Method for preparing alpha-type high-strength gypsum from phosphogypsum

Abstract

The invention relates to a method for preparing alpha-type high-strength gypsum from phosphogypsum, belonging to the technical field of building materials. The method for preparing alpha-type high-strength gypsum from phosphogypsum is characterized by employing a semi-liquid-phase process and comprising the following steps: 1) blending phosphogypsum with quicklime with an amount identical to the sum of P2O5 and F in the phosphogypsum so as to neutralize the phosphogypsum and then carrying out aging for 1 d ; 2) weighing, on the basis of the total mass of the phosphogypsum, 0.01-0.5% of ternary organic acid and 0.5-2% of hypervalent sulfate, mixing the ternary organic acid and the hypervalent sulfate, and dissolving the obtained mixture in water with a temperature of 80-90 DEG C so as to prepare a composite crystal-type control agent; 3) adding the composite crystal-type control agent and water in a solid-liquid ratio of 4: 1 to 2: 1 into the neutralized phosphogypsum so as to form thick slurry; and 4) spreading the prepared slurry in an autoclave in layers, each layer being 5-15 mm thick, carrying out constant-temperature treatment at 120-150 DEG C for 3-6h, and then carrying out drying and ball-milling so as to obtain alpha-type high-strength gypsum powder. With the method in the invention, the prepared alpha-type high-strength gypsum is in the form of a short-column-like crystal with stable quality, and has 2-hour flexural strength of 4.9 MPa and drying compressive strength of 32.3 MPa; and obvious social, environmental and economic benefits are obtained.

Description

technical field

[0001] The invention relates to a method for preparing alpha-type high-strength gypsum by using phosphogypsum, which belongs to the technical field of building materials. Background technique

[0002] Phosphogypsum is mainly an industrial by-product of phosphoric acid produced by wet process in phosphorous chemical enterprises. About 4-5 tons of phosphogypsum is emitted from 1 ton of phosphoric acid produced by wet process. In 2004, the emission of phosphogypsum in my country has exceeded 22 million tons, and with the increasing demand for phosphoric acid and ammonium phosphate in industry and agriculture, the emission of phosphogypsum is also increasing. The Implementation Plan points out that in 2010, the emission of phosphogypsum in my country has reached about 60 million tons. The open-air stacking of phosphogypsum not only occupies a large area of ​​land, but also pollutes the environment. The main component of phosphogypsum is dihydrate gypsum (CaSO 4...

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