Rotary feeders are one of the most widely used devices for regulating the flow of powdered and granular solid materials from storage facilities such as hoppers, silos, bins and bunkers. In this paper the performance characteristics of such feeders are examined, from both model and experimental standpoints, with a view to enhancing understanding of the operation of these devices. Through understanding the way in which materials flow through the inlet port and into the rotor pockets a model is developed that describes how the feed rate varies with the rotor speed. Experimental work confirms the general form of the characteristics predicted by the model studies. An approach is developed for predicting the feed rate characteristics when handling free-flowing materials having particle sizes greater than 5 mm. Further work is necessary to predict these characteristics when handling materials have particles smaller than this size. NOTATION a volume of one rotor pocket (m 3 ) b width of the inlet port to the rotary feeder (m) c number of pockets in the rotor d diameter of the rotor (m) g gravitational acceleration constant (m/s 2 ) h linear length of the inlet port to the rotary feeder (m) m . gravimetric feed rate (kg/s) n rotor speed (r/s) n 1 critical rotor speed (r/s) n 2 maximum critical rotor speed (r/s) t time (s) u linear pocket velocity (m/s) _ volumetric feed rate (m 3 /s) w volume of material flowing into a rotor pocket (m 3 ) x pocket width (m) y distance travelled by material falling into the rotor pocket (m) a pocket filling factor r b poured bulk density of material (kg/m 3 ) o rotor speed (rad/s)
This paper uses a case study to illustrate the problems which can occur when using small feeders to dose at low rates, with materials which are not totally free flowing. The general principles of good design for small feeders are enlarged upon, together with issues to look for when trouble shooting these equipment items.The system in question used a screw to dose a moist pelleted talc into a process at a nominal rate which was variable at around 1 t/h and originally suffered from poor flow in the hopper, a variable dosing rate and binding of the screw, thus needing constant attention from the operator to keep it working. Various types of mechanical flow assistance device had been tried, most of which made the problem worse. The Wolfson Centre redesigned the screw and hopper of the unit, and the performance problems were cleared. The problems with the original and intermediate designs serve to illustrate very well the points that need to be observed, in obtaining good performance from small feeders.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.