MXPA01004244A - Method for reducing the size of solvent extraction process steps and cell for using in the solvent extraction process - Google Patents

Abstract

A method described in the present invention is for reducing the size of the steps in the solvent extraction process. The first and last extraction cells of the extraction step are equipped with a conventional settler unit and at least one of the cells in the middle has a settler unit located around the pump unit and mixer unit. The invention also focuses on the cells used inside the solvent extraction step.

Description

METHOD TO REDUCE THE SIZE OF THE PROCESS STATIONS OF SOLVENT EXTRACTION AND CELL FOR USE IN THE PROCESS OF EXTRACTION OF SOLVENT DESCRIPTION OF THE INVENTION The method described in the present invention is to reduce the size of the stages in the solvent extraction process, so that a reduction occurs when the size of the average cells of the extraction stage decreases. The invention also focuses on the cells used in the solvent extraction stage. The extraction of liquid solvent - 1 fluid is often used as part of the hydrometallurgical production of metals. The solvent extraction process usually consists of several stages or steps where, for example, pre-extraction, re-extraction, etc. are carried out. Each extraction stage contains several extraction cells, in each of these there is usually a pump unit, which transfers the liquid phases of extraction from one cell to another; one or more mixing units, that is, a mixer; and a settling unit behind the mixer, that is, a settler, where the liquids supplied in the mixer settle in their own phases by gravity. A pump can also be combined with a mixer, so that the mixer also functions as a pumping device. In the reactions that occur during the solvent extraction process, then one or more metals moving from one phase (usually the aqueous phase) to another (organic) phase can be separated, and then reextraction is used. The function of the extraction cells is to provide good conditions for carrying out the extraction reactions and finally to separate the liquids from each other. The construction of the solvent extraction process varies considerably based on the metal that is extracted. Extractions with copper are usually very simple insofar as they consist only of some extraction and reextraction stages, but on the other hand, the size of the copper extraction cells has grown greatly with time, which establishes limits proper to extraction. However, the process of extracting other metals is much more complicated in terms of the number of stages, although their capacity is a fraction of the amount of copper produced in an extraction plant. In the solvent extraction cells that are currently used, almost all the components mentioned above are present: a pump, one or several mixers, an optional presedimentador and a main settler. The phases that are mixed are pumped from one cell to another, where they are dispersed, and a time of mixing and reaction is required for the transfer of metal ions from one phase to another in the mixer to take place. Pure phases are separated from each other in the settler. These methods are described, for example, in U.S. Patent Nos. 5,185,081 and 5,662,871. Within the extraction stages, all the extraction cells are similar, that is, the phase separation capacity is optimal in all the cells. U.S. Patent 4,391,711 discloses a solvent extraction distribution, comprising a chamber in the center of which phase delivery is carried out under a mixer. The space surrounding the mixer forms a dispersion band above which there is a space for the lighter phase of the band to be separated and below, a space for a heavier phase to be separated from the band. In this distribution, there is currently no traditional sedimentation unit. The extraction cells within the extraction stage and in the different stages of the extraction process are all similar. A new method has been developed to reduce the size of solvent extraction process steps where, as stated before, there are many stages of extraction, especially in the extraction of solvent from metals other than copper and where there are many similar cells within the stage. The guiding principle here is that a good separation capability of the phases is important, especially in the first and last cells of the extraction stage. However, within the stage, a larger amount of residual droplets is allowed, wherein the size of the extraction stage is reduced by decreasing the size of the cells within the stage. This happens when the settling unit of the cells within the stage is reduced and replaced by a more compact solution, where the cross-sectional area of the settling unit of at least one cell or preferably of all the cells in the middle part of the cell. the extraction stage is, at most, half the cross-sectional area of the first and last settling units in the stage. In accordance with the present invention, the settler unit of the extraction cell comprises a pump unit and a settling unit which are located around the mixers. The profile of the settling unit is preferably rectangular. The essential features of the invention will become apparent in the appended patent claims. In the developed method, the size of the extraction stages is reduced, which in practice means that the process is adjusted to a smaller space compared to a conventional process distribution. In addition, savings are made in terms of investment costs and the need for chemical substances for solvent extraction is also reduced. An additional benefit that deserves mention is that it also decreases the amount of capital involved in the process. In the diagrams appended hereto, a solvent extraction step and an extraction cell used within the step are described in greater detail according to the present invention: Figure 1 shows a solvent extraction cell according to the invention. present invention, as seen from the top, and Figure 2 shows a solvent extraction step distribution according to the present invention, as seen from the top. Figure 1 shows that a solvent extraction cell 1 according to the present invention comprises a settler 2 in essentially rectangular form, in which the pump unit 3 is located and in this case, has two mixers 4 and 5. Naturally , there may be only one mixer or more than two. If there is only one mixer, the settler can be almost square, as mentioned above, the mixing unit can also function as a pump unit, in which case the separate pump can be left outside. The liquids that are to be mixed are transported (which is not shown in the diagram) to the pump unit 3, which may be some prior art device such as, for example, the DOP overflow pump described in U.S. Patent 5,622,871. A dispersion of the liquids is carried out from the pump unit through a conduit 6 to the first mixer 4 and from there through a second conduit 7 to the second mixer 5. The mixers are equipped with impellers 8 and their speed of rotation is selected so that the dispersion is not emulsified. This class of mixing apparatus is described, for example, in U.S. Patent No. 5,185,081. A dispersion of well-mixed phases is carried out from the last mixer through a discharge outlet 9 into the settler space surrounding the mixer and the pump unit, where the dispersion flows first from the last mixer to the unit of pump so that the dispersion flows through at least one, or preferably through several fences 10, 11 and 12. The first of the fences in this case is held between the walls of the two mixers, the second in the wall of the first mixer and the settler, and the third is located between the first mixer and the overflow pump. Of course the fence can also be placed elsewhere, for example between the mixer 5 and the wall of the settler 2. The fences promote the sedimentation of the phases. The phases are removed through unloading ducts, of which the light phase extraction liquid duct 13 comes first in the flow direction and the aqueous solution duct 14 behind it. The solutions are removed from the conduits and transported to the next solvent extraction cell with a known method. Figure 2 illustrates a solvent extraction stage, which conventionally comprises 7 cells equally large, but according to the present invention, are constituted of cells of which the first and the last, the 15 and 16 are equipped with a unit 17 of pump and mixers 18 and 19 plus a normal size settler 20 outside the mixers. The cells in the middle part of the stage are the cells 1 shown in Figure 1. The liquid transfer tubes from one cell to another are not illustrated here, since they are known in advance. The method described above is suitable, for example, for cobalt extraction, but it can also be applied for solvent extraction of other metals such as those requiring complicated stages of solvent extraction.

Claims (15)

1. A method for reducing the size of the stages of solvent extraction process, characterized in that the first and last extraction cells of the extraction stage are equipped with a conventional settling unit and at least one of the cells in the middle part has a settling unit that is located around the pump unit and the mixing unit.

2. The method as described in patent claim 1, characterized in that the cross-sectional area of the settling unit in the extraction cell which contains a settling unit which is located around the pump unit and the mixing unit, is like maximum one half of the cross-sectional area of the settler unit of the first and last cells of the extraction stage.

3. The method as described in patent claim 1, characterized in that the dispersion leaving the settler unit in the extraction cell which contains a settling unit which is located around the pump unit and the mixing unit, is transported through of at least one fence before the separate phases flow into the discharging conduit.

4. The method as described in patent claim 1, characterized in that the extraction cell which contains a settling unit located around the pump unit and a mixing unit, the shape of the settler is essentially rectangular.

5. The method as described in patent claim 1, characterized in that all of the middle cells in the extraction stage are equipped with a settling unit which is located around the pump unit and the mixing unit.

6. The method as described in some of the preceding claims, characterized in that the mixing unit also constitutes a pump unit.

7. A solvent extraction cell, which is formed of a liquid extraction pump unit, at least one mixer and a settler, characterized in that the settling unit of the solvent extraction cell is formed around the pump unit of cell and cell mixer.

8. A solvent extraction cell, as described in patent claim 7, characterized in that the profile of the settler of the cell is essentially rectangular.

9. The solvent extraction cell, as described in patent claim 7, characterized in that the profile of the cell settler is essentially square.

10. The solvent extraction cell, as described in patent claim 7, characterized in that the settler of the cell is equipped with at least one fence.

11. The solvent extraction cell, as described in patent claim 10, characterized in that the settler of the cell is equipped with a fence which is supported on the walls of the mixers.

12. The solvent extraction cell, as described in patent claim 10, characterized in that the settler of the cell is equipped with a fence which is supported between the wall of the mixer and the wall of the settler.

13. The solvent extraction cell, as described in patent claim 10, characterized in that the settler of the cell is equipped with a fence which is supported between the wall of the mixer and the pump unit.

14. The solvent extraction cell, as described in patent claim 7, characterized in that the pump unit and the mixer are connected to each other by a conduit.

15. The solvent extraction cell, as described in patent claim 7, characterized in that the mixer also functions as a pump unit.