Thermodynamic modeling modification and experimental validation of entrained-flow gasification of biomass

In this work, entrained-flow gasification of pine sawdust (PS) was studied at 1300 degrees C in H2O-and CO2-enriched atmospheres by means of thermodynamic equilibrium modeling and experimentation. The experimental results indicated that the yield of effective gas (CO and H-2) was continuously improved by increasing the H2O content, but hindered by excess CO2. Moreover, solid products were reduced with the addition of H2O and CO2. Soot, the born carbon produced in entrained-flow gasification, was difficult to be removed completely under all conditions studied. Both experimental and modeling results indicated that CH4 yield increases with increasing H2O. To improve model performance, modifications were made by using the carbon conversion for carbon balance calculation and by calibrating the equilibrium constants of the methanation and water-gas shift reactions with two coefficients. The accuracy of the modified model was proved with mean absolute error (MAE, 1.11%-1.57%), root mean square error (RMSE, 1.33%-1.92%), and mean absolute percentage error (MAPE, 7%-18%), indicating the validity of the modification method. An empirical expression for carbon conversion with four operating variables was developed based on 12 sets of the experimental data, which greatly enhanced the validity and universality of the modified model. The syngas compositions predicted by the modified model were in good agreement with the experimental results.

Automated summary

In this study, entrained-flow gasification of pine sawdust was investigated using a combination of thermodynamic equilibrium modeling and experimentation. The results showed that increasing the H2O content improved the yield of CO and H2, while excess CO2 hindered the gas yield. The addition of H2O and CO2 reduced the solid products, but soot, a by-product of the gasification process, was difficult to remove completely. Both experimental and modeling results demonstrated that the CH4 yield increased with increasing H2O. The modeling approach was modified by considering carbon conversion for carbon balance calculation and adjusting the equilibrium constants of methanation and water-gas shift reactions. The modified model showed good accuracy, as indicated by low error values. An empirical expression for carbon conversion with four operating variables was also developed, enhancing the validity and applicability of the modified model. The predicted syngas compositions were in good agreement with the experimental results.