【摘要】 为了探究经过超声波预处理的污泥在热对流中的干燥效果,选用了频率为25和40 kHz的超声波,分别对污泥进行2和4 h的预处理,完成预处理的污泥在70、90、110、130℃下进行热对流干燥,并对实验数据进行数学拟合。结果表明,超声波预处理可以有效提升污泥的干燥速率,在整个干燥温度范围内,经过25 kHz的超声波预处理的污泥干燥速率更快,预处理时间2和4 h分别使干燥时间缩短了23.19%和29.15%,且热对流温度越高干燥时间就越短;在7种干燥模型中,Midilli模型更能精确表达预处理后污泥的薄层干燥行为。根据傅里叶变换的Fick第二定律表达式显示出D_eff呈现指数增长,25 kHz的超声波对污泥D_eff的提升要优于40 kHz,经过不同超声波预处理的污泥表观活化能E_a差异较小,但是25 kHz超声波使污泥具有更高的扩散因子D₀,约为3.146×10^-6 m²·s^-1。此外,超声预处理时间不宜过长,否则会导致复吸现象加剧。更多还原

【Abstract】 In order to investigate the drying effect of sludge after ultrasound pretreatment in convective drying,ultrasound with frequencies of 25 kHz and 40 kHz was used to pretreat the sludge for 2 and 4 h,respectively.The pretreated sludge was then subjected to convective drying at 70,90,110,and 130℃,and the experimental data was mathematically fitted.The results showed that ultrasound pretreatment can effectively increase the drying rate of the sludge.Within the entire drying temperature range,the sludge pretreated with 25 kHz ultrasound had a faster drying rate,with pretreatment times of 2 and 4 h reducing the drying time by 23.19% and29.15%,respectively.This improvement was more significant at higher convective drying temperatures.Among the seven drying models,the Midilli model more accurately represented the behavior of the pretreated thin-layer drying.According to the Fourier transform of the Fick’s second law,D_eff exhibited exponential growth,and the increase in D_eff for sludge treated with 25 kHz ultrasound was better than that for 40 kHz.The difference in apparent activation energy E_a of sludge pretreated with different ultrasound is small,but the 25 kHz ultrasound resulted in a higher D₀ for the sludge,approximately 3.146×10^-6 m²·s^-1.In addition,the ultrasound pretreatment time should not be too long,as it may lead to an exacerbation of reabsorption phenomenon.更多还原