Naoko Ellis

 
Prospective Graduate Students / Postdocs

This faculty member is currently not actively recruiting graduate students or Postdoctoral Fellows, but might consider co-supervision together with another faculty member.

Professor

Research Classification

Chemical Processes

Research Interests

CO2 capture and utilization
multiphase systems
thermochemical conversion of biomass
Interdisciplinary teaching and learning

Relevant Degree Programs

 

Research Methodology

Experimental
Process modelling

Graduate Student Supervision

Doctoral Student Supervision (Jan 2008 - May 2019)
Microwave-assisted catalytic pyrolysis of biomass for improving bio-oil and biochar properties (2018)

This thesis evaluates K₃PO₄, clinoptilolite, bentonite and their combinations as potential additives for enhancing microwave absorption, catalyzing pyrolysis of biomass and improving bio-oil and biochar qualities. Catalyst load ratio, pyrolysis temperature, liquid and solid product yields, bio-oil and biochar properties are examined to screen selected catalysts in terms of their effectiveness in increasing microwave absorption and improving bio-oil and biochar qualities. Thermogravimetric analysis (TGA) was also used to study the catalytic behaviour of those catalysts to interpret its performance in microwave-assisted catalytic pyrolysis and to study the catalytic pyrolysis kinetics for each of the three major biomass components, i.e., hemicellulose, cellulose and lignin, using the lumped three parallel reactions model. The performance of the produced biochars is evaluated in terms of their ability to improve soil water holding capacity (WHC), cation exchange capacity (CEC) and fertility of loamy sand soil. The capacity of those biochars in reducing bioavailability, phytotoxicity and uptake of heavy metals by wheat plants and the efficacy of those biochars in increasing soil fertility and plant growth in contaminated soil were also investigated.K₃PO₄, clinoptilolite and bentonite all showed good catalytic activities in microwave-assisted pyrolysis, resulting in reduced acidity, viscosity and water content of bio-oil product and catalyst loading and combination of different catalysts are controlling parameters on heating rate and product quality. The synergistic effects were observed in the combination of K₃PO₄ and clinoptilolite or bentonite, resulting in higher-than-expected microwave heating rate, in conjunction with improved bio-oil and biochar quality. Biochar produced from mixing K₃PO₄ and clinoptilolite or bentonite with biomass showed better performance in reducing toxicity and uptake of heavy metals than biochars produced from single catalyst. Catalytic microwave-assisted pyrolysis could be one potential approach for tailoring biochar quality to improve soil physiochemical properties. High microwave absorption, high water and nutrient affinity, desirable plant nutrients and high catalytic performance are the four key features of an effective additive for microwave-assisted biomass pyrolysis for making high quality bio-oil and biochars.

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Comparison of alternative advanced experimental techniques for measurement of hydrodynamic characteristics of gas-fluidized beds (2016)

A novel travelling fluidized bed, designed to facilitate deployment at different research centres, was used to compare advanced measurement techniques for the study of key hydrodynamic properties of gas-fluidized beds. Fast X-ray imaging was employed to visualize the internal flow structures of the bubbling and turbulent fluidization flow regimes. Transition between flow regimes based on X-ray system images were compared with results from pressure fluctuations. Average Shannon entropy reached a maximum plateau at superficial gas velocities close to Uc derived from pressure fluctuations, whereas average kurtosis and skewness leveled off at lower Ug’s. The degree of interference of a 4-mm intrusive probe inserted in the fluidized bed was found to be small by comparing the time-average voidage in a region with and without the probe present. Voidage data obtained by different measurement techniques in a previous study were extended by new data based on fast X-ray imaging and borescopy. Fair, but imperfect agreement among voidage results from alternate techniques was observed and quantified in terms of deviations from the overall average results of all measurement techniques at each gas velocity. Radial profiles of time-average particle velocity in FCC (a Geldart A powder) and sand (a Geldart B powder) fluidized beds at different operating conditions, obtained by radioactive particle tracking (RPT – non-invasive, Ecole Polytechnique), positron emission particle tracking (PEPT – non-invasive, University of Birmingham), optical fibre probe (invasive, UBC) and borescopic high-speed particle image velocimetry (invasive, PSRI) were directly compared. For FCC, each of these techniques provided similar trends with respect to profiles of time-average particle velocity, but with significant differences in some cases. For sand, there were significant quantitative differences among the profiles in many cases. The reasons for the discrepancies included lack of matching of tracer particles, probe intrusiveness, unmatched sensitivities to the direction of motion and different analysis procedures. The RPT, PEPT and borescopy data were further analyzed to obtain solid mass and momentum flux for identical operating conditions. All three techniques provided broadly similar time-average flux profiles. The experimental results obtained in this study provide a unique hydrodynamic benchmark database for validation of CFD codes and other models.

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Development and characterization of activated biochar as electrode material for capacitive deionization (2016)

Biochar, a by-product of biomass pyrolysis, was investigated as a carbon-based electrode material for a water treatment method based on electrostatic adsorption/desorption of ions in electric double layers (EDLs) formed on the charged electrodes (capacitive deionization, CDI). Surface area, porous structure, and functional groups of biochar were developed, and corresponding effects on EDL capacitive performance were studied. A novel method was explored to tailor the micro- and meso-porous structures of activated biochar by exploiting the interaction between pre-carbonization drying conditions and carbonization temperature (475–1000 C) in a thermo-chemical process (KOH chemical activation). The mechanism of porosity development was investigated; results suggest that the conversion of KOH to K₂CO₃ under different drying conditions has a major role in tailoring the structure. The resultant surface area, micro- and meso-pore volumes were: 488–2670 m² g-¹, 0.04–0.72 cm³ g-¹, and 0.05–1.70 cm³ g-¹, respectively. Tailored biochar samples were investigated using physico-chemical surface characterization and electrochemical methods. For electrochemical testing, activated biochar was sprayed onto Ni mesh current collectors using Nafion® as binder. The majorly microporous activated biochar showed promising capacitances between 220 and 245 F g-¹ when 0.1 mol L-¹ NaCl/NaOH was used as the electrolyte. Addition of mesoporous structure resulted in significantly reduced electrode resistance (up to 80%) and improved capacitive behaviour due to enhanced ion transport within the pores. CDI of NaCl and ZnCl₂ solutions was investigated in a batch-mode unit through the use of tailored biochar electrodes. For NaCl removal, all samples showed promising capacity (up to 5.13 mg NaCl g-¹) and durability through four consecutive cycles. In contrast, in the case of ZnCl₂, the microporous sample showed a considerable drop in removal capacity (>75%) from cycle 1 to 4, whereas the combined micro- and mesoporous sample exhibited relatively small electrosorption capacity. Interestingly, the sample with mostly mesoporous structure has shown the highest removal capacity (1.15 mg ZnCl₂ g-¹) and durability for Zn²⁺ removal. These results emphasize the importance of tailoring the porous structure of biochar as a function of the specific size of adsorbate ions to improve the CDI performance.

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Cold flow improvements to biodiesel through the use of heterogeneous catalytic skeletal isomerization (2013)

Biodiesel is a promising alternative to petroleum diesel with the potential to reduce overall net CO₂ emissions. However, the high cloud point of biodiesel must be reduced when used in cold climates. Cloud point is the temperature at which solid crystals first start to appear. Skeletal isomerization of biodiesel and/or its feedstocks was investigated to reduce the high cloud point. Catalytic isomerization and hydroisomerization reactions were carried out on pure unsaturated fatty acid (UFA) and saturated fatty acid (SFA) samples, respectively. The catalyst used for the experiments was a beta zeolite and 0.5 wt% Pt-doped beta zeolite for the isomerization and hydroisomerization reactions, respectively. Reaction conditions of temperature, pressure, co-catalyst and time were varied to find an optimal reduction in the cloud point of the products. It was concluded that isomerization was unsuccessful at reducing the cloud point; in contrast, hydroisomerization was successful at reducing cloud point. A 10 degree Celsius reduction was achieved at 285 degrees Celsius and 4.0 MPa H₂ pressure. The next stage of the research studied the combined effects of isomerization and hydroisomerization on a mixture of UFAs and SFAs, namely oleic and palmitic acids. It was shown that the combination of the reaction gave a cloud point reduction of 7.5 degrees Celsius on a 55/45 mass ratio of oleic to palmitic acids. These results led to the conclusion that SFAs and UFAs through skeletal isomerization can reduce the cloud point of a mixture of fatty acids. Thus, vegetable oil feedstocks can be improved for their biodiesel cloud point. A study of ten different oils was conducted with varying contents of fatty acids. Results have shown that high unsaturated fatty acid biodiesels increased in cloud point, due to the hydrogenation side reaction. In contrast, low unsaturated fatty acid biodiesels yielded cloud point reductions, and overall improvement in the flow properties. A maximum cloud point reduction of 16.5 degrees Celsius was observed with coconut oil as the starting material. These results led to the design of an optimal cloud point improvement process of for vegetable oil biodiesel of: hydrolysis (of vegetable oil → hydroisomerization (300 degrees Celsius, 4.0 MPa H₂ pressure → and esterification.

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Development of Sulfonated Carbon Catalyst for Integrated Biodiesel Production (2012)

No abstract available.

Chemical looping combustion : cold model hydrodynamics and modeling of methane combustion (2010)

A novel interconnected fluidized bed (IFB) reactor with a bypass line for chemical looping combustion (CLC) has been developed to overcome the problem of short residence time of oxygen carrier in the air reactor. A comprehensive hydrodynamic study was carried out on the cold-flow model of the proposed reactor. Detailed mapping of the operating conditions for the reactor system was studied. Pressure transducers were applied to investigate the pressure loops and the cross-sectional average solids hold-up along the air reactor. Solids circulation flux between the two reactors was measured using butterfly valves by estimating the time interval for collecting a given volume of solids. Helium was used as gas tracer for gas leakage measurement. The experiments examined the gas leakage from air reactor to fuel reactor, from fuel reactor to air reactor, from loop-seals to fuel reactor and from fuel reactor to the cyclone. For scaling consideration, the cold-flow reactor was operated with fluidizing gas mixture of helium and air to simulate the hydrodynamics of the hot unit. The effect of density ratio of solids to gas on the solids circulation flux, pressure loops and voidage distribution along the air reactor was investigated. The connection between cold unit and hot unit is achieved by applying a scaling law. It can be stated that the cold-flow model operated with fluidizing gas mixture of 96 vol% helium and 4 vol% air can be used to simulate the hydrodynamics of an atmospheric CLC hot unit. A comprehensive model for the investigation of the reactor is introduced by combining fluidization properties and a particle population balance for calculation of the bed particle conversion, considering the chemical reaction of a single particle. The dimensionless parameters, Mrfuel and Mrair, which represent the mass ratio of input oxidized-particles to the input fuel in unit time for the fuel reactor and the mass ratio of reduced-particles to the input oxygen in unit time for the air reactor, respectively, are introduced. The model shows that Mrfuel should be more than 50 for achieving fuel conversion of 90% in the fuel reactor and Mrair should be more than 60 for achieving oxygen conversion of 85% in the air reactor. A procedure for optimizing the performance of the atmospheric CLC reactor is developed. The modeling analysis indicated that the optimum operating condition of an atmospheric CLC reactor hot unit should be chosen as follows: fuel capacity is 80 kW, Ua0=6.6 m/s, Uf0= 0.076 m/s, UA1=4Umf, UA2=1Umf, and the temperature in air reactor is 1223 K and in fuel reactor is 1173 K.

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Gasification of bio-oil and bio-oil/char slurry (2010)

Economic utilization of biomass as a fuel has been limited by transportation cost. One suggested remedy to address the problems of processing biomass on a large scale is to pyrolyze solid biomass at numerous local sites and transport the resulting liquid or liquid/char slurry to a large centralized conversion plant. This research involves the gasification of biomass fast pyrolysis oil, so called bio-oil, and a slurry mixture of bio-oil and fast pyrolysis char into synthesis gas.Kinetics of the reaction of steam with chars was studied using a thermo-gravimetric analyzer. Slurry Char was produced by pyrolysis of an 80 wt% bio-oil/20 wt% char mixture at nominal heating rates of 100–10,000°C/s. The resulting Slurry Char was subjected to steam gasification with 10–50 mol% steam at 800–1200°C. Reactivity of the Slurry Chars increased with the pyrolysis heating rate, but was lower than that of Original Chars. Kinetic parameters were established for a power-law rate model. Some measurements were initially done of gasification in CO₂.A fluidized bed reactor, equipped with an atomization system, was constructed for gasification of bio-oil and slurry. The reactor contained either sand, or Ni-based catalyst. Experiments included gasification with pure steam and air. Effects of bed temperatures in the range 720–850°C, steam-to-carbon molar ratios of 2.0–7.5, and air ratios of 0–0.5 on gas composition and yields were tested. The carbon conversion of bio-oil to gas was found to be greater than that of slurry. The product gas composition was affected significantly by catalysis of the water-gas shift and the steam gasification. Greater yields of hydrogen and lesser yields of CO and hydrocarbons were found when catalyst was used. On a dry, inert-free basis, gases of up to 61% H₂ were obtained. The data were compared with a thermodynamic equilibrium model. The product gas yield was reasonably predictable by the model.A mass and energy balance model of steam gasification in a dual-bed gasifier-combustor revealed that energy requirements are sensitive to the steam/carbon ratio and to the recovery of latent heat in the produced gas.

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Master's Student Supervision (2010 - 2018)
Bio-oil upgrading through biodiesel emulsification and catalytic vapour cracking (2014)

With our limited fuel supplies struggling to keep up with our ever-increasing demand for energy, and the rising trend towards sustainable and cleaner technologies, the need to harness the potential of bio-oil as an alternative source of energy has never been more compelling. Although crude bio-oil can already be utilized to supplement heating oils and boiler fuels, its greater value lies in its potential as a source of transportation fuels and chemicals after upgrading.In collaboration with Diacarbon Energy Inc., the main objectives of this project were twofold: (1) investigating the effect of extraction location from their proprietary pyrolysis unit on crude bio-oil quality prior to its emulsification with biodiesel, and characterizing the resulting biodiesel- and lignin-rich layers; and (2) designing and building a catalytic test unit to perform in situ cracking of slow pyrolysis vapours.Experimental results confirmed that extraction location does affect the crude bio-oil quality. The effect of the surfactant on the emulsification was minimal as the resulting biodiesel-rich layer from the emulsification without the surfactant showed similar improvements in terms of water content, viscosity, TAN and HHV. A water mass balance confirmed that the majority of the water (~97%) is retained in the lignin-rich phase after emulsification. This is significant because the solvency of biodiesel can be utilized to upgrade bio-oils by selectively extracting its desirable fuel components into a biodiesel-rich phase, which can then be easily separated from the lignin- rich phase where the higher molecular weight compounds, such as pyrolytic lignin, as well as the majority of the water, are retained.The bio-oil samples obtained from the non-catalytic and catalytic vapour cracking experiments separated into two distinct layers – an aqueous and organic layer. While the aqueous layers were fairly similar in nature, the organic layer from the catalytic experiment showed a significant decrease in viscosity (94.3% less) and water content (64.3% less). The organic layer from the catalytic pyrolysis remained homogeneous while that from the non-catalytic pyrolysis split into a hazy aqueous layer (with suspended oil droplets) sandwiched between a thin organic layer on top and a thicker organic layer at the bottom.

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Developing biochar-based catalyst for biodiesel production (2010)

A biochar-based catalyst was successfully prepared by sulfonation of pyrolysis char with fuming sulphuric acid. Prepared catalyst was studied for its ability to catalyze transesterification of vegetable oils (i.e., Canola Oil) and esterification of free fatty acids (i.e., oleic acid) using methanol. Thus far, biochar-based catalyst has shown significant activity, >90% conversion, in esterification of FFAs while indicating limited activity for transesterification of triglyceride-based oils such as Canola Oil. The first step in catalyst development approach was to increase the transesterification activity through employing a stronger sulfonation procedure. The total acid density of the biochar-based catalyst increased by ~90 times resulting in significantly increased transesterification yield (i.e., from being almost negligible to ~9%). Further investigations on the biochar-based catalyst were conducted to determine the effect of sulfonation time (5 and 15 h) and surface area on the transesterification reaction. Two established activation techniques (i.e., chemical activation with KOH and the silica template method) have been utilized to develop the surface area and porosity of the biochar supports. The surface area of the biochar support increased from a typical 0.2 m²/g to over 600 m²/g. In the chemical activation method with KOH, the effect of activation temperature on the transesterification yield has been investigated. Three biochar-based catalysts with activated supports at three different temperatures (450, 675 and 875C) were prepared and compared for transesterification activity. The sulfonated catalysts were characterized using the following analyses: BET surface area, elemental analysis, total acid density, Fourier Transform Infra-Red (FT-IR) spectroscopy, and X-Ray Diffractioniii(XRD) spectroscopy. The catalyst supported on biochar activated at 675C resulted the maximum transesterification yield (18.9%). The reaction yield was dependent on both catalyst surface area and total acid density. The catalytic activity of the biochar-based catalyst with activated support at 675C remained significantly high for esterification of FFAs (conversion>97%).The structural study of the catalysts prepared from activated biochars at three different temperatures suggest that the higher activation temperatures cause an increasing re-orientation of the biochar’s carbon sheets towards a more graphite-like structure, causing a decrease (> 60%) in total acid density despite of the increase in surface area.

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Process simulation, economic analysis and synthesis of biodiesel from waste vegetable oil using supercritical methanol (2010)

Biodiesel production using supercritical methanol received attention as an alternative method to replace the conventional alkali-catalyzed method being practiced in industry. Due to its flexibility to feedstock compared to the conventional method, the supercritical method for waste vegetable oil conversion appears to be promising in environmental and economical points of views. Four industrial-scale biodiesel production processes were simulated using Hysys. Each process used either the conventional or the supercritical method. The first model simulated the alkali-catalyzed process using fresh vegetable oil. The second process model resembled the first one as it uses sodium hydroxide catalyst in transesterification, but pre-treatment process of waste vegetable oil was included. The third and fourth models were supercritical biodiesel production processes using waste vegetable oil. Fourth model had differences from the third one in terms of the amount of methanol being introduced to a plug flow reactor and the way of recovering methanol from reaction products, both of which can reduce energy consumption of the process. To improve the accuracy of the process simulations, properties of a model compound (triolein) of the vegetable oils were examined via thermogravimetric analysis, and the experimental data were incorporated into the simulation models. Economical aspects of the developed simulation models were then assessed using Aspen Icarus Process Evaluator. The economic assessment revealed that supercritical processes using waste vegetable oil were competitive to the conventional process based on their better profitability indicators such as discounted payback period and net present value. The net present value prediction formulas were derived for the four processes via statistical analysis of the vegetable oil price, biodiesel selling price, by-product selling price and interest rate that were found to most strongly affect the profitability of the biodiesel production processes by sensitive analysis. Experiments of biodiesel synthesis from waste canola oil were conducted using supercritical methanol. High methyl ester yields over 96% were achieved after 45 min of reaction time at 270°C/10 MPa with methanol to oil ratios of 1:1 and 2:1. Side reactions such as glycerol decomposition and glycerol methanolysis were confirmed by water content measurement using Karl-Fischer titration and Gas chromatography-mass spectrometry (GC-MS) analysis.

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