Empirical and chemical equilibrium modelling for prediction of biomass gasification products in bubbling fluidized beds

Model Reduction Applied to Empirical Models for Biomass Gasification in Downdraft Gasifiers

“…This same procedure of developing equilibrium models then fitting linear correlations to the model outputs has also been demonstrated by Rupesh et al, who also show that linear models can fit well with the output of an equilibrium type model but do not show a comparison of experimental values against the linear correlations [14]. More recently, Pio and Tarelho have compared the prediction accuracy of equilibrium and linear models for predicting the performance of bubbling fluidized bed reactors for biomass gasification [4]. They show that the linear models can accurately be used to predict the output composition of the thermodynamic model (R squared values of 0.93 and 0.79 for hydrogen and carbon monoxide) but have limited accuracy when used to predict the experimental output composition values (R squared values of 0.04 and 0.23 for hydrogen and carbon monoxide) [4].…”

“…Alternatively, Mirmoshtaghi et al have shown through partial least squares regression that higher prediction accuracy can be found from the resulting linear model expressions (R squared values of 0.8 and 0.53 for hydrogen and carbon monoxide) for circulating fluidized bed gasifiers [15]. Although this higher accuracy achieved by Mirmoshtaghi et al could be explained by the fact that they use a much larger number of different input values (18 different terms in the linear expressions) [15], compared to the two input values considered in the linear relations used by Pio and Tarelho (only considering temperature and equivalence ratio) [4].…”

“…To avoid the complexities associated with kinetic and CFD (computational fluid dynamics) models, a large number of studies have focused on equilibrium models, artificial neural networks, and other empirical or semi-empirical models which allow for the fast simulation, sensitivity analysis, and optimization of gasification systems. However, equilibrium models are known to have some inaccuracy because the real gasifier does not necessarily reach equilibrium and can lead to an overestimation of the hydrogen and carbon monoxide content of producer gas and an underestimation of methane content [4]. To address this inaccuracy, a number of studies have proposed adding correction factors or correlations to the equilibrium models to make the results closer to reality as detailed in the review of Ferreira et al [5].…”

“…More recently, Pio and Tarelho have compared the prediction accuracy of equilibrium and linear models for predicting the performance of bubbling fluidized bed reactors for biomass gasification [4]. They show that the linear models can accurately be used to predict the output composition of the thermodynamic model (R squared values of 0.93 and 0.79 for hydrogen and carbon monoxide) but have limited accuracy when used to predict the experimental output composition values (R squared values of 0.04 and 0.23 for hydrogen and carbon monoxide) [4]. This could be due to the high variability of experimental composition values for bubbling fluidized bed reactors as suggested by Pio and Tarelho [4].…”

“…They show that the linear models can accurately be used to predict the output composition of the thermodynamic model (R squared values of 0.93 and 0.79 for hydrogen and carbon monoxide) but have limited accuracy when used to predict the experimental output composition values (R squared values of 0.04 and 0.23 for hydrogen and carbon monoxide) [4]. This could be due to the high variability of experimental composition values for bubbling fluidized bed reactors as suggested by Pio and Tarelho [4]. Alternatively, Mirmoshtaghi et al have shown through partial least squares regression that higher prediction accuracy can be found from the resulting linear model expressions (R squared values of 0.8 and 0.53 for hydrogen and carbon monoxide) for circulating fluidized bed gasifiers [15].…”