Due to the new application of ammonium metatungstate in high-melting metals, ultra-fine alloys, petrochemical catalysts, nuclear energy, aerospace, and titanium casting, domestic and foreign scholars and tungsten industry scientific and technological workers through APT, AMT thermogravimetric analysis and differential thermal analysis As well as the research on the chemistry of hexavalent tungstate ion aqueous solution, using the functional relationship between the polymerization of tungstate anion and hydrated acid ion and the acid value function, the large molecular weight and high hydration of APT, the thermal decomposition of APT, the loss of crystalline water and the change of ammonia crystal form, etc., Developed organic reagent acid solution method, chemical precipitation, electrodialysis, ion exchange, extraction, neutralization, thermal dissociation and electrolysis (swimming) and other methods. According to the aqueous solution chemistry of tungsten and the thermal decomposition theory of APT and AMT, the production process of AMT is prepared by using AFT as raw material, acid neutralization method and thermal dissociation method.
In order to reduce the acid consumption and increase the conversion rate, a selectivity test was carried out on the addition of catalysts, and it was concluded that the addition of ammonium citrate and ammonium acetate can make the conversion rate of APT-AMT reach more than 99%, and the amount of acid is reduced by half; It is baked in a far-infrared rotary furnace, so that the conversion rate of thermal dissociation method is higher than 90%.
AMT can be prepared from sodium tungstate, tungstic acid, and ammonium tungstate, but the product purity and process are difficult to control. Although the electrolysis (swimming) method is a production method that can withstand industrial production verification, high product purity, short process, economical, and high recovery rate (above 97%), due to the difficulty in making the anode and the anode chamber, the one-time investment is large , and APT pulping, neutralization, and thermal dissociation furnaces can use production facilities, so there is a tendency to focus on improving the APT neutralization method and APT thermal dissociation process and equipment, and to AMT granulation, QZ-5 type Centrifugal spray drying and QP-1 spray drying device were tested.
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