Study On The Toluene Waste Gas’s Purification In Biotrikling Filters And CT Scan Was Induced To Detect The Filter’s Bed

The spray of nutrient solution is the key factor in biotrickling filter purificationtoluene gas.There is little study on the influence of nutrient solution intermittentspraying on the biological trickling filter. In order to study the influence of nutrientsolution intermittent spraying on the biological trickling filter，toluene was selected asthe target compound. The FX1N-14MR-001Programmable Logic Controller(PLC)was used to control the intermittent nutrient spraying pattern in the biotricklingfilters．The operation conditions including ambient temperature，concentration of totalnitrogen，spraying density，Spray/Stop time and mechanism of the intermittentspraying biological trickling filter was studied．There is no effective way to detectbiomass of biotrickling filter without destroy the structure of biomass. In this study, theCT scan was induced to detect the inner part of biotrickling filter treating toluene. Themethod to detect biomass characteristics by CT scan, such as biofilm thickness, bedhole rate and hole distribution et.al will be set up. The main results of this topic weredescribed below:①When gas residence time was40.70s，the total nitrogen concentration ofnutrient solution between100mg/L and150mg/L，the results showed that the the1#tower(biotrikling filter fill with Polypropylene multi-faceted hollow ball) optimumconditions was controlled at the spraying density of5.4L/(m2min)，the Spray/Stoptime of1min/3min．he the2#tower(biotrikling filter fill with ceramic raschig ring)optimum conditions was controlled at the spraying density of4.5L/(m2min)，theSpray/Stop time of2min/4min；②2#tower as the the research object,when the toluene inlet loading rate was lessthan88.29g/(m3h)，the removal efficiency was higher than95.0%. While the toluene inlet loading rate was186.04g/(m3h)，the removal efficiency was about87.6%；themaximum elimination capacity of toluene increased from169.63g/(m3h) to248.85g/(m3h) comparing with continuous spraying pattern．The long time timerecyclingflush experiment showed that excess biomass could be removed whensprinkle densitywas9.4L/(m2min) and at least running for2h/d. However, the channeling could notbe alleviated by recycling flush；③The system can recover in a short period of time when the system outage0.5,2and7d, spray nutrient solution can shorten the time of recover；The higher the tolueneinlet concentration，the smaller of The ratio of actual generated CO2with the theoreticalamount of CO2，This shows that the microbial degradation of toluene is not complete．④Medical CT scan could reveal the inner structure of biotriling filter bed. It waseasy for the microorganisms to recover from the damage of CT scan. The comparativestudies among polypropylene cascade ring and ceramic raschig ring showed thatceramic raschig ring was suitable to be stuffing of biochkling filter by CT scan. Usingthe PCVCDVW software，The Window width of ceramic raschig ring bed was set tobe2800Hu, and Window Level was set be400Hu according to the calculation. Thebed gap, biomass and padding could be distinguished under this design.⑤By further recognition and calculation of the CT imagine, using IPP(Image-ProPlus) software, the biomass accumulation parameters, such as biomass volume, biomasshomogeneity, bed hole rate, hole size and hole distribution, could be presented.The initialbed hole rate was52.31%for the biotrikling filter fill with ceramic raschig ring, and itbecame17.10%after169days running. The average biomass volume was0.739m3growth on the1m3padding. In the inner part of biotrikling filter bed with clogging andchanneling, the hole rate distributed homogeneously in vertical direction. While in thehorizontal direction, there was no obvious difference among the holes size. And theseholes distributed non-homogeneously.Nutrient solution intermittent spraying on the biological trickling filter can improvethe performance of biofilters. The study was very important for developing an attractiveapproach for treating volatile organic compounds (VOCs). The CT scan was induced todetect the inner part of biotrickling filter treating toluene, it is very important to resolvethe excess biomass accumulation problem in biotrickling filter.