Steam catalytic gasification of elephant grass pellets

Abstract

There is a worldwide consensus on the need to replace fossil energy sources with renewable ones. Biomass is a promising alternative for replacing the use of fossil fuels. In addition, biomass contributes to the reduction of greenhouse gas emissions, since when subjected to a thermal process, it releases carbon dioxide consumed by its photosynthesis, as is the case of the elephant grass. This biomass can be used as an energy source; nevertheless, its low density makes conversion processes difficult (especially in the feeding step). To solve this problem, its densification in the form of pellets can be applied. The main processes for obtaining energy from biomass are the thermochemical processes: pyrolysis, combustion, and gasification. Gasification has high energy efficiency, being a promising alternative for energy generation. The gasification process can be improved through the use of catalysts, in order to increase the yield in the production of syngas (H2 + CO). The alkali and alkaline earth metals (AAEM) can be present in the biomass, or be added to the gasification process, acting in the tar cracking for greater efficiency in the gasification reaction. Potassium (K) is an alkali metal present in biomass, which has a catalytic role in the gasification process, especially when steam is used as gasification agent. Its concentration in biomass can be modified according to the fertilization during the planting of the biomass. Another catalyst for the gasification process is iron (Fe), however this metal is present in low concentrations in the biomass itself and must be incorporated into it before its gasification. The use of iron as a catalyst becomes interesting due to its low toxicity and cost, having the ability to crack tar molecules, hence increasing the gasification yield. Based on this, the effect of potassium and iron as catalysts in the steam gasification process of elephant grass pellets was investigated in this work.