Phosphoric acid production tail gas recovery method

Abstract

The invention relates to a method for recovering tail gas from phosphoric acid production. The process flow is as follows: the fluorine-containing gas enters the Venturi scrubber through the tail gas duct, and performs first-stage downstream spray washing with the washing liquid from the first washing pump, and the washed gas enters the first washing tower and the first washing tower. The washing liquid sent by the washing pump is subjected to the first-stage countercurrent two-layer spray washing again, and the gas after washing enters the second washing tower and the washing liquid sent by the second washing pump is subjected to the second-stage countercurrent two-layer spray washing. After being pumped by the tail gas fan, it enters the defoaming tower for defoaming, and finally discharges into the atmosphere through the chimney; the process water for washing first enters the second washing tower and is preheated and sprayed by the second washing pump, and then overflows from the second washing tower into The first washing tower is sent to the Venturi scrubber and the spraying device of the first washing tower by the first washing pump for spray washing and absorption. The beneficial effects of the present invention are: 1) reduce the gas flow rate, increase the washing and absorption efficiency; 2) preheat the washing liquid through the second washing tower, accelerate the formation of H2SiF6, and further strengthen the washing and absorption effect; 3) reduce the adhesion of the fan impeller, Reduce fan failures and corrosion of related equipment; 4) Strengthen the stability of operating indicators and increase the operating rate.

Description

technical field [0001] The invention relates to a method for recovering tail gas from chemical production, in particular to a method for recovering tail gas from phosphoric acid production. Background technique [0002] The existing phosphoric acid production process is the dihydrate production process. It is difficult to collect and treat the tail gas of the phosphoric acid reaction. The reaction tank is often operated under positive pressure, which affects the surrounding environment and the stable operation of the reaction tank stirring paddle, low-level flash cooling axial flow pump and other equipment. had a greater impact. The basic process of the existing phosphoric acid reaction tail gas scrubbing system is shown in figure 1 . The fluorine-containing gas generated in the reaction tank passes through the tail gas duct and enters the Venturi tube scrubber for downstream washing with the washing water from the first washing pump. The washing liquid from the first was...

AI Technical Summary

Problems solved by technology

[0003] 1) The existing equipment leads to a large amount of non-condensable gas brought into the exhaust system, and at the same time, due to the unreasonable design, the height of the two overflow ports is correspondingly raised, resulting in an overall increase in the liquid level and a smaller gas phase space, which is likely to cause Reaction tank positive pressure

[0004] 2) The temperature of the reaction tank is high

Due to the use of a large amount of ore with high impurity content, in order to ensure the extraction rate, the only way to increase the reaction temperature is to take a large amount of fluorine-containing gas from the reaction tank, resulting in insufficient washing capacity.

[0005] 3) Venturi and gas phase pipelines are frequently blocked, and the cleaning workload is heavy and time-consuming

[0006] 4) The washing and spraying effect is poor and the absorption rate is low

[0007] 5) The impeller of the exhaust fan is seriously bonded, resulting in many fan failures and short service life

[0008] Due to the existence of the above problems, the phosphoric acid production system often causes equipment corrosion, fluctuations in operating indicators, frequent system shutdowns, and low operating rates due to tail gas scrubbing, which affect the production of subsequent processes.

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