Study On Chemical Heat Recovery Two-stage Combined Gasification And Materials Reaction Characteristics Of The Second-stage

The two-stage combined coal gasification with heat recovery through chemical reaction was mainly researched in this thesis. The hot-state experiments of two-stage gasification process were carried out. The temperature distribution in the gasifier and gasification reactivity of the second stage as well as the catalytic effects of additives to the secondary gasification reactions were also studied. The gasification reaction process of char in the mixtures of steam and CO2 as well as the inhibition effects of H2 and CO on char-steam and char-CO2 reactions were also investigated. This thesis is of great theoretical significance in guiding the subsequent research on the process of two-stage gasification.The amounts of coal for the second stage were studied in this paper. It was found that when the lump coal amounts of the second stage increased, the temperature gradient of gasifier was moved down to the second stage. When the lump coal amounts were 2kg, the content of the effective gas was increased from 73.94% to 75.01%. The increase of the effective gas and LHV were 1.43% and 1.31%, respectively. The appropriate lump coal adding amounts for the second stage were 2kg under current experimental devices and conditions, which were equal to 10% of equivalent amount of coal for the first stage. The catalytic effects of calcium and potassium on secondary gasification reaction were studied in this paper. When the potassium loading was larger than 5%, the catalytic effects for the gasification reaction was much more significant. When adding 8% potassium, the average effective gas concentration was increased by 3.51%, LHV by 4.58%, and the carbon conversion of the second stage lump coal was 89.5%. Compared with raw coal, the gasification reaction rates were effectively increased when adding 5% calcium or potassium to the second stage lump coal, and the effects of adding 5% potassium was better than adding 5% calcium.The gasification reaction characteristics of the Inner Mongolia coal char with H2O and CO2 were investigated in a tubular furnace experimental device. It was found that the activation energies of NMJ gasification with steam and CO2 were close to the study results of literatures. H2 and CO had obvious inhibition effects on gasification reaction. For the gasification reaction of NMJ in the mixtures of H2O and CO2, the L-H model based on the common active sites assumption fitted the experimental results very well, which indicated that common active sites assumption was more applicable to the gasification mechanisms of NMJ in the mixtures of H2O and CO2. The existences of H2 and CO will not change the mechanisms of mixture gasifcation reaction.