Hydrothermal methanol diffusion flame as internal heat source in a SCWO reactor

Abstract

Experimental results of a supercritical water oxidation (SCWO) system with a transpiring wall reactor (TWR) containing a turbulent hydrothermal methanol diffusion flame as internal heat source are presented. The present paper focuses on the hydrothermal flame combustion in a geometrically simple wall-cooled coaxial burner. Various kinds of hydrothermal flame experiments with methanol–water mixtures as fuel stream and pure oxygen as oxidizer were conducted at an operating pressure of 250 bar. Ignition was accomplished by heating-up the reactants to auto-ignition temperature (typical ignition temperatures 460–490 ° C). To investigate the flame stability, the injection temperature of the methanol–water mixture was lowered step-by-step to extinction. For methanol mass fractions higher than 11%, desired subcritical extinction temperatures are reached. The inlet temperature of the fuel stream can be lowered below 100 ° C with 27 wt.% methanol. The conversion ratios based on the analysis of the liquid effluent are generally above 99.95% for flame residence times in the order of magnitude of 100 ms.