Method for preparing water purifying agent containing poly-aluminum chloride from aluminum ash, hydrochloric acid and optional red mud

Abstract

The invention provides a method for preparing a water purifying agent containing poly-aluminum chloride from aluminum ash, hydrochloric acid and optional red mud. The method comprises the following steps that the aluminum ash, sodium carbonate and / or sodium hydroxide and a calcium-containing raw material are mixed uniformly and calcined at an oxidizing atmosphere at 400-1000 DEG C, the calcinationproduced material is reacted with hydrochloric acid and the optional red mud until the pH of the slurry filtrate is 3.5-4.5, Al2O3 is 3-12m%, the basicity is 40-100 and calcium is 0.01-0.5mol / L, filtering is performed, the filtrate is the water purifying agent containing poly-aluminum chloride, and solid residues obtained by washing filter residues is further utilized or subjected to storage andlandfill. The step A solves the flammable and explosive problem of metal aluminum hydrolysis or acid hydrolysis hydrogen release which needs to be processed by two or three steps in the prior art, theproblem of water-ammonium-nitrogen after purification due to the fact that acid hydrolysis of aluminum nitride produces ammonium to enter the water purifying agent, the activation of low-activity alumina, especially alpha-alumina, and the stabilization and detoxification of aluminum ash containing fluorine; and during the use of water purifying agent products, the hardness of treated water is less increased.

Description

technical field [0001] The invention belongs to the technical field of nonferrous metallurgy and environmental protection, and specifically relates to a method for preparing a water purifying agent containing polyaluminum chloride from aluminum ash, hydrochloric acid and optional red mud. 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 alumin...

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 ; The reaction of aluminum nitride and hydrochloric acid to generate ammonium chloride is not easy to separate, and it enters the water purifying agent to cause ammonium nitrogen problems, which limits 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