JPH0214288A - Continuous self-cooling type dewaxing apparatus - Google Patents

Abstract

PURPOSE: To efficiently obtain a dewaxed oil reduced in cloud point and pour point by continuously supplying an oil obtained by preliminarily diluting a wax-contained oil with a non-self cooled type dewaxing solvent to a vertical stage tower cooling band region at a temeprature equal to or higher than the cloud point.

CONSTITUTION: Most of a wax is preferably settled in a first cooing band region under the presence of a non-self coolant type dewaxing agent to form a wax- containing slurry. This is directly sent to a second cooling band formed of a vertical stage tower continuously operated at a fixed pressure. It is cooled there to a wax filtering temperature, and the additional wax is settled from the oil by the contact with a liquid self-coolant injected in a plurality of stages to provide an intended dewaxed oil.

COPYRIGHT: (C)1990,JPO

Description

[Detailed description of the invention] The present invention relates to a solvent dewaxing device for wax-containing oil.

More particularly, the present invention involves prediluting a waxy oil with a non-self-cooling dewaxing solvent and then continuously treating the prediluted oil at a temperature above its cloud point and at essentially constant pressure. The present invention relates to a continuous solvent dewaxing apparatus consisting of feeding a cooling zone consisting of an operating vertical stage field. In the cooling zone, the wax is precipitated from the oil to form a wax-containing slurry, and the slurry so formed is a liquid self-refrigerant injected in multiple stages at a rate of 0.1 to 20 submers/min. The slurry is further cooled to the wax filtration temperature by contact with a liquid self-refrigerant that evaporates at each stage to maintain an average slurry cooling rate of about 2 to 20 degrees below average temperature drop per stage. The dewaxed oil-containing slurry is then fed to a wax filter. This equipment is particularly useful for dewaxing wax-containing lubricating oil distillates and the like.

In a preferred embodiment, the present invention comprises precipitating a majority of the wax in a first cooling zone in the presence of a non-self-refrigerating dewaxing solvent to form a wax-containing slurry, which is then continuously processed at an essentially constant pressure. A continuous non-self-refrigerant/self-refrigerant combination solvent dewaxing process is provided that utilizes two cooling zones that feed directly to a second cooling zone that consists of an operated vertically staged group. In the second cooling zone, the slurry is cooled to super-wax temperature and additional wax is precipitated from the oil by contact with liquid autorefrigerant which is injected in multiple stages as described above.

It is well known in the art to dewax wax-containing hydrocarbon oils, particularly petroleum lubricating oil distillates, to remove at least a portion of the wax to obtain dewaxed oils with reduced cloud and pour points. The most common method of removing wax or waxy components from waxy hydrocarbon oils is through the use of various solvent dewaxing methods. In the solvent dewaxing method, the temperature of the wax-containing oil is
From there it is lowered enough to precipitate the wax as solid crystals. At the same time, solvents are added hydraulically to improve the flowability of the waxed oil and reduce its viscosity, so that various filtration or centrifugation methods are used to separate solid particles of wax from the dewaxed oil. Can be used. Strong wax anti-solvents (weak oil solvents) such as MgK are often added to reduce wax solubility in oil/solvent mixtures, whereas they allow wax precipitation and at the same time increase oil immiscibility at wax separation temperatures. MIBK to change the solubility of the solvent to avoid
or a strong oil solvent such as toluene (weak wax anti-solvent)
is used. Solvent dewaxing processes produce what is known as pour point -f overtemperature spread.

This is the temperature difference between the wax f supertemperature and the pour point of the dewaxed oil. The spread of this pour point-1 supertemperature is
It becomes thicker when using a non-polar hydrocarbon bath agent than when using a ketone 6o polar solvent. Thus, the self-cooled dewaxing process using propane has a pour point below 40 -
A 1 overtemperature spread can occur, which means that the wax filter must be conducted at -40''F to produce a dewaxed oil with a pour point below 0. When using ketones or mixtures of ketones and aromatic solvents, the pour point -f supertemperature spread may be in the range 0 to 2011'' depending on the oil and solvent used.

Both ketone and autorefrigerant dewaxing methods have certain benefits and disadvantages. Thus, although the ketone dewaxing process yields a lower pour point -1 supertemperature spread at the wax f supertemperature, it also grows larger wax crystals at the f)71 boundary than in a self-refrigerating environment without a dewaxing aid. Ketones are relatively non-volatile compared to self-refrigerants, and therefore the cooling of the solvent/oil mixture by either indirect means or by mixing the oil into the cold ketone solvent can be can be achieved. In the latter case, practical considerations limit the amount and temperature of cold ketone solvent that can be added and the temperature to which the solvent/oil mixture can be cooled. Therefore, all ketone dewaxing processes require some means of indirectly cooling the wax-containing slurry following the addition of a solvent to reduce the slurry to the required wax f supertemperature. The most common method of indirect cooling is through the use of surface scraper coolers, but these coolers are expensive and difficult to maintain. Also, coolers with scrapers tend to damage the wax crystals due to the shearing action of the scraper blades.

Wax crystals grown in a self-refrigerating environment such as counter pressure, propane or propylene are generally small and therefore require the use of expensive dewaxing aids to obtain good f-overrates (solvent dewaxing operations). (although wax 1 supertemperatures can be reached by subsequent vaporization of the autorefrigerant without the need to use surface scraper coolers or indirect heat exchangers). In addition, it has been found necessary to use non-cooling in the self-cooling dewaxing process to allow for a gradual reduction in pressure. This prevents rapid flashing and thereby avoids a sudden large temperature drop (shock cooling) of the oil slurry, which is caused by - a slow oxidation of the wax from the small wax crystals and the associated dewaxed oil; Bring speed.

In some ketone solvent dewaxing processes, the waxy oil and solvent are mixed at a temperature above the oil's cloud point before being cooled. The solution is then cooled uniformly and slowly under conditions that avoid agitation of the solution as the wax settles.

In other methods, the ketone dewaxing bath is added to the oil at several points along the cooling system, but the waxy oil remains in the solvent until some wax crystallization occurs and the mixture becomes quite thick. The oil is first cooled without washing, and then a first portion of solvent is introduced at oil temperature to maintain fluidity.

Cooling is continued, more of the wax is precipitated, and a second portion of solvent is added at the temperature of the mixture to maintain fluidity. This procedure is typically repeated until a temperature in the range of about 50 to 60 degrees below is reached, at which point an additional amount of bath agent is added at the same temperature as the mixture to reduce the viscosity of the mixture; The mixture is then further cooled to the desired supertemperature in a cooler with a surface scraper. In these processes, if the solvent is introduced at a temperature below that of the oil or oil/solvent mixture, shock cooling occurs resulting in the formation of small and/or acicular wax crystals and the associated overspeed. bring about.

Furthermore, poor shock cooling effects can be caused by introducing the waxy oil into an elongated staged cooling zone or tower at a temperature above its health point and then cooling the dewaxing oil into the zone along multiple points or stages of said zone. By introducing the common agent in portions and maintaining regular agitation during said stage so as to cause virtually instantaneous mixing of the solvent and wax/oil mixture as they progress through said zone. It is well known that it can be defeated. The basic concept of this industrially successful process is disclosed in U.S. Pat. registered service mark).

Commercially successful processes using self-cooling refrigeration, such as mixing a liquid self-refrigerant with a waxy oil and vaporizing it to cool the oil by its latent heat of vaporization, have been carried out in batch or semi-semi-operational mode. This mixture of liquid self-refrigerant and oil is introduced into an expansion chamber where the pressure is gradually reduced to achieve controlled vaporization of the self-refrigerant and controlled cooling of the oil, thus flushing the self-refrigerant. Shock cooling, such as that which occurs when the process is carried out, is avoided.However, batch processes can be cumbersome, difficult to operate, and energy inefficient.

Many attempts have been made to develop continuous two-self-refrigerant processes for dewaxing oils, including combination ketone/self-refrigerant processes. Thus, a self-cooling batch dewaxing process is disclosed which is operated by sequential use of expansion chambers. The waxy oil is diluted with an aromatic/ketone solvent mixture and with a liquid autorefrigerant, and cooling is controlled by reducing the pressure in each chamber so that the autorefrigerant evaporates at a controlled rate. This is accomplished by vaporization. U.S. Pat. A self-cooling dewaxing process is disclosed that precipitates a portion of the wax from the oil. U.S. Patent No. 2.202.
No. 542 proposes a continuous self-cooling dewaxing process in which a waxy oil is premixed with hot liquid propane above its cloud point. This mixture is introduced into a multi-stage cooling tower and injected into each stage such that the liquid C02 does not come into direct contact with the oil. This patent emphasizes that liquid CO2 must be introduced into each stage without direct contact with the oil in the column to avoid shock cooling. However, this is impractical because the column steam load far exceeds what can be accommodated in a moderately sized industrial column.

Also, the required cooling diet is five times that normally required, and conditions for wax crystal nucleation and growth are poor.

US Patent No. A72 Q, 599 discloses a continuous dewaxing process in which waxy petroleum feedstocks are premixed with attenuate. This mixture is then loaded into four horizontal elongated cooling vessels containing multiple stages operated at different pressures, the pressure of each stage being controlled by a back pressure regulator in each stage. Liquid self-refrigerant is introduced at each stage along the length of the cooling vessel while maintaining a high degree of agitation within the vessel to avoid shock cooling. The self-refrigerant is partially vaporized in each stage, and the amount of vapor is controlled by the pressure applied to each stage. Unfortunately, there are problems that have hindered the industrialization of this method, and in any case, it is difficult to use a multi-tube system without plugging the entire equipment with wax or using a multi-tube system, which is expensive and also tends to destroy the wax crystal structure. It is not a practical and efficient way to move slurry from stage to stage without the need for pumps. Other disadvantages are the impracticality of providing separately driven agitators for each stage and the mechanical difficulties associated with common horizontal drive shafts. In addition, U.S. Pat. No. 5,720,599 discloses that a substantial amount (i.e.
The nucleation and initial growth of the wax is carried out in the presence of a self-refrigerating solution of It has been found that subsequent self-cooling produces wax crystals that are inferior to those produced when nucleation is allowed to occur. For example, the use of mixtures of ketones and high percentages (41)% of propylene in the Deltil dewaxing process produced a distillate/wax slurry that was very poorly defiltered.

If one obtains large, stable spherical crystals without the use of a dewaxing aid and then further precipitates additional wax by direct contact with a self-refrigerant that evaporates without destroying the spheres, this results in ketone dewaxing. Process: Ketone dewaxing in a manner that carefully forms wax nuclei and initiates crystal growth in a non-self-refrigerating solvent environment such as ketones to avoid the need for subsequent surface scraper cooling. It would be an improvement over the prior art if both the dewaxing process and the self-refrigerated solvent dewaxing process could be combined.

In the present invention, when dewaxing a wax-containing oil with a solvent, (al) the wax-containing oil is pre-diluted with a non-self-refrigerating dewaxing solvent to form a mixture of the wax-containing oil and the solvent, +1) ) consists of a vertical, elongated, multi-stage column operated at constant pressure, and each stage includes a liquid space and a vapor space above the liquid space, each of which receives self-refrigerant vapor from it. fc) feeding the mixture from said step (a) at a temperature above its exothermic point to the top of a continuous self-cooling cooling zone comprising means for removing said mixture in said cooling zone; The mixture is cooled as it flows from stage to stage, thereby forming a slurry containing solid particles of wax and dewaxing oil/magent solution, and the slurry so formed is passed through the cooling zone - further cooling by contacting the liquid self-refrigerant with a liquid self-refrigerant, wherein said liquid self-refrigerant is introduced under flow controlled conditions into a plurality of stages within said cooling zone, and in said zone the slurry is 20
vaporize in the zone so as to obtain an average cooling rate within the range of 2 to 2°F per minute and an average temperature drop within the range of about 2 to 2 o'F across each stage in which the VG autorefrigerant is introduced and vaporized. The vaporized self-refrigerant is injected from each of said stages into which said liquid self-refrigerant is injected, such that the self-refrigerant vapor produced at any given stage is above said stage in the column. A continuous self-cooling solvent dewaxing process comprising steps in which the slurry in all stages is removed without passing through and the slurry slurry is separated to obtain a wax and dewaxed oil solution. A device was discovered for this purpose.

In a preferred embodiment of the invention, the predilution oil contains a dewaxing aid and is introduced at the top of the cooling zone at a temperature at or near its cloud point, and the slurry is passed through the wax filter in the cooling zone. cooled to temperature.

Alternatively, the present invention may be practiced using a cold, non-self-refrigerating dewaxing solvent, in which case the method involves Ia) first treating the waxy oil at a temperature above its stale point a cooling zone where a portion of the wax is precipitated from the oil by cooling the oil in the presence of a non-self-refrigerating dewaxing solvent to form a slurry of oil, solvent, and solid particles of wax; b) The slurry from said first cooling zone is transferred to a vertical multi-stage column operated at constant pressure, each stage comprising a liquid space and a vapor space above said liquid space, each of said vapor spaces therein. (C1) the slurry produced in said first cooling zone is cooled in said second cooling zone to a second cooling zone consisting of a multistage column comprising means for removing self-refrigerant vapor from cooling the wax to a supertemperature in said second zone by contacting with a refrigerant K and then precipitating additional wax, wherein said liquid autorefrigerant is present in said second cooling zone in a plurality of stages Kfi. is introduced under volume controlled conditions and with an average cooling rate of the slurry in the zone in the range of about 1-20 sub/min and about 2-20 sub/min across each stage in which the liquid autorefrigerant is introduced and vaporized. vaporized in the Km band to obtain an average temperature drop in the range of each step in which the self-refrigerant vapor is removed from passing through the slurry in all stages above that stage in the column, and (dl) the wax is separated from said slurry to obtain a wax and dewaxed oil solution. including.

The cloud point of an oil is defined as the oil under specified conditions (ASTMD-25
00-66) is defined as the temperature at which wax crystal haze first appears upon cooling. Details! The term "predilution" in refers to mixing a solvent and an oil before cooling the oil to a temperature below its reduced cloud point, and in one embodiment of the invention this is
Waxy oils are prediluted with at least about 11 volumes of a self-refrigerating predilution solvent per volume of feedstock or at least 5 volumes of a non-self-refrigerating predilution solvent per volume of feedstock to lower the phosphorus point of the feedstock. It includes those that cause a decline. If predilution is used, it is preferred to predilute with a non-self-refrigerating solvent, particularly a ketone. The term "self-refrigerating solvent" in the present MU refers to a dewaxing solvent which is liquid at normal temperatures and pressures, preferably ketones, but with a base pressure of about 50 LV for wax-containing oil feedstocks.
(Liquid volume %i, also includes the presence of a self-refrigerant in the second cooling zone.

The non-self-refrigerating dewaxing solvent used as the pre-dilution and/or first cooling solvent in the present invention includes one or more of (a) acetone, methyl ethyl ketone (MHK),
aliphatic ketones having 3 to 6 carbon atoms, such as methyl isobutyl ketone (MIBK), methyl propyl ketone and mixtures thereof; halogenated low molecular weight hydrocarbons such as (C15-10 carbon atoms normal or imparaffins, (dl benzene, toluene,
Aromatics such as xylene, petroleum naphtha and mixtures thereof;
The non-self-refrigerating solvents, such as those limited to
LV% of a self-refrigerating solvent. For example, ketones are often used in combination with one or more aromatic compounds such as benzene, toluene, xylene, and petroleum naphtha. Preferred solvents include ketones. Particularly preferred are mixtures of MEK and MIBK or MEK
It is a mixture of K and toluene/. Self-refrigerants used in the present invention include mixtures of propane, propylene, ethane, ethylene, and the like, as well as normally gaseous liquid C2-C4 hydrocarbons such as ammonia and normally gaseous fluorocarbons such as monochlorodifluoromethane (Freon 22). includes. Self-cooling solvents, such as those limited to
More preferably, at most 2 LV of non-self-refrigerating solvent may be included.

The self-cooled cooling zone is where the waxy oil and slurry flow by gravity from stage to stage in the tower and the cold liquid self-refrigerant is injected into each stage of the tower where it contacts the warmer oil or slurry and cools it. It is a vertical, perforated, multi-stage column operated in such a manner as to be cooled by self-cooled evaporation and at constant pressure. At least a portion of the cold liquid self-refrigerant is immediately vaporized upon contact with the warmer oil or slurry to achieve substantially instantaneous mixing (i.e., within about 1 second) of the oil or slurry with the cold liquid self-refrigerant. Sufficient agitation is provided at the contact surfaces, thus avoiding impact cooling effects. As previously described, each stage includes means for withdrawing autorefrigerant vapor therefrom, and the slurry flows down from stage to stage of the column under the action of specific gravity. The cooled slurry exiting this cooling zone is then sent to a means such as a rotary pressure strainer to separate the wax from the dewaxed oil/solvent mixture.

Generally, the self-cooled cooling zone or tower is about 0 to s
o psig Preferably operated at a constant pressure within the range of about 2-20 psig. The average cooling rate in the column is the difference between the temperature of the prediluted oil entering the column and the temperature of the slurry leaving the column divided by the residence time of the oil or slurry in the column, and is approximately [11-20 below]. /min preferably within the range of about 15-10 below/min. This is accomplished by controlling the self-refrigerant flow to each stage and the oil retention time therein, rather than by gradually lowering the system pressure as is done in batch chillers. That is, the control at each stage of the tower is
Upon direct contact with the oil or slurry, a pressure controlled amount of the self-refrigerant is vaporized. This is accomplished by injecting liquid self-refrigerant under flow-controlled conditions through spray nozzles submerged in the slurry or located above its surface at each stage of the column. Ultimately, this controls the temperature drop within the range of about 2-20"F' for each stage, where the stepwise cooling rate is determined by the liquid hold-up or residence time for each stage. The self-refrigerant vaporizes and cools the oil primarily by its latent heat of vaporization, resulting in extremely high heat transfer coefficients. drawn from.

In a preferred embodiment, this is done by passing the steam directly from the vapor space of each stage through the cooling zone or tower and not by passing the steam cumulatively through each successive stage above each stage as disclosed in the prior art. This is done by individually extracting it to the outside.

However, under certain circumstances, the steam produced in one or more predetermined stages may be removed from a stage above said one or more predetermined stages before the cumulative steam is withdrawn from the cooling zone or tower. It may be advantageous or necessary to pass some (but not all) of the air through the tower or cooling zone upwards.

- By way of example, it may be advantageous to withdraw steam from the zone or column in every second, third and fourth successive stages. An amount of autorefrigerant is added per stage to provide a stepwise temperature reduction in the range of 2 to 20, and more preferably 3 to 10"F. Of course, the final temperature to which the slurry is cooled in this column depends on the predilution oil. The temperature of the kernel oil when it enters it,
The liquid retention time in each stage depends on the amount, type and temperature of the autorefrigerant injected into each stage, as well as the column pressure and the number of column stages. Therefore, it is of course understood that depending on the feedstock and the dimensions of the column, it may not be necessary to inject liquid self-refrigerant at each stage of the column.

Generally, the cooling zone cools the slurry from about 10 to 40"F, preferably from 15 to 15"F, below the desired pour point of the dewaxed oil.
Allow to cool to 0″'F lower temperature.

When using cold, non-self-refrigerating solvents, the trap is that the first cooling zone is any type of cooling zone used in the conventional ketone dewaxing process described with respect to the prior art above, including scraped surface cooling zones. There may be. However, in a preferred embodiment of the invention, the first cooling zone is an incremental deltil zone of the type disclosed in the above-mentioned US Pat. That is, a waxy oil is introduced into an elongated staged cooling zone or column at a temperature above its cloud point, and a cold, non-self-refrigerating dewaxing solvent such as a ketone is introduced into the elongated staged cooling zone or column at a temperature above its cloud point. They are introduced into the deltil zone in portions along the stages while maintaining a high degree of agitation to cause their substantially instantaneous mixing as they pass through the zone. When using cold, non-self-refrigerating solutions, it is also preferred to precipitate most of the wax from the oil in this first cooling zone.

The slurry from the cooling zone with a cold non-self-refrigerant is sent directly to the top of the second cooling zone, which is a vertical, multi-stage, constant-pressure station using a self-refrigerating solvent, where the slurry is quenched with wax f as previously described. It is further cooled to supertemperature and additional wax is precipitated therefrom.

The apparatus of the present invention can be used to dewax all wax-containing petroleum feedstocks or distillates thereof. mosquito~
Examples of feedstock oils include, but are not limited to, (a
) distillate fractions having boiling points within a wide range of s o-o to about 15 oo"F (preferred feed stocks are about 560-120"
(b) heavy feedstocks containing at least about 10 weight fractions of residue having boiling points above t050'F); (
Examples include bridestock and deasphalted residues with initial boiling points above about below 800), and (topping or distilling the lightest material from CJ crude oil to a wide range of distillates ( Broadcut stocks, most of which boil above about soo'F or 650''F, are produced by K.

Additionally, any of these feedstocks can be hydrocracked prior to distillation, dewaxing, or topping. Distillate fractions include paraffinic crude oils obtained from Aramco, Kraate, Zarpanhandle, North Louisiana, etc., naphthenic crudes such as Chia Shuana, Corestal crudes, etc., and brightstocks with a boiling point range of 1050 F. It can originate from any source, such as relatively heavy feedstocks and synthetic feedstocks derived from Athabasca tar sands, coal liquors, and the like.

MWK as a non-self-refrigerating diluent and/or coolant
When using a mixture of MEK and MIBK,
) The ratio to 3 is 90% MgK/10% MIBK ~1
0 %MMK/90 %MIBK Huff o %M
nK/! ,o %MIBK ~70chiMIHK/30%
May vary between MEKs. The volume ratio of ketones to oil is [
It may vary between L5/1 and 10/1, preferably between tO/1 and 4/1. The predilution volume ratio of the solvent, either self-refrigerating or non-self-refrigerating, varies between 0/1 and 3/1, preferably 0/1 and 2/1, depending on the prediluent and feedstock. be able to. The cooling rate in the first cooling zone is between α1'F/min and 2011''/min, preferably α5'F/min.
It can vary between minutes and 10'F/minute. The exit temperature from the second cooling zone can vary from -20 to +90°F, preferably from 20 to 80'F.

Lower outlet temperatures are better for distillate feedstocks, whereas higher outlet temperatures are better for residual feedstocks. When using cold, non-self-refrigerating solvents, it is preferred that most of the wax crystallizes out from the oil in the first cooling zone.

When propylene is used as the self-refrigerant in a self-cooled cooling zone, it takes about 1 volume of waxy oil (12 to 2
．． 5 volumes of propylene, preferably from about tO to 2.0 volumes of propylene, the cooling rate in the self-cooled cooling zone is generally about 0.1 to 20'F/min, preferably about cL5 to 10'F/min. Within minutes. The temperature of the cold slurry entering the cooling zone is about -50111'' to produce a dewaxed oil with a pour point of about -50 to +80'F.
It may vary between +30°F. In a preferred embodiment, the slurry is heated between -50"F and +10"F to produce a dewaxed oil having a pour point of about -1o'F to +30@F.
exit the cooling zone at a lower temperature.

Referring now to FIG. 1, a warm paraffinic lubricating oil distillate at a temperature of about 160"F and having a viscosity of 1 sosus at 100 °F is mixed with a dewaxing aid from line 16; Next, to the M1 bow/MIBK's y
The ketone predilution solvent is prediluted in an amount of about t2 volumes of ketone predilution solvent per volume of waxy oil with a solvent containing an a/s o volume ratio mixture. The prediluted waxed oil/dewaxing aid mixture is then passed through line 10 to heat exchanger 12 where it is cooled to a temperature of about 906F or just above its cloud point and from there It is sent to a multi-stage self-cooling cooling tower 26. Liquid propylene at a temperature of -30'F is supplied to line 28, manifold 30 and a plurality of injection points 32.
It is supplied to each stage of the column 26 through. Multiple injection points 32
is in communication with each stage of column 26, where liquid propylene contacts the slurry of each stage via a sparger located below the surface of the slurry of each stage. In tower 26, line 24
Approximately 15 volumes of liquid propylene are used for each volume of slurry that enters the slurry. Column 26 operates at a pressure of approximately 2 psig. Approximately 12 volumes of liquid autorefrigerant per volume of fresh feed vaporizes upon contact with the slurry, and this autorefrigerant vapor passes from each stage via a plurality of column outlets 34, manifolds 36 and lines 38 to approximately 24'F. Thus, the vapor produced at any stage does not pass through the slurry in other stages of the column. Per volume of feedstock (L9gt residual propylene)
Becomes a liquid. The column 26 contains about 14 stages i, but this! The average slurry cooling rate at is about 3 mm/min and the average temperature drop across each stage is about 8.6 mm. The wax-containing slurry is further cooled in column 26 to a temperature of about -30°C below.

The slurry containing solid wax particles, oil, ketones and liquid propylene is then passed through line 40 to a rotary pressurized sieve 4.
2, where the wax from the dewaxed oil solution is
passed. The dewaxed oil exits the filter 24 via line 44 and is conveyed therefrom to a solvent recovery means, and the wax is withdrawn via line 46 to a solvent recovery means and, if desired, further to a wax treatment means. It will be done. This dewaxed oil solution yielded a dewaxed oil with a pour point of about -10'F.

FIG. 2 illustrates a preferred embodiment of a self-cooling cooling tower 26. The diameter of the column is sized to provide a surface steam velocity low enough to avoid entrainment of oil into the steam shell. The tower has approximately 14 individual stages 502-5Q
Contains n. Each stage consists of a self-refrigerant vapor collector, a vapor space,
Slurry Tracing Slurry - Includes downcomers, weirs and liquid self-refrigerant spreaders. To illustrate for stage SOa, reference numeral 52 is a steam collector, 54 is a steam space, 56 is a slurry tray, 58 is a slurry, 60 is a downcomer, 62 is a weir,
And 64 is a spreader. The sparge device 64 and the self-refrigerant vapor collector 52 are shown in FIGS.
) is shown in detail in fig. Distributor 64 is shown as a tube containing a plurality of small holes 66 , and steam collector 50 is shown as a tube containing a plurality of rectangular holes 68 . In operation, slurry from heat exchanger 12 is routed via line 24 to column 26 and enters downcomer 60 via feed port 68, where it is transferred below the surface of slurry 58 held in stage 50a. and directed downwards. Liquid propylene is introduced into stage 50 from injection point 52 via sparge 64 and holes 66. The six holes are sized to provide a level of agitation such that substantially instantaneous mixing (ie, within 1 second) occurs. The six holes are oriented downwardly, opposite the slurry flow through the stage. Some of the propylene vaporizes as it enters the warmer slurry, and the vapor bubbles up through the slurry, leaving the remainder of the propylene in solution. The propylene vapor is withdrawn via steam collector 52 and the cooled slurry overflows weir 62 where it enters downcomer 60 and is directed below the surface of the slurry at the next stage 50bK. This process is repeated at each stage as the slurry descends the column until it exits slurry exit lower 0 at wax f supertemperature and is sent to wax r strainer 42.

Referring to FIG. 3, warm paraffinic lubricating oil distillate at a temperature of approximately 160 hF and having a viscosity of 150 SUS at 100"F is transferred from line 10 to heat exchanger 11.
, where it is cooled to a temperature of about 84 below or just above that point and thence sent via line 14 to a multi-stage Deltyl (DIL (441LL)) column 16. In column 16: It consists of a cold (-30″F) ketone solvent consisting of a 70% MEK/30% MIBK (by volume) mixture that is injected into each stage of column 16 via line 18, manifold 20 and multiple injection points 22. Approximately 12 volumes of cold ketone dewaxing solvent per volume of feed enter the column. Each stage of column 16 (not shown) houses a rotating impeller so that the cold ketone dewaxing solvent entering therein is cooled by contact. The wax solvent is mixed into the waxy oil substantially instantaneously.

In column 16, most of the wax is precipitated from the waxy oil to form a slurry, which exits the bottom of column 16 via line 24 at a temperature of about 11'.

The cold ketone-containing slurry in line 24 is sent directly to a multi-stage cooling tower 26. Each stage of the column 26 includes a line 28,
-30″F via manifold 30 and multiple injection points 52
Liquid propylene is supplied at a temperature of . A plurality of injection points 32 lead to each stage of the column 26 where liquid propylene contacts the slurry of each stage via a sparger located below the surface of the slurry of each stage. Approximately 15 volumes of liquid propylene are used in column 26 for each volume of slurry entering it via line 24. Tower 26 is approximately 2 ps i
It operates at a pressure of g. Approximately 6 volumes of liquid autorefrigerant per volume of fresh feed vaporizes upon contact with the slurry, and the autorefrigerant vapor passes from each stage via a plurality of column outlets 34, manifolds 36, and lines 38 to approximately - 12'
It is extracted at an average temperature of F.

Thus, no vapor produced in any stage passes through slurry in other stages of the column.

α9 volumes of residual propylene per volume of feed goes into solution with the MgK/MIBK and dewaxed oil in the wax slurry. Column 26 includes about 7 stages, with an average slurry cooling rate of about 3 mm/min for each stage and an average temperature drop across it of about 8.6''F2. The wax-containing slurry is further cooled in column 26VC to a temperature of about -30K below. The slurry containing solid wax particles, oil, ketones, and liquid propylene is then fed via line 40 to a rotary pressurized strainer 42 where the wax is strained from the deoiling solution. The dewaxed oil solution exits the filter 24 via line 44 and thence to a solvent recovery means, and the wax is removed via line 46 to a solvent recovery means for further wax processing if desired. Sent to means. The dewaxed oil solution yields a dewaxed oil having a pour point of about -10'F.

The invention will be more easily understood by reference to the following examples.

Example 1 This example provides laboratory data illustrating the method of the present invention using a non-self-refrigerating solvent as the diluent solvent. The feedstock used was 6008 in 10011″
Trimmed with paraffin wax distillate having US viscosity (60ON). A pilot plant self-cooled chiller consisting of a vessel operating at a constant pressure of about 5 psig was used. Liquid propylene at a temperature of about -30'F was continuously injected below the surface of the slurry contained in the apparatus.

A portion of the liquid propylene was vaporized and this vapor was continuously withdrawn from a constant pressure vapor space above the slurry. A slurry cooling rate of approximately 5'F/min was maintained by controlling the rate of injection of liquid propylene into the slurry. Before the feedstock enters the self-cooling chiller, mix it with one volume of Paraflow'/"Acryloid" dewaxing aid and add them to one volume of the feedstock at a temperature above its cloud point. Pre-diluted with 1 volume of MEK.

The prediluted feedstock was then precooled to a temperature of 120'F (which was the web point of the prediluted feedstock) before it was added to the apparatus. As previously described, the prediluted feedstock is 5' in a self-cooling device.
Cooled at a rate of F/min. The wax-containing slurry produced by the apparatus is cooled to a temperature of -30"F and then heated to -30"F.
Filtered with F. The rate of propane dissolved in the oil in the unit was 15 volumes per volume of feedstock oil.

The results of this experiment are included in Table A below. These results illustrate the feasibility of implementing the present invention.

Table A Continuous constant pressure self-cooling dewaxing feedstock Type of dewaxing aid Amount of aid used, wt% to feedstock Predilution Solvent Predilution ratio to feedstock Precooling Start bottom end Bottom speed F7 min 0ON P/A 100 CH MEK 1゜0 10.8 pS1g Variable 2.5 4o/sof'wL Relevoban 5.0 &5 Self-cooling pressure Self-cooling Start lower end Lower speed lower 7 minutes Dilution rate f filtration for C3 replenishment filter to cooler filtration temperature of the solvent composition into the vessel,
/S ratio Wax oil content, wt average crystal diameter, micron crystals <10 microns, - WO pour point, Example 2 This example shows the results of the present invention using cooling with a cold non-self-refrigerating solvent and a self-refrigerating solvent. We provide laboratory data comparing the combination process to conventional deltyl ketone dewaxing followed by surface scraping cooling. Three S-paraffinic lubricating oil feedstocks were used, namely Brightstock and two distillate oils with viscosities of 1 sosU8 (1soN) and 6005US (60ON) at 10011''.For deltil dewaxing with ketone solvents A ketone-containing slurry consisting of solid particles of wax and a mixture of a partially dewaxed oil and a ketone dewaxing solvent was produced using a plant-type Deltil apparatus. The temperature of the cold ketone solvent fed to the Deltil apparatus was The bright stock was pre-diluted with 1 volume of warm ketone solvent per volume of feed before being fed to the Deltil unit. The wax-containing slurry produced in the Deltil unit was then diluted with wax The cooled slurry was then fed to either a surface scraper cooler or a simulated continuous self-cooling cooler for further cooling to 1 supertemperature.The cold slurry was then filtered to separate the wax from the dewaxed oil/solvent mixture, and Both the dewaxed oil and wax were recovered.

The self-cooling chiller consisted of a vessel operating at a constant pressure of about 2 psig, while liquid propylene was continuously injected below the surface of the slurry contained therein.

A portion of the liquid propylene was vaporized, but the vapor was continuously extracted from the constant pressure vapor space above the slurry.

A slurry cooling rate of approximately 2'F/min was maintained by controlling the rate of injection of liquid propylene into the slurry.

The results of these experiments are included in Table B below in relation to common dewaxed oil pour points. These results not only illustrate the feasibility of implementing the invention, but also illustrate its use to achieve excellent results. Thus, using the present invention, a faster feed filtration rate, a drier wax cake, and a wax cake containing less oil was provided than the Deltil dewaxing process followed by surface scraping cooling.

Furthermore, These ladies are De-wapping I was able to do it without using 1.P as a auxiliary agent.

[Brief explanation of the drawing]

FIG. 1 is a flowchart of an exemplary process embodying the invention using non-self-cooling dilution. Sections 2(a)-(c)
) IB is a schematic flow diagram of a preferred embodiment of a multi-stage vertical column containing a cooling zone of the present invention. FIG. 6 is a schematic flow diagram of a preferred embodiment of a process embodying the invention using cold non-self-cooling cooling. Reference numbers representing main parts in the above drawings are as follows. 16: Delcil tower 26: Multi-stage cooling tower 42: Wax filter Figure 2(a)

Claims (1)

[Claims] (1) In a continuous self-cooling dewaxing apparatus, a vertical, elongated column comprising a plurality of vertically spaced stages;
means for introducing wax-containing oil into the top of said apparatus and means for withdrawing a wax-containing slurry from the bottom of said apparatus, each of said stages having a liquid space and above said liquid space; a vapor space, tray means for retaining a liquid oil or slurry, weir means for maintaining a predetermined amount of liquid on said tray means, and said liquid being introduced into said stage from a position above said stage. downcomer means for providing a flow path to the liquid space and in such a manner that the cold liquid autorefrigerant is in direct contact with the oil or slurry within the stage, thereby vaporizing at least a portion of the autorefrigerant. means for introducing liquid self-refrigerant into said stage and means for withdrawing said vaporized self-refrigerant from said stage in such a manner that said vapor does not come into contact with liquid in any of the other stages of said apparatus; A continuous self-cooling dewaxing device comprising: