Silicon-containing sodium aluminate solution deep desiliconization method

Abstract

The invention belongs to a silicon-containing sodium aluminate solution desiliconization method and particularly relates to a silicon-containing sodium aluminate solution deep desiliconization method. In the invention, waste calcium chloride from industrial alkaline production is used to prepare a Friedel salt (FS:3CaO.Al2O3.CaC12.10H2O), and the FS is used as a desiliconizing agent to perform deep desiliconization of the silicon-containing sodium aluminate solution. The method of the invention can remove at least 60 percent of silicon dioxide from the silicon-containing sodium aluminate solution. The aim of the invention is to prepare FS by using the rich calcium chloride resource and apply the FS in the deep desiliconization of the silicon-containing sodium aluminate solution in an oxide aluminum industry. When the method is used, the recycling of waste resources can be realized, environmental pollution and the production cost of aluminum oxide can be reduced and the economic benefits of enterprises can be improved.

Description

technical field [0001] The invention belongs to a method for desiliconizing sodium aluminate solution containing silicon, in particular to a method for preparing Friedel salt (FS: 3CaO Al 2 o 3 ·CaCl 2 10H 2 O), and use FS as a desiliconizing agent to use the method of carrying out deep desiliconization to silicon-containing sodium aluminate solution. technical background [0002] my country's bauxite reserves are rich, but more than 80% of the aluminum-silicon ratio (Al in bauxite 2 o 3 and SiO 2 mass ratio) of 4 to 8 middle and low grade diaspore bauxite cannot be directly applied to the Bayer process with low production cost, it needs to undergo desiliconization to increase its aluminum-silicon ratio, and then use economical The Bayer process produces alumina. [0003] Bauxite contains, in addition to the hydrated form of alumina, impurities such as iron, titanium and silicon. The iron and titanium present in bauxite are generally insoluble in caustic soda solutio...

AI Technical Summary

Problems solved by technology

Therefore, bauxite containing large amounts of silica is difficult to process

The presence of silica in bauxite causes at least two problems when digesting bauxite: (i) dissolution and reprecipitation of silica as complex sodium silicate, thereby consuming caustic soda; (ii) complex Re-precipitation of sodium aluminosilicate on unit surfaces causes fouling buildup, which is particularly problematic when fouling builds up on heat exchange surfaces

[0005] There have been many studies on the deep desilication of silicon-containing sodium aluminate solutions. The calcium-containing compounds that can be used as desilication agents include calcium oxide, calcium hydroxide, calcium carbonate, cubic hydrated calcium aluminate and hydrated calcium aluminum carbonate. The desiliconization depth of the above desiliconization agent is not high

Increasing the amount of desiliconizing agent can increase the silicon content index of the refined solution, but at the same time cause a large loss of alumina

Moreover, the above-mentioned desiliconization agents will directly or indirectly consume CaO or Ca(OH) 2 , while CaO or Ca(OH) 2 It is a non-renewable resource, and the price is rising year by year. Therefore, the development of a new type of low-cost and high-efficiency desiliconization agent is an effective way to produce high-quality and high-yield alumina

In my country's soda industry, milk of lime (Ca(OH) 2 ) to deal with recovered ammonia, a large amount of calcium chloride produced is discharged, and piled up into mountains over time, commonly known as "white sea", which not only wastes resources, but also seriously pollutes the environment, so how to deal with the discharged calcium chloride has become a big problem burden

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