Process for extracting secondary salt from desulfurization waste liquid

Abstract

The invention discloses a process for extracting secondary salt from desulfurization waste liquid. An input quantity of the desulfurization waste liquid in a desulfurization waste liquid conveying pipe connected with a concentrated liquid conveying pipe is controlled at 0-5 t / h; a steam pipeline with a heat exchange area of 120-140 m<2> is mounted in an evaporator; a steam input pipe on the steampipeline has a steam temperature of 120-160 DEG C and a steam pressure of 0.2-0.5 MPa; a gas-liquid mixture conveying pipe is connected with a top end of the evaporator and an upper side wall of an evaporation chamber; the evaporation chamber has a volume of 12-14 m<3>, an internal pressure of 0.05 MPa and a top temperature of 90-100 DEG C; the concentrated liquid conveying pipe with a switch is connected with lower parts of the evaporator and the evaporation chamber, wherein bottom ends of the evaporator and the evaporation chamber has a position difference W; an ammonia-containing steam conveying pipe is connected between the evaporation chamber and a condensation cooler; a circulation cooling water pipeline is arranged in the condensation cooler; a water flow rate in a circulated waterinlet pipe is 25-35 t / h; cooled ammonia water is returned to a desulfurization system; the desulfurization waste liquid is subjected to two-stage evaporation and is separated and crystallized to extract the secondary salt. The process provided by the invention has excellent economic and environmental protection benefits.

Description

technical field [0001] The invention relates to a process for extracting salt, in particular to a process for extracting (NH 4 ) 2 S 2 o 3 , (NH 4 ) 2 SO 4 and NH 4 The process of SCN mixed auxiliary salt. Background technique [0002] The process or technology of extracting salt from coal coking desulfurization waste liquid has always been a difficult problem for technicians of coal coking enterprises to overcome, because coal coking desulfurization waste liquid contains a large amount of inorganic salts and has great recovery value. [0003] Before the present invention, the technologies for treating coal coking desulfurization waste liquid include ① extracting and refining sodium salt or ammonium salt technology, generally using multi-effect evaporation crystallization plus activated carbon filtration process, this process has a large investment, and there are pipeline corrosion and evaporation efficiency during operation low cost, difficult fine operation and hig...

AI Technical Summary

Problems solved by technology

However, the main problem in the operation of the HPF desulfurization process is: the absorbed H 2 Most of S is converted into elemental sulfur, which is recovered by air flotation during regeneration, and the rest is generated (NH4) 2 S 2 0 3 and (NH4) 2 S0 4 , the absorbed HCN (cyanic acid) is converted to NH 4 SCN exists in the desulfurization liquid, and these three ammonium salts (i.e. ammonium thiosulfate, ammonium sulfate and ammonium thiocyanate) are usually called secondary salts

Over time, more and more sulfides in the desulfurization waste liquid will accumulate, which will seriously reduce the desulfurization effect on the one hand, and cause serious corrosion to the production equipment on the other hand

At present, many domestic coal gas or coking enterprises adopt desulfurization process for coal gas. Because the desulfurization waste liquid contains thiocyanate ions, which have a strong bactericidal effect, it cannot be biochemically treated.

Therefore, if the desulfurization waste liquid is not treated and discharged directly, it will cause serious pollution of water sources and poor production site environment; if it is used as coal blending water, it will still cause secondary pollution and increase operating costs

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