一种改进的聚合模型在污泥絮凝-沉降模拟中的应用

An Improved Aggregation Model to Simulate Flocculation-Settling of Sludge

鉴于在试验中难以观测到污泥絮团的粒径分布情况,且以往类似模拟中鲜有考虑絮团分形特征及絮团黏结效率的问题,通过一种改进的聚合模型来模拟污泥颗粒间的分形聚合机理,并在群体平衡模型(PBM)和两相流Mixture模型基础上对污泥的絮凝-沉降进行三维数值模拟。模拟结果表明:建立的数学模型能较好地反映黏性污泥分形絮凝-沉降规律,具预测絮团粒径分布的能力;在同一时刻絮团的粒径分布范围随着分形维数的降低逐渐变宽,大粒径絮团数量迅速增加,小粒径絮团数量逐渐减少;初始颗粒数量的衰减速率随分形维数的增大而增大;絮团数量总体呈先增加后减少的趋势,但当分形维数不同时,其最大值随分形维数的增大而增大,出现时间随着分形维数的增大而有所缩短。

Since the particle size distribution of sludge is difficult to observe, and the fractal structure and the effi- ciency of flocculation are rarely considered in previous simulations, we established an improved aggregation model to simulate the mechanism of sludge particle aggregation and finally carried out three-dimensional simulation of floc- eulation-setding of sludge based on population balance model and two-phase flow mixture model. Results revealed that the established mathematical model and simulation method could well reflect the regularity of flocculation-set- tling of sludge. Furthermore, the particle size distribution range of floccules is widened with the decrease of fractal dimension, the number of large diameter floccules grows rapidly, and the number of small diameter floccules re- duces gradually; the decay rate of initial particle number increases with the rising of fractal dimension, and the number of floccules generally increases and then decreases with time, but the maximum floccules number increases with the rising of fraetal dimension, the oceurence time of the maximum floccule number is shortened with the rising of fractal dimension.