Chinese
The filter press consists of three parts:
I. Frame
The frame is the basic component of the filter press. It has thrust plates and pressing heads at both ends, connected by beams on both sides. These beams support the filter plates, filter frames, and pressing plates.
1. Thrust Plate: Connected to the support, it allows one end of the filter press to rest on the foundation. In a chamber filter press, the thrust plate has a feed hole in the center and four holes at the corners. The top two corner holes are for washing liquid or pressing gas inlets, and the bottom two corner holes are for outlets (or filtrate outlets in a concealed flow structure).
2. Pressing Plate: Used to press the filter plates and frames together. Rollers on both sides support the pressing plate as it rolls along the tracks on the beams.
3. Beams: These are load-bearing components. Depending on the corrosion requirements of the operating environment, they can be coated with rigid PVC, polypropylene, stainless steel, or new anti-corrosion coatings.
II. Clamping Mechanism
Manual clamping, mechanical clamping, hydraulic clamping.
1. Manual clamping: A screw-type mechanical jack pushes the clamping plate to clamp the filter plates.
2. Mechanical clamping: The clamping mechanism consists of a motor (equipped with an advanced overload protector), a reducer, a gear pair, a lead screw, and a fixing nut. During clamping, the motor rotates forward, driving the reducer and gear pair, causing the lead screw to rotate in the fixing nut, pushing the clamping plate to clamp the filter plates and filter frames. As the clamping force increases, the motor load current increases. When it reaches the current value set by the protector, the maximum clamping force is reached, the motor cuts off the power, and stops rotating. Because the lead screw and fixing nut have a reliable self-locking helix angle, the clamping state is reliably guaranteed during operation. During retraction, the motor reverses, and the retraction stops when the pressure block on the clamping plate contacts the limit switch.
3. Hydraulic Clamping: The hydraulic clamping mechanism consists of a hydraulic station, cylinder, piston, piston rod, and a Haflan card connecting the piston rod and the clamping plate. The hydraulic station consists of a motor, oil pump, relief valve (for pressure regulation), directional valve, pressure gauge, oil circuit, and oil tank. During hydraulic clamping, high-pressure oil is supplied by the hydraulic station, filling the component chamber formed by the cylinder and piston with oil. When the pressure exceeds the frictional resistance of the clamping plate, the clamping plate slowly clamps the filter plate. When the clamping force reaches the pressure value set by the relief valve (displayed by the pressure gauge), the filter plate, filter frame (plate-and-frame type), or filter plate (chamber type) is clamped, and the relief valve begins to unload. At this time, the motor power is cut off, and the clamping action is completed. During retraction, the directional valve reverses, and pressurized oil enters the rod chamber of the cylinder. When the oil pressure can overcome the frictional resistance of the clamping plate, the clamping plate begins to retract. When hydraulic clamping is in automatic pressure-holding mode, the clamping force is controlled by an electric contact pressure gauge. The upper and lower limit pointers of the pressure gauge are set to the values required by the process. When the clamping force reaches the upper limit of the pressure gauge, the power is cut off, and the oil pump stops supplying power. Due to potential internal and external leakage in the oil circuit system, the clamping force may decrease. When it drops to the lower limit of the pressure gauge, the power is turned on, and the oil pump starts supplying oil. When the pressure reaches the upper limit, the power is cut off, and the oil pump stops supplying oil. This cycle is repeated to maintain the clamping force during the filtration process.
III. Filtration Mechanism
The filtration mechanism consists of filter plates, filter frames, filter cloth, and pressing diaphragms. The filter plates are covered with filter cloth on both sides. When pressing diaphragms are required, a set of filter plates consists of a diaphragm plate and side plates. The base plate of the diaphragm plate is covered with rubber diaphragms on both sides, and the outside of the diaphragms is covered with filter cloth. The side plates are ordinary filter plates. Material enters each filter chamber through the feed holes on the thrust plate. Solid particles, due to their larger size than the pore size of the filter medium (filter cloth), are retained in the filter chambers, while the filtrate flows out through the outlet holes below the filter plates. When the filter cake needs to be dried, in addition to diaphragm pressing, compressed air or steam can be introduced through the washing port to flush away the moisture in the filter cake, thus reducing its moisture content.
1. Filtration Methods
The filtrate can be discharged through open-flow filtration or closed-flow filtration.
A. Open-flow filtration: Each filter plate has a water nozzle at its lower outlet hole, allowing the filtrate to flow directly out.
B. Closed-flow filtration: Each filter plate has an outlet channel hole at its lower part. The outlet holes of several filter plates are connected to form an outlet channel, and the filtrate is discharged through a pipe connected to the outlet holes below the thrust plate.
2. Washing Methods
When the filter cake needs washing, there are two methods: open-flow unidirectional washing and bidirectional washing, as well as closed-flow unidirectional and bidirectional washing.
A. In open-flow unidirectional washing, the washing solution enters sequentially through the washing solution inlet holes of the thrust plate, passes through the filter cloth and then the filter cake, and flows out from the non-porous filter plate. In this case, the outlet nozzles of the perforated plate are closed, while those of the non-porous plate are open.
B. In open-flow bidirectional washing, the washing solution enters sequentially through the washing solution inlets on both sides above the thrust plate, washing twice in succession. The washing solution first washes from one side and then from the other, with the outlet diagonally opposite the inlet. Therefore, it is also called bidirectional cross-washing.
C. In closed-flow unidirectional washing, the washing solution enters sequentially through the washing solution inlet holes of the thrust plate into the perforated plate, passes through the filter cloth and then the filter cake, and flows out from the non-porous filter plate.
D. Dark-flow bidirectional washing involves two separate washing processes, with the washing liquid entering from two inlets on either side of the stop plate. The washing proceeds first from one side, then from the other, with the washing liquid exiting diagonally. Therefore, it is also called dark-flow bidirectional cross-washing.
3. Filter Cloth: Filter cloth is a primary filtration medium. Its selection and use significantly impact filtration efficiency. When selecting filter cloth, factors such as the pH value and particle size of the filtered material should be considered to choose the appropriate material and pore size to ensure low filtration costs and high filtration efficiency. During use, the filter cloth should be kept flat and unpleasantly folded, with unobstructed pores.
A filter press is a mechanical device that uses a special filtration medium to apply pressure to the material, causing the liquid to permeate out. It is a commonly used solid-liquid separation device. It was first applied in chemical production in the early 18th century and remains widely used in industries such as chemical, pharmaceutical, metallurgical, dye, food, brewing, ceramics, and environmental protection. The filter plate is stable in performance, easy to operate, safe and labor-saving; the metal press cylinder is made of seamless steel pipe and precision cast plastic steel filter plate, which is resistant to high temperature and high pressure and durable.
