US2771408A

US2771408A - Method for washing adsorbents

Info

Publication number: US2771408A
Application number: US321371A
Authority: US
Inventors: Joe E Penick
Original assignee: Socony Mobil Oil Co Inc
Current assignee: ExxonMobil Oil Corp
Priority date: 1952-11-19
Filing date: 1952-11-19
Publication date: 1956-11-20
Anticipated expiration: 1973-11-20

Description

Nov. 20, 1956 J. E. PENICK 2,7

METHOD FOR WASHING ADSORBENTS Filed Nov. 19, 1952 3 Sheets-Sheet 1 19 21 INVEN TOR.

Jae E Pen ic/fl Nov. 20, 1956 J. E. PENICK METHOD FOR WASHING ADSORBENTS Filed Nov. 19. 1952 3 Sheets-Sheet 2 WASHER Emil Nov. 20, 1956 J. E. PENICK METHOD FOR WASHING ADSORBENTS Filed Nov. 19; 1952 3 Sheets-Sheet 3 INVENTOR .LT Penicfif iGf/VT United States Patent METHOD FOR WASHING ADSORBENTS Joe E. Penick, Augusta, Kans., nssignor to Socony Mobil Oil Company, Inc., a corporation of New York Application November 19, E52, Serial No. 321,371

7 Claims. (Cl. 196147) This invention is concerned with a method for treating liquid hydrocarbons and mineral oils, particularly lubricating oils, and lower boiling petroleum fractions with solid adsorbents for the purpose of removing small amounts of impurities. It is especially concerned with the washing of spent adsorbents which exist at a temperature above the boiling point of the wash solvent after use in such processes.

Typical of the processes to which this invention applies is the continuous percolation of liquid hydrocarbon oils of low asphalt content upwardly through a downwardly gravitating columnar mass of adsorbent to effect removal of small amounts of impurities and color bodies from the oil.

The adsorbent used in this invention should be made up of palpable particles of size within the range about 4-l()0 mesh and preferably 1060 mesh and still more preferably l530 mesh by Tyler Standard Screen Analysis. The particles may take the form of pellets, capsules, pills, spheres, or the like, or granules of irregular shape such as are obtained from grinding and screening. The terms adsorbent in palpable particulate form and palpable particle form adsorbent as employed herein in describing and claiming this invention are intended to generically cover particles of any or all of these shapes having substantial size as distinguished from finely divided particles.

In processes of the aforementioned type, the used adsorbent, after removal from the treating zone, will have tarry or coke-like carbonaceous contaminants and color bodies deposited thereon. This used adsorbent will also carry with it from the treating zone a substantial amount of cycle oil. The term cycle oil is used herein in describing and claiming this invention broadly to refer to the sum total of the oil discharged from the treater in the adsorbent pores, in the voids between the granules in the discharge stream and the supernatant oil or any one or more of them. It is necessary that all of these materials be removed so that the adsorbent may here-used in treating further oil. This is normally most easily accomplished by burning the objectionable components off the adsorbent with an oxygen-containing gas. However, it is not desirable to burn the cycle oil in this manner since this would result in increased operating costs for the process and, obviously, lower yields of purified products. For these reasons it is usually necessary to wash the cycle oil from the adsorbent with a suitable wash solvent before burning and then separate solvent and oil and return the oil to the treating zone. This is generally accomplished by passing a suitable wash solvent, such as naphtha, upwardly through a columnar mass of the adsorbent to dissolve the cycle oil from the adsorbent. A column or body of liquid wash solvent is normally provided above the columnar mass of adsorbent to provide for the disengaging of adsorbent from solvent, so that there will not be excessive carry-over of adsorbent with outgoing solvent. A difiiculty occurs here where, as is frequently the case, the operating temperature of the treating zone is above Patented Nov. 26, 1-956 2 the boiling point of the solvent being used in the washing zone. If the hot adsorbent from the treating zone is merely discharged into the top of the washing zone it will first drop on the upper surface of the column of solvent therein. The solvent will immediately begin to boil near the upper surface of the column and this boiling will cause excessive entrainment of the adsorbent so charged, in-the used solvent stream withdrawn from the column. Afurther difliculty occurs Where there is a high temperature in the Washing Zone. When the temperature in the washing zone is too high, for example, a temperature near the treating temperature, substantial amounts of color bodies are removed from the adsorbent by the Washing solvent. When the solvent is later separated from the oil recovered from the adsorbent, these color bodies remain with the recovered cycle oil and render it substantially darker than the oil feed to the treater, whereas without removal of the color bodies from the adsorbent, recovered oil in the process would have a color not substantially darker and usually somewhat lighter than the fresh feed to the treater. This contamination of the recovered oil is undesirable even where the recovered oil is passed to storage rather than recycled. Since, in the usual case, the amount of oil recovered in the washer is an appreciable fraction of the total feed to the treater, the treating capacity is greatly reduced by excessive amounts of color bodies in the cycle oil. In some cases the recovered oil may be so dark as to render its recycling to the treater entirely unfeasible.

A major object of this invention is to provide animproved continuous cyclic percolation process for treatment of hydrocarbons at elevated temperatures which overcomes the above-described difficulties.

Another object of this invention is to provide a method for washing a spent adsorbent of palpable particulate ice ' form used for the removal of impurities from liquid oils at high temperatures and bearing carbonaceous contaminants, color bodies and cycle oil, which avoids excessive entrainment of the adsorbent in the wash solvent.

Another object of this invention is to provide, in a mineral oil decolorizing process, a method for washing spent palpable particle form adsorbents bearing carbonaceous contaminants, color bodies and cycle oil, which provides for dissolving the cycle oil in a wash solvent without dissolving amounts of color bodies therein suificient to cause excessive loss in capacity in the oil decolorizing step.

These and other objects of the invention will be apparent from the following discussion of the invention.

In one aspect of this invention, a downwardly gravi tating columnar mass of adsorbent of palpable particulate form is maintained within the lower section of a confined washing zone. A suitable wash solvent, such as naphtha, is passed upwardly through this columnar mas to dissolve any cycle oil from the adsorbent in the wash solvent. Wash solvent is discharged from the upper end of the columnar mass and passes upwardly through the upper section of the washing zone or a disengaging zone as a column of liquid above the columnar mass of adsorbent. Spent adsorbent, bearing carbonaceous contaminants, color bodies and cycle oil, and existing at a temperature above the boiling point of the. solvent, is charged as a plurality of streams to the upper section of the washing zone and passed into heat exchange relationship with the liquid column therein whereby the adsorbout is cooled to a temperature substantially below that at which it entered the washing zone and a portion of the solvent in the liquid column vaporizes. This cooled adsorbent is then passed to the columnar mass of adsorbent and liquid and vaporized solvent are removed as separate streams from the upper section of the washing zone. The heat exchange relationship between the incoming adsorbent and the outgoing liquid column of solvent may be either direct or indirect and in either case the cooling is accomplished by the latent heat capacity of the solvent plus its sensible heat capacity. In every case a sufiicient percent of the solvent is vaporized to do the required amount of cooling. In some cases all of the cooling required to reduce the temperature of the adsorbent to a level below that at which prohibitive amounts of color bodies or other undesired components dissolve in the wash solvent may be accomplished by this vaporization and heat exchange with the liquid column. In others a part of the cooling may be done by outside cooling applied to the upper section of the columnar mass or by outside cooling applied to the liquid column. In still other cases a part of the required cooling may be done within the columnar mass by control of the inlet temperature and rate of wash solvent supply to the lower section of the columnar mass.

This invention will be best understood by referring to the attached drawings, of which Figure l is an elevational view showing the application of this invention to a continuous percolation process for the treatment of liquid hydrocarbon oils with solid adsorbents,

Figure 2 is an elevational view, partially in section, showing the internals of a typical washing vessel adapted to be used in this invention,

Figure 3 is an elevational view, partially in section, showing the upper section of a washer employing a modified form of this invention,

Figure 4 is an elevational view, partially in section, illustrating a second modification of this invention, and

Figure 5 is an elevational view, partially in section, illustrating a third modification of this invention.

All of these drawings are diagrammatic in form and like parts in all bear like numerals.

Turning to Figure 1, there is shown therein a portion f a continuous percolation system similar to that described in U. S. patent application, Serial Number 177,408, filed August 3, 1950, now Patent No. 2,701,786. Adsorbent of palpable particulate form gravitates from a supply hopper 10 into the upper section of a confined treating zone 11 through a conduit 12. Typical adsorbents which may be employed are -fullers earth, bauxite, bentonite and bone char, charcoal, magnesium silicate, heat and acid activated kaolin, activated carbon and synthetic silica or alumina or silica-alumina gel adsorbents. Adsorbent passes downwardly through the treater as a columnar mass. Liquid hydrocarbon charge oil, which may consist of a lubricating oil or fuel oil of low asphalt content, is heated in heater 13 and passes into the lower section of treater 11 through conduit '14. Charge oil passes upwardly through the olumnar mass of adsorbent in the treating zone to effect the removal of small amounts of undesirable impurities from the oil. Typical of the purposes for which the oil may be treated are decolorization, neutralization, removal of suspended, colloidal or dissolved impurities such as carbon or coke or oxygen and nitrogen containing impurities and other gum form ing compounds, and improvement of the demulsibility properties of the oil. This invention will be described in connection with a mineral oil decolorization process for purposes of clarity. The purified oil is removed through conduit 33. The temperature in the treating zone may fall within the range of atmospheric temperature to 700 F. but should generally be maintained below the flash point of the oil as measured by the A. S. T. M. Cleveland open cup method. It i frequently desirable to maintain the treating temperature at an elevated level substantially above atmospheric temperature and often at a level above the boiling point of the wash solvent used in the washing step described hereinbelow. This invention is particularly applicable to the latter case and is concerned only with cases where the treating is at elevated temperatures. The adsorbent, after use in the treating zone, will have deposited thereon a coky or tarry carto treater l1.

bonaceous contaminant, at least a part of which consists of the undesirable components, such as color bodies, desired to be removed from the hydrocarbon oil. This adsorbent is removed from the treating zone 11 through conduit 15 and carries with it adhering liquid oil which it is desirable to recover and return to the treating zone. The spent adsorbent passes to a flow dividing box 16 wherein stream 15 is split into a plurality of maller streams 17 which pass into the upper section of washing zone 18. A downwardly gravitating columnar mass of adsorbent is maintained within the lower section of zone 18. Washing solvent is supplied to the lower section of this columnar mass from an accumulation thereof within a tank 19 by means of conduit 20 and pump 21. Suitable wash solvents include petroleum naphtha boiling within the range 100-400 F., carbon tetrachloride, normal heptane, normal octane, and carbon disulfide. A paraffinic naphthat boiling within the range about ZOO-300 F. is generally perferable. The solvent passes upwardly through the columnar mass of adsorbent and dissolves cycle oil from the adsorbent. Wash solvent with dissolved cycle oil passes through the upper section of zone 18 as a column of liquid above the columnar mass of adsorbent. Spent adsorbent in streams 17, bearing carbonaceous contaminants, color bodies and cycle oil, passes into heat exchange relationship with the liquid column in the upper section of the washer whereby the adsorbent is cooled and a portion of the solvent in the liquid column is vaporized. The cooling of the adsorbent within the washing zone must be such that the temperature of the adsorbent is sufiiciently low to prevent removal of excessive amounts of the color bodies from the adsorbent during the washing step. By excessive amounts of color bodies is meant such amounts as would so contaminate the cycle oil that the product yields from the treater per unit weight of adsorbent throughput would fall to an impractically low level, for example, less than about seventy percent of that obtainable on the basis of one hundred percent fresh oil charge to the treater. In general, the amount of color bodies removed from the spent adsorbent should not exceed about fifty percent, and should preferably be below about twenty-five percent by weight of the total color bodies on the spent adsorbent leaving the treater (i. e., above those which would give a cycle oil of ame color as the fresh feed). In many operations it is preferred to exclude resolution of any substantial amount of color bodies in the washing step, i. e., an amount of color bodies 'which renders the recovered cycle oil substantially darker than the fresh oil supplied to the treater. Inert gas is admitted to dividing box 16 by conduit 22 and passes downwardly through conduits 17 at a pressure suflicient to prevent solvent from entering the lower ends of passages 17. Vaporized solvent is Withdrawn from the upper section of the washer through passage 23 and condensed by condenser 24 and then supplied to accumulator 19. Liquid solvent passes from the upper section of the washer 18 into a fractionating zone 25 by means of passage 26. In the fractionator 25 solvent is taken as an overhead vapor stream which passes outwardly through passage 27 and is condensed by cooler 28 and then passed to the accumulation in tank 19. Liquid cycle oil, freed of solvent, is Withdrawn from the bottom of 25 by pipe 29, heated by heater 30 and returned with the liquid charge Washed adsorbent is removed from the lower section of the washing zone by conduit 31. The adsorbent from 31 may then be passed to a suitable regeneration means wherein the carbonaceous contaminants and color bodies are removed. One method of regeneration is by controlled burning of the contaminants and color bodies with an oxygen-containing gas. Regenerated adsorbent may then be returned to hopper 10 through conduit 32.

Figure 2 illustrates the internals of the washer 18. Extending across the upper section of the washing zone 18 is an open topped trough or channel 34 for liquid withdrawal. The channel 34 has a plurality of horizontally spaced-apart orifices 35 lying on substantially the same horizontal line therethrough at a level intermediate the top and bottom of 34. One end of trough 34 connects into receptacle 36 and liquid withdrawal conduit 26 extends from 36 at a level below the bottom of 34. This system of liquid withdrawal is described and claimed in U. S. patent application, Serial Number 265,832, filed January 10, 1952. Across the lower section of vessel 18 is a solvent plenum chamber 37 defined by vertically spaced-apart

transverse partitions

38 and 39 extending across vessel 18. Conduits 40 extend through the plenum chamber. A plurality of uniformly spaced-apart liquid nozzles 41 extend through partition 38 into the lower section of the columnar mass of adsorbent 42 within the lower section of'vessel 18. Suitable nozzles are described and claimed in U. S. patent application, Serial Number 237,265, filed July 17, 195 1. A plurality of uniformly spaced apart adsorbent charge conduits 17 extend into vessel 18 to a level substantially below the horizontal row of orifices 35 in channel 34. Passages 17 have fins 43 on their outer peripheries as an aid to heat transfer. The upper section of vessel 18 is of greater lateral dimensions than the lower section and contains a column of liquid solvent 44 above columnar mass 42. Extending across vessel 18 at the bottom of the larger upper section of the vessel is a perforated pipe '45 with -a screen 46 thereon. A conduit 47 extends into liquid column 44 at a level above pipe 45.

Pipes

45 and 47 are joined together outside of vessel 18 and connect to pipe 48 which in turn connects into conduit 20. A level control device is provided to control the surface level of columnar mass 42 between the levels of

pipes

45 and 47. Pressure taps 49 and 50 pass through the wall of vessel 18 at vertically spaced-apart points shortly above and shortly below the desired surface level of 42. These taps connect to a manometer 51 which measures the pressure drop due to oil flow through the section of vessel 18 between

taps

49 and 50. Thus, if the surface level of 42 rises, the pressure drop will increase, if the level drops it will decrease. Controller 52 is adapted to adjust the position of valve 53 in adsorbent withdrawal line 15 in conformity withthe pressure drop shownby manometer 51. Thus, the greater the pressure drop the further controller 52 will open valve 53. The surface level of 42 will, therefore, be maintained constant within a narrow range of levels. This method of control is described and claimed in U. S. patent application, Serial Number 237,190, filed July 17, l951, now abandoned.

In one operation of the apparatus of Figure 2,

valves

54 and 55 in

pipes

45 and 47 are kept closed. Wash solvent is pumped from accumulator 19 through, passage 20 into plenum chamber 37. Solvent passes from the plenum chamber by means of nozzles 41 into the lower section of downwardly gravitating columnar mass of adsorbent 42 maintained within washing zone 18. Solvent passes upwardly throughv mass 42 and washes cycle oil from the adsorbent therein. Solvent with dissolved cycle oil is discharged from the upper surface of columnar mass 42 and passes through the upper section of zone 18 as a column of liquid 44 above columnar mass 42.- Liquid is withdrawn from 44 through orifices 35 in trough 34, so that the upper surface of column 44 is maintained at a level below the top of zone 18 and a gas space 56 is defined above column 44. Spent adsorbent of palpable particulate form, at an elevated temperature above the boiling point of the Wash solvent and bearing carbonaceous contaminants, color bodies and liquid cycle oil is passed into the upper section of zone 18 as a plurality of streams through passages 17. Passages 17 terminate at a level above the upper surface of columnar mass 42 and substantially below the upper surface of liquid column 44. Indirect heat exchange takes place between the adsorbent streams in passages 17 and the upper section of liquid column 44 through the walls of passages 17. As a result of this heat exchange, the ad sorbent is cooled to a temperature at least below the boiling point of the solvent and preferably below the temperature at which substantial amounts of color bodies will be removed by the washing solvent. Due to this cooling a portion of the solvent in the liquid column vaporizes and passes into gas space 56. Cooled adsorbent drops from the lower ends of passages 17 onto the surface of columnar mass 42. It will be noted that this method avoids the entrainment of adsorbent in the liquid flowing into trough 3-4, since all the boiling of solvent and resultant disruption of the liquid column 44 occurs above the lower ends of 17 Where there is no or very little adsorbent in the liquid-column. Liquid solvent with dissolved oil is withdrawn from the upper section of column 44 through orifices 35 into trough 34, from which it passes into receptacle 36 and then through conduit 26 to fractionator 25 as previously described. Vaporized solvent passes from gas space 56 above column 44 by means of conduit 23 and passes to tank 319 after condensation by condenser 24. Washed adsorbent passes through conduits 40 to the lower end of vessel 18 and is removed from the vessel by conduit 15 so as to promote downward movement of the adsorbent through columnar mass 42.

An alternative method of operation of the apparatus of Figure 2 is to open valve 54 while leaving valve 55 closed so as to charge solvent to the upper section of columnar mass 42 through pipe 45. This provides for an additional quantity of cool solvent in the upper section of the washing zone 18 and therefore assists in the cooling of the streams in passages 17. The same effect may be obtained by opening valve 55 while valve 54 is left closed. Additional cool solvent is then provided at a level above the upper surface of columnar mass 42. Also, part of stream 26 can be cooled and recycled to either 45 or 47 to aid in controlling temperature of column 44. Both of these latter systems are especially desirable where it is found that excessive amounts of color bodies dissolve in the wash solvent used at the temperature at which the adsorbent exits from the passages 17 when additional cooling of the solvent is not used. Normally, however, the indirect cooling through passages 17 cools the adsorbent to a temperature substantially below the boiling point. Only the solvent near the surface of column 44 will be at the boiling point, the solvent near the bed surface being at a suitable washing temperature at which substantial amounts of color bodies do not dissolve. This will be attained in many operations without addition of extra cool solvent through either 46 or 47. These latter streams are only necessary where the indirect cooling through passages 17 and the cooling accomplished as the adsorbent falls through the portion of liquid column 44 below passages 17 to columnar mass 44, is insufficient to cool the adsorbent to a suitable washing temperature at which excessive amounts of color bodies do not dissolve in the solvent.

Also, in a modified form of this invention, the hot adsorbent from the treater may be substantially cooled by vaporization of a part of the solvent and by heat ex change with the liquid body above the solvent, for example, from a treating temperature of 350 F to 200 F., while the average washing temperature is maintained at a still lower temperature, for example, about F., at which excessive amounts of color bodies are not removed from the adsorbent. This is accomplished by control of the rate and temperature of the Washing solvent supply to the lower section of the columnar mass. In this operation sufiicient heat is removed from the adsorbent before it is discharged into the body of liquid above the columnar mass by vaporization of solvent to at least prevent boiling of the solvent when the adsorbent is so discharged. In this form of the invention it is important that the heat capacity of the solvent supplied to the washing zone between its inlet temperature and the temperature of the partially cooled adsorbent falling onto the columnar mass be at least equal to the heat capacity of the adsorbent over the same temperature range, and preferably the heat capacity of the solvent should be ten per cent in excess of the amount above indicated. Heat capacity is here used to indicate the product of the specific heat of the particular material, the weight charged to the washer per unit time of the particular material and the specified temperature range all in consistent units. Under the conditions specified, the adsorbent is withdrawn from the washing zone at substantially the solvent inlet temperature and the solvent leaves the top of the columnar mass at or somewhat below the temperature of the partially cooled adsorbent falling from the liquid body onto the columnar mass. The advantages of this last mentioned method lies in the ability thereby to conduct the washing operation at suitably low washing temperatures, while the liquid body is maintained at a somewhat higher temperature where the viscosity of the oil-containing solvent than it would be if the liquid body were cooled all the way to the desired washing temperature. As a result, the fluid viscosity in the zone where the liquid is disengaged from the spent adsorbent feed is maintained at a level better suited for effecting the disengagement without adsorbent entrainment in the effluent liquid.

The upper section of washing zone 18 is of greater lateral dimensions than the lower section. This is to provide for the additional volume added to the washing solvent by dissolving the cycle oil from the adsorbent and for the higher viscosity of the solvent-oil mixture. By expanding the upper section in this manner, the superficial velocity of the liquid in the washing zone 13 is maintained at a level below that which would disrupt columnar mass 42 or carry over adsorbent into trough 34 even though the total liquid volume increases through the washing zone and the viscosity increases. While it is preferable, it is not necessary to this invention that the upper section of vessel 18 be expanded in this manner. The expansion, of course, becomes more desirable when solvent is added through

pipes

45 and 47. Inert gas, such as flue gas, may be passed through pipes 17 with the adsorbent at a pressure suflicient to keep any liquid from liquid column 44 from entering the lower ends of pipes 17 and vaporizing therein. In a less preferred form of the invention, pipes 17 may be shortened so that they extend only a short distance below the surface of column 44. Then most of the heat exchange between adsorbent and solvent will be direct rather than indirect. There may be boiling near the surface of the bed with this system, however, which may lead to entrainment of the adsorbent in the effiuent solvent as previously stated. A superior method of accomplishing this invention by direct heat exchange is shown in Figure and described herein'oelow.

Figure 3 illustrates an alternative method of this invention which is especially adapted to control the temperature of the columnar mass of adsorbent 42 below the temperature at which substantial amounts of color bodies dissolve in the solvent from the adsorbent. The washer 13 is divided into three separate superimposed sections or zones, 21 lower washing zone 57, a cooling zone 58 thereabove of lateral dimension greater than zone 57, and a disengaging zone 55 above the cooling zone and of greater lateral dimensions than the cooling zone. Columnar mass of adsorbent 42 extends throughout washing zone 57 and cooling zone 58 while liquid column of solvent 44 is maintained within disengaging zone 59 with gas space 56 thereabove. Liquid solvent passes upwardly through columnar mass 42 to dissolve the cycle oil from the adsorbent therein. Solvent with dissolved cycle oil passes from the upper end of columnar mass 42 and cooling zone 58 into disengaging zone 59 and then through zone 59 as a liquid column or body 44 from which entrained adsorbent settles. Adsorbent is supplied to the washer in the same manner as in Figure 2, entering through a plurality of confined passages 17 and cooled by indirect heat exchange with liquid column 44 to a temperature at least below the boiling range of the solvent, as a result of which a portion of the solvent in 44 is vaporized. Vaporized solvent is withdrawn through conduit 23 and liquid solvent through conduit 26. The adsorbent dropping onto the upper surface of columnar mass 42 from passages 17 may still be at a temperature above the temperature at which excessive amounts of color bodies will dissolve in the solvent. For this reason solvent is withdrawn from the upper section of cooling zone 58 at a level adjacent the upper surface of columnar mass 42 through conduit 60. The solvent so withdrawn is cooled by cooler 61 and then injected into an intermediate level in the columnar mass 42 at the lower end of cooling zone 58 by means of perforated pipe 62. The rate of solvent circulation through 60 and 62 and the temperature of the intermediate cooling by cooler 61 should be controlled so that the upper section of columnar mass 42 is reduced below the temperature at which there is excessive dissolving of color bodies in the solvent, and preferably below the temperature at which substantial amounts of color bodies dissolve in the solvent.

Figure 4 illustrates an apparatus which accomplishes the method of Figure 3 in a slightly different manner. Rather than cooling the upper section of columnar mass 42 by direct heat exchange with cooled solvent, the method of Figure 4 accomplishes this cooling by indirect heat exchange with a suitable cooling fluid, such as cold water, circulated through cooling coils 63.

Figure 5 illustrates a process of this invention wherein the cooling of the incoming adsorbent to the washer is accomplished by direct heat exchange rather than indirect heat exchange with the liquid solvent column as described previously. Adsorbent charge conduits 17 enter the upper section of the washer and terminate at uniformly spaced-apart points on a common level above the upper surface of liquid column 44. Tubes 64 of greater lateral dimensions than'conduits 17 and open on top and bottom are attached to the lower ends of conduits 17 and extend from a level above the upper surface of liquid column 44 to a level a substantial distance below the surface of 44. Since tubes 64 are open on top and at the bottom, solvent will seek its own level therein. The 'hot, spent adsorbent is discharged from conduits 17 into the solvent within tubes 64 where cooling of the adsorbent takes place by direct heat exchange with the solvent, as a result of which a portion of the solvent is vaporized. If any boiling of the solvent occurs within tubes 64, it will not result in entrainment of the adsorbent in the effluent solvent, since tubes 64 shield the boiling solvent from the liquid solvent draw-off through orifices 35. The remainder of the operation of the process of Figure 5 is similar to that of Figure 2. The various modifications of the process described in connection with Figure 2 are equally applicable in the process of Figure 5. Additional cooling may be supplied by cooling a portion of the solvent-oil mixture or by suitably controlling the solvent feed rate to perform a portion of the cooling in the columnar mass.

The various parts of apparatuses capable of conducting the method of this invention may, of course, take other forms than those shown and described hereinabove. The upper section of the washing vessel need not be of greater lateral dimensions than the lower but the entire washing vessel may have the same lateral dimensions. The expanded upper section is preferable, however, since it minimizes the possibility of adsorbent entrainment by reducing the velocity of the solvent before it is withdrawn. The expanded section is especially desirable where liquids are added to the upper section of the washer, as in Figure 2 when valve 54 is open. The fins 43 in conduits 17 are not necessary but are desirable to increase the rate of heat transfer from the adsorbent therein. Where large amounts of cycle oil are removed from the treating zone with the adsorbent, it may be desirable to drain the ad- 9 sorbent in a suitable drainer, such as a continuous moving screen before passing it to the washer and thereby decrease the load on the washer.

Where the indirect heat exchange method of cooling the adsorbent is used, the distance which conduits 17 extend below the surface of liquid column 44 will depend mainly on the temperature of the incoming adsorbent, the overall heat transfer coeificient, and the properties of the solvent. Generally, the pipes 17 should extend a distance within the range about two to six feet below the surface of liquid column 44. When the direct heat exchange method of Figure is used, the distance of tubes 64 below the surface of column 44 will depend on the temperature of the incoming adsorbent and the specific heat and heat of vaporization of the solvent. Generally, tubes 64 should extend a distance within the range about one foot to four feet below the surface of column 44. The fact that a method is characterized as being an indirect heat exchange method does not indicate that some direct heat exchange does not occur; it merely means that the major portion of the heat exchange is indirect. Conversely, when the method is characterized as direct heat exchange it does not negative indirect exchange.

When the indirect heat exchange method for cooling the incoming adsorbent is used, it may be desirable to pass inert gas in with the adsorbent as previously described. When such inert gas is employed, the pressure thereof should be maintained sufficient to prevent liquid solvent from entering the lower ends of the adsorbent charge conduits like 17. In many applications this inert gas may not be needed, particularly where the rate of adsorbent flow to the pipes 17 is controlled so that the adsorbent falls freely through pipes 17.

Where color bodies constitute one of the impurities re moved from the hydrocarbon feed in the treating zone, the temperature of the adsorbent column should be maintained preferably below the temperature at which the color bodies are removed from the adsorbent in substantial amount, i. e., an amount suificient to render the color of the recovered cycle oil substantially darker than that of the fresh oil feed to the treater. Substantially darker cycle oil than the fresh feed, when recycled, will result in decreased yields of oil product of specified color per unit of adsorbent throughput. It has been found feasible in many operations to accept a product yield down to seventy per cent of that obtainable on one hundred per cent fresh oil feed and to tolerate a cycle oil of darker color than the fresh feed. In no case, however, should the temperature in the washing column be perrnitted to rise to a level at which excessive amounts of color bodies would be removed from the adsorbent, i. e., amounts sufiicient to result in unfcasibly low product yield from the treater. in general, the amount of color bodies removed by the solvent in the washing operation shouldbe maintained below fifty per centby weight of the color bodies on the adsorbent. The temperature at which substantial or excessive color bodies will be dissolved can be determined by routine tests for any given system. As an example in the case of a 30- to 60' mesh granular fullers earth adsorbent which has become partially spent in decolorizing a bright stock oil from an original color of 180 Lovibond to a finished color of 90 Lovibond, the cycle oil amounted to about 0.12 part per part of oil product and to about 1.8 parts by weight per part of adsorbent. Using'a paraflinic naphtha wash solvent boiling in the range about 210330 F., suflicient color bodies were removed from the adsorbent to render the cycle oil color substantially darker than that of the original oil feed to the treater at Washing zone temperatures above 200 F.

The volumetric ratio of solvent to adsorbentcharged to thecolumnar mass in the washer may vary within the range about 0.25 to 3.0, and preferably 0.4 to 1.5. The length of the columnar mass in the washer should, be about 5 to 20 feet, while the length of the liquid body above the columnar mass should be about 1 to 6 feet in height.

As an example of the method of this invention, itsuse in washing -28 to 60 mesh adsorbent fullers earth in, a continuous mineral oil percolation process will be discussed. The method of operation was that described in connection with Figure 2 withvalves 54 and 55 closed. Adsorbent was charged at a temperature of about 360 F. through passages which extended a distance of three feet below the surface of liquid column 44. The adsorbent contained about 1.2 volumes of adhering liquid oil per volume of adsorbent. Adsorbeut was charged at a rate of one cubic foot per hour and solvent at a rate of 0.4 cubic foot per hour. The solvent used was petroleum naphtha boiling within the range about 2l0300 F. The adsorbent was cooled to a temperature of about 215 F. on discharge from pipes 17 and the columnar mass of adsorbent was maintained at a temperature of about F.

This invention should be understood to cover all changes and modifications of the examples of the inventionherein chosen for purposes of disclosure which do not constitute departures from the spirit and'scope of the invention.

I claim:

l. A continuous process for washing hot, spent adsorbent of palpable particulate form, having been used for purifying liquid hydrocarbon oils and bearing carbonaceous contaminants, color bodies and cycle oil, which comprises: maintaining a downwardly gravitating columnar mass of adsorbent within the lower section of a confined washing zone, maintaining a column of liquid solvent of sufiicient height to disengage adsorbent from the liquid solvent above said columnar mass within the upper section of the washing zone, passing cool washing solvent upwardly through said columnar mass to re move cycle oil from the adsorbent therein, passing washing solvent after passage through the columnar mass upwardly through said liquid column, introducing additional cool washing solvent at an intermediate level in said liquid column, passing a plurality of streams of hot, spent adsorbent downwardly through the liquid column and in heat exchange relationship therewith to effect cooling of'the adsorbent and vaporize a portion of the solvent, discharging said streams of adsorbent onto the upper surface of said columnar mass, removing liquid solvent from the upper section of said column, maintaining the adsorbent streams out of lateral communication with that portion of the liquid solvent column from which liquid solvent is removed during that portion of the heat exchange wherein solvent is vaporized, removing vaporized solvent from the upper section of said zone at a level above the upper surface of said column, and removing washed adsorbent from the lower section of said columnar mass.

2. A continuous process for the removal of cycle oil from spent adsorbent of palpable particulate form bearing carbonaceous contaminants and color bodies by washing with a washing solvent, which comprises: maintaining a columnar mass of spent adsorbent within the lower section of a confined washing zone, passing a liquid washing solvent upwardly through said columnar mass to dissolve the cycle oil on the adsorbent therein, discharging the solvent containing dissolved oil from the upper end of the columnar mass and passing said solvent through the upper sectionof the washing zone as a liquid column, passing a plurality of streams of spent adsorbent existing at a temperature above the boiling point of the solvent through a plurality of confined passages terminating at a common level substantially below the upper surface of said liquid column but above the upper surface.

of said columnar mass whereby said plurality of streams will be cooled by indirect heat exchange'with said liquid column and a portion of the solvent in said column will be vaporized, said passages being of such length that said vaporization is substantially completed before adsorbent is discharged therefrom, passing an inert gas through said passages with the adsorbent at a pressure suflicient to prevent any liquid from said column entering the lower ends of said passages, passing adsorbent from the lower ends of said passages onto the upper surface of said columnar mass, removing liquid solvent with dissolved oil from the upper section of the liquid column, removing vaporized solvent from the upper section of said washing zone at a level above the upper surface of the liquid column and removing washed adsorbent from the lower section of said columnar mass.

3. A continuous process for the removal of cycle oil from a spent adsorbent of palpable particulate form, having carbonaceous contaminants and color bodies deposited thereon and existing at an elevated temperature, by means of a wash solvent, which comprises: maintaining a downwardly gravitating columnar mass of spent adsorbent within the lower section of a confined washing zone, passing washing solvent from a confined accumulation thereof exterior to the washing zone into the lower section of the columnar mass, passing the washing solvent upwardly through the columnar mass to dissolve the cycle oil from the adsorbent therein in the washing solvent, discharging washing solvent with dissolved oil from the upper surface of the columnar mass and passing the washing solvent upwardly through the upper section of the washing zone as a liquid column above the columnar mass of adsorbent, passing a plurality of streams of spent adsorbent with cycle oil at a temperature above the boiling point of the solvent and above the temperature at which excessive amounts of color bodies dissolve in the solvent into said washing zone through a plurality of uniformly spaced-apart confined passages terminating at a common level above the upper surface of said columnar mass of adsorbent but substantially below the upper surface of the liquid column so that the spent adsorbent is cooled by indirect heat exchange with the liquid column to a temperature below the temperature at which more than about fifty percent by weight of the color bodies on the adsorbent are redissolved by the solvent and a portion of the solvent in the liquid column is vaporized, accomplishing all of said adsorbent cooling which results in vaporization of solvent prior to discharge of the adsorbent from said passages, discharging the spent adsorbent from said passages onto the upper surface of said columnar mass of adsorbent, withdrawing liquid solvent with dissolved oil from the upper section of said liquid column, passing the solvent so withdrawn to a fractionating zone and separating the solvent from the oil in the fractionating zone by vaporizing the solvent, removing liquid oil from the lower section of the fractionating zone, removing vaporized solvent from the upper section of the fractionating zone and condensing the solvent, passing the condensed solvent to said confined accumulation of solvent, removing vaporized solvent from the upper section of said washing zone at a level above the upper surface of the liquid column, condensing the vaporized solvent from the washing zone and passing the condensed solvent to said confined accumulation thereof and removing washed adsorbent from the lower section of said columnar mass.

4. A continuous process for removing hydrocarbon cycle oil, by means of a wash solvent, from a spent adsorbent of palpable particulate form bearing carbonaceous contaminants and color bodies as well as cycle oil existing at a temperature above the boiling point of the wash solvent and above the temperature at which excessive amounts of color bodies dissolve in the wash solvent from the adsorbent, which comprises: maintaining a downwardly gravitating columnar mass of spent adsorbent continuously throughout a confined washing zone and a confined cooling zone thereabove, said cooling zone having greater lateral dimensions than said washing zone, introducing wash solvent into the lower section of said washing zone, passing said wash solvent a confined disengaging zone above said cooling zone and of lateral dimensions greater than the lateral dimensions of said cooling zone, passing solvent upwardly through the lower section of said disengaging zone as a column of liquid, maintaining a gas space above said liquid column, passing aplurality of streams of spent adsorbent at a temperature above the boiling point of the solvent through a plurality of confined passages terminating at a common level substantially below the upper surface of said liquid column and substantially above the upper surface of said columnar mass of adsorbent whereby the adsorbent will be cooled by indirect heat exchange with the upper portion of said liquod column to a temperature below the boiling range of said solvent and a portion of the solvent in the liquid column will vaporize and pass into said gas space, discharging adsorbent from the lower ends of said passages and passing the adsorbent downwardly onto the upper surface of said columnar mass, passing an inert gas into the disengaging zone with the plurality of adsorbent streams at a pressure sufiicient to prevent liquid from said column from entering the lowor ends of said passages, withdrawing liquid solvent from the upper section of said liquid column, withdrawing vaporized solvent from said gas space, withdrawing liquid solvent from the upper section of said cooling zone at a level adjacent to the upper surface of said columnar mass, cooling the liquid solvent so withdrawn, introducing the cooled liquid solvent into said columnar mass at the lower end of said cooling zone, controlling the rate of solvent withdrawal from and introduction to said cooling zone and the temperature of the intermediate cooling so that the upper section of said columnar mass of adsorbent is reduced to a temperature below the temperature at which more than fifty percent by weight of the color bodies on the adsorbent would be removed by the wash solvent, and removing washed adsorbent from the lower section of said columnar mass.

5. A continuous process for washing with a wash solvent a spent adsorbent of palpable particulate form bearing carbonaceous contaminants, color bodies and mineral cycle oil and existing at a temperature above the boiling point of the solvent, which comprises: maintaining a downwardly gravitating columnar mass of spent adsorbent throughout a confined washing zone, passing the wash solvent upwardly through said columnar mass to dissolve the cycle oil from the adsorbent therein, discharging wash solvent with dissolved oil therein from the upper end of said columnar mass into the lower end of a confined disengaging zone superimposed on said washing zone of greater lateral dimensions than said washing zone, passing liquid solvent upwardly through said disengaging zone as a liquid column, maintaining a gas space in the upper section of the disengaging zone above the liquid column, passing a plurality of streams of spent adsorbent at a temperature above the boiling point of the wash solvent into the disengaging zone through a plurality of confined passages terminating at a level above the upper surface of the columnar mass and substantially below the upper surface of the liquid column whereby the adsorbent streams in the passages are cooled by indirect heat exchange with the liquid column to a temperature at least below the boiling range of said solvent and a portion of the solvent in the liquid column is vaporized and passes into the gas space thereabove, maintaining the length of said passages such that substantially all of the solvent vaporization will occur prior to adsorbent discharge from the passages, discharging cooled adsorbent from the lower ends of said passages onto the upper surface of said columnar mass, withdrawing liquid solvent with dissolved oil from the upper section of said liquid column, withdrawing vaporized solvent from said gas space, cooling the upper section of said columnar mass by indirect heat exchange with a cooling fluid to a temperature below the temperature at which more than fifty percent by weight of the color bodies on the adsorbent would be removed by the solvent and withdrawing washed adsorbent from the lower section of said columnar mass.

6. In a continuous cyclic process for decoloring mineral oils wherein a fresh oil feed is passed upwardly through a columnar mass of gravitating adsorbent of palpable particulate form within a confined treating zone at a rate and elevated temperature adjusted to efiect the desired decolorization of the oil without substantial disruption of the columnar mass due to oil fiow therethrough and wherein spent adsorbent along with some cycle oil and carbonaceous contaminants, including color bodies, is subjected to washing by a suitable wash solvent to remove the cycle oil, which wash solvent is also capable of removing excessive amounts of the color bodies from the spent adsorbent and wherein the washed adsorbent is regenerated by burning and recycled to the treating zone for re-use, the improved method of con ducting the washing of the adsorbent, which comprises: passing adsorbent downwardly through a confined washing zone as a gravitating columnar mass; maintaining a body of liquid wash solvent within said washing zone above the upper surface of said mass; removing adsorbent from said treating zone and passing said adsorbent into the washing zone as a plurality of confined streams at an elevated temperature, near the treating temperature, which is substantially above the boiling point of the wash solvent and above the temperature at which excessive amounts of color bodies are dissolved by the wash solvent from the adsorbent; passing said plurality of streams into indirect cooling heat exchange relationship with the liquid body within said washing zone; vaporizing a portion of the wash solvent in said liquid body by said heat exchange; removing the vaporized solvent from the washing zone above the liquid body and condensing said solvent and passing it as a liquid to an accumulation of wash solvent maintained exterior to said washing zone; maintaining said streams of adsorbent confined laterally from a level above the surface of said liquid body to a level therebelow but above the upper surface of said mass such that when said streams become unconfined the adsorbent is at a temperature below that at which substantial vaporization of solvent will occur and below the temperature at which about fifty percent by weight of the color bodies on the adsorbent will be dissolved by the solvent; dropping the adsorbent from said streams onto the upper surface of said columnar mass; passing wash solvent from said accumulation of wash solvent into the lower section of said columnar mass and upwardly through said mass at a rate and temperature suitable to dissolve cycle oil from the adsorbent and cool the adsorbent mass to a suitable washing temperature; removing wash solvent with dissolved cycle oil from the upper section of said liquid body and passing said solvent into a fractionation zone; separating solvent and cycle oil by fractionation within said fractionation zone and condensing the solvent and returning it as a liquid to said accumulation of solvent; removing the cycle oil from said fractionation zone and passing said cycle oil into said treating zone.

7. A continuous process for removing mineral cycle oil, by means of a wash solvent, from a spent adsorbent bearing carbonaceous contaminants and color bodies and existing at a temperature above the initial boiling point of the solvent and above the temperature at which ex cessive amounts of color bodies would re-dissolve in the wash solvent, which process comprises: maintaining a column of said adsorbent in the lower section of a confined washing zone; maintaining an accumulation of wash solvent exterior to said washing zone and passing wash solvent from said accumulation into the lower section of said column and passing the solvent upwardly through said column to remove the cycle oil; passing the liquid upwardly from the surface of said column and through a body of liquid maintained above said column and withdrawing the solvent and cycle oil from the upper section of said liquid body; withdrawing washed adsorbent substantially free of the cycle oil from the lower section of said column so as to promote downward flow of the adsorbent therethrough; passing spent adsorbent with cycle oil at said elevated temperature into the upper section of said washing zone and downwardly onto the surface of said column as a plurality of confined streams in indirect heat exchange relationship with said liquid body to vaporize a portion of said solvent and cool said adsorbent to a temperature below the initial boiling point of said solvent and below the temperature at which fifty percent by weight of the color bodies on the adsorbent will dissolve in the solvent but above the desired average washing temperature; withdrawing vaporized solvent from said washing zone; condensing said vaporized solvent and returning the condensed solvent to said accumulation of wash solvent; passing the solvent with dissolved cycle oil after removal from said liquid body into a confined fractionating zone and separating solvent and oil therein; condensing the solvent so separated and returning condensed solvent to said accumulation of solvent; controlling the rate and temperature of the solvent supplied to the lower section of said column to efiect a further cooling of said adsorbent to the desired average washing temperature.

References Cited in the file of this patent UNITED STATES PATENTS 2,482,137 Schutte Sept. 20, 1949 2,552,435 Knox et al. May 8, 1951 2,552,436 Bennett et al. May 8, 1951 2,571,380 Penick Oct. 16, 1951 2,602,044 Lupfer et al. July 1, 1952 2,631,727 Cichelli Mar. 17, 1953 2,696,305 Slover Dec. 7, 1954 2,696,462 Bodkin Dec. 7, 1954 2,701,786 Evans et al. Feb. 8, 1955

Claims

1. A CONTINUOUS PROCESS FOR WASHING HOT, SPENT ADSORBENT OF PALPABLE PARTICULATE FORM HAVING BEEN USED FOR PURIFYING LIQUID X X HEARING CARBONACEOUS CONTAMINANTS, COLOR BODIES AND CYCLE OIL, WHICH COMPRISES: MAINTAINING A DOWN WARDLY GRAVITATING COLUMNAR MASS OF ADSORBENT WITHIN THE LOWER SECTION OF A CONFINED WASHING ZONE, MAINTAINING A COLUMN OF LIQUID SOLVENT OF SUFFICIENT HEIGHT TO DISENGAGE ADSORBENT FROM THE LIQUID SOLVENT ABOVE AND COLUMNAR MASS WITHIN THE UPPER SECTION OF THE WASHING ZONE, PASSING COOL WASHING SOLVENT UPWARDLY THROUGH SAID COLUMNAR MASS TO REMOVE CYCLE OIL FROM THE ADSORBENT THEREIN, PASSING WASHING SOLVENT AFTER PASSAGE THROUGH THE COLUMNAR MASS UPWARDLY THROUGH SAID LIQUID COLUMN, INTRODUCING ADDITIONAL COOL WASHING SOLVENT AT AN INTERMEDIATE LEVEL IN SAID LIQUID COLUMN, PASSING A PLURALITY OF STREAMS OF HOT, SPENT ADSORBENT DOWNWARDLY THROUGH THE LIQUID COLUMN AND IN HEAT EXCHANGE RELATIONSHIP THEREWITH TO EFFECT COOLING OF THE ADSORBENT AND VAPORIZE A PORTION OF THE SOLVENT, DISCHARGING SAID STREAMS OF ADSORBENT ONTO THE UPPER SURFACE OF SAID COLUMNAR MASS, REMOVING LIQUID SOLVENT FROM THE UPPER SECTION OF SAID COLUMN, MAINTAINING THE ADSORBENT STREAMS OUT OF LATERAL COMMUNICATION WITH THE PORTION OF THE LIQUID SOLVENT COLUMN FROM WHICH LIQUID SOLVENT IS REMOVED DURING THAT PORTION OF THE HEAT EXCHANGE WHEREIN SOLVENT IS VAPORIZED, REMOVING VAPORIZED SOLVENT FROM THE UPPER SECTION OF SAID ZONE AT A LEVEL ABOVE THE UPPER SURFACE OF SAID COLUMN, AND REMOVING WASHED ADSORBENT FROM THE LOWER SECTION OF SAID COLUMNAR MASS.