Experimental Study On VOCs Treatment By Reverse Flow Catalytic Combustion Combined With Activated Carbon Fibers Adsorption

Nowadays,much attention is paid to air pollution caused by Volatile Organic Compounds (VOCs) in addition to the pollution of SO2, NOx. There are extensive discussions and researches on waste gas pollution control and treatment, especially the large flow and low concentration waste gas. This paper adopts reverse flow catalytic combustion and activated carbon fiber adsorption technology, combining the advantage of two methods. Toluene and benzene are selected as model pollutant for experiments. Typical features of activated carbon fiber adsorption and reverse catalytic combustion processing on decontaminating these two VOCs are studied. The main content as follows:First of all, nitrogen adsorption apparatus, scanning electron microscope, X-ray diffractometer are used to test and analyze the micro-structure, micro-surface morphology and elements of activated carbon fiber. The results show that activated carbon fiber has lots of micro-structure, large specific surface area and the surface contains rich oxygenic functional groups, which shows that activated carbon fiber is a good adsorbent.Secondly, study on activated carbon fiber to toluene/benzene adsorption and adsorbent desorption regeneration is carried out on a laboratory scale reactor. Results show that the activated carbon fibers have high efficiency on toluene and benzene adsorption and desorption. Toluene adsorption efficiency is higher than that of benzene, while adsorption capacity of toluene is rather high even with very lean toluene inlet concentration. Velocity and other factors have relative great influence on adsorption equilibrium. When hot air is used in desorption of saturated activated carbon fiber, the results show that with the increase of temperature and flow rate, the speed of desorption increases and the efficiency increases as well. The adsorption efficiency of activated carbon fiber after multi-regeneration is over 90%, with good recycling.The mechanism of the adsorption process is analyzed, and three classic absorption isotherm equations are used for fit to validate the characteristics of ACF. Among them, Langmuir equation has the best goodness of fit of isothermal adsorption curve, explaining that within certain concentration range, the majority of adsorption is based on single molecular layer adsorption.Experimental investigation on decontaminating of waste gas containing low concentration of benzene in reverse flow catalytic reactor under various operation conditions are carried out. Results show that temperature of each measuring point along the reactor varies periodically with flow reversal operation. The reactor thermal state is a combination of exothermic reaction and system heat loss. Operating conditions, including inlet concentration, flow reversal cycle time and superficial velocity etc, are able to change reactor thermal state, affecting benzene conversion. During the experiments, the conversion of benzene is almost 99% which shows that the reactor performance on benzene treatment is relatively good.Finally, the process design based on activated carbon fiber adsorption and catalytic combustion reaction has been calculated and analyzed by an industrial application with 100,000 m3/h waste gas containing low concentration of benzene. The designed continuous purification of low concentration waste gas with periodic operation exhibits high practicability and efficiency.