A packing for a liquid-liquid extraction column and a method for producing the same

Abstract

This invention relates to a structured packing for a liquid-liquid extraction tower and its preparation method. By setting type A packing and type B packing, and by specifically setting the specific combination of the packing, a high mass transfer specific surface area and a high mass transfer efficiency are achieved during extraction in the liquid-liquid extraction tower.

Description

Technical Field

[0001] This invention belongs to the field of extraction, specifically relating to a packing material for a liquid-liquid extraction tower and its preparation method. Background Technology

[0002] Liquid-liquid extraction is widely used in the petroleum and chemical industries. Packing material is the core component of packed extraction towers, and can be classified into random packing and structured packing according to its morphology. Currently used packing materials are all gas-liquid distillation system packings. However, liquid-liquid extraction differs from gas-liquid distillation systems. Firstly, extraction and distillation have some similar requirements for packing materials, both requiring high mass transfer efficiency and large porosity to prevent flow deviation and channeling. However, in distillation, the liquid phase flows along the surface of the packing, with the packing providing the mass transfer area. In extraction, mass transfer occurs between the droplet cluster and the continuous phase. The packing's role is to control backmixing and achieve a cycle of droplet breakage-coalescence-re-breakage, affecting the residence time of the dispersed phase. Therefore, while burr-like packing is beneficial for mass transfer in distillation, it is detrimental in extraction. Summary of the Invention

[0003] To address the aforementioned technical problems, the present invention aims to provide a packing material for a liquid-liquid extraction tower and its preparation method, thereby achieving the droplet breakage and aggregation process. Simultaneously, based on the selection of the packing material, the dispersed phase droplets can be effectively aggregated, thus improving the aggregation mass transfer efficiency.

[0004] This is achieved through the following technical means:

[0005] A packing material for a liquid-liquid extraction tower is provided, comprising type A packing and type B packing arranged by compression. The type A packing is stainless steel wire with a diameter of 0.8-1.2 mm, and the type B packing is stainless steel wire with a diameter of 0.3-0.6 mm coated with a composite filament formed of polytetrafluoroethylene (PTFE). The PTFE coating makes the diameter of the composite filament of the type B packing 0.85-1.25 mm. Each type A packing is bent into a zigzag shape with a bend angle of 15-60° and a bend length of 5-10 mm. Similarly, each type B packing is bent into a zigzag shape with a bend angle of 15-60° and a bend length of 5-10 mm.

[0006] Each vertices of the zigzag shape of the A-type or B-type packing are connected to the vertices of the zigzag shape of the adjacent A-type or B-type packing to form a surface. The surface formed by the interconnected A-type or B-type packing is a pressed wavy surface with a diameter of 1 to 6 cm.

[0007] The wavy surface formed by the interconnection of type A packing is called type A wavy surface, and the wavy surface formed by the interconnection of type B packing is called type B wavy surface. By stacking and assembling multiple types A wavy surfaces, a multi-layered AAA structure is formed; by stacking and assembling multiple types A wavy surfaces and multiple types B wavy surfaces, a circulating multi-layered ABB structure is formed; and by stacking and assembling multiple types B wavy surfaces, a multi-layered BBB structure is formed. The multi-layered AAA structure, the multi-layered ABB structure, and the multi-layered BBB structure are stacked and arranged to form the packing for the liquid-liquid extraction tower.

[0008] Preferably, when the interfacial tension γ of the material being processed is greater than or equal to the interfacial tension threshold, the angle of the bend of the type A packing is 45~60° and the angle of the bend of the type B packing is 45~60°; when the interfacial tension γ of the material being processed is less than the interfacial tension threshold, the angle of the bend of the type A packing is 15~45° and the angle of the bend of the type B packing is 15~45°, and the interfacial tension threshold is 18~26 mN / m.

[0009] Preferably, the packing material of the liquid-liquid extraction tower is arranged from top to bottom as a multi-layer stacked layer of BBB, a multi-layer stacked layer of ABB circulation, and a multi-layer stacked layer of AAA, and the thickness ratio of each layer is (0.8~1.1): (1.8~2.5): (7.5~8.5).

[0010] Preferably, the packing material of the liquid-liquid extraction tower is arranged from top to bottom as a multi-layer stacked layer of BBB, a multi-layer stacked layer of ABB circulation, and a multi-layer stacked layer of AAA, and the thickness ratio of each layer is (7.3~8.3): (1.6~2.3): 1 for the multi-layer stacked layer of BBB: the multi-layer stacked layer of ABB circulation: the multi-layer stacked layer of AAA.

[0011] Preferably, the diameter of the wavy surface is 2 to 5 cm.

[0012] Preferably, when the interfacial tension γ of the material being processed is greater than or equal to the interfacial tension threshold, the diameter of the wavy surface is 3-5 cm; when the interfacial tension γ of the material being processed is less than the interfacial tension threshold, the diameter of the wavy surface is 2-3 cm, and the interfacial tension threshold is 18-26 mN / m.

[0013] A method for preparing packing material for a liquid-liquid extraction tower, wherein the packing material is the aforementioned packing material for a liquid-liquid extraction tower, includes the following steps:

[0014] (1) Take a stainless steel wire with a diameter of 0.3~0.6mm, and wrap a polytetrafluoroethylene layer with a thickness of 0.2~0.3mm around the outside of the stainless steel wire to form a composite filament type B filler. Then bend the formed type B filler in a zigzag shape; bend the stainless steel wire of type A filler in a zigzag shape.

[0015] (2) Connect the multiple zigzag-shaped A-type packings obtained in step (1) with the vertices of each zigzag corner to the vertices of each zigzag corner of the adjacent A-type packings to form a surface; connect the multiple zigzag-shaped B-type packings obtained in step (1) with the vertices of each zigzag corner to the vertices of each zigzag corner of the adjacent B-type packings to form a surface.

[0016] (3) The surface of the A-type filler obtained in step (2) is pressed with a solid metal rod with a diameter of 1~6cm in both directions to form a single-layer A-type wavy surface; the surface of the B-type filler obtained in step (2) is pressed with a solid metal rod with a diameter of 1~6cm in both directions to form a single-layer B-type wavy surface.

[0017] (4) The single-layer A-type wave surface and the single-layer B-type wave surface obtained in step (3) are stacked in multiple layers to form a multi-layer AAA layer, a cyclic multi-layer ABB layer, and a multi-layer BBB layer.

[0018] (5) Stack the multilayer stacked AAA, the circulating multilayer stacked ABB and the multilayer stacked BBB obtained in step (4) respectively to obtain the packing material for the liquid-liquid extraction tower.

[0019] Preferably, in step (5), a multilayer stacked layer of AAA with a thickness of 3.2 to 3.8 is stacked on top of a multilayer stacked layer of AAA with a thickness of 1.6 to 1.9, and then a multilayer stacked layer of BBB with a thickness of 12 to 16 is stacked on top of the multilayer stacked layer of ABB to form a packing material for a liquid-liquid extraction tower.

[0020] Preferably, in step (5), a multilayer stacked layer of ABB with a thickness of 3.2 to 3.8 is stacked on top of a multilayer stacked layer of AAA with a thickness of 12 to 16, and then a multilayer stacked layer of BBB with a thickness of 1.6 to 1.9 is stacked on top of the multilayer stacked layer of ABB to form a packing material for a liquid-liquid extraction tower.

[0021] Preferably, when the interfacial tension γ of the material being processed is greater than or equal to the interfacial tension threshold, the diameter of the solid metal rod is 3-5 cm; when the interfacial tension γ of the material being processed is less than the interfacial tension threshold, the diameter of the solid metal rod is 2-3 cm, and the interfacial tension threshold is 18-26 mN / m.

[0022] The technical advantages of this invention are as follows:

[0023] Based on the exploration of the motion behavior and mass transfer results of dispersed phase droplets on the packing surface, it is found that when the interfacial tension of the droplets is large, larger droplets can be formed. The larger the bending angle, the larger the mass transfer surface formed by the droplets stretching on the bending gap. Conversely, when the interfacial tension is small, smaller droplets are formed. Only when the bending angle is small can small droplets be stretched on the bending surface to form a larger mass transfer surface. The specific material selection of this invention can give full play to the role of droplet surface tension and wettability. Therefore, this invention sets different materials for Type A packing and Type B packing as special packing for liquid-liquid extraction.

[0024] This invention achieves effective droplet breakage and coalescence through the specific arrangement of packing materials. Since the packing materials used in this invention are specifically designed for liquid-liquid extraction, this effect can be achieved, whereas they cannot be used in gas-liquid distillation systems. This allows the packing materials of this invention to be specifically applied to liquid-liquid extraction, thereby achieving optimal extraction results. By assembling packing materials of different materials, aqueous droplets can effectively coalesce on the surface of either type A or type B packing materials, and break up due to the non-wetting characteristics of the packing materials. This technology not only achieves effective droplet breakage and coalescence during the extraction process, but also, based on the interfacial tension and wettability of droplets, the droplets are stretched and spread on the corresponding packing surfaces, increasing the mass transfer specific surface area and improving the mass transfer efficiency by 30-60%. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of a single type A packing in one embodiment.

[0026] Figure 2 This is a top view schematic diagram of the interconnected structure of multiple type A packings in one embodiment.

[0027] Figure 3 This is a side view of a single-layer A-shaped wavy surface as one embodiment.

[0028] Figure 4 This is a side view schematic diagram of a multi-layered A-shaped wavy surface superimposed and assembled according to one embodiment.

[0029] Figure 5This is a schematic diagram of the cross-sectional structure of a single type B packing in one embodiment. Wherein: 1-a single type A packing, 11-the bent section of type A packing, 12-the apex of the zigzag bend of type A packing, 13-a single-layer type A corrugated surface, 21-a single-layer type B corrugated surface, 22-the stainless steel wire core of type B packing, 23-the polytetrafluoroethylene layer on the outside of type B packing, Ф-the diameter of the corrugated surface. Detailed Implementation

[0030] The process technology solution of the present invention will be further described below with reference to embodiments and accompanying drawings. Unless otherwise specified, each feature is merely one example of a series of equivalent or similar features. These embodiments are merely for the purpose of aiding understanding the present invention and should not be considered as specific limitations thereof.

[0031] Example 1

[0032] like Figure 1-5 The liquid-liquid extraction tower packing shown in this embodiment is used to process materials with low interfacial tension (less than the interfacial tension threshold), specifically 10.23 mN / m. The packing is composed of type A and type B packing arranged by compression. The type A packing is made of stainless steel wire with a diameter of 1 mm. Figure 5 As shown, the type B packing consists of a 0.5mm stainless steel wire coated with a composite filament formed of polytetrafluoroethylene (PTFE). The PTFE coating results in a 1mm diameter composite filament for the type B packing. Each type A packing is bent as shown... Figure 1 The zigzag shape shown has a 28° bend angle and each bend segment is 9mm long. Each of the B-type packings is bent into a zigzag shape with a 28° bend angle and each bend segment is 9mm long.

[0033] Each vertices of the zigzag shape of the type A or type B packing connect with the vertices of the zigzag shape of the adjacent type A or type B packing to form a surface. The surface formed by the interconnected type A or type B packing is a pressed wavy surface with a diameter Ф of 2.5 cm.

[0034] The wavy surface formed by the interconnection of type A packing is called type A wavy surface, and the wavy surface formed by the interconnection of type B packing is called type B wavy surface. By stacking and assembling multiple types A wavy surfaces, a multi-layered AAA structure is formed; by stacking and assembling multiple types A wavy surfaces and multiple types B wavy surfaces, a circulating multi-layered ABB structure is formed; and by stacking and assembling multiple types B wavy surfaces, a multi-layered BBB structure is formed. The multi-layered AAA structure, the multi-layered ABB structure, and the multi-layered BBB structure are stacked and arranged to form the packing for the liquid-liquid extraction tower.

[0035] like Figure 4 As shown, the packing material for the liquid-liquid extraction tower in this embodiment is arranged from top to bottom as a multi-layer stacked layer of BBB, a multi-layer stacked layer of ABB circulation, and a multi-layer stacked layer of AAA, with the thickness ratio of each layer being 1:2:8 for the multi-layer stacked layer of BBB: the multi-layer stacked layer of ABB circulation: the multi-layer stacked layer of AAA.

[0036] Comparative Example 1

[0037] This comparative example uses a multi-layered, circular arc mesh packing structure. Comparison with extraction experiments conducted under the same conditions as Example 1 revealed that the extraction efficiency of Example 1 was 68.3%, while the extraction efficiency of this comparative example was 45.63%. Therefore, it can be concluded that the type A and type B packings specifically configured in this invention can significantly improve extraction efficiency.

[0038] Comparative Example 2: This comparative example only uses type A packing material and does not use type B packing material. Other settings are the same as in Example 1. By comparing the extraction test under the same conditions as in Example 1, it was found that the extraction efficiency of this comparative example 2 was 59.1%, while the extraction efficiency of Example 1 was 68.3%. Therefore, it can be concluded that the specific combination of the two different types of packing material in this invention can improve the extraction efficiency.

Claims

1. A packing material for a liquid-liquid extraction tower, characterized in that, The packing material for the liquid-liquid extraction tower is formed by pressing and arranging type A and type B packing materials. The type A packing material is stainless steel wire with a diameter of 0.8~1.2mm, and the type B packing material is stainless steel wire with a diameter of 0.3~0.6mm coated with polytetrafluoroethylene (PTFE) composite filaments. The PTFE coating makes the diameter of the composite filaments of the type B packing material 0.85~1.25mm. Each type A packing material is bent into a zigzag shape with a bend angle of 15~60° and the length of each bend segment is 5~10mm. Similarly, each type B packing material is bent into a zigzag shape with a bend angle of 15~60° and the length of each bend segment is 5~10mm. The vertices of each bend in the zigzag shape of each type A or type B packing are connected to the vertices of each bend in the zigzag shape of the adjacent type A or type B packing to form a surface. The surface formed by the interconnected type A or type B packing is a pressed wavy surface with a diameter of 1 to 6 cm. The wavy surface formed by the interconnection of type A packing is called type A wavy surface, and the wavy surface formed by the interconnection of type B packing is called type B wavy surface. By stacking and assembling multiple types A wavy surfaces, a multi-layered AAA structure is formed; by stacking and assembling multiple types A wavy surfaces and multiple types B wavy surfaces, a circulating multi-layered ABB structure is formed; and by stacking and assembling multiple types B wavy surfaces, a multi-layered BBB structure is formed. The multi-layered AAA structure, the multi-layered ABB structure, and the multi-layered BBB structure are stacked and arranged to form the packing for the liquid-liquid extraction tower.

2. The packing material for a liquid-liquid extraction tower according to claim 1, characterized in that, When the interfacial tension γ of the material being processed is greater than or equal to the interfacial tension threshold, the angle of the bend of the type A packing is 45~60° and the angle of the bend of the type B packing is 45~60°; when the interfacial tension γ of the material being processed is less than the interfacial tension threshold, the angle of the bend of the type A packing is 15~45° and the angle of the bend of the type B packing is 15~45°, and the interfacial tension threshold is 18~26 mN / m.

3. The packing material for a liquid-liquid extraction tower according to claim 1, characterized in that, The packing material of the liquid-liquid extraction tower is arranged from top to bottom as a multi-layer stacked layer of BBB, a multi-layer stacked layer of ABB circulation, and a multi-layer stacked layer of AAA, with the thickness ratio of the multi-layer stacked layer of BBB: multi-layer stacked layer of ABB circulation: multi-layer stacked layer of AAA being (0.8~1.1): (1.8~2.5): (7.5~8.5).

4. The packing material for a liquid-liquid extraction tower according to claim 1, characterized in that, The packing material of the liquid-liquid extraction tower is arranged from top to bottom as a multi-layer stacked layer of BBB, a multi-layer stacked layer of ABB circulation, and a multi-layer stacked layer of AAA, with the thickness ratio of the multi-layer stacked layer of BBB: multi-layer stacked layer of ABB circulation: multi-layer stacked layer of AAA being (7.3~8.3): (1.6~2.3):

1.

5. The packing material for a liquid-liquid extraction tower according to claim 1, characterized in that, The diameter of the wavy surface is 2-5 cm.

6. The packing material for a liquid-liquid extraction tower according to claim 1, characterized in that, When the interfacial tension γ of the material being processed is greater than or equal to the interfacial tension threshold, the diameter of the wavy surface is 3-5 cm; when the interfacial tension γ of the material being processed is less than the interfacial tension threshold, the diameter of the wavy surface is 2-3 cm, and the interfacial tension threshold is 18-26 mN / m.

7. A method for preparing packing material for a liquid-liquid extraction tower, characterized in that, The packing material for the liquid-liquid extraction tower is the packing material for the liquid-liquid extraction tower according to any one of claims 1 to 6, and includes the following steps: (1) Take a stainless steel wire with a diameter of 0.3~0.6mm, and wrap a polytetrafluoroethylene layer with a thickness of 0.2~0.3mm on the outside of the stainless steel wire to form a composite filament type B filler. Then bend the formed type B filler in a zigzag shape; bend the stainless steel wire of type A filler in a zigzag shape. (2) Connect the multiple zigzag-shaped A-type packings obtained in step (1) with the vertices of each zigzag corner to the vertices of each zigzag corner of the adjacent A-type packings to form a surface; connect the multiple zigzag-shaped B-type packings obtained in step (1) with the vertices of each zigzag corner to the vertices of each zigzag corner of the adjacent B-type packings to form a surface; (3) The surface formed by the type A filler obtained in step (2) is pressed with a solid metal rod with a diameter of 1~6cm in both directions on the upper and lower surfaces to form a single-layer type A wave surface; the surface formed by the type B filler obtained in step (2) is pressed with a solid metal rod with a diameter of 1~6cm in both directions on the upper and lower surfaces to form a single-layer type B wave surface. (4) The single-layer A-type wave surface and the single-layer B-type wave surface obtained in step (3) are stacked in multiple layers to form a multi-layer superimposed layer of AAA, a cyclic multi-layer superimposed layer of ABB, and a multi-layer superimposed layer of BBB. (5) Stack the multilayer stacked AAA, the circulating multilayer stacked ABB and the multilayer stacked BBB obtained in step (4) respectively to obtain the packing material for the liquid-liquid extraction tower.

8. The preparation method according to claim 7, characterized in that, In step (5), a multilayer stack of AAA with a thickness of 1.6 to 1.9 is stacked on top of a multilayer stack of ABB with a thickness of 3.2 to 3.8, and then a multilayer stack of BBB with a thickness of 12 to 16 is stacked on top of the multilayer stack of ABB to form a packing material for liquid-liquid extraction towers.

9. The preparation method according to claim 7, characterized in that, In step (5), a multilayer stack of ABB with a thickness of 3.2 to 3.8 is stacked on top of a multilayer stack of AAA with a thickness of 12 to 16, and then a multilayer stack of BBB with a thickness of 1.6 to 1.9 is stacked on top of the multilayer stack of ABB to form a packing material for liquid-liquid extraction towers.

10. The preparation method according to claim 7, characterized in that, When the interfacial tension γ of the material being processed is greater than or equal to the interfacial tension threshold, the diameter of the solid metal rod is 3-5 cm; when the interfacial tension γ of the material being processed is less than the interfacial tension threshold, the diameter of the solid metal rod is 2-3 cm, and the interfacial tension threshold is 18-26 mN / m.

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