Project of extracting auxiliary salt from coke oven gas desulfurization liquid

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In the project of extracting auxiliary salt from coke oven gas desulfurization liquid, during the coking process, about 30% to 35% of the sulfur in the raw coal is converted into sulfides such as H2S, which together with NH3 and HCN form impurities in the gas. The H2S content in the gas is 5 to 8g/m3, and the HCN content is between 1 and 1.5 g/m3, and H2S and HCN are highly corrosive and toxic. H2S containing 0.1% in the air can be fatal. If H2S and HCN are not removed from coke oven gas, it will seriously corrode equipment during the transportation process. As a civilian fuel, it will pollute the environment and harm human health. ； When used as metallurgical fuel, it will seriously affect the quality of steel products and chemical products. At the same time, it will produce a large amount of harmful substances such as sulfur dioxide when burned, polluting the atmosphere, and in serious cases, it will form acid rain. At the same time, the resulting HCN-containing wastewater will be difficult to treat. 　　 There are many methods for removing H2S and HCN from coke oven gas. The HPF (Hgdroquinone, PDs, FerrousSulfate) method is a new process for wet liquid-phase catalytic oxidation desulfurization and decyanization. It is a new desulfurization and decyanization process that has emerged in recent years. The HPF process uses ammonia as an alkali source, and the HPF catalyst is a composite catalyst composed of PDS, hydroquinone, and ferrous sulfate. Since the HPF process can use the alkali source produced by the coking plant and can use the recovered hydrogen sulfide to produce a certain amount of sulfur, it has great advantages and economic significance. 　　 HPF desulfurization process In the process of removing H2S and HCN from coke oven gas in the desulfurization liquid, most of the absorbed H2S is converted into elemental sulfur, which is recovered by air flotation during regeneration. The rest generates (NH4)2S2O3 and (NH4)2SO4. The absorbed HCN is converted into NH4SCN and is present in the desulfurization liquid. These three ammonium salts are usually called As the catalyst is enriched in the waste liquid, in order to reuse the catalyst, the waste liquid is often merged into the absorption liquid for recycling. However, this will cause the secondary salt to continuously accumulate in the system. When the concentration of the three secondary salts accumulates to a certain concentration, it will seriously affect the reaction balance. At the same time, the increase in the viscosity of the desulfurization liquid will also reduce the activity of the desulfurization liquid, thereby causing the desulfurization effect to continue to decline. Actual data from coking enterprises show that when the secondary salt concentration in the desulfurization liquid increases to 350g/L, the desulfurization efficiency drops from the initial 90% to 30%. 　　 At present, the way domestic coking plants solve the problem of the accumulation of secondary salts in the desulfurization liquid is to use part of the desulfurization liquid as coal preparation water, discharge the other part of the desulfurization liquid, and then add new water. This approach does not fundamentally solve the problem. On the one hand, the auxiliary salt contained in the desulfurization liquid used as water for coal blending will eventually return to the desulfurization liquid, and the discharge of the desulfurization liquid will cause secondary pollution. The auxiliary salts NH4SCN and (NH4) 2S2O3 are inorganic salts with high economic value. If the auxiliary salts in the desulfurization liquid are separated and recovered, not only can the desulfurization liquid be recycled without being discharged, but economic benefits can also be created by recycling the auxiliary salts.