CA1049435A - Method and apparatus for wax deoiling - Google Patents
Method and apparatus for wax deoilingInfo
- Publication number
- CA1049435A CA1049435A CA229,394A CA229394A CA1049435A CA 1049435 A CA1049435 A CA 1049435A CA 229394 A CA229394 A CA 229394A CA 1049435 A CA1049435 A CA 1049435A
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- CA
- Canada
- Prior art keywords
- wax
- melting point
- plates
- wax composition
- temperature
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G73/00—Recovery or refining of mineral waxes, e.g. montan wax
- C10G73/36—Recovery of petroleum waxes from other compositions containing oil in minor proportions, from concentrates or from residues; De-oiling, sweating
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- Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Battery Electrode And Active Subsutance (AREA)
- Adhesives Or Adhesive Processes (AREA)
Abstract
ABSTRACT
The deoiling of slack wax or similar wax composition is accomplished while the wax is confined in cells provided by a series of plates which are spaced apart by only 1/16 to 1/2 inch and which are vertically or otherwise disposed for drain-age along the surfaces thereof from an upper margin to a lower margin. The plates are traversed by a multiplicity of conduits for a temperature-controlling fluid such as water. During the treatment the lower melting point constituents of the confined wax composition become progressively melted responsive to gra-dual increments of temperature increase and drain transversly along the plates through a distance which is from about 4 to 24 inches and preferably is of the order of 6 to 12 inches so as to become separated from the residual end product wax. The deoiling thus accomplished is much more effective and more rapid as compared with sweating procedures. It compares favorably in these respects to deoiling by solvent extraction. The instal-lation cost of this process is a fraction of the cost of conven-tional solvent deoiling.
The deoiling of slack wax or similar wax composition is accomplished while the wax is confined in cells provided by a series of plates which are spaced apart by only 1/16 to 1/2 inch and which are vertically or otherwise disposed for drain-age along the surfaces thereof from an upper margin to a lower margin. The plates are traversed by a multiplicity of conduits for a temperature-controlling fluid such as water. During the treatment the lower melting point constituents of the confined wax composition become progressively melted responsive to gra-dual increments of temperature increase and drain transversly along the plates through a distance which is from about 4 to 24 inches and preferably is of the order of 6 to 12 inches so as to become separated from the residual end product wax. The deoiling thus accomplished is much more effective and more rapid as compared with sweating procedures. It compares favorably in these respects to deoiling by solvent extraction. The instal-lation cost of this process is a fraction of the cost of conven-tional solvent deoiling.
Description
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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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 ,~
~ -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.
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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 -,' 7.
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 8.
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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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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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- 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.
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The cell battery is carried within the wax-receiving tray 16, which is sloped downwardly toward its center as indicated in . ~ ~
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.
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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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 .. .. . .
:' ,.. , . - , ..... , .'.. ' '' .: ~ .' : , . '~,' ~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.
--~
.
. , .
~ 20.
.'~' `' .
$, 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 ': ' 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 , . .
: : ,.
. :
: ':
. .
- 21.
.
, ~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.
. . .
~.` ' .
~ ', , 1 ,: ~
; 22.
- .
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 , .
', - ~ . ~ ,. .
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-. . ~ .
:
. . ~ .
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 .
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.
:i , .
, ~
~5~
. . . , :
, 3~
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 ,~
~ -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 -,' 7.
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 8.
:
.. . . . .
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 .
9.
g43~
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 ~:
, 10.
.. : . :. .
~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 .
11 .
~ . . . .
- 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 . ~ ~
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 .~ .
~` 13.
,~ , . . . . .
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.
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, ~' .
15.
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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 .
16.
, . ; - . . . . ..
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.
.~,, ~.
. .. . .
~4~4~S
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 .. .. . .
:' ,.. , . - , ..... , .'.. ' '' .: ~ .' : , . '~,' ~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.
--~
.
. , .
~ 20.
.'~' `' .
$, 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 ': ' 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 , . .
: : ,.
. :
: ':
. .
- 21.
.
, ~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.
. . .
~.` ' .
~ ', , 1 ,: ~
; 22.
- .
Claims (9)
1. A method of separating lower melting point components from higher melting point components of a wax composition which comprises confining in the solid state between opposed surfaces a body of wax composition about 1/16 to about 1/2 inch in thick-ness with an upper margin disposed sufficiently above its lower margin for permitting selective gravitational drainage of melted components of said wax composition downwardly in the direction from said upper margin to said lower margin leaving higher melting point components in the solid state confined between said opposed surfaces, said body of wax being from about 4 to about 24 inches in depth from said upper margin to said lower margin, gradually raising the temperature of said surfaces through a temperature range during which lower melting point components selectively drain from said body of wax composition leaving residual higher melting point wax in the solid state in the space between said surfaces, recovering the drained lower melting point components and thereafter melting and recovering said higher melting point components separated from said lower melting point components.
2. The method of claim 1 wherein the thickness of said body of wax composition is from about 1/8 inch to about 1/4 inch.
3. The method of claim 2 wherein the depth of said body of wax composition is from about 4 inches to about 12 inches.
4. The method of claim 1 wherein said wax composition is slack wax containing a normal paraffin wax and other components of lower melting point and wherein during said gradual heating said lower melting point components are selectively drained from normal paraffin wax retained between said surfaces.
5. The method of Claim 1 which comprises confining a succession of said bodies of said wax composition in the solid state between opposed surfaces presented by a succession of plates disposed at an angle at least about 45° to the horizontal, directing a liquid through a plurality of conduits that traverse said plates in thermally conductive relation therewith and gradually raising the temperature of said liquid thereby gradually raising the temperature of the surfaces of said plates in contact with said bodies of wax composition through said temperature range during which lower melting point components selectively drain from said bodies of wax composition.
6. The method according to claim 5 which comprises initially introducing the wax composition into the spaces between opposed surfaces of said plates while it is in the melted state until the depth is from about 4 to about 24 inches and cooling the bodies of wax composition until it occurs in the solid state by directing through said conduits liquid that is at a temperature lower than the melting point of said wax.
7. The method according to claim 6 which comprises equalizing the depth of the melted wax composition introduced into the spaces between said plates by flow of said wax composi-tion through openings in said plates which openings provide sufficient communication between adjacent bodies of said wax composition to equalize any initial difference in the depth of said adjacent bodies of the melted wax composition.
8. The method according to claim 6 or claim 7 which comprises closing off the spaces between said plates adjacent the bottoms thereof with cold water during the introduction of the wax composition in the melted state into the spaces between said plates and also during the subsequent cooling of the bodies of wax composition in the spaces between said plates from the melted state to the solid state and thereafter removing the water prior to gradually raising the temperature of the solidified wax compo-sition in said spaces with selective draining of lower melting point components therefrom.
9. The method according to any of claims 5, 6 or 7 which comprises carrying out the method of any of said claims within the confines of a first chamber, confining the atmosphere dis-posed about said first chamber within a second chamber at a pres-sure greater than the pressure prevailing in said first chamber, and venting atmosphere within said first chamber into atmosphere disposed about said second chamber that is at a pressure less than the pressure prevailing in said second chamber thereby mini-mizing any leakage of gases or vapors emitted in said first chamber from said first chamber into said second chamber.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US484217A US3926776A (en) | 1974-06-28 | 1974-06-28 | Method and apparatus for wax deoiling |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1049435A true CA1049435A (en) | 1979-02-27 |
Family
ID=23923234
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA229,394A Expired CA1049435A (en) | 1974-06-28 | 1975-06-16 | Method and apparatus for wax deoiling |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US3926776A (en) |
| BR (1) | BR7503999A (en) |
| CA (1) | CA1049435A (en) |
| DE (1) | DE2528185A1 (en) |
| IN (1) | IN143306B (en) |
| IT (1) | IT1040735B (en) |
| ZA (1) | ZA754018B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4013541A (en) * | 1974-06-28 | 1977-03-22 | Irwin Roy E | Method and apparatus for wax deoiling |
| EP0892033A1 (en) * | 1997-07-16 | 1999-01-20 | Sulzer Chemtech AG | Process and device for the production of paraffin and paraffin fractions |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1898930A (en) * | 1927-07-08 | 1933-02-21 | Indo Burma Petroleum Company L | Apparatus for sweating or treating paraffin wax or the like |
-
1974
- 1974-06-28 US US484217A patent/US3926776A/en not_active Expired - Lifetime
-
1975
- 1975-06-16 CA CA229,394A patent/CA1049435A/en not_active Expired
- 1975-06-21 IN IN1230/CAL/1975A patent/IN143306B/en unknown
- 1975-06-24 DE DE19752528185 patent/DE2528185A1/en not_active Withdrawn
- 1975-06-24 ZA ZA00754018A patent/ZA754018B/en unknown
- 1975-06-26 IT IT50242/75A patent/IT1040735B/en active
- 1975-06-26 BR BR5144/75D patent/BR7503999A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| US3926776A (en) | 1975-12-16 |
| BR7503999A (en) | 1976-06-29 |
| DE2528185A1 (en) | 1976-01-15 |
| IT1040735B (en) | 1979-12-20 |
| IN143306B (en) | 1977-10-29 |
| ZA754018B (en) | 1976-06-30 |
| AU8260175A (en) | 1977-01-06 |
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