Improved reactivity of large coal particles by K2CO3 addition during steam gasification

• Max. K loading obtainable for large coal particles is between 0.76 and 0.83 wt.%.
• The addition of K2CO3 increases the steam gasification rate, however, the effect of additive addition is more pronounced at lower gasification temperatures.
• The reaction rate is temperature sensitive, and independent of particle size.
• A slight decrease in activation energy is observed with the addition of K2CO3.
• The homogeneous model accurately describes the reaction kinetics.

In this study, the excess solution impregnation method was used to impregnate large coal particles (5 and 10 mm) with K2CO3, and the effect of the additive on steam gasification reactivity was investigated. A washed bituminous, medium rank-C Highveld coal, with an ash content of 12.6 wt.% (air-dried basis), was used for experimentation. The excess solution method was used to impregnate coal particles with the selected additive, K2CO3, and results from XRF analysis indicated that the potassium loading increased from 0.05 wt.% (raw coal) up to 0.83 wt.% (impregnated coal), on a coal basis. The potassium-impregnated large coal particles were used for low temperature (800–875 °C) steam gasification experiments. Results obtained for the reactivity of the parent coal were compared to that of the impregnated coal, which indicated that the addition of K2CO3 increased the reaction rate of large coal particles by up to 40%. It was also found that the addition of K2CO3 decreased the activation energy, from 191 kJ/mol (raw coal) to 179 kJ/mol (impregnated coal).