INVESTIGATION OF A DIRECT CATALYTIC ABSORPTION REACTOR FOR HAZARDOUS-WASTE DESTRUCTION

Direct Calatytic Absorption Reactors (DCARs) use a porous solid matrix to volumetrically absorb solar energy. This energy is used to promote heterogeneous chemistry on the catalytic surface of the absorber with fluid-phase reactant species. Experimental efforts at Sandia National Laboratories (SNL) are using a DCAR to destroy hazardous chemical was te. A numerical model, previously developed to analyze solar volumetri c air-heating receivers and methane-reforming reactors, is extended in this work to include the destruction of a chlorinated hydrocarbon che mical waste, 1,1,1-trichloroethane (TCA). The model includes solar and infrared radiation, heterogeneous chemistry, conduction in the solid absorber, and convection between the fluid and solid absorber. The pre dicted thermal and chemical conditions for typical operating condition s at the SNL solar furnace suggest that TCA can be destroyed in a DCAR . The temperature predictions agree well with currently available ther mocouple data for heating carbon dioxide gas in the DCAR. Feasibility and scoping calculations show trichloroethane destruction efficiencies up to 99.9997 percent at a trichloroethane flow rate of 1.7 kg/hr may be obtainable with typical SNL solar furnace fluxes. Greater destruct ion efficiencies and greater destruction rates should be possible with higher solar fluxes. Improvements in reactor performance can be achie ved by tailoring the absorber to alter the radial mass flux distributi on in the absorber with the radial solar flux distribution.