Kinetics of steam gasification of in-situ chars in a micro fluidized bed

•Steam gasification of in-situ char was conducted in a micro fluidized bed reactor.•Method avoided mutation effects and measured gasification efficiently and reliably.•Gasification is well described by shrinking core and random pore models.•Absolute conversion is used for kinetic calculations to avoid mutation effects.•Ex-situ chars are less reactive than in-situ chars.

In-situ char steam gasification was conducted using a multistage in-situ reaction analyzer based on a micro fluidized bed. Rapid pyrolysis was activated when pulverized coal was injected into the micro fluidized bed reactor. The temperature was adjusted to the gasification temperature, which was not higher than the pyrolysis temperature. In-situ char gasification was initiated by switching the atmosphere from Ar to H2O/Ar. The procedure avoided mutation effects and monitored in-situ reactions reliably and efficiently. Char was not completely gasified below 1000 °C. The kinetic parameters calculated from relative or absolute conversions differed from each other. Absolute conversion avoided mutation effects. Gasification accelerated with increasing steam concentration from 15% to 25% but was constant from 25% to 45%. The rate constants for in-situ char were preferable for determining in-situ reactivity. Ex-situ chars were less reactive than in-situ chars. Deactivation of highly reactive char was sensitive to cooling and reheating.