Simulation of carbon- monoxide rich syngas through gasification and co-gasification of biomass.

Sammanfattning: Syngas is an interesting energy source for metallurgical processes, as an energy carrier syngas is an efficient way of utilizing the energy in biomass. Utilizing syngas in fuming processes as a carbon source instead of coal was an approach to minimize carbon dioxide emissions produced in the fuming process. In the fuming process, secondary materials are processed to improve the extraction of copper, lead, and zinc.  The objective of this project was to find a suitable biomass and gasification agent that result in syngas with a high percentage of carbon monoxide and a low percentage of carbon dioxide. Because of the high need of carbon in the fuming process, syngas could be a suitable reduction agent. The most efficient thermo-chemical process for syngas production from biomass is gasification.  The investigated biomass where sawdust, wood, and a co-gasification with a percentage of peat. The gasification agents investigated where carbon dioxide, oxygen, air, and hydrogen. This was investigated by using FactSage8.1 to simulate the gasification and co-gasification of chosen biomasses and gasification agents. Stoichiometric calculations of the fuels and gasification agents were done to get the correct reduction and combustion reactions.  The results from the simulations showed that carbon dioxide was the best gasification agent and gasifying sawdust alone results in the highest simulated levels of carbon monoxide in the gasification temperature between 1000 to 1200 ᵒC.  Other studies showed that biomass gasification with carbon dioxide or a mixture of at least 60 percent of carbon dioxide as a gasification agent was a promising way for energy production and lowering carbon dioxide emissions. It also shows a correlation between increasing carbon dioxide as a gasification agent and higher level of carbon monoxide in the produced syngas. Other studies implied that the maximum level of carbon dioxide that results in the maximum fraction of carbon monoxide and methane was 60 percent.  Each gasification agent investigated have advantages and disadvantages, they lead to different gas composition, by-products, and heating value, which gasification agent to use depends on the result wanted. Carbon dioxide was the gasification agent that shows the best result in a simulated environment, but the same result cannot be guaranteed in real-life experiments, and discrepancies are to be expected. Further study in form of a real-life experiment are needed to compare with the simulated results, as the effects of ash forming elements and test of gasifier are needed.