Fly ash decomposition method

Abstract

The invention discloses a fly ash decomposition method. The method comprises the following steps: sending fly ash powder to an acidolysis process, adding sulfuric acid or hydrochloric acid or nitric acid to carry out a multistage acidolysis reaction with fluorite or industrial calcium fluoride as an activator in order to convert aluminum and iron elements in the fly ash powder into corresponding soluble salts entering a liquid phase, filtering, and separating to obtain an acid leachate containing aluminum salt and iron salt; washing acidolysis residues, mixing the acidolysis residues with water, adding sodium hydroxide to carry out an alkaline hydrolysis reaction, and filtering to prepare high modulus water glass; and washing alkaline hydrolysis residues, filtering, and sending the obtained acid leachate to a fore acidolysis process in order to be used for burdening. The decomposition rates of alumina and iron oxide in the fly ash reach above 90% and above 85% respectively; the modulus of the water glass is controlled between 3.2 and 3.8, the device investment is reduced, and the energy consumption and the raw material cost are reduced; and the method realizes recycling of decomposition residues, eliminates influences of secondary waste residues on environment, and lays a foundation for the preparation of aluminum, iron and silicon compounds.

Description

technical field [0001] The invention belongs to the technical field of comprehensive utilization of industrial waste, and specifically relates to a method for decomposing fly ash, in which aluminum and iron elements are converted into corresponding soluble salts, and silicon is converted into sodium silicate. Background technique [0002] Fly ash is a highly dispersed solid aggregate discharged from power plants, and its main chemical composition is SiO 2 、Al 2 o 3 , Fe 2 o 3 , Ca, Mg, S, K and unburned charcoal, etc. The preparation of high value-added products such as aluminum sulfate, alumina, polyaluminum chloride, polyaluminum ferric chloride, sodium silicate, and white carbon black from fly ash is an important way to comprehensively utilize fly ash as a resource. The premise of realizing this approach is to first obtain breakthroughs in key technologies such as the decomposition of fly ash. In particular, using an economical, reasonable, and effective method to d...

AI Technical Summary

Problems solved by technology

The disadvantage of this patent is that the reaction temperature of acidolysis is inversely proportional to the fineness of fly ash powder during mechanical activation, the fineness of fly ash is between 100 and 800 mesh, and the temperature of acidolysis reaction is between 230 and 160°C

The disadvantages of this method are: one, it is only applicable to the fly ash produced by the circulating fluidized bed boiler and the fly ash produced by the activated pulverized coal furnace. According to the known technology, the first method of activation treatment is mechanical activation, and the second is thermal activation. Both activation methods need to increase equipment investment and energy consumption, which is unfavorable for cost control.

Second, the decomposition rate is low, the alumina decomposition rate is only 60-70%, and the resource utilization level is not high

[0013] The disadvantage of this method is that the decomposition process needs to consume a large amount of fluosilicic acid, and because a large amount of hydrofluoric acid is produced in the reaction process, the requirements for equipment materials are relatively high.

There are few studies and reports on the acid leaching method, but from the reported processes, there are generally low decomposition rates, waste residue, waste gas or waste water, and certain environmental or safety burdens.

Images