Washing treatment system for silicon tetrafluoride in fluorine-containing tail gas

Abstract

The invention provides a washing treatment system for silicon tetrafluoride in fluorine-containing tail gas. The washing treatment system comprises two sets of washing absorption devices which are communicated with each other, each set of washing absorption device comprises a washer and a fluorine absorption tower which are communicated with each other, the fluorine absorption tower of the previous washing absorption device is communicated with the washer of the latter washing absorption device, the gas inlet of the washer of the previous washing absorption device is communicated with the fluorine-containing tail gas inlet pipe, and the gas outlet of the fluorine absorption tower of the latter washing absorption device is communicated with the purified tail gas outlet pipe; the washer andthe fluorine absorption tower are respectively provided with a washing liquid circulation loop; the washing liquid circulation loop of the washer in the previous washing absorption device is connectedwith a finished fluosilicic acid outlet pipe for discharging fluosilicic acid, and the washing liquid circulation loop of the fluorine absorption tower in the latter washing absorption device is provided with a first washing liquid supplementing pipe for inputting washing liquid to the outside; the two washing absorption devices and the washer and the fluorine absorption tower of each washing absorption device are communicated with each other through a liquid supplementing pipe network for supplementing washing liquid.

Description

technical field [0001] The invention relates to a washing treatment system for silicon tetrafluoride in fluorine-containing tail gas, belonging to the technical field of tail gas treatment. Background technique [0002] In the production of wet-process phosphoric acid and the concentration of phosphoric acid, because the phosphate rock used contains fluorine, a large amount of fluorine-containing compounds will be produced during the reaction, among which silicon tetrafluoride has a high content and escapes into the tail gas scrubbing system in the form of gas , is the main environmental pollutant, in order to reduce environmental pollution and achieve the purpose of comprehensive utilization, it must be recycled. [0003] Silicon tetrafluoride, also known as silicon fluoride, has the molecular formula SiF 4 , is a colorless, poisonous, irritating odor gas, easy to deliquescence, can produce dense smoke in humid air, human body can cause headache, nausea and different degre...

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Problems solved by technology

[0004] At present, the tail gas washing and absorption processes in phosphoric acid production and phosphoric acid concentration process have been reported, including water washing, lime water washing, quicklime powder and activated carbon dry method to treat fluorine-containing tail gas; among them, water washing process is relatively simple, mature technology and widely used. The wet-process phosphoric acid workshop mostly adopts the two-stage countercurrent washing mode of "monofluorine scrubbing and absorption tower + difluorine scrubbing and absorption tower". Using this scrubbing mode to treat tail gas with high silicon tetrafluoride content has the following problems: First, the scrubbing mode H 2 SiF 6 After the solution is continuously circulated to wash and absorb fluorine-containing tail gas, it is easy to produce scales such as fluorosilicate and silica gel in the fluorine absorption system, causing the problem of system equipment blockage; secondly, with the H 2 SiF 6 With the gradual increase of solution concentration, the gas-liquid mass transfer rate decreases, resulting in poor exhaust gas washing and absorption effect, so that the exhaust gas emission indicators (particulate matter emission concentration, particle emission rate, fluoride emission concentration and fluoride emission rate) usually cannot meet the "air pollution The requirements of the secondary standard limit value of the comprehensive discharge standard of pollutants (GB16297-1996); third, silicon tetrafluoride is absorbed by water to form low-concentration fluorosilicic acid, and low-concentration H 2 SiF 6 Direct production of Na 2 SiF 6 Or anhydrous HF technology is more difficult and the production cost is higher

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