CN115124156A

CN115124156A - Device and method for deoiling raffinate in rare earth extraction process

Info

Publication number: CN115124156A
Application number: CN202210625952.7A
Authority: CN
Inventors: 王勇; 齐涛; 张雨欣
Original assignee: Institute of Process Engineering of CAS; Ganjiang Innovation Academy of CAS
Current assignee: Institute of Process Engineering of CAS; Ganjiang Innovation Academy of CAS
Priority date: 2022-06-02
Filing date: 2022-06-02
Publication date: 2022-09-30

Abstract

The invention provides a device and a method for removing oil from raffinate in a rare earth extraction process, wherein the device comprises an extraction device, and the extraction device internally comprises a mixing chamber and a clarifying chamber; the mixing chamber is separated from the clarifying chamber by an overflow baffle; the height of the overflow baffle is lower than that of the extraction device; the middle rear part of the clarification chamber is provided with a conglomeration layer. The device realizes continuous oil removal of raffinate by arranging the aggregation layer at the middle rear part of the clarification chamber. The method comprises the following steps: mixing a diluent and an extracting agent to obtain an extracted organic phase, then mixing the extracted organic phase with a water phase through a stirring device of a mixing chamber for extraction, enabling the obtained mixed phase to flow into a clarifying chamber through an overflow baffle, standing for phase splitting, enabling the obtained raffinate to enter a conglomeration layer, enabling oil drops in the raffinate to conglomerate and float through the conglomeration layer, and discharging the deoiled raffinate through a water phase outlet. The method reduces the production cost by a physical technology without adding any chemical agent.

Description

Device and method for deoiling raffinate in rare earth extraction process

Technical Field

The invention belongs to the field of rare earth waste liquid treatment, and particularly relates to a device and a method for removing oil from raffinate in a rare earth extraction process.

Background

Rare earth is used as an important strategic resource and high-tech material, and has wide and vital application in the fields of national defense, metallurgy, aerospace, machinery, electronics, petroleum, chemical engineering, new materials and the like. Because of its excellent and unique physical and chemical properties such as photoelectromagnetism, it is often not substituted by other substances in application, also called "industrial vitamins".

The rare earth ore is generally leached by acid liquor, the solid-phase rare earth elements are transferred to liquid phase, and then separation and purification are carried out. The solvent extraction method is one of the most mature technologies for extracting and separating rare earth elements from a solution, and the P507-kerosene extraction agent system is the rare earth extraction separation system which is the most widely applied and has the longest history at present. Although mature, there are some problems in the practical extraction process, and the raffinate contains certain oil pollutants to affect the subsequent discharge to reach the standard, which is a very troublesome and urgent problem to be solved.

The oil in the rare earth raffinate has a complex existing form and can be divided into suspended oil, dispersed oil, emulsified oil and dissolved oil according to the particle size of oil drops. Common oil-containing raffinate oil-water separation methods include gravity settling, air flotation, flocculation, ultrasonic wave, resin adsorption, activated carbon adsorption and the like. CN106367622A discloses an efficient and green extraction method of ion-adsorption type rare earth by taking aluminum sulfate as leaching agent, wherein in the extraction method, raffinate is deoiled by adding alkali to hydrolyze part of aluminum to form colloidal aluminum hydroxide, and the colloidal aluminum hydroxide is aggregated with oily substances in a water phase, and then the colloidal aluminum hydroxide and the oily substances are scraped out through air flotation and machinery to achieve the aim of deoiling; CN110282799A discloses a rare earth carbon sink waste water and raffinate recycling device and method, aiming at high ammonia nitrogen waste water generated in the rare earth separation process of a P507-hydrochloric acid system and ammonia saponification, circularly filtering and concentrating raffinate through a ceramic membrane filtering device to concentrate oil in the raffinate from 0.1-0.5% to 5-10%, recycling an extracting agent, and evaporating the deoiled raffinate.

But the treatment effect on oil-water separation emulsion, namely emulsified oil and dissolved oil, is not ideal, and the problems of high cost, easy generation of secondary pollution, complex operation, low recycling rate and the like exist.

Disclosure of Invention

The invention aims to provide a device and a method for deoiling raffinate in a rare earth extraction process.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the invention provides a device for removing oil from raffinate in a rare earth extraction process, which comprises an extraction device, wherein the extraction device internally comprises a mixing chamber and a clarifying chamber;

the mixing chamber is separated from the clarifying chamber by an overflow baffle;

the height of the overflow baffle is lower than that of the extraction device;

the middle rear part of the clarification chamber is provided with a conglomeration layer.

As a preferred embodiment of the present invention, a stirring device is provided in the mixing chamber.

As a preferable technical scheme, the top of the clarifying chamber is provided with an oil phase outlet.

Preferably, the bottom of the clarification chamber is provided with a water phase outlet.

In a second aspect, the present invention provides a method for deoiling raffinate in a rare earth extraction process, wherein the method employs the apparatus of the first aspect, and the method comprises the following steps:

(1) mixing a diluent and an extractant to obtain an extracted organic phase, and then mixing the extracted organic phase with a water phase through a stirring device of a mixing chamber to extract to obtain a mixed phase;

(2) enabling the mixed phase in the step (1) to flow into a clarifying chamber through an overflow baffle, standing and phase splitting to obtain raffinate;

(3) and (3) allowing the raffinate obtained in the step (2) to enter a coalescence layer, allowing oil drops in the raffinate to pass through the coalescence layer, coalescing and floating, and discharging the deoiled raffinate through a water phase outlet.

According to the invention, by utilizing the different wettability of oil and water relative to the coalescence material, emulsified oil drops can be attached to oleophilic coalescence fibers and spread, and then the oil drops can be contacted with the oil drops attached to the fibers to be coalesced, and finally float up under the action of density difference and buoyancy along with the increase of the volume of the oil drops accumulated in the coalescence process, so that oil-water separation is realized. Oil drops in raffinate are easily captured by oleophilic fibers, and the fiber material has a good coalescence effect, but can cause the increase of pressure drop. The invention is optimized by adding proper hydrophilic fiber, which can improve the capture efficiency of emulsified oil without increasing the pressure drop of the system. In addition, the hydrophilic fiber provides a better channel for floating of oil drops. The invention reduces the production cost by a physical technology without adding any chemical agent.

As a preferred technical scheme of the invention, the diluent in the step (1) comprises kerosene.

Preferably, the extractant comprises any one of 2-ethylhexyl phosphate mono 2-ethylhexyl (P507), diisooctyl phosphate (P204), chloroform or tributyl phosphate (TBP), or a combination of at least two of these, typical but non-limiting examples being: a combination of P507 and P204, a combination of P204 and chloroform, a combination of chloroform and TBP, or the like.

Preferably, the volume ratio of the extractant to the diluent is (25-70): 30-75), and may be, for example, 25:30, 25:40, 25:50, 25:75, 35:30, 50:30 or 70:30, but is not limited to the recited values, and other values not recited within the range of values are equally applicable.

In a preferred embodiment of the present invention, the volume ratio of the organic phase to the aqueous phase in step (1) is (1-4):1, and may be, for example, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1 or 4:1, but is not limited to the values listed, and other values not listed within the range of the values are also applicable.

Preferably, the temperature of the extraction in step (1) is 20-25 ℃, for example 20 ℃, 21 ℃, 22 ℃, 23 ℃, 24 ℃ or 25 ℃, but is not limited to the recited values, and other values not recited in the range of values are equally applicable.

In a preferred embodiment of the present invention, the time for the standing in step (2) is 20 to 60min, for example, 20min, 25min, 30min, 35min, 40min, 45min, 50min, 55min or 60min, but is not limited to the above-mentioned values, and other values not listed in the above-mentioned range are also applicable.

In a preferred embodiment of the present invention, the coalesced layer in step (3) comprises 4 to 10 coalesced webs, for example, 4, 5, 6, 7, 8, 9 or 10 coalesced webs, but not limited to the values listed, and other values not listed in the range of the values are also applicable, and preferably 8 to 10 coalesced webs.

In the present invention, the larger the number of the coalesced mesh layers is, the larger the coalesced area of the oil droplets is, the more effective coalescence is likely to occur, and therefore, the oil-water separation effect is better.

Preferably, the length of the coalescing layer is between 1 and 4cm, and may be, for example, 1cm, 1.5cm, 2cm, 2.5cm, 3cm, 3.5cm or 4cm, but is not limited to the values recited, and other values not recited within the range are equally suitable, preferably between 3 and 4 cm.

As a preferred technical scheme, the coalescence net comprises hydrophilic fibers and oleophilic fibers.

Preferably, the ratio of the hydrophilic fibers to the lipophilic fibers is 1 (0.3-3), and may be, for example, 1:0.3, 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5 or 1:3, but is not limited to the recited values, and other values not recited in the range of values are also applicable.

Preferably, the hydrophilic fibers comprise glass fibers and/or stainless steel fibers.

Preferably, the oleophilic fibers comprise polytetrafluoroethylene fibers and/or polypropylene fibers.

As a preferred technical scheme of the invention, the method comprises the following steps:

(1) mixing (25-70) diluent and extractant according to the volume ratio of (30-75) to obtain an extracted organic phase, then mixing the extracted organic phase with the water phase through a stirring device of a mixing chamber, and extracting at 20-25 ℃ to obtain a mixed phase;

the volume ratio of the organic phase to the aqueous phase is (1-4) to 1;

(2) allowing the mixed phase obtained in the step (1) to flow into a clarifying chamber through an overflow baffle, standing for 20-60min, and performing phase separation to obtain raffinate;

(3) allowing the raffinate obtained in the step (2) to enter a coalescence layer, allowing oil drops in the raffinate to coalesce and float through the coalescence layer, and discharging the deoiled raffinate through a water phase outlet;

the coalescing layer comprises 4-10 coalesced webs; the length of the aggregation net is 1-4 cm.

The numerical ranges set forth herein include not only the recited values but also any values between the recited numerical ranges not enumerated herein, and are not intended to be exhaustive or otherwise clear from the intended disclosure of the invention in view of brevity and clarity.

Compared with the prior art, the invention has the following beneficial effects:

(1) according to the device provided by the invention, the coalescence layer is arranged at the middle rear part of the clarification chamber, so that the continuous oil removal of the raffinate is realized, and the coalescence layer is simple to prepare, convenient to replace and maintain and capable of being repeatedly used;

(2) the method provided by the invention can realize the oil removal of the rare earth extraction raffinate through a physical technology without adding any chemical agent, reduces the production cost, and is also suitable for the oil-water separation of oil-water mixed liquid in other industries.

Drawings

FIG. 1 is a schematic diagram of an apparatus for removing oil from raffinate in a rare earth extraction process as provided in example 1;

FIG. 2 is a schematic flow chart illustrating the oil removal process of raffinate from a rare earth extraction process as provided in example 2;

FIG. 3 is a schematic representation of a coalescing layer provided by the present invention;

wherein: 1-a mixing chamber, 2-a clarifying chamber, 3-an overflow baffle, 4-a coalescing layer, 5-a stirring device, 6-a liquid level height adjusting valve, 7-an oil phase outlet and 8-a water phase outlet.

Detailed Description

The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

Example 1

The embodiment provides a device for removing oil from raffinate in a rare earth extraction process, and as shown in fig. 1, the device comprises an extraction device, wherein the extraction device internally comprises a mixing chamber 1 and a clarifying chamber 2;

the mixing chamber 1 is separated from the clarifying chamber 2 by an overflow baffle 3;

the height of the overflow baffle 3 is lower than that of the extraction device;

a stirring device 5 is arranged in the mixing chamber 1;

the middle rear part of the clarification chamber 2 is provided with a coagulation layer 4;

the rear part of the clarifying chamber 2 is provided with a liquid level height adjusting valve 6;

an oil phase outlet 7 is arranged at the top of the clarifying chamber;

the bottom of the clarification chamber is provided with a water phase outlet 8.

Example 2

The embodiment provides a method for removing oil from raffinate in a rare earth extraction process, which adopts the device provided in embodiment 1, and the flow chart of the method is shown in fig. 2, and the method comprises the following steps:

(1) mixing P507 and kerosene according to the volume ratio of 25:75 to obtain an extracted organic phase, and then mixing the extracted organic phase with a water phase through a stirring device 5 of a mixing chamber 1 at the temperature of 20 ℃ to extract to obtain a mixed phase;

the volume ratio of the organic phase to the aqueous phase is 1: 1;

(2) allowing the mixed phase obtained in the step (1) to flow into a clarifying chamber 2 through an overflow baffle 3, standing for 20min, and performing phase separation to obtain raffinate;

(3) allowing the raffinate obtained in the step (2) to enter a coalescence layer 4 consisting of 4 coalescence nets, wherein the thickness of the coalescence layer 4 is 1cm, oil drops in the raffinate float upwards through coalescence of the coalescence layer 4, standing for 20min, and discharging the deoiled raffinate through a water phase outlet 8;

the aggregation net is formed by blending hydrophilic fibers and lipophilic fibers with the layer ratio of 1: 3; the hydrophilic fiber is glass fiber, and the oleophylic fiber is polytetrafluoroethylene fiber.

Example 3

This example is different from example 2 only in that it is the same as example 2 except that the coalescing layer 4 in step (3) is composed of 6 coalescing webs having a thickness of 2 cm.

Example 4

This example differs from example 2 only in that it is the same as example 2 except that in step (3) the polymeric layer 4 consists of 8 polymeric webs having a thickness of 3 cm.

Example 5

This example is different from example 2 only in that it is the same as example 2 except that the coalescing layer 4 in step (3) is composed of 10 coalescing webs having a thickness of 4 cm.

Example 6

This example is different from example 2 only in that it is the same as example 2 except that the coalescing layer 4 in step (3) is composed of 2 coalescing webs having a thickness of 0.5 cm.

Example 7

This example differs from example 2 only in that it is the same as example 2 except that in step (3) the polymeric layer 4 consists of 12 layers of polymeric mesh having a thickness of 5 cm.

Example 8

This example differs from example 5 only in that it is the same as example 5 except that in step (3) the coherent web is a blend of hydrophilic fibers and lipophilic fibers in a layer ratio of 1:1.

Example 9

This example differs from example 5 only in that it is the same as example 5 except that in step (3) the coherent web is a blend of hydrophilic fibers and lipophilic fibers in a layer ratio of 1: 4.

Example 10

This example differs from example 5 only in that it is the same as example 5 except that the coalesced webs in step (3) are all hydrophilic fibers.

Example 11

This example differs from example 5 only in that it is the same as example 5 except that in step (3) the coalesced webs are all oleophilic fibers.

Example 12

The embodiment provides a method for removing oil from raffinate in a rare earth extraction process, which comprises the following steps:

(1) mixing P204 and kerosene according to the volume ratio of 30:70 to obtain an extracted organic phase, and then mixing the extracted organic phase with a water phase through a stirring device 5 of a mixing chamber 1 at the temperature of 20 ℃ to extract to obtain a mixed phase;

the volume ratio of the organic phase to the aqueous phase is 2: 1;

(2) allowing the mixed phase obtained in the step (1) to flow into a clarification chamber 2 through an overflow baffle 3, standing for 30min, and performing phase splitting to obtain raffinate;

(3) allowing the raffinate obtained in the step (2) to enter a coalescence layer 4 consisting of 10 coalescence nets, wherein the thickness of the coalescence layer 4 is 4cm, oil drops in the raffinate float upwards through coalescence of the coalescence layer 4, standing for 30min, and discharging the deoiled raffinate through a water phase outlet 8;

the coagulation net is formed by blending hydrophilic fibers and oleophylic fibers in a mass ratio of 1:3, the hydrophilic fibers are stainless steel fibers, and the oleophylic fibers are polytetrafluoroethylene fibers.

Example 13

(1) mixing chloroform and kerosene according to the volume ratio of 40:60 to obtain an extracted organic phase, and then mixing the extracted organic phase with a water phase through a stirring device 5 of a mixing chamber 1 at 20 ℃ to extract to obtain a mixed phase;

the volume ratio of the organic phase to the aqueous phase is 3: 1;

(2) allowing the mixed phase obtained in the step (1) to flow into a clarification chamber 2 through an overflow baffle 3, standing for 40min, and performing phase splitting to obtain raffinate;

(3) allowing the raffinate obtained in the step (2) to enter a coalescence layer 4 consisting of 10 coalescence nets, wherein the thickness of the coalescence layer 4 is 4cm, oil drops in the raffinate float upwards through coalescence of the coalescence layer 4, standing for 40min, and discharging the deoiled raffinate through a water phase outlet 8;

Example 14

This example differs from example 7 only in that it is the same as example 7 except that in step (1) the TBP and kerosene are mixed at a volume ratio of 50:50 to give an organic phase for extraction which has a volume ratio of 4:1 to the aqueous phase.

Comparative example 1

This comparative example differs from example 1 only in that the middle rear part of the clarifying chamber of the apparatus is provided with an adsorption layer, and the rest is the same as example 1.

Comparative example 2

The comparative example provides a method for deoiling raffinate in a rare earth extraction process, which adopts the device provided in comparative example 1, and comprises the following steps:

(1) mixing P507 and kerosene according to the volume ratio of 25:75 to obtain an extracted organic phase, and then mixing the extracted organic phase with a water phase through a stirring device of a mixing chamber at 20 ℃ to extract to obtain a mixed phase; the volume ratio of the organic phase to the aqueous phase is 1: 1;

(2) allowing the mixed phase obtained in the step (1) to flow into a clarifying chamber through an overflow baffle, standing for 20min, and performing phase splitting to obtain raffinate;

(3) and (3) allowing the raffinate obtained in the step (2) to enter an adsorption layer, wherein the thickness of the raffinate is 1cm, standing for 20min, and discharging the adsorbed raffinate through a water phase outlet, wherein the adsorption layer is a fiber ball.

The oil contents of the raffinates in step (2) and the oil contents of the raffinates discharged in step (3) in examples 2 to 14 and comparative example 2 were measured using a COD meter, and the test results are shown in table 1.

TABLE 1

As can be seen from Table 1:

(1) the method provided by the invention can efficiently remove oil drops in the raffinate, and realizes the standard discharge of the raffinate;

(2) as can be seen from the comparison of examples 2 to 5, the higher the number of the coalescent mesh in the coalescent layer, the stronger the oil removing ability; as is clear from comparison between example 2 and examples 6 to 7, when the number of the coalescing networks in the coalescing layer is too small, the oil droplets do not have time to coalesce and float up because the effective coalescing area is too small; when the number of the aggregation net layers in the aggregation layer is too high, oil drops cannot float upwards after being aggregated due to too large space occupied by the aggregation layer, so that the oil removal capacity is reduced;

(3) compared with the example 5 and the example 9, when the proportion of the hydrophilic fibers and the oleophylic fibers in the knotted net is too small, the hydrophilic fibers have smaller proportion, so that the pressure drop is reduced, and the capacity of providing oil drop floating channels is lower than that of the example 5, so that the oil removing capacity is reduced;

(4) as can be seen from the comparison between example 5 and examples 10 to 11, when the coherent web is woven by only hydrophilic fibers, oil droplets of emulsified oil in the raffinate have insufficient wettability on the hydrophilic fibers, the oil droplets cannot spread on the fibers, wetting coalescence cannot occur, collision coalescence is the main coalescence mode, but collision coalescence is more difficult than wetting coalescence, resulting in reduced oil removal capability; when the aggregation net is only woven by oleophylic fibers, oil drops of emulsified oil are very easy to wet and spread on the fibers, an oil film is easily formed on the surface of the aggregation layer along with the increase of operation time, the subsequent oil drops can only be collided and aggregated, and the oil film is formed to cause the increase of system pressure drop and the reduction of oil removal capacity;

(5) compared with the comparative example 2, the comparison of the example 2 and the comparative example 2 shows that when the adsorption layer is adopted for filtration, the fiber ball is formed by tying single wetting fiber, is very compact, cannot achieve the purpose of coalescence and floating, and has insufficient removal capacity on emulsified oil drops; in addition, because the fibers cannot be dispersed in the back washing process, the intercepted floating oil is difficult to fall off, and the cleanliness of the filter material is reduced; in conclusion, the oil removing capability is inferior to that of the aggregation layer.

Fig. 3 is a schematic diagram of a coalescing layer provided by the present invention, which utilizes the difference in wettability of two phases of oil and water with respect to a coalescing material, so that emulsified oil droplets can adhere to oleophilic coalescing fibers and spread, and then the oil droplets come into contact with the oil droplets already adhered to the fibers to coalesce, and as the volume of the oil droplets accumulated in the coalescing process increases, the oil droplets float under the action of density difference and buoyancy, so as to achieve oil-water separation.

The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must be implemented depending on the above detailed structural features. It should be understood by those skilled in the art that any modifications of the present invention, equivalent substitutions of selected components of the present invention, additions of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.

The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.

It should be noted that, in the above embodiments, the various features described in the above embodiments may be combined in any suitable manner, and in order to avoid unnecessary repetition, the present invention does not separately describe various possible combinations.

In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.

Claims

1. The device for removing oil from raffinate in the rare earth extraction process is characterized by comprising an extraction device, wherein the extraction device internally comprises a mixing chamber and a clarifying chamber;

the height of the overflow baffle is lower than that of the extraction device;

2. The apparatus of claim 1, wherein an agitation device is disposed in the mixing chamber.

3. The apparatus according to claim 1 or 2, characterized in that the top of the clarification chamber is provided with an oil phase outlet;

4. A method for deoiling raffinate in rare earth extraction process, characterized in that the method adopts the device of any one of claims 1-3, and the method comprises the following steps:

5. The method of claim 4 wherein the diluent of step (1) comprises kerosene;

preferably, the extractant comprises any one of 2-ethylhexyl phosphate, mono 2-ethylhexyl phosphate, diisooctyl phosphate, chloroform or tributyl phosphate, or a combination of at least two thereof;

preferably, the volume ratio of the extracting agent to the diluting agent is (25-70) to (30-75).

6. The process of claim 4 or 5, wherein the volume ratio of the organic phase to the aqueous phase in step (1) is (1-4): 1;

preferably, the temperature of the extraction in step (1) is 20-25 ℃.

7. The method according to any one of claims 4 to 6, wherein the standing time in the step (2) is 20 to 60 min.

8. The method of any of claims 4-7, wherein the coalesced layer of step (3) comprises 4-10 layers of coalesced mesh, preferably 8-10 layers of coalesced mesh;

preferably, the length of the coalescing layer is 1-4cm, preferably 3-4 cm.

9. The method of claim 8, wherein the polymeric netting comprises hydrophilic fibers and oleophilic fibers;

preferably, the layer ratio of the hydrophilic fibers to the lipophilic fibers is 1 (0.3-3);

preferably, the hydrophilic fibers comprise glass fibers and/or stainless steel fibers;

10. Method according to any of claims 4-9, characterized in that the method comprises the steps of:

(1) mixing an extracting agent and a diluent according to the volume ratio of (25-70) to (30-75) to obtain an extracted organic phase, then mixing the extracted organic phase with a water phase through a stirring device of a mixing chamber, and extracting at 20-25 ℃ to obtain a mixed phase;

the volume ratio of the organic phase to the aqueous phase is (1-4) to 1;

(3) allowing the raffinate obtained in the step (2) to enter a coalescence layer, allowing oil drops in the raffinate to pass through the coalescence layer, performing coalescence and floating, and discharging the deoiled raffinate through a water phase outlet;

the coalescing layer comprises 4-10 coalesced webs; the length of the aggregation layer is 1-4 cm.