MODELING AND SIMULATION OF GASIFICATION OF SOLID FUELS FOR OPTIMIZED SYNGAS YIELD USING EQUILIBRIUM AND KINETIC MODELS

Abstract

The gasification of solid fuels has immense potential to overcome the reliance on fossil fuels to meet global energy demands. Gasification is the thermochemical conversion of solid fuel into a synthetic gas that can be used to produce heat and electricity, secondary biofuels, hydrogen gas, and industrial chemicals. Coal, forest biomass, municipal and industrial waste, algal biomass, etc., are some of the feedstocks suitable for gasification. Biomass is a versatile fuel source that ensures continuous energy supply when compared with renewable solar and wind energy sources. Thus, gasification is a versatile technology that can promote business in agriculture, energy, and industrial sector in a sustainable manner. A comprehensive literature review conducted as part of this research work reveals that the existing body of literature predominantly focuses on investigating the impact of operating parameters on the final gas yield during the gasification process. However, only limited literature is available that deals with numerical investigations aimed at optimizing control parameters to enhance the overall performance of the gasification process. Thus, the primary objective of this research is to conduct a detailed analysis of the gasification process using mathematical models under optimized reaction conditions. For a thorough understanding of the gasification process, it becomes imperative to explore the influence of the composition of solid fuel and oxidants supplied, reaction equilibrium, and reaction kinetics on the final gas composition. Furthermore, it is essential to consider the interaction between heat and mass transfer phenomena and the chemical thermodynamics that govern the process. Given that the performance of the gasification process is influenced by a wide range of design and operating parameters, the present research work aims at optimizing the process by employing innovative mathematical models to quantify the effects of critical control parameters. The said objectives are achieved using thermodynamic equilibrium models and kinetic models coupled with a robust optimization technique known as the Taguchi method. The equilibrium model is developed using a stoichiometric approach based on the solution of non-linear equations relating the equilibrium constants with thermo-physical parameters governing the chemical reactions that drive the gasification process. A two-zone kinetic model is developed and implemented to account for the influence of a converging-diverging type downdraft gasifier on the performance of the gasification process. A sequential optimization strategy is devised to maximize the carbon conversion efficiency for the gasification of rubber wood using a two-zone kinetic model.