(621e) Stability Assessment of Wood and Bark Derived Bio-Fuels

Heating value of bio-oils is reported to be half of conventional petroleum derived fuels. However, there are some engineering problems associated with these oils. Bio-oils are known to become unstable because of several self-catalyzed polymerization reactions. Polymerization reactions become evident with increasing storage time. Consequently, these polymerization reactions release more water into the bio-oil with time. If the water levels in the bio-oils exceed 30% by volume the bio-oils start phase separating as well. Viscosity of the bio-oils has been known to increase significantly also as a result of aging. Higher viscosities of bio-oils can increase the pumping costs and can also cause deposit build-up on fuel injectors.

Bio-oil is known to be highly polar in nature due to the presence of many oxygenated compounds (10-25%). Bio-oils are also known to be very acidic in nature due to the presence of organic acids (5-12%). Because of this reason the bio-oils are also known to be very acidic which can cause corrosion problems. The above problems put together can limit the use of bio-oils as potential fuels. Hence, The primary focus of this study is to isolate the potential additives to stabilize the bio-oils and retain their homogeneity over extended storage time periods.

Pyrolysis experiments were carried out using an auger reactor at Mississippi State University by varying vapor residence times and pyrolyis temperatures. The feedstocks utilized were wood and bark derived from pine and oak. The reactor was operated in a semi-batch mode at a set auger speed of 8rpm. Reactor yields of greater than 60% were obtained. Potential additives from different groups of organic compounds will be selected for the prescreening studies. Matrix selection factors will include the bulk chemical costs, radical inhibition, hydrogen ion (H⁺) donation, water inhibition, and solubilizing capabilities. Preliminary studies are underway for assessing the stability of bio-oils at a storage temperature of 80⁰C. A temperature of 80⁰C has been chosen to accelerate the testing of bio-oils. The overall objective of this study is to achieve the stability of bio-oils using different additives at different concentrations. Consequently, three additives with three concentrations (low, medium, and high) will be chosen to study the stability of bio-oils. By optimizing the additive concentrations of potential additives we will be able to present a cost-feasible solution to the bio-fuel stability problem.

Analytical tests will include the water content analysis of the bio-oils that will be measured periodically using Karl-Fisher titrator from Mettler Toledo^®. Rheological analysis will also be performed using Brookfield^® instrumentation. Heating values of bio-oils will be determined using a bomb calorimeter from Parr^®. Flash point and cloud points will also be determined using Pensky-Martens^® apparatus for the produced bio-oils. The results of this study will be presented at the meeting.