CA1144503A - Continuous autorefrigerative dewaxing process and apparatus - Google Patents
Continuous autorefrigerative dewaxing process and apparatusInfo
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- CA1144503A CA1144503A CA000399170A CA399170A CA1144503A CA 1144503 A CA1144503 A CA 1144503A CA 000399170 A CA000399170 A CA 000399170A CA 399170 A CA399170 A CA 399170A CA 1144503 A CA1144503 A CA 1144503A
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Abstract
ABSTRACT OF THE DISCLOSURE
A continuous combination non-autorefrigerant/autorefriger-ant solvent dewaxing process for dewaxing waxy hydrocarbon oils which comprises the steps of:
(a) passing the waxy oil into a first chilling zone wherein a portion of the wax is precipitated from the oil by cooling same in the presence of a non-autorefrigerant dewaxing solvent to form a slurry comprising an oil solvent mixture and solid particles of wax;
(b) passing said slurry from said first chilling zone to a second chilling zone which comprises a vertical, multi-staged tower operating at a constant pressure wherein each stage con-tains a liquid space and a vapor space above the liquid space, each of said vapor spaces also containing means for removal of autorefrigerant vapor therefrom;
(c) cooling said slurry produced in said first chilling zone down to wax filtration temperature and precipitating addi-tional wax therefrom in said second chilling zone by contacting same in said second zone with a liquid autorefrigerant which is introduced under flow rate control conditions into a plurality of the stages in said second zone and allowed to evaporate there-in so as to achieve an average cooling rate of the slurry in said zone ranging from between about 0.1° to 20°F. per minute with an average temperature drop across each stage into which said liquid autorefrigerant is introduced and evaporated ranging from between about 2° to 20°F. and wherein the evaporated auto-refrigerant is removed from each of said stages into which said liquid autorefrigerant was injected in a manner such that the autorefrigerant vapor formed in any given stage does not pass through all of the stages in the tower above said stage; and (d) separating the wax from the slurry to obtain wax and a dewaxed oil solution.
A continuous combination non-autorefrigerant/autorefriger-ant solvent dewaxing process for dewaxing waxy hydrocarbon oils which comprises the steps of:
(a) passing the waxy oil into a first chilling zone wherein a portion of the wax is precipitated from the oil by cooling same in the presence of a non-autorefrigerant dewaxing solvent to form a slurry comprising an oil solvent mixture and solid particles of wax;
(b) passing said slurry from said first chilling zone to a second chilling zone which comprises a vertical, multi-staged tower operating at a constant pressure wherein each stage con-tains a liquid space and a vapor space above the liquid space, each of said vapor spaces also containing means for removal of autorefrigerant vapor therefrom;
(c) cooling said slurry produced in said first chilling zone down to wax filtration temperature and precipitating addi-tional wax therefrom in said second chilling zone by contacting same in said second zone with a liquid autorefrigerant which is introduced under flow rate control conditions into a plurality of the stages in said second zone and allowed to evaporate there-in so as to achieve an average cooling rate of the slurry in said zone ranging from between about 0.1° to 20°F. per minute with an average temperature drop across each stage into which said liquid autorefrigerant is introduced and evaporated ranging from between about 2° to 20°F. and wherein the evaporated auto-refrigerant is removed from each of said stages into which said liquid autorefrigerant was injected in a manner such that the autorefrigerant vapor formed in any given stage does not pass through all of the stages in the tower above said stage; and (d) separating the wax from the slurry to obtain wax and a dewaxed oil solution.
Description
1~445~03 This application is a divisional application of Canadian Application No. 348,094 filed March 21, 1980.
BACKGROUND OF THE INVENTION
. .
1. Field of the Invention This invention relates to a continuous combination non-autorefrigerant/autorefrigerant solvent dewa~ing process for dewaxing waxy hydrocarbon oils which comprises the steps of:
(a) passing the waxy oi] into a first chilling zone wherein a portion of the wax is precipitated from the oil by cooling same in the presence of a non-autorefrigerant dewaxing solvent to form a slurry comprising an oil solvent mixture and solid particles of wax;
(b) passing said slurry from said first chilling zone to a second chilling zone which comprises a vertical, multi-staged tower operating at a constant pressure wherein each stage con-tains a liquid space and a vapor space above the liquid space, each of said vapor spaces also containing means for removal of autorefrigerant vapor therefrom;
tc) cooling said slurry produced in said first chilling zone down to wax filtration temperature and precipitating addi-tional wax therefrom in said second chilling zone by contactingsame in said second zone with a liquid autorefrigerant which is introduced under flow rate control conditions into a plurality of the stages in said second zone and allowed to evaporate there-in so as to achieve an average cooling rate of the ~lurry in said zone ranging from between about 0.1 to 20F. per minute with an average temperature drop across each stage into which said liquid autorefrigerant is introduced and evaporated ranging from between about 2 to 20F. and wherein the evaporated auto-refrigerant is removed from each of said stages into which saidliquid autorefrigerant was injected in a manner such that the autorefrigerant vapor formed in any given stage does not pass through all of the stages in the tower above said stage; and (d) separating the wax from the slurry to obtain wax and a dewaxed oil solution.
~ 3
BACKGROUND OF THE INVENTION
. .
1. Field of the Invention This invention relates to a continuous combination non-autorefrigerant/autorefrigerant solvent dewa~ing process for dewaxing waxy hydrocarbon oils which comprises the steps of:
(a) passing the waxy oi] into a first chilling zone wherein a portion of the wax is precipitated from the oil by cooling same in the presence of a non-autorefrigerant dewaxing solvent to form a slurry comprising an oil solvent mixture and solid particles of wax;
(b) passing said slurry from said first chilling zone to a second chilling zone which comprises a vertical, multi-staged tower operating at a constant pressure wherein each stage con-tains a liquid space and a vapor space above the liquid space, each of said vapor spaces also containing means for removal of autorefrigerant vapor therefrom;
tc) cooling said slurry produced in said first chilling zone down to wax filtration temperature and precipitating addi-tional wax therefrom in said second chilling zone by contactingsame in said second zone with a liquid autorefrigerant which is introduced under flow rate control conditions into a plurality of the stages in said second zone and allowed to evaporate there-in so as to achieve an average cooling rate of the ~lurry in said zone ranging from between about 0.1 to 20F. per minute with an average temperature drop across each stage into which said liquid autorefrigerant is introduced and evaporated ranging from between about 2 to 20F. and wherein the evaporated auto-refrigerant is removed from each of said stages into which saidliquid autorefrigerant was injected in a manner such that the autorefrigerant vapor formed in any given stage does not pass through all of the stages in the tower above said stage; and (d) separating the wax from the slurry to obtain wax and a dewaxed oil solution.
~ 3
2. Descri~tion of the Prior Art .
lt ic well known in the art to dewax wax containing hydrocarbon oils, particularly the lube oil fractions of petroleum oil, in order to remove at least a por~ion of the - wax therefrom to obtain a dewaxed oil of reduced cloud and pour points. The most common method of removing the wax or waxy constituents from waxy hydrocarbon oils is via the usP
of various solvent dewaxing processes. In solvent dewaxing processes the temperature of the wax-containing oil is low-ered sufficiently to precipitate the wax therefrom as solid crystals of wax. A~ the same time, solvents are added to the waxy oil in order to improve the fluidity and reduce the viscosity thereof so that various filtration or centrifuga-tion processes can be used to separate the solid particles of the wax from the dewaxed oiL. Strong wax antisolvents (weak oil solvents) such as MEK are often added ~o decrease wax solubility in the oil/solvent mixture while strong oil solvents (weak wax antisolvents~ such as MIBK or toluene are used to modi~y the solubility characteristics of the solvent so as to allow wax precipitation, while at the same time svoiding oil immiscibility at wax separation temperatures.
Solvent dewaxing processes produce what is known as a pour-filter temperature spread. This is the tempera~ure differ-ential between the wax filtering temperature and the pour point of the dewaxed oil. This pour-filter temperature spread is greater when more non-polar hydrocarbon solvents are used than with more polar solvents such as ketones. Thus, an autorefrigerant dewaxing process employing propane can produce a pour-filter spread of 40F, which means that the wax filtration must be done at -40F in order to pro-duce a dewaxed oil having a pour point of 0F. When ke~ones or mixtures of ketone and aromatic solven~s are used, the .. ~ , ~ .. _ .. . . .. .. ...... . ..... .... . .. .
il~4S03
lt ic well known in the art to dewax wax containing hydrocarbon oils, particularly the lube oil fractions of petroleum oil, in order to remove at least a por~ion of the - wax therefrom to obtain a dewaxed oil of reduced cloud and pour points. The most common method of removing the wax or waxy constituents from waxy hydrocarbon oils is via the usP
of various solvent dewaxing processes. In solvent dewaxing processes the temperature of the wax-containing oil is low-ered sufficiently to precipitate the wax therefrom as solid crystals of wax. A~ the same time, solvents are added to the waxy oil in order to improve the fluidity and reduce the viscosity thereof so that various filtration or centrifuga-tion processes can be used to separate the solid particles of the wax from the dewaxed oiL. Strong wax antisolvents (weak oil solvents) such as MEK are often added ~o decrease wax solubility in the oil/solvent mixture while strong oil solvents (weak wax antisolvents~ such as MIBK or toluene are used to modi~y the solubility characteristics of the solvent so as to allow wax precipitation, while at the same time svoiding oil immiscibility at wax separation temperatures.
Solvent dewaxing processes produce what is known as a pour-filter temperature spread. This is the tempera~ure differ-ential between the wax filtering temperature and the pour point of the dewaxed oil. This pour-filter temperature spread is greater when more non-polar hydrocarbon solvents are used than with more polar solvents such as ketones. Thus, an autorefrigerant dewaxing process employing propane can produce a pour-filter spread of 40F, which means that the wax filtration must be done at -40F in order to pro-duce a dewaxed oil having a pour point of 0F. When ke~ones or mixtures of ketone and aromatic solven~s are used, the .. ~ , ~ .. _ .. . . .. .. ...... . ..... .... . .. .
il~4S03
- 3 -1 pour-filter spread may range from CF to 20F depending 2 on the oil and solvent used.
3 Both ketone and sutorefrigerant dewaxing processes
3 Both ketone and sutorefrigerant dewaxing processes
4 have certain advantages and disadvantages. Thus, although S ketone dewaxing processes result in a lower pour-filter 6 spread at the wax filtration temperature and although larger 7 wax crystals can be grow,n in a ketone environment than in an 8 autorefrigerant environment without dewaxing aid, ketones g are relatively non-volatile compared to autorefrigerants, and, therefore, chilling of the solvent/oil mixture must be 11 accomplished by either indirect means or by mixing cold 12 ketone solvent with the oil. In the latter case, practical 13 considerations limit the amount and temperature of cold 14 ketone solvent that can be added and ehe temperature to which the solvent/oil mixture can be cooled. Therefore, some 16 means of indirectly chilling the waxy slurry following the 17 addition of solvent is required in all ketone dewaxing pro-18 cesses in order to bring the slurry down to the required 19 wax filtration temperature. The most common method of in-direct chilling is via the use of scraped surface chillers 21 which are expensive and difficult to maintain. Also, the 22 scraped surface chillers tend to damage the wax crystals by 23 the shearing action of the scraper blades.
24 Conversely, wax crystals grown in an autorefriger-ant environment, such as propane or propylene, are generally 26 small which necessitates the use of costly dewa~ing aids in 27 order to achieve good filcration rates, although evaporation 28 of the autorefrigerant ena~les one to reach the wax filtra-29 tion temperature without the necessity of employing scraped-surface chillers or indirect heat exchangers following the 31 solvent dewaxing operat$on. Additionally, it has been found 32 necessary to employ batch chilling in autorefr$gerant dewax-33 ing processes in order to allow a gradual reduction in a 34 pressure. This prevents sudden flashing of the autorefrig-erant at the point of pressure release, thereby avoiding sud-36 den large temperature drops of the oil slurry (shock chllling), 11'~4503 1 ~hich would result in even sm211er wax crystals and concomi-2 tant slower filter rates of the wax from the dewaxed oil.
3 In some ketone solvent dewaxing processes, the 4 waxy oil and solvent, at a temperature above the clo~d point of the oil, are mixed before being cooled. This solution is 6 then cooled at a uniform, slow rate under conditions which 7 avoid agitation of ehe solution as ~he wax precipitates out.
8 In another method) ketone dewaxing solvent is added to the 9 oil at several points along a chilling apparatus, but ~he waxy oil is first chilled without solvent until some wax ll crystallization has occurred and the mixture has thickened 12 considerably, after which a first increment of solvent, at 13 the temperature of the oil, is introduced in order to main-14 tain fluidity. Cooling continues, more wax is precipitated out and a second increment of solvent, at the temperature of 16 the mixture, is added to maintain fluidity. This process is 17 repeated until a temperature typically ranging from about 18 30~F to 60F is reached, ac which point an additional a unt l9 of solvent at the same tempersture as the mixture is added in order to reduce the viscosity of the mixture which is 21 further chilled in scraped-surface chillers to the desired 22 filtration temperature. In these processes, if the solvent 23 is introduced a L a temperature lower than that of the oil or 24 oil/solvent mixture, shock chilling occurs resulting in the formation of small and/or acicula shaped wax cry6tals with 26 attendant poor filter rate.
27 It is now well known that the adverse shock chil-28 l~ng effect can be overcome by introducing the waxy oil into 29 an elongated, staged cooling zone or tower at a temperature 30 above its cloud point and incrementally introducing cold ~l dewaxing solvent into said æone, along a plurality of po~nts 32 or stages therein, while maintaining a high degree of agita-33 tion in said stages, so as to effect substantially instantane-34 ous mixing of the solvent and waxloil mixture as they pro-35 gress through said zone. The basic concept of this commer-36 cially successful process is disclosed in U.S. Patent No.
:1144503
24 Conversely, wax crystals grown in an autorefriger-ant environment, such as propane or propylene, are generally 26 small which necessitates the use of costly dewa~ing aids in 27 order to achieve good filcration rates, although evaporation 28 of the autorefrigerant ena~les one to reach the wax filtra-29 tion temperature without the necessity of employing scraped-surface chillers or indirect heat exchangers following the 31 solvent dewaxing operat$on. Additionally, it has been found 32 necessary to employ batch chilling in autorefr$gerant dewax-33 ing processes in order to allow a gradual reduction in a 34 pressure. This prevents sudden flashing of the autorefrig-erant at the point of pressure release, thereby avoiding sud-36 den large temperature drops of the oil slurry (shock chllling), 11'~4503 1 ~hich would result in even sm211er wax crystals and concomi-2 tant slower filter rates of the wax from the dewaxed oil.
3 In some ketone solvent dewaxing processes, the 4 waxy oil and solvent, at a temperature above the clo~d point of the oil, are mixed before being cooled. This solution is 6 then cooled at a uniform, slow rate under conditions which 7 avoid agitation of ehe solution as ~he wax precipitates out.
8 In another method) ketone dewaxing solvent is added to the 9 oil at several points along a chilling apparatus, but ~he waxy oil is first chilled without solvent until some wax ll crystallization has occurred and the mixture has thickened 12 considerably, after which a first increment of solvent, at 13 the temperature of the oil, is introduced in order to main-14 tain fluidity. Cooling continues, more wax is precipitated out and a second increment of solvent, at the temperature of 16 the mixture, is added to maintain fluidity. This process is 17 repeated until a temperature typically ranging from about 18 30~F to 60F is reached, ac which point an additional a unt l9 of solvent at the same tempersture as the mixture is added in order to reduce the viscosity of the mixture which is 21 further chilled in scraped-surface chillers to the desired 22 filtration temperature. In these processes, if the solvent 23 is introduced a L a temperature lower than that of the oil or 24 oil/solvent mixture, shock chilling occurs resulting in the formation of small and/or acicula shaped wax cry6tals with 26 attendant poor filter rate.
27 It is now well known that the adverse shock chil-28 l~ng effect can be overcome by introducing the waxy oil into 29 an elongated, staged cooling zone or tower at a temperature 30 above its cloud point and incrementally introducing cold ~l dewaxing solvent into said æone, along a plurality of po~nts 32 or stages therein, while maintaining a high degree of agita-33 tion in said stages, so as to effect substantially instantane-34 ous mixing of the solvent and waxloil mixture as they pro-35 gress through said zone. The basic concept of this commer-36 cially successful process is disclosed in U.S. Patent No.
:1144503
- 5 -1 3,773,650, and shall hereinafter be referred to as 2 DILCHILL* dewaxing process.
4 Com~ercially successful processes employing auto-S refrigerative eooling, wherein the waxy oil is mixed with a
4 Com~ercially successful processes employing auto-S refrigerative eooling, wherein the waxy oil is mixed with a
6 liquid autorefrigerant which is oermitted to evaporate there-
7 by cooling the oil by ~he latent heat of evaporation, are
8 batch or semi-batch operations. This mixture of liquid auto-
9 refrlgeran~ and oil ar~ introduced into an expansion chamber wherein the pressure is slowly reduced to achieve controlled ll evaporation of the autorefrigerant and controlled cooling of 12 the oil, thus avoiding the shock chilling which would result 13 if the autorefrigerant were allowed to flash off. However, 14 batch processes are cum~ersome, difficult to operate and energy inefficient.
16 A n~mber of attempts have been made to develop a 17 cont m uous autorefrigerant process for dewaxing oils, includ-18 ing combinations of ketone/autorefrigerant processes. Thus, l9 U.S. Patent No. 3,549,513 discloses an autorefrigerative batch dewaxing process that is described as continuous but 21 which réally operates via the sequenti21 use of a multiple 22 number of batch chillers or expansion chambers. Waxy oil 23 is d~luted with an aromatic/ketone sol~ent mixture and w~th 24 li~uid autorefrigerant and cooling is achieved by controlled evaporation of the autorefrigerant by reducing the pressure 26 in each batch chamber in a manner such thst the autorefrigerant 27 evaporates at a controlled rate. U.S. Patent 3,658,688 28 discloses an autorefrigerant dewaxing process wherein a por-29 tion of the wax is precipitated from the oil in a DILCHILL
30 dewaxing tower wherein the cooling occurs by the injection 31 of cold autorefrigerant into the tower to produce a waxy 32 slurry, followed by autorefrigerative cooling of the slurry 33 in batch chillers. V.S Patent 2,202,542 suggest a contin-34 uous autorefrigerant dewaxing process where~n a waxy oil above 36 *Registered ser~ice mark of Exxon Research and Engineer~ng Co.
, .. ~ ... ., ._ ~445V3 1 it~ cloud point is premixed with warm, liquid propane. Thi~
2 mixture is introduced into a multi-staged cooling tower and 3 li~uid C02 is injected into each stage out of direct contact 4 with the oil. This patent emphasizes the point that the 5 liquid C02 must be introduced into each stage out of direct 6 cont~ct with the oil in the tower in order to avoid shock 7 chilling. However, this is impractical because the vapor 8 loadc on the tower would be far in excess of what could be 9 accommodated in a reasonably sized commercial tower. Also,
16 A n~mber of attempts have been made to develop a 17 cont m uous autorefrigerant process for dewaxing oils, includ-18 ing combinations of ketone/autorefrigerant processes. Thus, l9 U.S. Patent No. 3,549,513 discloses an autorefrigerative batch dewaxing process that is described as continuous but 21 which réally operates via the sequenti21 use of a multiple 22 number of batch chillers or expansion chambers. Waxy oil 23 is d~luted with an aromatic/ketone sol~ent mixture and w~th 24 li~uid autorefrigerant and cooling is achieved by controlled evaporation of the autorefrigerant by reducing the pressure 26 in each batch chamber in a manner such thst the autorefrigerant 27 evaporates at a controlled rate. U.S. Patent 3,658,688 28 discloses an autorefrigerant dewaxing process wherein a por-29 tion of the wax is precipitated from the oil in a DILCHILL
30 dewaxing tower wherein the cooling occurs by the injection 31 of cold autorefrigerant into the tower to produce a waxy 32 slurry, followed by autorefrigerative cooling of the slurry 33 in batch chillers. V.S Patent 2,202,542 suggest a contin-34 uous autorefrigerant dewaxing process where~n a waxy oil above 36 *Registered ser~ice mark of Exxon Research and Engineer~ng Co.
, .. ~ ... ., ._ ~445V3 1 it~ cloud point is premixed with warm, liquid propane. Thi~
2 mixture is introduced into a multi-staged cooling tower and 3 li~uid C02 is injected into each stage out of direct contact 4 with the oil. This patent emphasizes the point that the 5 liquid C02 must be introduced into each stage out of direct 6 cont~ct with the oil in the tower in order to avoid shock 7 chilling. However, this is impractical because the vapor 8 loadc on the tower would be far in excess of what could be 9 accommodated in a reasonably sized commercial tower. Also,
10 refrigeration requirements are three times those normally
11 needed and conditions for nucleation and growth of wax cry-
12 stals are poor. V.S. Paeent 3,720,599 discloses a continuous
13 process for dewaxing a waxy petroleum oil stock wherein ~he
14 oil is premixed with acetone. This mixture is then introduced lS into ~ hor~zon~al, elongated chilling vessel containing a 16 plurality of stages operating at different pressures, with 17 the pressure $n each stage controlled by a back pressure 18 regulator on each stage. Liquid autorefrigersnt is intro-19 duced into the stages along the length of the chilling vessel 20 while maintaining a high degree of agitation therein to 21 avoid shock chilling. The autorefrigerant is partially evap-22 orated in each stage, with the amount of evaporation being 23 controlled by the pressure in each stage. Unfortunately, 24 there are problems which currently preclude commercialization 25 of this process, not the leastof which is a practical, effic-26 ient way of getting th~ slurry to flow from stsge to stage 27 without plugging up the entire appzratus with wax or without 28 multiple transfer pumps which would be expensive and would 29 also tend to destroy the wax crystal structure. Another disadvantage entails the impracticality of providing sep-31 srately driven agitators for each stage and the mechanical 32 difficulties associated with a common horizontal drive shaft.
33 Additionally, 3,720,599 provides for the nucleation and 34 initial growth of wax to occur in the presence of substantial amounts (~.e.,~ 2~%) of autore~rigerant solvent, which, in 36 the absence of dewaxin~ aid, has been found to produce wax crystals inferior to those produced when nucleation occurs by chilling in the presence of ~etones or ketone/aromatic solvents followed by autorefrigeration. For example, when mixtures of ketone and high percentages (7 40~) of propylene were used in the DILCHILL dewaxing process, a distillate oil/wax slurry was produced which filtered very poorly.
It would be an improvement to the art if one could com-bine both ketone and autorefrigeran~ solvent dewaxing processes into a continuous process and in such a manner so as to carefully form the wax nuclei and begin crystal growth in a substantially non-autorefrigerant solvent environment such as ketone, to achieve large, stable, spherical crystals without the use of de-waxing aid and then further precipitate additional wax without destroying the spheres via direct contact with an evaporating autorefrigerant, thereby avoiding the need for scraped surface chillers following the ketone dewaxing step.
SU~ARY OF THE INVENTION
. _ The present invention provides a continuous autorefrig-erant solvent dewaxing process for dewaxing waxy hydrocarbon oils which comprises the steps of:
(a) prediluting the waxy oil with a non-autorefriger-ant dewaxing solvent to form a mixture of waxy oil and solvent;
(b) passing said mixture from step (a), at a tempera-ture above its cloud point, into the top of a continuous, auto-refrigerative chilling zone which comprises a vertical, elon-gated, multi-staged tower operating at a constant pressure wherein each stage contains a liquid space and a vapor space above ~14'~5V3 the liquid space, each of said vapor spaces also containing means for removal of autorefrigerant vapor th~refromJ
(c) cooling said mixutre as it passes down from stage to stage in said chilling zone to precipitate wax from said oil thereby forming a slurry comprising solid particles of wax and a dewaxed oil/solvent solution and further chilling the so-formed slurry by contacting same, in said chilling zone, with a liquid autorefrigerant which is introduced under flow rate control con-ditions into a plurality of the stages in said zone and allowed to evaporate therein so as to achieve an average cooling rate of the slurry in said zone ranging from between about 0.1 to 20F
per minute with an average temperature drop across each stage into which said liquid autorefrigerant is introduced and evapor-ated rangin~ from between about 2 to 20F. and wherein the eva-porated autorefrigerant is removed from each of said stages into which said liquid autorefrigerant was injected in a manner such that the autorefrigerant vapor formed in any given stages does not pass through all of the stages in the tower above said stage;
and (d) separating the wax from the slurry to obtain wax and a dewaxed oil solution.
In a preferred embodiment of this invention, the pre-diluted oil will contain a dewaxing aid and will be introduced into the top of the chilling zone at a temperature at or near its clond point and the slurry will be chilled down to the wax filtra-tion temperature in said chilling zone.
Alternatively, the invention may be practiced employing cold non-autorefri~erative dewaxing solvent in which case the pro-=
4~03 cess comprises the steps of:
(a) passing the waxy oil, at a temperature above its cloud point, into a first chilling zone wherein a portion of the wax is precipitated from the oil by cooling same in the presence of a non-autorefrigerant dewaxing solvent to form a slurry of oil, solvent and solid particles of wax;
(b) passing the slurry from the first chilling zone to a second chilling zone which comprises a vertical, multi-staged tower operating at a constant pressure wherein each stage contains a liquid space and a vapor space above the liquid space, each of said vapor spaces also containing means for removal of autorefrig-erant vapor therefrom;
(c) cooling said slurry produced in said first chill-ing zone down to wax filtration temperature and precipitating additional wax therefrom ~n sald second chilling zone by contact-~
ing same in said second zone with a liquid autorefrigerant which is introduced under flow rate control conditions into a plurality of the stages in said second zone and allowed to evaporate therein so as to achieve an average coolin~ rate of the slurry in said zone ranging from between about 0.1 to 20 F per minute with an average temperature drop across each stage into which said liquid autorefrigerant is introduced and evaporated ranging from ~tween about 2 to 20F and wherein the evaporated autorefriger-ant is removed from each of said stages into which said liquid autorefrigerant was injected in a manner such that the auto-refrigerant vapor formed in any given stage does not pass throu~h the slurry on all of the stages in the tower above said stage;
and (d) separating the wax from the slurry to obtain wax and a dewa~çd oil solution.
This alternative process is claimed in the afore-mentioned parent application.
The "cloud point" of the oil is defined as a tempera-ture at which a cloud or haze of wax crystals first appears when an oil is cooled under prescribed conditions (ASTM D-2500-66 _ g _ ~144503 procedure). "Predilution", as the term is used herein, refers to the mixing of solvent and oil prior to cooling the oil to a temperature below its depressed cloud point and comprises, in one embodiment of this invention, prediluting a waxy oil with at least about 0.1 volume of an autorefrigerative predilution solvent per volume of oil stock or at least 0.5 volume of a non-autorefriger-ative predilution solvent per volume of oil stock resulting in the depression of the cloud point of the oil stock. If predilu-tion is used, it is preferred to predilute with non-autore-frigerant solvents, especially ketones. Non-autorefrigerant solvent, as the term is used herein, refers to dewaxing sol-vents, preferably ketones, that are liquid at normal tempera-ture and pressure, but may include the presence of as much as about 30 LV (liquid volume) % of the autorefrigerant - 9a -5 ~ 3 - lC -1 used in the second chilling zone, based on the waxy oil feed.
2 The non-autorefrigerative dewaxi.ng solvent 3 employed as predilution and/or first chilling solvent in 4 this ~nvention includes one or more (a) aliphatic ketones 5 having from 3-5 carbon atoms, such as acetone, methyl-ethyl 6 ketone (MEK), methyl-isobutyl ketone ~MIBK)J methyl-propyl 7 ketone and mixtures thereof, (b) halogenated low molecular 8 weight hydrocarbons such as C2-C4 alkyl chlorides (e.g., g dichloromethane, dichlorethane, methylene chloride) and mix-10 tures thereof, (c) normal or isoparaffins having 5 to lC
11 carbon atoms, (d) aromatics such as benzene, toluene, xylene, 12 petroleum naphtha and mixtures thereof, and (e) mixtures of 13 any of the foregoing solvents. Non-autorefrigerant solvent 14 as herein defined may include up to 25 LV v/O of autorefriger-
33 Additionally, 3,720,599 provides for the nucleation and 34 initial growth of wax to occur in the presence of substantial amounts (~.e.,~ 2~%) of autore~rigerant solvent, which, in 36 the absence of dewaxin~ aid, has been found to produce wax crystals inferior to those produced when nucleation occurs by chilling in the presence of ~etones or ketone/aromatic solvents followed by autorefrigeration. For example, when mixtures of ketone and high percentages (7 40~) of propylene were used in the DILCHILL dewaxing process, a distillate oil/wax slurry was produced which filtered very poorly.
It would be an improvement to the art if one could com-bine both ketone and autorefrigeran~ solvent dewaxing processes into a continuous process and in such a manner so as to carefully form the wax nuclei and begin crystal growth in a substantially non-autorefrigerant solvent environment such as ketone, to achieve large, stable, spherical crystals without the use of de-waxing aid and then further precipitate additional wax without destroying the spheres via direct contact with an evaporating autorefrigerant, thereby avoiding the need for scraped surface chillers following the ketone dewaxing step.
SU~ARY OF THE INVENTION
. _ The present invention provides a continuous autorefrig-erant solvent dewaxing process for dewaxing waxy hydrocarbon oils which comprises the steps of:
(a) prediluting the waxy oil with a non-autorefriger-ant dewaxing solvent to form a mixture of waxy oil and solvent;
(b) passing said mixture from step (a), at a tempera-ture above its cloud point, into the top of a continuous, auto-refrigerative chilling zone which comprises a vertical, elon-gated, multi-staged tower operating at a constant pressure wherein each stage contains a liquid space and a vapor space above ~14'~5V3 the liquid space, each of said vapor spaces also containing means for removal of autorefrigerant vapor th~refromJ
(c) cooling said mixutre as it passes down from stage to stage in said chilling zone to precipitate wax from said oil thereby forming a slurry comprising solid particles of wax and a dewaxed oil/solvent solution and further chilling the so-formed slurry by contacting same, in said chilling zone, with a liquid autorefrigerant which is introduced under flow rate control con-ditions into a plurality of the stages in said zone and allowed to evaporate therein so as to achieve an average cooling rate of the slurry in said zone ranging from between about 0.1 to 20F
per minute with an average temperature drop across each stage into which said liquid autorefrigerant is introduced and evapor-ated rangin~ from between about 2 to 20F. and wherein the eva-porated autorefrigerant is removed from each of said stages into which said liquid autorefrigerant was injected in a manner such that the autorefrigerant vapor formed in any given stages does not pass through all of the stages in the tower above said stage;
and (d) separating the wax from the slurry to obtain wax and a dewaxed oil solution.
In a preferred embodiment of this invention, the pre-diluted oil will contain a dewaxing aid and will be introduced into the top of the chilling zone at a temperature at or near its clond point and the slurry will be chilled down to the wax filtra-tion temperature in said chilling zone.
Alternatively, the invention may be practiced employing cold non-autorefri~erative dewaxing solvent in which case the pro-=
4~03 cess comprises the steps of:
(a) passing the waxy oil, at a temperature above its cloud point, into a first chilling zone wherein a portion of the wax is precipitated from the oil by cooling same in the presence of a non-autorefrigerant dewaxing solvent to form a slurry of oil, solvent and solid particles of wax;
(b) passing the slurry from the first chilling zone to a second chilling zone which comprises a vertical, multi-staged tower operating at a constant pressure wherein each stage contains a liquid space and a vapor space above the liquid space, each of said vapor spaces also containing means for removal of autorefrig-erant vapor therefrom;
(c) cooling said slurry produced in said first chill-ing zone down to wax filtration temperature and precipitating additional wax therefrom ~n sald second chilling zone by contact-~
ing same in said second zone with a liquid autorefrigerant which is introduced under flow rate control conditions into a plurality of the stages in said second zone and allowed to evaporate therein so as to achieve an average coolin~ rate of the slurry in said zone ranging from between about 0.1 to 20 F per minute with an average temperature drop across each stage into which said liquid autorefrigerant is introduced and evaporated ranging from ~tween about 2 to 20F and wherein the evaporated autorefriger-ant is removed from each of said stages into which said liquid autorefrigerant was injected in a manner such that the auto-refrigerant vapor formed in any given stage does not pass throu~h the slurry on all of the stages in the tower above said stage;
and (d) separating the wax from the slurry to obtain wax and a dewa~çd oil solution.
This alternative process is claimed in the afore-mentioned parent application.
The "cloud point" of the oil is defined as a tempera-ture at which a cloud or haze of wax crystals first appears when an oil is cooled under prescribed conditions (ASTM D-2500-66 _ g _ ~144503 procedure). "Predilution", as the term is used herein, refers to the mixing of solvent and oil prior to cooling the oil to a temperature below its depressed cloud point and comprises, in one embodiment of this invention, prediluting a waxy oil with at least about 0.1 volume of an autorefrigerative predilution solvent per volume of oil stock or at least 0.5 volume of a non-autorefriger-ative predilution solvent per volume of oil stock resulting in the depression of the cloud point of the oil stock. If predilu-tion is used, it is preferred to predilute with non-autore-frigerant solvents, especially ketones. Non-autorefrigerant solvent, as the term is used herein, refers to dewaxing sol-vents, preferably ketones, that are liquid at normal tempera-ture and pressure, but may include the presence of as much as about 30 LV (liquid volume) % of the autorefrigerant - 9a -5 ~ 3 - lC -1 used in the second chilling zone, based on the waxy oil feed.
2 The non-autorefrigerative dewaxi.ng solvent 3 employed as predilution and/or first chilling solvent in 4 this ~nvention includes one or more (a) aliphatic ketones 5 having from 3-5 carbon atoms, such as acetone, methyl-ethyl 6 ketone (MEK), methyl-isobutyl ketone ~MIBK)J methyl-propyl 7 ketone and mixtures thereof, (b) halogenated low molecular 8 weight hydrocarbons such as C2-C4 alkyl chlorides (e.g., g dichloromethane, dichlorethane, methylene chloride) and mix-10 tures thereof, (c) normal or isoparaffins having 5 to lC
11 carbon atoms, (d) aromatics such as benzene, toluene, xylene, 12 petroleum naphtha and mixtures thereof, and (e) mixtures of 13 any of the foregoing solvents. Non-autorefrigerant solvent 14 as herein defined may include up to 25 LV v/O of autorefriger-
15 ant solvent, preferably no. more than lC LV /, and still more
16 preferably not more than 5 LV %. For example, the ketones are
17 often used in combinatlon with one or more aromatic compound~
18 such as benzene, .oluene, xylene and petroleum naphtha. Pre-
19 ferred solvents comprise ketones. Particularly preferred are ~0 mixtures of MEK and MIBK or MEK and toluene. hutorefrigerants 21 used in this inven:ion include llquid, normally gaseous C2-C4 22 hydrocarbons such as propane, propylene, ethane, ethylene and 23 mixtures thereof as well as ammonia and normally gaseous flour-24 carbons such as monochlorodifluoromethane (Preon 22). Autore 25 frigerative solvent as herein defined may contain up to about 26 50 LV l. of non-autorefrigerative solvent, preferably no re 27 than 10 LV % and preferably no more than 2 LV %.
28 The autorefrigerative chilling zone is a vertical, 29 elongated, multi-staged tower operating at a constant pre6 -30 sure and in a man~er such that the waxy oil and slurry pass 31 down from stage to stage of the tower by gravit~ and cold, 32 liquid autorefrigerant is injected into each stage of the 33 tower wherein it contacts the warmer oil or slurry and cools 34 same via autorefrigerative evaporation. At least a portion 3~ of the cold, liquid autorefrigerant immediate~y evaporates on 36 contact with the warmer oil or slurry which results in agi-37 tation in the area of contact sufficient to achieve sub ~4S03 .` . - 1 1 -1 stantially instantaneous mixing (i.e., about one second or 2 less of the oil or slurry with the cold liquid autorefriger-3 ant, thus avoiding the shock chilling effect. As herein-4 before stated, supra, each stage contains means for re-5 moving the autorefrigerant vapors therefrom and the slurry 6 flows down from stage to stage in the tower by the action 7 o gravity. The cooled slurry exiting this chilling zone 8 is then passed to means, such as rotary pressure filters, 9 for separating the wax from the dewaxed oil/solvent mixture.
In general, this autorefrigerative chilling zone 11 or tower will operate at a constant pressure within the 12 range of from about C to 5C psig and more preferably from 13 about 2 to 2~ psig. The average chilling rate in the tower 14 ic the difference between the temperature of the prediluted 15 oil entering the tower and the temperature of the slurry 16 exiting the tower divided by the recidence time of the oil 17 or slurry in the tower and will range from about 0.1 to 2CF/
18 minute and more preferably from about 0.5 to lCF/minute.
19 This is achieved by controlling the autorefrigerant flow
28 The autorefrigerative chilling zone is a vertical, 29 elongated, multi-staged tower operating at a constant pre6 -30 sure and in a man~er such that the waxy oil and slurry pass 31 down from stage to stage of the tower by gravit~ and cold, 32 liquid autorefrigerant is injected into each stage of the 33 tower wherein it contacts the warmer oil or slurry and cools 34 same via autorefrigerative evaporation. At least a portion 3~ of the cold, liquid autorefrigerant immediate~y evaporates on 36 contact with the warmer oil or slurry which results in agi-37 tation in the area of contact sufficient to achieve sub ~4S03 .` . - 1 1 -1 stantially instantaneous mixing (i.e., about one second or 2 less of the oil or slurry with the cold liquid autorefriger-3 ant, thus avoiding the shock chilling effect. As herein-4 before stated, supra, each stage contains means for re-5 moving the autorefrigerant vapors therefrom and the slurry 6 flows down from stage to stage in the tower by the action 7 o gravity. The cooled slurry exiting this chilling zone 8 is then passed to means, such as rotary pressure filters, 9 for separating the wax from the dewaxed oil/solvent mixture.
In general, this autorefrigerative chilling zone 11 or tower will operate at a constant pressure within the 12 range of from about C to 5C psig and more preferably from 13 about 2 to 2~ psig. The average chilling rate in the tower 14 ic the difference between the temperature of the prediluted 15 oil entering the tower and the temperature of the slurry 16 exiting the tower divided by the recidence time of the oil 17 or slurry in the tower and will range from about 0.1 to 2CF/
18 minute and more preferably from about 0.5 to lCF/minute.
19 This is achieved by controlling the autorefrigerant flow
20 rate into, and oil hold-up in, each stage, rather than by
21 gradually decreasing the pressure in the system as is done
22 in batch chillers. That is, a controlled quantity of autore-
23 frigerant is vaporized in direct contact with controlled
24 quantity of oil or slurry in each stage of the tower. This
25 is accomplished by in~ecting the liquid autorefrigerant
26 through spray nozzles either submerged in the slurry or above
27 the surface thereof in each stage of the tower under flow
28 rate control conditions. This in turn controls the temp-
29 erature drop for each stage which will range from about 2 to
30 20F. The stagewise chilling rate then depends on the li~uid
31 holdup or residence time for each s~age. The autorefrigerant
32 evapora_es and cools the oil primarily by.its latent heat of
33 vaporization which results in an extremely high heat transer
34 rate. The autorefrigerant vapor is withdrawn from each stage
35 in a manner so as to avoid vapor overload in the tower. In
36 a preferred embodiment, this is done by separately removing l the vapor from the vapor spece of each stage directly 2 through and outside of the cooling zone or tower, rather 3 than allowing the vapor to cumulacively pas~ up through each 4 upper, successive stage, as is disclosed in the prior art.
However, under certain circumstances, it may be advantage~us 6 to allow the vapor produced in one or more given stages 7 to pass up through the tower or cooling zone through some, ~ but not all, of the stages above said one or more given g stages before removing the cumulative vapor from the cooling zone or tower. By way of illustration, it may be ll advantageous to remove vapor from the zone or tower at every 12 ~econd, third and fourth successive s~age. An amount of 13 autorefrigerant is added per stage to give a stagewise temp-14 erature decrease ranging from 2 to 20F, and more preferably from 3 to lODF. Of course, the ultimate temperature to 16 which the slurry is cooled in this tower will depend on the 17 temperature of the prediluted oil as it enters same, the 18 liquid hold-up in each stage, the amoun~, type and temper-l9 ature of autorefrigerant injected into each stage as well 20 as the pressure in the tower and the number of stages in 21 ~he tower. Therefore, it is understood, of course, depending 22 on the feed and size o the tower, that it may not always 23 be necessary to in~ect liquid autorefrigerant into each 24 and every stage of the tower. The cooling zone will, in 25 general, cool and slurry down to a temperature ranging 26 from between about 10 to 40F and, more preferably, 15 to 30~F
27 below the desired pour point of the dewaxed oil.
28 When employing cold non-autorefrigerative solvents 29 the flrst chilling zone may be any type of chilling zone 30 used in conventional ketone dewaxing processes described 31 under DESCRIPTION OF THE PRIOR ART, supra, includin~ scraped-32 surface chilling zones. However, in a preferred embodiment 33 of this invent~on, the first chilling zone will be an incre-34 mental DI~CHIL~ zone o the type disclosed in U.S. Patent 35 3,773,650 discussed, supra, the disclosures of which are 36 incorporated herein by reference. That is, a waxy oil at ~1~4S(~3 ~, - 13 -1 a temperature above its cloud point is introduced into an 2 elongated, staged chilling zone or tower and cold, non-3 sutorefrigerant dewaxing solvent, such as ketone, is incre-4 mentally introduced into said DILCHILT zone along a plurality 5 of stages therein, while maintaining a hig'n degree of agi-6 tation so as to effect substantially instantaneous mixing of 7 the solven- and wax/oil mixture as they progress through said 8 zone. W~en employing cold non-autorefrigerative so}vent, it 9 is also preferred to precipitate most of the wax from the oil lo in this first chilling zone.
11 The slurry from the cold non-autorefrigerative 12 chilling zone is passed directly to the top of a sec~nd 13 chilling zone employing autorefrigerati~e solvent which is 14 the vertical, multi-staged, constant pressure tower wherein 15 the slurry is further cooled down to the wax filtration tem-16 perature and additional wax is precipitated therefromJ as 17 was previously described.
lB hny waxy petroleum oil stock or distilla~e fraction 19 thereof may be dewaxed employing the process of this invention.
20 Illustrative, but non-lLmiting examples of such stocks are 21 (a) distillate fractions that have a boiling range within 22 the broad range of 500F to about 13C0F, w~th preferred 23 stocks including a lubricating oil and specialty oil fractions 24 boiling within the range of between about 56CF and 1200F, 25 (b) heavy feedstocks containing at least about 10 wt.% of 26 residual material boiling above 1050F, examples of which 27 include bright stocks and deasphalted resids having an 28 initial boiling point of above about 800F and (c) broad 29 cut feedstocks that are produced by topping or distilling 30 the lightest material or for crude oil lea~ing a broad cut 31 oil, the major portion of which boils above about 50CF or 65GF.
32 Additionally, any of these feeds may be hydrocrac~ed prior to 33 dis~illing, dewaxing or topping. The distillate fraction 34 may come from any source such as the paraffinic crudes ob-35 tained from Aramc~, Kuwait, the Panhandle, North Louisiana>
36 etc., naphthenic crudes such as Tia Juana, Coastal crudes, 1 etc., as well ac the relatively heavy feedstocks such as 2 bright ~tocks having a boiling range of lC5~+F and syn-3 thetic feedstocks derived from Athabasca Tar Sands, coal 4 liquids, etc.
s l~hen mixtures of MEK ar.d MIBK are used as the 6 non-autorefrigerant dilution solvent and/or coolant, MEK to 7 MIBK ratios may vary f~om 9C% MEK/10% MIBI~ to lC% MEK/90%
8 MIBK and more preferably from 70% MEK/3C% MIBK to 70h MIBK/3CZ
9 ME~. Ketone eO oil volume ratios may vary from 0.5/1 to 10 lG/l and more preferably from 1.0/1 to 4/1. Predilution 11 volume ratios of either autorefrigerant or non-autorefrigerant 12 solvent may vary from C/l to 3/1 and more preferably from 13 0/1 to 2/1 depending on prediluent and feedstock. Chilling 14 rates in the first chilling zone may vary from 0.1F/min.
15 to 20F/min. and more preferably from 0.5F/min. to 10F/min.
16 Outlet temperatures from the first chilling zone may vary 17 from -20F to +90F and more preferably from 2CF to 80F.
18 Lower outlet temperatures are better for distillace stocks 19 while higher outlet temperatures are better for residual 20 stocks. When employing cold non-autorefrigerative solvents, 21 it is preferred that most of the wax crystallize out of the 22 oil ~n the first chilling zone.
23 When propylene is used as the autorefrigerant in 24 the autorefrigerant chilling zone, from about a.2 to 2.5 25 volumes of propylene per volume of waxy oil and more pref-26 erably from about 1.0 to 2.0 volumes per volume are used, to 27 reduce the temperature of the slurry down to the wax fil-28 t-ation temperature, and to reduce the viscosity of the 29 slurry sufficiently for wax filtration. Chilling rates in 30 the autorefrigerative chillin~ zone will generally rsnge from 31 about 0.1 to 20~/min. and more preferably from about C.5 to 32 10F/min. The temperature of the cold slurry exiting the 33 chilling zone may vary from about -50F ~o +30F to produce 34 a dewaxed oil having a pour point ranging between about 35 -30F to +80F. In a preferred embodiment, the slurry will 36 exit the chilling zone at a temperature of from -30F to ~4503 l +lCF in order to produce a dewaxed oil having a pour point 2 ranging from between abou. -10F to +30F.
4 Figure 1 ic 2 flow diagram of an embodiment of a pro-5 c ess incorporating the instant invention utilizing non-6 autorefrigerative dilution.
7 Figure 2 is a schem2tic diagram of a preferred 8 embodiment of a multi-sta~ed, vertical tower comprising 9 the chilling zone of this invention.
Figure 3 is a schematic diagram of a preferred ll embodiment of a process incorporating the instant invention 12 utilizing cold non-autorefrigerative chilling.
.
14 Referring to Figure 1, a warm paraffinic lube oil 15 distillate at a temperature of about 16QF and having a 16 viscosity of 150 SUS at 100F is mixed with dewaxing aid 17 from l~ne 16 and then prediluted with a solvent comprising 18 a 7C/30 volume mixture of MEK/MIBK in an amount of about 1.2 19 volumes of ketone predilution solvent per volume of waxy 20 oil. The prediluted waxy oil/dewaxing aid mixture is then 21 passed from line lO ~hrough heat exchanger 12 wherein it is 22 cooled to a temperature of about 90F or just above its 23 c~oud point and from there into multi-staged autorefrigerant 24 chilling tower 26. Li~uid propylene at a temperature of -30~.
25 is fed into the various stages of tower 26 via line 28, mani 26 fold 30 and multiple in~ection points 32. Multiple in~ec-27 tion points 32 are fed to each of the various stages in tower 28 2.6 wherein the liquid propylene contacts the slurry in each 29 stage via a sparger located under the surface of the slurry 30 in each st~ge. About 1.5 volumes of liquid propylene are 31 used in tower 26 per volume of slurry entering therein via 32 line 24, Tower 26 operates at a pressure of about 2 psig.
33 About 1.2 volumes of the liauid autorefrigerant per volume 34 of fresh feed evaporates upon contact with the slurry, with 35 the autorefrigerant vapors being removed from each stage via 36 multiple tower exit ports 34, manifold 30 and line 3B at 11~4S03 1 an average tem?erature of about 24F. Thus, none of the 2 vapor produced in any stage passes through the slurry on 3 any other stage in the tower. The remaining C~.9 volume of 4 propylene per volume of ~eed go into solution with the MEK/
5 MIBK and dewaxed oil in the wax slurry. Tower 26 contains 6 approximately 14 stages in which the average slurry chilling 7 rate is about 3F per minute with an average temperature drop 8 across each stage of about 8.6F. The waxy slurry is further 9 cooled in tower 26 to a temperature of about -30F. The 10 slurry comprising solid wax particles, oil, ketone and ll li~uid propylene io then fed to ro~ary pressure filter 42 12 vla line 40 wherein the wax is filtered from the dewaxed oil 13 solution. The dewaxed oil solution leaves filter 24 via 14 line 44 and from ~here is sent to solvent recovery while 15 the wax is removed via line 46 and cent to solvent recovery 16 and further wax process~ng if desired. The dewaxed oil 17 solution yields a dewaxed oil having a pour point of about 18 -lO~F-l9 Figure 2 illustra~es a preferred embodiment of20 autorefrigerant chilling tower 26. The diameter of the 21 tower is sized so as to provide a superficial vapor velocity 22 low enough to avoid entrainment of the oil in the vapor. The 23 tower comprises about 14 discrete stages, 50a through 50n.
24 Each stage contains an autorefrigerant ~apor collector, vapor 25 space, slurry tray, slurry downcomer, weir and liquid autore-26 fri8erant sparger. ~his is illustrated for ~tage 50a wherein 27 52 is the vapor collector, 54 represents the vapor space, 56 28 is the slurry tray, 58 is the slurry, 60 is the downcomer, 62 29 is the weir and 64 is the sparger. The sparger 64 and 30 autorefrigerant vapor collector 52 are detailed in Figures 31 2-b and 2-c, respectively. Sparger 64 comprises piping 32 containing a plurality of smsll holes 66. Vapor collector 30 33 is shown as B pipe contalning a plurality of rec~angular 34 holes 68. In operation, slurry from tower 16 is fed to tower 35 26 via line 24, entering tower 26 through feed ~nlet 68 36 passing through downcomer 60 wherein it is directed downward 1 and under the surface of the slurry 58 held up on stage 50a.
2 Liquid propylene is introduced into stage 50 from injection 3 point 32 through sparger 64 and holes 66. The holes are 4 sized so as to provide a level of agitation such tha~ there is substantially instantaneous mixing (i.e., 1 second or 6 less). The holes are directed downward, opposing slurry 7 flow chrough the stage. Some of the propylene vaporizes as 8 it enters the warmer slurry and the vapors bubble up g through the slurry, with ~he remainder of the propylene 10 going into solution. Propylene ~apors are removed through 11 vapor collector 52 and the cooled slurry flows over weir 12 62 wherein it enters downcomer 60 and is directed under the 13 surface of the slurry on the next stage 50b. This process 14 i~ repeaced from stage to stage as the slurry passes down 15 the tower until ic exits from slurry outlet 70 at wax 16 filtrat~on temperature and fed to wax filter 42.
17 Referring to Figure 3, a warm paraffinic lube oil 18 distillate at a temperature of about 160~F and having a 19 viscosity of 150 SUS at 100F is passed from line 10 20 through heat exchanger 12 wherein it ~s cooled to a temp-21 erature of about 84F or just above its cloud point and 22 from there into multi-staged DILCHILL tower 16 via line 14 23 In tower 16 it is cooled by contact with a cold (-30F) 24 ketone solvent comprising a mixture of 70% MEK/30% MIBK
(volume basis) which is in~ected into the various stages of 26 tower 16 ~ia line 18, manifold 20 and multiple in~ection 27 points 22. About 1.2 volumes of the cold ketone dewaxing 28 solvententers the tower per volume of feed. Each stage 29 (not shown) in tower 16 contains a rotating impeller so 30 that the cold ketone dewaxing solvent entering therein is 31 substanti~lly instantaneously mixed in the waxy oil. In 32 tower 16 mos, of the wax is precipitated from the waxy oil 33 producing a slurry which lea~es the bottom of tower 16 via 34 line 24 at a temperature of about 30~. The cold, ketone-35 containing slurry in line 24 is passed directly inso multi-36 staged chilling tower 26. Liquid propylene at a temperature ~44503 ~; ` - 18 --l o~ -30F is fed into the various s~ages of tower 26 via 2 line 28, manifold 30 and multiple injection points 32.
3 Multiple injection points 32 are fed to each of the various 4 stages in tower 26 wherein she liquid propylene contacts S the slurry in each stage via a sparger located under the 6 surface of the slurry in each stage. About 1.5 vol~mes of 7 liquid propylene are used in tower 26 per volume of slurry 8 entering therein via line 24. Tower 26 operates a, a pressure 9 of about 2 psig. About 0.6 volume of the liquid autore-lO frigerant per volume of fresh feed evaporates upon contact ll with the slurry, with the autorefrigerant vapors being 12 removed from each stage via multiple tower exit ports 34, 13 manifold 30 and line 38 at an average temperature ~f about 14 -12F. Thus, none of the vapor produced in any stage passes 15 through the slurry on any other stage ~n the tower. The 16 remaining 0.9 volume of propylene per volume of feed go 17 into solution with the MEK/MIBK and dewaxed oil in the wax 18 slurry. Tower 26 contains spproximately seven stages in l9 which the average slurry chilling rate is about 3F. per 20 minute with an average temperature drop across each stage 21 Of about 8.6F. The waxy slurry is further cooled in tower 22 26 to a temperature of about -30DF. The slurry comprising 23 solid wax particles, oil, ketone and liquid propylene is 24 chen fed to rotary pressure filter 42 via line 40 wherein 25 the ~ax is filtered from the dewaxed oil solution. The de-26 waxed oil solutlon leaves filter 24 vi8 line 44 and from 27 there is sent to solvent recovery while the wax is removed 28 v~a line 46 and sent to solvent recovery and further wax 29 processing if des~red. The dewaxed oil solution yields a 30 dewaxed oil having a pour po~ t of about -1~F.
31 The invention will be re readily understood by 32 reference to the following example:
34 This examDle provides laboratory data demonstrating 35 the process of this invention utilizing non-autorefrigerative 36 solv~nts as dilution solvents. The feedstock used was a 1~4450~
1 paraffinieJ waxy distillate having a viscosity of 600 SUS
2 at 100F (60¢N). A pilot plant autorefrigerant chilling 3 unit was employed which comprised a vessel operating at a 4 cons~ant pressure of about 5 psig. Liquid propylene, at a tem~erature of about -30F was continuously inj ected into 6 the unit below the surface of the slurry contained therein.
7 Part of the liquid propylene vaporized with the vapors being 8 continuously withdrawn from the constant pressure vapor 9 space above the slurry. A slurry chilling rate of about 5F/min. was maintained by controlling the rate of injection 11 of the liquid propylene into the slurry. Before the feed-12 stock was placed into the autorefrigerant chilli~g unit, i;
13 was mixed with a Paraflow/Acryloid dewaxing aid and pre-14 dilu~ed with MEX at a temperature above i~ cloud point in an amount of one volume of MEK per volume of feed. The 16 prediluted feed was then prechilled to a temperature of 12CF, 17 which was approximately the cloud point of the prediluted 18 feed, before being added to the unit. As hereinbefore stated, 19 the prediluted feed was chilledin the zutorefrigeration un~t at a rate of 5F/min. The waxy slurry formed in the 21 unit was chilled down to a temperature of -30F and then 22 filtered at -30F. The amount of propane that dissolved 23 in the o~l in the unit was 1.5 volume per volume of feed 24 oil.
The results of this experiment are contained in 26 Table A below. These results illustrate the operability of 27 the present invention.
AUTOREFRIG~RATION DEWAXING
31 Feedstock 600N
32 Dewaxing Aid Type PIA
33 ~id Dose, wt.% on Feed 0.2 34 Predilution Solvent lCO% MEK
~5 Predilution Ratio on Feed 1.0 36 Prechilling Start F 150
However, under certain circumstances, it may be advantage~us 6 to allow the vapor produced in one or more given stages 7 to pass up through the tower or cooling zone through some, ~ but not all, of the stages above said one or more given g stages before removing the cumulative vapor from the cooling zone or tower. By way of illustration, it may be ll advantageous to remove vapor from the zone or tower at every 12 ~econd, third and fourth successive s~age. An amount of 13 autorefrigerant is added per stage to give a stagewise temp-14 erature decrease ranging from 2 to 20F, and more preferably from 3 to lODF. Of course, the ultimate temperature to 16 which the slurry is cooled in this tower will depend on the 17 temperature of the prediluted oil as it enters same, the 18 liquid hold-up in each stage, the amoun~, type and temper-l9 ature of autorefrigerant injected into each stage as well 20 as the pressure in the tower and the number of stages in 21 ~he tower. Therefore, it is understood, of course, depending 22 on the feed and size o the tower, that it may not always 23 be necessary to in~ect liquid autorefrigerant into each 24 and every stage of the tower. The cooling zone will, in 25 general, cool and slurry down to a temperature ranging 26 from between about 10 to 40F and, more preferably, 15 to 30~F
27 below the desired pour point of the dewaxed oil.
28 When employing cold non-autorefrigerative solvents 29 the flrst chilling zone may be any type of chilling zone 30 used in conventional ketone dewaxing processes described 31 under DESCRIPTION OF THE PRIOR ART, supra, includin~ scraped-32 surface chilling zones. However, in a preferred embodiment 33 of this invent~on, the first chilling zone will be an incre-34 mental DI~CHIL~ zone o the type disclosed in U.S. Patent 35 3,773,650 discussed, supra, the disclosures of which are 36 incorporated herein by reference. That is, a waxy oil at ~1~4S(~3 ~, - 13 -1 a temperature above its cloud point is introduced into an 2 elongated, staged chilling zone or tower and cold, non-3 sutorefrigerant dewaxing solvent, such as ketone, is incre-4 mentally introduced into said DILCHILT zone along a plurality 5 of stages therein, while maintaining a hig'n degree of agi-6 tation so as to effect substantially instantaneous mixing of 7 the solven- and wax/oil mixture as they progress through said 8 zone. W~en employing cold non-autorefrigerative so}vent, it 9 is also preferred to precipitate most of the wax from the oil lo in this first chilling zone.
11 The slurry from the cold non-autorefrigerative 12 chilling zone is passed directly to the top of a sec~nd 13 chilling zone employing autorefrigerati~e solvent which is 14 the vertical, multi-staged, constant pressure tower wherein 15 the slurry is further cooled down to the wax filtration tem-16 perature and additional wax is precipitated therefromJ as 17 was previously described.
lB hny waxy petroleum oil stock or distilla~e fraction 19 thereof may be dewaxed employing the process of this invention.
20 Illustrative, but non-lLmiting examples of such stocks are 21 (a) distillate fractions that have a boiling range within 22 the broad range of 500F to about 13C0F, w~th preferred 23 stocks including a lubricating oil and specialty oil fractions 24 boiling within the range of between about 56CF and 1200F, 25 (b) heavy feedstocks containing at least about 10 wt.% of 26 residual material boiling above 1050F, examples of which 27 include bright stocks and deasphalted resids having an 28 initial boiling point of above about 800F and (c) broad 29 cut feedstocks that are produced by topping or distilling 30 the lightest material or for crude oil lea~ing a broad cut 31 oil, the major portion of which boils above about 50CF or 65GF.
32 Additionally, any of these feeds may be hydrocrac~ed prior to 33 dis~illing, dewaxing or topping. The distillate fraction 34 may come from any source such as the paraffinic crudes ob-35 tained from Aramc~, Kuwait, the Panhandle, North Louisiana>
36 etc., naphthenic crudes such as Tia Juana, Coastal crudes, 1 etc., as well ac the relatively heavy feedstocks such as 2 bright ~tocks having a boiling range of lC5~+F and syn-3 thetic feedstocks derived from Athabasca Tar Sands, coal 4 liquids, etc.
s l~hen mixtures of MEK ar.d MIBK are used as the 6 non-autorefrigerant dilution solvent and/or coolant, MEK to 7 MIBK ratios may vary f~om 9C% MEK/10% MIBI~ to lC% MEK/90%
8 MIBK and more preferably from 70% MEK/3C% MIBK to 70h MIBK/3CZ
9 ME~. Ketone eO oil volume ratios may vary from 0.5/1 to 10 lG/l and more preferably from 1.0/1 to 4/1. Predilution 11 volume ratios of either autorefrigerant or non-autorefrigerant 12 solvent may vary from C/l to 3/1 and more preferably from 13 0/1 to 2/1 depending on prediluent and feedstock. Chilling 14 rates in the first chilling zone may vary from 0.1F/min.
15 to 20F/min. and more preferably from 0.5F/min. to 10F/min.
16 Outlet temperatures from the first chilling zone may vary 17 from -20F to +90F and more preferably from 2CF to 80F.
18 Lower outlet temperatures are better for distillace stocks 19 while higher outlet temperatures are better for residual 20 stocks. When employing cold non-autorefrigerative solvents, 21 it is preferred that most of the wax crystallize out of the 22 oil ~n the first chilling zone.
23 When propylene is used as the autorefrigerant in 24 the autorefrigerant chilling zone, from about a.2 to 2.5 25 volumes of propylene per volume of waxy oil and more pref-26 erably from about 1.0 to 2.0 volumes per volume are used, to 27 reduce the temperature of the slurry down to the wax fil-28 t-ation temperature, and to reduce the viscosity of the 29 slurry sufficiently for wax filtration. Chilling rates in 30 the autorefrigerative chillin~ zone will generally rsnge from 31 about 0.1 to 20~/min. and more preferably from about C.5 to 32 10F/min. The temperature of the cold slurry exiting the 33 chilling zone may vary from about -50F ~o +30F to produce 34 a dewaxed oil having a pour point ranging between about 35 -30F to +80F. In a preferred embodiment, the slurry will 36 exit the chilling zone at a temperature of from -30F to ~4503 l +lCF in order to produce a dewaxed oil having a pour point 2 ranging from between abou. -10F to +30F.
4 Figure 1 ic 2 flow diagram of an embodiment of a pro-5 c ess incorporating the instant invention utilizing non-6 autorefrigerative dilution.
7 Figure 2 is a schem2tic diagram of a preferred 8 embodiment of a multi-sta~ed, vertical tower comprising 9 the chilling zone of this invention.
Figure 3 is a schematic diagram of a preferred ll embodiment of a process incorporating the instant invention 12 utilizing cold non-autorefrigerative chilling.
.
14 Referring to Figure 1, a warm paraffinic lube oil 15 distillate at a temperature of about 16QF and having a 16 viscosity of 150 SUS at 100F is mixed with dewaxing aid 17 from l~ne 16 and then prediluted with a solvent comprising 18 a 7C/30 volume mixture of MEK/MIBK in an amount of about 1.2 19 volumes of ketone predilution solvent per volume of waxy 20 oil. The prediluted waxy oil/dewaxing aid mixture is then 21 passed from line lO ~hrough heat exchanger 12 wherein it is 22 cooled to a temperature of about 90F or just above its 23 c~oud point and from there into multi-staged autorefrigerant 24 chilling tower 26. Li~uid propylene at a temperature of -30~.
25 is fed into the various stages of tower 26 via line 28, mani 26 fold 30 and multiple in~ection points 32. Multiple in~ec-27 tion points 32 are fed to each of the various stages in tower 28 2.6 wherein the liquid propylene contacts the slurry in each 29 stage via a sparger located under the surface of the slurry 30 in each st~ge. About 1.5 volumes of liquid propylene are 31 used in tower 26 per volume of slurry entering therein via 32 line 24, Tower 26 operates at a pressure of about 2 psig.
33 About 1.2 volumes of the liauid autorefrigerant per volume 34 of fresh feed evaporates upon contact with the slurry, with 35 the autorefrigerant vapors being removed from each stage via 36 multiple tower exit ports 34, manifold 30 and line 3B at 11~4S03 1 an average tem?erature of about 24F. Thus, none of the 2 vapor produced in any stage passes through the slurry on 3 any other stage in the tower. The remaining C~.9 volume of 4 propylene per volume of ~eed go into solution with the MEK/
5 MIBK and dewaxed oil in the wax slurry. Tower 26 contains 6 approximately 14 stages in which the average slurry chilling 7 rate is about 3F per minute with an average temperature drop 8 across each stage of about 8.6F. The waxy slurry is further 9 cooled in tower 26 to a temperature of about -30F. The 10 slurry comprising solid wax particles, oil, ketone and ll li~uid propylene io then fed to ro~ary pressure filter 42 12 vla line 40 wherein the wax is filtered from the dewaxed oil 13 solution. The dewaxed oil solution leaves filter 24 via 14 line 44 and from ~here is sent to solvent recovery while 15 the wax is removed via line 46 and cent to solvent recovery 16 and further wax process~ng if desired. The dewaxed oil 17 solution yields a dewaxed oil having a pour point of about 18 -lO~F-l9 Figure 2 illustra~es a preferred embodiment of20 autorefrigerant chilling tower 26. The diameter of the 21 tower is sized so as to provide a superficial vapor velocity 22 low enough to avoid entrainment of the oil in the vapor. The 23 tower comprises about 14 discrete stages, 50a through 50n.
24 Each stage contains an autorefrigerant ~apor collector, vapor 25 space, slurry tray, slurry downcomer, weir and liquid autore-26 fri8erant sparger. ~his is illustrated for ~tage 50a wherein 27 52 is the vapor collector, 54 represents the vapor space, 56 28 is the slurry tray, 58 is the slurry, 60 is the downcomer, 62 29 is the weir and 64 is the sparger. The sparger 64 and 30 autorefrigerant vapor collector 52 are detailed in Figures 31 2-b and 2-c, respectively. Sparger 64 comprises piping 32 containing a plurality of smsll holes 66. Vapor collector 30 33 is shown as B pipe contalning a plurality of rec~angular 34 holes 68. In operation, slurry from tower 16 is fed to tower 35 26 via line 24, entering tower 26 through feed ~nlet 68 36 passing through downcomer 60 wherein it is directed downward 1 and under the surface of the slurry 58 held up on stage 50a.
2 Liquid propylene is introduced into stage 50 from injection 3 point 32 through sparger 64 and holes 66. The holes are 4 sized so as to provide a level of agitation such tha~ there is substantially instantaneous mixing (i.e., 1 second or 6 less). The holes are directed downward, opposing slurry 7 flow chrough the stage. Some of the propylene vaporizes as 8 it enters the warmer slurry and the vapors bubble up g through the slurry, with ~he remainder of the propylene 10 going into solution. Propylene ~apors are removed through 11 vapor collector 52 and the cooled slurry flows over weir 12 62 wherein it enters downcomer 60 and is directed under the 13 surface of the slurry on the next stage 50b. This process 14 i~ repeaced from stage to stage as the slurry passes down 15 the tower until ic exits from slurry outlet 70 at wax 16 filtrat~on temperature and fed to wax filter 42.
17 Referring to Figure 3, a warm paraffinic lube oil 18 distillate at a temperature of about 160~F and having a 19 viscosity of 150 SUS at 100F is passed from line 10 20 through heat exchanger 12 wherein it ~s cooled to a temp-21 erature of about 84F or just above its cloud point and 22 from there into multi-staged DILCHILL tower 16 via line 14 23 In tower 16 it is cooled by contact with a cold (-30F) 24 ketone solvent comprising a mixture of 70% MEK/30% MIBK
(volume basis) which is in~ected into the various stages of 26 tower 16 ~ia line 18, manifold 20 and multiple in~ection 27 points 22. About 1.2 volumes of the cold ketone dewaxing 28 solvententers the tower per volume of feed. Each stage 29 (not shown) in tower 16 contains a rotating impeller so 30 that the cold ketone dewaxing solvent entering therein is 31 substanti~lly instantaneously mixed in the waxy oil. In 32 tower 16 mos, of the wax is precipitated from the waxy oil 33 producing a slurry which lea~es the bottom of tower 16 via 34 line 24 at a temperature of about 30~. The cold, ketone-35 containing slurry in line 24 is passed directly inso multi-36 staged chilling tower 26. Liquid propylene at a temperature ~44503 ~; ` - 18 --l o~ -30F is fed into the various s~ages of tower 26 via 2 line 28, manifold 30 and multiple injection points 32.
3 Multiple injection points 32 are fed to each of the various 4 stages in tower 26 wherein she liquid propylene contacts S the slurry in each stage via a sparger located under the 6 surface of the slurry in each stage. About 1.5 vol~mes of 7 liquid propylene are used in tower 26 per volume of slurry 8 entering therein via line 24. Tower 26 operates a, a pressure 9 of about 2 psig. About 0.6 volume of the liquid autore-lO frigerant per volume of fresh feed evaporates upon contact ll with the slurry, with the autorefrigerant vapors being 12 removed from each stage via multiple tower exit ports 34, 13 manifold 30 and line 38 at an average temperature ~f about 14 -12F. Thus, none of the vapor produced in any stage passes 15 through the slurry on any other stage ~n the tower. The 16 remaining 0.9 volume of propylene per volume of feed go 17 into solution with the MEK/MIBK and dewaxed oil in the wax 18 slurry. Tower 26 contains spproximately seven stages in l9 which the average slurry chilling rate is about 3F. per 20 minute with an average temperature drop across each stage 21 Of about 8.6F. The waxy slurry is further cooled in tower 22 26 to a temperature of about -30DF. The slurry comprising 23 solid wax particles, oil, ketone and liquid propylene is 24 chen fed to rotary pressure filter 42 via line 40 wherein 25 the ~ax is filtered from the dewaxed oil solution. The de-26 waxed oil solutlon leaves filter 24 vi8 line 44 and from 27 there is sent to solvent recovery while the wax is removed 28 v~a line 46 and sent to solvent recovery and further wax 29 processing if des~red. The dewaxed oil solution yields a 30 dewaxed oil having a pour po~ t of about -1~F.
31 The invention will be re readily understood by 32 reference to the following example:
34 This examDle provides laboratory data demonstrating 35 the process of this invention utilizing non-autorefrigerative 36 solv~nts as dilution solvents. The feedstock used was a 1~4450~
1 paraffinieJ waxy distillate having a viscosity of 600 SUS
2 at 100F (60¢N). A pilot plant autorefrigerant chilling 3 unit was employed which comprised a vessel operating at a 4 cons~ant pressure of about 5 psig. Liquid propylene, at a tem~erature of about -30F was continuously inj ected into 6 the unit below the surface of the slurry contained therein.
7 Part of the liquid propylene vaporized with the vapors being 8 continuously withdrawn from the constant pressure vapor 9 space above the slurry. A slurry chilling rate of about 5F/min. was maintained by controlling the rate of injection 11 of the liquid propylene into the slurry. Before the feed-12 stock was placed into the autorefrigerant chilli~g unit, i;
13 was mixed with a Paraflow/Acryloid dewaxing aid and pre-14 dilu~ed with MEX at a temperature above i~ cloud point in an amount of one volume of MEK per volume of feed. The 16 prediluted feed was then prechilled to a temperature of 12CF, 17 which was approximately the cloud point of the prediluted 18 feed, before being added to the unit. As hereinbefore stated, 19 the prediluted feed was chilledin the zutorefrigeration un~t at a rate of 5F/min. The waxy slurry formed in the 21 unit was chilled down to a temperature of -30F and then 22 filtered at -30F. The amount of propane that dissolved 23 in the o~l in the unit was 1.5 volume per volume of feed 24 oil.
The results of this experiment are contained in 26 Table A below. These results illustrate the operability of 27 the present invention.
AUTOREFRIG~RATION DEWAXING
31 Feedstock 600N
32 Dewaxing Aid Type PIA
33 ~id Dose, wt.% on Feed 0.2 34 Predilution Solvent lCO% MEK
~5 Predilution Ratio on Feed 1.0 36 Prechilling Start F 150
37 Finish F 12C
38 Rate F/Min. lC.8
39 Autorefrig. Pressure S psig 1 ~u~orefrig. Start F 12C
2 Finish F -30 3 Rate F/Min. 5 4 C3 M~keu~ to Chiller Variable 5 Dilution to Filter 2.5 6 Solv. Como. to ~ilter 40/60 MEK/Pro~ane 7 Filtration Te~p. F -30 8 Feed Filter RB e GPHPSF 5.0 9 Wax L/S Ratio 6.3 lG W~x Oil Content, wt.% 62 11 Mean Crystal Dia., Microns 1 12 Crystal C 10 Microns, % 3 13 DWO Pour, F o This e~mple provides laboratory data comparing the 16 combination process of this invention employirg cold non^
17 autorefrigerative solvents and autoregrigerative solvent chil-18 ling with conventional DILCHILL ketone dewaxing followed by 19 scraped surface chilling. Three paraffinic lube oil feedstocks 20 were used, a bright stock, and two distillates having viscos-21 ities of 15G (lSON) and 60C SUS (60CN) at 10~F. A pilot plant 22 DILCHILL unit was used for the DILCHILL dewaxing with ketone 23 solvent to produce a ketone-containing slurry compri~ing solid-24 particles of wax and a mixture of partially dewaxed oil and 25 ke~one dewa~ing solvent. ~he temperature of the cold ketone 26 solvent fed into the DILCHILL unit was about ~30DF. The bright 27 stoc~ was prediluted with 1 volume of warm ketone solvent 28 per volume of feed before being fed into the DILCHILL unit.
29 The waxy slurry produced in the DILCHILL unit was then fed to 30 either scraped surface chillers or to a simNlated continuous, 31 autorefrigerant chilling unit for further chilling down to 32 wax filtration temperature. The cold slurry was then filtered 33 to separate the wax from the dewaxed oil/solvent mixture and 34 both the dewaxed oil and w~x were recovered.
The autorefrigersnt chilling ~nit comprised a ves-36 sel operating at a constant pressure of about 2 psig wherein 37 liquid propylene was continuously injected into the unit, 38 below the surface of he slurry contained therein. Part of 39 the liquid propylene vaporized with the vapors being continu-
2 Finish F -30 3 Rate F/Min. 5 4 C3 M~keu~ to Chiller Variable 5 Dilution to Filter 2.5 6 Solv. Como. to ~ilter 40/60 MEK/Pro~ane 7 Filtration Te~p. F -30 8 Feed Filter RB e GPHPSF 5.0 9 Wax L/S Ratio 6.3 lG W~x Oil Content, wt.% 62 11 Mean Crystal Dia., Microns 1 12 Crystal C 10 Microns, % 3 13 DWO Pour, F o This e~mple provides laboratory data comparing the 16 combination process of this invention employirg cold non^
17 autorefrigerative solvents and autoregrigerative solvent chil-18 ling with conventional DILCHILL ketone dewaxing followed by 19 scraped surface chilling. Three paraffinic lube oil feedstocks 20 were used, a bright stock, and two distillates having viscos-21 ities of 15G (lSON) and 60C SUS (60CN) at 10~F. A pilot plant 22 DILCHILL unit was used for the DILCHILL dewaxing with ketone 23 solvent to produce a ketone-containing slurry compri~ing solid-24 particles of wax and a mixture of partially dewaxed oil and 25 ke~one dewa~ing solvent. ~he temperature of the cold ketone 26 solvent fed into the DILCHILL unit was about ~30DF. The bright 27 stoc~ was prediluted with 1 volume of warm ketone solvent 28 per volume of feed before being fed into the DILCHILL unit.
29 The waxy slurry produced in the DILCHILL unit was then fed to 30 either scraped surface chillers or to a simNlated continuous, 31 autorefrigerant chilling unit for further chilling down to 32 wax filtration temperature. The cold slurry was then filtered 33 to separate the wax from the dewaxed oil/solvent mixture and 34 both the dewaxed oil and w~x were recovered.
The autorefrigersnt chilling ~nit comprised a ves-36 sel operating at a constant pressure of about 2 psig wherein 37 liquid propylene was continuously injected into the unit, 38 below the surface of he slurry contained therein. Part of 39 the liquid propylene vaporized with the vapors being continu-
40 ously withdrawn from the constant pressure vapor space above ~44503 1 the slurry. A slurry chill~ng rate of about 2~/min. was 2 maintained by controlling the ra.e o injection of the 3 liquid propylene into -he slurry.
4 The results of these ex~eriments, correlated to common dewaxed oil pour points, are contained in Table B, 6 below. These resul~s illustrate not only the operability of 7 the present invention, but also that superior results can 8 be achieved by its use. Thus, using the present invenLion 9 gave faster feed filter rates, drier wax cakes and wax 10 cakes containing less oil than the DILCHILL dewaxing process 11 followed by scraped surface chilling. Further, these results 12 were obtained without the use of dewaxing aid.
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4 The results of these ex~eriments, correlated to common dewaxed oil pour points, are contained in Table B, 6 below. These resul~s illustrate not only the operability of 7 the present invention, but also that superior results can 8 be achieved by its use. Thus, using the present invenLion 9 gave faster feed filter rates, drier wax cakes and wax 10 cakes containing less oil than the DILCHILL dewaxing process 11 followed by scraped surface chilling. Further, these results 12 were obtained without the use of dewaxing aid.
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Claims (17)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1, A continuous combination non-autorefrigerant/autore-frigerant solvent dewaxing process for dewaxinq waxy hydrocarbon oils which comprises the steps of:
(a) passing the waxy oil into a first chilling zone wherein a portion of the wax is precipitated from the oil by cooling same in the presence of a non-autorefrigerant dewaxing solvent to form a slurry comprising an oil solvent mixture and solid particles of wax;
(b) passing said slurry from said first chilling zone to a second chilling zone which comprises a vertical, multi-staged tower operating at a constant pressure wherein each stage contains a liquid space and a vapor space above the liquid space, each of said vapor spaces also containing means for removal of autorefrigerant vapor therefrom;
(c) cooling said slurry produced in said first chilling zone down to wax filtration temperature and precipitating additional wax therefrom in said second chilling zone by contacting same in said second zone with a liquid autorefrigerant which is introduced under flow rate control conditions into a plurality of the stages in said second zone and allowed to evaporate therein so as to achieve an average cooling rate of the slurry in said zone ranging from between about 0.1° to 20°F. per minute with an average temperature drop across each stage into which said liquid autorefrigerant is intro-duced and evaporated ranging from between about 2° to 20°F. and wherein the evaporated autorefrigerant is removed from each of said stages into which said liquid autorefrigerant was injected in a manner such that the autorefrigerant vapor formed in any given stage does not pass through all of the stages in the tower above said stage; and (d) separating the wax from the slurry to obtain wax and a dewaxed oil solution.
(a) passing the waxy oil into a first chilling zone wherein a portion of the wax is precipitated from the oil by cooling same in the presence of a non-autorefrigerant dewaxing solvent to form a slurry comprising an oil solvent mixture and solid particles of wax;
(b) passing said slurry from said first chilling zone to a second chilling zone which comprises a vertical, multi-staged tower operating at a constant pressure wherein each stage contains a liquid space and a vapor space above the liquid space, each of said vapor spaces also containing means for removal of autorefrigerant vapor therefrom;
(c) cooling said slurry produced in said first chilling zone down to wax filtration temperature and precipitating additional wax therefrom in said second chilling zone by contacting same in said second zone with a liquid autorefrigerant which is introduced under flow rate control conditions into a plurality of the stages in said second zone and allowed to evaporate therein so as to achieve an average cooling rate of the slurry in said zone ranging from between about 0.1° to 20°F. per minute with an average temperature drop across each stage into which said liquid autorefrigerant is intro-duced and evaporated ranging from between about 2° to 20°F. and wherein the evaporated autorefrigerant is removed from each of said stages into which said liquid autorefrigerant was injected in a manner such that the autorefrigerant vapor formed in any given stage does not pass through all of the stages in the tower above said stage; and (d) separating the wax from the slurry to obtain wax and a dewaxed oil solution.
2. The process of claim 1 wherein said second chilling zone operates at a constant pressure ranging from about 0 to 50 psig.
3. The process of claim 2 wherein most of said wax is precipitated from said waxy oil in said first chilling zone.
4. The process of claim 3 wherein the slurry in the second chilling zone is cooled at a rate of from about 0.1° to 20°F. per minute.
5. The process of claim 4 wherein said liquid autorefrig-erant used in said second chilling zone is selected from the group consisting essentially of normally gaseous C2-C4 hydrocarbons, ammonia and normally gaseous fluorocarbons.
6. The process of claim 4 wherein said waxy oil is at a temperature at or above its cloud point when it enters the first chilling zone.
7. The process of claim 5 wherein said first chilling zone is a DILCHILL chilling zone.
8. The process of claim 7 wherein the waxy oil is at a temperature above its cloud point when passed into the first chilling zone.
9. The process of claim 8 wherein said non-autorefrig-erant solvent used in said first chilling zone comprises one or more solvents selected from the group consisting essentially of (a) C3-C6 aliphatic ketones, (b) C2-C4 alkyl chlorides and (c) mixtures of C3-C6 aliphatic ketones with one or more aromatic compounds including benzene, toluene, xylene and petroleum naph-tha.
10. The process of claim 8 wherein said non-autorefriger-ative solvent comprises one or more C3-C6 aliphatic ketones mixed with one or more aromatic compounds selected from the group con-sisting essentially of benzene, toluene, xylene, petroleum naph-tha and mixtures thereof.
11. The process of claim 10 wherein no more than 30 LV %
of autorefrigerant, based on said waxy oil feed, is present in said first chilling zone.
of autorefrigerant, based on said waxy oil feed, is present in said first chilling zone.
12. The process of claim 11 wherein no autorefrigerant is present in said first chilling zone.
13. A continuous, combination non-autorefrigerant/autore-frigerant process for solvent dewaxing waxy petroleum oil frac-tions which comprises the steps of:
(a) passing said waxy petroleum oil fraction at a tempera-ture above its cloud point into a DILCHILL dewaxing zone comprising an elongated chilling zone divided into a plurality of stages and passing said waxy oil from stage to stage of said zone while injecting cold ketone dewaxing solvent into at least a portion of said stages and maintaining a high degree of agitation in a plur-ality of the ketone dewaxing solvent-containing stages so as to achieve substantially instantaneous mixing of said waxy oil and said solvent-waxy oil mixture as it progresses from stage to stage through said chilling zone to precipitate a portion of wax from said oil under conditions of said high degree of agitation to form a first slurry of oil, solvent and solid particles of wax;
(b) passing said first slurry from the DILCHILL dewaxing zone to the top of a second chilling zone which com-prises a vertical, multi-staged tower operating at a constant pressure ranging between about 0 to 50 psig wherein each stage contains a liquid space, a vapor space above the liquid space and means for removing autorefrigerant vapor from each vapor space;
(c) cooling said first slurry down to wax filtration temp-erature and precipitating additional wax therefrom by contacting said slurry in said second zone with a liquid autorefrigerant which is introduced under flow rate control conditions into a plurality of the stages in said second zone and allowed to evaporate therein at a controlled rate so as to achieve an average cool-ing rate of the slurry in said second zone ranging from between about 0.1° to 20°F./minute with an aver-age temperature drop across each stage into which said liquid autorefrigerant is introduced into and evapor-ated in ranging from between about 2° to 20°F. and wherein the evaporated autorefrigerant is removed from each of said stages into which said liquid auto-refrigerant was injected in a manner such that the autorefrigerant vapor formed in any given stage does not pass through all of the stages in said zone above said stage; and (d) filtering the wax from the slurry to obtain wax in a dewaxed oil solution.
(a) passing said waxy petroleum oil fraction at a tempera-ture above its cloud point into a DILCHILL dewaxing zone comprising an elongated chilling zone divided into a plurality of stages and passing said waxy oil from stage to stage of said zone while injecting cold ketone dewaxing solvent into at least a portion of said stages and maintaining a high degree of agitation in a plur-ality of the ketone dewaxing solvent-containing stages so as to achieve substantially instantaneous mixing of said waxy oil and said solvent-waxy oil mixture as it progresses from stage to stage through said chilling zone to precipitate a portion of wax from said oil under conditions of said high degree of agitation to form a first slurry of oil, solvent and solid particles of wax;
(b) passing said first slurry from the DILCHILL dewaxing zone to the top of a second chilling zone which com-prises a vertical, multi-staged tower operating at a constant pressure ranging between about 0 to 50 psig wherein each stage contains a liquid space, a vapor space above the liquid space and means for removing autorefrigerant vapor from each vapor space;
(c) cooling said first slurry down to wax filtration temp-erature and precipitating additional wax therefrom by contacting said slurry in said second zone with a liquid autorefrigerant which is introduced under flow rate control conditions into a plurality of the stages in said second zone and allowed to evaporate therein at a controlled rate so as to achieve an average cool-ing rate of the slurry in said second zone ranging from between about 0.1° to 20°F./minute with an aver-age temperature drop across each stage into which said liquid autorefrigerant is introduced into and evapor-ated in ranging from between about 2° to 20°F. and wherein the evaporated autorefrigerant is removed from each of said stages into which said liquid auto-refrigerant was injected in a manner such that the autorefrigerant vapor formed in any given stage does not pass through all of the stages in said zone above said stage; and (d) filtering the wax from the slurry to obtain wax in a dewaxed oil solution.
14. The process of claim 13 wherein the ketone dewaxing solvent is selected from the group consisting of (a) ketones hav-ing from 3 to 6 carbon atoms in the molecule and mixture thereof and (b) a mixture of 3 to 6 carbon atom ketones and aromatic com-pounds.
15. The process of claim 14 wherein the liquid autorefrig-erant injected into the second chilling zone is selected from the group consisting of from 2 to 4 carbon atom hydrocarbons, ammonia and normally gaseous chlorofluorocarbons.
16. The process of claim 15 wherein the ketone dewaxing solvent is a mixture of MEK/MIBK or MEK/toluene and the autore-frigerant is propylene.
17 . A continuous, combination ketone/autorefrigerant pro-cess for solvent dewaxing wax-containing heavy petroleum oil frac-tions which contain at least about 10 wt. % of residual material having an initial boiling point of about 1050°F. which comprises the steps of:
(a) mixing said oil with a predilution solvent;
(b) introducing said mixture into a DILCHILL dewaxing zone and passing said mixture from stage to stage of said zone while injecting cold ketone dewaxing solvent into at least a portion of said stages and maintaining a high degree of agitation in a plurality of the solvent-containing stages so as to achieve substantially in-stantaneous mixing of said ketone dewaxing solvent and said waxy oil/solvent mixture as it progresses from stage to stage through said chilling zone, thereby precipit-ating most of the wax from the oil to form a first slurry of oil, solvent and solid particles of wax;
(c) passing said first slurry from the DILCHILL dewaxing zone to the top of a second chilling zone which com-prises a vertical, multi-staged tower operating at a constant pressure ranging from between about 0 to 50 psig wherein each stage contains a liquid space, a vapor space above the liquid space and means for moving autorefrigerant vapor from each vapor space;
(d) cooling the first slurry down to wax filtration temper-ature and precipitating additional wax therefrom by contacting said slurry in said second zone with a liquid autorefrigerant which is introduced under flow rate control conditions into a plurality of the stages in said second zone and allowed to evaporate therein at a controlled rate so as to achieve an average cooling rate of the slurry in said second zone ranging from between about 0.1° to 20°F./minute and wherein the eva-porated autorefrigerant is removed from each of said stages into which said liquid autorefrigerant was in-jected in a manner such that the autorefrigerant vapor found in any given stage does not pass through all of the stages in said zone above said stage; and (e) filtering the wax from the slurry to obtain wax in a dewaxed oil solution.
(a) mixing said oil with a predilution solvent;
(b) introducing said mixture into a DILCHILL dewaxing zone and passing said mixture from stage to stage of said zone while injecting cold ketone dewaxing solvent into at least a portion of said stages and maintaining a high degree of agitation in a plurality of the solvent-containing stages so as to achieve substantially in-stantaneous mixing of said ketone dewaxing solvent and said waxy oil/solvent mixture as it progresses from stage to stage through said chilling zone, thereby precipit-ating most of the wax from the oil to form a first slurry of oil, solvent and solid particles of wax;
(c) passing said first slurry from the DILCHILL dewaxing zone to the top of a second chilling zone which com-prises a vertical, multi-staged tower operating at a constant pressure ranging from between about 0 to 50 psig wherein each stage contains a liquid space, a vapor space above the liquid space and means for moving autorefrigerant vapor from each vapor space;
(d) cooling the first slurry down to wax filtration temper-ature and precipitating additional wax therefrom by contacting said slurry in said second zone with a liquid autorefrigerant which is introduced under flow rate control conditions into a plurality of the stages in said second zone and allowed to evaporate therein at a controlled rate so as to achieve an average cooling rate of the slurry in said second zone ranging from between about 0.1° to 20°F./minute and wherein the eva-porated autorefrigerant is removed from each of said stages into which said liquid autorefrigerant was in-jected in a manner such that the autorefrigerant vapor found in any given stage does not pass through all of the stages in said zone above said stage; and (e) filtering the wax from the slurry to obtain wax in a dewaxed oil solution.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000399170A CA1144503A (en) | 1980-03-21 | 1982-03-23 | Continuous autorefrigerative dewaxing process and apparatus |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000348094A CA1140067A (en) | 1980-03-21 | 1980-03-21 | Continuous autorefrigerative dewaxing process and apparatus |
| CA000399170A CA1144503A (en) | 1980-03-21 | 1982-03-23 | Continuous autorefrigerative dewaxing process and apparatus |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1144503A true CA1144503A (en) | 1983-04-12 |
Family
ID=25669058
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000399170A Expired CA1144503A (en) | 1980-03-21 | 1982-03-23 | Continuous autorefrigerative dewaxing process and apparatus |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1144503A (en) |
-
1982
- 1982-03-23 CA CA000399170A patent/CA1144503A/en not_active Expired
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