Mass flow rate of fine and cohesive powders under differential air pressure

Abstract

Air-powder interactions are of practical importance in the production of pharmaceuticals, food and high value added chemicals manufactured using powders. For examples, air-powder effects enable consistent and effective dosing of fine cohesive powders into dies on high productivity rotary presses due to the suction fill effect. A purpose built experimental testing rig was developed and calibrated in order to develop a basic understanding of effect of air pressure on the mass flow rate of fine and cohesive powders. The powder materials were selected to enable the study of the effect of particle properties, such as size and density, and processing conditions such as differential air pressure, on the mass flow rate of powders. The models available in the literature developed for coarse free flowing sands under differential pressure were found inadequate to describe the experimental observations and to predict the flow behaviour of fine and cohesive powders. A new powder flow model was developed using established dimensional analysis methods based on the experimental data. The proposed model includes terms that account for the effect of differential pressure and reduces to the classic Beverloo model in absence of differential pressure. The models was validated and can be used for formulation and process design for flow regimes where air-powder interactions are important.

Research regarding the common problems of design of the bunkers – A review

“…The predominant importance of bunkers and silos for a wide variety of industries is evident by the intense efforts of many researchers to obtain models for the unloading behavior of the particular storage devices [10,11,12,13]. The size of the mass flow itself and the difficulties in maintaining reliable and uniform flow behavior are of great interest, as these problems can have major impact consequences.…”

Powder die filling under gravity and suction fill mechanisms

“…The pressure transducers were calibrated using a hot-wire anemometer and a calibrated 220 manometer where the steady flow of air results in a pressure drop inside the unit. Figure 7 shows a schematic diagram of the calibration system (Baserinia and Sinka 2018). The velocity of the shoe and the punch were calibrated using a high-speed video camera whereby the motion of the shoe and the punch was captured and the velocity was determined based on the fps of the video and the total number of frames captured for a set distance.…”

“…Schematic diagram of the pressure transducer calibration system. Reprint from(Baserinia and Sinka 2018), with permission. 230…”

The Challenge of Die Filling in Rotary Presses—A Systematic Study of Material Properties and Process Parameters

“…Several studies were carried out to understand the filling process using a linear filling device [2,3,[7][8][9][10][11][12]. Wu et al examined the flow of metallurgical powders in stationary simple and stepped dies from a moving feeding shoe in air and vacuum [3].…”