Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
9172
" ~ 0 6'~
This invention relates in general to an
ultrafiltration apparatus and process ~or the treatment
of liquids. In another aspect, this inven~ion is directed
to an apparatus and a process for the concentration and`
separation of components contained in liquids. In a
further aspect, this invention is directed to a process
for the treatment of chemically stabilized emulsified
oils and other liquids containing large diameter molecules.
In recent years a variety of processes have
been disclosad in the literature relating to ultra-
filtration techniques. A majority of work in the
ultrafiltration area was developed at the Oak Ridge
National Laboratories of the United States Atomic
Energy Commission where extensive studies of ultra-
filtration, or cross-flow filtration, as it is some-
times called~ have been carried out. The work there was
primarily concerned with high pressure (500-9SO psi)
systems using porous tubular support structures of carbon
or alumino~silicates or a microporous membrane on a
perforated stainless steel sleeve.
The investigators at Oak Ridge found that for
some aqueous systems, a bed of particles uniformly dispersed
onto a porous substrate functions as an eficient filter
medium which rejects the passage of particles and moleculPs
whose size exceed the openings between adjacent particles
-- 2 --
~9172
.
~ ~ 67 ~1 ~
in the porous bed. It was suggested that the partlcles
deposited on the substrate surface may be of any material
inert to the solutions in contact with the surface. A
variety of materials such as diatomaceou$ earth, perlite,
asbestos flbers, cellulose fibers, dr~ed silica gel,
and carbon have been used.
In other experiments at Oak R~dge it was shown
that colloidal hydrous oxides may be used as permeation
barriers for the hyperfiltration ln raverse osmosis
treatment of solutions, thereby c~ntrating still lower
molecular weight solutes in water, provided that the
aqueous solution is pumped over the surface of the
permeable membrane under high pressure (50-1000 psi).
In this case the colloids are fonmed from polyvalent
metal salts by heating an aqueous solution of the salt
until a turbid solution is obtained. To form the membrane,
small concentrations of the turbid solution (greater than
10 ppm) are circulated over the support structure at
moderate velocity and at pressure. This procedure resuits
in the formation of a thin boundary layer (thickness up
to O.05 millimeters) which serves as an interface between
the waste solution and the porous substrate. (See, for
example, U.S. Patents 3,413,219; 3 9 449,245; and 3,537,988).
It is indicated in U.S. Patent 3,413,21g at
column 2, lines 43 et seq., that membranes formed from
9172
1~674~6
the colloidal hydrous oxides will continue to have
rejecting properties for a day or more, thou~h
rejection gradually decreases. However, :Lt is indicated
that the continued presence of an additivl~ in ~he solution
will improve the rejection properties and repair defects
which might occur in ~he membrane. In addition ta the
necessity for the continued presence of an additive to
maintain the desired properties, it has also been found
that many of the prior art methods are useful only for
the treatment of certain types of liquids. For example,
prior to the present invention no completely satisfactory
method was available for the treatment of liquids such
as those containing chemically stabilized emulsified
oils. Thus, while the pr~or art discloses a variety
of ultrafiltration methods, to date no completely
satisfactory method has been provided which avoids or
minimizes many of the difficulties inherent with
such processes.
Accordingly, one or more of the following
objects will be achieved by the practice of this invention.
It is an object of this invention to provide an ultra-
filtration apparatus which is useful for the separation
and concentration of components contained in liquids.
Another object of this invention is to provide an ultra-
filtration apparatus which is useful for the
separation and concentration of waste liquids fr~m lndus-
trial processes. A further object is to provide a novel,
~`: 9172
~OG74~L6
e~onomical and continuous ultrafiltration process for
the separation and concentration of llquids containing
molecules o~ a relatively large diameter from those of
a relatively small d~ameter. Another object is to provide
a process for the separation of large, dissolved polymeric
molecules, such as proteins from solutions. A further
object of this invention is to provide an ultrafiltration
apparatus which is useful for separating emulsified oil,
dirt and various other suspended materials from solution~.
Another object is to provide a process for the concentra-
tion and separation of components contained in textile
mill liquids. A still further object is to provide a
process for the separation and concentration of poly-
vinyl alcohol from textile mill liquids. A still
further object is to provide a process for the
separation and concentration of materials employed in
processing paper pulp. A further object is to provide
a process for the separation of materials employed in
electropaint primer operations.
Ano~her object of this invèntion i9 to provide
a process for coating the surfaces of the tubular
members contained in the ultrafiltration module. A
still further object is to provide a process for coating
the inner surfaces of carbon tubes with a preformed
metal oxide. Another object is to provide a process for
coa~ing the inner surfaces of carbon tubes with zirconia.
A further object is to provide a process for coating the
outer surface of carbon tubes with a preformed metal oxide.
Another object is to provlde a process for coating the
outer surfaces of carbon tubes with zirconia.
-- 5 --
9172
10674 6
A further ob~ect is ~o provide a process for seallng the
tubular members in the ultrafiltration module. These
and othar objects will readily become apparent to those
skilled in the art in the light of the teachings herein
set ~orth.
In its broad aspect, this i~vention ls directed
to an ultrafiltration apparatus and a ~rocess for the
treatment of liquids. The apparatus i.s comprised of,
in combination:
(a~ at least one module having:
(i) at least one entranee port,
(ii) at least one exit port,
(iii) a permeate collection zone having
at least one exit port
(iv) a multiplicity of axially aligned
hollow tubular members disposed in the zone
in close proximity to one another, said
members having a pore volume of at least about
0.08 cc/gm in the distributlon peak in the
pore diameter range wherein the majority of
the pores are from about 0.1 to about 2.0
microns in diameter, the members being
supported and sealably mounted in the zone so
that fluid entering the module must contact
the members and any components o~ the fluid
which permeat~ the walls of the members collect
in the permeate zone, and
-- 9172
1067~16
(v) contained on one selected sur~ace o
the members a substantially uniorm, continuous,
adherent porous coating of preonned, aggregated
metal oxide particles ha-ving an average mean
size of less than about 5.0 microns, and a
coating of from about 0.01 to about 10 . O
microns in`thickness without substantial --
penetration into the members of more than about
5.0 micron.
(b) means for supplying a feed liquid
to the module,
(c) means for withdrawing a concentrated
liquid from the module, and
(d) means for withdrawing a permeate liquid
from the permeate collection zone.
:
~ The objects of the invention and the preferred
:~ - embodiments thereof will best be understood by reference
to the accompanying drawings. Figure 1 illustrates
one form of the ultrafiltration system of this invention.
Figures 2 shows a cut away view of the multi-tube ultra-
filtration module. Figures 3-6 show methods for assembling
the tubular ultrafiltration module.
Figure 7 is a drawing depicting a longikudinal,
cross-sectional view of one of the hollow tubular members.
Figure 8 depicts an enlarged view of a portion of th~
cross-sectional view showing thepcrous substrate and
metal oxide coating.
With reference to the drawings, the ul tra-
filtration system of this invention as shown in Figure 1
9172
~i74~6
is comprised of the ultra~ltration module 10, a tank
12, pumps 14 and 16, and valve control means 18. The
liquid to be concentrated and separated is pumped
from tank 12 via conduits 20, 22, 24 and 26 into the
ultrafiltratlon module 10. As shown in l:he cut-away
view of Figure 2 module 10 is comprised of a pluraLity
of closely packed tubes 32 which are held in place at
each end by tube sheets 34 and 36. The tubes are
positioned in the module in such a manner that li~uid
entering the module via Fonduit 26 must pass through
the tubes. The liquid and low molecular weight .!1
dissolved phases, i.e., small diameter molecules,
permeate the walls of the tubes into chamber 38 and pass
out via conduit 28. The high molecular weight dissolved
phases, i.e., large diameter molecules, as well as any
non-dissolved material pass out through conduit 30.
Figure 3 shows one means for positioning
tubes 32 in the module shell 40. Tube sheet 42 has a
plurality of openings 44 of sufficient diameter to
receive the ends of the tubes. 0-rings 46 are then
inserted over the ends of the tubes and plate 48 posi-
tioned over the tube ends. Cap 50 is then affixed to
the tube sheet 42 compressing the 0 rings to form a
tight seal.
Figures 4, 5 and 6 show another method for
positioning the tubes 32 in the module shell. The tube
9172
~o67~l6
sheet 34 has openings through which the tubes 32 can
be inserted. The outer sid~ of the tube sheet has
openings of greater diamater than the tubes which
pxovides a recess for gasket seal 52 whic]h can be
composed o rubber or rubber-like material. The
module shell 56 containing the tubes 32 and equipped
with a permeate port 54 is shown in Figure 4 with a portion
of its end 58 removed to view the interior.
Figure 7 illustrates a cross-seceional view
taken longitudinally along the axis of one of the hollow
tubular members 32. Feed liquid enters at location 60,
passes through the tubular member 32 and exists at
location 62. The low molecular weight dissolved phases
permeate the walls 64 of the tubular member into permea-
tion zone 66.
Figure 8 illustrates an enalrged cross-sectional
view, approximately 2000 X, o a portion of the tubular
member 32 taken, for example, at location 68. The tubular
member 32, for example a carbon tube, is composed of bonded
carbon particles 70 and has essentially continuous coating
of aggregated metal oxide particles 72. The particles 72
only partially penetrate into pores 74 which pores are
characteristic of the carbon tubes employed in this invention.
invention. The aggregated metal oxide particles typically
penetrate to a depth M. of no more than about 5.0
' ~o67~6
micron. ~he pores below about 0.05 micron ln diameter are
essentially free of the rnetal oxide coatings. When in use
a filter cake 76 composed of higher molecular we:Lght
dissolved phases,i.e.,large diameter molecules or
undissolved particles may form on the coated surface.
~- The module of the apparatus can be designed and
assembled in such a manner that the metal oxide coating
can be either on the inner hollow interior surface or on the
outer surface of the tubular members. In either case~ the
coating of metal oxide particles is on that surface of the
tubular member which is in direct contact with the feed
liqu;d. For example~ if the module is designed as shown
in Figure 2 where the feed liquid enters through conduit 26
and leaves at eonduit 30, the metal oxide coating is on the
hollow interior of the tubular members. If the coating is
on the ou~er surface of the tubular members, then the
feed liquid would enter through conduit 28, contact the
outer surface of the tubular members and exit from module
10 through a conduit not shown in Figure 2. The permeate
which passed through the walls of the tubular members could
then be withdrawn through conduit 30.
- Of the two types of modules, the one shown in Figure
2 is preferred, because of enhanced hydrodynamic character-
istics compared to the arrangement where~he feed liquid
contacts the outer surface of the mPmbers. The feed fluid
passes through the inner hollow portion of the tubular members
and the permeate collects in the permea~e zone and can be
withdrawn ~hrough conduit 28.
- 10 -
9172
~0674~6
As hereinbe~ore indicated the apparatus o
this invention is ideally suited for operation over
extended periods of time with a high degree of concentra-
tion and separation of components contained in l~quids.
In contrast to many of the ultrafiltrati.on units
currently available, the apparatus of this invention
maintains a high level of throughput without the need
for additives.
As previously mentioned ~he apparatus of this
invention is comprised of an ultrafiltration module
together with means for supplying feed liquid and
means for collecting and withdrawings a concentrate liquid
and a permeate liquid. The module itself is comprised
of a multiplicity of axially aligned hollow tubular
members disposed in the permeate collection zone of the
module. As set forth in Figure 2 the tubular members 32
are aligned in a parallel fashion and supported and
sealably mounted in place by tube sheets 34 and 36.
Although the tubular members can be fabricated from a
varlety of material, it is preferred that they be
largely inorganic in composition. It has been observed
.. .. _ _ ... .... ... .
that tubular members composed of inorganic materials are
more resistant to abrasion and can wi~hstand higher
temperatures than those largely composed of organic
materials. In practice, it has been found that tubular
members composed of carbon, alumina, alumino silicate,
and the like, can be utilized in the apparatus of this
invention.
- 11 -
9172
~067~6
It is critical for the s~ccess~ul practLce of
this invention that the tubular members~have ~ well
defined poroslty. If the pore diameter iS too large-
separation will not be selective and the lnner pores may
even become blocked by the larger diameter molecules.
If the pore diameter is too small ~he rate at whlch liquid
passes to the permeate collection zone wi:Ll be greatly
reduced and thus the overall efficiency of the apparatus
lowered.
It has been found that tubular members which~are ~~
characterized by a pore volume of at least about 0.08 cc/gm
in the distribution peak in the pore diameter range wherein
the majority of the pores are from about 0.1 to about 2.0
microns in diameter, are ideally suited for use in the
ultrafiltration apparatus. Particularly preferred are
tubular members composed of carbon and which have the
majority of pore diameters within the above range. Pore
size measurements on samples of carbon tubes employed in
the modules indicate that they are sharply peaked in the
range of 0.10=0.50 microns. Pores in this size range
account for nearly 50 per cent of the distribution through-
out the tube. The preferred tubular members are fabricated
by a binder-coking process followed by a subsequent heat
treatment. The carbon tubes employed are known in the
art~ for example, those normally used for the fabrication
of commercial cored arc carbons for motion picture projection
machines. The carbon tubes serve as the outer shell which
is subsequently filled with graphite and rare earth oxides
to provide the desired light intensity.
- 12 -
` 9172
i~i7~
The size of the tubular members and the length
to diameter ratio can vary over a wide range. The
particular slze chosen will undoubtedly be influenced
by the overall size o~ thf.~Ddule as well as the type
of liquid and components to be separated. In practice,
however, tubular members having an internal diameter of
from about 0.10 inch to about l.0 inch and a wall thickness
of from about 0.03 to about 0.25 inch and a length of
about 48 inches have been employed with excellent results.
10 Tubular members having an internal diameter of 0.25 inch,
a wall thickness of about 0.06 inch and a length of
about 48 inches are particularly preferred.
In addition to the well defined poro~sity of ~he~
tubular members, it has been found that optimum ultra-
filtration can be achieved if the inner surface of the
porous tubular members is coated with certain aggregated
metal oxide particles as hereinafter defined. The utili-
zation of a selected size range, metal oxide coating
represents a significant improvement over the prior art
with respect to the development of a microporous ultra-
filtration filter for cros~-flow filtration. Based upon
the use of carbon, alumina or other porous tubular members
as substrate materials, with the addition of aggregated
metal oxide particles, i.e., a microporous metal oxide
coating, it has been discovered that several different
industrial process and waste streams can be treated in
which suspended solids, collids, oils, or high molecular
weight polymers are separated by ultrafiltration at rates
- 13 -
9172
~067~L6
,.
several times higher than the bare ~ube or the previously
preferred hydrous zirconia oxide membrane of the prior
art.
The present invention utilizes as the coating
aggregated metal oxide particles having a narrow size
range below about 5 microns and largely between about 0.1
and about 2.0 microns. The aggregated particles can be
further sized and classified as fine (less than 0.1 microns),
medium (0.1 to 1.0 micron) and coarse ~l.0 micron and
largèr). Particularly preferred are aggregated metal
oxide particles wherein a sizeable portion, i.e., at
least about 50 per cent, is from about 0.1 to about 1.0
microns in size.
- Although commercially available metal oxides
powders can be employed, in some instances they may
require prolonged grinding times to reduce the particle
size to the proper range. Particularly preferred metal
oxide powders which have been found to be id~lly suited
for use in this invention are those prepared by the so
called "precursor procsss." This process comprises first
contacting a metal compound with a carbohydrate material,
igniting the material to decompose and remove the carbo-
hydrate material and to insure conversion of substantially
all of said metal compound to fragile agglomerates of its
metal oxide, followed by comminution of ~he thus formed
agglomerates to give the finer microporous aggregatecl
particle employed in the invention.
`` 9172
~067~
For example, a supply of the metal oxide powder
aggregate, prepared by the precursor process, such as
zirconia containing about 8 to 10 per cent yttria, can be
ball milled by placing 1500 grams ln a one gallon contalner
and adding zirconia beads. The container is then filled
about three-quarters full with deionized water and acidified
to a pH of 4 with acetic acid. Thereafter, the contents are
milled for about 18 hours.
The particles prepared by the precursor process
are so small that settling rates are slow, thus aggregates
which have not been completely disrupted during wet ball
milling can be separated from dispersed suspension of
liberated particles by sedimentation, centrifugation, or
other separation procedures based on particle size or mass.
For example, sizing can be effected by centrifuging from a
broad distribution of particles sizes to obtain aggregated
metal oxide particles largely within thë desired range ~ - ~
as hereinafter indicated. Once the separation has been
made, the liberated particles remaining in suspension can
- 20 be conveniently collect~d by treatments that reduce the
surface charge and render the colloidal suspension unstable.
Typical treatments are the addition of an acid to lower the
pH of the suspension, or the addition of a salt having a
multivalentanion. The suspensions treated in this manner
revert ~o a flocculated condition, and in this form, the
powder can be separated from the bulk of the suspending
medium by filtration or sedimentation.
9172
'i~67~L6
It has been observed that tha mean individual
particle size from which the preferred Q.l to 1.0 micron
aggregates are obtained, is below 1.0 micron, and usually
below 0.1 micron. The individual particles remain un-
resolved at 11,000 magnification. X-ray powder di~frac~ion
analysis indicates an ultimate par~icle size within the
range of from about 0.01 to about 0.1 microns.
A variety of metal oxide particles can be
employed as the coating in this invention. For e~ample,
the metal of the metal oxide can, either singly or in
mixtures thereof, include beryllium, magnesium, calcium,
aluminum, titanium5 strontium, yttrium, lanthanum,
zirconium, hafnium, thorium, iron, manganese, sillcon,
and the like.
When the metal oxide powder employed is
zirconia, in many cases it is preferred to produce the
zirconia powder in a stabilized form. Therefore; a
compound of yttrium, calcium, magnesium, rare earth
metal or other known me~al that forms a stabilizer
oxide can be employed along with the zirconium
containing compound in producing the loaded material.
The proportions of the zirconium compound and
- 16 -
- 9172
~ 0674~6
stabilizer metal compound should be selected to produce
the type of stabilized zirconia desired.
A ~urther and more detailed description of
the precursor process for making the metal oxide
powders employed in ~ present invention is set orth
in Belgiàn Patent No. 766,962 entitled "Finely Divided
Metal Oxides and Sintered Objects Therefrom" by B.H.
H~mling and A.W. Naumann.
In practice, ~e metal oxide coating is
applied to the tubular members by circulating and
aqueous suspension of the aggregated particles through
the tubes at linear flow velocities of from about 0.5
feet per second to about 40 feet per second, and at
pressures from 30 to 500 psi. The concentration ~f
aggregated particles in the suspension typically
ranges from about 10 to about 100 milligrams per
liter. The suspension is generally maintained at
a pH sufficient to maintain a stable suspension
of the aggregates. As the water filters through
the pores of the tubes, the particles are filtered
out and cover the pore opening of the substrat~
with a very fine pored layer. It is thisuniorm,
continuous, highly porous, very fine pore structure
which provides the higher throughput and improved
resistance to fouling as compared to either bare tubes
or tubes coated with less porous materials. For
- 17 -
` 9172
~067416
optimum efficiency and throughput, it has been found
that t~e coating should be from about 0.01 to about
10,0 microns in thickness without substantial pene-
tration into the tubular member of more than about 5.0
microns, It is also desirable but not necessary to coat
the tubular members at pressures at least equal to,
and at flow rates no greater than, those which will
be employed when the module is in operation.
For most applications the tubular members
are coated with the aggregated metal oxide particles to
provide an average coating of about 8.5 milligrams per
square inch of the surface of the tubular member. ~or
certain applications it may be desirable to add a
second coating on top of the first of the fine size
particles.
For the majority of applications, it has been
found that a level of about 1 milligram of aggregated
metal oxide particles per square inch tube surEace is
the minimum amount that should be applied. Higher
amounts yield higher and more stable flux levels. For
example, while an average metal oxide coating o~ 8.5
milligrams is useful, it may be desirable to coat as
much as 30 milligrams per square inch.
The coating of the tubular members with the
metal oxides preferably is effected within a selected
- 18 -
` 9172
~o67~6
pH range. The particular pH range chosell -19 that range
in which the metal oxide particles remain in suspension.
For example, when the tubular members are coated with
zirconia particles, the preferred pH range is from
about 1 to about 5 and more preferably from about 2
to about 3.5. Ad~ustment of the pH can be accomplished
by the addition of an acid such as acetic, oxalic~
hydrochloric and the like. In practice~ oxalic acid
or hydroehloric acid is preferred since it tends to
keep in solution any iron which might be present.
It should be noted that in contrast to methods
disclosed in the prior art, it is not necessary to form
a colloid before depositing the metal oxide on the
surface of the tubular member such as is disclosed for
the hydrous zirconia gel (3,413,219). The metal oxide
aggregates are preformed and separated into the proper
particle size range prior to the coating step. The
coating is mainly a mechanical step with ~he metal
oxide aggregates penetrating to a degree the pores of
the tubular members and building up the desired coating
on the surface. The aggregated metal oxide particles
do not "fill" the pores of the tubular members in the
sense that they are plugged, but "brldge" the pores
which permits the small diameter molecules of the feed
stream to pass through at a hlgh rate.
~ L9 -
9172
~74~6
As previously indicated the ultrafiltration
apparatus of this invention can operate efficiently at
pressures o~ about 500 psi and lower. Various ~ac~ors
such as temperature, pressure and flow velocities, will, of
course~ vary depending upon the particular ~eed stream.
Additionally, the actual geometric configuration of the
interior of the tubular members wilL also be a ~actor.
For example, the interior of the members need not be
cylindrical but can be star-shaped, hexagonal, octagonal,
saw tooth, or the like.
It has been found that for the concentration
and separation of certain dissolved phases, optimum
results are obtained if the hollow tubular members
containing the metal oxide coating are covered with
an additional coating, such as for example, the fine
grade of metal oxide powder (C 0.1 microns) or a
hydrous zirconia gel. Method for applying hydrous
zirconia gel coating are known in the art and are
disclosed, for example, in U.S. Patent 3,537,988.
It should be no~ed that such coatings are
in addition to the metal oxide coating. Attemped use
of the hydrous zirconia gels alone on the tubular members
doesnOt prov-ide the high degree of concentration and
separation as in the present invention. For instance,
examples 4 and 5 of this invention are directed to the
use of the ultrafiltration apparatus for the concentration
of polyvinyl alcohol in a textile liquids. As ind;cated
in Table V of example 5 both the metal oxide coated
carbon tube and the tubes having an addition hydrous
- 20 -
_- 917z
~ 0674'L6
metal oxide coating gave markedly improved resuLts over
the uncoated carbon tube.
As illustrated in Figure 8, when ln operation a
~ilter cake composed of the larger diameter molecules as
well as solid or suspended ma~ter in the feed liquid will
form initially on the coated tubular members. When the
ultrafiltration appara~us is in operation, the feed stream,
such as an aqueous oil emulsion, is fed, under pressure,
over the filter surface at velocities high enough to
shear away most of the accumulated filtered substances.
Since this flow is perpendicular to the direction of flow
of the filtered liquid through the filtering surface, the
term "cross-flow" filtration is employed. I~ is important
that the flow rate through ~e tubular members be such that
turbulent conditions are achieved. The liquid should pass
through the tubular members at a rate of at least about
1.0 linear feet per second and at a Reynolds Number of
at least about 2000.
~or instance, an ultrafiltration apparatus
containing a single module with approximately 151 tubular
members (0.25 inch internal d~ameter and 48 inches in Length)
can process over 3,000 gallons per day at a pressure of
100 psi and a feed stream temperature of abou~ 72 F.
- 21 -
9172
~67416
~hen two or more modules are employed in the same apparatus,
or when ~he num~er of tubular members is increasad, voLumes
as large a~ tens of thousands of gallons per da~, and higher,
can be processed efficiently.
In conventional ~iltration the filtered material
would build up as thick ~ilter cake whiclh greatly reduces
the filtration rate. Depending on the geometry of the
system and the type of material being ~iltered, the
velocities parallel to the filtering surface may be from
about 0.5 ~o about 40 feet per second. A most significant
feature of the present process is that the f~lter interface
is such that di~solved, colloidal or suspend~d particles of
the feed liquid in the size range of 10 microns and higher
to as low as 0.002 microns may be removed at iltratio~
rates through th~ surface as high as several hundred gallons
per day per square foot at pressures ~f 100 psi or lower.
Whereas ultrafiltration has been used for ~he
removal of suspensions, colloids and high moLecular
weight materials dissolved in aqueous solutions, the
discovery that oil emulsions could be concentrated a~d
separated from the bulk aqueous phase by ultrafiltration
through coated fine pored tubes was unexpected. Such
oil emulsions are, for example, those used in ~he
preparation of steel and rolling mill coolants and lubri-
cants or such e~ulsions as used in eutting, drawing,
stamping, or other metal-working operations. In addition,
the types of oil-water-dirt-metal chip emulsions obtained
- 2~ -
9172
1067416
in the detergent washing of fabricated metal parts, etc.,
may also be separa~ed into a concentrated oil~dirt-particle
retentate solution plus a clear water plus solubla detergent
filtrate phase.
At present, accumulations of oil~ dirt and
various other suspended solids in an aqueous system are
removed by additions of acid and/or other chemicals
at relatively high temperatures to break the emulsion
and separate the oil from the suspension; the water is
then settled in large storage tanks to remove particulate
matter and the remaining soluble components are either
neutralized or otherwise chemically treated by additions
of acid or a~kali and then directed to a sewer or trans-
ported to a suitable dumplng or processing site.
Transportation is relatively costly and in no cases are
water soluble components of the waste water separated
cleanly for recycling. Further, the costs of the
processing with chemicals are substantial, both for
materials and labor as well as for the processing
facilities. Sewer surcharges for the chemiGal laden
water phase are often quite high. In an increasing
number of localities, such discharges are being pro-
hibited by pollution control laws. As a result still
further treatment of the aqueous phase is required before
the water itself may be discarded.
~067416 9172
The ultrafiltration process of this lnvention
can reduce the volu~e of the oil-dirt-water phase b~ as
much as a actor of five to thirty or higher depending
on the oil content of the starting mat:erial. m us, the
volume o material requiring furthar ~.reatment for
disposal is greatly reduced. Further5 because the oil
level i~ this concentrate phs~e may typically be brought
to a level of 20 to 40 per cent, which iB a high enough
level to typically sustain combustion without ad~itional
fuel be~ng added, the disposal problem can be greatly
simplified by burning. This also permits the recovery
of the bulk of the heating energy of the oil.
The oil-free aqueous phase may be rejected into
a se~er or recycled back into the process. The r~use of
the water promotes closed cycle operation, highly desirable
from the water conservation standpoint. In ad~ition,
where there are valuable wate~ soluble substances, such
as detergents, which are carried through with the filtrate,
an operating economy is r~ali7ab~e by avoid~ng the loss of
these materials in the usual waste stream.
_ . .
~ nother maJor advantage accruing from the
use of the process of the invention to continuously
remove the dirt and oil from a metal washer on a paint
line, for example, is that the cleaner washer liquid
improves the cleanlinsss of the following rinse and other
- 24 -
`` 9172
~ OG74~6
commonly used pre-paint processing baths. As a result,
~he quality of the paint coating on the cleaner metal
part may be improved considerably.
A fuxther embodiment, of the present invention
is directed to the ultrafiltration module itself and to
methods or assembling the tubular mem~ers. Although
, .;
even a ~ingle tubular member can effect concentration and
separation, it is, or course, more practical to construct
; a module having a multiplicity of tubes. The number of
tubular members employed will vary depending upon a variety
of factors. Modules containing as few as 25 or less, or
up to 1000 or more tubular members have been constructed.
As indicated in Figure 2, the tubular members
are~aligned in a parallel fashion and in close proximity
to one another. Each tubular member is held in place
by tube sheets 34 and 36. The tube sheets themselves are
moun~ed in the module so as to provide a permeate zone
38 which is sealed from feed fluid entering the entrance
port via conduit 26. ~he only liquid which ~an enter
the penmeate zone is that which filters through the walls
of the tubular members.
The ~uter shell of the module and the ~ube sheets
can be fabricated from a variety of materials. For
example, a wide variety of plastics, such as polyvinyl
chloride and the like, or metals such as stainless steel
can be used. Due to the wide variety of liquids which
can be treated and ~emperature ~ariations of the feed
streams, it is preferred to construct the module oE
- 25 -
` 9172
~0674~t;
stainless steel or other material which is compatible with
the feed liquid and operating conditions.
As hereinbefore indlcated, Figures 3 and 4
illustrate two types of methods for assembl~ng the tubular
members in the tube sheets so that a liquid-tight seal
is o~tai~ed. In both instances the ends of the tubular
members are sealed and cushioned by a rubber or rubber-
like seal. As opposed to a cemented or other fixed
sealing means, the assembly method employed ln this
invention provides somewhat of a "floating seal" so that
brittle tubular members, for example, those composed of
carbon~ can withstand a certain amount of shock.
The assembly shown in Figure 3, utilizes "O"
rings 46 which are fitted over the ends of the tubular
members. The plate 48 is then placed over the tube ends
and "O" rings. When the cap 50 is attached to end sheet
42 the "O" rings are compressed, sealing and securing the
tu~ular members in place.
Figures 4-6 illustrate'a more preferred assembly
of the tubular members in the ultrafiltration module.
As shown in Figure 6, the end sheet 34 contains
openings of sufficient diameter to admit the tubular
members. The surface of the end sheet opposite the
per~eate zone is recessed to permit a gasket seal 52 to
be placed over the end of the tube and forced into the
recessed area. Th~ seals and secures the tubular
- 26 -
9172
~674~L6
members in pLace. An advantage of this type of
assembly over the previous one is that iLt penmits the
tùbular members to be aligned in very cLose proximity
to one another. For certain applications and due to
space requirements it may be advantageous to fabricate
a relatively co~act module wi~hout sacr~icing the
desired number of tubular members.
For the most ef~icient utilization o~ the
~ ultrafiltration apparatus of this invention it is often
preferred to operate a çlosed loop system, that is, the J
feed stream after passing through the module where it
becomes slightly more concentrated with the larger
molecular we~ght molecules~ is recycled back to the
module. As ~he liquid increases to a sufficient
concentration, it can then be drawn off from the system.
A variety of automatic control means can be utilized in
removal of concentrate as well as circulating the feed
stream.
Although Figure 1 illustra~es an ultra~
filtration apparatus employing a single module 10, for
certain applicatlons it may be desirable to use t~o or
more modules in the same apparatus. In such instances,
the modules can be arranged in series, i.e., the
concentrate from a first module serving as the feed
stream to a second, and so on, or in parallel wherein
the same feed stream simultaneously enters all moclules.
' 9172
~ ,o674~6
A variety of factors can influence which arrangement
- will optimize the concentration and separation o~
components for a particular application.
Due to the excellent features of tha apparatus
of this invention, it i8 ideally suited for the separation
and concentration of components contained in a wide
variety of liquids. As previously inldica~ed, a parti-
cularly attractive application of the ultrafiltration
apparatus of this invention is in ~he concentration and
separation o oil-water emulsions. Such emulsions are
encountered in a wide variety of metal-working and
metal-washing operations. Prior to the present invention
there was no sa~isfactory method for concentrating such
liquids efficiently ln order to minimizing waste disposal
and reclaimed many of the useful components in the liquids.
However, the apparatus of this invention has been outstand-
ingly successful in the treatment of a wide variety of
liquids which contain emulsified and/or chemically
stabilized oil.
As demonstrated in the examples, the ultra-
filtration apparatus is also useful for the concentration
and separation of solutions employed in textile operations.
For example, polyvinyl alcohol is readily concentrated
and separated from textile sizing solutions with a high
degree of efficiency.
The apparatus is also useful for recovering and
recycling detergents from a variety of wash waters,
such as car washes~ laundries, and the like.
~. 9172
74~6
It has also been noted that the ultrafiltration
apparatus of this invention is useful in electrophoretic
coating operations. For example, after a painted article
is removed from an electro-painting bath in many instances
it is sprayed with water to remove excess drag-out. By
passing this wa~h wat~r containing paint through the
apparatus of this invention paint sollds can be concentrated
and returned to the psint bath. The apparatus is a~so
useful in removing excess waterj soluble salts, or
excess solubilizers from the paint bath. As indicated
in Example 6, the xejection o~ the pigment phase can be
as high as 99.95 per cent. In contrast to methods
disclosed in the prior art such as, for example, in
U.S. Patent 3,663,399, the penmeation rates obtained
with the apparatus of this invention are much higher.
Additionally the apparatus of this invention
has been found to be useful in the treatment of a variety
of food and beverage products. For instance, the apparatus
is useful in the concentration and separation of spent
grain liquors in ~ preparation of beer and ale. It has
also been found to be useful in concentrating proteins
from cheese whey, clarification of vinegar, and the like.
In certain applications such as in the desali-
nization of sea water, the ultrafiltration apparatus can
~e employed as an initial step to clarify the water prior
to its passage through a reverse osmosls unit.
- 29 -
,--. 9172
1067~1~
It has also been observed that the ultra-
filtration apparatus is useful for the concentration
and separation of bovill3 animal blood serum, egg albumin,
enzymes and the like.
- 30 -
9172
~0674~i
The following ex~mples are illustrative:
Example 1
An aqueous solution (solution A) containing
approximately 2 per cent by weight of tramp and so1uble
oil~ with about 3 per cent by we~ght of soluble indus-
trial detergent and caustic soda was circulated through
an ultrafiltration module at various pressures and flow
velocities. me waste itself can~from the holding
- tank for an industrial washer which is used to clean
the dirt, metal chips and remnants of oil from the
metal parts after they are fabricated. Various oils
are on the finished parts including lubricating oils
used ~or the drawing operation7 soluble oils from the
shaping operation~ and various cutting olls from the
machining operation. The concentration of total oil
- in ~ feed material was determined by sulfuric acid
addition and subsequent separation.
me operating condltions and results obtained
are set forth in Table I below:
2Q Table I
O eratin~ Conditions of Ultrafiltration
Solution A
Operating pressure 100 psi
Circulation velocity 18 ft/sec
~ 31 -
--- 9172
~067~
Filtrate flux 90 GFD ~gallons per square
foot per day)
Operating temperature 140F
Total Operating time 30 hours
Characteristics of Feed, Filtrate and
Concentrate
_ _ __
Feed Filtrate Concentrate
pH 12.5 12.5 12.5
Oil content 2% C100 ppm 16%
Detergent content 3% 3% 3%
As is evident from the Table there was an eight-fold
concentration of the feed. The filtrate had less than
100 ppm of oil but still had the same detergent
concentration as the feed making it suitable for
reuse.
Example 2
A second oil-water-detergent solution
(solution B) was tested in which the main oil
constituent consisted of the soluble oil used in a
metal stamping operation. In this case the feed
stream contained about 0.4% of oil by volume as
determined by sulfuric acid ~eparation. Operating
characteristics and characteristics of the feed,
filtrate and concentrate are indicated in Table II
below. Flux values greater than 100 GFD were measured
over operating periods greater than 30 days at various
- 32 -
" ~
~;
~67416 9172
concentrations of oil. A 55-fold concentration was
achieved,
Table II
Charac~eristics of Ultrafiltration System
for Processin~ Oil-Water-Detergent Solution_B
Operating pressure 100 psi
Circulation velocity 15 ftlsec
Operating temperature 150F
Filtrate flux 1~4 GFD
Total operating time 720 hours
Characteristics of Feed, Filtrate
and Concentrate
Feed Filtrate Concentrate
pH 9.5 9.5 9.5
Oil content 0.4 ~ 100 ppm 22%
Detergent content 3% 3% 3%
.
Example 3
In a third experiment Texaco Soluble Oil
type C was run in a single tube system at a feed
concentration of about 5 per cent. Data o Table III
indicate operating charcteristcs for a 30-hour run,
during which time the concentration of oil was increased
from 5 per cent to 20 per cent.
Table III
Operating Conditions of Ultrafiltration
System for Processing Texaco-C Oil/Water
Emulsion
,
Operating pressure 100 psi
- 33 -
9172
~0674~6
Circulation veloci~y 22 t/sec
Average filtrate flux 138 GFD
Average operating tempera~ure 130F
Total operating time 24 hours
Characteri~t~s of Feed, Filtrate
and Concentrate _ _
Feed Filtrate Concentrate
Oil Content 5% C 100 ppm 29%
Example 4
To illustrate the versatility of the ultra-
filtration system for various other industrial wastes9
samples of polyvinyl alcohol-water solutions were run
at concen~rations of l.O to 4.0 per cent. Data of
Table IV indicate the operating characteristics of
the system and the properties of eed, filtrate and
concentrate. m e polyvinyl alcohol was within the
molecular size range 50,000-lOO,OOO such as used in
a textile sizing bath. In this case a particulate
bed coating of zirconia was covered with a second
coating of a hydrous zirconium oxide gel. The
hydrous zirconium oxide was prepared by boiling a
0.25 M ZrOC12 solution for 30 hours to hydrolyze tha
oxy-chloride. For the 37" long, 1/4 in. I.D. tube,
12.5 milllliters of tk~s stock solution was added to 3
li~ers of distilled water to produce the feed which
was fed through the tube at 100 psi for approximately
- 34 -
. ~ 917~
~,o67~6
an hour, with the permeate being returned to the
reservoir, to deposit the hydrous zirconia gel on top
o~ the previous coatlng. In use, the apparatus provided
grea~er ~han 97 per cent rejection o~ the polyvinyl
alcohol.
Table IV
Operating Conditions of Ultraflltration
System wi h I~Ly~ __ohnl Solution
Operat~ng Pressure 100 psig
Circulation velocity 20 ftlsec
Average filtrate flux at 1% concentration 70GFD
at 4% concentration 21GFD
Average operating temperature 180F
Total operating time 112 hours
Characteristics of Feed9 Filtrate,
Concentrate_ _
Feed Filtrate Concentrate
p~ 6.8 6.8 6.8
PVA 1% 0.03% 4~/O
Experiment 5
Comparison experiments in the concentration
of polyvinyl alchohol were performed with carbon tubes
uncoated 9 with carbon tubes coated wlth a particula~e
bed, and with carbon tubes coated with a part~culate
bed plus the hydrous zirconia. All measurements were
performed at 100 psi inlet pressure and flow velocity
near 20fps. Data of Table V indicate comparative
rejection and flux characteristics fo~ the thrlee
experiments, showing the grea~ly improved flux
afforded by the zirconia particle and the improved
- 35 -
9172
~067~6
rejection with sustained high flux when the hydrous
zirconia gel layer was added.
.. .... .. . _ .
Table V
Comparison of Reject~on and Flux Characteristics
for Carbon Tube Permeator, Carbon Tube-Particula~e
Bed P~rmea~or, Carbon Tu~e - Particulate Bed -
Hydrous Metal Oxide Permeator Using 1% PVA
Solution as Feed
. .
.
Flux Rejection Temperature
. ~ 10 ~GFD? ~%~ ( F2
Carbon tube alone 15 0-50 134
Carbon tube - particulate 100 63-66 188
Carbon tube - particulate -
hydrous met~l ~xide100 97-99 177
- 36 -
. ~ 9172
~L0~74~L6
Example 6
The ultrafiltration apparatus of this
invention was employe~ ~or the concentration of
a primer pain~ from an electrodeposition system.
A porous carbon tube with a pore volume of about
0.2 g/cc and the majority of the pores in the 0.1
to 1.0~ diameter range, as detenmined by Hg poro-
simetry, was coated with 6 mg/cm2 of precursor ZrO2
particleæ, sized in the 0.1 to 1.~ range by centri-
fuging. The coating was performed by adding the
Zr2 to about 3 liters of acidified water and
circulating the water through the interior of the
; tube at 100 psi for 1 hour whLle the water permeating
through the tube waLl was returned to the circulating
feed. The tube was th~n insert d in a circulation
syst~m in which a 7-1/2% solid solution of an electro-
depositable paint, Forbes 2000, was fed at 100 psi
and 80F through the tuke at a linear flow velocity
of 15 to 25 ft/sec. Over a 214 hour period, the
permeation rate held between 85 and 100 (GFD). In
other experiments with this paint and this tube extending
over 412 more hours, the flux held between 50 a~d 65 GFD.
Rejection of the pigment phase was 99. 95% and of ~he ionic
constitu~nts, was 48.8%. Typical permeation rates ~or
film type ultrafiltration systems on this type of paint
is lQ-30 GFD.
. - 37 -
9172
:
~674~16
Example 7
In another e~ample in which a different type
of high porosity, high ~ur~ace area powder was used
as a pre-coat, a slurry of y-alumnla, ground in size
to appro~imately the same range as the precursor
2irconia, tha~ ~s, from 0.1 to 1.~ was used. I~e
carbon tube was of the same type as in the previous
example. Its flux at 100 psi with pure water was over
400 GFD at 110F. With the pre-coat applied it had
dropped to 280 GFD at an operating ~emperature of
160F. mis tube was used to process a sample of the
black liquor from wood pulp digestion. Fluxes of the
: order of 70 to 80 GFD were obtained with color reJec-
tion greater than 90% and about 30% rejection of the
, ionlc constituents.
Example 8
In another experiment wi~h the paper mill
black liquor, a carbon tube as above was coated first
wieh the par~iculate zirconia and ~hen wi~h the hydrous
zirconia oxide from the zrocQ,2 solution as indicated in
example 4. After ntnning the black liquor overnight
at 100 psi and 140F, the permeation rate was 80 GFD with
greater than 90% rejection of the color. The ~eed had
a conductivity of 32,000 mhos while the permeate had
a conductivity of approximately 17,000 mhos, indicating
an ionic rejection of the order of 47%.
- 38 -
~~~
9172
1~)674~6
Exam~le 9
A comparison was made on a (number of carbon
and alumina tubes to ~emonstrate the wide variety in
characteristics which are related to pore diameter,
pore volume and air and water permeabi:Lity. As indicated
previously, tubular members having a pore diameter of
from about 0.1 to about 2.0 micron~ such as sample
numbers 1-7 of Table VI, have b~en found to provide
optimum concentratlon and separation of components
from liquids.
Those tubular members having pore diameters
generally larger than about 2.0 microns (sample number
8-15) tended to plug the pores in dep~h with the metal
oxide particles and ultrafiltered materials in the
retentate and give undesirably low permeation rates.
Additionally, when the bulk of the pore volume had
pore diameters less ~han about 0.1 micron the water flow
rate of the uncoated tube was too low and ~herefore the
permeation rate was unacceptably low. In contrast
sample numbers 1-7 having a pore volume in the distri-
bution peak of about 0.08 cubic centimeters per gram
Gr greater, in the pore diameter range primarily of
from about 0.1 to about 2.0 microns gave excellent
results. Such carbon tubes are also distinguished by
having a bulk density of less than about 1.60 grams per
cubic centimeters.
- 39 -
9172
67~ lL6
Sample Number 7 was a useful tubular member
compos~d of alumina wheraas the others were composed
of carbon.
hll measurements were made using standard
techniques for the determlnation o~ pore volume, pore
diame~er, air and water flow rates and bulk densities.
- 40 -
674~L6 9172
,~ m ~ ~ ~ n n In ~n ~ ~o
~o
.
.~ .~ ~ ~ o 0~ l o ~ ~ o oo o
n, I , ~ c~l I ~ ,1 ~ ,1 ~ o ~ In
h 1~ u~ ~ u
~ o
a~ ,,
~ ~ ~ o o o o o o o O o o o
~1 li~ U') I o o o~ o o o o o
~1 ~ U') ~ ~ 1~ ~1 o~7 ~ ~~ o~ o
P~ O~ o
~ ~C td V
C
, ~ ~ ~ ~ ~ u~ In ~ ~ ~ ~ ~
~I ~ o o o o o o o _I ~ ~ ~ ~ ~ ~ o
P¦ ~ o All O o o O o o O O O o o oo O o
~1 V P _~;
E~
~ U~
E~ ~ ~ O ~ ~ ~ u~ ~ ~ ~1 ~
O . I ~0 ~ ~ ~ ,1 ~ U~ o o o o o ,~ o o ~>
1:~ -I-- ~ 0 0 0 00 0 0 0 0 0 0
O V o o o o o o o ~ o s~> o o o O O
S~
a~ ~ ~ In oo u~
E~ o o o o o o ~ oo ~ ~ C~l C~l C~l
' oo _l ,~ ,_, _,
~ n ~
2 ~ ~ ~ OD cr.
~ o ~ ~ ~ c~
o ~ ~, . . . . . . . . . . . . . .
P~ o ~4 o o o ~ o o o 1~ C~l C~l ~ ~ ~ oo
U 'td
oo 'D ~~ o oo o~ r~ I~
~ 1 ~-- --I ~ ~ ~1 0 0 ~ O ~ ~ ~ O O o O
o ~I C~ . . . . . . . . . . . . . .
o ~ C~ o o ~ o ~ o o C) o o o o o o o
P
u~ ~n U~ u~
o o cr~ ~ ~ c~l ~ u~ ~ ~ ~ c~l ~ ~1 1
J O r~l U
E-l ~ P t.~ o o o o o o o o o o o o o o o
a? S~
r~
U~ ~Z
~0~7~ 9172
Exam~ 10
The ultrafiltration apparatus of this invention
~as also employed for the concentration and separation
of the protein fraction of cottage chee~se whey from
the bulk of the water, lactose and dissolved salts.
Porous carbon tubes with pore volumes w:ithin the
preferred range previously indicated were coated with a
"precursor" magnesium-aluminum spinel in a manner similar
to that of ~xample 6. A feed solution with 90 per
cent of the liquid phase extracted was passed through the
apparatus of 120F for 20 hours keeping essentially all
of the protein in the concentrate. The permeation rate
at the end of the run was 60 GFD. The tubes were cleaned
with distilled water and a new feed solution passed
through the apparatus. After 6.5 hours of operation
the permeation rate dropped from 51 to 33 GFD. After
washing with a Tergitol(l) 15-S-5 wash the permeation rate
of the feed solution returned to 57 GFD. The tubular
members were then cleaned with the Tergitol(l) wash and
purged with steam at 8 psig. to sterilize the tubes and
remove particulate matter.
A new feed solution was fed to the apparatus
and the initial permeation rate was 63 GFD. After 2 hours
of continuous operation the permeation rate was 51 GFD
and after 24 hours, 36 GFD. It was therefore evident
(l)Trademark oE Union Carbide Corporation for a group
of higher sodi~m alkyl sulfates.
- 42 -
9172
~0 67 ~ ~
that the tubular membex and metal oxide coating could
be cleaned and sterilizad with ste~l to return the
performance to a high level.
Although the invention has been illustrated
by the preceding examples it is not to be construed
as being limited to the materials etnployed thereln,
but rather, the invention relates to t~e ganerlc area
as hereinbefore disclosed. Various modifications and
embodiments can be made without departing ~orm the
spirit and scope thereof.
- ~3
