【作者】 刘先锋；

【导师】 杨春平；

【作者基本信息】 湖南大学 ， 环境科学与工程， 2008， 硕士

【摘要】 生物滴滤器(Bio-trickling Filters, BTFs)是一种处理低浓度挥发性有机物(Volatile Organic Compounds, VOCs)的有效手段,它通过生长在填料表面的生物膜内的微生物捕获并降解污染物来实现污染物的治理,具有成本低、操作简便、无二次污染等优点,它克服了传统生物过滤器运行过程中出现的气体短流、营养液分布不均等问题,能一定程度上减轻反应器内生物膜的过度蓄积或堵塞。对不同操作条件下生物滴滤器去除VOCs、生物膜生长动力学、生物膜时空分布规律、生物膜蓄积率等进行模拟研究,对于了解生物法处理机理、促进生物膜反应器在VOCs控制方面的研发与应用,具有重要的理论和实际意义。本研究在气液双膜理论的基础上,依据质量守恒定律和莫诺特动力学方程,建立了挥发性有机物在生物滴滤器气相、水相和生物膜相中的传质降解模型。模型考虑了因生物膜增长而导致的介质比表面积和空隙率变化,及其对去除效率的影响。通过忽略液相传质阻力来简化模型,分别运用配置法、解析法、龙格—库塔法来数值求解生物膜相和气相的传质降解和生物膜的增长模型方程,并在MATLAB软件环境编程求解。模型研究结果表明:甲苯去除效率随气体停留时间的增加而增加,随进气有机负荷的增加而减小,在进气口处甲苯降解速度最大,随着到进气口轴向距离的增大,去除效率增加速率呈递减趋势;进气口处填料孔隙率随气体停留时间的增加而下降,随进气有机负荷的增加而下降;生物滴滤器内生物膜蓄积率随气体停留时间的增加而增加,随进气有机负荷的增加而增加;生物滴滤器内甲苯浓度分布模拟曲线说明进气口处的填料层对甲苯去除起最重要的作用,甲苯的去除效率增加速度随到进气口轴向距离的增加而减小。试验结果证明该模型能较好地模拟生物滴滤器去除VOCs的动态运行性能。有助于更好的理解系统运行机理并优化系统设计参数,为实现生物过滤法在废气治理中的应用和推广奠定基础。更多还原

【Abstract】 Bio-trickling Filters (BTFs) is an effectively control means for volatile organic compounds (VOCs), which utilizes microbe attached on the packing media to capture volatile organic compounds (VOCs) and biodegrade them. It has advantages in some aspects such as low cost, handy operation costs and no recontamination. Additional, the technology can overcome the disadvantages including the short of gas flow, the uneven distribution of organic loading and nutrients in conventional biofilters, and to an extent released the biomass excess accumulation or clogging in the filter bed. It would be important theory and practical significance in the research and application of bioreactors for VOCs removal to simulate the complex processes, such as the BTFs for VOC removal at different operating conditions, the dynamic kinetics of biomass growth, the spatial and temporal changes in biomass distribution, and the biomass accumulation rate.A mathematical model was developed on the basis of mass transport and mass balance equations in a BTF, the two-film theory, and the Monod kinetics. This model took account of mass transfer and biodegradation of VOC in the gas-water-biofilm three-phase system in the biofilter, and could simulate variations of VOC removal efficiency with a changing specific surface area and porosity of the media due to the increasing of biofilm thickness in the biofilter. This model was further simplified by neglecting the water phase due to the small mass transfer resistence. The equations for the biofilm phase, gas phase, and biofilm accumulation in this model were solved using collocation method, analytic method, and the Runge-Kutta method separately. A computer program was written down as MATLAB to solve this model.The results of numerical solutions show that toluene removal efficiency increased with the gas resistence time increased and decreased with the organic loading increased. The porosity of the packing in the inlet decreased with the gas resistence time increased and decreased with the organic loading increased. The biomass accumulation rate in the bio-trickling filter increased with the gas resistence time increased and increased with the organic loading increased. The concentration profile of toluene in bio-trickling filter revealed that the packing layer which is the closest to inlet played the most important role in toluene biodegradation.The dynamic removal efficiencies from this model correlated reasonably well with experimental results for toluene removal in a BTF. It provides the basis for the spreading and application of biofiltration on the waste gas treatment.更多还原