In most parts of China, postpartum grain moisture is generally higher than the safe moisture (14%), is not conducive to storage, storage and use of natural precipitation, not only time-consuming, laborious, accounting for space, but also difficult to achieve the purpose of the desired effect. So many food banks are artificial precipitation.

By grain drying methods can be divided into the dryer; dryer heat convection, conduction drying dryer, and a high frequency electric field radiation dryer drying machines. Wherein the conductive drying dryer in the early 1980s and 1990s are widely used for food companies. This dryer also called steam boilers, storage silos, pre-heating tower, drying tower, cooling towers and a variety of transportation equipment. Its advantages are: large rainfall, one can of precipitation 10% -15%, the production volume, high degree of automation. The disadvantage is the high cost, fuel consumption, maintenance inconvenient.

The dryer works are:

This drying method, steam is not directly in contact with the food, only through metal pipes, the outer pipe flow food to absorb heat, heat food after the temperature rises, so that the internal transfer of moisture from the surface of vaporization, the vaporization of the water away from the drying medium , thereby reducing grain moisture.

According to its working principle, saving measures are as follows:

1, to improve the drying medium. When drying of grain, can be mixed with steam and taking substances called drying medium. According to the definition of the apparent drying medium, if the drying medium to maximize the drying process of heating food; and to continue to vaporize water vapor away, so food will be dry. And it depends on the capacity of the drying medium pack to water vapor, that is the absolute humidity of the air. The number of different absolute humidity of air at different temperatures, at a certain temperature, wet air contain water vapor there is a limit in the atmosphere when the quantity of water vapor and accommodated in the air condenses into water vapor of dynamic equilibrium when the amount of water which contain water to maximize the number of steam, when the air is called saturated air, it is called absolute saturation humidity absolute humidity. The same kind of air saturation humidity at different humidity values are different, such as 20 ℃ saturated humidity value of 17.2g / m3,34 ℃ when compared to 37.3 g / m3. Visible, saturated humidity higher the value, the stronger the drying capacity.

Conventional steam dryers, flue gas after the preheating tower on into a large vapor, not only pollute the environment, but also a waste of energy. In order to improve energy use efficiency, the flue gas can be directly used as a drying medium. Specific reconstruction measures after the flue gas directly into the preheated heating tower from the smoke box. This allows the heat source without increasing the premise that the most effective way of raising the temperature of the drying medium. It should be noted that the production should pay attention to the furnace gas temperature, if the temperature is too high will affect the quality of food, the temperature of the drying medium under normal circumstances should be controlled between 80 ℃ -130 ℃.

2, drying - ventilation drying. The traditional method of drying food usually dried to a moisture content of 14% -15%, then cooled storage. The drying - dry and ventilated rule first high-temperature drying of grain. It fell to 18% moisture, and then the moisture into the grain bin tempering within 5-7 hours, so that food grains between internal and surface temperature and moisture tend to balance, then subjected to a slow ventilation, air volume a 25m3 50 m3 / h, aeration time of about 8 hours to allow the food temperature and atmospheric temperature, which is generally higher food into the compartment temperature, the more moisture is removed (about 4% or so). The advantage of this method is as follows: (1) increase the amount of drying. Due to the moisture content to 18% rather than 14%; (2) reduce energy consumption. Because of low rainfall in the food equipment; performing tempering process, slow ventilation when using the food itself heat energy savings further precipitation. (3) to ensure food quality. Because the post-baking food directly cooling often results in food grain fissuring, while the use of this law to reduce crack ratio, broken rate; (4) the use of this method can reduce the drying cost about 13%.