Characterization of several kinds of coal and biomass for pyrolysis and gasification

•Pyrolysis and gasification of different fuels have been experimentally assessed.•Wood chips and different coals have been considered as reference fuels.•Thermogravimetric analysis allows to design the pilot-scale gasification tests.•Lignites are more performing than other fuels for fixed-bed air-blown gasification.

Sotacarbo is currently developing several research projects to optimize a coal and biomass gasification process for small- and medium-scale power generation and hydrogen production. To achieve this goal, between 2007 and 2008, Sotacarbo built a flexible pilot platform in its Research Centre in the Serbariu former coal mine (Sardinia, Italy), which is still very much into operation. The platform includes a demonstration and a pilot air-blown fixed-bed gasifiers, the latter tested for more than 2200 h and equipped with a flexible syngas treatment line for combined power generation and CO2-free hydrogen production.This paper reports the characterization of several kinds of fuels in terms of pyrolysis and gasification performance. In particular, a number of different coal and biomass samples have been tested, including South African bituminous coal, Sardinian high sulphur Sulcis sub-bituminous coal, lignites from Alaska and Hungary and stone pine wood chips.An improved understanding of coal and biomass pyrolysis may be useful to predict the reactor performance in a gasification process and also to optimize the experimental campaigns in the pilot plant. Therefore, before the tests in the pilot-scale gasification unit, fuels are typically characterized by a thermogravimetric analysis to evaluate the pyrolysis behavior.Among all the tested coals, Usibelli lignite from Alaska is the most reactive one. Its derivative thermogravimetric (DTG) profile presents a clear pyrolysis peak at 478 °C. The pilot-scale experimental results show that the gasification of 24 kg/h of Usibelli lignite allows the production of 79.67 kg/h of raw syngas, characterized by a lower heating value of 5.14 MJ/kg. An opposite behavior is shown by the South African bituminous coal, which does not present a peak in the DTG curve, as a consequence of the low volatile content in the fuel structure. This is confirmed by the gasification tests in the atmospheric fixed-bed plant, which show a low coal consumption and, as a consequence, a low syngas production (46.83 kg/h). Wood chips presents a very significant peak in the DTG profile at the temperature of 318 °C but, due to the low energy density, its gasification involves a low syngas production (23.31 kg/h).