FI20180107A1

FI20180107A1 - Filter element, disc filter apparatus and method

Info

Publication number: FI20180107A1
Application number: FI20180107A
Authority: FI
Inventors: Kari Vänttinen; Mika Illi; Rolf Hindström
Original assignee: Outotec Finland Oy
Priority date: 2015-07-03
Filing date: 2016-06-29
Publication date: 2018-09-19
Also published as: FI20180107A; BR212018000147Y1; WO2017005970A1; BR212018000147U2; ZA201800261B; FI20155528A; CL2017003417U1; BR212018000147Y8; CN208161158U

Abstract

A filter element of a disc filter apparatus, a disc filter apparatus, and a method. The filter element comprises filter members on both sides of the element, and the filter member comprises a microporous permeable membrane layer. The filter member is formed to cause a capillary phenomenon in a filtering process. The filter element has outer edge surface comprising said microporous material, and a porous substrate arranged between the filter members. The filter element further comprises an elastic layer arranged on a peripheral outer edge surface of the filter element and covering the microporous material on said peripheral outer edge surface.

Description

Background

The invention relates to a filter element of a disc filter apparatus, the filter element comprising filter members on both sides of the element, the filter 5 member comprising a microporous permeable membrane layer, the filter member formed to cause a capillary phenomenon in a filtering process, the filter element having outer edge surface comprising said microporous material, and a porous substrate arranged between the filter members.

The invention further relates to a disc filter apparatus comprising one 10 or more consecutive co-axial filter disc(s) with sectors formed by a plurality of the filter elements.

The invention still further relates to a method for regeneration of a disc filter apparatus.

Filtration is a widely used process whereby a slurry or solid liquid mixture is forced through a filter member, with the solids retained on the filter member, as a cake, and the liquid phase passing through. This process is generally well understood in the industry. Examples of filtration types include depth filtration, pressure and vacuum filtration, and gravity and centrifugal filtration.

The cake formation in vacuum filtration is based on generating suc20 tion within the filtrate channels. The most commonly used filter members for vacuum filters are filter cloths and coated media, e.g. the ceramic filter members. These filter members are commonly used in filter apparatuses having filter comprising multiple filter elements, e.g. in rotary vacuum disc filter apparatuses.

Rotary vacuum disc filters are used for the filtration of relatively free filtering suspensions on a large scale, such as the dewatering of mineral concentrates. The dewatering of mineral concentrates requires large capacity in addition to producing a cake with low moisture content. Such large processes are commonly energy intensive and means to lower the specific energy consumption are needed. The vacuum disc filter may comprise a plurality of filter discs arranged in line co-axially and around a central pipe or shaft. Each filter disc may be formed of a number of individual filter elements or sectors, called filter plates, that are mounted circumferentially in a radial plane around the central pipe or shaft to form the filter disc, and as the shaft is fitted so as to revolve, each filter plate or sector is, in its turn, displaced into a slurry basin and further, as the shaft of rotation revolves, rises out of the basin. When the filter member

20180107 prh 19 -09- 2018 is submerged in the slurry basin where, under the influence of the vacuum, the cake forms onto the medium. Once the filter sector or plate comes out of the basin, the pores are emptied as the cake is deliquored for a predetermined time which is essentially limited by the rotation speed of the disc. The cake can be 5 discharged by a back-pulse of air or by scraping, after which the cycle begins again. Whereas the use of a cloth filter medium requires heavy duty vacuum pumps, due to vacuum losses through the cloth during cake deliquoring, the ceramic filter member, when wetted, does not allow air to pass through, which further decreases the necessary vacuum level, enables the use of smaller vac10 uum pumps and, consequently, yields significant energy savings.

The filter element is affected by slurry particles and extraneous compounds, especially in the field of dewatering of mineral concentrates. Therefore, the filter elements have to be regenerated. The filter element is periodically regenerated with the use of one or more of three different methods, for example: 15 (1) backwashing, (2) ultrasonic cleaning, and (3) acid washing. Whereas the regenerative effect of backwashing and ultrasound are more or less mechanical, regeneration with acids is based on chemistry.

The regeneration with acids is performed by applying acid, i.e. typically acid-water -compound, by elevated pressure or positive pressure created 20 in a backwashing equipment inside the filter element. However, the pressure used in the regeneration may create cracks or crazes or expand already existing cracks or crazes in the microporous material. The acid may spurt or spray through the cracks out from the filter element and, in some circumstances, may create a risk for operators of the apparatus to be exposed to the acid.

This risk is highest regarding cracks in the area of a peripheral outer edge surface of the filter element are, because acid spray is directed there outwards from the filter element, i.e. in direction where the operators typically are working. It is to be noted, however, that the probability to the acid spurts or sprays is practically very low, but there is still a need for further increase already 30 high user safety by protecting the operators from potential acid leakages.

Brief description

Viewed from a first aspect, there can be provided a filter element of a disc filter apparatus, the filter element comprising filter members on both sides of the element, the filter member comprising a microporous permeable mem3

20180107 prh 19 -09- 2018 brane layer, the filter member formed to cause a capillary phenomenon in a filtering process, the filter element having outer edge surface comprising said microporous material, and a porous substrate arranged between the filter members, the filter element further comprising an elastic layer arranged on a periph5 eral outer edge surface of the filter element and covering the microporous material on said peripheral outer edge surface.

Thereby a filter element the use of which is safe may be achieved.

Viewed from a further aspect, there can be provided a disc filter apparatus, comprising one or more consecutive co-axial filter disc(s) with sectors 10 formed by a plurality of filter elements, the filter arranged around a central shaft and being rotatable around longitudinal axis of the central shaft, the filter apparatus, the disc filter apparatus further comprising a filter element of a disc filter apparatus, the filter element comprising filter members on both sides of the element, the filter member comprising a microporous permeable membrane layer, 15 the filter member formed to cause a capillary phenomenon in a filtering process, the filter element having outer edge surface comprising said microporous material, and a porous substrate arranged between the filter members, the filter element further comprising an elastic layer arranged on a peripheral outer edge surface of the filter element and covering the microporous material on said pe20 ripheral outer edge surface.

Thereby a disc filter apparatus the use of which is safe may be achieved.

Viewed from a still further aspect, there can be provided a method for regeneration of a disc filter apparatus, the disc filter apparatus comprising the 25 filter element according to any one of claims 1-13, the method comprising creating an elevated pressure in the interior space of the filter element by feeding a washing agent into said interior space with a backwashing equipment.

Thereby a method that has a high user safety level may be achieved.

Some other embodiments are characterised by what is stated in the 30 claims. Inventive embodiments are also disclosed in the specification and drawings of this patent application. The inventive content of the patent application may also be defined in other ways than defined in the following claims. The inventive content may also be formed of several separate inventions, especially if the invention is examined in the light of expressed or implicit sub-tasks or in view 35 of obtained benefits or benefit groups. Some of the definitions contained in the following claims may then be unnecessary in view of the separate inventive

20180107 prh 19 -09- 2018 ideas. Features of the different embodiments of the invention may, within the scope of the basic inventive idea, be applied to other embodiments.

Brief description of figures

Some embodiments illustrating the present disclosure are described in more detail in the attached drawings, in which

Figure 1 is a perspective top view of an exemplary disc filter apparatus,

Figure 2 illustrates an embodiment of a disc filter element, and

Figure 3 is another view of the filter element shown in Figure 2.

In the figures, some embodiments are shown simplified for the sake of clarity. Similar parts are marked with the same reference numbers in the figures.

Detailed description

Principles of the embodiments can be applied for drying or 15 dewatering fluid materials in any industrial processes, particularly in mineral and mining industries. In embodiments described herein, a material to be filtered is referred to as a slurry, but embodiments are not intended to be restricted to this type of fluid material. The slurry may have high solids concentration, e.g. base metal concentrates, iron ore, chromite, ferrochrome, copper, gold, cobalt, nickel, 20 zinc, lead and pyrite.

Figure 1 is a perspective top view of an exemplary disc filter apparatus 1. In the disc filter apparatus 1, the actual filter 2 comprises at least one filter disc 3, each of which comprises number of sector-shaped filter elements 4 that are mounted circumferentially in a radial planar plane around 25 the central axis of the disc filter apparatus 1. The number of the filter elements 3 included in a filter disc may be 12 or 15, for example. The number of the filter discs 3 may range from 2 to 20, for example. The diameter of each disc 3 may be ranging from 1.5 m to 4 m, for example. Examples of commercially available disc filters include Ceramec CO filters, models CC-6, CC-15, CC-30, CC-45, CC30 60, CC-96 and CC-144 manufactured by Outotec Inc.

The structure of the filter elements 4 is decribed more detailed later in this description.

As the filter disc 3 rotate, each filter element 4 is, in its turn, displaced into a slurry basin and further, as the rotation continues, rises out of the basin.

Figure 2 is a perspective exploited view of an exemplary disc filter

20180107 prh 19 -09- 2018 element, and Figure 3 is a view of the filter element shown in Figure 2 assembled.

The filter element 4 comprises filter members 11 on both sides of the element 4. The filter member 11 comprises a microporous permeable mem5 brane layer 7 which is formed to cause a capillary phenomenon in the filtering process. There is a porous substrate 8 arranged between the filter members 11, the material of which may be ceramics. An advantage of the ceramics is good filtering properties and ability to create said capillary phenomenon.

However, due to its nature, the microporous material has susceptibil10 ity to brittle fracture.

The filter element 4 is a truncated-sector-shaped filter element 4. Thus it is suitable for use in common disc filter apparatuses.

The filter element 4 has an outer edge surface 12 that circulates around the element 4. This outer edge surface 12 also comprises the mi15 croporous material. The part of the outer edge surface 12 lying in the wider end of the truncated-sector-shaped filter element 4 is the peripheral outer edge surface 9 of the filter element 4.

The filter element 4 further comprises an elastic layer 13 arranged on the peripheral outer edge surface 9. The elastic layer 13 may be attached to the 20 peripheral outer edge surface 9 by e.g. gluing, vulcanizing, welding etc.

The elastic layer 13 covers at least part of the microporous material on said peripheral outer edge surface 9. The elastic layer has a solid structure,

i.e. there are no holes extending through the elastic layer 13.

In an embodiment the elastic layer 13 may comprise thermoplastic material. An advantage is that thermoplastic materials are usually easy to convert into shape of product, i.e. the manufacturing process of the elastic layer 13 is easy.

In another embodiment, the elastic layer 13 may comprise thermoset material. An advantage is that thermoset materials have usually good chemical 30 and mechanical properties.

In an embodiment, the elastic layer 13 is made of rubber. An advantage is that rubber has good elastic properties.

The elastic layer 13 may be an independent and stand-alone layer or element, or alternatively, it may be combined with another layer or element that 35 may have a non-elastic nature. Furthermore, the elastic layer 13 may comprise one or multiple layers of elastic material(s).

20180107 prh 19 -09- 2018

In an embodiment, the length of the elastic layer 13 is 90 % -100 % of the length of the peripheral outer edge surface 9. The elastic layer 13 being less than 100 % of said dimension may be arranged symmetrically or asymmetrically with respect to the width of the peripheral outer edge surface 9.

In another embodiment, the width of the elastic layer 13 is 90 % -100 % of the width of the peripheral outer edge surface. The elastic layer 13 being less than 100 % of said dimension may be arranged symmetrically or asymmetrically with respect to the width of the peripheral outer edge surface 9.

An advantage is that the protection against leakages through cracks 10 in peripheral outer edge surface 9 is good enough when 90 % of the length or the width is covered, and very good when 100 % of the peripheral outer edge surface 9 is covered. Thus the user safety may be increased.

In an embodiment, the thickness of the elastic layer 13 is 2 mm - 9 mm, preferably 3 mm - 5 mm. The elastic layer of this thickness may assure 15 that at least typical jet/flush of washing agent does not penetrate through elastic layer 13.

In an embodiment, the filter element 4 comprises an indicator 5 arranged to generate a break indication upon breakage of the filter element 4. At least a portion of the indicator 5 may be arranged on the microporous material 20 on the peripheral outer edge surface 9 and under the elastic layer 13. Other portions, if any, of the indicator 5 may extend along the filter element 4 to form a continuous circuit and arranged to break upon breakage of the filter element

4.

The indicator 5 may increase user safety by creating the break indi25 cation, such as visual and/or audible alarm, in case the filter element 4 is breaking or crazing. This way operators of the apparatus are able to be vigilant and avoid thus potential safety risks caused e.g. by spurting or spraying acid. In other words, the user safety is assured two ways: firstly by the elastic layer 13 that increases the passive safety of the filter process, and secondly by actively func30 tioning indicator 5 that gives the alarm. In an embodiment, as a consequence of the break indication, the control system of the filter apparatus is arranged to stop automatically the filter apparatus.

In an embodiment, the indicator 5 comprises an electrically conductive layer, e.g. a printed electric wire, a casted electric wire, a microstrip line, 35 separate electric wire, a metal tape or a painted electric circuit, for example.

The indicator 5 may be attached to the microporous material by a

20180107 prh 19 -09- 2018 brittle adhesive. An advantage is that the development of a break or craze comes across to the indicator 5 without substantive dampening.

There is an interior space defined between the opposed filter members 11, i.e. in the substrate 8

The interior space provides a flow canal or canals where a negative pressure is maintained, i.e. a pressure difference is maintained over the filter members 11, during the filtration process. Under the influence of the negative pressure, the cake forms onto the filter members 11.

In a regeneration stage performed by washing agent, e.g. acid or 10 acid-water composition is fed into the interior space with a certain backwashing pressure. The regeneration stage is performed by backwashing equipment 15 comprising e.g. necessary pumps, washing agent containers, and feeding channels.

In this stage there are used regeneration means of the filter apparatus 15 1. The objective of the acid washing is to remove impurities etc. attached to the filter members 11 and micropores therein back and out from the filter members.

The backwashing pressure creates an elevated or positive pressure in the interior space. The positive pressure may create such cracks and crazes in the brittle microporous material that the acid leaks out form the filter element 20 4. Especially problematic, or even dangerous, to users of the filter apparatus are spray- or spurt-like leaks in the peripheral outer edge surface 9. Now, the elastic layer 13 arranged on the peripheral outer edge surface 9 prevents or at least restrains these leaks so that the safety of the personnel can be improved.

In an embodiment, the filter element comprises an RFID tag 14 that 25 includes the identification data of the filter element 4. The RFID tag 14 can be arranged under the elastic layer 13, thus the RFID tag is protected against mechanical wear and chemical stresses. The peripheral outer edge surface 9 is usually an advantageous place for the RFID tag because it can be read there easily by RFID reader arranged in a frame of the filter apparatus.

The invention is not limited solely to the embodiments described above, but instead many variations are possible within the scope of the inventive concept defined by the claims below. Within the scope of the inventive concept the attributes of different embodiments and applications can be used in conjunction with or replace the attributes of another embodiment or application.

The drawings and the related description are only intended to illustrate the idea of the invention. The invention may vary in detail within the scope of the inventive idea defined in the following claims.

20180107 prh 19 -09- 2018

Reference symbols

3

9 filter apparatus filter filter disc filter element indicator membrane layer substrate peripheral outer edge surface filter member outer edge surface elastic layer RFID tag

Claims

A filter element (4) on a disk filter device comprising filter members (11) on both sides, which filter member (11) comprises a microporous permeable mem5 layer (7), the filter member (11) being formed to provide a capillary effect in the filtering process with the filter element (4) has an outer peripheral surface (12) comprising said microporous material and a porous substrate (8) arranged between the filter members (11),

Each filter element (4) further comprising a detector (5) arranged to cause a rupture notification when said filter element breaks, and at least a portion of the detector (5) being disposed on a microporous material and an elastic layer (13)

The elastic layer (13) is arranged on a peripheral outer peripheral surface (9) of the filter element to cover the microporous material of said peripheral outer peripheral surface (9), and wherein said portion of the detector is affixed with a brittle adhesive to the microporous material.

A filter element according to claim 1, which is a truncated sector-shaped filter element (4), and a peripheral outer peripheral surface (9) is disposed at a wider end of the truncated sector-shaped filter element.

A filter element according to claim 1 or 2, wherein the microporous material is susceptible to brittle fracture.

A filter element according to any one of the preceding claims,

30 ti where microporous material is collected.

A filter element according to any one of the preceding claims, wherein the elastic layer (13) has a length of 90% to 100% of the length of the peripheral outer peripheral surface (9).

20180107 prh 19 -09- 2018

A filter element according to any one of the preceding claims, wherein the width of the elastic layer (13) is 90% to 100% of the width of the peripheral outer peripheral surface (9).

5

A filter element according to any one of the preceding claims, wherein the elastic layer (13) has a thickness of 2 mm to 9 mm, preferably 3 mm to 5 mm.

A filter element according to any one of the preceding claims, wherein the elastic layer (13) comprises a thermoplastic material.

A filter element according to any one of claims 1 to 7, wherein the elastic layer (13) comprises a thermosetting material.

15

The filter element of claim 9, wherein the elastic layer (13) comprises rubber.

The filter element according to any one of the preceding claims, further comprising an RFID tag (14) including a filter element.

20 ment identification where

The RFID sensor is arranged under the elastic layer (13).

A disc filter device comprising one or more successive sectorial coaxial filter discs (3) formed by

A plurality of filter elements (4), the filter (2) being disposed about a central axis and rotatable about a longitudinal axis of the central axis, characterized in that the disk filter device further comprises a filter element (4) according to any one of the preceding claims.

The disk filter device of claim 9, comprising backwash means for backwashing the filter elements.

14. A method of regenerating a disk filter device which

The filter device comprises a filter element (4) according to any one of claims 1 to 11, wherein the method comprises creating an elevated pressure in the interior of the filter element (4) by supplying said interior with detergent by counter-current cleaning means.