1.Feed Filtration
As material enters the plate and frame filter press, feed pressure forces the filtrate through the filter cloth, trapping solids and forming a filter cake. As filtration progresses, the filtration pressure continues to rise, gradually filling the filter chamber with filter cake. The feed pressure reaches a high value (approximately 1.2 MPa) and remains constant for a long time. Due to the varying moisture content of the feed sludge, the feed time is generally controlled between 1.5 and 2 hours. Sludge feed is provided by high- and low-pressure sludge screw pumps.
2.Backflushing
Backflushing is performed twice during each complete process. The first time, after sludge feeding is complete, air backflushing is performed to increase the solids content of the filter cake and prevent clogging of the center pipe. The second time, after the pressing is complete, the compressed air system is operated to backwash the residual sludge in the filter press’s center inlet pipe and the filtrate in the membrane cavity. The backflushed sludge is returned to the conditioning tank through a DN100 backflush sludge pipe installed at one end of the filter press. Both air backflush cycles take only 5-10 seconds to complete. It’s important to note that, because backflush generates high instantaneous pressure and lasts only a short time, if conditions permit, the backflush sludge pipes can be connected separately to the sludge conditioning tank. This effectively prevents one filter press from affecting the normal operation of other filter presses while backflush is in progress.
3.Diaphragm Pressing
Close the pneumatic feed ball valve and inject high-pressure water into the diaphragm plates. The high water pressure is 2 MPa, typically maintained at 1.5-1.8 MPa. The diaphragm tension squeezes and dehydrates the sludge, typically lasting approximately 1.5 hours. The squeezed water returns to the squeeze water tank through a pipe, and the filtrate is discharged through the filter cloth. Solids are trapped by the filter cloth, further increasing the sludge solids content. Plate Pull Unloading
After pressing is complete, the unloading process begins: First, the pressing plate retracts until it stops at the limit switch. The plate puller then advances to remove the plate. When the plate is pulled to the center of the unloading space, the limit switch senses the sensor on the side of the filter plate and transmits a signal to the PLC. The cylinder’s striking section moves forward, stopping just above the filter plate. The vibrating cylinder then descends. The vibrating head at the end of the cylinder rapidly strikes the top of the filter cloth support mechanism and quickly retracts upward, rapidly compressing and releasing the compression spring of the filter cloth support mechanism. This causes the filter cloth to vibrate under the support mechanism, assisting in unloading the filter cake. The entire unloading process takes approximately 1.5 hours.
4.Water Washing
After a period of operation, the filter cloth can become clogged, affecting filtration performance. Normally, the filter press requires water washing every 7-15 days, supplied by a water wash pump. The single cleaning cycle of each filter press is 20-30 minutes. This process is completed by the high-pressure water washing rack provided by the equipment, and the water washing process is fully automatically controlled.
