Method for purifying sodium chromate
A purification method and technology of sodium chromate, applied in the direction of chromate/dichromate, etc., can solve the problems of easy clogging of crystallization equipment and difficult separation of sodium chromate crystals.
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Embodiment 1
[0048] The present embodiment provides a kind of purification method of sodium chromate, as figure 1 As shown, the steps are as follows:
[0049] Put 1 ton of sodium chromate coarse crystals obtained by the sub-molten salt method vanadium-chromium co-extraction process into a calcification tank, then add 1.5 tons of condensed water, 0.4 tons of chromium crystal washing solution, and add 1.46 tons of 20wt% milk of lime after dissolving Mixing, control the alkali concentration of the reaction slurry in the calcification tank to 250-260g / L, and then react at 80-85°C for 3 hours, then carry out solid-liquid separation through a plate and frame filter press, and the separated liquid enters the chrome buffer tank for storage ;
[0050] Then transfer the impurity-removed solution in the chrome buffer tank to the evaporator, and control the evaporator to evaporate at 120-130°C and -0.4-0.2Mpa until the concentration of sodium hydroxide in the concentrated solution is 460-470g / L. The...
Embodiment 2
[0055] The present embodiment provides a kind of purification method of sodium chromate, and its steps are as follows:
[0056] Put 1 ton of coarse sodium chromate crystals obtained by the sub-molten salt method vanadium-chromium co-extraction process into the calcification tank, then add 1.3 tons of condensed water, dissolve and then add 1.9 tons of 5wt% milk of lime for mixing to control the reaction in the calcification tank The alkali concentration of the slurry is 200-210g / L, and after reacting at 90-95°C for 1.5 hours, the solid-liquid separation is carried out through a plate and frame filter press, and the separated liquid is stored in a chromium buffer tank;
[0057] Then transfer the impurity-removed solution in the chrome buffer tank to the evaporator, and control the evaporator to evaporate at 130-140°C and 0.5-0.9Mpa until the concentration of sodium hydroxide in the concentrated solution is 470-480g / L. The concentration of sodium bicarbonate is 18-25g / L, and the ...
Embodiment 3
[0062] The present embodiment provides a kind of purification method of sodium chromate, and its steps are as follows:
[0063] Put 1 ton of coarse sodium chromate obtained by the sub-molten salt method vanadium-chromium co-extraction process into a calcification tank, then add 1.72 tons of condensed water and 0.18 tons of chromium crystal washing solution, and then add 2.3 tons of 12wt% milk of lime after dissolving Mixing, control the alkali concentration of the reaction slurry in the calcification tank to be 290-300g / L, and then react at 75-80°C for 5 hours, then carry out solid-liquid separation through a plate and frame filter press, and the separated liquid enters the chrome buffer tank for storage ;
[0064] Then transfer the impurity-removed solution in the chrome buffer tank to the evaporator, and control the evaporator to evaporate at 110-120°C and -0.6-0Mpa until the concentration of sodium hydroxide in the concentrated solution is 450-460g / L. The concentration of ...
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Abstract
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