Study On Two-Phase Fluid And Characteristics Of Degradation Of Organic Waste Gases In Biotrickling Filters With Porosity Packed-Materials

Biotrickling filter with porous media is a kind of effective equipment used for purifying waste gases, its performance is mutually affected by many factors such as strains function, gas flux, liquid flux , character of pollutant, value of pH, characteristics of packed material, which involve knowledge of microbiology, biochemistry, fluid mechanics,mass-transfer theory, et al. To accomplish the process of degradation, pollutant degraded by microorganism must be transferred: First, it is diffused into liquid film through interface between gas and liquid. Second, it is transferred into biofilm. Third, it is diffused into cells. Because volatile toluene is difficult to be soluble in water, process of mass-transfer is controlled by liquid-film. Therefore, the thickness of liquid-film on surface of biofilm affects the performance of biotrickling filter greatly. The main work of this paper is mentioned as follows: 1 A kind of strain that could effectually degrade toluene was obtained through five-period domestication. Constituents of culture medium and the best growth conditions of this kind of the strain were studied, which laid solid foundation for future works.2 When others parameters were constant, degradation efficiency of biotrickling filters went down with the increase of gas flux, owing to gas staying time shrinking.3 When others parameters were constant, degradation efficiency of biotrickling filters went down with the increase of liquid flux, because of friction of mass-transfer going up, owing to increasing thickness of liquid-film.4 When others parameters were constant, purification efficiency of biotrickling filters went down with the increase of concentration of toluene.5 The purification efficiency of biofilters was up to maximum, when the value of pH of circling liquid was 7. Whether increasing or decreasing value of pH of circling liquid, the purification efficiency of biofilters went down.6 The experiments of this paper involved the mutual relation between two-phase fluid flow and the distribution of biofilm, and found that after startup the rate of porosity in the bottom of packed-bed was minimum, and the rate of porosity increased with the increasing height of packed-bed, which denoted that the distribution of biofilm in packed-bed is unhomogeneous。 7 In the process of experiment of visualized biotrickling filter, the phenomenon of increasing thickness of liquid-film was observed when the gas flux or the liquid flux was raised. Even the phenomenon of center convergence in the bottom of packed-bed, resulting from affection of gravity and surface tension, was seen, which affected distribution of biofilm.8 After succeeding startup, the pressure drop of packed-bed was greater than before startup, and when gas flux was constant, fluid flux had more influence upon the pressure drop of packed-bed than gas flux.After all, it is difficult to describe biotrickling filter using traditional mass-transfer theory and biofilm theory. The degradation process of waste gas should be intensively learned from principle, and the key is to consider the characteristics of complicated ecosystem in biotrickling filter and its influence on mass-transfer in order to develop more effective reactor and reasonable application systems.