Ammonia-evaporating process by circularly heating flash evaporation method

Abstract

The invention relates to an ammonia-evaporating process by a circularly heating flash evaporation method. In the process, ammonia-evaporating wastewater at the bottom of an ammonia-evaporating tower is heated outside the tower to form superheated water; and vapor, which is obtained by performing flash evaporation on the superheated water returning into the ammonia-evaporating tower, serves as a heat source of the ammonia-evaporating tower and is used for evaporating the ammonia. The process comprises the following steps of: performing thermolysis on a raw material, namely ammonia water entering the ammonia-evaporating tower, so that the ammonia dissolved into the water is evaporated and volatile ammonium salt in the water is subjected to thermolysis to the maximum degree; and adding alkali liquid for decomposing fixed ammonium salt, so that the alkali liquid is completely used for decomposing the fixed ammonium salt, and the all ammonia content of the ammonia-evaporating wastewater discharged from the bottom of the tower is obviously reduced. The process has the advantages that: the ammonium is volatized after complete thermolysis and then the fixed ammonium salt is decomposed by the alkali, so that the alkali liquid can be utilized completely; the vapor phase concentration of each layer of tower plate in the tower can be reasonably arranged through two vapor phase channel pipes arranged outside the ammonia-evaporating tower; the all ammonia content of the discharged wastewater can be effectively reduced; and the total amount of the discharged wastewater can be reduced. The process can be applied to a process of independently treating residual ammonia water and can also be applied to a process for washing ammonia with water through combined treatment on circularly washing ammonia water and the residual ammonia water.

Description

technical field [0001] The invention relates to an ammonia distillation process for efficiently treating residual ammonia water in a coking plant. Background technique [0002] In coking production, the surface wet water and combined water of coking coal are converted into redundant residual ammonia water, which contains many harmful compounds such as phenol, cyanide and ammonia. Although ammonia is a fertilizer that promotes plant growth, when the ammonia-containing wastewater is discharged into rivers and lakes, it will cause eutrophication of the water body and reduce the self-purification ability of the water body. For this reason, the function of the ammonia distillation tower in the coking plant has changed from the earliest recovery of ammonia from the top of the tower to produce fertilizers, to a device that minimizes the ammonia content of the wastewater discharged from the bottom of the tower to protect the ecological environment. [0003] At present, the ammonia ...

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Problems solved by technology

[0004] 1) Only volatile ammonia is processed; this process has a high content of total ammonia in the effluent due to undecomposed and fixed ammonia;

[0005] 2) Two sets of treatment devices for volatile ammonia and fixed ammonia are installed; the process is complicated, the floor area is large, the infrastructure investment is high, and the operating cost is large;

In this method, because the volatile ammonia in the place where the alkali is added has not yet been pyrolyzed, the lye cannot fully exert its effectiveness.

[0007] Most of the existing ammonia distillation towers use external direct steam as the heat source, and the direct steam condensation will be mixed with the ammonia distillation wastewater, which increases the amount of discharged wastewater treatment

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