Catalysed and uncatalysed steam gasification of eucalyptus char: influence of variables and kinetic study

A study of the steam gasification of Eucalyptus chars has been carried out, using Li, Na and K chlorides as catalysts, in order to characterise the gas phase with a view to its energy use, analysing the influence of steam flow rates, initial mass of char, particle size and temperature. The main gases generated were H2, CO and CO2, with a higher heating value between 9 and 10 MJ/N m3. The presence of alkaline metals as catalysts resulted in a high process rate. The catalyst concentration had a positive effect up to a given level (1% for LiCl and 3% for NaCl and KCl), above which there was saturation due to the blocking of the carbon pores. A kinetic model based on gas generation gave the activation energy and the reaction order with respect to each catalyst. These activation energies were in all cases lower than that of the uncatalysed process. This, together with a decrease in the Arrhenius pre-exponential factor, leads to isokinetic points, i.e. temperatures at which the catalysed and uncatalysed processes take place at the same rate. These isokinetic points were 903, 1356 and 998°C for Li, Na and K chlorides, respectively.