GB1600553A

GB1600553A - Filters

Info

Publication number: GB1600553A
Application number: GB1460/78A
Authority: GB
Original assignee: BECKER APPARATEBAU GEB
Current assignee: BECKER APPARATEBAU GEB
Priority date: 1977-01-17
Filing date: 1978-01-13
Publication date: 1981-10-21
Also published as: IT1091847B; IT7819263A0; FR2377219A1; BR7706915A; BE862938A; ES233273Y; NL7800138A; ES233273U; DE2701697A1

Description

(54) IMPROVEMENTS IN AND RELATING TO FILTERS (71) We, FIRMA GEBR BECKER APPARATEBAU, a German Company, of D472 Beckum, Ostwall 47, Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a method of filtering and to a filter in particular for filtering liquids by passing the liquid through a filter substance, preferably filter cloths.

Filters are known in a variety of forms, for example rotary filters, vacuum filters, cartridge filters, alluvial filters, filter presses or suction filters, filter cells etc.

Common to all the known filters is the fact that practically the entire filtering surface is effective from the beginning of the filtering process. As a result the rate of flow through the filter gradually decreases with time since the solid or floating particles are carried buy the flow of liquid to the filter substance upon the input side of which they are deposited, the particles forming a cake of continually increasing thickness which has to be cleaned off from time to time.

An object of the invention is to enable a practically constant rate of flow to be maintained throughout filtering.

According to one aspect of this invention we propose a method of filtering liquid, in which the turbid liquid flows into at least one filter chamber defined by a vertically extending filter medium, and in which the clear filtrate is withdrawn outside the filter chamber, wherein the turbid liquid is introduced into the bottom of the filter chamber and the inflow is so controlled that the level of the turbid liquid rises during filtration from a low initial level to an upper level corresponding to the height of the filter medium, so that the effective filter surface increases continuously during filtration until the upper level is reached, the clear filtrate passing out through the filter medium into a clear filtrate compartment in which the level of clear filtrate is lower than the level of turbid liquid throughout filtration.

According to another aspect of this invention, a filter for putting into effect the method according to the said one aspect of the invention comprises a filter chamber defined by a vertically extending filter medium disposed within a housing, an inlet for introducing turbid liquid at the bottom of this chamber, a clear filtrate outlet from the housing outside the filter chamber, and means within the chamber arranged to create turbulence in the flow of liquid therein.

In a preferred embodiment of the invention, the level of the clear filtrate is maintained substantially below the filtering substance so that the output side of the filtering substance, for instance the filter cloth, is in contact with flowing clear filtrate, but is not submerged therein.

The unfiltered liquid is introduced from the bottom of the filter such that the level of the unfiltered liquid rises during filtering due to clogging of the filter substance. Because the level of the unfiltered liquid is initially very low areas of the filter substance not acted upon by the unfiltered liquid remain initially completely clean. With increasing clogging of the active submerged portion of the filtering substance, the level of the unfiltered liquid rises gradually, given a predetermined rate of flow, to increase the effective filter area. New clean areas of the filter substance are continually made available for filtering.

It has proved especially advantageous to provide distributing means, agitating means or the like for the unfiltered liquid. These means may take the form of helical guide ribs, which are arranged to create turbulence in the unfiltered liquid, and thereby prevent the particles from settling. By maintaining the sediment in the unfiltered liquid continuously in suspension the formation of a solid filter cake on the filter substance is prevented. As a result, the concentration of solid matter contained in the unfiltered liquid gradually increases. The level of the unfiltered liquid therefore changes continually as a function of the density of the unfiltered liquid and the working time. The filter has to be cleaned off when the level of the unfiltered liquid has risen to the upper extreme of the filtering substance since at this point, the efficiency of the filter, which had previously remained constant, begins to gradually decrease.

The filter substance defines a chamber and to avoid the use of supports, the flow of liquid is directed from the inside to the outside of the chamber.

In a preferred embodiment, the filter chamber comprises the interior of a filter hose or filter bag.

A displacement body may be placed inside the filter chamber, this having the advantage that the quantity of fluid required for washing or cleaning out the filter can be kept small. The displacement bodies enable the use ofa relatively large filter surface with only a relatively small space for the liquid.

The outer contour of the displacement body may correspond substantially with the inner contour of the filter chamber, to define therebetween a space having approximately the same width throughout.

In the preferred embodiment the distributing means are disposed on the displacement body.

A preferred embodiment of the invention will now be described by way of example with reference to the accompanying drawing which is a longitudinal cross-section of a filter.

The liquid to be filtered is gravity-fed from a high reservoir I, or pumped by a pump 2 into a manifold 3 on the filter housing 4 which in the illustrated embodiment is in the form of a cylindrical tank.

The unfiltered liquid passes from the manifold 3 into two filter cartridges 5 inside which are cylindrical displacement bodies 15 having conical ends. Arranged around the outsides of the displacement bodies 15 are helical guide ribs 14. The outer walls of the cylindrical filter cartridges 5 are defined by filter hoses 6.

The issuing filtrate runs down the outsides of the filter hoses 6 in the space 4a, collects on the base 10 and is drained off for further pro cessing in the direction of the arrow 11, by opening a valve 21 situated in the drain outlet 24 protruding from beneath the filter container 4.

The flow of clear filtrate down the outsides of the filter hoses 6 is indicated by the arrows 9.

The level of unfiltered liquid rises in the annular spaces 8 defined between the displaceanent bodies 15 and the filter hoses 6 as the solid particles and suspended matter are collected on the insides of the filter hoses 6, the upper limit of the particles 12 rises gradually and clogging of the filter hoses increases. When the particles reach the tops of the filter hoses 6 the rate of flow through the filter is reduced as in known filters. Excess unfiltered liquid results which flows though the display tubes 17 and the pipe-lines 25, 26 and 28, and can be recirculated by means of the pump 2. This occurs when the filter is not yet to be cleaned. It is possible thereby, with the aid of the adjusting means 16 and 16a to increase the back pressure in the lines 25 and 26.

The valves 19, 29 and 30 are closed for cleaning. The two-way valve 21 is set in the position in which the drain 24 is dosed. The valves 20 and 18 are opened, and washing water enters the filter through the valves 18.

If it is intended to wash out residual filtrate from the filter cake before cleaning out the filter cartridges, washing water can be admitted via the pipe-line 31 and the valve 22. This is useful, for example, when the filter has been used for thick juice filtration from sugar solu- tions. In this case, the valves 18 remains closed and instead of an input through line 28, the input takes place via valve 22 through line 31.

The filter hoses are enclosed in spiral coils 23.

WHAT WE CLAIM IS: 1. A method of filtering liquid, in which the turbid liquid flows into at least one filter chamber defined by a vertically extending filter medium, and in which the clear filtrate is withdrawn outside the filter chamber, wherein the turbid liquid is introduced into the bottom of the filter chamber and the inflow is so controlled that the level of the turbid liquid rises during filtration from a low initial level to an upper level corresponding to the height of the filter medium, so that the effective filter sur- face increases continuously during filtration until the upper level is reached, the clear filtrate passing out through the filter medium into a clear filtrate compartment in which the level of clear filtrate is lower than the level of turbid liquid throughout filtration.

2. A filter for filtering liquid by the method according to Claim 1 and comprising a filter chamber defined by a vertically extending filter medium disposed within a housing, an inlet for introducing turbid liquid at the bottom of this chamber, a clear filtrate outlet from the housing outside the filter chamber, and means within the chamber arranged to create turbulence in the flow of liquid therein.

3. A filter according to Claim 2 wherein the filter chamber is defined by a filter hose or a filter bag.

4. A filter according to Claim 3 wherein the said means comprise helically arranged guide ribs.

5. A filter according to one or more of Claims 2 to 4 and comprising at least one displacement member disposed within the filter chamber.

6. A filter according to Claim 5, wherein the outer contour of the displacement member substantitlly conforms to the inner contour of the filter chamber so as to define therebetween a gap of substantially uniform thickness.

7. A filter according to Claim 5 as dependent upon Claim 4 wherein the guide ribs are disposed on the displacement member.

8. A method of filtering liquid substantially

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. efficiency of the filter, which had previously remained constant, begins to gradually decrease. The filter substance defines a chamber and to avoid the use of supports, the flow of liquid is directed from the inside to the outside of the chamber. In a preferred embodiment, the filter chamber comprises the interior of a filter hose or filter bag. A displacement body may be placed inside the filter chamber, this having the advantage that the quantity of fluid required for washing or cleaning out the filter can be kept small. The displacement bodies enable the use ofa relatively large filter surface with only a relatively small space for the liquid. The outer contour of the displacement body may correspond substantially with the inner contour of the filter chamber, to define therebetween a space having approximately the same width throughout. In the preferred embodiment the distributing means are disposed on the displacement body. A preferred embodiment of the invention will now be described by way of example with reference to the accompanying drawing which is a longitudinal cross-section of a filter. The liquid to be filtered is gravity-fed from a high reservoir I, or pumped by a pump 2 into a manifold 3 on the filter housing 4 which in the illustrated embodiment is in the form of a cylindrical tank. The unfiltered liquid passes from the manifold 3 into two filter cartridges 5 inside which are cylindrical displacement bodies 15 having conical ends. Arranged around the outsides of the displacement bodies 15 are helical guide ribs 14. The outer walls of the cylindrical filter cartridges 5 are defined by filter hoses 6. The issuing filtrate runs down the outsides of the filter hoses 6 in the space 4a, collects on the base 10 and is drained off for further pro cessing in the direction of the arrow 11, by opening a valve 21 situated in the drain outlet 24 protruding from beneath the filter container 4. The flow of clear filtrate down the outsides of the filter hoses 6 is indicated by the arrows 9. The level of unfiltered liquid rises in the annular spaces 8 defined between the displaceanent bodies 15 and the filter hoses 6 as the solid particles and suspended matter are collected on the insides of the filter hoses 6, the upper limit of the particles 12 rises gradually and clogging of the filter hoses increases. When the particles reach the tops of the filter hoses 6 the rate of flow through the filter is reduced as in known filters. Excess unfiltered liquid results which flows though the display tubes 17 and the pipe-lines 25, 26 and 28, and can be recirculated by means of the pump 2. This occurs when the filter is not yet to be cleaned. It is possible thereby, with the aid of the adjusting means 16 and 16a to increase the back pressure in the lines 25 and 26. The valves 19, 29 and 30 are closed for cleaning. The two-way valve 21 is set in the position in which the drain 24 is dosed. The valves 20 and 18 are opened, and washing water enters the filter through the valves 18. If it is intended to wash out residual filtrate from the filter cake before cleaning out the filter cartridges, washing water can be admitted via the pipe-line 31 and the valve 22. This is useful, for example, when the filter has been used for thick juice filtration from sugar solu- tions. In this case, the valves 18 remains closed and instead of an input through line 28, the input takes place via valve 22 through line 31. The filter hoses are enclosed in spiral coils 23. WHAT WE CLAIM IS:

1. A method of filtering liquid, in which the turbid liquid flows into at least one filter chamber defined by a vertically extending filter medium, and in which the clear filtrate is withdrawn outside the filter chamber, wherein the turbid liquid is introduced into the bottom of the filter chamber and the inflow is so controlled that the level of the turbid liquid rises during filtration from a low initial level to an upper level corresponding to the height of the filter medium, so that the effective filter sur- face increases continuously during filtration until the upper level is reached, the clear filtrate passing out through the filter medium into a clear filtrate compartment in which the level of clear filtrate is lower than the level of turbid liquid throughout filtration.

8. A method of filtering liquid substantially

as hereinbefore described with reference to the accompanying drawing.

9. A filter for filtering liquid by the method according to Claim 1 constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.