Tungsten Oxide

In the production, sometimes for some reason lead to part of the APT products in the classics or physical performance on the failure, may also occur in the production process a small amount of ammonium paratungstate waste recycle, which are recyclable. Recycle of unqualified ammonium paratungstate method is mainly after the dissolution of the filter, and recrystallization, for this reason, the APT is dissolved at a higher temperature directly with ammonia as a solvent, however, APT solubility in aqueous ammonia is limited, resulting in dilute solution concentration, it takes for a long time to dissolution. Therefore, the modern industry began to use of APT thermal decomposition into ammonium metatungstate for recycle. Thermal decomposition of the working mechanism is to control the appropriate temperature, calcined APT can be converted to ammonium metatungstate (AMT). According to the high temperature decomposition performance of APT·4H 2 O, when heated APT·4H 2 O in t...

Ammonium paratungstate (APT) preparation is an important part of smelting tungsten, whether it is using chemical precipitation method, ion exchange method or extraction method, it all have to go through the process of ammonium trioxide to produce qualified APT. APT is an important tungsten intermediate product, the higher the purity the greater the value, so APT preparation process is also the further purification of tungsten. Commonly used method for preparing ammonium paratungstate is evaporation crystallization method, neutralization crystallization method and frozen crystallization method. Evaporation crystallization method is heating evaporation solvent, so that the solution from unsaturated to saturated, continue to evaporate, the excess solute will be crystal precipitation, called evaporation crystallization method. This method of technology and equipment is simple, easy to large-scale, this method technology and equipment is simple, easy to large-scale, at the s...

Ammonium paratungstate (APT) is an important tungsten intermediate product, mainly with white crystals. It have flakes, needles and strips three kind, used in the manufacture of tungsten trioxide or blue tungsten oxide, TP,  also used for manufacturing ammonium metatungstate and other tungsten compounds. Because the production of tungsten oxide, morphology and particle size of tungsten powder has genetic relationship with APT, so the production process is not only to the tungsten APT purification, but also to control the crystal morphology and particle size of paratungstate tungstate. In the 1950s, in the book "Tungsten and Molybdenum Metallurgy" by A.H rickman, used the reaction 5(NH 4 ) 2 O·12WO 3 ·nH 2 O to describe the APT formula, used the evaporation crystallization process to get n = 5 flaky crystal, and used the acid neutralization process for n = 11 needle crystal. After that in China are all using this view, that of ammonium tungst...

Ammonium paratungstate (APT) preparation is an important part of smelting tungsten, whether it is chemical precipitation method, ion exchange method or extraction method,they all have to go through the process of ammonium trioxide to produce qualified APT.   APT is an important tungsten intermediate products , the higher the purity the greater the value, so APT preparation process is also the further purification of tungsten. Neutralization is one of the most commonly used manufacturing method of para-ammonium tungstate, and it's settlement with hydrochloric acid and (NH 4 )  2   wo 4  solution, precipitation crystallization of ammonium paratungstate, and the energy consumption is small, crystallization speed is fast, easily to recovery the fine particle APT. The neutralization method is carried out in a reaction tank with a liner rubber. Heating with hydrochloric acid and (NH 4 )  2 WO 4  solution, ammonium paratungstate crystalliz...

Evaporation crystallization method is the most commonly used method of preparation of ammonium paratungstate , this method of technology and equipment is simple, easy to large-scale, have a certain role in the purification at the same time,it has been favored by industrial production. When the ammonium tungstate solution heated, the ammonia concentration decreased, (NH 4 ) 2WO 4  solution concentration gradually increased, ammonium paratungstate crystallization, the reaction is: 12(NH 4 )2WO 4 ==5(NH 4 )2O·12WO 3 ·5H 2 O+14NH 3 ↑+2H 2 O In industrial production, the degree of evaporation crystallization is generally based on the amount of molybdenum allowed in the solution and the product. There are usually two ways of batch intermittent operation and continuous crystal operation. The batch intermittent operation was carried out in a jacketed heated stirred tank, and a solution of (NH 4 ) 2WO 4  having a density of 1.16-1.28 g / cm3 was added to the reactor an...

Ammonium paratungstate (APT) is an important part of tungsten smelting, whether it is using chemical precipitation method, ion exchange method or extraction method, they all have to through the process of ammonium trioxide to produce qualified APT.  APT is an important tungsten intermediate products , the higher the puritythe greater the value, so APT preparation process is also the further purification of tungsten. Freezing crystallization method is one of the most commonly used methods for the preparation of ammonium paratungstate, which is the use of liquid ammonia to freeze the APT, so called frozen crystals.  The freeze crystallization method was carried out in a liquid nitrogen cooled vacuum drier, and the ammonium tungstate solution was poured into an enamel plate pre-filled with liquid nitrogen (the volume ratio of ammonium tungstate solution to liquid nitrogen was 1: 2), stirring it and then   crystallized water and APT at the same time, Along w...