Tungsten Oxide

Tungsten ore is mainly scheelite. The world's scheelite accounts for more than 2/3 of total, and China accounts for 72.1%. Some scholars have improved the method of using ammonium sulphate to decompose scheelite to prepare ammonium partrungstate . (1) Tungsten containing sulphuric acid and phosphorus mixed acid solution, wherein the concentration of tungsten trioxide is 25-150g/L, the concentration of phosphoric acid is 10 ~ 200g/L, and the concentration of sulphuric acid is 1.5 ~ 2.5mol/L. (2) The obtained tungsten containing mixed solution of sulphuric acid and phosphoric acid was mixed with oil to extract the two phase volume ratio of oil phase: water phase = 3:1-1:3, and the loading organic phase was obtained. (3) The obtained load organic phase was extracted by distilling water with volume ratio as oil phase: water phase = 3:1-10:1, and the stripping solution was obtained. (4) Ammonia was added to the stripping solution to control the free ammonia in the solution at 1-2mol/L a...

Tungsten ore is mainly scheelite. The world's scheelite accounts for more than 2/3 of total, and China accounts for 72.1%. Some scholars have improved the method of using ammonium sulphate to decompose scheelite to prepare ammonium partrungstate . (1) Tungsten containing sulphuric acid and phosphorus mixed acid solution, wherein the concentration of tungsten trioxide is 25-150g/L, the concentration of phosphoric acid is 10 ~ 200g/L, and the concentration of sulphuric acid is 1.5 ~ 2.5mol/L. (2) The obtained tungsten containing mixed solution of sulphuric acid and phosphoric acid was mixed with oil to extract the two phase volume ratio of oil phase: water phase = 3:1-1:3, and the loading organic phase was obtained. (3) The obtained load organic phase was extracted by distilling water with volume ratio as oil phase: water phase = 3:1-10:1, and the stripping solution was obtained. (4) Ammonia was added to the stripping solution to control the free ammonia in the solution at 1-2mol/L ...

Ammonium Paratungstate (APT) is an important raw material product in tungsten smelting process, the appearance is white crystalline. It is mainly used for the reduction of tungsten oxide or ammonium metatungstate, and also used as catalysts or additives in chemical industry. The tungsten concentrate is screened and pressed, ammonium tungstate solution was prepared by ion exchange or extraction process, after the crystallization process, ammonium paratungstate was obtained. In the process of smelting, ammonium paratungstate solution (Na2WO4) was obtained from tungsten concentrate by ion exchange or extraction, in order to truly use ammonium paratungstate, an important process is needed: crystallization process. The crystallization process of ammonium paratungstate is one of the important processes in the tungsten smelting process, the crystallization methods of APT in industry mainly include evaporation crystallization method, neutralization crystallization method and freezing crystalli...

Ultra coarse tungsten powder is an important raw material for the preparation of ultra coarse tungsten carbide. Compared with ultrafine tungsten powder, it has a series of advantages, such as less high-temperature defects, higher microhardness and smaller micro strain. The common process of reduction of ultra coarse tungsten powder by ammonium paratungstate is usually the reduction of ammonium paratungstate into blue tungsten or yellow tungsten, and then by hydrogen reduction furnace. The tungsten powder prepared by this method is regular polycrystalline, and the particle size is mostly controlled between 2 microns and 5 microns, and the powder size is moderate. In order to prepare ultra coarse tungsten powder, Li or Na was added to tungsten oxide, as far as the average degree of tungsten powder is concerned, the process of adding Li to ammonium paratungstate is the most effective, but there is a large amount of residue in the powder; At the same time, studies have shown that adding a ...

Ammonium paratungstate (APT) is the main raw material for the production of tungsten powder, tungsten carbide powder, tungsten wire and tungsten products. As everyone knows, the tungsten particle size, crystal morphology of its APT has a great "inherited" relationship, so, if want to produce nanometer tungsten powder and tungsten carbide powder, we first need to prepare ultrafine ammonium paratungstate (APT). It is an innovative method to prepare superfine ammonium paratungstate (APT) by microwave ultrasonic combined crystallization. Many scholars have shown that compared with traditional heating crystallization, microwave ultrasonic combined crystallization has obvious advantages in speeding up the crystallization rate, refining the particle size and improving the purity of products. So what's the difference between microwave - ultrasonic combined crystallization and traditional evaporation crystallization? Some scholars have used microwave-ultrasonic combined crystalli...

The crystalization method of evaporation and extraction method in the preparation of APT will produce crystallization liquor, leaving about 5% -10% of the WO 3   and part of the S, P, As, Mo, K, Na and other impurities.  It resulting in it can not directly return to the process, in order to improve the recycle of metal, it is necessary to set up auxiliary processes to recycle WO 3  in the liquor. Artificial scheelite was the method of ammonium paratungstate crystallization liquor treatment, the main precipitant is CaCl 2 , the main purpose of the artificial scheelite method is to convert the WO 3  in the crystallization liquor into a very insoluble calcium tungstate (artificial scheelite), then return to the acid process or hot ball milling process. Artificial scheelite made in three directions: 1. CaCl 2  precipitated artificial scheelite → acid decomposition and partial molybdenum → crude tungstic acid → return to the main...

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...

Ammonium paratungstate (APT) is an important tungsten intermediate product, not only in the purity and process requirements, as well as crystal grain size and crystal distribution requirements. Seemingly negligible some of the objective factors often play a key role in the final product often For these reasons the difference between the least, lost thousands of miles. 6. The impurities in the solution: As the solution P, As, Mo, Si and other impurities easily adsorbed on the crystal growth of the active point, hinder the crystal growth, but also makes the ammonium paratungstate grain thinning, make the quality of deterioration, and easy to enter the product during the evaporation crystallization process, affecting product quality, and even lead to product failure, so in the crystallization process, should take the control of crystallization rate, improve the concentration of NH 4 Cl in ammonium tungstate solution, stirring and washing agents and other methods, to achieve th...

Ammonium paratungstate (APT) is an important tungsten intermediate product, mainly white crystals, there are two kinds of flakes or needle-like, used in the manufacture of tungsten trioxide or blue tungsten oxide tungsten powder. The quality of tungsten products depends largely on the chemical purity of APT, particle size and particle size distribution. APT quality standards from the domestic manufacturers, the process and chemical purity are almost the same, but the production of APT products vary widely, this is because APT is a system engineering, not only the purity and process requirements, as well as crystal grain size and crystal distribution requirements, seemingly insignificant on some of the objective factors often play a key role in the final product is often because of these reasons the difference between the least, lost thousands of miles. There are lots of influence factors of ammonium tungstate, mainly include: the temperature of the solution, the degree...

Warn-out tungsten oxide including tungsten trioxide and blue tungsten oxide ect. which have been scrapped, and substandard thus must be reworked. This warn-out tungsten oxide which can not directly be used in tungsten smelting or other industries can be recycling. In this paper we will present a method for recovering ammonium paratungstate from warn-out tungsten oxide. 1. Handling the raw material Screen the warn-out tungsten oxide by a 60~80 mesh sieve to remove caking tungsten oxide and mechanical inclusions; then the grinding caking tungsten oxide and also screen it; 2. Autoclaving with ammonia for preparing ammonium tungstate solution 1) Dilute the concentrated ammonia in deionized water or use water to absorb liquid ammonia, get ammonia with concentrate of 8~20%; and then formulating the slurry with stirring at the ratio that weight of tungsten oxide: volume of ammonia is 150~350g/L; 2) Add hydrogen peroxide when the material contains blue tungsten oxide, compress the k...