Jae-Goo Lee

Numerical study on the coal gasification characteristics in an entrained flow coal gasifier

The coal gasification process of a slurry feed type, entrained-flow coal gasifier was numerically predicted in this paper. By dividing the complicated coal gasification process into several simplified stages such as slurry evaporation, coal devolatilization and two-phase reactions coupled with turbulent flow and two-phase heat transfer, a comprehensive numerical model was constructed to simulate the coal gasification process. The k–e turbulence model was used for the gas phase flow while the Random-Trajectory model was applied to describe the behavior of the coal slurry particles. The unreacted-core shrinking model and modified Eddy break-up (EBU) model, were used to simulate the heterogeneous and homogeneous reactions, respectively. The simulation results obtained the detailed information about the flow field, temperature and species concentration distributions inside the gasifier. Meanwhile, the simulation results were compared with the experimental data as a function of O2/coal ratio. It illustrated that the calculated carbon conversions agreed with the measured ones and that the measured quality of the syngas was better than the calculated one when the O2/coal ratio increases. This result was related with the total heat loss through the gasifier and uncertain kinetics for the heterogeneous reactions.

Gasification of biodiesel by-product with air or oxygen to make syngas

In the present study, gasification of biodiesel by-product, crude glycerin, was performed in an entrained flow gasifier. Gasification was conducted in a temperature range of 950-1500 degrees C and excess air ratio of 0.17-0.7 for air or oxygen as a gasification agent. From the results, syngas heating value, carbon conversion and cold gas efficiency of more than 2500 kcal/Nm(3), 92% and 65% were achieved, respectively. The H(2)/CO ratio of the product gas was varied from 1.25 to 0.7 with the excess air ratio and this gas composition was favorable for DME synthesis. The optimum excess air ratio for gasification of biodiesel by-product was evaluated to be an approximately 0.35-0.4. The present results indicate that crude glycerin can be utilized as a feedstock for gasification to make syngas.

Experimental studies of 1 ton/day coal slurry feed type oxygen blown, entrained flow gasifier

Experimental Studies of a 1 Ton/Day coal slurry feed type oxygen blown, entrained flow gasifier have been performed with the slurry concentration and gasifier temperature at 65% and above 1,300 ‡C, respectively. The characteristics of ash fusion temperature with addition of CaO as a flux were investigated to maintain the proper slag tapping condition in the range of reaction temperature. As the flux addition increased, ash fusion temperature showed a eutectic effect with the eutectic at around 20–30% CaO. In order to analyze the gasification characteristics, the effects of O2/coal feed ratio on the product gas composition, heating value, gasifier temperature and cold gas efficiency were evaluated. From the results, it was shown in the case of Kideco coal that the cold gas efficiency was 44–60% and the heating value was 1,700-2,200 kcal/Nm3, while Drayton coal showed a cold gas efficiency of 55–62% and a heating value of 1,800-2,200 kcal/Nm3. In the case of Datong coal, the cold gas efficiency was 38–65%, and the heating value was 2,000-2,300 kcal/Nm3. Also, the results showed that the optimal operating condition of O2/coal ratio for the three different coals was 0.9.