A Comparative Study of Syngas Production From Two Types of Biomass Feedstocks With Waste Heat Recovery

Abstract

This paper deals with an integrated biomass system developed for syngas production with waste heat recovery option and analyzes this system thermodynamically using both energy and exergy approaches. Also, an aspenplus simulation model is developed to demonstrate comparative gasification analyses of wood (Birch) and olive waste using Gibbs reactor for syngas production. Gibbs free energy minimization technique is applied to calculate the equilibrium of chemical reactions. In this newly developed model, the heat of the product syngas and the waste heat from the flue gas are recovered through a unique integration of four heat exchangers to produce steam for the gasification process. The sensitivity analyses are performed to observe the variations in the concentration of the methane, carbon monoxide and carbon dioxide in syngas against various operating conditions. Furthermore, the performance of gasifier is indicated through cold gas energy efficiency (CGE) and cold gas exergy efficiency (CGEX). The overall energy and exergy analyses are also conducted, and the comparisons reveal that the biomass composed of olive waste yields high magnitude of overall and cold gas energy efficiencies, whereas wood (Birch) yields high magnitude of overall and cold gas exergy efficiencies. Moreover, the energy of the product syngas is recovered through an expander which enhances energy and exergy efficiencies of the overall system. The present results show that the CGE, CGEX, and overall energetic and exergetic efficiencies follow a decreasing trend with the increase in combustion temperature. The proposed system has superior and unique features as compared to conventional biomass gasification systems.