Pyrolysis and gasification studies of Indian and Turkish high ash coal samples have been performed using coupled TGA-MS method. Coal samples were heated in the TGA apparatus in an argon, steam, CO2 and blended mixtures of CO2 and steam in a temperature range from 25-1250°C with heating rates from 35 to 1000 K/min. Gas evolution measurements is performed using the mass spectrometry system. During the devolatilisation stage (350-700°C), the maximum mass loss has observed in which O2, CO2, CO, H2 and small amount of hydrocarbon compounds are released. Char gasification is mainly influenced by operating conditions such as heating rate and reaction temperature and also the char production method, its physical structure and size and chemical composition of the char. The steam and CO2 gasification rates of the chars are carried out at the temperatures of 850, 900, 950, and 1000°C. Three kinetic models are applied to describe the char conversion rates: volumetric model, grain model, and random pore model. The activation energy of Indian coal-char is varying from 122 to 177 kJ mol-1 under steam gasification and from 130 to 214 kJ mol-1 for CO2 gasification. The activation energy for char-steam gasification is 156-173 kJ/mol, whereas in the steam blended with CO2 gasification, it ranges between 162 and 196 kJ/mol for 3 mm particles. Similar trends are observed for the Arrhenius constant values for both sized particles.
Part of the book: Gasification for Low-grade Feedstock