GB2202166A

GB2202166A - Fluid-fluid contacting apparatus

Info

Publication number: GB2202166A
Application number: GB8706251A
Authority: GB
Inventors: John Desmond Thornton
Original assignee: UK Atomic Energy Authority
Current assignee: UK Atomic Energy Authority
Priority date: 1987-03-17
Filing date: 1987-03-17
Publication date: 1988-09-21
Anticipated expiration: 2007-03-17
Also published as: DE8803095U1; JPS63164902U; GB8706251D0; GB2202166B; JPH0630241Y2

Abstract

Apparatus for contacting immiscible or partially miscible fluids comprises an injector nozzle (14) for producing a dispersion of fluids entering at inlets (10, 12), a contacting section (20) for maintaining the resulting two phase dispersion for a sufficient holding time to allow extraction to proceed as far as is required, and a hydrocyclone (26) for effecting separation of the two phases. Various embodiments of the baffles 22 in the contacting section and different arrangements of the contacting section, injector and cyclone are described. <IMAGE>

Description

Fluid - fluid contacting apparatus This invention relates to contacting apparatus for contacting immiscible or partially miscible fluids, for example in solvent extraction processes.

According to the present invention there is provided apparatus for contacting immiscible or partially miscible fluids comprising a mixing device for effecting, by virtue of the initial kinetic energy of at least one of the fluids, mixing of the fluids to produce a dispersion, cyclone means for separating the fluid components of the dispersion from one another, and a contacting section for conducting the dispersion from the mixing device to the cyclone means.

The mixing device, cyclone means and contacting section of the invention need not incorporate any moving parts for bringing the fluids into intimate contact, agitating them or separating them, ie no mechanical energy is required other than that imparted to at least one of the fluids prior to entry into the mixing device.

The mixing device may comprise a fluidic injector.

The contacting section is preferably designed so as to subject the dispersion to turbulence and may incorporate turbulence-promoting elements and/or subject the dispersion to repeated or continual change of flow direction as the dispersion passes from the mixing device to the cyclone means.

The turbulence-promoting elements may for instance comprise internal baffles and/or randomly or orderly-arranged packing elements within the contact section.

Preferably, the residence time of the dispersion within the contacting section is substantially greater (preferably by at least one order of magnitude) than in the mixing device and/or the cyclone means.

The flow path defined by the contacting section may be of meandering or labyrinthine configuration to achieve, within a compact construction, a relatively long residence time in which the fluids are in initimate contact.

A feature of the invention is that the residence time for intimate contact between the fluids may be provided primarily by the contacting section. This allows the fluids to be fed into the cyclone means at a relatively high velocity as is desirable for efficient separation of the fluid components. In the past, the practice has been to feed the dispersion directly into the cyclone means with the consequence that the time available for intimate contact between the fluids is governed by the velocity of feed into the cyclone means.

,Thus, attempts to secure relatively extended residence times have involved reduced feed velocities and hence less efficient separation, ie increased residence time results in reduced separation efficiency and vice versa.

To promote further understanding of the invention, embodiments thereof will now be described by way of example only with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic view of contacting apparatus in accordance with the invention; Figure 2 illustrates a modification of the separating section of the apparatus; Figure 3 illustrates another embodiment of the apparatus; Figure 4 illustrates a further embodiment of the apparatus; Figure 5 is a sectional view in the direction 5-5 in Figure 4t Figure 6 is a diagrammatic view illustrating a modified form of contacting section; Figure 7 is a plan view of the mixing section of Figure 6; and Figures 8 and 9 are diagrammatic views of further,, modified forms of contacting section.

Referring to Figure 1, two fluids, veg a solvent such as tributyl phosphate in an odourless kerosene diluent and an aqueous solution derived from nitric acid treatment of irradiated nuclear fuel, are mixed in order to carry out solvent extraction of plutonium and/or uranium from the aqueous solution. One liquid is pumped via inlet nozzle 12 so that it flows through nozzles 16 and into nozzle 18. The fluid velocity is at a maximum in the region of the gap between nozzles 16, 18 and hence the pressure is at a minimum whereby the second liquid is induced into the injector 14 via inlet 10 thus creating a dispersion of the two liquids within the injector.

The two phase dispersion then passes into a contacting section 20 which is designed to provide the necessary holding time for the extraction to proceed as far as is required. If the volume of the section 20 is V cubic metres then the holding time t is given by: t= V/(fl + f2) where f1 and f2 are the volumetric flow rates (cubic metres/sec) of the two phases.

In the embodiment of Figure 1, the contacting section comprises an elongate chamber enclosing a number of flow direction-changing elements 22 which are in the form of helical ribbon baffles mounted on a central rod 24 in such a way that adjacent helical baffle sets are wound in opposite directions to cause the dispersion to periodically change direction as it passes along the contacting chamber. Intense mixing occurs at each point where the direction of spin changes and the contacting chamber is provided with a sufficient number of helical baffles to maintain a high level of turbulence in the mixed phases.

After leaving the contacting chamber, the mixed phases enter the hydrocyclone 26 generally tangentially so as to form a vortex, the cyclone 26 including a suitably located tube 28 which functions as a vortex finder. The spin imparted to the fluids in the cyclone results in centrifugal separation of the two phases, one phase leaving the cyclone via outlet 30 and the other phase leaving via the vortex finder 28.

Because the holding time required for effecting the desired degree of intimate contact between the phases is provided primarily by the contacting section 20, it will be appreciated that the flow velocity of the dispersion on entry into the cyclone 26 may be relatively high thereby promoting efficient separation of the phases.

Figure 2 shows an alternative cyclone arrangement in which the cyclone is disposed generally coaxially within the contacting chamber 20 so as to produce an in-line geometry. The mixed phases enter the cyclone 26 via a tangentially extending inlet port 32. One phase leaves via the outlet tube 28 while the other phase leaves via the vortex finder 34. In this embodiment, the helical baffle sets 22 are arranged so that the last set, ie the set closest to the cyclone 26, imparts spin to the mixed phases in a direction compatible with the tangential inlet port 32 so that the fluids spiral naturally into the port 32 and thence into the cyclone 26.

hep semi3 illustrates another modification in which the injector 14 is located transversely of the contacting chamber 20 so that one phase can leave the cyclone 26 via an extension 36 which extends lengthwise through the contacting chamber 20 and serves to support the helical baffles 22.

Figures 4 and 5 illustrate an alternative form of contacting section 40 interconnecting injector 14 and cyclone 26. In this embodiment, the contacting section provides a flow path (see arrows) which spirals around the cyclone 26 so as to provide a compact construction, the flow path being defined by a spiral baffle 42. At the innermost end of the spiral flow path, the mixed fluids enter the cyclone tangentially via inlet opening 44, one phase leaving through vortex finder 28 and the other through outlet 30. If desired, the arrangement may be such that the mixed fluids from the injector enter at the centre of the spiral and leave at its periphery for tangential entry into the cyclone - see Figure 9.

In Figures 6 and 7, the contacting section 60 is in the form of a drum with the injector 14 located to introduce the dispersion at the central region of the drum, the drum interior being fitted with generally radial baffles 62, 64 whose outer ends and inner ends respectively terminate short of the inner wall 66 and outer wall 68 respectively of the drum to define a labyrinthine flow passage (as indicated by the arrows in Figure 6) extending from inlet opening 70 to outlet 72, the outlet being connected to the cyclone (not shown).

Such a baffle arrangement defines a radially undulating flow path and will be seen to generate a high degree of turbulence each time the fluid stream changes direction, thus serving to maintain the dispersion of one phase within the other. In Figures 6 and 7, the injector is connected to the central region of the contacting section while the cyclone is connected to its peripheral region; however, the arrangement may be reversed, ie injector at the periphery and cyclone at the centre.

Figure 8 illustrates a further modification of contacting section 80 in which internal baffles 82 define a maze-like configuration for flow of the dispersion.

The baffles 82 are arranged to produce a series of annular flow passages which communicate with each other via openings 84 which are circumferentially offset from one annular passage to the next, the fluids entering each annular passage being constrained to flow in both directions over an angle of the order of 90 before being allowed to discharge into the next annular passage.

Again the injector and the cyclone may be located respectively at the centre and periphery of the contacting section as shown in Figure 8, or vice versa.

In each of the embodiments described above, the contacting section may additionally incorporate random or ordered packing materials in the flow path of the dispersion through the contacting section.

Claims

1. Apparatus for contacting immiscible or partially miscible fluids comprising a mixing device for effecting, by virtue of the initial kinetic energy of at least one of the fluids, mixing of the fluids to produce a dispersion, cyclone means for separating the fluid components of the dispersion from one another, and a contacting section for conducting the dispersion from the mixing device to the cyclone means.

2. Apparatus as claimed in Claim 1 in which the contacting section includes means for repeatedly or continually changing the flow direction of the dispersion as it passes from the mixing device to the cyclone means.

3. Apparatus as claimed in Claim 1 or 2 in which the flow passage of the dispersion through the contacting section is such that the residence time of the dispersion within the contacting section is greater than in the mixing device and/or the cyclone means.

4. Apparatus as claimed in Claim 3 in which said residence time within the contacting section is at least one order of magnitude greater than in the mixing device and/or the cyclone means.

5. Apparatus as claimed in any one of Claims 1 to 4 in which the flow passage through the contacting section is of meandering, labyrinthine or maze-like configuration.

6. Apparatus as claimed in any one of Claims 1 to 5 in which the contacting section incorporates random or ordered packing elements or materials in the flow passage of the dispersion through the contacting section.

7. Apparatus as claimed in any one of Claims 1 to 6 in which the cyclone means extends at least partway into the contacting section.

8. Apparatus as claimed in Claim 7 in which the flow passage of the dispersion in the contacting section extends at least in part around the cyclone means.

9. Apparatus as claimed in Claim 7 or 8 in which the axis of the vortex produced by the cyclone extends generally lengthwise of the flow passage defined by the contacting section.

10. Apparatus as claimed in any one of Claims 1-6 in which the contacting section includes means for constraining the dispersion to flow in a path encircling the axis of the cyclone means or the mixing device.

11. Apparatus as claimed in Claim 10 in which said flow path extends spirally.

12. Apparatus as claimed in Claim 10 in which said flow path extends helically.

13. Apparatus as claimed in Claim 10 in which said flow path is of radially undulating configuration.

14. Apparatus for contacting immiscible or partially miscible fluids substantially as hereinbefore described with reference to, and as shown in, any one of the embodiments illustrated in the accompanying drawings.