Basics of safe drying of seeds

In seed-production farms, the temperature of drying agent is often limited by the maximum permissible temperature of heating; the simultaneous moisture removal is 3-6%; seeds are dried to a moisture content that exceeds the normal one by 2-3%; the layer is stirred several times during drying process. All of this increases the process cost and could lead to crop losses. The paper analyzes the essential factors influencing the safe drying of seeds in dense layer. It is found that along with the maximum permissible temperature of heating, account must be taken of the rate of dehydration, the specific surface of seeds, the heat transfer coefficient and the unevenness of moisture of basic material and of a dried-up one. The estimation of parameters for safe drying of seeds is carried out on the basis of mathematical models and well-known empirical expressions of the heat resistance and maximum permissible moisture removal. The article proposes the calculation of drying agent temperature that ensures the complete safety of the process, for breeder seeds also. Permissible temperature of drying agent is calculated by the expression that takes into account the specific surface of grain, the heat transfer coefficient, the heat of vaporization and the coefficient that depends on the permissible rate of dehydration, as well as the maximum permissible temperature of seeds heating. The maximum height of the layer of seeds being dried without stirring depends on the speed of drying agent, the diameter of grain, the porosity of layer, the mass transfer coefficient and the moisture content of drying agent before and after the layer. The maximum permissible temperature of seeds heating should be calculated according to the formula of S.D. Ptitsyn, but the maximum humidity of 10% of weighed portion should be used as a basis.

seeds, safe drying, process intensification, temperature of drying agent