Method for extracting two secondary salts from desulfurized salt-containing waste liquid of coke oven gas

Abstract

The invention relates to a method for extracting two secondary salts from a desulfurized salt-containing waste liquid of coke oven gas. The waste liquid treatment and secondary salt extraction process comprises the following steps: decolorizing, removing impurities, performing reduced pressure concentration on the salt-containing filtrate, separating ammonium thiocyanate, concentrating and crystallizing the ammonium thiocyanate ethanol filtrate, drying the ammonium thiocyanate product, separating ammonium sulfate, concentrating and crystallizing the ammonium thiosulfate filtrate, drying the ammonium thiosulfate product and the like. According to the invention, the desulfurized waste liquid is thoroughly treated, the products are high in recovery rate, no mixed salts or waste water is discharged, no secondary pollution is caused, and the process is clean and environment-friendly. Meanwhile, the invention also has the remarkable characteristics of high adaptability, high production elasticity, high resource utilization rate and the like.

Description

technical field [0001] The invention belongs to the technical field of coking industry waste treatment. The invention relates to a treatment method for coke oven gas desulfurization waste liquid, and also relates to a method for separately extracting ammonium thiosulfate and ammonium thiocyanate from the desulfurization waste liquid produced in the HPF method or PDS method desulfurization production process of a coking plant. Background technique [0002] The coke oven gas produced during the coal coking process contains 5-8g / m 3 of hydrogen sulfide (H 2 S) and 1~1.5g / m 3 Hydrogen cyanide (HCN), the sulfur oxides and nitrogen oxides generated after its combustion seriously pollute the environment, and the above two gases are toxic substances. Therefore, at present, domestic coking enterprises are equipped with coke oven gas desulfurization and decyanation equipment, and the desulfurization and decyanation processes used by the equipment can be divided into two categories:...

AI Technical Summary

Problems solved by technology

At present, although the first treatment method of desulfurization waste liquid solves the discharge of desulfurization waste liquid from the surface, the salt in the waste liquid will be decomposed and discharged again after entering the coking process, and will repeatedly enter the desulfurization and decyanation system, resulting in a vicious circle. The two treatment processes are not perfect. At present, coking plants generally adopt the method of spraying into coking coal to solve the problem of waste liquid discharge.

[0004] There are currently three main treatment methods for recovering ammonium sulfate from HPF desulfurization wastewater: the first is to use the principle of co-saturated multi-component system phase diagram to concentrate multiple times and separate ammonium thiocyanate and thiosulfuric acid Separation and purification of ammonium (CN201110180361.5, CN200810128357.2), because the solubility difference between ammonium thiocyanate and ammonium thiosulfate is not large, the process is cumbersome, the requirements for crystallization concentration and temperature control are high, and the purity of the obtained salt is low, which is economical. The benefit is poor, and it is not suitable for waste water solutions with high ammonium sulfate content; the second is to oxidize the ammonium thiosulfate in the desulfurization liquid into ammonium sulfate by catalyst and then fractional crystallize and purify ammonium thiocyanate and ammonium sulfate (CN201210147582.7 , CN2007101395747, Japanese Patent Publication No. 55-126531), the disadvantage of this method is that when using copper salt to purify ammonium thiocyanate, high temperature regenerated copper salt is required, and ammonium thiosulfate with high economic value cannot be purified, and the economic benefit is poor. The copper salt lost in the process becomes a new source of pollution, and more industrial wastewater is discharged; the third is to convert all the ammonium salt in the wastewater into ammonium sulfate under high temperature and pressure and under the action of a catalyst for recovery (Japanese Patent No. 57 -7852), this method requires high equipment conditions, high operating costs, and the economic value of ammonium sulfate obtained by oxidation is low, and general enterprises cannot use this method

[0005] Based on the above situation, the present invention adopts a novel environmental protection technology process route to solve the environmental protection treatment and recycling problems of the above-mentioned desulfurization waste liquid

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