GB2088744A - Air filtering apparatus - Google Patents

Abstract

An air filter comprises a housing having a partition 10 dividing the housing into first and second airtight zones, a plurality of tubular pleated paper filter elements located horizontally within the first zone and having open ends communicating with apertures formed in the said partition whereby air from said first zone can pass to the said second zone via the said filter elements, an inlet 71 for dirty air into the top of the first said zone and a baffle plate 27 located between the inlet and the filter elements whereby incoming air is deflected over and around the said filter elements. Preferably there is also provided a perforated screen on either side of the filter elements extending from below the baffle plate, said screens containing 55-65% open spaces and acting as coarse filters for removal of fibrous materials from the dirty air before it passes through the filter elements. The elements are cleaned by reverse flow jets. <IMAGE>

Description

SPECIFICATION Air filtering apparatus The present invention relates to apparatus for filtering air containing suspended particulate matter.

It is known to construct air filters to provide a housing divided into clean and dirty air chambers through the use of a horizontal partition containing a plurality of apertures, each of which apertures communicates with cylindrical filter element. Air containing suspended matter is drawn through the element in a substantially radial direction and passes from the centre of the element through the apertures contained in the partition into the clean air chamber from which it is extracted, the suspended particulate matter remaining deposited on the outside of the filter. The element is periodically cleaned by arranging that the air flow through the filter is reversed so that the deposited material is removed therefrom and is collected in means located beneath the elements for subsequent removal.

The frequency of cleaning required by the elements depends not only on the rate of air flow, but also on the amount and type of particles in the air. When such apparatus is used to filter air containing a large amount of particulate material, such as air from blast furnaces that contains a high proportion of heavy particles, the elements rapidly become clogged and require frequent cleaning and frequent replacement, thus reducing the overall efficiency of the filter.

We have now found that the frequency of cleaning and of replacement of the elements may be reduced, and the efficiency of the filter thereby improved, if the individual elements are mounted horizontally within the housing and the dirty air is drawn through the top thereof and initially deflected away from the elements, by a baffle contained between the air inlet and the elements, so that heavy particles suspended in the air then tend to fall downwards past the elements into a collecting means located in the bottom of the housing.

Accordingly, therefore, the present invention provides an air filter comprising a housing, a vertical partition member dividing the housing into air tight first and second zones, a plurality of cylindrical filter elements closed at one end and releasably mounted horizontally within the first said zone, said filter elements having their open ends sealed against the said partition and being axially aligned with apertures provided therein to allow communication between the second said zone and the interior of the filter elements, means located at the top of the said housing to enable the ingress of dirty air into the first said zone, a baffle plate positioned between said inlet for dirty air and said filter elements and dimensioned to extend substantially over said filter elements to allow air entering the zone to be deflected over and around the said filter elements, means to extract air from the second said zone whereby air is caused to flow radially through the walls of the cylindrical filter elements and particulate matter contained therein to be deposited on the outside walls of the said element, a plurality of means located within said second zone and positioned opposite each said aperture in the partition member to provide pulses of air, at predetermined times, in direction opposite the air flow to cause the deposited particulate material to be released from the outside walls of the filter elements, and means contained in the bottom of the housing to collect said released particulate material.

Preferably the filter elements are positioned in vertical groups and a perforated screen positioned either side of each said group, said screens being parallel to the axes of the filter element and extending vertically beneath the baffle plate to below the level of the lowest filter element and across the housing from the partition to the opposite wall thereof, the said screen preferably containing 55-65% open spaces to permit the dirty air to pass therethrough. The said screen acts as a coarse filter to remove fibrous material from the air prior to its passage through the filter elements; fibrous material otherwise deposited on the outer walls of the filter elements would cause rapid decrease in filter efficiency, the said material not being adequately removed by pulses of reverse air flow.

The filter elements are preferably formed from pleated paper to provide a maximum surface area through which air may pass.

One embodiment of the invention will now be more fully described with reference to the accompanying drawing which is a perspective view of an air filter part broken away to reveal the interior.

An air filter unit, generally indicated at 1, comprises a housing 2 carried by four legs 3.

Housing 2 includes a back wall 4, a front wall 6, side walls 5, top 7 and a double outlet Vform hopper 8 having outlets 9 to permit removal of particulate material deposited therein.

A partition 10 extends across the housing parallel to and spaced from the back wall 4 and is welded to side walls 5 for air tight attachment therewith. The top and bottom portions 1 0a are bent at right angles and welded to back wall 4 to provide a clean air chamber 30 and an inlet, or dirty air, chamber 20.

Two filter element support structures 21, (one only shown) each containing a bank of eight cylindrical cartridge filter elements 22 arranged in two vertical rows of four elements, are located in chamber 20. The filter elements 22 have open ends facing partition 10 and closed ends facing the front wall of the housing 2. Partition 10 contains a plurality of apertures 11 (only one shown) and the filter elements 22 are axially aligned therewith. Each filter element includes, at its open end, a rubber sealing ring (not shown) and the filter elements are urged against partition 10 through clamp members 23, and screw threaded adjusters 24 that bear against the closed end of the cartridge filters, to compress the sealing rings against partition 10 to provide an airtight seal between the said elements around each aperture.

Venturi tubes 25, one to each aperture 11, are mounted on the opposite side of the partition 10 in chamber 30 and are axially aligned with the apertures 11 and the filter elements 22. Compressed air jets 26, one to each venturi tube, are mounted in the back wall 4 and again are axially aligned with the venturii 25. Each jet 26 has an associated diaphragm valve (not shown) to which air is supplied by suitable piping (not shown) from a source of compressed air. Also mounted on the back wall 4 is a solenoid valve box (not shown) containing one valve for each diaphragm valve and connected to the pilot portion thereof. The solenoid valves are activated by electrical pulses from a remotely mounted solid state time control card (not shown).

Above each bank of filter elements 22 is a rigid baffle plate 27 supported by the frame 21 and extending lengthwise between the front wall 6 of the housing 2 and partition 10.

The width of the baffle is such as to cover the bank of filter elements 22 Ibut to allow air to flow down either side oli the filter elements.

Inlets 71 for dirty air, that is air containing suspended particulate material, are contained in the top 7 of the housing 2 and positioned directly over the baffle plates 27.

Access doors 61 are provided in the front wall 6 of housing 2 to allow removal of the spent cartridge filters as necessary.

A vent 51 is provided in wall 5 communi- cating with the clean air chamber 30. The vent is connected to an air extractor means, such as an extractor fan, to pull air through the filter.

In use air is drnwn through inlets 71, by the action of the air extractor means, and is deflected by baffles 27 to flow initially downwardly along the sides of the banks of cartridge filters 22, the air flow then turns inwardly and is drawn radially through the ff ters 22 into the interior thereof and then into clean air chambers 30 and out through vent 55.

After deflection of the air by baffles 27 the heavier particles of material suspended in the air loose some of their momentum and generally fall downwardly alongside of the filter banks onto the hopper 8 of the housing 2, whilst the lighter particles travel with the current of air and are deposited on the outsides of the filter elements 22.

As previously noted the air filters are periodically subjected to reverse air flow to cause deposited particles to be released and these then drop down to the base of the housing 2.

Cleaning is controlled by the timer control card which adjusts the frequency of the compressed air pulses and also their duration.

Pulsews of compressed air flow through air jet nozzles 26 and the venturii 25 entraining air from the clean air chamber and thus creating the reverse flow through filter elements 22 to release the particules deposited on the outside walls thereof.

It is preferred that the filters also include two perforated screens located adjacent and either side of each filter element 22 and parallel to walls 5. The said screens desirably extend across the full width of the chamber 20 and are under the umbrella of the baffle plates 27 so that air deflected by the baffle plates then has to pass through the perforated screen before passing through the filter elements. The perforated screens which preferably have 40-50% spaces uniformly distributed thereover thus act as a coarse filter and are especially useful in removing fibrous material suspended in the air prior to filtering by the filtering elements. The screens may conleniently be formed from expanded metal with the projecting ridges thereof turning towards the baffle 27.

Claims (6)

1. An air filter comprising a housing, vertical partition member dividing the housing into airtight first and second zones and containing a plurality of apertures, an equivalent number of cylindrical filter elements open at one end and closed at the opposite end releasably mounted within said first zone and having their open ends sealed around the apertures in said partition and axially aligned with said apertures whereby the said filter elements are substantially horizontal and there is communication between the said second zone and the interior of the filter elements; inlet means located at the top of the said housing to enable ingress of dirty air into the first said zone, a baffle plate positioned between said inlet means and said filter elements and dimensioned to extend substantially over said filter elements whereby air entering the said zone is deflected over and around said filter elements; means to extract air from the said second zone whereby air is caused to flow from the said first zone radially through the walls of the cylindrical filter elements into said second zone and particulate matter contained therein to be deposited on the outside walls of the said elements; a plurality of means located within said second zone and positioned opposite each said aperture to provide pulses of air, at predetermined times, in a direction opposite to the air flow to cause said deposited particulate material to be released from the outside walls of the filter elements; and means contained in the bottom of the housing to collect said released particulate material.

2. A filter according to claim 1 wherein the apertures in the said vertical partition are formed in vertical groups whereby the said filter elements are positioned in vertical groups.

3. A filter according to claim 2 wherein a perforated screen is positioned either side of each said vertical group of filter elements, each said screen being parallel to the axes of the filter elements and extending vertically beneath the baffle plates to below the level of the bottom most filter element and across the housing from the said partition to the opposite housing wall.

4. A filter according to claim 3 wherein the said perforated screens contain 55 to 65% open spaces.

5. A filter according to any one of the preceding claims wherein the filter elements are formed from pleated paper.

6. An air filter substantially as herein described with reference to the drawings.