Note: Descriptions are shown in the official language in which they were submitted.
~V~3
~ACK~OUND OF THE INYENTION
This invention relates in general to an improved method of
and apparatus for clarifying liquids and, in particular, to a
filtration systern especially adapted for use in processing ed-
ible oils. More specifically, but without restriction to theparticular use which is shown and described, this invention re-
lates to a vertical leaf filtration system which automatically
cleans the filter elements upon accumulation of a predetermined
amount of rnaterials from the influent without opening the fil-
ter chamber and maintains fiIter cake integrity during precoat-
ing and drying of the expended fiIter cake and accumulated
materials.
While tl-e instant invention has many applications, it is
especially useful in process fiItration of edible oils and for
convenience of illustration will be described with reference to
its use in edible oils processing. As is well known, seeds
such as soybeans, cotton seeds, peanuts, and others, as well as
animal fats such as tallow, lard, and others, contain suffi-
cient quantities of vegetable oils and animal fats to justify
commercial recovery and processing for edible and other indus-
trial uses. In such processing, the oil or fat is removed from
the oil bearing material by extraction with solvents such as
hexane, alcohol, acetone, furfural~ or other such suitable sol-
vent, by such equipment as an expeller, press, or a combination
thereof. The oil, or miscella, thereby removed is clarified by
passing through fiIters which separate the liquid from the sol-
id for the recovery and processing of the oil.
In some applications it is desirable to degum the crude
oil to remove the water and soluble phosphatides, gums, etc.
In such applications the crude oil is treated with water and
phosphoric acid, or any other suitable reagent, to precipitate
--2--
~,/
the gums. While these precipitated gums are presently removed
by centrifuge, with a suitable filtration system the gum remov-
al would be more complete. The degummed oil is then trea-ted
for the reduction of the Eree fatty acids. The more complete
the removal of the gum, phosphatides, etc.~ the better the re-
covery of the free fatty acids reduced by physical refining.
However, if the gums are not completely removed, or if there is
no degumming, the gums in the free fatty acids must be removed
by caustic neutralization of the free fatty acids with a slight
caustic excess. Such caustic neutralization hydrates the gum
and converts the free fatty acids to soaps which are subsequent-
ly removed by a centrifuge. The refined, or neutralized and
degummed oil (which desirably has a free fatty acids content be-
low 0.05%) is treated with bleaching agents (earth) under heat
and vacuum to reduce the color. These bleaching agents are
then removed by filtration.
If it is desirable to lower the melting point of the oil,
the oil is hydrogenated by bubbling hydrogen gas thro~lgh the
oil in the presence of a catalyst. While nickel has been found
to be a suitable catalyst, it is difficuJt to remove the nickel
from the oil requiring some filter aid ma-terial to be added to
the material to facilitate catalyst removal. This nickel cat-
alyst and filter aid is subsequently removed by filtration and
the oil post bleached -- a process referred to as re-bleaching
after hydrogenation. The bleaching agent, generally a neutral
earth, is then removed from the oil by filtration along with
any residual catalys-t.
The edible oil may then be further processed9 such as by
winteri~ing and/or deodorizing, which require fiItration to in-
sure the removal of all the solids from the oil. After deodor-
--3--
,/ ~,,
izing a final processing step, filling, is effected whereintheliquid ingredients are filtered to remove foreign materials.
In the various -iltration steps required in edible oil pro-
cessing, the filtration systems heretofore employed were such
that -the filter apparatus had to be disassembled whenever the
filter elements required cleaning for removal of the accumulat-
ed sludge or accumulant bearing expended filter cake. Such dis-
assembly released vapors, which were sometimes toxic, into the
atmosphere in the presence of the system opera-tors and others
creating an undesirable and sometimes hazardous working environ-
ment. The filter elements were then removed from the filter
chamber and the filter septum scraped by hand which frequently
resulted in damage to the filter elements by puncturing or dis-
torting the filter cloth wire mesh septum. Once cleaning had
been accomplished, the filter elements had to be reassembled
within the filter chamber and frequently were not properly
sealed. Such improper sealing in combination with the punctur-
ing or distorting of the filter septum frequently resulted in
influent contaminating the fiItrateO In an attempt to minimize
this problem, fiber filter aids were used with the precoat fil-
ter aids to create a proper seal and to attempt to maintain sep-
tum integrity. The use of such fiber filter aids is very
costly and the necessity to effect such seals resulted in a
very expensive and inefficient fiItration system.
SUv~RY OF THE INYENTION
It is, therefore9 an object of this invention to improve
filtration systems.
Another object of this invention is to maintain the integ-
rity of filter cake formed on large filter septum during pre-
coat and filtration.
--4--
...~.
~P~g4~3
A further object of this invention is to maintain the in-
tegrity of filter cake during draining of the filter chamber in
preparation for removal of the expended filter cake and accumu-
lants frorn the filter septum.
Still anotller object of this invention is to automa-tically
maintain the filter elements clean for optirnum systern efficien-
cy without removing the filter elements from the filter
chamber.
Yet another object of this ir-vention is to provide a dry
waste or sludge discharge without heating the waste or dis-
charge materials.
These and other objects are attained in accordance with
the present invention wherein there is provided a filtration
system utilizing a plurality of coaxial, vertically disposed,
fiIter elements for clarifying a liquid passed therethrough.
Upon the accumulation of a predetermined amoun-t of materials on
or in the fiIter cake, the fiIter chamber is sealed and the con-
tents drained creating a pressure differential across the fil-
ter elements to maintain the integrity of the fiIter cake on
the filter septum. After the contents of the filter chamber
have been drained7 the chamber is positively pressurized to re-
move any filtrate remaining in the fiIter cake and to dry the
filter cake on the filter septum prior to removal. The expend-
ed filter cake and accumulants are removed from the filter sep-
tum and conveyed from the filter chamber by a discharge systemThe filter chamber is filled with liquid and the filter septum
mechanically scrubbed to remove any residual ma-terials there-
from. A quantity of precoat or filter aid material is added to
the liquid in the filter chamber and the filter aid bearing liq-
uid circulated through the filter elements and the filtrationsystem in a closed loop to form a precoat filter cake on the
--5--
~"; f'
,! ,~
filter septum. The flow rate of the circulation is sufficient
to maintain the integri-ty of the filter cake so formed until
such time as the filter cake removes a sufficient amount of
accumulants from the influen-t to create a predetermined
pressure differential thereacross which will maintain the
integrity of the filter cake on the filter sep-tum at the
influent flow rate.
DESCRIPTION OF THE D~AWINGS
Further objects of the invention, together with additional
features contributing thereto and advantages accruing there-
from, will be apparent from the following description of a pre-
ferred embodiment of the invention which is shown in the
accompanying drawings with like reference numerals indicating
corresponding parts throughout, whereino
FIG. I is a perspective view of a fiItration system embody-
ing the invention with portions of the internal structure of
the fiIter chamber removed and shown in phantom for greater
clarity,
FIG. 2 is a frontal perspective view of a portion of the
filtration system shown in FIG. I with parts removed and por-
-tions broken away to better illustrate the internal structure
of the fiIter chamber;
FIG. 3 is an enlarged sectional view of the vertical fil-
ter elements within the filter chamber to better illustrate the
manner in which the expended filter cake and accumulants are re-
moved from the fiIter septum;
FIG. 4 is a sectional view of the fiIter elements shown in
FIG. 3; and
FIG. 5 is a perspective view of a portion of -the precoat
unit with portions broken away to better illustrate the inter-
nal structure thereof.
--6--
DES~RIPTIO~ OF THE PREFERRED ~ODIMENT
Referring now to Fl~. 1, there is shown a filtration sys-
tem including a fiItration unit 100 and a precoa-t unit 200.
The two units are connected in fluid communication with a
source of influent 20 by means of interconnecting valve-con-
trolled piping. A filtrate and a solid waste materials dis-
charge outlets 40 and 50, respectively, are provided to remove
liquid and solids material from the units, all of which will be
hereinafter described in greater detail.
Unclarified liquid or influent is pumped into the filtra-
tion system through influent inlet 20 by means of an inlet pump21 which may be of any suitable commercially available type.
The influent is pumped through pneumatically controlled valve
22 in an influent inlet line 23, through a serially coupled
filter pump 24 (whose function will be hereinafter discussed in
greater detail), through a filter pump discharge conduit 25 for
delivery into the filter unit 100 through an upper filter inlet
manifold 26 and a lower fil-ter inlet manifold 27. Suitable
check valves 28 are provided in the fluid connections from the
filter pump discharge conduit 25 to the inlet manifolds 25 and
27 to prevent reverse flow of the influent.
The filter unit 100 includes a filter chamber 110 enclosed
at both ends by covers 111 which are removably sealed to facil-
itate servicing of the in~ernal mechanism, such as replacing
worn parts. A trough 112 is formed in the bottom of the filter
chamber 110 and through suitable supports journals a rotatably
driven discharge auger 113 in bearings 114. A discharge auger
drive motor 115, when activated, rotates the discharge auger
113 to forward solids materials falling into the trough 112 to
the discharge outlet 50 whereat impellers 116 secured to the
auger shaft 113a compress the solids materials within a
--7--
~.~
pneumatically controlled butterfly valve 117 which is period-
ically opened to discharge the solids materials from the system
through the discharge outlet 50. Any liquid removed by the
compressing action passes through a fiIter chamber drain con-
duit 118 (through which the contents of the filter chamber aredrained) and a pneumatically controlled valve 119 to a filter
drain pump 120.
Unclarified liquid which is delivered into the filter cham-
ber 110 through the upper and lower inlet manifolds 26 and 27,
respectively, is passed through coaxial vertical filter ele-
ments 160 into a hollow fiIter tube 162 and out through the
filter outlet 40 or through filtrate discharge line 30 to be
passed through pneumatically controlled valves 31, 32 or 33 de-
pending upon the phase cycle of system operation, to be herein-
after discussed in detail.
The fiIter elements 160 are mounted coaxially upon the fil-
ter tube 162 and separated by a plurality of spacers 16~ such
that perforations 167 formed in the filter tube 162 are in com-
munication with the interior of the fiIter disc as best shown
in FIG. 3. The hollow filter tube 162 is rotatably mounted in
a suitable sealed bearing 151 secured to one end 111 of the fil-
ter chamber 110 and in another sealed bearing in the filter out-
let housing 109 at the opposi~e end. The filter tube 162 is
closed at both ends and has perforations 163 formed therein in
communication with the interior of the filter elements 160
through which the clarified liquid passes to be discharged ~0)
from the fiIter unit.
Each filter element 160 comprises a support structure or
spacer 167 covered with a fine mesh screen or septum 16~. The
support structure 167 supports the fine mesh screen or septum
168 in an outwardly tapering manner from the center of the ele-
_~ _
, ,~
~J ~
ment -to the outer edge. The fiJter cloth or fine mesh screen
or septum 168 covering the support structure 167 is of a mesh
si~e such that all solid particles suspended in the liquid of a
size at least approximately 47 microns are retained on the
screen when liquid is pumped through the fiIter element. How-
ever, the mesh size will be dependent upon the particle size of
the filter aid used and the particle size of the suspended con-
taminants. The outer periphery of each of the filter elements
160 has a metallic rim 169 fixed thereon that slightly overlaps
the screen or septum and seals the outer periphery of each
fiIter element 160.
A plurality of wipers 180 are positioned between the fil-
ter elements 160 to clean the outer surfaces thereof. The wip-
ers 180 are each supported on a spacer 164 which separates the
individual fiIter elements so that each wiper is in contact
with the opposing face of two adjacent filter elements. A fil-
ter element drive motor 165 is operatively connected to fiIter
tube 162 to rotate the tube. When the filter elements 160 are
thereby rotated relative to the wipers 180 (during a portion of
the phase cycle of system operation to be hereinafter described
in detail) the relative motion between the wipers and the fil-
ter elements 160 will cause the entire surface of each filter
elernent to be subjected to the wiping action.
Each of the wiper elernents 180 includes an arm portion 181
to which brush fibers 182 are appropriately secured. The wiper
arm 181 extends radially outward from the filter tube 162 and
about the spacer element 164 to be supported thereby. A pair
of stops 186 are appropriately secured to the internal walls of
the fiIter chamber 110 to prevent the wipers from rotating when
the filter tube 162 and the filter elements 160 are rotated.
Therefore, the wipers 180 will remain stationary and the brush
~,o,~,
fibers 182 will mechanically scrub the entire surface of the
filter elements 160 when the filter element drive motor 165 is
actuated.
It has been found that a speed of rotation such that the
relative movement between the brush fibers and the filter ele-
ments 160 should be no greater than 1,000 inches per minute and
preferably between approximately 200 and 400 inches per minute
to cause the filter cake to be removed from the filter septum
168.
For a better understanding of the invent;on, the phase cy-
cles of system operation of the filtration systern will now be
set forth at which time additional structural features will be
described in detail.
Upon initial start up, both the filtration unit 100 and
the precoat unit 200 are emptied of any liquid, ancl the fiIter
elements 160 do not have any filter cake formed on the fil-ter
septum 16~. Influent pump 21 and filter pump 24 are actuated
purnping in influent from the inlet 20 through open pneumatical-
ly controlled valve 22 in influent inlet line 23, through fil-
ter pump 24, filter pump discharge line 25, through inlet mani-
folds 26 and 27, and into the filter chamber 110. A curved
baffle plate 108 is supported within the filter chamber 110 at
the point of influent discharge from the upper manifold 26 to
prevent the influent from discharging directly onto the filter
elements 160.
When influent :fills the filter charnber 110, the influent
flows through the filter elements 160 into the filter outlet
housing 109, through fiItrate discharge line 30, through pneu-
matically controlled valve 31 in recirculation line 34, and
through pneumatically con-trolled valve 33 in liquid rnake-up
line 36. Influent will continue to flow through liquid make-up
-10 -
~ ,~
:f
line 36 until such time as a predetermined liquid level is ob-
tained in a precoat tank 210 at which time a liquid level con-
trol 212 will be actuated to close the open pneumatically
controlled valve 33 thereby terminating flow through the liquid
make-up line 36. .~iquid does not flow through precoat fill
line 35 until such time as filter aid material is added for the
formation of the precoat filter cake hereinafter discussed in
detail.
When the filter chamber 110 and the precoat tank 2lO have
been filled with influent, the filtration system is ready to be-
gin the precoat phase cycle of sys-tem operation. To initiate
precoating the septum l68 of the filter elements 160, the pneu-
matically controlled valve 22 is closed and a precoat pump 213
and the filter pump 24 are energized to circulate ~he liquid
from the precoat tank 210 through the precoat pump 213, precoat
pump discharge line 214, through the upper filter inlet man-
ifold 26 into the filter chamber 110. When the precoat pump
213 is energized, the pneumatically controlled valve 32 in pre-
coat fill line 35 opens allowing liquid to be circulated
therethrough from the filtrate discharge line 30 to the precoat
tank 210. The circulating liquid passes through the fiIter el
ements 160, the filter tube 162, through the filtrate discharge
line 30, the recirculation line 34, and the liquid make-up
lines 36 since energi~ation of the precoat pump 213 will lower
the liquid level of the liquid contained within -the precoat
tank 210 thereby opening the pneumatically controlled valve 33
in response to a second liquid level controller 211. nergi-
zation of the filter pump 24 will draw the liquid through the
recirculation line 34, through the filter pump 249 into the
fiIter pump discharge line 25 and into the upper and lower fil-
ter inlet manifolds 26 and 27, respectively.
j~/7
While the liquid is being circulated through the system in
this closed loop manner9 dry filter aid or precoat material is
added to the liquid contained in the precoat tank 210 by means
of a filter aid feeder 220. the filter aid feeder 220 com-
prises a hopper 221 having a shaft 222 extending longitudinally
within the feed hopper and having secured thereto an agitator
223 and feed auger 224. The bottom of the hopper 225 is formed
in a conical shape and secured ~ithin he hopper chamber 221 to
prevent any of the precoat or filter aid material contained
therein from being discharged except through an outlet 226 in
the bottom of the cone. The shaft 222 is suitably journaled in
bearing surfaces and bracl<ets secured to the walls of the fil-
ter aid hopper 22l on the bottom and in the top of the hopper
for rotation by means of a precoat feeder drive motor 227 me-
chanically connected to the shaft 222 such that upon energiza-
tion of the feeder drive motor 227, the shaft 222, agitator
223, and feed auger 224 will rotate. Due to the gearing and
pitch of the feed auger 224, a controlled, premeasured amount
of fiIter aid material or media contained in the hopper 221 is
added into the precoat tank 210. The turbulence of liquid pass-
ing through the precoat tank 210 causes a slurry to be formed
int he precoat tank which is pumped by the precoat pump 213
through the precoat purnp discharge line 214 to be circulated
through the filtration sys-tem in a closed loop.
When the desired amoun-t of filter aid material~ or media,
has been added to the precoat tank 210, the precoat feeder
drive motor 227 is deenergized, but the precoat pump 213 contin-
ues to operate circulating the contents of the precoat tank 210
to the fiIter chamber 110, through the fiIter elements 160, and
returning into the precoat tank or passing through the :fiIter
pump 24 for recirculation through the filter chamber 110.
12-
Actuation of both the precoat pump 213 and the filter pump 24
provides a high flow rate of circulation through the filter
chamber 110 and the filter elements 160 which quickly forms a
uniform filter cake precoat on the septum 168 oE the filter
elements 160. The :EiIter aid material added to the liquid is
circulated in the closed loop to adhere to the filter septum
168 forming the desired fiIter cake precoat. The liquid con-
tinues to be circulated in the closed loop until a sight glass
45, positioned in the discharge line to the upper filter inlet
manifold 26, appears completely cleaned and polished indicat-
ing that all of the filter aid material has been removed from
the liquid and collected on the filter septum to :form a com-
plete filter precoat on the filter elements 160.
When the fil-ter septum 168 of the filter elements 160 have
been precoated, the influent pump 21 is energized and the pneu-
matically controlled valve 22 opens delivering liquid in:Eluent
through inlet 20. Since the liquid level in the precoat tank
210 is at the desired level from the precoating phase cycle of
operation, the pneumatically controlled valve 33 is closed by
operation of the liquid level controllers 212. Precoat pump
213 is deenergized, valve 32 is closed and the valve associated
with the filter outlet 40 is opened to allow filtrate to be re-
moved from the fiIter chamber 110.
After precoating has been completed and in order to main-
tain the integrity of the precoat on the filter septum 168, the
filter pump 24 is energized during a ini~ial portion of the fil-
tration cycle to maintain a sufficient pressure differential
across the filter cake to prevent the filter cake from slipping
on the fiIter septum 168. In order to main~ain this increased
flow rate, the pneumatically controlled valve 31 is opened al-
lowing the filtrate which passes through the filter elements
13-
160 to be recircula-ted to filtrate discharge line 30, recircula-
tion line 3~, and back into influent inlet line 23 to be deliv-
ered to the filter pump 24 for return into the filter chamber
110. the unclarified liquid passing through the inlet 20 into
the influent inlet line 23 is joined by the recirculating fil-
trate from recirculation line 34 and the serial connection of
the influent pump 21 and the filter pump 24 maintains a higher
rate of flow through the filter elements 160 in order to main-
tain a predetermined pressure di:fferential across the filter
cake of the filter elements 160. As the unclarified influentis passed through the filter elemen-ts 160 the pressure across
the filter elements increases due to the removal of materials
from the influent which accumu.late on or in the filter cake.
After a predetermined amount of accumulants are entrained
in or on the filter cake, a pressure differential is created be-
tween he pneumatically controlled valves 31 and 22. If this
pressure differential were allowed to increase sufficiently, a
back flow of unclarified liquid could enter the filter outlet
housing 109 through he pneumatically controlled valve 31 in the
recirculation line 34. Therefore, when the pressure across the
fiIter elements 160 reaches a predetermined point, a pressure
sensitive switch 61 is ac-tivated to close the pneumatically con-
trolled valve 31 to prevent any unclarified liguid from flowing
up the recirculation line 34 into the filter outlet housing
109. The closing of pressure switch 61 also terminates oper-
ation of the filter pump 24 so that filtration will proceed at
the flow rate determined by the inlet or influent pump 21.
Filtration then continues until such tirne as the pressure
drops across the filter elements 160 rises to a level deter~-
mined by pressure responsive switch 62 which is actuated in re-
sponse to the pressure inclicatecl on a pressure gauge 63. When
such pressure is reached, the filtration cycle is in-terrupted
in order to drain the contents from the filter chamber 110,
clean the expended filter cake and accumulants from the filter
elements 160, and discharge the solids materials from the fil-
ter chamber 110 in preparation for precoating the cleaned fil-
ter septum 168 and automatically returning the filtration
sys-tem for further filtration operation.
As solids materials are separated from the influent and ac-
cumulate on the septum supported filter cake and dissolved gas-
eous materials are adsorbed by the filter cake material, theseaccumulants increase the pressure differential across the fil-
ter elements until such time as the filter cake is expended and
the accurnulants rnus-t be removed from the filter elements 160 in
order to continue efficient filtration of the influent. When
the fiItration phase cycle of operation is ended due to expend-
ing the filter cal<e, the influent pump 21 and filter pump 24
are deenergized and influent valve 22 is closed, the filter
drain pump 120 is actuated and normally closed pneumatically
controlled valves 119 and 129 are opened for draining the en-
tire liquid contents of the filter chamber 110. The contentsof the filter chamber 110 may be pumped to a holding tank for
introduction back into the influent line or into any other sui-t-
able reservoir.
In order to prevent the filter cake from slipping during
draining, the drain pump 120 must be sized sufficiently to cre-
ate a pressure differential across the filter elements 160 to
compress the expended filter cake into the filter septum 16~.
Vacuum breakers 65 are provided on the fiIter chamber 110 to
permit -the rapid withdrawal of the contents of the filter
chamber to create this pressure differentialt The liquid con-
tained in the chamber is drained through the trough 112 and
-15-
"~,..~,
through a filtrate drain line 128 which is connected between
the filter outlet housin~ 109 and the drain line ll8 with the
pneumatically controlled valve 129 positioned therebetween.
Liquid passing through the filter elements 160 into the filter
outlet housing 109 passes through he pneuma-tically controlled
valve 129 carried in the filtrate drain line 128 and is passed
into the drain line 118. The liquid contained in the filter
chamber 110 which is not passed through the filter elements 160
is drained through the drain line 118 which is in fluid communi-
cation with the trough 112. During this drain sequence, allvalves are automatically closed except the two drain valves 119
and 129. When the contents of the fiIter chamber 110 have been
drained9 valves 119 and 129 are closed and an air injection
valve 66 and the filter outlet valve l~0 are opened allowing air
or other gas to enter and pressurize the filter chamber 110
driving any liquid entrapped in the filter cake out -through -the
filter cake into the filter tube 162 and thereby drying the fil-
ter cake material to obtain additional fiItrate product recov-
ery and to maximize the filter cake dryness prior to rernoval
from the filter septum 168 and discharge frorn the filter cham-
ber 110.
When the contents of the filter chamber 110 have been
drained and the pressurized air introduced into the chamber 110
has driven the residual liquid through the filter cake, the fil-
ter cake is compressed on the septum, dried, and ready to be re-
moved from the filter chamber 110. The filter drive motor 165
is energized, rotating the filter tube 162 and the filter ele-
ments 160 against the stationary brush or wipers 180. Rotation
of the filter elements 160 against the wipers 180 will cause
the expended filter cake and accumulants to be removed from the
fiIter septum 168 and dropped downwardly into the -trough 112
-16-
~ .~
whereat the rotating auger 113 will convey these materials form
the filter chamber 110.
In order to assure complete discharge of the filter cake
and accumulants and to avoid any buiIdup in the transition area
between the cylinclrical filter chamber 110 and the trough por-
tion 112, vibratory side plates 145 are supported from a por-
tion of the filter chamber 110 such that the materials removed
from the fiIter septum 168 will fall onto the vibratory side
plates 145 which, through a vibratory action, will convey the
material downwardly into the trough ll2 for removal by the au-
ger 113. As the discharge auger 113 is rotated, the expended
filter cal<e material and accumulants are conveyed outwardly
form the filter chamber 110 throu~h a pneumatically controlled
butterfly valve 117 for disposal. After a predetermined time
period when the materials have been removed, the filter drive
motor 165 and the discharge auger drive motor 115 are deener-
gized and butterfly valve 117 is closed.
When the expended filter cake and accumulants are dis-
charged from he filter chamber 10, a certain amount of liquid
loss occurs which causes the liquid level in the precoat tank
210 to lower. When this occurs the tank is filled to the prop-
er level by the actuation of the liquid level control 211 which
opens valve 33 to allow enough filtrate to enter through liquid
make-up line 36 to raise the liquid level in the precoat tank
210 to the desired level determined by controller 212.
It has been found that when the expended filter cake and
accumulants are in a semi-dry state, the wipers lgO positioned
between each filter element 160 do not completely clean the fil-
ter septum 16g sufficiently for use in some applications such
as in edible oil processing. Therefore, after the filter cham-
ber 110 has been errlptied of the solids materials and the dis-
-17-
charge operation terminated, the filter chamber 110 is again
filled with liquid. This refilling may be done by reintrodue-
ing the liquid which has been previously drained from the
filter chamber 110 into a holding tank, or it may be done by
energizing the influent pump 21 and the filter pump 24 to in-
troduce influent through inlet 20 to fill -the filter chamber
llO with influent in the manner previously described.
After a predetermined tirne period to insure that the fil-
ter chamber 110 has been completely filled, the inlet pump 21
and fil-ter pump 2~ are stopped and the filter drive motor 165
is energized. The filter elements 160 are rotated against the
stationary wipers 180 to achieve a thorough cleaning of the sep-
tum 168 by scrubbing the septum against the wipers 180 while im-
mersed in the liquid contained in the filter chamber 110.
After a predetermined time period the filter drive mo-tor 165 is
deenergized and the filtration system is now ready to again en-
ter the precoat phase cycle of operation previously described.
While the invention has been described with reference to a
preferred embodiment, it will be understood by those skilled in
the art that various changes may be made and equivalents may be
substituted for components thereof without departing frorn the
scope of the invention. In addition, many modiEications may be
made to adapt a particular situation or material to the teach-
ings of the invention without departing from the essential
scope thereof. Therefore, it is intended that the invention
not be limited to the particular embodiment disclosed as the
best mode contemplated for carrying out this invention, but
tha-t the invention will include all embodiments falling within
the scope of the appended claims.
-I ~-
~.
