bulk-online, the Powder/Bulk Portal

Biography:
Education

B.Sc. Chemistry, Mount Allison University 1987
B.Sc. Chemical Engineering, University of New Brunswick 1990
M.Sc. and Ph.D. Chemical Engineering, University of Calgary 1992 & 1995

Professional Experience

Post-Doctoral Fellow, Technical University Hamburg 1995
Assistant Professor Chemical Engineering, University of New Brunsick, 1996 - 1999
Associate Professor, Chemical Engineering, University of New Brunswick, 1999 - 2000
Associate Professor, Chemical Engineering, University of Saskatchewan, 2000 - 2005
Professor, Chemical Engineering, University of Saskatchewan, 2005 -

Know-how and experience:
The fluidization laboratory of Saskatchewan (FLASK) is a state-of-the-art research facility located in the Chemical Engineering wing at the University of Saskatchewan. FLASK consists of a range of pilot and laboratory scale fluidized beds as well as particle characterization equipment. Our University setting gives us access to additional instruments available in the College of Engineering and in the College of Arts and Science. We also have close ties to the facilities in Innovation Place. Innovation Place is located just north of campus and is considered to be the most successful research park in North America. Between the U of S campus and Innovation Place is the Canadian Light Source Synchrotron, Canada’s first such facility.

The following is a summary of equipment available to FLASK researchers:

• Malvern Mastersizer S Longbench – This device uses the principle of laser light scattering to determine the size distribution of a particulate sample. We have used this device on particles as small as 5 microns and as large as 2 mm. Particles analyzed to date include cracking catalyst pharmaceutical binders, excipients, and granules milled flours silt, sand, and clay. Our Longbench is equipped with wet and dry feeder capabilities.
• Quantachrome Helium Pycnometer – This device determines the skeletal or solid density of a particulate sample based on the displacement of helium. Helium is able to penetrate into the pores of the sample (if it is porous), thus giving the true density of the solid material.
• Tyler Standard Sieve Series and Gilson Shaker – This is a mechanical technique for determining particle size distribution. Sieves are stacked vertically with the largest aperture screens at the top. A particulate sample is poured onto the uppermost screen and the stack is placed in the shaker. After twenty minutes, the stack is removed and the mass retained on each sieve is determined in order to give a particle size distribution based on mass percentage in each size class. The size classes are based on the screen apertures.
• JEOL 840A Scanning Electron Microscopy (SEM) – This device is housed in the Geological Sciences department and FLASK researchers have access to it for a nominal fee. In SEM, a fine beam of electrons scans along the surface of the sample, interacting with that surface and producing an image on a screen. The JEOL 840A has the capacity to capture the screen as a photograph or save it as a digital image for further analysis. The SEM system also has a gold coater for preparing the samples prior to scanning. Several image analysis software packages are available on campus. FLASK researchers are presently assessing these different programs.
• Powder Shear Cells – Although not a Jenike shear cell, the operating principle is the same and ASTM D6128-00 standard, which is based on the Jenike cell, is followed. These cells of different sizes are housed in the Soil Sciences laboratory in the Department of Civil Engineering. The strain gauge used to measure the lateral deflection of the shear cell is connected to a computerized data acquisition system. This gives the shear force as a function of time for a given normal compressive loading. This data is analyzed to obtain the flow index for the powder using the classic approach of Jenike. We also have the capacity to store samples in a shear cell for several days under a compaction force and then perform shear testing. This simulates the “ageing” effects on powders that are stored for several days during shipping.
• BET Surface Area Analyzer – This device determines the specific surface area of a powder sample based on the measured adsorption of a gas (usually nitrogen) on the solid surface. The Brunauer-Emmett-Teller (BET) equilibrium isotherm is used to determine the total volume of gas adsorbed in a monolayer on the surface of the sample. The specific surface area is then estimated knowing the cross-sectional area of the gas molecules projected onto the powder surface.
• Mettler HB43 Drying Balance – This is our primary method of measuring moisture content of a powder sample. A sample is placed on the sample tray and the apparatus closed. The drying balance contains an electrical heating element which is used to reach the set-point temperature input by the user. The sample is dried while the balance simultaneously determines the change in the sample’s mass. This technique does not account for crystalline water. We are hoping to purchase a Karl-Fischer titrator later this year.
• Environmental chambers – Three walk-in environmental chambers with control of temperature, humidity, and light are housed in the Chemical Engineering pilot plant area. These are useful in our studies of powder flowability since powders can be stored in these chambers under controlled humidity conditions. This allows us to maintain the moisture content of powder samples at a desired level prior to shear testing.
• Lab Scale Fluidized and Spouted Bed Dryers – The FLASK laboratories are very active in the area of fluidized bed drying of pharmaceuticals and biological products. We have available two laboratory-scale Plexiglas fluidized bed dryers with truncated cone product bowls, a Plexiglas straight-walled laboratory-scale dryer, and a laboratory-scale spouted bed dryer. All of these are equipped with feedback loops for the automatic control of inlet air temperature and humidity and are instrumented to measure product and exhaust air temperature and windbox pressure. Fluidizing air flow is measured with an orifice plate designed to ASME standards.
• Lab Scale Fluidized Bed Coater – The fluidized beds described above may also be modified to operate as a coater by adding a central insert (i.e. draft tube or Wurster insert) and a special distributor and two-fluid nozzle arrangement. The partition gap between the nozzle and the bottom of the Wurster insert is fully adjustable. Inserts of different diameters are also available. Coating uniformity of a powder sample is measured with a UV spectrophotometer (we coat with a methylcellulose solution containing blue dye) and individual particle coating is measured with a dissecting microscope.
• Pilot Scale Fluidized Bed Multiprocessor – This unit has been purchased from FluidAir Inc. (Aurora, IL, USA) and comes with a 50-L truncated cone product bowl. The unit may be operated as a dryer, bottom-spray coater, or top-spray granulator. The granulating spray lance may be move up or down as may the position of the Wurster insert in when the unit is operated in coating mode. This multiprocessor also ships with a second 5-L product bowl which will allow us to investigate the effects of scale on drying, coating, and granulation.
• Hot and cold flow pilot-scale Circulating Fluidized Beds – These units have been designed to operate at high rates of solids circulation and gas velocity. Both are 14-cm ID with the high-temperature stainless steel unit being 10 m tall and the cold flow acrylic unit being 13.5 m tall. In addition the cold flow unit is equipped with a fluid bed stripper in the downcomer side. The riser section is instrumented with a moveable capacitance tomography system and multiple measurement ports for gas tracing and solid sampling.
• Low-Shear Granulator – FLASK researchers prepare wet granule from pharmaceutical powders using a Kitchen-Aid Classic Mixer. Water is added dropwise from a peristaltic pump. Batches of up to 1 kg (dry basis) may be prepared in this granulator.
• Electrical Capacitance Tomography (ECT) System – ECT is a non-invasive measurement technique for fluidized beds. We have ECT sensors for our lab-scale dryers. The ECT sensor consists of 8 electrodes placed around the periphery of the vessel to be imaged. In the measurement sequence, each electrode is sequentially supplied with an electrical potential while the others remain grounded. Thus, an electrical field is applied across the measurement cross-section. From the interaction of this electric field with the material within the sensor, the distribution of phases within the measurement plane can be determined. The charge-discharge sequence is very rapid so that 100 images of the fluidized bed cross-section are collected per second, allowing the dynamic features of the bed to be captured. Our ECT system was supplied to us by Process Tomography Ltd. (Cheshire, UK) and contains two planes of electrodes. This allows us to monitor the movement of the dispersed phase and calculate bubble velocities in a fluidized bed. We also have sensors on a 7.6-cm tube that is connected to a variable speed motor. We are attempting a novel application of ECT with this small tube: measuring the dynamic angle of repose of fine powders.
• Radioactive Particle Tracking (RPT) System – An RPT system consists of an irradiated tracer particle (a mixture of gold powder and epoxy resin in our case) that mimics the physical properties of the fluidized bed material. The movement of the tracer inside the bed is measured with an array of NaI scintillation counters (12 in our case) mounted around the outside of the bed. There are countless applications of this technique, including tracking of granules as they grow in a fluid bed or shear granulator, monitoring the circulation patterns of powders and tablets in a Wurster coater, and determining the flow patterns of fine powders in a hopper.
• Deaeration test system – We are presently building a deaeration test bed based on the Englehardt approach for cracking catalyst deaeration testing. The bed is 14-cm ID and the static bed depth is about 50 cm. A pressure tap is placed inside the bed 30 cm above the distributor plate. The bed is fluidized and then the flow of air is abruptly halted. The plot of pressure versus time after air flow is stopped can be used to characterize the propensity of a powder to remain in the fluidized state. While our work with this test has been related to catalytic reactor applications, we are interested in extending it to the flow of fine pharmaceutical powders.