LU84333A1 - PROCESS AND INSTALLATION FOR RE-EXTRACTING, IN MULTIPLE SUCCESSIVE STAGES, URANIUM FROM AN EXTRACTANT - Google Patents

Description

! 2.

i a ï *

The present invention relates to a process for re-extracting, in several successive stages, uranium from an extractant comprising a dialkylphosphorigic acid and a 5-trialkylphoschine oxide dissolved in an organic solvent immiscible with water, using an aqueous solution of phosphorous acid containing ferrous ions, each stage comprising the following steps: a) bringing the extractant in the organic solvent into contact with the aqueous solution of phosphorous acid, a fraction of this aqueous solution being formed by recycled solution loaded with uranium, thereby producing an organic phase depleted in! uranium and an aqueous phase of phosphorous acid enriched in uranium and ferrous ions; b) separation of the organic phase depleted in; uranium of the aqueous phase enriched in uranium; c) recycling a fraction of the uranium-enriched aqueous phase resulting from step (b) to step (a) and d) adjusting the ferrous ion content of the fraction recycled by putting the aqueous phase enriched in uranium and resulting from step (b) in /: ^ / contact with metallic iron. /! "; / / i '3.

A method for carrying out the re-extraction of uranium from such an extractant is among other things known by the patent in the United States of America No. 3,737,513, the European patent application No. 0031172 and the article »5 "Recovery of Uranium from Wet-Process Phoshoric Acid" BY FJ Hurst et Al in the review "Industrial and Engineering Chemistry: Process Design and Development", Volume II, N ° 1, 1972.

However, all of these methods have various relatively significant drawbacks.

Thus, these known methods lead to the production of an uranium-containing aqueous phase, the 2+ 3+ content of Fe -f Fe of which is between 25 and 45 2+ 3+ g / 1 depending on the content of Fe + Fe of l pre-reduced P5 acid used for re-extraction.

However, it is well known in the chemistry of the manufacture of phosphoric acid that the 3+ solubility of Fe in phosphoric acid is low and that, for phosphorous acids with a 2o content of 30 to 35%, the solubility limit is around 3+ around 25 g / 1 Fe

Any content above this limit gives rise to massive precipitation of iron salts. Rigues of the type FeE ^ (P0 „) 4E„ 0.

In the subsequent recovery of uranium from the uranium-containing aqueous phase by the well-known method 6, which consists in oxidizing the U to U, a

That

extract the U 'with an extractant consisting of a solution of D ^ EHPA and Tooo in a diluent ali- / * ". 6+ / 30 phatiçue inert and re-extract the ü by an eo-„ f / if f 4.

aguous lution of (NH ^^ CO ^, the first operation consists in oxidizing this uraniferous agressive phase of 2+ 3+ so that all of the Fe + Fe is found in 3+ the state of Fe and precipitates of FeH type ( PO) 4H „0 2+ 3+ 3 4 2 2.

5 are formed as soon as the Fe + Fe content is greater than 25 g / 1 of Fe.

These precipitates are deposited in the various apparatuses, create obstructions in the pipes and the flow control orifices, so that the conduct of subsequent operations is seriously compromised. This precipitation also appears during the re-extraction operation itself with the same harmful effects as soon as the Fe ^ + content exceeds 25 g / 1.

In addition, the process according to the patent in the United States of America N ° 3,737,513 requires | very important safety precautions due to the risk of explosion.

In the process according to the aforementioned European patent application, the phosphoric acid used must be subjected to a prior reduction, which mistletoe also requires isolation of the installation from ambient air. Such insulation being ï; · Also required in the process described by F.J. Hurst jj 25 in the industrial review "Industrial and Engineering f Chemistry".

j A g 0 s tîLitiE θ ser. 0 i. 0 2_ s ne 0 ssr. χη * ~ j vention is to remedy these various drawbacks I and to provide a very simple process in leguel! 30 iron content in the aqueous phase is maintained at, y / 5.

minimum, thus avoiding any risk of precipitation.

To this end, according to the invention, contact is made with the metallic iron and the aqueous phase enriched in uranium by putting at least one; 5 part of this metallic iron in movement with respect to said aggressive phase, so as to create an abrasion of the iron.

Advantageously, at least part of the metallic iron is subjected to stirring in the above-mentioned aqueous phase, limiting the amount of air entrained in the latter.

The invention also relates to an installation for re-extracting uranium from an organic extractant, in particular for the implementation of the pro-ceded as described above.

This installation comprises a series of successive mixer-settlers each comprising a mixing compartment provided with a pumping agitator, a settling compartment, a drip tray for evacuating the organic phase, an outlet chamber provided with a overflow, to evacuate part of the decanted aqueous phase, and a container intended to contain metallic iron which can be brought into contact? tact with the aqueous phase, the outlet chamber 25 being connected by a recycling line to the mixing compartment allowing the other part of the aqueous phase to be recycled.

According to the invention, the aforementioned container comprises means for setting the metallic iron in motion and creating, on the one hand, an abrasion of this iron, j / and, on the other hand, an intimate contact between the latter and the ohase aaueuse. -, ·, ~ Ί f // i <6.

Advantageously, these means comprise an agitator making it possible to stir the metal iron in the form of pieces, in intimate contact with each other in the agous phase, the aforementioned container preferably having a passage. intake near its bottom and an evacuation passage above the level of the metallic iron.

Other details and particularities of the invention will emerge from the description given below, by way of nonlimiting example, of a particular embodiment of the subject of the invention with reference to the appended drawings.

FIG. 1 represents a diagram of an installation for carrying out the method according to the present invention.

Figure 2 is a plan view, on a larger scale, of a part of this installation.

Figure 3 is a perspective view, with partial breaking of this same part of the in-2o stallation.

In the different figures, the same elements are designated by the same reference numbers.

"Generally, the process according to the invention for re-extracting uranium from an extractant comprising a dialkylphosphorous acid and a diaikylphosphine oxide dissolved in an organic solvent immiscible with water using a

The action of phosphorous acid containing ferrous ions is carried out in several successive stages, f * f each stage comprising several courts at its core.

7-

In a first step, the extractant in the organic solvent is brought into contact with the aqueous solution of phosphorous acid, a fraction of which is formed by recycled solution loaded with uranium.

During this contacting, an organic phase depleted in uranium occurs and an aqueous phase of phosphorous acid enriched in uranium and ferrous ions.

These two phases are then separated in a second step and a fraction of the aqueous phase enriched in uranium resulting from this second step is sent, during a third step, to the first step.

Then, in a last step, the content of ferrous ions in the recycled fraction is adjusted by bringing the aqueous phase enriched in uranium and resulting from the second step into contact with pieces of metallic iron set in motion in this aqueous phase, so as to create a 2o abrasion of said iron and thus form tiny and active particles of iron rapidly entering into solution to react almost instantaneously with Fe3 + ions.

The particular characteristics of this process will be described below by means of some 25 concrete embodiments.

Example 1.

We start with an organic extractant consisting of a solution of 0.5 K of ci- (2-ethylhexyl) phosphorigue acid (D ^ EHPA) and 0.075 M of trioctylphosphine oxide (TOPO) in an aliphatic diluent inert C'ESCAID-110 "j from the company ESSO C ^ E ^ ICAL Cv 'containing 255 trcr / 1 of u6t' '., -

J

yj. / “I 8.

This extractant has been used to extract uranium from phosphorous acid produced by leaching with sulfuric acid from uranium phosphate rocks.

5 The re-extraction is carried out with an aqueous solution of phosphorous acid containing 37% of P 2 O 3. Pra "prepared by mixing phosphorous acids with 30% of and 42% of * This solution which, according to the invention, has not been pre-reduced contains approximately 3 g / l _ 3+ 10 of Fe.

The re-extraction is carried out in three stages using for this purpose three identical mixer-settlers 1, 2 and 3 from an installation shown in FIG. 1.

15 Chague mixer-settler comprises a mixing compartment 4 provided with a stirrer 5 with pumping effect, a settling compartment 6 and an outlet chamber 7 for the evacuation of the separated phases.

20 The extractant, from which the uranium must be removed, is introduced into the mixing compartment j 4 of the mixer-settler 1, as shown by the arrow; 8, and the installation through the outlet chamber 7! - the mixer-settler 3.

I 25 On the other hand, the re-extraction solution j enters the installation through the compartment of; mixture 4 of the mixer-settler 3 / as shown by arrow 9, and guitar this installation by the / »outlet chamber 7 of the mixer-settler 1. rj! 30 U ’9.

The course followed by the extractant was shown in solid lines, while the course followed by the re-extraction solution was shown in broken lines.

5 The extractant is introduced at 8 of the installation at a flow rate of 30 m / h and at a temperature of the order of 35 ° C., while the re-extraction solution is introduced at 9 at a flow rate of 682 1 / h and at a temperature of the order of 50 ° C.

10 The extractant / entering at 8 in the compartment 4 of the mixer-settler 1, leaves the chamber 7 of the latter by a line 8 'to then enter the mixing compartment 4 of the mixer-settler 2 and leave it by a line 8 "15 to the mixing compartment 4 of the mixer-settler 3. The extractant is finally evacuated from the installation by the chamber 7 of the latter mixer-settler, as shown by the arrow 8 '".

The re-extraction solution, which enters 2o at 5 in the mixing compartment 4 of the mixer-settler 3, separates into two circuits in the chamber 7, a part being recycled to compartment 4 of the same mixer-settler, through a recycling line 13, while the other part passes to the mixing compartment 4 of the preceding mixer-decanter 2, through the line 7 '.

Similarly, at the outlet of chamber 7, part of this solution is recycled to the same mixing compartment while 3q the other part is transferred to the mixing compartment of the first mixer - decanter 1 rar la - pipe recycling container 7 ". // w.

10.

At the outlet of the chamber 7 of the mixer-decanter 1, a part is again recycled to compartment 4 of the same decanter, while the other part is evacuated from the installation by line 7 "'.

5 Given that the organic phase / aqueous phase ratio is, in this concrete example, 30,000 / 682 and that the aqueous phase must be maintained as a continuous phase during the re-extraction, most of the aqueous phase is recycled via the recycling line 13 and only a minor part passes to the next mixer-settler, as indicated by the references 7 'and 711 or is evacuated from the installation as indicated by the reference 7' ".

Each of the stages described above is therefore produced in one of the mixer-settlers 1, 2 and 3.

Advantageously, the metallic iron is added to each stage in the outlet chamber 7 of the three j mixer-settlers.

j 2o In these chambers, at least a portion of this metallic iron is subjected to agitation in the -gious phase in such a way as to limit to the strict minimum the amount of air entrained in this: strict phase.

In order to obtain, on the one hand, a sufficient abrasive effect, an energy consumption as reduced as possible and a minimal entrainment of this iron particles sol: 5th in the aqueous phase through the conduit 13, we ! use pieces of iron whose average diameter I 3q preferably varies between and 5 and 30 mm for at least? f 50% by weight of the total amount of iron used. · '[I • / 7 11.

In addition, to ensure as intimate contact as possible with the active solution, at least part of the metallic iron is suspended in it.

J 5 The quantity of metallic iron added to the aqueous phase of each stage corresponds appreciably to the quantity of uranium to be reduced on the stage considered, with an excess of 50 to 100% in iron.

Furthermore, an aqueous solution of 35 to 45% P 2 O 3 of phosphoric acid is advantageously used as the re-extraction solution. ^ natural redox bran, containing for example 3-j- at least 75% iron in the form of Fe

The temperature is maintained in the three mixer-settlers between 40 and 55 ° C and preferably between 45 and 55 ° C. so as to obtain 4+ a distribution coefficient of U between the agous phase and the organic phase as high as possible and ensure a rapid reaction between the active phase and the metallic iron.

In the case of the present example, under regime, 11 g / h of metallic iron is added in the mixer-settler 3.3 kg / h in the mixer-settler 2 and • Blcg / h in the mixer-settler 1.

2 ~ v 3+ 25 The concentrations of uranium, Fe and Fe, are as follows: 2- 3+ U (ie;) Fe ç / 1 Fe g./l Mixer-settler 1 7 500 ppm 10 g./l 10 g / i Mixer-settler 2 4000 ppm 6 g / 1 10 g / i 30 Mixer-settler 3 1000 ppm 2.5 g / 1 6 g / 1- / / • / 12.

Under these conditions, it can be seen that the ex-tractor exits in 8 '"from the mixer-settler 3 with an uranium content of less than 5 ppm and even of the order of 1 ppm.

5 This extractant can then be reused to extract the uranium from the phosphorous acid produced by leaching with sulfuric acid from uraniferous phosphate rocks.

The uranium can be recovered from the "aqueous phase leaving in 7 '" according to a known method such as that already described above.

Example 2.

The raffinate from the uranium extraction operation, that is to say the phosphorous acid from the sulfuric attack on the phosphate, is used, which has been oxidized and from which the extract has been extracted. uranium using D ^ EHPA-TOPO solvents according to the well known process.

This phosphorigue acid contains 2.2 g / 1 of iron, se, 2 - * - 3+ dividing into 0.3 g / 1 Fe and 1.9 g / 1 Fe 20 The temperature is 54 ° C. After passing through the installation shown in FIG. 1, the acid contains 13.5 g / 1 of Fe, of which 13 g / 1 of Fe2 + and 0.5 g / 1 of Fe3 +.

Example 3.

The starting acid is the raffinate originating from the second cycle of uranium extraction, that is to say the aqueous phase loaded with uranium leaving the re-extraction from which, after oxidation, the uranium using solvents D ΞΗΡΑ.-TOPO according to the known process. This ^ 2 'acid contains 14.3 g / 1 of Fe including 0.5 g / 1 of Fe T and 3-f 3q 13.8 g / 1 of Fe. The working temperature is 52CC.

After passing through the installation shown in flower 1, the acid contains 24 g / L of Fe, of which 17.2 g / 1 of Fe and 6.8 g / 1 of Fe ^ '.

These examples show that the process allows this to be reduced to scrap metal so as to find the iron in solution essentially in the form of Fe2 + but also to reduce to Fe, a proportion that is appreciable of the Fe present in the starting acid. '/ 13.

This is obtained essentially thanks to the fact that, according to the invention, the iron scrap is dissolved in a dynamic manner thus making it possible to reduce the reaction of the dis-5 sou s iron, which has been reoxidized either by the mechanism of oxidoreduction: 2 Pe2 + + U6 + - »2 Fe3 + + U4 + (1) either by simple contact with air.

2+

The Fe is obtained by dissolving 10 grapes in phosphorous acid according to the reaction: 3 Fe + 6 H + - »4 Fe2 + + 3 H (2)

4M

and again by the reduction of the ferrous iron, produced by 6+ the reaction with the U following the reaction (1), which takes place as follows: 15 Fe + 2 Fe3 + - * 3 Fe2 + (3)

The process according to the invention consists in promoting reaction (3) to the detriment of reaction (2) by putting, by abrasion, microparticles of active iron in solution which can react directly with Fe T.

Unlike this mistletoe is the case for known processes, iron does not dissolve essentially by acid attack, but especially by this phenomenon of abrasion.

Another advantage of the present invention is to allow the use of coarse and low-cost machine-guns such as those obtained from perforation, punching or punching operators, without any specific surface limitation, as is the case for example. 30 in the process described by the European patent application! f péen 0031172. / -1 t 14.

The method as described above and in particular in the examples can advantageously be implemented by means of an installation shown diagrammatically in FIGS. 1 to 3.

5 As already indicated above, this installation comprises a series of successive mixer-settlers, which are three in number in this specific embodiment, each comprising a mixing compartment 4 provided with an agitator 5 to 10 pumping effect, a settling compartment 6 and an outlet chamber 7, into which metallic iron is introduced at regular intervals.

Between the settling compartment 6 and the outlet chamber 7 is provided a gutter 15 10 for evacuating the organic phase, the aqueous phase, forming the lower decanted phase, passes below this gutter in the outlet chamber 7, as shown by arrow A.

Part of this aqueous phase is 2o evacuated by an overflow 26 to the pipe 7 ', 7 "or 7"' depending on whether it is the mixer-settler 3, 2 or 1 respectively (see Figure 1).

The other part of the aqueous phase passes through a container 16 containing the metallic iron 22, of which 25 question above.

The part of the aqueous phase having passed through the container 16 is then recycled through the recycling line 13.

According to the invention, means are provided for setting the metallic iron 22 in motion, having created, on the one hand, an abrasion of this iron and, on the other hand, an intimate contact with the latter. 15.

and the aggressive phase passing through the container 16.

These means are, in the embodiment shown in FIGS. 2 and 3, formed by an agitator 23 making it possible to stir the pieces of iron '5 contained in the container 1, in intimate contact with each other, and thus causing the aforementioned abrasion.

The aqueous phase enters the container 16 near its bottom by an admission passage 10 in the leg is provided with a grid 20 or other means permeable to the aqueous phase to retain the metallic iron ctens the receptacle L.

The stirring phase passes through the container from bottom to top to overflow above a discharge threshold 21 and to flow towards the recycling pipe 13.

The direction of flow of the recycled active phase is indicated by arrows AR, while the flow of organic phase in chamber 7 has been indicated by arrows 0.

As shown diagrammatically in FIG. 2, each of the recycling pipes 13 is surrounded by a heating element 19, for example with steam.

This pipe 13 is further provided with a valve 14 making it possible to adjust the flow rate of the recycled current 25.

2+. Finally, the Fe content is determined at regular periods, in particular every hour, for example by measurement by means of a coiorimeter on a sample taken at any point of the circuit, / 30 for example with painted 15. / /, // / 16.

When the system is in operation, the amount of iron to be added to the container 16 is predetermined by the amount of residual uranium in the extractant and it is no longer necessary to vary the frequency of the addition of iron.

This addition can be carried out manually or by any usual mechanical weighing and dosing system.

It is understood that the invention is not limited to the embodiment described and that many variants can be envisaged without departing from the scope of this patent.

Thus, for example, the number of mixer-settlers may vary according to the nature of the extractant to be treated and that the container containing the metallic iron may have a substantially different construction. j Λ Ί, \ \ Ë

Claims (18)

17. CLAIMS. 1. Process for re-extracting, in several = successive stages, uranium from an extractant comprising a dialkylphosphorigic acid and a trialkylphosphine oxide dissolved in an organic solvent immiscible with water, using an aqueous solution of phosphoric acid containing ferrous ions, each stage comprising the following stages: a) bringing the extractant into contact with the organic solvent with the aqueous solution of phosphoric acid, a fraction of this aqueous solution being formed by recycled solution loaded with uranium, thereby producing an organic phase depleted in uranium and an aqueous phase of phosphoric acid enriched in uranium and ferric ions; B) the separation of the organic phase depleted in uranium from the active phase enriched in uranium; c) recycling a fraction of the uranium-enriched aqueous phase resulting from step (b) to step (a) and d) adjusting the ferrous ion content of the recycled fraction by putting the stirring phase enriched in uranium and resulting from step (b) in contact with metallic iron, this process being characterized in that contact is made with metallic iron and the stirring phase enriched in uranium by putting at least one part of this metallic iron in rare movement returns to the / / so-called aggressive phase, so as to create abrasion / iron. / y 18. 2. Method according to claim 1, charac- ï terized in that metallic iron is added to each j stage. 3. Method according to either of Claims 1 or 2, characterized in that at least part of the metallic iron is subjected to stirring in the above-mentioned aqueous phase, limiting the amount of air entrained in the latter. 4. Method according to either of claims 1 or 2, characterized in that pieces of iron are used whose average diameter varies between 5 and 30 mm for at least 50% by weight of the total amount iron used. 5. Method according to any one of the aforementioned claims, characterized in that at least part of the metallic iron is kept in suspension in the aqueous phase. 6. Method according to any one of claims 2 to 5, characterized in that 2o adds a quantity of metallic iron to the stirring phase of each stage corresponding substantially to the quantity of uranium to be reduced to the stage considered with a 50 to 100% excess iron. 7. Process according to any one of the claims 1 to 5, characterized in that the re-extraction is carried out with an aqueous solution of phosphorous acid in its state of oxidation — natural reduction, containing for example at least 7Ξ n of iron under farm /? of Fe ‘+‘. f \ / '»hf Ί. i | 19. 8. Method according to any one of the preceding claims, characterized in that the re-extraction of the uranium is carried out by means of an aqueous solution of phosphoric acid at 35 de 5 to 45% PO. 9. Method according to any one of the preceding claims, characterized in that the re-extraction of the uranium is carried out at a temperature of the order of 40 to 55 ° C. 10. A method according to any one of claims 1 to 9, characterized in that main- ++ +++ holds the content of Fe + Fe in the aqueous solution of phosphorigue acid enriched in uranium and leaving the latter step less than 25 g / 1. 11. Method for re-extracting uranium from an organic extractant, as described above or shown in the accompanying drawings. 12. Installation for re-extracting uranium from an organic extractant, in particular for implementing the method according to any one of the preceding claims, comprising a series of successive mixer-settlers each comprising a mixing compartment provided a pump effect agitator, a settling compartment, a gutter for discharging the organic phase, an outlet chamber provided with an overflow for discharging part of the cecanated aqueous phase, and a container intended for contain metallic iron which can be brought into contact with the aqueous phase, the outlet chamber being connected by a recycling line to the ^ / '/ // J'i 7 / - 20. mixing compartment for recycling the other part of the ageuse phase, characterized in that the container comprises means for setting the metal-league iron in motion and creating, on the one hand, an abrasion 5 of this iron, and, on the other hand, an intimate contact between the latter and the-p hase agieuse .. 13. Installation according to claim 11, characterized in that the container intended to contain metallic iron is mounted in the outlet chamber 10, near the discharge to the recycling line. 14. Installation according to either of claims 12 and 13, characterized in that the means for putting pieces of metallic iron in movement in the aforementioned container comprise - an agitator making it possible to stir these pieces of iron in contact intimate with each other in said aggressive phase. 15. Installation according to one guelcongue 20 of claims 12 to 14, characterized in that the aforementioned container has an inlet passage of the agous phase near its bottom and an evacuation passage above the level of the metal iron - * league in the container ^ so as to create an upward current of the agous phase through the iron. 16. Installation according to claim 15, characterized in that a grid is provided in the intake passage to retain the metallic iron in said container. 17. Installation according to either of claims 15 and 15, characterized in that the evacuation passage has a discharge threshold at the cuguex ± & acuse cessation, crsrgee rar of iron in solution / can flow towards the conduct of / / recvclace. 21. 18. Installation for re-extracting uranium from an organic extractant, as described above or shown in the accompanying drawings. »Drawings: _ £ U _... pages pages including ........ λ ......... cover page ...... AU ..... description pages .. ........ pages of claims - descriptive abstract Luxembourg, ie AUGUST 13, 1982 The agent: /) / Charles München aw