Method for preparing alpha high-strength gypsum from freezing method nitrophosphate byproduct calcium nitrate tetrahydrate

Abstract

The invention discloses a method for preparing alpha high-strength gypsum from a freezing method nitrophosphate byproduct calcium nitrate tetrahydrate. The method comprises the following steps: decomposing phosphorite by utilizing nitric acid; filtering out acid-insoluble substances, carrying out freezing crystallization on an acidolysis solution, filtering out calcium nitrate tetrahydrate, regulating the concentration of calcium ions in a calcium nitrate solution, respectively preheating the calcium nitrate solution, phosphoric acid and ammonium sulfate mixed solution to 95-110 DEG C, mixingin a crystallization tank, and carrying out constant-temperature reaction for 8-12 hours to directly obtain the alpha-type high-strength gypsum product; the mass percent of the decalcifying acid solution for preparing the mixed solution of phosphoric acid and ammonium sulfate in the step (5) is less than or equal to 35%, and the mass percent of the decalcifying acid solution for preparing the calcium nitrate solution in the step (4) is less than or equal to 50%. The method disclosed by the invention has the beneficial effects that the high-purity and high-quality alpha high-strength gypsum isproduced by utilizing the byproduct calcium nitrate tetrahydrate of the existing freezing method nitrophosphate fertilizer process flow, the new application of the calcium nitrate tetrahydrate is increased, the operation is simple, and the cost is low.

Description

technical field [0001] The invention relates to a method for preparing α-high-strength gypsum from calcium nitrate tetrahydrate, in particular to a method for preparing α-high-strength gypsum from calcium nitrate tetrahydrate by-product of freezing nitrophosphate fertilizer. Background technique [0002] The mineral composition of α-type high-strength gypsum is α-type hemihydrate gypsum. The α-type hemihydrate gypsum with different crystal forms has different gel strength, and the strength of the needle-like α-type hemihydrate gypsum is the lowest, even worse than that of the scale-like β-type hemihydrate gypsum. Short columnar α-type hemihydrate gypsum has the characteristics of small water-to-paste ratio, short setting time and high flexural and compressive strength under standard consistency. It is widely used in gypsum ceramic molds, precision casting, building decoration materials and other fields. Therefore, the production of short columnar α-type hemihydrate gypsum i...

AI Technical Summary

Problems solved by technology

The Norsk Hydro frozen nitric acid phosphate fertilizer plant imported from Norway by our country is produced by using domestic phosphate rock with low grade and high impurity content, and it is difficult to freeze and separate calcium nitrate. There are only a few sets of phosphate fertilizer installations

The disadvantages of this process are huge equipment investment, long process, harsh requirements on raw materials, complicated operation, and equipment not suitable for domestic phosphate rocks. At present, Guizhou Batian Ecological Engineering Co., Ltd. has successfully completed the first domestic A set of 300,000 tons of domestically produced frozen nitrophosphate fertilizer plant was put into trial operation, and the by-product calcium nitrate is mainly used to produce calcium ammonium nitrate fertilizer

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