Experimental study on the mixing characteristics inside an inner preheating transpiring-wall reactor for supercritical water oxidation

The mixing characteristics between bulk flows and transpiring water are critical to feed degradation and water film formation inside a transpiring-wall reactor (TWR). In this study, a supercritical water oxidation system with an inner preheating TWR is established, and special experiments are designed by adding organic matter (glycerol) to the transpiring water to evaluate the mixing degree between the bulk flows and transpiring water in the hydrothermal flame zone. Although the chemical oxygen demand concentration of the reactor effluent increases significantly due to the addition of glycerol to the transpiring water, a certain amount of glycerol is entrapped into the flame zone and degraded. The increase in jet velocity with increased heat source flow or temperature is favorable for mixing and enhances jet entrainment. Moreover, increasing the transpiring coefficient and transpiring water temperature can increase the radial velocity of transpiring water, which also benefits mixing. Possible applications utilizing the mixing characteristics are further proposed. © 2019 Elsevier B.V.