Method for improving washing efficiency for tail gas from wet-process phosphoric acid manufacture

Abstract

The invention discloses a method for improving the washing efficiency of tail gas during wet process phosphoric acid production, and relates to tail gas treatment in wet process phosphoric acid production. The method comprises the following steps: firstly, sealing a reaction tank, that is, completely insulating the inside of a reaction digesting chamber from the outside thereof by adding oil sealonto stirring equipment of the reaction tank and sealing a service port cover board; secondly, washing tail gas through first class Venturi and third class hollow-spraying-tower in a counter current washing manner, the Venturi and a first washing tower require a small quantity of water to accomplish washing, and cleaning solution is reserved for a phosphoric acid concentration fluorine absorptionsystem, while for second class and third class washing, a large quantity of water is required, cleaning solution is sent back to a phosphoric acid reaction system and consumed to guarantee the washing efficiency. When the method is applied in the negative pressure operation of the reaction digesting chamber, air outside the chamber cannot enter the reaction digesting chamber through the gap between the equipment and the reaction chamber, so that the volume of tail gas is greatly reduced, the concentration of fluoride in tail gas is increased, and the washing efficiency is improved. As washingis more frequently carried out, the concentration of the cleaning solution is increased, so that the recycling of the cleaning solution can be facilitated.

Description

technical field [0001] The present invention relates to phosphoric acid, specifically, to the process of producing wet-process phosphoric acid by dihydrate method, especially to the treatment method of process tail gas. technical background [0002] The tail gas produced in the production of wet-process phosphoric acid is mainly fluorine-containing waste gas produced by acid hydrolysis of fluorine in phosphate rock, mainly from the reaction digestion tank. Since the reaction digestion tank is operated under a slight negative pressure, a large amount of air enters the tank from the gap between the equipment, which greatly increases the amount of exhaust gas, reduces the concentration of fluoride in the exhaust gas, and increases the load of the washing system. The escaped fluorine-containing tail gas first enters the Venturi scrubber for washing with water, and then enters the two-stage tail gas scrubber or enters the cyclone scrubber combined with water for countercurrent wa...

AI Technical Summary

Problems solved by technology

Although these inventions have some effects, they do not solve the problem of low exhaust gas scrubbing efficiency, and the fluorine content in the exhaust gas basically does not meet the emission standards stipulated by the state.

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