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Processing method for removing crystal substances of sodium oxalate during alumina production

A technology of production process and treatment method, applied in chemical instruments and methods, preparation of alkali metal aluminate/alumina/aluminum hydroxide, aluminum compounds, etc., can solve harsh reaction conditions, low utilization value, and low production efficiency and other problems, to achieve the effect of high recovery rate and high industrial application value

Active Publication Date: 2018-05-08
GUIZHOU BRANCH CHINA ALUMINUM IND
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, because the production of milk of lime and the causticization reaction of sodium oxalate belong to the internal diffusion control reaction model, the particle size of the reactants and the reaction temperature have a greater impact on the causticization of sodium oxalate, so the reaction conditions are relatively harsh.
In addition, the redissolution of aluminum hydroxide in the mixture into the sodium aluminate solution needs to be carried out under certain temperature and pressure conditions. After the aluminum hydroxide dissolves, it will be decomposed and separated in the process again, making the aluminum hydroxide in the system invalid. Circulation, low production efficiency; the industrial application value of calcium oxalate obtained from causticization is not high, and the amount of caustic alkali recovered is small, the utilization value is not high, the production process is complicated, and the reaction conditions are harsh

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0029] After drying, the spherical co-crystal of sodium oxalate and aluminum hydroxide with a particle size of -100 mesh and 100% sodium oxalate content of 37.0% is added to a hot water tank at 95-100°C with a stirrer at a solid-to-liquid ratio of 120g / L. Dissolution: pump the slurry obtained after 30 minutes of dissolution to a vacuum filter for filtration, the obtained primary filtrate contains sodium oxalate at a concentration of 41.10g / L, and the primary filter residue contains 96.8% aluminum hydroxide; the primary filtrate is pumped to the centrifuge Type spray dryer system, drying in the dryer, the dried product obtained is solid sodium oxalate with a purity of 99.5%, and the water in the filtrate is evaporated to obtain hot water after rapid cooling; the primary filter residue containing more aluminum hydroxide is used The hot condensed water is washed and filtered to obtain a secondary filtrate with a sodium oxalate concentration of 3.67g / L and a finished aluminum hydro...

Embodiment 2

[0031] After drying, the spherical co-crystal of sodium oxalate and aluminum hydroxide with a particle size of -100 mesh and 100% sodium oxalate content of 37.0% is added to a hot water tank at 95-100°C with a stirrer at a solid-to-liquid ratio of 150g / L. Dissolution: pump the slurry obtained after 30 minutes of dissolution to a vacuum filter for filtration, the obtained primary filtrate contains sodium oxalate at a concentration of 51.72g / L, and the primary filter residue contains aluminum hydroxide 96.2%; the primary filtrate is pumped to the centrifuge Type spray dryer system, drying in the dryer, the dried product obtained is solid sodium oxalate with a purity of 99.5%, and the water in the filtrate is evaporated to obtain hot water after rapid cooling; the primary filter residue containing more aluminum hydroxide is used The hot condensed water is washed and filtered to obtain a secondary filtrate with a sodium oxalate concentration of 4.20g / L and a finished aluminum hydro...

Embodiment 3

[0033]After drying, the spherical co-crystal of sodium oxalate and aluminum hydroxide with a particle size of -100 mesh and 100% sodium oxalate content of 37.0% is added to a hot water tank at 95-100°C with a stirrer at a solid-to-liquid ratio of 180g / L. Dissolution: pump the slurry obtained after 30 minutes of dissolution to a vacuum filter for filtration, the obtained primary filtrate contains sodium oxalate at a concentration of 55.14g / L, and the primary filter residue contains 90.8% aluminum hydroxide; the primary filtrate is pumped to the centrifuge Type spray dryer system, drying in the dryer, the dried product obtained is solid sodium oxalate with a purity of 99.5%, and the water in the filtrate is evaporated to obtain hot water after rapid cooling; the primary filter residue containing more aluminum hydroxide is used The hot condensed water is washed and filtered to obtain a secondary filtrate with a sodium oxalate concentration of 12.73g / L and a finished aluminum hydro...

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Abstract

The invention relates to a processing method for removing crystal substances of sodium oxalate during alumina production. The processing method is characterized in that the processing method comprisesthe following steps: (1) drying the crystal substances; (2) finely grinding the dried crystal substances; (3) adding the finely-ground crystal substances into water for stirring and dissolution; (4)filtering dissolution slurry; (5) drying filtrate containing the sodium oxalate to obtain solid sodium oxalate; (6) washing and filtering filter residue containing aluminum hydroxide, wherein the filter residue is used as finished aluminum hydroxide. The method disclosed by the invention effectively separates and recycles the sodium oxalate and the aluminum hydroxide co-crystallized from a sodiumaluminate solution to obtain the sodium oxalate with higher purity and the metallurgical grade aluminum hydroxide. An entire process has no wastewater and waste residue, purity of the recovered sodiumoxalate reaches 99.5%, and a total recovery rate of the sodium oxalate in a sodium oxalate and aluminum hydroxide crystal community can reach 100%, and the recovery rate is high.

Description

technical field [0001] The invention discloses a treatment method for removing sodium oxalate crystals in the alumina production process, and relates to a treatment method for the co-crystallization and precipitation mixture of sodium oxalate and aluminum hydroxide obtained by adding crystallization aids during the decomposition process of sodium aluminate solution. Background technique [0002] In the process of producing alumina by the Bayer process, the humic acid macromolecular organic matter brought in from the bauxite forms various sodium humates under the action of alkali and high temperature, and then gradually transforms into easily soluble sodium oxalate and Sodium carbonate. Sodium carbonate in the solution can be discharged from the system through a special production process, but sodium oxalate is difficult to remove. This substance precipitates with aluminum hydroxide when the temperature is low, dissolves in the solution when the temperature is high, and accum...

Claims

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Application Information

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IPC IPC(8): C01F7/14
CPCC01F7/144
Inventor 顾松青齐利娟杨桂丽郑洁尹中林
Owner GUIZHOU BRANCH CHINA ALUMINUM IND