Falling film distillation system for separation of dichloromethane and white oil

Abstract

The present invention relates to a falling film distillation system for separating dichloromethane and white oil, which comprises a distillation tower and an evaporator, wherein the distillation tower comprises an upper tower body and a lower tower body; the evaporator comprises an upper tube plate and a lower tube plate respectively arranged at the top and bottom of the upper tower body and forming a closed evaporation chamber with the circumferential inner wall of the upper tower body, a plurality of evaporation tubes, and a steam supply component, wherein the plurality of evaporation tubes are arranged spaced apart from each other, and the upper ports of the plurality of evaporation tubes are connected to the liquid inlet pipe, and the lower ports are connected to the cavity formed by the lower tower body; the distillation system also comprises a gas-liquid separator that can be connected to the gas outlet pipe. The present invention adopts a falling film evaporator, the material residence time is short, the steam working pressure is small and the steam consumption is low, and the evaporated white oil concentrate has a low temperature, light color and high purity, and the evaporated dichloromethane gas is separated and subsequently condensed and dehydrated, and the white oil content in the dichloromethane is within 20ppm.

Description

Technical Field

[0001] The invention belongs to the field of distillation, and in particular relates to a falling film distillation system for separating dichloromethane and white oil. Background Art

[0002] At present, in the field of oil refining, the wet process of lithium battery separator production needs to recycle dichloromethane and white oil. White oil is mostly used as a pore-forming agent. After the film is formed, the white oil is extracted with dichloromethane to form a dichloromethane and white oil mixture, which contains 5% white oil and 95% dichloromethane. In this process, white oil and dichloromethane are used in large quantities, so separating and treating the mixture, thereby recovering and recycling dichloromethane and white oil, is the key to reducing the production cost of lithium battery separators.

[0003] Some domestic distillation methods are used to separate and purify dichloromethane and white oil. The light phase at the top of the tower is used to separate dichloromethane, and the bottom liquid is used to separate white oil. The main disadvantages are: it will cause the light component in the mixed liquid to be partially oxidized, destroy the white oil structure, and the removal effect of polar substances such as trace water is not good. The dichloromethane content in the white oil is too high. In addition, the steam consumption is high, which makes the energy too large. The dichloromethane gas temperature is high, which increases the condensation load of the condenser, resulting in an increase in the circulating water volume, the white oil temperature is too high, and the color of the white oil is deepened. The amount of white clay used during bleaching will increase, increasing production costs, and the product indicators are not good. The white oil content in the dichloromethane after condensation is as high as 400ppm, and the dichloromethane content in the finished white oil is also as high as 500ppm. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a new falling film distillation system for separating dichloromethane and white oil.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A falling film distillation system for separating dichloromethane and white oil, comprising a distillation tower and an evaporator, wherein the distillation tower extends in a vertical direction and comprises an upper tower body and a lower tower body, wherein a liquid inlet pipe is located at the top of the upper tower body, a liquid outlet pipe is located at the bottom of the lower tower body, and an air outlet pipe is located at the upper side of the lower tower body;

[0007] The evaporator is arranged in the upper tower body, and comprises an upper tube plate and a lower tube plate which are respectively arranged at the top and the bottom of the upper tower body and form a closed evaporation cavity with the circumferential inner wall of the upper tower body, a plurality of evaporation tubes whose two ends are connected with the upper tube plate and the lower tube plate and extend along the height direction of the upper tower body, and a steam supply component which provides steam to the evaporation cavity formed by the upper tower body, wherein the plurality of evaporation tubes are arranged to be separated from each other, and the upper ports of the plurality of evaporation tubes are connected with the liquid inlet pipe, and the lower ports are connected with the cavity formed by the lower tower body;

[0008] The distillation system also includes a gas-liquid separator which can be communicated with the gas outlet pipe.

[0009] Preferably, the evaporator further comprises a shaping plate arranged in the upper tower body and used for positioning the evaporation tube, and a fixed tie rod used for hoisting the lower tube plate, wherein there is at least one shaping plate, and a channel for steam flow is formed between each shaping plate and the inner wall of the upper tower body, and the fixed tie rod is arranged parallel to the evaporation tube, and the upper end is fixed on the shaping plate, and the lower end is fixed on the lower tube plate. The setting of the shaping plate and the fixed tie rod can not only realize the positioning of the evaporation tube in the evaporation chamber; but also the steam flow channel formed by the shaping plate improves the fluidity of the steam in the steam chamber to ensure the evaporation effect.

[0010] According to a specific implementation and preferred aspect of the present invention, there are multiple shaping plates, each of which is horizontally arranged and has a fitting side that can fit on the inner wall of the upper tower body, and a disconnected side that is disconnected from the inner wall of the corresponding upper tower body to form a channel, wherein the multiple shaping plates are spaced apart vertically along the length direction of the evaporation tube, and the multiple channels formed are relatively staggered. Here, through the staggered channels, not only can the contact between the steam and the evaporation tube be fully achieved to achieve indirect heating of the mixed liquid, but also a stable steam flow direction can be formed, which is conducive to the evaporation of the mixture.

[0011] Preferably, the multiple channels are spaced apart vertically and staggered left and right. There are two fixed tie rods, which respectively fix the shaping plate on the same side of the channel and the lower tube plate at the bottom in series.

[0012] Preferably, the dichloromethane and white oil mixed liquid flows downward from the upper part of the evaporation tube, the steam in the steam chamber flows in the same direction as the mixed liquid, and the steam flows in the steam chamber to form a negative pressure. This can not only optimize the evaporation of the mixed liquid, but also further improve the effect of gas-liquid separation under negative pressure.

[0013] According to another specific implementation and preferred aspect of the present invention, the gas-liquid separator is a hydrocyclone separator and is located outside the lower tower body, wherein the inlet of the hydrocyclone separator is connected to the gas outlet pipe.

[0014] According to another specific implementation and preferred aspect of the present invention, the falling film distillation system further includes a liquid separation chamber connected to the liquid inlet pipe and located above the upper tube plate, the liquid separation chamber includes a liquid separation plate located above the upper tube plate, a surrounding plate arranged around the liquid separation plate, and a connector connecting the surrounding plate to the upper tower body, wherein the upper end of the surrounding plate is open, the lower end of the liquid inlet pipe extends into the liquid separation chamber, and the liquid separation plate is provided with a diversion hole capable of evenly diverting the mixed liquid to the corresponding upper tube opening below. Here, by setting the liquid separation chamber, it is easy to achieve even flow of the mixed liquid to each evaporation tube.

[0015] Preferably, there are multiple diverter holes and they are divided into multiple groups, each diverter hole group corresponds to the circumferential distribution of the upper tube opening of an evaporating tube below, and the center of the circle formed by the hole center of each group of diverter holes is set on the center line of the corresponding upper tube opening below, wherein the diameter of the circle is larger than the tube diameter of the upper tube opening, and the mixed liquid flowing out of each group of diverter holes flows downward from the periphery of the corresponding upper tube opening below and adheres to the inner wall of the evaporating tube. Due to the corresponding arrangement of each group of diverter holes and the evaporating tube, the liquid flowing out of the diverter holes can flow downward from the circumference of the upper tube opening and adhere to the inner wall of the evaporating tube, so as to improve the evaporation efficiency.

[0016] Furthermore, multiple evaporation tubes are arranged in a circular array between the upper tube plate and the lower tube plate, and multiple groups of flow holes are arranged one by one corresponding to the multiple evaporation tubes, and a flow splitting hole is provided between the two groups of flow splitting holes corresponding to the upper tube openings of two adjacent evaporation tubes. Through the layout of the evaporation tubes, the position of each group of separation holes is easily positioned, thereby achieving a uniform flow splitting effect.

[0017] Preferably, the lower end of the liquid inlet pipe is located above the liquid separation plate, and a spray head is also provided at the lower end of the liquid inlet pipe, wherein the flow rate of the dichloromethane and white oil mixture flowing out of the spray head is greater than the flow rate flowing out of the diverter hole. In this way, a certain liquid level height should be formed in the liquid separation chamber to ensure that the liquid flows out evenly from each diverter hole.

[0018] In addition, the falling film distillation system also includes an upper partition extending upward from the top of the upper tube plate, a lower partition extending downward from the bottom of the lower tube plate, and an extension plate extending upward from the bottom of the lower tower body and aligned with the lower partition, wherein the upper partition divides the upper tower body into two or more mixed liquid feed areas, a liquid separation cavity is correspondingly arranged in the mixed liquid feed area, a liquid inlet pipe is arranged one-to-one with the liquid separation cavity, and each liquid separation cavity is correspondingly provided with a liquid inlet pipe; the lower partition divides the upper part of the lower tower body into gas phase areas corresponding to the mixed liquid feed areas, and the lower partition is separated from the aligned extension plates, the gas phase area extends downward to the top of the extension plate, two or more gas phase areas are connected from the separation between the lower partition and the extension plate, and the gas outlet pipe is located in the gas phase area and on the upper side of the extension plate; the extension plate divides the lower part of the lower tower body into liquid phase areas corresponding to the gas phase areas, and each liquid phase area is correspondingly provided with a liquid outlet pipe. The purpose of this arrangement is to achieve multiple entries and exits in the distillation tower and to implement the distillation process when entering different evaporation zones to ensure the distillation effect.

[0019] Due to the implementation of the above technical solution, the present invention has the following advantages compared with the prior art:

[0020] The present invention adopts a falling film evaporator, the material residence time is short, the steam working pressure is small and the steam consumption is low. At the same time, the evaporated white oil concentrate has a low temperature, light color and high purity. After the evaporated dichloromethane gas is separated and subsequently condensed and separated, the white oil content in the dichloromethane is within 20ppm. In addition, the structure is simple and the implementation is convenient. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] Figure 1 It is a structural schematic diagram of the distillation system of the present invention;

[0023] Figure 2 for Figure 1 Schematic diagram of the partial structure (distillation tower and evaporator);

[0024] Figure 3 for Figure 2 The enlarged schematic diagram of the structure of the evaporator;

[0025] Figure 4 for Figure 2 An enlarged schematic diagram of the structure of the upper part of the middle distillation tower;

[0026] Figure 5 for Figure 4 A top view of the liquid separation chamber on the middle right;

[0027] Wherein: 1, distillation tower; 10, upper tower body; 11, lower tower body; 1a, liquid inlet pipe; 1b, liquid outlet pipe; 1c, gas outlet pipe;

[0028] 2. Evaporator; 20. Upper tube sheet; 21. Lower tube sheet; 22. Evaporation tube; 23. Steam supply assembly; 230. Steam inlet; 231. Steam condensate outlet; 24. Forming plate (baffle); 24a. Fitting side; 24b. Disconnecting side; t. Channel; 25. Fixing rod;

[0029] 3. Gas-liquid separator;

[0030] 4. liquid separation chamber; 40. liquid separation plate; 40a. flow separation hole; k. flow separation hole group; 41. enclosure; 42. connecting piece;

[0031] 5. Upper baffle; 6. Lower baffle; 7. Extension plate; h1, h2, mixed liquid feeding area; q1, q2, gas phase area; y1, y2, liquid phase area; 8. Sprinkler head. DETAILED DESCRIPTION

[0032] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0033] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0034] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0035] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0036] In the present application, unless otherwise clearly specified and limited, the first feature "above" or "below" the second feature may be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature "above", "above" and "above" the second feature may be that the first feature is directly above or obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. The first feature "below", "below" and "below" the second feature may be that the first feature is directly below or obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature. It should be noted that when an element is referred to as "fixed to" or "set on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected" to another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "up", "down", "left", "right" and similar expressions used herein are for illustrative purposes only and do not represent the only implementation method.

[0037] See also Figure 1 According to the falling film distillation system for separating dichloromethane and white oil in this embodiment, it includes a distillation tower 1, an evaporator 2, and a gas-liquid separator 3.

[0038] Specifically, the distillation tower 1 extends in a vertical direction and includes an upper tower body 10 and a lower tower body 11, wherein a liquid inlet pipe 1a is located at the top of the upper tower body 10, a liquid outlet pipe 1b is located at the bottom of the lower tower body 11, and an air outlet pipe 1c is located at the upper side of the lower tower body 11.

[0039] In this example, the distillation tower 1 is cylindrical and has a circular cross section.

[0040] Combination Figure 2 As shown, the evaporator 2 is arranged in the upper tower body 10, and includes an upper tube plate 20 and a lower tube plate 21 which are respectively arranged at the top and bottom of the upper tower body 10 and form a closed evaporation chamber with the circumferential inner wall of the upper tower body 10, a plurality of evaporation tubes 22 whose two ends are connected with the upper tube plate 20 and the lower tube plate 21 and extend along the height direction of the upper tower body 10, a steam supply component 23 for providing steam to the evaporation chamber formed by the upper tower body, a shaping plate 24 which is arranged in the upper tower body 10 and used for positioning the evaporation tubes 22, and a fixing rod 25 for hoisting the lower tube plate 21.

[0041] The plurality of evaporation tubes 22 are spaced apart from each other, and the upper ends of the plurality of evaporation tubes 22 are connected to the liquid inlet pipe 1 a , and the lower ends of the plurality of evaporation tubes 22 are connected to the cavity formed by the lower tower body 11 .

[0042] Specifically, the plurality of evaporation tubes 22 are arranged in a circular array and are spaced apart from each other in sequence between the upper tube plate 20 and the lower tube plate 21 .

[0043] The steam supply assembly 23 is a conventional component, comprising a steam inlet 230 and a steam condensate outlet 231 , as well as a steam generator and a steam pipe for connecting the steam generator with the steam inlet.

[0044] Combination Figure 3 As shown, there are multiple shaping plates 24 (also called baffles), and a channel t for steam flow is formed between each shaping plate 24 and the inner wall of the upper tower body 10, and a fixed tie rod 25 is arranged in parallel with the evaporation tube 22, and the upper end is fixed on the shaping plate 24, and the lower end is fixed on the lower tube plate 21. The setting of the shaping plate and the fixed tie rod can not only realize the positioning of the evaporation tube in the evaporation chamber, but also the steam flow channel formed by the shaping plate improves the fluidity of the steam in the steam chamber (forming baffles) to ensure the evaporation effect.

[0045] In this example, each shaping plate 24 is arranged horizontally, and has a fitting side 24a that can fit on the inner wall of the upper tower body 10, and a disconnected side 24b that is disconnected from the inner wall of the corresponding upper tower body 10 to form a channel t, wherein multiple shaping plates 24 are spaced apart and distributed vertically along the length direction of the evaporation tube 22, and the multiple channels t formed are relatively staggered. Here, through the staggered channels, not only can the contact between the steam and the evaporation tube be fully realized to achieve indirect heating of the mixed liquid, but also a stable steam flow direction can be formed, which is conducive to the evaporation of the mixture.

[0046] In this example, multiple channels t are spaced apart vertically and staggered horizontally, and there are two fixing rods 25, which respectively connect the shaping plate 24 on the same side of the channel t and the lower tube plate 21 at the bottom in series. In this way, the positioning and installation of the evaporating tube is more stable.

[0047] At the same time, the mixed liquid of dichloromethane and white oil flows downward from the upper part of the evaporation tube 22, and the flow direction of the steam in the steam chamber is the same as that of the mixed liquid, so that the evaporation of the mixed liquid is optimized.

[0048] In this example, due to the difference in boiling points between dichloromethane and white oil (dichloromethane has a low boiling point of 39.8°C, while white oil has a high boiling point of more than 350°C), the mixed liquid can be preheated before being added to the distillation tower. As long as the temperature of the mixed liquid in the evaporation tube is greater than or equal to 39.8°C, the mixed liquid can be separated into gaseous dichloromethane and liquid white oil. Therefore, the stable temperature difference between the steam temperature in the evaporation chamber and the mixed liquid in the evaporation tube is small, so the amount of steam used is significantly reduced.

[0049] In this example, the gas-liquid separator 3 is a hydrocyclone separator and is located outside the lower tower body 11, wherein the inlet of the hydrocyclone separator is connected to the gas outlet pipe 1c.

[0050] As for the hydrocyclone separator, it is a conventional product in the art and can be obtained by direct outsourcing, and is mainly used to separate white oil from dichloromethane gas.

[0051] At the same time, the hydrocyclone separator generates a slight negative pressure of about 0.074 MPa, which draws the gaseous dichloromethane in the gas phase region into the hydrocyclone separator for gas-liquid separation.

[0052] Combination Figure 4 As shown, the falling film distillation system also includes a liquid separation chamber 4 connected to the liquid inlet pipe 1a and located above the upper tube plate 20, an upper partition 5 extending upward from the top of the upper tube plate 20, a lower partition 6 extending downward from the bottom of the lower tube plate 21, and an extension plate 7 extending upward from the bottom of the lower tower body 11 and aligned with the lower partition 6.

[0053] Specifically, the upper partition 5, the lower partition 6 and the extension plate 7 are all one piece, so that the upper partition 5 divides the upper tower body 10 into two mixed liquid feeding areas h1 and h2; the lower partition 6 divides the upper part of the lower tower body 11 into two gas phase areas q1 and q2 corresponding to the mixed liquid feeding areas h1 and h2; the extension plate 7 divides the lower part of the lower tower body 11 into two liquid phase areas y1 and y2 corresponding to the gas phase areas q1 and q2.

[0054] In this example, there are two liquid separation chambers 4 which are respectively arranged in two mixed liquid feeding areas h1 and h2 , and the liquid inlet pipes 1a are arranged one-to-one correspondingly to the liquid separation chambers 4 , and each liquid separation chamber 4 is correspondingly provided with a liquid inlet pipe 1a .

[0055] The liquid separation chamber 4 includes a liquid separation plate 40 located above the upper tube plate 20, a surrounding plate 41 arranged around the liquid separation plate 40, and a connecting piece 42 connecting the surrounding plate 41 to the upper tower body 10, wherein the upper end of the surrounding plate 41 is open, and the lower end of the liquid inlet pipe 1a extends into the liquid separation chamber 4, and the liquid separation plate 40 is provided with a diversion hole 40a that can evenly divert the mixed liquid to the corresponding upper pipe opening below.

[0056] Combination Figure 5 As shown, there are multiple diversion holes 40a and they are divided into multiple groups. Each diversion hole group k corresponds to the circumferential distribution of the upper tube opening of an evaporating tube 22 below, and the center of the circle formed by the hole center of each group of diversion holes is set on the center line of the corresponding upper tube opening below, wherein the diameter of the circle is larger than the tube diameter of the upper tube opening. In this way, the mixed liquid flowing out of each group of diversion holes respectively flows downward from the periphery of the corresponding upper tube opening below, adhering to the inner wall of the evaporating tube 22, so as to improve the evaporation efficiency and ensure the evaporation effect.

[0057] In this example, the lower partition 6 is separated from the aligned extension plate 7, so that the gas phase zone extends down to the top of the extension plate 7, and the two gas phase zones q1 and q2 are connected and arranged at the separation between the lower partition 6 and the extension plate 7. The advantage of this arrangement is that no matter whether the gas and liquid flow out through the left or right evaporation tube, the gas part will float in the gas phase zones q1 and q2, and under the guidance of the gas outlet pipe 1c on one side, the gas can be sent to the cyclone separator to further complete the separation of white oil in the dichloromethane gas.

[0058] At the same time, the lower part of the lower tower body 11 is divided into liquid phase areas y1 and y2 corresponding to the gas phase areas q1 and q2 by the bottom extension plate 7, and each liquid phase area y1 and y2 is provided with a corresponding liquid outlet pipe 1b. Here, the applicant explains why the bottom is divided into two liquid phase areas y1 and y2. The main reason is that the white oil separated from the upper evaporation tube 22 can be collected respectively. In this way, when the mixed liquid is introduced into the left liquid inlet pipe 1a and evaporated, the mixed liquid is separated into gaseous dichloromethane and liquid white oil, wherein the gaseous dichloromethane is sent from the gas outlet pipe to the cyclone separator to separate the white oil contained in the gaseous dichloromethane, and the liquid white oil after evaporation is discharged from the left liquid outlet pipe 1b. At this time, the discharged white oil can enter the evaporation pipe 22 on the right side from the liquid inlet on the top of the distillation tower 1 to achieve secondary distillation of the white oil. After the secondary distillation, the gaseous dichloromethane separated is sent to the cyclone separator for gas-liquid separation, and the liquid white oil after the secondary distillation is discharged from the right liquid outlet pipe 1b, and then the white oil is cooled, that is, the separation of dichloromethane and white oil can be completed.

[0059] In this example, the lower end of each liquid inlet pipe 1a is located above the liquid separation plate 40, and a spray head 8 is also provided at the lower end of the liquid inlet pipe 1a, wherein the flow rate of the dichloromethane and white oil mixed liquid flowing out of the spray head 8 is greater than the flow rate flowing out of the diverting hole 40a. In this way, a certain liquid level height should be formed in the liquid separation chamber to ensure that the liquid flows out evenly from each diverting hole.

[0060] In addition, this embodiment adopts the above-mentioned distillation system, and after secondary distillation, the content of dichloromethane in the finished white oil is: ≤0.008% (80ppm); the content of white oil in dichloromethane is: ≤0.002% (20ppm); the water content in the finished white oil is: ≤0.02%. However, the above indicators in the existing equipment can generally only achieve: the content of dichloromethane in the finished white oil is: ≤0.05% (500ppm); the content of white oil in dichloromethane is: ≤0.04% (400ppm). Therefore, the distillation system of the present application can greatly improve the effect of separating white oil and dichloromethane, ensuring that the technical purpose of low content of dichloromethane in white oil and low content of white oil in dichloromethane is achieved.

[0061] In summary, the distillation system in this example adopts the most advanced micro-negative pressure falling film evaporation process in China, and its characteristics are:

[0062] 1) The material residence time is short, the steam working pressure is small, and the steam consumption is low;

[0063] 2) The temperature of dichloromethane gas is low (below 50°C), which will not cause corrosion to the equipment during long-term use. In addition, the condensing load of the condenser is small, and the circulating water consumption is low, which can reduce production costs;

[0064] 3) After evaporation, the temperature of the white oil concentrate is low, the color is light, and the purity is high. The amount of white clay added during bleaching is reduced, which reduces production costs;

[0065] 4) After evaporation, the dichloromethane gas is first captured by efficient flash capture and then condensed by a condenser. The dichloromethane liquid has high purity and is then separated from the water. Therefore, the content of white oil in the dichloromethane can be within 20ppm.

[0066] The above is a detailed description of the present invention, the purpose of which is to enable people familiar with the technology in this field to understand the content of the present invention and implement it, and it is not intended to limit the scope of protection of the present invention. The present invention is not limited to the above-mentioned embodiments. Any equivalent changes or modifications made according to the spirit of the present invention should be covered by the scope of protection of the present invention.

Claims

1. A falling film distillation system for separating dichloromethane and white oil, comprising a distillation tower and an evaporator, characterized in that: The distillation tower extends in a vertical direction and comprises an upper tower body and a lower tower body, wherein the liquid inlet pipe is located at the top of the upper tower body, the liquid outlet pipe is located at the bottom of the lower tower body, and the gas outlet pipe is located at the upper side of the lower tower body; The evaporator is arranged in the upper tower body, and comprises an upper tube plate and a lower tube plate which are respectively arranged at the top and the bottom of the upper tower body and form a closed evaporation cavity with the circumferential inner wall of the upper tower body, a plurality of evaporation tubes whose ends are connected with the upper tube plate and the lower tube plate and extend along the height direction of the upper tower body, and a steam supply component which provides steam to the evaporation cavity formed by the upper tower body, wherein the plurality of evaporation tubes are arranged to be separated from each other, and the upper ports of the plurality of evaporation tubes are connected with the liquid inlet pipe, and the lower ports are connected with the cavity formed by the lower tower body; The distillation system also includes a gas-liquid separator that can be connected to the gas outlet pipe; the gas-liquid separator is a cyclone separator, and is located outside the lower tower body, and the inlet of the cyclone separator is connected to the gas outlet pipe; The falling film distillation system also includes an upper baffle extending upward from the top of the upper tube plate, a lower baffle extending downward from the bottom of the lower tube plate, and an extension plate extending upward from the bottom of the lower tower body and aligned with the lower baffle, wherein the upper baffle divides the upper tower body into two or more mixed liquid feed areas, the mixed liquid feed areas correspond to the gas phase areas one by one, and the lower baffle is separated from the aligned extension plates, the gas phase area extends downward to the top of the extension plate, two or more gas phase areas are connected from the separation between the lower baffle and the extension plate, and the gas outlet pipe is located in the gas phase area and on the upper side of the extension plate; the extension plate divides the lower part of the lower tower body into liquid phase areas corresponding to the gas phase areas, and each liquid phase area is correspondingly provided with a liquid outlet pipe; the dichloromethane and white oil mixed liquid flows downward from the upper part of the evaporation tube, the steam flow direction in the evaporation chamber is the same as the mixed liquid flow direction, and the steam flows in the evaporation chamber and forms a negative pressure.

2. The falling film distillation system for separation of dichloromethane and white oil according to claim 1, characterized in that: The evaporator also includes a shaping plate arranged in the upper tower body and used for positioning the evaporation tube, and a fixed pull rod used for hoisting the lower tube plate, wherein there is at least one shaping plate, and a channel for steam flow is formed between each shaping plate and the inner wall of the upper tower body, and the fixed pull rod is arranged parallel to the evaporation tube, and the upper end is fixed to the shaping plate, and the lower end is fixed to the lower tube plate.

3. The falling film distillation system for separation of dichloromethane and white oil according to claim 2, characterized in that: There are a plurality of shaping plates, each of which is horizontally arranged and has a fitting side that can fit on the inner wall of the upper tower body, and a disconnecting side that is disconnected from the inner wall of the upper tower body on the corresponding side to form the channel.

4. The falling film distillation system for separation of dichloromethane and white oil according to claim 3, characterized in that: The plurality of shaping plates are spaced apart and distributed vertically along the length direction of the evaporating tube, and the plurality of channels formed are relatively staggered.

5. The falling film distillation system for separation of dichloromethane and white oil according to claim 4, characterized in that: The plurality of channels are spaced apart vertically and are relatively staggered in left and right directions.

6. The falling film distillation system for separation of dichloromethane and white oil according to claim 5, characterized in that: There are two fixed pull rods, which respectively fix and connect in series the shaping plate and the lower tube plate at the bottom on the same side of the channel.

7. The falling film distillation system for separation of dichloromethane and white oil according to claim 1, characterized in that: The falling film distillation system also includes a liquid separation chamber connected to the liquid inlet pipe and located above the upper tube plate, the liquid separation chamber includes a liquid separation plate located above the upper tube plate, a surrounding plate arranged around the liquid separation plate, and a connecting piece connecting the surrounding plate to the upper tower body, wherein the upper end of the surrounding plate is open, the lower end of the liquid inlet pipe extends into the liquid separation chamber, and the liquid separation plate is provided with a diversion hole that can evenly divert the mixed liquid to the corresponding upper tube opening below.

8. The falling film distillation system for separation of dichloromethane and white oil according to claim 7, characterized in that: There are a plurality of diversion holes which are divided into a plurality of groups, and each diversion hole group corresponds to the circumferential distribution of the upper tube opening of one of the evaporation tubes below.

9. The falling film distillation system for separation of dichloromethane and white oil according to claim 8, characterized in that: The center of the circle formed by the centers of the holes of each group of diversion holes is arranged on the center line of the corresponding upper pipe opening below.

10. The falling film distillation system for separation of dichloromethane and white oil according to claim 9, characterized in that: The diameter of the circle is larger than the diameter of the upper pipe opening, and the mixed liquid flowing out of each group of the diversion holes respectively flows downward from the periphery of the corresponding upper pipe opening below and adheres to the inner wall of the evaporation tube.

11. The falling film distillation system for separation of dichloromethane and white oil according to claim 8, characterized in that: The plurality of evaporating tubes are arranged in a circular array in sequence and at intervals between the upper tube plate and the lower tube plate. The plurality of groups of diversion holes are arranged in one-to-one correspondence with the plurality of evaporating tubes, and the two groups of diversion holes corresponding to the upper tube openings of two adjacent evaporating tubes share one diversion hole.

12. The falling film distillation system for separation of dichloromethane and white oil according to claim 11, characterized in that: The lower end of the liquid inlet pipe is located above the liquid separation plate, and a spray head is also provided at the lower end of the liquid inlet pipe, wherein the flow rate of the dichloromethane and white oil mixed liquid flowing out of the spray head is greater than the flow rate flowing out of the diversion hole.

13. The falling film distillation system for separation of dichloromethane and white oil according to claim 7, characterized in that: The liquid separation chamber is correspondingly arranged in the mixed liquid feeding area, the liquid inlet pipes are arranged in a one-to-one correspondence with the liquid separation chambers, and each of the liquid separation chambers is correspondingly provided with one liquid inlet pipe.

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