Improvement of the air distribution system of the pneumatic-mechanical drum separator

Abstract

The separation of bulk granular materials in a blocked fluidized bed (BFB) is discussed. The properties of standard and blocked fluidized beds are compared. The key feature of the new separation system - the blocked fluidized bed - is that by varying the solid phase and airflow parameters it is possible to achieve “effective density” intermediate between the densities of the components of the heap being fed. To improve the separator efficiency, we studied the uniformity of airflow distribution in a drum separator using a BFB as the separation system. In particular, we examined single- and double-sided airflow supply into the separator. Double-sided supply proved preferable and was adopted as the design basis. To further improve the uniformity of airflow distribution, an additional screen with a variable clear cross-section increasing from the center of the drum to its edges was installed under the tension string mounting frame. An experimental airflow distribution diagram was obtained. It exhibits a wave-like shape due to the stepwise change in the screen effective cross-section across the drum width. Analyzing the obtained a priori data, we adopted the following hypothesis. To equalize the convex shape of the diagram across the drum width, an additional screen with a smooth, concave effective cross-section across the drum width should be placed in the drum cavity under the tension string mounting frame. The methodology was developed for experimental studies which revealed that the most stable pressure distribution across the drum width occurred in the upper portion of the drum, from 90° to 180°, where it was appropriate to organize technological processes for separating bulk granular materials of various groups.