Some problems in gypsum powder production

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Some problems in gypsum powder production
The crystalline water in CaSO4 • H2O is in two states: bound water and zeolite water. In combination with the water desorbed during the water heating process, zeolite water is half of the water left behind, which can only be desorbed when it is transformed into anhydrous water. The formation amount of hemihydrate gypsum is directly related to the proportion of these two kinds of water, and the proportion of these two kinds of water is different for gypsum from different sources, which is the main reason why gypsum in different places has their own processing technology.
The different crystal structure of dihydrate gypsum plays a controlling role in the crystal morphology growth of hemihydrate gypsum products, and determines the growth rate of each crystal surface. However, it cannot be ignored that the morphology growth also depends on environmental conditions such as temperature, pressure, concentration, viscosity, pH value, eddy current, impurities and external ions. Edinger studied the effect of external ions (HSO4 -, H +, NO3 -, Na +, Ag +, Sr2 +, oh -) on the crystal surface growth. Under the condition of certain saturation concentration, gypsum: hydrogen, strontium and silver ions are selectively adsorbed on the (110) surface, which is composed of calcium and sulfate, and absorbs both positive and negative ions, but has strong adsorption to the above ions. Sodium, (or sodium calcium complex ion) sulfite Nitrate is selectively adsorbed on the (111) surface, which is composed of calcium ions and has strong adsorption to the above ions, while hydroxide is adsorbed on the (010) surface. To sum up, ions that increase the crystal size include hydrogen and nitrate ions. Ions that reduce the crystal size include sodium, strontium, silver and hydroxide ions.
Dehydration temperature of calcium sulfate dihydrate: 128 degrees to 1.5 water molecules, 163 degrees to 0.5 water molecules, and endothermic peaks at 145 degrees and 180 degrees. When the water vapor pressure is high, there are two completely separated endothermic peaks, and with the decrease of the water vapor pressure, the two peaks gradually coincide.
Anhydrous type III calcium sulfate has strong water absorption. It can be used as a desiccant and absorb moisture in the air. It is obtained from anhydrous tri type calcium sulfate after aging β Compared with ordinary hemihydrate gypsum, this type of hemihydrate gypsum has nearly doubled strength, reduced surface area ratio by three-quarters, and greatly reduced standard consistency.
In the production of gypsum powder, the process of adjusting the standard thickness is to increase the dehydration temperature, try to generate anhydrous gypsum III, and get hemihydrate gypsum through aging, which has both higher strength and smaller standard thickness. Standard consistency is inversely proportional to strength.
Between α、β There is an intermediate between gypsum - low pressure α Gypsum writing α BP——CaSO4·1/2H2O。 Whether it exists is still controversial.
Anhydrous type II gypsum formed at 400 degrees has strong water absorption and hydration ability, which is called low-temperature anhydrite type II in the academic world. Whether it is anhydrous type III or anhydrous anhydrite type II is also known.
Fiber gypsum, also known as gypsum whisker (onoda-gpf), currently has only 600 tons of output from Shenyang onlay new materials Co., Ltd., which needs to be verified.
There are many harmful impurities in phosphogypsum. Besides potassium, sodium and green ions, organic impurities and eutectic phosphorus are the key factors affecting its high quality. Water washing can remove all impurities except eutectic phosphorus, which needs to be calcined at 800 degrees to eliminate its influence.
For chemical gypsum modification, impact and splitting are the best grinding forms to expand the surface area ratio, followed by breaking and grinding, which maintain the bond breaking and surface activity of gypsum, and extrusion is the worst. It bridges the bond breaking on the surface and eliminates part of the surface activity.
Shijiazhuang Jingjin machinery equipment installation Co., Ltd. ---- Zhou Yanhui 13833456715