Method for firstly extracting silicon and secondly extracting aluminum from fly ash

Abstract

The invention relates to a method to withdraw silicon and aluminum in sequence from coal ash; a NaOH solution with a mass concentration larger than 40 percent is used for leaching the coal ash, the silicon of the coal ash is dissolved in the form of sodium silicate, and after being separated, sodium silicate solutions and alkaline leaching residues with a ratio between aluminum and silicone more than or equal to 2 are produced; the dissolved sodium silicate solution is condensed into sodium silicate solutions of different concentrations, or used for preparing white carbon through a carbonation method; the alkaline residues are used for producing Al(OH)3 through a sodalime sintering method or limestone sintering method and further producing Al2O3, and the residues after the aluminum being extracted are made into stuff or used for producing concrete. The invention breakthroughs the original idea of directly extracting Al2O3 from the coal ash, and adopts the wholly novel technical route of extracting silicon first and aluminum secondly, thereby enhancing the aluminum silicon ratio of the alkali leached residues, simplifying the technique of extracting Al2O3, and increasing the extracting rate of aluminum from the coal ash.

Description

technical field

[0001] The invention belongs to the resource comprehensive utilization of fly ash, and relates to a method for extracting silicon dioxide and alumina from fly ash, in particular to a method for extracting silicon dioxide from fly ash to make the remaining ash The aluminum-silicon ratio of the slag is ≥ 2, and the lime or soda lime sintering method is used to produce metallurgical grade alumina, and the residue is used as a filler or a method for preparing cement. Background technique

[0002] A large amount of fly ash emitted by coal-fired power plants has caused serious pollution and damage to the surrounding agricultural production and natural ecology. The comprehensive utilization of fly ash has become an urgent problem to be solved.

[0003] Fly ash is also a mineral resource. Fly ash generally contains Al 2 o 3 About 15-40%, containing SiO 2 Most of them are above 40%, and the fly ash in some places contains Al 2 o 3 Above 40%, containing SiO 2 Ab...