Method for recycling alumina and sodium oxide from bayer process red mud

Abstract

The invention relates to a method for recycling alumina and sodium oxide from bayer process red mud. In the method, by adopting a high molecular ratio and high alkali concentration sodium aluminate solution, aluminum extracting reaction can be rapidly carried out under mild operating conditions, so that the recovery rate of alumina in the red mud reaches more than 85%, and the defects, such as equipment scabbing and the like can be effectively prevented and even eliminated; by implementing an efficient crystallization process of an intermediate product of hydrated sodium aluminate, the cycle efficiency of a dissolution medium is greatly improved; due to complete transformation of a phase in the aluminum extracting reaction, a reaction process of recycling sodium oxide can be performed at low temperature and normal pressure; and after secondary sodium removal reaction, the sodium oxide content in final red mud is not more than 1% and is far less than 6-8% of the bayer process red mud. Therefore, the red mud can be doped in large proportion for preparing cement, brick and roadbed materials, concrete additives, environmental remediation materials and other fillers, and the problems such as resource utilization of the red mud, potential environment hazard and the like are hopefully solved.

Description

technical field [0001] The invention relates to the field of resource recovery, in particular, the invention relates to a method for cleanly and efficiently recovering aluminum, alkali and other components from the red mud waste residue of a Bayer process alumina plant. Background technique [0002] The metal aluminum and alumina industry is an important basic raw material industry for the development of the national economy. More than 90% of the total output of industrial alumina is used for electrolytic production of metal aluminum, and the rest is used in the fields of electronics, refractory materials, petroleum, chemical industry, ceramics, environmental protection and pharmaceuticals. [0003] At present, the industrial production method of alumina is basically alkali method, mainly including Bayer method, sintering method and Bayer-sintering combined method. At the same time, the resources faced by my country's alumina industry are characterized by the fact that 98% ...

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Problems solved by technology

At the same time, the resources faced by my country's alumina industry are characterized by the fact that 98% of the bauxite is hard and difficult to dissolve diaspore type bauxite, and the A / S (aluminum-silicon ratio) is 4-7. Low-grade ores are mainly low-grade ores, and the internationally accepted Bayer method is used to treat ores in my country, which requires high temperature and high pressure dissolution conditions; The alkali content is high, and the red mud stockpiled in large quantities in the industry not only wastes resources such as alkali aluminum, but also has potential environmental hazards

Comalco first proposed a hydrothermal method with relatively mild operation in the patent. The recovery rate of alkali reaches 80-90%, but the recovery rate of alumina is low, and the A / S in red mud is still greater than 1. Even if the operating temperature is as high as 300 ° C, oxidation Improvements in aluminum recycling rates are still very limited

In 1982, Cresswell used the hydrothermal method to recover alumina and sodium oxide from the red mud of the Bayer process. The dissolution process was high temperature and high pressure, and the medium circulation was realized by evaporating a large amount of water, which required high energy consumption.

[0006] Patent CN101607725B provides a method for recovering alumina and sodium oxide from Bayer process red mud under low temperature and low pressure conditions. The process has too high requirements for the crystallization process of sodium aluminate, and it is difficult to meet the premise of efficient medium circulation, and then it is difficult to realize Economical and efficient recovery process of sodium oxide from red mud

Patent CN101538058B discloses a method for recovering alumina and sodium oxide in red mud by low-temperature and low-pressure hydrochemical method, but this method cannot solve the problem of equipment scarring in the process of extracting aluminum from red mud, and consumes much energy during the recovery process of sodium oxide higher

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