Studies on Pneumatic Conveying with Extra Low Pressure Ejector (3)

Conveying Characteristics of Cereal Grains

Abstract

Pneumatic conveying characteristics of cereal grains was examined with extra low pressure ejector, which had been investigated on rice hull in our previous reports.
The experimental results were as follows,
1. Conveying the grains required larger quantity of energy P_s with respect to conveying rate W than conveying the rice hull. The fact might come from the reasons that the terminal velocity vt of the grain was larger than that of rice hull and the average velocity v of the air in the tube became greater for the grain than for rice hull. By comparison of wheat and unhulled rice, smoothness of the kernel seemed to relate to this result.
2. As for energy efficiency η at the ejector part, conveying the rice hull was particularly inferior to conveying the unhulled rice. The result was caused by the fact that the values l_best of conveying the rice hull were remarkably larger than those of conveying the unhulled rice.
3. The values of conveying effectiveness W/P_f which summed up those of the ejector part and conveying tube part were almost same in every our experiments. Consequently extra low pressure ejector was practically available to pneumatic conveying of cereal grains if the values of lift head H and conveying distance L were smaller than those of this study.
4. If the static pressure h_f at the nozzle part was increased, effective pressure h₂ and conveying rate W were increased. But the increased quantity of conveying rate was quite small. Therefore energy efficiecny η of the ejector was decreased remarkably and conveying effectiveness W/P_s resulted in very small value. These results showed that this system was favorable to the conveying which was performed under the condition of low static pressure.