Note: Descriptions are shown in the official language in which they were submitted.
49~3~ii
This invention relates to the separation of lower melting
point constituents (generally oil and isoparaffins) of a slack
wax for recovery of a deoiled commercially acceptable parafin
wax.
The invention makes refined paraffin waxes from slack waxes
by a novel method and apparatus requiring a low cost installa-
tion and giving yields comparable to those accomplished in a
solvent deoiling process.
Solvent dewaxing of lubricating oil distillates results in
the occurrence of large quantities of slack wax. Slack wax is
a mixture containing isoparaffins, normal paraffins and also
lower melting point constituents usually referred to as oils
and napthenic constituent5. The slack wax may contain from about
5% - 25~ of oil as determined by ASTM test #D 721.
For many years it has been known that the oil content of some
oil-containing waxes may be reduced by resort to the so-called ~-
sweating process. This, essentially, involves providing a mass
of the oil-containing wax at a temperature sufficiently low for
it to be solid and then very gradually raising the temperature of
the solidified ~ass whereby the components of lower melting point
will tend to beco~e liquefied and drain away at least in part from
the higher melting point wax. While there have been various pro-
posed procedures for accomplishing sweating, it has been recognized
that sweating, at least as heretofore practiced, is very inefficient
~. .
~ 25 and time consuming. The time required for processing a given stock
: ~ .
` completely may vary from several days to as long as several weeks.
The wax sweating as heretofore carried out also is inefficient
ln that the separation of the oil and other lower melting point
constituents is far from complete, with the result that in order
to reduce the oil content of the hard wax to desired specifications
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it is not unusual to employ several successive sweating operations.
The disadvantages incident to sweating as a method for reducing
the amount of low melting point constituents in a wax composi-
tion such as slack wax has led the industry to place reliance
for the most part on the solvent extraction procedure wherein a
wax such as slack wax is dissolved in a solv~nt such as methyle-
thylketone (or methylisobutylketone) followed by chilling the
solution to cause precipitation of the desired portion of the
; wax which is filtered out using a rotary vacuum filter. For
most purposes solvent extraction does not reduce the oil con-
tent of the wax to a sufficient extent in one stage and the
wax-rich product resulting from the initial extraction is reslurried
at least once with additional solvent followed by cooling and subse- ~ ;
quent filtration. By two or more successive operations the re-
sulting product is expected to contain less than 1% of oil. Ascompared with the equipment required for this invention, the equip-
ment for solvent extraction requires a very substantially greater
capital investment. Moreover, the equipment used for solvent
extraction as a matter of economics does not lend itself to the
economic constructlon of processing equipment for small-scale
operation.
It is apparent from the foregoing there has been a recognized
need for a deoiling procedure applicable to slack wax or the like
which would be comparable in effectiveness to the solvent extrac-
tion procedure but which could be installed and placed in opera-
tion at much less expense and which lends itself not only to large-
scale operations but also to scaled-down operations.
It is a principal object of this invention to provide improved
method and apparatus whereby lower melting point constituents may be
removed from a wax composition such as slack wax at much less ex-
. . ~ .
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9~0~9a~s
pense for equipment and plant installation as compared with the
re~uirements for solvent extraction but at comparable operating
costs and yields.
It is a further and more particular object of this invention
to improve upon prior procedures so as to realize very substan-
tial economic advantages not only as compared with prior sweating
procedures but also as compared with the solvent extraction pro-
cedure.
A still further object of this invention is to provide an
economic procedure for deoiling slack wax or similar wax com-
position which may be employed to advantage as to the production
of lubricating oil distillates. In the manufacture of lubricating
oils the various section units including those for accomplishing '
distillation, solvent extraction for the removal of low
viscosity index oilsj dewaxing the extracted oils or raffinates ;~
and final finishing by clay treatment of hydrogenation are
fairly balanced to capacity in each section to produce the
maximum throughput of finished oils. If a refiner wishes to
make hard or refined waxes from the slack waxes, it is
' 20 necessary to stop the operation of lubricating oil pro-
i duction and carry out a blocked operation to produce the
refined paraffin waxes unless the refiner has gone to the
expense of providing deoiling equipment that can be used for
this purpose and that is of sufficient capacity to complement
the continuous production of lubricating oil. Deoiling by
sweating as heretofore known and practiced has not been
regarded as feasible for this purpose because it is so
' inefficient and time consuming. The solvent extraction
procedure for deoiling slack wax is more expeditious but the
equipment cost for doing so at a capacity commensurate with
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943~
the continuous production of lubricating is so great coupled
with the relatively slow amortiza-tion of such equipment
that refiners are hesitant to install such equipment for the
special purpose of wax deoiling. The improvements afforded
according to this invention make it possible to accomplish
the deoiling o-f slack wax much more rapidly as compared with
prior sweating procedures at an equipment: cost that is only a
fraction of the cost of solvent extraction deoiling equipment.
And since the operating cost is less, this invention makes it
possible for the first time to accomplish the deoiling of
slack waxes on an economically feasible basis without inter-
rupting the recovery of lubricating oil distillates.
Thus, in accordance with the present teachings, a
method is provided of separating lower melting point components
from higher melting point components of a wax composition.
! The method comprises confining in the solid state between
opposed surfaces a bcdy of wax composition about 1/16 to about
1/2 inch in thickness with an upper margin disposed sufficiently
above its lower margin for permitting selective gravitational
drainage of melted components of wax composition downwardly in
the direction from the upper margin to the lower margin leaving
higher melting point components in the solid state confined
between the opposed surfaces. The body of wax is from about
4 to about 24 inches in depth ~rom the upper margin to the
~, lower margin and the temperature of the suraces o~ the body
are gradually raised through a temperature range during which
lower melting point components selectively drain from the body
, , . : 1 : ':,
' of wax composition and leaving residual higher melting point
wax in the solid state in the space between the surfaces. The
drained lower melting point components are recovered and
therea~ter the higher melting point components are melted and
, recovered separated from the lower melting point components.
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In the practice of ~his invention a body of slack wax
or the equivalent is confined so as to be caused to occur in the
form of a slab which ranges in thickness from about 1/16 inch
to 1/2 inch and the width of which is of the order of 4 to 24 ;
inches. The slab is confined between surfaces, the temperature
of which is subject to control, and the slab as so confined is
so disposed that drainage of oil or other lower melting point
constituents occurs across the aforesaid width of the slab
provides a depth of about 4 to 24 inches going from the upper
margin to the lower margin. The length of the slab is not ~ -
critical and may be determined according to the desired size
of the plant installation. Thus, the length of the slab may
range from only a few inches to as long as 30 feet or more.
The lower margin of the slab as thus held between the two
surfaces is open in order to permit such lower melting point
constituents as may become formed to drain therefrom for
collection in a suitable receptacle. The upper margin of
the device is open so that the space between the surfaces
may initially be filled with a charge of slack wax or
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~ -5a-
s
recycled wax by flowing it in when in the melted state. The
slack wax or recycled wax is cooled by means of the conduits to
become a solid mass having a temperature usually several degrees
lower than the melting point of the wax in process. At this time
the temperature of the surfaces which confine the slab of wax
is gradually increased from an initial temperature at which
the wax is solid through temperatures at which the lower melt-
ing point of constituents tend to become selectively melted. An
environment is provided wherein the lower melting point consti-
10 tuents as they become reduced to the liquid state find escapepaths such that their removal is much more effective and rapid
as compared with the wax sweating procedures heretofore used.
In our commercial installation the thin slabs of oil-con-
taining wax are confined in the spaces between a succession of
plates or sheets which are vertically disposed and which are
spaced from each other so as to afford a battery of cells wherein
;
the spacing between the plates is the aforesaid distance of about
1/16 inch to about 1/2 inch, the width of each of the plates
being such that a slab of wax may be confined between them which,
as aforesaid, is of the order of 4 inches to 24 inches in depth
from its upper margin to its lower margin. The space-s between
the plates are open at the top and at the bottom. While the
spacing between the plates may be even less than 1/16 inch, the
overall operation becomes more costly. If the spacing exceeds
1/2 inch, difficulties may be encountered because of increased
tendency of the wax to prematurely drop out and the rate of heat
:
transfer is lower than desired. Moreover, the drainage of the
lower melting point constituents hecomes less efficient with
wider spacing. Preferably the spacing between the plates is from
. :~
about 1/8 inch to 1/4 inch. In like manner the drainage of the
6.
. .
lower melting point constituents becomes less efficient and the
yield becomes decreased if the depth of the cell across which
drainage occurs is substantially greater than 24 inches. Ordinarily
the cells are produced so that the depth across which drainage
occurs is of the order of 6 inches to 12 inches. In a commer-
cial installation it ordinarily is the case that the cell
plates are disposed with the width across which drainage occurs
at or close to the true vertical, namely, 90 to the horizon~
tal. However, while this is preferred, it is not critical.
Thus satisfactory results have been obtained when the plates are
dlsposed so that the width across which drainage occurs is at
an angle of 45 to the horizontal. Accordingly, the term
"vertically disposed" as used herein and in the claims is to ~-
be understood as comprehending any disposition of the plates
other than the true vertical so long as the vertical disposition
relative to the horizontal is sufficient to induce effective
, ~,. . .
gravitational drainage of the lower melting point constituents
leaving the desired hard wax within the cells.
The temperature of the plates is controlled by conduits for
a temperature-controlling fluid which may be gaseous such as high
velocity air but preferably is a fluid such as water. These
,~
conduits successively traverse the plates of the battery of
cells and the cells between the plates and they are distributed
about the plates in thermally-conductive relation therewith so
that the entire surface of each plate may have its temperature
controlled substantially uniformly throughout. The conduits
typically are in the form of pipes about 1/4 inch to 3/4 inch in
internal diameter and distributed so that there are suEficient
pipes to maintain rapid heat transfer. The conduits are supplied
30 with the temperature-controlling fluid in any suitab:Le way, as -
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by the employment of a header that is connected with a source
which supplies fluid at the desired temperature for use during
the different phases of the deoiling process. Similarily, the
conduits discharge into a complementary header from which the
fluid may be returned so as to be recycled. The plates may
be made of any suitable structural heat-conductive material.
Ordinarily the plates are in the form of sheets of a metal such
as tinned copper, tinned brass, aluminum, stainless steel, or
protected iron. Best results are obtained by the use of a ma-
terial having a high degree of thermal conductivity. Plates or
sheets of tinned copper or of aluminum are preferred. For similar
reasons the conduits preferably are made from tinned copper or
aluminum.
The battery of cells may be filled with the wax when it
is at a temperature somewhat above its melting point. In order
that the heat-liquified wax may remain confined in the space
between the plates, the wax-receiving receptacle below the
battery of cells is adapted and arranged so that it may be fill-
ed with cold water to a level at or slightly above the lower
margin of the plates. The wax, because of its lesser specific
gravity floats on the water and likewise becomes cooled sufficien-
tly to solidify. Moreover, the plates themselves at this stage
are maintained at a temperature below the melting point of the
; wax. The wax, therefore, fills the interstices between the
plates and becomes solidified. A~ter the cells have been filled ;
with solidified wax the water is arained from the receptacle and
, :
the temperature of the plates is gradually increased so as to
cause the lower melting point constituents to drain off to the
desired extent. These constituents are collected and removed
for further process. The residual wax rom which the oil has
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9435
been largely removed may now be recovered by heating the plates
to a temperature sufficiently above the melting point o~ the wax
to cause the wax to melt relatively rapidly and so that it may be
collected and separately recovered.
While the practice of this invention is to be regarded as
generally applicable to the removal of lower melting point
constituents from certain wax compositions, it is especially
adapted for us in connection with the deoiling of slack wax
of the type that occurs during the production of lubricating
oil distillates. Such slack waxes usually have a melting point
in the range from about 112 to 140F. The oil content may be
from about 5~ to about 30%. However, the amount and nature of
the lower melting point constituents such as oil and isoparaffins
varies depending on the source from which the slack wax was ob-
tained, and the method of refining. The objective of the com-
plete deoiling procedure is to recover the hard wax, generally
normal paraffins wherein the oil content has been reduced to a
prescribed value such as 1/2~ to 1~.
In the practice of this invention the slack wax is heated
to a temperature of about 15F above its melting point. However,
before doing so, the wax-receiving receptacle is filled with
~ water at a temperature below the melting point of the wax, e.g.
; ~ about 70F, to a level at or just above the bottom margins of the
cells. At the same time cooling water at a temperature of about
50F to about 80F below the melting point of the wax is caused
to flow through the conduits in the cell battery. Under these
! condltions the wax becomes solidified first in the lower portion
of the cells and thereafter throughout the cells. The tempera~
ture of the confined solidified wax may, for example,~ be from
about 10 F to about 20F below its melting point. A~ter draining
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9.
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the water from the wax-receiving receptacle the removal of the
lower melting point constituents is initiated by causing the
temperature of the cell plates to be gradually increased, e.g.
at the rate of about 1F to about 5F per hour, and this is
; 5 continued until the temperature reaches a predetermined maximum
which may, for example, be from about 2F to about 5F below the
melting point of the wax. As the heating progresses, the oil
and any other lower melting point constituents find avenues
for readily draining through channels adjacent the plate sur-
faces, leaving the harder wax behind. During this period theseparated oil is collected in the wax-receiving pan and is removed
to a suitahle container. Having extracted as much oil as may be
regarded as practical for a single treating operation, the
` plates are then heated rapidly to a temperature of about 10F
to about 20F above the melting point oE residual hard wax. Under
these conditions the cells are rapidly cleared;and the deoiled wax
is collected in the wax-receiving pan and recovered.
During a single deoiling operation the oil content of the
original slack wax may be reduced by 40% - 80% of the original oil
content. This may be accomplished in about 12 hours creating by-
product in the form of foots oil (heating oil or cracking stock).
The loss in the form of foots oil may be in the order of
30% to 50% of the weight of the original slack wax. The foots
oil is largely a combination of oils and isoparaffins. The re-
.:
duction of oil content accomplished varies with the original oilcontent of the slack wax. High oil contents in slack waxes, such
as 30%, are less responsive to treatment than those having an oil
content of 7% to 20%. As an oiI content in the hard wax of less
than 1% is desirable, the best ultimate yields of hard wax are
obtainable by a second deoiling treatment carried out substantially
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~4~;35
in the same manner as the first deoiling treatment. Since the
oil content in the hard wax has been substantially reduced by the
first treatment, the amount of foots oil produced is much less in
the second treatment. The decrease in weight in the second de-
oiling treatment will be substantially less than in the prim- ~`
mary treatment. By performing two deoiling operations, each
operation requiring about 12 hours' duration, it is possible to
reduce the oil content of the residual hard wax to around 0.3%
to 0.9%. The results may vary depending upon the original com-
position of the slack wax and the nature of the crystal structure
produced in changing the slack wax from liquid phase to solid
phase in the cells. The yieIds of hard wax with a certain oil
content are of the same order as those obtained by the solvent
extraction process but use much less costly processing equipment.
The recovered wax, after conventional finishing treatment, fully
.~j
meets industrial specifications for a wax of the type in ques- ~ `
tion.
Further objects, features and advantages of this invention
will become apparent in connection with the following description `
; 20 of certain illustrative embodiments of the apparatus of this invention and the use thereof in practicing the method~of this
invention, wherein:
` Figure 1 is a perspective view of a battery of wax deoiling
.~ cells embodying and using the invention;
~-~ 25 Figure 2 shows a section taken on the line 2-2 of Figure 1
in combination with the tray that is used therewith to provide
; the deoiling unit;
Figure 3 is a section on an enlarged scale, with the central
portion broken away, taken on the line 3-3 of Figure 2;
Figure 4 is a diagrammatic representation of the deoiling
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11 .
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- unit comprising a single cell battery and tray together with
accessory supply and product recovery equipment which illustrates
the practice of this invention in a typical wax deoiling procedure;
and
Figure 5 is an end elevation that is illustrative of a typical
arrangement of a plurality of the deoiling units suitable for a
commercial installation.
The cell battery is indicated generally hy the reference
character 10. It ~omprises a succession of sheets or plates 11
which extend between the side bars 12. In the illustrative
embodiment shown, the plates are spaced from each other by a
; distance of 1/8 inch and the width from top to bottom is 8 inches.
Twenty-gauge aluminum sheeting, for example, affords a preferred
material for the cell plates. The plates 11 and the cell spaces
between them are traversed by a plurality of conduits for a tem-
perature-controlling fluid which ordinarily is water. In the em-
bodiment shown, the conduits are copper tubes having an inside
diameter of about 3/8 inch. These conduits are distributed through-
out the lateral area of the plates 11 and since they are in heat-
conductive relation therewith, the temperature of the plates 11
j may be controlled and adjusted substantially uniformly throughout.
There is, therefore, a large heat-conductive surface area which
transmits heat rapidly and provides a largely uniform temperature
throughout the mass of confined wax in the cells of the battery.
At one end, the conduits 13 open into a header 14 and at the other
end they open into a header 15 so that the temperature-controlling
fluid may be caused to flow through the conduits 13 from one header
`l to the other.
.. .
The cell battery is carried within the wax-receiving tray 16,
which is sloped downwardly toward its center as indicated in
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12.
~49435
Figure 2 in order to facilitate the withdrawal of liquid material
from the tray. The tray may be made of appropriate material, e.g.
steel plate with a rust-resistant coating or stainless steel.
One arrangement of the cell battery with associated equip-
ment that is illustrative of the practice of this invention is
indicated largely diagrammatically in Figure 4. As aforesaid,
the first step in carrying out the invention using the exempli-
fied equipment shown in the drawings is to fill the lower por-
tion of the tray 16 with water at a temperature below the melt-
ing point of wax. Water is supplied from any available sourcesuch as the water main 17 and by opening the valves 18 and l9 the
water is directed by the line 20 into the tray 16. The level of
` the water 21 in the tray l6 is determined by the level of the
outlet line 22, which directs any overflow to the settling
tank 23 and which is steam-traced, as partially indicated at
23A. This line preferably is steam-traced so as to minimize
the possibility of blockage due to any wax particles that might
flow into this line. As soon as the desired water level in
the tray 16 has been attained, the valves 18 and l9 are closed.
As aforesaid, this water level is at or slightly above the bot-
tom margins of the plates ll in the cell battery 10.
` Slack wax obtained from storage (not shown) is pumped by ;~
line 24 into the wax-heating tank 25 wherein the wax is heated
~ to a temperature above the melting point of the wax by the em-
i 25 ployment of a suitable heating eIement such as the steam coil
26. The desired temperature may be maintained by the use of
the temperature controller 27 which controls the action of the
valve 28 so as to supply the amount of heat required to maintain
the wax at the desired temperature. When the wax has attained
the proper temperature it is pumped by pump 29 through the line
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30, which is steam-traced as indicated partially at 30A, to -the
distributor pipe 31 which distributes the melted wax over the
extent of the cell ba-ttery so as to fill al] of the cells. Uni-
form filling of the individual cells is promoted by the provision
in the plates 11 of openings 32 which permit the wax to flow from
one cell to the other so that the wax in the various cells will
assume the same level. When the cells have become filled to the
top any excess wax is permitted to drain from the battery 10
through the line 33 to the overflow slack wax tank 34 wherein the
desired temperature is maintained by the heating unit in the form
of steam coil 35 sub~ect to the temperature controller 36 which
controls the operation of the valve 37. The overflow wax is
pumped from the overflow tank 34 to the wax-heating tank through
the line 38 by the pump 39.
When all of the cells in the battery 10 have been filled to
the desired level with the wax the pumping of the wax is discon-
tinued and cold water is caused to flow through the conduits 13
in the cell battery so as to lower the temperature of the plates
and correspondingly lower the temperature of the wax confined be-
tween the plates. To this end water is admitted into the water
tank 42 by the line 40 controlled by the valve 41 from the main
17~, the valve 18 being open. Cold water is pumped by the pump
43 through the line 44 to the header 15 for passage through the
plurality of conduits 13 to the header 14 from which the water
is returned by the line 45 to the water tank 42. To the extent
; necessary to maintain the desired minimum temperature for solidi-
fying the wax, the water may be drained from the water tank 42
-
by the line 4~ controlled by the valve 47. The water thus drawn
off may be disposed of in any suitable manner as by discharge in
a sewer. In order to take its place, additional cold water is
14.
104943S
supplied to the tank 42 from the main 17.
During the supply of the wax to the cell the cold water 21
in the tray 16, the level of which is at or slightly above the
lower margin of the plates of the cell battery, serves to float
the wax during its solidification and cause it to be retained
confined between successive plates of the battery. When the
cold water is likewise circulated through the conduits in the
battery of cells, the entire mass of wax within the respective
cells becomes converted to the solid state as the result of cool-
ing the wax to a temperature below the melting point of the wax.When the wax has become sufficiently cooled the circulation of
the cold water is stopped and the water 21 in the tray 16 is
drained out through the line 48 controlled by the valve 49 and
is directed by line 22 to the settling tank 23.
The wax in the battery of cells has now been prepared for i
the removal of the lower melting point constituents of the wax
by appropriate and controlled heat treatment. To this end the
water in the tank 42 is initially brought to a temperature which,
for example, may be about 10 below the melting point of the wax.
The temperature in the tank 42 is controlled by the heating
element 50 which is in the form of a steam coil. The tempera-
. ~
ture of the water in the tank 42 may be controlled by the tem-
perature controller 51 which regulates the valve 52, as desired,
for admitting steam from the steam line 53 in sufficient amount
25 to maintain the desired water temperature. These controls for -
the water in the water tank 42 are arranged so as to gradually
increase the water temperature at a predetermined rate which or-
dinarily varies from about 1 to about 5 per hour. As the tem-
perature of the wax in the battery 10 is gradually increased re-
sponsive to the gradual increase of the temperature of the plates,
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9~35
which in turn respond to the temperature of the water, the lower
melting point constituents such as oil and isoparaffins begin to
drain from the wax mass transversely across the width of the pla-tes
11 so as to flow down by gravity and drop from the lower margins
5 of these plates into the tray below. At this point, flow from .
the tray 16 is permitted to occur only through line 54 controlled
by the valve 55 which is open, thereby allowing the oil mixture
to be discharged into the foots oil storage tank 56. The gra~
dual heating of the wax is continued until the residual wax has
the composition that is sought to be obtained. This composition
: corresponds with that which has been found to be desirable as the ::
result of prior laboratory evaluations. Once the correct composi-
tion has been predetermined by laboratorv evaluation, commercial ..
operations can readily be controlled accordingly so as to obtain
the desired composition of the retained wax.
When the temperature for obtaining the desired wax composi-
. tion has been attained the valve 55 controlling the removal of
the foots oil is closed and the temperature of the water from the
water tank 42 that is flowed through the battery 10 is rapidly in~ :~
creased to a temperature sufficiently above the melting point of
the wax that remains in the battery so that the cells will become :
substantially cleared of any retained wax. The melted wax is drain-
; ed from the tray 16 through the steam-traced line 57 upon open-
. ing the valve 58, which is closed as soon as the tray has been
completely drained. The finished wax is directed by the line 57
into the finished wax-holding tank 61 from which it may be pumped .... --
by the pump 59 in line 60 for such working up as may be desired.
The~sequence having been completed, the heated water in
. ` .
. : the conduits 13 and headers 14 and 15 and in the water tank 42
is drained off and replaced by cold water whereupon the sequence
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16.
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9~3~i
of operations above-described may be repeated.
While the practice of the invention has been described in
connection with the use of a single battery of cells disposed as
a unit which also comprises a wax-receiving tray, it is apparent
that in an ordinary operation on a commercial scale it is con-
sistent with economy to employ a number of units each comprising
a cell battery and its associated wax-receiving tray. In such
case, the units would ordinarily be connected by appropriate
valve-controlled piping for accomplishing the supply and re-
moveal of the materials as hereinabove described. For example,as illustrated in Figure 5, in a wax deoiling installation twelve
or more units 62 supported by frame members 63 may be housed
in a wax deoiling chamber 64 having thermally insulated walls 65
and operatively connected by suitable valve-controlled conduits
under common control to common supply sources of water and wax
and to common receivers for the different effluents, as illustrated
hereinabove and in Figures 1-4 in connection with a single unit.
If desired, trays 66 may be provided to catch any accidental
spillage. As shown in Figure 5, the chamber 65 desirably is -
within a larger building 67 the walls of which likewise prefer-
ably are provided with thermal insulation. A 2-inch layer
of polyurethane foam provides satisfactory thermal insulation
for both the building 67 and for the wax deoiling chamber 65,
respectively. The insulation is desirable in order to obtain
better temperature control during the various stages of the
deoiling procedure. The building 67 provides protec-tion not
only for the operator but~also for the supply tanks, receiving
`~ receptacles, pumps, control devices, etc., that have been de-
scribed hereinabove. The chamber 64 may be supplied with obser-
vation windows 68 the upper one having an observation platform 69
17.
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associated therewith. The atmosphere within the building 67 may
be kept fresh for breathing by maintaining the pressure oE the
atmosphere in the building 67 slightly higher than that of the
atmosphere in deoiling chamber 64 so that, to the extent that
there may be any seepage, the air will seep into the chamber 64
from the building 67 with concomitant expulsion in correspond-
ing amount of contaminated air from the chamber 64 through the
outlet duct 70 and to the outside atmosphere.
EXAMPLE
The following example using laboratory-scale tests illustrates
the utility and advantages of this invention in comparison with
conventional sweating and in comparison with the solvent extrac-
tion method for the removal of oil and isoparaffins, essentially
the same slack wax starting material being used in each case.
The wax used in each test was typical slack wax having an oil
content of 8-9% (ASTM-D-721-68), a melt point of 123.8F
(ASTM-D-87-66) and a penetration of 77F of 30/32 ~ASTM-D-1321-70).
In carrying out the invention of the present application, a bat-
tery of 144 cells was employed made up using aluminum plates
of 26 gauge separated from each other by 1/12 inch and traversed
by conduits 1/4 inch in inside diameter for the flow therethrough
of the water used to control the temperature of the plates. The
cell battery which was use~ contained 144 cells defined by ver-
tical plates, the vertical dimension being such as to be con-
fined between each pair of plates a body of wax substantially 8inches in depth from the upper margin to the lower margin. For
laboratory use, the plates were substantially 1 3/4 inches in
horizontal lenyth. In carrying out the test, the wax was in-
troduced into the cells in the manner hereinabove described when
at a temperature of 140F and it was reduced to the solid state
18.
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by cooling to 100E'. The deoiling was accomplished by
increasing the temperature of the temperature-controlling water
at the varying rate of 1F to 5F per hour over a period of 12
hours. At the conclusion of the 12-hour period, deoiling was
discontinued and the residual hard wax was recovered by raising
the temperature of the temperature-controlling water to 150F
at which the residual hard wax became melted and was drained
from the cells. The ce]l battery was then charged a second time
with the slack wax having the properties aforesaid and the de-
ln oiling was carried out in the same way so as to obtain a
i second quantity of the residual wax. The two quantities of de-
oiled wax were then commingled and the commingled quantities
of slack wax were subjected to deoiling following the same regime.
For the test procedure illustrative of conventional sweat-
ing, a sweating pan was used of the type currently employed by
- oil refineries that employ this sweating procedure. For pur-
poses of the test, a block of solidified slack wax measuring
8" x 8" x 8" and having the properties aforesaid was supported
so as to permit drainage and was exposed to gradually increasing
temperature in a temperature-controlled oven wherein the
temperature was increased at the rate of about 1/2F to 5F
~; per hour from a starting temperature of 105F, the total sweat-
ing period being 30 hours.
~n testing the solvent extraction method, methylethylke- ~ -
tone-toluol was used as the solvent and conventional plant
; solvent dewaxing procedure was adapted to a laboratory-scale
operation suitable for application to slack wax having the pro-
perties hereinabove mentioned. In this procedure an amount of
50 grams of slack wax was weighed and added to 150 grams of a
50% MEK - 50% toluol mixture in a flask. The temperature was
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~4~35
raised until the wax was completely dissolved in the MEK-toluol
mixture. With vigorous stirring of the mixture, the flask was
cooled at a rate of about 2F per minute until a uniform mixture
resulted. At this point, tempera-ture reduction rate was
increased until the temperature was lowered to 40F or 50F.
Previously, a glass funnel with a fritted glass bottom was
covered with medium filter paper for the following procedure.
The funnel discharged the filtrate into an Erlenmeyer flask with
a side neck which was connected to a vacuum pump and receiver.
The funnel was maintained at a constant temperature of 50F,
while the slurry was filtered through the filter paper in the
funnel. A wax cake was formed, removed from the funnel and
weighed. The cake was then heated under vacuum until all the
ketone mixture was distilled. The yield of wax was then deter-
mined by weighing. The second solvent extraction was then carriedout in the same manner as described above for the primary solvent
operation. The yield by weight of the wax was determined, after
which a laboratory analysis determined oil content, penetration
and melting point of the wax.
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The comparative results obtained from the above-described
comparative tests are listed below:
DEOILING DEOILINC~
BY BY
CONVENTIONAL IMPROVED SOLVENT
SWEATING METHOD EXTRACTION
After First Solvent
Treatment
After First 3/1 Solvent Ratio
After 30 Hrs Treatment 12-Hr. Treat. (50% MEK-50% Toluol)
Oil Content % 1.26 1.13 1.77
Melt Pt. F 124 128 126
Penetration
at 77F - 20 23
Yield % of
Orig. Chge. 40 55 62
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DEOILING DEOILING
BY BY
CONVENTIONAL IMPROVED SOI,VENT
- SWEATING METHOD EXTRACTION
;~ After Second Treat.
After Second 3/1 Solvent Ratio
No Second Treatment 12-Hr. Treat. (50% MEK-50~ Toluol)
Oil Content % - 0.49 0.86
Melt Pt. F - 132 132
Penetration
at 77F - 16 17
Yield % of
Orig. Chge. - 41 42
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~49435
It is apparent from the foregoing that as compared with con-
ventional wax sweating procedure the present invention enables
the oil to be removed much more efficiently and with better
yield. As compared with solvent extraction, the present in-
vention enables oil to be removed with substantially greater
effectiveness. This may be accomplished commercially at approxi-
mately the same operating cost. While as compared with solvent
extraction the time required for deoiling a given amount of
slack wa~ is somewhat greater, this is more than offset by the
fact that for a given throughput the expense for plant installa-
tion is much less than that for a solvent extraction deoiling
system. It also is important commercially that the equipment
requirements for the practice of this invention can be scaled up
or down roughly in proportion to difference in throughput capaci-
ty whereas the equipment used for solvent extraction does not
lend itself to scaling down without a disproportionate increase
in cost.
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