CA1067439A - Process and apparatus for re-refining used petroleum products - Google Patents

Abstract

IMPROVED PROCESS AND APPARATUS
FOR RE-REFINING USED PETROLEUM PRODUCTS

Abstract of the Disclosure Used petroleum products, such as crankcase oils, are reclaimed by an initial treatment step consisting of flash vaporization with continuous recirculation of a substantial portion of the unvaporized liquid. At atmospheric pressure and 210 - 240° F, water comprises substantially all of the overhead product and this may be vented to the atmosphere. The unva-porized liquid product is mechanically filtered through a vibratory filter and then successive cannister filters to pro-duce a product which may be used as a fuel oil or further re-fined into various fuel and/or lubricant products in successive flash distillation stages. In the preferred embodiment, three such stages are operated, respectively, at 300 - 400° F and 24 - 28 inches mercury, 600 - 650 ° F, and 7 torr, and 630 - 680° F and 1-1/2 - 3 torr.

Description

~ ` 1g;)~7439 . ' 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.

,~ - 3 -~ .

67~39 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.

- 3a -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.

-~; 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).

:
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 .

~o- 7~
679i39 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 ! : ~
~ 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.
: .
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.

-.
, .

~)6743 : ` .
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.
- :
- 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 ~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, ~6743 ;

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 , 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 "~
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.

Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In 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 - 240°F, 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.

2. A process of re-refining a used hydrocarbon oil, as recited in claim l, wherein at least a portion of unvaporized liquid removed from the bottom of said evaporator is passed at relatively low pressure through a vibratory filter having a horizontally disposed screen filter element having openings on the order of 40-45 microns.

3. A process of re-refining a used hydrocarbon oil, as recited in claim 2, wherein the filtrate from said vibratory filter is further filtered to remove remaining particles having a maximum dimension larger than 3 microns.

4. A process of re-refining a used hydrocarbon oil, as recited in claim 3, wherein said filtered liquid is subsequently flash vaporized at 24 - 28 inches Hg and 300 - 400°F.

5. The process, as recited in claim 4, wherein the overhead vapor stream from said subsequent flash vaporization is condensed and water therein is separated by gravity separation.

6. The process, as recited in claim 5, wherein unvaporized liquid removed from said subsequent evaporator is heated to 600 -680° F and successively flash evaporated at 7 torr and 1 1/2 -3 torr, the vaporized overhead streams from said 7 and 1 1/2 - 3 torr evaporation steps being condensed and steam stripped.

7. The process, as recited in claim 1, wherein the fresh feed stream of said used oil is mixed with a substantially larger quantity of recycled, heated, unvaporized liquid removed from the bottom of said flash evaporator, said mixing taking place as said fresh feed stream is introduced into the vessel where said 210 - 240° F, atmospheric pressure flash evaporation occurs.
,

8. 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 210-240°F, means for maintaining a preselected liquid level in said evaporator with a vapor space above said liquid level, means for introducing said combined re-cycled and used oil stream into said vapor space, and means for filtering a portion of unvaporized liquid removed from said evaporator, said filtering means comprising a mechani-cal filter.

9. An improved apparatus as recited in Claim 8, wherein said mechanical filter consists of a horizontally vibrating screen filter with screen openings of 40-45 microns.

10. An improved apparatus, as recited in claim 9, in combination with at least one additional flash evaporator, each such flash evaporator including means for introducing into the vapor space thereof a portion of the unvaporized liquid from the preceding evaporator, means for removing unvaporized liquid from the bottom thereof, means for col-lecting and condensing overhead vapors therefrom, means for maintaining the pressure therein at or below that of the preceding evaporator and means for maintaining the tempera-ture therein at or above that of the preceding evaporator.