Pelletization and Gasification of Waste for Heat Generation and Syngas Production

Abstract

The global population is increase and so is the demand for energy. While energy demand is increasing there is also a need for renewable and carbon neutral energy sources to reduce the emissions of greenhouse gases. Gasification is an old technology that has renewed interest in its carbon neutral fuel production possibilities. The use of biomass in gasification reactors produces carbon neutral hydrogen, carbon monoxide and methane. This thesis investigates how to optimize a reactor for hydrogen production though experiments and simulations. The experiment uses pelletized waste coffee grounds as feedstock to a 20-kW bubbling fluidized bed gasifier. The experiment shows the increased yield when running at a higher temperature the gas yield was enhanced to 1.2-2.45 Nm3/h and carbon conversion rate 40-83%. A CFPD model was developed mirroring the experiment gasifier, to see the effect of steam in the fluidizing agent and steam injection into the freeboard area in the gasifier. The hydrogen yield increases with higher steam biomass ratio and lower equivalence ratio, a maximum of 0.6 Nm3/kg biomass compared to the base case of 0.45 Nm3/kg biomass at equal equivalence ratio of 0.178 where found. For the model with injection an average of hydrogen yields 0.55 Nm3/kg biomass where found. Showing that running a gasifier at high temperature and the use of steam in gasification reactors can help meet the demand for clean carbon neutral energy.