Thermodynamic considerations in the application of reverse mode gasification to the destruction of hazardous substances

Previous studies by us have demonstrated the effectiveness of reverse mode gasification using a granular char matrix for treatment of hazardous wastes . Calculations pertaining to this gasification are presented, including a o ne-dimensional temperature profile and a thermodynamic analysis. Equilibriu m compositions were calculated by free energy minimization using commercial ly available software. The calculated results were compared with experiment al data for gasification of mixtures containing water, selected hydrocarbon s, and used motor oil. Batch and continuous feed reactors were used with op timized operating parameters to generate the data. The dry gas product obta ined from gasification of water and selected hydrocarbons contains carbon d ioxide, carbon monoxide, methane, and hydrogen, in agreement with thermodyn amic predictions, and the compositions agree well with predictions obtained assuming that chemical equilibrium is attained at a temperature of 650 deg rees C. The dry gas product from gasification of motor oil contains small a mounts of law molecular weight hydrocarbons, which are not thermodynamicall y stable, but the composition of the major products generally agrees with t he thermodynamic predictions. Under optimized conditions, the aqueous conde nsate contains between 1 and 100 ppm organics. Heat balance terms for the p rocess were also calculated, and these demonstrate the efficiency of gasifi cation as a treatment method.