CA2197545A1

CA2197545A1 - Method and apparatus for filtering edible oils

Info

Publication number: CA2197545A1
Application number: CA002197545A
Authority: CA
Inventors: Donald B. Stevens; Leonard R. Castellano; Thomas C. Gsell; Jeffrey M. Seibert; Barry J. Weissman
Original assignee: Individual
Current assignee: Pall Corp
Priority date: 1994-08-17
Filing date: 1995-08-17
Publication date: 1996-02-22
Also published as: US5628916A; JPH10504241A; EP0777517A1; WO1996004974A1; AU3414195A

Abstract

A method for filtering edible oils utilizing a backwashable filter assembly (10). A filter system having at least two filter assemblies (A, B) may be utilized to remove bleaching clay and/or nickel catalyst from oil being processed for human consumption. The filter assemblies may be connected in a tandem manner to provide continuous and uninterrupted filtering of the edible oil. Each filter assembly preferably comprises multiple, substantially cylindrical filter elements (18) having a porous filter medium which may be formed from polyaramid fibers. The filter elements are designed to withstand the elevated temperatures used in edible oil processing and for ease of cleaning during backwashing.

Description

~ I 5 ' ~WO 96/04974 2 1 9 7 ~ ~ 5 1 ~ ".,~,~, lU /44 METHOD AND APPARATUS FOR FILTERING EDIBLE OILS

The present invention relates to a method for filtering edible oils, and more yc~ ula~ to a method for filtering edible oils utilizing a la~,k~a,Ldl,le filterassembly.
The processing of oil for human . ,: is a multistep procedure which may include bleaching and h~uo~ . Generally, oils are h,~ O ' ' and bleached in sequential orPr~tinn~ The edhble oil is bleached by passing the oil tbrough a bleaching clay such as acid activated calcium bentonite to stabilize the oil and to decolorize the oil in order to prevent oxidation and achieve a clear amber 0 hue to the oil. The edible oil is L~ uO_.Iat~,d by reacting the oil with hydrogen in the presence of a catalyst, such as a nickel powder catalyst, to alter the melting point such that the edible oil will solidify at low 1~ s, e.g., room t~
II~JIuO_~aLion is not performed for all the edible oils, but rather just those that are intended to be solid at low ~ ,i.. The bleaching and h,~ O of the 15 edible oils results in the edible oil containing solid particulate matter in the form of bleaching clay and nickel catalyst which must be removed from the edhble oil before The filtering of edible oils which have been bleached and/or h,.L~,O_~ted as part of a ,ulu.~,S~uo procedure is currently s , ~ ~ -1 by pressure leaf filter 2û ~ .~.l,li~; having a .1'-l~,--, - ~.,..~ earth precoat. An exemplaly pressure leaf filter assembly, as pa~ ulall~ described in U.S. Patent No. 3,648,844, comprises a tankcontaining a stack of closely spaced, generally d~ s~red leaf filters mounted along a central conduit. Each leaf filter may include a plate having two oppositely disposed faces. Porous media are mounted on both faces of the plate, and the plate 25 has passages which cnmm--n: ' between the porous media and the central conduit.
Before the edible oil is illhU-lUCt~ into the tank of the leaf filter assembly, a ~ slurry of a precoat material, such as ~ earth, in a liquid is directed into the tank. The liquid passes through the porous media along the passages in the plate to the central conduit and exits the leaf filter assembly via the central conduit. As 3 o the liquid passes through the porous media, the precoat material is deposited on the w09610497~ 2~97~
porous media, forming a layer of precoat material on each face of each leaf filte~
Once a sufficient layer of precoat material is deposited on each leaf filter, the flow of slurry into the tank may be i i and the edible oil containing the particles of nickel catalyst and bleaching clay is iulludu. cd into the tank. As the 5 edible oil flows through the precoat layers of each leaf filter, the particles of nickel catalyst and bleaching clay are trapped in the precoat layer. The filtered edible oil then flows through the porous media of the leaf filter along the passàges in the plate tû the central conduit and exits the leaf filter assembly via the central conduit.
The precoat layer eventually becomes fouled with the particles ûf nickel 0 catalyst and bleaching clay which are filtered from the oil stream. E~ , the build-up of p~ ~ dLt~ solids in the precoat increases the pressure drop across each leaf filter, thereby degrading the p r....,.~ of the filter. fr - -, 1~" the flow of edible oil into the tank of the leaf filter assembly is periodically ~ d and the leaf filter assembly is ba~ k~Lcd to remove the precoat layer and the build-up 15 of ~u~Li~ldt~ solids trapped in the precoat layer. Typically, a cleaning liquid, referred to as a backwash liquid, is forced at a high flow rate, pressure, and/or volume in a reverse direction through the central conduit along the passages in the plate of each leaf filter and through the porous media on each face of the plate.
The backwash Lquid flowing in the reverse direction to the porous medium forces 2 o the precoat layer and the particles of nickel catalyst and bleaching clay off of the porous medium and flushes them to the bottom of the tank where the backwash liquid and the solids material is removed via a drain. Once the leaf filter assembly has been b~ hF~1 another cycle of iu~ the precoat slurry into the tank to form the precoat layer, ~ ~ ~ the, ' edible oil into the tank to 25 remove the particles of nickel catalyst and bleaching clay, and 1.~ the fouled precoat layer is begun.
While this process of filtering edible oils through a leaf filter assembly is very effective for removing particles of nickel catalyst and bleaching clay, it ~
has several problems. For example, this process generates a huge amount of 3 o r~ d waste. The volume of precoat material is very large compared to the volume of nickel catalyst and bleaching clay, but all of the solids material must be properly disposed of once it is flushed down the drain of the leaf filter assembly.
Further, once the spent precoat layer has been b..~k~Y~hcd from the leaf filters, a ~1~7~4~
~wo 96/04974 . I ~IIU..~L 144 ~ new precoat layer must again be deposited on each face of each leaf filter. This is a time . ,, portion of the cycle which detracts from the overall efficiency of the process since none of the edible oil is being filtered while the precoat layer is being deposited. In additiorl, because the leaf filters are closely spaced to one ~ 5 another it is difficult to remove all of the precoat from each leaf filter, especially in the area of the leaf filters near the central conduit.
~ In an alternate design, the leaf filters are stacked on a rotatabie hollow shaft.
Once the precoat layer on the leaf filters becomes fouled, filtration may be suspended and the shaft is rotated to remove the caked on llal i- ' matter. The shaft is rotated at a speed sufficient to generate a ~~ " ' force which causes the caked on matter to fly off the leaf filters. Accordingly, as with the ba~k~N ' ~ "
method described above, the rotation not only serves to remove the caked on matter, but also the ~ v precoat as well.
In a culd with a first aspect, the present invention is directed to a method for filtering edible oils. The method comprises passing processed edible oils containing solid p~rt~ te matter into a b =~ ''- filter assembly. In the b-- L..._~ l.lr filter assembly, solid particulate matter contained in the edible oil is removed therefrom by directing the edible oil through at least one ~b~' t;~
cylindrical filter element contained within the ba~ LLwa~LalJle filter assembly. The at 20 least one ~ cylindrical filter element comprises a fibrous filter medium having a graded pore structure. The edible oil is passed through a coarser pore upstream region and than a finer pore du..~LI~,a~ region. The solid pali-matter ~ t~c directly on the filter element and forms a cake thereon. Aftera ~ d~ ~ ...i..~d period of filtration time, the filter element is l~a~k~a~Lcd to clean 25 the filter element and remove the solid pa~ ulal~; matter collected thereon. The filter element is l~a~kwa~Lcd by passing a backwash fluid through the finer poredu..ll~LI~ia u region and then the coarser pore upstream region. The ba.Lwa,LalJlc filter system cyclically alternates between removing the solid particulate matter and ba~.. ' ' ~, of the filter element.
In a~.vldal.. with a second aspect, the present invention is also directed to a filter assembly and a filter system which provide for a simple and effective procedure for removing ya~ àLe matter such as bleaching clay, e.g., acid activated calcium bentonite and nickel catalyst from oils processed for human .;~ io~

W096104974 21~7545 PCT/US95110744 Accordingly, the ba~Lwaah~ic~ edible oil filter assembly or system of the presen~
invention is utilized to remove the unwanted soLds from the edible oil in a safe and efficient manner.
In ac~uld with a third aspect, the present invention is directed to a 5 method of filtering fluids. The method comprises passing a fluid containing solid ~J~Ii~,uldle matter into a first br~LwaahalJlc filter assembly and into a secondb L~ l,lr filter assembly, and removing the solid particulate matter from the fluid by directing the fluid through at least one filter element in the first 1~ L.~ lr filter assembly, including ~ ;",. a cah-e of the solid particulate 10 matter on the at least one filter element in the first l, -~ L-- l l/lr filter assembly, and through at least one filter element in the second ba~Lwa~llal~lc filter assembly, including .~ ...L a cake of the solid p~ àle matter on the at least one filter element in the second ba~Lwaah~lc filter assembly. The method also comprises L~,LwaaLill6 the at least one filter element in the first l,~.~,LwaaLdl,le filter assembly aLter the cake of solid pal Li~,ulaLc matter is formed on the at least one filter element of the second La~,LwaaL~ lc filter assembly, and ba~,LwaaLi~2 the at least one filter element in the second ba~,LwaaLdlJle filter assembly a'her the cake of solid particulate matter is formed on the at least one filter element of the first b~L~LwaaLalJle filter assembly.
In ac~ d with a fourth aspect, the present invention is directed to a bà~,Lwa3Lal~lc filter system for removing solid particulate matter from a fluid. The ba~LwaaLa~lc filter system comprises a first bà~LwaaLa~lc filter assembly including at least one filter element for removing solid p~li~ lalc matter from the fluid, a second b~-L~ lr filter assembly including at least one filter element for removing solid pal ' matter from the fluid, and a valve and pipe ~ -alt~ ali.-l~ c~ llF~ , the first and second l.,.-L~ ,1F filter .~ 1, in tandem and non-tandem.
In accoldal.~e with a fifth aspect, the present invention is directed to a method of filtering fluids. The method comprises passing a fluid containing solid 3 0 particulate matter into am inlet of a first bd~LwaaLdble filter assembly, removing the solid particulate matter from the fluid by directing the fluid through the at least one filter element in the first l . - L ~ ,lr filter assembly, including building a cake of the solid particulate matter on the at least one filter element in the first ~wo 96/04974 2 1 9 7 ~ ~ S Pcr/usss/l0744 b L~ lr filter assembly, ~ --; c passing of the fluid containing solid u~. Li~ul~t~ matter into the inlet of the first 1. L ~ lr filter assembly, passing the fluid containing solid ~u Li~Ld~ matter into an inlet of a second l,~Ackw~LdlJle filter assembly through an outlet of the second ba~,~w~Lal~lc filter assembly and into the 5 inlet of the first b~ekw~L,Al,lc filter assembly, removing the solid ,u~A i ' matter from the fluid by directing the fluid through the at least one filter element in the second l.~ 1r filter assembly, including ~ - , 1 I;"g a cake of the solid u~A i ' matter on the at least one filter element in tbe second b~J~w ~ filter assembly, and through the at least one filter element in the first b~ ~,Lw ~ ~~ filter 10 assembly, including - ' ~ a cake of the solid palLi~ e matter on the at least one filter element in the first b~-L..,~ l,lr filter assembly, ~
passing the fluid from the outlet of the second l,~kw~hahle filter assembly to the inlet of the first b~A~W ~ filter assembly,. I,v L~ g the at least one filter element in the first bV~L~Y~ hle filter assembly, " ~ passing of the fluidlS containing solid particulate matter into the inlet of the second ~.=- L~ filter assembly, passing the fluid containing solid particulate matter into an inlet of the first b~ W ' ''~ assembly through the outlet of the first bA~I~w~L~AlJlc filter assembly and into the inlet of the second 1, ~- L ~__l . ~l ,lr filter assembly, removing the solid particulate matter from the fluid by directing the fluid through the at least one 2o filter element in the first b~l- L w 1 ~1 ~lr filter assembly, including a ~ , ,1 -~; r; a cake of the sohd ~ui ' matter on the at least one filter element in the first b~kw~Ldl:lc filter assembly, and through the at least one filter element in the second IJa~l.wv hdl~le filter assembly, including ~ lqting a cake of the solid ,u~u ~ ' matter on the at least one filter element in the second bv- L ~-- 1~ 1 ~lr filter 25 assembly, .1~ L passing the fluid from the outlet of the first b~A~Lw ' ''-filter assembly, and b~A~L.~. ~ the at least one filter element in the second b~A~kw~LaAble filter assembly.
The l,a~LAw~LaAl~lc~ edible oil filter assembly may comprise multiple hollow, cylindrical filter elements which may be b~A k w~Led. Additionally, the multiple filter 3 0 elements have a porous filter medium, and preferably a ~ U,UUI UU~ filter medium, which requires no IU~ u~ALil.g to remove the unwanted solid materials contained in the edible oil. The porous filter medium is preferably formed from a pu~
fibrous material which is chosen because of its ability to withstand the relatively high wos6/04974 21~7S~5 r~"~JI.,s~ 144 involved in the processing of the edible oils. The porous filter mediu~
may have a variable pore size ~ o, I;~ ~ e.g., a coarser outer layer and a finerinner layer. This design efficient]y collects solids directly on the filter element, where the solids form a p~ alJlc cake during the filtration procedure. During the 5 backwash cycle of operation, a reverse flow is initiated, thereby .~ V the collected sohds from the filter elements. Upon ,. ",1 1;. . of the backwash cycle, the filter assembly is returned to full forward flow for normal filtration of the edible oiL
The filter system comprises a tandem all v of filter :~cc~nlhli~c and 10 provides for the ~ , UIP~ and highly efficient filtration of the edible oiL The size of the particulate matter, especially of the nickel catalyst, is extremely small. E the removal rating of the filter elements is not buLriCi~,..lly fine to remove all of the l~a~ .ulali matter, the edible oil may not be sllcrici~ lly filtered by a clean filter element. Accordingly, the filter system provides a tandem ~.. c,... l of first 15 and second filter ' ' to effectively remove the pa~ uL,t~ matter, including the nickel catalyst. Once a filter assembly completes the backwash cycle of operation, its filter elements are clean. The flow of edible oil to be filtered is direaed to this clean filter assembly wherein the edible oil may not be , ' filtered; therefore, the filtrate exiting from this first filter assembly is direaed to the 20 second filter assembly, which is currently waiting to enter the backv"ash cycle of operation and therefore, has a cake buildup on the filter elements. The cake of particulate matter ~ the filtration aaion of the filter element, ensuring 1~ complete removal of the particulate matter. Thus, any remaining nickel catalyst particles are removed in this second filter assembly. After a given period of 25 time, a cake of ~ ulàt~ matter builds up direaly on the filter elements of the first filter assembly, and these caked filter elements are sufficient to remove all the uL.t~ matter from the edible oil without passing the oil through the caked filter elements of the second filter assembly. The second filter assembly is then switched into the backwash cycle of operation for cleaning while the first filter assembly is 30 used to filter the oil. The entire process is cyclic and provides for ~... I;,. ...~ and ~ u~ d operation.
The b~ k~L~ble~ edible oil filter system of the present invention provides for a faster, longer lasting, and more ~ l procedure for filtering oils for human w0 96/04974 2 ~ g 7 ~ 4 5 , ~ , /44 The procedure is faster, i.e., higher process rates are r ~
because there is no down-time associated with a prevoat operation. Filter - -- '-" - -e~l" :~ v the present invention effectively filter the edible oil without the need for a precoat. Further, the filter assembly, including the filter elements, are longer 5 lasting because of the ~ cylindrical shape and the surface vll,holo~,~ of the porous filter medium which allow for complete backwash cleaning of the filter elements while remaining structurally intact over the course of a 'ti," ~ of filter/backwash cycles. Methods, ' " , and systems . ' ~ '~ v the invention are more e~ . .... _l for a variety of reasons. The filter assembly is a self-clearling 10 unit; therefore, no 1~ r filter elements are necessary. There is little or no system down time. r ' personnel are not required on a regular basis to clean the filter ~ ' ' Since the filter elements do not require a precoat layer,no time or money is expended on the precoat or its a~ ... In addition, the compact size of the filter assembly mir~imizes product hold-up, backwash fluid 15 volume, space l~ Li.C~ t~ and ~' costs.
The filter assembly and l,~ w ' v method ~".,I,od~; the present invention are highly efficient in that they provide for cllhct~ y reducing waste and cost while increasing process rates. In prior art systems, ~ alLlE; of the filter elements is required to effectively remove ~ ,Ldalc matter. A~w,~ , during backwash ycles, the precoat material is removed from the filter elements along with the collected particulate matter. In addition to the cost associated with replacing the precoat, the amount of waste vastly increases due to the presence of the precoat.
Since the filter elements of the present invention do not require a precoat, waste is greatly reduced.
The ba~ wcwh~ le~ edible oil filter assembly of the present invention utilizes high strength and high durability filter elements which are able to witbstand the elevated ~ ~ ,o,,,c~ of edible oil processing and the cyclic loads applied during reverse flow cleaning cycles. The filter assembly ensures high efficiency operation leading to improved product quality, I . - . ;...: ~ l ;.... of solids recovery and protection 30 of system operators, e-~ and the ellvll~ The filter assembly may be utihzed over a wide array of filtering - rr" ' Figure 1 is a cross se~liullal view of the 1 ackw~Lal,lc, edible oil filter assembly of the present invention.

21g~45 4 ' ' PCT/US95/10744 Figure 2 is a ~ laiiull of the filter element utilized in t L,.,, 1 =~,1r edible oil filter assembly of ~the present invention.
Figure 3 is an; w ' view of a sample section of porous filter medium utilized by the filter element of Figure 2.
5Figure 4 is a cross _. Iio~l ~ ~liu of the filter element of Figure 2 Figure 5 is a ~ of the filter element of Figure 2 having a mesh outer winding.
Figure 6 is a cross 3e.,1iulldl view of two b~ Dh~l~lc, edible oil filter ' " of the present invention connected in tandem.
1ûThe processing of oils for hurnan ,: typically ~ - - 5 a multi-stage procedure including bleaching of the oil and hJ~u~ aliull of the oil.
Although neither bleaching nor h~ub_ll~liu~ is absolutely necessary, both are frequently utilized; The oil is bleached by passing the oil through a bleaching clay to stabilize the oil and to decolorize the oil in order to prevent oxidation and to 5 create a clear amber oil, while the oil is hJIlu~_llat~,d to alter the melting point such that the oil will solidify at low ~ u~ liu therefore, is not p. ' ' for all edible oils, but rather those that are intended to be solid at low U'U,D, such as room t~ .al~ci.
The bleaching of oil is a relatively simple procedure wherein the oil is heated 20 to a ~ d - ~ u~,t; within a given: r - ' i range and mLxed with a bleaching clay, such as acid activated calcium bentonite in a slurry tank. The slurry of oil and bleaching clay is pumped into a vacuum bleacher where it is ~ ly agitated. During residence in the vacuum bleacher, coloring matters, gums, otherpigments and trace elements present in the oil are adsorbed by the bleaching clay 25 to produce a clear amber oil. Additionally, the bleaching clay serves to stabilize the oil to prevent oxidation.
The L~u~ fiu~ of the oil is also a relatively simple procedure wherein the oil is mixed with a specific catalyst, such as a nickel catalyst, in a slurry tank.
Hydrogen gas is pumped into the slurry of oil and catalyst under precise control, 3 o wherein the hydrogen reacts with the oil in the presence of tne catalyst to produce a h r.Lu~ at~ A oil with an altered melting point such that the oil solidifies at low As a result of bleaching and/or L~Lug_~lion, the edible oil contains solid 2197~4~
wo 96/04974 ~ ~ - Pcr/u~ss/la744 particles of the bleaching clay and/or nickel catalyst. The bleached and/or h,.L~ v ' oil must then be filtered to remove these In a~uldGul~e with one aspect of the present invention, a backwash filter assembly employing hollow cylindrical filter elements having a porous filter medium 5 are utilized to filter the edible oil without the presence of a precoat layer. The porous filter mediurn of each filter element is designed having pore sizes which will effectively collect particles of bleaching clay and nickel catalyst as a cake directly on the filter element, i.e., on the surface or in the pores of the filter element. This cake r ~ r~ ' the filtration action of the filter medium and allows the filter assembly 10 to remove virtually all of the particles of bleaching clay and nickel catalyst without the use of a precoat. Once the cake deposits reach a certain level, however, d~ ...... of filter F r.. -... occurs. r ~, the buildup of solids on the filter medium inhibits flow through the filter element and/or increases the pressure drop across the filter element, thereby reducing its utility. Accordingly, the filter assembly is bG~k~YG~Ldl/le, allowing each filter element to be cleaned to remove the caked-on ~ ~ ~I t~'d solids. A backwash filter assembly .,.IL~...6 the present invention provides a practical approach for effectively filtering edible oils while ~ ~ ~ ~ clean and efficient filter elements, and it is particularly alv ~ in where the solids waste may not be Wll.. - '~, released to the As is shown in Figure 1, an exemplary 1.=- L~G~ edible oil filter assembly for ~ ,' ~ the ~ of the present invention includes a housing 10 which is divided by a partition 12, such as a tube sheet, into first and second chambers 14 and 16. At least one, and preferably a plurality of hollow, cylindrical 25 filter elements 18 are disposed inside the first chamber 14 and are attached to the partition 12. The partition 12 is preferably ....~ )U~ to the edible oil, as well as to gas, and is sealingly commected to the irmer wall of the housing 10. The partition 12 may be formed from stainless steel or any other suitable material illl~ J~ tothe flow of edible oiL
~ 30 The i.. ~.. g~ .,.. l illustrated in the figure may be used both for filtering edible oil by means of the filter elements 18 and for cleaning the filter elements 18 by bG~L~ During normal filtering operation, processed edible oil to be filtered flows from the first chamber 14 into the second chamber 16 through the hollow, W0 96/04974 i ~ 1..,3/l /44 cylindrical filter elements 18, and during b~. L ~ operation, a l. = L A' 1'-' Ig flui~
either filtrate or an extemaLly supplied fluid, flows in the reverse direction from the second chamber 16 into the first chamber 14 through the filter elements 18.
The housing 10 is preferably co ~ ' so that the f;lter elements 18 can be 5 readily accessed to pem~it their ~ For example, the housing 10 can include upper and lower sections d.,L~I~ L~L~I~ connected to one another.
, a sealable access port can be formed in the wall of the housing 10 to permit access to the inside of the first and/or second chambers 14, 16.
The housing 10 need not have any partiaalar shape or size. Generally, the shape 0 of the housing 10 and the material(s) utilized for ~ u~~ Liùn thereof will be selected on strength c..~ so that the housing 10 will have sufficient strength to withstand the pressures exerted on it during f;ltration or b~ kw Additional ~ .. .~ , including the type of liquid being filtered, may effect the choice of materials. For example, the material of which the housing is ~ ted15 is preferably ~ with the fluid contained therein. Typically, the housing 10 is co~LlL_t~d from stainless steel. For simplicity of structure and operation, the partition 12 is disposed in the housing 10 ~"l ,- ~ " " " .1 11~. In the illustrated exemplary ~ .1-o-~ the first chamber 14 is disposed below the second chamber 16; however, the ~Ul~L~l of the housing 10 may be reversed, i.e., the second 20 chamber 16 may be disposed below the first chamber 14.
A plurality of pipes may be connected to the housing 10 for ~ various fluids into and removing various fluids from the housing 10. In the exemplary , '~o,l;~". 1 an edible oil feed pipe 20 and a lower drain pipe 22 are connected to the housing 10 so as to ~ v~ith the inside of the first chamber 14. The 25 edible oil feed pipe 20 is used to introduce the solids laden edible oil to be filtered into the first chamber 14 from a source not shown, and the lower drain pipe 22 is used to remove unwanted materials from the first chamber 14 and also to drain the first chamber 14. Arrows 21 and 23 indicate the direction of flow through the edible oil feed pipe 20 and the lower drairi pipe ~ lCi ~,uC~,L;~ r. A make-up gas feed pipe 30 24 may . with the first chamber 14 preferably just below the partition 12. The make-up gas feed pipe 24 supplies a make-up gas, such as air, to facilitate draining the first chamber 14 through the lower drain pipe 22. When the first chamber 14 is drained, a vacuum lock can occur above the fluid line, thereby ~l g~4 ~

~ impedmg drainage. Accordingly, by supplying a make-up gas, the problem is a~leviated. The make-up gas feed pipe 24 may also serve to vent the first chamber 14. Arrow 25 indicates the direction of rdow through the make-up gas feed pipe.
The edible oil feed pipe 20, the lower drain pipe 22, and the gas feed pipe 24 are equipped with ~ g control valves 26, 28, and 30 for . u.. ~l " ,, the flow through their respective pipes 20, 22, amd 24. The edible oil feed valve 26, the lower ~ drain valve 28, and the make-up gas feed valve 30 may be of amy suitable valve type, such as a gate valve, amd may be manually operated or lly operated.
A filtrate discharge pipe 32, an upper drain pipe 34, a backwash liquid feed pipe lû 36, and a ,ul~ ' gas feed pipe 38 may be conmected to the housmg 10 so as to ~ with the inside of the second chamber 16. The filtrate discharge pipe 32 is used to remove filtrate, i.e., edible oil which has passed through and wasfiltered by the filter elements 18. The upper drain pipe 34 is used for removingunwanted materials from the second chamber 16. The backwash liquid feed pipe 36 5 may be used to supply a suitable backwash liquid to the second chamber 16 from any suitable source. The ~ d gas feed pipe 38 supplies the second chamber 16 with a cu~~ d gas also from any suitable source. Arrows 31, 33, 35, and 37 indicate the direction of flow through the filtrate discharge pipe 32, the upper drain pipe 34, the backwash liquid feed pipe 36 and the ~l ~ ' gas feed pipe 38, 2û .
Each of the pipes 32, 34, 36, and 38 may be equipped with a cul-~ r " ~
control valve 40, 42, 44, and 46. The filtrate discharge valve 40, the upper drain valve 42, the backwash liquid feed valve 44, and the ~ d gas feed valve 46 may be of any suitable valve type such as a gate valve. The control valves 40, 42, 44, 25 and 46 for their respective pipes can be controlled manually, or they can be 'ly controlled, for example, made to operate according to a prescribed sequence by any suitable l~lv~ 1F control unit.
In the exemplary e..ll~o-li~_..L, each pipe 20, 22, 24, 32, 34, 36, and 38 serves a single function, but it is possible to have a single pipe serve a plurality of functions.
~ 3 o For example, one pipe could be used both as a filtrate discharge pipe 32 and as a drain pipe 34 or one pipe could be used both as a filtrate discharge pipe 32 and as a backwash liquid feed pipe 36. It is also possible to use filtrate ~r~lm~ t~d in the second chamber 16 as a backwash liquid, in which case the backwash liquid feed pipe 2197~4~ . ;,' l ' w0 96/04974 . ~ 44 36 may be ~liminqt~l In addition, it is possible to have more pipes tban in th~
exemplary ~ ~ " illustrated in Figure 1. A second lu~ ~d gas feed pipe may be coupled to the first chamber 14 to supply a ~UI~ d gas to the chamber14, or a second make-up gas feed pipe may be coupled to the second chamber 16 to5 supply make-up gas as the filtrate is drained. FuuLL~Illul~ the figure is merely a schematic ~ and the locations of the pipes 20, 22, 24, 32, 24, 26, and38 on the housmg 10 are not limited to tbose shown in the figure.
For each of the filter elements 18, an opening 48 which, between the first and second charnbers 14 and 16 is formed in the partition 12. Each filter 10 element 18 is commected at one end to the partition 12 so that fluid from the first chamber 14 can enter the opening 48 only by first passing through tbe filter element 18. Preferably, tbe filter elements 18 are dcla~LalJI~ moumted on the partition 12 so that they can be easily replaced. A threaded mounting device 50 may be utilized to secure tbe filter element 18 in position. The size of the opening 48 can be selected 15 based on fluid flow ~ uh~ during filtration. The filter elements 18 generally range in size from one inch to two inches in outside diameter; however, custom sized filter elements may also be easily utilized. In this exemplary ~ each filter element 18 is disposed entirely within the first chamber 14, although it is possible for the filter elements 18 to extend part way mto the second chamber 16. Each filter20 element 18 may also be comnected at the other end to a support plate, not shown, which extends across the housing 10 parallel to the partition 12. The support plate functions to secure the filter elements 18 in position, and mamtain them in a 5 ~ 'ly parallel . .~
Figure 2 illustrates an exemplary c h - " of a smgle hollow, cylindrical filter 25 element 18 that is used in the backwash filter assembly of Figure 1. The filter element 18 preferably comprises a hollow perforated core 100, a porous filter medium 102 formed around the core 100, a blind end cap 104 on a first end of thefilter medium 102 and the core 100, and an open end cap 106 on a second end of the filter medium 102 and the core 100. The hollow perforated core 100, in the 30 exemplary ~, I o.l ~ is ~ ly cylindricaUy shaped and may be formed of stainless steeL Other materials may be utilized for the core 100 such as a rigidpolymeric material. The core 100 provides support for the porous filter medium 102 against radiaUy inwardly directed forces. The end caps 104 and 106 may be formed wos6/04s74 2 1 9 7 ~ ~ 5 l -lr~ 744 ~ fromglassfiberfilledpol~luu,llncwhicharethermallybondedtotheporousfilter medium 102 arld the core 100 to provide a strong, uuiform seal. Other materials rnay be utilized for cu~h .,~hul, of the end caps 104 and 106, including any suitable , ~,;uu~ metal or polymeric material. Other methods may be utilized for attaching the end caps 104 ard 106 to porous filter medium 102 aud the core 100,including spin or sonic welding, pol~ or bonding by means of an adhesive or a solvent.
The filter medium 102 is preferably made of a pol~. ' fiber such as a KEVLAR0 fiber which is layered onto the perforated cûre 100. The pGI~ ' û fiber is preferred in this ~-r r ~ ~ ' ~ because it can withstand the higher ~ ~D
involved in the ~IU~ of edible oils and, - l~ n ~ it can be formed in finer grades. The filter medium 102 preferably has a graded pore structure in which anupstream section of the filter medium has a different removal rating, e.g., a coarser rating, than a dU..IL~ section of the filter medium. For example, the outer 15 section of the cylindrical filter medium may have a fiber diameter and/or pore size which increases gradually to the outermost surface of the filter medium, while the inner section has a fiber diameter and/or pore size which is constant and finer than the outer section. The upstream section may provide effective ~UI~LilLIdliUI~ for many solid particles and aids in quickly building a cake of particulate matter, including 20 bleaching clay and nickel catalyst, directly on the filter element 18. This pore size and fiber diameter variation may be achieved through a process wherein the fiberdiameter is changed, ~ as the fibers are deposited on the core 100 while ~ ~ ~ ~, uniform high void volume. The inner section may be formed from extremely fine fibers in order to increase the number of pores while decreasing the 25 effective diameter of each of the pores.
Figure 3 illustrates an exemplary ~u~L" of a porous filter medium 102.
As is illustrated in the figure, the outer or upstream section 110 of the porous filter medium 102 comprises larger fibers and larger pores. The fibers and pores which comprise the outer section 110 graduaDy decrease in size towards the inner or du.. ~,l~,~ section 112 of the porous filter medium 102. The outer section 110 may comprise the bulk of the porous filter medium 102 at ~Iy~lu~ two-thirds of the thickness thereof. The region 114 of decreasing fiber diameter and pore size is part of the outer section 110. The inner section 112 is comprised of extremely srnall ~) wo s6/04974 ~ ~ ~ ~ 4 ~ J~ 44 fibers forming extremely small pores. The net effect of this design is a filter elemen 18 which filters fluid by an efflcient sieving and trapping action, and which has a high dirt capacity. In addition, this structure allows the filter element 18 to be easily cleaned during 1,..~ }~w~Ll.6.
A cross sc~liuL,al view of the filter element 18 is illustrated in Figure 4. Thefilter medium 102 is preferably ~ u~t~ d from at least two layers, and preferably, a plurality of layers of pOl~a~d fiber webbing which are helically wrapped around the core 100, each layer having a fiber and pore size d ' by its upstream or du..~hG~ proximity. For example, each layer of the filter medium 102 may have 10 a constant pore size and successive du .. ~t~ l layers may have succc~ ly smaller pore sizes. T ~u~cd between the core 100 and the filter medium 102, and between adjacent layers of the pul~. 1 fiber webbing are diffusion layers 103.
ThediffusionlayerslO3maybeofanysuitablematerialandc.. 1~v.. ,.l.. which allow for, and preferably assist in, the lateral or edgewise flow of the edible oil within the filter element 18 between the inner most filter medium 102 layer and the core 100, and/or between adjacent filter medium 102 layers. Such a lateral flow assists in ~ the pressure drop across the filter element 18. When the diffusion layer 103 is positioned between the core 100 and the innermost filter medium 102 layer, the diffusion layer 103 facilitates the passage of edible oil through the previous core 100, which will typically be of a perforated or r . . ~
U~ LiU,I with a multitude of holes, and the innermost filter medium 102 layer by. "g the use of the filter medium 102 surface area through which the edible oil can flow with equal ease beyond those portions of tbe filter medium 102 in close proximity to the holes of the core 100 through which edible oils will flow. When the diffusion layer 103 is positioned between adjacent filter medium 102 layers, thediffusion layer 103 similarly ma~mizes the use of the filter medium 102 surface area for filtration. The diffusion layer 103 also acts as a reservoir for q P~L;~UI~-LG matter, i.e., bleaching clay and nickel catalyst, which provides for a relatively high dirt capacity, for the filter element 18. The diffusion layer 103 is 3 o porous so as not to interfere with the flow of edible oil, and so as not to inbctqntiqlly contribute to the pressure drop across the filter element 18.
A desirable diffusion layer 103 will generally be of a wire mesh, such as of stainless steel, ~u Li~,ulo,lly in high L~ all,l G eU..l ~ ', or will be a woven or wo 96l04974 2 1 9 7 5 4 5 P~
non-woven web prepared from coarse fibers, preferably of the same material used in the filter medium 102, such as a ~,ul~ 1, having a high loft. The diffusion layer 103 utilized between the core 100 and the innermost filter medium 102 layer may be of one material such as stainless steel, while the diffusion layer 103 lut~,.,uu~_d between adjacent layers of filter medium 102 may be of a second material such as pol~ ~ ' fibers. The diffusion layer 103 is preferably made of a material which is ~ and chemically . 1 ' '- with the core 100, thè filter medium 102 and the edible oil. Generally, the diffusion layer will have a high voids volume and a low edge-wise flow resistance.
The filter medium 102 layers may be helically wrapped such that the edges of the filter medium 102 layers are abutting or u._lla~ . The u._llau~, of the filter medium 102 within a layer is preferred in that as the effective thickness of filter media is thereby increased, and edible oil flow pathways which bypass the filtermedium 102 are mir~ 7~1 The amount of u._lla~uillg may vary from 0% to as much as about 95~o, preferably about 25 to 75%, and most preferably about 50% ofthe width of the filter medium 102 web. An overlap of about 67% will effectivelytriple the filter medium 102 thickness in each layer, while and overlap of about 50%
will effectively double the filter medium 102 thickness of the filter element 18. U.S.
Patent No.5,290,446, assigned to the same assignee as the present invention provides a cwmplete ~ of helically wrapped filter elements, including a detailed of the W~llU~lioll and use of diffusiûn layers.
Intheexemplary ,'.û.1 ,.. .l apul~ ~'fiberisusedtofabricatethefilter medium 102 because of its ability to withstand the higher t' ~''1'' ~'1'll~;- associated with edible oil lul. ~ g However, other materials may also be utilized. The filter 25 medium 102 may be prepared from any suitable organic materials, such as nylon, aramid, fluulu,uol~ pol~u~ ue~ pol~lh,.e.lc, polyester, pol~ llc, and pol~ uc resin, or from inorganic materials such as glass, carbon, stainless steel, and ~lllmin--m Some of these materials are suitable for lower t~ ,l, ,l ,ci and some of these materials are suitable for higher t 1~ ,u c:
30 ~1-~l;- ~l;...,~ C~ .~l.. .-1;. .~ of various materials may also be utilized.In addition to alternate materials, the structure of the filter medium 102 may be w~h~ d in a different maùner and geometry. For example, the filter medium 102 may include a mass of fibers, fibrous mats, porous, .. ' .. ~ , such as supported or ~ WO 96/04974 ~ ~ 9 ~ 5 ~ ~ PCTNS95/10744 non s~,~pult~d ~ UIJUIUU:~ i ' formed, e.g., from a polymeric material,~
porous foam and porous metals or ceramics. Alternatively, the filter medium may be of a pleated structure, as disclosed, for example, in T,.s " -~;. . .l ~bL~Lun No.
WO 94/11082.
A stainless steel mesh 108, illustrated in Figure 5, may be wound helically around the filter medium 102 in order to provide a uniform, smooth outer surfacefor the effective release of collected solids during backwash. In addition, the staiuless steel mesh 108 provides structural support for the porous filter medium 102 against outwardly directed forces. Added support may be p~u L~ , adv due to the repeated filtering/l,= L~ )' cycles of operation.
The filter element 18 may be made to any size to fit particular system uil~ , including outer diameters from one inch or less to two inches or more.
The porous filter medium may have any suitable removal rating. The filter medium102 is preferably U~UIUIL~. For example, it may have an absolute rating in the range from about 0.1 micron or less to about 20 microns or more.
During filtration, all of the valves except the edible oil feed valve 26 and thefilhrate discharge valve 40 are typically closed. The processed edhble oil to be filtered is i~ udu~d into the first chamber 14 through the edible oil feed pipe 20 and ispassed generally radially through the hollow filter elements 18 to become filtrate.
2 o As the processed oil contauDng particles of, for example, bleaching clay and nickel catalyst passes through each filter element 18, particulate solids are deposited on the filter element 18, s lqhn~ a cake of ~al ' directly on the filter element.
The filtrate which passes through the filter medium 102 then passes along the hollow interior of each of the filter elements 18, through the openings 48 in the partition 12 and into the second chamber 16. The filtrate then exits the second chamber 16 through the filtrate discharge pipe 32 and may be collected in a reservoir not shown.
Usually, during filhration, the first chamber 14 will be ~o~,!. t. l~ filled with the processed edible oil contauDng particulates such as bleaching clay or nickel catalyst, and the second chamber 16 will be ~ulll~ t~ filled with filtrate. Essentially, during the filtration process, the volume of the filter assembly is preferably filled with unfiltered fluid and filhrate and no gases such as air. Higher filtering efficiency of the edible oil is achieved when the gas volume is reduced.
The P~ l~ti~n of a cake of p~L~uL-t~,i, directly on each filter element 18 2197~45~ ;.

-rr~ the filh-ation action of the filter medium m the filter element 18 and ensures that virblally all of the palLi~ulaLe matter is removed from the processed edible oil. Depending on the size of the ~al L~ ula~ matter and the removal rating of the filter elements 18, some of the ~al i ' matter may pass v~ith the filh ate through the filter elements 18 until a sufficient cake of I ' ~al ' has been deposited directly on the filter elements 18. (~r~ " it maybe preferable to ~ u. ~Jlat~ the filtrate back to the first chamber 14 until the cake of ~al has - ~ ~ ' on the filter elements 18 to remove virlually all of the pau L~ uI.lt~ matter from the processed edible oil. Recirculation of the filhrate would 0 be p~,lîu.lu~d when the filter element 18 is clean. Of course, if the removal rating of the filter medium is ~- '~ fine to remove an a~ O~Iidt~ amount of the pau ' matter from the edible oil without the r l-hnn of a cake on the filter elements 18, recirculation may be I - y.
For a period of time, the cake of particulate matter on the filter elements 18 is beneficial in that it enhances the filhation action of the filter element 18. However, once the buildup of palL~ uL,t~, matter begins to eA~ inhibit flow through and/or umduly increase the pressure drop across the filter elements 18, the filter elements 18 are fouled. After the filter elements 18 are fouled by the cake of pau ' imcluding the bleaching clay and nickel catalyst, the filter elements 18 2 o are cleaned by ba~k~ Generally, in filtering edible oils, the particle load is not too high and the filter assembly may be ba~ Y~hed in the range from about every half hour to about hwo hours. Of course, depending on the particle load, the filter assembly may be ba~ k~hed more often than once every half hour or less often than once every hwo hours.
During bacl~a L;llg. the edible oil feed valve 26 and the filhrate discharge valve 40 are closed to cut off the supply of edible oil through the feed pipe 20 and the exit of filtrate through the filtrate discharge pipe 32. The lower drain valve 28 mayremain closed and the edible oil may remain in the first chamber 14. Alt~ IllaL._l~, in order to minimize the fluid forces which must be overcome during ba~k~a~ lg, 3 o the first chamber 14 is preferably drained so that the edible oil in the first chamber 14 is at or below the bottoms of the filter elements 18. For example, the lower drain valve 28 and the make-up gas feed valve 24 may be opened so the first chamber 14is partially or wl.l~,l.,t~l~ drained of the edible oil through the lower drain pipe 22.

2197~4~
WO 96/04974 Pf'TlUS9!j/10744 The drained first chamber 14 may be ...~ d at ~ .. ;r pressure, or it ma~
be ~ Jl~d to a value just below the bubble point of the porous filter medium 102 of the filter elements 18. P.. ~ ~ the first chamber 14 is done in order to impede the flow of filtrate witbin the cores lJ0 of the filter elements 18 through the 5 filter elements 18 and into the first chamber 14 ~ a~ as is explained below.
The drained first chamber 14 may be plc~ d to a value of at least about seventy-five percent of the bubble point or, more preferably, of at least a~u.~t r.. l. q percent of the bubble point.
The second chamber 16 preferably remains full of filtrate, which may be used 0 as the backwash liquid, or the second chamber 16 may be drained of filtrate to a specific desired level by means of the upper drain valve 4~ and the upper drain pip 34 and used as the backwash liquid. Alternatively, the filtrate may be ~ull.~l~ tcl~
drained from the second chamber 16 and a backwash liquid may be ~..ud..~ cd intothe second chamber 16 via the backwash feed pipe 38 and the backwash feed valve l5 46. The backwash liquid may be any fluid which is f~.,..l.-l;l lr with the filter elements 18 and the edible oil. Further, the backwash liquid may be treated in various ways, for example, by heating it or shifting the pH.
In a preferred ~ .o~ 1, the backwash would be a gas assisted backwash utilizing the filtrate as the backwash medium. After the edible oil is drained to an 2 0 ~ r ~ level in the first chamber 14, the lower drain valve 28 is closed. With the valves 26 and 28 closed and the second chamber 16 containing the backwash fluid, both the first chamber 14 and the second chamber are ~ .~d, for example, via the ,u.. ~ d gas feed pipe 36 and the gas feed valve 44 in the second chamber 16 and the make-up gas feed pipe 24 and valve 30 in the first chamber 14.
25 The first chamber 14 is ~ d as described above and the second chamber 16is ~ d to any suitable backwash pressure, for example, to about seventy to ninety psi. With both chambers 14 and 16 ~ and the backwash liquid - ' .. in the interiors of the filter elements 18 and the second chamber 16, thelower drain valve 28 is opened, venting the first chamber 14 directly through the 3 o lower drain pipe ~, and venting the second chamber 16 through the lower drain pipe ~ via the filter elements 18. This pressure pulse forces the backwash liquid and the gas m the second chamber 16 through the filter elements 18, dislodging the ~uLi~,ulrL~; cake from each filter element 18 and cleaning each filter element 18 of wo s6/~4s74 ~ 44 ~ ~al Li..llat~ matter. In particular, the increased pressure in the second chamber 16 causes a pressure pulse to abruptly force the bachvash liquid e lqt~d above and in the interiors of tbe filter elements 18 to flow in the reverse direction through the filter elements 18 when the drain valve 28 is opened. The force of the outwardly5 flowing backwash liquid dislodges the pal ' matter trapped in or on the outer surface of the filter elements 18, and the matter is blown out from the filter elements 18 together with the backwash liq ud. The backwash liquid forced through the filter elements 18 and the llal L;~ ~llale matter may be removed via the lower drain pipe 22, or if the lower drain valve 28 is closed, it may collect on the bottom of the first lo chamber 14.
~ a~ k w~L;l.~ may be, _ ~ flushing all of the backwash hquid contained in the second chamber 16 through the filter elements 18 in one ~...,l,., --,.l~ stream, or ~' For ex mple, after a ~I~A~ ".:..rd period of time or after a amount of backwash liquid has been flushed through the filter 15 elements 18, the lower drain valve 28 may then be closed, allowing any backwash liquid in the second chamber 16 to fill into the interiors of tbe filter elements 18.
The first and second chambers 14 and 16 are then ~~ d and another bà~ k w ' ~ ~ cycle may be initiated. Similar ba~Lw ' ~ ,, cycles may be continued as long as there is sufficient ba~k~ ~ ~ liquid in the second chamber 16 or as long a o as l~a~kwa ,h;..~g~ hquid is supplied to the second chamber 16.
The filter assembly of the present invention may be equipped with any suitable - ' ~ for "~ d: ~ ~ " when the backwash hquid is at a suitable leveL such as a level sensor disposed in the housing 10 or a timer. The level of the backwash liquid in the second chamber 16 will depend upon many factors, including 25 the size of the filter elements 18 and the amount of b -- L~ , liquid which it is desired to flush through the filter elements 18. For some c ,llb ' the level of the backwash liquid may be selected so that the volume of the backwash liquid ranges from about one to about ten times the total volume of the interiors of all of the filter elements 18. The ~ 1 gas provides the energy for balw~ g~ and 3 o any gas which is ~ .." ,~ I; blr with the filter assembly, the l,a~L.... ' ~ , liquid, and the edible oil may be used. FI~ ..LI~ d air or nitrogen is used.
The ~ of the reverse pressure pulse, e.g., the ~ ' of the di~ , ~1 pressure between the second and first chambers 16 and 14 and the WO 96/04974 2 1 9 7 5 4 ~ PCI/U~95/10744 duration of the pulse, may vary depending on such factors as the ability of the filte~
elements 18 to withstand reverse pressure differentiaLs amd the desired reverse ~low velocity for cleaning the ~;lter elements 18.
In a~vld~. ~ with another aspect of the inventior~ a multi-assembly backwash 5 iiltration system may be used to .' the ~ of the present invention. Figure 6 is a cross sc~ Lu,l~l view of two ba~ L~.Dhal,le filter ~cc~Tnhlj~5 comnected in a tandem n l l ,~ I ~J, . . I. . 1 Each of the filter ! ' ~' may be identical to the one illustrated in Figure l; ac~ùld~61~, identical elements re labelled with identical reference numerals. The two i;lter ~ce~mhli~s ' ~ e' as assembly A
10 and assembly B, I~,uc~ , of the backwash filtration system are preferably operated m a tandem and non-tandem ~
As previously discussed, the removal rating of the filter elements 18 may not besufficiently fine to remove cnltrtq-ltiqlly all of the p~uL~ Le matter, especially the nickel catalyst, umtil a sufficient cake of parLculate matter has built up on the filter 5 elements 18. Thus, once a filter assembly is placed in the filtering mode of operation with clean filter elements 18, some of the nickel catalyst may pass through the filter elements 18 until a cake of particulate matter, including bleaching clay and nickel catalyst, forms directly on the filter elements 18. Accordingly, operating the filter ~ ~ " in a tandem r ~nL~~~ ' for a period of time solves the problem.

2 o For example, the filter elements 18 in one filter assembly, e.g. assembly A, may be caked, e.g., by ~ ~h~ Liull. Rc~ Lu~l of the filtrate would be performed when the filter elements 18 are clean. Once a cake has a ' ' on the filter elements 18 of assembly A, the edible oil to be filtered may be directed m a single pass through the filter assembly A, where the mckel catalyst amd bleaching clay are removed by the caked filter elements 18 until it is time to backwash the filter elements 18 of the filter assembly A. The flow of edible oil to be filtered is then switched to the second filter assembly B, having clean filter elements 18, and filter assembly B is commected via a t~mdem ~. ,...,,~ ...l to filter assembly A, having caked filter elements 18. The flow of oil would then proceed first through the clean 3 o filter elements 18 of filter assembly B and some of the particulate matter might pass through the clean filter elements 18 and end up in the filtrate. However, the two filter ~CC~hli~5 A and B are connected via a tandem ~l~ L with assembly A

_wo 96l04974 - ' Pcr/usss/l0744 ~lu..~.lci~ of assembly B, and thus the filtrate oil exiting filter assembly B, which is currently in the filtering mode of operation, would be passed through filter assembly A, which already has a cake built-up on the filter elements 18 from theprior filtering mode and thus will ~;u~L,t~ remove the ~
5matter from the oil. Once the filter elements 18 in the second filter assembly B have built up a sufficient cake of ~i ' matter to cu.~ ,t~ remove all of the ~ p~ ' from the edible oil, filtration could proceed through filter assembly B
only and the other filter assembly A could be b~.,L ~ ~ - ' to clean the caked filter elements 18 of the first filter assembly A.
0The process is ~,u~l~,t~ cyclic. Once the cake builds up enough to foul the filter elements 18 in the filter assembly currently filtering the oil, the flow of oil is directed in tandem first through the other filter assembly having clean filter elements 18 and then through the filter assembly having caked filter elements. After the clean filter elements 18 of the one filter assembly build up a cake sufficient to remove the p.u Li~,.Jldt~,~, the filter ~ 1' , are decoupled in a non-tandem v and the other filter assembly is l, -- L..._~1,.'.1 In the exemplary e~lv " illustrated in Figure 6, the two filter: ~ ' A and B are comnected in a tandem or ; ' v by four pipes 52, 54, 64, and 66. Pipe 52 is comnected between the filtrate discharge pipe 32 of the 20first filter assembly A, on one end, and edible oil feed pipe 20 of the second filter assembly B on the second end thereof. One or more control valves 56 and 58 control the flow of fluid through pipe 52. Pipe 54 is comnected between the filtrate discharge pipe 32 of the second filter assembly B, on one end, and into the edible oil feed pipe 20 of the first filter assembly A, on the second end thereof. One or 2 5more control valves 60 and 62 control the flow of fluid through pipe 54. Pipe 64 is comlected between the edible oil feed pipes 20 of the first and second filter ' ' A and B, and to an edible oil supply (not illustrated). Control valves 68 and 70 control the flow of fluid through pipe 64. Accordingly, if control valve 70 is closed, control valve 60 closed, control valve 26 of filter assembly A open, and30control valve 68 open, the edible oil from the supply flows through the edible oil feed pipe 20 and into filter assembly A. If, however, control valve 68 is closed, control valve 58 closed, control valve 26 of filter assembly B open, and control valve 70 open, the edible oil from the supply flows through the edible oil feed pipe 20 and WO 96/04974 2 1 9 7 ~ ~ ~ PCTIIJS9~110744 into filter assembly B. Pipe 66 is connected between the filtrate discharge pipes 3 of the first and second filter assemblies A and B, and to a filtrate collection tank (not illustrated). Control valves 72 and 74 control the flow of fluid through pipe 66.
Accordingly, if control valve 40 of filter assembly A and control valve 72 are open 5 and control valves 56 and 74 are closed, then the filtrate flows from filter assembly A to the filtrate collection tank. If, however, control valve 74 and control valve 40 of filter assembly B are open, and control valves 62 and 72 are ciosed, then thefiltrate flows from filter assembly B to the filtrate collection tank. The control valves 56, 58, 60, 68, 70, 72, 74, and 62 utilized in, ; with i.. ",l~l.. " l;.~.~ pipes 0 52, 64, 66, and 54 may be manually or 'ly operated and may be any suitable type of valve such as a gate valve.
Assuming that the filter elements 18 of filter assembly A have a sufficient cakedeposited thereon, filtration may proceed solely in filter assembly A. Filtration may proceed solely in filter assembly A by closing control valves 70, 58, 62, 60, 74, and 56 and control valves 26 and 40 of filter assembly B and opening control valves 68 and 72 and control valves 26 and 40 of filter assembly A. Filter assembly A
continues to process the edible oil preferably until a point prior to the time that the filter elements l8 require l. =- ~ w~ . Ihis point in time may be a ~l~ A- ~ d time or may be a ~ - d pressure build-up.
2 o Once this point in time or pressure is reached, control valves 68, 58, 74 and 56 are closed and control valves 70, 62, 60, and 72 and control valves 26 and 40 of filter qCcp..lhliPC A and B are opened. The edible oil from the supply may flow throughpipe 64 to filter assembly B. Since the filter elements 18 of filter assembly B are clean, i.e., no cake deposited thereon, the filtration of the edible oil rnay not be 25 ,~ic;~ ..;l~ effective because, as discussed previously, the removal rating of the filter elements 18 may not be ~ lly ffne to remove Cllh~ ' qrltiqlly all of the ~,~ li. ul~.Le matter until a sufficient cake of ~ L. ,llat~ matter has built up on the filter elements 18. Accordingly, the filtrate exiting from filter assembly B through the filtrate discharge pipe 32 may be ported in a tandem A ~ ~ " ~ -L,. '' 1- ''I to filter assembly A for 30 additional filtration. T-h-e filtrate from filter assembly B flows from the outlet of filter assembly B through pipe 54 and into the inlet of filter assembly A for additional filtration. Since the filter elements 18 of filter assembly A are caked, the filtration may be completed in filter assembly A. Filtrate exiting filter assembly A

2197~4~
_ W O 96/04974 PC~rrUS95/10744 through filtrate discharge pipe 32 may flow through pipe 66 to the filtrate storage tank.
Once a cake is built up in the filter elements 18 of filter assembly B, control valves 68, 60, 58, 62, 72, and 56 and control valves 26 and 40 of filter assembly A
may be closed and control valves 70 and 74 and control valves 26 and 40 of filter assembly B may be opened thereby porting the filtrate exiting filter assembly B
directly to the filtrate storage tank through pipe 66. The two filter ~CCF mhliF C A and B are now decoupled in a non-tandem: ~ Filtration may now proceed solely in filter assembly B; a~v.d~ , the filter elements 18 of filter assembly A
may be l,~ w~_d.
When the filter elements 18 of filter assembly B reach the point in time prior to the time that they require h~.~,k.. ' ~ control valves 60, 70, 72, and 62 may be closed and control valves 68, 56, 58, and 74 and control valves 26 and 40 of filter ...1,1 F ~ A and B may be opened, thereby directing the flow of edible oil from the supply into filter assembly A and in tandem into filter assembly B. Since the filter elements 18 of filter assembly A have been ba~L.~ ~ - ' and are clearl, the filtration may not be complete for the reasons described above. Accordingly, the filtrate exiting filter assembly A is ported in a tandem: ~ to filter assembly B
wherein the filter elements 18 have a sufficient cake to complete the filtration.
2 o Once a sufflcient cake is built up on the filter elements 18 of filter assembly A5 the control valves may be set as previously indicated to allow filtration to proceed solely in filter assembly A. The two filter: ' '5 A and B are now decoupled in a non-tandem ;.. .~ .~, . ..l The filtrate exiting from filter assembly A may be ported via pipe 66 to the filtrate storing tank and filter assembly B may be 25 ba~Lwa~Lc;l The filtration process utilizing the above described tandem and ~ lPm t~iscyclicandmaybecontinuediud~ ..it~ withouti~t.,llu~lio dueto the ability of l.=- L~ l,;,.g and filtering ~;.. ll -. v 1~
A filter assembly or system and a 1, -~ L~ .,g method ~ od~6 the present 30 invention are highly effective. The ba~kw ~ method decreases the flow resistance of the filter elements 18 by removing ~ , ., l -t. d ~u ii.uL.t~ and colloidal matter which can foul the porous filter medium, as a result of which the efficiency of the filter assembly can be increased. The filter assembly and ba~l~wa~L;u6 method 2197~$
WO 96/04974 ~ ' PCTNS95/10744 ..,..~(:-~,~5 the present invention ' ' lly reduces waste, and reduces cost, whil~
increasing process rates. In prior art systems for the filtering of edible oils, the filter elements require a precoat. Accordingly, during backwash cycles, the precoat material is removed from the filter elements along with the collected p~uLi.,ulat., 5 matter. In addition to the cost associated with replacing the precoat, the amount of waste is vastly increased due to the presence of the precoat. Since the filter elements of the present invention do not require a precoat, the waste is greatlyreduced. The entire filtering process rate is increased due to the fact that no cycling is required to precoat the filter elements and because the filtering and b.l~L~
10 cycles proceed in parallel. Therefore, the filtering cycle is and , ~ u~,l Also aiding in increasing the process rates is the use of the - 1l~ cylindrical filter elements in a l,~.~L~Lh.6 assembly. The design of the filter elements, as stated above, facilitates the removal of ;~ ' ~' particulates during b~ l,;,, thereby making 1, ~ 6 quicker and more efficient.
Although shown and described is what is believed to be the most practical and preferred c .l.o~l;.- .,t~, it is apparent that departures from specific methods and designs described and shown will suggest IL~_h_~ to those sLilled in the art andmay be used without departing from the spirit and scope of the invention. The present invention is not restricted to the particular w~llu~ ~ described and 20 illl-ctr~t.o~l but should be construed to cohere with all, --..1;1;. _l;....~ that may fall within the scope of the appended claims.

Claims

What is claimed:

1. A method of filtering edible oils comprising:
(a) passing edible oil containing solid particulate matter into a backwashable filter assembly;
(b) removing the solid particulate matter from the edible oil by directing the edible oil through a fibrous filter medium having a graded pore structure, including passing the edible oil through a coarser pore upstream region and then a finer pore downstream region of at least one substantially cylindrical filter element contained within the backwashable filter assembly and accumulating the solid particulate matter directly on the at least one substantially cylindrical filter element;
(c) backwashing the at least one substantially cylindrical filter element after the cake of solid particulate matter accumulates on the at least one substantially cylindrical filter element by directing a backwash fluid through the fibrous filter medium having a graded pore structure, including passing the backwash fluid through the finer pore downstream region and then the coarser pore upstream region, to clean the at least one substantially cylindrical filter element having the solid particulate matter removed from the edible oil accumulated thereon; and (d) cyclically alternating between removing the solid particulate matter from the edible oil by passing the edible oil through the at least one substantially cylindrical filter element and backwashing the at least one substantially cylindrical filter element to clean the at least one substantially cylindrical filter element having solid particulate accumulated thereon.

2. A backwashable filter assembly for removing solid particulate matter from processed edible oils, the backwashable filter assembly comprising:
(a) a housing having first and second chambers, a partition mounted between the first and second chambers and providing a fluid impervious barrier between the first and second chambers, and at least one conduit communication with each of said first and second chambers for facilitating the flow of edible oil into and out of the housing; and (b) at least one substantially cylindrical filter element connected to the partition and extending at least partially into the first chamber for removing solid particulate matter from processed edible oils, the at least one substantially cylindrical filter element having a polyaramid filter medium having first and second ends and first and second end caps mounted to the first and second ends of the filter medium, wherein at least one of said first and second end caps has an opening therein for edible oil flow through the filter element.

3. A method of filtering fluids comprising:
(a) passing a fluid containing solid particulate matter into a first backwashable filter assembly and into a second backwashable filter assembly;
(b) removing the solid particulate matter from the fluid by directing the fluid through at least one filter element in the first backwashable filter assembly, including accumulating a cake of the solid particulate matter on the at least one filter element in the first backwashable filter assembly, and through at least one filter element in the second backwashable filter assembly, including accumulating a cake of the solid particulate matter on the at least one filter element in the secondbackwashable filter assembly;
(c) backwashing the at least one filter element in the first backwashable filter assembly after the cake of solid particulate matter is formed on the at least one filter element of the second backwashable filter assembly; and (d) backwashing the at least one filter element in the second backwashable filter assembly after the cake of solid particulate matter is formed on the at least one filter element of the first backwashable filter assembly.

4. A backwashable filter system for removing solid particulate matter from a fluid, the backwashable filter system comprising:
(a) a first backwashable filter assembly including at least one filter element for removing solid particulate matter from the fluid;
(b) a second backwashable filter assembly including at least one filter element for removing solid particulate matter from the fluid; and (c) a valve and pipe arrangement alternatively connecting the first and second backwashable filter assemblies in tandem and non-tandem.

5. A method of filtering fluids comprising:

(a) passing a fluid containing solid particulate matter into an inlet of a first backwashable filter assembly;
(b) removing the solid particulate matter from the fluid by directing the fluid through the at least one filter element in the first backwashable filter assembly, including building a cake of the solid particulate matter on the at least one filter element in the first backwashable filter assembly;
(c) discontinuing passing of the fluid containing solid particulate matter into the inlet of the first backwashable filter assembly;
(d) passing the fluid containing solid particulate matter into an inlet of a second backwashable filter assembly through an outlet of the second backwashable filter assembly and into the inlet of the first backwashable filter assembly;
(e) removing the solid particulate matter from the fluid by directing the fluid through the at least one filter element in the second backwashable filter assembly, including accumulating a cake of the solid particulate matter on the at least one filter element in the second backwashable filter assembly, and through the at least one filter element and the cake of the solid particulate matter on the at least one filter element in the first backwashable filter assembly, (f) discontinuing passing the fluid from the outlet of the second backwashable filter assembly to the inlet of the first backwashable filter assembly;
(g) backwashing the at least one filter element in the first backwashable filter assembly;
(h) discontinuing passing of the fluid containing solid particulate matter into the inlet of the second backwashable filter assembly;
(i) passing the fluid containing solid particulate matter into the inlet of the first backwashable assembly through the outlet of the first backwashable filter assembly and into the inlet of the second backwashable filter assembly;
(j) removing the solid particulate matter from the fluid by directing the fluid through the at least one filter element in the first backwashable filter assembly, including accumulating a cake of the solid particulate matter on the at least one filter element in the first backwashable filter assembly, and through the at least one filter element and the cake of the solid particulate matter on the at least one filter element in the second backwashable filter assembly;
(k) discontinuing passing the fluid from the outlet of the first backwashable filter assembly; and (l) backwashing the at least one filter element in the second backwashable filter assembly.