1、 Drying process of handicrafts
The drying technology of ceramic handicrafts generally adopts hot air drying technology. The energy sources include natural gas combustion, coal combustion and electric furnace. However, the long drying cycle leads to slow capital turnover and poor uniformity. In addition, the ceramic drying kiln covers a large area and consumes large energy. The hot air rapid drying means that the drying atmosphere changes according to the different green bodies and the drying degree of the green bodies, so as to maintain the best drying atmosphere at all times and improve the drying speed. The rapid drying chamber with automatic temperature and humidity regulation has the following characteristics:
① Small space, fast response and high accuracy during parameter adjustment;
② Different drying curves can be set according to the conditions of the green body;
③ Industrial personal computer control, high degree of automation, reduction of human error factors, high pass rate of green body drying. This system consists of six parts: room structure, hot air stove, air distribution system, mixing system, control system and humidity system.
The moisture content of ceramic body is generally between 5% and 25%. The water content of ceramic body is composed of equilibrium water and free water. Under certain air conditions, the drying limit is to make the body reach equilibrium water. The balance water is a part of the combined water, and its amount depends on the temperature and relative humidity of the drying medium. When the combined water is discharged, the green body volume does not shrink, which is safer.
When the drying conditions are stable, the surface temperature, moisture content, drying rate and time of the green body have a certain relationship. According to the changing characteristics of their relationship, the drying process can be divided into three stages: heating stage, constant speed drying stage and reduced speed drying stage:
- Heating stage
Since the heat transferred from the drying medium to the surface of the green body in a unit time is greater than the heat consumed by the evaporation of surface water, the temperature of the heated surface gradually increases until it is equal to the wet bulb temperature of the drying medium. At this time, the heat obtained from the surface and the heat consumed by evaporation reach a dynamic balance, and the temperature remains unchanged. At this stage, the moisture content of green body decreases and the drying rate increases.
- Constant rate drying stage
At this stage, unconsolidated water is still discharged. Due to the high moisture content of the green body, the amount of water evaporated on the surface can be replenished internally. That is, the internal moisture movement speed (internal diffusion speed) of the green body is equal to the surface moisture evaporation speed and the external diffusion speed, so the surface is kept moist. At the end of the constant velocity drying stage, the material moisture decreases to the critical value. At this time, although the interior of the material is still non bound water, bound water begins to appear in the surface layer.
- Slow drying stage
In this stage, the water content of the green body decreases, the internal diffusion speed can not catch up with the evaporation speed of the surface water and the external diffusion speed, the surface is no longer kept moist, and the drying rate gradually decreases. As the heat required for evaporation of surface water is reduced, the material temperature starts to increase gradually. The partial pressure of water vapor on the material surface is less than that of saturated water vapor at the surface temperature. At this stage, the combined water is discharged, and the green body will not produce volume shrinkage and dry waste. When the water content of the material is equal to the equilibrium moisture, the drying rate becomes zero and the drying process is terminated.
2、 Advantages of Ansiman drying dehumidifier drying solution
(1) The fully automatic control system can select the best drying temperature and humidity according to the process requirements of different products. It completely solves many problems existing in other drying methods, such as long drying time, high temperature, large energy consumption, and has incomparable tabletop characteristics.
(2) High efficiency centrifugal fan is adopted, featuring strong wind force, uniform air supply, low noise, and even and fast material drying.
(3) During the drying process, the materials will not be deformed, cracked, discolored, deteriorated, oxidized, dried thoroughly, with good rehydration property after drying, less loss of nutrients, long storage period, and more effectively protect the color, fragrance, taste, type and effective ingredients of the dried materials.
(4) The unit is designed as a whole, and can be used after connecting the pipeline and power supply on site; It is easy to operate. After the parameters are set, automatic control can be realized with high reliability.
(5) It is simple and convenient to use old kilns, garages, etc. for reconstruction, relocation and floor space saving due to less investment and quick effect.
