Evaporation Characteristics of a Liquid Bio-Fuel from Chicken Litter

Abstract

Alternative fuels are becoming more important as fossil fuels become more expensive. This thesis describes the production and properties of a bio-oil produced from waste biomass, in this case chicken litter. A higher quality fuel was produced through thermal and chemical upgrading of the raw bio-oil; this fuel is similar in some respects to fossil fuels, as it has a high hydrocarbon content and energy density comparable to gasoline. Combustion of liquid fuels commonly occurs in clouds of droplets, and studying the evaporation of single liquid drops provides information on the evaporation characteristics of the fuel as a whole. Droplet evaporation tests on the chicken litter fuel were carried out using the suspended droplet/moving furnace technique. For some tests, a fine wire thermocouple was used as the droplet suspension in order to measure the distillation characteristics of the fuel. An existing computational model based on continuous ther- modynamics was used to model the evaporation of the fuel. The modelled composition of the fuel was based on an existing pyrolysis field ionization mass spectrometry (Py-FIMS) analysis and used five major groups of compounds. The properties for these groups re- quired for the model were determined using several prediction methods and the values then used in a numerical model. Model predictions of droplet temperatures calculated for the fuel showed good agree- ment with the measured temperatures, indicating that the modelled composition gave an accurate picture of the fuel. Droplet evaporation histories also agreed well with mea- surements, but were not capable of reproducing the observed disruption of the droplet produced by internal boiling at higher temperatures, nor the formation of a solid residue at the end of evaporation. Further enhancements to the model should allow the prediction of residue formation.Model predictions of droplet temperatures calculated for the fuel showed good agree- ment with the measured temperatures, indicating that the modelled composition gave an accurate picture of the fuel. Droplet evaporation histories also agreed well with mea- surements, but were not capable of reproducing the observed disruption of the droplet produced by internal boiling at higher temperatures, nor the formation of a solid residue at the end of evaporation. Further enhancements to the model should allow the prediction of residue formation.