Effect on Combustion Properties of Coal Treated by Microwave Irradiation Combined with Sodium Hydroxide Solution

A Kentucky coal sample treated by microwave irradiation (MI) combined with sodium hydroxide solution was performed using a thermo-gravimetric analyzer (TGA) coupled to a Fourier transform infrared spectrometer (FTIR). The combustion properties and structural changes of coal under different conditions were investigated and compared. The results show that the desulfurization efficiency of coal samples increases with the increase of sodium hydroxide solution concentration. Microwave irradiation can significantly improve the desulfurization efficiency. The whole combustion process of the treated coal sample becomes longer; the combustion performance becomes worse. The total mass loss of coal treated samples is significantly reduced, and the temperature corresponding to the maximum weight loss rate decreases with the increase of sodium hydroxide concentration. The infrared spectra of the coal samples treated with microwave and 5% sodium hydroxide solution were basically unchanged, while the O containing groups and aromatic C-H groups increased in the coal samples treated with 20% sodium hydroxide solution.