Currently the most widely used SCR denitration catalyst is the V₂O₅-WO₃(MoO₃)/TiO₂ type monolithic catalyst, which takes titanium dioxide as its carrier, vanadium pentoxide and tungsten trioxide or molybdenum trioxide as the active ingredients. With the flue gas denitrification carrying out intensive, more and more inactivated catalysts come out during their running, which will result in waste of resources and environmental pollution if not dealt with.

 

In addition, with the increasingly stringent environmental laws and regulations, and the increasing scarcity of metal resources, the recovery of waste catalyst will be get more and more attention and favor by the market.

 

Metals in the tungsten trioxide waste denitration catalyst can be recovered in the form of metal oxides, which is showing as bellow:

1. Crush the waste flue gas denitration catalyst, and then calcine it at a high temperature of 650 °C to remove Hg, As and the organic impurities which absorbed on the surface;

2. Add sodium carbonate to mix and pulverize to obtain a mixed powder, and calcined at the high temperature of 650~700°C to form the agglomerates;

3. Put the agglomerates into hot water of 80~90°C after crushed, then get the titanate crude and filtrate by stirring uniformly, soaking, precipitating, filtering;

4. Recovering titanium dioxide powder by pickling, filtering, washing with water and baking the titanate crude;

5. Add the sulfuric acid into filtrate for adjusting the pH value to 8.0~9.0, and then add the ammonium chloride to get the precipitate, then give a secondary filtrate and ammonium vanadate after filtered;

6. Decompose the ammonium vanadate at 800~850°C after washed to prepare a molten vanadium pentoxide, and then get the sheeted products;

7. Adjusting the pH of secondary filtrate to4.5~5.0 by adding hydrochloric acid, and then adding calcium chloride to precipitate calcium tungstate and molybdate calcium;

8. Filtering and handling the filter cake by hydrochloric acid at the temperature of 40~50°C, and then get the tungstic acid and molybdic acid by acid precipitation, filtration, finally we obtain the tungsten trioxide and molybdenum trioxide by calcining.