Design and operational characteristics of a gasification-combustion process: flammability model

• Main Author: Muchai, Jesse G.
• Other Authors: Agricultural Engineering
• Format: Others
• Language: en
• Published: Virginia Tech 2014
• Subjects: producer gas; flammability limit; wood; LD5655.V855 1995.M834
• Online Access: http://hdl.handle.net/10919/41408; http://scholar.lib.vt.edu/theses/available/etd-03042009-040746/

The research reported here explored the flammable range of gasification product “producer gas” in a combustion chamber to ensure complete combustion. Rising fuel prices has led to increased research in renewable energy sources. Biomass is a renewable resource whose use does not result in a net increase of CO₂ in the atmosphere. Wood was selected as the biomass for this research. Applications for wood as a fuel source includes crop drying, space heating, and power generation. Flammability limit and chemical equilibrium theory were used to model the flammable range of the gasification product in a combustion chamber. The model predicted an adiabatic flammable zone within an equivalence ratio of 0.56 to 1.67 for oak with 20 percent moisture content (w.b.), and a maximum adiabatic flame temperature of 2025°C for dry oak. Chemical equilibrium theory was used to predict gasification-combustion product concentration. Based on the analysis of the data, the following conclusions were made: (1) Flammability of gas-air mixture is largely determined by the amount of heat loss prior to combustion, (2) At equivalence ratios greater than 1.25, CO appears in the combustion products, (3) Adiabatic Flame Temperatures are largely influenced by moisture and excess air, (4) Combustion temperature is a critical parameter that influences composition distribution of the gasification-combustion product. (Product compositions are important to the designer, for both energy and environmental impact), and (5) Maximum benefit for a gasifier-combustor system could be obtained if heat loss, excess air, moisture content, mixing effectiveness, and residence time are optimized. === Master of Science