Method for producing alumina by using pulverized fuel ash

Abstract

The invention discloses a method for producing alumina by using pulverized fuel ash. The method comprises the following steps of: (1) mixing pulverized fuel ash with a roasting additive, and roasting to obtain roasting clinkers, wherein the roasting additive comprises calcium chloride; (2) adding water into the roasting clinkers, and filtering to obtain a filter cake a and a filtrate b; and (3) leaching the filter cake a with sulfuric acid, filtering to obtain a filter cake c and a filtrate d, and concentrating and roasting the filtrate d to obtain the alumina. The method provided by the invention has low roasting temperature, and contributes to saving energy; when the roasting additive is added, only the content of alumina in the pulverized fuel ash is required to be considered, and a complex burdening adjusting process is not required; a leaching time period is shortened, and leaching efficiency is increased; the siliceous modulus of a crude product is high, and the requirement of metallurgical grade can be met without further performing desiliconization; a plurality of products are coproduced, and special requirements on the content of alumina in the pulverized fuel ash are eliminated; the method can be applied to recycling of radioactive pulverized fuel ash containing uranium and thorium; and major components of tailings are calcium sulfate and calcium silicate and can be directly applied to building material production, and secondary pollution is avoided.

Description

technical field [0001] The invention relates to a method for producing alumina from fly ash, which can be widely used in the field of resource utilization of fly ash. Background technique [0002] The main components of fly ash are aluminum oxide and silicon dioxide, which account for more than 85% of its weight, so it is a relatively large source of silicon and aluminum. In 2010, the annual production of fly ash in my country was about 500 million tons, and based on the calculation of 30% content, the alumina content in the fly ash produced in my country was about 150 million tons. In 2010, the total output of alumina in my country was only 29.94 million tons, and the total output of the world (including my country) was only 86.28 million tons. In addition, fly ash from certain sources contains high concentrations of iron oxide and scattered and scarce metal elements such as gallium and germanium. The fly ash produced by pit-mouth power plants in Southwest my country and s...

AI Technical Summary

Problems solved by technology

The alkali / lime sintering method has the following disadvantages: a. If sodium carbonate, calcium oxide, and sodium carbonate / calcium oxide are used in combination for sintering, the sintering temperature is relatively high. In order to achieve a high alumina dissolution rate, the sintering temperature is generally It needs to be above 1100°C, and the energy consumption is high; b. If sodium hydroxide and sodium hydroxide / calcium oxide are used together for sintering, the sintering temperature is low, but the requirements for the sintered container are strict

Since alumina exists in the phase of mullite in fly ash, and according to experimental research, treatment such as mechanical grinding cannot cause phase transformation of mullite, therefore, whether sulfuric acid or hydrochloric acid is used, the leaching rate of alumina is relatively low. Low

In addition, the patents mentioned above mostly use high temperature and high pressure. Operating concentrated acid under such conditions will be very dangerous, and the requirements for containers are also very high.

[0005] To sum up, the patented technologies for resource utilization of fly ash that have been disclosed now all have some shortcomings, such as high energy consumption, harsh operating conditions, complicated process, high comprehensive cost, etc., and there are tailings treatment And secondary pollution and other issues, in addition, are not applicable to radioactive fly ash containing uranium and thorium

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