MVR evaporative concentration and recovery process for waste acid containing hydrochloric acid

Abstract

The invention relates to a MVR evaporative concentration and recovery process for waste acid containing hydrochloric acid. The process comprises the following four steps: preheating; MVR evaporative concentration; recovery of hydrochloric acid; and cooling crystallization of a concentrate. During preheating, a high-temperature concentrate containing considerable ferrous chloride and obtained after concentration by an evaporator No. 1 is used for preheating raw waste acid, and waste acid enters a preheating system via a feeding pump and is heated to an evaporation temperature; during MVR evaporative concentration, the preheated waste acid enters an evaporator system No. 1 and is mixed with circulating feed liquid in an evaporator No. 2, then the obtained mixture enters the evaporator No. 2, and then vapor-liquid mixed feed liquid is separated; during recovery of hydrochloric acid, process water and hydrochloric acid steam are subjected to heat exchanging in the evaporator No. 2, and hydrochloric acid steam is condensed to form thermal-state dilute hydrochloric acid; during cooling crystallization of the concentrate, changes of the concentration of the ferrous chloride concentrate are controlled, and discharging is reasonably controlled; and the ferrous chloride concentrate enters a concentrate cooling crystallization system so as to obtain ferrous chloride crystals. The MVR evaporative concentration and recovery process provided by the invention is stable in system, energy-saving and friendly to environment and can effectively overcome the problem of corrosion of high-temperature hydrogen chloride gas to equipment.

Description

technical field [0001] The invention relates to a regeneration and recovery process of waste acid containing hydrochloric acid, in particular to recovery of hydrochloric acid in waste acid by using an MVR evaporation concentration process. Background technique [0002] Hydrochloric acid is an important inorganic chemical product, which is widely used in dyestuffs, organic synthesis, food processing, printing and dyeing, rinsing, leather, metallurgy, steel and other industries. Such as a cold-rolled steel pickling unit with an annual output of 450,000 tons, it needs about 20,000 tons of hydrochloric acid per year, and the hydrochloric acid-containing waste liquid (about 5% hydrochloric acid, 10%-20% ferrous chloride) produced is nearly At 20,000 tons / year. In chemical production, the amount of waste acid containing hydrochloric acid produced every year cannot be counted. [0003] If the above waste acid is directly discharged to the environment, it will not only cause serio...

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Problems solved by technology

[0005] Aiming at the above-mentioned deficiencies existing in the prior art, the technical problem to be solved by the present invention is, aiming at the high energy consumption faced in the current process of recovering hydrochloric acid from waste acid, high operating cost, large floor area, and secondary pollution etc. Unfavorable problems, such as the use of MVR (Mechanical Vapor Recompression Technology) to evaporate and concentrate the recovery of hydrochloric acid from waste acid evaporation process, reduce energy consumption and operating costs, to achieve the recovery of hydrochloric acid from waste acid "zero discharge" process

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