US2111957A - Method for depropanizing waxpropane mixtures - Google Patents

Description

March 22, 1938.,

METHOD FOR DEPROPANVIZING -wAX PROPANE MIXTURES v -Filed Aug. 1s. 1955- hlx au fr I W/rA/Ess.-

D. B. BANKS ET AL `s sheets-sheet' 1 Jaw/v Mnl/Ess.-

March 22, 1938- D. B. BANKS ET AL. 2,111,957

METHOD FOR DEPROPANIZING WAXl PROPANE MIXTURES Filed Aug.' 13; 1935 s sneets-snei 2 J 'a @f6.24

March 22, 1938., Q E BANKS ET AL 2,111,957

METHOD FOR DEPROPANIZING WAX PROPANE MIXTURES I Filed Aug. 13. 1955 3 Sheets-S1169?.- 3

Patented Mar. 22, 1938 UNITED Sixers OFFiCE lvlETl-IOD FOR DEPROPANIZING WAX- PROPANE MIXTURES Application August 13,

7 Claims.

The present invention relates to a process for depropanizing wax-propane or Wax-asphalt-propane mixtures formed in the propane dewaxing of hydrocarbon oils.

In dewaxing hydrocarbon oils b-y methods involving the use of propane (with which a minor proportion of propylene is usually dissolved) or other liqueed normally gaseous hydrocarbons, such as butane, iso-butane, propylene and the like and mixtures of the same, which will hereinafter be referred to only as propane, the wax bearing oil is lirst dissolved in propane, and the solution thus obtained is then chilled to the proper Wax crystallizing temperature by evaporation of a portion of the propane, or by indirect refrigeration or a combination of the two chilling methods. After the solution has been sufficiently lowered in temperature, the wax separates from the solution of oil and propane in the form of crystals. The solution of oil and propane with solidied wax suspended-therein is then filtered or centrifuged to separate the crystallized wax from the `solution of Wax free oil and propane, the wax being recovered in the form of a wax filter cake, or in the form of a wax 'slurry if the centrifuge method is used. The wax iilter cake or slurry, thus obtained, will contain, in addition to the wax, considerable quantities of propane and oil. If the Wax-bearing oil being dewaxed is a mazoot or bottoms derived from a mixed base crude, the wax and asphalt may be separated from the solution of asphalt and wax bearing oil and 'propane together, the wax usually agglomerating around particles of asphalt. The Wax-asphalt filter cake or slurry obtained from this type of crude will contain, in addition to the wax and asphalt, considerable quantities of propane and oil.

In order toV prevent repetition hereinafter, it is to be understood that Where the word wax is used, it is meant to include wax containing small proportions of unseparated oil and also wax and asphalt with or without small proportions of oil not removed by the filtration or centrifugation.

Such wax-lter cakes or slurries or other waxpropane mixtures present a very difficult depropanizing problem since they are at extremely low temperatures and do not readily conduct heat. For instance, if a bucket is filled with the material and placed over a steam bath, it will take two hoursV or more for sufficient heat topenetrate through the wax-propane mixture to distill off the major portion of the propane.

It is, therefore, an object of the present invention to provide a process and apparatus which 1935, Serial No. 35,980

insures an intimate Contact between such waxpropane mixtures and a heating medium at a tern.- perature high enough to insure substantially complete vaporization of the propane.

It is a further object of the invention to prcvide a process and apparatus whereby the deprepanized Wax mixture may be heated and re-circulated to vaporize the propaneV from further quantities of Wax-propane mixtures.

In carrying out the present invention, the cold wax-propane mixture from the filter or other` separating means is conducted to a chamber from which it is fed by a multiplicity of jets, a pump being provided for each jet. To the jets there is also fed hot depropanized Wax. The jets are.V so constructed as to provide a very intimate admixture and Contact between the cold Wax propane and hot depropanized Wax. The outlets of these jets open into a vapor disengaging chamber and heater. The mixture is so broken up by u the action of the jets as to be in a very nely divided condition, thus insuring a quick separation or disengagement of Vthe propane vapor. The wax, which has been reduced to a liquid condition by the heat so far added to it, falls to the bottom oi the chamber, in which are placed steam coils to add additional heat to the depropanized Wax, so that a portion of it may be readily pumped from the chamber to storage or purification means and other portions pumped back to jets for heating further quantities of cold wax-propane mixture.

There is provided, at one end of the chamber into which the jets open, a bubble tower through which the disengaged propane vapor is passed in i contact with reflux comprising hot depropanized Wax in order to remove any entrained particles of wax. The disengaging chamber is maintained under such pressure as will insure the condensation of the propane or other solvent, when re` moved from the chamber and cooled.

A better understanding of the invention will be had by reference to the following drawings, of which: l

Fig. 1 is` a side elevation of the complete apparatus;

Fig. 2 is an end elevation of the paratus;

. Fig. 3 is a section taken on line 3--3 of Fig. l;

Fig. 4 is a cross section taken through one of the jets; and Y Fig. 5 is a detail of that portion of the jet in Fig. 4 designated by a dotted circle and marked 56X.

Turning now to Figs. l andZ ofthe drawings,

complete ap- CIK CTI

A represents a feeding chamber to which the cold wax propane mixture is fed from the ilters or centrifuges. B represents the disengaging chamber and the heater. C represents a bubble tower at one end of the disengaging heating chamber for removing entrained liquid from the gaseous propane. D represents a pressure equalizing line between the top of chamber B and feed chamber A. In operation, the cold wax propane mixture is admitted to the feed chamber A through line I. After suiicient head is built up in the feed chamber, the material will, by its own weight, be forced into the gear pumps 2 which rest upon plate 3, forming the bottom of the chamber, a head 4 being added below plate 3 merely to provide strength.

The gear, or booster, pumps 2 are in parallel rows, each row having a number of pumps therein as shown in Fig. 3. Each pump feeds a single valve controlled line 5 leading to a jet or nozzle 6. Within the jet or nozzle 6 the cold wax propane mixture is intimately admixed with hot depropanized wax which is admitted to each nozzle through lines l, fed by a manifold connection 8. Manifold connection 8 is in turn supplied with hot depropanized wax from the bottom of the chamber B, by means of line 9, pump IQ, valved line II and line I2. When the hot depropanized wax is brought into direct and com,- plete ccntact with the cold propane wax mixture,

, it heats such mixture suiciently to render the wax fluid, and to vaporize the propane. The then heated mixture leaves the jets and passes into the disengaging chamber and heater B. The chamber B is surmounted by a dome I3 having a cover plate I4, to which the nozzles 6 are aliixed. Within the dome I3 there is supported on angle irons I5 an inclined plate I 6. Above the plate I6 there are arranged steam coils Il. On entering the dome the heated wax and propane separate from each other, the wax in a molten condition falling to the inclined plate I6 and the propane vapors passing off to the side and down into the chamber proper between the wall of the dome I3 and the cylindrical baffle I8 supported within and spaced from the walls of the dome I3. The liquid wax in falling to the plate IS passes over the steam coils I1, which serve to heat it sufliciently to vaporize some of the propane not vaporized in the jets or nozzles 6. The liquid wax then overflows the edge of plate I5 into the bottom of the chamber B. Within the chamber B proper there are placed a series of hairpin heating coils I9, which are fixed to a tube sheet 20, held in place by head 2I. There is provided within the head a partition 22. Steam is fed to one side of partition 22, passes through the coils I 9, and is removed from the other side of partition 22. At the opposite side of chamber B there is provided a weir or partition 23 which serves to maintain a predetermined liquid level within the chamber B. When this predetermined liquid level is reached the liquid wax overflows weir 23 into the end chamber which contains a oat mechanism 24, operating through head 25 to control valve 26 in line II. By means of this provision, there is maintained a constant liquid level in the major portion of chamber B and the excess melted wax is withdrawn as it overiiows the weir 23, thereby at all times assuring a constant level within the major portion of chamber B. Chamber B is further provided with a valved outlet 21 which is used only on draining the chamber after a run or for inspection and repair. Such of the hot depropanized wax overflowing Weir 23 and passing out through line 9 as is not recirculated through line I 2 to the jets E or tower C, is withdrawn through iloat controlled valve to storage or wax purication apparatus.

The propane vapors, after being disengaged from the melted wax, pass up through bubble tower C positioned at one end of the chamber B. To the topmost trays in the tower there is supplied molten wax drawn from line I2, by means of valved line 2B. This liquid wax overows from tray to tray, and provides a washing medium through which the propane vapors must bubble on their way from the apparatus, thus insuring that all entrained wax particles are removed, the propane vapors passing to a condenser (not shown) wherein they are cooled sutil,- ciently to condense them at their existing pressure. This pressure will, of course, vary with the solvent used in the dewaxing process, whether it be propane or, for example, butane, or a mixture of ethane, propane and butane. The higher boiling the solvent, the lower, of course, the pressure required for condensation at a given temperature.

Of the heated and depropanized wax that is continuously withdrawn from chamber B, through line 9 by means of pump IB, and passed through lines II and I2, a portion is used for reflux in the tower C, and the balance is fed through manifold 8 to line 7 and the jets 6, for admixture with incoming cold wax-propane mixture. As already stated, the pressure between the chamber B and feed chamber A is equalized by means of valved line D. Since the propanewax mixture entering chamber A through line I may be from F. to 60 F., and since the pressure within the tower C and chambers B and A is sulicient to condense the vaporized propane on cooling, it is evident that the propane which is contained above the cold wax propane mixture in chamber A will be in part chilled and condensed within the chamber A above the propane wax mixture therein. This condensed propane may be withdrawn from time to time through valved lines 29 set at the various levels in chamber A and line 3U, and passed to the lower part of chamber B wherein it comes into contact with heated depropanized wax and is vaporized, thereafter passing off with the balance of vaporized propane.

When first starting up the apparatus, the valve in line D is closed and cold propane wax mixture is admitted to the chamber A, through line II.

When suicient head has built up in the chambery A, an inert gas is admitted to the valved line 3I, thereby creating additional pressure at the bottom of chamber A. The pump 9 is started, then pump 2, it being assumed that there is already a charge of heated and depropanized wax in cham.

ber B. As soon as the rst wax passes into dome I3 of the chamber B, an atmosphere of propane will be formed, the pressure of which will be gradually increased as cold wax propane mixture is pumped from chamber A. As soon as the requi= site pressure has built up in chamber B and tower C, the valve at the exit of the tower C is opened and hot reux is admitted to the trays in tower C. The valve in line D is then opened, and the valve in line 3l closed. The apparatus will then function automatically, so long as cold waxpropane mixture is fed to the chamber A. If the feed of the cold wax-propane mixture to chamber A is cut down, the head in chamber A will decrease, thereby decreasing the amount which is Cil picked up by the pumps 2 and fed to the' jets or depropanizing nozzles S. The cold wax-propane mixture does not function as a liquid, since it is a more or less gummy mass, depending on the temperature of admission, and the proportion of oil propane and asphalt contained therein. It is, therefore, necessary that a considerable head be maintained in the chamber A, from which it follows that the greater the head the greater the feed to the pump 2, and the lower the head the less the feed to pump 2, the head, of course, being controlled automatically by the rate of admission of cold propane wax mixture.

Referring now to Figs. 4 and 5 which illustrate the depropanizing nozzle 6, the cold wax-propane mixture enters the nozzle 3 through line 5 which is tapped into bell shaped chamber 35 in top section 34 of the nozzle. The top section all is bolted to central section 36 by tap bolts 3l, suitable packing 38 being provided between the top and central sections of the nozzle. The top section 34 and central section 36 are cut away to form an annular chamber 39 in the nozzle 5. Hot deprepanized wax enters 'the nozzle through line E which is tapped into opening 4i) leading to chame ber 39. A cup shaped member 42 is held in a bell shaped opening Ill, in central section 35, by ribs 43, attached to central section 36 and cup d2. The cup 42 has a threaded opening 55, in. the bottom thereof, through which a shaft Ml, having a pear shaped head 45, is screwed. By turning shaft 44, the pear shaped head 45 may be raised or lowered to adjust the size of the annular opening 46 between chambers 35 and M. Shaft lid may be locked against rotation by lock nut 48.

An annular insert 48 is screwed into the central section 3B of the nozzle 5 so as to form a part of the walls of' annular chamber 39. This insert 49 is spaced uniformly from top section 3d by set screws 50 in insert 49 pressing against top section 35 so as to form a uniform annular opening 41 between chambers 39 and 4|. There are pref erably at least three such set screws i! placed equidistantly around insert i9 and held in place by set screws 5l, used as jam screws. Insert 43 may be held against rotation by set screws 52. An annular flange 53 is screwed onto central section 36 and welded thereto as at 5t. Nozzle 6 is connected to chamber B by bolting ange 53 to cover plate Hl. Y

The operation of the nozzle is as follows: Cold wax-propane mixture from line 5 enters chamber 35 and passes through annular opening d6, in the form of an annular stream, to chamber lil. Hot depropanized wax from line 1 enters chamber 39 and passes through annular opening d1, also in the form of an annular stream, to chamber 4l. The annular stream of hot depropanized wax, issuing from annular opening il hits the annular stream of cold wax-propane mixture, issuing from annular opening 4B, the two streams meeting at high velocity at an angle of about 30, as will be clear by reference to Fig. 4. The cold wax-propane mixture is thus thoroughly mixed with hot depropanized wax in chamber lll. Since the Volume of hot depropanized wax issuing from opening 41 is preferably'about l0 times the volume of the cold wax-propane mixture issuing from opening 46, the cold. wax-propane mixture willV be heated, by its intimate admixture with thehot depropanized wax, sufficiently to vaporize the propane contained therein. The ration of l above expressed is by no means fixed. The proper proportion is established by the composition and temperature of the cold wax component and the temperature ofthe hot depropanized liquid.

While the present invention has so far been described only in respect to its application to depropaniz'ing cold wax-propane and cold waxasphalt-propane mixtures, it is apparent that it is readily adaptable to other analogous uses.

For instance, when an asphalt bearing oil is deasphaltized by mixing the asphalt bearing oil with propane, or other similar normally gaseous hydrocarbons having selective solvent properties between oil and asphalt, under pressure and at ordinary atmospheric temperatures, and the mixture is allowed to settle, the asphalt will precipitate. The solution of the lubricating oil and wax, if wax was present in the original stock, in liquid solvent is withdrawn from the pressure precipitator, leaving a residue of asphalt. This asphaltic residue will contain a small amount of propane which must be recovered in order to render the operation an economic one and the asphalt t for use. The method and apparatus of the present invention are very valuable for depropanizing the asphalt-propane mixture thus obtained.

The operation of depropanizing such an asphalt-propane mixture is similar to that described above in connection with depropanizing wax-propane mixtures. The asphalt-propane mixture is admitted to tank A through line I and is forced by pumps 2 through lines 5 to jets or nozzles B where it is mixed with hot depropanized asphalt which is withdrawn from the bath of hot depropanized asphalt in chamber B.

The depropanized wax-asphalt mixture or asphalt obtained as described above. is frequently made into a fuel oil by mixing it with gas oil to obtain a fuel oil of the'desired characteristics as to viscosity, flash point, fire point, etc. However, it Vis possible to utilize the method of the present invention for'blending the gas oil with the asphalt-propane mixture or wax-asphalt-propane mixture, so as to vaporize the propane and give a fuel oil of the desired characteristics.

In case it is desired to blend the asphalt or wax-asphalt mixture with gas oil to obtain fuel oil, the asphalt-`propane mixture or wax-asphaltpiopane mixture is admitted to tank A through line l, and Ywithdrawn therefrom by pumps 2 and forced through lines 5 to jets or nozzles 6. Hot gas oil is admitted through valved line 32 to manifold 8 and thence through lines 'l to jets or nozzles E where it is intimately mixed with the propane bearing mixtures introduced to the jets or nozzles 6 from lines 5, and heats the same to vaporize a large part of the propane. The propane vapors separate from the fuel oil blend of gas o-il and asphalt, or asphalt and wax, in the dome I3 and pass off to the side and into the chamber B and thence into the tower C. The fuel oil blend falls to the plate l5 and flows over the heating coils l'l which heat it and vaporize additional quantities of propane. The liquid from plate i6 falls into the body of hot fuel oil blend maintained in chamber B and flows over the Weir 23 and is withdrawn through line 9 by pump lil, a portion iiows through line VIl past float controlled valve 25 to` storage and the remainder is circulated through line l2 and valved line 2S to'tower C. The amountof gas oil admitted through line 32 will of course depend on the specifications for the fuel oil which it is desired to obtain and the characteristics of the ma- *ferial being blended. In case the gas oil alone does not supply suicient heat to vaporize the pro-pane, the valve 33 may be opened and part of the hot fuel oil blend, from chamber B, which is being circulated in line I2 may pass to manifold 8 with the hot gas oil and thence through lines l to jets or nozzles 6, and thus supply part of the heat necessary to vaporize the propane.

What we claim and desire to protect by Letters Patent is as follows:

1. The method of depropanizing a cold mixture of propane and a high boiling point hydrocarbon, which comprises continuously flowing separate streams of said mixture and of a heated high boiling point hydrocarbon toward a common locus of mixing and evaporation while imparting to both streams a substantially increased velocity and at such velocity intimately mixing them, thereby promoting evaporation of propane by mechanically breaking up the newly formed mixture as Well as by elevating the temperature of the constituents of said propane mixture and removing separated propane vapors from said locus.

2. The method of depropanizing a cold mixture of propane and a high boiling point hydrocarbon, which comprises continuously flowing separate streams of said mixture and of a heated high boiling point hydrocarbon to a common locus and thereat substantially increasing the velocity of both streams to thus nely divide and mix them and thereby, as well as by elevating the temperature of the said propane-containing mixture, promoting the evaporation of propane, and conducting away the separated propane vapors.

3. The method of depropanizing a cold mixture of propane and a high boiling point hydrocarbon, which comprises continuously flowing separate streams of said mixture and of a heated high boiling point hydrocarbon to a common locus of mixing and evaporation while imparting to both streams a substantially increased velocity and at such velocity impinging said streams one upon the other to thereby intimately mix and mechanically break up as well as elevate the temperature of said propane-containing mixture and thereby promote the vaporization of propane, removing evaporated propane from such locus and immediately conveying the high boiling hydrocarbon together with any unevaporated p-ropane to a pool of the high boiling hydrocarbon and heating the pool and thereby effecting evaporation of substantially all the remaining propane.

4. The method of depropanizing a cold mixture of propane and a high boiling point hydrocarbon, which comprises continuously ilowing separate streams of said mixture and of a heated high boiling point hydrocarbon to a common locus of mixing and evaporation while imparting to both streams a substantially increased velocity and at such velocity impinging said streams one upon the other to thereby intimately mix and mechanically break up as well as elevate the temperature of said propane-containing mixture and thereby promote the vaporization of propane, still further raising the temperature of the finely divided new mixture and conducting away evaporated propane, and conveying the high boiling hydrocarbon together with any unevaporated propane to a pool thereof and heating the pool to thereby eiect evaporation of substantially all the remaining propane,

5. The method of depropanizing a cold mixture of propane and a high boiling point hydrocarbon, which comprises continuously flowing separate streams of said mixture and of a heated high boiling point hydrocarbon toward a locus of mixing and evaporation and thereat impinging them one upon the other by discharging them through two concentric annular adjacent openings of restricted width to thereby impart to both streams a` high velocity and mechanically break up the said propane mixture and promote evaporation of propane.

6. The method of depropanizing a cold mixture of propane and a high boiling point hydrocarbon, which comprises continuously flowing separate streams of said mixture and of a heated high boiling point hydrocarbon toward a locus of mixing and evaporation in the form of two concentric annular adjacent streams of progressively decreasing width to thereby impart to both streams a high velocity and effect the intimate mixture of said adjacent concentric annular high velocity streams to thereby mechanically break up the said propane mixture and promote evaporation of propane.

7. The method of depropanizing a cold mixture of propane and a high boiling hydrocarbon which consists in owing separate streams of said mixture and of a heated high boiling hydrocarbon to an expanded space constituting a common locus of evaporation and thereat simultaneously mixing the streams and elevating the temperature of the constituents of the cold mixture, with consequent evaporation and separation of propane, owing the mixture of hydrocarbons through said locus to a pool of such hydrocarbons and in the course of its ow through said locus and in said pool successively heating the hydrocarbons, with consequent further evapioration and separation of propane, thereby separating substantially all of the propane, and immediately conducting away the propane vapors from said locus and pool.

DANIEL B. BANKS. PAUL D. BARTON.

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