Method for producing ultrawhite aluminum hydroxide and by-products from high-alumina fly ash by using high-temperature alkaline leaching

Abstract

The invention belongs to the technical field of metallurgy and in particular relates to a method for producing ultrawhite aluminum hydroxide and by-products from high-alumina fly ash by using high-temperature alkaline leaching. The method comprises the following steps of: carrying out two-stage pre-desilicication on the high-alumina fly ash, and then carrying out leaching reaction for 1.5-2.5 hours at 230-280 DEG C to respectively produce the ultrawhite hydroxide as well as wollastonite and ferrugination hydrogarnet as by-products. According to the method, a high-temperature sintering process in which low alumina-silica ratio firing temperature is difficult to control in the process of extracting aluminum hydroxide from the high-alumina fly ash is avoided, the energy consumption is reduced, the comprehensive utilization value of the fly ash is improved, and meanwhile, products in each link can be recycled in each procedure; and an economic and effective technical approach is provided for preparation of the ultrawhite aluminum hydroxide and alumina from the high-alumina fly ash.

Description

technical field [0001] The invention belongs to the technical field of metallurgy, and in particular relates to a method for producing ultra-white aluminum hydroxide and by-products by high-temperature alkali leaching of high-alumina fly ash. Background technique [0002] Fly ash is rich in resources, and the output is large and concentrated. Every time a power plant generates 1000Kwh of electricity, an average of 87kg of fly ash is produced. With the continuous increase in power demand, its emissions will increase year by year. It also pollutes the environment; at the same time, with the depletion of bauxite resources in my country and the world, extracting alumina from fly ash is in line with my country's industrial policy of developing circular economy and building a resource-saving and environment-friendly society , has become a focus of attention and research in related industries in recent years. [0003] Common methods for extracting alumina from high alumina fly ash i...

AI Technical Summary

Problems solved by technology

Among them, the alkali method includes limestone sintering method and soda lime sintering method. The traditional limestone sintering method uses fly ash as raw material to produce alumina by limestone sintering method. The main steps include: raw material preparation and pulverization, alumina alkali Liquid leaching, liquid-solid separation, carbon content of alumina solution, Bayer dissolution, seed separation, aluminum hydroxide separation and roasting, and cement clinker calcination, etc. Limestone sintering method has high energy consumption (sintering temperature 1300-1400 ℃) , the one-time resource consumption is large (about 2.3 tons of limestone resources are consumed per 1 ton of fly ash), and the discharge of silicon-calcium slag is large (about 3.2 t of silicon-calcium slag is produced per 1 ton of fly ash); pre-desilication + soda lime The sintering method is a technology independently developed by Inner Mongolia Datang International Renewable Resources Development Co., Ltd. to use high-alumina fly ash to extract alumina and co-produce silicon products such as white carbon black and active calcium silicate. Silicon technology, improve the ratio of aluminum to silicon, reduce the amount of slagging, mainly including: pre-desiliconization, white carbon black (active calcium silicate) preparation, raw slurry preparation, clinker firing, first and second stage desiliconization at atmospheric pressure, carbon black sorting, sorting and roasting; the improved soda-lime sintering method is a technology independently developed by the China University of Geosciences (Beijing) Mineral Materials National Professional Laboratory, etc., using fly ash to extract alumina and co-produce wollastonite. The main difference of the Datang process is that the calcium ratio of the sintering ingredients is reduced from 2 to 1, which reduces the energy consumption and slag formation of sintering, but the sintering reaction of the above-mentioned soda-lime sintering method is complicated, and the dissolution rate of alumina is not high

The more representative method in the acid method is the sulfuric acid leaching method. This method is: first soak the fly ash with a certain concentration and volume of NH4F as a cosolvent, and then use a certain concentration and volume to soak the fly ash. The volume of H2SO4 is dissolved at a certain temperature, and Al is dissolved in the form of Al2(SO4)3 The form is leached from the fly ash, removes the impurity Fe and then adds (NH4)2SO4 to react with it to form NH 4Al(SO4)212H2O, and finally NH4 heated at 950 °C >Al(SO4)212H2O can get Al2O3; At present, there is also hydrochloric acid method for acid treatment of fly ash. This method is: react fly ash with hydrochloric acid with a concentration of 26%, keep the temperature at about 100 ℃ for 1 to 2 hours, filter, After separation, a qualified eluate is obtained, then evaporated and crystallized, and the crystalline aluminum chloride product is precipitated, and the alumina product is obtained by calcination, but the extensive use of acid severely corrodes the equipment, and it is difficult to achieve large-scale industrial production. The process of acid-base combined method The process is more complicated and the consumption of alkali is large

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