Falling film distillation process for separating dichloromethane and white oil
阅读说明：本技术 二氯甲烷和白油分离用的降膜式蒸馏工艺 (Falling film distillation process for separating dichloromethane and white oil ) 是由 曾凡中 马志强 高建锋 袁秋红 徐晓红 王健 叶志刚 于 2020-06-28 设计创作，主要内容包括：本发明涉及二氯甲烷和白油分离用的降膜式蒸馏工艺,步骤如下：1)、向蒸汽腔通入蒸汽,蒸汽自顶部向底部流动；2)、将二氯甲烷和白油混合液自一根进液管加入下方的蒸发管；3)、混合液在蒸汽的加热下,分离出气相的二氯甲烷和液相的白油,其中气相的二氯甲烷流向气液分离器进行气液分离；液相的白油自出液管流出蒸馏塔；4)、流出蒸馏塔的蒸馏白油回流至顶部的另一根进液管,并重复步骤2)和3),实现蒸馏白油的二次蒸馏,或者完成蒸馏白油的二次蒸馏后,并且重复上述二次蒸馏过程实现蒸馏白油的多次蒸馏。本发明通过两次或多次进行白油的蒸馏,成品白油中二氯甲烷含量80ppm以内,二氯甲烷中白油含量20ppm以内。(The invention relates to a falling film distillation process for separating dichloromethane and white oil, which comprises the following steps: 1) introducing steam into the steam cavity, wherein the steam flows from the top to the bottom; 2) adding a dichloromethane and white oil mixed solution into the evaporation tube below from one liquid inlet tube; 3) under the heating of steam, the mixed solution is separated into gaseous dichloromethane and liquid white oil, wherein the gaseous dichloromethane flows to a gas-liquid separator for gas-liquid separation; the liquid-phase white oil flows out of the distillation tower from the liquid outlet pipe; 4) and refluxing the distilled white oil flowing out of the distillation tower to the other liquid inlet pipe at the top, and repeating the steps 2) and 3) to realize secondary distillation of the distilled white oil, or after finishing the secondary distillation of the distilled white oil, repeating the secondary distillation process to realize multiple times of distillation of the distilled white oil. The invention carries out the distillation of the white oil for two times or more, the dichloromethane content in the finished product of the white oil is within 80ppm, and the white oil content in the dichloromethane is within 20 ppm.)
1. A falling film distillation process for separating dichloromethane and white oil is characterized in that: the distillation system adopted by the process comprises a distillation tower, an evaporator, a gas-liquid separator, an upper partition plate, a lower partition plate and an extension plate, 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 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 gas-liquid separator is communicated with the gas outlet pipe; the upper baffle plate extends upwards from the top of the upper tube plate and divides the upper tower body into two or more mixed liquid feeding areas, the liquid inlet pipes and the mixed liquid feeding areas are arranged in a one-to-one correspondence manner, and each mixed liquid feeding area is correspondingly provided with one liquid inlet pipe; the lower baffle plate extends downwards from the bottom of the lower tube plate, the extension plate extends upwards from the bottom of the lower tower body and is aligned with the lower baffle plate, the lower baffle plate and the aligned extension plate are arranged in a spaced manner, the lower baffle 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 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 baffle plate and the extension plate, the gas outlet pipe is positioned in the gas phase areas and is positioned above the sides of the extension plates, the extension plate divides the lower part of the lower tower body into liquid phase areas which are corresponding to the gas phase areas, and each liquid phase area is correspondingly provided with one liquid outlet pipe,
the distillation steps are as follows:
1) introducing steam into the steam cavity, wherein the steam flows from the top to the bottom;
2) adding a dichloromethane and white oil mixed solution into a mixed solution feeding area below from one liquid inlet pipe, shunting the mixed solution to an evaporation pipe corresponding to the lower part by the mixed solution feeding area, and enabling the mixed solution to flow downwards along the inner wall of the evaporation pipe;
3) under the heating of the steam, the mixed solution separates dichloromethane in gas phase and white oil in liquid phase, and the dichloromethane in gas phase flows to the lower tower body cavity, wherein the dichloromethane in gas phase is suspended in the corresponding gas phase area and flows to the gas-liquid separator from the gas outlet pipe, so that the gas-liquid separation of the dichloromethane in gas phase is realized; the liquid phase white oil flows to a liquid phase zone below and flows out of the distillation tower from the liquid outlet pipe;
4) the distilled white oil flowing out of the distillation tower flows back to the other liquid inlet pipe at the top and falls into the mixed liquid feeding area below from the liquid inlet pipe, the steps 2) and 3) are repeated, secondary distillation of the distilled white oil is realized, the secondarily distilled white oil flows out of the distillation tower from the liquid outlet pipe corresponding to the bottom, and gas-phase dichloromethane enters a gas-liquid separator from a gas outlet pipe of the gas-phase area for gas-liquid separation; or after finishing the secondary distillation of the distilled white oil, repeating the secondary distillation process to realize N times of distillation of the distilled white oil, wherein N is not less than 3 and is an integer.
2. The falling film distillation process for the separation of methylene chloride and white oil of claim 1, wherein: before the mixed solution of dichloromethane and white oil is added into the liquid inlet pipe, the mixed solution is preheated to ensure that the temperature of the mixed solution is 36 +/-3 ℃.
3. The falling film distillation process 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 the hoist and mount 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, in step 1), steam forms the baffling from the steam intracavity to flow downwards along the passageway.
4. The falling film distillation process for the separation of methylene chloride and white oil of claim 3, 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.
5. The falling film distillation process for the separation of methylene chloride and white oil of claim 4, wherein: a plurality of the passageway is from top to bottom spaced, and control relative dislocation and distribute, fixed pull rod has two, and will be located the passageway homonymy respectively the stereotype board is fixed concatenating with the lower tube sheet of bottom, and in step 1), steam is continuous S-shaped and flows to the bottom from the top, and the water that condenses flows out the steam chamber from the bottom of last shaft.
6. The falling film distillation process 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 process 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 process 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 process 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 process for the separation of methylene chloride and white oil of claim 1, wherein: the gas-liquid separator is a hydrocyclone, and in the step 3), the white oil separated by the hydrocyclone is mixed with the distilled white oil for secondary distillation or N times of distillation.
Technical Field
The invention belongs to the field of distillation, and particularly relates to a falling film distillation process 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 dichloromethane liquid after condensation 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 process for separating dichloromethane and white oil.
In order to solve the technical problems, the invention adopts the following technical scheme:
a falling film distillation process for separating dichloromethane and white oil adopts a distillation system which comprises a distillation tower, an evaporator, a gas-liquid separator, an upper partition plate, a lower partition plate and an extension plate, 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 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 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 gas-liquid separator is communicated with the gas outlet pipe; the upper baffle plate extends upwards from the top of the upper pipe plate and divides the upper tower body into two or more mixed liquid feeding areas, the liquid inlet pipes are arranged in one-to-one correspondence with the mixed liquid feeding areas, and each mixed liquid feeding area is correspondingly provided with one liquid inlet pipe; the lower baffle extends downwards from the bottom of the lower tube plate, the extension plate extends upwards from the bottom of the lower tower body and is aligned with the lower baffle, the lower baffle and the aligned extension plate are arranged in a spaced manner, the lower baffle 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 gas phase areas extend downwards to the top of the extension plate, two or more gas phase areas are communicated with each other from the spaced positions of the lower baffle and the extension plate, the gas outlet pipe is positioned above the side of the extension plate and in the gas phase areas, the extension plate divides the lower part of the lower tower body into liquid phase areas which are corresponding to the gas phase areas, and each liquid phase area is correspondingly provided with a liquid outlet pipe,
the distillation steps are as follows:
1) introducing steam into the steam cavity, wherein the steam flows from the top to the bottom;
2) adding a dichloromethane and white oil mixed solution into a mixed solution feeding area below from one liquid inlet pipe, shunting the mixed solution to an evaporation pipe corresponding to the lower part by the mixed solution feeding area, and enabling the mixed solution to flow downwards along the inner wall of the evaporation pipe;
3) under the heating of the steam, the mixed solution separates dichloromethane in gas phase and white oil in liquid phase, and the dichloromethane in gas phase flows to the lower tower body cavity, wherein the dichloromethane in gas phase is suspended in the corresponding gas phase area and flows to the gas-liquid separator from the gas outlet pipe, so that the gas-liquid separation of the dichloromethane in gas phase is realized; the liquid phase white oil flows to a liquid phase zone below and flows out of the distillation tower from the liquid outlet pipe;
4) the distilled white oil flowing out of the distillation tower flows back to the other liquid inlet pipe at the top and falls into the mixed liquid feeding area below from the liquid inlet pipe, the steps 2) and 3) are repeated, secondary distillation of the distilled white oil is realized, the secondarily distilled white oil flows out of the distillation tower from the liquid outlet pipe corresponding to the bottom, and gas-phase dichloromethane enters a gas-liquid separator from a gas outlet pipe of the gas-phase area for gas-liquid separation; or after finishing the secondary distillation of the distilled white oil, repeating the secondary distillation process to realize N times of distillation of the distilled white oil, wherein N is not less than 3 and is an integer.
Preferably, the mixture of dichloromethane and white oil is preheated before being added into the liquid inlet pipe, so that the temperature of the mixture is 36 +/-3 ℃. The preheating benefits are as follows: the boiling point difference between the dichloromethane and the white oil (the boiling point of the dichloromethane is low, 39.8 ℃, the boiling point of the white oil is high, more than 350 ℃) can be preheated before the mixed liquid is added into the distillation tower, and as long as the temperature of the mixed liquid in the evaporation tube is more than or equal to 39.8 ℃, the mixed liquid is separated into the dichloromethane in a gas phase and the white oil in a liquid phase, so the temperature difference between the steam in the evaporation cavity and the stable temperature difference of the mixed liquid in the evaporation tube is smaller, and the consumption of the steam is obviously reduced.
According to a specific implementation and preferred aspect of the present invention, the evaporator further includes at least one sizing plate disposed in the upper tower body for positioning the evaporation tubes, and a fixing pull rod for hoisting the lower tube plate, wherein a channel for steam to flow is formed between each sizing plate and the inner wall of the upper tower body, the fixing pull rod is disposed parallel to the evaporation tubes, and the upper end portion of the fixing pull rod is fixed to the upper end portion of the sizing plate, and the lower end portion of the fixing pull rod is fixed to the lower tube plate, and in step 1), steam forms a baffle from the steam cavity and flows downward along the channel. 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.
Preferably, the stereotype board has the polylith, and each stereotype board is the level setting, and has and can laminate go up the laminating side of shaft inner wall and with correspond the side go up the disconnection of shaft inner wall and form the disconnection side of passageway, wherein the polylith the stereotype board along interval distribution about the length direction of evaporating pipe, and the formed is a plurality of the passageway setting of staggering 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.
Furthermore, it is a plurality of the passageway is from top to bottom the interval, and control relative dislocation distribution, fixed pull rod has two, and will be located the passageway homonymy respectively the stereotype board is fixed concatenating with the lower tube sheet of bottom, and in step 1), steam is continuous S-shaped and flows to the bottom from the top, and the steam chamber is flowed from the bottom of upper tower body to the water that condenses.
According to still another specific implementation and preferred aspect of the present invention, the falling film distillation system further includes a liquid separation chamber in communication with the liquid inlet pipe and above the upper pipe plate, the liquid separation chamber includes a liquid separation tray above the upper pipe plate, a surrounding plate surrounding the liquid separation tray, and a connecting member connecting the surrounding plate and the upper tower body, wherein an upper end of the surrounding plate is open, a lower end of the liquid inlet pipe extends into the liquid separation chamber, and the liquid separation tray is provided with a branch hole capable of uniformly dividing the mixed liquid to a lower portion 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 respectively adheres to the inner wall of the evaporation pipe from the periphery of the upper pipe orifice corresponding below and flows downwards. 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, many evaporating pipes are the mode of annular array and are covered at interval in proper order between last tube sheet and the lower tube sheet, the multiunit the reposition of redundant personnel hole with 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 reposition of redundant personnel hole.
Preferably, the lower end of the liquid inlet pipe is located above the liquid distribution disc, a spray header 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 header is larger than the outflow flow of the mixed liquid from the liquid distribution 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.
Further, the gas-liquid separator is a hydrocyclone, and in the above step 3), the white oil separated by the hydrocyclone is mixed with the distilled white oil to be subjected to secondary distillation or N-fold distillation. After two or more times of distillation, the white oil has higher quality.
Due to the implementation of the technical scheme, compared with the prior art, the invention has the following advantages:
on one hand, the content of dichloromethane in the finished product white oil is within 80ppm by distilling the white oil twice or for multiple times; on the other hand, the falling film evaporator has short material retention time, small steam working pressure and low steam consumption, and simultaneously the evaporated white oil concentrate has low temperature, light color and high purity, and the evaporated dichloromethane gas has the white oil content within 20ppm after separation and subsequent condensation water separation.
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 process for separation of methylene chloride and white oil according to the present embodiment employs a falling film distillation system including 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
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
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.
In this example, the pressure was 0.15Mpa, and the boiling point difference between methylene chloride and white oil (methylene chloride boiling point low, 39.8 ℃, white oil boiling point high, 350 ℃ or more) was established, and the mixture was preheated before being fed into the distillation column, so that the mixture separated methylene chloride in the vapor phase and white oil in the liquid phase when the temperature of the mixture in the evaporation tube was 39.8 ℃ or higher, and therefore, the difference between the temperature of the vapor in the evaporation chamber and the temperature of the mixture in the evaporation tube was small, and the amount of vapor used was remarkably small.
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 of 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
Specifically, the
In this embodiment, two
The
Referring to fig. 5, the plurality of
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
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.
Specifically, the distillation process is implemented as follows:
1) introducing steam into the steam cavity, wherein the steam flows from the top to the bottom;
2) preheating a mixed solution of dichloromethane and white oil to enable the temperature of the mixed solution to reach 39 ℃, then enabling the mixed solution to flow into the
3) the steam flows downwards along the continuous S-shaped deflection direction, condensed water flows out of the steam cavity from the bottom of the upper tower body, and the dichloromethane in a gas phase and the white oil in a liquid phase are separated to flow into the lower tower body cavity under the heating of the mixed liquid by the deflection steam, wherein the hydrocyclone generates micro negative pressure of 0.074Mpa, the dichloromethane in the gas phase is suspended in the corresponding gas phase region q1 and flows to the hydrocyclone 3 from the gas outlet pipe 1c (micro negative pressure adsorption), so that the gas-liquid separation of the dichloromethane in the gas phase is realized; the white oil in the liquid phase flows to the lower liquid phase region y1 and flows out of the distillation column 1 through the liquid outlet pipe 1 b;
4) the white oil flowing out of the distillation tower 1 and the white oil flowing out of the hydrocyclone 3 are mixed and refluxed to a mixed liquid feeding area h2 at the top, and fall into a
Generally, after the white oil is subjected to secondary distillation, the dichloromethane content 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. Of course, if the separation effect of the white oil and the dichloromethane is further improved, the secondary distillation process can be repeated to realize N times of distillation of the distilled white oil, wherein N is not less than 3 and is an integer.
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.
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