Kinetic study of polish hard coal and its char gasification using carbon dioxide

The kinetics of polish hard coal and its char gasification using carbon dioxide as gasifying agent was studied at atmospheric pressure between 293 and 1223 K at different linear heating rates. Calculations using isoconversional method showed that coal gasification has two separate steps: pyrolysis in the range from 600 to 850 K and gasification in the range from 1000 to 1273 K. This proves the additivity of pyrolysis and gasification steps. The apparent activation energy calculated using the F1 model for coal char gasification is equal to 245 kJ/mol, and log A is equal to 7.4 1/s, which is similar to the value obtained by the isoconversional method. Coal gasification reaction with carbon dioxide is faster and takes place in a lower temperature range than the gasification process of the char obtained in a separate process. The stabilized and chemically deactivated char is harder to gasify, and the same conversion is achieved at the higher temperature. The estimated shift may be as high as 150 K.

► Two reaction steps during gasification was shown using isoconversional method.
► Additivity of coal pyrolysis and gasification steps was proved.
► Coal char is harder to gasify than coal.
► Gasification should be studied in the one step reaction because char reactivity is very much dependent on process conditions.