GB2167555A

GB2167555A - Sampling from liquid - liquid extraction columns

Info

Publication number: GB2167555A
Application number: GB08429600A
Authority: GB
Inventors: Susan Jean Lonie; Peter James Thompson
Original assignee: UK Atomic Energy Authority
Current assignee: UK Atomic Energy Authority
Priority date: 1984-11-23
Filing date: 1984-11-23
Publication date: 1986-05-29
Also published as: GB2167555B; GB8429600D0; JPS61181936A; FR2573869A1; FR2573869B1

Abstract

A liquid sample collector for a liquid-liquid extraction column comprises an upwardly facing linear trough (13) and a downwardly facing linear trough (14) which are coextensive and extend transversely of the cross-section of the column (1). The troughs are connected to respective sample pipes (18, 19), and each faces the direction of flow of the liquid phase it is intended to sample. <IMAGE>

Description

SPECIFICATION Liquid sampling collectors This invention relates to liquid sampling collectors, and in particular to collectors for sampling phases in a liquid/liquid extraction column. One example of the latter is the forward and back extraction of uranium (U) and plutonium (Pu) from a nitric acid (HNO3) aqueous solution (which also contains fission products from irradiation of nuclear fuel in a nuclear reactor) by tributyl phosphate in odourless kerosene (TBP/OK), employing pulsing to obtain the necessary mixing of the organic phase (TBP/ OK) and the aqueous phase which will result in separation of the fission products from U and Pu.

To obtain optimum performance from a liquid/liquid extraction plant it is helpful to be able to measure the concentration of the material to be extracted at various points along the column, and for this purpose sample collectors are required which not only obtain as close an approximation to perfectly representative samples as possible but also involve minimum interference with the efficient operation of the column.

It is an object of the invention to provide a sample collector which possesses at least in part the above desiderata.

According to the invention, a sample collector for a liquid/liquid extraction column consists in a linear trough disposed transversely relative to the axis of the column and with its open end facing the direction of flow of the liquid phase which it is intended to sample, the trough occupying a minor part of the cross-section of the column, and means for conveying sample collected by the trough to the exterior of the column.

In the case where it is desired to sample both liquid phases, a second trough may be provided coextensive with the first trough but in back to back relationship therewith so as to face the direction of flow of the second liquid phase where this is countercurrent to the direction of flow of the first liquid phase.

The trough or troughs may extend diametrically or part diametrically across the column. Alternatively, the trough or troughs may extend chordwise or part-chord-wise relative to the cross-section of the column.

A constructional example embodying the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a diagrammatic side view in section of a pulsed liquid/liquid extraction column, Figure 2 is a plan view in section on line Il-Il of Figure 1, and Figure 3 is a fragmentary enlarged side view in section of a detail of Figure 1.

Figures 1 and 2 illustrate a typical pulsed liquid/ liquid extraction column 1, for example for the extraction of uranium and plutonium from irradiated nuclear fuel which also contains fission products.

The irradiated fuel is handled remotely and dissolved in aqueous nitric acid. After removal of any solid residue, the aqueous solution is fed to the column 1 at aqueous inlet 2 and leaves at aqueous outlet 3 at the lower end of the column. Organic solvent consisting of tributylphosphate in odour less kerosene (TBP/OK) is fed to the column 1 at solvent inlet 4 and leaves at solvent outlet 5 at the upper end of the column. The column 1 has a plu rality of perforated plates 6 (seven in the example illustrated) arranged in spaced relationship along the column between the inlets 2 and 4. A pulsing pipe 7 communicates with the column 1 at 8 and has pulsing means 9 at its upper end. The pulsing means 9 is conventional and consists either of a mechanically oscillated diaphragm or a fluidic device.Aqueous/organic interfaces should be situated at locations 10, 11 once column operation has settled down and flow and pulsing rate have been adjusted in optimum manner. The operation of the column is with continuous countercurrent flows, the organic solvent being recycled after back extraction and clean up. The effect is for the organic solvent to extract uranium and plutonium nitrates from the aqueous solution, the fission products remaining in the aqueous raffinate which is concentrated and stored. The uranium and plutonium after extraction from the organic solvent are dealt with in further processes to separate and purify them for incorporation in nuclear fuel.

In order to adjust controls to achieve optimum extraction and steady state operation, it is helpful if not essential to be able to monitor concentration at various positions along the column. To this end, sample collectors 12 are in the illustrated example arranged at positions between the perforated plates 6. Each collector 12 consists of transversely extending troughs 13, 14 arranged back to back, conveniently with a common floor member 15, see particularly Figure 3. Each sample collector 12 is situated at a necked penetration 16 of the side of column 1, the troughs being mounted on a cap 17 which also serves to close off the respective penetration 16. In an alternative, not shown, the sample collectors may be mounted at junctions of column sections by employment of suitable adaptors.The cap 17 is itself penetrated in sealing manner by sample pipes 18, 19 arranged so that pipe 18 communicates with trough 13 to sample the contents thereof, and the other pipe 19 samples from the trough 14 in like manner.

The dimensions and dispositions of the transversely arranged troughs are chosen so that the troughs occupy only a minor part of the cross-section of the column 1, see particularly Figure 2, thereby ensuring minimum interference with flow and pulsing in the column. In the illustrated example, the troughs extend diametrically about 2/3 across the column, but other arrangements, such as full width troughs which may be narrower, or troughs arranged chord-wise or part chord-wise relative to the column cross-section (not shown), can be employed as expedient, so long as the desirability of minimum interference with flow and pulsing and as close an approach to fully representative sampling as possible, is complied with.

The operation of the sample collector 12 can best be appreciated from Figure 3, where it can be seen that the trough 13 faces the oncoming flow of aqueous phase (shown by arrow 20) and collects samples therefrom, and the trough 14 faces the oncoming solvent phase (shown by arrow 21) and collects samples therefrom, the pipes 18, 19 removing the respective samples as expedient for analysis for feedback of information thereby gained for control adjustment as necessary.

It is preferable to employ for the troughs and sample pipes materials which are wetted by the phase being collected.

In the illustrated embodiment, the collection point is at the same side of the column for both troughs. In a modification, applicable particularly to the case where the sample collector extends across the fuel width of the column, one trough may have its outlet at one side of the column and the other trough may have its outlet at the opposite side. Such an arrangement may be implemented relatively easily when the sample collectors are mounted at the junctions between adjacent column sections.

Claims

1. A sample collector for a liquid/liquid extraction column consists in a linear trough disposed transversely relative to the axis of the column and with its open end facing the direction of flow of the liquid phase which it is intended to sample, the trough occupying a minor part of the cross-section of the column, and means for conveying sample collected by the trough to the exterior of the column.

2. A sample collector as claimed in Claim 1 including a second trough which is coextensive with the first trough but in back to back relationship therewith so as to face the direction of flow of the second liquid phase where this is countercurrent to the direction of flow of the first liquid phase.

3. A sample collector as claimed in Claim 1 or 2 in which the trough(s) extends diametrically or part-diametrically across the column.

4. A sample collector as claimed in Claim 1 or 2 in which the trough(s) extends chord-wise or partchord-wise relative to the cross-section of the column.

5. A sample collector for a liquid-liquid extraction column, substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.