A method for preparing alumina by circulating and continuously electrolyzing sodium aluminate solution

Abstract

The invention provides a method for preparing aluminum oxide by circularly and continuously electrolyzing a sodium aluminate solution, and belongs to the technical field of production of aluminum oxide. The method for preparing the aluminum oxide by circularly and continuously electrolyzing the sodium aluminate solution comprises the steps that the sodium aluminate solution and a diluted NaOH solution are guided into an anode chamber and a cathode chamber separated by an ion exchange membrane correspondingly, the NaOH solution is subjected to reductive electrolysis on the cathode while the sodium aluminate solution is oxidized on the anode, and seed precipitation is conducted on an electrolyte, obtained after electrolysis, in the anode chamber, so that aluminum hydroxide is separated out, and electrolysis can be conducted again after solid-liquid separation; and the high-concentration NaoH solution, obtained through electrolysis, in the cathode chamber can be used for the leaching process of the aluminum oxide. According to the method for preparing the aluminum oxide by circularly and continuously electrolyzing the sodium aluminate solution, a hug seed precipitation tank is not needed, seed crystals do not need to be added, the decomposition rate is increased while energy is saved, and meanwhile, the high-concentration alkaline solution which can be used for leaching of the aluminum oxide is obtained.

Description

technical field [0001] The invention belongs to the technical field of alumina production, in particular to an oxygen cycle continuous electrolysis of sodium aluminate solution to prepare alumina, and belongs to the fields of nonferrous metal industry and chemical industry. Background of the invention [0002] Aluminum and its aluminum alloys have many excellent properties in terms of electrical conductivity, thermal conductivity, and antimagnetic properties, and have become the most widely used non-ferrous metals. The production and consumption of aluminum oxide, the raw material for electrolysis, are also increasing year by year. According to statistics, in the first half of 2014, the global alumina production was 53.46 million tons, of which my country's alumina production was 24.9 million tons, accounting for 46.58% of the global total. [0003] At present, the methods of alumina production at home and abroad mainly include Bayer method (Bayer), sintering method and comb...

AI Technical Summary

Problems solved by technology

[0005] 1. The tank voltage in the electrolysis process is as high as 3V, which exceeds the economical electrolysis level of 1.7V, resulting in higher power consumption costs

[0006] 2. During the electrolysis process, the oxygen evolution of the anode and the continuous acidification will cause part of the aluminum hydroxide to flocculate directly on the cation exchange membrane, blocking the ion channel of the cation exchange membrane, making the life of the ion membrane prematurely terminated, and aggravating the resistance of ion diffusion during the electrolysis process. Further increase energy consumption

[0008] 1. It is necessary to add additional sodium carbonate as an intermediate transition medium, which increases the amount of material circulation

[0009] 2. Since the sodium aluminate solution contains excess NaOH, the process utilizes NaHCO 3 to acidify NaAlO 2 process, additional NaHCO 3 To neutralize this part of NaOH, resulting in increased energy consumption and material cycle pressure

[0010] 2. The energy consumption of electrolysis is high, and the electrolysis effect is 100mA / cm 2 The cell voltage is about 2.6V under the current density, resulting in high energy consumption of the system. The electrolysis energy consumption per ton of alumina is as high as 1700 kWh, which greatly increases the production cost.

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