CN111659141A - Falling film distillation system for separating dichloromethane and white oil - Google Patents

Abstract

The 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, a lower tube plate, a plurality of evaporation tubes and a steam supply assembly, wherein the upper tube plate and the lower tube plate 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; the distillation system also includes a gas-liquid separator capable of communicating with the outlet duct. The falling film evaporator is adopted, the material retention time is short, the working pressure of steam is low, the steam consumption is low, the temperature of the evaporated white oil concentrate is low, the color and the purity are light, and the content of the white oil in the dichloromethane is within 20ppm after the evaporated dichloromethane gas is separated and subjected to subsequent condensation and water separation.

Description

Falling film distillation system for separating dichloromethane and white oil

Technical Field

The invention belongs to the field of distillation, and particularly relates to a falling film type distillation system for separating dichloromethane and white oil.

Background

At present, in the field of oil product refining, methylene dichloride and white oil need to be recovered in a wet-process lithium battery diaphragm production process, wherein the white oil is mostly adopted as a pore-forming agent, the white oil in the film is extracted by the methylene dichloride after the film is formed, and a mixed solution of the methylene dichloride and the white oil is formed, wherein the mixed solution contains 5 percent of the white oil and 95 percent of the methylene dichloride. In the process, a large amount of white oil and dichloromethane are used, so that the mixed solution is separated, and the dichloromethane and the white oil are recycled and reused, which is the key for reducing the production cost of the lithium battery diaphragm.

The distillation method is adopted in China for separating and purifying dichloromethane and white oil, a light phase at the top of the tower is used for separating dichloromethane, and a bottom liquid of a kettle is used for separating white oil, and the main defects are as follows: the method can oxidize light components in the mixed solution to destroy the structure of the white oil, has poor effect of removing polar substances such as trace moisture and the like, has high dichloromethane content in the white oil, has high steam consumption to cause excessive energy, has high dichloromethane gas temperature, increases the condensation load of a condenser, causes the increase of circulating water quantity, has high white oil temperature, deepens the color of the white oil, increases the clay consumption during decolorization, increases the production cost, has poor product indexes, has the white oil content in the condensed dichloromethane as high as 400ppm, and has the dichloromethane content in the finished product white oil as high as 500 ppm.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a brand-new falling film distillation system for separating dichloromethane and white oil.

In order to solve the technical problems, the invention adopts the following technical scheme:

a falling film distillation system for separating dichloromethane and white oil comprises a distillation tower and an evaporator, wherein the distillation tower extends along the vertical direction and comprises an upper tower body and a lower tower body, a liquid inlet pipe is positioned at the top of the upper tower body, a liquid outlet pipe is positioned at the bottom of the lower tower body, and a gas outlet pipe is positioned at the upper side part 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 of which two end parts are communicated with the upper tube plate and the lower tube plate in a penetrating way and extend along the height direction of the upper tower body, and a steam supply assembly for supplying steam to the evaporation cavity formed by the upper tower body, wherein the plurality of evaporation tubes are arranged in a spaced way, the upper ports of the plurality of evaporation tubes are communicated with the liquid inlet tube, and the lower ports of the plurality of evaporation tubes are communicated with the cavity formed by the lower;

the distillation system also includes a gas-liquid separator capable of communicating with the outlet duct.

Preferably, the evaporator further comprises at least one shaping plate arranged in the upper tower body and used for positioning the evaporating tubes, and a fixing pull rod used for hanging the lower tube plate, wherein a channel for steam to flow is formed between each shaping plate and the inner wall of the upper tower body, the fixing pull rod is arranged in parallel with the evaporating tubes, and the upper end part of the fixing pull rod is fixed on the upper end part and the lower end part of the shaping plate and fixed on the lower tube plate. The arrangement of the shaping plate and the fixing pull rod can realize the positioning of the evaporation tube in the evaporation cavity; and the steam flow channel formed by the shaping plate improves the fluidity of the steam in the steam cavity so as to ensure the evaporation effect.

According to a specific implementation and preferable aspect of the invention, each shaping plate is horizontally arranged and has an attaching side edge capable of attaching to the inner wall of the upper tower body and a disconnecting side edge which is disconnected from the inner wall of the upper tower body on the corresponding side to form a channel, wherein the shaping plates are distributed at intervals up and down along the length direction of the evaporation tube, and the formed channels are arranged in a staggered manner relatively. Here, through the passageway that staggers, not only can be abundant realize the indirect heating of mixed liquid is realized to the contact of steam and evaporating pipe, can form stable steam flow direction moreover, be favorable to the evaporation of mixing.

Preferably, the channels are vertically spaced and are distributed in a staggered manner, and the fixed pull rods are two and are respectively used for fixedly connecting the shaping plate positioned on the same side of the channels in series with the lower tube plate at the bottom of the channel.

Preferably, the dichloromethane and white oil mixed liquid flows downwards from the upper part of the evaporation tube, the steam in the steam cavity flows in the same direction as the mixed liquid, and the steam flows in the steam cavity and forms negative pressure. Not only can the evaporation of the mixed liquid be realized optimally, but also the effect of gas-liquid separation is further improved under negative pressure.

According to yet another embodiment and preferred aspect of the present invention, the gas-liquid separator is a hydrocyclone and is located outside the lower body, wherein the inlet of the hydrocyclone is in communication with the outlet duct.

According to another specific implementation and preferred aspect of the present invention, the falling film distillation system further comprises a liquid separation chamber which is communicated with the liquid inlet pipe and located above the upper pipe plate, the liquid separation chamber comprises a liquid separation disc located above the upper pipe plate, a surrounding plate surrounding the liquid separation disc, and a connecting piece connecting the surrounding plate and the upper tower body, wherein the upper end of the surrounding plate is arranged in an open manner, the lower end of the liquid inlet pipe extends into the liquid separation chamber, and the liquid separation disc is provided with a diversion hole capable of evenly diverting the mixed liquid to the lower part corresponding to the upper pipe orifice. Here, through the setting of passing through the sap cavity, be convenient for realize that the miscella flows to every evaporating pipe evenly.

Preferably, the distribution holes are multiple and divided into multiple groups, each distribution hole group corresponds to the circumferential distribution of the upper pipe orifice of one evaporation pipe below, the circle center of the circle formed by the hole center of each distribution hole group is arranged on the central line of the upper pipe orifice corresponding below, the diameter of the circle is larger than the pipe diameter of the upper pipe orifice, and the mixed liquid flowing out of each distribution hole group flows downwards from the periphery of the upper pipe orifice corresponding below to be attached to the inner wall of the evaporation pipe. By the corresponding setting of every group reposition of redundant personnel hole and evaporating pipe for the liquid that flows from the reposition of redundant personnel hole can be from the circumference of last nozzle and the inner wall of laminating evaporating pipe downflow, in order to improve evaporation efficiency.

Furthermore, a plurality of evaporating pipes are sequentially distributed between the upper pipe plate and the lower pipe plate at intervals in an annular array mode, the multi-component flow holes and the plurality of evaporating pipes are arranged in a one-to-one correspondence mode, and a flow distribution hole is used between two groups of flow distribution holes corresponding to the upper pipe orifices of two adjacent evaporating pipes. Through the overall arrangement of evaporating pipe to the location of every group separation hole position of being convenient for, thereby reach the effect of even reposition of redundant personnel.

Preferably, the lower end of the liquid inlet pipe is located above the liquid separating plate, and a spray header is further arranged at the lower end of the liquid inlet pipe, wherein the outflow flow of the dichloromethane and white oil mixed liquid from the spray header is greater than the outflow flow of the dichloromethane and white oil mixed liquid from the flow dividing holes. Thus, a certain liquid level height should be formed in the liquid-separating chamber to ensure that the liquid flows out from each of the shunting holes uniformly.

In addition, the falling film type distillation system also comprises an upper partition plate extending upwards from the top of the upper tube plate, a lower partition plate extending downwards from the bottom of the lower tube plate, and an extension plate extending upwards from the bottom of the lower tower body and aligned with the lower partition plate, wherein the upper partition plate divides the upper tower body into two or more mixed liquid feeding areas, liquid separating chambers are correspondingly arranged in the mixed liquid feeding areas, liquid inlet pipes and the liquid separating chambers are arranged in a one-to-one correspondence manner, and each liquid separating chamber is correspondingly provided with one liquid inlet pipe; the lower partition board correspondingly divides the upper part of the lower tower body into gas phase areas which are in one-to-one correspondence with the mixed liquid feeding areas, the lower partition board is arranged at a position separated from the aligned extension plates, the gas phase areas extend downwards to the tops of the extension plates, two or more gas phase areas are communicated from the separated positions of the lower partition board and the extension plates, and the gas outlet pipe is positioned in the gas phase areas and above the sides of the extension plates; the extension plate divides the lower part of the lower tower body into liquid phase regions corresponding to the gas phase regions, and each liquid phase region is correspondingly provided with a liquid outlet pipe. The purpose of this is: the distillation process is carried out in different evaporation zones in order to realize multiple times of entering and exiting of the distillation tower so as to ensure the distillation effect.

Due to the implementation of the technical scheme, compared with the prior art, the invention has the following advantages:

the falling film evaporator is adopted, the material retention time is short, the working pressure of steam is low, the steam consumption is low, the temperature of the evaporated white oil concentrate is low, the color is light, the purity is high, the content of the white oil in the dichloromethane is within 20ppm after the evaporated dichloromethane gas is separated and subjected to subsequent condensation and water separation, in addition, the structure is simple, and the implementation is convenient.

Drawings

The invention is described in further detail below with reference to the figures and specific examples.

FIG. 1 is a schematic diagram of the distillation system of the present invention;

FIG. 2 is a schematic view of a partial structure of FIG. 1 (distillation column and evaporator);

FIG. 3 is an enlarged schematic view of the evaporator of FIG. 2;

FIG. 4 is an enlarged schematic view of the structure of the upper part of the distillation column of FIG. 2;

FIG. 5 is a schematic top view of the right hand side chamber of FIG. 4;

wherein: 1. a distillation column; 10. mounting the tower body; 11. a lower tower body; 1a, a liquid inlet pipe; 1b, a liquid outlet pipe; 1c, an air outlet pipe;

2. an evaporator; 20. an upper tube sheet; 21. a lower tube plate; 22. an evaporation tube; 23. a steam supply assembly; 230. a steam inlet; 231. a steam condensate outlet; 24. a setting plate (baffle plate); 24a, attaching side edges; 24b, break side edges; t, a channel; 25. fixing a pull rod;

3. a gas-liquid separator;

4. a liquid separation cavity; 40. a liquid separating disc; 40a, a shunt hole; k. a group of branch holes; 41. enclosing plates; 42. a connecting member;

5. an upper partition plate; 6. a lower partition plate; 7. an extension plate; h1, h2, mixed liquid feeding zone; q1, q2, gas phase region; y1, y2, liquid phase region; 8. and a spray header.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present application more comprehensible, embodiments accompanying the present application are described in detail below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. This application is capable of embodiments in many different forms than those described herein and that modifications may be made by one skilled in the art without departing from the spirit and scope of the application and it is therefore not intended to be limited to the specific embodiments disclosed below.

In the description of the present application, it is to be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the present application and for simplicity in description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the present application.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present application, "plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In this application, unless expressly stated or limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can include, for example, fixed connections, removable connections, or integral parts; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.

In this application, unless expressly stated or limited otherwise, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through intervening media. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature. It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like as used herein are for illustrative purposes only and do not denote a unique embodiment.

Referring to fig. 1, the falling film distillation system for separation of methylene chloride and white oil according to the present embodiment includes a distillation column 1 and an evaporator 2, and a gas-liquid separator 3.

Specifically, distillation column 1 extends along vertical direction, and includes upper tower body 10 and lower tower body 11, and wherein feed liquor pipe 1a is located the top of upper tower body 10, and drain pipe 1b is located the bottom of lower tower body 11, and outlet duct 1c is located the side upper portion of lower tower body 11.

In this example, the distillation column 1 is columnar and has a circular cross section.

Referring to fig. 2, the evaporator 2 is disposed in the upper tower 10, and includes an upper tube plate 20 and a lower tube plate 21 respectively disposed at the top and the bottom of the upper tower 10 and forming a closed evaporation cavity with the circumferential inner wall of the upper tower 10, a plurality of evaporation tubes 22 having two ends communicated with the upper tube plate 20 and the lower tube plate 21 and extending along the height direction of the upper tower 10, a steam supply assembly 23 for supplying steam to the evaporation cavity formed by the upper tower, a shaping plate 24 disposed in the upper tower 10 and used for positioning the evaporation tubes 22, and a fixing pull rod 25 for hanging the lower tube plate 21.

The evaporation tubes 22 are arranged in a mutually separated mode, the upper end ports of the evaporation tubes 22 are communicated with the liquid inlet tube 1a, and the lower end ports of the evaporation tubes 22 are communicated with a cavity formed by the lower tower body 11.

Specifically, a plurality of evaporation tubes 22 are sequentially and alternately distributed between the upper tube plate 20 and the lower tube plate 21 in an annular array.

The steam supply assembly 23, which is a conventional component, includes a steam inlet 230 and a steam condensate outlet 231, as well as a steam generator, a steam conduit for communicating the steam generator with the steam inlet.

Referring to fig. 3, the calibration plates 24 (also called as baffles) are provided with a plurality of channels t for steam to flow between each calibration plate 24 and the inner wall of the upper tower 10, the fixing rods 25 are arranged in parallel with the evaporation tubes 22, and the upper ends of the fixing rods are fixed to the upper ends and the lower ends of the calibration plates 24 and fixed to the lower tube plate 21. The arrangement of the shaping plate and the fixing pull rod can realize the positioning of the evaporation tube in the evaporation cavity; and the steam flow channel formed by the shaping plate improves the fluidity (forms baffling) of the steam in the steam cavity so as to ensure the evaporation effect.

In this embodiment, each shaping plate 24 is horizontally disposed and has an attaching side 24a capable of attaching to the inner wall of the upper tower 10 and a disconnecting side 24b for disconnecting from the inner wall of the upper tower 10 to form a channel t, wherein the shaping plates 24 are vertically spaced along the length direction of the evaporation tube 22, and the formed channels t are disposed in a staggered manner. Here, through the passageway that staggers, not only can be abundant realize the indirect heating of mixed liquid is realized to the contact of steam and evaporating pipe, can form stable steam flow direction moreover, be favorable to the evaporation of mixing.

In this embodiment, the channels t are spaced from each other vertically and are distributed in a staggered manner from left to right, and two fixing pull rods 25 are provided to respectively fix and connect the fixing plate 24 located on the same side of the channels t and the lower tube plate 21 at the bottom in series. Thus, the evaporator tube is positioned and installed more stably.

Meanwhile, the mixed liquid of dichloromethane and white oil flows downwards from the upper part of the evaporation tube 22, and the steam in the steam cavity flows in the same direction as the mixed liquid. The evaporation of the mixed liquid is realized optimally.

In this example, the boiling point difference between dichloromethane and white oil (dichloromethane boiling point is low, 39.8 ℃, white oil boiling point is high, 350 ℃ or more) can be preheated before the mixed liquid is added into the distillation column, and as long as the temperature of the mixed liquid in the evaporation tube is higher than or equal to 39.8 ℃, the mixed liquid separates out dichloromethane in gas phase and white oil in liquid phase, so that the temperature difference between the steam in the evaporation cavity and the stable temperature difference of the mixed liquid in the evaporation tube is small, and the amount of steam is obviously reduced.

In this example, the gas-liquid separator 3 is a hydrocyclone, and is located outside the lower tower 11, wherein the inlet of the hydrocyclone is communicated with the outlet pipe 1 c.

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

Meanwhile, the hydrocyclone separator generates micro negative pressure about 0.074Mpa, and the gaseous dichloromethane in the gas phase area is sucked into the hydrocyclone separator for gas-liquid separation.

As shown in fig. 4, the falling film distillation system further includes a liquid separation chamber 4 communicating with the liquid inlet pipe 1a and located above the upper pipe plate 20, an upper partition plate 5 extending upward from the top of the upper pipe plate 20, a lower partition plate 6 extending downward from the bottom of the lower pipe plate 21, and an extension plate 7 extending upward from the bottom of the lower column body 11 and disposed in alignment with the lower partition plate 6.

Specifically, the upper partition plate 5, the lower partition plate 6 and the extension plate 7 are all one, so that the upper partition plate 5 divides the upper tower body 10 into two mixed liquid feeding areas h1 and h 2; the lower partition plate 6 correspondingly divides the upper part of the lower tower body 11 into two gas phase areas q1 and q2 which are in one-to-one correspondence with the mixed liquid feeding areas h1 and h 2; the extension sheet 7 partitions the lower portion of the lower column 11 into two liquid phase zones y1, y2 corresponding to the gas phase zones q1, q 2.

In this embodiment, two liquid separating chambers 4 are respectively disposed in the two mixed liquid feeding regions h1 and h2, the liquid inlet pipes 1a are disposed in one-to-one correspondence with the liquid separating chambers 4, and each liquid separating chamber 4 is correspondingly disposed with one liquid inlet pipe 1 a.

The liquid separating cavity 4 comprises a liquid separating disc 40 positioned above the upper tube plate 20, a coaming 41 arranged around the liquid separating disc 40 and a connecting piece 42 connecting the coaming 41 with the upper tower body 10, wherein the upper end part of the coaming 41 is arranged in an open manner, the lower end part of the liquid inlet tube 1a extends into the liquid separating cavity 4, and the liquid separating disc 40 is provided with a liquid separating hole 40a which can uniformly divide the mixed liquid to the lower part corresponding to the upper tube opening.

Referring to fig. 5, the plurality of branch holes 40a are divided into a plurality of groups, each group k of branch holes corresponds to the circumferential distribution of the upper pipe orifice of one evaporation pipe 22 below, and the center of the circle formed by the hole center of each group of branch holes is arranged on the central line of the upper pipe orifice corresponding below, wherein the diameter of the circle is larger than the pipe diameter of the upper pipe orifice, so that the mixed liquid flowing out from each group of branch holes flows downwards from the inner wall of the upper pipe orifice corresponding below, which is attached to the evaporation pipe 22, to improve the evaporation efficiency and ensure the evaporation effect.

In this case, the lower partition 6 is spaced from the aligned extension plate 7 so that the gas phase region extends to the top of the extension plate 7, and the two gas phase regions q1, q2 are disposed in communication with each other at the spacing between the lower partition 6 and the extension plate 7, so that the gas portion floats in the gas phase regions q1, q2 regardless of the gas and liquid flowing out through the left or right evaporation tubes, and the gas can be introduced into the hydrocyclone under the guidance of the outlet pipe 1c on one side, thereby further completing the separation of the white oil from the dichloromethane gas.

Meanwhile, the lower part of the lower body 11 is divided by the bottom extension plate 7 into liquid phase regions y1, y2 corresponding to the gas phase regions q1, q2, and one liquid outlet pipe 1b is provided for each liquid phase region y1, y2, and here, the applicant explains why the bottom is divided into two liquid phase regions y1, y2, mainly because: the white oil separated from the upper evaporation tube 22 can be collected correspondingly. Thus, after the mixed liquid is introduced into the left liquid inlet pipe 1a and evaporated, the mixed liquid separates out gaseous dichloromethane and liquid white oil, wherein the gaseous dichloromethane is sent into the hydrocyclone from the gas outlet pipe to separate the white oil contained in the gaseous dichloromethane, the evaporated liquid white oil is discharged from the left liquid outlet pipe 1b, at the moment, the discharged white oil can enter the right evaporation pipe 22 from the liquid inlet on the right side of the top of the distillation tower 1 to realize the secondary distillation of the white oil, the gaseous dichloromethane is sent into the hydrocyclone to be subjected to gas-liquid separation after the secondary distillation, the liquid white oil after the secondary distillation is discharged from the right liquid outlet pipe 1b, and then the white oil is cooled, so that the separation of the dichloromethane and the white oil can be completed.

In this embodiment, the lower end of each liquid inlet pipe 1a is located above the liquid separating plate 40, and the lower end of the liquid inlet pipe 1a is further provided with a shower head 8, wherein the flow rate of the mixed liquid of dichloromethane and white oil flowing out from the shower head 8 is greater than the flow rate of the mixed liquid flowing out from the liquid separating hole 40 a. Thus, a certain liquid level height should be formed in the liquid-separating chamber to ensure that the liquid flows out from each of the shunting holes uniformly.

In addition, in the embodiment, the distillation system is adopted, and after the secondary distillation, the content of dichloromethane in the finished white oil is as follows: less than or equal to 0.008 percent (80 ppm); white oil content in methylene chloride: less than or equal to 0.002% (20 ppm); the finished white oil contains water: less than or equal to 0.02 percent. However, the indexes in the existing equipment can only reach the following indexes that the dichloromethane content in the finished white oil is: less than or equal to 0.05 percent (500 ppm); white oil content in methylene chloride: less than or equal to 0.04 percent (400 ppm). Therefore, the distillation system can greatly improve the separation effect of the white oil and the dichloromethane, and ensure that the technical purposes of low content of the dichloromethane in the white oil and low content of the white oil in the dichloromethane are achieved.

In conclusion, the distillation system in the embodiment adopts the most advanced domestic micro-negative pressure falling film evaporation process, and is characterized in that:

1) the material retention time is short, the working pressure of steam is low, and the steam consumption is low;

2) the temperature of dichloromethane gas is low (below 50 ℃), the device is not corroded when being used for a long time, the condensation load of the condenser is small, the circulating water consumption is low, and the production cost can be reduced;

3) the evaporated white oil concentrated solution has low temperature, light color and high purity, the addition amount of carclazyte is reduced during decoloring, and the production cost is reduced;

4) and the dichloromethane gas after evaporation is firstly subjected to efficient flash capture and then condensed by a condenser, and then the dichloromethane liquid is high in purity and is subjected to water diversion, so that the content of white oil in dichloromethane is within 20 ppm.

The present invention is described in detail in order to make those skilled in the art understand the content and practice the invention, and the invention is not limited to the above embodiments, and all equivalent changes or modifications made according to the spirit of the invention should be covered by the scope of the invention.

Claims (10)

1. A falling film type distillation system for separating dichloromethane and white oil comprises a distillation tower and an evaporator, and is characterized in that:

the distillation tower extends along the vertical direction and comprises an upper tower body and a lower tower body, wherein the liquid inlet pipe is positioned at the top of the upper tower body, the liquid outlet pipe is positioned at the bottom of the lower tower body, and the gas outlet pipe is positioned at the lateral upper part 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 of which two end parts are communicated with the upper tube plate and the lower tube plate in a penetrating way and extend along the height direction of the upper tower body, and a steam supply assembly for supplying steam to the evaporation cavity formed by the upper tower body, wherein the evaporation tubes are arranged in a spaced way, the upper ports of the evaporation tubes are communicated with the liquid inlet tube, and the lower ports of the evaporation tubes are communicated with the cavity formed by the lower tower body;

the distillation system also comprises a gas-liquid separator which can be communicated with the gas outlet pipe.

2. The falling film distillation system for the separation of methylene chloride and white oil of claim 1, wherein: the evaporimeter is still including setting up in going up the shaft and being used for the stereotype board of evaporating pipe location, being used for hoist the fixed pull rod of tube sheet down, wherein the stereotype board has at least one, and each stereotype board with go up and form the passageway that supplies steam flow between the shaft inner wall, fixed pull rod with evaporating pipe parallel arrangement, and the upper end is fixed the upper and lower tip of stereotype board is fixed down on the tube sheet.

3. The falling film distillation system for the separation of methylene chloride and white oil of claim 2, wherein: the shaping plate has the polylith, each the equal level of shaping plate sets up, and has and to laminate the laminating side of going up the shaft inner wall and with correspond the side go up the shaft inner wall disconnection and form the disconnection side of passageway, wherein the polylith the shaping plate along interval distribution about the length direction of evaporating pipe, and the formed is a plurality of the passageway setting of staggering relatively.

4. The falling film distillation system for the separation of methylene chloride and white oil of claim 3, wherein: a plurality of the channels are vertically spaced and are distributed in a left-right relative staggered manner, and the two fixed pull rods are respectively used for fixedly connecting the shaping plate positioned at the same side of the channels in series with the lower tube plate at the bottom.

5. The falling film distillation system for the separation of methylene chloride and white oil of claim 1, wherein: the mixed liquid of dichloromethane and white oil flows downwards from the upper part of the evaporation tube, the steam flow direction in the steam cavity is the same as the flow direction of the mixed liquid, and the steam flows in the steam cavity and forms negative pressure.

6. The falling film distillation system for the separation of methylene chloride and white oil of claim 1, wherein: falling liquid film formula distillation system still include with feed liquor pipe intercommunication and being in go up the minute liquid chamber of tube sheet top, divide the liquid chamber including being located go up the branch liquid dish of tube sheet top, enclose and establish divide the peripheral bounding wall of liquid dish and will the bounding wall with go up the connecting piece that the shaft tower is connected, wherein the upper end of bounding wall opens the setting, the lower tip of feed liquor pipe stretches into in dividing the liquid chamber, divide to set up on the liquid dish and to correspond orificial reposition of redundant personnel below with mixed liquid.

7. The falling film distillation system for the separation of methylene chloride and white oil of claim 6, wherein: the flow distribution holes are multiple and divided into multiple groups, each flow distribution hole group corresponds to one part below the upper pipe orifice of the evaporation pipe and is circumferentially distributed, each group of flow distribution holes is formed in a way that the circle center of a circle formed by the hole centers of the flow distribution holes is arranged on the central line of the upper pipe orifice corresponding to the lower part, the diameter of the circle is larger than the pipe diameter of the upper pipe orifice, and the mixed liquid flowing out of the flow distribution holes from each group of flow distribution holes respectively corresponds to the lower part of the mixed liquid flowing out of the upper pipe orifice and is attached to the periphery of the upper pipe orifice, and the inner wall.

8. The falling film distillation system for the separation of methylene chloride and white oil of claim 7, wherein: many the evaporating pipe is the mode of annular array and is covered at interval in proper order go up the tube sheet with down between the tube sheet, the multiunit branch flow hole and many the evaporating pipe one-to-one sets up, and adjacent two the last mouth of pipe of evaporating pipe corresponds two sets of supply one between the branch flow hole.

9. The falling film distillation system for the separation of methylene chloride and white oil of claim 6, wherein: the lower end of the liquid inlet pipe is located above the liquid distribution disc, a spray head is further arranged at the lower end of the liquid inlet pipe, and the outflow flow of the mixed liquid of dichloromethane and white oil from the spray head is larger than the outflow flow of the flow distribution holes.

10. The falling film distillation system for the separation of methylene chloride and white oil of claim 6, wherein: the falling film distillation system also comprises an upper partition plate extending upwards from the top of the upper tube plate, a lower partition plate extending downwards from the bottom of the lower tube plate, and an extension plate extending upwards from the bottom of the lower tower body and aligned with the lower partition plate, wherein the upper partition plate divides the upper tower body into two or more mixed liquid feeding areas, the liquid separation chambers are correspondingly arranged in the mixed liquid feeding areas, the liquid inlet tubes and the liquid separation chambers are arranged in a one-to-one correspondence manner, and each liquid separation chamber is correspondingly provided with one liquid inlet tube; the lower partition plate correspondingly divides the upper part of the lower tower body into gas phase areas which are in one-to-one correspondence with the mixed liquid feeding areas, the lower partition plate is arranged at a position separated from the aligned extension plates, the gas phase areas extend downwards to the tops of the extension plates, two or more gas phase areas are communicated from the separated positions of the lower partition plate and the extension plates, and the gas outlet pipe is positioned in the gas phase areas and above the sides of the extension plates; the extension plate divides the lower part of the lower tower body into liquid phase regions corresponding to the gas phase regions, and each liquid phase region is correspondingly provided with one liquid outlet pipe.

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