Entrained flow gasification behaviour of Victorian brown coal char at low temperature

This paper presents gasification data for two Victorian brown coal chars (Yallourn and Morwell) in CO2 at temperatures between 700 and 1000 °C. The effects of temperature, gas-particle contact mode (entrained mode vs drop-tube mode), reactant gas concentration and residence time on carbon conversion, and syngas yield and composition was investigated. The results indicate that at a higher temperature and CO2 concentration, carbon conversion increases as expected, along with syngas yield and composition. It is found that gasification under entrained mode achieves higher carbon conversion and gas yield than that under the drop-tube mode, even at a shorter residence time. The finding suggests that the gasification experiments should be conducted under entrained flow condition (gas velocity > particle velocity) to truly reflect gasification performance. At 1000 °C, with an increase in residence time, the carbon conversion and syngas yield gradually increases to nearly 100% and an estimated equilibrium value, respectively. The experimental data establishes that for a complete char conversion, around 17 s and 21 s residence times are required for Yallourn and Morwell, respectively, if gasification is conducted at 1000 °C in an environment of 20% CO2. This finding indicates that Victorian brown coals need to be gasified at a temperature above 1000 °C to shorten the residence time considering that the typical residence time of industrial entrained-flow gasifier is 6-10 s.