JPH0811795B2 - An improved dewaxing method for cooling solvent-oil and wax slurries to wax filtration temperatures using a stirred heat exchanger - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an improved dewaxing process for hydrocarbon oils, especially petroleum, and most particularly lubricating oils, wherein the waxy oil is raised above its cloud point. The wax-containing oil is introduced directly into the chilling zone divided into a plurality of stages at a temperature, the wax-containing oil is passed from the stage of the chilling zone to the stage, and the cold dewaxing solvent is introduced into at least a part of the stage to remove the solvent-containing solvent. Forming a wax oil mixture and maintaining a high degree of agitation in at least some of the stages containing solvent and wax oil, whereby the solvent-wax oil mixture progresses through the direct chilling zone. Preferably about 1 to
The temperature at which the wax is separated from the oil by cooling at a rate of 8 ° F / min (0.6 to 4.4 ° C / min), that is, at a temperature higher than the wax separation temperature, the solvent and the wax-containing oil are substantially Instant mixing is carried out whereby a majority of the wax is precipitated from the waxy oil under the conditions of the high agitation to form a solvent-oil mixture containing the precipitated wax (Slurry I) and the precipitated wax Is removed from the direct chilling zone and cooled in the indirect chilling zone to a wax separation temperature to further precipitate a wax portion from the wax-containing oil, and the precipitated wax is solidified.
A method for dewaxing a hydrocarbon oil which is separated from a wax-oil-solvent mixture in a liquid separation means, characterized in that an indirect heat exchanger means operated in a high-level stirring mode is used as an indirect chilling zone. . Stirring is expressed using the impeller Reynolds number and is approximately 1,000 to 1,0.
00,000, preferably 5,000 to 1,000,000, most preferably
It is about 10,000 to 1,000,000.

The staged stirring direct chilling zone is instead replaced entirely by high stirring indirect heat exchanger means. A multi-point solvent injection facility can be optionally created whereby any combination of indirect and direct chilling of the waxy feedstock can occur simultaneously. In this way, the wax-containing feedstock is brought directly from the temperature above its cloud point to the wax separation temperature in the indirect heat exchanger unit or units.

By using this high agitation to avoid sudden temperature changes above 40 ° F (22 ° C) in the heat exchange chilling zone, and by using a combination of direct and indirect chilling, the feed filtration rate is increased and dewaxed. An increase in oil yield is achieved.

BACKGROUND OF THE INVENTION In the past, wax precipitation has been carried out under low or no agitation conditions. The process was continued because precipitation under conditions of high agitation formed fine wax particles, which were believed to clog the liquid-solid separator. A typical wax precipitation technique is scraped surface chillers.
r) was used. In such a unit, the wax-containing oil and the dewaxing solvent are premixed at a sufficient temperature to completely dissolve the oil and the wax. If necessary, the waxy oil is heated (either prior to solvent addition or after addition) to ensure complete dissolution of the wax contained therein.

Then, while precipitating the wax, the solution is brought to a constant cursing speed, eg 1 ° to 5 ° F, under conditions which avoid significant stirring of the solution.
/ Min (0.6 ° -2.8 ° C / min) for indirect cooling. In the indirectly cooled heat exchanger, the wax adheres to the surface of the heat exchanger and the heat exchanger walls become dirty, so the wax is removed using a scraping device. However, by physically crushing the wax crystals formed on the chiller wall by the action of the scraping device, uneven crystal growth occurs, the filtration rate is slowed down, and the wax crystals are enclosed in the wax. The amount of oil that is removed increases.

 Solving the inherent limitations and disadvantages of scraped surface chilling dewaxing
DILCHILL to erase ) (Dale Chill
Exxon Research and Engineering, Inc. registered service
(A Bismark) process was developed. Daychill
In the process, cooling is done in a staged tower.
Move wax-containing oil through the tower, and place multiple cold solvents along the tower.
Inject directly into some of the stages (some or all of the stages
Inject the cold solvent in either). Cold solvent injection
At least some of the stages containing waxy oil and solvent
The degree of stirring between the cold solvent and the waxy oil
Ensure instantaneous mixing. Chill to about 0 ° to 50
Bring to a temperature between ° F (-18 ° -10 ° C). Cold solvent injection
The majority of waxes from waxy oils under these conditions of high stirring
To precipitate. US Patent for Dale Chill Process
Further details can be found in No. 3,773,650.
Are incorporated herein by reference.

A variation of the Dailchill process is presented in US Pat. No. 3,775,288, which is also incorporated herein by reference. In the modified Dailchill process, cooling is performed by cold solvent injection and high agitation to separate the wax from the oil, that is, above the wax separation temperature, usually about 40 ° F (22 ° C) above the separation temperature, preferably At a temperature no higher than about 35 ° F (19 ° C), thereby precipitating at least a portion of the wax from the waxy oil. The oil-solvent-wax slurry is then withdrawn from the chill chilling zone and introduced into the second chilling zone where it is cooled to the wax separation temperature to further precipitate the wax portion from the wax containing oil. The cooling rate in this region is in the range of 5 to 20 ° F / min (2.8 to 11 ° C / min).

This deformation is carried out with the purpose of avoiding the use of a large amount of cold solvent.In the absence of this deformation, a large amount of cold solvent is required to reduce the temperature of the oil-solvent-wax slurry to the wax separation temperature throughout the entire process. Would be. In this embodiment, the second chilling zone can incorporate any conventional cooling process such as scraped chilling, self cooling, etc., but scraped chilling is preferred. In a scraped chiller, the partially cooled oil-solvent-wax slurry is indirectly cooled to the wax separation temperature without the addition of more solvent. Use a scraper to remove any wax that adheres to the chiller wall. The disadvantages of the scraping chiller in this embodiment are the same as those encountered when using the scraping chiller as a single cooling unit. The scraper physically comminutes the wax crystals that form on the chiller wall, thereby reducing the wax filtration rate and increasing the amount of oil contained in the wax.

U.S. Pat.No. 4,140,620 to Porette describes cooling a lube feedstock at a temperature above the cloud point with vigorous agitation in the cooling zone to a temperature below the cloud point, then agitating to a minimum and gradually increasing the solvent. After adding and cooling to the final temperature, the wax is filtered off. Rapid stirring is provided during the early part of the cooling period. The cooling zone is described as being a conventional double wall heat exchanger with means for stirring the oil while cooling it by the more rapid rotation of the scraping device. The base stock feedstock is diluted with solvent during the initial stirred chilling. Most of the solvent is added to the system after the formation of the first wax crystals, that is, after the temperature of the diluted or undiluted oil-based feedstock reaches a temperature slightly below the cloud point of the waxy petroleum cut. . From the patent figure, the cooling zone consists of a double-walled chiller, the wax-containing raw material is introduced into the internal zone, the low temperature filtrate is supplied to the outer jacket of the chiller, and the rotation speed of the scraping device is increased. It can be seen that the stirring is increased.

It is clear that a large amount of solvent is added after the initial high agitation cooling, before or during the final agitation step with low agitation or no agitation.

DESCRIPTION OF THE INVENTION High speed agitation indirect cooling, optionally in combination with multi-point solvent injection, can be used as a single dewaxing chilling process or with dale chill dewaxing instead of scraped surface chilling to effectively wax from waxy oils. I found that it can be removed.

In the process of the present invention, the pre-diluted or non-pre-diluted, preferably non-pre-diluted waxy oil is heated to ensure complete dissolution of the wax in the oil. Next, this wax-containing oil enters the zone of high-speed stirring and indirect heat exchange, where it is heated to 40 ° F.
If necessary, dewaxing solvent may be added simultaneously from multiple points to avoid a sharp temperature drop above (22 ° C) and to perform the necessary dilution at the wax separation temperature in a single step (single in a direct chilling unit). (Using high agitation or both) or at a cooling rate of 1 to 20 ° F / min (0.6 to 11 ° C / min) to the wax separation temperature. The final oil-solvent ratio is in the range of 1: 2 to 1: 5 depending on the feedstock. Although the chilling is done by an indirect heat exchanger, the solvent need not be cold, but cold solvent (-20 ° F (-29 ° C if cold)) can be used to reduce cooling requirements. A novel feature of this embodiment of the invention is the use of high agitation throughout the process to bring the wax separation temperature. The precipitated wax is separated from the wax-oil-solvent slurry by liquid-solid separation means.

Alternatively, the scraper chiller described herein may be replaced by the instant stirrer indirect heat exchanger to provide a U.S. Pat.
The Dale Chill process described in 3,775,288 can be modified. In this embodiment, the partially cooled, partially dewaxed oil from the Dylchill column is either above or below the wax separation temperature, either with or without the additional solvent added first. Chill to the final wax separation temperature towards the high speed agitator indirect heat exchanger at a temperature not as high as about 50 ° F (28 ° C). Chilling to wax separation temperature in a stirring chiller is 1 to 20 ° F / min (0.6 to 11 ° C / min)
Is the speed of.

High speed agitation helps ensure uniform crystal growth and causes high slurry velocities at the heat exchanger surfaces. High agitation prevents wax from adhering to the chilling surface of the exchanger,
It gives the same heat transfer coefficient as the scraped surface chilling. High agitation in an indirect heat exchanger can be achieved by any number of methods: high speed turbine, propeller or paddle type blades; vibration with plate collar, donuts, paddles or reciprocating shaft; Obtainable. The preferred method uses either a rotating turbine propeller or paddle type blades or an oscillating shaft with one or more plates attached. There is no restriction on the type, number or shape of propellers, turbines, paddles or plates used in the high speed agitator.

A clearly suitable rapid stirrer-heat exchanger is presented in the attached figure. The stirrer-heat exchanger unit is an indirect double-walled heat exchanger 1, which is a passage (P) defined between an inner wall 3 and an outer wall 4 of the unit by introducing a chilling fluid (cooling liquid) from an inlet 2. The material (slurry) to be chilled (slurry) is introduced from the inlet 6 into the central passageway (CP). Additional solvent necessary to avoid a sharp drop in temperature or to achieve the desired dilution at the wax separation temperature can be added via line B (controlled by valve B).

The high agitation is performed by a plurality of blades, which are supported shafts formed by jointly connecting a plurality of members, which are radially attached to the respective members. A shaft (S) formed by articulating a plurality of members attached with a plurality of vanes is arranged in the central passage of the double-wall heat exchanger to provide a high level of agitation to the substance passing therethrough. The multiple blades 7 may be paddles, propeller blades or turbine blades, but are preferably propeller blades installed in a shaft to increase agitation and flow in the direction of the slurry passing through the central passage. Articulated shafts consist of two or more rigid members (8A-8Z, four members shown in the figure, but it will be understood that articulated shafts may include any number of members. ) One end of one member (PA) is connected to the driving means 9 to provide shaft rotation of the shaft. The other end of the shaft member 8A is supported by a fixed bearing 10 and is connected to the second shaft member 8B by a joint connection or a deformable joint or universal joint 11, and each shaft member has the same joint connection or deformation. Sequentially tied to the next shaft member (8Y, etc.) by a universal joint or universal joint 11, each shaft member also being fixed by a fixed bearing located in the central passage of the double wall heat exchanger. Supported and held. The fixed bearing is preferably at the end of the shaft opposite the articulating or flexible joint or universal joint. These fixed bearings mounted on the shaft remain self-stationary in the central passage without the need to slide into the central passage and be welded, bolted or otherwise tied to the inner wall of the central passage. Is preferably mechanized. The partitioned features of the agitating unit allow any agitator shaft of any desired length to be fabricated and installed in existing double wall heat exchangers. This design, which combines a universal joint and a fixed bearing with a shaft member having propeller blades, prevents vibrations and shaft alignment errors from being transmitted along the shaft length, and accommodates slack or slight bending of the shaft. Becomes a unit that matches

Stirring is known as the impeller Reynolds number, N _Re (Perry, Chemical Engineers Handbook, 5th Edition, pages 19-6, McGraw-Hill, New York (197).
3)) Explained as high or turbulent if the dimensionless number exceeds 10,000. The impeller Reynolds number is defined by: (In the formula, L is the impeller direct system, n is the rotation speed, l is the fluid density, and μ is the fluid viscosity (the unit makes the group dimensionless)). Values of N _Re between 10 and 10,000 form a transition zone in which the flow is turbulent in the impeller and laminar (smooth) in distant portions of the vessel, such as at the vessel wall. ).

The waxy oil is diluted with a wax solvent as described above. This solvent can be selected from any of the known and readily available solvents. Typical examples of the solvent include acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIB
K) and the like, aliphatic ketones having 3 to 6 carbon atoms; low molecular weight hydrocarbons such as ethane, propane, butane and propylene, and mixtures of the above-mentioned ketones with C _{6 to} C ₁₀ aromatics such as benzene and toluene. . In addition, C ₂ -C ₄ chlorinated hydrocarbons,
For example, halogenated low molecular weight hydrocarbons such as dichloromethane and dichloroethane, and mixtures thereof can be used as a solvent. Specific examples of suitable solvent mixtures are methyl ethyl ketone and methyl isobutyl ketone, methyl ethyl ketone and toluene, dichloromethane and dichloroethane,
Propylene and acetone.

The preferred solvent is a ketone, with methyl ethyl ketone, methyl isobutyl ketone and mixtures thereof being especially preferred.

The method of the present invention is carried out at sufficient pressure to prevent solvent flashing. Atmospheric pressure is sufficient when using ketones, ketone / aromatic mixtures or halocarbons, but when using low molecular weight hydrocarbons such as propane, overpressure to avoid the autorefrigeration effect associated with loss of diluent solvent ( superalmospheric pressure) is required.

Any waxy hydrocarbon oil, petroleum, lubricating oil or other distillate fraction can be dewaxed by the process of the present invention. Usually, the boiling point range of these wax-containing raw materials is about 50.
It covers a wide range from 0 ° F to about 1300 ° F (about 260 ° C to about 704 ° C). Suitable oil feedstocks are lubricating oils and boiling points from 550 ° F to 1200 ° F
It is a special oil fraction in the range of (288 ℃ -649 ℃). These fractions may come from any source such as paraffinic crude oil obtained from Aramco, Kuwait, Panhandle, North Louisiana, Western Canada, Teijuaiana and the like. Hydrocarbon oil feedstock is also coal liquefaction,
It may be obtained from any of the current or future synthetic crude processes such as synfuels, tar sands extraction, sheer oil recovery and the like.

Example 1 A Western Canadian Dicrude 600N oil was fed to a Dale Chiller crystallizer at 134 ° F (57 ° C), 5 ° F (2.8 ° C) above its cloud point. -20 ° F (-29 ° C) solvent (methyl ethyl ketone 25%, methyl isobutyl ketone 75%)
3.2 volumes were added incrementally to the Dylchille crystallizer stage under conditions of high agitation and the wax-solvent-oil slurry (I) exiting the crystallizer was 39 ° F (4 ° C). Scraping (I) first scraping device rotates at 24RPM, inner diameter 4 inches (1
High speed agitated indirect chiller (inner diameter: 4 cm) with a 2.7 inch (6.9 cm) diameter propeller that rotates through 1000 RPM. Inch (10 cm), length 8 feet (2.4
m)) (flow B) (impeller Reynolds number = 3
3,000, slurry density 0.85g / cc, slurry viscosity 2.0 centipoise). Streams A and B are respectively separated in a scraper chiller or a high speed stirred indirect chiller at a wax separation temperature of -10 ° F (-23
C.) and sampled slurry (II) from each chiller stream to measure filtration characteristics. The results are presented below.

The high-speed stirred indirect chiller has a lower oil retention in the wax cake caused by the lower liquid / solids value compared to the slurry exiting the scraped surface chiller, resulting in an 18% increase in filtration rate and dewatering. This gives a final slurry showing a 7% increase in wax oil yield (= 10.6% increase in the dewaxed oil obtained).

Example 2 In order to determine the general applicability of the present invention, a number of different waxy oil feedstocks were used in a comparison of a day chill / scraped surface chiller and a day chill / high speed stirred indirect chiller. The procedure adopted is that of Example 1. The impeller Reynolds number in this example was 50,000. The results are presented below.

A-24rpm speed is directed to scraping chilling, 1500r
pm is directed to stirred chilling.

Example 3 Heat transfer coefficient comparison data was obtained using a Dale Chill / Scraped Surface Chiller Train and a Dale Chill / High Speed Stirred Indirect Chiller Train. In the Dail Chill / Oak surface chiller train and Dale Chill / high speed stirring indirect chiller train,
Initially 4 inches (10 cm) in diameter and 5 feet long (1.5 m)
The scraped surface chiller was operated as is, and then the internal was replaced with a high speed stirring internal. The results are presented below.

It is clear that the superior advantage of fast stirred indirect chilling over scraped indirect chilling lies in improved liquid / solid and dewaxing yields.

Example 4 Western Canadian canned crude oil containing 600N wax
After pre-diluting with 0.2% of K45%, MIBK55% solvent, a row of commercial scraping surface chillers (total row length 2700 feet ( 820m))
Supplied to. The solvent is premixed with the raw material above the cloud point before entering the scraping chiller. The slurry is gradually cooled as it passes through each row of scraper exchangers, and additional solvent (MEK 45%, MIBK 55%) increments are added at the flow temperature from the point of introduction to make the slurry a final scraper chiller. Was discharged at the filtration temperature (14 ° F (-10 ° C)) to contain 2.5 volumes of solvent. The inner diameter of the scraping chiller was 12 inches (30 cm). Operate the scraping device at 30 RPM, and chill at 1.6 ~
The speed was 3.9 ° F / min (0.9 to 2.2 ° C / min).

Another portion of the Western Canadian Dicrude 600N wax containing oil was similarly fed at 136 ° F (58 ° C) to a row of high speed stirred indirect chillers (trained operation). 60 ° F (16
2.5 ° C.) solvent was added to the wax-containing feedstock in the first chiller unit. This mixture was passed through all three stirred chillers, each containing a propeller. 1000 and 1500 RP
Two types of rotation speed tests of M were performed.

The high-speed stirring chiller used was a propeller having an inner diameter of 4 inches (10 cm), a length of 8 feet (2.4 m), and a diameter of 2.7 inches (6.9 cm). Impeller Reynolds number is 33 at 1000 RPM,
It was 50,000 at 000 and 1500 RPM. The stirrer used in this example had the articulated design described above and shown in the accompanying drawings.

The oil flow rate in the pilot stirred chiller was chosen to give the same chilling speed and residence time as the scraping surface chillers used in commercial units. The stirring chilling speed is 2.
8 to 3.8 ° F / min (1.6 to 2.1 ° C / min) (residence time 40 minutes), and the chilling speed is 1.6 to 3.9 for the scraped surface chiller.
° F / min (0.9-2.2 ° C / min) (residence time 41.7 min). As can be seen, the stirring chiller (24 feet total (7.3
m)) through the superficial cross-section velocity of the fluid, in order to make the residence times almost equal, the scraper chiller (total 2700 feet (82
It was smaller than the speed passing through (0m)).

Slurries use these trains at wax filtration temperatures (14 ° F).
(-10 ° C)). The data obtained from this comparison is presented below.

28% increase in filtration rate at 1000 rpm with a stirring chiller
And 16% at 1500 rpm. Liquid / solid drop is 100
It is of equal importance, reaching 9% at 0 rpm and 24% at 1500 rpm. This result makes the wash use more effective and in effect allows an increase in dewaxed oil yield of 3.9% at 1000 rpm and 6.3% at 1500 rpm.

Example 5 Western Canadian Dicrude 600N oil was fed to a Pyrotoplant Dailchill crystallizer at 137 ° F (58 ° C), 5 ° F (28 ° C) above its cloud point. -20 ° F
2.6 volume of solvent (45% methylethylketone, 55% methylisobutylketone) at (-29 ° C) was added to the Daletyl crystallizer stage under increasing agitation conditions, leaving the crystallizer wax-solvent-oil The slurry reached 39 ° F (3.9 ° C). Then cool the slurry to 20 ° F (-
The filtration performance was measured at a filtration temperature of 7 ° C. The same oil feed was then fed at 137 ° F (58 ° C) to a row of high speed stirred indirect chillers (trained operation). 80 ° F (27 ° C)
The solvent (MEK45%, MIBK55%) of 2.7 volume is added to the wax-containing raw material in the first chiller unit to cool the slurry at a rate of 5-8.
The wax was separated at a wax separation temperature by cooling at ° F / min (2.8 to 4.5 ° C / min). The results are presented in Table V.

Dale chill results do not have the effect of SS (scraping surface) chilling or stirring chilling. A sample of the slurry was taken at the outlet of the dale chill tower and cooled in the laboratory to the filtration temperature with a dash pot. The slurry does not accommodate the drawbacks of SS chilling. The agitation chilling results show that it can be comparable to the Dale chill performance and can eliminate the drawbacks of SS chilling with a wide range of filtration temperatures.

[Brief description of drawings]

Attached FIG. 1 illustrates a stirred heat exchanger suitable for use in the present method. 1: Heat exchanger 2: Coolant inlet 3: Inner wall 4: Outer wall 5: Coolant outlet 6: Slurry inlet 7: Multiple blades 8: Shift member 9: Drive means 10: Fixed bearing 11: Universal joint

Continuation of the front page (56) References JP-A-54-14404 (JP, A) JP-A-53-54205 (JP, A) JP-A-56-65089 (JP, A) JP-B-51-20526 (JP , B2)

Claims (3)

[Claims] 1. A wax-containing hydrocarbon oil is directly introduced into a chilling zone divided into a plurality of stages at a temperature higher than its cloud point, and the wax-containing oil is passed from the stage of the cooling zone to the stage to carry out cold temperature removal. A wax solvent is introduced into at least a portion of the stage to form a solvent-wax containing oil mixture, maintaining a high degree of agitation in at least a portion of the stage containing the solvent and wax containing oil thereby maintaining the solvent. The temperature at which the waxy oil mixture separates the wax from the oil as it progresses through the direct chilling zone, i.e.
Higher than wax separation temperature 28 ° C (50 ° F) higher than the separation temperature
Substantially instantaneous mixing of the solvent and the wax-containing oil with cooling to a temperature not above is carried out, whereby most of the wax is precipitated from the wax-containing oil under the conditions of high stirring. To form a wax-oil-solvent slurry, which is withdrawn from the direct chilling zone and cooled in the indirect heat exchanger zone to a wax separation temperature to further precipitate the wax portion from the slurry, and the wax-oil- In a method for dewaxing a wax-containing hydrocarbon oil in which the precipitated wax is separated from a solvent slurry by a solid-liquid separation means, a high level such that an indirect heat exchanger is represented by an impeller Reynolds number in a range of 1,000 to 1,000,000. The method as described above, which is operated in the stirring mode of 2. A dewaxing solvent containing a C _{3 to} C ₆ aliphatic ketone, a low molecular weight hydrocarbon, a mixture of a C _{3 to} C ₆ aliphatic ketone and a C _{6 to} C ₁₀ aromatic compound, and a C _{1 to} C ₆ halogen. The method of claim 1 selected from the group consisting of modified hydrocarbons. 3. The method according to claim 1 or 2, wherein the wax-containing oil is diluted with a dewaxing solvent to obtain an oil-solvent ratio of 1: 2 to 1: 5.