Key Words:Calcium compounds;Carbon dioxide - Coal - Coal combustion - Fuels - Hydrogen production - Oxygen - Reaction kinetics - Scanning electron microscopy - Spectrometers - Synthesis gas - Thermoanalysis;Chemical-looping combustion process - Chemical-looping process - Energy dispersive spectrometers - Environmental friendliness - Iso-conversional method - Parallel competing reaction - Thermo dynamic analysis - Thermo-gravimetric experiments

Abstract:Chemical looping combustion process for gaseous and solid fuel has been investigated widely. Recently, particular attention is paid to syngas and hydrogen generation from natural gas or solid fuels. CaSO<inf>4</inf>has been proved to be a promising oxygen carrier for the chemical looping process with the merit of low price and environmental friendliness. The reaction mechanism of coal and pure CaSO<inf>4</inf>for syngas production in the CO<inf>2</inf>atmosphere was investigated using the simultaneous thermal analyzer in this paper. First, the thermodynamic analysis of reaction between coal and CaSO<inf>4</inf>with different mass ratios was carried out respectively in N<inf>2</inf>and CO<inf>2</inf>atmospheres. It predicted that the CO<inf>2</inf>can promote the reactions, while the coal-CaSO<inf>4</inf>mass ratios affected the fate of sulfurous gaseous species greatly. Subsequently, thermogravimetric experiments were conducted by the peak fitting technique. It concluded that the drying and pyrolysis of the coal were main reactions before 800 &deg;C, while the complex reactions, including the reaction between CaSO<inf>4</inf>and coal char, gasification of coal char, and the decomposition of CaSO<inf>4</inf>, occurred during 800-1100 &deg;C. The reaction kinetics and types of the reaction between coal and CaSO<inf>4</inf>for syngas in the CO<inf>2</inf>atmosphere were explored by isoconversional method. It indicated that the complex processes were controlled by the diffusion of gas-solid or solid-solid first, followed by parallel competing reactions. Finally, the reaction residues between coal and pure CaSO<inf>4</inf>with different mole ratios were analyzed using scanning electron microscopy and energy dispersive spectrometer (SEM-EDS). &copy; 2012 American Chemical Society.<br/>

Volume:51

Issue:31

Translation or Not:no