依据VOC浓度变化优化场地SVE通风流量的研究

OPTIMIZATION OF SVE VENTILATION QUANTITY OF A FIELD BASED ON CHANGE IN VOC CONCENTRATION

土壤气相抽提(SVE)中挥发性有机污染物(VOC)的扩散速度是确定SVE抽提流量的依据。为了优化场地SVE通风流量,结合试验现场土壤的土质条件和含水率,测试了污染物在不同均质土质中的扩散速度,绘制了污染物浓度随时间变化曲线。研究表明污染物的扩散在不同种土质和含水率的条件下,浓度的变化具有相似规律:快速上升阶段,出现拐点,浓度稳定阶段;在测试的压力场范围内,结合场地不同的抽提流量(Flow rate)的通风以及停止通风进行浓度恢复的试验,同样获取了场地污染物的浓度变化曲线,即场地污染物浓度平衡破坏和浓度平衡的恢复。测试数据显示,不同土质结构的场地内不同区域的污染物浓度恢复曲线和单一土质的污染物扩散具有相同的规律。因此可以采用扩散速度来求解抽提的通风流量。根据室内外的测试数据,文中给出了理论计算的场地优化通风速率建议。

Optimized flow rate of soil vapor extraction(SVE) affects the facilities performance,power consumption and the removal rate of volatile organic compounds(VOCs).Base on the VOCs diffusion capacity,the air flow rate could be defined in unit time and space.That means the amount of the VOCs diffusion quantity should be equal to VOCs of extraction quantity.For the condition,the column and plot are having pressure gradient from vacuum source,the VOCs diffusion principles are the same in different soil conditions,in sole soil column or field plot. The concentration figure shows that the concentrationis first changing sharply, following an inflection point and then the even changing stage appears.With a flow rate of 4m^3/h and continues venting for 12h.The recovering concentration of the VOCs was testing;the results show that the concentrationis changing,but it's same in different type soil and water content.According to the experiment result,the optimized SVE flow rate can be calculated based on the VOCs diffusion velocity.