Tungsten Products Extraction from Ammonium Paratungstate Solid Waste

Ammonium paratungstate is an important tungsten intermediate chemical products, mainly white crystals, there are two kinds of flake or needle, used to make tungsten trioxide or blue tungsten oxide metal tungsten powder, also used to make ammonium metatungstate and other tungsten compounds.

The traditional method of preparing tungsten powder with ammonium paratungstate is to use calciner and other equipment to calcine the solid waste residue of ammonium paratungstate, which can remove water and ammonia gas and prepare oxide; then use reducing furnace to reduce tungsten oxide to tungsten powder with hydrogen as reducing agent. Today, with the increasingly stringent environmental protection, this traditional method consumes energy. Huge cost and serious waste of raw materials have not kept pace with the growing social needs.

For this reason, some scholars have provided a method to extract tungsten products from ammonium paratungstate solid waste residue to solve the problems raised in the above background technology.

(1)Using ammonium paratungstate solid waste as raw material, the powder of ammonium paratungstate solid waste was fused with liquid nitrogen (1:4) in a certain volume ratio, then injected into the enamel plate with liquid nitrogen pre-filled, stirred slightly, and kept for 2.5 hours. Finally, the paste product was obtained.

(2)The paste product was quickly transferred into the drying equipment together with the enamel disc. The temperature was raised to 95 ℃ and kept for 50 minutes. Then the white ammonium paratungstate slag crystals were obtained by biochemical dewatering and impurity removal at 55 Pa.

(3)The crystals of ammonium paratungstate waste residue were calcined by microwave, and the power was 810W. The crystals were calcined by microwave for 20 minutes.

(4)The crystals of ammonium paratungstate residue after calcination for 20 minutes were placed in calciner to remove water and ammonia, and oxides were prepared simultaneously. At the same time, the crystals of ammonium paratungstate residue were filtered by softening sludge with pH value of 7.5-8.5, and the slag containing copper and the filtrate containing tungsten and molybdenum were separated. The filtrate containing tungsten and molybdenum remained until the next step. The slag containing copper was leached by alkaline boiling, in which the alkali was NaOH. When the concentration of alkali was 35-45g/L, the alkali was stopped, boiled and kept for 1.5-2.5h. Tungsten oxide was obtained after washing.

(5)Then the tungsten oxide is reduced to tungsten powder by reducing furnace with hydrogen as reducing agent.

(6)The tungsten powder is returned to the furnace for deep forging, the forging time is 5 hours, then cooled, and then screened to get the finished product.

Compared with the traditional method, the above-mentioned process solves the shortcomings of low refining efficiency of calciner and other equipment in the past and produces more impurities. Microwave calcination in the process can achieve the characteristics of high heating speed, low heat loss and easy operation. It can shorten the process time and reduce the consumption of physics, less pollution, high efficiency and so on. It greatly saves the production resources of enterprises.

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