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Research interests
Multiphase systems impact a wide variety
of industries including advanced materials (e.g. production of silicone for
semiconductors), environmental (e.g. aerobic and anaerobic wastewater treatment),
chemical (e.g. synthesis reactions and cracking of hydrocarbons), mineral
(e.g. reduction of iron oxide), energy (e.g. combustion and gasification of
coal), agricultural (e.g. drying and roasting of foods), and pharmaceutical
(e.g. production of plant and animal cells). Because of their commercial
importance and complex flow patterns, the analysis and design of multiphase
reactors is one of the most intensely studied areas of chemical
engineering. Below is a
schematic of an industrial three-phase fluidized bed hydroprocessor
used to upgrade bitumen, from the Canadian oil sands, into crude oil.
Here is a short description of current research
projects:
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Transport
phenomena in high pressure multiphase reactors
Most slurry bubble columns and
three-phase fluidized bed reactors of commercial interest operate under
pressure, e.g. hydrocracking of petroleum resids (5-21 MPa) and
hydrocarbon synthesis via Fischer-Tropsch
reactions (1-5 MPa). Pressure strongly influences bubble
dynamics, which in turn affects transport phenomena (phase holdups and
mixing, mass and heat transfer) and ultimately the reactor performance
(conversion, yield, selectivity). Elevated pressures usually lead to
greater gas holdups and higher dispersed to coalesced bubble flow regime
transition velocities due to reductions in bubble mean size and size
distribution
The overall goal of this program is to
elucidate various transport phenomena occurring in high pressure multiphase
reactors, particularly three-phase fluidized beds. The pilot
plant has two columns of 0.1 m in inner diameter and 1.8 m in height
with several sight windows to allow for visualization. The gas and liquid superficial
velocities can be respectively varied up to 0.4 m/s and 0.1 m/s for
pressures up to 10 MPa. This research program is done in
collaboration with Syncrude Canada Ltd.
·
Synthesis of gas
hydrates in slurry bubble columns
Gas hydrates are non-stoechiometric
crystalline compounds that belong to the group known as Clathrates. Hydrates occur when water molecules
attach themselves through hydrogen bonding and form cages that can be
occupied by a gas molecule.
Naturally occurring hydrates, containing mostly methane, exist in
vast quantities within and below the permafrost zone and in sub-sea
sediments and are being looked upon as a future energy source. Work is also being conducted on
capturing CO2 by transforming it into hydrates. Another important benefit of gas
hydrates deals with the transportation and storage of natural gas. This is being considered as a cost-effective
alternative over current methods such as liquefied or compressed natural
gas since each volume of hydrate can contain as much as 184 volumes of gas
at standard temperature and pressure.
The overall goal of this research program
is to develop a slurry bubble column reactor for producing gas
hydrates. This program bridges
research in thermodynamics with fluid dynamics and is done in collaboration
with Professor Phillip
Servio from McGill University. One of the two columns in the pilot
plant can be cooled to 273 K to allow of the formation of gas hydrates.
·
Multiphase flow in microchannels
Process intensification is quickly
becoming an important aspect in the production of fine chemicals and active
pharmaceutical ingredients. Continuous flow microreactors
are an integral part of process intensification as they overcome many of
the heat transfer and safety drawbacks of traditional batch and semi-batch
stirred reactors.
The goal of this research program is to
investigate the impact of channel geometry on the transport phenomena in
gas-liquid and liquid-liquid microreactors over a
range of production associated to clinical trial phases I to III. This research program is done in
collaboration with Lonza Group AG.
·
CO2
capture systems for combustion and gasification flue gases
The connection between increasing
atmospheric CO2 concentrations and climate change is now
recognized by a number of international organizations including the United
Nations Framework Convention on Climate Change. In 2008,
generation of electricity and heat were responsible for 41% of the world CO2
emissions (IEA).
The overall goal of this research program
is to develop a high-volume CO2 capture system for combustion
and gasification flue gases using either limestone-derived sorbents in a
dual fluidized bed or direct oxy-fuel combustion. Technology costs are strongly
connected to the behaviour of the sorbent in multiple cycles and the main
hurdles are overcoming the deactivation and loss of sorbent through
sintering and attrition. This
research program is done in collaboration with CanmetENERGY-Ottawa.
Research Group
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