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A method for improving the Bayer process high-carbon alkali solution evaporation and salt precipitation process

A process improvement, alkaline solution technology, applied in chemical instruments and methods, aluminum compounds, inorganic chemistry, etc., can solve the problems of high evaporation steam consumption, high carbon and alkali in the system, difficult salt precipitation, etc., and achieve the improvement of product particle size. Effect

Active Publication Date: 2022-05-13
GUIZHOU BRANCH CHINA ALUMINUM IND
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0005] This application aims at the problem of frequent water washing of the evaporator due to the increase of carbon and alkali in the existing process, high steam consumption of evaporation, difficulty in salt separation, and long-term high carbon and alkali in the system. In-depth study of the supersaturation system, aiming at the high carbon alkali system, put forward the evaporator optimized operating process technical conditions, and strengthen the measures of salt discharge, so as to improve the operation rate of the evaporator, reduce the system carbon alkali, and reduce the evaporation steam consumption

Method used

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  • A method for improving the Bayer process high-carbon alkali solution evaporation and salt precipitation process
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  • A method for improving the Bayer process high-carbon alkali solution evaporation and salt precipitation process

Examples

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Effect test

example 1

[0044] Example 1. Evaporating the N of the stock solution K The concentration is 160g / L, N C / N T is 0.15, and the discharge concentration of the falling film evaporator is controlled at N K 200g / L, forced discharge N K At 270g / L, two flashes are used for salt discharge operation, the forced discharge temperature is 105°C, once flashed to 95°C, flashed again to 90°C, flashed to N K The concentration is 295g / L. Final output N C / N T Dropped to 0.06, the washing cycle of the falling film evaporator is 20 days, and the washing cycle of the forced circulation evaporator is 5 days. After one month of operation, circulating lye N C / N T down to 0.1, after two months N C / N T down to 0.09, N after three months C / N T down to 0.08. The consumption of steam per ton is reduced to 0.26.

example 2

[0045] Example 2. Evaporating the N of the stock solution K The concentration is 160g / L, N C / N T is 0.14, and the discharge concentration of the falling film evaporator is controlled at N K It is 220g / L, forced discharge N K At 260g / L, two flashes are used for salt discharge operation, the forced discharge temperature is 105°C, once flashed to 95°C, flashed again to 90°C, flashed to N K The concentration is 295g / L. Add evaporative discharge salt to make seeds before flash evaporation, and the amount of seeds added is 80g / L. Final output N C / N T Dropped to 0.06, the washing cycle of the falling film evaporator is 20 days, and the washing cycle of the forced circulation evaporator is 5 days. After one month of operation, circulating lye N C / N T down to 0.1, after two months N C / NT down to 0.09, N after three months C / N T down to 0.08. The consumption of steam per ton is reduced to 0.26.

example 3

[0046] Example three, evaporate the N of stock solution K The concentration is 160g / L, N C / N T is 0.13, and the discharge concentration of the falling film evaporator is controlled at N K It is 220g / L, forced discharge N K At 270g / L, the method of one-time flash evaporation is used for salt discharge operation, the forced discharge temperature is 105°C, one-time flash evaporation to 90°C, and flash evaporation to N K The concentration is 290g / L. Before flash evaporation, add evaporative drainage salt as seeds, and the amount of seeds added is 30g / L. Final output N C / N T Dropped to 0.07, the washing cycle of the falling film evaporator is 25 days, and the washing cycle of the forced circulation evaporator is 4 days. After one month of operation, circulating lye N C / N T down to 0.09, after two months N C / N T down to 0.08. The consumption of steam per ton is reduced to 0.26.

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Abstract

The invention discloses a method for improving the evaporation and salt precipitation process of high-carbon alkali solution in the Bayer process. C / N T Different control of the output concentration of the falling film evaporator, when evaporating the raw liquid N C / N T <0.12, the falling film evaporator discharge concentration N K It is 230‑260g / L, when the original solution N is evaporated C / N T at 0.12≤N C / N T ≤0.14, the falling film evaporator discharge concentration N K It is 220‑240g / L, when the original solution N is evaporated C / N T When >0.14, the discharge concentration N of the falling film evaporator K It is 200‑220g / L; the ratio of carbon to total alkali to N C / N T For solutions greater than or equal to 0.12, control the discharge concentration of the forced circulation evaporator, and use forced forced discharge flash evaporation for salt precipitation or add caustic soda for salt precipitation. The invention can shorten the cycle of falling film evaporator and forced water washing, and circulate mother liquor N C / N T Gradually drop from above 0.12 to 0.06‑0.08.

Description

technical field [0001] The invention belongs to the field of Bayer method high-carbon alkali solution evaporation and salt precipitation process methods, and specifically relates to a method for optimizing raw solution evaporation process conditions with high carbon alkali content and improving salt precipitation process in the process of producing alumina by Bayer process. Background technique [0002] During the production of alumina by the Bayer process, the balance of water is achieved through the evaporation process, and the concentration is increased to meet the needs of the dissolution of diaspore ore. Generally by stock solution concentration N K About 160g / L, increased to mother liquor N by evaporation K The concentration is about 240-260g / L, N C / N T Generally within 0.09. At present, the domestic industry generally adopts energy-saving six-effect falling film evaporator to realize the concentrated operation of raw liquid. Due to the carbonate minerals such as...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C01F7/0666
CPCC01F7/0666
Inventor 李新华齐利娟张树朝邵帅杨志民李晓萍晏唯真
Owner GUIZHOU BRANCH CHINA ALUMINUM IND
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