Ammonium para tungstate (APT) is composed of ammonium tungstate solution prepared by crystallization unit operation. The main methods of evaporation and crystallization, crystallization and freezing crystallization. APT morphology, particle size and particle size distribution on the performance of the subsequent oxidation of tungsten, tungsten powder, tungsten carbide powder has a great influence.

In tungsten smelting, ammonium chloride is recycled by evaporation crystallization, and ammonia nitrogen is recycled. The existing technology has low ammonia nitrogen recovery rate and high energy consumption of evaporation crystallization. Low recycling rate will cause poor working environment and waste water difficult to reach standard discharge. At the same time, the cost of evaporation recycling will also be higher and higher. Therefore, it is of great significance to develop a low energy recovery process to replace the current evaporation crystallization process.

Although tungsten is mainly derived from scheelite, there is a considerable proportion of wolframite. The largest tungsten ore reserves in China are 747 thousand T, and the ratio of wolframite and scheelite is 3:7. For such minerals, the sulphuric acid phosphoric acid mixed acid process is used directly, and the wolframite does not react completely, and all of them enter the leaching residue. In fact, it is difficult to decompose wolframite without sulphuric acid phosphoric acid mixed system. Even if other acids are used, the leaching reaction of wolframite is very slow.

In the mineral processing of tungsten minerals, single scheelite or wolframite recovery of tungsten concentrate is easy, but it is relatively difficult for tungsten ores in scheelite and wolframite ore bodies, mainly because the heavy magnetic separation is difficult to have good indicators in the recycling of fine-grained scheelite and wolframite, and therefore, Flotation is usually used in ore mixing.

In view of the shortage of raw tungsten resources, it is of great significance to reuse the waste hard alloy products and reuse it after recycling, and it is very important to make full use of the protection resources. In the United States, 35% of tungsten products are derived from recycled tungsten.

The content of bismuth in the earth's crust is only about 10^‑6％, which is symbiosis with other metal minerals such as tungsten and molybdenum. Generally, bismuth is recycled from the by-products of other main metal refining processes, such as the exploitation of tungsten ore and the production of bismuth ore.

Ammonium para tungstate is prepared mainly by caustic soda or soda decomposition, and pure ammonium tungstate solution is obtained. Then APT products are obtained by evaporation crystallization. No matter which method is adopted, the result is large water consumption and large amount of waste water is needed.

The traditional tungsten tailings recovery mostly uses a mineral processing method to recycle an element in the tailings, and other valuable metals can not be recycled. In order to improve the benefit of recycling, a large mine adopts a combination of gravity separation and flotation, and a reasonable control of the pH value of the pulp. By controlling the ratio of the flotation agents at various stages, the low grade valuable elements in the tungsten tailings are recycled, and the methods of recycling the three kinds of metal elements, tin and molybdenum are mainly used. The whole process of recycling is divided into four stages.

In the classical process, the removal of molybdenum in ammonium tungstate solution is a method of combining selective precipitation with ion exchange. By sulfurizing the ammonium tungstate solution in advance, Mo and S2- in ammonium tungstate solution are formed into thiomolybdenum root, most of which are precipitated and removed with the added copper salts, and the unprecipitated thiomolybdate root is passed through. The exchange column is further purified by resin adsorption.

During the treatment of ammonium para tungstate, the high temperature oxidation roasting of tungsten mineral materials was carried out in the rotary kiln, and the tungsten mineral raw materials were derived from the low temperature end of the kiln tail and out of the kiln head after the high temperature section. The fuel and air enter and burn after the kiln head, and the flue gas is discharged from the low temperature end of the kiln. The flotation reagents and other organic substances contained in tungsten mineral raw materials are partly removed at high temperature and partly evaporate in the low temperature section of the kiln bottom and enter the roasting flue gas. Tungsten minerals usually contain arsenic containing minerals. Under roasting conditions, some forms of arsenic, such as As₂S₃ and As₂S₅, will be roasted in the form of gaseous state and will also enter the roasted flue gas. Dust and sulfur and phosphorus can also enter into the roasting flue gas.