Nmp dynamic rectification device and control method thereof

Abstract

The application discloses NMP dynamic rectification equipment and a control method thereof, and relates to the technical field of NMP waste liquid treatment.The application is characterized in that a roughness larger peristaltic diffusion layer, a roughness second radiation diffusion layer and a relatively smooth wetting escape layer are arranged on the surface of the evaporator in the molecular distillation cylinder, and the roughness of the peristaltic diffusion layer and the radiation diffusion layer is linearly reduced from top to bottom, so that a stronger solid-liquid surface energy is formed when the waste liquid contacts the evaporation surface, the liquid slides down under the action of its own gravity, continuously diffuses, forms a multiple linearized "scattered" liquid state from top to bottom, and efficiently completes molecular distillation in the wetting escape layer, thereby reducing the rolling boiling phenomenon of the waste liquid on the evaporation surface of the evaporator and improving the falling film molecular distillation effect.

Description

Technical Field

[0001] This invention relates to the field of NMP waste liquid treatment technology, and in particular to a dynamic NMP distillation equipment and its control method. Background Technology

[0002] Molecular distillation is a special liquid-liquid separation technique. Unlike traditional distillation, which relies on boiling point differences, it separates substances based on the difference in the mean free path of molecular motion. When a liquid mixture flows along a heating plate and is heated, lighter and heavier molecules escape from the liquid surface and enter the gas phase. Due to the different mean free paths of these molecules, they travel different distances after escaping from the liquid surface. If a condenser plate is appropriately placed, the lighter molecules reach the condenser plate and are condensed and discharged, while the heavier molecules do not reach the condenser plate and are discharged along the mixture. This achieves the separation of substances. The pressure difference between the boiling film and the condenser surface is the driving force for the vapor flow; even a small pressure drop will cause vapor to flow.

[0003] NMP waste liquid, as an industrial waste liquid with recyclable main components, has significant recovery value. Molecular distillation can significantly improve recovery accuracy when separating and recovering NMP waste liquid. However, centrifugal molecular distillation equipment has high requirements for overall equipment sealing, structural cost, and operating environment. While falling film molecular distillation equipment has a simple structure, the large liquid flow rate when the waste liquid first enters the evaporator surface causes a large amount of liquid to roll and boil, severely affecting the molecular distillation separation effect. Therefore, reducing the boiling phenomenon on the evaporator surface and improving the efficiency of falling film molecular distillation is a problem that needs to be solved when using falling film molecular distillation equipment to process NMP waste liquid. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a dynamic NMP distillation equipment and its control method, thereby reducing the boiling phenomenon of waste liquid on the evaporation surface of the evaporator and improving the effect of falling film molecular distillation.

[0005] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0006] This invention provides a dynamic NMP distillation apparatus, including a molecular distillation cylinder connected to a vacuum pipe, an evaporator with an evaporation surface built into the molecular distillation cylinder, a distributor located above the evaporator and a feed pipe connected to the distributor, and a condenser built into the molecular distillation cylinder, the condenser having a condensation surface facing the evaporator, and a molecular free-travel space formed between the evaporation surface and the condensation surface.

[0007] The evaporation surface is continuously composed of a peristaltic diffusion layer, a radiation diffusion layer, and a humidification escape layer from top to bottom. The surfaces of the peristaltic diffusion layer and the radiation diffusion layer are continuous isosceles trapezoidal surfaces, while the surface of the humidification escape layer is rectangular. Among them, the top side width of the peristaltic diffusion layer is the smallest, and the bottom side width of the radiation diffusion layer is the same as the width of the humidification escape layer.

[0008] The surface roughness of the creep diffusion layer, radiation diffusion layer, and wettability escape layer decreases sequentially. Specifically, the surface roughness of the creep diffusion layer and radiation diffusion layer gradually decreases from top to bottom, with the roughness at the lowest point of the creep diffusion layer being greater than the roughness at the highest point of the radiation diffusion layer. The wettability escape layer has a uniform surface roughness, while the roughness at the lowest point of the radiation diffusion layer is the same as that of the wettability escape layer. Let the average surface roughness of the creep diffusion layer be... Let the average roughness of the radiation diffusion layer surface be... Let the surface area of ​​the peristaltic diffusion layer be... Let the surface area of ​​the radiation diffusion layer be... ,but .

[0009] The molecular distillation cylinder has a built-in heavy component collection mechanism located below the evaporator, and the vertical distribution range of the heavy component collection mechanism is located in the inner area of ​​the condenser surface.

[0010] As a preferred technical solution of the distillation equipment of the present invention: the condenser is equipped with a cooling pipe with dynamic circulating coolant.

[0011] As a preferred technical solution of the distillation equipment of the present invention: in the vertical direction, the distribution range of the condensing surface of the condenser matches the distribution range of the evaporating surface of the evaporator.

[0012] As a preferred embodiment of the distillation apparatus of the present invention: the bottom of the molecular distillation cylinder is provided with a heavy component pipeline and a light component pipeline. The heavy component pipeline is equipped with a first flow meter, and the light component pipeline is equipped with a second flow meter. The heavy component pipeline is connected to the heavy component collection mechanism, and the light component pipeline is connected to the cavity at the bottom of the molecular distillation cylinder.

[0013] As a preferred technical solution of the distillation equipment of the present invention: the molecular distillation cylinder is equipped with a vacuum sensor for sensing and monitoring the vacuum level inside the molecular distillation cylinder.

[0014] As a preferred technical solution of the distillation apparatus of the present invention: The peristaltic diffusion layer is divided into m continuous horizontal unit height surface regions, and the roughness of the m continuous horizontal unit height surface regions from top to bottom is as follows: ,but Suppose the radiation diffusion layer is divided into n consecutive horizontal unit height surface regions, and the roughness of the n consecutive horizontal unit height surface regions from top to bottom is as follows: ,but .

[0015] This invention provides a control method for a dynamic NMP distillation apparatus, comprising the following steps:

[0016] Step 1, "affinity" peristaltic diffusion of waste liquid: NMP waste liquid is diverted downward through the distributor to the peristaltic diffusion layer on the evaporation surface, and flows from top to bottom on the surface of the peristaltic diffusion layer, forming a peristaltic state on the surface of the peristaltic diffusion layer.

[0017] Step 2, rapid radiation diffusion of waste liquid: NMP waste liquid falls through the peristaltic diffusion layer in an "affinity" state and gradually splits. After entering the radiation diffusion layer with reduced roughness, the splitting rate of the single original liquid flow of NMP waste liquid along the surface of the radiation diffusion layer accelerates.

[0018] Step 3, Waste Liquid Film Evaporation: After the NMP waste liquid undergoes linear acceleration and diffusing through the radiation diffusion layer, the cross-sectional area of ​​each diffusing NMP waste liquid reaches its minimum at the bottom of the radiation diffusion layer. The NMP waste liquid then enters the wet escape layer with the lowest surface roughness, where a liquid film is formed. This liquid film evaporates in the vacuum environment of the molecular distillation cylinder. Lighter components with larger molecular free paths reach the condensation surface of the condenser and fall to the bottom of the molecular distillation cylinder after condensation. Heavier NMP components with smaller molecular free paths cannot reach the condensation surface of the condenser and fall into the heavy component collection mechanism.

[0019] Compared with existing technologies, the beneficial effects of this invention are:

[0020] This invention creates a multi-linear diffusion state from top to bottom by setting a rough peristaltic diffusion layer, a moderately rough radiative diffusion layer, and a relatively smooth wet escape layer on the surface of the evaporator in a molecular distillation cylinder. The roughness of the peristaltic diffusion layer and the radiative diffusion layer are set to decrease linearly from top to bottom. This not only creates a strong solid-liquid surface energy when the waste liquid comes into contact with the evaporation surface, but also causes the liquid to "peristally" slide down under its own gravity and continuously diffuse (the roughness decreases, the solid-liquid surface energy decreases, and the diffusion ability is enhanced under the same gravity). This results in a highly efficient molecular distillation in the wet escape layer, thereby reducing the boiling phenomenon of the waste liquid on the evaporation surface of the evaporator and improving the effect of falling film molecular distillation. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the molecular distillation cylinder in this invention.

[0022] Figure 2 This is a schematic diagram of the evaporator in this invention.

[0023] Figure 3This is a schematic diagram of the evaporator creep diffusion layer, radiation diffusion layer, and humidification escape layer in this invention.

[0024] Figure 4 This is a schematic diagram of the horizontal unit height area in this invention.

[0025] Wherein: 1-Molecular distillation cylinder; 2-Evaporator, 2a-Evaporation surface, 201-Peristaltic diffusion layer, 201a-Horizontal unit height area, 202-Radiative diffusion layer, 203-Wet escape layer; 3-Condenser, 3a-Condensation surface; 4-Cooling pipe; 5-Vacuum pipe; 6-Feed pipe; 7-Distributor; 8-Heavy component collection mechanism; 9-Heavy component pipeline; 10-Light component pipeline; 11-First flow meter; 12-Second flow meter; 13-Vacuum sensor. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0027] Example 1: This invention relates to a dynamic NMP distillation apparatus, the main structure of which is as follows:

[0028] Please see Figure 1 Vacuum pipe 5 is connected to molecular distillation cylinder 1. Molecular distillation cylinder 1 is equipped with vacuum sensor 13, which is used to sense and monitor the vacuum level inside the molecular distillation cylinder 1. Molecular distillation cylinder 1 has an evaporator 2 with an evaporation surface 2a. Molecular distillation cylinder 1 is equipped with a distributor 7 located above the evaporator 2. The upper side of the distributor 7 is connected to the feed pipe 6. Molecular distillation cylinder 1 has a condenser 3 with a cooling pipe 4 inside. The cooling pipe 4 dynamically circulates coolant. The condenser 3 has a condensation surface 3a facing the evaporator 2. In the vertical direction, the distribution range of the condensation surface 3a of the condenser 3 matches the distribution range of the evaporation surface 2a of the evaporator 2, forming a molecular free-travel space between the evaporation surface 2a and the condensation surface 3a. Molecular distillation cylinder 1 is equipped with a heavy component collection mechanism 8 located below the evaporator 2. The vertical distribution range of the heavy component collection mechanism 8 is located within the inner area of ​​the condensation surface 3a of the condenser 3. The bottom of the molecular distillation cylinder 1 is equipped with a heavy component pipeline 9 and a light component pipeline 10. The heavy component pipeline 9 is equipped with a first flow meter 11, and the light component pipeline 10 is equipped with a second flow meter 12. The heavy component pipeline 9 is connected to the heavy component collection mechanism 8, and the light component pipeline 10 is connected to the bottom cavity of the molecular distillation cylinder 1. The sum of the liquid flow rate monitored by the first flow meter 11 and the liquid flow rate monitored by the second flow meter 12 serves as a reference for the amount of NMP liquid dynamically supplied downwards by the distributor 7. (In conjunction with...) Figure 2 , Figure 3 This allows for more precise control of the amount of liquid on the surface of the evaporator 2, ensuring that the liquid flow state generated in real time by the peristaltic diffusion layer 201, the radiation diffusion layer 202, and the wet escape layer 203 reaches its optimal state.

[0029] Please see Figure 2 , Figure 3 The evaporation surface 2a is provided with a peristaltic diffusion layer 201, a radiation diffusion layer 202, and a moisture escape layer 203 continuously from top to bottom. The surfaces of the peristaltic diffusion layer 201 and the radiation diffusion layer 202 are both continuous isosceles trapezoidal surfaces, while the surface of the moisture escape layer 203 is rectangular. The top side of the peristaltic diffusion layer 201 has the smallest width, while the bottom side of the radiation diffusion layer 202 and the rectangular width of the moisture escape layer 203 are the same.

[0030] Please see Figure 3 , Figure 4 The surface roughness of the peristaltic diffusion layer 201, radiation diffusion layer 202, and wettability escape layer 203 decreases sequentially, meaning the surface roughness of the peristaltic diffusion layer 201 is the roughest, followed by the radiation diffusion layer 202, and the surface roughness of the wettability escape layer 203 is the smoothest. The surface roughness of the peristaltic diffusion layer 201 and radiation diffusion layer 202 gradually decreases from top to bottom, with the roughness at the lowest point of the peristaltic diffusion layer 201 being greater than the roughness at the highest point of the radiation diffusion layer 202. Furthermore, the roughness of the entire surface of the wettability escape layer 203 is the same, and the roughness at the lowest point of the radiation diffusion layer 202 is the same as the roughness of the wettability escape layer 203. Let the average roughness of the surface of the peristaltic diffusion layer 201 be... Let the average roughness of the surface of the radiation diffusion layer 202 be... Let the surface area of ​​the peristaltic diffusion layer 201 be... Let the surface area of ​​the radiation diffusion layer 202 be... ,but .

[0031] The average roughness of the creep diffusion layer 201 and the radiation diffusion layer 202 is the average roughness of all horizontal unit height surface regions 201a from top to bottom: Assume the creep diffusion layer is divided into m consecutive horizontal unit height surface regions 201a, such as... Figure 4 The unit height of the horizontal unit height region 201a is △D. Figure 4 The diagram uses the creep diffusion layer 201 as an example, and the same applies to the radiation diffusion layer 202. The roughness of m consecutive horizontal unit height surface regions 201a from top to bottom is as follows: ,but Suppose that the radiation diffusion layer 202 is divided into n consecutive horizontal unit height surface regions, and the roughness of the n consecutive horizontal unit height surface regions 201a from top to bottom is as follows: ,but .

[0032] Example 2: In this invention, the liquid flows from top to bottom. The roughness of the peristaltic diffusion layer 201 on the upper side of the evaporation surface is large, that is, the interface energy of the peristaltic diffusion layer 201 and the evaporation surface 2a is larger, and the solid-liquid surface energy generated is larger. For the liquid that continuously accumulates at the top (falls down), the external force (that is, gravity) required to roll downwards is large, and it can only naturally "perist" and diffuse downwards along the evaporation surface.

[0033] The same applies to the radiation diffusion layer 202. Its roughness is relatively smaller than that of the creep diffusion layer 201. However, in order to reduce fine boiling, the roughness cannot be too low. It is necessary to further divert the liquid flow, so that the liquid flow forms a rapid "radiation diversion" diffusion.

[0034] The lower the evaporation surface 2a is, the smoother the surface becomes. When the liquid flows to the wet escape layer 203, the wet escape layer 203 is relatively smooth and has a small surface interface energy, resulting in a small solid-liquid surface energy. At the bottom of the radiation diffusion layer 202, a relatively dense "fine" liquid flow has already formed. Once these dense "fine" liquid flows enter the wet escape layer 203, the solid-liquid surface energy decreases sharply, forming a thin liquid film that tends to be "completely wetted".

[0035] Example 3: This invention relates to a control method for a dynamic NMP distillation apparatus, including peristaltic diffusion, radiation diffusion, and liquid film formation.

[0036] First, the waste liquid undergoes "affinity" peristaltic diffusion in the peristaltic diffusion layer 201: the NMP waste liquid is diverted downward through the distributor 7 to the peristaltic diffusion layer 201 on the evaporation surface, and flows from top to bottom on the surface of the peristaltic diffusion layer 201. The NMP waste liquid forms a peristaltic state on the surface of the peristaltic diffusion layer 201. The NMP waste liquid rolls evenly downward along the surface of the peristaltic diffusion layer 201. During the downward rolling process, the surface roughness of the peristaltic diffusion layer 201 continuously decreases, and the peristaltic NMP waste liquid also continuously generates "diversion" outward.

[0037] Then, the waste liquid rapidly diffuses radiatively in the radiation diffusion layer 202: the NMP waste liquid falls in an "affinity" state through the peristaltic diffusion layer 201 and gradually splits. After entering the radiation diffusion layer 202 with reduced roughness, the splitting rate of the single original liquid flow of the NMP waste liquid along the surface of the radiation diffusion layer 202 accelerates. The splitting rate of a single original liquid flow is defined as the number of branches that diffuse outwards from a unit cross-sectional area of ​​flowing liquid within a unit longitudinal distance. For example, a cross-section with a diameter of 1... If a flowing liquid forms three branches (including the original flow, there are actually two additional new flow branches) within a flow distance of 100 mm, then the branching velocity is 3. For example, a cross-section of 1.5... If a flowing liquid forms three branches within a 100mm flow distance, then the branch velocity is 2. For example, a cross-section of 2... If a flowing liquid forms 5 branches within a flow distance of 100 mm, then the branching rate is 2.5.

[0038] Finally, the waste liquid forms a liquid film for evaporation in the wet escape layer 203: After the NMP waste liquid undergoes linear acceleration and diffusing through the radiation diffusion layer 202, the cross-sectional area of ​​each diffusing of the NMP waste liquid reaches its minimum at the bottom of the radiation diffusion layer 202. The NMP waste liquid enters the wet escape layer 203 with the lowest surface roughness, and a liquid film is formed on the wet escape layer 203. The liquid film evaporates in the vacuum environment of the molecular distillation cylinder 1. Among them, the light components with larger molecular free stroke reach the condensation surface 3a of the condenser 3 and fall to the bottom of the molecular distillation cylinder 1 after condensation. The heavy NMP components with smaller molecular free stroke cannot reach the condensation surface 3a of the condenser 3 and fall into the heavy component collection mechanism 8.

[0039] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A dynamic NMP distillation apparatus, comprising a molecular distillation cylinder (1), the molecular distillation cylinder (1) being connected to a vacuum pipe (5), the molecular distillation cylinder (1) having an evaporator (2) with an evaporation surface (2a) inside, the molecular distillation cylinder (1) being configured with a distributor (7) located above the evaporator (2) and a feed pipe (6) communicating with the distributor (7), the molecular distillation cylinder (1) having a condenser (3) inside, the condenser (3) having a condensation surface (3a) facing the evaporator (2), and a molecular free-travel space being formed between the evaporation surface (2a) and the condensation surface (3a), characterized in that: The evaporation surface (2a) is provided with a creep diffusion layer (201), a radiation diffusion layer (202), and a humidification escape layer (203) in a continuous sequence from top to bottom. The surfaces of the creep diffusion layer (201) and the radiation diffusion layer (202) are both continuous isosceles trapezoidal surfaces, and the surface of the wet escape layer (203) is rectangular; Among them, the top side width of the peristaltic diffusion layer (201) is the smallest, and the bottom side width of the radiation diffusion layer (202) is the same as the width of the wet escape layer (203). The surface roughness of the creep diffusion layer (201), the radiation diffusion layer (202), and the wet escape layer (203) decreases sequentially. The surface roughness of the creep diffusion layer (201) and the radiation diffusion layer (202) gradually decreases from top to bottom, and the roughness of the lowest point of the creep diffusion layer (201) is greater than the roughness of the highest point of the radiation diffusion layer (202). The roughness of the entire surface of the wet escape layer (203) is the same, and the roughness of the lowest point of the radiation diffusion layer (202) is the same as that of the wet escape layer (203). Wherein, the average roughness of the surface of the peristaltic diffusion layer (201) is set to be Let the average roughness of the radiation diffusion layer (202) surface be... Let the surface area of ​​the peristaltic diffusion layer (201) be... Let the surface area of ​​the radiation diffusion layer (202) be... ,but ; The molecular distillation cylinder (1) has a heavy component collection mechanism (8) located below the evaporator (2), and the vertical distribution range of the heavy component collection mechanism (8) is located in the inner area of ​​the condensation surface (3a) of the condenser (3).

2. The NMP dynamic distillation equipment according to claim 1, characterized in that: The condenser (3) is equipped with a cooling pipe (4) for dynamically circulating coolant.

3. The NMP dynamic distillation apparatus according to claim 1, characterized in that: In the vertical direction, the distribution range of the condensing surface (3a) of the condenser (3) matches the distribution range of the evaporating surface (2a) of the evaporator (2).

4. The NMP dynamic distillation apparatus according to claim 1, characterized in that: The bottom of the molecular distillation cylinder (1) is provided with a heavy component pipeline (9) and a light component pipeline (10). The heavy component pipeline (9) is equipped with a first flow meter (11), and the light component pipeline (10) is equipped with a second flow meter (12). The heavy component pipeline (9) is connected to the heavy component collection mechanism (8), and the light component pipeline (10) is connected to the bottom cavity of the molecular distillation cylinder (1).

5. The NMP dynamic distillation apparatus according to claim 1, characterized in that: The molecular distillation cylinder (1) is equipped with a vacuum sensor (13) for sensing and monitoring the vacuum level inside the molecular distillation cylinder (1).

6. The NMP dynamic distillation apparatus according to claim 1, characterized in that: Suppose the creep diffusion layer is divided into m consecutive horizontal unit height surface regions (201a), and the roughness of the m consecutive horizontal unit height surface regions (201a) from top to bottom is as follows: ,but ; Suppose the radiation diffusion layer (202) is divided into n consecutive horizontal unit height surface regions, and the roughness of the n consecutive horizontal unit height surface regions (201a) from top to bottom is as follows: ,but .

7. A control method for an NMP dynamic distillation apparatus, characterized in that, The NMP dynamic distillation apparatus according to any one of claims 1 to 6 includes the following steps: Step 1: Affinity-based peristaltic diffusion of waste liquid The NMP waste liquid is diverted downwards by the distributor to the peristaltic diffusion layer on the evaporation surface, and flows from top to bottom on the surface of the peristaltic diffusion layer, forming a peristaltic state on the surface of the peristaltic diffusion layer. Step 2: Rapid Radiation and Diffusion of Waste Liquid The NMP waste liquid falls through the peristaltic diffusion layer in an "affinity" state and gradually splits. After entering the radiation diffusion layer with reduced roughness, the splitting rate of the single original liquid flow of NMP waste liquid along the surface of the radiation diffusion layer increases. Step 3: Waste liquid film evaporation After the NMP waste liquid undergoes linear acceleration and diffusing through the radiation diffusion layer, the cross-sectional area of ​​each diffusing NMP waste liquid reaches its minimum at the bottom of the radiation diffusion layer. The NMP waste liquid then enters the wet escape layer with the lowest surface roughness, where a liquid film is formed. This liquid film evaporates in the vacuum environment of the molecular distillation cylinder. The lighter components with larger molecular free paths reach the condensation surface of the condenser and fall to the bottom of the molecular distillation cylinder after condensation. The heavier NMP components with smaller molecular free paths cannot reach the condensation surface of the condenser and fall into the heavy component collection mechanism.

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