城市污泥填埋气集气井收集系统的优化研究

对城市污泥填埋场填埋气集气井收集系统进行了优化研究,考察了城市污泥水平方向的渗透系数(以下简称污泥渗透系数)对集气井影响半径的影响、集气井抽气负压随填埋时间的变化规律、填埋气的经济收集年限。结果表明,当抽气负压为25000～30000Pa时,污泥渗透系数分别取1.04×10-7、2.60×10-8、1.04×10-8m2/(Pa.s)时,集气井的影响半径分别为10.0～11.0、6.0～7.0、5.0～5.5m,过小的污泥渗透系数会严重影响集气井的集气效率,因此污泥渗透系数最好不应小于1.00×10-8m2/(Pa.s);随城市污泥填埋时间的增加,集气井抽气负压总体呈指数型降低趋势,从第8年起,抽气负压由起初的25000Pa降低到5000Pa以下,此时CH4产率约为2kg/(m3.a),到第20年时CH4产率接近于零,故从城市污泥填埋后第8年起,对填埋气继续进行收集的意义已经不大。

Study on optimum design of vertical extraction well based sewage sludge landfill gas collection system

The vertical extraction well based sewage sludge landfill gas collection system was optimum designed to investigated the effect of permeability coefficient on influence radiuses of vertical extraction well, change of pumping negative pressure with landfill time, and economical period for landfill gas collecting. Under the pumping negative pressure of 25 000-30 000 Pa, lower permeability coefficient resulted in smaller radiuses of influence, when permeability coefficient was 1. 04×10~(-7) , 2. 60×10~(-8), 1. 04×10~(- 8) m~2(Pa·s) , the obtained radiuses of influence were 10. 0-11. 5, 6. 0-8. 0, 5. 0-6. 0 m, respectively. Lower permeability coefficient could decrease the efficiency of vertical extraction well for gas collecting, so the permeability coefficient of sludge had better higher than 10~( -8) m~2/(Pa·s). The pumping negative pressure reduced exponentially with increasing the landfill time. After 8 year of landfill, pumping negative pressure decreased from 25 000 Pa to lower than 5 000 Pa with CH_4 yield of 2 kg/(m~3·a), while after 20 year of landfill, CH4 yield was approaching to 0. Therefore, it was no sense in collecting the landfill gas after 8 year of landfill.