CA1227153A - Dewaxing process using agitated heat exchanger to chill solvent-oil and wax slurry to wax filtration temperature - Google Patents
Dewaxing process using agitated heat exchanger to chill solvent-oil and wax slurry to wax filtration temperatureInfo
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- CA1227153A CA1227153A CA000444548A CA444548A CA1227153A CA 1227153 A CA1227153 A CA 1227153A CA 000444548 A CA000444548 A CA 000444548A CA 444548 A CA444548 A CA 444548A CA 1227153 A CA1227153 A CA 1227153A
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- oil
- wax
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- waxy
- agitation
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G73/00—Recovery or refining of mineral waxes, e.g. montan wax
- C10G73/02—Recovery of petroleum waxes from hydrocarbon oils; Dewaxing of hydrocarbon oils
- C10G73/32—Methods of cooling during dewaxing
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- Oil, Petroleum & Natural Gas (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An improved process for dewaxing waxy hydro-carbon oils, wherein said waxy oil is introduced at a temperature above its cloud point into a direct chill-ing zone divided into a plurality of stages, passing said waxy oil from stage-to-stage of said chilling zone, introducing a cold dewaxing solvent into at least a portion of said stages, maintaining a high degree of agitation in at least a portion of the stages containing solvent and waxy oil, thereby ef-fecting substantially instantaneous mixing thereof while cooling said solvent-waxy oil mixture, to a temperature greater than the wax separation tempera-ture, whereby a substantial portion of the wax is precipitated from said waxy oil and forming a sol-ventoil mixture containing precipitated wax (slurry I), withdrawing said slurry I from said direct chill-ing zone and cooling same to the wax separation tem-perature in an indirect chilling zone thereby preci-pitating a further portion of wax from said waxy oil and separating said precipitated wax from the wax-oil-solvent mixture in solid-liquid separation means, the improvement comprising using as the indirect chilling zone an indirect heat exchanger means operated at a high level of agitation. Expressed in terms of Impeller Reynolds Number the agitation is on the order of about 1,000 to 1,000,000.
Alternatively, the staged, agitated, direct chilling zone is totally replaced by the high agita-tion indirect heat exchanger means.
An improved process for dewaxing waxy hydro-carbon oils, wherein said waxy oil is introduced at a temperature above its cloud point into a direct chill-ing zone divided into a plurality of stages, passing said waxy oil from stage-to-stage of said chilling zone, introducing a cold dewaxing solvent into at least a portion of said stages, maintaining a high degree of agitation in at least a portion of the stages containing solvent and waxy oil, thereby ef-fecting substantially instantaneous mixing thereof while cooling said solvent-waxy oil mixture, to a temperature greater than the wax separation tempera-ture, whereby a substantial portion of the wax is precipitated from said waxy oil and forming a sol-ventoil mixture containing precipitated wax (slurry I), withdrawing said slurry I from said direct chill-ing zone and cooling same to the wax separation tem-perature in an indirect chilling zone thereby preci-pitating a further portion of wax from said waxy oil and separating said precipitated wax from the wax-oil-solvent mixture in solid-liquid separation means, the improvement comprising using as the indirect chilling zone an indirect heat exchanger means operated at a high level of agitation. Expressed in terms of Impeller Reynolds Number the agitation is on the order of about 1,000 to 1,000,000.
Alternatively, the staged, agitated, direct chilling zone is totally replaced by the high agita-tion indirect heat exchanger means.
Description
~2Z7153
2 This invention relates to an improved pro-
3 cuss for dew axing hydrocarbon oils, particularly
4 petroleum oils, most particularly lube oils wherein said waxy oil is introduced at a temperature above its 6 cloud point into a direct chilling zone divided into a 7 plurality of stages, passing said waxy oil from stage-8 to-stage of said chilling zone, introducing a cold 9 dew axing solvent into at least a portion of said stages, whereby a solvent-waxy oil mixture is formed, 11 maintaining a high degree of agitation in at least a 12 portion of the stages containing solvent and waxy oil, 13 thereby effecting substantially instantaneous mixing 14 of said solvent and said waxy oil while cooling said solvent-waxy oil mixture, preferably at a rate of from 16 about 1 to 8F/min., as it progresses through said 17 direct chilling zone to a temperature greater than the 18 temperature at which the wax is separated from the 19 oil, i.e., the wax separation temperature, whereby a substantial portion of the wax is precipitated from 21 said waxy oil under conditions of said high degree of 22 agitation and forming a solvent-oil mixture containing 23 precipitated wax (slurry I), withdrawing said mixture 24 containing precipitated wax from said direct chilling zone and cooling same to the wax separation tempera-26 lure in an indirect chilling zone thereby precipitate 27 in a further portion of wax from said waxy oil and 28 separating said precipitated wax from the wax-oil-29 solvent mixture in solid-liquid separation means, the improvement comprising using as the indirect chilling 31 zone an indirect heat exchanger means operated at a 32 high level of agitation. Expressed in terms of issue Impeller Reynolds Number the agitation is on the order of about 1,000 to 1,000,000 preferably 5,000 to 1,000,000 and most preferably 10,000 to 1,000,000.
Alternatively, the staged, agitated, direct chilling zone is totally replaced by the high agitation indirect heat exchanger means.
Optionally, provision for multi-point solvent injection can be made, so that any combination of indirect and direct chilling of the waxy oil feed can take place simultaneously. In this way, the waxy oil feed is taken from a temperature above its cloud point directly to the wax separation temperature in a single or plurality of said indirect heat exchanger units.
By employing this high agitation, and using a combination of direct and indirect chilling so as to avoid sudden temperature changes in excess of 40 F, in the heat exchange chilling zone, increases in feed filter rate and improvements in dockside oil yield are realized.
Thus, more precisely, the invention in its broadest aspect provides in a process for dew axing waxy hydrocarbon oils wherein said waxy oil is introduced, at a temperature above its cloud point, into a direct chilling zone divided into a plurality of stages, passing said waxy oil from stage-to-stage of said chilling zone, introducing cold dew axing solvent into at least a portion of said stages whereby a solvent-waxy oil mixture is formed, maintaining a high degree of agitation in at least a portion of the stages containing solvent and waxy oil, thereby effecting substantially instantaneous mixing of said solvent and said waxy oil while cooling said solvent-waxy oil mixture as it progresses through said direct chilling zone to a temperature greater than the temperature at which the wax is separated from the oil, i.e., the wax separation temperature, but less than about 50 F above said separation temperature, whereby a substantial portion of the wax is precipitated from said waxy oil under conditions of said high degree of agitation and forming a wax-oil-solvent slurry, withdrawing said slurry from said direct chilling zone and cooling same to the wax separation temperature in an indirect heat exchanger zone thereby precipitating a further portion of said wax from said slurry, and separating said ~Z27153 precipitated wax from the wax-oil-solvent slurry in solid-liquid separation means, the improvement comprising operating the indirect heat exchanger at a high level of agitation.
In another aspect, the invention provides in a process for dew axing waxy hydrocarbon oils wherein said waxy oil is introduced, at a temperature above its cloud point, into a direct chilling zone divided into a plurality of stages, passing said waxy oil from stage-to-stage of said chilling zone, introducing cold dew axing solvent into at least a portion of said stages whereby a solvent-waxy oil mixture is formed, maintaining a high degree of agitation in at least a portion of the stages containing solvent and waxy oil, thereby effecting substantially instantaneous mixing of said solvent and said waxy oil while cooling said solvent-waxy oil mixture as it progresses through said direct chilling zone to a temperature greater than the temperature at which the wax is separated from the oil, i.e., the wax separation temperature, but less than about 50 F above said separation temperature, whereby a substantial portion of the wax is precipitated from said waxy oil under conditions of said high degree of agitation and forming a wax-oil-solvent slurry, withdrawing said slurry from said direct chilling zone and cooling same to the wax separation temperature in an indirect heat exchanger thereby precipitating a further portion of said wax from said waxy oil, and separating Swede precipitated wax from the wax-oil-solvent slurry in solid-liquid separation means, the improvement comprising operating the indirect heat exchanger at a high level of agitation expressed in terms of Impeller Reynolds Number in the range of about 10,000 to 1,000,000 wherein the high level of agitation is achieved by means of an articulated multi section shaft having blades radially attached thereto, each section of said shaft being supported by means of a steady bearing.
Finally, there is provided a method of Dixon hydrocarbon oils comprising diluting the waxy oil with dew axing solvent, introducing the oil-solvent mixture into an indirect heat exchanger operated at a high level of agitation expressed in terms of repeller Reynolds Number in the range of about 10,000 to 1,000,000 wherein the high level of agitation is achieved by means of an articulated multi-section shaft having blades radially attached - pa -lZ27~3 thereto, each section of said shaft being supported by means of a steady bearing, chilling the oil-solvent mixture to the wax separation temperature whereby wax is precipitated to form a wax-oil-solvent slurry, and separating the precipitated wax from the wax-oil-solvent slurry in liquid-solid separation means.
BACKGROUND OF THE INVENTION
In the past, wax precipitation was conducted under conditions of low or no agitation. This procedure was followed since it was believed that precipitation under conditions of high agitation would result in the formation of fine wax particles which would clog the liquid-solid separators. The typical wax precipitation technique employed scraped surface chillers. In such a unit a waxy oil and a dew axing solvent are premixed at a temperature sufficient to - 2b -~Z27153 1 effect complete solution of the oil and wax. If nieces-2 spry, the waxy oil is heated (either prior to or after 3 additions of solvent) to insure complete solution of 4 the wax contained therein.
The solution is then indirectly cooled at a 6 uniformly slow cooling rate, e.g., 1 to 5F/min., 7 under conditions which avoid substantial agitation of 8 the solution during precipitation of the wax. Because 9 of fouling of the exchanger wall in the indirectly cooled heat exchangers due to wax deposition on the 11 exchanger surface, scrapers are employed to remove the 12 wax. However, because of the physical crushing of the 13 wax crystals formed on the chiller wall by the action 14 of the scrapers, nonuniform crystal growth occurs which results in slow filtration rates and large 16 amounts of occluded oil in the wax.
17 The DILCHILL~ (DILCHILL is a registered 18 service mark of Exxon Research and Engineering 19 Company) process was developed so as to overcome the inherent limitations and disadvantages of scraped 21 surface chilling dew axing. In the DILCHILL process, 22 cooling is accomplished in a staged tower. The waxy 23 oil is moved through the tower while cold solvent is 24 injected along the tower directly into a plurality of the stages (either some or all of the stages have cold 26 solvent injected into them). The cold solvent inject 27 lion is accompanied by a high degree of agitation in 28 at least a portion of the stages containing waxy oil 29 and solvent so as to insure substantially instant an-eons mixing of the cold solvent and waxy oil. Chilling 31 is conducted to a temperature of between about 0 and 32 50F. A substantial portion of the wax is precipitated ~227~53 from the waxy oil under these conditions of cold sol-vent injection and high agitation. The DILCHILL pro-cuss is described in greater detail in US. 3.773,650.
A modification of the DILCHILL process is presented in US. 3,775,288.
In the modified DILCHILL process, cool-in by means of cold solvent injection and high agile-lion is conducted to a temperature greater than the temperature at which the wax is separated from the oil, i.e., the wax separation temperature but goner-ally less than about 40F above said separation them-portray and preferably less than about 35F above said separation temperature, thereby precipitating at least a portion of the wax from the waxy oil. This oil-solvent-wax slurry is then withdrawn from the DILCHILL chilling zone and introduced into a second chilling zone wherein it is cooled to the wax swooper-lion temperature, thereby precipitating a further portion of the wax from the waxy oil. Cooling rates in this zone are in the range 5-20F/min.
This modification is practiced so as to avoid employing the large volumes of cold solvent which would otherwise be necessary to reduce the them-portray of the oil-solvent-wax slurry all the way down to the wax separation temperature. In this em-bodiment, the second chilling zone may incorporate any conventional cooling process such as scraped surface chilling, auto refrigeration and the like; however, scraped surface chilling is preferred. In scraped surface chillers, the partially cooled oil-solvent-wax slurry is indirectly cooled to the wax separation temperature without the addition of more solvent. The scrapers are used to remove any wax which adheres to ~,~
, I
lZZ71~3 1 the walls of the chillers. A disadvantage of the 2 scraped surface chiller in this embodiment is the same 3 as that encountered when employing scraped surface 4 chillers as the sole cooling unit. The scrapers physically crush the wax crystals formed on the 6 chiller wall thereby reducing the wax filtration rates 7 and increasing the amounts of occluded oil in the wax.
8 US. 4,140,620 to Paulette describes an in-9 cremental dilution dew axing process wherein a Libra-acting oil stock, at a temperature above its cloud 11 point is cooled in a cooling zone with vigorous agile-12 lion to a temperature below its cloud point and then 13 further cooled with minimum agitation and incremental 14 solvent addition to its final temperature, followed by filtration for the removal of wax. Rapid stirring is 16 provided during the early part of the cooling period.
17 The cooling zone is described as being a conventional 18 double wall heat exchanger provided with means for 19 agitating the oil during cooling by more rapid rota-lion of the scrapers. The base oil stock is diluted 21 with solvent, during the initial agitated chilling.
22 The major portion of the solvent is added to the soys-23 them after the initial wax crystals have formed, i.e., 24 after the temperature of the oil base stock, with or without dilution, has reached a temperature slightly 26 below the cloud point of the waxy petroleum fraction.
27 From the figure in the patent it is seen that the 28 cooling zone comprises a double wall chiller wherein 29 the waxy oil feed is introduced into the inner zone with cold filtrate supplied to the outer jacket of the 31 chiller, with increased agitation being provided by 32 increased rotational speed of the scrapers.
~2Z71~3 1 It is clear that the bulk of the solvent is 2 added after the initial high agitation cooling and 3 before or during the low or no agitation final cooling 4 steps.
DESCRIPTION OF THE FIGURE
6 Figure 1 is a schematic of an agitated heat 7 exchanger suitable for use in the present process.
g It has been discovered that wax can be effi-ciently removed from waxy oil employing high speed 11 agitation indirect cooling, optionally in combination 12 with multi point solvent injection, either as the sole 13 dew axing chilling process, or in conjunction with 14 DILCHILL dew axing in place of scraped surface chill-in.
16 In the process of the instant invention, the 17 waxy oil with or without predilution, preferably with-18 out, is heated to insure the complete solution of the 19 wax therein. This waxy oil then enters the zone of high speed agitation and indirect heat exchange where 21 dew axing solvent is simultaneously added at a plural-22 fly of points, if needed, so as to avoid sudden them-23 portray reductions in excess of 40F and to achieve 24 the diluting required at the wax separation tempera-lure, and cooled in a single step (using either a 26 single, or plurality of high agitation in direct 27 chilling units) to the wax separation temperature at a 28 cooling rate of 1-20F/min. The final oil-solvent 29 ratio is in the range of 1:2 to 1:5, depending on feed stock. It is unnecessary that the solvent be cold, 12Z71~
1 since chilling is conducted by the indirect heat ox-2 changer, but cold solvent ego. -20F,) can be used to 3 reduce refrigeration requirements. The novel feature 4 of this embodiment of the instant invention is the employment of high agitation all the way to the wax 6 separation temperature. The precipitated wax is 7 separated from the wax-oilsolvent slurry in liquid-8 solid separation means.
g Alternatively, the DILCHILL process desk cried in US. 3,775,288 can be modified by subset-11 tuition of the instant high speed agitator indirect 12 heat exchanger for the scraped surface chillers desk 13 cried therein. In this embodiment, the partially 14 cooled, partially dockside oil from the DILCHILL tower is directed, either with or without the prior addition 16 of additional solvent, at a temperature above the wax 17 separation temperature, but less than about 50F above 18 said separation temperature to the high speed agitator 19 indirect heat exchanger for chilling to the final wax separation temperature. Chilling in the agitated 21 chiller to the wax separation temperature is at a rate 22 of from 1-20F/min.
23 The high speed agitation serves the purpose 24 of insuring uniform crystal growth and of inducing high slurry velocities at the exchanger surfaces. The 26 high agitation prevents deposition of wax on the ox-27 changer chilling surface and gives heat transfer co-28 efficient equivalent to scraped surface chilling. The 29 high agitation in the indirect heat exchangers can be obtained by any number of methods, i.e., high speed 31 rotating turbines, propellers or paddle blades; oscil-32 feting or reciprocating shafts with plate collars, 33 "donuts", paddle etc. attached thereto; high frequency 34 sonic vibrations, etc. The preferred method employs lZ271S3 1 either the rotating turbine, propeller or paddle blade 2 or the oscillating shaft with plate or plates attached 3 thereto. No limit is placed on the type, number or 4 configuration of the propellers, turbines, paddles or plates used in the high speed agitators.
6 A specifically preferred high speed agile-7 turret exchanger is presented in Figure I. The ago-8 titrate exchanger unit comprises an indirect double 9 wall heat exchanger (1) wherein the chilling fluid (coolant) is introduced via inlet (2) and passed 11 through the passageway (P) defined between the inner 12 (3) and outer (4) walls of the unit to the outlet (5) 13 and the material to be chilled (slurry), introduced 14 into the unit via inlet (6) is passed through the central passageway (CUP). Additional solvent is needed 16 to avoid sudden temperature reduction or needed to 17 achieve the dilution required at the wax separation 18 temperature may be added via line B (controlled by 19 valve B).
High agitation is effected by means of a 21 supported, articulated multi-section shaft having 22 multiple blades radially attached to each section. The 23 multi section articulated shaft having multiple blades 24 attached thereto (S) is positioned within the central passageway of the double wall heat exchanger so as to 26 produce a high level of agitation in the material 27 passing there through. The multiple blades (7) may be 28 paddles, propeller blades or turbine blades, but are 29 preferably propeller blades sited on the shaft so as to augment agitation and fluid flow in the direction 31 of the slurry passing through the central passageway.
32 The articulated shaft comprises two or more rigid 33 sections (ASSAY, four sections being shown in the 34 figure it being understood that the articulated shaft ~Z271~;3 g 1 may contain any number of sections), one section (PA) 2 being coupled at one end to a drive means (9) to pro-3 dupe the axial rotation of the shaft. The opposite end 4 of said shaft section (PA), supported by a steady bearing (10), is secured by means of an articulation 6 or flexible coupling or universal joint (11) to the 7 second shaft section (8B), each shaft section being in 8 turn secured by similar articulation or flexible g couplings or universal joints (11) to the next shaft section (MY etc.), each shaft section also being sup-11 ported and maintained within the central passageway of 12 the double wall heat exchanger by a steady bearing 13 (11) positioned within the central passageway. Pro-14 fireball, the steady bearing is located on the shaft at the end opposite the articulation or flexible coupling 16 or universal bearing. These steady bearings attached 17 to the shaft are preferable machined so as to just 18 slide into the central passageway and remain motion-19 less themselves within the passageway without the need for being welded, bolted or any other way secured to 21 the internal walls of the central passageway. Because 22 of the segmented nature of the agitation unit, an 23 agitator shaft of any desired length can be fabricated 24 and installed into existing double wall heat exchan-gets. This design of universal joints and steady bear-26 ins in combination with the shaft sections bearing 27 propeller blades results in a unit in which vibration 28 and shaft misalignment are not transmitted along the 29 length of the shaft, and allows the shaft to conform to tubes containing sags or slight bends.
31 Agitation is described as being high, or 32 turbulent, when the dimensionless number known as the 33 Impeller Reynolds Number (Perry, Chemical Engineer's 34 Handbook, Thea Ed., Page 19-6, McGraw-Hill, New York (1973), Ore, which is defined by the equation:
~2Z71S3 1 N = L no 2 wherein L is the impeller diameter, N is the rota-3 tonal speed, 1 is the fluid density and u is the 4 fluid viscosity, (units being such that the group is dimensionless), exceeds 10,000. Values of Ore between 6 10 and 10,000 form a transition zone where flow is 7 turbulent at the impeller and luminary (quiet) in 8 remote parts of the vessel such as at the vessel g walls.
As previously stated, the waxy oil is 11 diluted with a wax solvent. This solvent can be 12 selected from any of the known, readily available 13 solvents. Representative examples of such solvents are 14 the aliphatic kittens having from 3 to 6 carbon atoms, such as acetone, methyl ethyl kitten (ME) and methyl 16 isobutyl kitten (MINK); the low molecular weight 17 hydrocarbons such as ethanes propane, and butane and 18 propylene, as well as mixtures of the aforementioned 19 kittens with C6 to C10 aromatic compounds such as Bunsen and Tulane. In addition, halogenated low 21 molecular weight hydrocarbons, such as C2 to C4 color-22 inated hydrocarbons, e.g., dichloromethane, dichloro-23 ethanes etc., and mixtures thereof, may be used as 24 solvents. Specific examples of suitable solvent mix-lures are methyl ethyl Acetone and methyl isobutyl 26 kitten, methyl ethyl kitten and Tulane, dichlorom-27 ethanes and dichloroethane, and propylene and acetone.
28 The preferred solvents are the kittens with 29 methyl ethyl kitten, methyl isobutyl kitten and mix-lures thereof being especially preferred.
~Z27~53 1 The process of the instant invention will be 2 practiced at a pressure sufficient to prevent flashing 3 of the solvent. Atmospheric pressure is sufficient 4 when kittens, ketones/aromatics mixtures or halo car-buns are employed; however, when low molecular weight 6 hydrocarbons such as propane are used, suppertime-7 spheric pressures are necessary to avoid autorefri-8 gyration effects accompanied by the loss of delineate 9 solvent.
Any waxy hydrocarbon oil, petroleum oil, 11 lube oil or other distillate fraction may be dockside 12 by the process of this invention. In general, these 13 waxy oil stocks will have a boiling range within the 14 broad range of about 500F to about 1300F. The pro-furred oil stocks are the lubricating oil and special-16 fly oil fractions boiling within the range of 550F
17 and 1200F. These fractions may come from any source 18 such as the paraffinic cruxes obtained from Aramco, 19 Kuwait, the Panhandle, North Louisiana, Western Canada, Tic Juan, etc. The hydrocarbon oil stock may also be 21 obtained from any of the synthetic crude processes now 22 practiced or envisioned for the future such as coal 23 liquefaction, sinful, tar sands extraction, shale oil 24 recovery, etc.
Example 1 26 A Western Canadian Crude 600 N oil was fed 27 to a DILCHILL crystallizer at 134F, 5F above its 28 cloud point. 3.2 volumes of -20F solvent (25% methyl-29 ethylketone, 75% methylisobutylketone) were added incrementally to the DILCHILL crystallizer stages 31 under conditions of high agitation so that the wax-32 solvent-oil slurry (I) leaving the crystallizer was at 33 39F. The slurry (I) was first passed, (stream A) to a 1 conventional scraped surface chiller internal diameter 2 4 inches, length 5 feet with scrapers rotating at 24 3 RPM, and then (stream B) passed to a high speed agile-4 lion indirect chiller fitted with 2.7 inch diameter propellers rotating at 1000 RPM (internal diameter 4 6 inches, length 8 feet) (Impeller Reynolds Number =
7 33,000, slurry density 0.85 g/cc, slurry viscosity 2.0 8 centipoise). Streams A and B were chilled in the 9 scraped surface chiller or high speed agitation in-direct chiller respectively to the wax separation 11 temperature of -10F, slurry samples (II) were taken 12 from each chiller stream and the filtration character-13 is tics measured. The results are presented below.
DILCHILL Plus 16 Scraped SurfaceDILCHILL Plus 17 Chiller Agitated Chiller 18 Feed Filter 19 Rate (m3/m2 day 4.76 5.61 20 Liquids/Solids6.68 4.76 21 Dockside Oil Yields 22 After Wash (%)67.3 74.5 23 The high speed agitation indirect chiller produces a 24 final slurry which demonstrates an 18% increase in filter rate and 7% increase in dockside oil yield 26 (= 10.6% increase in dockside oil produced) due to less 27 oil retention in the wax cake caused by the lower 28 liquid/solids value, as compared to the slurry exiting 29 the scraped surface chiller.
~2271:53 1 Example II
2 To determine the general applicability of 3 the present invention, a number of different waxy oil 4 feeds were employed in a comparison of DILCHILL/
Scraped Surface Chiller with DILCHILL/High Speed Ago-6 station Indirect Chiller. The procedure employed is 7 that of Example I. The Impeller Reynolds Number in 8 this example was 50,000. The results are as presented g below.
TABLE II
11 Etch. Filter Liquids Dockside sty Stage 12 Speed Rate SolidsYieldContent 13 Feed rpmA m3/m2 day w/w % %
14 Western 24 4.76 6.68 67.3 15 Canadian 16600N 1500 5.28 4.5874.3 buyers 5624 4.63 6.3264.0 37.0 18 1500 4.78 4.2672.0 18.0 eve 24 4.58 6.4875.7 30.0 neutral 4.62 5.3880.8 20.0 button 24 4.09 7.1578.0 26.0 22600N 1500 4.41 4.6681.8 11.0 button 24 8.06 5.2376.7 31.5 24150N 1500 7.72 4.2382.0 10.6 A-24 rum speed refers to s-raped surface chilling, and 26 1500 rum refers to agitated chilling.
Sue 1 Example III
2 Heat transfer coefficient comparison data 3 was obtained employing the DILCHILL/Scraped Surface 4 Chiller train and the DILCHILL/High Speed Agitation indirect chiller train wherein the 4 inch diameter by 6 5 feet long Scraped Surface Chiller was first run as 7 such as then had its internals replaced with high 8 speed agitation internals. The results are presented 9 below.
` ~zz7~53 o C Us Us _ . ... ..
V I ED Us X
a us CO
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Alternatively, the staged, agitated, direct chilling zone is totally replaced by the high agitation indirect heat exchanger means.
Optionally, provision for multi-point solvent injection can be made, so that any combination of indirect and direct chilling of the waxy oil feed can take place simultaneously. In this way, the waxy oil feed is taken from a temperature above its cloud point directly to the wax separation temperature in a single or plurality of said indirect heat exchanger units.
By employing this high agitation, and using a combination of direct and indirect chilling so as to avoid sudden temperature changes in excess of 40 F, in the heat exchange chilling zone, increases in feed filter rate and improvements in dockside oil yield are realized.
Thus, more precisely, the invention in its broadest aspect provides in a process for dew axing waxy hydrocarbon oils wherein said waxy oil is introduced, at a temperature above its cloud point, into a direct chilling zone divided into a plurality of stages, passing said waxy oil from stage-to-stage of said chilling zone, introducing cold dew axing solvent into at least a portion of said stages whereby a solvent-waxy oil mixture is formed, maintaining a high degree of agitation in at least a portion of the stages containing solvent and waxy oil, thereby effecting substantially instantaneous mixing of said solvent and said waxy oil while cooling said solvent-waxy oil mixture as it progresses through said direct chilling zone to a temperature greater than the temperature at which the wax is separated from the oil, i.e., the wax separation temperature, but less than about 50 F above said separation temperature, whereby a substantial portion of the wax is precipitated from said waxy oil under conditions of said high degree of agitation and forming a wax-oil-solvent slurry, withdrawing said slurry from said direct chilling zone and cooling same to the wax separation temperature in an indirect heat exchanger zone thereby precipitating a further portion of said wax from said slurry, and separating said ~Z27153 precipitated wax from the wax-oil-solvent slurry in solid-liquid separation means, the improvement comprising operating the indirect heat exchanger at a high level of agitation.
In another aspect, the invention provides in a process for dew axing waxy hydrocarbon oils wherein said waxy oil is introduced, at a temperature above its cloud point, into a direct chilling zone divided into a plurality of stages, passing said waxy oil from stage-to-stage of said chilling zone, introducing cold dew axing solvent into at least a portion of said stages whereby a solvent-waxy oil mixture is formed, maintaining a high degree of agitation in at least a portion of the stages containing solvent and waxy oil, thereby effecting substantially instantaneous mixing of said solvent and said waxy oil while cooling said solvent-waxy oil mixture as it progresses through said direct chilling zone to a temperature greater than the temperature at which the wax is separated from the oil, i.e., the wax separation temperature, but less than about 50 F above said separation temperature, whereby a substantial portion of the wax is precipitated from said waxy oil under conditions of said high degree of agitation and forming a wax-oil-solvent slurry, withdrawing said slurry from said direct chilling zone and cooling same to the wax separation temperature in an indirect heat exchanger thereby precipitating a further portion of said wax from said waxy oil, and separating Swede precipitated wax from the wax-oil-solvent slurry in solid-liquid separation means, the improvement comprising operating the indirect heat exchanger at a high level of agitation expressed in terms of Impeller Reynolds Number in the range of about 10,000 to 1,000,000 wherein the high level of agitation is achieved by means of an articulated multi section shaft having blades radially attached thereto, each section of said shaft being supported by means of a steady bearing.
Finally, there is provided a method of Dixon hydrocarbon oils comprising diluting the waxy oil with dew axing solvent, introducing the oil-solvent mixture into an indirect heat exchanger operated at a high level of agitation expressed in terms of repeller Reynolds Number in the range of about 10,000 to 1,000,000 wherein the high level of agitation is achieved by means of an articulated multi-section shaft having blades radially attached - pa -lZ27~3 thereto, each section of said shaft being supported by means of a steady bearing, chilling the oil-solvent mixture to the wax separation temperature whereby wax is precipitated to form a wax-oil-solvent slurry, and separating the precipitated wax from the wax-oil-solvent slurry in liquid-solid separation means.
BACKGROUND OF THE INVENTION
In the past, wax precipitation was conducted under conditions of low or no agitation. This procedure was followed since it was believed that precipitation under conditions of high agitation would result in the formation of fine wax particles which would clog the liquid-solid separators. The typical wax precipitation technique employed scraped surface chillers. In such a unit a waxy oil and a dew axing solvent are premixed at a temperature sufficient to - 2b -~Z27153 1 effect complete solution of the oil and wax. If nieces-2 spry, the waxy oil is heated (either prior to or after 3 additions of solvent) to insure complete solution of 4 the wax contained therein.
The solution is then indirectly cooled at a 6 uniformly slow cooling rate, e.g., 1 to 5F/min., 7 under conditions which avoid substantial agitation of 8 the solution during precipitation of the wax. Because 9 of fouling of the exchanger wall in the indirectly cooled heat exchangers due to wax deposition on the 11 exchanger surface, scrapers are employed to remove the 12 wax. However, because of the physical crushing of the 13 wax crystals formed on the chiller wall by the action 14 of the scrapers, nonuniform crystal growth occurs which results in slow filtration rates and large 16 amounts of occluded oil in the wax.
17 The DILCHILL~ (DILCHILL is a registered 18 service mark of Exxon Research and Engineering 19 Company) process was developed so as to overcome the inherent limitations and disadvantages of scraped 21 surface chilling dew axing. In the DILCHILL process, 22 cooling is accomplished in a staged tower. The waxy 23 oil is moved through the tower while cold solvent is 24 injected along the tower directly into a plurality of the stages (either some or all of the stages have cold 26 solvent injected into them). The cold solvent inject 27 lion is accompanied by a high degree of agitation in 28 at least a portion of the stages containing waxy oil 29 and solvent so as to insure substantially instant an-eons mixing of the cold solvent and waxy oil. Chilling 31 is conducted to a temperature of between about 0 and 32 50F. A substantial portion of the wax is precipitated ~227~53 from the waxy oil under these conditions of cold sol-vent injection and high agitation. The DILCHILL pro-cuss is described in greater detail in US. 3.773,650.
A modification of the DILCHILL process is presented in US. 3,775,288.
In the modified DILCHILL process, cool-in by means of cold solvent injection and high agile-lion is conducted to a temperature greater than the temperature at which the wax is separated from the oil, i.e., the wax separation temperature but goner-ally less than about 40F above said separation them-portray and preferably less than about 35F above said separation temperature, thereby precipitating at least a portion of the wax from the waxy oil. This oil-solvent-wax slurry is then withdrawn from the DILCHILL chilling zone and introduced into a second chilling zone wherein it is cooled to the wax swooper-lion temperature, thereby precipitating a further portion of the wax from the waxy oil. Cooling rates in this zone are in the range 5-20F/min.
This modification is practiced so as to avoid employing the large volumes of cold solvent which would otherwise be necessary to reduce the them-portray of the oil-solvent-wax slurry all the way down to the wax separation temperature. In this em-bodiment, the second chilling zone may incorporate any conventional cooling process such as scraped surface chilling, auto refrigeration and the like; however, scraped surface chilling is preferred. In scraped surface chillers, the partially cooled oil-solvent-wax slurry is indirectly cooled to the wax separation temperature without the addition of more solvent. The scrapers are used to remove any wax which adheres to ~,~
, I
lZZ71~3 1 the walls of the chillers. A disadvantage of the 2 scraped surface chiller in this embodiment is the same 3 as that encountered when employing scraped surface 4 chillers as the sole cooling unit. The scrapers physically crush the wax crystals formed on the 6 chiller wall thereby reducing the wax filtration rates 7 and increasing the amounts of occluded oil in the wax.
8 US. 4,140,620 to Paulette describes an in-9 cremental dilution dew axing process wherein a Libra-acting oil stock, at a temperature above its cloud 11 point is cooled in a cooling zone with vigorous agile-12 lion to a temperature below its cloud point and then 13 further cooled with minimum agitation and incremental 14 solvent addition to its final temperature, followed by filtration for the removal of wax. Rapid stirring is 16 provided during the early part of the cooling period.
17 The cooling zone is described as being a conventional 18 double wall heat exchanger provided with means for 19 agitating the oil during cooling by more rapid rota-lion of the scrapers. The base oil stock is diluted 21 with solvent, during the initial agitated chilling.
22 The major portion of the solvent is added to the soys-23 them after the initial wax crystals have formed, i.e., 24 after the temperature of the oil base stock, with or without dilution, has reached a temperature slightly 26 below the cloud point of the waxy petroleum fraction.
27 From the figure in the patent it is seen that the 28 cooling zone comprises a double wall chiller wherein 29 the waxy oil feed is introduced into the inner zone with cold filtrate supplied to the outer jacket of the 31 chiller, with increased agitation being provided by 32 increased rotational speed of the scrapers.
~2Z71~3 1 It is clear that the bulk of the solvent is 2 added after the initial high agitation cooling and 3 before or during the low or no agitation final cooling 4 steps.
DESCRIPTION OF THE FIGURE
6 Figure 1 is a schematic of an agitated heat 7 exchanger suitable for use in the present process.
g It has been discovered that wax can be effi-ciently removed from waxy oil employing high speed 11 agitation indirect cooling, optionally in combination 12 with multi point solvent injection, either as the sole 13 dew axing chilling process, or in conjunction with 14 DILCHILL dew axing in place of scraped surface chill-in.
16 In the process of the instant invention, the 17 waxy oil with or without predilution, preferably with-18 out, is heated to insure the complete solution of the 19 wax therein. This waxy oil then enters the zone of high speed agitation and indirect heat exchange where 21 dew axing solvent is simultaneously added at a plural-22 fly of points, if needed, so as to avoid sudden them-23 portray reductions in excess of 40F and to achieve 24 the diluting required at the wax separation tempera-lure, and cooled in a single step (using either a 26 single, or plurality of high agitation in direct 27 chilling units) to the wax separation temperature at a 28 cooling rate of 1-20F/min. The final oil-solvent 29 ratio is in the range of 1:2 to 1:5, depending on feed stock. It is unnecessary that the solvent be cold, 12Z71~
1 since chilling is conducted by the indirect heat ox-2 changer, but cold solvent ego. -20F,) can be used to 3 reduce refrigeration requirements. The novel feature 4 of this embodiment of the instant invention is the employment of high agitation all the way to the wax 6 separation temperature. The precipitated wax is 7 separated from the wax-oilsolvent slurry in liquid-8 solid separation means.
g Alternatively, the DILCHILL process desk cried in US. 3,775,288 can be modified by subset-11 tuition of the instant high speed agitator indirect 12 heat exchanger for the scraped surface chillers desk 13 cried therein. In this embodiment, the partially 14 cooled, partially dockside oil from the DILCHILL tower is directed, either with or without the prior addition 16 of additional solvent, at a temperature above the wax 17 separation temperature, but less than about 50F above 18 said separation temperature to the high speed agitator 19 indirect heat exchanger for chilling to the final wax separation temperature. Chilling in the agitated 21 chiller to the wax separation temperature is at a rate 22 of from 1-20F/min.
23 The high speed agitation serves the purpose 24 of insuring uniform crystal growth and of inducing high slurry velocities at the exchanger surfaces. The 26 high agitation prevents deposition of wax on the ox-27 changer chilling surface and gives heat transfer co-28 efficient equivalent to scraped surface chilling. The 29 high agitation in the indirect heat exchangers can be obtained by any number of methods, i.e., high speed 31 rotating turbines, propellers or paddle blades; oscil-32 feting or reciprocating shafts with plate collars, 33 "donuts", paddle etc. attached thereto; high frequency 34 sonic vibrations, etc. The preferred method employs lZ271S3 1 either the rotating turbine, propeller or paddle blade 2 or the oscillating shaft with plate or plates attached 3 thereto. No limit is placed on the type, number or 4 configuration of the propellers, turbines, paddles or plates used in the high speed agitators.
6 A specifically preferred high speed agile-7 turret exchanger is presented in Figure I. The ago-8 titrate exchanger unit comprises an indirect double 9 wall heat exchanger (1) wherein the chilling fluid (coolant) is introduced via inlet (2) and passed 11 through the passageway (P) defined between the inner 12 (3) and outer (4) walls of the unit to the outlet (5) 13 and the material to be chilled (slurry), introduced 14 into the unit via inlet (6) is passed through the central passageway (CUP). Additional solvent is needed 16 to avoid sudden temperature reduction or needed to 17 achieve the dilution required at the wax separation 18 temperature may be added via line B (controlled by 19 valve B).
High agitation is effected by means of a 21 supported, articulated multi-section shaft having 22 multiple blades radially attached to each section. The 23 multi section articulated shaft having multiple blades 24 attached thereto (S) is positioned within the central passageway of the double wall heat exchanger so as to 26 produce a high level of agitation in the material 27 passing there through. The multiple blades (7) may be 28 paddles, propeller blades or turbine blades, but are 29 preferably propeller blades sited on the shaft so as to augment agitation and fluid flow in the direction 31 of the slurry passing through the central passageway.
32 The articulated shaft comprises two or more rigid 33 sections (ASSAY, four sections being shown in the 34 figure it being understood that the articulated shaft ~Z271~;3 g 1 may contain any number of sections), one section (PA) 2 being coupled at one end to a drive means (9) to pro-3 dupe the axial rotation of the shaft. The opposite end 4 of said shaft section (PA), supported by a steady bearing (10), is secured by means of an articulation 6 or flexible coupling or universal joint (11) to the 7 second shaft section (8B), each shaft section being in 8 turn secured by similar articulation or flexible g couplings or universal joints (11) to the next shaft section (MY etc.), each shaft section also being sup-11 ported and maintained within the central passageway of 12 the double wall heat exchanger by a steady bearing 13 (11) positioned within the central passageway. Pro-14 fireball, the steady bearing is located on the shaft at the end opposite the articulation or flexible coupling 16 or universal bearing. These steady bearings attached 17 to the shaft are preferable machined so as to just 18 slide into the central passageway and remain motion-19 less themselves within the passageway without the need for being welded, bolted or any other way secured to 21 the internal walls of the central passageway. Because 22 of the segmented nature of the agitation unit, an 23 agitator shaft of any desired length can be fabricated 24 and installed into existing double wall heat exchan-gets. This design of universal joints and steady bear-26 ins in combination with the shaft sections bearing 27 propeller blades results in a unit in which vibration 28 and shaft misalignment are not transmitted along the 29 length of the shaft, and allows the shaft to conform to tubes containing sags or slight bends.
31 Agitation is described as being high, or 32 turbulent, when the dimensionless number known as the 33 Impeller Reynolds Number (Perry, Chemical Engineer's 34 Handbook, Thea Ed., Page 19-6, McGraw-Hill, New York (1973), Ore, which is defined by the equation:
~2Z71S3 1 N = L no 2 wherein L is the impeller diameter, N is the rota-3 tonal speed, 1 is the fluid density and u is the 4 fluid viscosity, (units being such that the group is dimensionless), exceeds 10,000. Values of Ore between 6 10 and 10,000 form a transition zone where flow is 7 turbulent at the impeller and luminary (quiet) in 8 remote parts of the vessel such as at the vessel g walls.
As previously stated, the waxy oil is 11 diluted with a wax solvent. This solvent can be 12 selected from any of the known, readily available 13 solvents. Representative examples of such solvents are 14 the aliphatic kittens having from 3 to 6 carbon atoms, such as acetone, methyl ethyl kitten (ME) and methyl 16 isobutyl kitten (MINK); the low molecular weight 17 hydrocarbons such as ethanes propane, and butane and 18 propylene, as well as mixtures of the aforementioned 19 kittens with C6 to C10 aromatic compounds such as Bunsen and Tulane. In addition, halogenated low 21 molecular weight hydrocarbons, such as C2 to C4 color-22 inated hydrocarbons, e.g., dichloromethane, dichloro-23 ethanes etc., and mixtures thereof, may be used as 24 solvents. Specific examples of suitable solvent mix-lures are methyl ethyl Acetone and methyl isobutyl 26 kitten, methyl ethyl kitten and Tulane, dichlorom-27 ethanes and dichloroethane, and propylene and acetone.
28 The preferred solvents are the kittens with 29 methyl ethyl kitten, methyl isobutyl kitten and mix-lures thereof being especially preferred.
~Z27~53 1 The process of the instant invention will be 2 practiced at a pressure sufficient to prevent flashing 3 of the solvent. Atmospheric pressure is sufficient 4 when kittens, ketones/aromatics mixtures or halo car-buns are employed; however, when low molecular weight 6 hydrocarbons such as propane are used, suppertime-7 spheric pressures are necessary to avoid autorefri-8 gyration effects accompanied by the loss of delineate 9 solvent.
Any waxy hydrocarbon oil, petroleum oil, 11 lube oil or other distillate fraction may be dockside 12 by the process of this invention. In general, these 13 waxy oil stocks will have a boiling range within the 14 broad range of about 500F to about 1300F. The pro-furred oil stocks are the lubricating oil and special-16 fly oil fractions boiling within the range of 550F
17 and 1200F. These fractions may come from any source 18 such as the paraffinic cruxes obtained from Aramco, 19 Kuwait, the Panhandle, North Louisiana, Western Canada, Tic Juan, etc. The hydrocarbon oil stock may also be 21 obtained from any of the synthetic crude processes now 22 practiced or envisioned for the future such as coal 23 liquefaction, sinful, tar sands extraction, shale oil 24 recovery, etc.
Example 1 26 A Western Canadian Crude 600 N oil was fed 27 to a DILCHILL crystallizer at 134F, 5F above its 28 cloud point. 3.2 volumes of -20F solvent (25% methyl-29 ethylketone, 75% methylisobutylketone) were added incrementally to the DILCHILL crystallizer stages 31 under conditions of high agitation so that the wax-32 solvent-oil slurry (I) leaving the crystallizer was at 33 39F. The slurry (I) was first passed, (stream A) to a 1 conventional scraped surface chiller internal diameter 2 4 inches, length 5 feet with scrapers rotating at 24 3 RPM, and then (stream B) passed to a high speed agile-4 lion indirect chiller fitted with 2.7 inch diameter propellers rotating at 1000 RPM (internal diameter 4 6 inches, length 8 feet) (Impeller Reynolds Number =
7 33,000, slurry density 0.85 g/cc, slurry viscosity 2.0 8 centipoise). Streams A and B were chilled in the 9 scraped surface chiller or high speed agitation in-direct chiller respectively to the wax separation 11 temperature of -10F, slurry samples (II) were taken 12 from each chiller stream and the filtration character-13 is tics measured. The results are presented below.
DILCHILL Plus 16 Scraped SurfaceDILCHILL Plus 17 Chiller Agitated Chiller 18 Feed Filter 19 Rate (m3/m2 day 4.76 5.61 20 Liquids/Solids6.68 4.76 21 Dockside Oil Yields 22 After Wash (%)67.3 74.5 23 The high speed agitation indirect chiller produces a 24 final slurry which demonstrates an 18% increase in filter rate and 7% increase in dockside oil yield 26 (= 10.6% increase in dockside oil produced) due to less 27 oil retention in the wax cake caused by the lower 28 liquid/solids value, as compared to the slurry exiting 29 the scraped surface chiller.
~2271:53 1 Example II
2 To determine the general applicability of 3 the present invention, a number of different waxy oil 4 feeds were employed in a comparison of DILCHILL/
Scraped Surface Chiller with DILCHILL/High Speed Ago-6 station Indirect Chiller. The procedure employed is 7 that of Example I. The Impeller Reynolds Number in 8 this example was 50,000. The results are as presented g below.
TABLE II
11 Etch. Filter Liquids Dockside sty Stage 12 Speed Rate SolidsYieldContent 13 Feed rpmA m3/m2 day w/w % %
14 Western 24 4.76 6.68 67.3 15 Canadian 16600N 1500 5.28 4.5874.3 buyers 5624 4.63 6.3264.0 37.0 18 1500 4.78 4.2672.0 18.0 eve 24 4.58 6.4875.7 30.0 neutral 4.62 5.3880.8 20.0 button 24 4.09 7.1578.0 26.0 22600N 1500 4.41 4.6681.8 11.0 button 24 8.06 5.2376.7 31.5 24150N 1500 7.72 4.2382.0 10.6 A-24 rum speed refers to s-raped surface chilling, and 26 1500 rum refers to agitated chilling.
Sue 1 Example III
2 Heat transfer coefficient comparison data 3 was obtained employing the DILCHILL/Scraped Surface 4 Chiller train and the DILCHILL/High Speed Agitation indirect chiller train wherein the 4 inch diameter by 6 5 feet long Scraped Surface Chiller was first run as 7 such as then had its internals replaced with high 8 speed agitation internals. The results are presented 9 below.
` ~zz7~53 o C Us Us _ . ... ..
V I ED Us X
a us CO
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_ O
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u? sun 2~;3 1 Clearly, a major advantage of high speed agitation 2 indirect chilling over scraped surface indirect chill-3 in is in improved liquid/solid and in dockside yield.
4 Example IV
A Western Canadian Crude 600N waxy oil was
... ..
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H I V I Or\ en O D
H I C ::~ . .
a) o o I
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E 'Lo ox ED Al ED to o a o us En I
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u? sun 2~;3 1 Clearly, a major advantage of high speed agitation 2 indirect chilling over scraped surface indirect chill-3 in is in improved liquid/solid and in dockside yield.
4 Example IV
A Western Canadian Crude 600N waxy oil was
6 fed to a bank of commercial scraped surface chillers
7 (total bank length 2700 feet) at 137F, 5F above its
8 cloud point, after having been prediluted with 0.2 g volumes of solvent MOHAWK, 55%MIBK. Solvent is pro-mixed with feed above cloud point before entering 11 scraped surface chillers. The slurry was gradually 12 cooled as it passed through each bank of scraped sun-13 face exchangers, with additional solvent (45~ ME, 14 55%MIBK) increments being added at stream temperature at the point of introduction, until the slurry left 16 the final scraped surface chiller at the filtration 17 temperature (14F) containing 2.5 volume of solvent.
18 The scraped surface chiller had an internal diameter 19 of 12 inches. The scraper was run at 30 RPM and chill-in was conducted at a rate of 1.6-3.9F/min.
21 A second portion of Western Canadian Crude 22 600N waxy oil was similarly fed at 136F to a bank of 23 high speed agitation indirect chillers (run in train) 24 2.5 volumes of solvent (MOHAWK, 55%MIBK) at 60F was added to the waxy oil feed in the first chiller unit.
26 This mixture was passed through a total of three ago-27 toted chillers each containing propellers. Two rota-28 tonal speeds were tested, 1000 and 1500 RPM.
29 The high speed agitated chiller was 4 inches in internal diameter and 8 feet in length and employed 31 a propeller of 2.7 inches diameter. At 1000 RPM the ~;2z~ I
1 Impeller Reynolds Number was 33,000 and at 1500 RPM
2 the Impeller Reynolds Number was 50,000. The agitator 3 employed in this example was of the articulated design 4 previously described and presented in Figure 1.
Throughput in the pilot agitated chiller was 6 chosen so as to give the same chilling rate and nest-7 dunce time as the scraped surface chillers employed in 8 the commercial unit. The agitated chilling rate was
18 The scraped surface chiller had an internal diameter 19 of 12 inches. The scraper was run at 30 RPM and chill-in was conducted at a rate of 1.6-3.9F/min.
21 A second portion of Western Canadian Crude 22 600N waxy oil was similarly fed at 136F to a bank of 23 high speed agitation indirect chillers (run in train) 24 2.5 volumes of solvent (MOHAWK, 55%MIBK) at 60F was added to the waxy oil feed in the first chiller unit.
26 This mixture was passed through a total of three ago-27 toted chillers each containing propellers. Two rota-28 tonal speeds were tested, 1000 and 1500 RPM.
29 The high speed agitated chiller was 4 inches in internal diameter and 8 feet in length and employed 31 a propeller of 2.7 inches diameter. At 1000 RPM the ~;2z~ I
1 Impeller Reynolds Number was 33,000 and at 1500 RPM
2 the Impeller Reynolds Number was 50,000. The agitator 3 employed in this example was of the articulated design 4 previously described and presented in Figure 1.
Throughput in the pilot agitated chiller was 6 chosen so as to give the same chilling rate and nest-7 dunce time as the scraped surface chillers employed in 8 the commercial unit. The agitated chilling rate was
9 2.8 to 3.8F/min. (residence time of 40 min.) while for the scraped surface chillers the chilling rate was 11 1.6 to 3.9F/min. (residence time of 41.7 min.). As is 12 clear, the superficial velocity of the fluid through 13 the agitated chiller (24 feet total) was much less 14 than the velocity through the scraped surface chiller (2700 feet total) in order to achieve approximately 16 equal residence times.
17 The slurry exited these trains at wax lit-18 traction temperature (14F). The data from this Compaq 19 risen is presented below.
~2~i3 TABLE IV
2 Incremental 3 Dilution Incremental 4 Dew axing Using Dilution Scraped Surface Dew axing Using 6 Chillers Agitated Chillers 7 1000 rum 1500 rum feed Filter Rate g(m3/m2 day) 4.87 6.23 5.67 10Liquids/Solids 6.55 5.95 5.00 dockside Oil yowled After wish 76.7 80.6 83.0 14 The increase in filter rate is 28% at 1000 rum, and 16% at 1500 rum, using the agitated chiller. Of equal 16 importance is the reduction in liquids/solids which 17 amounts to 9% at 1000 rum, and 24~ at 1500 rum. This 18 result permits more effective wash application, and a 19 consequent increase in dockside oil yield of 3.9% at 1000 rum, and 6.3% at 1500 rum.
21 Example V
22 A Western Canadian Crude 600N oil was fed to 23 a Pilot Plant DILCHILL crystallizer at 137F, 5F
24 above its cloud point. 2.6 volumes of -20F solvent (45% methylethylketone, 55~ methylisobutyl kitten) 26 were added incrementally to the DILCHILL crystallizer 27 stages under conditions of high agitation so that the 28 wax-solvent-oil slurry leaving the crystallizer was at 29 39F. The slurry was then dash pot chilled to tune ~ZZ~ 3 1 filtration temperature of 20~, and filtration per-2 pheromones measured. The same oil feed was then fed at 3 137F to a bank of high speed agitation indirect 4 chillers (run in train). 2.7 volumes of solvent (MOHAWK, 55~MIBK) at 80F was added to the waxy oil 6 feed in the first chiller unit, and the slurry chilled 7 to the wax separation temperature of 20F, at a cool-8 in rate 5-8F/min. The results are presented in Table 9 V.
TABLE V
12 Liquid DUO Yield Filter Rate solid after Wash 13 Pilot Plant 14 DILCHILL &
15 Dash pot 6.29 5.11 78.3 16 Agitated 17 Chilling 18 (lOOORPM) 7.14 5.86 77.2 19 The DILCHILL result is with no effect of SO chilling or agitated chilling. The slurry is sampled at the 21 DILCHILL tower outlet, and dash pot chilled in the lab 22 to the filtration temperature. It contains no debit 23 due to SO chilling. The agitated chilling result shows 24 we can match DILCHILL performance and eliminate SO
chilling debit all the way to the filter temperature.
17 The slurry exited these trains at wax lit-18 traction temperature (14F). The data from this Compaq 19 risen is presented below.
~2~i3 TABLE IV
2 Incremental 3 Dilution Incremental 4 Dew axing Using Dilution Scraped Surface Dew axing Using 6 Chillers Agitated Chillers 7 1000 rum 1500 rum feed Filter Rate g(m3/m2 day) 4.87 6.23 5.67 10Liquids/Solids 6.55 5.95 5.00 dockside Oil yowled After wish 76.7 80.6 83.0 14 The increase in filter rate is 28% at 1000 rum, and 16% at 1500 rum, using the agitated chiller. Of equal 16 importance is the reduction in liquids/solids which 17 amounts to 9% at 1000 rum, and 24~ at 1500 rum. This 18 result permits more effective wash application, and a 19 consequent increase in dockside oil yield of 3.9% at 1000 rum, and 6.3% at 1500 rum.
21 Example V
22 A Western Canadian Crude 600N oil was fed to 23 a Pilot Plant DILCHILL crystallizer at 137F, 5F
24 above its cloud point. 2.6 volumes of -20F solvent (45% methylethylketone, 55~ methylisobutyl kitten) 26 were added incrementally to the DILCHILL crystallizer 27 stages under conditions of high agitation so that the 28 wax-solvent-oil slurry leaving the crystallizer was at 29 39F. The slurry was then dash pot chilled to tune ~ZZ~ 3 1 filtration temperature of 20~, and filtration per-2 pheromones measured. The same oil feed was then fed at 3 137F to a bank of high speed agitation indirect 4 chillers (run in train). 2.7 volumes of solvent (MOHAWK, 55~MIBK) at 80F was added to the waxy oil 6 feed in the first chiller unit, and the slurry chilled 7 to the wax separation temperature of 20F, at a cool-8 in rate 5-8F/min. The results are presented in Table 9 V.
TABLE V
12 Liquid DUO Yield Filter Rate solid after Wash 13 Pilot Plant 14 DILCHILL &
15 Dash pot 6.29 5.11 78.3 16 Agitated 17 Chilling 18 (lOOORPM) 7.14 5.86 77.2 19 The DILCHILL result is with no effect of SO chilling or agitated chilling. The slurry is sampled at the 21 DILCHILL tower outlet, and dash pot chilled in the lab 22 to the filtration temperature. It contains no debit 23 due to SO chilling. The agitated chilling result shows 24 we can match DILCHILL performance and eliminate SO
chilling debit all the way to the filter temperature.
Claims (29)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a process for dewaxing waxy hydro-carbon oils wherein said waxy oil is introduced, at a temperature above its cloud point, into a direct chilling zone divided into a plurality of stages, passing said waxy oil from stage-to-stage of said chilling zone, introducing cold dewaxing solvent into at least a portion of said stages whereby a solvent-waxy oil mixture is formed, maintaining a high degree of agitation in at least a portion of the stages con-taining solvent and waxy oil, thereby effecting sub-stantially instantaneous mixing of said solvent and said waxy oil while cooling said solvent-waxy oil mixture as it progresses through said direct chilling zone to a temperature greater than the temperature at which the wax is separated from the oil, i.e., the wax separation temperature, but less than about 50°F above said separation temperature, whereby a substantial portion of the wax is precipitated from said waxy oil under conditions of said high degree of agitation and forming a wax-oil-solvent slurry, withdrawing said slurry from said direct chilling zone and cooling same to the wax separation temperature in an indirect heat exchanger zone thereby precipitating a further portion of said wax from said slurry, and separating said precipitated wax from the wax oil-solvent slurry in solid-liquid separation means, the improvement com-prising operating the indirect heat exchanger at a high level of agitation.
2. A method of dewaxing hydrocarbon oils comprising diluting the waxy oil with dewaxing sol-vent, introducing the oil-solvent mixture into an indirect heat exchange operated at a high level of agitation thereby chilling the oil-solvent mixture to the wax separation temperature and separating the precipitated wax from the resulting wax-oil solvent slurry in liquid-solid separation means.
3. A method of dewaxing waxy hydrocarbon oils comprising introducing the waxy oil into an in-direct heat exchanger operated at a high level of agitation and simultaneously adding incremental volumes of dewaxing solvent at a plurality of points along the length of the indirect heat exchanger and indirectly chilling the oil-solvent mixture therein to the wax separation temperature and separating the precipitated wax from the resulting wax-oil-solvent slurry in liquid-solid separation means.
4. The process of claims 1, 2 or 3 wherein the high level of agitation, expressed in terms of Impeller Reynolds Number, ranges from about 1,000 to 1,000,000.
5. The process of claims 1, 2 or 3 wherein the dewaxing is selected from the group con-sisting of C3 to C6 aliphatic ketones, low molecular weight hydrocarbons, mixtures of C3 to C6 aliphatic ketones with C6 to C10 aromatic compounds, C1 to C6 halogenated hydrocarbons.
6. The method of claims 1, 2 or 3 wherein the waxy oil is diluted with dewaxing solvent to an oil-solvent ratio in the range of 1:2 to 1:5.
7. An apparatus for producing a high level of agitation comprising an articulated multi-section shaft, each section of which is supported by means of a steady bearing and each section having multiple blades radially attached thereto.
8. The apparatus of claim 7 wherein the multiple blades are propeller blades.
9. In a process for dewaxing waxy hydrocarbon oils wherein said waxy oil is introduced, at a temperature above its cloud point, into a direct chilling zone divided into a plurality of stages, passing said waxy oil from stage-to-stage of said chilling zone, introducing cold dewaxing solvent into at least a portion of said stages whereby a solvent-waxy oil mixture is formed, maintaining a high degree of agitation in at least a portion of the stages containing solvent and waxy oil, thereby effecting substantially instantaneous mixing of said solvent and said waxy oil while cooling said solvent-waxy oil mixture as it progresses through said direct chilling zone to a temperature greater than the temperature at which the wax is separated from the oil, i.e., the wax separation temperature, but less than about 50°F above said separation temperature, whereby a substantial portion of the wax is precipitated from said waxy oil under conditions of said high degree of agitation and forming a wax-oil-solvent slurry, withdrawing said slurry from said direct chilling zone and cooling same to the wax separation temperature in an indirect heat exchanger thereby precipitating a further portion of said wax from said waxy oil, and separating said precipitated wax from the wax-oil-solvent slurry in solid-liquid separation means, the improvement comprising operating the indirect heat exchanger at a high level of agitation expressed in terms of Impeller Reynolds Number in the range of about 10,000 to 1,000,000 wherein the high level of agitation is achieved by means of an articulated multisection shaft having blades radially attached thereto, each section of said shaft being supported by means of a steady bearing.
10. The process of claim 9 wherein the cooling rate in said indirect heat exchanger ranges from 1° to 20° F per minute.
11. The process of claim 9 wherein the dewaxing solvent is selected from the group consisting of C3 to C6 aliphatic ketones, low molecular weight hydrocarbons, mixtures of C3 to C6 aliphatic ketones with C6 to C10 aromatic compounds, C1 to C6 halogenated hydrocarbons.
12. The process of claim 11 wherein the dewaxing solvent is selected from the group consisting of methylethylketone, methylisobutylketone, and mixtures thereof, methylethylketone and toluene, dichloromethane and dichloroethane, and propylene and acetone.
13. The process of claim 9 wherein the waxy hydrocarbon oil is a petroleum oil.
14. The process of claim 9 wherein the waxy hydrocarbon oil is a lube oil.
15. A method of dewaxing hydrocarbon oils comprising diluting the waxy oil with dewaxing solvent, introducing the oil-solvent mixture into an indirect heat exchanger operated at a high level of agitation expressed in terms of Impeller Reynolds Number in the range of about 10,000 to 1,000,000 wherein the high level of agitation is achieved by means of an articulated multi-section shaft having blades radially attached thereto, each section of said shaft being supported by means of a steady bearing, chilling the oil-solvent mixture to the wax separation temperature whereby wax is precipitated to form a wax-oil-solvent slurry, and separating the precipitated wax from the wax-oil-solvent slurry in liquid-solid separation means.
16. The method of claim 15 wherein the chilling rate is from 1 to 20° F per minute.
17. The method of claim 15 wherein the waxy oil is diluted with dewaxing solvent to an oil-solvent ratio in the range of 1:2 to 1:5.
18. The method of claim 17 wherein the dewaxing solvent is selected from the group consisting of C3 to C6 aliphatic ketones, low molecular weight hydrocarbons, mixtures of C3 to C6 aliphatic ketones with C6 to C10 aromatic compounds, C2 to C4 halogenated hydrocarbons.
19. The method of claim 15 wherein the dewaxing solvent is selected from the group consisting of C3 to C6 aliphatic ketones, low molecular weight hydrocarbons, mixtures of C3 to C6 aliphatic ketones with C6 to C10 aromatic compounds, C2 to C4 halogenated hydrocarbons.
20. The process of claim 19 wherein the dewaxing solvent is selected from the group consisting of methylethylketone, methylisobutylketone, and mixtures thereof, methylethylketone and toluene, dichloromethane and dichloroethane, and propylene and acetone.
21. The method of claim 15 wherein the waxy hydrocarbon oil is a petroleum oil.
22. The method of claim 15 wherein the waxy hydrocarbon oil is a lube oil.
23. A method of dewaxing waxy hydrocarbon oils comprising introducing the waxy oil into an indirect heat exchanger operated at a high level of agitation expressed in terms of Impeller Reynolds Number in the range of about 10,000 to 1,000,000 wherein the high level of agitation is achieved by means of an articulated multi-section shaft having blades radially attached thereto, each section of said shaft being supported by means of a steady bearing, and simultaneously adding incremental volumes of dewaxing solvent at a plurality of points along the length of the indirect heat exchanger and indirectly chilling the mixture therein to the wax separation temperature whereby wax is precipitated to form a wax-oil-solvent slurry, and separating the precipitated wax from the wax-oil-solvent slurry in liquid-solid separation means.
24. The method of claim 23 wherein the chilling rate is from 1 to 20° F/min.
25. The method of claim 23 wherein the waxy oil is diluted with dewaxing solvent to a final oil-solvent filtration ratio in the range of 1:2 to 1:5.
26. The method of claim 23 or 25 wherein the dewaxing solvent is selected from the group consisting of C3 to C6 aliphatic ketones, low molecular weight hydrocarbons, mixtures of C3 to C6 aliphatic ketones with C6 to C10 aromatic compounds, C2 to C4 halogenated hydrocarbons.
27. The method of claim 26 wherein the dewaxing solvent is selected from the group consisting of methylethylketone, methylisobutylketone and mixtures thereof, methylethylketone and toluene, dichloromethane and dichloroethane and propylene and acetone.
28. The method of claim 23 wherein the waxy hydrocarbon oil is a petroleum oil.
29. The method of claim 23 wherein the waxy hydrocarbon oil is a lube oil.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000444548A CA1227153A (en) | 1984-01-03 | 1984-01-03 | Dewaxing process using agitated heat exchanger to chill solvent-oil and wax slurry to wax filtration temperature |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000444548A CA1227153A (en) | 1984-01-03 | 1984-01-03 | Dewaxing process using agitated heat exchanger to chill solvent-oil and wax slurry to wax filtration temperature |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1227153A true CA1227153A (en) | 1987-09-22 |
Family
ID=4126854
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000444548A Expired CA1227153A (en) | 1984-01-03 | 1984-01-03 | Dewaxing process using agitated heat exchanger to chill solvent-oil and wax slurry to wax filtration temperature |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1227153A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104512971A (en) * | 2014-12-30 | 2015-04-15 | 河南开祥精细化工有限公司 | Dimethyl ether wastewater wax removing device |
-
1984
- 1984-01-03 CA CA000444548A patent/CA1227153A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104512971A (en) * | 2014-12-30 | 2015-04-15 | 河南开祥精细化工有限公司 | Dimethyl ether wastewater wax removing device |
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