Solving Premature Bag Wear in a Fabric Filter

Shiller Station, a 150 MW coal and oil fired station owned by Public Service Company of New Hampshire, was experiencing high bag wear in their fabric filter (FF) unit that was causing unscheduled outages for repair. Using computational fluid dynamic (CFD) modeling to simulate the ash laden gas flow through the fabric filter system, causes of the bag wear were identified, and modifications were developed to stop the issue. The plant has installed the recommended flow controls, and have reported that not only is the bag wear issue resolved, they also gained over 1-inwg of pressure savings from the modifications.

Work Performed

Using a CFD model of the complete fabric filter system, including connecting ductwork, inlet and outlet manifolds, and each FF compartment with bags, the cause of the high bag wear rate was identified—poor gas flow distributions in the inlet manifold and entering each compartment. Modifications were developed to create more uniform gas velocities through the inlet ductwork and entering each compartment, and to reduce the gas velocity magnitude impacting the bags. The final design created smooth flow throughout the connecting ductwork and manifolds. The design also eliminated the high velocity jets that were impinging on the bags.

Results

The plant has reported that they are no longer experiencing premature bag wear and ash deposition in the ductwork has been minimized. As a result of this modification, the plant also reported a gain of over 1-inwg due to the pressure loss savings.