Taking the lumps out of your stored material — Part I
Lumps can create a range of problems in bulk solids handling and processing operations: Small lumps can produce inconsistent mixtures, and large falling lumps can create safety hazards and cause structural damage in storage vessels. Part I of this two-part article examines how lumps cause flow blockages and other problems and how lumps are formed. Part II, which will appear in the December 1998 issue, explains how lump formation can be prevented with various retrofit equipment and other solutions. The article explores these topics by examining how lump problems stopped flow in a food processing plant's sugar silo.
Midwestern food processing plant received between 200,000 and 250,000 pounds of granulated sugar per week in railcar loads. The plant's pneumatic unloading system used cool, dry air to transfer the sugar from the railcars to a carbon steel silo, as shown in Figure 1. The 6,000-cubic-foot, 12-foot-8-inch-inside-diameter silo had a 56-foot-tall cylinder and a 7-foot-tall conical hopper section with a 60-degree slope [Figure la]. A 4-foot-diameter vibrating bin bottom was mounted on the hopper's lower section [Figure lb]. A rotary valve at the hopper outlet controlled flow and delivered the required amount of sugar to a second pneumatic conveying line for transfer to a weigh hopper.