Prof. J. Zhu - Technologies

Novel Aids to the Fluidization of Ultrafine (Group C) Particles
High Quality Powder Coating Process Using Ultrafine Powders
Hydrophobic Surface Coatings
Pulmonary Drug Delivery
Dry Powder Coating of Solid Pharmaceutical Dosages
Detailed Information about Technologies:
Novel Aids to the Fluidization of Ultrafine (Group C) Particles

Many products such as catalysts, pigments, fertilizers, cements, ceramics, and pharmaceuticals are currently manufactured in particulate forms. In the chemical industry, for example, more than half of the products and at least three-quarters of the raw materials are in granular form. According to Prof. Geldart, particles can be classified into four groups and very fine particles (20-30 mm or smaller in size) are classified as cohesive particles (Geldart group C powders). Group C particles are difficulty to handle due to the presence of very strong interparticle forces. When subject to fluidization, those fine and cohesive particles tend to channel and agglomerate significantly, resulting in poor fluidization or even complete de-fluidization. On the other hand, ultrafine particles are very useful in many cases such as in chemical, advanced material, food and pharmaceutical industries, given their smaller size and large surface area.

To effectively utilize the benefits of group C particles, the most important issue is to properly fluidize those fine and cohesive particles. We have carried out systematic studies to investigate the fundamentals of interparticle forces and to develop novel techniques to overcome inter-particle forces so as to achieve the smooth fluidization of ultrafine Geldart Group C powders. A variety of fluidization aids including mechanical vibration, acoustic agitation and surface modification by dry particle coating with novel flow conditioners have been carefully studied. Among other things, effective technologies have been developed to incorporate nanosized flow conditioners to significantly enhance the flowability of very fine Group C particles (US Patent 6,833,185, plus more patents pending). By employing this novel dry-particle surface-coating technique and a variety of patented flow conditioners, fine powders can be made to fluidize smoothly and behave like Group A powders with large bed expansion. This novel surface-coating technology has been found very useful in many cases and has formed a platform technology which support several of our key technologies developed such as the ultrafine powder coating technology and the tablet coating technology. 

This technology with comprehensive patent protection can also benefit many industries. For example, finer powders generally results in better quality of the final products in the ceramic industry; finer catalyst particles lead to higher catalyst activity in chemical reactions; and finer particles enhance the mechanical properties of powder metallurgy products. More than a dozen of articles and patens have been published so far by our group in this field.

High Quality Powder Coating Process Using Ultrafine Powders

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 and reused. However, only coarse paint powders of 30-60 microns have been used for powder coating so far since powder of smaller sizes is extremely difficult to flow. The main problem with coarse paint powders is that they cannot form a smooth enough layer on the surface, so that the coating is not very uniform after curing. This prevents 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 (10-20 microns), if flow well, has been shown to overcome the above problem since it can apply a very uniform layer of paint powder on the surface. However, because of the very strong interparticle forces, finer powders become very sticky and do not flow well or not at all in the powder coating application equipment, resulting in poor surface finishing. To handle those ultrafine paint powders effectively, we have developed novel techniques (US Patent 6,833,185, plus more patents pending) that can effectively eliminate those interparticle forces. In the research and development work, we applied our novel ultrafine powder handling method in the powder coating process and very high-quality surface finishing has been achieved. This technology has also led to thin film coatings, that was not achievable with coarser powders given their larger diameter. Thinner coatings leads to significant savings when thicker films are not needed and also allow powder coatings to compete with liquid coating. The coating film using our ultrafine powder has also been shown to be more consolidated and durable than the regular powder coating. This technology has now been licensed and commercialized by a couple of licensees. 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. This research and development project is expected to lead significant changes to the whole ultrafine powder coating process. Limited world-wide license on this technology is still available for potential licenses.

Hydrophobic Surface Coatings

Based on the ultrafine powder coating technology developed in the past few years, a special technology that can produce coating surfaces with super hydrophobicity has been developed. The coating surface thus produced has water contact angle consistently higher than 150-160 degree, something that has not been possible.

Pulmonary Drug Delivery

In collaboration with several industrial partners, a series of new technologies haven been developed for administering minute amounts of powdered drugs through inhalation. Instead of delivering drugs through the human digestive system or intravenously, inhalation and diffusion of powdered drug through the lung directly into the blood stream is a much more effective, safer and painless drug delivery method. Compared to oral intake, only a small fraction of the drug is needed for each dose for pulmonary intake, since the first-pass GI (gastrointestinal) metabolism is significantly reduced. It also allows peptides, such as insulin, that cannot be taken through the digestive system to be administered through the lung. For respiratory diseases, it provides a direct and therefore more effective treatment with minimum side effect.

For pulmonary drug delivery, drug powders have to be extremely fine (< 5 microns) and doses of those effective drugs exceedingly tiny (0.05-1.0 milligrams). This presents a challenge because it is extremely difficult to accurately dispense a very small quantity of medicinal powder into the tiny blisters of an inhaler, given the strong inter-particle forces that exist between ultrafine particles. Using fluidization technology, which suspends powders in air flow, we have constructed a prototype dispensing apparatus to demonstrate the effectiveness and accuracy of this technology (US Patent 6,684,917, plus more patents pending). In this apparatus, a new rotating fluidized bed with a controlled particle out-flow device is used to precisely meter the particle discharge and to fill the small drug blisters that contain only 20 microgram to 1.0 milligram of drugs. Special technique is used to ensure very smooth and uniform fluidization so that the filling is very accurate. This provides a new method for handling ultrafine dry drug powders in such small quantities, without the use excipient particles (fillers). In addition, a novel type of Dry Powder Inhaler has also been developed. Animal tests show that the new inhaler invented that can effectively deliver the ultrafine drug powder from the blister into human the lungs, with the efficiency reaching as high as of 80%, which is much higher than most of the other DPIs currently on the market (~20%). The new inhaler is breath driven and does not require any auxiliary power source such as propellant or compressed gas. License opportunities are still available except for certain regions of the world.

Dry powder coating of solid pharmaceutical dosages

Pharmaceutical solid dosage forms include tablets, pellets, pills, beads, spherules and so on are often coated for various reasons, such as odour/taste masking, protection from moisture, prevention from destruction by gastric acid or gastric enzymes, enhanced mechanical strength, aesthetics and controlled release. Currently, the most common technology for coating solid dosage forms is the liquid coating technology. In liquid coating, a mixture of polymers, pigments and excipients is dissolved in an organic solvent (for water insoluble polymers) or water (for water soluble polymers) to form a solution, or dispersed in water to form a dispersion, and then sprayed onto the dosage forms in a pan coater (for tablets) and dried by continuously providing heat, typically using hot air, until a dry coating film is formed. However, vaporizing the liquid is extremely energy consumptive. Air cleaning is also a huge burden to the process, as the hot air has to be cleaned at both intake and outlet. Small dosages such as pellets and particles are currently coated in fluidized beds which requires even larger amount of hot air. Using organic solvents further results in environmental pollution, solvent recycling cost and operation dangers of explosion.

Our research team has developed a new ultrafine powder coating technology for the automobile and other industries and has several patents for its. This technology has now been successfully adapted for coating tablets and beads at the laboratory scale, showing a great potential for a new processes. In dry powder coating, no solvent or water solution is used, and the coating is carried-out in a pan coater by spraying dry-powders on the surface of the dosages directly. After curing, a compact and uniform layer of film is formed.

This new dry powder coating process (patent-pending) has many advantages over the aqueous coating: much lower energy requirements, efficient utilization of coating materials, environmentally friendliness, and lower operating costs. The same coating pan used in aqueous coating systems can be used for this new dry powder coatings process with only minor modifications. In term of energy saving, this new process uses only about 5% of the hot air currently used and saves about 70-80% in energy. It also eliminates the huge air cleaning system, which is normally 70% of the capital cost for tablet coating machines. A patent has been filed on this technology and a tentative licensed agreement has been signed with a Toronto-based pharmaceutical company to co-develop this technology towards commercialization. Selected licenses in certain parts of the world are still available.

Novel Waste Water Treatment System Using LSCFB-BNR Technology

In response to increasingly stringent effluent nutrient criteria as a result of deteriorating surface water quality, Biological Nutrient Removal (BNR) processes have become increasingly popular. In BNR processes, nitrogen and phosphorus can be removed simultaneously. These BNR processes employ a combination of anaerobic, anoxic, and aerobic suspended growth biological reactors. BNR processes are known to offer several advantages over the more conventional activated sludge processes, namely superior effluent quality, a significant reduction in aeration energy requirements due to utilization of formed nitrates to remove organic matter, improved sludge settling characteristics, a reduction in sludge quantities due to lower bacterial yields in the anoxic tanks, and the elimination/ minimization of chemical sludge. However, the reliability of the activated sludge BNR process in response to influent changes both in terms of quantity and characteristics have been questioned to the extent that many BNR plants have standby chemical dosing systems for phosphorus removal. Incomplete denitrification and low food to microorganisms ratio have been observed to cause filamentous bulking conditions in BNR activated sludge systems. In some cases, external sources of carbon may be required to achieve phosphorus and nitrogen removal, because of low concentrations of readily biodegradable organics.

To overcome the aforementioned shortcomings of the suspended growth BNR processes, a gas-liquid-solids circulating fluidized bed bioreactor (GLSCFBBR or simply CFBBR) has been developed to adopt a fixed-film, BNR wastewater treatment process (US Patent 7,261,811, plus more patents pending). This new system encompasses the aerobic, anaerobic, and annex processes in a single system and can be used to accomplish simultaneous carbon, nitrogen, and phosphorous removal. The integrated system consists of a riser column (anoxic bed in the lower portion and anaerobic in the upper portion), a downer column (aerobic bed), a liquid-solid separator, and a clarifier. Particles circulate from the top of the riser to the top of the downer and also from the bottom of the downer to the bottom of the riser. Given the very high liquid-solid contact efficiency and the large flowrates through the fluidized beds, the CFBBR-BNR process is very compact and highly efficient.

This unique system has the many advantages:
Increased process stability and reliability
Better effluent quality
Higher liquid-solid contact mass transfer efficiency
Higher throughput
Reduced capital equipment costs
Reduced land requirements
Reduced energy requirements
Reduced sludge volume and therefore reduced disposal costs

A pilot-scale demonstration study has shown that the new system has much higher contact efficiency and mass transfer rate compared to other conventional bioreactors and contactors, giving many advantages such as significantly reduced hydraulic retention time (from ~24 hours to 2 hours), reduced sludge formation (by 2/3) and better effluent quality (close to tertiary). The results clearly show that the invention represents a breakthrough in the area of wastewater treatment. Potential applications include municipal waste water treatment, industry waste water treatment, landfill leachates treatment, contaminated groundwater treatment, and surface waters treatment at industrial sites.

A large scale demonstration is currently undergoing at one of the City of London's wastewater treatment facilities, with financial supports from private sector, the City of London, the Province of Ontario through the Ontario Centre of Excellence, and the Natural Science and Engineering Research Council of Canada. The results have duplicated those from the smaller pilot-scale unit. This technology is now ready for licensing.

Continuous Protein Recovery Using Liquid-Solid Circulating Fluidized Bed Ion Exchange System

Conventional ion-exchange processes using packed beds have been established for decades as versatile tools for protein recovery due to their high selectivity and easiness in control. However, a packed bed column operation requires the cyclic operation of four procedures (adsorption, washing, desorption and regeneration) in a batch mode and such an operation is laborious and time-dependent. In addition, a typical biochemical broth usually contains large amounts of colloidal particulates, which must be removed before being treated by a conventional packed bed ion-exchange system, but the removal of small solids using filtration or centrifugation is very difficult. Furthermore, adsorption capacity of ion exchangers to proteins is usually low since a large portion of the internal surface of ion exchangers is not accessible to protein molecules due to size rejection. To overcome the those disadvantages, a liquid-solid circulating fluidized bed (LSCFB) ion exchange system has been constructed and investigated for the continuous recovery of protein from unclarified whole broth. The LSCFB ion exchange system has been patented as an innovative technology for continuous protein recovery (US patents 6716344, 6887368).

The LSCFB comprises of a riser, a downcomer, a liquid-solid separator and other auxiliary components. In the LSCFB ion exchange system, proteins are adsorbed onto the adsorbents in the downcomer (absorber) and the loaded adsorbents are regenerated simultaneously in the riser (stripper) in a continuous mode thus maintaining the adsorbents in the active form. Another unique feature of the LSCFB system is that the downcomer operates as an expanded bed with adsorbent falling down and liquid phase moving up. The bed voidage can be enlarged to make possible the treatment of feed containing particulates without clogging the bed. That is, the liquid velocity in the downcomer can be controlled in such a range that the particulates are discarded with the deproteinized feed liquor while permitting the ion exchange particles to settle to the bottom and return to the riser. This eliminates the costly solids removal (pre-clarification) operation and significantly simplifies the overall purification scheme.

A liquid-solid circulating fluidized bed continuous ion exchange system (LSCFB) has been constructed the successful continuous recovery of bovine serum albumen (BSA) and whey proteins from unclarified broths using Diaion HPA25 anion exchanger demonstrated. Under the optimal operating conditions, up to 80% of total protein was removed from the whey feed stream and an overall recovery of approximately 80% was achieved. In the case of BSA recovery, up to 98% BSA was adsorbed in the downcomer and an overall protein recovery of up to 84% was obtained in the LSCFB system.

Proteins are the core components of numerous bio-industry products including foods, pharmaceuticals, detergents, and etc. in the forms of functional proteins, vaccines, and enzymes. Due to the low concentration of target proteins in most raw biological broths and the complexity of those broths, the recovery of those proteins are extremely challenging and the cost for recovery commonly counts for more than 80% of the overall production cost. Therefore, this technology will generate remarkable interests in relevant industries.

Continuous Phenolic Wastes Treatment by Entrapped Soybean Seedhulls Peroxidase Enzymes using LSCFB (Liquid-Solid Circulating Fluidized Bed)

Removal of phenolic contaminants from wastewater is a major problem for many chemical industries. Chemical oxidation is a currently available technique to treat phenolic wastewater. Microbial degradation and corona discharge have also been proposed to treat phenolic compounds. However, these techniques are suffering from slower degradation time, higher cost and sometimes ineffective to treat higher concentration of phenolic compounds. There are also concerns to the toxic nature of end products after degradation.

In comparison to the above described methods, enzymatic treatment is a promising way of treating the phenolic pollutants. Our new technology uses soybean peroxidase enzymes as biocatalysts to degrade phenolic pollutants. It is found that soybean peroxidase enzymes have a quick ability to degrade phenols in presence of hydrogen peroxide and to produce polyphenols. Required SBP enzymes can be purified from raw soybean seed hulls. Using our patented liquid-solid circulating fluidized beds technology (LSCFB, US patents 6716344, 6887368) developed in our lab, the continuous bioprocess to polymerize phenol in presence of hydrogen peroxide by using the entrapped SBP enzymes is successfully demonstrated. Enzymes are entrapped within sol-gel / calcium alginate (inorganic/organic) biocomposites and uniform size of peroxidase particles are produced using a multi-nozzle encapsulator. An advantage of accommodating the two process streams of different properties without intermixing is utilized to keep reacting and regenerating process streams separate in the LSCFB system. A simultaneous and a continuous reaction and regeneration of the biocatalysts are realized in the two inter-connected fluidized beds. High biovolumetric productivity, continuous treatment of phenolic wastewater, the demand of continuous regeneration of peroxidase particles, independent residence time for reaction and regeneration are the main advantages of introducing LSCFB this as an new attractive immobilized bioreactor system.

The proposed bioprocess will provide a simultaneous degradation of phenolic pollutants and production of non-toxic bio-based products using LSCFB system. The advantage of the LSCFB system can be extended to the downstream biorefining processes to extract the bio-based products continuously and efficiently at a high throughput.

Novel Wear Tester for the Testing of Dental and other Materials

In order to produce materials that can better withstand the demands of their environment, there is a need to create tests of their resistance to wear. Standard tests include the pin and disk method that requires the tested material, normally in pin form, to be in contact with another material, normally in disk form, under a given applied load. Such methods are not suitable for testing wear resistance under long-term conditions as the load is only applied for a short period of time. In addition, such tests also do not give accurate representations of the actual wear process under long-term but low-loading conditions, since the results represent much harsher loading conditions than would actually occur. For example, wear of restorative dental materials implanted in the human mouth is a relatively slow process and the mechanism can be significantly different than that observed in a test of small duration and relatively high loading, such as the pin and disk tester. Therefore, results obtained using the given standard tests are unlikely to produce the representative wear rate. 

For the purpose of testing dental restorative materials, two basic methods are involved, in vivo and in vitro. In vivo is the clinical method that operates in the oral environment. Investigations utilizing this method are time-consuming, as a period of at least 6 to 12 months is usually required to produce a measurable amount of wear. In addition, the complexity of the oral environment across a given group of subjects makes it almost impossible to establish a standard in vivo measurement. Typical in vitro tests are the pin and plate method and the toothbrush/dentifrice abrasion test. The main problems with the existing in vitro methods are; (1) the test conditions do not adequately simulate the in vivo wear environment and (2) the tests are too short to establish the long-term wear properties of the dental materials.

To overcome this problem with in vitro testing, we have successfully developed a new wear tester. The tested materials are exposed to gently moving small particles that produces a loading representative of the actual environment, and are subject to repeated impact and abrasion over an extended period of time. The system is flexible since by changing the particle properties and the frequency of the particle movements this device can be used to mimic the long-term wear process for many types of materials. Furthermore, this flexibility allows closer approximations to the actual conditions of the intraoral environment for dental restorative materials since the intensity of the loading to which the material is exposed to can be controlled. Thus the wear resistance in given materials under long-term and low exposed loading conditions can be tested properly. In addition, by adding liquids of different properties into the system, the new device can also better mimic properties of the natural environment such as the pH value and corrosiveness.

This device has been applied to test several different dental materials and the results are consistent with that reported in the literature. It is also shown that this device can easily be used for the testing of other materials, metal or non-metal, for their long-term wear resistance. This technology is available for licensing.

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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