Investigation of the evolved gases from Sulcis coal during pyrolysis under N2 and H2 atmospheres

The evolution of gases and volatiles during Sulcis coal pyrolysis under different atmospheres (N2 and H2) was investigated to obtaining a clean feedstock of combustion/gasification for electric power generation. Raw coal samples were slowly heated in temperature programmed mode up to 800 °C at ambient pressure using a laboratory-scale quartz furnace coupled to a Fourier transform infrared spectrometer (FTIR) for evolved gas analysis. Under both pyrolysis and hydropyrolysis conditions the evolution of gases started at temperature as low as 100 °C and was mainly composed by CO and CO2 as gaseous products. With increasing temperature SO2, COS, and light aliphatic gases (CH4 and C2H4) were also released. The release of SO2 took place up to 300 °C regardless of the pyrolysis atmosphere, whilst the COS emissions were affected by the surrounding environment. Carbon oxide, CO2, and CH4 continuously evolved up to 800 °C, showing similar release pathways in both N2 and H2 atmospheres. Trace of HCNO was detected at low pyrolysis temperature solely in pure H2 stream. Finally, the solid residues of pyrolysis (chars) were subjected to reaction with H2 to produce CH4 at 800 °C under 5.0 MPa pressure. The chars reactivity was found to be dependent on pyrolysis atmosphere, being the carbon conversions of 36% and 16% for charN2 and charH2, respectively.