Grain drying technology is one of important agricultural storage and fresh-keeping processing techniques. According to statistics, China's grain harvest every year due to the damp climate, wet Valley a chance to dry or has failed to meet the safety germination loss of moisture causes mildew, grain up to 5%, if calculated according to an annual output of 500 million t of grain, equivalent to a loss of 25 million t of grain. This shows the importance of grain drying equipment application in agriculture. Actively carry out testing and research of grain drying machinery, drying technology in more and more applications in agriculture.

Many different types of grain drying mechanical equipments are classification by mode of heat transfer, grain drying methods including convection, conduction and radiation in three categories. Convection heat drying, heat to the food is drying (heating the air or gas) in direct contact with the food, by way of heat convection. Conductive drying which rely on direct contact between the food and the heating surface, by way of heat conduction of heat to the food. Radiation drying, heat to food is realized by means of radiation. Drying method is included in two or more heat transfer modes. Convection thermal drying method is the most widely used method for grain drying. Convection heat drying of drying equipment, movement by drying, drying temperature and drying medium flows in various combinations, there are the following types:

1. Sort by medium temperature and drying speed: slow air drying at low temperature, high temperature and rapid drying.

2. According to grain movement category: fixed bed (Valley floor) dry, moving bed and fluidized bed drying, fluidized bed dryer and vibrating bed.

3. According to the grain direction category: top flow drying, counterflow dryer, cross flow type drying and Francis dry.

4. By job classification, drying equipment can be divided into two kinds of periodicity and continuity.