Thermodynamic analysis of some volatile species at elevated pressure and temperature during combustion of Pakistani Lakhra and Thar lignite chars

Abstract

Volatile species (e.g. Na-,K-,Cl-, and S) are released during thermal conversion of coal causing eventual problems such as fouling, slagging and corrosion, especially in gas turbines, on super heaters and in the colder part of heat recovery systems. Thermodynamic study of the released inorganic compounds is supportive before eventually launching experimental work. Therefore, thermodynamic equilibrium was calculated using FactSage 5.2, simulating combustion conditions at elevated pressure (5, 10 and 15 bar) and elevated temperature (1000, 1400 and 1600°C). Their releasing order of various volatile species was estimated by plotting mole fraction of each species at temperature 1000°C and pressure 1 bar. These calculations predict that SO2 is the most stable species for combustion. At all pressure the lowest amount of NaCl and KCl volatilized for LKH and THR lignite char. Evolution of NaCl, KCl and HCl depends on the amount of Cl present in both lignite chars.   Key words: Combustion, fact sage, equilibrium calculations, release of volatile species.