Sustainable Development of Phosphogypsum in Building Materials Industry


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2020-03-16

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The increasing development of industry has brought a large number of industrial waste, such as phosphogypsum, a by-product of phosphate compound fertilizer industry, and desulfurization gypsum produced by flue gas desulfurization in thermal power plants. The quantity of phosphogypsum and desulfurization gypsum is huge. If it is not treated in time, it will erode the land, occupy farmland, destroy the environment, pollute the air and water.

The increasing development of industry has brought a large number of industrial waste, such as phosphogypsum, a by-product of phosphate compound fertilizer industry, and desulfurization gypsum produced by flue gas desulfurization in thermal power plants. The quantity of phosphogypsum and desulfurization gypsum is huge. If it is not treated in time, it will erode the land, occupy farmland, destroy the environment, pollute the air and water. From the perspective of the development model of circular economy, phosphogypsum and desulfurization gypsum are industrial waste residues, and they are also available gypsum resources. As long as we adopt advanced technology and equipment, we can fully realize the comprehensive utilization of resources. The prospect of using phosphogypsum or desulfurized gypsum to produce gypsum-based self-leveling cement, paper-faced gypsum board, gypsum block, RBS gypsum board, whitewashed gypsum and other gypsum wall materials is very broad. Gypsum wall material is light, safe and comfortable, with fire prevention, "warmth" and "breathing function". It is the most humanized building material in the room and the most ideal substitute for traditional wall materials. At the same time, the production process has low energy consumption and does not produce harmful gases, and the product can be recycled repeatedly after use. It is an environmentally friendly building material. Therefore, gypsum building materials are green building materials that can truly achieve clean production and sustainable development standards, and they are also energy-saving building materials with low energy consumption and good thermal insulation performance. The development of gypsum building materials industry has great potential for saving energy, resources and reducing environmental load, and will not make the economy break through the boundary of ecological security, and can realize the sustainable development of gypsum building materials industry itself. Phosphogypsum or desulfurization gypsum is a good building materials resources, many physical and chemical properties and natural gypsum close.

In Europe, Japan or the United States, almost all phosphogypsum or desulfurization gypsum has been effectively used. The industrial comprehensive treatment technology of desulfurization gypsum in China has been initially mature, while the comprehensive treatment of phosphogypsum has just started. At present, the state has introduced relevant industrial policies on the comprehensive utilization of resources, the development of circular economy, the promotion of new wall materials and the encouragement of green building materials, which will bring good opportunities for the development of gypsum building materials by using phosphogypsum and desulfurization gypsum.

 

phosphogypsum

Phosphogypsum is a solid waste of phosphate fertilizer industry. With the rapid development of high concentration compound fertilizer industry in China in recent years, a large amount of phosphogypsum is discharged from phosphate fertilizer chemical enterprises every year. As the utilization rate of phosphogypsum is less than 5%, it is still treated by enclosure stacking, occupying a large amount of land and seriously polluting the environment. It has begun to seriously inhibit the development of phosphate fertilizer industry, and it is urgent to expand the way out of phosphogypsum. Phosphogypsum is used in the production of gypsum building materials. On the one hand, the production of building materials can consume a large amount of phosphogypsum without causing new pollution, and the country has explicitly stipulated the use of new wall materials to replace clay bricks and shale bricks; on the other hand, the use of phosphogypsum to produce wall blocks, plates or powder materials can not only obtain better economic benefits, but also achieve the purposes of energy saving, soil saving and waste, and helping to solve the pollution of phosphogypsum, the phosphate fertilizer industry can enter a virtuous cycle of sustainable development.

The production of gypsum building materials with phosphogypsum is also very mature in technology. Japan is the country with the best comprehensive utilization of phosphogypsum. Almost all phosphogypsum is used, among which the production of building gypsum powder and gypsum products accounts for more than 75% of the total amount of phosphogypsum. In China, the comprehensive utilization of phosphogypsum large-scale production of gypsum building materials has just started, according to the characteristics of raw materials to choose a reasonable process line and the selection of key equipment is very important.

 

desulfurization gypsum

FGD gypsum, also known as flue gas desulfurization gypsum, sulfur gypsum or FGD gypsum, is an industrial by-product gypsum obtained by desulfurization and purification of flue gas generated after the combustion of sulfur-containing fuels (mainly coal). In the 1980 s, China began to implement the demonstration project of flue gas desulfurization in power plants, and built flue gas desulfurization devices in Luohuang Power Plant, Zhejiang Banshan Power Plant and Taiyuan No.1 Thermal Power Plant, and achieved good results. During the "11th Five-Year Plan" period, the state has arranged 221 key projects. About 0.137 billion kilowatts of existing coal-fired units will realize flue gas desulfurization. By the end of 2010, SO2 emissions from thermal power plants nationwide will drop from 13 million tons in 2005 to 5.02 million tons, a drop of 61.4. The annual production of desulfurization gypsum exceeds 10 million tons. Therefore, the output of desulfurization gypsum is very large. If it cannot be utilized, it will become solid waste residue pollution.

FGD gypsum is different from natural gypsum, which is bonded together in the original state; FGD gypsum exists as individual crystalline particles. The main mineral phase of desulfurization gypsum is calcium sulfate dihydrate, and the main impurities are related minerals associated with limestone (such as calcium carbonate, aluminum oxide and silicon oxide, iron oxide, calcite, feldspar, feldspar, fangmei stone, etc.), which have no effect on the building performance of gypsum. The particle size of flue gas desulfurization gypsum is relatively average, its distribution band is very narrow, the particles are mainly concentrated in (30~60) m, the gradation is far worse than the natural gypsum ground after the gypsum powder. The hydration kinetics, condensation characteristics and process of desulfurization gypsum are the same as those of natural gypsum, but the speed is fast. The physical and chemical properties of desulfurization gypsum are basically the same as those of natural gypsum. The grade of dihydrate gypsum (CaSO4 · 2H2O) in desulfurization gypsum can reach (90~93)%, free water content is 10% ~ 12%, low alkali content, no radioactivity, less harmful impurities, and can replace natural gypsum as raw materials for building materials industry.

Almost 100 per cent of desulphurization gypsum is used in Japan, with 2.5 million tons per year, of which more than 95 per cent is used in gypsum board and cement production. In Germany, the rapid development of new gypsum building materials, all of the desulfurization gypsum have been applied, each year 3.5 million tons of desulfurization gypsum is mainly used for the production of gypsum and gypsum board. In the United Kingdom, the government has enacted a decree to force the use of desulfurization gypsum. Desulfurization gypsum must be used in preference to natural gypsum. Its main products are whitewashed gypsum and paper-faced gypsum board. Desulfurization gypsum in the United States is mainly used in the production of gypsum wallboard. In 1998, the first thermal power plant in Taiyuan, Shanxi Province carried out comprehensive utilization of desulfurization gypsum to produce building gypsum powder and plastering gypsum, which opened the prelude to the comprehensive utilization of desulfurization gypsum in China. At present, the domestic desulfurization gypsum calcination and deep processing technology and equipment gradually mature, the application of desulfurization gypsum is in a very rapid development stage.

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