WO2022000280A1

WO2022000280A1 - Pressure filter

Info

Publication number: WO2022000280A1
Application number: PCT/CN2020/099336
Authority: WO
Inventors: Zhihong Li; Geoffrey FOSTER; Linlin GE; Huan YAN
Original assignee: Outotec Suzhou Co Ltd; Metso Outotec Finland Oy
Current assignee: Outotec Suzhou Co Ltd; Metso Finland Oy
Priority date: 2020-06-30
Filing date: 2020-06-30
Publication date: 2022-01-06
Anticipated expiration: 2022-12-30
Also published as: CN216604186U; CN113856263A; CN113856263B; AR122803A1

Abstract

A kind of pressure filters (100), and more particularly to horizontal plate pressure filters, in which filter chambers are formed between horizontally extending superimposed filter plates (101). Such filters are also known as tower presses. A displacement sensor (107) is provided to measure the displacement of a lower pressing plate (103) when moving from a retracted position to a sealed position. The change in the displacement between cycles of the pressure filter (100) is compared to a baseline and an indication that the plate seals should be changed is provided when the displacement sufficiently changes with respect to the baseline.

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 superimposed filter plates. Such filters are also known as tower presses.

Background

Horizontal plate pressure filters have a plurality of horizontally extending superimposed filter plates, between which filter chambers are formed. During operation the filter plates are pressed against each other to seal filter chambers between the filter plates. Slurry is then fed into the filter chambers and filtrate is separated therefrom while the solid contents of the slurry form filter cakes within the filter chambers. Subsequently, the filter plates are moved away from each other to open the filter chambers so that the filter cake may be discharged therefrom, and further moved towards each other to close the filter chamber again. This sequence is then repeated.

Summary of the Invention

According to a first aspect of the invention, a pressure filter is disclosed according to claim 1.

According to a second aspect of the invention, a method of determining when plate seals in a pressure filter should be replaced is disclosed according to claim 10.

Additional advantageous features of the invention are set out in the dependent claims.

Brief Description of the Drawings

Figure 1 shows horizontal filter press in accordance with the present invention.

Figure 2 shows filter plates and plate seals as may be used with the present invention.

Figure 3 shows a method for determining when plate seals in a pressure filter should be replaced in accordance with the present invention.

Detailed Description

Figure 1 depicts a pressure filter 100. The pressure filter includes a plurality of filter plates 101 which are arranged in a vertical stack, i.e. arranged in a column extending along the Z axis as shown in Figure 1. Each filter plate 101 lies in a horizontal plane, that is the two major dimensions of the filter plate lie in the X-Y plane as shown in Figure 1, perpendicular to the Z axis. 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 such that when the filter plates 101 are pressed together, filter chambers are formed between each adjacent pair of filter plates 101.

Above the filter plates 101 is an upper pressing plate 102, sometimes referred to as a head plate, and below the filter plates 101 is a lower pressing plate 103, sometimes referred to as a tail plate, rear plate or end plate. By moving the upper pressing plate 102 and lower pressing plate 103, the filter plates 101 can be moved away and towards one another in order to open and close the filter chambers.

Upper actuator 104 is configured to move the upper pressing plate and lower actuator 105 is configured to move the lower pressing plate. The pressure and force required for sealing the filter chambers is much greater that that required for opening and closing the filter chambers, and thus the

actuators

104 and 105 must be correspondingly dimensioned for each purpose. In the arrangement shown in Figure 1, upper actuator 104 is configured to produce the large displacement and low force required to open and close the filter chambers and lower actuator 105 is configured to produce the lower displacement and large force required to seal the filter chambers. The upper pressing plate 102 may be locked in place by locking pins 106 once the upper pressing plate 102 and filter plates 101 are in the closed position following actuation of the upper actuator 104.

As a result of the different displacement and force requirements of the upper and

lower actuators

104, 105, different types of actuators may be used. In a preferred embodiment, the upper actuator 104 is an electrical actuator that may be coupled with mechanical means, such as gears and chains or pulleys, in order to product the required displacement. The lower actuator 105 is preferably a hydraulic actuator, which is capable of providing the required force for sealing the filter chambers. However, the specific type of actuator that is used for each of the upper and

lower actuators

104, 105 is not central to the present invention and the present invention may indeed be used with any horizontal pressure filter regardless of the types of actuators used to move the upper and lower pressing plates.

Furthermore, even though Figure 1 shows a pressure filter in which the large-displacement, low force actuator drives movement of the upper pressing plate and the low-displacement, larger force actuator drive movement of the lower pressing plate, the arrangement may be reversed, in which case locking pins 106 will also be present on the lower pressing plate 103 instead of the upper pressing plate 102. Thus, while this disclosure refers to “upper” and “lower” pressing plates, as depicted in Figure 1, it will be appreciated that the arrangement may be reversed and the actual position of the pressing plates as “upper” or “lower” is not essential to the invention.

The lower pressing plate 103 –i.e. the pressing plate that is driven by the lower displacement, higher force actuator –is moveable between a retracted position and a sealed position. The retracted position the lower pressing plate 103 is a set position at which the lower pressing plate 103 is located before the actuator 105 drives movement of the pressing plate 103 in order to seal the filter chambers between filter plates 101 and to which the lower pressing plate 103 returns after a filter cycle is complete, i.e. after the actuator 105 retracts the pressing plate 103. Thus, in the context of this disclosure, the term “retracted position” does not mean simply any position that is somewhat retracted from the sealed position, but it is in fact a set position of the pressing plate which is consistent across cycles of the pressure filter.

The sealed position is the position of the lower pressing plate 103 after the actuator 105 drives movement of the lower pressing plate 103 towards the filter plates 101 in order to seal the filter chambers between pressing plates. The sealed position is therefore the position of the lower pressing plate 103 after the sealing force, which is a predetermined force, is applied to the lower pressing plate 103 by the actuator 105 and before the filter chambers are pressurised. For example, when the actuator 105 is a hydraulic actuator, 40-50 bar of hydraulic pressure may be applied to the lower pressing plate 103. The predetermined force that is applied to the lower pressing plate 103 by the actuator 105 is consistent between filter cycles.

Plate seals (shown in Figure 2) are located between filter plates 101 and in the sealed position, i.e. when the predetermined sealing force is applied, form pressure seals between the filter plates 101 to form the filter chambers. The plate seals are typically made from natural rubber, EPDM, butyl or other rubber material, or a combination of these materials.

The pressure filter 100 also includes a displacement sensor 107, which measures the displacement of the lower pressing plate 103 relative to the stationary elements of the pressure filter 100, e.g. to the lower frame 108. It will be appreciated that in a pressure filter where the functions of the upper and lower pressing plates and actuators are reversed, the displacement sensor will instead measure the displacement of the upper pressing plate relative to the upper frame of the pressure filter.

The displacement sensor is preferably a string displacement sensor connected between the lower pressing plate 103 and the lower frame 108. A string displacement sensor, also known a string pot displacement sensor, typically includes a variable resistor with a spring-loaded string that can be pulled out to measure displacements. The resistance of the device changes depending on how much displacement is applied to the string. The spring-loading mechanism is attached to one of the lower pressing plate 103 and lower frame 108 while the opposite end of the string is fixed to the other of the lower pressing plate 103 and lower frame 108, such that movement of the lower pressing plate 103 relative to the lower frame 108 causes the spring to be pulled out from or retracted by the spring loading mechanism. It will be appreciated that while the invention is described at using a string displacement sensor, the specific type of sensor that is used is not essential to the invention and any displacement sensor capable of measuring displacement of the lower pressing plate 103 across the required range may be used.

During operation of the pressure filter 100, the displacement sensor 107 is used to measure the displacement of the lower pressing plate 103 relative to the lower frame 108 when moving from the retracted position to the sealed position. Since the plate seals between the filter plates 101 degrade over time and over repeated cycles of the pressure filter 100, the displacement of the lower pressing plate 103 increases over time and between cycles as the seals wear out and can be compressed to smaller thicknesses by the same force. Therefore, by monitoring the change in the displacement of the lower pressing plate 103 between cycles, the condition of the plate seals can be inferred. Once the change in displacement between a baseline displacement –typically the displacement measured on the first cycle or on a test cycle after new plate seals have been installed –and the displacement of a subsequent cycle exceeds a threshold, i.e. once the seals have degraded enough, the pressure filter 100 notifies the operator of the pressure filter that the plate seals should be replaced.

The baseline displacement is preferably established during a test cycle of the pressure filter 100 immediately following the installation of new plate seals. However, the baseline may also be established during the first or another early cycle following the replacement of the plate seals.

The threshold displacement, which when exceeded triggers the plate seal replacement notification, may be calculated based on the number of plate seals and a maximum decrease in thickness under pressure for each plate seal. The calculation of the threshold may be a simple multiplication of the maximum decrease in thickness per seal and the number of seals, or may take into account potentially uneven wear of the plate seals and therefore be set lower than the simple multiplication value.

Figure 2 shows a filter plate 200, e.g. one of the filter plates 101 of the pressure filter 100, and the location of a plate seal 201 on the filter plate. The plate seal 201 extends around the perimeter of the filter plate 200 such that when adjacent filter plates are pressed together, a seal is formed between the adjacent plates and the filter chambers are formed in the cavities between the filter plates that is defined by the plate seals.

Figure 3 shows a method of determining when plate seals in a pressure filter should be replaced in accordance with the present invention.

At step 301, the lower pressing plate 103 is moved from the retracted position to the sealed position. The displacement of the pressing plate 103 between the retracted position and the sealed position is measured.

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

At step 303, if the displacement does not exceed the threshold, then the pressure filter 100 continues operation as normal, i.e. it completes the current filter cycle and continues to the next cycle, where the pressing plate is moved and displacement measured again back at step 301.

At step 304, if the displacement does exceed the threshold, then a notification that the seals should be replaced is provided. This may terminate the filter process, or the process may continue to the next cycle via step 303.

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

In an optional additional step, the displacement of the lower pressing plate 103 may be monitored as it is moved into the sealed position. If the displacement exceeds a different threshold before the sealing position is reached, an alarm is activated and the movement of the lower pressing plate is stopped. This prevents the actuator from extending too far when moving the pressing plate, which could cause damage to the system. The threshold may be at the maximum extension of the actuator, for example 100mm of displacement, or slightly below, e.g. 90mm. This threshold is consistent between cycles of the pressure filter since it does not relate to the changing condition of the plate seals.

Claims

A pressure filter, comprising:

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

a plurality of plate seals disposed between the filter plates;

a moveable pressing plate configured to be moved from a retracted position to an sealed position to form filter chambers between adjacent filter plates by applying a predetermined force to the filter plates and plate seals; and

at least one displacement sensor configured to measure the displacement of the moveable pressing plate between the retracted position and the sealed position;

wherein the pressure filter is configured to monitor to displacement of the moveable pressing plate between the retracted position and the sealed position relative to a baseline and to provide a notification that the plate seals should be replaced when the displacement relative to the baseline exceeds a threshold.
The pressure filter of any preceding claim, wherein, prior to monitoring the displacement of the moveable pressing plate relative to the baseline, the baseline is established by measuring the displacement of the moveable pressing plate between the retracted position and the sealed position when new plate seals are installed.
The pressure filter of any preceding claim, wherein the threshold is calculated based on number of plate seals and maximum reduction in thickness for each seal.
The pressure filter of any preceding claim, wherein the displacement sensor is a string sensor.
The pressure filter of any preceding claim, wherein the pressure filter is a horizontal plate filter, and wherein the stack of filter plates is arranged vertically.
The pressure filter of claim 5, wherein the moveable pressing plate is a lower pressing plate positioned below the stack of filter plates.
The pressure filter of claim 5, wherein the moveable pressing plate is an upper pressing plate positioned above the stack of filter plates.
The pressure filter of any preceding claim, wherein the plate seals are made of one or more of natural rubber, EPDM, butyl or other rubber material.
The pressure filter of any preceding claim, wherein the system is further configured to monitor displacement of the moveable pressing plate during movement of the moveable pressing plate from the retracted position into the sealed position and, if the displacement exceeds a second threshold, before the sealing position is reached, the system is configured to activate an alarm and/or stop the movement of the moveable pressing plate.
A method for determining when plate seals 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 moveable pressing plate, the method comprising:

moving the moveable pressing plate from a retracted position to a sealed position to create to form filter chambers between the filter plates by applying a predetermined force to the filter plates and plate seals;

measuring the displacement of the moveable pressing plate between the retracted position and the sealed position;

monitoring the measured displacement relative to a baseline displacement; and if the displacement relative to the baseline exceeds a threshold, providing a notification indicating that the plate seals should be replaced.
The method of claim 10, wherein, prior to monitoring the displacement of the moveable pressing plate relative to the baseline, the baseline is established by measuring the displacement of the moveable pressing plate between the retracted position and the sealed position when new plate seals are installed.
The method of claim 10 or 11, wherein the threshold is calculated based on number of plate seals and maximum reduction in thickness for each seal.
The method of any one of claims 10 to 12, wherein the displacement sensor is a string sensor.
The method of any one of claims 10 to 13, wherein the pressure filter is a horizontal plate filter, and wherein the stack of filter plates is arranged vertically.
The method of claim 14, wherein the moveable pressing plate is a lower pressing plate positioned below the stack of filter plates.
The method of claim 14, wherein the moveable pressing plate is an upper pressing plate positioned above the stack of filter plates.
The method of any one of claims 10 to 16, wherein the plate seals are made of one or more of natural rubber, EPDM, butyl or other rubber material.
The method filter of any one of claims 10 to 17, wherein the method further comprises monitoring displacement of the moveable pressing plate during movement of the moveable pressing plate from the retracted position into the sealed position and, if the displacement exceeds a second threshold, before the sealing position is reached, activating an alarm and/or stopping the movement of the moveable pressing plate.