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 本研究旨在评估红外辐射应用于辣木（Moringa oleifera）籽粒热风干燥过程中，对干燥机内空气温度、籽粒温度、能耗及籽粒品质的影响。2013年采用析因试验设计开展相关实验，以确定空气温度（30~58℃）与红外辐射施加时长（2.0~4.8 min）的最优组合，考察其对含水率、干燥时间、干燥速率、干燥机内空气温度、籽粒温度、能耗以及用作水处理天然絮凝剂的辣木籽粒品质的影响。所得试验结果如下：湿基含水率介于4.40%~4.76%；干燥时长介于0.50~2.00 h；干燥速率介于0.70×10⁻³~2.05×10⁻³ kg水·kg干物质⁻¹·min⁻¹；干燥机内空气温度介于42.24~61.82℃；籽粒温度介于56.32~76.19℃；风机能耗介于0.05~0.20 kWh，干燥机电热电阻能耗介于1.41~4.49 kWh，红外加热器能耗介于0.48~1.56 kWh；水处理后水体浊度介于1.36~5.76 NTU；籽粒蛋白质含量介于34.93%~37.93%；籽粒过氧化值介于0.009~0.052 meq·kg⁻¹。两个试验因素均可提升干燥机内空气温度与籽粒温度。电热电阻对总能耗的贡献最大，但红外辐射可降低整体能耗。当采用44℃空气温度、3.4 min红外辐射时长的干燥工艺时，辣木（Moringa oleifera L.）籽粒的蛋白质浓度最高，且水处理过程中水体浊度去除效果最优。