All ETDs from UAB

Advisory Committee Chair

Heng Ban

Advisory Committee Members

Thomas K Gale

Peter M Walsh

Document Type


Date of Award


Degree Name by School

Master of Science in Mechanical Engineering (MSME) School of Engineering


Electricity from biomass and biomass–derived fuels has become an attractive and viable alternative energy source. Alkali metals, mainly sodium and potassium, together with other ash forming inorganic components in biomass, increase fouling, slagging, and high temperature corrosion of heat transfer surfaces in boilers thus reduces efficiency during biomass combustion. Future biomass-to-electricity facilities will benefit from increased efficiencies, by incorporating integrated gasification combined cycle systems that use biomass syngas directly in gas turbine. These systems will have even lower tolerances for alkali vapor release, because accelerated erosion and corrosion of turbine blades results in shorter turbine life. One solution to the fouling and slagging problem is to develop methods of hot gas cleanup to reduce the amount of alkali vapor. A detailed understanding of the mechanism of alkali metals release during biomass gasification could greatly benefit the development of hot gas cleanup technology. In this study, thermodynamic equilibrium predictions were made of the distribution and mode of occurrence of gaseous chlorine and alkali metals of three types of biomass (corn stover, switch grass, and wheat straw) in combustion and gasification processes. The influence of temperature, pressure, and air-fuel ratio was also evaluated. Results show that the percent stoichiometric air has limited influence on the speciation of chlorine and potassium during combustion. However, the influence of the percent i i stoichiometric air is significant during gasification. Increasing percent stoichiometric air enhances the formation of vapor HCl and KOH as well as reduction in vapor KCl and K2Cl2. In biomass combustion and gasification, increasing pressure increases vapor HCl and K2Cl2 and reduces the amount of vapor KCl and KOH. At higher temperatures (>1100K), the gaseous alkali species increased greatly.

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Engineering Commons



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