Crank Case Oil Refining

Abstract

Lubricating oils are reclaimed from used crankcase oils obtained from gasoline or diesel internal combustion engines, or mixtures thereof, by flash vaporization of substantially all the water content of the used oil at noncoking temperatures; admixing the dried oil with a hydrocarbon oil having an ASTM boiling range of about 150.degree.-250.degree. F. and a 50 percent point of about 200.degree. F., to precipitate carbonaceous solids; said admixing taking place in the presence of a concentrated aqueous alkali metal hydroxide in a minor amount and at a moderately elevated temperature; centrifugally separating the solid precipitate from the treated liquid oil admixture; subjecting the separated treated liquid oil admixture to a first fractional distillation under conditions which will preclude coking or degradation of the lubricating components thereof; removing undesirable water-soluble components from a water-containing overhead fraction; and subjecting the bottoms fraction to a second fractional distillation to obtain lubricating oil cuts and a usable bottoms product. The water from the flash vaporization may be combined with the water-containing overhead fraction for removal of undesirable water-soluble components.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the refining of hydrocarbon oils, and, more particularly, to the reclaiming of used crankcase oils by the removal of liquid and solid impurities therefrom, and to the recovery of lubricating oil fractions from the reclaimed oil.

2. Description of the Prior Art

Lubricating oil used in the crankcase of an internal combustion engine, gasoline or diesel, eventually must be discarded because of buildup of liquid and solid impurities therein. The discarded oil is referred to as "used crankcase oil." The impurities are, in part, the result of oxidation of the oil itself to form tarry solids and oxygenated organic compounds. Solid carbon particles also collect in the crankcase oil through blowby past the piston rings. Gasoline may also dilute, and contaminate, the oil through blowby. Other impurities are contributed by decomposition of "additives" present in the fresh lubricating oil. Water is usually present in the used crankcase oil from condensation or contamination. It is known that water-soluble organic acidic and phenolic materials are also present in the impurities.

Many processes for reclaiming (refining) used crankcase oils are known. In general, these involve the use of distillation, followed by acid treatment and then clay treatment. These processes produce acid sludges which are difficult to dispose of without creating pollution, and even the used clay is not easily disposed of.

U.S. Pat. No. 3,173,859, issued Mar. 16, 1965, describes an effective process for the refining of used crankcase oil which does not utilize either acid treatment or clay treatment and which substantially decreases pollution problems. However, in the commercial operation of the process of this patent, it has been observed that corrosion of the first fractional distillation tower has occurred and this is believed due to the acidic material in the used oil. In addition, a considerable carbon deposit buildup in both fractionators of the process has been noted. These deposits are thought to be mainly due to solids in the used oil. Also, the efficiency of the overhead distillate fraction condenser following the first fractionator is impaired by a buildup of gummy material. This undesired buildup of gummy material is believed caused by cracked light ends entering the crankcase from the engine combustion chambers.

OBJECTS OF THE INVENTION

One object of the invention is the reclaiming of used crankcase oil without the need for acid and/or clay treatment thereof.

Another object of the invention is the reclaiming of used crankcase oil without creating a water byproduct that cannot be reasonably safely disposed of in natural water bodies without causing pollution thereof.

Still another object of the invention is a process for the reclaiming of used crankcase oil that is more economical by reason of a more valuable byproduct utility.

The main objects of the invention are to provide an improvement of the process of U.S. Pat. No. 3,173,859 but which does not lead to, or cause, fouling of the equipment and corrosion as has been observed in the practice of the process of that patent, and which otherwise possesses all the advantages of the process of that patent, and, which, in addition, serves to produce a valuable carbon byproduct.

SUMMARY OF THE INVENTION

The process of the invention is directed to the reclaiming and purification of feedstocks comprising used crankcase oils, petroleum lube oils containing impurities, and the like, to obtain cuts of lubricating oils substantially odor free and of good color, which process comprises, in its broader aspects: pretreating the feedstock to remove a substantial amount of the water content thereof by flash vaporization at a temperature below the coking point, preferably below about 400.degree. F.; admixing said dried feedstock, heads oil (a product hereinafter defined) and concentrated aqueous alkali metal hydroxide, at a temperature of about 200.degree.-300.degree. F., the alkali metal hydroxide being present in an amount of about 0.2-2.0 weight percent based on dried feedstock (i.e., after the water content has been reduced by flash vaporization), and the volume ratio of heads oil present to dried feedstock present in said admixture being from about 15/85 to about 30/70 with at least enough heads oil present to cause a precipitate of solid carbonaceous material to form; centrifugally separating a liquid oil mixture from a semisolid oil-precipitate mixture; subjecting the liquid oil mixture to a first fractional distillation to obtain a first bottoms product, a lube oil forecut as a side stream, and a first overhead product; condensing said first overhead product to obtain a first substantially dry reflux stream and a first water fraction; maintaining the temperature of said first substantially dry reflux stream above the boiling point of water at the pressure at which said first fractional distillation is conducted; subjecting said first water fraction to gravity separation to obtain a heads oil and a first substantially oil-free water fraction having dissolved impurities therein; subjecting the first bottoms product to a second fractional distillation to obtain a second overhead product, a second bottoms product, and a plurality of cuts of lubricating oil as side streams; condensing said second overhead product to obtain an oil fraction and a second water fraction; subjecting said second water fraction to gravity separation to remove oil components therefrom and to obtain a substantially oil-free second water fraction having dissolved impurities therein; and subjecting the first and second substantially oil-free water fractions to steam stripping to remove dissolved impurities therefrom.

Desirably, the flash vaporization overhead is separated into a water fraction and a gasoline range fraction, and said flash water fraction is passed to said steam stripping to remove dissolved impurities therefrom.

Preferably, a stream of fresh feedstock is heated to flash temperature by being intermingled with a circulating stream of flash vessel bottoms, said combined stream containing about 5-10 volume percent of fresh feedstock.

Preferably, the flash vaporization is carried out at a temperature of about 225.degree.-325.degree. F., under vacuum to afford the desired amount of vaporization.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. I is a schematic flow sheet illustrating the pretreatment of the used crankcase oil in accordance with the process of this invention; and

FIG. II is a schematic flow sheet illustrating operations to be performed, subsequent to pretreatment, in accordance with the process of the invention.

DESCRIPTION OF THE INVENTION

IN CONNECTION WITH THE DRAWINGS

Referring to the drawings, generally, it will be observed that the process utilizes equipment of the type normally found in petroleum fractionation and separation installations, and the drawings are intended to be illustrative of typical apparatus which may be used in the practice of the invention. This equipment includes heaters, fractionation towers, condensers, separators and strippers. In addition, suitable pumps, valves, and piping are provided. Appropriate instrumentation may be easily incorporated within the system, as desired, to regulate the various operations of the process, and to record the conditions of operation at each or any point of the process.

In FIG. I, fresh feedstock as hereinbefore defined, preferably used crankcase oil, is withdrawn from source "F" and passed by way of line 2', pump 3', line 4', and line 5' into flash vaporization vessel 6'. Flash vessel 6' is provided with a liquid level controller (LLC) 7' which controls the opening of valve 8' positioned in fresh feedstock line 4'. Flash vessel 6' is shown here as a simple vertical cylinder but may be any form of conventional flash vessel. For example, vessel 6' may be provided with a demister pad to knock back entrained liquid droplets from the vapor stream. A large volume of liquid is maintained within vessel 6' as this aids in the suppression of cracking of the less stable components of the feedstock.

Liquid is withdrawn from a lower level of vessel 6' by way of line 9' and passed through pump 11' and line 12' through heat exchanger 13'. In this illustrative embodiment, heat exchanger 13' is heated by steam (unnumbered steam inlet and condensate outlets are shown). The oil is heated in exchanger 13' to a noncoking temperature, preferably below about 400.degree. F. The heated oil emerges from exchanger 13' by way of line 14'. A portion of the oil is passed through valved line 16', through mixing changer 17', where fresh feedstock and the hot oil from exchanger 13' are intermingled, and the combined stream passed by way of line 5' into vessel 6'.

The fresh feedstock is normally charged at ambient temperature, i.e., about 60-100.degree. F., in most of the United States. Although the fresh feedstock may be directly heated to a flash temperature, thereby eliminating the circulating stream, it is preferred to use the illustrated operation, as intermingling of the fresh feedstock with a large amount of hot oil reduces the coking tendency of the fresh feedstock components. Although elevated but noncoking temperatures may be used within vessel 6', it is desirable to operate at a temperature below about 400.degree. F. Preferably, the flash temperature is within the range of about 225.degree.-325.degree. F. The proper degree of flash vaporization may be obtained at any given temperature by controlling the pressure in vessel 6'. The preferred operating pressure is a moderate, subatmospheric pressure, i.e., under vacuum conditions.

In the preferred embodiment illustrated, the fresh feedstock forms a small proportion of the stream charged to vessel 6' through line 5' . In general, the combined stream contains about 5-15 volume percent of fresh feedstock, more usually, about 8-11 volume percent.

The vapor produced in vessel 6' is taken overhead by way of line 18' into condenser 19'. Condenser 19' is water cooled having water inlet and outlet lines (unnumbered). Vacuum is maintained on condenser 19' and vessel 6' by means of steam actuated jet 21'. Condenser 19' is provided with a drawoff chamber 22', provided with liquid level controller, LLC 27', which controls the opening of valve 28'. The condensed overhead from vessel 6' is passed from chamber 22' by way of line 23', pump 24' and line 25', and includes liquid level controlled valve 28', into gravity separator 26'.

In separator 26', the condensed overhead separates into a gasoline range fraction, which is withdrawn by way of line 31', and a water fraction removed through line 29'. The water fraction includes a substantial proportion of the water soluble organic impurities present in the feedstock. This water fraction may be disposed of as is, if it presents no pollution disposal problem. Normally, the impurities present therein may pose a disposal problem for this water fraction.

A preferred mode of rendering this water fraction disposable, without being a source of pollution, is to free it of the water soluble impurities along with the water fractions produced in the subsequent oil treatment described in connection with FIG. II. Thus, it is preferred to pass the water fraction from separator 26' by way of valved line 29' and through line 77 into stripper A-3 (see FIG. II). A portion of the flash bottoms oil from vessel 6', after passing through exchanger 13' and line 14', is withdrawn by way of valved line 41'. The amount withdrawn corresponds to the fresh feedstock charged, minus the amount taken overhead in vessel 6'. It should be noted that the stream in line 41' is at a higher temperature than the stream sent to vessel 6'. The stream in line 41' is substantially dehydrated and of decreased gasoline range hydrocarbon content. This stream is hereafter referred to as the dried oil stream, but it should be appreciated that significant amounts of water may be present. It is an advantage of this process that the feedstock need not be completely dried in this first distillation operation, because the remaining water is removed in the subsequent treating operation to be described in connection with FIG. II of the drawings.

The dried oil stream from line 41' is discharged into a mixer vessel 42'. Mixer vessel 42' is shown herein as a cone bottom tank provided with a stirrer. However, the mixer vessel may be any form of intermingling or mixing device which provides for thorough intermingling of the three streams entering mixer vessel 42'.

A light hydrocarbon fraction is also introduced into mixer vessel 42'. A suitable material has an ASTM boiling range of about 150.degree.-250.degree. F., with a 50 percent point of about 200.degree. F. The heads oil (heads product) produced in the process of U.S. Pat. No. 3,173,859 and also produced in the subsequent treating operation of this invention as illustrated in FIG. II, is a suitable hydrocarbon fraction for use in mixer vessel 42'. The heads oil is the preferred fraction for use in the process of this invention. Heads oil is taken from valved heads product line 61 by way of valved line 43' (see FIG. II) and passed into mixer vessel 42'. In a continuous process, the stream in line 43' will be the circulating heads oil used in mixer vessel 42' plus makeup for losses in operating, which makeup will be taken from heads product.

A third stream consisting of concentrated aqueous alkali metal hydroxide, desirably at least about 40 weight percent hydroxide content, is introduced into mixer vessel 42'. It is to be understood that a stream of solid alkali metal hydroxide may be introduced instead of the aqueous solution, although the aqueous solution form is preferred. It should be understood that the solid and aqueous forms of the alkali metal hydroxide may be used interchangeably, and in this specification and claims the term "concentrated solution" includes "solid" hydroxide. Because of its relatively low cost, sodium hydroxide is the preferred hydroxide. However, some used crankcase oils may respond better to potassium hydroxide or one of the other alkali metal hydroxides.

In mixer vessel 42' there is obtained a dispersion of solid and semisolid particles. A very fine dispersion of mostly carbon particles and a very fine dispersion of semisolid materials is traceable to the used crankcase oil. Also present in vessel 42' are solid and/or semisolid materials formed during the heating for flash vaporization or by the action of the alkali metal hydroxide on various components of the dried oil and heads oil. Hereinafter, these solid and semisolid particles are referred to collectively as "precipitate."

Heads oil is charged to mixer vessel 42' at the temperature existent in line 61, normally about 100.degree. F., or at ambient temperature. Thus, the temperature in mixer vessel 42' is controlled by the temperature of the dried oil and will, in general, be between about 200-300.degree. F. The temperature may be somewhat higher or lower, but the given range is the preferred operating range.

Sufficient heads oil must be charged to mixer vessel 42' to permit agglomeration and separation of the precipitate. In general, the volume ratio of heads oil present in mixer vessel 42' to the dried oil present in mixer vessel 42' is from about 15/85 to 30/70 , subject, of course, to the condition that enough heads oil be present to cause the precipitate to separate.

Sufficient concentrated alkali metal hydroxide is added to mixer vessel 42' to give a mixture which is neutral or slightly alkaline in character. In terms of pH, this is a range of about 7-8 . In general, the amount of alkali metal hydroxide used will fall in the range of about 0.2-2.0 weight percent based on dried feedstock, subject to the condition that the mixture in the mixer vessel 42' be neutral, at least.

After the precipitate has agglomerated, at least in part, and separated, the dispersion of oil and precipitate is withdrawn from mixer vessel 42' by way of line 46' and pump 47' and through line 48' to a centrifugal separator 49', for example, a DeLaval MAPX 307 centrifuge. In separator 49', the liquid oil is essentially free of solids and aqueous alkali metal hydroxide solution; preferably the liquid oil effluent discharged from separator 49' by way of line 51' contains about 0.1-0.5 percent bottom settlings and water according to the ASTM procedure.

The underflow product of separator 49' is mainly controlled by the viscosity that can be handled by discharge line. The underflow product is in the nature of slurry of the solids, semisolids and aqueous solution dispersed in liquid oil. In general, separator 49' is controlled to produce a slurry product having 40-60percent bottom settlings and water content. The slurry product is passed by way of line 52' into a small surge tank 53', provided with a liquid level controller 54' which controls valve 58' in line 59'. From tank 54' the slurry product is passed by way of line 56', pump 57' and valved line 59' to a "carbon-oil" storage facility, not shown.

The carbon-oil is an excellent source of a high quality carbon black, or it can be used as a binding oil for road surfaces, and the like. The presence of alkaline material may not be objectionable for many commercial uses of carbon blacks.

The liquid effluent oil product of separator 49' is passed by way of line 51' to surge tank 61'. From this tank 61', the oil is fed to the subsequent treating operation described in connection with FIG. II by way of line 30, pump P-1 and line 37 (see FIG. II).

We shall now describe the further treatment of the liquid effluent oil product. Reference may also be had to U.S. Pat. No. 3,173,859, as it contains a detailed description of the apparatus and methods utilized, in part, in the further treatment of the liquid effluent oil product to complete the purification and refining of the crankcase oil into desired fractions. The further treatment takes place, however, without the troublesome equipment fouling and corrosion which otherwise would occur had not the used crankcase oil feedstock been pretreated as hereinabove described in accordance with this invention.

In FIG. II, heaters H-1 and H-2 are conventional heating apparatus. Each of these heaters may be provided with a burner (not shown) supplied with fuel oil through lines 31 and 32, respectively, and may also be provided with suitable thermostatic controls to regulate the amount of fuel oil throughput for controlling the heat output of each heater. Heater H-1 is also provided with heating coils 33, which heat the high boiling portion of the used crankcase feedstock flowing therethrough. Heater H-2 is provided with a similar heating coil 34 for the purpose of supplying heat to the liquid materials passed therethrough.

Heater H-3 is a steam superheater for converting high pressure steam as from an external source, to low pressure superheated steam. In this embodiment, heater H-3 is adapted to conveniently supply the steam requirements for all units of this system. Steam from an external source is admitted into heater H-3 through line 40, then flows through the parallel paths 42 and 43 and is superheated therein. Suitable outlets 44 and 45 are provided in heater H-3 for taking off the process steam and directing it to appropriate units. In this embodiment, the steam in outlets 44 and 45 is at a pressure of about 15 p.s.i.g. and at a temperature of about 700.degree. F.

Units A-1 and A-2 are fractionation towers. Referring to A-1 which is sometimes hereinafter termed the "heads column," it has been found in one embodiment of the invention that 14 trays, designated respectively by the numeral in parentheses, are suitable for the reclaiming of used crankcase oils. These trays are, for the most part, conventional bubble trays, designated 47. However, at least one tray, located in the vicinity of the feed oil entry port, is not a bubble tray. Thus, it is contemplated that one of these trays 48 be a total drawoff tray and another 49 be a combined bubble tray and trapoff tray. Drawoff tray 48 is provided with a vapor chimney 50 and a trapoff tray 49 is provided with downpipe 51. In the preferred embodiment, it has been found that the feed oil best be introduced between tray 48 and tray 49. Line 53 provides for the flow of liquid from tray 49 around the total drawoff tray 48 to the lower section of the tower. Suitable valves and meters may be incorporated in line 53 to control the amount of liquid taken off the trapoff tray.

Fractionator A-2, which is sometimes hereinafter referred to as the "lube oil column," includes a plurality of conventional bubble trays 106, as well as a plurality of corrugated bubble trays. Preferably, at least three corrugated bubble trays, designated A, B and C, are utilized. These trays comprise the lowermost trays of the fractionator. Each of the corrugated trays is provided with a downpipe 90 to permit downward flow of liquid to the subjacent tray. The vapors formed in the tower flow upwardly through slots formed in the corrugated bubble trays. Between the uppermost corrugated tray and the first conventional bubble tray, a demister pad 93 is utilized to knock back liquid particles entrained in the rising vapors.

Hereinafter, the respective bubble trays of towers A-1 and A-2 will be referred to by the number found in parentheses above each tray. The corrugated bubble trays of tower A-2 will be referred to by the respective letters A, B and C.

Tower A-3 is a water stripper of the usual form and is provided with conventional bubble trays, indicated at 105. Provision is made for the introduction and removal of various fluid streams from the water stripper in a manner more fully described hereinafter.

Condensers T-1 and T-2 are associated with towers A-1 andA-2, respectively. Condenser T-1 is a stage condenser provided with three zones or compartments 56, 57 and 58, as generally indicated in FIG. II. Condensers T-1 and T-2 are structurally the same. A preferred form of these condensers is shown and described in greater schematic detail in FIG. 2 of U.S. Pat. No. 3,173,859. Condensers T-1 and T-2 are each designed to operate under a vacuum of about 100 mm. Hg and serve to reduce the load on the settling vessels or decanters D-1 and D-2 which are described hereinafter.

Condensers T-1 and T-2 are essentially shell and tube exchangers which are suitably baffled to separate the liquid products produced during the various stages of condensation. Extending downwardly from the outermost circular row of tubes of the bundle, and spaced therefrom, and in contact with the inner surface of the bottom of the tube shell, is baffle 56a which, in addition to any vapor directing function it may perform, serves to prevent flow of condensed liquids from zone 56 to subsequent zone 57 and to 58. A separate stream 60 from zone 57 and a separate stream 65 from zone 58 may be withdrawn from T-1, or a single unified stream 65 may be withdrawn. Cooling water is admitted into tubes 114 through line 63 and leaves the condenser by line 64.

The overhead products from tower A-1 are fed via line 52 into condenser T-1 and first pass downwardly into zone 56. The cooling water introduced through line 63 is controlled such that the water fraction in the overhead products from tower T-1 does not condense during the passage of said overhead products through the first and second stages of the three stage condenser, but condense substantially only in the third stage. To achieve this result, the temperature in the first and second stages is maintained above the dew point of water at the operating pressure of the condenser. Under these conditions, a substantially dry lube oil forecut will condense in zone 56 which may be taken off through line 55 and returned to tower A-1 as recycle. A naphtha fraction will condense in zone 57 which may, if desired, be taken off through line 60. A water fraction containing gasoline and smelly heads product will condense in zone 58 and may be removed through line 65. Line 59 provided at the exit end of condenser T-1 permits ready removal of the noncondensables. A light oil fraction is also available through line 62 for recycle as a light hydrocarbon fraction into mixer vessel 42', either alone or as a component of a mixture including the heads oil product from line 61, as hereinabove described. For convenience, the heads product and/or light oil recycled to mixer 42' will be referred to collectively as "heads product."

Condenser T-2 is similar in construction and operation to condenser T-1. Suitable connections are provided for communicating with jet pumps 70a and 70b which supply the desired vacuum for condensers T-1 and T-2. Suitable air bleed lines 79 are provided for each of the condensers.

Associated with condenser T-1 is a decanter D-1, and a similar decanter D-2 is associated with condenser T-2. In the preferred embodiment, the stream entering decanter D-1 will contain oil and water fractions which may be separated by a settling technique. In this way, an oil layer may be removed through line 53 and a water layer removed through line 77.

Decanter D-2 performs a similar function in separating the oil and water components obtained from condenser T-2 with the feed streams to the decanter D-2 entering via line 80. The oil layer is decanted from D-2 by means of line 80, and the water layer removed through line 78. The water fraction, including soluble components dissolved therein obtained from decanters D-1 and D-2, is taken by lines 77 and 78 to water stripper column A-3. Condensers T-1 and T-2 serve to reduce the load on decanters D-1 and D-2 because the decanters effectively remove most of the oil before the water stream enters the respective decanters.

Unit T-3 is a total condenser for condensing the overhead vapor taken off through lines 72 and 73, as well as that entering through lines 71a and 71b, from water stripper A-3. The overhead products stream from stripper A-3 will consist generally of volatile organic oils, phenolic compounds and water vapor, which upon condensation may be taken through line 66 for treatment in decanter D-1.

Suitable pumps P-1 to P-9 are provided for circulating the various streams from unit to unit to maintain steady and continuous operation of the system.

The process of the invention is now described on the basis of a continuous operation. It will be understood that the specific operating conditions such as temperature and pressure, mentioned in the detailed description, are offered as exemplary only and are not intended, nor should be construed, as limiting the scope of the invention.

Used crankcase oil feedstock is passed into line 4' at a rate of about 30 gallons per minute (g.p.m.); at mixing chamber 17' it is intermingled with about 400 g.p.m. of circulating oil from line 16', which is at about 300.degree. F. The combined stream is passed into flash vessel 6' operating at about 380 mm. Hg vacuum with a liquid depth of about 5 feet.

The total overhead is condensed and separated into a gasoline range fraction and a water fraction, which water fraction is passed to water stripper A-3.

Thirty gallons per minute of dried oil is withdrawn by way of line 41' and passed to mixer vessel 42' where it is intermingled with heads product from line 61 in a volume ratio of heads oil to dried oil of 20/80 . A 50 percent aqueous sodium hydroxide solution in an amount of 1 weight percent based on dried oil is passed into mixer vessel 42' from line 44'. The temperature in mixer vessel 42' is maintained at about 250.degree. F.

The discharge from the mixer vessel 42' is passed to a centrifuge. The liquid effluent oil product contains about 0.4 percent bottom settlings and water and becomes the feed to line 30 (see FIG. II). The underflow product of the centrifuge is a semisolid slurry having about 50 percent bottom settlings and water.

The feed oil from tank 61' is passed by pump P-1 into tower A-1. The feed oil enters A-1 between the fifth and sixth plates, that is, between drawoff plate 48 and trapoff plate 49. The feed oil enters at about ambient temperature, in this case about 100.degree. F. In this embodiment a liquid depth of about 3 feet is maintained on tray 48 for the purpose of providing surge capacity to aid pump P-2 pull off liquid to heater H-1. Steam from heater H-3 is introduced into the bottom of tower A-1 through line 45 and controls the temperature of the liquid bottoms accumulating in the base of the tower. The hot liquid accumulating on tray 48 is taken off through line 39 and pumped by pump P-2 through line 35 into heater H-1. The quantity of this liquid passed through coils 33 and back into tower A-1 is such that oil need be heated only moderately before being returned to the tower, for example, about 20.degree.-25.degree. F. By this small temperature rise, we prevent vaporization and coking of the feed oil in the heater coils permitting long continuous use of the heater since there is no need for relatively frequent stoppage to clean coke out of the coils.

The temperature of the hot liquid portion taken from tower A-1 and passed through heater H-1 is raised from about 650.degree. F. to about 675.degree. F. It is returned to A-1 at a point between tray 49 and the seventh tray, both being conventional bubble trays. A portion of the hot feed entering A-1 through line 36 is taken off tray 49 through line 38 and mixed with fresh feed oil entering through line 37. In this way, a preheating of the feed oil entering through line 30 and a vaporization of the water content and lower boiling components is effected by the hot oil supplied the tower A-1 by heater H-1.

Because tray 49 does not have a downpipe, line 53 permits the net downflowing liquid with A-1 to pass from the upper section (above tray 49) to the lower section onto a control bubble tray, the fourth tray, and thus bypass collecting tray 48. The flow of downflowing liquid may be controlled by a suitable valve level controller 53a in line 53. Thus, vaporization of the water and lower boiling components of the feed oil is obtained in a zone of tower A-1, between the sixth and seventh trays, where deposition of any solid material may take place without fouling of the bubble caps. It should be appreciated that the pretreatment has effectively decreased the amount of such deposition which might otherwise occur.

The water and lower boilers vaporized at this point help to carry upwardly a portion of the lube oil fractions present in the feed oil. Tower A-1 is under a mild vacuum but can be operated at pressures up to atmospheric such that the liquid bottoms, even though at a relatively high operating temperature, are at a temperature still far below their boiling point to permit vaporization of the lube oil fraction sufficient to give a reflux stream sufficient to effect substantially complete separation of the undesired lower boiling components.

The overhead vapor removed through line 52 includes water, heads product, gasoline and lube oil forecut fractions. The overhead vapor is taken to the vacuum condenser T-1 through line 52 where the lube oil forecut and the gasoline fraction are condensed under conditions previously described to produce a substantially dry product for use as reflux in the heads column A-1 and to produce the heads product and/or a light oil fraction for recycle and use in mixer vessel 42'.

The water fraction condenses in zone 58 and may be taken off through line 65 connected to decanter D-1. The structure of T-1 is such that only small amounts of oil will be carried through with the water vapor to be condensed in zone 58. This markedly decreases the load on decanter D-1. When the gasoline yield is low, the gasoline fraction from zone 57 may be combined with the water fraction from zone 58, with the total being taken off through line 65.

Decanter D-1 separates any oil components from the water fraction, which oil components comprise the smelly heads product. The heads product may be combined with the lube oil forecut and the gasoline and sent to tower A-1 as reflux. The water fraction is passed to stripper A-3. The water fraction includes water and water soluble impurities.

In order to provide the necessary recycle stream to mixer vessel 42', a portion may be taken from line 61 or 62. The amount not needed in vessel 42' is sent to storage. It should be noted that the heads product carries with it sulfur bodies and other impurities present in the fresh feedstock.

Other side stream cuts may be taken from tower A-1 in order to have material for blending with the bottoms from tower A-2 to produce a heavy residual fuel oil equivalent to Bunker C fuel oil.

The charge to water stripper A-3 comprises water removed by Decanter D-1 and by Decanter D-2, and, preferably, water from the pretreatment operation which is passed by way of valved line 29' and line 77 into A-3. Steam is introduced into the lower end of A-3 through line 74, and is passed countercurrently to the water charge fed at the top of stripper A-3. The bottoms product leaving A-3 through line 76 consists essentially of clean water, while the overhead vapor from A-3 contains the organic materials, such as oils, sulfur compounds and phenolic compounds.

The stream in line 73 is passed to total condenser T-3 where it is condensed. The condensate from T-3 is taken off by way of line 66 and is combined with the water fraction taken from zone 58.

The charge to fractionator A-2 comprises the liquid bottoms taken from fractionator A-1 through line 91 by means of pump P-9. The bottoms liquid is caused to enter the tower just above the modified corrugated tray C. Steam is supplied to the bottom of tower A-2 through line 44. A portion of the bottoms product of tower A-2 is removed from tower A-2, passed through pump P-3 and line 88, and heating coils 34 of heater H-2. The temperature of this stream is about 650.degree. F. as it leaves tower A-2, and is at least 675.degree. F. after leaving heating coil 34. Again, the passage of this stream through heating coil 34 is such as to prevent coking and vaporization. This stream is combined through line 89, with the bottoms product taken from tower A-1 through line 91. In this way, the bottoms product fed to tower A-2 is preheated in a manner similar to that for preheating the feed to tower A-1.

The live steam supplied through line 44 to tower A-2 depresses the effective boiling point of the feed to tower A-2 and makes the use of a high vacuum unnecessary. Tower A-2 is operated under a moderate vacuum of about 100 mm. Hg.

The overhead vapors from tower A-2 are taken overhead through line 87 and consist essentially of water from the stripping steam, spindle oil, and a fraction from cut No. 1 for refluxing. The overhead vapors are taken to stage condenser T-2 and are condensed therein. Reflux for tower A-2 is taken from condenser T-2 through lines 82 and 83. Water and residual oils are removed through line 80 and taken to separator D-2. The oil fraction taken from D-2 is taken through line 81 and may be used in part as reflux to tower A-2 and also as part of the reflux to tower A-1. The water fraction from D-2 is taken by way of line 78 to stripper A-3 and therein treated in the same manner as the water layer from D-1, as heretofore described.

The desired lubricating oil cuts reclaimed are removed as side streams from various plates of tower A-2. The first cut is taken off through lines 97 and 98. A second cut is taken off through lines 96 and 99. A third cut is taken off through lines 95 and 100. A fourth cut is taken off through lines 94 and 101.

The lower separating plates in tower A-2 are not conventional bubble trays, but, preferably, comprise corrugated trays having slots therein, with downpipes 90 provided in each tray to permit contacting of the oil stream and steam so as to minimize plugging of these trays.

It is pointed out that a portion of cut No. 4 is taken off through line 102 and sent back to tower A-2 between the first and second bubble trays. This stream is wash material and advantageously may comprise about 20 percent of the total streams taken off by way of lines 98-101.

The various lube oil cuts may be blended in various proportions to obtain oils having the viscosity desired for different commercial purposes. Also these may be further treated with acid or clays to obtain desired color character, but such optional treatment will be minimal because of the efficiency of the purification process of this invention.

It is seen that the process of this invention provides for the treatment of used crankcase oils to obtain cuts of lubricating oils of good color and odor character; to provide a water fraction that may be used as makeup water or that may be discharged into streams without danger of pollution. Undesirable components of the feed stock, i.e., the smelly heads products which include the phenolic and other water soluble organic compounds removed from the feedstock, are conveniently disposed of by burning. In addition, the pretreatment of the used crankcase oil produces a valuable carbon black product which enhances the economy of the process. It can also be seen that the process of the invention permits the reclamation of used crankcase oil without the use of acid or clay and without production of pollutants now difficult to dispose of.

Although the invention has been described with particular reference to specific embodiments, the same are not to be construed as in any way limiting the invention. Reference is, therefore, to be had solely to the appended claims for the purpose of determining the scope of the invention.

Claims

What is claimed is:

1. In a process for the purification and reclamation of a feedstock comprising crankcase oils, petroleum lube oil stocks containing impurities, and the like, which would tend to crack and coke and containing carbonaceous solids tending to promote coking, to obtain sharp cuts of lubricating oils substantially odor and color free, the improvement comprising; pretreating said feedstock to reduce the water and solids content thereof, said pretreating comprising the steps of: subjecting said feedstock to flash vaporization at a temperature below the coking point of said feedstock to remove a substantial quantity of the water contained in said feedstock; contacting the feedstock having the reduced water content with a concentrated alkali metal hydroxide and a light hydrocarbon oil at a temperature of about 200-300.degree. F., the alkali metal hydroxide being present in an amount to adjust the pH of the resulting mixture to about 7-8, the volume ratio of light hydrocarbon oil to reduced water containing feedstock being from about 15/85 to about 30/70, and with the light hydrocarbon oil also being present in an amount effective to precipitate solid carbonaceous materials from said admixture; and thereafter, separating the liquid oil constituent of said admixture from said precipitate of solid carbonaceous materials.

2. The process of claim 1, wherein the precipitate contains a carbon black precursor, and the liquid oil constituent is purified to obtain said sharp cuts of lubricating oils substantially odor and color free.

3. The process of claim 1, wherein the water containing flash overhead from the flash vaporization is separated into a water fraction and a gasoline range fraction and said water fraction is subjected to steam stripping to remove dissolved impurities therefrom.

4. The process of claim 1, wherein the flash vaporization temperature is between about 225.degree. and 400.degree. F. and the light hydrocarbon oil has an ASTM boiling range of about 150.degree.-250.degree. F., with a 50 percent point of about 200.degree. F.

5. The process of claim 4, wherein at least a portion of the bottoms oil from said flash vaporization is recirculated and admixed with the fresh feedstock to be subjected to flash vaporization.

6. The process of claim 1, wherein the alkali metal hydroxide is present in an amount of 0.2-2.0weight percent based on the weight of the reduced water containing feedstock.

7. In the process for the purification and reclaiming of used crankcase oils, petroleum lube oil containing impurities, and the like, to obtain sharp cuts of lubricating oils substantially odor and color free, comprising; subjecting said feedstock to a first fractional distillation to obtain a first overhead product, a first bottoms product, and a lube oil forecut as a side stream; condensing said first overhead product to obtain a first substantially dry reflux stream and a first water fraction; maintaining the temperature of said first substantially dry reflux stream above the boiling point of water at the pressure at which said first fractional distillation is conducted; subjecting said first water fraction to gravity separation to obtain a heads oil product and a first substantially oil-free water fraction having dissolved impurities therein; subjecting the first bottoms product to a second fractional distillation to obtain a second overhead product, a second bottoms product and a plurality of cuts of lubricating oil as side streams; condensing said second overhead product to obtain an oil fraction and a second water fraction; subjecting said second water fraction to gravity separation to remove oil components therefrom and to obtain a substantially oil-free second water fraction having dissolved impurities therein; and subjecting the first and second substantially oil-free water fractions to steam stripping to remove dissolved impurities therefrom, the improvement which comprises:

subjecting said feed stock to flash vaporization to remove a substantial quantity of the water content thereof at a noncoking temperature; admixing together with said dried feedstock, at least a portion of the heads oil product obtained from said first water fraction and a concentrated aqueous alkali metal hydroxide at a temperature of about 200-300.degree. F., the alkali metal hydroxide being present in an amount to adjust the pH of the resulting admixture to a pH of about 7-8, the volume ratio of heads oil product to dried feedstock being from about 15/85 to about 30/70, and the heads oil product being present, in an amount effective to precipitate solid carbonaceous material from said admixture; and thereafter separating a liquid oil constituent from the precipitate of solid carbonaceous materials.

8. The process of claim 7, wherein, a stream of fresh feedstock is heated to flash temperature by being intermingled with a circulating stream of flash vessel bottoms, said combined streams containing about 5-15 volume percent of fresh feedstock.

9. The process of claim 7, wherein, said flash temperature is about 225-325.degree. F.

10. The process of claim 7, wherein, the water containing flash overhead is separated into a water fraction and a gasoline range fraction and said water fraction is subjected to steam stripping to remove dissolved impurities therefrom.

11. In the process for the purification and reclaiming of feedstocks comprising used crankcase oils, petroleum lube oil stocks containing impurities and the like, to obtain sharp cuts of lubricating oils substantially odor and color free comprising; feeding said feedstock at ambient temperature onto a first tray zone of a first fractional distillation zone; removing a portion of the liquid on said first tray zone from said first fractional distillation zone, increasing the temperature of said portion, and reintroducing said heated portion into said first fractional distillation zone at a point in said first fractional distillation zone above said first tray; introducing high temperature steam into the bottom of said first fractional distillation zone; obtaining a first overhead product and a first bottoms product from said first fractional distillation zone; condensing said first overhead product to obtain a first substantially dry reflux stream for said first fractional distillation zone and a first water fraction; maintaining the temperature of said first substantially dry reflux stream above the boiling point of water at the pressure in said first fractional distillation zone; removing from said first water fraction heads oil product components contained therein to obtain a substantially oil-free first water fraction having dissolved impurities therein; feeding said first bottoms product onto a tray in a second fractional distillation zone; introducing high temperature steam into said fractional distillation zone at a point at least one tray zone above the bottom of said fractional distillation zone; removing hot liquid from said second fractional distillation zone at a point below said one tray zone above said bottom; further heating said hot liquid and combining said further heated hot liquid with said bottoms product feedstock fed to said second fractional distillation zone to effect preheating of said bottoms product feedstock; obtaining a second overhead product, a second bottoms product and at least one cut of a lubricating oil as a side stream from said second fractional distillation zone; condensing said second overhead product to obtain a second substantially dry reflux stream for said second fractional distillation zone and a second water fraction; maintaining the temperature of said second substantially dry reflux stream above the boiling point of water at the pressure of said second fractional distillation zone; removing from the said second water fraction oil components contained therein to obtain a substantially oil-free second water fraction having dissolved impurities therein; subjecting said first and said second substantially oil-free water fractions to steam stripping to remove substantially all of said impurities therefrom to obtain water having a substantially reduced quantity of dissolved impurities, the improvement which comprises:

pretreating said feedstock by flash vaporization of a substantial amount of the water content thereof at a temperature below about 400.degree. F.; admixing with said dried feedstock, at least a portion of the said heads oil product and a concentrated aqueous alkali metal hydroxide at a temperature of about 200-300.degree. F., the alkali metal hydroxide being present in an amount of about 0.2-2.0 weight percent based on dried feedstock, sufficient to give an admixture with a pH of 7-8, and the volume ratio of heads oil product to dried feedstock being from about 15/85 to 30/70 , with heads oil product being present in an amount sufficient to precipitate solid carbonaceous materials from said admixture; and centrifugally separating a liquid oil constituent from the precipitate of solid carbonaceous materials.

12. The process of claim 11, wherein, a stream of fresh feedstock is heated to flash temperature by being intermingled with a circulating stream of flash vessel bottoms, said combined streams containing about 5-15 volume percent of fresh feedstock.

13. The process of claim 12, wherein, said flash temperature is about 225.degree.-325.degree. F.

14. The process of claim 13, wherein the water containing flash vessel overhead is separated into a water fraction and a gasoline range fraction and said water fraction is subjected to said steam stripping to remove dissolved impurities therefrom.