Method for preparing high-concentration calcium chloride solution by decomposing ammonium chloride with lime powder

Abstract

The invention discloses a method for preparing high-concentration calcium chloride solution by decomposing ammonium chloride with lime powder. The method is characterized by including steps of mixing wet ammonium chloride in soda production process II with lime powder to feed into a primary reactor, adding light liquid from a light liquid distillation tower for sufficient reaction, subjecting generated primary reaction liquid to ammonia distillation process by a primary distillation tower, subjecting primary distillation liquid overflowing into a secondary reactor for subsequent reaction, and pumping generated secondary reaction liquid for ammonia distillation in a secondary distillation tower, and subjecting the obtained secondary distillation liquid to flash steam distillation to obtain high-concentration calcium chloride solution. The high-concentration calcium chloride solution is fed to a calcium chloride production system by a concentrated-calcium conveying pump, gas discharged by the secondary distillation tower is used as heat source for ammonia distillation of the primary distillation tower, and ammonia gas of the primary distillation tower and the light liquid distillation tower is recovered by an ammonia cooler and fed to an ammonia absorption tower. The method for preparing high-concentration calcium chloride solution has the advantages that concentration of the calcium chloride solution can reach 38% or above, ammonia content is lower than 100mg / L, consumption of 0.5MPa steam for producing double-water calcium chloride per ton is reduced by more than 30% as compared with before, and discharge of dry white-base mud is reduced by about 30% as well.

Description

technical field [0001] The invention relates to a method for preparing high-concentration calcium chloride solution by using lime powder to decompose ammonium chloride. Background technique [0002] As the world's largest soda ash producer, my country's current annual output of soda ash has reached more than 20 million tons. There are three production methods: ammonia soda method, combined soda method and trona method, of which the ammonia soda method accounts for 20~40% of the total output about. Ammonia-alkali white mud is mainly produced in the distillation recovery process of ammonia and brine refining process, and the distillation waste liquid is about 9~10m 3 / t of soda ash, about 200~300kg dry base lime mud / t of soda ash is produced, and the waste liquid contains about 10% calcium chloride and about 5% sodium chloride. Due to the large amount of waste liquid discharge, it is difficult to achieve thorough treatment. Pollution of the environment also leads to the wast...

AI Technical Summary

Problems solved by technology

Ammonia-alkali white mud is mainly produced in the distillation recovery process of ammonia and brine refining process, and the distillation waste liquid is about 9~10m 3 / t of soda ash, about 200~300kg dry base lime mud / t of soda ash is produced, and the waste liquid contains about 10% calcium chloride and about 5% sodium chloride. Due to the large amount of waste liquid discharge, it is difficult to achieve thorough treatment. It pollutes the environment and also leads to the waste of substances such as sodium chloride and calcium chloride

At present, most ammonia-alkali enterprises use the waste liquid recovery method to produce calcium chloride, but this method is to directly evaporate the distillation waste liquid after clarification and purification. Due to the low concentration of calcium chloride (about 10%), the steam consumption is large and the cost is high.

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