Abstract It is very important to know how operating condition of a coaxial impinging stream dryer affects the drying time, parboiled rice quality and energy consumption. The drying temperature, parboiled paddy feed rate, drying air velocity and impinging distance were experimentally investigated. Increases in drying temperature and air velocity and a decrease in paddy feed rate provided higher evaporation rate whilst impinging distance, ranging from 5 to 13 cm, did not affect the evaporation rate. Collision between kernels within the impinging zone caused the hull’s lemma splitting from the kernel and the percentage of the split kernel strongly depended on the air velocity and feed rate. The acceleration in the rate of drying by changing the above operating parameters did not affect the head rice yield. In addition, the collision of kernels also did not influence the head rice yield since the mechanical properties of rice are strengthened during steaming step in the parboiling process. However, the change of head rice quality was only governed by the moisture content after drying. The total energy consumption including electricity and heat was strongly depended on the air velocity and feed rate whilst it was slightly changed with the drying temperature. From the present study, it was recommended that the parboiled paddy should not be dried below 25% d.b. and the highest temperature that could possibly be used was 190 °C and the inlet air velocity should not be below 15 m/s.

中文翻译：

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冲击流干燥机运行参数对蒸谷米品质及能耗的影响

摘要 了解同轴冲击流干燥机的运行条件如何影响干燥时间、蒸谷米品质和能耗是非常重要的。试验研究了干燥温度、预煮稻谷的进料速度、干燥空气速度和撞击距离。干燥温度和空气速度的增加以及稻谷进料速率的降低提供了更高的蒸发率，而撞击距离为 5 至 13 厘米，不影响蒸发率。撞击区内的谷粒之间的碰撞导致外壳的外稃从谷粒分裂，分裂谷粒的百分比很大程度上取决于空气速度和进料速率。通过改变上述操作参数加快干燥速度不会影响整精稻产量。此外，籽粒的碰撞也没有影响整粒稻米的产量，因为在蒸煮过程中的蒸步骤中，稻米的机械特性得到了加强。但整粒米品质的变化仅受干燥后水分含量的影响。包括电和热在内的总能耗很大程度上取决于空气速度和进料速度，而随着干燥温度的变化略有变化。根据目前的研究，建议预煮稻谷的干燥度不应低于 25% db，可能使用的最高温度为 190 °C，入口风速不应低于 15 m/s。整粒米品质的变化仅受干燥后水分含量的影响。包括电和热在内的总能耗很大程度上取决于空气速度和进料速度，而随着干燥温度的变化而略有变化。根据目前的研究，建议预煮稻谷的干燥度不应低于 25% db，可能使用的最高温度为 190 °C，入口风速不应低于 15 m/s。整粒米品质的变化仅受干燥后水分含量的影响。包括电和热在内的总能耗很大程度上取决于空气速度和进料速度，而随着干燥温度的变化略有变化。根据目前的研究，建议预煮稻谷的干燥度不应低于 25% db，可能使用的最高温度为 190 °C，入口风速不应低于 15 m/s。