Method for preparing type II anhydrous gypsum by fluidizing and roasting beta-semi-hydrated gypsum

Abstract

The invention discloses a method for preparing type II anhydrous gypsum by fluidizing and roasting beta-semi-hydrated gypsum, which comprises the following steps: step 1, fluidizing and roasting beta-semi-hydrated gypsum powder in a small fluidized bed, keeping the gas-solid ratio at 0.2320-0.2680 L.( g.min)-1, and controlling the heating rate at 5-15 DEG C / min; 2, when the temperature of a roasting furnace is increased to 700-900 DEG C, carrying out heat preservation for 100-200 min; 3, after the heat preservation stage is finished, naturally cooling to normal temperature, and taking out the gypsum. According to the method, efficient mass transfer and heat transfer of the fluidized bed are utilized, the roasting efficiency is improved, and the content of the II-type anhydrous gypsum can reach 85% or above; impurities can be removed through high-temperature fluidized roasting, and the quality of the II-type anhydrous phosphogypsum subjected to high-temperature roasting is slightly influenced by the impurities.

Description

technical field [0001] The invention relates to a method for preparing type II anhydrous gypsum by fluidized roasting of β-hemihydrate gypsum, belonging to the field of calcining gypsum powder. Background technique [0002] Phosphoric acid is an important industrial product. Its production is mainly based on sulfuric acid wet process. The by-product of this method is mainly phosphogypsum. Every ton of phosphoric acid produced produces about 7 tons of phosphogypsum containing about 20% of free water. The output of the product is huge, with a total of more than 20 million tons by phosphate fertilizer chemical companies and other companies every year, which not only takes up a lot of storage space, but also brings serious pollution to the surrounding environment. Therefore, the recovery and resource utilization of phosphogypsum is essential, and a large number of researchers have begun to study the comprehensive utilization of phosphogypsum. [0003] Phosphogypsum is an effect...

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Problems solved by technology

At present, the preparation of β-hemihydrate gypsum is an important research direction for the resource utilization of phosphogypsum. However, compared with type II anhydrous gypsum, the strength of ordinary building β-hemihydrate gypsum is lower, and the cementation strength of type II anhydrite is the same as that of phosphogypsum. The water resistance is better than that of ordinary building β-hemihydrate gypsum, and the high compression resistance makes Type II anhydrous gypsum a valuable building material

Chinese patent CN200810031163.0 announced "a high-strength water-resistant plaster plaster and its production method". Although this method can produce type II anhydrite, it will also be accompanied by other outputs. The output of type II anhydrite is not Not high enough to homogenize the material and pass the finished product during the gypsum calcination process

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