A method for desulfurization and decyanation of coke oven gas using uni- and binary synergistic catalysis

Abstract

This invention discloses a method for desulfurization and decyanation of coke oven gas using synergistic unary and binary catalytic desulfurization. The method includes the following steps: dividing the coke oven gas desulfurization system into one unary catalytic desulfurization unit and multiple binary catalytic desulfurization units, with each unit performing catalytic desulfurization in parallel and synergistically; the unary catalytic desulfurization unit processes 25-30% of the total gas volume, and the combined binary catalytic desulfurization units process 70-75% of the total gas volume. The unary catalytic desulfurization unit uses a phthalocyanine cobalt sulfonate compound desulfurizing agent as a single catalytic system; each binary catalytic desulfurization unit uses a complexed iron catalyst; the unary catalytic filtrate containing PDS catalyst produced by the unary catalytic desulfurization unit is sent to each binary catalytic desulfurization unit for secondary utilization; the coke oven gas after unary and binary synergistic catalytic desulfurization contains H2S < 50 mg / Nm³. 3 The desulfurization process of this invention requires a low alkalinity, which can effectively reduce alkali source consumption and side reactions, resulting in stable desulfurization performance, low waste liquid volume, and no clogging of the desulfurization tower packing.

Description

Technical Field

[0001] This invention relates to the field of coke oven gas purification technology, and in particular to a method for desulfurization and decyanation of coke oven gas using uni- and binary synergistic catalysis. Background Technology

[0002] Currently, the PDS wet desulfurization and decyanation process for coke oven gas remains the mainstream technology in China. Using sodium salts or ammonia as alkali sources, this process suffers from rapid side reactions. Sodium salts such as Na2SO4, Na2S2O3, and NaSCN, or ammonium salts such as (NH4)2SO4, (NH4)2S2O3, and NH4SCN, in the desulfurization liquid will rapidly increase. Once a certain concentration is reached, the catalyst activity will decrease, resulting in a significant decrease in desulfurization efficiency, high alkali consumption, and the generation of a large amount of desulfurization waste liquid, which will significantly increase the operating costs of desulfurization and salt extraction.

[0003] Some coal chemical enterprises use complexed iron catalysts (referred to as complexed iron) to catalytically remove H2S from coke oven gas, while simultaneously removing HCN from the coke oven gas. During the desulfurization process, H2S reacts with Na2CO3 in the desulfurization liquid to form NaHS, or reacts with hydrolyzed NH3 to form NH4HS, and then utilizes Fe... 3+ The oxidizing properties of the complexed iron catalyst oxidize NaHS or NH4HS into elemental sulfur. Due to the extremely fast reaction rate of the complexed iron catalyst, elemental sulfur sol rapidly precipitates within the desulfurization tower and easily adheres to the packing material, causing the tower resistance to exceed the standard within a short period. Therefore, periodic shutdowns are required to replace the packing material, making continuous desulfurization impossible. Furthermore, the complexed iron catalyst is highly corrosive, easily causing corrosion and leakage in the desulfurization equipment, affecting the safe and stable operation of the desulfurization system.

[0004] In summary, in the process of desulfurization and decyanation of coke oven gas, there is a contradiction between emission reduction and energy consumption reduction and maintaining the desulfurization and decyanation effect in the existing technology. Summary of the Invention

[0005] The technical problem that this invention aims to solve is how to reduce emissions and energy consumption while maintaining the desulfurization and decyanation effect during the desulfurization and decyanation process of coke oven gas.

[0006] To achieve the above objectives, embodiments of the present invention propose a method for desulfurization and decyanation of coke oven gas using uni- and binary synergistic catalysis, the method comprising the following steps:

[0007] Coke oven gas is fed into the desulfurization unit, 25-30% of the coke oven gas is fed into the single-stage catalytic desulfurization unit, and 70-75% of the coke oven gas is fed into each binary catalytic desulfurization unit.

[0008] PDS catalyst is added to the unary catalytic desulfurization circulating liquid to catalyze the removal of H2S and HCN from coal gas, while complexed iron catalyst is added to the binary catalytic desulfurization circulating liquid.

[0009] The PDS-containing catalytic filtrate produced by the catalytic desulfurization unit is sent to each binary catalytic desulfurization unit for secondary use, and PDS and complexed iron binary catalysts are formed in the binary catalytic desulfurization circulating liquid to catalytically remove H2S and HCN from the coal gas.

[0010] After treatment by both the single-stage and binary-stage catalytic desulfurization units, the H2S content of the coke oven gas was <50 mg / Nm³. 3 ;

[0011] The desulfurization waste liquid generated in the binary catalytic desulfurization unit is sent to the salt extraction system for evaporation, concentration and salt extraction.

[0012] Specifically, the desulfurization unit includes one unary catalytic desulfurization unit and multiple binary catalytic desulfurization units. The unary catalytic desulfurization unit and the binary catalytic desulfurization unit are used to process coke oven gas in parallel to remove H2S and HCN from the coke oven gas.

[0013] Specifically, an alkaline source is added to the PDS catalytic reaction in the unary catalytic desulfurization unit and to the complexed iron catalytic reaction in the binary catalytic desulfurization unit. The alkaline source is Na2CO3 or NH3.

[0014] Specifically, the by-salts generated in the unary catalytic desulfurization circulating liquid are Na2SO4, Na2S2O3, and NaSCN trisalts, or (NH4)2SO4, (NH4)2S2O3, and NH4SCN trisalts, and the total concentration of by-salts generated in the unary catalytic desulfurization circulating liquid is controlled to be 120–170 g / L.

[0015] Specifically, the by-salts generated in the binary catalytic desulfurization circulating liquid are Na2SO4, Na2S2O3, and NaSCN trisalts, or (NH4)2SO4, (NH4)2S2O3, and NH4SCN. The total concentration of by-salts generated in the binary catalytic desulfurization circulating liquid is controlled to be 250–300 g / L.

[0016] Specifically, in the unary catalytic desulfurization unit, the content of elemental suspended sulfur in the desulfurization circulating liquid entering the unary catalytic desulfurization tower is controlled to be <1g / L.

[0017] Specifically, in the binary catalytic desulfurization unit, the total content of elemental suspended sulfur and elemental sulfur sol in the desulfurization circulating liquid entering the binary catalytic desulfurization tower is controlled to be less than 1 g / L.

[0018] Specifically, the liquid-to-gas ratio of each desulfurization tower should be greater than 35.

[0019] Specifically, the desulfurization waste liquid discharged from the binary catalytic desulfurization unit is purified by ceramic filtration and activated carbon adsorption filtration in the filtration unit and then sent to the salt extraction system for evaporation, concentration and salt extraction.

[0020] Specifically, the waste gas condensate and steam condensate generated during the evaporation, concentration and salt extraction processes of desulfurization wastewater are recycled.

[0021] This invention also provides a device for desulfurization and decyanation of coke oven gas using synergistic unary and binary catalysis, comprising: multiple desulfurization units, including one unary catalytic desulfurization unit using a PDS catalyst and multiple binary catalytic desulfurization units using both PDS and complexed iron catalysts. The unary catalytic desulfurization unit includes a desulfurization tower, a reaction tank, a regeneration tower, etc., and the binary catalytic desulfurization units include multiple desulfurization towers, multiple reaction tanks, multiple regeneration towers, etc. Additionally, it is equipped with an auxiliary unary catalytic filter press, a binary catalytic filter press, and a desulfurization wastewater filtration unit comprising a ceramic filter and an activated carbon adsorption filter. Specifically, it includes: a single-stage catalytic desulfurization tower 1, a single-stage catalytic regeneration tower 2, a single-stage catalytic reaction tank 3, a single-stage catalytic desulfurization circulation pump 4, a single-stage catalytic sulfur foam tank 21, a single-stage catalytic filter press 22, a binary catalytic desulfurization tower 31, a binary catalytic regeneration tower 32, a binary catalytic reaction tank 33, a binary catalytic desulfurization circulation pump 34, a binary catalytic sulfur foam tank 41, and a binary catalytic filter press 42; the method of desulfurizing and decyanating coke oven gas by using equipment that employs single-stage and binary synergistic catalysis is realized.

[0022] The desulfurization process of this invention requires a low alkalinity, which can effectively reduce the consumption of alkali source and the occurrence of side reactions. It has good sulfur foam generation effect, strong oil resistance, stable desulfurization effect, low waste liquid generation, and does not clog the desulfurization tower packing. The residual PDS catalyst and alkali source in the excess filtrate discharged from the unary catalytic desulfurization unit are reused in the binary catalytic desulfurization unit. The tail gas condensate and steam condensate generated during the evaporation, concentration and salt extraction of desulfurization waste liquid are returned to each desulfurization unit as makeup water for recycling.

[0023] The present invention also has the following beneficial effects:

[0024] 1) Effectively reduces catalytic side reactions and wastewater generation; the amount of desulfurization wastewater generated, calculated based on a tri-salt concentration of 250 g / L, is <0.15 m³. 3 / 10,000 Nm 3 Compared to using PDS catalytic desulfurization technology alone, the desulfurization waste liquid from coke oven gas is reduced by more than 60%.

[0025] 2) Effectively control the reaction rate of complex iron catalytic desulfurization, avoid the generation of a large amount of elemental sulfur sol in the desulfurization tower and its adhesion to the packing, and eliminate the blockage of the desulfurization tower that is prone to occur when using complex iron desulfurization catalyst.

[0026] 3) It exhibits strong oil resistance, excellent sulfur foam generation in the regeneration tower, high desulfurization efficiency, and strong operational stability. It can remove over 99% of H2S and over 30% of organic sulfur from coke oven gas. Single-stage desulfurization can stably achieve an H2S content of <50 mg / Nm³ in the gas exiting the desulfurization tower. 3 ;

[0027] 4) The tail gas condensate and steam condensate generated during the evaporation, concentration and salt extraction of desulfurization wastewater are added to each desulfurization unit to realize the secondary use of salt extraction wastewater. Under normal operating conditions, each desulfurization unit no longer needs to add new water.

[0028] 5) The filtrate from the unary catalytic converter is discharged into the binary catalytic desulfurization unit to become the desulfurization circulating liquid of the binary catalytic desulfurization unit. This allows for the reuse of the residual PDS catalyst and alkali source in the unary catalytic converter filtrate. The system requires lower alkalinity and catalyst concentration. Compared with desulfurization and decyanation methods that use PDS catalyst alone or complexed iron catalyst alone, it can effectively reduce alkali source consumption by more than 40% and PDS catalyst and complexed iron catalyst consumption by more than 30%.

[0029] 6) The binary catalytic desulfurization unit introduces PDS catalyst for synergistic catalysis, requiring a lower concentration of complexed iron catalyst. At a low concentration of complexed iron catalyst, the corrosion rate of carbon steel towers and pipelines is <0.3mm / a. Compared with the method of desulfurization and decyanation using complexed iron catalyst alone, the corrosion rate of carbon steel equipment is reduced by 70%. Attached Figure Description

[0030] Figure 1 A flowchart of a coke oven gas desulfurization and decyanation method using uni- and binary synergistic catalysis is provided for embodiments of the present invention;

[0031] Figure 2 This is a flowchart illustrating a first embodiment of a coke oven gas desulfurization and decyanation method employing uni- and binary synergistic catalysis, as provided in this invention.

[0032] Explanation of icon numbers:

[0033] 1. Single-stage catalytic desulfurization tower; 2. Single-stage catalytic regeneration tower; 3. Single-stage catalytic reaction tank; 4. Single-stage catalytic desulfurization circulation pump; 21. Single-stage catalytic sulfur foam tank; 22. Single-stage catalytic filter press; 31. Binary catalytic desulfurization tower; 32. Binary catalytic regeneration tower; 33. Binary catalytic reaction tank; 34. Binary catalytic desulfurization circulation pump; 41. Binary catalytic sulfur foam tank; 42. Binary catalytic filter press; 51. Alkali addition tank; 52. PDS catalyst tank; 53. Complexed iron catalyst tank; 54. Alkali metering pump; 55. PDS metering pump; 56. Complexed iron metering pump; 61. Ceramic filter; 62. Activated carbon adsorption filter; 7. Sulfur melting unit; 8. Salt extraction system. Detailed Implementation

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] This invention provides a method for desulfurization and decyanation of coke oven gas using uni- and binary synergistic catalysis, such as... Figure 1 The method includes the following process cycle steps:

[0036] 25-30% of the total gas volume is fed into the single-stage catalytic desulfurization tower 1, and 70-75% of the total gas volume is fed into each of the two-stage catalytic desulfurization towers 31.

[0037] PDS catalyst is added to the unary catalytic desulfurization circulating liquid to catalyze the removal of H2S and HCN from coal gas, and complexed iron catalyst is added to each binary catalytic desulfurization circulating liquid.

[0038] The PDS-containing filtrate from the single-stage catalytic desulfurization unit is fed into each binary catalytic desulfurization unit for secondary utilization. In the binary catalytic desulfurization circulating liquid, PDS and complexed iron catalysts are formed to remove H2S and HCN from the coal gas. The H2S content in the coke oven gas after both the single-stage and binary catalytic desulfurization towers is <50 mg / Nm³. 3 The desulfurization waste liquid generated during the operation of each binary catalytic desulfurization unit is sent to the salt extraction system 8 for evaporation, concentration and salt extraction treatment.

[0039] The desulfurization unit is divided into one unary catalytic desulfurization unit using PDS catalyst and multiple binary catalytic desulfurization units using both PDS and complexed iron catalysts. Each desulfurization unit (including one unary catalytic desulfurization unit and multiple binary catalytic desulfurization units) processes coke oven gas in parallel to remove H2S and HCN from the coke oven gas.

[0040] The unary catalytic desulfurization unit is equipped with a phthalocyanine cobalt sulfonate compound (PDS) catalyst, forming a single catalytic system.

[0041] Complexed iron catalyst is added to each binary catalytic desulfurization unit. The filtrate containing PDS catalyst produced by the unary catalytic desulfurization unit is sent to each binary catalytic desulfurization unit for secondary utilization. In fact, a binary catalytic system of PDS and complexed iron is formed in each binary catalytic desulfurization unit.

[0042] The amount of coal gas processed by the single-stage catalytic desulfurization unit and each binary catalytic desulfurization unit is 25-30% and 75-70% of the total coal gas processed, respectively, so that the single-stage catalytic filtrate produced by the single-stage catalytic desulfurization unit can be fully reused by each binary catalytic desulfurization unit.

[0043] An alkaline source is added to the PDS-catalyzed neutralization reaction in the complexed iron-based catalytic reaction, wherein the alkaline source is Na2CO3 or NH3.

[0044] The byproduct salts generated in the unary catalytic desulfurization circulating liquid are either Na2SO4, Na2S2O3, and NaSCN trisalts, or (NH4)2SO4, (NH4)2S2O3, and NH4SCN trisalts, with the total concentration of byproduct salts controlled in the range of 120–170 g / L.

[0045] The byproduct salts generated in the binary catalytic desulfurization circulating liquid are Na2SO4, Na2S2O3, and NaSCN trisal salts, or (NH4)2SO4, (NH4)2S2O3, and NH4SCN. The total concentration of byproduct salts is controlled within the range of 250–300 g / L.

[0046] The content of elemental suspended sulfur in the desulfurization circulating liquid entering the unary catalytic desulfurization tower is controlled to be <1g / L.

[0047] The total content of elemental suspended sulfur and elemental sulfur sol in the desulfurization circulating liquid entering the binary catalytic desulfurization tower is controlled to be less than 1 g / L.

[0048] Control the liquid-to-gas ratio of each desulfurization tower (desulfurization liquid circulation spray rate L / h to coal gas rate Nm³). 3 The value of / h) is greater than 35.

[0049] The desulfurization waste liquid discharged from the binary catalytic desulfurization unit is purified by ceramic filtration and activated carbon adsorption in the filtration unit and then sent to the salt extraction system for evaporation, concentration and salt extraction.

[0050] The tail gas condensate and steam condensate generated during the evaporation, concentration and salt extraction of desulfurization waste liquid are recycled and utilized.

[0051] Specific process methods include:

[0052] Step 1 (Addition of alkali source and catalyst):

[0053] An alkaline source, namely Na2CO3 or NH3, is added to both the unary catalytic desulfurization circulating liquid and the binary catalytic desulfurization circulating liquid.

[0054] Na2CO3 is added to the alkali addition tank 51, and PDS desulfurization rich liquid from the unary catalytic desulfurization circulation pump 4 is added for dissolution, or tail gas condensate and steam condensate generated from the salt extraction process of desulfurization waste liquid evaporation and concentration are added for dissolution. After dissolution, the alkali metering pump 54 delivers it to the unary catalytic reaction tank 3 and each binary catalytic reaction tank 33, respectively, to replenish the unary catalytic desulfurization unit and the binary catalytic desulfurization unit.

[0055] The PDS catalyst is added into the PDS catalyst tank 52 and a small amount of PDS desulfurization rich liquid from the single-stage catalytic desulfurization circulation pump is added to dissolve it. Then, the PDS metering pump 55 delivers it to the single-stage catalytic reaction tank to replenish the single-stage catalytic desulfurization unit. The single-stage catalytic desulfurization unit includes: a single-stage catalytic desulfurization tower, a single-stage catalytic regeneration tower 2, a single-stage catalytic reaction tank, and a single-stage catalytic desulfurization circulation pump.

[0056] The complexed iron catalyst (liquid and solid) is added to the complexed iron catalyst tank 53, and a small amount of tail gas condensate and steam condensate generated during the salt extraction process of the desulfurization waste liquid evaporation and concentration are added to dissolve it. Then, the complexed iron metering pump 56 delivers it to each binary catalytic reaction tank to replenish the binary catalytic desulfurization unit. The binary catalytic desulfurization unit includes: a binary catalytic desulfurization tower, a binary catalytic regeneration tower 32, a binary catalytic reaction tank, and a binary catalytic desulfurization circulation pump 34.

[0057] Step Two (Unary Catalytic Desulfurization and Regeneration):

[0058] 25-30% of the total coke oven gas enters the single-stage catalytic desulfurization tower 1 (single-stage catalytic desulfurization tower) from the bottom. The PDS desulfurization lean liquor, containing Na2CO3 and PDS catalyst, flows by gravity from the top of the single-stage catalytic regeneration tower into the top of the single-stage catalytic desulfurization tower. After being sprayed by nozzles, it comes into counter-current contact with the coke oven gas from top to bottom. Under the alkaline conditions produced by the hydrolysis of Na2CO3, the H2S in the coke oven gas is absorbed into the PDS desulfurization lean liquor through the gas-liquid concentration difference, forming H2S. - More than 99% of the H2S in the coke oven gas is removed, and the H2S content in the coke oven gas after H2S removal is <50 mg / Nm³. 3 The unary catalytic desulfurization tower flows out from the top of the tower to the next process or user;

[0059] The content of elemental suspended sulfur in the desulfurization circulating liquid entering the unary catalytic desulfurization tower is controlled to be <1g / L;

[0060] Controlling the liquid-to-gas ratio in the uni-stage catalytic desulfurization tower (desulfurization liquid circulation spray rate L / h versus coal gas rate Nm³) 3 The value of / h) is greater than 35;

[0061] In the unary catalytic reaction, the by-salts produced are Na2SO4, Na2S2O3, and NaSCN trisalts, or (NH4)2SO4, (NH4)2S2O3, and NH4SCN trisalts. The concentration of the trisalts in the unary catalytic desulfurization circulating liquid is controlled to be 120–170 g / L.

[0062] After absorbing H2S from the coke oven gas in the single-stage catalytic desulfurization tower, the PDS desulfurization lean liquid becomes PDS desulfurization rich liquid, and flows by gravity from the bottom of the single-stage catalytic desulfurization tower into the single-stage catalytic reaction tank 3 (single-stage catalytic reaction tank). In the single-stage catalytic reaction tank, the PDS in the PDS desulfurization rich liquid will convert H2S into H2S. -- Adsorbed onto the surface of highly reactive ions, the previously adsorbed activated oxygen is used to convert HS... - Oxidation produces sulfur and polysulfides, along with thiosulfates and disulfides. This is then extracted by the unary catalytic desulfurization circulation pump 4 and fed from the bottom of the tower into the unary catalytic regeneration tower 2. Inside the unary catalytic regeneration tower, the PDS catalyst, whose activated oxygen has been consumed, is regenerated by adsorbing oxygen from the air blown in from the bottom of the tower. After regeneration, it becomes PDS desulfurization lean solution and flows by gravity from the top of the unary catalytic regeneration tower into the unary catalytic desulfurization tower for recycling.

[0063] Step 3 (Unary catalytic sulfur foam pressure filtration and filtrate treatment):

[0064] In the PDS desulfurization rich solution, elemental suspended sulfur precipitates in the unary catalytic regeneration tower 2 (unary catalytic regeneration tower) and forms sulfur foam on the surface of the desulfurization liquid at the top of the unary catalytic regeneration tower through air flotation. The sulfur foam overflows from the top of the unary catalytic regeneration tower to the unary catalytic sulfur foam tank 21 and is then pumped into the unary catalytic filter press 22 for pressure filtration. After pressure filtration, sulfur paste and unary catalytic filtrate are obtained. The sulfur paste is transferred by vehicle to the sulfur melting unit 7 for sulfur melting, and the unary catalytic filtrate is returned to the unary catalytic reaction tank. The concentration of the three salts in the unary catalytic desulfurization circulating liquid is controlled within the range of 120-170 g / L. If the concentration is too high or exceeds the standard, part or all of the unary catalytic filtrate is discharged into each binary catalytic reaction tank.

[0065] When the liquid level in the uni-catalytic reaction tank is lower than the control height, replenish the tail gas condensate and steam condensate generated during the evaporation and concentration process of the desulfurization waste liquid returned from the salt extraction system.

[0066] Step Four (Establishment, Desulfurization, and Regeneration of the Binary Co-catalytic System):

[0067] 70-75% of the total coke oven gas to be desulfurized and decyanated enters each binary catalytic desulfurization tower 31 (binary catalytic desulfurization tower) from the bottom of the tower. Each binary catalytic reaction tank 33 receives the unary catalytic filtrate (i.e., the excess unary catalytic filtrate that the unary catalytic reaction tank cannot collect). Since the unary catalytic filtrate contains approximately 120-170 g / L of Na2SO4, Na2S2O3, and NaSCN trisales, the residual PDS catalyst and OH- in the filtrate are also present. - The existing alkaline source is reused in each binary catalytic desulfurization unit, thus forming a PDS and complexed iron binary catalytic system in the desulfurization liquid of each binary catalytic desulfurization unit.

[0068] Lean liquor containing Na2CO3, complexed iron catalyst, and PDS catalyst enters each binary catalytic desulfurization tower from the top. After being sprayed by nozzles, it comes into counter-current contact with the coke oven gas from top to bottom. Under the alkaline conditions produced by the hydrolysis of Na2CO3, H2S in the coke oven gas is absorbed into the desulfurization liquor through the gas-liquid concentration difference and forms H2S. - More than 99% of the H2S in the coke oven gas is removed, and the H2S content in the coke oven gas after H2S removal is <50 mg / Nm³. 3 Each binary catalytic desulfurization tower flows out from the top of the tower to the next process or user;

[0069] Inside the binary catalytic desulfurization tower 31 (binary catalytic desulfurization tower), some HS in the desulfurization liquid... - Fe from complexed iron catalyst 3+ The action directly oxidizes it into elemental sulfur sol, Fe 3+ Reduced to Fe 2+ The complexed iron catalyst is deactivated;

[0070] After absorbing H2S from the coke oven gas in the binary catalytic desulfurization tower 31 (binary catalytic desulfurization tower), the lean liquid of the binary catalytic desulfurization becomes the rich liquid of the binary catalytic desulfurization. It then flows from the bottom of the binary catalytic desulfurization tower into the binary catalytic reaction tank 33 for further reaction. After that, it is extracted by the binary catalytic desulfurization circulation pump 34 and sent from the bottom of the tower into the binary catalytic regeneration tower 32 (binary catalytic regeneration tower).

[0071] In the rich solution of binary catalytic desulfurization liquid, in addition to containing Fe ionized from complexed iron, 3+ In addition, it also contains PDS, and some HS in the binary catalytic reactor. - ByFe 3+ Oxidation into elemental sulfur sol, Fe 3+ Reduced to Fe 2+ The complexed iron catalyst is deactivated; on the other hand, PDS will partially deactivate the HS. -- Adsorbed onto the surface of highly reactive ions, the previously adsorbed activated oxygen is used to convert HS... -Oxidation produces sulfur and polysulfides, along with thiosulfates and disulfides;

[0072] Inside the binary catalytic regeneration tower 32 (binary catalytic regeneration tower), the Fe in the binary catalytic desulfurization rich solution... 2+ Inside the tower, it is oxidized by oxygen in the air blown in from the bottom of the tower into Fe. 3+ The deactivated complexed iron catalyst is regenerated; at the same time, the PDS catalyst, whose activated oxygen has been consumed, is regenerated by re-adsorbing oxygen from the air blown in from the bottom of the column.

[0073] When the deactivated complexed iron catalyst and PDS catalyst in the rich solution of binary catalytic desulfurization are simultaneously regenerated in the binary catalytic regeneration tower, they become the lean solution of binary catalytic desulfurization and flow from the top of the binary catalytic regeneration tower into the binary catalytic desulfurization tower for recycling.

[0074] The total content of elemental suspended sulfur and elemental sulfur sol in the desulfurization circulating liquid entering each binary catalytic desulfurization tower is controlled to be <1g / L.

[0075] Control the liquid-to-gas ratio of each binary catalytic desulfurization tower (desulfurization liquid circulation spray rate L / h to coal gas rate Nm³). 3 The value of / h) is greater than 35.

[0076] In binary catalytic reactions, the by-salts produced are either Na2SO4, Na2S2O3, and NaSCN trisalts, or (NH4)2SO4, (NH4)2S2O3, and NH4SCN trisalts.

[0077] Step 5 (Binary Catalytic Sulfur Foam Filtration and Filtrate Treatment):

[0078] As the rich liquid from the binary catalytic desulfurization enters each binary catalytic regeneration tower 32 (binary catalytic regeneration tower), the elemental sulfur sol and elemental suspended sulfur gradually accumulate under the flotation of air, forming sulfur foam on the surface of the desulfurization liquid at the top of each binary catalytic regeneration tower. The sulfur foam overflows into the binary catalytic sulfur foam tank 41, and is then pumped into the binary catalytic filter press 42 for filter pressing. The sulfur paste obtained after filter pressing is transported by vehicle to the sulfur melting unit for sulfur melting. The binary catalytic filtrate obtained after filter pressing is returned to the binary catalytic reaction tank. The concentration of the three salts in the binary catalytic desulfurization circulating liquid is controlled within the range of 250-300 g / L. If the concentration is too high or exceeds the standard, part or all of the binary catalytic filtrate is treated as desulfurization waste liquid and filtered sequentially through the ceramic filter 61 and activated carbon adsorption filter 62 in the waste liquid filtration unit before being sent to the salt extraction system 8 for evaporation, concentration, and salt extraction.

[0079] When the liquid level in the binary catalytic converter is below the control height, replenish the condensate from the tail gas generated during the evaporation and concentration process of the desulfurization waste liquid returned from the salt extraction system, as well as the steam condensate.

[0080] Step Six (Waste Liquid Salt Extraction and Water Balance):

[0081] After undergoing processes such as evaporation, concentration, decolorization, crystallization, centrifugation, and drying in the desulfurization wastewater extraction system, solid sulfate, solid or solution thiocyanate products are obtained.

[0082] The tail gas condensate and steam condensate generated during the evaporation and concentration of desulfurization waste liquid are recycled and reused to maintain the water balance of each desulfurization unit.

[0083] This invention also provides a device for desulfurization and decyanation of coke oven gas using synergistic unary and binary catalysis, comprising: multiple desulfurization units, including one unary catalytic desulfurization unit using a PDS catalyst and multiple binary catalytic desulfurization units using both PDS and complexed iron catalysts. The unary catalytic desulfurization unit includes a desulfurization tower, a reaction tank, a regeneration tower, etc., and the binary catalytic desulfurization units include multiple desulfurization towers, multiple reaction tanks, multiple regeneration towers, etc. Additionally, it is equipped with an auxiliary unary catalytic filter press, a binary catalytic filter press, and a desulfurization wastewater filtration unit comprising a ceramic filter 61 and an activated carbon adsorption filter 62. Specifically, it includes: a single-stage catalytic desulfurization tower 1, a single-stage catalytic regeneration tower 2, a single-stage catalytic reaction tank 3, a single-stage catalytic desulfurization circulation pump 4, a single-stage catalytic sulfur foam tank 21, a single-stage catalytic filter press 22, a binary catalytic desulfurization tower 31, a binary catalytic regeneration tower 32, a binary catalytic reaction tank 33, a binary catalytic desulfurization circulation pump 34, a binary catalytic sulfur foam tank 41, and a binary catalytic filter press 42;

[0084] The method of desulfurizing and decyanating coke oven gas by using equipment that employs synergistic catalysis of unary and binary components is realized.

[0085] The co-catalytic desulfurization and decyanation method for coke oven gas of the present invention has the following beneficial effects:

[0086] 1) Effectively reduces catalytic side reactions and wastewater generation; the amount of desulfurization wastewater generated, calculated based on a tri-salt concentration of 250 g / L, is <0.15 m³. 3 / 10,000 Nm 3 Compared to using PDS catalytic desulfurization technology alone, the desulfurization waste liquid from coke oven gas is reduced by more than 60%.

[0087] 2) Effectively control the reaction rate of complex iron catalytic desulfurization, avoid the generation of a large amount of elemental sulfur sol in the desulfurization tower and its adhesion to the packing, and eliminate the blockage of the desulfurization tower that is prone to occur when using complex iron desulfurization catalyst.

[0088] 3) It exhibits strong oil resistance, excellent sulfur foam generation in the regeneration tower, high desulfurization efficiency, and strong operational stability. It can remove over 30% of organic sulfur and over 99% of H2S from coke oven gas. Primary desulfurization can stably achieve an H2S content of <50 mg / Nm³ in the gas exiting the desulfurization tower. 3;

[0089] 4) The tail gas condensate and steam condensate generated during the evaporation, concentration and salt extraction of desulfurization wastewater are added to each desulfurization unit to realize the secondary use of salt extraction wastewater. Under normal operating conditions, each desulfurization unit no longer needs to add new water.

[0090] 5) The excess filtrate from the unary catalytic desulfurization unit is discharged into the binary catalytic desulfurization unit to become the circulating liquid of the binary catalytic desulfurization unit. This allows for the reuse of residual PDS catalyst and alkali source in the unary catalytic desulfurization filtrate. The alkalinity and catalyst concentration required by the entire desulfurization system are relatively low. Compared with desulfurization and decyanation methods that use PDS catalyst or complexed iron catalyst alone, this method can effectively reduce alkali source consumption by more than 40% and PDS catalyst and complexed iron catalyst consumption by more than 30%.

[0091] 6) The binary catalytic desulfurization unit introduces PDS catalyst for synergistic catalysis, requiring a lower concentration of complexed iron catalyst. At a low concentration of complexed iron catalyst, the corrosion rate of carbon steel towers and pipelines is <0.3mm / a. Compared with the method of desulfurization and decyanation using complexed iron catalyst alone, the corrosion rate of carbon steel equipment is reduced by 70%.

[0092] The desulfurization process of this invention requires a low alkalinity, which can effectively reduce the consumption of alkali source and the occurrence of side reactions. It has good sulfur foam generation effect, strong oil resistance, stable desulfurization effect, low waste liquid production, and does not clog the desulfurization tower packing. The residual PDS catalyst and alkali source in the uni-catalytic filtrate are reused in the binary catalytic desulfurization unit. The tail gas condensate and steam condensate generated during the evaporation, concentration and salt extraction of desulfurization waste liquid are returned to each desulfurization unit as makeup water for recycling.

[0093] The following embodiments are only for further illustration of the present invention and do not limit the scope of the present invention.

[0094] Example 1:

[0095] This embodiment provides a method for desulfurization and decyanation of coke oven gas using uni- and binary synergistic catalysis, such as... Figure 2 The system includes multiple desulfurization units, consisting of one primary catalytic desulfurization unit using PDS catalyst and multiple secondary catalytic desulfurization units using both PDS and complexed iron catalysts. The primary catalytic desulfurization unit includes one desulfurization tower, one reaction tank, and one regeneration tower, while the secondary catalytic desulfurization units include multiple desulfurization towers, multiple reaction tanks, and multiple regeneration towers. It also includes auxiliary primary and secondary catalytic filter presses, as well as a desulfurization wastewater filtration unit comprising ceramic filters and activated carbon adsorption filters.

[0096] Alkali sources, namely Na2CO3 or NH3, are added to the reaction tanks of both the unary catalytic desulfurization unit and the binary catalytic desulfurization unit. PDS catalyst and complexed iron catalyst are also added, respectively. The dosage of catalyst and alkali source is adjusted based on data such as catalyst concentration, alkalinity, redox potential, and online H2S content in the gas after desulfurization, guided by monitoring data from the desulfurization circulating liquid. The goal is to control the H2S content in the desulfurized gas to be <50 mg / Nm³. 3 .

[0097] During operation, the concentrations of Na₂SO₄, Na₂S₂O₃, and NaSCN trisal salts or (NH₄)₂SO₄, (NH₄)₂S₂O₃, and NH₄SCN trisal salts in the desulfurization circulating liquid of the unary catalytic desulfurization unit are controlled within the range of 120–170 g / L. At this concentration, the PDS catalytic desulfurization efficiency is optimal. If the trisal salt concentration is too high or exceeds the standard, part or all of the unary catalytic filtrate is discharged into each binary catalytic reactor to replenish each binary catalytic desulfurization unit. In each binary catalytic desulfurization unit, the residual PDS catalyst and alkali source in the unary catalytic filtrate are reused, and complexed iron catalyst and insufficient alkali source are added. In this way, a PDS and complexed iron binary catalytic system is formed in the binary catalytic desulfurization circulating liquid. Utilizing the synergistic catalytic effect of the two types of catalysts, the H₂S content in the coal gas after binary catalytic desulfurization is achieved to be <50 mg / Nm³. 3 .

[0098] The method for discharging the filtrate from the single-stage catalytic converter into the two-stage catalytic desulfurization unit is as follows: the mixture of sulfur foam and desulfurization liquid generated by the single-stage catalytic regeneration tower is sent to the single-stage catalytic filter press for filtration. The resulting filtrate is returned to the single-stage catalytic reaction tank. Excess filtrate that cannot be received by the single-stage catalytic reaction tank is sent to each of the two-stage catalytic reaction tanks. When the single-stage catalytic filter press is under maintenance, PDS desulfurization rich liquid can be continuously sent to each of the two-stage catalytic reaction tanks through the outlet of the single-stage catalytic desulfurization circulation pump.

[0099] The concentration of the three salts in the binary catalytic desulfurization circulating liquid is controlled within the range of 250-300 g / L. If the concentration is too high or exceeds the standard, part or all of the binary catalytic filtrate will be sent to the salt extraction system as desulfurization waste liquid for evaporation, concentration and salt extraction treatment. This concentration of three salts takes into account the desulfurization efficiency of the binary catalytic desulfurization unit and the economy of catalyst and alkali source consumption, as well as the economy of desulfurization waste liquid salt extraction treatment.

[0100] The implementation method of the binary catalytic desulfurization circulating liquid salt extraction system is as follows: the sulfur foam and desulfurization liquid mixture generated by the binary catalytic regeneration tower are sent to the binary catalytic filter press for filter pressing. The binary catalytic filtrate obtained by filter pressing is returned to the binary catalytic reaction tank. The excess binary catalytic filtrate that cannot be received by the binary catalytic reaction tank is sent to the salt extraction system 8 for treatment after being purified by ceramic filtration and activated carbon adsorption and filtration in the waste liquid filtration unit.

[0101] The H2S content of the coal gas treated by both the single-stage catalytic desulfurization unit and the binary catalytic desulfurization unit is <50 mg / Nm³. 3 And then directly delivered to the subsequent processes or the user.

[0102] The ratio of the amount of coal gas processed by the primary catalytic desulfurization unit to that processed by the secondary catalytic desulfurization unit is 1:3 to 1:4, so as to maintain a basic balance between the excess primary catalytic filtrate generated by the primary catalytic desulfurization unit and the desulfurization liquid required to be replenished by the secondary catalytic desulfurization unit. The primary catalytic desulfurization unit does not directly generate desulfurization waste liquid. The amount of desulfurization waste liquid generated by primary and secondary catalytic desulfurization and decyanation is about 40% of the amount of waste liquid generated by all PDS catalytic desulfurization and decyanation.

[0103] Example 2:

[0104] This invention provides a method for desulfurization and decyanation of coke oven gas using uni- and binary synergistic catalysis, comprising a desulfurization system consisting of 7 process units and a salt extraction system:

[0105] 1) A single-stage catalytic desulfurization unit, including: a single-stage catalytic desulfurization tower, a single-stage catalytic regeneration tower, a single-stage catalytic reaction tank, and a single-stage catalytic desulfurization circulation pump;

[0106] 2) A single-stage catalytic sulfur foam filter press unit, including: a single-stage catalytic sulfur foam tank and a single-stage catalytic filter press;

[0107] 3) Binary catalytic desulfurization unit, including: multiple binary catalytic desulfurization towers, multiple binary catalytic regeneration towers, multiple binary catalytic reaction tanks, and multiple binary catalytic desulfurization circulation pumps;

[0108] 4) Binary catalytic sulfur foam filter press unit, including: binary catalytic sulfur foam tank and binary catalytic filter press;

[0109] 5) Alkali and catalyst dosing unit, including: alkali addition tank, PDS catalyst tank, complexed iron catalyst tank, alkali metering pump, PDS metering pump, and complexed iron metering pump;

[0110] 6) Waste liquid filtration unit, including: ceramic filter and activated carbon adsorption filter;

[0111] 7) Sulfur melting unit;

[0112] 8) Salt extraction system.

[0113] The following section provides a more detailed description of a coke oven gas desulfurization and decyanation method employing uni- and binary synergistic catalysis:

[0114] 1) Removing sulfur and cyanide from coke oven gas using Na2CO3 as an alkali source

[0115] The ammonia in the coke oven gas before entering the desulfurization system has been reduced to <0.05 g / Nm³. 3When Na2CO3 is added as an alkali source to the desulfurization system, the desulfurization and decyanation are achieved as follows:

[0116] (1) Uni-catalytic H2S removal (PDS catalytic H2S removal)

[0117] 25-30% of the total coke oven gas to be desulfurized and decyanated enters the single-stage catalytic desulfurization tower from the bottom. The PDS desulfurization lean liquor, containing Na2CO3 and PDS catalyst, flows by gravity from the top of the single-stage catalytic regeneration tower to the top of the single-stage catalytic desulfurization tower. After being sprayed by nozzles, it comes into counter-current contact with the coke oven gas from top to bottom. Under the alkaline conditions produced by the hydrolysis of Na2CO3, the H2S in the coke oven gas is absorbed into the PDS desulfurization lean liquor through the gas-liquid concentration difference, forming H2S. - More than 99% of the H2S in the coke oven gas is removed. The H2S content of the coke oven gas after H2S removal is <50 mg / Nm³. 3 It flows out from the top of the unary catalytic desulfurization tower to the next process or user.

[0118] (2) Regeneration of unary catalytic desulfurization liquid (PDS catalytic desulfurization liquid regeneration)

[0119] After absorbing H2S from coke oven gas in the single-stage catalytic desulfurization tower, the PDS desulfurization lean liquor becomes PDS desulfurization rich liquor, and flows by gravity from the bottom of the single-stage catalytic desulfurization tower into the single-stage catalytic reaction tank. In the single-stage catalytic reaction tank, the PDS in the PDS desulfurization rich liquor will convert H2S into H2S. -- Adsorbed onto the surface of highly reactive ions, the previously adsorbed activated oxygen is used to convert HS... - Oxidation produces sulfur and polysulfides, along with thiosulfates and disulfides. This is then extracted by a single-stage catalytic desulfurization circulation pump and fed from the bottom of the tower into a single-stage catalytic regeneration tower. Inside the single-stage catalytic regeneration tower, the PDS catalyst, whose activated oxygen has been consumed, is regenerated by adsorbing oxygen from the air blown in from the bottom of the tower. After regeneration, it becomes a PDS desulfurization lean solution and flows by gravity from the top of the single-stage catalytic regeneration tower into the single-stage catalytic desulfurization tower for recycling.

[0120] (3) Binary catalytic H2S removal (PDS-complexed iron catalytic H2S removal)

[0121] 70-75% of the total coke oven gas to be desulfurized and decyanated enters each binary catalytic desulfurization tower from the bottom. The lean desulfurization solution containing Na2CO3, complexed iron catalyst, and PDS catalyst enters each binary catalytic desulfurization tower from the top. After being sprayed through nozzles, it comes into counter-current contact with the coke oven gas from top to bottom. Under the alkaline conditions produced by the hydrolysis of Na2CO3, the H2S in the coke oven gas is absorbed into the desulfurization solution through the gas-liquid concentration difference, forming H2S. - More than 99% of the H2S in the coke oven gas is removed, and the H2S content in the coke oven gas after H2S removal is <50 mg / Nm³. 3The sulfur dioxide flows out from the top of each binary catalytic desulfurization tower to the next process or user.

[0122] In each binary catalytic desulfurization tower, some HS in the desulfurization liquid - Fe from complexed iron catalyst 3+ The action directly oxidizes it into elemental sulfur sol, Fe 3+ Reduced to Fe 2+ The complexed iron catalyst is deactivated.

[0123] (4) Regeneration of binary catalytic desulfurization liquid (PDS-complexed iron catalytic desulfurization liquid regeneration)

[0124] After absorbing H2S from the coke oven gas in each binary catalytic desulfurization tower, the lean liquid of the binary catalytic desulfurization becomes rich liquid of the binary catalytic desulfurization. It flows from the bottom of each binary catalytic desulfurization tower into each binary catalytic reaction tank, and is then extracted by each binary catalytic desulfurization circulation pump and sent from the bottom of the tower to each binary catalytic regeneration tower.

[0125] In the rich solution of binary catalytic desulfurization liquid, in addition to containing Fe ionized from complexed iron, 3+ In addition, it also contains PDS, and some HS in the binary catalytic reactor. - ByFe 3+ Oxidation into elemental sulfur sol, Fe 3+ Reduced to Fe 2+ The complexed iron catalyst is deactivated; on the other hand, PDS will partially deactivate the HS. -- Adsorbed onto the surface of highly reactive ions, the previously adsorbed activated oxygen is used to convert HS... - Oxidation produces sulfur and polysulfides, along with thiosulfates and disulfides;

[0126] In the binary catalytic regeneration tower, Fe in the binary catalytic desulfurization rich solution 2+ Inside the tower, it is oxidized by oxygen in the air blown in from the bottom of the tower into Fe. 3+ The deactivated complexed iron catalyst is regenerated; at the same time, the PDS catalyst, whose activated oxygen has been consumed, is regenerated by re-adsorbing oxygen from the air blown in from the bottom of the column.

[0127] When the deactivated complexed iron catalyst and PDS catalyst in the rich solution of binary catalytic desulfurization are simultaneously regenerated in the binary catalytic regeneration tower, they become the lean solution of binary catalytic desulfurization and flow from the top of the binary catalytic regeneration tower into the binary catalytic desulfurization tower for recycling.

[0128] (5) Sulfur foam filtration, sulfur melting and filtrate treatment

[0129] In the PDS desulfurization rich solution, elemental suspended sulfur precipitates in the primary catalytic regeneration tower and undergoes air flotation. Sulfur foam forms on the surface of the desulfurization liquid at the top of the primary catalytic regeneration tower. The sulfur foam overflows from the top of the primary catalytic regeneration tower to the primary catalytic sulfur foam tank, and is then pumped into a primary catalytic filter press for filtration to obtain sulfur paste and primary catalytic filtrate. The sulfur paste is transferred by vehicle to sulfur melting unit 7 for sulfur melting; the primary catalytic filtrate is returned to the primary catalytic reaction tank. The total concentration of by-product salts Na2SO4, Na2S2O3, and NaSCN in the primary catalytic desulfurization circulating liquid is controlled to be approximately 120–170 g / L. If the concentration is too high or exceeds the standard, part or all of the primary catalytic filtrate is sent to each binary catalytic reaction tank. The residual PDS catalyst and OH- - The alkaline source in the form of waste is reused in the binary catalytic desulfurization unit. Therefore, a binary catalytic system of PDS and complexed iron is formed in the binary catalytic desulfurization circulating liquid.

[0130] As the rich liquid from the binary catalytic desulfurization enters the binary catalytic regeneration tower, the elemental sulfur sol and elemental suspended sulfur gradually accumulate under the flotation of air, forming sulfur foam on the surface of the desulfurization liquid at the top of the binary catalytic regeneration tower. The sulfur foam overflows into the binary catalytic sulfur foam tank and is then pumped into the binary catalytic filter press for filtration to obtain sulfur paste and binary catalytic filtrate. The sulfur paste is transported by vehicle to the sulfur melting unit for sulfur melting, and the binary catalytic filtrate is returned to each binary catalytic reaction tank. The total concentration of by-product salts Na2SO4, Na2S2O3, and NaSCN in the binary catalytic desulfurization circulating liquid is controlled to be approximately 250-300 g / L. If the concentration is too high or exceeds the standard, part or all of the binary catalytic filtrate is filtered sequentially through the ceramic filter and activated carbon adsorption filter in the waste liquid filtration unit and then sent to the salt extraction system for salt extraction treatment as desulfurization waste liquid.

[0131] (6) Alkali and catalyst replenishment

[0132] Na2CO3 is added to the alkali addition tank, and PDS desulfurization rich liquid from the single-stage catalytic desulfurization circulation pump is added for dissolution, or tail gas condensate and steam condensate generated during the evaporation, concentration and salt extraction process of desulfurization waste liquid returned from the salt extraction system are added for dissolution. After dissolution, the alkali metering pump is used to transport the solution to the single-stage catalytic reaction tank and each binary catalytic reaction tank, respectively, to replenish the single-stage catalytic desulfurization unit and the binary catalytic desulfurization unit.

[0133] PDS catalyst is added to the PDS catalyst tank and a small amount of PDS desulfurization rich liquid from the single-stage catalytic desulfurization circulation pump is added to dissolve it. Then, it is transported by the PDS metering pump to the single-stage catalytic reaction tank to replenish the single-stage catalytic desulfurization unit.

[0134] The complexed iron catalyst (liquid and solid) is added to the complexed iron catalyst tank, and a small amount of tail gas condensate and steam condensate generated from the evaporation, concentration and salt extraction process of the desulfurization waste liquid in the salt extraction system are added to dissolve it. Then, the complexed iron metering pump is used to transport it to each binary catalytic reaction tank to replenish each binary catalytic desulfurization unit.

[0135] (7) Catalytic removal of organic sulfur

[0136] While removing inorganic sulfur (H2S) from coke oven gas, PDS catalyst and complexed iron catalyst also have a certain removal effect on organic sulfur such as carbon disulfide (CS2), carbonyl sulfur (COS), thiophene (C4H4S), and mercaptan compounds in coke oven gas. In this method, the removal rate of organic sulfur by both the unary catalytic desulfurization unit and the binary catalytic desulfurization unit reaches more than 30%.

[0137] (8) Cyanide removal from coke oven gas

[0138] In each desulfurization tower, the desulfurization lean liquid absorbs H2S from the coke oven gas while simultaneously absorbing HCN gas from the coke oven gas. The HCN in the coke oven gas is removed at the same time, and the removal rate of HCN in the coke oven gas is >95%.

[0139] (9) Reuse of tail gas condensate and steam condensate generated from desulfurization wastewater salt extraction

[0140] In the salt extraction system, the desulfurization waste liquid is heated and evaporated by steam, and the tail gas condensate and steam condensate generated during the salt extraction process are added to the desulfurization system makeup water and added to the unary catalytic reaction tank, or sent to the alkali addition tank as makeup water for dissolving Na2CO3. Under normal operating conditions, the unary catalytic desulfurization unit does not directly discharge desulfurization waste liquid to the salt extraction system, and the binary catalytic desulfurization unit does not need to add new water. Excess steam condensate is sent to the cooling circulating water system.

[0141] (10) Formation of secondary salts

[0142] In each regeneration tower, a small portion of elemental sulfur and Na2CO3 are oxidized by oxygen in the air to generate Na2S2O3 byproduct salt.

[0143] Due to the presence of PDS catalyst, polysulfides (Sx) are formed during the absorption of H2S by the lean desulfurization solution in each desulfurization tower. 2- HSx - Polysulfides belong to intermediate active species and react with HCN absorbed by the desulfurization liquid to form CN. - The reaction produces SCN - During the regeneration of desulfurized rich liquor, some SCN - It was oxidized to form S2O3 2- S2O3 2- And unoxidized SCN -Na produced by hydrolysis of Na2CO3 + The secondary salts NaSCN and Na2S2O3 are formed.

[0144] Some of the Na2S2O3 was further oxidized in the regeneration tower, forming the byproduct salt Na2SO4 and elemental sulfur.

[0145] In the process of desulfurization catalyzed by complexed iron, Fe 3+ It can directly remove HS from the desulfurization liquid - Oxidation forms elemental sulfur sol, and no polysulfides are produced in the process, i.e., CN. - It cannot react with polysulfides to form SCN. -- This avoids SCN - During the regeneration process, it is directly oxidized by oxygen in the air to form S2O3. 2- This also avoids S2O3. 2- It is further oxidized into SO4 2- .

[0146] Furthermore, in the process of catalytic desulfurization using complexed iron, some CN... - Will with Fe 2+ Ferrocyanide is formed and discharged into the salt extraction system along with the desulfurization waste liquid, thus being carried out of the binary catalytic desulfurization circulating liquid.

[0147] The desulfurization circulating fluid did not react with polysulfides, nor with Fe. 2+ The residual trace amount of CN that forms ferrocyanide - They will be gradually oxidized and decomposed in the air within each regeneration tower, eventually generating nitrogen, ammonium salts, etc., which will be removed.

[0148] The desulfurization principle clearly shows that PDS catalysis promotes the formation of polysulfides, leading to the large-scale generation of byproduct salts. Complex iron catalysis can inhibit S2O3 at its source. 2- SCN - and SO4 2- Therefore, the amount of Na2SO4, Na2S2O3, and NaSCN trisales produced in the complex iron catalytic desulfurization process is less than that produced in the PDS catalytic desulfurization process.

[0149] (11) Anti-clogging of desulfurization tower

[0150] Because the binary catalytic desulfurization unit contains a PDS catalyst, it avoids the situation where a large amount of elemental sulfur sol precipitates in the desulfurization tower, which is prone to clogging the packing, when using a complexed iron catalyst alone. On the other hand, because the large-particle elemental suspended sulfur generated by PDS in each binary catalytic desulfurization unit during the synergistic catalytic desulfurization process effectively improves the aggregation performance, foaming performance, and oil resistance performance of elemental sulfur sol generated during the complexed iron catalytic desulfurization process in the binary catalytic regeneration tower, the generated sulfur foam is abundant. The small amount of wash oil or tar entrained in the coke oven gas will not cause a large amount of sulfur foam to disappear. The content of elemental suspended sulfur and elemental sulfur sol in the binary catalytic desulfurization lean liquid entering the binary catalytic desulfurization tower from the binary catalytic regeneration tower is controlled to be less than 1 g / L, which can effectively prevent the elemental sulfur sol generated by the use of complexed iron catalyst from depositing a large amount on the packing in the desulfurization tower and avoid clogging the packing.

[0151] (12) Low-yield desulfurization waste liquid

[0152] Because the complexed iron catalyst inhibits S2O3 2- and SCN - The generation of H2S in coke oven gas was reduced by more than 60% compared to using PDS monocatalysis and PDS-complexed iron binary catalysis for synergistic desulfurization and decyanation, compared to using PDS monocatalysis alone. This reduced H2S content in coke oven gas from 6000 mg / Nm³. 3 Remove to <50m / Nm 3 Under the given process conditions, the amount of desulfurization wastewater generated (based on a trichloride concentration of 250 g / L) is <0.15 m³. 3 / 10,000 Nm 3 Coke oven gas.

[0153] 2) Removing sulfur and cyanide from coke oven gas using NH3 as an alkali source.

[0154] If the NH3 in the coke oven gas is not removed before entering the desulfurization system, the NH3 in the gas is used as an alkali source for desulfurization and decyanation. Any insufficient NH3 is replenished by ammonia vapor distilled from ammonia water, which is then directly fed into each desulfurization unit along with the gas. The desulfurization circulating liquid contains NH4+. + The process involves adding a catalyst, eliminating the need for additional Na2CO3 addition. Other steps are the same as those described above for desulfurization and decyanation using Na2CO3 as the alkali source.

[0155] In the desulfurization and decyanation process using NH3 as the alkali source, H2S in the coke oven gas in each desulfurization tower reacts with NH4 in the desulfurization liquid under the action of a catalyst. + The reaction produces NH4HS, and H2S in the coke oven gas is removed. The main tri-salt components in the desulfurization circulating liquid are (NH4)2SO4, (NH4)2S2O3, and NH4SCN.

[0156] Example 3:

[0157] This invention proposes a method for desulfurization and decyanation of coke oven gas using uni- and binary synergistic catalysis, the method comprising the following process steps:

[0158] 1) Desulfurization process

[0159] 25-30% of the total coal gas volume is fed into a single-stage catalytic desulfurization tower, and 70-75% is fed into each binary-stage catalytic desulfurization tower. PDS catalyst is added to the circulating liquid of the single-stage catalytic desulfurization tower to remove H2S from the coal gas. Complexed iron catalyst is added to the circulating liquid of each binary-stage catalytic desulfurization tower. The single-stage catalytic desulfurization unit's filtrate containing PDS catalyst is then fed into each binary-stage catalytic desulfurization unit for secondary utilization, forming a PDS and complexed iron binary catalyst in the circulating liquid, which synergistically removes H2S from the coal gas. The H2S content of the coke oven gas after both the single-stage and binary-stage catalytic desulfurization towers is less than 50 mg / Nm³. 3 .

[0160] 2) Reaction and regeneration processes (the same for both the single-stage catalytic desulfurization unit and each binary catalytic desulfurization unit):

[0161] After absorbing H2S and HCN from the coal gas in each desulfurization tower, the desulfurization liquid enters the corresponding reaction tank. After the reaction takes place in the reaction tank, elemental sulfur is released from the desulfurization liquid, and the catalyst in the desulfurization liquid is deactivated.

[0162] The desulfurization liquid from each reaction tank enters the regeneration tower. Compressed air is introduced into the regeneration tower to regenerate the deactivated catalyst in the desulfurization liquid, and elemental sulfur is precipitated and forms sulfur foam on the surface of the desulfurization liquid at the top of each regeneration tower.

[0163] 3) Unicomponent catalytic sulfur foam pressure filtration and waste liquid treatment process:

[0164] After the sulfur foam from the unary catalytic desulfurization unit is filtered, sulfur paste and unary catalytic filtrate are obtained. The sulfur paste is sent to the sulfur melting unit for processing, and the unary catalytic filtrate is returned to the unary catalytic reaction tank. The total concentration of by-product salts Na2SO4, Na2S2O3, and NaSCN, or by-product salts (NH4)2SO4, (NH4)2S2O3, and NH4SCN in the unary catalytic desulfurization circulating liquid is controlled within the range of 120-170 g / L. If the concentration is too high or exceeds the standard, part or all of the unary catalytic filtrate is sent to each binary catalytic reaction tank.

[0165] 4) Binary catalytic sulfur foam filter press and waste liquid treatment process:

[0166] After the sulfur foam from each binary catalytic desulfurization unit is filtered, sulfur paste and binary catalytic filtrate are obtained. The sulfur paste is sent to the sulfur melting unit for processing, and the binary catalytic filtrate is returned to each binary catalytic reaction tank. The total concentration of by-product salts Na2SO4, Na2S2O3, and NaSCN, or by-product salts (NH4)2SO4, (NH4)2S2O3, and NH4SCN in each binary catalytic desulfurization circulating liquid is controlled within the range of 250-300 g / L. If the concentration is too high or exceeds the standard, part or all of the binary catalytic filtrate is purified by ceramic filtration and activated carbon adsorption and filtration, and then sent to the salt extraction system as desulfurization waste liquid for evaporation, concentration, and salt extraction treatment.

[0167] 5) Chemical dosing and water replenishment procedures:

[0168] The desulfurization wastewater generated during the operation of each binary catalytic desulfurization unit is sent to the salt extraction system for evaporation, concentration, and salt extraction. Soda ash or ammonia water, dissolved from the tail gas condensate and steam condensate returned from the salt extraction system, is added to the reaction tanks of each desulfurization unit to replenish the required alkali source. PDS catalyst is dissolved and added to the unary catalytic desulfurization reaction tank, and complexed iron catalyst is dissolved and added to each binary catalytic desulfurization reaction tank. Additionally, tail gas condensate and steam condensate returned from the salt extraction system are injected into each catalytic reaction tank to replenish the water lost by each desulfurization unit due to the failure of all filtrate to return to the reaction tanks after sulfur foam filtration, thus maintaining water balance.

[0169] The desulfurization process of this invention requires a low alkalinity, which can effectively reduce alkali source consumption and side reactions. It has good sulfur foam generation effect, strong oil resistance, stable desulfurization effect, low waste liquid production, and does not clog the desulfurization tower packing. The residual PDS catalyst and alkali source in the excess filtrate discharged from the unary catalytic desulfurization unit are reused in the binary catalytic desulfurization unit. The tail gas condensate and steam condensate generated during the evaporation, concentration and salt extraction of desulfurization waste liquid are returned to each catalytic desulfurization unit as makeup water for recycling.

[0170] The present invention also has the following beneficial effects:

[0171] 1) Effectively reduces catalytic side reactions and wastewater generation; the amount of desulfurization wastewater generated, calculated based on a tri-salt concentration of 250 g / L, is <0.15 m³. 3 / 10,000 Nm 3 Compared to using PDS catalytic desulfurization technology alone, the desulfurization waste liquid from coke oven gas is reduced by more than 60%.

[0172] 2) Effectively control the reaction rate of complex iron catalytic desulfurization, avoid the generation of a large amount of elemental sulfur sol in the desulfurization tower and its adhesion to the packing, and eliminate the blockage of the desulfurization tower that is prone to occur when using complex iron desulfurization catalyst.

[0173] 3) It exhibits strong oil resistance, excellent sulfur foam generation in the regeneration tower, high desulfurization efficiency, and strong operational stability. It can remove over 99% of H2S and over 30% of organic sulfur from coke oven gas. Single-stage desulfurization can stably achieve an H2S content of <50 mg / Nm³ in the gas exiting the desulfurization tower. 3 ;

[0174] 4) The tail gas condensate and steam condensate generated during the evaporation, concentration and salt extraction of desulfurization wastewater are added to each desulfurization unit to realize the secondary use of salt extraction wastewater. Under normal operating conditions, each desulfurization unit no longer needs to add new water.

[0175] 5) The unfinished filtrate from the unary catalytic reactor is discharged into the binary catalytic desulfurization unit to become the circulating liquid of the binary catalytic desulfurization unit. This allows for the reuse of residual PDS catalyst and alkali source in the excess unary catalytic filtrate. The alkalinity and catalyst concentration required by the entire desulfurization system are relatively low. Compared with desulfurization and decyanation methods that use PDS catalyst or complexed iron catalyst alone, this method can effectively reduce alkali source consumption by more than 40% and PDS catalyst and complexed iron catalyst consumption by more than 30%.

[0176] 6) The binary catalytic desulfurization unit introduces PDS catalyst and complexed iron catalyst for synergistic catalysis. The required concentration of complexed iron catalyst is low. The corrosion rate of desulfurization liquid on carbon steel towers and pipelines at low complexed iron catalyst concentration is <0.3mm / a. Compared with the desulfurization and decyanation method using complexed iron catalyst alone, the corrosion rate of carbon steel equipment is reduced by 70%.

[0177] The above description is merely an illustrative embodiment of the present invention and is not intended to limit the scope of the invention. The various components of the present invention can be combined with each other without conflict. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principles of the present invention should fall within the scope of protection of the present invention.

Claims

1. A method for desulfurization and decyanation of coke oven gas using monobasic and dibasic co-catalysis, characterized in that, The method comprises the following steps: The coke oven gas is sent into a desulfurization unit, 25-30% of the coke oven gas is sent into a one-unit catalytic desulfurization unit, and 70-75% of the coke oven gas is sent into each two-unit catalytic desulfurization unit; PDS catalyst is added into the one-unit catalytic desulfurization circulating liquid to catalytically remove H2S and HCN in the coke oven gas, and complex iron catalyst is added into the two-unit catalytic desulfurization circulating liquid; The one-unit catalytic filter liquid containing PDS catalyst generated in the one-unit catalytic desulfurization unit is sent into each two-unit catalytic desulfurization unit for secondary use, and PDS and complex iron two-unit catalyst are formed in the two-unit catalytic desulfurization circulating liquid to catalytically remove H2S and HCN in the coke oven gas; The H2S content of the coke oven gas treated by the mono-catalytic desulfurization unit and the bi-catalytic desulfurization unit is less than 50 mg / Nm 3 ; The desulfurization waste liquid generated in the two-unit catalytic desulfurization unit is sent to a salt extraction system for evaporation, concentration and salt extraction treatment.

2. A process for the removal of H2S and CN" from coke oven gas by using mono and bi-catalysis as claimed in claim 1 wherein, The desulfurization unit comprises one one-unit catalytic desulfurization unit and multiple two-unit catalytic desulfurization units, and the one-unit catalytic desulfurization unit and the two-unit catalytic desulfurization units are used to process the coke oven gas in parallel to remove H2S and HCN in the coke oven gas.

3. A process for the removal of H2S and CN" from coke oven gas by using mono and bi-catalysis as claimed in claim 2, wherein the process is characterized by, An alkali source is added in the PDS catalytic reaction of the one-unit catalytic desulfurization unit and in the complex iron catalytic reaction of the two-unit catalytic desulfurization unit, and the alkali source is Na2CO3 or NH3.

4. A process for the removal of H2S and CN" from coke oven gas by using mono and bi-catalysis as claimed in claim 1, wherein, The by-product salt generated in the one-unit catalytic desulfurization circulating liquid is Na2SO4, Na2S2O3 and NaSCN, or is (NH4)2SO4, (NH4)2S2O3 and NH4SCN, and the total concentration of the by-product salt generated in the one-unit catalytic desulfurization circulating liquid is controlled to be 120-170 g / L.

5. A process for the removal of H2S and CN" from coke oven gas by using mono and bi-catalysis as claimed in claim 1, wherein the process is characterized by, The by-product salt generated in the two-unit catalytic desulfurization circulating liquid is Na2SO4, Na2S2O3 and NaSCN, or is (NH4)2SO4, (NH4)2S2O3 and NH4SCN, and the total concentration of the by-product salt generated in the two-unit catalytic desulfurization circulating liquid is controlled to be 250-300 g / L.

6. A process for the removal of H2S and CN" from coke oven gas by using mono and bi-catalysis as claimed in claim 1, wherein the process is characterized by, In the one-unit catalytic desulfurization unit, the content of elemental suspended sulfur in the desulfurization circulating liquid entering the one-unit catalytic desulfurization tower is controlled to be less than 1 g / L.

7. A process for the removal of H2S and CN" from coke oven gas by using mono and bi-catalysis as claimed in claim 1, wherein the process is characterized by, In the two-unit catalytic desulfurization unit, the total content of elemental suspended sulfur and elemental sulfur sol in the desulfurization circulating liquid entering the two-unit catalytic desulfurization tower is controlled to be less than 1 g / L.

8. A process for the removal of H2S and CN" from coke oven gas by using mono and bi-catalysis as claimed in claim 7, wherein the process is characterized by, The liquid-gas ratio of each desulfurization tower is controlled to be greater than 35.

9. A process for the removal of H2S and CN" from coke oven gas by using mono and bi-catalysis as claimed in claim 1, wherein, The desulfurization waste liquid discharged from the two-unit catalytic desulfurization unit is filtered, adsorbed and purified by activated carbon after ceramic filtration, and then is sent to a salt extraction system for evaporation, concentration and salt extraction treatment.

10. A process for the removal of H2S and CN" from coke oven gas by using mono and bi-catalysis as claimed in claim 8, wherein the process is characterized by, Tail gas condensate and steam condensate generated in the evaporation and concentration salt extraction process of the recovered desulfurization waste liquid are recovered.

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