Note: Descriptions are shown in the official language in which they were submitted.
1~ )3
BACKGROUND OF THE INVENTION
1. Field of the ~nvention
This invention related to the removal of solids
from an organic liquid by using electrical fields. The
invention more particularly rela-tes to the removal from
organic liquids of solids by their induced adherence upon
a particulate bed under the action oE d.c. electrical
fields.
2. Description oE the Prior Art
Non--petroleum organic liquids include fats,
vegetable and animal oils which may be used for human
consumption~ but are no-t necessarily limited to such
utilization. These organic li~uids can be purified by
removing solids to improve chemical properties, color and ~.
visual appearance, and for other reasons. In one example,
the hydrogenation of edible oils for preparing more suitable
products.for human consumption has been known for nearly
one hundred years. The modern hydrogenation process for
edible oils originated in research work conducted at the turn
of this century. In this process, the edible oils, such as
cottonseed, soybean, and corn oil, are placed within a reaction
vessel (commonly termed a "converter") and brought into
contact with hydrogen at elevated temperature and pressure in
the presence of a small amount of metal hydrogenation catalyst.
bm.~
; . .; ,. ;, ,
:- , . : .~ :. - . ~, ., . : ~ .
, .. ..
~O~gO3
For example, the catalyst is usually present in s~all amounts
which may range ~ro~l .01% to about 0.5% by wei~ht based upon
the total weight of the edible oils subjected to h~drogenation.
Various types of hydrogenation catalysts, such as copper
chromite, are known for providiny the reaction between hydrogen
and the edible oil. For example, one commercial hydrogenation
catalyst includes the metal nicke:l as the principal catalytic
agent, but it also may have minor amounts of copper, alumina,
or other materials. The metal hydrogenation catalysts are
employed principally in a finely deEined divided form and are
prepared by special methods. Commonly, the nickel me-tal is
placed upon a finely divided, highly porous, inert refractory
material, such as diatomaceous earth, or other highly siliceous
material. The cat~lys-t is suspended in the edible oils during
the hydrogenation process as oil-coated insert solids, which
may adsorb soaps or other impurities found in the oil. After
the hydrogenation reaction is completed to the desired degree,
~he hydrogenation reaction materials are removed from the
converter. Then, these materials are passed through a
filtration system for removing the inorganic solids from the
hydrGgenated edible oil product.
Various inorganic materials are added to the
hydrogenated edible oil product to enhance its filterability.
Filteraids usually are employed to promote the product
filtration procedure. Various types of relatively so~histicated
and expensive filtration equipment are employed. Generally,
pressurized filter press assemblies are used, in parallel flow
arrangements, to pass the product through a multitude of
filter elements which may comprise screen supports carrying
~,~, ~ .
- .x
-2
bm:'~
1)9~3
paper, canvas or other types of filter medium. These filter
elements may be precoa-ted with some type of diatomaceous earth
or filteraid to improve oil ~ilterabili-ty. The hydrogenated
edible oil pro~uct is passed through these filters to remove
as much as possible of the hydrogenation catalyst material and
other inorganic solids materials. However, the fllters canno-t
remove substantially all of the inorganlc solids. ~dditionally~
the filters pass decreasin~ amounts of inorc~anic solids as the
filtration procedure progresses to~ards an ultimate removal
level.
~ he edible oil industry employs two basic tests to
determine the effectiveness of filtration on a hydrogenated
edible oil product. In one test, a pound of the edible oil is
passed through a filter disc at regulated physical conditions
of temperature and time. The filter disc retains impurities
above a certain size magnitude leaving a "dark spot" which is
compared to a standard set of filter discs The test is known
as the 'IFilter Disc Impurities Test"~ The standard discs are
numbered 1 through 10, with number 10 being that disc which
shows no change in "color" over the unused filter disc. Another
test is the analysis of the edible oil for nickel content. The
filtration procedure produces an edible oil with from one to
several parts per million (ppm) of nickel content For consumer
acceptance and long term storage and other reasons, the nickel
content is preferred to be iess than 1 ppm of nickel.
Mechanical filtra-tion equipment employed in the edible
oil industry usually passes some solids during the filtration
procedure. As an example, the edible oil product has a color of
relatively low value, e.g., ~ at the beginning of filtration~
bm~
.- ~
,: ~ .. .
,, ~ : ., , .. ~:
- : , : . -
9~3
but then its color test rapidly improves towards a filter disc
color of 9 or better. For this reason, the fil-ter equipmen-t
cannot produce throughout the edible oil filterecl product a
~ilter disc color of 9 or be-tter.
The filtered edible o:il, a-t eleva-ted -temperatures, is
subjected to additional treating steps which may include
treatment with bleaching earth, phosphoric or citric acid or
other metal scavengersr with the addition oE fll-teraids, so
that the finely divlded resldual inorganic catalyst and other
solids are removed. The edlble oil accep-ted by consumers must
have a color of ~ or better. Thus~ filtration or o-ther color
improvement procedures are employed with each edible oil
subjected to the hydrogenation. Substantial time elapses in
these procedures and subjects the edible oils to aging. The
procedures are practiced until the edible oil has a filter disc
color of 9 or better~ and residual hydrogenation catalyst sblids,
and possibly colloidal nickel metal, is at an acceptable low
value
Nearly forty years ago, it was purposed to purify
edible oils by adding a small amount of a loader-type solids,
such as "10% activated clay" in a finely divided admixture to
the edible oil This mixture was then flowed horizon-tally in a
zigzag path between closely spaced electrodes which were
energized to elevated potentials~ The impurities and the loader
solids were to migrate to one or the o-ther electrodes for -their
removal from the edible oil Accumulated solids might "drop off"
after reaching a certain thickness on the electrodes or they
could be removed by interrupting or reversing the current.
Mechanical removal of the solids from the electrodes could
~ I .
4 bm~
~o9v~
also be used. Unfortunately, the unpacked dielectric zone
between the electrodes will not remove substantially all of
the impurities from the edible oil. One reason for this result
may be that the elec-tric field cannot be made o:E sufficient
intensity even with closely spaced electrodes that substantially
all of the inorganic solids could be removed from the edible
oils, Some solids pass through the spaces between the electrodes
without being attracted to them Eor removal from the edible oil,
It has been proposed :Eor nearly as many years to
employ electro~iltration systems for removing inorgan:ic and
organic solids from dielectric natural and petroleum oils.
For this purpose, the dielectric oil carrying the solids is
passed through a particulate material within an elevated d.c~
electric potential field. The d c. field can have potentials
of between 5 to 200 kilovolts established across the bed. The
bed might be composed of particles of materials such as furnace
slag, sand, gravel, limestone, crushed glass, glass bead,
ceramics palletized clay, and like solid materials. Various
types of electroae arrangements have been advocated for providing
the high voltage d.c electrical field for these electrofilter
aevices~ The electrofilter devices, which have been known in
the past, have been highly effective for removing inorganic :~
solids from dielectric liquids such as the hydrocarbon products
of cruae oil refining~ Unfortunately, these electrofilters are
very effective in attracting solids to the particulate bed
materials. These removed solids adhere very strongly to the bed
material even with the d.c. electric field remove~ from the
electrofilter device. Once the bed is subject to a solids-fillup,
substantial changes in electrical conductivity occur which induce
-S-
bm~
.: - .. ~ . .
. -, ~ . -
~Q L)~3~)3
arcing in many instances, Arcing can produce a sudden releaseof solids into the dielectric liquid! Then, the bed must be
cleaned before being reused.
The tenacious adherence of inorganic solids upon the
particulate bed of electrofilters has required special techniques
for regeneration, Example may be taken to U.S. Pa-ten-ts 3,39~067,
3,799,855, 3,799,856, and 3~799,~57 for illustrat:Lons of various
types of practical and commercial bed cleanup systems. These
patents describe cleanup procedures which produced a very hiyh
mechanical agita-tion between the particles of the electrofilter
bed for mechanically removing adhering inorganic solids.
Naturally, high levels of mechanical contact between these
particles cause abrasion and could result in a small amount of
abraded particle material being released from the bed, As a
result, the bed would hav`e to be scrupulously cleaned of the
small fragmented portions of the particulate material unless
these residues were not critical to the dielec-tric liquid being
treated. In the electrofiltration purification of hydrocarbon
materials, such as distillates and residual streams or inorganic
materials, a small amount of residue from abraded particulate
bed material would not be a problem, However, these abraded
materials are intolerable in edible oils,
The prior art has included proposals to employ
electrofiltration for purification of various types of
dielectric organic liquids for about four decades~ However, no
electrofilter device has produced the purfication of organic
liquids which contain finely-divided inorganic and organic solids
for several impor-tant reasons. In the first instance, the
electrofilter equipment must eEfect complete removal from solids
without either an unaccep-table pressure buildup or deleterious
-6-
~- I
bm~
~ . , . . . ~ . - . ;
)3
change in electrical characteristics inducing arcing, shor-ting
and like problems. In the second instance, the electrofilter
must be capable of h~ndlin~ effectively the organic liquid
stream containlng widely varying amoun-ts of solids. In -the
third instance, the electrofilter system must contain a
particulate bed material of special characteris-tics so tha-t (1
the organic liquid product is produced with extremely low
amount of residual solids, without undue pressure buildup or
arcing, (2) the particula-te bed material is readily cleaned of
adhering solids/ and ~3) no abrasion or loss of the particula-te
bed material itself occurs to contaminate the organic liquid.
The foregoing reasons summarize the incapability of prior art
electrofiltration system in being used in the purification of
organic liquids containing finely divided solids,
The present invention is an electrofiltration system
for purifying organic liquids by removal of finely-divided solids
without the foregoing recited problems of prior art electrofilters~-
In particular, the present invention is a novel electrofilter,
electrofiltration process, and organic liquid product. A
selected material in the bed of the electrofilter system produces
a substantially complete removal of the solids, irrespective
of the solids loading content, and without the electrofilter
system having any appreciable pressure buildup or electrical
arcing in the bed. The bed is chemically inert, and no
contamination of the organic liquid stream occurs in use. The cleaning of
the bed of accumulated soIids is not complicated and produces an environment
for continuous and repeated elec~^ofiltration for producing a product
organic liquid equal in physical and chemical charac-teristics to ccmmercial
product prepQred by extended time! multistep p~ocedures Additional fea-tures
-of the present invention will be appreciated from the-following description.
~, - -
~ 7-
-
. , . . . - ~ , , : : - .
- ' ': ;~ , ;
39(~3
SUM~IARY OF THE INVENTION
In accordance with this invention, there is provided an
electrofiltration system, including apparatus, process, and
product, for the purification of an organic liquid stream of
high resistivity. In particular, the organic liquid gtream~
at suitablP temperature, is passed through a chemically inert
bed having multitudinous flow channels between rigid masses of
a solid material having a dielectric constant not in excess of
about 7. A d.c. electric field within the bed provides a
sufficient intensity for removing solids from the organic
liquid stream by the electrically induced adhesion oE the solids
on the material to provide a purified organic liquid stream
removed to a subsequent utilization. The bed material, at
least in part, is selectively cleaned of adhering solids by
interruption of the electrical field, passing a cleaning fluid
through the material to remove adhering solids, and then removing
the fluid with the removed solids from the material being cleaned.
In a preferred embodiment, the purified organic liquid stream
is monitored to provide an indicating signal when to undertake
the selective cleaning of the bed material. The purified
organic liquid stream is a novel product, quickly prepared
- without aging, and having comparable chemical and physical
properties to conventional multistep treated commercial product.
In one particular aspect the present application, which is
a division of copending Canadian Application No. 266,570, filed
November 25, 1976, is concerned with the provision of an
electrofiltration process for removing hydrogenation catalyst
- and other undissolved solids from a stream of edible oil which
~ has been subjected to catalytic hydrogenation,-&~ process
comprising:
j 1/ ~` `` --8-
.: . : : . :: ~- -
V3
(a) providing the stream of so hydrogenat~d edible oil
at a sufficient temperature that organic solids such as
stearine are in solution and cannot plug an electrofilter bed
adapted to remo~e the undissolved solids carried therein;
~b) passing said stream of oil through a chemically inert
bed having multitudinous flow channels between rigid masses of
a solid material having a dielectric constant not in excess of
about 7;
(c) establishing a d.c. electrical Eield within said bed
havlng an intensity sufEicient of removing the undissolved
solids from said stream of oil by electrically induced adhesion
of the solids in said bed material;
(d) removing the purified oil stream with reduced
undissolved solids content from said bed; and
(e) cleaning at selected intervals at least a portion of
said material of adhering solids by interruption of said
r o, u ~ ~ ~ h ~ J Q /
electrical field~ passing a cleaning fluid~to remove adhering
solids from said material and removing the fluid with the
removed solids from said material. '
In another particular aspect the present application, which
is a division of copending Canadian Application No. 266,570,
filed November 25, 1976, is concerned with the provision of an
electrofiltration process for removing solids from an organic
liquid stream comprising:
~a) passing said liquid stream through a bed of chemically
inert, hard granular particles of a rigid, substantially
incompressible material, said particles being non-spheroidal
with a relatively discontinuous surface configuration and a
dielectric constant not in excess of about 7;
~ 8a-
- . :, . . .
09~3
(b) establishing a d.c. electrical field within
said bed haviny an intensi,ty sufficient for removing the
solids from the organic liquid stream by electrically incluced
adhesion of t.he solids on said particles;
(c) removing the purifled'organic liquid stream
with reduced solids content from saicl bed; and
(d) cleaning at selected intervals at least a portion
of said particles of adhe~ing solids by interruptincJ said
electrical field, passing a cleaning fluid through the bed to
remove adhe.rin~ solids from said particles and re~loving the
fluid with the removed solids from.said particles being clearled.
In a further particular aspect the present application,
which is a divisional of copending Canadian Application No.
266,570, filed November 25, 1976, is concerned with the
provislon of an electrofi,ltration process for removing
hydrogenation catalyst and other undissolved solids from
a stream of edible oil which has been subjected to catalytic
hydrogenation, said process comprising:
(a) providing the stream of so hydrogenated edible
oil at a sufficient temperature that organic solids such as
~ 8b-
bm~
. . : , :, , ~
,. : -
. :; .: . .
~0~03
stearine are in solution and cannot plug an electrofilter
bed adapted to remove the undissolved solids carried therein;
(b) passing said stream of oil through a
chemically inert bed having multitudinous flow channels
between rigid masses of a solid material having a dlelectric
constant not in excess of about 7;
~ c) establishing a d.c~ electrical field within
said bed having an intensity suficient for removing the
undissolved solids from said stream oE oil by electrically
induced adhesion of the solids in said bed material; and
(d) xemoving the purified oil stream with reduced
undissolved solids content from said bed.
DESCRIPTION OF THE DRAWINGS
Figure 1 is a diagrammatical illustration, in flow
schematic, of the present electrofilter system applied to a
prior art
-8c-
bm~
'~
~0()903
hydrogenation plant for producing edible oil as an exarnple of
an organic liquid;
Figure 2 is a vertical cross-section illustrating the
construction of the electrofilter sho~n in the system of
Figure l; and
jl/,'`l-, -8d-
:.::., ., : .
. -: ~ , , ,;
: . :: .::
' :. :- ' :~' ' - :
)9~3
Figure 3 is a graphic comparison of several bed
materials employea in the electrofilter of Figure 1 and a
typical mechanical filtration relative to the Eilter disc
impurities color of an edible oil puri.fied in the present
electrofiltration system~
D~SCRIPTION OF SP~CIFIC EMBODIMENTS
The present electro~il-ter system will he described
in the purification of one type oE organic liquid, namely,
an edible oil. However, it will be apprecia-ted -that the
invention is equally applicable and o:E utili-ty with other
-types of organic liquids, e~g~, fa-ts, animal and veyetable ~A
oils. Referring now to Figure l, there is shown an embodiment
of the present electrofilter system associated with an
appropriate portion of a prior art hydrogenation plant, wherein
edible oils are contacted with hydrogen at elevated tempera-ture
and pressure in the presence of a finely-divided catalytic
- material~ More particularly, the hydrogenation plant is
enclosed within the chainline 12 with the designation of prior
art being applied as an example o-f commercial operations~
An edible oil, such as soybean oil, is brought from storage
through an inlet conduit 13 and a heat exchanger 14 directly
into the hydrogenation converter 16. The hea-t exchanger 14
- raises the temperature of the edible oil to a suitable level,
e.g., above 250 F. The converter 16 is a steel vessel
usually with an upright axis which contains the charge of
edible oil to be hydrogenated~ The edible oil in the
converter is admixed with a suitable amount of metal catalyst.
In most instances, a dia-tomaceous earth or a filteraid
material is intermixed with the catalyst iTI suitable
bm~
.:
- . , ' :
.
:
~0~)9~3
proportions with an edible oil carrier in the catalyst mix
tank 17. Then, this mixture is displaced by pump 18
through a control valve 19 into the converter 16. The
converter 16 usually has an internal mixer arrangement for
maintaining a suspension o:E the catalyst materials within
the edible oil. Hydrogen is added to the converter 16. The
hydrogenation reaction ta~es place over a suitable length
of time, such as one hour, depending upon the mass of edible
oil charge and the des:ired hydrogenation degree to be produced
in t~e edible oil product,
The converter 16 may be of any suitable size. For
description, the converter 16 will receive an edible oil
charge of about 40,000 pounds, and the hydrogenation catalyst
material is of the nickel metal variety, which is introduced
to a suitable concentration of between ~01 and ,5 percent by
weight. The nickel catalyst is approximately 25% by weight
of nickel with the remainder being Kieselguhr or other
diatomaceous earth material,
After the hydrogenation reaction is completed~ the
contents of the converter 16 are moved through the valve 21
into a drop tank 22 where the hydrogenated edible oil product
is held while being.processed for the removal of the finely-
divided hydrogenation catalyst and other inorganic solids.
Presently, the contents of the drop tank 22 are moved
through a control valve 23 by centrifugal pump 24~ an optional
heat exchanger 26, and through a piping loop con-taining
several control valves to the inlet 27 of the filter press 28.
The filter press is conventional with a plurality of filter
elements, The filtered edible oil is removed from the filter
bm:
, ~ ;. . -
... .
~00903
press 2~ throu~h the outlets 29 or 31 dependlng upon whether
the sections are operated in parallel or in separate
sections. The outlets 2~ and 31 connect to a filtere* edible
oil line 32 for directing this stream to subsequent processing
for the removal of res.idual amounts of the hydrogenation
catalyst and other inorganic solids.
For example, the filtered edible oil in the line 32
may contain about several parts per million of nickel metal
(suspended and colloidal) so as to have a pronounced green-
to-black colo.r, and several parts per million of lnorganic
solids, such as filteraid, and a filter disc color of 6 or
worse. Thus, the filter press 2~ cannot produce an acceptable
edible oil product that could be used for human consumption
The filtered edible oil in line 32 now usually is subjected
to additional processing steps. One step is treatment with
citric acid or phosphoric acid and a filteraid material, and
filtration to remove the chelated hydrogenation catalyst.
Another step is a bleaching operation wherein a small amount
of bleaching clay is added to the edible oil, and then
filtered to provide the edible oil product. The edible oil
product after one or more of these steps is an edible oil
product directly suitable for consumer use Sometimes, this
product is subjected also to a winterizing and/or deodorizing
step to produce certain types of edible oils.
In the present invention, all mechanical filtration
steps are avoided. The hydrogenated edible oil in the drop
tank 22 is passed through the novel electrofilter system of
the present invention . Referring specifically to that portion
of Figure 1 outside the chainline 12, the edible oil from the
bm:~
- : . -. ~
". ,. ~,
,
.
. .
03
drop tank 22 is diverted through the block valve 33 in-to a
raw oil line 34. The edible oil in the line 34, by use of
the heat ex~hanger 26, is adjus-ted in temperature, usually
above 150 F., so that organic solids, such as stearine,
are in total solution in the edible oil stream and cannot
plug the electrofilter. The line 34 connects in-to an inlet
manifold 36 associated with the electroE~ ter 37. The
manifold 36 h~s a plurality o~ motor control valves 35, 38,
and 39, whose functions will be hereinafter described. With
this arrangement o~ the inlet mani~old 36, the edible oil is
passed upwardly through the electrofilter 37 and removed
through the outlet manifold 42 which includes motor control
valves 43 and 44. However~ it may be desired to have the
edible oil passed downwardly through the electrofilter 37
and the-functions of the inlet and outlet manifolds would then
be reversed. The piping for the present system is arranged
for this purpose as will be appreciated by examination of
the respective manifolds and their connections in-to the
system shown in Figure 1,
- The electrofilter 37 is arranged so that substantially
all of the solids, including the hydrogenation catalyst,
filteraid, dia-tomaceous earth, etc., and any insoluble organic
solids, are removed from the edible oil stream The
electrofilter 37 has a selected bed forming an inner electrode
space subjected to a high intensity d.c. electric field for
removing substantially all of these solids from the edible
oil. The purified edible oil stream is removed through a
product line 46 and a three-way control valve 47 into an
edible oil product conduit 48 for removal to a subsequent
-12-
bm:
- : . . .. :
.... , ,~ . , : - ~
, . ~ .; . . , ,:
~iO0~(~3
utilization~ Preferably, the edible oil product line ~6
includes a moni~or of the purified edible oil product ~rom
the electrofilter 37 to detexmine the approach of a suddenly
increased solids content which occurs on the approach of
solids-fillup in the bed of the electrofilter 37.
The present invention involves the selection of
a certain type of material :Eormin~ -the bed o~ the electro-
filter 37. The bed is chemically inert and has multitudinou.s
flow channels between rigid masses of a solid material. The bcd
material should havc a dielec-tric constant no-t in excess of
about 7. The bed material should have sufficient rigidity
so that in operation it cannot be compressed in a degree to
reduce the flow channels, thereby producing an unacceptable
pressure drop across the bed.
One of the cha.racteristics of the electrofil-ter 37
with this selected bed is that substan-tially all of the solids,
including even colloidal nickel and filteraid materials, are
removed .rom all the edible oil passing into the product line
~6, and this purity is maintained until the bed has accumulated
its capacit~ of removed solids as the solids-fillup condition :~
is approached. As this solids-fillup condition is approached
- in the bed of the electrofilter 37~ no significant changes
occur in the electrical parameters or measurable physical
operation conditions concerning the electrofilter~ However,
there is a sudden increase in the solids content of the trea~ed
edible oil. More particulaxly, -the pressure drop across the
eletrof.ilter 37 is small and does not change within -the
measurement error of conventional pressure gauges. In addition,
no significant change in electrical parame-ters, voltage or
~r 1 3
! bm:~
. , : ' ,
~ .
~1~0~(~3
current, occurs in the high vol~age el~c-tric field imposed
upon the bed within the electrofilter 37~ These phenomena of
the electrofil-ter 37 are more appar~nt from -the following
discussion of the preferred design and operation of ~he
elec-trofilter 37.
The edible oil treated in the electrofilter 37 enters
the product line 46 in such a completely puriEied form,
relatively free oE inor~anic solids, colloidal me-tals, etc~,
that it has a unique appearance classified by experienced
workers in the food indus-try as "br:ight and clear" in
appearance. Edible oil of -this bri~ht and clear appearance
has a filter disc impurity number generally of about 10~
The reason for this unexpected product result is not completely
understood except that the electrofilter 37 produces
substantially complete removal of nickel catalyst, colloidal
nickel, and other solids from the edible oil, In addition,
the electrofilter 37 maintains the production of outstanding
edible oil product unitl the solids-fillup condition of the
bed of the electrofilter 37 is reached. Only at this solids-
fillup condition does the edible oil entering the outletmanifold 42 rapidly deteriorate towards the proper-ties of
the raw edible oil flow in the line 34 from the drop tanic 22,
As a result, the electrofilter 37 for maximum
efficiency and best operation requires a mechanism to predict
the onset of this rapid deterioration in edible oil quality
when solids-fillup of the electrofiiter bed is reached. One
means of accomplishing this result is by a fixed time cleaning
cycle. Alternatively, the initial appearance of a small amount
of inorganic solids in the edible oil within the product line
-14-
=~ bm:~
... ..
9(93
46 can be detected as solids-fillup condition is approached,
l~hen the electrofilter 37 is operating satisfactorily, the
edible oil in product line 4~ is bright and clear in
appearance and also shows no Tyndall effect~ At the very
onset of solids-*illup in the bed of the electrofilter 37,
a slight Tyndall effect occurs in the edible oil, If desired,
a sight glass 49 is placed in the product line 46 to de-tect
this Tyndall effect. A narrow beam, high intensity light,
throu~h the sight glass 49 displays the occurrence of the
Tyndall effect. At this t:ime~ the electrofilter 37 is
"shu~ down" for a selective cleaning of the bed by the through
removal of adhering inorganic solids.
If desired, the monitoring of the edible oil stream
for the occurrence of increased solids content can be
undertaken by a monitor 51, including an optical cell 52 in
the product line 46, to provide an output signal 53, The
- monitor 51 may be a nephalometer. The output signal can give
a visual or arcual indication to an operator. Preferably,
the output signal is adapted to adjust the various valves and
other switching functions for cleaning the electrofilter 37
The controller 54 upon receipt of the output signal can provide
a plurality of output signals 56 to operate the various control
valves associated with the elec-trofilter 37t conduct the
stepwise sequence of cleaning steps in the electrofilter 37,
and control the operation of a high voltage power supply 40
which is associated with the electrofilter 37. The controller
54 may be convenient and employ either pneumatic or electrical
control signals 56 in the necessary sequencing functions for
the desired control of the various elements associated with
~ -15-
- `' bm ',l
.
V~
the electrofilter 37. The d.c. electrical field in the
electrofil-ter 37 is removed from the bed material Eor the
cleaning process.
The bed material in the electrofilter 37 is cleaned
at least in par-t, but preferably in its entirety by use oE
a cleaning fluid. Also, the bed material may be cleaned in
place, externally or in any manner whexein -the cleaning fluid
flow removes solids Erom the material. If desired, the
cleanillg Eluid rna~ be a portion of the raw edible oil in line
3~ -taken from the drop tank 22. In other instances, it may
be desired to use other fluids -Eor cleaning -the bed material
of the electrofilter, such as edible oil product taken from
the conduit 48. The cleaning fluid can be used in a single
pass mode but preferably is recirculated in the cleaning
process. In one example, edible oil as a cleaning fluid is
placed into the charge tank 57 wherein its temperature can be
elevated as desired by use of a steam heating system 58.
Then, the pump 59 moves the edible oil through the cleaning
line 61, and with the block valve 62 in a closed position,
the edible oil flows into the inlet manifold 36 to pass
upwardly through the electrofilter 37 into the outlet
manifold 42. The circulating edible oil returns in the line
46 through the three-way valve 47, the return conduit 63
through block valve 64 and then into the charge tank 57.
However, the electrofil-ter may be also cleaned with downflowing
edible oil. The circulating flow through the cleaning the
line 61 of edible oil is adjusted in rate so that the bed of
electrofilter 37 is only sllghtly expanded but no-t displaced
or mechanically abraided in the absence of the d.c. electric
field. The edible oil in the charge tank 57 containing the
-16-
bm:~
: ' ' : -: . . ~ : : . i: `
. i . . ` ': : '
.: ' `'' , ~ ' , : :` .
- .,. - ` ` ~: :: ."
9qP3
removed solids can be passed through the filter press 28
-for recovery of the edible oil which may then be recycled
throu~h line 34 and the electrofilter 37. Al~ernatively,
this mixture of edible oil and solids inclu~ing catalyst
may be recycled into the converter 16 Eor reuse.
Preferably, the cleaning process is carried out
in the electrofilter 37 by first terminating the E:Low through
the line 34 of the edible oil Erom the drop tank 22. Then,
the valved manifolds are arranged so that a flow of nitorgen
from the line 66 is passed clownwardly through the electrofil-ter
37 to displace the residual liquid volume of purified edible
oil into the produc-t line 46 and through the valve 47 into
the edible oil conduit ~8. In this manner, the amoun-t of
"slippage" or recycle of purified edible oil is minimized
in the use of the electrofilter 37. As long as the power
supply 40 is energized and an electric field exists in the
bed material of the electrofilter 37, the adhering solids
will not be displaced from the bed by the flow of nitrogen.
Then, the flow of nitrogen through line 66 is terminated and
the power supply 40 is de-energized. The cleaning fluid can
now be circulated through the electrofilter 37 as previously
described.
The volume of the circulating cleaning :cluid is
not as critical as the flow rate through the bed of the
electrofilter 37 which will usually be in the range of at
least 16 inches per minute super-ficial velocity through the
bed material. Under those condi-tions, -the volume of
recirculating cleaning fluid may be as small as three times
the liquid volumetric capacity of the electrofilter 37. The
-17
_ .,~ I
bm;i~
::- :, : - ,
~0~99~3
optical properties of the cleaning fluicl and entxained solids
flowing through th.e line 46 can be employed to determine when
ultimate cleaning of the bed material has cccurred since solids
amounts become constan-t. For example, the monitor 51 reaches
a peak reading of opacity which indicates the encl of the
eleaning eycle. At this time, the cleaning fluid is removed
from the electrofilter 37 by switchin~ the necessary valves
to be displaced by the ineoming edible oil in line 34.
Preferably, the cleaning fluid is cl.isplaced from -the eleetro-
filter 37 by a small ~uantity oE the edible oil produc-t from
the product line 46. Al.ternatively, nitrogen :is applied
through line 66 (as previously deseribed) to displace the
liquid eontents of the eleetrofilter 37 downwardly through
the manifold 36 and into the various lines and conduits for
its recovery. Now, the bed material of the eleetrofilter :~
37 is elean and ean be returned to purification of the raw
edible oil in line 34. The power supply 40 is energized, the
valves adjusted to reinstate the operation of electrofilter 37,
and the flow of the edible oil through the eonduit 34 from
the drop tank 22 is resumed. Thus, the eleetrofilter 37
employs a selected bed material whieh not only produees
optimum cleaning of the edible oil, but also permits ready
eleaning of adhering solids.
The electrofilter 37 has a suitable construetion
whieh in one embodiment is illustrated in vertieal seetion in
Figure 2. The eleetrofilter 37 comprises an upright vessel 71
having inlet connections 72 connected to the inlet manifold
36 and an outlet distributor 73 eonnected to the outlet
manifold 42. Preferablyr the inlet 72 is provided by a
-18-
. ~ ,
~- bm~
9~)3
plurality of well screens 74 which are dimensioned so as to
prevent the passage of the material 76 comprisiny the bed 77.
Energized electrodes are positioned within the bed 77 and may
take any usual form. For example, an inlet bushing 78 extends
upwardly into the vessel 71 and carries a spider 79 on which
are mounted in a concentric arrangement an çnergized rod 81,
and metal cylinders 82, 83 and 84. Th~ rod 81 is connected
by a lead 86 to the power supply 40 so that the electrodes
carried on spider 79 are energiæed to a d.c. potential
relative to the grounded shell of the vessel 71. A similar
system of grounded concentric electrodes is suspended from
a spider 87 supported upon a mounting bracket 88 carried
about the internal perimetry of the vessel 71. Suspended from
the spider 87 in concentric relationship are a plurality of
cylindrical electrodes 89, 91, and 92. It will be apparent
that the concentric relationship of the energized and grounded
cylindrical electrodes provide for establishing an electrical
field within the bed 77. For example, the spacing between
the energized and grounded electrodes can be one inch with
a like spacing about the rod electrode 81 and to the internal
cylindrical surface of the metal shell of the vessel 71. With
this arrangement, the power supply 40 should provide at leas-t
20 kilovolts per inch d.c. electrical potential to lead 86.
Preferably, the power supply 40 provides a d.c. potential of
at least 40 kilovolts per inch within the bed 77. Excessive
high intensity potentials in the d.c. electric field within
the bed 77 should be avoided. Excessively high d.c. potentials
could lead to gas (hydrogen) ionization and arcing within the
electrofilter 37. The finely-divided solids carried in the
- --19-
bm ~
~, .-.
edible oil into the bed 77 axe acted upon by the d.c. electric
field which electrically induces the adhesion of these solids
onto the surfaces of particles 76. For practical purposes,
no solids can escape the bed 77 in the presence of the ~.c.
elec-tric field un-til the solids-fillup condition is reached.
The electrically in~uced adhesion of solids is so great a
force that a flow of nitrogen gas e~ual in rate to cleaning
fluid flows cannot remove them. However, removal of the d.c.
electxic field allows a simple washing of the bed to remove
completely these solids. The electrofilter 37 is a system
similar to known electrofilters haviny particulate materials
in their inner electrode spaces. However, the particular
selection of the particles ~6 forming the bed-77 of the present
electrofilter 37 produces an electrofilter system unique in apparatus and
process, and this system produces une~xcted purification of organic liquids,
such as oil streams, into a bright and clear product equal to
commercial products obtained by multistep filtration procedures.
More particularly, the bed 77 of the electrofilter 37
is preferably comprised of chemically inert, hard granular
particles of a rigid, and substantially incompressible
material. Furthermore, these particles are in the majority
non-spheroidal with a relatively discontinuous surEace
configuration and a dielectric constant not in excess of about
7 (at 1 kilohertz~. The term "non-spheroidal" is intended
to include by definition particles other than true spheres,
such as oval and other non-round shapes having minor to major
axes in ratios exceeding 4 to 6. By the terminology
"relatively discontinuous surface configuration" is meant a
surface that is not planar or unbroken such as the surface
-20-
~ .
~, bm ~
,- , ~ .
~0~03
of a glass be~cl, and p~rticularly included are multifaceted
particles haviny meeting edges be-tween multitudes o-f s~all
surfaces which may bé planar, concave, convex and combinations
thereof, regular or ixregular in arrangement.
The exact reason for the novel functioning of the
bed 77 in the electrofilter 37 cannot be determined with an
exact scientific definition. Ilowever, it is helieved that
the particularly selected particles 76 in conjunction with
the electrical characteristics of the organic liquids
(e.c3., edible oil) and the contaminating solids, such as the
metal hydrogenation catalyst and filteraid, interrelate to
prod~lce the novel results of the present invention. For
example, edible oils have a dielectric constant of about 3.5.
The diatomaceous earth carrier (Kieselguhr), the metal
hydrogenation catalyst, and filtera~d all have a dielectric
constant of about 4. The metal hydrogenation catalyst and
the filteraid materials have h~ghly developed pore surfaces
which appear to be completely saturated wi-th edible oil.
The particles 76 which are selected for the purpose of the
present invention also have a dielectric constant not greatly
in excess of about 7, and preferably below about 5. Thus,
all of the dielectric materials within the elec-trofilter 37
have very similar dielectric constantsr and all these materials
have extremely high resistivity (e.g., 1 x 10 ohm-cm) and
dielectric strength (e.g., above 10 kv, dc/mm). It is
believed that these dielectric properties permit the bed 77
to function exceptionally within the high intensity d.c.
e]ectric field for electrically inducing the tenaceous adhesion
of the solids, such as filteraid, to the par-ticles 76. However,
-21-
.~ ~, 1 1
5. bm,"~
, .
)9Q3
terminating the d.c. electric field within the bed 77 allows
the adhering s~lids to be easily removed by a relatively lo~
rate of flow of a cleaning fluid without disruption of th~
particles 76. For example, the elec-trofilter 37 will operate
to remove solids with a flow o:E 12 inches per minute super-
Eicial velocity of edible oil through the bed 77. However,
the particles 76 in the bed 77 are cleaned thoxoughly (wi.th
the d.c. electric field removed) at the flow rate of above
abou-t 1~ inches per minute super:Eicial velocity w;.th ed;.ble
oil as the cleanin~ flu~d. The bed 77 does not need to be
made turbulent or suffer particle movement, but pre:Eerably,
it merely expands slightly during the flow of cleaning fluid.
The particles 76 should be chemically inert and not
contamina-te the edible oil. The particles 76 should have a
relatively discontinuous surface configration in contrast to
a highly polished smooth surface such as glass bead or marble.
In addition, the particles 76 should have a relatively high
density or specific gravity and a substantial hardness
co~.pared to the solids which are to ~e removed. Par-ticles ;
selected for use in the present electrofiltration sys-tem are
preferably selected from materials in the group consisting
of a mineral containing crystalline silicon dioxide such as
flint, garnet, granite and fused quartz. These particles 76
selected from this mineral group have a hardness value of at
least 7 on the Mohs scale of ha.rdness, a specific gravity
between about 2.5 and about 2.9, a:dielectric constant of
about 4, and a discontinuous surface configuration provided
in nature. The particles 76 may range in size from about 1 mm
to about 13 mm for good results. A crushed flint with an
-22- -
- -.
-~s bm~
'~ , :.. ,.' .. ..
' ~.' ,,: ' : , , '
09~3
avera~e (50 percentile) particle size (smallest dimension)
of 2.5 mm gives excellent results~ These particles in the
electrofilter 37 will not contaminate the edible oil during
either elec-troEi:Ltration or the cleaning cycle for removing
adhering solids from the bed 77. In addition, these particles
provide an unexpected ease in cleaning the adhering solids
rom the bed 77 with a cleaning fluid.
An experimental electrofilter system was placed
into a commercial edible oil refinery ancl -tested with several
edible oils and bed ma-terials -to document the outstanding
results. The experimen~al system was essentially similar
to that illustrated in Figure 1 using the electrofilter 37
shown in Figure 2. The electrofi]ter was a cylindrical metal
vessel having a 15 inch internal diameter with a 30 inch
total vertical height. The vessel was placed on an upright
axis and arranged with electrodes as is shown in Figure 2.
The concentric electrodes had an engagement length (taken in
the vertical) of 14 inches. The interior of the vessel was
substantially filled with selected particles according to
the guidelines of the present invention. A one inch spacing
of the electrodes existed over their engagement length. The
electrodes electrically confined in the bed l.~ cubic feet of
these particles. The power supply energized selectively
these electrodes to be-tween 20 and 40 kilovolts. An edible
oil stream of soybean oil was taken directly from the drop
tank of the commercial operation. The drop tank held the
hydrogenation edible oil which contained nickel metal in -the
amount of several hundred parts per million and solids of
several hundred parts per million. The experimental
-23-
bm G;~-
,~
- , .. , ~ : .
09(~3
electrofilter system was operated on this edible oil charge
under pr~cise test procedures on three types of particle
media, desi~nated as F~ M-l, and G-l. These media were
commercial Flintabrise~M brane sandblasting materials which
are commercially available from Clemtex Limited o~ ~anada
at Ilouston, Texas, More particularly, the medium F-ll was
a crushed flint roc~ with an average ~50 percen-ti:Le) particle
size (least dimension) of 2.5 millimeters, The medium M-l
was a commerci~l "No l marine sand" which had been screened
0 50 tha-t all particle sizes were between 8 and 20 mesh on Tyle.r
s~andard screens. The medium G-l was a river gravel (grani-te)
which had been screened to sizes between one-fourth and one-
half inch. These media are all minerals.containing crystalline
silicon dioxide, have specific gravities between abou-t 2.5
and about 2.9, dielectric constants less than about 5 and
usually about 4, and high dielectric stengths, A11 media
were scrupulously cleaned by carefully screening, water-washing,
and air-drying so that no possible contamination of the edible
oil stream could occur. ~ach medium was placed within the
experimental electrofilter and subjected to test conditions
of the samé nature as described for the electrofilter 37,
The incoming raw edible oil stream was taken directly from
the drop tank 22 and passed upwardly through the electrofilter
at a rate of about 9 gallons per minute and at temperatures
between 150 and 200 F. The product edible oil stream from
the electrofilter was tested in accordance with the filter disc
impurities test, analyzecl for nickel content, and visual
appearance. The total throughput volume of the electrofilter
was recorded until the onset of product edible oil degradation
-24-
.
bm:~
, - , , ; ,: - .
, : :
: : : ,: ::. ,
9~3
by increased solids content arising :Erom the onset of
solids-fillup of the bed of the electrofilter as detected by
the initial observance of a Tyndall ef f ec t, The data f.rorn
these tests of the media are set forth in the following
Tables 1, 2 and 3.
T~BIE 1
Medi~n F-ll Fil-tex Disc Ni./p~Vol/~a~ Ap~e
40 kv @ 0.13-0.30 an~ps 8-~ - 178 C].ear
Rate 7.5 - 9 gFrn eclible oil 10 1.0 326 Very Clear
@ 165 F. 10 .7 823 Cl~r
Bed loading 6~4Lbs,/ft.3 10 ~ 1010 Clear
- 1295 Clear
3 . 4 1416 Clear
9 - 1656 Clear
4 - 1895 Gray Tint
- . TA~E 2
Medi~n ~1 Filter Disc Ni/ppmVol/gal Appearance
40 kv @ 0~2-0.22 amps 8 - 98 Clec~c
Rate 6 - 7 gEm edible oil 7 - 168 Clear
@ 185 - 192 F~ 10 . - - ~7ery Clear
~3ed loading 3.8 lbs~/ft.3 10 - 359 Very Clear
- - - 408 Very Clear
- - Very Clear
- 654 Very Clear
- - 925 Dark Gray
--25--
bm ~
- .~; - ~ , . . .
.-- . : -
:.:. : : . - :, ,. :
- : . ~ .: : ,
903
TABLE 3
Medium G-l Filter Disc Ni/ppm Vol/gal Appearance
. ~,, . . . :
30 kv @ 6.0 - 3.0 amps. 10 0.2 170 Clear*
~ate 8 - 9 gpm Edible oil 10 1,1 441 Clear
@ 202 - 194 F. g~ - 580 Clear
Bed Ioadin~ 7~3 lbs./ft.9 9 - 855 Clear
9 ~ 993 Clear
- - 1131 Clear
- - 1166 Clear
lQ 8-~ - 1276 Clear
8-~0~9 1399 Clear
6 - 1523 Hazy
Slight Tyndall effect
Inspection of the three Tables illustrates the unique
operation of the electrofilter system of the present invention
in producing a product edible oil ~hi-ch consi$tently contains no
inorganic solids and also has a nickel content of about one
part per million, Additionally, the edible oil product was
characterized by employees af the food industry as "bright and
clear". No Tyndall effect was observed in "clear" appearance
in the edible oil product. Unexpectedly~ the product edible
oil had a "clear" appearance until the filter disc color went
from 10 to 8 when the Tyndall effect indicated the approach
of a solids-fillup condition in the bed of the electrofilter~
Some slight Tyndall effect was indicated initially with the
medium G-l, but this was believed to have occurred as a result
of the start-up operation on the excessively larye sizes of
the media employed in the bed of the electrofilter
-26-
. .~ . .
~ bm:
. . .: . ~ ,. , ... . : :
V9~3
The data from the above Tables i~ represented
graphically in Fi~ure 3, wherein the throughput capacity
of the experimental electrofilter is displayed as one axis
while the other axis displays the filter disc impurities
number of the edible oil product. It is noted that the
medium F-ll gave outstanding results, and it is preferred
for the purposes of the present invention. The other media,
G-l and M-l, also gave acceptable results~ However, the
medium M-l did not have the capacity to remove inoryanic
solids as do m~clia F-ll or G-l. All three media do indicate
that the edibl~ oil product maintains outstanding puri-ty
until the onset of solids-fillup of the bed in the electrofilter.
Then, the deterioration by increased inorganic solids content
in the edible oil is very sudden and pronounced. The curve
deno~ed "A" is one example of the filtered edible oil
produced by a commercial filter press operation in an edible
oil plant wherein the filter disc impurity varies from about
2 to about 6. The .nitial nonlinear portion of the media
F-ll and M-l curves (until about 400 gallons throughput was
reached) is believed to result from bringing a relatively
small volume pilot plant unit onto equilibrium conditions
at 9 gallons per minute connected to a drop tank having
several ten thousands pounds of hydrogenated edible oil.
.
Slight fluctuations in temperature and pressure occurred
during the startup which may also e~plain these abnormalities.
An acceptable edible oil product in the commercial
operations, after bleaching or acid treating, and several
filtrations, has a filter disc impurity color o-f 9. In
comparison, the electrofilter of the present invention produces
~ -27-
. ,~, , .
bm ,3,.
.... . . ;" . . . ~ . . -
~- , , ' - -, ~ .
~()9~)3
the maximum quality of edible oil product in one quick step
which may take less than two minutes in comrnercial operations.
The edible oil product frc~m the electrofilter system
of the present invention at any ti~e before the onset of
solids--fillup of the bed has a filter disc color of 1~ on an
average basis, a nickel content of about 1 ppm, and a visual
appearance of brigh-t and clear. This edible o:il product
from -the electrofilter, without any subsequent treatment, is
equal. in chemical and physical prope.rties ~AO the commercial
procluc-t obtain~d by scveral filtra~:ion steps ta]~ing several
hours within the present day commercial food industry plant.
In addition the edible oil product from electrofiltration
is substantially free from all suspended and colloidal
inorganic and orgar,ic solids. For example, the nickel
content of the edible oil. taken from the drop tank 22 is
in the range of several hundred parts per million. It is
believed that the colloidal nickel content of this oil is
substantially in the tens of parts per million. However, the
edible oil product provided by the experimental electrofilter
always averaged in the range of about one part per million or
less of ni-ckel content. ~hus, edible oil product produced
by the system of this invention is equal in appearance, and
physical and chemical properties to that edible oil product
of the commercial plant.
Returning to Figure 1, the electrofilter 37 upon
initial installation should be scrupulously cleaned so that
the particulate bed does not contain any type of deleterious
material ~hich can enter the edible oil. For this purpose,
the electrofilter 37 can be flushed with a heated volume of
-28-
.
bm:;.
: . -, . ' ' -: ' . : : -
~. : . - ,, , - , :
9~3
commercial edible oil from the charge tank 57, cleaning
line 61 and throuyh the valved manifolas. In addition, stea~
can be applied throu~h the line 66 to displace congealed
edible oil from the electrofiltcr ~7 and/or rernove any other
types of organic materials from the bed and/or raise the
temperature o~ the bed to such a degree tha~ a stream of
nitro~en will bring it in a subs-tantially dry condition.
The edible oil, stream and drain-down liquid Erom the
elec-trofilter 37 in this cleaning step may be passed to a
blowdown tank 96 through the drain line 94 for sultable
disposal.
In addition, the described arrangemen-t for cleaning
the electrofilter 37 is important in the case of an
inadvertent displacement into the drop tank 22 of improperly
hydrogenated material, soap, or fatty material of such
undesired characteristics that it would contaminate the
electrofilter bed 77. In this instance, the use of the system
as an initial cleanup can be employed to remove such
deleterious or undesired soaps, acids and the like from
the bed of the electrofilter ~7.
Although the specific organic liqui.d has been
described as an edible oil, the present invention is not
limited to such non-petroleum oil and is equally applicable
to other types, such as fats, animal and vegetable oils,
and related organic liquids.
From the foregoing, it will be apparent that there
has been provided an electrofiltration system of appara-tus
and process well adapted for removing inorganic solids from
organic liquid streams. In particular, the system can be
-29-
bm:'`
operated for extended periods of time with a relatlvely
- simple cleaning procedure. No contamination of the organic
liquid product can occur from the electroEilter system
durin~ operation or cleanup. In addltion, the organic liquid
product prepared quickly in one electrofiltration s-tep is
equal to commercial produc-ts conventionally obtained by
multistep filtration. It w111 be ~mderstood that certain
features and alterations of the present system may be employed
without departing from the spirit of this invention. This is
contemplated by, ~nd is within, the scope oE the appended
claims. It is intended that the present invention is to be
~aken as an illustration of the present system.
-30-
bm:J, -
.. - .. : ,.:::-.. : . . . -,. : ,.
