MIL-HDBK-1005/9A
A pressure filter consists of metal plates covered by a
fabric filtering medium. The covered plates are hung in a frame
equipped with both a fixed and a moveable head. The plates are
forced together with a chamber left between the cloth surfaces.
Sludge is pumped through a central opening in the plates to the
cloth-lined chamber. Sludge is retained on the fabric and liquid
is forced through the fabric to the plate surface where it drains
away. At the end of the filtration cycle, the plates are
separated, and the sludge cake is discharged from the unit. Feed
pressures ranging between 80 and 225 psig are common. Filter
presses achieve 40 to 50 percent solids concentration.
c) Belt Filter Press. For larger facilities with
higher sludge production consider a belt filter press. The
performance of belt presses depends on factors such as
conditioning, maximum pressure, and number of rollers. Determine
polymer type and required dosage for sludge conditioning by bench
scale or pilot plant tests. Consider the effect of oil blinding
of media and methods and efficiency of media cleaning in equipment
selection and specification. Consider handleability of sludge
cake and cake discharge characteristics in equipment selection and
specification.
A belt type filter press will normally produce a sludge
cake with 60 to 70 percent moisture content. The units are
mechanically complex and require frequent maintenance attention to
check and adjust roller clearances and lubricate roller bearings.
However, full time operator attention is not required during
operation. Since sludge cake is discharged continuously, a
conveyor belt might be required to carry off the sludge to a
storage area.
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