The influence of a cone-in-cone insert on flow pattern and wall pressure in a full-scale silo

A Silo insert is sometimes placed inside the hopper to improve the flow pattern of solids in a funnel flow silo. This paper describes a recent experimental investigation of the flow pattern and wall pressures observed during filling and emptying of a cylindrical silo with and without a cone-in-cone insert. The 2.5 m diameter silo had an 8 m high cylindrical section and a 44 degrees conical hopper, and was filled with crushed quartz sand. The wall pressures were measured at ten chosen locations using pressure cells mounted on the wall. To investigate the solids flow pattern, markers were placed at fixed positions in the silo during filling and the residence time for each marker during discharge was observed. The flow pattern can be inferred from the residence time measurements for the markers and the surface profile observations during discharge. These tests show that a cone-in-cone insert can have a strong influence on both the flow pattern during discharge and the pressure acting on the silo wall and its industrial use should be considered cautiously and implemented with care. (C) 2008 Published by Elsevier B.V. on behalf of The institution of Chemical Engineers.