IMPROVEMENTS IN AND RELATING TO FLUIDIC CONTACTORS

Abstract: A fluidic contactor comprising a vortex stage and a separator stage. The vortex stage is in the form of a vortex chamber (7) whereby fluids of different densities when introduced into the chamber (7) through one or more tangential inlets (9) are caused to swirl through the chamber before passing into the separator stage which is in the form of a column (6) forming an extension of an axial outlet from the vortex chamber. In passing along the column (6) the fluids become separated and emerge through separated outlets (11, 12) at the end of the column remote from the chamber. The fluids can be mixed together before entry into the chamber or separate fluids can be intimately mixed together in swirling through the chamber, in each case to permit mass transfer of constituents between the fluids.

Description: The present invention concerns fluidic contactors. In the solvent extraction process a liquid to be treated is thoroughly mixed with an appropriate other liquid to achieve mass transfer of constituents from the liquid being treated to the other liquid; this being followed by the physical separation of the two immiscible liquids. Apparatus for mixing and then separating the two liquids is termed a contactor and existing forms of known contactors include packed columns, which can be pulsed, mixer-settlers, and centrifugal contactors. Centrifugal contactors are efficient but are mechanically complex. Consequently they are expensive to manufacture and to maintain in operation. The aim of the present invention is to provide a fluidic contactor which functions in a manner analogous to that of the centrifugal contactor and which avoids the disadvantages associated with the centrifugal contactor. US-A-3,261,593 discloses at least a pair of adjacent vortex chambers inducing opposite rotation in liquids to be mixed and a mixing chamber to receive the oppositely rotating liquids from the vortex chambers. In GB-A-746,814 a flow of dirty oil is caused to swirl up a cylindrical cavity whereby dirt particles in the oil are thrown against the wall of the cavity whilst being carried upwardly by the flow. According to the present invention a fluidic contactor includes a mixing stage and a separator stage, in which the mixing stage comprises a vortex chamber having at least one tangential inlet and an axial outlet, the separator stage comprises a channel enclosed by a tubular member, forming an extension of the axial outlet and having at or adjacent its end remote from the vortex chamber spaced apart openings whereby fluids of different densities introduced into the chamber through the inlet or inlets are mixed by swirling through the chamber and the swirling flow from the chamber passing along the channel effects separation of the fluids with the separated fluids emerging from the channel at the spaced apart openings. Preferably the chamber and the channel form a unit and a plurality of units can be joined together to form a cascade. The invention will be described further, by way of example, with reference to the accompanying diagrammatic drawings; in which:- Figure 1 is a diagrammatic longitudinal sectional elevation of an embodiment of a fluidic contactor; Figure 2 is a section on A-A in Figure 1; Figure 3 is a diagrammatic longitudinal sectional elevation of an alternative embodiment of a fluidic contactor; Figure 4 is a schematic arrangement of a plurality of fluidic contactors arranged for cross-current operation; and Figure 5 is a schematic arrangement of a plurality of fluidic contactors arranged for counter-current operation. A fluidic contactor depicted in the drawings is formed as a unit from a three-part housing, namely, a base member 1, a tubular member 2 having a flange 3 to seat on the base member 1 and a closure member 4 carried on the tubular member 2. The inner wall of the tubular member 2 can be parallel or inclined to its axis. The members can be bolted or otherwise secured together into an integral assembly. A central, upright stem 5, which can be conical or cylindrical in section is located on the base member 1 and extends axially for the full or partial length of the tubular member 2 to form an annular channel 6 within the tubular member. The opposing faces of the base member 1 and the flange 3 are recessed and cooperate to form a chamber 7, the vortex chamber, when the base member 1 and the flange 3 are brought into abutment at their mating outer radial surface portions 8. The axial cross section through the vortex chamber can have a suitable profile which may be other than parallel sided. Diametrically located ports 9 and 10 are provided to introduce tangential flows into the vortex chamber 7. At its end opposite the base member 2 the closure member 4 cooperates with the end of the stem 5 and the end of the annular channel 6 to form inner and outer annular exit openings 11 and 12 respectively. The opening 11 communicates with outlet passage 13. Similarly, the opening 12 communicates by way of an annular weir 14 and an annular compartment 15 formed in the body of the member 2 with an outlet passage 16. In operation a first liquid is fed into the vortex chamber 7 through the tangential inlet port 9 and a second liquid is fed into the chamber 7 through the tangential inlet port 10. For example, the liquid introduced at the port 10 can be an organic solvent such as tributyl phosphate in odourless kerosene as used in the reprocessing of nuclear fuel and the liquid introduced at the port 9 can be an aqueous phase comprising nuclear fuel dissolved in nitric acid. Due to the tangential inlets swirling of the two liquids occurs in the chamber 7 to effect thorough mixing whereby mass transfer of constituents can take place between the liquids. The swirling flow passes from the chamber 7 to spiral up the annular channel 6. Due to centrepetal acceleration and the difference in density between the two liquids, on rising up the channel, the lighter liquid moves towards the stem 5 and the heavier liquid moves towards the wall of the channel 6. In the aforementioned example the solvent, being the lighter liquid, emerges at the top of the channel through the annular opening 11 and the outlet passage 13. The heavier aqueous liquid emerges through the annular opening 12 and passage 16. Although the vortex chamber 7 is shown having two tangential inlets it will be realised that the number of inlets is a matter of choice. For example, in situations where the liquids are in admixture prior to entry into the chamber it is possible to utilise a chamber having a single tangential inlet. An alternative embodiment of a contactor is shown in Figure 3. As in the embodiment of Figure 1, the contactor comprises a vortex chamber 7 and an annular channel 6. However, the geometrical profiles at the upper end of the tube have been altered whereby to avoid sharp edges and abrupt changes in flow paths. In Figure 3 the profiles are such as to encourage stream-line flows. As before, the swirling flow from the chamber 7 spirals up the channel 6 and the lighter or less dense phase moves towards the centre of the channel and the heavier phase moves towards the wall of the channel. The heavier phase tends to follow a path indicated by the arrows 17 to collect at the bottom of chamber from which it can be discharged through outlet 18. The lighter phase tends to follow a path indicated by the arrows 19 and flows smoothly into the upper regions of the chamber from which it can be discharged through outlet 20. Alternatively, the outlet 20 can be positioned in the upper closure member 21. It will be appreciated that in use the contactor is completely filled and that an interface between the phases forms in compartment 22. The liquids can be introduced into the chamber by means of a known fluidic pump system. Such a pump system does not include moving parts and is particularly advantageous when pumping toxic and hazardous liquids. A plurality of contactors can be connected to provide a cross flow or counter flow cascade and the operating principles are equally applicable to any combination of gaseous and liquid inlet flows. A single contactor or a plurality of contactors can be orientated in any suitable plane. The mass transfer of constituents between the fluids followed by the physical separation of the fluids will be determined by the degree of mixing and the residence time in the contactor. To obtain effective mass transfer it is possible to employ a cascade of individual contactors which can be connected together, for example, in a cross-current or a counter-current mode. Figure 4 depicts schematically a cascade of contactors 25 arranged for cross-current operation. For a better understanding of the manner of the connections between the individual contactors the inlets and outlets thereof are indicated by the reference numerals employed in Figure 1. Thus a first fluid driven by a first fluidic pump in flow line 26 flows through inlet 9 into the first contactor of the cascade and a second fluid driven along flow line 27 by a second fluidic pump flows through inlet 10 into the first contactor. As example only and with reference to the reprocessing of nuclear fuel, the first fluid can be an aqueous phase comprising nuclear fuel dissolved in nitric acid and the second fluid can be an organic solvent such as tributyl phosphate in odourless kerosene. It will be seen from Figure 4 that fresh solvent is fed into each individual contact or as the aqueous phase flows through the contactors. Alternatively, and as shown in Figure 5, contactors 30 can be arranged for counter-current operation. In this arrangement the aqueous phase flow is denoted by the full line and the solvent phase flow is denoted by the dotted line. The phases are again driven by fluidic pumps and in order to create favourable driving pressures across the cascade it is desirable to provide interstage pumping. Such interstage pumping can conveniently be provided by jet pumps 31. A jet pump is a three terminal device in which an inlet flow at a first terminal passes through a nozzle or jet to enter a co-axial diffuser section spaced from the nozzle or jet and forming a second terminal of the device. A third terminal communicates with the interspace between the nozzle and diffuser with the result that flow therefrom is entrained in the flow from the nozzle to the diffuser. Thus, with reference to Figure 5, aqueous flow pumped along line 32 is connected to the first terminal of the jet pump to entrain solvent flow emerging from the preceding contactor in the cascade. In this arrangement each contactor is provided with a single inlet which receives the outflow from the respective jet pump. At the opposite end of the cascade the reverse occurs in that the solvent flow pumped along line 33 is connected to the first terminal of the associated jet pump to entrain aqueous flow from the next following contactor in the cascade. It will be realised that the number of individual contactors in the cascades can be chosen to suit working requirements and is not limited to four as shown in the drawings.

Claims: A fluidic contactor including a mixing stage and a separator stage characterised in that the mixing stage comprises a vortex chamber (7) having at least one tangential inlet (9) and an axial outlet, the separator stage comprises a channel (6) enclosed by a tubular member (2), forming an extension of the axial outlet and having at or adjacent its end remote from the vortex chamber (7) spaced apart openings (11,12) whereby fluids of different densities introduced into the chamber (7) through the inlet or inlets (9, 10) are mixed by swirling through the chamber (7) and the swirling flow from the chamber (7) passing along the channel (6) effects separation of the fluids with the separated fluids emerging from the channel (6) at the spaced apart openings (11, 12). A fluidic contactor according to Claim 1 characterised in that the vortex chamber (7) and the channel (6) are comprised in integral assembly (1, 2). A fluidic contactor according to Claim 1 or 2 characterised in that the channel (6) is annular in section. A fluidic contactor according to Claim 1, 2 or 3 characterised by surfaces defining streamline flow paths (17,19) for the fluids emerging from the channel (6). A fluidic contactor according to Claim 2 characterised by a plurality of integral assemblies (25,30) forming a cascade. A fluidic contactor according to Claim 5 characterised in that the assemblies are joined together in a cross-current mode. A fluidic contactor according to Claim 5 characterised in that the assemblies are joined together in a counter-current mode.

Inventors: BOWE, MICHAEL JOSEPH, ORUH, SAMUEL NDUKA, SINGH, JASWANT
Applicants: UNITED KINGDOM ATOMIC ENERGY AUTHORITY
Application year: 1985
Main classification: B01D11
IPC codes: G21C19, B01D17, B01D11