Modelling a counter-diffusive reactor for methane combustion

The counter diffusive reactor containing a catalyst supported on a fibre pad is often used as a radiant heater. Fuel fed from the inlet of the pad is combusted by oxygen diffusing from the reactor exit. This paper describes the development of a two dimensional model of this heater with methane as the fuel. The detailed transport equations are solved using the finite element method. The correct implementation of the boundary conditions is emphasized. The effects of external mass transfer, reaction rate and feed flow rate on the reactor performance are studied. Comparisons are made to experimental results obtained in an earlier investigation. It is shown that the primary limiting step that controls the conversion of fuel is the rate of mass transfer of oxygen through the boundary layer that develops in front of the reactor. Combustion efficiencies approaching 100% can be achieved at sufficiently high rates of reaction.

► We model the catalytic counter diffusive radiant heater for methane combustion.
► The importance of the correct boundary conditions is stressed.
► The effects of reaction rate and mass transfer are studied.
► The rate limiting step is oxygen mass transfer through the external boundary layer.