Thick layer self leveling-let phosphogypsum turn waste into treasure


Release time:

2020-05-25

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Phosphogypsum is an industrial solid waste residue produced when phosphate rock is treated with sulfuric acid in the process of phosphoric acid production, and its main component is CaSO4 · 2H2O. China is the world's largest producer of phosphate fertilizer and the largest by-product of phosphogypsum. According to the statistics of China Phosphate Fertilizer Industry Association, at present, the historical stock of phosphogypsum in China exceeds 0.5 billion tons, and the annual new production is about 70 million tons. The comprehensive utilization rate is less than 40%, and the stock of phosphogypsum is still increasing. The soluble phosphorus, heavy metals and fluoride contained in phosphogypsum are easy to leak with wind and rain, which not only occupies a lot of land, but also has major safety hazards and environmental risks, which has become a bottleneck restricting the sustainable development of phosphorus chemical industry. With the increasingly stringent environmental protection requirements and green development constantly put forward higher requirements for the industry, phosphogypsum has reached the point where it must be disposed of vigorously.
 
Phosphogypsum is a useful base material in many fields. The comprehensive utilization of phosphogypsum can not only solve the problem of stacking phosphogypsum but also solve the problem of environmental pollution. Phosphogypsum modification and its application is one of the current research hotspots. Phosphogypsum is mainly in the process of phosphoric acid production, phosphate rock after sulfuric acid erosion of solid waste, is a recyclable material, especially in the current cycle of sustainable development ideas, phosphogypsum is in a number of areas have been applied. Phosphogypsum is a color is off-white or yellowish white and mainly in the needle-like crystals, polycrystalline nuclear crystals, monodisperse plate-like crystals, dense crystal crystalline form of fine powder solid. The main mineral component of phosphogypsum is gypsum, which accounts for about 96% ~ 97% in the whole material of phosphogypsum, followed by quartz and mineral selection agent residue, which accounts for about 3% of phosphogypsum. The moisture content of phosphogypsum increases rapidly with the increase of temperature, the solubility of phosphogypsum is very small and the solubility decreases with the increase of temperature, the permeability between layers is greater than the permeability in the horizontal layer, and the phosphogypsum material is a strain softening material. The main chemical components of phosphogypsum are calcium oxide and sulfur trioxide. Phosphogypsum also contains a certain amount of crystal water and impurities such as sulfur dioxide, phosphorus, fluorine and organic matter. The particle size of phosphogypsum is normally distributed and the distribution is relatively concentrated. The amount of impurities in phosphogypsum is closely related to the morphology of phosphogypsum. Phosphogypsum has the characteristics of high temperature resistance and chemical corrosion resistance. The biggest advantage of phosphogypsum is high strength and good toughness. Phosphogypsum has a very strong affinity with polymers, which makes phosphogypsum easy to be surface treated with polymers and can also be processed with polymers to form composite materials.
 
To realize the large-scale utilization of phosphogypsum, it is necessary to break through the high-value utilization technology and develop high value-added products. In the past 10 years, the use of phosphogypsum to produce new gypsum building materials has made great progress. New gypsum building materials products to paper gypsum board, gypsum block, high-strength gypsum powder, gypsum-based dry-mixed mortar, gypsum-based self-leveling and assembly building technology has also made a major breakthrough. The level of comprehensive utilization of industrial by-product gypsum technology and equipment has been significantly improved. my country has developed processes and equipment with Chinese characteristics for large-scale utilization of phosphogypsum, and has reached a relatively advanced level in core technology and equipment such as impurity removal process, drying and calcination. And realize industrial application. There are also significant improvements in large-scale, supporting, automation, intelligence, energy saving and consumption reduction. The comprehensive utilization industry of phosphogypsum resources has shown a certain degree of industrial concentration, and the development trend of industrial agglomeration and park is obvious. In Guizhou, Shandong, Hubei, Yunnan, Sichuan and other places have formed a comprehensive utilization of phosphogypsum agglomeration area. Guiyang was successfully selected as the first batch of demonstration bases for comprehensive utilization of industrial resources by the Ministry of Industry and Information Technology. A number of leading enterprises for comprehensive utilization of phosphogypsum have emerged in various places. Lubei Group, Guizhou Wengfu and Guizhou Kailin use phosphogypsum to produce cement and building materials products, which have been selected as national circular economy pilot units by the National Development and Reform Commission. Private enterprises are active, and there have been a number of platform enterprises that have the ability to provide comprehensive utilization system solutions for industrial by-product gypsum resources. Such enterprises attach importance to technological innovation and business model innovation, and there is an urgent need to expand the scale of development.
 
Xindadi processes FGD gypsum or phosphogypsum into self-leveling material technology, which can provide a technical route for large-scale and resource utilization of FGD gypsum, realize the ecological closure of FGD, and promote the healthy development of FGD in China. On the one hand, it can greatly reduce the land occupation and stacking cost of FGD gypsum, on the other hand, it can make up for the blank of natural gypsum resources in some areas, and promote the development of gypsum building materials in areas, promote the development of self-leveling materials. FGD gypsum is converted into self-leveling material, which eliminates the secondary pollution of FGD gypsum and has the characteristics of circular economy. Thick layer self-leveling main raw materials are cementitious materials, aggregates, additives and other components. The cementitious material is mainly industrial by-product desulfurization gypsum, and the aggregate is solid waste, steel slag, steel mud, tailings slag, etc., which saves resources, turns waste into treasure, and has high economic benefits and good environmental benefits.
 

Key words:

Thick layer self-leveling