Method for producing aluminum oxide based on calcification-carbonization transformation

Abstract

The invention belongs to the field of production of aluminum oxide, and particularly relates to a method for producing aluminum oxidizing based on calcification-carbonization transformation. The method comprises the following steps of: performing a calcification transformation reaction on white lime and middle and low-grade alumyte serving as a raw material in a caustic alkali solution of 1400-260g / L to obtain primarily-transformed slag; intruding CO2 into the primarily-transformed slag in clear water or a low-concentration sodium aluminum solution under an enclosed condition for carbonating obtain the secondarily-transformed slag; and dissolving the secondarily-transformed slag out by adopting a sodium hydroxide solution of 30-120g / L or a sodium aluminate solution of a corresponding concentration at the temperature of 40-100 DEG C to obtain novel structure slag which takes calcium silicate and calcium carbonate as main components and of which the aluminum to silicon ratio is 0.0-0.4, wherein the soda content can be lowered below 0.5 percent, and the comprehensive yield of aluminum oxide in a mineral raw material can be up to 90-100 percent. Due to the adoption of the method, the novel structural slag can be completely taken as a raw material in the cement industry, the problem of environmental pollution such as red mud space occupation and the like is solved completely, and a large amount of CO2 can be absorbed simultaneously in a production process; and the method is an environment-friendly and economical aluminum oxide production method.

Description

technical field [0001] The invention belongs to the field of alumina production, and in particular relates to a method for producing alumina based on calcification-carbonization transformation. technical background [0002] Most of the bauxite resources in China are diaspore bauxite, and most of them are low-grade aluminum resources with high aluminum and high silicon. At present, there are many methods of producing alumina in China with low- and medium-grade bauxite as raw materials. Among them, "a combined desiliconization method for low-grade bauxite invented by Chen Xiangqing et al. of Aluminum Corporation of China, China Patent Application No.: 200810115455" discloses the combined process of selective desliming and positive flotation for desiliconization Si, so as to increase the A / S ratio of raw ore, to achieve the purpose of reducing production costs; "A method for the joint production of aluminum hydroxide by lime sintering and Bayer process invented by Ma Wuquan and...

AI Technical Summary

Problems solved by technology

[0009] (1) After adding lime, the A / S in red mud dissolved by Bayer method is higher than that dissolved by conventional Bayer method, and the unit consumption of aluminum ore increases under the same dissolution conditions. Although the increase of lime helps to reduce the alkali consumption, But it reduces the comprehensive utilization efficiency of ore

[0010] (2) The consumption of lime increases, so the consumption of limestone and coke also increases

[0011] In summary, although the alkali consumption is reduced with the increase of lime addition, it will also increase the aluminum content in red mud, which will lead to a decrease in the comprehensive utilization rate of valuable elements in bauxite.

Therefore, in the alumina production process using the lime Bayer process, the amount of slaked lime usually used is 10% to 15% of the mineral amount. Under this condition, the mass ratio of alumina to silica in the residue generated during the production process is still 1.3 ~1.4, which is very unfavorable for processing low-grade bauxite, and the content of sodium oxide in red mud is more than 4%, so it is difficult to use

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