Analysis

The very fine Super Absorbent Polymers (SAP) powders increase static electricity and absorb the humidity and creates membrane on the surface of the filter bag which accumulates on Filtermedia surface restrict the airflow and results a high pressure drop. Furthermore, the membrane sticked tightly on the glazed surface of the filter media, cannot remove by pulse jet air as well as manual wash clean.

Old bags without PTFE membrane, dust creates membrane and blind surface of the filter bag

Solution

ST Filter introduced ‘MX/MX 500 as PTFE ANTI-HD’ for this application:
Scrim: Aramid
Fiber: Aramid fibers and Stainless steel fiber
Static is easy to create in Polymer powders. Permanent static dissipation by Stainless steel fibers reduces the accumulation of the bulk polymer powders, help the pulse jet cleaning.
Resistance value: <105Ω. This figure is well below the maximum permissible resistance value of <108Ω,which is stipulated for conductive filter materials. Permanent static dissipation by Stainless steel fiber even the filer bags are broken.
Surface treatment:

· ePTFE membrane--

Laminated PTFE membrane is a surface filtration conception. Expended PTFE membrane contributes a very smooth surface and acts as a primary dust cake requiring no precoat before or during operation, maintaining optimum airflow at a reduced pressure drop. Furthermore, cakes are easy remove in case polymer absorbs vapor and sticked on to the ePTFE membrane.

· Anti-Hydrolysis--

Aramid fiber is easy to hydrolysis under hot vapor. ST Filter introduced a PTFE latex-dipping surface finishing, each fiber was cover with PTFE, which will protect the fibers from being attacked by hot vapor, consequently extended the life of the filter media.
Filter bag making: Aramid yarns may hydrolysis, so PTFE Yarn is recommended as the most suitable yarn. PTFE yarn ensures the stitching tightly even the filter bags broken.

Replacement bag with PTFE membrane, the bag surface keeps clean after half year running.

The cuff has no PTFE membrane, dusts blind on the material, while PTFE membrane tube keeps smooth surface after half a years running.

Result

The plant manager reported that the production was double increased and reduced the break time for maintenance. The replacement filter bags were still working after 18months operation.