Pressurized Spouted Fluidized Bed Coal Partial Gasification Test And Mathematical Model

A comprehansive study on coal partial gasification of a pressurized spout-fluidized bed has been performed in a 89mm inner diameter, 4.2m total height spout-fluidized gasifier. The gasifying agent is the mixture of air and steam with high temperature. Experiment is carried out at elevated pressure in order to reduce char loss and improve the efficiency of coal utilization.In the experiment, investigation into the effect of gasification pressure,bed temperature, air-coal ratio and steam-coal ratio on gas composition and heating value has been conducted.It is seen from experimental results that increasing bed temperature could improve the quality of coal gas by means of enhancing the reactions such as steam gasification and CO2 gasification,and too high bed temperature would result in heat loss and coal agglomeration.The air-coal ratio and steam-coal ratio has the same effect on gas composition and heating value. Based on the mechanism of coal gasification, the results achieved from experiments indicate that there exists a suitable range of gasification temperature, air-coal ratio and steam-coal ratio for air-blown fluidized bed gasifier.The rate of gasification reaction is strongly influenced by gasification temperature, the solids recirculation and heat exchange flow from spout to annulus.A one-dimensional nonisothermal numerical model for a pressurized spout-fluidized bed is developed,treating the grid,bubble and freeboard zones in series.Sub-model including coal devolatilization, hydrodynamics of gas-solid fluidization, reactions of partial gasification,mass equation and heat balance are taken into account.Based on the comparison with the experimental data, simulative results have a good agreement with experimental data, especially for CO2 and H2,but have some error with CO and CH4. Although it could predict the trend of gas composition and heating value, the model needs to be futhur modified.