A large packaging company near Baltimore, Maryland was expanding their plant and adding an extrusion line for polypropylene rigid packaging products. From experience at another plant owned by the same company, it was known that a few pounds per hour of waxy particulate would be emitted from the new line – at the die (melt section) and from the extruder vent.
The company installed two APC Technologies UHF® filter units, one on the die exhaust and one on the extruder vent. To minimize deposit of the waxy particulate in the duct, the unit for the die emissions was located on a mezzanine level just two feet above the die exhaust hood, with the exhaust flowing upward into the bottom of the filter unit.
The UHF® filter units installed are designed for applications having very fine, sticky fumes and particulate. The units utilize dry filter media, presented in rolls that provide high control efficiency (i.e., high 90%’s) on submicron particulate. The filter units maintain steady air flow by automatically indexing a clean section of filter media into the filtration chamber when the previous filter section becomes caked with particulate. The units thus operate within a steady differential pressure band (and thus steady air flow rate band) until the entire roll is spent. Filter roll replacement takes approximately 5-10 minutes and is completed while the units and process are running, which was a necessity for the 24/7 plant.
The two filter units provided very steady exhaust air flow from the process, operating within a narrow pressure drop range. The units were installed with manually-adjustable variable frequency drives (VFDs) on the fan motors, allowing dial up / down of the fan speed, as the total required exhaust air flow was originally unclear. After passing through the unit, the cleaned air passed through the exhaust fan and out a stack. There were no visible emissions (opacity) from the stack, nor any material deposits of any kind around the stack.