WO2009156671A1

WO2009156671A1 - Improved process for separating compounds present in a continuous aqueous phase of an effluent to be treated, especially a petrochemical effluent, by phase inversion

Info

Publication number: WO2009156671A1
Application number: PCT/FR2009/051027
Authority: WO
Inventors: Michel Reynes
Original assignee: S.A.R.L. Firmus
Priority date: 2008-05-30
Filing date: 2009-05-29
Publication date: 2009-12-30
Also published as: FR2931815A1; FR2931815B1

Abstract

The invention relates to a process for separating compounds present in a continuous aqueous phase of an effluent to be treated, comprising the following steps: an emulsion of organic droplets (13) that include the compounds (10) to be separated from the aqueous phase, is formed from the effluent to be treated; the emulsion is injected in the form of globules (11); the organic droplets (13) are separated from the globules (11); and the globules (11) that have coalesced at the bottom of the column (3) are removed. According to the invention, the separation process includes the following preliminary control steps: the size of the organic droplets (13) of the emulsion (8) is controlled so as to have a set value (d_min); the size of the globules (11) of the emulsion is controlled so as to have an optimum value (D_3,2). The invention also relates to the phase-inversion separator employing this method and to the uses of this process in the fields of petrochemistry and hydrometallurgy.

Description

"Improved process for separating compounds present in a continuous aqueous phase of an effluent to be treated, in particular petrochemical by phase inversion"

The invention relates to a process for separating compounds present in a continuous aqueous phase of an effluent to be treated, by phase inversion.

Such a process can be used in the petrochemical field to separate organic droplets dispersed in the aqueous phase of a petrochemical effluent.

The wastewater treated by these processes is free from most of the oil they contain, but it is not possible to reject them as they are, because they do not comply with the discharge standards in force.

It is therefore common to use a complementary processing method, which involves additional time and cost.

In addition, the implementation of such a process involves the use of bulky devices, while the space available on a petrochemical platform or in a refinery is limited. Moreover, in the field of hydrometallurgy, the separation of the solubilized metal ions in the aqueous phase of an effluent to be treated, obtained by an extraction process, does not make it possible to achieve satisfactory separation efficiencies.

The invention aims to overcome these problems.

For this purpose, the invention relates to a process for separating the compounds present in a continuous aqueous phase of an effluent to be treated, comprising the steps of: forming, from the effluent to be treated, an emulsion of organic drops including the compounds to be separated, in the aqueous phase,

introduction of the emulsion in the form of globules, including the organic drops and the aqueous phase, into an organic extractant which is miscible with the organic solvent and contained in a column of a phase-inversion separator,

- separation of organic drops of globules, during the migration of globules under the effect of gravity, by migration of organic drops contained in these globules to the top of the globules under the effect of the thrust of Archimedes to the interface between the globules and the organic extractant where the organic drops are captured by this extractant,

- recovery of the globules having coalesced at the bottom of the column.

According to the invention, the method comprises the preliminary stages of control: from the size of the organic drops of the emulsion to a set value,

the size of the emulsion globules at an optimum value.

According to a characteristic of the invention, the control of the size of the organic drops is carried out by providing these drops of homogeneous sizes, greater than the set value.

In this case, the set value for the size of the organic drops depends on the size of the compounds.

Preferably, the set value for the size of the organic drops is a multiple of the size of the compounds. Advantageously, the size of the organic drops and the size of the compounds are in a set ratio greater than 2.

Preferably, the reference ratio between the size of the organic drops and the size of the compounds is between 3 and 10.

According to one possible embodiment, specific experimental conditions for the formation of the emulsion of organic drops are chosen to provide the drops of homogeneous sizes greater than the set value.

In this case, the formation of the emulsion of organic drops is carried out by mixing the effluent to be treated with a miscible organic solvent with the compounds to be recovered.

Preferably, the mixture of the effluent to be treated with the organic solvent is carried out in a mixer disposed upstream of the perforated plate.

According to a possible variant embodiment, the mixer is of the rotary type, and the specific experimental conditions for forming the emulsion comprise the speed of rotation of the mixer.

In this case, the mixer is housed within an introduction tank which is mounted at the top of the column, the passage of the emulsion from the mixer to the mixing vessel is carried out by overflow, and the experimental conditions Emulsion specific formation rates include the feed rates within the mixer of the effluent to be treated and the organic solvent, which are chosen to prevent the emulsion from leaving the mixer before the average size of the drops do not reach the set point.

According to another characteristic of the invention, the control of the size of the globules is performed by equipping these globules with homogeneous sizes, greater than the optimum value.

In this case, the optimal value for the size of the globules depends on the size of the organic drops.

Preferably, the optimum value for the size of the globules is a multiple of the size of the organic drops.

Advantageously, the size of the globules and the size of the organic drops are in an optimal ratio greater than 8.

More precisely, the optimum ratio between the size of the globules and the size of the organic drops is between 10 and 20.

According to one possible embodiment, specific experimental conditions for introducing the emulsion into the extractant are chosen to provide the globules with homogeneous sizes greater than the optimum value.

According to an alternative embodiment, the introduction of the emulsion in the form of globules into the extractant is carried out by passing this emulsion through a perforated plate interposed between the mixer and the column, the control of the size emulsion globules at the optimum value, being made by sizing the perforated plate. Preferably, the size of the perforated plate is made by choosing the size and the number of perforations of the plate.

Advantageously, the organic solvent used for the mixing step and the organic extractant of the column are identical.

The invention also relates to a phase reversal separator implementing the above method.

Advantageously, this separator comprises a reservoir for introducing the working emulsion into the extractant of the column, this reservoir surmounting the perforated plate and accommodating the mixer.

Preferably, the dimensions of the mixer are chosen so that the working emulsion passes overflow from the mixer to the feed tank once the organic drops of the emulsion formed have reached the desired value.

The invention also relates to the use of the above method, in the field of petrochemistry, for the separation of the droplets of an organic liquid dispersed in the continuous aqueous phase of a petrochemical effluent to be treated, the organic solvent used for the mixing step being chosen miscible with the organic droplets of the effluent.

The invention also relates to the use of the process previously mentioned, in the field of hydrometallurgy, for the separation of solubilized metal ions in the continuous aqueous phase of a hydrometallurgical effluent to be treated, the organic solvent used for the hydrometallurgical effluent step. mixture, being chosen to be miscible with the metal ions of the effluent. In this case, the organic solvent miscible with the metal ions of the hydrometallurgical effluent may comprise an extractant specifically chosen according to the nature of the metal ions to be separated.

The invention will be better understood and other objects, advantages and characteristics thereof will become apparent on reading the following description, with reference to the appended figures among which:

FIG. 1 is a schematic view of the installation for implementing the method according to the invention,

- Figure 2 is a schematic view illustrating more particularly one of the steps of the method according to the invention.

The method according to the invention allows the separation of the compounds present in a continuous aqueous phase of an effluent to be treated, by means of a SIP phase reversal separator.

In general, and as illustrated in FIG. 1, a SIP comprises: a reservoir 5 intended to accommodate an emulsion to be treated consisting of organic drops dispersed in an aqueous phase, a vertical separation column 3 filled with an extractant organic material 4 miscible with the organic solvent drops of the emulsion, and disposed in line with the tank 5, a perforated plate 6 interposed between the reservoir 5 and the column 3, by means of which 1 emulsion is introduced within extractant from the column, in the form of globules 11 including the aqueous phase and the organic drops dispersed therein, and - A recovery tank 7 disposed at the base of the column.

Once introduced into the organic extractant of column 3, the emulsion globules 11, mainly composed of aqueous phase, migrate downwardly thereof under the effect of gravity.

At the same time, given the differences in density between the aqueous phase of the emulsion globules 11 and the organic phase of the drops 13 contained in these globules, the organic drops 13 of the globules 11 migrate upwards of the globules 11 under the effect of the Archimedes' thrust up to the interface 16 between the globules 11 and the organic extractant 4. At this interface 16, the organic drops 13 are captured by the extractant 4. They are removed from the column, at the same time as a part of the extractant, through the recirculation line 17 marked in FIG.

On the other hand, the globules reached the bottom of the column, and purified of their organic drops, coalesced at the interface 17 and are recovered in the tray 7.

The process according to the invention makes it possible, using a SIP, to rid an aqueous phase of an effluent to be treated of 99% of the compounds present in this aqueous phase, whether the effluent to be treated is a petrochemical emulsion or a hydrometallurgical effluent.

The method according to the invention will firstly be described in its application to the petrochemical field, and then its use in the field of hydrometallurgy will be described.

1. Petrochemicals As can be seen in FIG. 1, a petrochemical effluent 21 consists of an initial emulsion of droplets of an organic liquid 10 to be recovered, hereinafter referred to as "organic droplets", in a continuous aqueous phase 12.

The compounds which it is desired to separate from the aqueous phase with a yield of approximately 99% are in this case the organic droplets of the petrochemical effluent.

To achieve this objective, the method according to the invention provides for controlling the size of organic droplets 13 of the emulsion and control the size of the globules of emulsion ¹ 11 formed within the column.

These two checks are necessary for the following reasons:

The more the organic drops have a large diameter d, the more their rise within a globule towards the separation interface is fast, because the rate of rise of these drops is proportional to the square of their diameter d. Thus, phase separation in the column is faster.

In fact, SIP separation experiments carried out on a primary kerosene emulsion in water showed that when the size of the organic drops of the working emulsion was varied, thanks to the solvent added to the primary emulsion, the following purge rates were obtained for the same diameter of the emulsion - 1.03 mm:

Table A: Purification rate in percent according to the diameter of the organic drops

It is found that the rate of purification is even better than the size of the organic drops is important. The size of the organic drops therefore has an influence on the purification rate and must be controlled to obtain the desired purification rate.

However, it is not enough that the organic drops have a large size, because if the globules that contain them also have a large size, their rise in the blood cells to the interface will be too long and thus lengthen the delay of seperation. Indeed, for a median diameter of the organic drops in the initial emulsion - 33 μm (case of kerosene in water), when the size of the globule formed in the separation column is varied, by modifying the diameter of the perforations of the Plate 6, the following results are obtained:

Table B Purification rate in percent according to the diameter of the emulsion globules

As shown in the column showing the sewage rate, it varies with size globules of emulsion, and is all the better that these globules are small.

However, the blood cells should not be too small so as not to reach the bottom of the column after too long a residence time.

Control of the size of the drops

The control of the size of organic drops is performed by setting the size of these drops to a set value.

This setpoint value depends on the size of the organic droplets of the petrochemical effluent to be treated. More precisely, this setpoint is set equal to a multiple of the size of the organic droplets.

Thus, the control of the size of the organic drops will consist in obtaining a set ratio between the sizes of the drops and the droplets.

To achieve the best separation rates, this set ratio between the size of the organic drops and that of the organic droplets is set greater than 2. Preferably, it is between 3 and 10.

According to a preferred method of obtaining the set value for the size of the drops, a working emulsion 8 is prepared from the initial emulsion, and of a chosen organic solvent miscible with the organic liquid of the initial emulsion. upstream of the perforated plate.

The organic solvent enlarges the size of the organic droplets to form drops, hereinafter referred to as "organic drops", including the organic liquid to be recovered and the organic solvent added.

22 and dispersed in the aqueous phase. It is the size of these organic drops that will be controlled so that it defines with the size of the organic droplets, the set point ratio.

In order to manufacture this working emulsion, the process according to the invention comprises additional elements compared with a conventional separator:

a mixer 2 placed inside the tank 5 of the separator, consisting of a mixing tank and a rotary stirrer,

a storage tank 24 of the organic solvent 22,

a line 26 connecting the reservoir 24 of the organic solvent 22 to the inlet of the mixer 2, on which are mounted a pump and a solenoid valve,

a line 20 for supplying the effluent to be treated 21 to the mixer inlet, on which a pump and an associated solenoid valve are mounted,

and when the organic solvent is chosen identical to the extractant contained in the column, a recirculation line connects the contents of the column to the organic solvent reservoir 22 to withdraw the extractant 4 from the column 3 continuously in order to recycle, and redirect it to mixer 2 by means of line 26.

As the passage of the working emulsion from the mixer 2 to the receiving vessel 5 is overflow, the rate of introduction of the initial emulsion F ₁ and the rate of introduction of the additional organic solvent 22 into the mixer 2, as well as the agitation speed ω of the stirrer 23 are adapted so that the working emulsion 8 formed in the mixer 2 does not leave this mixer 2 before the Organic drops formed did not reach the set size.

To achieve the desired ratio, the organic solvent, the rotation speed of the agitator and the appropriate dimensions for the mixer will be selected. This choice can be made by experimentation.

Control of the size of the globules

The control of the size of the globules is done by setting the size of these globules to an optimal value. This optimum value depends on the size of the organic drops of the working emulsion produced within the mixer.

More precisely, this optimum value is set equal to a multiple of the size of these organic drops.

Thus, the control of the size of the globules will consist in obtaining an optimal ratio between the sizes of the globules and drops.

This optimal ratio between the size of the globules and that of the organic drops is set higher than 8 to achieve the best separation yields. Preferably, it is between 10 and 20.

According to a preferred method of obtaining the optimum value for the size of the globules, the dimensions of the perforated plate, the size and the number of its perforations are chosen appropriately. This choice can be made by experimentation.

Experiments conducted to separate organic droplets from petrochemical effluents from aqueous a petrochemical effluent, controlling the size of globule size of drop ratios and - to maintain size drop droplet size in the above defined value ranges, have achieved a separation yield of more than 97% and more precisely greater than 99%.

Moreover, when the aqueous and organic phases of the petrochemical emulsion have close densities, and for this reason the migration of the droplets of organic phase towards the periphery of the globule is slowed down, the fact of adding an organic solvent has allowed to change the density of the organic phase and accelerate the separation of the droplets.

Thus, phase separation of near densities, which until now was difficult or impossible, is allowed and largely optimized.

2. Hydrometallurgy

The method according to the invention can also be implemented in the field of hydrometallurgy, with a hydrometallurgy effluent consisting of a continuous aqueous phase and of metal ions solubilized in this aqueous phase, to recover the solubilized metal ions. .

To do this, the working emulsion which will be introduced into the separator is carried out with an organic solvent chosen for its high affinity with the metal ions to be recovered. This solvent may comprise an extractant specifically chosen as a function of the metal ions to be recovered.

The working emulsion formed during the mixing thus consists of organic drops which include the added organic solvent and the metal ions to be recovered, dispersed in the aqueous phase.

During its passage in the form of globules within the extractant of the column, the organic drops, and therefore the metal ions they contain, are captured by the extractant and thus separated from the aqueous phase.

Columns of purified aqueous phase are recovered from their column of metal ions.

The size of these organic drops, and that of the globules will be controlled to meet the desired and optimal ratios described above for application in the petrochemical field, and a separation efficiency of greater than 99% is also obtained.

The method according to the invention thus makes it possible to separate the compounds present in an aqueous phase from an effluent to be treated, with an optimized purification rate.

In addition, this method makes it possible to recover the organic droplets of a petrochemical effluent, as well as the metal ions of a hydrometallurgical effluent.

Moreover, it can be used on any effluent to be treated which contains in its aqueous phase compounds as soon as they can be captured by an organic solvent.

Moreover, the mixing phase of the effluent to be treated with the chosen organic solvent, implemented with a mixer provided with a rotary stirrer according to the embodiment described above, can of course be implemented with any another type of mixer capable of producing an emulsion from a predominantly aqueous effluent and an organic solvent. In this case, the step of controlling the size of the organic drops will consist in adapting the dimensions or the operation of this "mixer other than dynamic" according to the size of organic drops to be reached in the emulsion.

Thanks to this process, it is possible:

1) to obtain a separation more quickly, 2) to increase the flow rate of the wastewater to be treated, or 3) to reduce the height of the separation column.

Claims

REVENDI CATIONS

1. A process for separating the compounds present in a continuous aqueous phase of an effluent to be treated, comprising the steps of:

- formation from the effluent to be treated, an emulsion of organic drops (13) including the compounds to be separated (10), in the aqueous phase, - introduction of the emulsion in the form of globules (11) including the organic drops and the aqueous phase, in an organic extractant (4) miscible with the organic solvent (22) and contained in a column (3) of a phase-reversal separator, - separation of the organic drops (13) globules (11), during the migration of the globules (11) under the effect of gravity, by migration of the organic drops (13) contained in these globules up the globules (11) under the effect of the thrust Archimedes to the interface (16) between the globules (11) and the organic extractant (4) where the organic drops (13) are captured by this extractant (4),

recovery of the globules (11) having coalesced at the bottom of the column (3), the separation process comprising the preliminary steps of controlling: from the size of the organic drops (13) of the emulsion (8) to a set value,

the size of the emulsion globules (11) at an optimum value, a function of the size of the organic drops.

2. Method according to claim 1, characterized in that the control of the size of organic drops (13) is performed by providing these drops (13) of homogeneous sizes, greater than the set value.

3. Method according to claim 2, characterized in that the set value for the size of the organic drops (13) depends on the size of the compounds (10).

4. Method according to claim 3, characterized in that the set value for the size of the organic drops (13) is a multiple of the size of the compounds (10).

5. Method according to claim 4, characterized in that the size of the organic drops (13) and the size of the compounds (10) are in a set ratio greater than 2.

6. Method according to claim 5, characterized in that the reference ratio between the size of the organic drops (13) and the size of the compounds (10) is between 3 and 10.

7. Method according to one of claims 2 to 6, characterized in that to provide the drops (13) of homogeneous sizes greater than the set value, specific experimental conditions are chosen for forming the emulsion (8) of organic drops (13).

8. Method according to claim 7, characterized in that the formation of the emulsion (8) of organic drops (13) is carried out by mixing the effluent to be treated (21) with an organic solvent (22) miscible with the compounds to be recovered.

9. Method according to claim 8, characterized in that the mixture of the effluent to be treated (21) with the organic solvent (22) is carried out in a mixer (2) arranged upstream of the perforated plate (6). ).

10. The method of claim 9, characterized in that the mixer (2) is of the rotary type, and in that the specific experimental conditions for forming the emulsion comprise the speed of rotation of the mixer.

11. Method according to claim 9 or 10, characterized in that the mixer (2) is housed within an introduction tank (5) which is mounted at the top of the column (3), in that the passage of the emulsion from the mixer to the mixing vessel is carried out by overflow, and in that the specific experimental conditions for the formation of the emulsion comprising the feed rates within the mixer of the effluent to be treated and the organic solvent, which are chosen to prevent the emulsion from leaving the mixer before the average size of the drops reach the set value.

12. Method according to one of claims 1 to 11, characterized in that the size control of the emulsion globules (11) is performed by setting the size of these globules (11) to the optimum value.

13. The method of claim 12, characterized in that the optimum value for the size of the globules

(11) is a multiple of the size of the organic drops (13).

14. The method of claim 13, characterized in that the size of the globules (11) and the size of the organic drops (13) are in an optimal ratio greater than 8.

15. Method according to claim 14, characterized in that the optimum ratio between the size of the globules

(11) and the size of the organic drops (13) is between 10 and 20.

16. Method according to one of claims 1 to 15, characterized in that to set the size of the globules (11) to the optimum value, specific experimental conditions for introducing the emulsion (8) into the the extractant (4).

17. Method according to one of claims 1 to 16, characterized in that the introduction of the emulsion in the form of globules within the extractant is carried out by passing this emulsion (8) through a plate perforation (6) interposed between the mixer (2) and the column (3), the control of the size of the emulsion globules (11) at the optimum value being carried out by sizing the perforated plate (6).

18. The method of claim 17, characterized in that the sizing of the perforated plate (6) is performed by choosing the size and number of perforations of the plate (6).

19. Method according to one of claims 8 to 18, characterized in that the organic solvent (22) used for the mixing step and the organic extractant (4) of the column (3) are identical.

20. phase inversion separator implementing the method according to any one of claims 1 to 19 comprising: a mixer (2) ensuring the formation of the emulsion of organic drops (13) by mixing the effluent to be treated (21) with the organic solvent, a separation column (3) filled with an organic extractant, a perforated plate (6) interposed between the mixture (2) and the column (3) and ensuring the passage of the emulsion in the form of globules within 1 extractant from the column,

a globule recovery tank (11) having coalesced at the bottom of the column, the mixing speed within the mixer, the rate of introduction of the effluent to be treated (21), the rate of introduction of the organic solvent; (22) in the mixer being chosen so that the size of the organic drops of the emulsion formed in the mixer reaches the set value, the perforated plate being sized so that the size of the globules reaches the optimum value.

21. Separator according to claim 20, characterized in that it comprises a reservoir for introducing the working emulsion into the extractant of the column, this tank surmounting the perforated plate and accommodating the mixer.

22. Separator according to claim 21, characterized in that the dimensions of the mixer are chosen so that the working emulsion passes overflow from the mixer to the feed tank once the organic drops of the emulsion formed have reaches the set point.

23. Use of the method according to any one of claims 8 to 19, in the field of petrochemistry, for the separation of the droplets (10) of an organic liquid dispersed in the continuous aqueous phase of a petrochemical effluent to be treated ( 21), the organic solvent (22) used for the mixing step being chosen to be miscible with the organic droplets (10) of the effluent (21).

24. Use of the method according to any one of claims 8 to 19, in the field of

Hydrometallurgy, for the separation of solubilized metal ions in the continuous aqueous phase of a hydrometallurgical effluent to be treated, the organic solvent used for the mixing step being selected miscible with the metal ions of the effluent.

25. Use according to claim 24, characterized in that the organic solvent (22) miscible with the metal ions of the hydrometallurgical effluent comprises an extractant specifically selected according to the nature of the metal ions to be separated.