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How Desiccant Dryer Is Used in Wood Drying

2018-05-25
The dehumidifying dryer has the characteristics of simple structure, stable performance, high volume utilization factor, easy operation and high cost performance of the equipment. Small desiccant drying equipment fully considers the technical level of many small wood processing companies. Small-scale drying equipment is competitive, and it has broad application prospects in small wood processing companies.

Now many domestic small wood processing companies. Without drying equipment, a small number of drying equipments are mostly dry clay kilns with poor drying quality. Therefore, it is necessary to develop a small-scale wood drying equipment with low investment, energy saving, good drying quality, and easy operation.

Whether it is conventional steam heating or desiccant drying equipment, it is conservative. The drying process used is based on the different drying stages in which the real-time moisture content of the wood is located. The temperature and humidity of the moist air in the dryer are controlled only by the lower temperature level used for dehumidification and drying. The method of temperature measurement is basically the same, both measure the actual temperature of the humid air inside the dryer (dry-bulb temperature). There are three general forms of humidity measurement:

Wet bulb temperature method: a traditional method. The kiln is equipped with a thermometer or temperature sensor, wrapped in wet gauze, and measures the saturation temperature corresponding to the partial pressure of water vapor in the wet air in the dryer. This method has high precision and long instrument life, but requires high accuracy of operation.

Hygrometer method: Directly read the relative humidity of the moist air in the dryer. This method is less accurate and uses hygrometers such as hair hygrometers, lithium bromide hygrometers, and the like. At present, the technology is not yet completely clear.

Balanced moisture content method: Uses its basic moisture absorption and desorption characteristics. Humidity is measured by the equilibrium moisture content of the wood corresponding to the measured humidity. Put the veneer or paper into the moist air in the dryer. In a short period of time, the moist air in the dryer is in equilibrium with the moisture content of the wood chips or paper sheets to measure the humidity in the dryer.

Simplify operations to reduce the difficulty of using drying equipment. Against the characteristics of small businesses, it broke through the conservative drying process model. Although it is also controlled by the temperature and humidity of the moist air in the dryer, the temperature and humidity are not controlled based on the moisture content, but the proportion of the temperature dehumidifier operating time is set based on the moisture content.

The temperature controls the on/off of the heater according to the difference between the set temperature and the actual temperature and the deviation range; and the setting of the proportional parameter of the dehumidifier operation is the same as other drying methods. It is necessary to make appropriate adjustments according to the results of the daily reduction in the wood moisture content and the reference values in the reference table. If the moisture content of the wood is 35% and the temperature is maintained at about 38°C, the moisture content of the wood decreases by 6% per day, which is greater than the moisture content value that should be lowered in the table. The proportion of the dehumidifier's running time should be reduced. Thus, the dehumidification amount is reduced. The air humidity is properly increased to prevent the wood from drying too quickly and a relatively large stress is generated. On the contrary, the dehumidifier must be set to increase the running ratio so that the drying can reach a certain speed. This method is more similar to fuzzy control, and the technical difficulty requirements are not high. It is suitable for small wood processing enterprises.

The above is the application and analysis of dehumidifying dryer in wood drying.
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