Method for preparing water purifying agent containing polyaluminum sulfate from aluminum ash, sulfuric acid and optional red mud

Abstract

The invention provides a method for preparing a water purifying agent containing polyaluminum sulfate from aluminum ash, sulfuric acid and optional red mud, and the method comprises the following steps: uniformly mixing the aluminum ash with sodium carbonate and / or sodium hydroxide and a calcium-containing raw material, roasting at 400-1000 DEG C in an oxidizing atmosphere, reacting a roasted product with the sulfuric acid and the optional red mud until the pH value of slurry filtrate is 3.0-4.0, Al2O3 accounts for 5-12m%, and the basicity is 40-75, filtering to obtain filtrate as the water purifying agent containing the polyaluminum sulfate, and washing filter residue to obtain solid residue for further utilization or tockpiling and landfill. Through the steps of mixing and roasting, theflammable and combustible problems of hydrogen released by metal aluminum hydrolysis or acidolysis, the ammonium nitrogen problem in purified water caused by entering of ammonium produced by acid hydrolysis of aluminum nitride into the water purifying agent, the activation problem of low-activity alumina, especially alpha-alumina, and the problems of stabilization and harmlessness of fluorine in the aluminum ash which need two or three steps to be treated in the prior art can be solved in one time. The hardness of treated water increases slightly during the use of the water purifying agent product.

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 sulfate from aluminum ash, sulfuric 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 aluminum as...

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