GB2033244A

GB2033244A - Solvent Extraction of Solids and Slurries

Info

Publication number: GB2033244A
Application number: GB7932833A
Authority: GB
Original assignee: RTL Contactor Holding SA
Current assignee: RTL Contactor Holding SA
Priority date: 1978-09-22
Filing date: 1979-09-21
Publication date: 1980-05-21
Also published as: GB2033244B

Abstract

A solids/liquid contactor comprises a container through which solids-containing liquid phases flow in countercurrent. A rotor 14 is mounted for rotation in the container and a plurality of discs 13, dividing the container into interconnected compartments, rotate therewith. A plurality of buckets (not shown) between the discs carry material from one phase to the other phase during rotation. The contactor is mounted so that the angle the axis makes with the horizontal can be adjusted, e.g. by jacking screw 22. A preferred use of the contactor is in extracting hydrocarbons from tar-sands. <IMAGE>

Description

SPECIFICATION Apparatus For and Methods of Contacting Materials This invention relates to apparatus for, and methods of, contacting materials, and is particularly concerned with a solids/liquid or slurry/liquid contactor and contacting method.

Thus the invention may be applied, for example, to the treatment of oil-sand as with a solvent for the extraction of bitumen oils constituents of the oil-sand, as described for example in British Patent Applications Nos. 32989/76 and 2939/77.

More specifically, the invention is concerned with a solids/liquid contactor which comprises a container through which the phases can flow, a rotor within the container which rotor is mounted for rotation within or with, the container and which includes a plurality of discs which divide the container into a series of compartments, a passage or passages in and/or round each disc enabling the phases to move from compartment to compartment, and, for each of at least some of the compartments, a plurality of receptacles extending between the discs of the compartment and designed to receive material of one phase and to discharge it into the other phase as the rotor turns. Such a contactor will be referred to hereinafter as "a contactor of the type described" and is exemplified by the apparatus described and illustrated in British Patent Specification No.

972,035.

When attempting to contact a solids phase, such as tar-sands, with a liquid phase, such as an extractant for the tarsands, flowing countercurrent thereto in such a contactor, there is a large pressure drop from one end to the other end of the contactor. The extent of the pressure drop will depend on such factors as the input pressures of the phases, the rate of throughput, the speed of rotation of the contactor and the percentage solids present. However the overall effect will be to incline the interface between the phases so that the heavier phase, e.g. an aqueous tar-sands slurry, has a reduced cross-section at its outlet end and therefore outlets at high speed.

Conversely the extractant is entering at that end of the contactor with a relatively low speed. This results in a danger of entraining extractant in the discharging slurry with loss of extractant and lowering in the efficiency of the process.

According to one aspect of the present invention, we provide a solids/liquid contactor comprising a container through which solids containing liquid phases can flow in countercurrent, a rotor mounted for rotation within or with the container, a plurality of discs for rotation with the rotor and dividing the container into a plurality of interconnected compartments and a plurality of receptacles extending between the discs of at least some of the compartments and intended to transfer material of one phase to the other phase during rotation, the contactor being mounted so as to enable. the angle the axis makes to the horizontal to be adjusted.

Preferably there are passages in each of at least some of the discs, which passages are aligned with receptacles on opposite sides of the disc, the passages in some of the discs being staggered in relation to those of others; the passages permit the movement of solids from receptacles of one compartment to the receptacles of an adjacent compartment and enhance the flow of phases through the contactor. Such a contactor is described inter alia in U.K. specification No. 7917804.

Preferably, the passages in successive discs are staggered so that, in any one compartment, some of the receptacles are connected to the aligned receptacles in one adjacent compartment and the receptacles not so connected are connected to receptacles in the other adjacent compartment.

Preferably, provision may also be made for restricting the flow of the lower density phase through the gaps between the discs and the container at the top of the contactor. Thus, baffles may be appropriately carried by the container to overlie the discs at the upper portion of the contactor. Alternatively, the rotor may be mounted eccentrically of the container with the result that the container-discs gaps are greater at the top of the container than at the bottom.

The invention also includes a method of treating solids with a treatment liquid in which the solids with a carrier liquid are passed through a contactor as specified above with the container mounted so that its axis makes an angle with the horizontal, a treatment liquid, which is immiscible with the carrier liquid, is passed through the contactor in counter-direction, the treated solids and carrier liquid are removed at or adjacent one end of the contactor and the treatment liquid at or adjacent the other end. Preferably the container is mounted so that that end at which the solids enters and the treatment liquid leaves is higher than that end at which the solids leaves and the treatment liquid enters.The invention can suitably be applied to a slurry of oil-sand and water and a treatment liquid consisting of, or including, a solvent for the bitumen oils of the oil-sand be passed counter-current through the contactor in order to extract the bitumen oils.

In a preferred feature of the invention, the receptacles in one or more of the compartments are either omitted or are arranged on a smaller diameter than in other compartments, to form a settling chamber in which the solids can settle. In any compartment in which the buckets are omitted or on a smaller diameter, there may be stirring rods to retain the solids in suspension.

The invention will be more readily understood by way of example from the following description of contactors in accordance therewith, reference being made to the accompanying drawings, in which:~ Figure 1 is an axial section through a contactor of the type described, and Figure 2 is a detail of a screw jack arrangement.

The contactor shown in the drawings is employed for contacting solids, or a slurry, with a liquid. The example to be described concerns the solvent extraction of oil-sand but the treatment of other solids can be similarly accomplished.

The contactor comprises a stationary, cylindrical, container or shell 12, and a rotor within the shell consisting of a number of radially arranged, and spaced, circular discs 13, which are carried on a central shaft 14 and the edges of which are spaced from the inner wall of the container 12 to leave an annular gap between the rotor and the container. The rotor shaft is mounted in bearings 1 5, 16 in the end plates 17, 18 of the container and is driven at one end.

The common axis of the shell 12 and the rotor is inclined downwardly to the solids discharge end by a slight angle to the horizontal, e.g. 70.

The inclination of the axis assists the movement of the solids through and out of the contactor and preferably the contactor is mounted in such a way that the inclination can be adjusted to suit the solids being treated. Thus by adjustment of the axis, optimum cross sectional areas can be achieved at the ends of the contactor. The interface between the phases may in fact be adjusted so that it is always above the axis or above the axis in the region of the solids discharge. The axis is adjusted by mounting the shell 12 on a base plate 19 and the rotor bearings on pedestals 20, 21. The base plate is provided at its left-hand end with two screw jacks which enable that end to be raised relative to the ground or foundations on which base plate 1 9 is mounted. A detail of one of the screw jack mountings is shown in Figure 2.Thus a jacking screw 22 can be adjusted via a welded nut 23 (Figure 1) with respect to a nut 24 welded to an angled plate 25 welded to base plate 19. The foot of screw 22 can be provided with any conventional foot device for supporting the lefthand end of the contactor assembly.

A slurry of oil-sand and water is continuously introduced into the container 12 through a connection 26 at one end and is discharged through connection 27 at the other, connections 26, 27 being near the bottom of the container.

Simultaneously, a treatment stream which is immiscible with water and which consists of a solvent for the bitumen oils of the oil-sand, is fed into the other end through connection 28 and passes in countercurrent to the flow of the oilsand slurry, before leaving the container through connection 29 at the first end. The two streams~ the slurry and the treatment liquid-move countercurrent through the container 12 in two separate phases, the lighter solvent phase being uppermost and the interface being approximately at the axis of the container.

Each of the compartments, into which the container 12 is divided by the discs 13, carries receptacles or buckets, for example, six, which buckets extend between the discs. There is the same number of buckets in each compartment and corresponding buckets in the compartments are aligned with one another in a direction parallel to the rotor axis. As the rotor turns, the buckets raise the lower phase and discharge it into the upper phase so that the tar-sand material comes into intimate contact with the solvent. The buckets also draw the lighter phase downwards into the heavier phase.

The oil-sand solids are largely carried through the contactor with the flow of the water of the slurry. In order to increase the movement of the oil-sand solids through the container 12 (from left to right in Figure 1), each of the discs 1 3 may have passages aligned with buckets 22 on either side of the disc. In each compartment, every second bucket is preferably aligned with passages of one disc and the other three buckets are aligned with passages in the other disc.

As the rotor turns, some of the oil-sand solids scooped up by the buckets of each compartment migrates into the buckets of the next compartment so that flow of the solids through the contactor is not limited to the annular gap between the discs and the shell. Staggering the passages in successive discs ensures that the solids are frequently showered from the buckets through the solvent phase during their passage through the contactor.

Although not illustrated in the drawings, the buckets may be formed by bucket tubes which pass from end to end through the contactor and which are arranged parallel to the rotor axis. In that case, each bucket tube passes through the discs 13 via slots, which closely confine the tube and which prevent the passage of liquids or solids therethrough, and via passages which permit that passage, the slots alternating with the passages in successive discs. As before the passages are relatively staggered in successive discs in order to prevent the possibility of the solids remaining in the bucket tubes and passing therein the entire length or a substantial part of the length of the contactor.

It is desirable that a substantial proportion of the treatment liquid entered through connection 28 should pass through the passages in the discs 13 so as to obtain proper contacting with the solids-containing phase. Particularly where the annular gaps between the discs 13 and the shell 1 2 are large to facilitate the movement of the solids, there is the danger that the treatment liquid will by-pass the compartments by flowing through the annular gaps at the top of the contactor. To avoid that danger, the shell may carry baffles which obstruct the gaps only at the upper half of the contactor. The baffles may be made of flexible material and each may extend over about two thirds of the periphery of the upper half of the shell. Each baffle may be formed with a part-annular slot in which the rim of the disc is received without contact so that the baffle extends below the rim on either side.

The gaps between the edges of the disc and the internal wall ofthe#hejt#atthetap of the contactor can alternatively be restricted to encourage flow of the treatment liquid through the passages in the discs by mounting the rotor slightly eccentrically of the shell i.e. the rotor axis is located slightly above the shell axis so that the gaps between the discs and shell are greater at the bottom of the contactor than at the top.

Figure 1 shows that at the solids discharge end of the contactor a chamber is formed between the end plate 1 6 of the shell 12 and the end plate of the rotor to allow phase settlement prior to solids discharge so that treatment liquid is not carried out with the solids. In some cases, as in the treatment of oil-sands, a larger settlement chamber may be needed for that purpose. Then the buckets in the last compartment or compartments of the rotor may be dispensed with. However the rods (not shown) on which the buckets are carried and which extend from end to end of the rotor are advantageously retained to act as stirrers which maintain the solids in suspension and thus enable the solids to be discharged from the contactor.A settlement chamber at the solids inlet end of the contactor may be similarly modified; further, where a discharge occurs intermediate the ends of the contactor as described for example in our U.K.

Patent application No. 35906/78, a similar settlement chamber may be formed by the omission of the buckets in an intermediate chamber or chambers while retaining the rods for stirring.

Instead of removing the buckets entirely from the settling compartment or compartments, buckets may be provided but on a smaller diameter than the buckets in the remaining compartments. In those settling compartment or compartments, the buckets scoop up little or none of the solids, which therefore do not entrain and remove from the contactor the treatment liquid.

At the same time the buckets cause intermingling of the treatment liquid with the carrier liquid for the solids. That arrangement is particularly useful where the solids originally carry a constituent to be removed but are spent by the time they arrive at the settlement compartments. Even when the settlement compartments have buckets on a reduced diameter, the rods are continued into those compartments to act as stirrers for the solids.

This expedient of having buckets on a reduced diameter can be utilised in settlement compartments at either end of the rotor, and/or in compartments intermediate the rotor ends where materials are injected into or drawn off from the contactor; the location of the buckets away from the peripheries of the discs has the added advantage that it facilitates the introduction or removal of flows of e.g. reagent, in that it enlarges the space between the shell and the buckets available for the necessary injection and/or drawoff equipment.

Some compartments of the rotor may have a first set of buckets arranged as shown in the drawings and a second set on a reduced diameter.

That arrangement is of value where, for example, concurrent leaching and stripping is to be effected as described in U.K. patent application No.

49178/77.

Claims

1. A solids/liquid contactor comprising a container through which solids containing liquid phases can flow in countercurrent, a rotor mounted for rotation within or with the container, a plurality of discs for rotation with the rotor and dividing the container into a plurality of interconnected compartments and a plurality of receptacles extending between the discs of at least some of the compartments and intended to transfer material of one phase to the other phase during rotation, the contactor being mounted so as to enable the angle the axis makes to the horizontal to be adjusted.

2. A contactor according to claim 1, wherein the container is mounted so that that end at which the solids enters and can be adjusted to be higher than that end at which the solids leaves the container.

3. A contactor according to claim 1 or 2, wherein one end of the container is mounted on screw jacks.

4. A contactor according to any one of claims 1 to 3, wherein there are passages in at least some of the discs aligned with receptacles on opposite sides of the disc, the passages in some of the discs being staggered in relation to those of the others.

5. A contactor according to any one of claims 1 to 4, wherein means are provided for restricting the flow of the lower density phase through gaps between the discs and the container at the top of the contactor.

6. A contactor according to claim 5, wherein the means comprises baffles carried by the container to overlie the discs at the upper portion of the contactor.

7. A contactor according to claim 5, wherein the means comprises mounting the rotor eccentrically of the container.

8. A contactor according to any one of the preceding claims, wherein the receptacles in one or more of the compartments are either omitted or arranged on a smaller diameter than in the other compartments to form a settling chamber.

9. A solids/liquid contactor according to claim 1, substantially as described herein with reference to the drawings.

10. A method of treating solids with a treatment liquid in which the solids with a carrier liquid are passed through a contactor in accordance with any one of the preceding claims with the container mounted so that its axis makes an angle with the horizontal, a treatment liquid, immiscible with the carrier liquid, is passed through the contactor in counter-direction, the treated solids and carrier liquid are removed at or adjacent one end of the contactor and the treatment liquid at or adjacent the other end of the contactor.

11. A method according to claim 10, wherein the solids and carrier liquid comprises a slurry of oil-sands in water and the treatment liquid comprises a solvent for the bitumen oils of the oilsands.