Other impurities: Chloride ions have a great influence on the adhesion of desulfurized gypsum, and potassium and sodium ions are more harmful to desulfurization gypsum. However, the content of these impurities in the desulfurized gypsum is small and may not be considered under normal conditions.
In addition to the ordinary limestone/lime-gypsum wet flue gas desulfurization system, there is also a simple limestone/lime-gypsum wet flue gas desulfurization system (or wet fast desulfurization), which narrows the reaction tower and simplifies the auxiliary facilities. The requirements for dust removal efficiency of the power plant and the purity and fineness of the desulfurizer limestone are reduced, thereby reducing the cost and operation cost, and of course reducing the desulfurization efficiency and the quality of by-product desulfurization gypsum. The simple method adopted by the first thermal power plant in Taiyuan, China.
(2) Particle characteristics of desulfurization gypsum ball press for desulfurization gypsum: natural gypsum is blocky, and desulfurized gypsum is moist powder. Its particle properties are quite different from those of natural gypsum after pulverization. The main descriptions are as follows:
(1) The shape of the particles is different, the natural gypsum is irregularly pulverized, and the desulfurized gypsum is a crystal, and the particles are regular columnar, fibrous, flake or hexagonal plate.
(2) Different particle gradation, Figure 2-2 shows the particle distribution curve of desulfurized gypsum and natural gypsum. After the natural gypsum is pulverized, the particle size is better, and both coarse and fine particles are available. However, the unpulverized desulfurization gypsum particles are not well graded, the particle distribution is relatively concentrated, there is no fine powder, the specific surface area is small, and the specific surface area is only 40%_60% after the grinding of the right natural gypsum, and the particle distribution after calcination The characteristics have not changed, resulting in poor rheology of the gypsum powder after adding water, particle separation, stratification is serious, and the volume is significant. Therefore, the desulfurized gypsum used to produce building gypsum should be modified and ground to increase the proportion of fine particles and increase the specific surface area.
(3) Because of the difference in the grindability between the impurities and the gypsum, the coarse particles of the natural gypsum after grinding are mostly impurities, while the desulfurized gypsum is the opposite, the coarse particles are mostly gypsum, and the fine particles are mostly impurities.
(3) Influence of desulfurization gypsum ball press on main impurities of desulfurization gypsum:
1. Coke and soot: coke and soot are combustible organic matter. According to the European desulfurization gypsum industry standard, the content of combustible organic matter in desulfurized gypsum should not exceed 0.1%. Because of its high conductivity, it is easy to mix when the dust removal effect of the electrostatic precipitator is not good. In plaster. The shape is mostly porous, round, sometimes elongated and black. It is easy to distinguish from gypsum with the naked eye and magnifying glass. The coke and soot in the calcination of the desulfurized gypsum does not change. When gypsum is mixed with water, it is easy to float on the surface because of its light density. Therefore, when the gypsum board is made of desulfurized gypsum, since it is concentrated at the interface between the gypsum and the paper, the adhesion of the gypsum to the paper surface is affected, and the coke and the soot can damage the foam, thereby affecting the addition of the gypsum board to the paper. The role of the foaming stalk increases the bulk density of the gypsum board. When using the desulfurization gypsum to produce plaster, the coke and soot will cause black spots on the plaster, which will affect the appearance, and the coke and soot will float on the surface. It is difficult to wet the wall due to the hydrophobicity, which will affect the construction quality. Adding about 0.1% of calcium carbonate to the coal-fired power plant can effectively eliminate coke and soot in the desulfurized gypsum.
2. Alumina and silica: If alumina and silica are present as coarser particles, their hardness is greater than that of gypsum, which affects the grindability of the desulfurized gypsum, reduces the grinding efficiency, and increases equipment wear. When the desulfurized gypsum is used in a ceramic mold, the wear resistance and corrosion resistance of the alumina and the silica differ from the gypsum to affect its service life. When the desulfurized gypsum is used as a filler for paper, adhesive or plastic, the hard coarse particles will reduce the processing efficiency, the processing equipment will be lost, and the surface gloss of the product will be affected.
3. Iron compound: The iron compound in the desulfurized gypsum is derived from an absorbent, and is classified into coarse-grained magnetic iron and fine-grained non-magnetic iron. A coarse-grained magnetic iron affects the wear resistance of the desulfurized gypsum, and can be removed by a separator. Fine powder
Magnetic iron cannot be removed by the iron remover and will affect the color of the desulfurized gypsum. 1%, the content of the iron compound in the desulfurization gypsum can not exceed 0.15%,
4. Calcium Carbonate and Magnesium Carbonate: Unlike natural gypsum, some of the calcium carbonate and magnesium carbonate are converted to calcium oxide and magnesium telluride when calcined desulfurized gypsum. When using this kind of hot gypsum to produce gypsum board, calcium oxide and magnesium oxide will increase the pH of the gypsum slurry. If the pH value is greater than 8.5, the adhesion between the paper surface and the gypsum will be affected. Therefore, the content of calcium carbonate and magnesium carbonate in the desulfurized gypsum used for the gypsum board should be limited to 1.5% or less.
5.
6. Trace elements and radioactive elements: The detection and use of domestic and foreign sources prove that the content of trace elements and radioactive elements in desulfurized gypsum is far below the accepted limit. Like natural gypsum, desulfurized gypsum can be used as an ideal building material.
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