Waste acid concentration multistage treatment method

Abstract

The invention relates to a waste acid concentration multistage treatment method which comprises the following steps of: heating 20-22% waste acid by a preheater, evaporating by a one-effect evaporation heater and a double-effect evaporation heater, cooling by a cooler and crystallizing by a crystallizer; heating by a triple-effect evaporation heater and separating by a separator to obtain 65% concentrated acid. The secondary steam part is used as a heat source part of the next stage heater and is condensed by spraying cooling water, wherein the one-effect evaporation heater and the double-effect evaporation heater are falling film graphite tube array evaporation heaters; the triple-effect evaporation heater is a floating head tube array graphite heat exchange. The water evaporation capability of the method is increased from 2.5 tons to 10 tons, and the stage number is 3 or more. A large amount of steam and cooling water is saved, and the pollution to the environment is reduced. The heat exchange area of equipment is reduced by 30%, and materials are saved and manufacturing cost is reduced correspondingly. The heat of steam is fully utilized, more than 35% of steam is saved, and more than 30% of cooling water can be saved. The condensed water part of the steam is used as the hear source part of the preheater and is recycled for other uses.

Description

technical field [0001] The invention relates to a low-concentration waste acid recovery and emission reduction method, in particular to a method for utilizing the evaporation characteristics of decompression and flash evaporation of the bath liquid to evaporate the water in the bath liquid so as to achieve the purpose of concentrating and recycling the waste acid A multistage treatment method for waste acid concentration. Background technique [0002] Sulfuric acid is the main raw material for the production of titanium dioxide by the sulfuric acid method, and a large amount of waste acid is produced during the production process. According to different processes, hydrolysis waste acid with a concentration of 17%-22% is generally called concentrated sulfuric acid, and 4-10% is bleaching waste acid. Generally speaking, 1 ton of finished product can produce 3.5 tons of dilute sulfuric acid, of which the total amount of dilute acid is 15%-20% is returned to the acid hydrolysis...

AI Technical Summary

Problems solved by technology

The implementation steps are to put the waste acid into the waste acid concentration device after settling, filtering and deslagging, and then pass in water vapor for heat exchange. Through fog making, vapor-liquid separation, and discharge of soda water, 37% concentrated sulfuric acid is obtained. The process flow is as follows figure 1 It is shown in the document, and it is pointed out in the document that if the mass fraction is increased on the basis of 37% concentrated acid, the recycling rate of spent acid will be increased again, but it will pose a great challenge to the concentration equipment and concentration process, which will affect the maturity of equipment operation , and will increase the cost, because with the increase of the mass fraction of concentrated acid, the boiling point of sulfuric acid rises rapidly, and the thermal efficiency decreases

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