Influence of gypsum calcining equipment on product stability

The production process of building gypsum is the process of converting dihydrate gypsum into hemihydrate gypsum, and the quality of building gypsum powder is largely determined by the proportion of converted hemihydrate gypsum and other gypsum phases; This conversion process is completed in the calcination equipment and is determined by the calcination equipment. Therefore, gypsum calcining equipment has a direct impact on the quality of building gypsum powder; This effect is mainly the product stability.

The influence of gypsum calcining equipment on product stability is determined by many factors, such as equipment type, heat exchange mode, equipment structure, control mode, process parameters, heating mode, feeding mode, etc; Equipment structure, heat exchange mode, heating mode and feeding mode are common influencing factors.

When the equipment structure is reasonable, the gypsum raw materials tend to be uniformly heated in the calcination equipment, the heating degree and heating time of the raw materials in the calcination equipment tend to be consistent, the dehydration degree is very close, and the equipment with better structure treatment can even achieve that after the raw materials of different fineness enter the calcination equipment, the fine powdery materials and granular gypsum all leave the calcination equipment at different calcination times that they just reach the better calcination state; Thus, the proportion of semi aqueous phase is high, the proportion of unstable phase AIII affecting product quality is low, and the proportion of dihydrate gypsum affecting setting time is low.

Heat exchange mode: each type of equipment has designed its own suitable heat exchange mode, and different heat exchange forms have different effects on the heat exchange process. At present, there are two common forms of heat exchange, such as direct heat exchange and indirect heat exchange; Direct heat exchange means that the hot flue gas generated by fuel combustion is introduced into the calcination equipment to directly contact with gypsum raw materials for heat exchange. In order to achieve higher output, this type of equipment generally uses the flue gas with higher temperature to quickly contact with gypsum for heat exchange, with higher heat exchange efficiency and faster heat exchange speed. Because the heat exchange process is high temperature and quick contact, it is difficult to control the process. The temperature fluctuation of high temperature flue gas, the fluctuation of gypsum particle size and feeding amount, and the fluctuation of air flow will affect the heat exchange effect. The uniformity of the heat exchange process is difficult to control. The proportion of hemihydrate gypsum phase in the product is relatively low, and the proportion of dihydrate gypsum phase and AIII phase is very high. Therefore, the quality of gypsum products fluctuates greatly, and the product setting time is fast; Indirect heat exchange refers to the indirect heat exchange between high-temperature flue gas or other thermal medium (heat transfer oil, steam) and gypsum through heat exchange pipes or equipment outer walls. The thermal medium does not contact gypsum raw materials, the heat exchange process is slow, and the heat exchange is relatively gentle. Gypsum gradually accumulates heat to complete the heat exchange process through a relatively long process, and the temperature curve is obvious during the heat exchange process; The temperature curve of heat transfer process is obvious; In the process of heat exchange, the small fluctuation of heat medium and feeding amount needs a process to affect the calcination effect; Because the calcination process is long, the heat exchange time of gypsum in the calcination equipment is long, and it is easier to be even in the dynamic heat exchange process through the continuous churning of logistics; The thermal medium does not pollute gypsum products during calcination, which is conducive to the recycling of tail gas; The calcined products generally have a high proportion of hemihydrate gypsum phase. The production of dihydrate gypsum phase and AIII phase is easy to control, the production adjustment is relatively easy, and the product setting time is long, which is suitable for the configuration of mortar, production mold, gypsum powder and other products with high requirements.