U.S. patent number 3,625,881 [Application Number 05/068,389] was granted by the patent office on 1971-12-07 for crank case oil refining.
This patent grant is currently assigned to Berks Associates, Inc.. Invention is credited to John M. Chambers, Herbert A. Hadley.
United States Patent |
3,625,881 |
Chambers , et al. |
December 7, 1971 |
**Please see images for:
( Certificate of Correction ) ** |
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.
Inventors: |
Chambers; John M. (Westfield,
NJ), Hadley; Herbert A. (Birdsboro, PA) |
Assignee: |
Berks Associates, Inc.
(Pottstown, PA)
|
Family
ID: |
22082252 |
Appl.
No.: |
05/068,389 |
Filed: |
August 31, 1970 |
Current U.S.
Class: |
208/179; 208/184;
208/187 |
Current CPC
Class: |
C10M
175/0016 (20130101) |
Current International
Class: |
C10M
175/00 (20060101); C10g 027/100 () |
Field of
Search: |
;208/179,187,183,184,301,226 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Gantz; Delbert E.
Assistant Examiner: Nelson; J. M.
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.
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.
* * * * *