Heat transfer model for regenerative beds

Regenerative catalytic oxidizers (RCO) are an economic and effective means of controlling volatile organic compounds with concentrations exceeding 1,200 mg/m(3) in a gas stream. However, factors influencing the performance of RCO when treating volatile organic compounds in gas streams have seldom been addressed. Therefore, this study presents a convection-dispersion model with an effective thermal diffusivity alpha(e) as a parameter to simulate the performance of RCO. To verify the effectiveness of the proposed model, a pilot-scale aco was constructed with two 20 X 200 cm (inside diameter X height) regenerative beds. Gravel was used as the thermal regenerative solid material. Experimental results indicated that the model with an alpha(e) of 2.0-3.8 X 10(-6) m(2)/s can be used to describe the time variation of solids temperature with the packing height at superficial. gas velocities LI of 0.080-0.382 m/s. Values of alpha(e) for the bed are closer to those for the gravel solids (alpha(s) = 1.0 X 10(-6) m(2)/s) than for air (alpha(e) = 54 X 10(-6) m(2)/s). Those results further demonstrate that the conductive heat transfer in the solid material in the axial direction of the bed is a major controlling factor for the performance of the RCO and the convective one is a minor factor in the present case.