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Process and apparatus for re-refining used petroleum products
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.degree.-240.degree. F, water comprises
substantially all of the overhead product and this may be vented to the
atmosphere. The unvaporized liquid product is mechanically filtered
through a vibratory filter and then successive cannister filters to
produce a product which may be used as a fuel oil or further refined into
various fuel and/or lubricant products in successive flash distillation
stages. In the preferred embodiment, three such stages are operated,
respectively, at 300.degree.-400.degree. F and 24-28 inches mercury,
600.degree.-650.degree. F, and 7 torr, and 630.degree.-680.degree. F and
Primary Examiner: Gantz; Delbert E.
Assistant Examiner: Nelson; Juanita M.
Attorney, Agent or Firm:Miller, Frailey & Prestia
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.degree.-240.degree. 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 for re-refining a used hydrocarbon oil, as recited in claim 1, 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 wherein said filtered liquid is subsequently flash vaporized at 24-28 inches Hg and 300.degree.-400.degree. 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.degree.-680.degree. F and successively flash evaporated at 7 torr and 11/2 - 3 torr, the vaporized overhead streams from
said 7 and 11/2 - 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.degree.-240.degree.F, atmospheric pressure flash evaporation occurs.
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 variety of processes and apparatus have been suggested for re-refining crankcase oil and other types of used petroleum products. One disadvantage of many of these processes is their reliance on complex fractionation columns as a
means 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 additives, tend to collect and to
interfere in the complex plumbing associated with a multi-stage distillation column.
Thus, as an improvement on the crankcase oil refining process disclosed in U.S. Pat. No. 3,173,859 to Chambers, one notes the flash vaporization pre-treatment for that process disclosed in U.S. Pat. No. 3,625,881 to Chambers.
Similarly, in the re-refining process of U.S. Pat. No. 3,791,965 to FitzSimons et al. (of common assignment herewith) a complex evaporator used in the initial treatment of the used petroleum products was found to interfere with process
efficiency, due to fouling and coking, as solid and semi-solid impurities in used oil built up on the various mechanical components in the device referred to in that patent as the "stripper."
Having in mind these problems, it is the general objective of the present invention to provide an improved process and apparatus for refining used petroleum products.
A more specific object of this invention is to provide a sequential flash evaporation process and apparatus which is efficient, dependable and flexible in its mode of operation.
Still another object of this invention is to provide a relatively simple apparatus and process for reclaiming lower grade, though saleable, petroleum products, from used petroleum products, such as crankcase oil, with a minimum of apparatus and
These and other objects, which will be apparent in the course of the subsequent description, are met, briefly, by a process and apparatus wherein a used oil feed stream is flash vaporized at atmospheric pressure and 210.degree. - 240.degree. F;
fine solids are then mechanically separated from the unvaporized bottom stream to produce a saleable fuel oil. In the preferred embodiments of this invention, this residual fuel oil is further refined in a second flash evaporator operated at
300.degree.-400.degree. F, 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 liquid from the second flash evaporator may be
passed on successively to third and fourth flash evaporators operated, respectively, at 600.degree.-650.degree. F and 7 torr, and at 630.degree. - 680.degree. F and 11/2 - 3 torr.
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 filtration 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 heating and recirculating unvaporized bottom liquid from a specific evaporator to the vapor space above a liquid level in the same
evaporator. At the same time, feed to the respective flash evaporator is added to the recycled liquid as it is introduced, almost simultaneously with this mixing, into the evaporator (in a manner similar to that disclosed in U.S. Pat. No, 2,799,628).
This invention may be better understood by reference to the claims appended hereto and the following detailed description, taken in conjunction with the accompanying FIGURE, which is a schematic view of the process and apparatus of the preferred
embodiment of the present invention.
Referring more specifically to the FIGURE, there is shown first flash evaporator 10, including atmospheric vent 12. A feed stream of used petroleum products (such as crank-case 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 liquid level controller 18 operating valve 20 in feed stream line 14. A temperature
on the order of 210.degree.-240.degree.F is maintained in flash evaporator 10 by heating the recycled liquid from the bottom of flash evaporator 10 in heat exchanger 22, wherein the heating medium is preferably steam at a pressure of 100-150 lbs./sq.in.
Product draw-off line 24 passes a portion of the unvaporized liquid in flash evaporator 10 to a mechanical filtration system comprising, in the preferred embodiment of this invention, a vibratory filter 26 having a horizontally vibrating screen
filter element 28, with screen openings less than 100 microns and preferably on the order of 40 to 45 microns, and a feed dispersing member 30 located above filter element 28. Waste sludge containing heavy particle contaminants and insolubles is removed
at the periphery of vibrating screen element 28 while the filtrate passes through to the bottom of filter 26 and to a surge tank, from which a product saleable as a residual fuel may be withdrawn. Alternatively, this liquid may be forwarded for future
processing to a sequence of pairs 32, 34 and 36 of cartridge filters of successively smaller pore size in the filter elements. Preferably, these cannister filters house filter elements ranging progressively from 25 microns to 15 microns to 3 microns in
maximum pore size.
The initial removal of water at relatively low temperature and the subsequent filtration comprises a practical process which may be operated for extended periods of time without equipment fouling and relatively low energy consumption 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 percent water; this more typically lies in the range of 1 - 15 percent. In any event, this system is designed for a
relatively low proportion of that feed stream to be combined with the recycled liquid entering flash evaporator 10 in order to maintain a relatively constant temperature there and thereby to operate flash evaporator 10 with a high degree of efficiency.
The proportion of this mixture will therefore change depending 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 equilibrium 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.
Vapors leaving flash evaporator 10 through atmospheric vent 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
situations, 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 additional stages further upgrades the filtered atmospheric
pressure 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 is 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 overhead removal line 42 through which collected vapors from evaporator 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 evaporator 40. Liquid level controller 48 associated with valve 50 on filtrate line 38 holds
the liquid level in evaporator 40 at a predetermined point, maintaining 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 heated 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
temperature level in the second flash evaporator 40 on the order of 300.degree.-400.degree.F, and preferably about 350.degree. F. To prevent excess acidity (and possible corrosion) anhydrous ammonia may be injected into the liquid phase in evaporator
Condensate from overhead condenser 44 is collected in an accumulator 58 and then pumped to decanter 56 through line 39. The liquid level is determined by level control 41 controlling a valve 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 stream may be sold or used inplant as a fuel. The volatility of this product stream is
generally comparable to that of kerosene. The bottom liquid drawoff not recycled to evaporator 40 may also be sold as a fuel oil product, but preferably it is further upgraded by passage to subsequent flash evaporation 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, (wherein a hot
heat exchange liquid, such as "Dowtherm" liquid, a commercial product of the Dow Chemical Co., is the heating media), which provides the heat input 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 of 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 cold water as the cooling fluid, to which a steam aspirator 72 is connected to maintain the pressure 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.degree.-650.degree.F (preferably 625.degree.F) to maintain a temperature in evaporator 60 on that order.
Condensate product 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 of steam stripper 74 is a lube oil within the range
of SAE 10. The bottom liquid draw-off of evaporator 60 may also be used or sold as fuel oil (with volatility characteristics comparable to to that of Number 5 or 6 fuel 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 accumulator 81 to steam stripper 86. The product of stripper 86 is a lubricant within the viscosity range of SAE 20 or 30 oil.
Steam aspirator 82 in connection with the vapor side of condenser 84 maintains the pressure in evaporator 80 at about 11/2 - 3 torr. Liquid level controller 83 in accumulator 81 controls valve 85 to draw-off condensate from accumulator 81 to steam
stripper 86. Unvaporized liquid from evaporator 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 required. 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 exchanger 78. In heat exchanger 78, the liquid is heated to 630.degree.-680.degree.F to maintain a temperature in that range, and preferably
about 650.degree.F, 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
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 again be noted, a useful saleable product. A feasible used oil refining process and apparatus may therefore encompass the first flash evaporation 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 used oil supply. Similarly, 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.