Experimental investigations on unmixed combustion for heat transfer applications

Abstract

The potential of Unmixed Combustion (UMC), a novel variant of Chemical Looping Combustion (CLC), is demonstrated for heat transfer applications. A purpose-built test rig, based on a dynamically operated packed bed reactor concept, was designed, fabricated and commissioned. Experiments were conducted using representative Cu based Oxygen Storage and Release Material (OSRM) which was alternately reduced and oxidized in the bed using methane and zero air (21mol% O2) respectively. The energy generated in both reactions due to exothermicity was radially transferred by conduction and convection to coolant air under sustained combustion conditions. For a specific loading of 1.25kg of OSRM and fixed reaction cycle times, the effect of varying zero air flowrate, methane concentration and coolant flowrate on the radial heat transfer was investigated. The radial heat transfer rate was maximized at 95±2% of total energy in the bed at zero air, methane and coolant flowrates of 15LPM, 2LPM and 150LPM respectively. Under “cyclic” steady state conditions, the variation of bed temperature and coolant outlet temperature was restricted to within ±30K and ±3K respectively and the combustion process was observed to be self-sustaining. The results obtained present a strong argument for using UMC based reactor systems as an alternative to “premixed” combustion for process heat transfer applications subject to suitable combination of operating conditions inclusive of cycle time, reactor material of construction and choice of OSRM.