Sulcis coal char reactivity under high-pressure H2

Abstract

The hydrogasification reactivity of charN2 and charH2, obtained from Sulcis coal pyrolysis at 900°C in inert and reductive atmospheres, respectively, was investigated in a commercial microreactor under temperature programmed reaction (TPR) at high-temperature (700–800°C) and high-pressure H2 (1.0–5.0MPa) conditions. The flue gases were analyzed online by FTIR spectrometry for the identification of volatile species produced. The emissions of carbon (CO2 and CO) coming from both chars reached the maximum releasing rate below 500°C, whereas nitrogen-based compounds (HCNO and NH3) were solely detected during the hydrogasification reaction of charN2. Meanwhile, the main product of char hydrogasification CH4 was detected at temperature as low as 450°C. Generally, the carbon conversion values of charN2 were higher than those of charH2. At low-temperature and pressure reaction conditions the carbon conversion of charH2 rapidly went down. A first-order reaction rate dependence on H2 pressure at 800°C was found for charN2, whereas the reaction order was almost double for charH2. The apparent activation energies of charN2–H2 reaction at 1.0 and 5.0MPa pressures were 96 and 78kJmol−1, respectively, whereas the apparent activation energy for charH2–H2 reaction under 5.0MPa pressure was 140kJmol−1. The Sulcis coal reactivity during the hydrogasification process was significantly impacted by the pyrolysis conditions used in getting chars.