Chamber filter press

Filter Press

Filter press uses a special filter medium to apply a certain pressure to the object, so that the liquid is dialyzed out. It is a mechanical device that is commonly used for solid-liquid separation. It was used in chemical production in the early 18th century and is still widely used in chemical, pharmaceutical, metallurgical, dye, food, brewing, ceramic and environmental protection industries.

The filter plate has stable performance, convenient operation, safety and labor saving; the metal pressing cylinder is processed by seamless steel pipe and precision-cast plastic steel filter plate, which is resistant to high temperature and high pressure and durable.

Chinese name: Filter Press

Foreign name: Filter Press

Category: Solid-liquid separation equipment

Application: Chemical, pharmaceutical, metallurgical

Origin: early 18th century

Product introduction:

Function: Extract solids from the mixed liquid to achieve the effect of solid-liquid separation.

Subject: Coal Science and Technology (first-level subject); Mining Machinery Engineering (second-level subject); Coal Preparation Machinery (third-level subject).

History: The first filter press equipment appeared in the early 18th century and was used in chemical industry production.

Scope of application of filter press:

Medicine, chemical industry, standard parts, pharmaceuticals, metallurgy, non-standard screws, dyes, food, brewing, ceramics, oil refining, sewage treatment and other environmental protection industries

Technical parameters:

Model performance parameters

Filtration area (m2) Filter plate dimensions (mm) Filter plate thickness (mm) Filter cake thickness (mm) Number of filter chambers (pieces) Theoretical volume of filter chamber (L), (m3) Overall dimensions of the whole machine (length × width × height) (mm) Installation base dimensions (mm) Working pressure in the filter chamber (MPa) Motor power (KW) Machine weight (KG) Filter plate performance Filter plate structure: plate and frame type, box filter plate.

Filter plate material: stainless steel, cast iron, rubber, reinforced polypropylene (plastic), polymer PE, etc.

Other properties: acid and alkali resistance, filtration temperature (℃), filtration pressure (MPa).

Function configuration

Manual clamping, motor clamping, automatic hydraulic clamping, automatic pressure maintenance, electrical control/computer program control, automatic plate pulling, automatic liquid connection flip plate, etc.

Feeding method

Middle feed, or corner feed, middle and upper feed.

Open effluent, dark effluent

Components:

The structure of the filter press consists of three parts:

Frame

The frame is the basic component of the filter press. The two ends are thrust plates and clamping heads. The beams on both sides connect the two. The beams are used to support the filter plate, filter frame and clamping plate.

1. Thrust plate: It is connected to the support to place one end of the filter press on the foundation. The middle of the thrust plate of the chamber filter press is the feed hole, and there are four holes in the four corners. The holes in the upper two corners are the inlet of washing liquid or compressed gas, and the lower two corners are the outlet (the dark flow structure is still the filtrate outlet).

2. Clamping plate: It is used to clamp the filter plate and filter frame. The rollers on both sides are used to support the clamping plate to roll on the rails of the beam.

3. Beam: It is a load-bearing component. According to the requirements of the anti-corrosion of the use environment, it can be coated with hard polyvinyl chloride, polypropylene, stainless steel coating or new anti-corrosion coatings. [1]

Clamping mechanism

Manual clamping, mechanical clamping, hydraulic clamping.

1. Manual clamping: The clamping plate is pushed by a screw mechanical jack to clamp the filter plate.

2. Mechanical clamping: The clamping mechanism consists of a motor (equipped with an advanced overload protector), a reducer, a gear pair, a screw and a fixed nut. When clamping, the motor rotates forward, driving the reducer and gear pair, causing the screw to rotate in the fixed nut, pushing the clamping plate to clamp the filter plate and filter frame. When 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 supply and stops rotating. Since the screw and the fixed nut have a reliable self-locking spiral angle, they can reliably ensure the clamping state during the working process. When retracting, the motor reverses, and when the pressure block on the clamping plate touches the travel switch, the retraction stops.

3. Hydraulic clamping: The hydraulic clamping mechanism consists of a hydraulic station, a cylinder, a piston, a piston rod, and a Havlan card hydraulic station that connects the piston rod and the clamping plate. The structure of the station includes: a motor, an oil pump, a relief valve (pressure adjustment), a reversing valve, a pressure gauge, an oil circuit, and an oil tank. When the hydraulic clamping machine is clamped, the hydraulic station supplies high-pressure oil, and the component cavity formed by the cylinder and the piston is filled with oil. When the pressure is greater than the friction resistance of the clamping plate, the clamping plate slowly presses the filter plate. When the clamping force reaches the pressure value set by the overflow valve (displayed by the pressure gauge pointer), the filter plate, filter frame (plate and frame type) or filter plate (box type) is clamped, and the overflow valve begins to unload. At this time, the motor power supply is cut off, and the clamping action is completed. When retracting, the reversing valve is reversed, and the pressure oil enters the rod cavity of the cylinder. When the oil pressure can overcome the friction resistance of the clamping plate, the clamping plate begins to retract. When the hydraulic clamping is automatic pressure maintenance, 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. The clamping force decreases due to possible internal and external leakage of the oil system. When it drops to the lower limit pointer of the pressure gauge, the power is turned on and the oil pump starts to supply 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 achieve the effect of ensuring the clamping force during the filtering process. [1]

Filtering mechanism

The filtering mechanism consists of a filter plate, a filter frame, a filter cloth, and a pressing diaphragm. The filter plate is covered with filter cloth on both sides. When a pressing diaphragm is required, a set of filter plates consists of a diaphragm plate and a side plate. The base plate of the diaphragm plate is covered with a rubber diaphragm on both sides, and the outside of the diaphragm is covered with filter cloth. The side plate is an ordinary filter plate. The material enters each filter chamber from the material hole on the thrust plate. The solid particles are retained in the filter chamber because their particle size is larger than the pore size of the filter medium (filter cloth), and the filtrate flows out from the outlet hole below the filter plate. When the filter cake needs to be squeezed dry, in addition to using diaphragm pressing, compressed air or steam can also be used from the washing port. The airflow flushes away the moisture in the filter cake to reduce the moisture content of the filter cake.

(1) Filtration method

The filtrate outflow method is divided into open flow filtration and dark flow filtration.

A. Open flow filtration: A water nozzle is installed on the outlet hole below each filter plate, and the filtrate flows out directly from the water nozzle.

B. Dark flow filtration: There is a liquid outlet channel hole below each filter plate. The outlet holes of several filter plates are connected into a liquid outlet channel, which is discharged from the pipe connected to the outlet hole below the thrust plate.

(2) Washing method

When the filter cake needs to be washed, there are open flow unidirectional washing and bidirectional washing, and dark flow unidirectional washing and bidirectional washing.

A. Open flow unidirectional washing is that the washing liquid enters from the washing liquid inlet hole of the thrust plate in sequence, passes through the filter cloth and then the filter cake, and flows out from the non-porous filter plate. At this time, the liquid outlet nozzle of the perforated plate is in a closed state, and the liquid outlet nozzle of the non-porous plate is in an open state.

B. Open flow bidirectional washing is that the washing liquid is washed twice from the washing liquid inlet holes on both sides above the thrust plate, that is, the washing liquid is washed from one side first and then from the other side, and the outlet of the washing liquid is in a diagonal direction with the inlet, so it is also called bidirectional cross washing.

C. Undercurrent unidirectional washing is that the washing liquid enters the perforated plate from the washing liquid inlet hole of the thrust plate in sequence, passes through the filter cloth and then the filter cake, and flows out from the non-porous filter plate.

D. Undercurrent bidirectional washing is that the washing liquid is washed twice from the two washing liquid inlet holes on both sides above the stop plate, that is, the washing is washed from one side first and then from the other side, and the outlet of the washing liquid is in a diagonal direction, so it is also called undercurrent bidirectional cross washing.

(3) Filter cloth: Filter cloth is a main filter medium. The selection and use of filter cloth plays a decisive role in the filtering effect. When selecting, the appropriate filter cloth material and pore size should be selected according to the pH value of the filter material, solid particle size and other factors to ensure low filtering cost and high filtering efficiency. When using, the filter cloth should be flat and not folded, and the pore size should be unobstructed.

Classification

Plate and frame filter press

1. Plate and frame filter press (plate and frame filter press) consists of a group of filter chambers composed of alternately arranged filter plates and filter frames. There are grooves on the surface of the filter plate, and its protruding parts are used to support the filter cloth. There are through holes on the corners of the filter frame and the filter plate. After assembly, a complete channel is formed, which can pass the suspension, washing water and lead out the filtrate. There are handles on both sides of the plate and frame to support the crossbeam, and the plate and frame are pressed by the clamping device. The filter cloth between the plate and frame acts as a sealing gasket. The feed pump presses the suspension into the filter chamber to form filter residue on the filter cloth until the filter chamber is filled. The filtrate passes through the filter cloth and flows along the filter plate groove to the corner channel of the plate frame and is discharged in a centralized manner. After the filtration is completed, clean water can be introduced to wash the filter residue. After washing, compressed air is sometimes introduced to remove the remaining washing liquid. Then open the filter press to remove the filter residue, clean the filter cloth, re-press the plate and frame, and start the next working cycle.

2. The plate and frame filter press can be used for suspensions with high compressibility or nearly incompressible filter residues. The solid particle concentration of the suitable suspension is generally less than 10%, and the operating pressure is generally 0.3-0.6 MPa, and special ones can reach 3 MPa or higher. The filtration area can be increased or decreased with the number of plates and frames used. The plate frame is usually square, the inner side length of the filter frame is 200-2000 mm, the frame thickness is 16-80 mm, and the filtration area is 0.5-1200 square meters. The plate and frame are pressed by manual screw, electric screw and hydraulic pressure. The plate and frame are made of wood, cast iron, cast steel, stainless steel, polypropylene and rubber.

Chamber filter press

The structure and working principle of the chamber filter press are similar to those of the plate and frame filter press. The difference is that the filter plates are recessed on both sides, and every two filter plates are combined into a chamber-shaped filter chamber, eliminating the filter frame. There is a circular hole in the center of the filter plate through which the suspension flows into each filter chamber. This filter is suitable for suspensions that need to be filtered at a higher pressure and the filter residue does not need to be washed.

Vertical filter press

The filter plates of the vertical filter press are stacked horizontally and up and down to form a group of filter chambers, which occupies a small area. It uses a continuous filter belt. After the filtration is completed, the filter belt is moved to unload the residue and clean the filter belt, and the operation is automated. The filter press has a wide range of applications and a relatively simple structure. The pressing and pulling of the plate and frame, the unloading of the residue and the cleaning of the filter cloth can all be automated, which is conducive to the development of the filter press towards large-scale. After adding an elastic rubber diaphragm to the filter chamber of the filter press, the filter residue can be compressed with high-pressure water or compressed air with the help of the rubber diaphragm at the end of the filtration, so that the filter residue is further squeezed and deliquated, forming a diaphragm squeeze filtration with variable filter chamber volume and compressed filter residue, and the pressure can reach 1-2 MPa.

Belt filter press

Belt filter press is widely used for sludge dewatering in urban sewage treatment, chemical industry, oil refining, metallurgy, papermaking, leather making, food, coal washing, printing and dyeing and other industries. The machine operates continuously, has a high degree of automation, energy saving, high efficiency, and easy use and maintenance. It is an ideal equipment for sludge dewatering.

Structural features

1. It adopts advanced Australian technology and has a beautiful appearance.

2. The structure has high rigidity, stable operation and low noise.

3. It is equipped with advanced concentration pretreatment equipment (good sludge flocculation effect) and low operating cost.

4. The gravity dehydration area is equipped with advanced distributors to make the material evenly distributed and extend the life of the filter belt.

5. With extra-long gravity dehydration area and wedge-shaped dehydration area, the material is fully dehydrated to ensure that the material will not overflow in the pressing area.

6. The roller system is arranged scientifically and orderly, and gravity dehydration, wedge-shaped dehydration, and pressing dehydration are discharged separately without interfering with each other. The pressing dehydration roller has a large diameter ratio and a good dehydration effect. Therefore, the production capacity is large, energy-saving and efficient.

7. The continuous operation from feeding to discharging mud cake has a high degree of automation. PLC interface can be set as needed to facilitate centralized control by microcomputer.

8. The power transmission mechanism adopts mechanical or variable frequency stepless speed regulation, with a large speed regulation range and wide adaptability.

9. The filter belt is equipped with a reliable backwashing device to ensure the dehydration effect of the filter belt.

10. Pneumatic tensioning and pneumatic automatic deviation correction devices are adopted to ensure the safe and normal operation of the filter belt.

11. The operation is safe and reliable, and infrared safety protection and a full range of emergency safety parking devices are adopted.

12. The filter belt with different structures can be configured according to different materials, and the filtering accuracy is high.

Working principle

The hydraulic clamping mechanism of the filter press consists of a hydraulic station, a cylinder, a piston, a piston rod, and a Havlan card connecting the piston rod and the clamping plate. The structure of the hydraulic station consists of a motor, an oil pump, a relief valve (adjusting pressure), a reversing valve, a pressure gauge, an oil circuit, and an oil tank.

Filtration method: The filtrate outflow method is divided into clear flow filtration and dark flow filtration. In clear flow filtration, a water nozzle is installed on the outlet hole below each filter plate, and the filtrate flows out of the water nozzle intuitively. In dark flow filtration, a liquid outlet channel hole is provided below each filter plate, and the outlet holes of several filter plates are connected into a liquid outlet channel, which is discharged from the pipe connected to the outlet hole below the thrust plate.

Washing method: When the filter cake needs to be washed, there are one-way washing and two-way washing in the current, and one-way washing and two-way washing in the dark flow.

Dehydration application

1. As a mature dehydration equipment, the filter press is widely used in the field of environmental protection and has become an important equipment for sewage sludge treatment.

2. Mechanical dehydration of sludge mainly removes capillary water between sludge particles. The moisture content of sludge after ordinary mechanical dehydration is usually 65%-80%, in the form of mud cake.

3. In the past, mechanical dehydration equipment mainly included belt filter press, plate and frame filter press and horizontal screw sedimentation centrifuge. Now, chamber filter press, vertical hydraulic filter press, diaphragm press and high-pressure plate and frame press are commonly used.

4. When sludge is landfilled, sludge dehydration can greatly reduce the sludge accumulation site and save the cost incurred during transportation; when composting sludge, sludge dehydration can ensure the smooth progress of composting (the composting process generally requires the sludge to have a lower moisture content); if sludge is incinerated and centrally treated, the high sludge dehydration rate can greatly reduce heat energy consumption and reduce the cost of hazardous material treatment.

5. However, the sludge has complex composition, low relative density, fine particles, and is often in a colloidal state, which determines its characteristics of being difficult to dehydrate. Therefore, except for the ultra-high pressure vertical hydraulic filter press, the other filter presses all add a drying process to reduce the residual oil (liquid) rate.

6. The belt filter press has low power consumption. The filter cake of the plastic plate and frame filter press has a low moisture content, but the horizontal screw sedimentation centrifuge has strong adaptability to sludge flow fluctuations, good sealing performance, large processing capacity, and small footprint. In the past, most sewage treatment plants in my country used centrifuges, belt filter presses, and plate and frame filter presses, and small sewage treatment plants generally used concentrated dehydration integrated machines. Now commonly used chamber filter presses, diaphragm filter presses, and ultra-high pressure vertical hydraulic filter presses have unique technology and are ideal equipment for sludge dehydration.

Belt filter press:

It can work continuously. The belt press dehydrator has three working areas, namely gravity dehydration area, wedge-shaped dehydration area and shear dehydration area. Its pressing type belongs to two-dimensional pressing, which is mainly used for sludge dehydration, but its application range is expanding. The dehydration effect of the belt filter press is more dependent on chemical agents, resulting in high sludge treatment costs.

Plate and frame filter press:

1. Intermittent pressurized filtration equipment, used for solid-liquid separation of various suspensions.

2. Chamber filter press, which was developed after the 1960s. Its characteristics are high filtration pressure, the highest pressure has reached 4.5MPa; single machine filtration area is large, foreign products with 2050 square meters have been launched, and the largest filtration area in China has reached 2000 square meters; the filter cake has low liquid content, and the moisture content of the filter cake after pressing can be further reduced by 5% to 15%; good corrosion resistance, the filter plate can use a variety of reinforced plastics, light weight, good elasticity, corrosion resistance, and wide adaptability; low operating costs, can achieve multiple continuous operation and online control. Modern filter presses are mostly box-type.

Diaphragm filter press:

1. Intermittent pressurized filtration equipment, used for solid-liquid separation of various suspensions. The filter press is equipped with a rubber pressing diaphragm to dehydrate the filter cake. The medium that expands the diaphragm can be compressed air (used when below 0.7MPa) or water (used when above 0.7MPa).

2. Ultra-high pressure vertical hydraulic filter press: unique filter chamber structure, secondary pressing of sludge, sludge moisture content after pressing ≤50%; low residual oil rate of pressed edible oil, leading technology in China, currently preferred by many manufacturers.

Sludge conditioning:

Generally, domestic sludge is mechanically dehydrated by adding high molecular polymers, and generally has to undergo “conditioning” treatment. There are many methods for conditioning, including thermophysical methods, such as “thermal hydrolysis”, “hydrothermal drying”, “wet oxidation”, etc., physical methods, such as ultrasound, microwave, etc., and the most common is chemical methods. By adding certain inorganic chemical salts (agents), it can change the charge polarity of sludge molecules, increase particle pores, and improve filter pressing characteristics. The most common and cheapest technology on the market is a combination of “chemical conditioning of sludge + filter press treatment”.

Installation and commissioning

1. The filter press should be installed on a flat concrete foundation. The thrust plate foot at the feed end is fixed to the foundation with anchor bolts; the bracket end does not use anchor bolts, or the anchor bolts are locked with two nuts after positioning, and an appropriate gap is left between the nut gasket and the foot seat, so that the foot can be slightly extended and retracted. Before positioning, the installer should correct the verticality of the beam and the large plane of the thrust plate.

2. The foundation structure should be designed by the construction engineering personnel according to the equipment load, and the anchor bolts should be grouted twice in the reserved holes.

3. There should be enough operating and maintenance space around the filter press. The hydraulic station should be placed in an appropriate position for the hydraulic pressing filter press to ensure that the hydraulic station can work normally.

4. Place the filter plate according to the work requirements, and arrange the feed, washing and drainage pipelines. Equipped with a filter pressure display gauge and a reflux channel to control the filter pressure. If it is a diaphragm squeeze type, a compressed air pipeline is arranged.

5. Hydraulic filter press: Inject clean 20#-40# hydraulic machine oil into the oil tank of the hydraulic station, and use the temperature >-5℃; if the ambient temperature is low, hydraulic oil with similar viscosity and low freezing point can be selected. The hydraulic oil must be added through an 80-100 mesh filter.

6. Mechanical or hydraulic clamping device: The motor should work correctly when the power is turned on. The pressure gauge should rise steadily during hydraulic clamping and pressurization, and there should be no leakage in the hydraulic system. The working pressure of the hydraulic station should be adjusted correctly according to the size of the machine. If the oil tank is found to be insufficient after the test, it must be replenished.

Maintenance matters

1. The filter press can only be fed after it is debugged normally, and the whole machine should be fully inspected before each shift. The mechanical pressing transmission parts and the reduction box must be filled with sufficient lubricating oil; the hydraulic pressing rechecks the oil storage tank and the working pressure of the hydraulic station. The hydraulic oil is generally replaced once a year. When replacing, the hydraulic system should be fully cleaned. The working pressure of the hydraulic station is less than the maximum working pressure of the oil cylinder, but the minimum cannot be lower than the allowable value of the filtration pressure. Too small will cause large leakage, and too large will damage the machine parts.

2. It is forbidden to start the machine when the number of filter plates is less than the specified number to avoid damage to the machine parts. Check the arrangement of the filter plates before adding materials. The filter cloth cannot be folded to prevent large leakage; after unloading the cake, the filter plates must be pressed and arranged neatly.

3. After everything is normal, the filter plates can be pressed and filtered. The filtration pressure and filtration temperature must be within the specified range. Too high filtration pressure will cause leakage. If the filtration temperature is too high, the plastic filter plate is easy to deform. The concentration of the suspension should be uniform when adding materials. There must be no impurities; after unloading the cake, the filter cloth and filter plate must be rinsed clean, and no residue is allowed to stick to the sealing surface or feed channel, otherwise it will affect the smooth feed and the sealing of the filter plate, thereby causing the pressure imbalance on both sides of the filter plate, resulting in deformation and damage of the filter plate.

4. The selection of filter cloth must meet the filtering technical requirements of the filter paddle. The new filter cloth should be shrunk before making, and the opening diameter should be smaller than the filter plate aperture. When matching the filter plate, the cloth hole and the plate hole should be relatively concentric, and the feed hole cloth should be close to the cylinder wall, otherwise it will cause unclear filtration, low filtration rate, cloth cylinder rupture, and fail to achieve the expected filtration purpose.

5. In the early stage of filtration, the filter press is turbid. When a layer of filter cake is formed on the filter cloth, the filtrate will become clear. If the filtrate is always turbid or becomes turbid, it may be that the filter cloth is damaged or the cloth hole and the plate hole are deviated. At this time, the valve should be closed or the feed should be stopped to replace the filter cloth. A small amount of leakage caused by the capillary phenomenon of the filter cloth is allowed between the filter plates.

6. When moving the filter plate, the force should be uniform and appropriate, and no collision or knocking should be done to avoid damaging the sealing surface and the filter wrench handle. The filter cloth will become hard and its performance will decline after a period of use. Therefore, it needs to be checked regularly. If there is a change that affects the filtration rate, it can be neutralized and cleaned with a corresponding low concentration of weak acid and weak alkali to restore the function of the filter cloth. If it cannot be restored, it should be replaced in time.

7. The slurry, washing liquid or compressed air valve must be enabled according to the operating procedure and cannot be enabled at the same time. The compressed air pressure during diaphragm squeezing cannot exceed the filtration pressure

Solution

1) In the working state of the filter press, the suspension will definitely occur. If the push is not in place during the suspension, it will have a serious impact on the subsequent work. Through observation and analysis of the machine operation process, it was found that this phenomenon occurred because the feed pipe of the quick-opening diaphragm filter press uses a steel ring rubber tube. Under the action of pressure filtration, the pipe itself will form a reaction force applied to the clamping plate, which will offset the force of the oil cylinder to a certain extent, causing the clamping plate to rebound, and the push pin cannot be closed in place during the suspension, resulting in machine failure.

Based on this situation, the following transformation plan is proposed: the direction of the feed hose and protective sleeve of the quick-opening diaphragm filter press is adjusted to a certain extent, specifically, it is to turn 180° on the original basis, and change the clockwise bending to counterclockwise bending. In this way, the reaction force in the feed pipe will not only not offset the force of the oil cylinder, but also strengthen the squeezing effect, thereby ensuring the working state of the clamping plate and eliminating the failure problem during the suspension.

2) When the filter press is working, the tightening and loosening of the filter plate is carried out on the main beam track. During the operation, derailment also occurs from time to time. The study found that the main reason for this phenomenon is that when the filter plate is tightened, the small chain connecting the filter plate falls off, resulting in inconsistent work progress on both sides of the track, which in turn causes failures.

Based on the problem of the small chain connection method, the following modification plan is proposed: in the original equipment, the 7-ring small chain is reduced to a 3-ring small chain. Observational studies have shown that the occurrence of chain twisting is an important cause of chain falling off. After the small chain structure is modified in this way, when detecting the operation of the small chain, 3 rings can detect problems more promptly than 7 rings, and prevent the occurrence of chain twisting.

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