Date of Award
2008
Degree Type
Thesis
Degree Name
Master of Engineering Science
Program
Chemical and Biochemical Engineering
Supervisor
Dr. Franco Berruti
Second Advisor
Dr. Cedric Briens
Abstract
This thesis investigates the production of pesticides through the fast pyrolysis of three biomass feedstocks: tobacco leaves, dried coffee grounds and pinewood killed by beetles. It was observed that a significant fraction of the bio-oil escaped the condensing train as a fine mist; this is a common problem in pyrolysis operations. An electrostatic demister was, therefore, developed to recover this mist. Tobacco leaves were pyrolyzed to produce bio-oil. Pyrolysis was carried out at six different temperatures from 350°C to 600°C and at three different vapor residence times (5, 10 and 17 s), to study the effect of operating conditions on the bio-oil yield. The trends clearly indicated a strong effect of temperature and vapor residence time on the bio-oil yield. A temperature of 500°C was then selected and the pyrolyzer was operated again at the lowest vapor residence time of 5 s to obtain accurate liquid, gas and char yields. Tobacco bio-oils produced at different temperatures (350-600oC) and at a vapor residence time of 5 s were tested for their bactericidal, fungicidal and insecticidal activities against pests found on plants in Canada that currently require improved control options. A significant finding of the research was that even fractions containing no nicotine had significant activity towards the aforementioned pests. Dried coffee grounds were pyrolyzed to produce bio-oil. Pyrolysis was carried out at five different temperatures from 400°C to 600°C and at a vapor residence time of 5 s, to study the effect of temperature on the bio-oil yield. The trends clearly indicated a strong effect of temperature on the bio-oil yield. Coffee grounds bio-oils produced at different temperatures (400-600oC) were tested for their bactericidal and insecticidal activities against pests found on plants in Canada that currently require improved control options. While some compounds in the bio-oil, such as phenols, were active against both beetles and bacteria, the coffee bio-oil contained in chemicals that provided additional insecticidal activity but had no bactericidal activity. Single-stage and two-stage tubular electrostatic precipitators were designed for the recovery of bio-oil mist. Because of concerns regarding bio-oil stability, an inert fogging oil was used for the development of the demisters. A nitrogen stream containing very fine droplets of fogging oil was forced through the electrostatic precipitator chamber. It was found that 98.6 wt% of the oil droplets present in the turbulent jet were mechanically collected on the inner walls of the test chamber. When the electrode was energized at 13 K V, 92.37wt%ofthedropletsthathadnot been mechanically separated were collected in single-stage mode. The collection efficiency was increased to 93.18 wt%, when the electrostatic precipitator was operated in two-stage mode. Voltage-current (V-I) characteristics of the singlestage and two-stage electrostatic precipitators were studied in detail for different test conditions. Nitrogen impurities played a major role in determining the V-I characteristics. They became less relevant with the introduction of mist in the nitrogen stream, presumably due to the presence of water vapor in the gas. The two- stage tubular electrostatic precipitator was scaled up and tested on a fluidized bed pilot plant used for the pyrolysis of biomass. A droplet collection efficiency of 95 wt% was observed. Such demisters will extend, to the product recovery train, the process intensification gains of short residence time processes such as fast pyrolysis.
Recommended Citation
Bedmutha, Rohan, "Pesticides from fast pyrolysis of agricultural and forestry residues" (2008). Digitized Theses. 4778.
https://ir.lib.uwo.ca/digitizedtheses/4778