1.Equipment specification
The selection of dryer model is according to the actual situation of local conditions, and two important indicators of the productivity and precipitation.
If there are 3000t corns with moisture content of 26%, the average environment temperature is -5℃, corns can be stored for 15 days. If the dryer works 20h every day, safe moisture reduces to 14% after 30 days by drying, we can use the dryer with small processing capacity of 5t/h and greater drying capacity.
If the quantity of grain is large during the drying season. We can use the large, high efficiency and fast dryer.
2.Production capacity
The dryers’ selection should not be too small. Because we usually use dryer only when it’s rainy days during the harvest season. The dryers with large volume and small productivity cannot work pretty well.
State and local reserve depots, large and medium-sized dryers should be built in the regions with concentrated grain. The service radius of stationary dryers should not be too large, to reduce the transportation distance, costs and increase efficiency.
Mobile dryers can be used in rural areas with dispersed grain and areas with small food production. The productivity is generally 2 to 5 t/h. The service radius should be larger to play the role of mobile dryer.
3.Heat sources
When selecting a dryer, it is necessary to consider the local energy resources, to achieve reasonable utilization and reduce costs.
Coal, anthracite and coke are suitable as energy resources in coal mining areas. The cost is low, but the coal-burning furnace has a large investment.
Light diesel oil, heavy oil, natural gas, and propane can be used as hot-blast stove fuel, in the food production areas with oil fields and natural gas. The cost of the fuels is high, but hot-blast stove has a smaller investment.
Hot-blast stove with fuel or natural gas is suitable for seed dryer, because it has stable air temperature, easy control, and can ensure the germination rate of dried seeds.
4.Environment
Because of the different harvest seasons of various crops, and the temperature difference between the north and the south, it is necessary to consider the drying effect and the operating cost.
For example, it is better to avoid drying grains during low-temperature and humid weather in coastal areas. Otherwise, the dehydration effect is poor, the productivity is low, and the drying cost is high.
The lower the outside temperature is, the larger the required unit heat consumption relatively becomes. Therefore, the heat insulation layer should be added to the outer wall and the hot blast pipe of the dryer when it works under 0 ℃, to reduce the loss of heat.
5.Attached device
To complete the drying, dryer must be equipped with some ancillary equipment.
Continuous dryers should be equipped with upper and lower material levelling device (or overflow pipes). The temporary storage bins in the process should use full bin levelling device, the elevator should have automatic shutdown and plugging alarm devices.
Motors shall be installed with overload protection devices and can realize manual and automatic interlock control. The grain discharging device should be able to achieve speed adjustment or continuously variable speed.
The temperature control instrument should be able to display the hot air temperature and the grain temperature of each section, and alarm at high temperature. To test the moisture content of grain, a fast moisture tester should be installed.