GB1601803A - Solvent deasphalting apparatus and process - Google Patents

Description

(54) SOLVENT DEASPHALTING APPARATUS AND PROCESS (71) We, UOP INC., a corporation organized under the laws of the State of Delaware, United States of America, of Ten UOP Plaza, Algonquin & Mt. Prospect Roads, Des Plaines, Illinois, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to the deasphalting of black oils by means of a solvent.

Solvent deasphalting or decarbonization is used for the removal of asphaltic and resinous materials from heavy petroleum stocks.

These feed materials may be broadly characterized as having boiling points, as determined by the appropriate ASTM distillation procedure, above about 316"C at one atmosphere of absolute pressure. They will normall contain appreciable amounts of sulfur and various metals, such as nickel or vanadium. The asphaltic material is generally associated with these impurities by chemical combination. The asphaltic materials are high molecular weight, non-distillable coke precursors which are insoluble in light hydrocarbons such as pentane or heptane. The charge stock to a solvent deasphalting operation is often broadly classified in the art as a black oil, a term which is intended to refer to and include atmospheric tower bottoms, vacuum tower bottoms (vacuum residuum), topped crude oils, coal oil extract, shale oils and heavy oils recovered from tar sands.

Specific examples of those charge stocks to which the process is applicable include a vacuum column bottoms having a gravity of 7.1 API and containing 4.05 wt.% sulfur and 23.7 wt.% asphaltenes; a 11.0 API topped crude oil which contains 10.0 wt.% asphaltenes and 5.2 wt.% sulfur; and a vacuum residuum containing about 2.0 wt.% sulfur, having a gravity of about 8.8 API and a 20 volume percent distillation point temperature of approximately 568 C.

According to the present invention there is provided a process for solvent deasphalting black oils which comprises the steps of: (a) passing a feed stream comprising liquid hydrocarbonaceous compounds having boiling points above 316"C and containing metals and asphaltenes into a liquid-liquid extraction column at an intermediate feed point and then downward through the extraction column; (b) passing a solvent stream upward through the extraction column countercurrent to the feed stream at extraction promoting conditions and thereby forming a solvent rich extract stream comprising hydrocarbonaceous compounds having boiling points above 316"C; (c) passing the extract stream upward above the intermediate point through liquidliquid contacting trays countercurrent to a descending asphaltic liquid stream;; (d) raising the temperature of the extract stream from 11 to 56 Centigrade degrees by upward passage through a heating zone contained within the extraction column; (e) bringing the extract stream to a uniform temperature by upward passage through a sigmoid mixing zone, and then passing the extract stream upward into a quiescent separation zone and effecting the separation of denser asphaltic materials from the extract stream to thereby produce the asphaltic liquid stream, and removing the extract stream overhead as a product stream comprising a deasphalted portion of the feed stream.

The invention also provides an apparatus for use in the deasphalting of black oil by countercurrent solvent extraction, which comprises (a) a vertical separating vessel provided with separate inlets for solvent and charge stock from separate sources at intermediate points, the former below the latter, and outlets for asphaltic material for deasphalted product plus solvent in the region of the top and bottom of the vessel, respectlvely, (b) heat-exchange means located solely above the charge stock inlet and arranged so as to regulate the temperature of essentially all material rising above said inlet, and (c) alternating flow diversion means mounted in the vessel above the heat-ex change means to define a sigmoid mixing zone, whereby substantially uniform mixing of the material passing the heat-exchange means is achieved, (d) the vessel being designed and arranged to define a quiescent settling zone above the sigmoid mixing zone but below the outlet for deasphalted product plus solvent, said zone being free from flow diversion means causing substantial diversion of the flow of material through it.

It will be thus apparent that the invention provides a new and useful process and apparatus for the solvent deasphalting of heavy black oil charge stocks in which top heating of the solvent rich extract is accomplished by passage through at least one layer of heat exchange elements which are preferably formed by two bundles of U-shaped heat exchange tubes. The bundles may be inserted into the column through opposite sides of the column to lie in the same horizontal plane.

The thus heated extract stream is then brought to a uniform temperature by upward passage through a sigmoid mixing zone which is preferably formed by a centrally disposed horizontal shroud located directly above the heat exchange tubes and two horizontal baffles attached to the wall of the column above the shroud and adjacent to the shroud's straight exterior edges. The extract stream is then retained within a quiescent settling zone located above the baffles to ensure complete separation of the precipitated asphaltic material.

The accompanying drawing illustrates a preferred embodiment of apparatus according to the invention. FIGURE 1 is a vertical cross-section of a solvent deasphalting column constructed according to the preferred embodiment of the invention. FIGURE 2 is a horizontal cross-section of the column taken just above shroud 13 and looking downward. For simplicity and clarity of presentation numerous items, such as valves, manways, structural supports and control systems which are necessary for operation of the apparatus but which do not form a part of the inventive concept have been deleted.

This description of a preferred embodiment is not intended to preclude modification of the invention in a manner obvious to those skilled in the art or as otherwise described herein or which otherwise continues to fall within the scop of the invention.

Referring now to FIGURE 1, a feed stream of a liquid phase vacuum bottoms charge stock is passed into an intermediate point of the column 1 through line 2. This feed stream is distributed across the crosssection of the column by a branched array of perforated horizontal conduits 7. The feed stream is denser than the other liquid in the column and therefore descends, passing over a plurality of horizontal liquid-liquid contacting trays 6. A solvent stream comprising butanes and pentanes is fed into the column through line 3 and distributed through a second array of perforated conduits 16. This solvent rises through perforations in the contacting trays countercurrent to the feed stream. The more desirable components of the feed stream, such as lube oil base stock, enter the solvent phase to form an extract stream.Heavier asphaltic materials do not enter the solvent phase and eventually settle to the bottom of the column and are removed in line 4.

The extract stream which is formed in this manner rises above the feed point and passes through a second plurality of contacting trays 6. This is done to remove from a descending stream of asphaltic material formed above whatever materials are soluble in the solvent at the conditions imposed. The extract is then channeled upward toward the center of the column by two symmetrically flow guides 10. The extract stream is thereby caused to pass upward through either of two bundles of U-shaped heat exchange tubes 9 held apart by a circular spacer 8. A horizontal shroud 12 prevents upward passage of the extract between the two bundles. A pair of horizontal baffle plates 11 then directs the extract stream through a second pair or layer of U-shaped heat exchangers.The resulting increase in the temperature of the extract stream causes the precipitation of the asphaltic material which descends through the second group of contacting trays. These baffles and the other baffles and shrouds are preferably slanted downward in a direction opposite the flow of the extract to guide descending asphaltic liquid. Each of the upper pair of heat exchange bundles passes through the side wall on an opposing side of the vessel from bundle directly below it.

The extract stream is then brought to a uniform temperature by passage through a sigmoid mixing zone. The curved path of the mixing zone is created by a second shroud 13 positioned above the tube bundles and aligned with the bundles and by another pair of baffle plates 14. This mixing zone is intended to prevent cold extract liquid from moving past the sides of the heat exchangers and remaining unheated. Above the baffles a settling zone 15 is provided to allow small droplets of asphaltic material to coalesce and settle out of the extract stream, which is then removed in line 5 for separation of the solvent and the extracted hydrocarbons.

FIGURE 2 is presented to more clearly describe the arrangement of the two bundles of heat exchange tubes 9 within the outer vessel of the column 1. The heating fluid is carried to and from the heat exchangers by conduits 17 attached to the outer end or head 18 of each tube bundle. The fluid passes through a stationary tube sheet into the individual U-shaped tubes 9. Only a single tube is illustrated, but a large number of tubes at differing elevations are provided.

These tubes are held in position by the spacer plates 8. The two bundles enter the column from diametrically opposed positions, are parallel and at the same elevation. In this view the preferred chordal shape of the horizontal baffle plates 11 is apparent. These baffles terminate with straight edges which are parallel with each other and the heat exchange tubes. The edges of the baffle plates are under the shroud 13, which also terminates in straight edges parallel to the heat exchange tubes. The shroud is preferably symmetrically positioned above the two heat exchange bundles as shown.

Basic to the deasphalting process is the multi-stage countercurrent contacting of the black oil feed stream with a rising solvent stream. The solvent may be any suitable hydrocarbonaceous material which is a liquid within suitable temperature and pressure ranges for operation of the column, is less dense than the feed stream, and has the ability to readily and selectively dissolve desired components of the feed stream and reject the asphaltic materials. The solvent may be a mixture of a large number of different hydrocarbons having from 5 to 14 carbon atoms per molecule, such as a light naptha having an end boiling point below 93"C. The solvent may be a relatively light hydrocarbon such as ethane, propane, butane, isobutane, hexane and heptane or the corresponding mono-olefinic hydrocarbons.

Preferably, the solvent is comprised of paraffinic hydrocarbons having from 3 to 7 carbon atoms per molecule and is a mixture of two or more hydrocarbons. For instance, a preferred solvent comprises a 50 vol.% mixture of normal butane and isopentane.

Solvent extraction promoting conditions may include a temperature of from 10to. to 316"C. or higher, but the extraction operation is preferably performed within the temperature range of 38 to 204"C. These solvent extraction temperatures refer to the conditions present in the lower section of the apparatus and up to the level of the heat exchangers. A higher temperature is maintained above the heat exchangers. This temperature is from 11 to 56or. above that maintained in the lower section of the apparatus. The pressure utilized within the extraction column will be the same at all points except for pressure differentials caused by liquid flow and the hydrostatic head of the retained liquids.The pressure must be sufficient to maintain liquid phase conditions, with no advantage being apparent to the use of elevated pressures which greatly exceed this minimum. A broad range of suitable pressures is from 8 atm. to 69 atm.. with a preferred range being from 15 to 42 atm. An excess of solvent to charge stock must be maintained. The solvent/charge stock volumetric ratio is suitably from 2:1 to 20:1, preferably from 3:1 to 9:1. The extraction column should be sized to provide a residence time of from 20 to 40 minutes.

It is preferred that the process is performed in a vertical cylindrical column containing a number of stationary horizontal contacting trays. A rotating disk contactor may also be.

used as shown in United States Patent 3,627,675.

For purposes of description, the configuration of various elements of the apparatus will be described in the form preferred for use with the specific process streams set out below by way of example. In this preferred apparatus the liquid-liquid contacting trays are vertically spaced apart by from 46 to 102 cm. and contain a large number of circular perforations in the middle third (by width) of the tray. A larger vertical spacing is used at the charge stock feed point. The perforations may be between 1.3 and 2.5 cm. in diameter.

The preferred tray has no weir to retain liquid on its upper surface, but has a lip which extends downwards, as illustrated in the drawing, by from 10 to 30 cm. A void space for vertical liquid transfer is provided by the deletion of about one-third of the tray on alternating sides of the tray. From 10 to 18 trays are provided between the charge stock feed point and the lower solvent feed point.

An additional two to four trays are provided above the charge stock feed point.

Both the charge stock and the solvent stream are preferably charged to the extraction column through horizontal branched distribution arrays. Suitable arrays for use with the hereinafter exemplary flow rates comprise three parallel 10.2cm. schedule 80 pipes having a total of between 200 to 400 1.6 cm. perforations. The perforations face downward for the feedstock and upward for the solvent. Other distribution means including nozzles and perforated sheets may be employed. Alternatively, these streams may simply be charged into the column without the use of a distributor. A liquid outlet is provided at both the bottom and the top of the vessel. No straining device or collector is necessary and the outlets may be simple openings flush with the vessel's interior surface. A vortex breaker may be installed in the bottom of the vessel above the asphalt outlet.

The outer vessel is of conventional design and comprises a cylindrical outer wall sealed at its upper and lower ends with concave caps. Customary design standards will dictate its wall thickness, etc. Carbon steel is a suitable construction material for the vessel, baffles, trays and distributors under the preferred process conditions. A vessel suitable for the flow rates set out below is about 24 m. high tangent and has an inside diameter of about 4.1 m. This outer vessel and the entire apparatus is divided into upper and lower sections by the charge stock feed point. Preferably this feed point is within the middle vertical one-third of the apparatus.

The upward flow of the solvent-rich extract stream in the upper section of the column is at laminar flow conditions. The shell side heat transfer coefficient is therefore rather low and large surface areas are required for the heat exchangers used for top heating. A considerable amount of tubing is therefore required to be placed within the apparatus. This often requires a large number of joints and connections which tend to develop leaks. Prior art heat exchangers either have inlets at one side of the column and outlets on the other as shown in U. S.

Patent 3,423,308 or consist of U-tubes inserted from just one side of the column.

These configurations are often difficult to service, as for the removal of tube bundles or the replacement of individual tubes, because of the close proximity of a large number of tube endings or of the ends of one or more bundles. It is therefore one objective of the invention to provide an apparatus for solvent deasphalting of black oils in which the heat exchangers are easy to service and which have a high degree of reliability and availability. It is another objective to provide an apparatus which provides uniform top heating of the extract and which promotes the complete precipitation and settling of asphaltic material from the extract stream.

In the subject apparatus the heat exchangers comprise an even number of bundles of U-tubes which are inserted horizontally into the extraction column from opposite sides of the column. Any two bundles at the same elevation do not share the same longitudinal axis. That is, they do not face one another.

Rather, the longitudinal axis of each bundle is horizontally offset from the other. They are, however, parallel and at the same elevation as shown in the drawing. Preferably four such bundles are used in two layers, with the side from which the bundle is inserted also alternating from top to bottom.

That is, the upper of two vertically adjacent bundles is inserted through the opposite side of the column from that directly below.

A series of horizontal baffle plates and shrouds are provided to direct the extract phase through the heat exchange tubes in a substantially upward direction. Preferably, the shrouds and baffles have a configuration similar to that shown in the drawing. The baffles and shrouds have a 15 degree inclination from horizontal. The baffles are preferably imperforate and chordal in shape and terminate with a horizontal straight edge parallel to the longitudinal axis of the heat exchange tubes. The tube bundles are preferably supported by two or more horizontal beams which are perpendicular to the tube bundles. The straight edges of the baffles which are at the same level as the tube bundles are preferably attached to these beams or to supports extending upward from the beams to the bundles.In the preferred embodiment the straight edges of the baffles terminate close to or at the vertical planes passing through the outermost heat exchange tubes. The same is true of the shroud above the upper layer of heat exchangers. Each circular edge of the baffles is preferably welded to the interior surface of the vessel.

Other baffle configurations may be used with the subject process. Possible variations include baffles having different inclinations, shapes or cross-sectional areas and the provision of a limited number of perforations in the baffles.

A lower shroud is operatively positioned between the two layers of heat exchangers to prevent channeling of the extract upward between both pairs of heat exchanger bundles. It preferably has the inverted Ushape illustrated, but may be curved or flat.

This shroud is relatively narrow compared to the upper shroud. In the preferred embodiment the width of the upper shroud is slightly greater than twice the radius of a tube bundle. The upper shroud may be located about 1.8 m. above the bottom of the upper layer of tube bundles, with the next pair of baffles located about 0.8 m. above the shroud. It is preferred that these upper baffles have substantially the same size, location and shape as the baffles adjacent the upper pair of tube bundles. This forms a sigmoid liquid path which mixes the extract stream to a uniform temperature.

Although asphaltic material will be precipitated in the initial passage of the extract stream through the heat exchangers, a portion of the extract may not be heated to an adequate temperature without an additional degree of admixture. This factor must be taken into effect in the design of solvent deasphalting apparatus and processes.

Another consideration is that small globules of the asphaltic material may be formed in the initial heating step, and that these small particles may remain suspended in the rising extract. Furthermore, mixing operations to remove temperature gradients are often not conducive to effective separation, agglomeration and settling of small particles. It is an objective of the subject invention to provide a solvent deasphalting process which effects a mixing of the top heated extract to a uniform temperature and which effects complete and effective settling and separation of the resultant precipitated asphaltic material.

This objective is accomplished in part through the use of a mixing zone, such as that just described, above the heating means used to accomplish the top heating. In addition the extract stream is then passed into a quiscent settling or separation zone.

Preferably, this zone has no cross members, baffles or structural elements which would tend to agitate the extract. A coalescing means such as a mesh blanket may be provided. This zone in its simplest and preferred form is a void cylindrical volume in the upper section of the apparatus as illustrated. It should have a height greater than the radius of the cylindrical outer wall of the extraction column. An upper limit on its height is about three times this radius. In the apparatus for the exemplary flow streams the distance from the top of the uppermost baffle plate to the top of the side wall of the vessel is about 3.8 meters.

Accordingly a preferred embodiment of the invention may be characterized as apparatus useful for solvent deasphalting black oils which comprises (a) a vertically oriented vessel having an internal volume formed by a cylindrical side wall which has an internal surface, the vessel being divided into an upper section and a lower section and having upper and lower ends; (b) a solvent inlet means communicating with the internal volume of the vessel at a first point in the lower section of the vessel and above the lower end of the vessel; (c) a charge stock inlet means communicating with the internal volume of the vessel at a higher second point in the vessel: (d) a first plurality of vertically spaced apart and substantially horizontal liquidliquid contacting trays located within the vessel above the solvent inlet means and below the charge stock inlet means; (e) an indirect heat exchange means located in the upper section of the vessel above the charge stock inlet means and comprising a first and a second bundle of horizontal U-shaped heat exchange tubes which extend across the internal volume of the vessel, each bundle passing through the side wall at only one point, with this point being on the opposite side of the vessel from the point at which the other bundle passes through the side wall and at the same vertical elevation, the two bundles being positioned adjacent each other: (f) a second plurality of vertically spaced apart and substantially horizontal liquid-liquid contacting trays located within the vessel above the charge stock inlet means and below the indirect heat exchange means; (g) a first liquid outlet means communicating with the internal volume of the vessel at the upper end of the vessel, and a second liquid outlet means communicating with the internal volume of the vessel at the lower end of the vessel: (h) a substantially imperforate horizontal shroud operably positioned above the indirect heat exchange means, the longitudinal axis of the shroud being in alignment with the longitudinal axis of the first and the second bundles of heat exchange tubes, the shroud having two opposing curved edges which abut the internal surface of the side wall at points directly above the intersection of the heat exchange means with the side wall, the shroud also having two parallel and opposing substantially straight edges which extend between the curved edges, with the straight edges being separated by a distance greater than the combined width of the two heat exchange bundles, and thereby providing for vertical liquid flow two opposing chordal openings in the cross-section of the vessel defined by the straight edges of the shroud and the internal surface of the side wall; (i) a first pair of chordal liquid baffle plates located within the vessel above the shroud, the first pair of plates being operably positioned on opposing sides of the side wall at points directly above the two chordal openings in the cross-section of the vessel defined by the shroud, with each baffle plate having a curved edge which abuts the internal surface of the side wall and a straight edge which is parallel to the straight edges of the shroud, the vertical distance between the first pair of baffle plates and the upper end of the vessel being greater than the radius of the vessel, with the internal volume of the vessel above the first pair of baffle plates being devoid of structural components which extend across the cross-section of the vessel; and (j) a second pair of chordal liquid baffle plates located within the vessel, the second pair of plates being operably positioned on opposing sides of the side wall at point directly below the two chordal openings in the cross-section of the vessel defined by the shroud, each baffle plate having a curved edge which abuts the internal surface of the side wall and a straight edge which is parallel to the straight edges of the shroud, the straight edge of each baffle plate being located below a horizontal centreline through the first and second bundle heat exchange tubes.

The invention is further illustrated by the following Example.

EXAMPLE The charge stream to the process is a 13,400 barrel per day (BPD) stream of 8.8 API vacuum column bottoms. This stream is admixed with a 2680 BPD stream of solvent and passed into the extraction column at a pressure of about 26 atm. and a temperature of about 110 C. This admixture of a small portion of the total solvent flow with the charge stream is a customary method of decreasing the viscosity of the charge stream in order to more easily pump and heat it. The charge stream is countercurrently contacted with a rising solvent stream comprising 50 vol.% normal butane and 50 vol.% isopen tane at a total solvent to feed volume ratio of about 5.The resulting extraction of the feed stream produces an asphalt bottoms stream removed at a rate of about 3,640 BPD at a temperature of about 107"C. This material has a gravity of approximately 7.5 "APT, a pressure of 26 atm. and an average molecular weight of 176. The resultant extract stream is passed upward above the feed point through three contacting trays and then through two layers of heat exchangers. Each layer comprises two U-tube bundles arranged as illustrated in the drawing. The addition of approximately 25.7 million BTU/hr. heats the solvent rich extract from about 106"C. to 132"C. This causes the precipitation of asphaltic material which eventually descends to the bottom of the column to form part of the asphalt stream.The extract stream is then passed through the sigmoid mixing zone of the preferred apparatus and into a superior settling zone. This produces a deasphalted oil or extract product having a gravity of about 82.6 "API and a temperature of about 132"C.

This stream has a flow rate of about 76,760 BPD and a pressure of about 25 atm. The asphalt bottoms stream is heated, flashed and stripped for the recovery of the solvent.

Other separatory steps recover the solvent from the extract stream. The solvent is then collected and recycled to the extraction column.

Although the apparatus of the present invention is described in the specification (including the claims) with reference to the vessel described as being vertically oriented, it will be appreciated that the invention is not restricted to the apparatus solely when it is in this orientation but also covers apparatus capable of being oriented in this way.

Subject to this explanation, WHAT WE CLAIM IS: 1. A process for solvent deasphalting black oils which comprises the steps of: (a) passing a feed stream comprising liquid hydrocarbonaceous compounds having boiling points above 3 16'C. and containing metals and asphaltenes into a liquid-liquid extraction column at an intermediate feed point and then downward through the extraction column; (b) passing a solvent stream upward through the extraction column countercurrent to the feed stream at extraction promoting conditions and thereby forming a solvent rich extract stream comprising hydrocarbonaceous compounds having boiling points above 316"C.; (c) passing the extract stream upward above the intermediate point through liquidliquid contacting trays countercurrent to a descending asphalt liquid stream;; (d) raising the temperature of the extract stream from 11 to 56 Centigrade degrees by upward passage through a heating zone contained within the extraction column; (e) bringing the extract stream to a uniform temperature by upward passage through a sigmoid mixing zone, and then passing the extract stream upward into a quiescent separation zone and effecting the separation of denser asphaltic materials from the extract stream to thereby produce the asphaltic liquid stream, and removing the extract stream overhead as a product stream comprising a deasphalted portion of the feed stream.

2. A process as claimed in Claim I wherein the extraction promoting conditions include a temperature of from 10"C. to 316"C., a pressure of from 8 to 69 atm. and a solvent/oil volumetric ratio of from 2:1 to 20:1.

3. A process as claimed in Claim 1 or 2 wherein the solvent stream comprises a hydrocarbon having from 3 to 7 carbon atoms per molecule.

4. A process as claimed in Claim 1 or 2 wherein the solvent stream comprises a normally liquid naphtha fraction having an end boiling point below 93"C.

5. A process as claimed in any of claims I to 4 in wherein the separation zone has a height in excess of the radius of the extraction column.

6. A process for the solvent deasphalting of black oil carried out substantially as hereinbefore specifically described or exemplified.

7. An apparatus for use in the deasphalting of black oil by countercurrent solvent extraction, which comprises (a) a vertical separating vessel provided with separate inlets for solvent and charge stock from separate sources at intermediate points, the former below the latter, and outlets for asphaltic material and for deasphalted produce plus solvent in the region of the top and bottom of the vessel, respectively, (b) heat-exchange means located solely above the charge stock inlet and arranged so as to regulate the temperature of essentially all material rising above said inlet, and (c) alternating flow diversion means mounted in the vessel above the heat-exchange means to define a sigmoid mixing zone, whereby substantially uniform mixing of the material passing the heat-exchange means is achieved, (d) the vessel being designed and arranged to define a quiescent settling zone above the sigmoid mixing zone but below the outlet for deasphalted produce plus solvent, said zone being free from flow diversion means causing substantial diversion of the flow of material through it.

8. An apparatus as claimed in claim 7 wherein the heat-exchange means is made up

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (16)

**WARNING** start of CLMS field may overlap end of DESC **. tane at a total solvent to feed volume ratio of about 5. The resulting extraction of the feed stream produces an asphalt bottoms stream removed at a rate of about 3,640 BPD at a temperature of about 107"C. This material has a gravity of approximately 7.5 "APT, a pressure of 26 atm. and an average molecular weight of 176. The resultant extract stream is passed upward above the feed point through three contacting trays and then through two layers of heat exchangers. Each layer comprises two U-tube bundles arranged as illustrated in the drawing.The addition of approximately 25.7 million BTU/hr. heats the solvent rich extract from about 106"C. to 132"C. This causes the precipitation of asphaltic material which eventually descends to the bottom of the column to form part of the asphalt stream. The extract stream is then passed through the sigmoid mixing zone of the preferred apparatus and into a superior settling zone. This produces a deasphalted oil or extract product having a gravity of about 82.6 "API and a temperature of about 132"C. This stream has a flow rate of about 76,760 BPD and a pressure of about 25 atm. The asphalt bottoms stream is heated, flashed and stripped for the recovery of the solvent. Other separatory steps recover the solvent from the extract stream. The solvent is then collected and recycled to the extraction column. Although the apparatus of the present invention is described in the specification (including the claims) with reference to the vessel described as being vertically oriented, it will be appreciated that the invention is not restricted to the apparatus solely when it is in this orientation but also covers apparatus capable of being oriented in this way. Subject to this explanation, WHAT WE CLAIM IS:

1. A process for solvent deasphalting black oils which comprises the steps of: (a) passing a feed stream comprising liquid hydrocarbonaceous compounds having boiling points above 3 16'C. and containing metals and asphaltenes into a liquid-liquid extraction column at an intermediate feed point and then downward through the extraction column; (b) passing a solvent stream upward through the extraction column countercurrent to the feed stream at extraction promoting conditions and thereby forming a solvent rich extract stream comprising hydrocarbonaceous compounds having boiling points above 316"C.; (c) passing the extract stream upward above the intermediate point through liquidliquid contacting trays countercurrent to a descending asphalt liquid stream;; (d) raising the temperature of the extract stream from 11 to 56 Centigrade degrees by upward passage through a heating zone contained within the extraction column; (e) bringing the extract stream to a uniform temperature by upward passage through a sigmoid mixing zone, and then passing the extract stream upward into a quiescent separation zone and effecting the separation of denser asphaltic materials from the extract stream to thereby produce the asphaltic liquid stream, and removing the extract stream overhead as a product stream comprising a deasphalted portion of the feed stream.

2. A process as claimed in Claim I wherein the extraction promoting conditions include a temperature of from 10"C. to 316"C., a pressure of from 8 to 69 atm. and a solvent/oil volumetric ratio of from 2:1 to 20:1.

3. A process as claimed in Claim 1 or 2 wherein the solvent stream comprises a hydrocarbon having from 3 to 7 carbon atoms per molecule.

4. A process as claimed in Claim 1 or 2 wherein the solvent stream comprises a normally liquid naphtha fraction having an end boiling point below 93"C.

5. A process as claimed in any of claims I to 4 in wherein the separation zone has a height in excess of the radius of the extraction column.

6. A process for the solvent deasphalting of black oil carried out substantially as hereinbefore specifically described or exemplified.

7. An apparatus for use in the deasphalting of black oil by countercurrent solvent extraction, which comprises (a) a vertical separating vessel provided with separate inlets for solvent and charge stock from separate sources at intermediate points, the former below the latter, and outlets for asphaltic material and for deasphalted produce plus solvent in the region of the top and bottom of the vessel, respectively, (b) heat-exchange means located solely above the charge stock inlet and arranged so as to regulate the temperature of essentially all material rising above said inlet, and (c) alternating flow diversion means mounted in the vessel above the heat-exchange means to define a sigmoid mixing zone, whereby substantially uniform mixing of the material passing the heat-exchange means is achieved, (d) the vessel being designed and arranged to define a quiescent settling zone above the sigmoid mixing zone but below the outlet for deasphalted produce plus solvent, said zone being free from flow diversion means causing substantial diversion of the flow of material through it.

8. An apparatus as claimed in claim 7 wherein the heat-exchange means is made up

of at least one layer of heat-exchange elements which are formed by two bundles of U-shaped heat-exchange tubes lying in the same horizontal plane on opposite sides of the column.

9. An apparatus as claimed in claim 8 wherein the sigmoid mixing zone is constituted by a centrally disposed horizontal shroud located directly above the heatexchange tubes and two horizontal baffles attached to the wall of the column above the shroud and adjacent to the shroud's straight exterior edges.

10. An apparatus useful for solvent deasphalting black oils which comprises: (a) a vertically oriented vessel having an internal volume formed by a cylindrical side wall which has an internal surface, the vessel being divided into an upper section and a lower section and having upper and lower ends; (b) a solvent inlet means communicating with the internal volume of the vessel at a first point in the lower section of the vessel and above the lower end of the vessel; (c) a charge stock inlet means communicating with the internal volume of the vessel at a higher second point in the vessel; (d) a first plurality of vertically spaced apart and substantially horizontal liquidliquid contacting trays located within the vessel above the solvent inlet means and below the charge stock inlet means;; (e) an indirect heat exchange means located in the upper section of the vessel above the charge stock inlet means and comprising a first and second bundle of horizontal Ushaped heat exchange tubes which extend across the internal volume of the vessel, each bundle passing through the side wall at only one point, with this point being on the opposite side of the vessel from the point at which the other bundle passes through the side wall and at the same vertical elevation, the two bundles being positioned adjacent each other:: (f) a second plurality of vertically spaced apart and substantially horizontal liquidliquid contacting trays located within the vessel above the charge stock inlet means and below the indirect heat exchange means; (g) a first liquid outlet means communicating with the internal volume of the vessel at the upper end of the vessel, and a second liquid outlet means communicating with the internal volume of the vessel at the lower end of the vessel;; (h) a substantially imperforate horizontal shroud operably positioned above the indirect heat exchange means, the longitudinal axis of the shroud being in alignment with the longitudinal axis of the first and the second bundles of heat exchange tubes, the shroud having two opposing curved edges which abut the internal surface of the side wall at points directly above the intersection of the heat exchange means with the side wall, the shroud also having two parallel and opposing substantially straight edges which extend between the curved edges, with the straight edges being separated by a distance greater than the combined width of the two heat exchange bundles, and thereby providing for vertical liquid flow two opposing chordal openings in the cross-section of the vessel defined by the straight edges of the shroud and the internal surface of the side wall;; (i) a first pair of chordal liquid baffle plates located within the vessel above the shroud, the first pair of plates being operably positioned on opposing sides of the side wall at points directly above the two chordal openings in the cross-section of the vessel defined by the shroud, with each baffle plate having a curved edge which abuts the internal surface of the side wall and a straight edge which is parallel to the straight edges of the shroud, the vertical distance between the first pair of baffle plates and the upper end of the vessel being greater than the radius of the vessel, with the internal volumne of the vessel above the first pair of baffle plates being devoid of structural components which extend across the cross-section of the vessel; and (j) a second pair of chordal liquid baffle plates located within the vessel, the second pair of plates being operably positioned on opposing sides of the side wall at points directly below the two chordal openings in the cross-section of the vessel defined by the shroud, each baffle plate having a curved edge which abuts the internal surface of the side wall and a straight edge which is parallel to the straight edges of the shroud, the straight edge of each baffle plate being located below a horizontal centerline through the first and second bundle heat exchange tubes, whereby a stream of solvent may be fed to the lower section of the vessel through the solvent inlet means to countercurrently contact a black oil charged through the charge stock inlet means in the first plurality of contacting trays and then to countercurrently contact a second liquid phase in the second plurality of contacting trays, with the resulting extract stream being caused to pass upward through the heat exchange means by the action of the second pair of baffle plates and admixed to a uniform temperature by the action of the shroud and the first pair of baffle plates, with the extract stream then being retained within a quiescent settling zone above the first pair of baffle plates before being discharged from the vessel.

11. An apparatus as claimed in Claim 10 wherein there is provided a third and a fourth bundle of horizontal U-shaped heat exchange tubes located directly below and aligned with the first and the second bundles at a point below the second pair of chordal liquid baffle plates, the third and the fourth bundles passing through the side wall on opposing sides of the vessel from the bundle located directly above.

12. An apparatus as claimed in claim 11 wherein a second horizontal shroud is operably positioned below the first and the second bundles of heat exchanger tubes and above the third and fourth bundles, the longitudinal axis of the second shroud being aligned parallel to the straight edges of the first shroud, the second shroud having two parallel straight edges which are parallel to the longitudinal axis of the first shroud and which are separated by a distance which is less than that between the straight edges of the first shroud.

13. Apparatus as claimed in claim 7 and substantially as illustrated in the accompanying drawing or hereinbefore specifically described.

14. A process as claimed in claim I when carried out in apparatus as claimed in any of claims 7 to 13.

15. A deasphalted material when obtained by a process as claimed in any of claims I to 6 or 14 or by use of an apparatus as claimed in any of claims 7 to 13.

16. A petroleum product when obtained from a deasphalted material as claimed in claim 15 by a refinery or hydrocarbon conversion technique.