CN113856263B

CN113856263B - Pressure filter

Info

Publication number: CN113856263B
Application number: CN202110732597.9A
Authority: CN
Inventors: 李志鸿; G·福斯特; 葛林林; 颜欢
Original assignee: Metso Outotec Finland Oy
Current assignee: Metso Finland Oy
Priority date: 2020-06-30
Filing date: 2021-06-30
Publication date: 2023-06-20
Anticipated expiration: 2041-06-30
Also published as: WO2022000280A1; CN216604186U; CN113856263A; AR122803A1

Abstract

The present disclosure relates to pressure filters, and more particularly to horizontal plate pressure filters in which filter chambers are formed between horizontally extending and stacked filter plates. Such filters are also known as tower presses. The displacement sensor is configured to measure a displacement of the lower squeeze plate from the retracted position to the sealing position. The amount of change in displacement between cycles of the pressure filter is compared to a baseline and when the change in displacement relative to the baseline is sufficiently large, an indication is provided that the plate seal should be replaced.

Description

Pressure filter

Technical Field

The present disclosure relates to pressure filters, and more particularly to horizontal plate pressure filters in which filter chambers are formed between horizontally extending and stacked filter plates. Such filters are also known as tower presses (tower presses).

Background

The horizontal plate pressure filter has a plurality of horizontally extending and stacked filter plates with filter chambers formed therebetween. During operation, the filter plates are pressed against each other so as to seal the filter chamber between the filter plates. The slurry is then fed into a filter chamber and the filtrate is separated therefrom, while the solid components of the slurry form a filter cake within the filter chamber. The filter plates are then moved away from each other to open the filter chambers, so that the filter cake can be discharged from the filter chambers, and further moved towards each other to close the filter chambers again. This sequence is then repeated.

Disclosure of Invention

According to a first aspect of the invention, there is provided a pressure filter comprising: a plurality of filter plates, wherein the filter plates are arranged as a stack; a plurality of plate seals disposed between the filter plates; a movable compression plate configured to move from a retracted position to an engaged position by applying a predetermined force to the filter plates and the plate seals to form filter chambers between adjacent filter plates; and at least one displacement sensor configured to measure a displacement of the movable compression plate between the retracted position and the sealing position; wherein the pressure filter is configured to monitor displacement of the movable compression plate between the retracted position and the sealing position relative to a datum line and to provide notification that the plate seal should be replaced when the displacement relative to the datum line exceeds a threshold.

In one embodiment, the datum line is established by measuring the displacement of the movable stripper plate between the retracted position and the sealing position when a new plate seal is installed prior to monitoring the displacement of the movable stripper plate relative to the datum line.

In one embodiment, the threshold is calculated based on the number of plate seals and the maximum reduction in thickness of each plate seal.

In one embodiment, the displacement sensor is a chord sensor.

In one embodiment, the pressure filter is a horizontal plate filter, and wherein the stack of filter plates is vertically disposed.

In one embodiment, the movable compression plate is a lower compression plate located below the stack of filter plates.

In one embodiment, the movable compression plate is an upper compression plate located above the stack of filter plates.

In one embodiment, the plate seal is made of one or more of natural rubber, EPDM, butyl rubber, or other rubber materials.

In one embodiment, the pressure filter is further configured to monitor displacement of the movable compression plate during movement of the movable compression plate from the retracted position to the sealing position, the pressure filter being configured to activate an alarm and/or to stop movement of the movable compression plate if the displacement exceeds a second threshold before reaching the sealing position.

According to a second aspect of the present invention, there is provided a method for determining when a plate seal in a pressure filter should be replaced, the pressure filter comprising: a plurality of filter plates arranged in a stack; a plurality of plate seals disposed between the filter plates for creating a plate seal between the filter plates when under pressure; and a movable compression plate, the method comprising: moving the movable compression plate from a retracted position to a sealing position by applying a predetermined force to the filter plates and the plate seals to form a filter chamber between the filter plates; measuring displacement of the movable compression plate between the retracted position and the sealing position; monitoring the measured displacement relative to a baseline displacement; and providing a notification indicating that the plate seal should be replaced if the displacement exceeds a threshold value relative to the datum line.

In one embodiment, the threshold is calculated based on the number of plate seals and a maximum reduction in thickness of each plate seal.

In one embodiment, the displacement sensor is a chord sensor.

In one embodiment, the method further comprises: monitoring displacement of the movable compression plate during movement of the movable compression plate from the retracted position to the sealing position, and if the displacement exceeds a second threshold before the sealing position is reached, activating an alarm and/or stopping movement of the movable compression plate.

Additional advantageous features of the invention are listed below.

Drawings

Fig. 1 shows a horizontal filter press according to the invention.

Figure 2 shows a filter plate and a plate seal that can be used in the present invention.

Fig. 3 shows a method according to the invention for determining when a plate seal in a pressure filter should be replaced.

Detailed Description

Fig. 1 shows a pressure filter 100. The pressure filter comprises a plurality of filter plates 101 arranged as vertical stacks, i.e. as cylinders extending along the Z-axis, as shown in fig. 1. Each filter plate 101 lies in a horizontal plane, i.e. the two major dimensions of the filter plate lie in an X-Y plane perpendicular to the Z axis as shown in fig. 1. Each filter plate 101 is parallel to and offset from the other filter plates. The filter plates 101 and other components located between the filter plates are shaped so that when the filter plates 101 are pressed together, a filter chamber is formed between each pair of adjacent filter plates 101.

Above the filter plate 101 is an upper squeeze plate 102, sometimes referred to as a head plate (head plate), and below the filter plate 101 is a lower squeeze plate 103, sometimes referred to as a tail plate, back plate or end plate. By moving the upper and

lower squeeze plates

102, 103, the filter plates 101 can be moved away from each other and towards each other to open and close the filter chambers.

The upper actuator 104 is configured to move the upper squeeze plate and the lower actuator 105 is configured to move the lower squeeze plate. The pressure and force required to seal the filter chamber is much greater than the pressure and force required to open and close the filter chamber, so the

actuators

104 and 105 must be sized accordingly for each purpose. In the arrangement shown in fig. 1, the upper actuator 104 is configured to produce the large displacement and small force required to open and close the filter chamber, while the lower actuator 105 is configured to produce the small displacement and large force required to seal the filter chamber. Once the upper press plate 102 and the filter plate 101 are in the closed position after actuation of the upper actuator 104, the upper press plate 102 may be locked in place by the locking pins 106.

Different types of actuators may be used due to the different displacement and force requirements of the upper and

lower actuators

104, 105. In a preferred embodiment, the upper actuator 104 is an electric actuator that can be coupled with mechanical devices such as gears and chains or pulleys to produce the desired displacement. The lower actuator 105 is preferably a hydraulic actuator capable of providing the force required to seal the filter chamber. However, the particular type of actuator employed by each of the upper and

lower actuators

104, 105 is not the focus of the present invention, and the present invention may be used with virtually any horizontal pressure filter, regardless of the type of actuator used to move the upper and lower squeeze plates.

Further, although in the pressure filter shown in fig. 1, the high displacement, low force actuator drives the upper squeeze plate to move, and the low displacement, high force actuator drives the lower squeeze plate to move, this arrangement may be reversed, in which case the locking pin 106 will also appear on the lower squeeze plate 103 instead of the upper squeeze plate 102. Thus, while the present disclosure is directed to "upper" and "lower" squeeze plates, as shown in FIG. 1, it should be understood that this arrangement may be reversed and that it is not essential to the present invention that the actual location of the squeeze plates be "upper" or "lower".

The lower squeeze plate 103 is movable between a retracted position and a sealing position, i.e., a squeeze plate driven by a small displacement, high force actuator. The retracted position of the lower squeeze plate 103 is a set position where the lower squeeze plate 103 is located before the actuator 105 drives the squeeze plate 103 to move to seal the filter chamber between the filter plates 101, and where the lower squeeze plate 103 is returned after the filtration cycle is completed (i.e., after the actuator 105 retracts the squeeze plate 103). Thus, in the context of the present disclosure, the term "retracted position" does not simply mean any position retracted from the sealing position, but in fact is a set position where the compression plate is consistently consistent through multiple cycles of the pressure filter.

The sealing position is a position of the lower squeeze plate 103 after the actuator 105 drives the lower squeeze plate 103 to move toward the filter plate 101 to seal the filter chamber between squeeze plates. Therefore, the sealing position is the position of the lower squeeze plate 103 after the actuator 105 applies a sealing force (which is a predetermined force) to the lower squeeze plate 103 and before the filter chamber is pressurized. For example, when the actuator 105 is a hydraulic actuator, a hydraulic pressure of 40-50 bar may be applied to the lower squeeze plate 103. The predetermined force applied by the actuator 105 to the lower squeeze plate 103 is uniform between each filtration cycle.

A plate seal (shown in fig. 2) is located between the filter plates 101 in a sealing position, i.e. when a predetermined sealing force is applied, a pressure seal is formed between the filter plates 101 to form a filter chamber. These plate seals are typically made of natural rubber, EPDM, butyl rubber, or other rubber materials, or a combination of these materials.

The pressure filter 100 further comprises a displacement sensor 107 that measures the displacement of the lower squeeze plate 103 relative to a stationary element of the pressure filter 100, e.g. relative to the lower frame 108. It will be appreciated that in a pressure filter in which the functions of the upper and lower squeeze plates and the actuator are reversed, the displacement sensor will instead measure the displacement of the upper squeeze plate relative to the upper frame of the pressure filter.

The displacement sensor is preferably a string displacement sensor (string displacement sensor) connected between the lower squeeze plate 103 and the lower frame 108. The chordal displacement sensor, also referred to as a chordal canister displacement sensor (string pot displacement sensor), typically includes a variable resistor with a spring-loaded chord that can be pulled out to measure displacement. The resistance of the device varies according to the magnitude of the displacement applied to the string. The spring-loaded mechanism is attached to one of the lower squeeze plate 103 and the lower frame 108, while the opposite end of the string is fixed to the other of the lower squeeze plate 103 and the lower frame 108, such that movement of the lower squeeze plate 103 relative to the lower frame 108 causes the spring to be pulled out or retracted by the spring-loaded mechanism. It should be understood that while the present invention is described as employing a chordal displacement sensor, the particular type of sensor employed is not essential to the invention and any displacement sensor capable of measuring displacement of the lower squeeze plate 103 over a desired range may be employed.

During operation of the pressure filter 100, a displacement sensor is used to measure the relative displacement of the lower squeeze plate 103 as the lower frame 108 moves from the retracted position to the sealed position. Since the plate seals between the filter plates 101 degrade over time and with repeated cycles of the pressure filter 100, the displacement of the lower squeeze plate 103 increases over time and between cycles due to seal wear and can be compressed to a smaller thickness with the same force. Thus, by monitoring the change in displacement of the lower squeeze plate 103 between cycles, the condition of the plate seal can be inferred. Once the displacement variation between the baseline displacement (which is typically the displacement measured during the first cycle, or during a test cycle after a new plate seal is installed) and the displacement of a subsequent cycle exceeds a threshold, i.e., once the seal has sufficiently degraded, the pressure filter 100 notifies the operator of the pressure filter that the plate seal should be replaced.

Preferably, the baseline displacement is established immediately after installation of the new plate seal during the test cycle of pressure filter 100. However, the baseline may also be established during the first or another early cycle after replacement of the plate seal.

The threshold displacement (which triggers a plate seal change notification when it is exceeded) may be calculated based on the number of plate seals and the maximum reduction in thickness under pressure for each plate seal. The threshold value may be calculated as a simple product of the maximum reduction in thickness of each seal and the number of seals, or it may be set to be less than the simple product value, considering that the individual plate seals are likely to wear unevenly.

Fig. 2 shows the position of a filter plate 200, for example one of the filter plates 101 in the pressure filter 100, and a plate seal 201 on the filter plate. The plate seals 201 extend around the perimeter of the filter plates 200, whereby when adjacent filter plates are pressed together a seal is formed between the adjacent plates and a filter chamber is formed in the cavity between the filter plates defined by the plate seals.

Fig. 3 shows a method according to the invention of determining when a plate seal in a pressure filter should be replaced.

In step 301, the lower squeeze plate 103 is moved from the retracted position to the sealing position. The displacement of the squeeze plate 103 between the retracted position and the sealing position is measured.

At step 302, the measured displacement is compared to a threshold. As described above, the threshold is based on the baseline displacement plus the maximum amount of variation in the thickness of the plate seal between the filter plates 101.

If the displacement does not exceed the threshold value, at step 303, the pressure filter 100 continues normal operation, i.e. the pressure filter completes the current filtration cycle and continues with the next cycle, where the squeeze plate is moved and the displacement is measured again, returning to step 301.

In step 304, if the displacement does exceed the threshold, a notification is provided that the seal should be replaced. This may terminate the filtering process or the process may proceed to the next cycle via step 303.

A further step 305 is shown for establishing a baseline shift, which is used to determine a threshold. Preferably, the baseline displacement is established during an immediately proceeding test cycle of the pressure filter 100 after installation of a new plate seal. However, the baseline may also be established during the first or another early cycle after replacement of the plate seal.

In an optional additional step, the displacement of the lower squeeze plate 103 may be monitored as the squeeze plate moves to the sealing position. If the displacement exceeds a different threshold before the sealing position is reached, an alarm is activated and the movement of the lower stripper plate is stopped. This prevents the actuator from extending too far when moving the stripper plate (which could damage the system). The threshold may be set at the maximum extension of the actuator, for example a displacement of 100mm, or slightly lower, i.e. 90mm. This threshold is consistent between cycles of the pressure filter because it is independent of changes in the condition of the plate seals.

Claims

1. A pressure filter, comprising:

a plurality of filter plates, wherein the filter plates are arranged as a stack;

a plurality of plate seals disposed between the filter plates, the plate seals extending around the perimeter of the filter plates;

a movable compression plate configured to move from a retracted position to a sealing position by applying a predetermined force to the filter plates and the plate seals to form filter chambers between adjacent filter plates; and

at least one displacement sensor configured to measure a displacement of the movable compression plate between the retracted position and the sealing position;

wherein the pressure filter is configured to monitor displacement of the movable compression plate between the retracted position and the sealing position relative to a datum line and to provide notification that the plate seal should be replaced when the displacement relative to the datum line exceeds a threshold.

2. The pressure filter of claim 1 wherein the datum line is established by measuring displacement of the movable compression plate between the retracted position and the sealing position when a new plate seal is installed prior to monitoring displacement of the movable compression plate relative to the datum line.

3. The pressure filter of claim 1 or 2, wherein the threshold value is calculated based on the number of plate seals and a maximum reduction in thickness of each plate seal.

4. A pressure filter as claimed in claim 1 or 2, wherein the displacement sensor is a chord sensor.

5. The pressure filter of claim 1 or 2, wherein the pressure filter is a horizontal plate filter, and wherein the stack of filter plates is vertically disposed.

6. The pressure filter of claim 5, wherein the movable compression plate is a lower compression plate positioned below the stack of filter plates.

7. The pressure filter of claim 5, wherein the movable compression plate is an upper compression plate positioned over a stack of filter plates.

8. The pressure filter of claim 1 or 2, wherein the plate seal is made of one or more of natural rubber, EPDM, or butyl rubber.

9. The pressure filter of claim 1 or 2, wherein the pressure filter is further configured to monitor displacement of the movable compression plate during movement of the movable compression plate from the retracted position to the sealing position, the pressure filter being configured to activate an alarm and/or to stop movement of the movable compression plate if the displacement exceeds a second threshold value before the sealing position is reached.

10. A method for determining when a plate seal in a pressure filter should be replaced, the pressure filter comprising: a plurality of filter plates arranged in a stack; a plurality of plate seals disposed between the filter plates for creating a plate seal between the filter plates when under pressure; and a movable compression plate, the method comprising:

moving the movable compression plate from a retracted position to a sealing position by applying a predetermined force to the filter plates and the plate seals to form a filter chamber between the filter plates;

measuring displacement of the movable compression plate between the retracted position and the sealing position;

monitoring the measured displacement relative to a baseline displacement; and

if the displacement exceeds a threshold value relative to the datum line, a notification is provided indicating that the plate seal should be replaced.

11. The method of claim 10, wherein the datum line is established by measuring displacement of the movable compression plate between the retracted position and the sealing position when a new plate seal is installed prior to monitoring displacement of the movable compression plate relative to the datum line.

12. The method of claim 10 or 11, wherein the threshold value is calculated based on the number of plate seals and a maximum reduction in thickness of each plate seal.

13. The method of claim 10 or 11, wherein the displacement sensor is a chordal sensor.

14. The method of claim 10 or 11, wherein the pressure filter is a horizontal plate filter, and wherein the stack of filter plates is vertically disposed.

15. The method of claim 14, wherein the movable compression plate is a lower compression plate positioned below the stack of filter plates.

16. The method of claim 14, wherein the movable compression plate is an upper compression plate positioned over a stack of filter plates.

17. The method of claim 10 or 11, wherein the plate seal is made of one or more of natural rubber, EPDM, or butyl rubber.

18. The method of claim 10 or 11, wherein the method further comprises: monitoring displacement of the movable compression plate during movement of the movable compression plate from the retracted position to the sealing position, and if the displacement exceeds a second threshold before the sealing position is reached, activating an alarm and/or stopping movement of the movable compression plate.