Method for preparing water purifying agent containing polyaluminium chloride from aluminium ash

Abstract

The invention provides a method for preparing a water purifying agent containing polyaluminium chloride from aluminium ash, comprising the steps of: roasting aluminium ash, calcium carbonate and / or calcium oxide in an oxidizing atmosphere; allowing the roasted product to react with hydrochloric acid to prepare the water purifying agent containing polyaluminium chloride, and water washing the obtained filter residue to be used as the solid residue used for other purposes or being piled up and buried. The method oxidizes the metal aluminum contained in the aluminum ash into aluminum oxide, oxidizes the contained aluminum nitride into aluminum oxide and nitrogen, allows the aluminum oxide with low reaction activity to react to generate calcium aluminate, and thus the aluminum oxide is activated, thereby solving the flammable and explosive problems of generating hydrogen gas during metal aluminum hydrolysis or acidolysis, and solving the problem of purified water containing ammonium nitrogen caused by ammonium generated by ammonium nitride hydrolysis enters the water purifying agent; furthermore, polyaluminum chloride water purifying agent and polyaluminum ferric chloride composite water purifying agent are prepared. The process is simplified, the investment and operation cost are low, and the filter residue is a general solid waste.

Description

technical field [0001] The invention belongs to the technical field of nonferrous metallurgy and environmental protection, and in particular relates to a method for preparing a water purifying agent containing polyaluminum chloride from aluminum ash. Background technique [0002] Aluminum ash is an important solid waste in the aluminum industry. According to different sources and metal aluminum content, it is generally divided into primary aluminum ash and secondary aluminum ash; in addition to metal aluminum, aluminum ash generally also contains sodium chloride, potassium chloride, Fluoride salts, alumina, aluminum nitride. Primary aluminum ash has a relatively high metal aluminum content, and metal aluminum is usually recovered by methods such as salt bath treatment. Secondary aluminum ash includes the residue after recycling metal aluminum from primary aluminum ash, and its metal aluminum content is lower than that of primary aluminum ash; secondary aluminum ash can also...

AI Technical Summary

Problems solved by technology

Secondary aluminum ash has complex components and many impurities, so it is difficult to return to use after simple purification or treatment

[0008] 1. The hydrolysis of the contained metal aluminum or the reaction with hydrochloric acid to produce hydrogen gas requires higher requirements on the flame-proof and explosion-proof conditions of the equipment. Sometimes the combustion of hydrogen gas can be seen in the open reaction pool, and some often produce explosion sounds, which is a safety hazard. Hidden dangers, it is not easy to use low-cost FRP reaction vessels or reaction pools lined with FRP coatings; some aluminum ash also contains a small amount of cyanide, which may release extremely poisonous hydrogen cyanide gas in the early and middle stages of the reaction with hydrochloric acid , causing hidden dangers to the health and safety of operators, and when entering the water purifier product, it may cause the cyanide content of the purified water to exceed the standard;

[0009] 2. If the contained aluminum nitride is hydrolyzed to produce ammonia gas and ammonia water, it needs to be useful or can be sold. If the reservoir is blocked, it will affect the production of water purifiers. The preparation of ammonium chloride by hydrochloric acid absorption requires equipment investment and operating costs ; If it reacts with hydrochloric acid to generate ammonium chloride, it will not be easy to separate, and it will enter the water purifying agent to cause ammonium nitrogen problems, limiting the use of polyaluminum chloride water purifying agent;

[0010] 3. After water washing or pickling, the roasting of filter residue with calcium oxide and calcium carbonate activated alumina generally adopts a relatively high temperature of 1200-1400 ° C, and the equipment cost and energy consumption are high;

[0011] 4. The existing process usually requires two slurry reaction processes, two filtration and washing processes and a high-temperature roasting process for wet materials. In the two filtration and washing processes, the filter residue contains very fine solids, which are difficult to clean, and the filtration and washing are relatively slow. Difficult, consumes more fresh water, lower efficiency, needs to use leaf filter or plate-frame filter with higher pressure, cannot use high efficiency, fast speed, more fresh water consumption, less manual labor, less labor Vacuum belt filter with low strength and low operating cost; when the filter residue is sprayed with water, the finer parts are easy to lose and cause environmental pollution;

[0012] 5. The overall process is relatively complicated, the operating cost is high, the equipment investment is high, and the site and workshop area are large

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