The Effect of Combustion Energy Recuperation in an Annular Double-layer Catalytic Converter

The following contribution deals with catalytic combustion of lean gaseous fuels in an annular double-layer catalytic micro-converter with integrated exhaust energy recuperation. With the proposed design industrially preferred auto-thermal operation was attained for 112 ppmv propane content in adiabatic conditions with inlet temperature of 300 K. The miniaturized recuperative converter exhibited bifurcational changes for very low combustible content with extinction fold located below Tin = 300 K. The increase in fuel concentration enabled compensation of external cooling to certain level. For well insulated modular set of converters internal converter may be treated as adiabatic and external converters non-adiabaticity should be compensated by an additional increase in fuel concentration. For a given converter and fuel a strict range of gas velocities (or GHSV) should be specified. The low value of gas velocity was the key parameter in efficient heat recuperation. The high value of gas velocity led to higher combustion energy release. With too low value of gas velocity combustion energy release was too small with relation to wall heat conduction so as appropriate axial temperature gradient might not develop and higher temperature in the catalytic section of the converter was not attained leading to extinction. With too high value of gas velocity heat recuperation efficiency was too low and extinction was exhibited. To attain higher value of GHSV a more efficient recuperator should be applied, which may be attained with listed heat transfer enhancement techniques.