An improved adsorption–catalytic process for removing volatile organic compounds from exhaust gases

Mathematical Modeling of the Adsorption-Catalytic Process with Internal Heater in a Multisectional Arrangement

“…The positive effect of bed sectioning was earlier studied in our preceding works, − which were based on a one-dimensional adiabatic model of catalyst bed. In fact, the possible nonadiabatic behavior of the real three-dimensional (3D) beds may produce significant differences in simulation results.…”

“…The chemistry of the processes was described by the simplified kinetic scheme that includes the reversible VOC adsorption (eq ), the transition of physically adsorbed VOCs ([A]) into the irreversibly adsorbed chemisorbed form ([P]) (eq ), and the oxidation of the chemisorption intermediates into deep oxidation products (eq )­ The model equations were defined as follows. The velocity field and pressure were set by Brinkman (eqs and ) and Navier–Stokes (eqs and ) equations for porous and free domains The material balance considered convection and diffusion in the gas phase (eq ), mass transfer between gas and pellet (eq ), diffusion of gas components in pellet pores (eq ), and surface compound variation during the – reactions (eq )­ The energy balance with one common temperature for gas and pellets (eq )­ The reaction – rates were presented as follows And the reaction rates for the bulk and surface species are as follows …”

“…As in previous works, − the application of the commercial copper–chromia–alumina deep oxidation catalyst ICT-12–8 (manufactured by Katalizator Co., Novosibirsk, Russia) was considered, so the “alumina” was chosen as the basic solid phase material in COMSOL for the definition of the physical and thermophysical properties of the catalyst.…”

“…The reduction of peak concentrations and temperatures in the outlet streams can be achieved through the use of a sectional system. − The mixture to be cleaned is fed into all parallel sections concurrently, and regeneration is carried out in turn. Thus, the flow at the outlet of the regenerated section is diluted with the flows, leaving the remaining sections operating in the adsorption mode.…”

“…The advantages of this process include the rejection of the constant heating of the supplied gases and the ability to process gases containing VOCs over a wide range of concentrations. The disadvantages include parasitic heating of the inlet gas pipe when the reactor is heated from an external heater, partial desorption of VOCs during catalyst heating (in this case, the concentration of VOCs at the outlet can significantly exceed the inlet concentration), and the possibility of high-temperature gas (300–500 °C) being released into the exhaust gas duct …”