Recycling Ammonium Tungstate from Ammonium Tungsten Compound Tail Gas

The calcined ammonium tungsten compound is the source of tungsten powder metallurgy raw material. The tail gas of calcined ammonium tungsten compound contains a large amount of water vapor, ammonia and ammonia slag. Recycling ammonium tungstate from the tail gas of the calcined ammonium tungsten compound usually requires the recycled tail gas, the treatment of the recycled liquid, the separation of solid and the filtration of the slag.

The process of recycling the tail gas from the calcined ammonium tungsten compound is divided into three stages: the first stage is the cyclone exhaust gas recycle tail gas in the front section of the flue, and the second stage is in the middle section of the flue gas to recycle the tail gas from the condensing of water, and the third stage is to use the deionized water spray to recover the tail gas with the conductivity less than 50μs/Cm in the rear section of the flue, and all the processes are connected in series, and the flue is connected. Maintain micro negative pressure within 24 hours and clean up the ammonia residue in the recycle bin.

Recycled liquid treatment requires three procedures: first, the recycled liquid from the tail gas recycling system is transferred to the reactor with ammonia slag, and the liquid-solid ratio is (5~3) / 1. Second, The concentration of free ammonia in the solution was determined. The concentration was controlled at 5%~10%, the concentration was below 8%~10%, and the concentration of ammonia was added. The concentration was higher than 8%~10%, adding deionized water. Third, open the steam interlayer heating device at the bottom of the reactor and steam around it. The temperature of the solution in the reactor rises to 80~100°C, holding for 5~15h.

After the heat preservation time is required, the material is placed to the static slot for 2~5h in the sealed state, and the supernatant solution is pumped into the ammonium tungstate solution storage tank and transferred into the crystallization process of ammonium paratungstate.

The bottom sediment of ammonium tungstate solution storage tank is filtered into sodium hydroxide decomposition process. After ammonia decomposition of ammonium tungsten compound, there are some undecomposed furnace junctions. In order to recover valuable tungsten, it must be decomposed with more alkaline sodium hydroxide and converted into sodium tungstate.

Through the above process, the tail gas of the tungsten compound is converted into ammonium tungstate, which not only improves the utilization of tungsten, but also reduces the environmental pollution of the harmful gas. 

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