Ammonium Paratungstate Crystallization Optimization Scheme

Ammonium paratungstate (APT) is an important intermediate compound in the production of tungsten powder, tungsten wire, tungsten-based alloy and all tungsten materials. It is also a bulk export commodity in China. Due to genetic relationship, APT crystal characteristics such as crystal morphology, lattice parameters, average particle size and particle size distribution, bulk specific gravity and fluidity have great influence on the material properties of tungsten powder, tungsten wire and tungsten alloy.

In the production process of ammonium paratungstate (APT), the content of WO₃ in APT crystallization mother liquor (ammonium tungstate solution) generally accounts for 5%-15% of the whole process, in addition to containing Mo, P, As and other impurities, the existing crystallization of ammonium paratungstate products with more impurities, low purity, larger particle size. Some enterprises use a method of separating and purifying ammonium paratungstate in ammonium tungstate solution. The ammonium tungstate solution is pretreated with nitrogen gas, then the composite active agent is added, stirred with a graphite stirring rod, and the temperature is lowered to obtain the purity of the ammonium paratungstate crystal. It is high in size, small in particle size, has a regular hexahedral crystal structure, and has few impurities. The specific process is as follows:

(1)The ammonium tungstate solution was placed in an open container, placed in a light-proof place, at the same time in the solution through nitrogen, kept for 8 hours after filtration, filtrate;

(2)The composite active reagent was added into the filtrate, the mass ratio of the filtrate and the composite active reagent was 10:1.3, the water bath was heated to 70 ℃, and the composite solution was stirred for 50 minutes.

(3)Cooling the composite solution after stirring, stirring with graphite stirring rod while cooling, rotating speed of 50r/min, cooling to 40 ℃ for 30 minutes, precipitating crystalline a, filtering, crystalline A and filtrate;

(4)The filtrate was cooled to 20 degrees, maintained for 10 minutes, precipitated and crystallized and filtered to obtain crystalline B.

(5)The crystallization of a and crystalline B are combined to dry, so that regular cubic hexahedron can be crystallized.

The compound active reagent is composed of dodecyl trimethyl ammonium chloride and octadecyl dimethyl betaine. The mass ratio of dodecyl ethanolamine sulfate, dodecyl trimethyl ammonium chloride and alkyl dimethyl betaine is 14.2:5.5.

Aiming at the coupling effect of pretreatment, composite active reagent and graphite stirring rod, this process abandons the conventional process parameters, designs a stage cooling process, improves the crystallization effect, and produces ammonium paratungstate product with uniform particle size, regular hexahedron crystal morphology, crystallization rate greater than 97%, less impurities, after conforming to the requirements. The need for continued application.

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