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Method for controlling precipitation of crystal alkali in evaporator

A technology to control evaporator and internal crystallization, which is applied in multi-effect evaporation, solution crystallization, alkali metal aluminate/aluminum oxide/aluminum hydroxide preparation, etc. It can solve the problems of increasing steam consumption, fouling of evaporator heating surface, and affecting Evaporation efficiency and other issues, to achieve the effect of reducing steam consumption, slowing down scaling speed and improving evaporation efficiency

Active Publication Date: 2014-08-13
GUIZHOU BRANCH CHINA ALUMINUM IND
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] Provide a method for controlling the precipitation of crystallization alkali in the evaporator, so as to solve the technical problems in the prior art that scaling on the heating surface of the evaporator due to crystallization alkali precipitation seriously affects the evaporation efficiency and increases steam consumption

Method used

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  • Method for controlling precipitation of crystal alkali in evaporator
  • Method for controlling precipitation of crystal alkali in evaporator

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0018] Take the plate falling film evaporator with 6-effect operation and 4-stage self-evaporation in countercurrent flow as an example.

[0019] as attached figure 1 As shown: the evaporated raw liquid (seeding mother liquid) is sent to the 6th effect and 5th effect of the evaporator 2 by the raw liquid pump 1 to evaporate, and the circulation pump 3 is continuously pumped to circulate the cloth film to evaporate, and then passed through the feeding pump 4 The solution evaporated in this stage is transported to the next-stage evaporator for evaporation. In this way, after the 6-stage evaporation, the solution enters the 1st to 4th-stage self-evaporator 5 through self-pressure in the 1-effect evaporator for further evaporating. Self-evaporation concentration, after 4 stages of self-evaporation, the solution is sent into the mother liquor settling tank 7 through the discharge pump 6 to separate carbonate and sulfate, and the overflow after separation (evaporation mother liquor)...

Embodiment 2

[0021] Take the externally heated natural circulation evaporator with 4-effect operation and 1-stage self-evaporation in countercurrent flow as an example to illustrate.

[0022] As shown in the attached figure: the evaporated raw liquid (seeding mother liquor) is transported to the fourth effect preheater 2 by the raw liquid pump 1, and then enters the fourth effect evaporator 3 to evaporate after being preheated by the preheater, and then passes through the middle pump 4. Transport the evaporated solution of this stage to the 3-effect preheater, and then enter the 3-effect evaporator for evaporation after being preheated by the preheater, and then transport the evaporated solution of this stage to the 2-effect preheater through the intermediate pump After being preheated by the preheater, it enters the 2-effect evaporator for evaporation, and then transports the evaporated solution of this stage to the 1-effect preheater through the intermediate pump, and then enters the 1-ef...

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Abstract

The invention discloses a method for controlling precipitation of crystal alkali in an evaporator. The evaporation mother solution after carbonate and sulfate are precipitated and separated is partially returned to one of final three-effect evaporators in the evaporation process to reduce the crystal precipitation amount of the carbonate and the sulfate in the final three effects. The method can be used for the countercurrent flow operation of the evaporation process. The evaporation mother solution is partially returned into the three-effect evaporators in the evaporation process to reduce the crystal precipitation amount of the carbonate and the sulfate in the final three effects. The ratio of the part of the evaporation mother solution returned to the evaporation process to the total amount of the evaporation mother solution is 0.5-1.5: 3. The method is suitable for a plate type falling film evaporator, and also suitable for an external heating type natural circulating evaporator. After the method is adopted, compared with the prior art, the precipitation amount of the crystal alkali on the heating surface of the evaporator is remarkably reduced, the scaling speed of sodium carbonate and sodium sulfate on the high temperature effect heating surface is slowed down, and the period of washing a boiling tank is prolonged so that washing water entering the production flow is reduced and the consumption of steam is reduced. Because the scales of the sodium carbonate and the sodium sulfate on the heating surface of the evaporator are reduced, the evaporation efficiency is greatly improved, and the average productivity of the evaporator is improved by 10 to 15 percent compared with the prior art.

Description

technical field [0001] The invention belongs to the technical field of alumina production in various metallurgical industries, and in particular relates to a method for controlling the precipitation of crystalline alkali in an evaporator during an evaporation process. Background technique: [0002] In the process of alkaline production of alumina, the carbonates and sulfides brought in by ore and lime react with caustic soda during the leaching (dissolution) process. Part of the sodium carbonate and sodium sulfate formed gradually accumulates. When decomposed in the mother liquor When sodium carbonate and sodium sulfate accumulate to a certain content after several cycles, when the mother liquor is evaporated to the required concentration, supersaturated sodium carbonate and sodium sulfate begin to crystallize until the equilibrium content at this concentration is reached. The amount of sodium carbonate and sodium sulfate precipitated in the evaporation process is equal to t...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C01F7/06B01D9/02B01D1/26
Inventor 王奎龚智远张成林王文志卢智勇陈世平刘华龙杨贵军尹建刚谷金安刘忠泉周立勋敖永黔王传跃吴建明杨拯房
Owner GUIZHOU BRANCH CHINA ALUMINUM IND
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