implementation

[0045] The present invention will be further described below with reference to embodiments.

[0046] Example 1

[0047] like Figure 1As shown, the process for producing sulfur from sulfur dioxide involves a reaction apparatus at a temperature of 160-320℃, where hydrogen introduced by a hydrogen gas stream selectively reduces SO2 introduced by the sulfur dioxide gas stream to elemental sulfur. The reaction apparatus consists of four stages of selective reduction reactors, each a fixed-bed catalytic reactor. The first, second, third, and fourth stages of selective reduction reactors are connected sequentially. A heater A and a gas flow mixer A are connected sequentially before the first stage of selective reduction reactor. An elemental sulfur condenser A and a water condenser are connected sequentially after the fourth stage of selective reduction reactor. A pressurized blower is connected to the gas flow outlet of the water condenser. Liquid sulfur discharged from elemental sulfur condenser A is buffered in a liquid sulfur tank, and condensate discharged from the water condenser is buffered in a condensate tank. The total volumetric flow rate of H2 introduced into the reaction apparatus is [missing information - likely a percentage] of the total volumetric flow rate of SO2 introduced. The total volumetric flow rate of O2 is 1.9-2.1 times that of the four-stage selective reduction reactor. The exhaust gas from the reactor is cooled in stages by the elemental sulfur condenser A and the water condenser, and liquid sulfur and condensate are separated. More than 95% or even 97% of the gas flow from the pressurized blower outlet is used as circulating gas to the reactor. The remaining gas flow is treated as the tail gas and discharged after purification. The SO2 content, H2 content and reaction effect in the reaction gas flow of the reactor are controlled by adjusting the flow ratio of sulfur dioxide gas flow, hydrogen gas flow, circulating gas flow and supplementary dilution gas flow, the flow ratio at each specific inlet point and the temperature conditions of the selective reduction catalyst bed. The supplementary dilution gas flow is nitrogen, which is introduced at the inlet of the gas mixer A (introduced directly at the beginning of the plant, and then first purged by the liquid sulfur pool to purify the liquid sulfur and obtain gas flow C containing H2S, and then introduced at the inlet of the gas mixer A).

[0048] The four-stage selective reduction reactors are each equipped with a catalyst bed and loaded with the selective reduction catalyst produced by the method of Example 4. The inlet gas flow conditions A of the first-stage selective reduction reactor include: temperature 160-200℃, water vapor content 15-40 v%, SO2 content 5-12 v%. Gas mixers B1, B2, and B3 are respectively installed in the three connecting pipelines between the four-stage selective reduction reactors. At least two of the following gas flows are added to the inlets of gas mixers B1, B2, and B3: sulfur dioxide gas flow, hydrogen gas flow, or circulating gas flow. These gas flows are combined with the outlet gas flow of the previous stage selective reduction reactor, mixed, and reach a temperature of 180-250℃ before entering the next stage selective reduction reactor. During the reaction, the selective reduction catalyst is in a sulfided state.

[0049] The airflow mixers A, B1, B2, and B3 are all pipeline-type static mixers;

[0050] The selective reduction reactors described herein are all self-limiting reactors (a type of internally cooled reactor) with controllable maximum catalyst bed temperature and a vertical water-cooled jacket structure, employing a radial reaction structure, as described in CN106629625A. Figure 2 Either Figure 3 or Figure 3 is acceptable; the selective reduction reactor removes heat through the vaporization of liquid water in the outer tubes of the tube side, and the maximum temperature of the catalyst bed can be controlled by adjusting the pressure of the produced steam; the gas hourly space velocity in the catalyst bed of each selective reduction reactor is 500-2000 h⁻¹. -1 ;

[0051] In the inlet gas stream of each catalyst bed, the H2 content is controlled to be ≤12v%, and the volume content of SO2 and H2 is controlled to be ≤6v%. SO2 +0.5C H2 The concentration should be ≤15v%, in order to achieve a balance between the stability of the reaction process, the reliability of bed temperature control, reactor cost, and catalyst lifetime.

[0052] The maximum temperature of the catalyst bed in the first, second and third stage selective reduction reactors is controlled at 290-310℃ to obtain a higher reaction rate and a higher bed space velocity; the maximum temperature of the catalyst bed in the fourth stage selective reduction reactor can be controlled at 290-310℃ to obtain a higher bed space velocity, or it can be controlled at 250-260℃ to obtain a higher yield of elemental sulfur.

[0053] In the inlet gas flow of elemental sulfur condenser A, the elemental sulfur content (S2) can be controlled at 10-15% v, and the water vapor content is capped at 60% v, in order to obtain higher single-pass reaction efficiency and lower heating and cooling costs per unit sulfur output.

[0054] The temperature of the gas flow at the outlet of elemental sulfur condenser A is controlled at 140-160℃; the temperature of both the sulfur dioxide gas flow and the gas flow at the outlet of the water condenser is controlled at 60-75℃.

[0055] The tail gas stream from the reaction apparatus first passes through heater B and a tail gas treatment reactor. Under conditions where the elemental sulfur content and bed temperature in the gas stream are relatively low (compared to a selective reduction reactor), the composition of the outlet gas stream is controlled to have H2S content ≤ 0.5v%, SO2 content ≤ 0.15v%, and less than 35% of the H2S content. The gas is then cooled to 140-150℃ by elemental sulfur condenser B, where liquid sulfur is separated. It is then cooled to 20-60℃ by a low-temperature cooler, where condensate is separated. Afterward, it is treated by oxidation adsorption desulfurization to improve the overall operational flexibility and economic efficiency of the reactor series. At this point, the volume content of SO2 and H2S in the outlet gas stream of the water condenser is controlled to be: 1.5v% ≤ (C SO2 +C H2S)≤3v%; The tail gas treatment reactor also adopts the self-limiting temperature reactor with a vertical water-cooled jacket structure and controllable maximum catalyst bed temperature. It is filled with the selective reduction catalyst produced by the method in Example 4. The gas flow inlet temperature is 170-180℃ and the maximum catalyst bed temperature is 210-230℃. The liquid sulfur separated from the elemental sulfur condenser B enters the liquid sulfur pool, and the condensate separated from the low temperature cooler enters the condensate pool.

[0056] Sulfur foam on the surface of the water in the condensate pool is collected periodically and sent to the sulfur melting device to recover liquid sulfur at 150-160℃ and then into the liquid sulfur pool.

[0057] Using the required flow rate of gas stream (pressurized by a compressor) obtained from the purification treatment of the reaction tail gas and / or supplementary dilution gas stream (nitrogen), the polysulfides and hydrogen sulfides contained in the liquid sulfur buffer in the liquid sulfur pool are removed as H2S, thereby purifying the liquid sulfur; the resulting gas stream C containing H2S is then used at the inlet of the gas stream mixer A.

[0058] The purified liquid sulfur obtained from the liquid sulfur pool, after removing H2S, can be further processed into powder products for storage and transportation, or it can be directly transported in liquid sulfur form.

[0059] The sulfur dioxide gas stream is supplied by the Cansolv process or its modified process unit, with an SO2 content ≥99.5 v on a dry basis; the hydrogen gas stream has an H2 content ≥98 v, a CO content ≤0.5 v, and the remainder is mainly N2. The hydrogen gas stream is obtained from raw materials such as coal, natural gas, or methanol, and is finally separated by a pressure swing adsorption (PSA) unit. Using the hydrogen raw material with the lower CO content can control the CO2 concentration generated during the reaction process and reduce the purification cost of the reaction tail gas. The supplementary dilution gas stream is a nitrogen stream with an N2 content ≥99 v; nitrogen is required as a dilution gas during the initial operation of this process unit, but is no longer required thereafter because the industrial hydrogen produced from coal and natural gas conversion and concentrated by PSA separation will always contain N2 and its content can be adjusted. The gas stream circulation can maintain the N2 content in the reaction gas stream at the required level.

[0060] The outlet gas flow from the tail gas treatment reactor is cooled and liquid sulfur is separated by elemental sulfur condenser B, and then cooled and condensate is separated by low-temperature cooler. It is then processed through two or more oxidation adsorption desulfurization towers that can be connected in series and parallel. An appropriate amount of air is first added and mixed before entering the oxidation adsorption desulfurization towers. The oxidation adsorption desulfurization towers are filled with Z979G activated carbon modified desulfurizer produced by Shandong Xunda Chemical Group Co., Ltd., which has a sulfur capacity of ≥30wt% and an H2S removal accuracy of ≤0.5ug / L, as well as a COS removal accuracy of ≤1ug / L. The oxidation adsorption desulfurization towers can be thermally regenerated using steam at 250-300℃. During the thermal regeneration process, the gas flow containing elemental sulfur is blown out and processed by elemental sulfur condenser A. The Z979G activated carbon modified desulfurizer can withstand more than 10 thermal regeneration cycles.

[0061] Example 2

[0062] The process for producing sulfur from sulfur dioxide involves two reaction units. At temperatures of 160-320℃, hydrogen gas introduced from the sulfur dioxide gas stream selectively reduces SO2 to elemental sulfur. Each reaction unit is equipped with a selective reduction reactor, which is a fixed-bed catalytic reactor. A heater A and a gas mixer A are connected sequentially before the selective reduction reactor. An elemental sulfur condenser A and a water condenser are connected sequentially after the selective reduction reactor. The gas outlet of the water condenser is connected to a pressurized blower. The liquid sulfur discharged from the elemental sulfur condenser A is buffered in a liquid sulfur tank, and the condensate discharged from the water condenser is buffered in a condensate tank. The two reaction units share one liquid sulfur tank and one condensate tank. In the reactions of each reaction unit, the total volumetric flow rate of H2 introduced is equal to the total volumetric flow rate of SO2 introduced. The amount is 2.05-2.2 times the normal amount. The reaction exhaust gas is cooled stepwise by the elemental sulfur condenser A and the water condenser to separate liquid sulfur and condensate. More than 98% of the flow rate of the gas from the pressurized blower outlet is used as circulating gas to each reaction unit. The remaining flow rate is used as the reaction tail gas and is purified before being discharged in compliance with standards. The SO2 content, H2 content and reaction effect in the reaction gas of each reaction unit are controlled by adjusting the flow ratio of sulfur dioxide gas, hydrogen gas, circulating gas and supplementary dilution gas, the flow ratio at each specific introduction point and the temperature conditions of the catalyst bed. The supplementary dilution gas is nitrogen, which is introduced at the inlet of the gas mixer A (directly introduced at the beginning of the unit start-up, and then first purged by the liquid sulfur pool to purify the liquid sulfur and obtain gas C containing H2S, and then introduced at the inlet of the gas mixer A).

[0063] The selective reduction reactor contains four (four-stage) catalyst beds connected in series along the overall airflow direction. Each catalyst bed is filled with the selective reduction catalyst produced by the method in Example 4. A gas mixing structure, consisting of a mixing space and mixing components, is provided between the three catalyst beds, and gas flows b1, b2, and b3 are introduced respectively. The inlet gas flow A of the first-stage catalyst bed, i.e., the selective reduction reactor, has the following conditions: temperature 160-200℃, water vapor content 15-40 v%, SO2 content 5-12 v%. The gas mixing structure (i.e., the mixing space and mixing components) between the catalyst beds mixes the exhaust gas flow from the previous stage catalyst bed with the introduced gas flow to a temperature of 160-250℃ before entering the next stage catalyst bed. The introduced gas flows b1, b2, and b3 are mixtures of at least two of the following: sulfur dioxide gas flow, hydrogen gas flow, or circulating gas flow, and are mixed by gas flow mixers B1, B2, and B3 respectively. During the reaction, the selective reduction catalyst is in a sulfidated state.

[0064] The airflow mixer A is a pipeline-type static mixer;

[0065] The selective reduction reactor is an internally cooled reactor where the maximum temperature of each catalyst bed is controllable. It can employ either a radial or axial reaction structure. The internally cooled reactor removes heat through the vaporization of liquid water in the tubes; adjusting the pressure of the produced steam allows control of the maximum temperature of each catalyst bed. This reactor is widely used in methanol synthesis and sulfur-resistant conversion processes. The gas hourly space velocity (HSV) in each catalyst bed is 1000-5000 h⁻¹. -1 ;

[0066] In the inlet gas stream of each catalyst bed, the H2 content is controlled to be ≤12v%, and the volume content of SO2 and H2 is controlled to be ≤6v%. SO2 +0.5C H2 The concentration should be ≤15v%, in order to achieve a balance between the stability of the reaction process, the reliability of bed temperature control, reactor cost, and catalyst lifetime.

[0067] In the inlet gas flow of elemental sulfur condenser A, the elemental sulfur content (S2) can be controlled at 10-12% v, and the water vapor content is capped at 60% v%.

[0068] In the selective reduction reactor, the maximum temperature of each catalyst bed is controlled at 290-310℃ in order to use a higher bed space velocity. The fourth-stage catalyst bed can also be controlled at 250-260℃ to obtain a higher yield of elemental sulfur.

[0069] The hydrogen gas stream has an H2 content ≥98 v, a CO content ≤0.2 v, and the remainder is mainly N2; the reaction tail gas stream is directly treated by two or more oxidation adsorption desulfurization towers that can be connected in series and parallel (no tail gas treatment reactor is set up); the reaction tail gas stream is first mixed with an appropriate amount of air and then enters the oxidation adsorption desulfurization tower; the oxidation adsorption desulfurization tower is filled with Z979G activated carbon modified desulfurizer product produced by Shandong Xunda Chemical Group Co., Ltd.; the other conditions are the same as in the process of Example 1.

[0070] The beneficial effects of the sulfur production processes from sulfur dioxide in Examples 1 and 2 above include: selective reduction of SO2 to elemental sulfur using H2; a relatively simple reaction process; a short process flow; high efficiency; and the presence of water or almost water as a byproduct other than sulfur. When using high-purity hydrogen, almost no tail gas is generated, and even when using hydrogen with a purity of 98% or higher, the amount of tail gas generated is very small, reducing the burden of tail gas purification. The selective reduction catalyst used exhibits relatively stable and high reaction performance under conditions of a low inlet gas flow temperature of 160-180℃, a high water vapor content of up to 60v%, and a maximum bed temperature of 280-320℃, enabling a single-pass conversion of up to 10-25v% SO2 to elemental sulfur. This process is economically competitive and has certain application prospects. The process in Example 1 is suitable for production plants with an annual sulfur production capacity of 60,000 tons or more, while the process in Example 2 is suitable for production plants with an annual sulfur production capacity of less than 30,000 tons.

[0071] The physicochemical properties and preparation steps of the selective reduction catalysts in Examples 3-4 below have been described in the prior application CN202512027394.0 (Selective reduction catalyst for sulfur production from sulfur dioxide and its application method); Example 3 of the present invention corresponds to Example 1 in the prior application CN202512027394.0, and Example 4 of the present invention corresponds to Example 4 in the prior application CN202512027394.0. The following related descriptions are to ensure the completeness of the present invention.

[0072] Example 3

[0073] The selective reduction catalyst is prepared by the following steps:

[0074] (A) Prepare metatitanic acid dry powder (-600 mesh, SO4) 2- With a content of 0.21 wt%, after calcination at 450℃ for 3 hours, it has a content of 146 m 2 TiO2 powder was obtained by calcining (specific surface area of ​​0.29 mL / g and pore volume of 0.29 mL / g) at 560℃ for 4 h; pseudoboehmite dry powder (-600 mesh, after calcination at 450℃ for 3 h, has a specific surface area of ​​335 μm / g and a pore volume of 0.29 mL / g) was further obtained by calcination at 560℃ for 4 h. 2The TiO2 powder was calcined at 775℃ for 4 hours with a specific surface area of ​​0.84 mL / g and a pore volume of 0.84 mL / g to obtain Al2O3 powder. The obtained TiO2 powder and Al2O3 powder were mixed and ball-milled in a ball mill at a weight ratio of 1:2 to obtain TiO2-Al2O3 mixed powder of -200 mesh.

[0075] (B) Add metatitanic acid powder (-600 mesh, SO4) to a small kneader. 2- With a content of 0.21 wt%, after calcination at 450℃ for 3 hours, it has a content of 146 m 2 The specific surface area ( / g) and pore volume (0.29 mL / g) of pseudoboehmite dry powder (-600 mesh, after calcination at 450℃ for 3 h, it has 335 m... 2 The specific surface area (g) and pore volume (0.84 mL / g) were mixed evenly to obtain a powder. A 25 wt% acetic acid aqueous solution was sprayed into the powder through an atomizing nozzle. The weight ratio of the pseudoboehmite dry powder to the acetic acid aqueous solution was 1:0.65. After the acetic acid aqueous solution was added, mixing continued for 60 min. Mixing was stopped, and the mixture was covered and sealed for 15 h to obtain a powder with good flowability. Basic zinc carbonate dry powder (-200 mesh), the TiO2-Al2O3 mixed powder from step (A), and the organic pore-forming agent powder were then added and mixed evenly. Water was sprayed into the mixture through an atomizing nozzle, and the mixture was kneaded until the material was uniform. The mixture was then discharged, extruded, and granulated, and dried at 120℃ for 10 minutes. h, calcined at 465℃ and in air for 3h, to obtain a clover-shaped TiO2-Al2O3 carrier containing ZnO with equivalent external dimensions of Φ(3.1-3.2)×(4-6)mm; the total amount of water contained in the acetic acid aqueous solution and the injected water added to the mixed powder of TiO2-Al2O3, the organic pore-forming agent powder, and the acetic acid aqueous solution were 2.5kg, 2kg, 0.22kg, 5.5kg, 0.3kg, and 12kg, respectively, where the amount of the mixed powder of TiO2, the amount of the mixed powder of boehmite, the amount of the basic zinc carbonate, and the amount of the basic zinc carbonate were ZnO.

[0076] (C) In a small spray drum, 5000g of TiO2-Al2O3 support containing ZnO obtained in step (B) (with a saturated water absorption rate of 0.55mL / g) was added. 2613mL of cobalt-molybdenum ammonia solution was sprayed through an atomizing nozzle for 26min. After spraying, the drum continued to rotate for 8min until the support surface dried. Then the drum was stopped and placed in a sealed container for homogenization treatment for 12h. The material was discharged, dried at 120℃ for 6h, and calcined at 465℃ for 3h to obtain a selective reduction catalyst.

[0077] In steps (A) and (B), the metatitanic acid powder is prepared by the following method: using SO4 2-Using wet metatitanic acid from the sulfuric acid process with a content of 3.7 wt% (on a dry basis) and an average particle size of 0.65 μm as raw material, a washing solution (aqueous solution) containing 2 wt% ammonia was added at a weight ratio of 1:3 and the mixture was pulped for 8 hours. The pulp was then filtered, washed with water, dried, and pulverized to obtain dry metatitanic acid powder.

[0078] In step (B), the organic pore-forming agent powder is made by mixing guar gum powder (-600 mesh) and polyacrylamide (-200 mesh, molecular weight 12 million) in a weight ratio of 1:3.

[0079] The cobalt-molybdenum ammonia solution in step (C) is prepared by the following method: 143.4 g of ammonium tetramolybdate and 78.4 g of cobalt nitrate are added to a 1000 mL volumetric flask, and then ammonia water (concentration of 15 wt%) is added to a total volume of 850 mL. The mixture is shaken until completely dissolved, and then ammonia water is added again to a total volume of 1000 mL. The mixture is shaken well and left to stand for 15 h to obtain the cobalt-molybdenum ammonia solution. This solution is prepared in multiple batches for use.

[0080] The selective reduction catalyst contains 1 wt% cobalt (CoO), 4 wt% molybdenum (MoO3), and 2 wt% zinc (ZnO). The catalyst has a saturated water absorption rate of 0.51 mL / g, and its specific surface area and pore volume, determined by low-temperature nitrogen adsorption, are 193 m² / g. 2 / g and 0.42mL / g indicate that the volume of macropores in the catalyst is above 0.09mL / g.

[0081] Example 4

[0082] The selective reduction catalyst of Example 4 was prepared by basically following steps (A)-(C) of Example 3, with the main difference being:

[0083] In step (A), the metatitanic acid powder was calcined at 570℃ for 3 hours to obtain TiO2 powder; the pseudoboehmite powder was calcined at 800℃ for 3 hours to obtain Al2O3 powder; the obtained TiO2 powder and Al2O3 powder were mixed and ball-milled in a ball mill at a weight ratio of 1:3 to obtain a TiO2-Al2O3 mixed powder of -200 mesh.

[0084] In step (B), the amounts of basic zinc carbonate dry powder (calculated as ZnO), organic pore-forming agent powder, water contained in acetic acid aqueous solution, and sprayed water are changed to 0.34 kg, 0.40 kg, and 13 kg, respectively.

[0085] In step (C), the saturated water absorption rate of the TiO2-Al2O3 support containing ZnO was measured to be 0.62 mL / g. 95% of the saturated water absorption volume of the support was sprayed into a cobalt-molybdenum ammonia solution. The cobalt-molybdenum ammonia solution was prepared by the following method: 237.0 g of ammonium tetramolybdate and 108.9 g of cobalt nitrate were added to a 1000 mL volumetric flask, and ammonia water (concentration of 15 wt%) was added to a total volume of 900 mL. 6 g of ethylenediamine was added, and the mixture was shaken until a solution was formed. Ammonia water was added to a total solution volume of 1000 mL, and the mixture was shaken well and allowed to stand for 10 h to obtain the cobalt-molybdenum ammonia solution, which was prepared multiple times for use.

[0086] The selective reduction catalyst contains 1.5 wt% cobalt (CoO), 7.5 wt% molybdenum (MoO3), and 3 wt% zinc (ZnO). The catalyst has a saturated water absorption rate of 0.53 mL / g, and its specific surface area and pore volume, determined by low-temperature nitrogen adsorption, are 179 m² / g. 2 / g and 0.42mL / g indicate that the volume of macropores in the catalyst is above 0.11mL / g.

[0087] Evaluation Example 1

[0088] like Figure 2As shown, the sulfur recovery catalyst evaluation device used in this evaluation example 1 is an improved version of the sulfur recovery catalyst evaluation device used in evaluation example 1 of the prior application CN202512027394.0. It employs a tubular stainless steel reactor with two reaction sections, vertically installed in a two-stage electric heating furnace. The upper section (first stage) of the tubular stainless steel reactor is a low-temperature reaction section (a quartz sand preheating section is provided above the first stage catalyst bed), and the lower section (second stage) is a high-temperature reaction section (a gas mixing space is provided above the second stage catalyst bed). The two reaction sections are... The upper and lower brass heat-spreading sleeves are tightly nested (the upper and lower heat-spreading sleeves do not contact each other, and each heat-spreading sleeve is composed of two semi-cylindrical cylinders joined together). The upper and lower brass heat-spreading sleeves are also in close contact with the upper and lower electric heating sleeves of the two-stage electric heating furnace (the upper and lower electric heating sleeves do not contact each other, and each electric heating sleeve is also composed of two silicon carbide semi-cylindrical cylinders with internal and external insulated heating wires joined together). By controlling the temperature of the upper and lower electric heating sleeves of the two-stage electric heating furnace, the maximum temperature of the upper and lower catalyst beds in the tubular stainless steel reactor can be basically controlled to the required level. The specific structure of the tubular stainless steel reactor includes: a catalyst loading and unloading pipe at the upper end, two gas supply pipes on the middle side wall (which also serve as catalyst loading and unloading pipes), and a sulfur collection cylinder at the lower end (which condenses and collects elemental sulfur by cooling the outer wall). The thermocouple sheath (with its central axis coinciding with the reactor's central axis) extends downwards from the top of the tubular stainless steel reactor, through a quartz sand preheating section and a first-stage catalyst bed (i.e., a first-stage low-temperature reaction bed), to a second-stage catalyst bed (i.e., a second-stage high-temperature reaction bed). The thermocouple sheath contains multiple K-type armored thermocouples (the thermocouple measuring the highest temperature of the first-stage bed can move vertically within the height range of that bed, while the other thermocouples are fixed in the vertical position).

[0089] The first gas chromatograph has two channels for detecting sulfide content: one for macro and one for micro. The second gas chromatograph detects CO and CO2 content; COS or CO2 is introduced through the inlet pipe.

[0090] In the tubular stainless steel reactor, the first catalyst bed is filled with 40 mL of catalyst (bed height-to-diameter ratio of approximately 4), and the second catalyst bed is filled with 100 mL of a mixture of catalyst and quartz sand (volume dilution ratio of 1:1.5) (bed height-to-diameter ratio of approximately 10). That is, the total catalyst loading in both reaction sections is 80 mL (40 mL each). The size of both the pre-crushed and sieved catalyst and the quartz sand is 1.1-1.3 mm. In the preheating section above the first catalyst bed, the quartz sand loading is 170 mL.

[0091] After catalyst loading and pressure testing of the tubular stainless steel reactor, pre-sulfurization of the catalyst is carried out. The pre-sulfurization process is as follows: the two reaction sections are heated simultaneously, with gas introduced through the first section at a flow rate of 80 NL / h; after purging with nitrogen for 15 min at a bed temperature of 150℃, the gas composition is controlled to be H2S 2v%, H2 6v%, and N2 balance, with a heating rate of 10℃ / min, and the temperature is held at 250℃ for 2 h to complete the sulfurization operation; under the condition of gas flow rate of 30 NL / h and gas composition of H2S 0.5v% and N2 balance, the temperature of the catalyst bed is adjusted to 160-170℃ for the first section and 280-290℃ for the second section before activity evaluation tests are conducted.

[0092] The selective reduction catalyst prepared in Example 4 was evaluated for its activity under the following reaction conditions one through nine.

[0093] Reaction Condition 1: The first-stage inlet gas flow rate is 80 NL / h, and the composition of the first-stage inlet gas is 10 v% SO2, 10 v% H2, 5 v% elemental sulfur (S2), 40 v% water vapor, and the balance N2. The temperature at the bottom of the quartz sand preheating section is controlled at 230-242℃ by controlling the external heating temperature of the first stage at 240-250℃ and adjusting it appropriately within this range (the temperature measuring point is close to the outer wall of the brass heat spreader). The highest temperature of the first-stage bed is measured by the thermocouple that can move vertically within the height range of the bed. The second-stage inlet gas is 9 NL / h H2, 1 NL / h H2S, and CO. A mixed gas flow of 1 NL / h was used, with the temperature at the vertical center of the two-stage catalyst bed as the control temperature for the external heating of the two stages, which was set to 310℃; the steady-state evaluation time was 3-4 hours; among them, the elemental sulfur and water vapor in the first-stage inlet gas composition were generated and introduced in a gasifier with a gasification temperature of 300℃ by metering the sulfur-aqueous liquid in the storage bottle via a horizontal flow pump. The sulfur-aqueous liquid used contained 30.7 wt% elemental sulfur and 69.0 wt% water.

[0094] Reaction Condition Two: The first-stage inlet gas flow rate is 80 NL / h, and the composition of the first-stage inlet gas is 10v% SO2, 10v% H2, 0.03v% COS, 5v% elemental sulfur (S2), 40v% water vapor, and the balance N2. The bottom temperature of the quartz sand preheating section is controlled at 230-242℃ by controlling the external heating temperature of the first stage at 240-250℃ and adjusting it appropriately within this range (the temperature measuring point is close to the outer wall of the brass heat spreader). The highest temperature of the first-stage bed is measured by the thermocouple that can move vertically within the height range of the bed. The second-stage inlet gas is a mixed gas flow of 9 NL / h H2 and 1 NL / h H2S. The temperature at the vertical center of the second-stage catalyst bed is used as the control temperature for the external heating of the second stage and is set at 310℃. The steady-state evaluation time is 3-4 hours. Among them, the elemental sulfur and water vapor in the first-stage inlet gas composition are added according to the method of reaction condition one.

[0095] Reaction Condition 3: The first-stage inlet gas flow rate is 80 NL / h, and the composition of the first-stage inlet gas is 10v% SO2, 10v% H2, 0.03v% COS, 5v% elemental sulfur (S2), 40v% water vapor, and the balance N2. The bottom temperature of the quartz sand preheating section is controlled at 230-242℃ by controlling the external heating temperature of the first stage at 240-250℃ and adjusting it appropriately within this range (the temperature measuring point is close to the outer wall of the brass heat spreader). The highest temperature of the first-stage bed is measured by the thermocouple that can move vertically within the height range of the bed. The second-stage inlet gas is a mixed gas flow of 9 NL / h H2, 1 NL / h H2S, and 1 NL / h CO. The temperature at the vertical center of the second-stage catalyst bed is used as the control temperature for the external heating of the second stage and is set at 310℃. The steady-state evaluation time is 3-4 hours. Among them, the elemental sulfur and water vapor in the first-stage inlet gas composition are added according to the method of reaction condition 1.

[0096] Reaction Condition 4: The first-stage inlet gas flow rate is 80 NL / h, and the composition of the first-stage inlet gas is 10 v% SO2, 10 v% H2, 0.03 v% COS, 5 v% elemental sulfur (calculated as S2), 40 v% water vapor, and the balance N2. The temperature at the vertical center of the first-stage catalyst bed is used as the control temperature for the first-stage external heating and is set at 310℃. The second-stage inlet hydrogen flow rate is 10 NL / h, and the temperature at the vertical center of the second-stage catalyst bed is used as the control temperature for the second-stage external heating and is set at 250℃. The steady-state evaluation time is 3-4 hours. The elemental sulfur and water vapor in the first-stage inlet gas composition are prepared according to the method described in Reaction Condition 1.

[0097] Reaction condition 5: Based on condition 4, change the second-stage air intake to a mixed airflow of H2 9 NL / h and H2S 1 NL / h; other conditions remain unchanged.

[0098] Reaction condition six: Based on condition four, the intake gas composition is changed to contain 10v% SO2, 10v% H2, 2v% CO2, 5v% elemental sulfur (calculated as S2), 40v% water vapor and the balance N2; other conditions remain unchanged.

[0099] The sulfur-aqueous sol solution used is prepared by shear dispersion and ball milling of sulfur powder with a purity of 99.9 wt%, water, and additives in the required proportions, according to relevant existing technical methods. The additive content is 0.8 wt%, including sodium stearate as a dispersant and diethylhydroxylamine as an antioxidant. The sulfur-aqueous sol solution can be stably metered and transported by a horizontal flow pump. The viscosity is not high and the fluidity is good. After dilution with 50 times the volume of water, it becomes a transparent solution. When exposed to light, it exhibits the Tyndall effect in the visible light path, indicating that the elemental sulfur is dispersed in the form of nanoparticles. The sodium stearate, diethylhydroxylamine, and other components in the sulfur-aqueous sol solution will decompose significantly under the vaporization temperature of 300℃ and steam conditions. The sodium-containing components will remain in the vaporizer. No negative impact of the additive components in the sulfur-aqueous sol solution on the catalyst reaction performance in the reactor was found.

[0100] The results include: the selective reduction catalyst prepared in Example 4 showed that the elemental sulfur yield (based on the total amount of SO2 and H2S contained in the inlet gas) was in the range of 84.5-85.5% during the evaluation processes under reaction conditions one, two, and three (valid results were measured 1-2 times every 1 hour, and the highest temperature of the first bed layer did not exceed 310℃); the elemental sulfur yield was in the range of 86-86.5% during the evaluation processes under reaction conditions four, five, and six, and the elemental sulfur content in the reactor outlet gas stream was approximately 9.2v% (S2) and the COS content was less than 0.005v; the COS content in the reactor outlet gas stream was less than 0.0003v during the evaluation process under reaction condition six; the CO conversion rate was higher than 87% during the evaluation processes under reaction conditions one and three (valid results were measured 1-2 times every 1 hour, and CO2 was generated); the evaluation reaction effects were very stable. The slightly higher elemental sulfur yield during the evaluation of reaction conditions four and five indicates that using conditions above the dew point, appropriately low temperature, and appropriately low space velocity in the final reactor or catalyst bed helps to improve the elemental sulfur yield. The reasons should include: an appropriately low reaction temperature is conducive to the Claus reaction of SO2 and H2S to form elemental sulfur; the reaction volume is large and it is not advisable to use excessively high space velocity; and the amount of COS generated due to CO2 contained in the feed gas is very small.

[0101] Reaction Condition 7: The first stage inlet gas flow rate is 80 NL / h, with an inlet gas composition of 1v% SO2, 2v% H2S, 1.2v% H2, 0.005v% COS, 30v% water vapor, and the balance N2. No gas is introduced into the second stage. The temperature at the vertical midpoint of the catalyst beds in both stages is used as the control temperature for external heating of both stages and is set at 230℃. The steady-state evaluation time is 8-10 hours. The water vapor in the first stage inlet gas composition is introduced through deionized water in a storage bottle, with a vaporization temperature of 220℃.

[0102] Reaction condition eight: Based on condition seven, the temperature at the vertical center of the first and second stage catalyst beds is used as the control temperature for the external heating of the two stages and set to 210℃; other conditions remain unchanged.

[0103] The evaluation process of reaction conditions seven and eight examined the reaction performance of the selective reduction catalyst prepared in Example 4 in the tail gas treatment reactor of the present invention. The results included: after removing elemental sulfur and moisture from the outlet gas stream, the content of H2S was 0.35-0.5v%, SO2 ≤ 0.05v%, and COS ≤ 0.002v%. Therefore, the outlet gas stream of the tail gas treatment reactor is cooled to 140-150℃ by elemental sulfur condenser B and liquid sulfur is separated, and then cooled to 20-60℃ by low temperature cooler and condensate is separated. After treatment by oxidation adsorption desulfurization, the emission standards can be met. The catalyst prepared by the method of Example 4 is suitable for the tail gas treatment reactor.

[0104] Reaction condition nine: First-stage intake airflow rate 80 NL / h, first-stage intake air composition containing 10 vol% SO2 and H2 The catalyst bed contains 10% volatile sulfur (S2), 8% volatile sulfur (S2), 40% water vapor, and the remainder N2. The temperature at the bottom of the quartz sand preheating section is controlled to 230-242℃ by maintaining the external heating temperature at 240-250℃ and adjusting it appropriately within this range (the temperature measuring point is close to the outer wall of the brass heat-spreading sleeve). The highest temperature of the first-stage bed is measured by a thermocouple that can move vertically within the height range of the bed. Hydrogen is introduced in the second stage at a flow rate of 8 NL / h. The temperature at the vertical center of the second-stage catalyst bed is used as the control temperature for the external heating of the second stage and set at 310℃. The steady-state evaluation time is 3-4 hours. The elemental sulfur and water vapor in the first-stage inlet gas composition are generated and introduced in a gasifier at a gasification temperature of 300℃ using a sulfur-aqueous sol solution from a storage bottle, metered by a horizontal flow pump. The sulfur-aqueous sol solution used contains 41.6 wt% elemental sulfur and 58.2 wt% water.

[0105] The results include: the selective reduction catalyst prepared in Example 4, under the evaluation of reaction condition nine, had an elemental sulfur content of about 12v% in the reactor outlet gas stream; the highest temperature of the first bed layer did not exceed 310℃; the elemental sulfur yield was higher than 80% (valid results were measured 1-2 times every 1 hour); and the evaluation of the reaction effect was very stable.

Claims

1. A process for producing sulfur from sulfur dioxide, characterized in that... Through one or more reaction devices, at a temperature of 160-320℃, hydrogen introduced by a hydrogen gas flow selectively reduces SO2 introduced by a sulfur dioxide gas flow to elemental sulfur. Each reaction device is equipped with one or more selective reduction reactors connected in series. The first-stage selective reduction reactor is connected in sequence to a heater A and a gas flow mixer A. The final-stage selective reduction reactor is connected in sequence to an elemental sulfur condenser A and a water condenser. The gas flow outlet of the water condenser is connected to a pressurized blower. The liquid sulfur discharged from the elemental sulfur condenser A is buffered in a liquid sulfur pool or liquid sulfur tank. The condensate discharged from the water condenser is buffered in a condensate pool or tank; each selective reduction reactor is equipped with one or more catalyst beds, each filled with selective reduction catalyst; in the reaction of each reactor, the total volumetric flow rate of H2 is 1.9-2.2 times the total volumetric flow rate of SO2; the reaction exhaust gas is cooled stepwise by elemental sulfur condenser A and water condenser to separate liquid sulfur and condensate; more than 95% of the gas flow from the pressurized blower outlet is used as circulating gas to each reactor, and the remaining flow is treated as reaction tail gas and discharged after purification to meet standards; The selective reduction catalyst contains 1-2 wt% cobalt (based on CoO), 4-10 wt% molybdenum (based on MoO3), and 2-4 wt% zinc (based on ZnO), with TiO2-Al2O3 as the support; it is prepared through the following steps: (A) The dry powder of metatitanic acid was calcined at 550-570℃ for 3-5 hours to obtain TiO2 powder; the dry powder of boehmite was calcined at 750-800℃ for 3-5 hours to obtain Al2O3 powder; the obtained TiO2 powder and Al2O3 powder were mixed and ball-milled in a ball mill to obtain TiO2-Al2O3 mixed powder; (B) In a kneader, add metatitanic acid powder and pseudoboehmite powder, mix evenly to obtain powder; spray acetic acid aqueous solution into the powder through an atomizing nozzle, continue mixing after the acetic acid aqueous solution is added, stop mixing and cover and seal; then add zinc compound powder, TiO2-Al2O3 mixed powder from step (A) and organic pore-forming agent powder, mix evenly, spray water through an atomizing nozzle, knead until the material is uniform, then discharge, extrude, granulate, dry, and calcine under air conditions to obtain a TiO2-Al2O3 carrier containing ZnO; (C) In the spray drum, the TiO2-Al2O3 support containing ZnO obtained in step (B) is added, and the cobalt-molybdenum ammonia solution is sprayed into it through the atomizing nozzle. After the cobalt-molybdenum ammonia solution is sprayed, it is placed in a sealed place for homogenization treatment, the material is discharged, dried, and calcined to obtain a selective reduction catalyst for the production of sulfur from sulfur dioxide. In step (C), the cobalt-molybdenum ammonia solution is prepared from raw materials, including ammonium molybdate, cobalt nitrate, and ammonia.

2. The process for producing sulfur from sulfur dioxide according to claim 1, characterized in that... The selective reduction reactor is an internally cooled reactor.

3. The process for producing sulfur from sulfur dioxide according to claim 2, characterized in that... When the reaction apparatus is equipped with multiple selective reduction reactors connected in series and each selective reduction reactor is equipped with a catalyst bed, the internally cooled reactor is a self-limiting temperature reactor with a vertical water-cooled sleeve structure.

4. The process for producing sulfur from sulfur dioxide according to claim 1, characterized in that... In the inlet gas stream of each catalyst bed, the volume content of SO2 and H2 is controlled to be: 6v%≤( The content of elemental sulfur (S2) in the inlet gas stream of elemental sulfur condenser A is 10-15% vol, and the upper limit of water vapor content is 60% vol. The gas hourly space velocity in each catalyst bed is 500-5000 h⁻¹. -1 .

5. The process for producing sulfur from sulfur dioxide according to claim 1, characterized in that... When each reaction unit is equipped with a selective reduction reactor, multiple catalyst beds are arranged in series in the selective reduction reactor along the overall airflow direction. An airflow mixing structure composed of a mixing space and mixing components is set between the catalyst beds and airflow is added. The inlet gas flow conditions for the first catalyst bed include: a temperature of 160-220℃, a water vapor content of 15-40% v%, and an SO2 content of 5-12% v%. The gas flow mixing structure between catalyst beds mixes the exhaust gas flow from the previous catalyst bed with the replenishment gas flow to a temperature of 160-250℃ before entering the next catalyst bed. The replenishment gas flow is a mixture of at least two of the following: sulfur dioxide gas flow, hydrogen gas flow, or circulating gas flow.

6. The process for producing sulfur from sulfur dioxide according to claim 1, characterized in that... When multiple selective reduction reactors are connected in series in each reaction unit, a gas flow mixer B is installed in the connecting pipeline between the selective reduction reactors. The outlet gas flow of the previous selective reduction reactor is combined with the feed gas flow, and then mixed by the gas flow mixer B to reach a temperature of 180-250°C before entering the next selective reduction reactor. The feed gas flow is a mixture of at least two of the following: sulfur dioxide gas flow, hydrogen gas flow, or circulating gas flow.

7. The process for producing sulfur from sulfur dioxide according to claim 1, characterized in that... The sulfur dioxide gas stream is supplied by the Cansolv process or its modified process unit, with an SO2 content ≥99.5v on a dry basis; the hydrogen gas stream has an H2 content ≥98v and a CO content ≤0.5v; the outlet gas temperature of the elemental sulfur condenser A is 140-160℃, and the outlet gas temperatures of the sulfur dioxide gas stream and the water condenser are both controlled at 60-75℃.

8. The process for producing sulfur from sulfur dioxide according to claim 1, characterized in that... The volumetric content of SO2 and H2S in the outlet gas flow of the water condenser is controlled as follows: 1.5v%≤( The H2S content is ≤3v%; the tail gas flow first passes through heater B and tail gas treatment reactor, and the gas flow composition is controlled to be H2S content ≤0.5v% and SO2 content ≤0.15v%, with H2S content below 35%. The gas flow is cooled to 140-150℃ by elemental sulfur condenser B and liquid sulfur is separated. Then it is cooled to 20-60℃ by low temperature cooler and condensate is separated. After that, it is treated by oxidation adsorption desulfurization method. The tail gas treatment reactor is filled with the selective reduction catalyst, and the gas flow inlet temperature is 170-180℃. The liquid sulfur separated by elemental sulfur condenser B enters the liquid sulfur pool or liquid sulfur tank, and the condensate separated by low temperature cooler enters the condensate pool or condensate tank.

9. The process for producing sulfur from sulfur dioxide according to claim 1, characterized in that... A gas stream obtained by purifying the reaction tail gas stream and / or a supplementary dilution gas stream is introduced into the liquid sulfur pool or liquid sulfur tank to remove the hydrogen polysulfide and hydrogen sulfide contained in the buffer liquid sulfur into H2S, thereby purifying the liquid sulfur. The supplementary dilution gas stream is a nitrogen gas stream with an N2 content ≥99% v%. The resulting gas stream C containing H2S is used at the inlet of the gas stream mixer A. Sulfur foam on the surface of the water in the condensate pool or condensate tank is collected and sent to the sulfur melter to recover liquid sulfur at 150-160℃ and then fed into the liquid sulfur pool or liquid sulfur tank.

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