SCR Waste Catalyst Cleaning and Recycling

In general, SCR catalyst must be replaced after three years, because the waste catalyst contains a large number of metal elements, improper treatment will cause pollution to the environment. The waste catalyst contains high value added metals such as titanium, tungsten and vanadium.

Some scholars have provided a method to recycle tungsten, vanadium and titanium from the waste catalyst of SCR flue gas denitrification, including the following steps:

(1) The SCR waste catalyst is cleaned, dried and broken and ground to a particle size of less than 150μm.

(2) The sintered material was sintered at high temperature after mixing the SCR waste catalyst powder and sodium carbonate at high temperature. The leaching solution obtained by adding water in the sintered material was heated and stirred to extract tungsten and vanadium. The leaching solution obtained by solid-liquid separation was a mixed solution of sodium salt containing tungsten and vanadium, and the leaching residue was a titanium rich material.

(3) The leaching solution is adjusted to more than 12, and the leaching solution is in contact with the organic phase for multistage extraction of tungsten, and the tungsten into the organic phase. In the extractive solution after the extraction of tungsten, the vanadium and impurity phosphorus, arsenic and silicon are left after the extraction of tungsten, the negative tungsten organic phase and the extractive tungsten are obtained. The negative tungsten organic phase is used in the ammonium salt solution for the single or multistage reaction. The aqueous phase extracted from tungsten after extraction of tungsten is a solution of ammonium tungstate containing a small amount of vanadium. The organic phase after the extraction of tungsten can be reused.

(4) The extracted solution after extraction of tungsten is adjusted to 9.5 ~ 11.5, and the solution is in contact with the organic phase for multistage extraction of vanadium, and vanadium enters the organic phase, and the impurity phosphorus, arsenic and silicon are left in the extractive solution after the extraction of vanadium, that is, the negative vanadium organic phase and the extractive extract after the extraction of vanadium are obtained. The negative vanadium organic phase is made by a strong alkali solution. The water phase after reverse extraction of vanadium is a sodium vanadate solution containing a small amount of tungsten. The organic phase after the extraction of vanadium can be reused after the reextraction of vanadium.

The process can be used to extract tungsten and vanadium in order under alkaline conditions. Separation of tungsten and vanadium and separation of tungsten, vanadium and impurities P, As, Si and so on are obtained. The high purity ammonium tungstate solution and sodium vanadate solution are obtained respectively. Ammonium (APT) products and ammonium salt precipitation vanadium process are prepared from ammonium vanadate solution.

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