Detoxification and energy recovery by wet air oxidation of waste streams

The Wet Air Oxidation process can be used for cleaning up high energy containing solid-water mixtures as well as low energy containing toxic effluents. Conversion of reaction enthalpy to mechanical energy, thus attaining a selfsustaining steady state W.A.O. process, can become a possibility under certain conditions.

This paper discusses the potential feasability of a relatively simple energy recovery system. The system is simulated on a microcomputer after development of a mathematical model describing the W.A.O. reactor and utilities. Simulations point out, that the system becomes thermally self-sustaining when ΔCOD values are above 1O–20 g/kg, the mean operating temperature being 275°C at a reactor pressure of 1O3 bar. Even at very high mechanical efficiencies of the compressor no excess mechanical energy is produced with the recovery system used in the present study. The results of predicted influences of other independent variables such as reactor pressure, oxygen use efficiency and heat loss show satisfying agreement with those of other authors. Assumed utility efficiencies appear to be of major importance in calculating maximum attainable relative excess mechanical energy.