Method for preparing high-purity dihydrate gypsum whiskers by using industrial byproduct calcium chloride

Abstract

The invention relates to a method for preparing high-purity dihydrate gypsum whiskers by using an industrial byproduct calcium chloride. The method comprises the following steps: 1) preparing a calcium chloride solution from an ammonia-soda-process industrial byproduct calcium chloride slurry, heating the calcium chloride solution to 30-80 DEG C, and adding a nucleation accelerator and a crystal form control agent to obtain a reaction mother solution; and 2) adding a 40-60-DEG C sodium sulfate solution into the reaction mother solution, stirring to react for 30-40 minutes, keeping the temperature for 0.5-3 hours to obtain a dihydrate gypsum whisker slurry, and carrying out after-treatment to obtain the high-purity dihydrate gypsum whiskers. The surplus byproduct in the salt chemical industry production process is used as the raw material to prepare the dihydrate gypsum whiskers, of which the length-diameter ratio is 10-100, the crystal length is 50-500 mu m, the purity is 98% or above and the whiteness is 90 or above. The invention provides a high-added-value utilization scheme for the calcium chloride slurry byproduct; and the obtained gypsum whisker can be widely used in the fields of papermaking, chemical industry, novel construction materials, composite materials and the like.

Description

technical field [0001] The invention relates to a method for preparing high-purity dihydrate gypsum whiskers by using calcium chloride, an industrial by-product. Background technique [0002] Gypsum whiskers are calcium sulfate whiskers, also known as gypsum fibers, which combine the advantages of reinforcing fibers and ultrafine inorganic fillers. They are non-toxic, high strength, high toughness, high insulation, acid and alkali resistance, wear resistance, and High temperature, easy surface treatment, easy to compound with polymers, good infrared reflectivity and many other excellent physical and chemical properties, can be used as reinforcement and toughening agent or functional type in papermaking, rubber, coatings, paints, asphalt, anti-wear and sealing materials The filler can be directly used as filter material, heat preservation material, refractory heat insulation material, infrared reflective material and high insulation material for covering wires, and has good a...

AI Technical Summary

Problems solved by technology

[0003] At present, there have been some researches at home and abroad on the preparation process of gypsum whiskers. Most of the current processes for the preparation of gypsum whiskers have problems such as harsh process conditions, long production cycles, high production costs, and low product purity levels.

For example, in the patent "A Preparation Method of Gypsum Whiskers" (CN102797030A) disclosed by Tao Jun et al., raw gypsum is used as raw material, crystal aids are added, and gypsum whiskers are prepared by hydrothermal reaction. The reaction temperature is 105-130°C, and the pressure It is 202.65-506.63kPa, and the reaction time is 0.5-5h. This method requires higher temperature and longer reaction time; in the patent "preparation method of gypsum whiskers" (CN104264227A) disclosed by Feng Jinyang et al., using waste plaster mold as raw material, the Grind it into gypsum slurry, remove impurities, add a certain amount of hydroxyapatite whiskers and gypsum crystal conversion accelerator, and carry out hydrothermal reaction. The reaction temperature is 100-120°C, the pressure is 200kPa, and the reaction time is 4 —12h, the raw material of this process adopts waste and old gypsum molds, which has better environmental protection effect and lower production cost, but the synthesis temperature of the overall process is higher, requires a certain pressure, and the reaction rate is slow; Method for Whiskers" (CN104499040A) uses limestone sludge and dilute sulfuric acid as raw materials, prepares hemihydrate gypsum whiskers through hydrothermal reaction, and can obtain anhydrite whiskers after drying treatment. This method uses waste as raw materials to reduce production Cost, but the purity of the prepared gypsum whiskers is difficult to guarantee, the reaction conditions are required to be high pressure, strong acidity, and the reaction temperature is 115-125°C, which requires high durability of production equipment

[0004] At present, a large number of salt chemical enterprises adopt the "ammonia-alkali method" to prepare soda ash, which produces a large amount of calcium chloride by-products. Calcium chloride is mainly used in deicing agents, desiccants and additives in chemical production, but at this stage, it is generally in small batches. use, the demand is small, and the fluctuation is large. There is no method for large-scale utilization of calcium chloride in the relatively mature application field of calcium chloride. Therefore, a large amount of calcium chloride is unsalable and difficult to handle. storage and disposal, occupy a large amount of land resources, and cause adverse effects on groundwater, seriously affecting the development of salt chemical enterprises

Sodium sulfate, another important product of Salt Chemicals, is currently in the predicament of overcapacity, and most enterprises are operating at a loss

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