Experimental and Computational Studies on Biomass Gasification in Fluidized Beds

Abstract

The world’s energy consumption is increasing, and research regarding utilization of renewable energy sources is crucial. Biomass for direct heating has been used for thousands of years, while in the last decades alternative ways to exploit biomass have emerged. In order to increase the efficiency and to produce more applicable products, gasification of biomass is becoming a more and more promising technology. For the gasification technology to be competitive, the understanding of the various aspects regarding the gasifier operation, which in turn influences the quality of the product gas, is of utmost importance. The main objective of this work is to investigate the effect of the air to biomass ratio on the produced gas composition in terms of the high-energy components H2, CH4 and CO. Experiments were performed with wood chips in a pilot scale gasification reactor. The results show that an air-to-biomass ratio less than one gives the most applicable gas composition. Biomass, like wood chips, has a peculiar shape, has a large particle size, is cohesive, and is therefore difficult to fluidize. In a fluidized bed gasifier, a bed material is used to improve the fluidization quality. Experiments were carried out in a cold bed model to study the fluidization properties of the bed material. Minimum fluidization velocities were predicted based on pressure drop in the bed.