Infrared radiation drying of Moringa oleifera grains for use in water treatment

ABSTRACT This study aimed to evaluate the effects of using infrared radiation in the hot-air drying of Moringa oleifera grains on the inner dryer and grain temperatures, energy consumption, and grain quality. An experiment was conducted in a factorial scheme in 2013 to identify the optimum values of the air temperature (30 to 58 ºC) and infrared radiation application time (2.0 to 4.8 min) on moisture content, drying time, drying rate, inner dryer air temperature, grain temperature, energy consumption and quality of grains used as a natural coagulant for water treatment. The results obtained were moisture content from 4.40 to 4.76% wet basis; drying time from 0.50 to 2.00 h; drying rates from 0.70 × 10-3 to 2.05 × 10-3 kgwater kg-1 dry matter min-1; inner dryer air temperatures from 42.24 to 61.82 ºC; grain temperatures from 56.32 to 76.19 ºC; energy consumptions of the fan from 0.05 to 0.20 kWh, electrical resistances from 1.41 to 4.49 kWh; resistances of the infrared heaters from 0.48 to 1.56 kWh; water turbidities from 1.36 to 5.76 NTU; grain protein contents from 34.93 to 37.93%; and peroxide value of grains from 0.009 to 0.052 meq kg-1. Both evaluated factors increased the inner dryer air temperature and grain temperature. The electrical resistances contributed the most to the energy consumption. However, the infrared radiation reduced this consumption. The drying performed with air temperature of 44 °C and infrared radiation time of 3.4 min resulted in the highest protein concentration in the Moringa oleifera L. grains and in greater removal of the water turbidity in the water treatment.

摘要
本研究旨在评估辣木（Moringa oleifera L.）籽粒热风干燥（hot-air drying）过程中，于干燥腔内部施加红外辐射（infrared radiation）对干燥腔空气温度、籽粒温度、能耗（energy consumption）以及籽粒品质的影响。本研究于2013年采用析因设计（factorial scheme）开展试验，以探究热风温度（30~58 ℃）与红外辐射施加时长（2.0~4.8 min）对作为水处理天然混凝剂（natural coagulant）的辣木籽粒的水分含量、干燥时长、干燥速率（drying rate）、干燥腔内部空气温度、籽粒温度、能耗及籽粒品质的最优参数组合。
试验结果如下：湿基（wet basis）水分含量为4.40%~4.76%；干燥时长0.50~2.00 h；干燥速率为0.70×10⁻³~2.05×10⁻³ kg水·kg干物质⁻¹·min⁻¹；干燥腔内部空气温度42.24~61.82 ℃；籽粒温度56.32~76.19 ℃；风机能耗0.05~0.20 kWh（千瓦时），电阻加热器能耗1.41~4.49 kWh，红外加热器能耗0.48~1.56 kWh；水处理后水体浊度1.36~5.76 NTU（浊度单位）；籽粒蛋白质含量34.93%~37.93%；籽粒过氧化值（peroxide value）0.009~0.052 meq·kg⁻¹（毫克当量每千克）。
两个受试因素均可提升干燥腔内部空气温度与籽粒温度。电阻加热器对总能耗的贡献占比最高，但红外辐射的施加可降低总能耗。当热风温度设置为44 ℃、红外辐射时长为3.4 min时，所得辣木（Moringa oleifera L.）籽粒的蛋白质浓度最高，且水处理后的水体浊度去除效果最优。