GOALI: Measurement of Stresses in Bulk, Flowing Powders and Application to Scale-Up of Powder Processes

Cuny City College, New York NY

Investigators

Abstract

Abstract CTS-0355417 G. Tardos, CUNY City College The proposal addresses the key issue of force-and stress-measurements in dry or wet (cohesive) moving (flowing) powders in several unit operations and the application of stress-measurement criteria to scale-up in different kinds of powder processing equipment. We propose to use the method of calibrated test particles of known yield strength to interrogate forces (stresses) in the bulk of the moving powder and to capture the point where the stresses on the particle equals its yield strength and starts to deform. Scale-up to larger size machines of the same or different geometry is then achieved by adjusting the operating conditions in the larger machine so as to achieve stresses of equal magnitude. Preliminary work on wet granulation in a vertical-axis mixer-granulator (see also Tardos et al., 2003b) has clearly shown the feasibility of such an approach and has demonstrated that using this kind of scale-up rule yields product of similar properties at both scales. This was the first time that forces in a cohesive, flowing powder were measured on freely moving objects inside the bulk. The main goal of the proposed research is to show that this kind of measurement is general to many different powder-flow systems and to apply it to the most common and most difficult applications such as mixers, granulators of different kinds, fluidized beds and rotating drums containing both wet and dry powders. The involvement of the industrial partner in this research is crucial since it will allow, on one hand, use of existing modern instrumentation and large-size industrial equipment during the project, and on the other hand, direct use of the knowledge gained in several industrial processes specifically in pharmaceutical applications. In addition, the co-PI is a very well known Powder Technologist (a former university professor himself) that will contribute greatly to advising students, directing the research and disseminating the knowledge gained at the industrial site and at conferences. Intellectual Merit The proposed research is aimed at substantially improving understanding in an area of Powder Science and Technology where precise measurements and basic knowledge were slow to develop due to the extreme complexity of underlying phenomena and the difficulty in experimentation. The area is however of great industrial relevance especially scale-up of powder-flow processes in different equipment where large amounts of time and funds are presently spent. The proposed measuring method, if successfully developed and generalized, will give industry a real, practical tool to undertake scale-up even of equipment that is geometrically dissimilar. This will be the first time that such a tool will be generally available to industrial practitioners. It will enable the transfer of powder processes from different types of equipment assuring constant product attributes by keeping internal stresses in the bulk powder constant. Broader Impact The research will have very broad academic and industrial impact due to its dual location as an industry-academy type research project. Both groups will use and disseminate information in their respective communities by actually applying the obtained results and by presenting them widely at conferences, seminars and symposia. The graduate and undergraduate students will be trained in a relatively unknown and mostly under-funded branch of engineering where progress has been slow and relatively few trained practitioners exist. In addition, small amount of funds are requested to support high school students (juniors and seniors) who attend the college routinely in the framework of a high-school-university exchanges program (SPICE) that is in operation at the college for at least ten years. This project will enable these students to try their hand in this relatively unknown field. Finally, since CCNY qualifies as a minority institution. 50-60% of students involved in all aspects of the research will be underrepresented minorities and they will actively participate in the project at all levels.