Method for decontaminating potassium sub-molten salt soluble crystal liquid and preparing chromic oxide

Abstract

The invention discloses a method for decontaminating potassium sub-molten salt soluble crystal liquid and preparing chromic oxide. The method comprises the following steps: (1) introducing CO2 to potassium sub-molten salt soluble crystal liquid, neutralizing potassium hydroxide in the solution, then adding seed crystals, controlling the temperature of the solution at 30-90 DEG C and removing aluminum and silicon; (2) introducing CO2 to the solution obtained in the step (1) to carry out room-temperature pre-carbonation; (3) adding a reducing agent to pre-carbonated feed liquid obtained in the step (2), heating to 120-170 DEG C, and carrying out heat preservation and solid-liquid separation after reaction is ended, so as to obtain a chromium hydroxide filter cake; and (4) drying and calcining the chromium hydroxide filter cake obtained in the step (3), so as to obtain a chromium sesquioxide product. By adopting a pre-acidification mode, the reducing agent is not added in pre-carbonation; no CO2 is introduced after the pre-carbonated feed liquid and the reducing agent are mixed; the method is high in conversion rate of hydrothermal reduction, fewer in intermediate products, high in total yield of chrome, high in purity of the sintered chromic oxide and fewer in impurities by controlling a proper pre-carbonation condition.

Description

technical field [0001] The invention relates to the field of chromium salt production, in particular to a new method for removing impurities in a crystal solution and preparing chromium oxide after the sub-molten salt reaction of chromium salt production. Background technique [0002] At present, the production methods of chromium salt are divided into calcium roasting, calcium-free roasting and liquid phase oxidation. Calcium roasting technology will be gradually eliminated due to low conversion rate and large amount of slag discharge. At present, the main methods of chromium salt production in my country are calcium-free roasting and sub-molten salt liquid phase oxidation. The main purpose is to reduce the emission of harmful chromium slag and reduce the pollution of the chromium salt production industry to the environment. [0003] The sub-molten salt liquid phase oxidation method has a high conversion rate, and can convert 99% of chromium into chromate into the leaching...

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Problems solved by technology

U.S. Patent US3899568 uses sodium dichromate to neutralize and add seeds, but the time for neutralization and heat preservation is as long as 9 to 12 hours

Chinese patent CN1070892 adopts chromium-containing sodium bisulfate as a neutralizing agent, which contains AlPO under stirring 4 and CrPO 4 One of sodium phosphate and phosphoric acid is added to the bottom liquid of the seed crystal at the same time, so that the aluminum in the solution and the trivalent chromium in the chromium-containing sodium bisulfate are converted into AlPO 4 -CrPO 4 It is difficult to solve the problem of high chromium strip loss while consuming sulfuric acid

For example (Guangye Wei, 2012, International Journal of Minerals, Metallurgy and Materials), in the presence of a large amount of carbonate, basic sodium chromium carbonate is formed, and this intermediate product can also generate chromium oxide when calcined at high temperature, as shown in the following formula However, a large amount of chromate is formed at the same time, which reduces the overall recovery in the redox process

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