Two-Phase Flow And Transport Characteristic In Trickling Biofilter

With the development of society, people increasingly hope to acquire a further well survival surrounding, and pay more attention to the environmental pollution problem, such as air pollution. The recovery of low concentration VOC waste gas is valueless and its treatment is very difficult and expensive for traditional physical and chemical treatment technologies. The biological treatment technology of VOC waste gas has become a research hotspot in the world because of high purification efficiency, low charge of investment and run, and no secondary pollution etc. Up to now, many practical installations have been used in the West Europe, while there are only a few reports about its application in our country. In this work, the microorganism is cultivated and domesticated. A visual experiment apparatus is designed and made firstly and then the two-phase flow friction characteristic and purification of toluene are studied visually. From the viewpoint of mass and heat transfer in engineering thermophysics, combined with biochemical reaction kinetics considering the limitation of oxygen, a new capillary model has been proposed to study the degradation characteristic of trickling biofilter. By virtue of this model, the purification efficiency of trickling biofilter with the subsection inlet and outlet is studied, and a new concept of modularized trickling biofilter is brought forward. Based on the metabolism and heat transfer theories, a new metabolized heat transport model is developed. The remarkably conclusions are drawn as follows:1,Through two-phase flow visualization experiment in packed bed with regular porous structure, it is found that as the flow rate of gas and liquid increase, the flow resistance of gas increases. A correlation of flow friction factor is obtained from the experimental data by using Reynolds number, Weber number, Bond number, and the dimensionless flow parameter. In addition, the phenomena of liquid collection in packed bed can be observed during experiment.2,From the experiment of toluene purified in packed bed with regular porous structure, it is found that with the increase of the of gas flow rate, liquid flow rate, and the inlet toluene concentration, the purification efficiency decreases. Effect of pH on purification efficiency is studied also. When pH is litmusless, the purification efficiency is the largest. The unhomogeneity of liquid flow results in the uneven biofilm growth. The flow resistance after start-up is significantly larger than that before start-up, whichprovides a method to monitor the biofilm growth.3,The packed bed is simplified to a series of straight capillary tubes covered by the biofilm. The two-phase flow and mass transport, biochemical reaction kinetics, and the limitation of oxygen are taken account of in this model. The results of model are basically in agreement with the experimental data. The computed results show that with the increase of gas flow rate, liquid flow rate, the inlet toluene concentration, the purification efficiency decreases; while as the specific surface area of packed material and the coverage fraction of biofilm increasing, the purification efficiency increases. Additionally, it is found that there exists an optimal porosity of packed bed corresponding to the maximal purification efficiency.4,Based on capillary tube model, the purification efficiency of trickling biofilter with subsection inlet and outlet is firstly analyzed. It is found that for the tricking biofilter with multi sub-inlets and one outlet, with the increase of the number of sub-inlet, the purification efficiency decreases; for the trickling biofilter with multi sub-inlets and multi sub-outlets, with the increase of the number of subsection, the purification efficiency basically keeps constant. As a result, the application of the trickling biofilter with multi sub-inlets and sub-outlets can enhance the utilization of microorganism at the top of packed bed, which reduces the block possibility of trickling biofilter, without causing the decrease of purifi...