Heat pump rice dryer must ensure the quality of corn after drying, that is, after drying and cooling, the color and luster should not be obvious changes; does not produce scorched grains; for the characteristics of corn, according to the principle of drying, the collection of a large number of raw data, computer simulation, the design of the drying process equipment with smooth countercurrent drying → slow su → reverse downstream cooling. Drying with downstream, the thermal efficiency is very high, the exhaust gas discharged nearly saturated; and when the temperature of the grain has risen to more than 30 ℃, the moisture content of 22% or less, switch to countercurrent drying, you can continue to be highly efficient precipitation. This is not in the foreign downflow dryer. The use of countercurrent cooling can only ensure that the hot grain is slowly cooled down, fully cooled and prevented from entrapping the grain. Drying - slow tasseled grain drying after the setting of slow tasseled section is very necessary. In the slow Su section does not supply hot air, the grain itself for the wet heat balance, the surface layer of heat to the internal conduction, the internal moisture to the surface layer transfer, the slow Su process both energy saving, but also to ensure the quality of the grain, to avoid the production of shock, reduce the drying of the mechanical broken ocarina.