Tungsten Trioxide Separation from Waste SCR Denitrification Catalyst

At present, most power plants in our country mainly use coal as fuel. The direct combustion of coal will produce a large number of nitrogen oxides which pollute the environment. At present, flue gas denitrification technology is widely used in developed countries to reduce the emission of nitrogen oxides, and the denitrification rate can reach more than 90%.

On the other hand, the composition of SCR denitrification catalyst is relatively expensive, and 38,000 tons of scrap SCR denitrification catalyst are produced annually, of which about 1520 tons of tungsten trioxide are produced. If the scrap SCR catalyst can not be disposed of reasonably, it will cause a great waste of strategic resources. For this reason, according to the chemical properties and characteristics of waste SCR denitrification catalysts, some scholars have developed a technical scheme which is simple to operate, high recovery and suitable for large-scale production. The process includes the following steps:

(1)First, the waste SCR denitrification catalyst was crushed to dry powder and roasted at high temperature.

(2)The sealed reactor is heated by adding a solution of soluble tungsten trioxide and the dry powdered waste SCR denitrification catalyst obtained from the above steps (1).

(3)After fully dissolving, the supernatant is collected by standing until the liquid-solid layer is separated.

(4)The lower solid residue obtained in step (3) is added to the reactor together with the solution of soluble tungsten trioxide component, and the above steps (2) are repeated.

(5)Collect supernatant liquid obtained by repeatedly dissolving tungsten trioxide components, evaporate water and fully dry solid;

(6)The solid obtained in step (6) is calcined at high temperature to obtain tungsten trioxide, and the recovery of tungsten trioxide from scrap SCR denitrification catalyst is completed.

The solution of soluble tungsten trioxide can be used to separate tungsten trioxide directly from scrap SCR denitrification catalyst. At the same time, the system will not dissolve other components of SCR denitrification catalyst (titanium dioxide, vanadium pentoxide, glass fiber, kaolin, etc.) to ensure the separation of high purity tungsten trioxide. The recovery rate can be guaranteed above 95%, and the purity of tungsten trioxide is above 98.5%. It can be directly used to prepare SCR denitrification catalyst without any other components of catalyst.

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