Theoretical background of calculation of the parameters of the device for grain cleaning from ergot sclerotia

Resumo

A grain pile delivered from the combine harvesters to the postharvest handling stations contains, besides the full-value grain, foreign materials, including the poisonous ergot sclerotia. The use of air-sieveseparating machines and other devices does not provide any positive results during cleaning of the grain material from the ergot due to the similarity of its properties and properties of the cleaned crop. The grains of the main cereal crops (wheat, barley, rye, oats) has specific gravity of (1.2–1.5) × 10³ kg/m³ and that of ergot sclerotia is (0.9–1.15) × 10³ kg/m³. Cleaning of the grain from the ergot sclerotia is possible in saline solution. The estimation of the height of location of the charging hopper as to the level of the saline solution was made to develop the device for cleaning the grain material by the specific gravity using the wet method. It is stated that, taking into account the geometrical dimensions (l_kernel = 8.0 × 10^–3 m³ and r_kernel = 1.0 × 10^–3 m) of the grain of the main grain crops upon the saline solution density ρr = 1.15 × 10³ kg/m³ corresponding to the maximum density value ρ_s of the ergot sclerotia, the coefficient of the solution surface tension σ = 0.0816 n/m and the coefficient of the hydrodynamic resistance c = 0.9, the height h of location of the hopper as to the surface of the saline solution makes from 21.35 × 10–3 m for the grain with the density ρz = 1.5 × 103 kg/m3 to 34.01 × 10–3 for the grain with the density ρz = 1.2 × 103 kg/m3.