How to Recovery Tungsten from Failed Flue Gas Denitrification Catalyst

SCR denitrification technology, namely selective catalytic reduction technology, is an environmental protection and pollution control measure adopted by many thermal power plants in China. In the presence of oxygen and the role of catalysts, it can preferentially react with NO_x to produce N₂ and H₂O instead of oxidizing with oxygen in flue gas.

During the operation of denitrification unit in thermal power plant, with the passage of time, the denitrification catalyst will gradually fail, and when it fails, the waste SCR denitrification catalyst will become a toxic pollution source, which belongs to hazardous solid waste.

At present, the development of new technology for recovering tungsten from failed flue gas denitrification catalysts is relatively single in our country. The existing technology has the problems of low efficiency and high cost. In order to improve this situation, some researchers have adopted a new way. The central idea is to directly ammoniate tungsten in catalysts to produce soluble tungsten in supercritical ammonia-water system. Sex ammonium metatungstate. The process is as follows:

(1)The catalyst powders with particle size of 200-2000 mesh were obtained by crushing and sieving the failed denitrification catalyst, and then the molar percentage content of tungsten in the catalyst powders was determined.

(2) Catalyst powder obtained from molar step A (1) is put into the supercritical reactor, and then B molar liquid ammonia and C molar water are added into the supercritical reactor.
The molar percentage content of tungsten in catalyst powder B=A* is mol%*0.5.
B: C = 6:1;

(3)Heating the supercritical reactor, the temperature in the supercritical reactor reaches 310 C, and the liquid-solid product can be obtained by reacting under its own pressure for 10 hours.

(4)After the reaction, the liquid-solid products obtained in step (3) were separated and washed in turn to obtain ammonia metatungstate solution.

According to the calculation, the tungsten recovery rate of the above method can reach more than 95%, which is difficult to achieve by ordinary leaching method.

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