微波场中褐煤水分脱除规律及影响因素分析

Lignite dewatering rule and related influencing factors in the microwave field

为高效便捷地脱除褐煤中的水分,以提高褐煤品质,运用微波干燥实验设备,对锡林郭勒褐煤进行微波干燥脱水及影响因素试验,分析了微波场中褐煤水分脱除规律,探索了煤颗粒粒度、微波辐射功率和初始含水率对微波干燥脱水的影响。结果表明,褐煤微波干燥存在预热、压力升高、恒速干燥和降速干燥4个阶段。预热阶段褐煤温度迅速上升,含水率基本不变。压力升高阶段内部蒸汽压力迅速升高,形成较高的总压力差,促使渗透流出现,脱水率显著增大。恒速干燥阶段蒸汽压力和脱水率保持不变。降速干燥阶段,脱水率下降,温度升高。粒度在0.6-3.0 mm时,干燥速率最快,最大为11%/min。辐射功率小于600 W时,功率越大,干燥速率越快,温升越快。初始含水率越高干燥速率越快,温升越慢。

In order to remove the moisture and upgrade the quality of lignite with efficient methods,a specially-designed microwave equipment was used to remove water from the lignite and the key influencing factors during the process were analyzed. The effects of coal particle sizes,radiation powers and initial moisture contents on the dewatering process were investigated. The results indicate that there were conceptually four stages（ preheating stage,pressurizing stage,constant-rate drying stage and falling-rate drying stage） during the whole drying process in microwave. The temperature of lignite rose quickly while the moisture content is nearly constant in preheating stage. The dehydration rate increases notably in the pressurizing stage as the seepage flow generated from the large pressure gradient between internal and external particles. The vapor pressure and dehydration rate is steady in the constant-rate drying stage. The dehydration rate decreases while the lignite temperature increases in the falling-rate drying stage. The peak drying rate could reach 11% per minute when the particle size is 0. 6-3. 0 mm. The drying rate increases with the increasing microwave output power when the power is less than 600 W. Generally,the high initial moisture content of coal would cause high drying rate,but slow increase in lignite temperature.