Prof. J. Zhu - Research Contributions and Interests

Prof. Zhu's major research contributions include:
The establishment of an important new concept of the high-density/flux riser fluidized bed
The development of liquid-solid fluidized bed system for biochemical and wastewater treatment processes
The milestone work for a comprehensive characterization of downer reactors
Scaleup of riser fluidized bed reactor
The development of new circulating turbulent fluidized bed reactors
Prof. Zhu's major research interests include:
Fundamentals of particulate and multiphase systems: bulk powder properties, powder flow enhancement technologies, powder feeders and dispensers
Circulating fluidized bed reactors: hydrodynamics of conventional low solids flux risers and high solids flux/density risers, regime transition, operating stability, modelling, scale-up, reactor design, length of acceleration and flow development
Gas-solid downer reactors: hydrodynamics, reactor design, gas and solids mixing, heat transfer, mass transfer, regime demarcation, modelling, applications in pyrolysis
Gas-solid circulating turbulent fluidized bed reactors: Hydrodynamics, mass transfer and regime demarcation
Gas-solids counter-current (gas up, solids down) vertical flow systems: hydrodynamics, regime demarcation
Computational Fluid Dynamics: use of CFD for modelling of gas-particle two phase flow, circulating fluidized beds, liquid-solid fluidized beds with applications in biochemical industry, powder coating booth and pulmonary drug delivery processes
Fluidization of cohesive fine and ultrafine powders and development of navel fluidization aids
Applications using cohesive fine and ultrafine powders in various industrial processes
Fluidization and handling of ultrafine powders for pulmonary drug delivery, development of new dry powder inhalers
Fluidization and handling of fine and ultrafine powders for high surface quality ultrafine powder coating/painting
Fluidization and handling of fine and ultrafine powders for direct dry powder coating for pharmaceutical tablets
Powder flow in spray booth: tracing of particle flow by PDA (Particle Doppler Anemometry), CFD FLUENT modelling of gas and particle flows, charge-to-mass ratio, transfer efficiency
Liquid-solid circulating fluidized bed reactors: hydrodynamics, regime transition, reactor modelling and application to chemical and biochemical reaction systems
Three-phase circulating fluidized bed reactors:  hydrodynamics, regime transition, high velocity operation, reactor scale-up, and application in waste water and biochemical reaction systems
Applications of liquid-solid and gas-liquid-solid circulating fluidized bed systems in the biochemical, agri-food and wastewater industries
Gasification of biomass and solids waste, biomass co-firing, pyrolysis of solids
Pneumatic transport of solids and its modelling
Chemical reactor modelling
Detailed information about research contributions:
The establishment of an important new concept of the high-density/flux riser fluidized bed

The concept of "high-density riser/circulating fluidized bed" was first proposed by Prof. Zhu in 1993. While many industrial circulating fluidized bed reactors are operating at bed density up to 10-15% and solids flux higher than 400 kg/m2·s, all academic research has been concentrated on low flux (<200 kg/m2·s) and low density (<5%) operations. In order to make people aware of this situation, two papers (1993 and 1995) were published and a new concept of "high-density operation" vs. "low density operation" was established to distinguish the high-density operations in CFB chemical reactors from the low density operations in CFB coal combustors. This concept was later further extended to also include "high-flux operation" vs "low-flux operation". This concept has now been widely accepted by theresearchers in this field and the papers been widely referred to. Over 20 papers have been published on the detailed studies of the high-density/high-flux riser/CFB. Research projects on high-density and high-flux CFB are still continuing, with new results and understanding generated on a continuous basis.


The development of liquid-solid fluidized bed system for biochemical and wastewater treatment processes

The liquid-solid circulating fluidized bed and gas-liquid-solid circulating fluidized bed technology was developed with the emphases on their application to biochemical and waste water treatment processes. It is a new reactor which combines two fluidized bed reactors into one system, a riser and a downflow fluidized bed (or downer). LSCFB provides excellent mass transfer and give extremely high efficiency. With the combined system, two reactions or processes can be realized in one system. Basic hydrodynamics have been studied and over 30 papers published to establish the flow structure and operating regime of this new fluidized bed reactor. With several reactor units at UWO, and with the advanced instrumentation available in the research laboratory, full radial and axial profiles of local solids concentration and liquid velocity were obtained and key understandings about this new type of reactors have been obtained. A new liquid-solid circulating fluidization flow regime was also proposed by the applicant. Models were also established to characterize the liquid and solids flow behaviour inside this new type of reactor. This system has now been applied for technology developments on efficient protein extraction process heavy metal recovery process, soybean protein separation, and for waste water treatment. Compared to the more conventional methods, those technologies provide significant savings and make the processes much simpler and shorter. Three patents are issued and several more pending on their applications. This secures UWO's leading position in LSCFB applications.

The milestone work for a comprehensive characterization of downer reactors

Extensive research has been carried out on the development of downer fluidized bed reactors. In 1995 and 1996, the first two comprehensive review papers were published with Prof. Zhu as the main author. Those laid the foundation for the large scale research work in this university. The world's tallest (16 m) downer/riser unit (in academia) was set up in 1995, supported by an NSERC strategic grant, which was listed by NSERC as the best examples of strategic grant applications for 1994-95. Many studies including mapping full axial and radial flow structures have been carried out so far in the 16 meter riser/downer set-up and over 20 papers have been published. Those work established the fundamentals of downer reactors and also established UWO as a leading downer study research site in the world.

Scaleup of riser fluidized bed reactor

Almost all circulating fluidized bed (CFB) reactors in industry have bed diameters later than 1 m, but all except for a few laboratory risers have diameters less than 0.1 m, providing unreliable data for commercial use. No systematic study was carried out to study the scaleup effect in the past. Therefore, we have carried out studies in two risers of exact geometry except for the diameter and sharing the same return column. The results, for the first time, show that there are significant scaleup effect with increasing riser diameter and the larger diameter unit gives less uniform radial distribution, contrary to what have been thought.

The development of new circulating turbulent fluidized bed reactors

Among fluidized bed reactors, turbulent fluidized beds (TFB) and circulating fluidized beds (CFB) cover most of the key commercial applications given their specific hydrodynamic features. However, they both have their own limitations. TFB reactors provide high reaction intensity and compact size as well as high mass transfer, but suffers from particle backmixing, while CFB reactors have less backmixing and high mass transfer, but are more dilute, bulky and costly to build. In the past few years, we have have developed a new concept of circulating turbulent fluidized bed (CTFB) reactor that combines the benefits of both. Our work has shown that such CTFB can be realized in a particle circulating loop and CTFB does have many advantages over both CFB and CTFB, such as near plug flow when compared to TFB and much higher bed density when compared to CFB. CTFB is also shown to be different than the high-density CFB as well as dense phase pneumatic transport in that it has very high bed density (30% or more) and can be operated continuously in a complete particle circulation loop. Our work has further shown that circulating turbulent fluidization is a new regime, independent of turbulent, fast fluidization and dense suspension upflow.

The invention of novel techniques for the enhancement of the fluidizability and flowability of ultra-fine powders

Extensive research has been carried out to achieve the smooth fluidization and to increase the handlability of ultrafine powders less than 30 microns. Those Geldart C powders are normally very difficult to handle because of the strong interparticle forces that cause them to agglomerate. Studies were performed to systematically evaluate the effect of various fluidization aids in order to enhance the flowability, and an invited review chapter was published in 2003 for the fluidization of ultrafine powders, followed by a dozen of papers and patents. While there have been many research including our earlier efforts to apply "aids" to increase the flowability of those cohesive powders, none of such "aids" has been found to be universally effective. Rather than applying external energy, typically through vibration, we have invented a series of methods to use fluid or nano-sized particles to "passivate" the surface of the ultrafine powders. Such methods can substantially reduce or essentially eliminate the interparticle forces, so that the ultrafine powders become fluidizable. Using our methods, most Geldart Group C powders can be made to behave like Group A powders, with proper fluidization, high bed expansion (typically 50-100%) and lower angle of repose (less than 40 degrees). Several patents have been filed. This represents a major breakthrough in the handling of ultrafine powders and can result in considerable technological and economical gains, given that the use of ultrafine powders can lead to revolutionary changes in areas ranging from daily life activities to industrial processes. For example, inhaling micronized drugs is a highly efficient and convenient method for drug delivery and replacing liquid paint with powdered paint in automobile coatings eliminates solvent emission. These techniques have been applied to significantly enhance the handlability of ultrafine powders in different applications. For example, they results have been utilized for the precise metering and dispensing of very small dosage of ultrafine pharmaceutical powders for pulmonary drug delivery, and for the uniform spraying of fine paint powders for surface coating processes. The drug dispensing technology provides the only dry method that can handle ultrafine drug powders (1-5 microns) in a very small quantity (20-500 microgram doses), without the use of excipients. The ultrafine powder coating technology produces surface quality comparable to that of liquid paint, something that has not been achieved by anyone before in the coating industry.

Ultrafine powder painting process

Powder paint coating is superior to liquid paint coating in that (1) it eliminates the use of petroleum-based solvents that are both expensive and harmful to the environment, and (2) it allows overspray paint powder to be recycled. However, only coarse paint powders of 30-60 microns have been used for powder coating so far since smaller powders make the powder extremely difficult to flow. Unfortunately, coarse paint powders cannot form a uniform enough coating, preventing the environmentally-friendly powder coating technique from being used for high-quality surface finishing such as the exterior surface of automobiles. The use of ultrafine powder can overcome the above problem, resulting in a very uniform surface, if those ultrafine paint powders can be fluidized. With our novel ultrafine powder handling technology, a new ultrafine powder technology that can apply 10-20 micron fine paint powders has been developed with several licenses granted. Commercial production with ultrafine powder coating in a local company over a period of two years has shown superb finishing quality and 45% savings on powder usage. Limited world-wide license on this technology is still available for potential licenses. This patented technology can also be used in many other areas where ultrafine powders are used.

New devices for pulmonary drug delivery

Pulmonary drug delivery is a much more effective and efficient method than taking drugs through the digestive system, and a much more convenient and safer method than injecting drugs intravenously. Given the extremely small sizes (<5 microns) required, strong interparticle forces cause severe agglomeration, making the handling of these ultrafine drug powders a serious problem. Current methods to make them flow better are (1) to blend them with a large amount of coarser excipient powders or (2) to suspend them in liquid. However, those methods cause other problems such as giving too large a dose for inhalation and restricting the actual delivery efficiency to about 20% at most. Our approach is to utilize a rotation fluidized bed dispensing technology to meter and deliver the drugs, so that these ultrafine drugs can be used alone, without the "aids" of coarse powder or liquid. More efficient and easy-to-use inhalers have also been developed. The main achievements are to accurate dispensing a tiny quantity (in the order of 0.02 to 0.5 milligrams per dose) of the ultrafine drugs (< 5 microns) without the use of any excipient particles, and the new inhaler designs. This research project has produced a combination of new drug handling processes and new inhalers that will eventually set an industry standard for pulmonary drug delivery in the very near future. Several patents are available for licensing.


Also from this web page:

Contact Info


Department of Chemical and Biochemical Engineering,
Faculty of Engineering,
The University of Western Ontario,
London, Ontario, Canada N6A 5B9

Tel: 1-519- 661-3807

Fax: 1-519- 850-2441