Note: Descriptions are shown in the official language in which they were submitted.
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This invention pertains to an improved process and
apparatus for re-refining used oils through a sequential flash
evaporation process. More specifically, it relates to improved
process and apparatus wherein saleable products are obtainable
; at any one of various stages including a very early stage,
whereby useful product may be reclaimed from used oils with a
minimum of apparatus and treatment.
Heretofore, a varietv of processes and apparatus have
been suggested for re-refining crankcase oil and other types of
used petroleum produc~s. One disadvantage of many of these pro-
cesses is their reliance on complex fractionation columns as ameans of separating various components in the used petroleum
products. Impurities in these products, typically including
solid carbon particles, tarry solids and oxidation products of
both petroleum components and addltives, tend to collect and to
interfere in the complex plumbing associated with a multi-stage
i distillation column.
:
Thus, as an improvement on the crankcase oil refining
process disclosed in U. S. Patent No. 3,173,859 to Cha~bers,
one notes the flash vaporization pre-treatment for that process
disclosed in U. S~ Patent No. 3,625,881 to Chambers.
Similarly, in the re-refining process of U. S. Patent
No. 3,791,965 to FitzSimons et al (of common assignment here-
with) a complex evaporator used in the initial treatment of the
used petroleum products was found to interfere with process effi~
ciency, due to fouling and coking, as solid and semi-solid im-
purities in used oil built up on the various mechanical compo-
nents in the device referred ~o in that patent as the "stripper".
~067~3~
Having in mind these problems, it is the general
objective of the present invention to provide an im-
proved process and apparatus for refining used petroleum
products
According to one aspect of the invention there is
provided on a process of refining a used hydrocarbon oil
wherein a used oil is distilled and filtered for re-use,
the improvement comprising flash vaporizing said used
oil in an evaporator in which the internal conditions
are maintained at atmospheric pressure and 210 - 240F,
and continuously separating a vaporized portion from an
unvaporized liquid portion and continuously removing
said unvaporized liquid portion from the bottom of said
evaporator, and then mechanically filtering at least
a portion of the unvaporized liquid removed from said
evaporator.
According to another aspect of the invention there
~ .
is provided an improved-apparatus for refining used oil
characterized by a flash evaporation vessel with means
for removing overhead vapors therefrom at atmospheric
.
pressure, means for heating and recycling a substantial
portion of liquid removed therefrom, means for combining
said recycled liquid with a substantially smaller portion
of~used oil to be refined, means for maintaining the
temperature in said evaporator at 210-240F, means for
maintaining a preselected liquid level in said evaporator
with a vapor space above said liquid level, means for
introducing said combined recycled and used oil stream
into said vapor space, and means for filtering a portion
of unvaporized liquid removed from said evaporator, saLd
filtering means comprising a mechanical filter.
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An advantage of this invention, at least in the
preferred forms, is that it can provide a sequential
flash evaporation process and apparatus which is
efficient, dependable and flexible in its mode of
operation.
Another advantage of this invention, at least in
preferred forms, is that it can provide a relatively
simple apparatus and process for reclaiming lower grade,
though saleable, petroleum products, from used petro-
~ 10 leum products, such as crackcase oil, with a minimum of
`~ apparatus and treatment.
; In preferred forms, the invention provides a process
and apparatus wherein a used oil feed stream is flash
vaporized at atmospheric pressure and 210 - 240F; fine
solids are then mechanically separated from the unvap-
orized bottom stream to produce a saleable fuel oil.
This residual fuel oil is preferably further refined in
a second flash evaporator operated at 300 - 400F, and
24 - 28 inches mercury. The overhead from this second
~ flash evaporator is condensed and decanted to remove
residual water, the product being a kerosene-like fuel.
The bottom liquld from the second flash evaporator may
be passed on successively to third and fourth flash
evaporators operated, respectively, at 600 - 650F and
7 torr, and at 630 - 680F and l-1/2 - 3 torr.
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1067439
The mechanical filtration associated with the liquid
bottom product from the first flash evaporation stage consists
primarily of a vibratory filter with a horizontal screen having
openings on the order of 40-45 microns from which waste material
is removed at the edges. The filter product proceeds through
the screen to successive cartridge filters, having a final filt-
ration range (i.e., filter element capable of removing) of 3
microns in size.
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~; Preferably also, one or more, and most preferably all,
of the flash evaporators are operated by continuously haating~and recirculating unvaporized bottom liquid from a specific eva-
porator to the vapor space above a liquid level in the same eva-
porator. At the same time, feed to the respective flash evapo-
' rator is added to the recycled liquid as it is introduced, al-
most simultaneously with this mixing, into the evaporator (in a
:,
~ manner similar to that disclosed in U.S. Patent No. 2,799,628).
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This invention may be better understood by reference to
the claims appended hereto and the following detailed descrip-
tion, taken in conjunction with the accompanying Figure, which is
20 a schematic view of the process and apparatus of the preferred
embodiment of the present invention.
Referring more specifically to the figure, there i5
shown first flash evaporator 10, including atmospheric vent 12.
A feed stream of used petroleum products (such as crankcase
oil) introduced through feed line 14, is combined with recycled
liquid from evaporator 10, near the terminus of recycle line 16.
A predetermined liquid level in flash evaporator 10 is maintained
by li~uid level controller 18 operating valve 20 in feed stream
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line 14. A t~pera~ure on the order of 210-240~F is
maintained in flash evaporator lO by heating t~e recycled
liquid from the bottom of ~lash evaporator 10 in heat
exchcmger 22, wherein the he~ting medinm is preferably
5. steam aL a pressure of lO0 - 150 lbs./sq.in.
Product draw-o~f line 2~ passes a portion of
: the unvaporized liquid in flash evaporator lO to a mechanical
~iltr~tion system comprising, in the pre~erred embodiment
of this invention, a vi~rator~ filter ~6 havlng a horizon-
lO. tally vibrating screen filter element 28, with-screen .
ope~ings less than lO0 microns and preferably on the or.der
of 40 to 45 microns, and a feed dispersing ~ember 30
located above filter element 28. Waste slud~e containing
heavy particle contamin~nts and insolubles is remo~ed at
15. the periph~ry of vibrating screen element 28 while the
~iltrate passes through to the bottom of filter 26 and
to a surge tank, ~rom ~ich a product saleable as a resîdual
fuel may be withdra~m. Alternatlvely, this liquid m~y be
j fo~7arded;for ~uture processing to a sequence of pairs
20. 32, 34 and 36 of cartridge fi~ters of success.ively smaller pore
size in the fllter elements. Prefer~bly, these cannister
~- . filters house filter elem~nts ranging progressively from .
25 mi~rons ~o 15 mLcron~ to 3 mic~ons in maximum ~ole size.
~067439
The initial removal of water at relatively low
temperature and the subsequent filtration comprises a prac-
;~ tical process which may be operated for extended periods of
time without equipment fouling and relatively low energy con-
sumption to produce a useful product. Similarly, a still
more refined ~and valuable) product is produced in the final
filter train. This product may be sold, for example, as a
cutting oil or as a quench oil.
With respect to~the operation of this apparatus, it
should be noted that the used oil feed stream may comprise
from 0 to 40~ water; This more typically lies in the range of
1-15%. In any event, this system is designed for a relati-
vely low proportion of that feed stream to be combined with
the recycled liquid entering flash evaporator 10 in order to
maintain a relatlvely constant temperature there and thereby
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~ to operate flash evaporator 10 with a high degree of efficien-
:` : :
~ cy. The proportion of this mixture will therefore change de-
,l ~pending on~water content of the feed stream in order that the
heat contributed by heat exchanger 22 will balance the heat
loss through evaporation of water in flash evaporator 10.
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Another important factor in maintaining the equili-
brium in flash evaporator 10 is the mixing of the feed stream
and recycle liquid just as these materials are introduced into
the flash evaporator in the vapor space above the liquid level
therein.
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Vapors leaving flash evaporator 10 through atmosphericvent 12 are predominantly water, and may ordinarily be released
to the atmosphere. This is a further advantage of the simple
reclamation technique described to this point. However, in some
`~ situahi~ns, it may be necessary or desirable to collect the
vapors exiting vent 12 and perhaps to remove or to recover
residual non-aqueous contaminants in the vapors.
While an apparatus and process as described, consisting
of a single flash evaporator, associated heat exchanger and a
mechanical filter or filter train, provides a practical and
economical approach to the re-refining of used petroleum products,
such as crankcase oil, this apparatus and process is combined,
in the preferred embodiments of the present invention, with one
~ or more subsequent flash evaporation stages. Each of these ad-
j ditional stages further upgrades the fil~ered atmospheric pres-
sure flash evaporated filtrate stream described above.
Thus, the filtrate stream from cartridge filters 32,
~34 and 36 passes through filtrate line 38 to a second flash
evaporator 40. Evaporator 40 lS similar-to flash evaporator 10,
both in design and operation, but differs in design operating
conditions and in the absence of an atmospheric vent.
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- More specifically, flash evaporator 40 includes over-
head removal line 42 through which collected vapors from evapo-
rator 40 are passed to condenser 44. In condenser 44, a cooling
medium, such as cold water, cools the vapors and causes them to
condense. Vacuum pump 46, in communication with the vapor space
in condenser 44, maintains a pressure of about 24-28 (preferably
about 26) inches mercury in evaporat~r 40. Liquid level controller
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~067439
48 associated with valve 50 on filtrate line 38 holds the
liquid level in evaporator 40 at a predetermined point, main-
~` taining a vapor space of some vertical height in evaporator 40.
Into this vapor space is introduced the combined filtrate stream
from line 38 and, in a much larger proportion, heated recycled
liquid from the bottom of flash evaporator 40. Recycle line
52 carries hea*ed recycle liquid after its passage through a
~ heat exchanger 54 wherein steam at 130-150 psi (preferably 150
: psi) provides the necessary heat input to maintain a tempera-
. 10 ture level in the second fla=h evaporator 40 on the order of
300-400F, and preferably about 350F. To preven~ excess aci-
dity (and possible corrosion) anhydrous ammonia may be injected
into the liquid phase in evaporator 40.
Condensate from overhead condenser 44 is collected in
an accumulator 58 and th=n pumped to decanter 56 through line
39. The liquid level is determined by level control~41 control- ;
~ I
. : ling = v=lve 43 in line 39. A small amount of residual water
: is removed from decanter 56. The pH of this residual water is
;: : .
: . controlled at or near 7.5 by the addition of caustic soda to
the vapors in line 42. The remaining product stre=m may be
sold or used inplant as a fuel. The volatility of this product
stream is generally comparable to that of kerosene~ The bot-
tom liquid draw-off not recycled to evaporator 40 may also be
sold as a fuel oil product, but preferably it:is further up-
~ graded by passage to subsequent flash euaporation stages.
:- More specifically, bottom liquid draw-off product
passes through line 58 to a third flash evaporator 60 where it
is introduced into the vapor space, along with recycled and
heated liquid from recycle line 62 and heat exchanger 64,
; 30 (wherein a hot heat exchange liquid, such as "Dowtherm" liquid,
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a commercial product of the- Dow Chemical Co., is the heating
media), which provides the heat i-nput to evaporator 60.
Again, as in the previous evaporator stages, recycle liquid
in line 62 is combined with stage feed in line 58 just prior
to release in the vapor space o~ evaporator 60. The liquid
is maintained at a predetermined level in evaporator 60 by
liquid level controller 66 associated with a stage output
` valve 68. Overhead vapors are collected and condensed in a
cooler 70, usually with coId water as the cooling fluid, to
which a steam aspirator 72 is connected to maintain the pres-
sure in evaporator 60 at 6-8 torr, preferably about 7 torr.
The recycled liquid draw-off is heated in heat exchanger 64
to a temperature in the range of 600-650F ~preferably 625F)
to maintain a temperature in evaporator S0 on that order.
Condensate produc~ from cooler 70 after passing
through accumulator 73 is steam stripped in stripper 74, the
overhead vapors of which are condensed in cold water cooler
75. The bottom product o~ steam stripper 74 is a lube oil
within the range of SAE 10. The bottom liquid draw-off of
evaporator 60 may also be u~ed or sold as fuel oil ~with ~ !
volatility characteristics comparable to that of Number 5 or
6~f~uel oil). However, it is preferably fed through line 76
to fourth flash evaporator 80. A cold water condenser 84
receives and condenses the overhead product from evaporator
80 and passes the condensate through accumula~or 81 to steam
stripper 86. Tha product of stripper 86 is a lubricant with-
in the viscosity range of SAE 20 or 30 oil. Steam aspirator
82 in connection with the vapor side of condenser 84 main-
tains the pressure in evaporator 80 at about 1-1/2-3 torr.
~OG7439
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Liquid level controller 83 in accumulator 81 controls valve
85 to draw-off condensate from accumulator 81 to steam strip-
per 86. Unvaporized liquid from evaporat:or 80 is drawn off
and may be sold as a high boiling point residual oil product
or for other purposes where a heavy petroleum fraction is re-
` quired. A substantial proportion of the liquid drawn off
from evaporator 80 is recycled through recycle line 87 to
evaporator 80, after passing through Dowtherm-heated heat ex-
changer 78. In heat exchanger 78, the liquid is heated to
630-680F to maintain a temperature in that range, and prefer-
ably about 650F, in evaporator 80.
While this invention has been described with respect
to its essential components, it should be understood that
some variation and modification of these components may be
made by those skilled in the art without departing from the
scope of the invention.
As indicated throughout the description, many of the
; intermediate streams in the preferred embodiment of this
invention may be withdrawn in whole or in part as product
streams~ In particular, the filtered product stream from the
first flash evaporation stage is, it should ayain be ~oted, a
useful saleable product. A feasible used oil refining process
and apparatus may therefore encompass the first flash evapo-
ration stage and subsequent filter alone.
It should be further noted that some preliminary
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filtration of the feed stream introduced in flash evaporator
10 may be desirable, and in some cases necessary, depending
on the degree of contamination in the usd oil supply. Simi-
larly, any one or more of the products of this invention may
be further refined and treated, such as by clay percolation
to pick up color bodies.
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