Abstract: The chemical looping gasification uses an oxygen carrier for solid fuel gasification by supplying insufficient lattice oxygen. The effect of gasifyingmedium on the coal chemical looping gasification with CaSO₄ as oxygen carrier is investigated in this paper. The thermodynamical analysis indicates that the addition of steam and CO₂ into the system can reduce the reaction temperature, at which the concentration of syngas reaches its maximum value. Experimental result in thermogravimetric analyzer and a fixed-bed reactor shows that the mixture sample goes through three stages, drying stage, pyrolysis stage and chemical looping gasification stage, with the temperature for three different gaseousmedia. The peak fitting and isoconversional methods are used to determine the reaction mechanism of the complex reactions in the chemical looping gasification process. It demonstrates that the gasifying medium (steam or CO₂) boosts the chemical looping process by reducing the activation energy in the overall reaction and gasification reactions of coal char. However, themechanism using steamas the gasifying medium differs from that using CO₂.With steam as the gasifying medium, parallel reactions occur in the beginning stage, followed by a limiting stage shifting from a kinetic to a diffusion regime. It is opposite to the reaction mechanism with CO₂ as the gasifying medium.

Key words: Chemical looping gasification, CaSO₄ oxygen carrier, Reaction mechanism, Syngas generation

摘要： The chemical looping gasification uses an oxygen carrier for solid fuel gasification by supplying insufficient lattice oxygen. The effect of gasifyingmedium on the coal chemical looping gasification with CaSO₄ as oxygen carrier is investigated in this paper. The thermodynamical analysis indicates that the addition of steam and CO₂ into the system can reduce the reaction temperature, at which the concentration of syngas reaches its maximum value. Experimental result in thermogravimetric analyzer and a fixed-bed reactor shows that the mixture sample goes through three stages, drying stage, pyrolysis stage and chemical looping gasification stage, with the temperature for three different gaseousmedia. The peak fitting and isoconversional methods are used to determine the reaction mechanism of the complex reactions in the chemical looping gasification process. It demonstrates that the gasifying medium (steam or CO₂) boosts the chemical looping process by reducing the activation energy in the overall reaction and gasification reactions of coal char. However, themechanism using steamas the gasifying medium differs from that using CO₂.With steam as the gasifying medium, parallel reactions occur in the beginning stage, followed by a limiting stage shifting from a kinetic to a diffusion regime. It is opposite to the reaction mechanism with CO₂ as the gasifying medium.

关键词: Chemical looping gasification, CaSO₄ oxygen carrier, Reaction mechanism, Syngas generation