Effects of potassium carbonate on acetaldehyde gasification in supercritical water

Abstract

ABSTRACTAcetaldehyde is a key intermediate to explore the biomass gasification process in supercritical water. To investigate the effects of potassium carbonate on acetaldehyde gasification in supercritical water at different temperatures (500 ~ 600 °C), pressures (22.5 ~ 27 MPa), residence time (6 ~ 12 s) and K2CO3 concentrations (0 ~ 2 wt.%), the experiments using the continuous reactor and the kinetics analysis using the lumped kinetic model were carried out, respectively. The experimental results showed that the operating parameters affected the yields of gaseous products during the acetaldehyde gasification in supercritical water, which were on the order of temperature>residence time>pressure. Effects of K2CO3 on the gaseous products were highly related to the temperatures. At the high temperature of 550 ~ 600 °C, K2CO3 significantly promoted the gasification efficiency and yields of H2, CO2, CH4, and C3H6, while reduced the yield of CO. At the low temperature of 500 ~ 525 °C, K2CO3 obviously inhibited the yields of H2 and CH4. Besides, with the increasing pressures from 22.5 MPa to 27 MPa, the effects of K2CO3 kept in the similar level. In addition, with the increasing residence time from 6 s to 12 s, the increased K2CO3 concentrations improved acetaldehyde gasification. The lumped kinetic results indicated that the effects of K2CO3 on main gaseous products were explained by promoting the direct decompositions of acetaldehyde/intermediates and methanation reaction (CO+3H2→CH4+H2O), while inhibiting the water gas reverse reaction (CO+H2O←CO2+H2). Moreover, with the increasing K2CO3 concentration, the value of ktotal generally improved. Higher K2CO3 concentration facilitated the acetaldehyde decomposition in supercritical water.