Aspen Plus model of a downdraft gasifier for lignocellulosic biomass adjusted by Principal Component Analysis

Abstract

The development and improvement of biomass gasification processes have been accelerated by the use of computational tools for process simulation, exploring their feasibility under different conditions and identifying key parameters that are validated through real experiments, contributing to maturing a gasification technology from laboratory to commercial scale. This work presents an Aspen Plus model of a small-scale downdraft gasifier using biomasses with different elemental and proximate analyses, combining stoichiometric and non-stoichiometric equilibrium approaches. The pyrolysis, oxidation, and reduction processes in the proposed model were separated into distinct steps, with the first one based on Gibbs energy minimization and the latter based on stoichiometric equilibrium models. A representative tar composition, with a production ratio to gas production based on literature, was considered as an input parameter to the model. The obtained data were analyzed using principal component analysis (PCA) to investigate the relations between equivalence ratio (ER), fixed carbon and volatile material ratio FCMV, the CO conversion through methanation (Mconv), carbon conversion via hydrogasification (Hconv), and the mean residual sum of square MRSS. The most significant results obtained from this study include the successful adjustment of the model to represent the gasification of different biomasses, particularly in correcting the H2 and CH4 concentrations. Notably, the adjustment resulted in a substantial reduction of the MRSS deviation from an average of 94.7% to an average of 7.2% concerning reported results in the literature. These findings demonstrate the accuracy of the model in simulating the gasification process and highlight the importance of considering CH4 reactions adjustment for more reliable predictions. The achieved adjustments are valuable insights for advancing gasification technology towards engineering applications.