Brief description of the process flow of each section of coking gas purification - desulfurization section (HPF desulfurization method)

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The 25th National "Safety Production Month" in 2026. Everyone pays attention to safety and everyone will investigate and rectify potential risks on an emergency basis -------------------------------------------------- Why should we remove sulfur from gas? The sulfur content in coal gas generally changes with the sulfur content in coking coal. 90% of the sulfur in coal gas exists in the form of H2S, which generally fluctuates between 4 and 10g/m3 (coal gas). The sulfur content in coking coal reaches 1%, which is equivalent to the H2S content in coal gas of 10g/m3. The HCN content depends on the nitrogen content in the coal and the carbonization temperature, generally 1 to 2.5g/m3 (coal gas). H2S and HCN are both toxic compounds. When H2S is inhaled into the human body, it can cause poisoning in mild cases and death in severe cases. The H2S content allowed in the production workshop is less than 10g/m3. HCN is more toxic and a person can die if he inhales 50mg. The HCN content allowed in the production workshop is less than 0.3mg/m3. Aqueous solutions of H2S and HCN are also highly toxic. HCN in water containing 0.04 to 0.1 mg/kg can cause fish death. Factory wastewater requires the content of H2S and HCN to be less than 0.05mg/L. Equipment and pipelines will be corroded during gas transportation ； When burned as fuel, SOx and NOx are generated, seriously polluting the atmosphere and even forming acid rain. When coke oven gas is used to smelt high-quality steel and supply chemical synthesis industry, the requirements for H2S content are more stringent, and some even require less than 1mg/m3. To sum up, H2S and HCN must be removed from coke oven gas. In addition, waste can be turned into treasure to produce chemical products such as sulfur and sulfuric acid. 1. The process flow desulfurization device is a wet oxidation desulfurization process using ammonia in the coal gas as the alkali source and HPF as the catalyst. The regeneration is a jet regeneration method. The injection regeneration tank is located at the upper part of the desulfurization tower. Use negative pressure desulfurization process. In order to ensure that the desulfurized coal gas contains H2S ≤ 20 mg/m3, the desulfurization device adopts a three-tower series design with HPF as catalyst. The gas captured by the drum cooling device enters the desulfurization sections of the three desulfurization regeneration towers in sequence. The desulfurization liquid sprayed from the top of the desulfurization section contacts the coal gas in countercurrent to absorb the hydrogen sulfide in the gas (and at the same time absorbs the ammonia in the gas to supplement the alkali source in the desulfurization liquid). After desulfurization, the gas contains about 20 mg/m3 of hydrogen sulfide and is sent to the blower room for pressure increase. The desulfurization liquid that has absorbed H2S and HCN in the desulfurization section of the desulfurization regeneration tower is collected at the bottom of the tower, and then pumped into the regeneration section at the top of the desulfurization regeneration tower. Air is sucked in through the ejector in the regeneration section to allow the solution to be oxidized and regenerated in the tower. The regenerated solution flows from the top of the tower back to the desulfurization section of the desulfurization regeneration tower through the liquid level regulator to absorb H2S and HCN in the gas. The sulfur foam floating on the top of the desulfurization regeneration tower flows into the foam tank automatically by utilizing the position difference, and is sent to the super centrifuge through the sulfur foam pump. The super centrifuge is a countercurrent horizontal spiral discharge sedimentation centrifuge with a drum speed of 3000 rpm. The separated sulfur cake has a water content of ≤35% and is collected in a sulfur pool for take-out regularly. The filtrate is collected into the filtrate tank, and most of the filtrate is returned to the desulfurization system through the filtrate pump. In order to prevent the accumulation of NH4SCN and (NH4)2S2O3 salts in the HPF desulfurization unit, part of the filtrate is sent to the salt extraction unit to extract salts. The salt extraction unit operates intermittently, and one kettle is operated for 8 hours. The filtrate is pumped from the filtrate raw material tank into the ammonium thiosulfate evaporator and heated and concentrated with steam. In order to prevent the temperature from being too high and the salts to decompose, the evaporation needs to be carried out under vacuum conditions, and the evaporation temperature is controlled to 90°C. After the evaporation is completed, the material liquid is put into the vacuum filter through the rotatable chute, and impurities such as (NH4)2CO3 are hot filtered out. The filter residue is dissolved with filtrate in the residue tank and then returned to the desulfurization system. The filtrate is cooled to about 20°C with jacketed cooling water (low-temperature water) in the ammonium thiosulfate crystallization tank, and the same seed crystal is added to crystallize it. Finally, it is separated in a centrifuge to obtain crude ammonium thiosulfate, which is shoveled out manually and put into plastic bags as a product for shipment. The filtrate after centrifuging ammonium thiosulfate is pressed into the ammonium thiocyanate raw material tank through the intermediate tank, and then pumped into the ammonium thiocyanate evaporator, heated and concentrated with steam. After the evaporation is completed, the material liquid is put into the vacuum filter through the rotatable chute to further remove (NH4)2CO3 and other impurities. The filter residue is dissolved with filtrate in the residue tank and then returned to the desulfurization system. The filtrate is cooled to about 30°C with jacketed cooling water (low-temperature water) in the ammonium thiocyanate crystallization tank, and the same seed crystal is added to crystallize it. Finally, it is separated in a centrifuge to obtain crude ammonium thiocyanate, which is shoveled out manually and put into plastic bags as a product for shipment. The centrifugal filtrate can be returned to the evaporator for recycling. After repeated application, due to the gradual accumulation of impurities, the desulfurization liquid needs to be returned to the desulfurization system regularly. The water vapor evaporated from the evaporator enters the steam condenser. After removing the water, it enters the exhaust cleaning tower and is counter-currently contacted with the ammonia evaporation wastewater from the ammonia evaporation unit for purification. The non-condensable gas is directly discharged to the atmosphere through a vacuum pump. The wastewater condensed by the steam condenser flows to the liquid seal tank and is returned to the desulfurization liquid system.