Method for co-producing dawsonite and tobermorite from fly ash

Abstract

The invention provides a method for extracting alumina from fly ash. According to the mol ratio of CaO to SiO2 being 0.3 to 1.5 and the liquid-to-solid ratio being 5ml/g to 50ml/g, quick lime, fly ash and water ingredients are mixed; 5g/L to 100g/L of NaOH is added for regulating the pH value of slurry; the reaction is performed for 0.5h to 12h in a high-pressure sealed container with the temperature being 120 DEG C to 260 DEG C; through solid-liquid separation, digestion solution containing sodium metaaluminate as main ingredients and digestion slag containing tobermorite as main ingredients are obtained; then, CO2 gas with the volume concentration being 10 percent to 100 percent is introduced into the digestion solution; along with the reduction of the pH of the solution, aluminum oxide compounds are separated out in a crystal form; when the pH is 9.5 to 8.0, the gas introduction is completed; then, through the solid-liquid separation operation, crystals containing the dawsonite as the main ingredients are obtained. The method has the advantages that the low-cost recovery and utilization on aluminum resources in the fly ash can be realized; the obtained dawsonite can be used for producing aluminum salt chemical products, or can be used for producing metallurgy grade aluminum oxide and the like after being purified; the obtained tobermorite is used as ingredients for producing cement and concrete, and the product intensity can be improved.

Description

technical field [0001] The invention belongs to the technical field of resource utilization of solid waste, in particular to a method for extracting and co-producing alumina and calcium silicate hydrate from fly ash. Background technique [0002] Fly ash is one of the industrial solid wastes with the largest emissions and stockpiles in the world, and it is also one of the raw materials widely used in cement, building materials, and chemical industries. Dry fly ash is usually gray or off-white, while water-containing fly ash is gray-black, and the main oxide composition is SiO 2 、Al 2 o 3 , Fe 2 o 3 , CaO, MgO, TiO 2 、K 2 O, Na 2 O, MnO, SO 3 etc., where SiO 2 and Al 2 o 3 content of more than 70%. The application of fly ash can be divided into three levels: low, medium and high. The low-level application refers to road construction, soil improvement, mine backfill, etc.; the middle-level application refers to the use as building materials, such as for production ...

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Problems solved by technology

[0006] In order to solve the problems of complex process and low aluminum-silicon ratio of aluminum eluate in the prior art, the present invention provides a method for extracting and co-producing dawsonite and calcium silicate hydrate from fly ash; Improving the separation effect of aluminum / silicon under the premise of shortening the preparation process

In view of this, the present inventor attempts to shorten the process flow on the basis of the prior art, and carry out one-step reaction desiliconization to directly produce calcium silicate hydrate and aluminum products, but it has been difficult to overcome the low separation purity of Si / Al and the low purity of aluminum-silicon. Low ratio and other problems, the purity of the sodium aluminate eluate obtained by the separation of silicon / aluminum is not high

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