A multi-stage rectification purification system for methyl ethyl carbonate production

Abstract

The utility model discloses a multistage rectification purification system for methyl ethyl carbonate production relates to chemical production technical field, the utility model discloses a light removal rectification tower, main rectification tower and heavy removal rectification tower and each tower installation's conveying pump, condenser etc. component from left to right are installed in proper order to realize multistage rectification, in addition, the main rectification tower is internally provided with multilayer structured packing layer and upper groove tray type liquid distributor, and the material reaction area is increased, through the installation's three -way regulating valve, the mode of changing the gas -liquid load proportion in the tower, the solvent purity of tower top output is maintained in the set range, the problem that the rectification series is insufficient when the single -column structure handles complex component is solved, and the purity of finished product solvent is improved.

Description

Technical Field

[0001] This utility model relates to the field of chemical production technology, specifically a multi-stage distillation and purification system for the production of ethyl methyl carbonate. Background Technology

[0002] In the chemical production of methyl ethyl carbonate, traditional purification equipment often faces problems such as limited distillation stages and high energy consumption when dealing with complex mixtures of multiple components, and it also has limitations in the deep separation of trace impurities.

[0003] Existing technologies such as CN108854128A, which improve yield by adding alkaline catalysts for purification, are prone to introducing new chemical impurities and increasing processing costs. Furthermore, the single-stage reflux structure has limited effectiveness in separating near-boiling-point components. While the CN111689833A scheme features multi-stage characteristics, it is primarily designed for specific waste materials, resulting in weak system versatility. In continuous production, its overall thermal energy utilization rate is low, and it lacks a refined control structure, leading to limited system stability when feed composition fluctuates, making it difficult to ensure continuous production of ultra-high purity products. Utility Model Content

[0004] To overcome the above shortcomings, this utility model provides a multi-stage distillation purification system for the production of methyl ethyl carbonate. The purpose is to solve the problems in the existing technology of low separation purity and high production energy consumption caused by the limited number of distillation stages in the purification process of methyl ethyl carbonate, as well as the poor system stability and difficulty in effectively removing trace impurities near the boiling point when the feed composition fluctuates.

[0005] To achieve the above objectives, this utility model adopts the following technical solution: a multi-stage distillation and purification system for the production of methyl ethyl carbonate, comprising a support base, on the top of which, from left to right, are sequentially and fixedly connected a light component removal distillation column, a main distillation column, and a heavy component removal distillation column. A preheating feed pipe is fixedly connected to the middle side wall of the light component removal distillation column, and the other end of the preheating feed pipe is connected to a feed pump. The top of the light component removal distillation column is connected to a first condenser via a steam conduit, and the bottom outlet of the first condenser is connected to a first reflux tank. The bottom of the first reflux tank is divided into two paths via a pipeline: one path connects to the reflux port at the top of the light component removal distillation column, and the other path connects to a light component collection tank. The bottom outlet of the light component removal distillation column is connected to the middle inlet of the main distillation column via a first intermediate conveying pump. The main distillation column is internally equipped with multiple layers of structured packing. A tray-type liquid distributor is installed above the structured packing. The top of the main distillation column is connected to a second condenser via a vapor pipeline. The liquid outlet of the second condenser is connected to a second reflux tank. The bottom outlet of the second reflux tank is connected to the central feed inlet of the heavy component removal distillation column via a second intermediate transfer pump. The top of the heavy component removal distillation column is connected to a third condenser via a pipeline. The outlet of the third condenser is connected to a third reflux tank. The bottom outlet of the third reflux tank is connected to a finished product storage tank. The bottom of the heavy component removal distillation column is equipped with a heavy component discharge outlet.

[0006] As a further description of the above technical solution: The light-removal distillation column, the main distillation column, and the heavy-removal distillation column are all externally connected to reboilers.

[0007] As a further description of the above technical solution: A shell-and-tube heat exchanger is fitted on the outside of the preheating feed pipe. The heat medium inlet of the shell-and-tube heat exchanger is connected to the heavy component discharge outlet at the bottom of the de-heavy distillation column via a pipeline. The heat medium outlet of the shell-and-tube heat exchanger is connected to the waste tank.

[0008] As a further description of the above technical solution: The structured packing layer of the main distillation column includes packing blocks made of stacked stainless steel wire mesh corrugated packing. The corrugation directions of adjacent packing blocks are arranged at a 90-degree angle. A grid-type packing support plate is provided at the bottom of the structured packing layer. The periphery of the grid-type packing support plate is welded to the inner wall of the main distillation column.

[0009] As a further description of the above technical solution: The tray-type liquid distributor includes a central tank and multiple sub-tanks arranged perpendicular to the central tank. Liquid distribution holes are provided at the bottom of the central tank and the sub-tanks. A liquid guide pipe is provided below the liquid distribution hole, and the bottom end of the liquid guide pipe extends above the structured packing layer.

[0010] As a further description of the above technical solution: A three-way regulating valve is installed on the connecting pipe between the second condenser and the second reflux tank. The other two ports of the three-way regulating valve are respectively connected to the reflux port of the second reflux tank and the main distillation column. The control terminal of the three-way regulating valve is electrically connected to a temperature sensor installed at the top of the main distillation column.

[0011] As a further description of the above technical solution: The lower end of the de-heavy distillation column is equipped with a baffle demister, which is located above the heavy component discharge outlet. The baffle demister includes multiple baffles arranged in a sawtooth pattern, and the baffles form an S-shaped airflow channel.

[0012] As a further description of the above technical solution: The cooling water inlets of the first condenser, the second condenser, and the third condenser are all connected to a cooling water main pipe, and an electromagnetic flow valve is installed on the cooling water main pipe. The cooling water outlets of the first condenser, the second condenser, and the third condenser are all connected to a return water main pipe.

[0013] The beneficial technical effects of this invention are as follows: By employing a three-stage series structure of a light-weight removal distillation column, a main distillation column, and a heavy-weight removal distillation column, combined with a structured packing layer and a tray-type liquid distributor inside the columns, the contact area and mass transfer efficiency between the gas and liquid phases are increased. The raw material first undergoes low-boiling-point impurities removal in the light-weight removal distillation column, followed by deep separation of the main components from near-boiling-point impurities in the main distillation column, and finally, high-boiling-point heavy components are removed in the heavy-weight removal distillation column. This multi-stage distillation physical spatial layout extends the effective distillation path of the material, solves the problem of insufficient distillation stages in single-column structures when processing complex components, and improves the purity of the finished solvent. Attached Figure Description

[0014] Figure 1 A schematic diagram of the system layout is shown.

[0015] Reference numerals in the attached diagram: 1. Preheated feed pipe; 2. Light component removal distillation column; 3. Main distillation column; 4. Heavy component removal distillation column; 5. Three-way regulating valve; 6. First condenser; 7. First reflux tank; 8. Light component collection tank; 9. Structured packing layer; 10. Tray-type liquid distributor; 11. Second condenser; 12. Second reflux tank; 13. Third condenser; 14. Third reflux tank; 15. Finished product storage tank; 16. Waste tank. Detailed Implementation

[0016] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0017] This invention proposes a multi-stage distillation purification system for the production of methyl ethyl carbonate, which includes a light-light distillation column 2, a main distillation column 3, and a heavy-light distillation column 4. The outer sides of the columns of the light-light distillation column 2, the main distillation column 3, and the heavy-light distillation column 4 are all wrapped with an aluminum silicate fiber insulation layer, and the outer side of the insulation layer is covered with a stainless steel sheet protective shell to reduce heat loss during the distillation process.

[0018] The material input begins at the middle side wall of the light component removal distillation column 2. A preheating feed pipe 1 is fixedly connected at this location. The diameter of the preheating feed pipe 1 is determined according to the production scale, and its other end is connected to the outlet of the raw material pump via a flange. The raw material pump is a centrifugal pump with a frequency converter, used to feed the crude methyl ethyl carbonate to be purified into the system. A shell-and-tube heat exchanger is installed outside the preheating feed pipe 1. This heat exchanger consists of two concentric tubes, an inner and an outer tube. The inner tube is the preheating feed pipe 1, and the outer tube's cavity serves as the heat medium channel. The heat medium inlet of the shell-and-tube heat exchanger is connected to the heavy component discharge outlet at the bottom of the heavy component removal distillation column 4 via a stainless steel pipe, while the heat medium outlet is connected to the waste tank 16 in the plant area via a pipe. This physical connection allows the high-temperature heavy component waste liquid discharged from the heavy component removal distillation column 4 to transfer the heat it carries to the internally flowing raw material through the pipe wall of the preheating feed pipe 1 as it flows towards the waste tank 16, achieving countercurrent heat exchange.

[0019] The internal space of the light component removal distillation column 2 is divided into an upper rectification section and a lower stripping section. A steam outlet is located at the top of the column, which is connected to the vapor inlet of the first condenser 6 via a stainless steel steam conduit. The first condenser 6 is a vertical shell-and-tube heat exchanger; the top vapor enters the tube side, while circulating cooling water flows through the shell side. The bottom liquid outlet of the first condenser 6 is connected to the first reflux tank 7 via a pipe. The first reflux tank 7 is a horizontal cylindrical pressure vessel, and its bottom outlet is divided into two paths via a three-way pipe: the first path extends upwards and connects to the reflux port at the top of the light component removal distillation column 2, and is equipped with a manual regulating valve and a rotor flow meter; the second path connects downwards to the light component collection tank 8. A discharge port is located at the bottom of the light component removal distillation column 2, which is connected to the suction end of the first intermediate transfer pump via a stainless steel pipe. The discharge end of the first intermediate transfer pump is connected to the middle feed port of the main distillation column 3 via a pipe.

[0020] As the core separation unit of the entire system, the main distillation column 3 has multiple layers of structured packing 9 arranged along its height inside the column. Each layer of structured packing 9 is composed of several stacked stainless steel wire mesh corrugated packing blocks. At the bottom of each layer of structured packing 9, a grid-type packing support plate is provided. This support plate is welded from parallel stainless steel strips, and its peripheral edges are fully welded to the inner wall of the main distillation column 3. It is used to support the weight of the upper packing and maintain the unobstructed flow of air.

[0021] Above the structured packing layer 9, a tray-type liquid distributor 10 is installed. The tray-type liquid distributor 10 includes a main tray (central tray) located at the center and multiple branch trays extending vertically from both sides of the central tray. Multiple distribution holes with a diameter of 5mm to 10mm are arrayed at the bottom of both the central tray and the branch trays. A liquid guide pipe is welded vertically below each distribution hole, with its bottom end extending downwards and maintaining a distance of 30mm to 50mm from the upper surface of the structured packing layer 9. This multi-stage tray structure ensures that the return liquid or feed liquid can be evenly and multi-pointly dripped onto the surface of the packing layer through the liquid guide pipes under gravity, avoiding liquid deviation within the packing layer.

[0022] A vapor outlet pipe is installed at the top of the main distillation column 3, which connects to the vapor inlet of the second condenser 11. The liquid outlet of the second condenser 11 is connected to the second reflux tank 12. An electronic three-way regulating valve 5 is installed on the connecting pipe between the second condenser 11 and the second reflux tank 12. A high-precision platinum resistance temperature sensor is installed at the vapor outlet at the top of the main distillation column 3. This sensor is electrically connected to the actuator of the three-way regulating valve 5 via a shielded cable. When the sensor detects a fluctuation in vapor temperature, the three-way regulating valve 5 automatically adjusts the valve core position, thereby changing the amount of liquid refluxed into the main distillation column 3.

[0023] The discharge end of the second intermediate transfer pump is connected to the central feed inlet of the heavy distillation column 4 via a stainless steel pipe. The internal structure of the heavy distillation column 4 is similar to that of the main distillation column 3, but an additional baffle demister is installed at its bottom. The baffle demister consists of multiple sets of serrated stainless steel baffles, forming a series of narrow S-shaped airflow channels. When the rising steam passes through these S-shaped channels, due to inertia, the tiny droplets entrained in the steam will collide with the surface of the baffles and gradually condense into larger droplets, which are then returned to the bottom of the column by gravity. The top of the heavy distillation column 4 is connected to the third condenser 13 via a pipe, and the outlet of the third condenser 13 is connected to the third reflux tank 14. The bottom outlet of the third reflux tank 14 is connected to the finished product storage tank 15 via a finished product conveying pipeline. The finished product storage tank 15 is a vertical cylindrical tank with a breather valve installed at the top, a transparent tubular level gauge installed on the side wall, and a finished product sampling port with a ball valve at the bottom.

[0024] To provide the energy required for distillation, the light distillation column 2, the main distillation column 3, and the heavy distillation column 4 are all connected to independent reboilers.

[0025] The system's cooling water circulation network consists of a main cooling water pipe and a return water pipe. The cooling water inlets of the first condenser 6, the second condenser 11, and the third condenser 13 are all connected to the main cooling water pipe via branch pipes. Electromagnetic flow valves are installed on each branch of the main cooling water pipe to regulate the cooling water flow into each condenser. The cooling water outlets of each condenser are connected to the return water pipe via branch pipes, returning the water to the cooling tower in the plant area for cooling circulation.

[0026] In actual operation, crude methyl ethyl carbonate is pumped into the preheated feed pipe 1 via a feed pump. The material first exchanges heat with the heavy component waste liquid from the bottom of the heavy component removal distillation column 4 in a shell-and-tube heat exchanger, raising its temperature to near its boiling point before entering the light component removal distillation column 2. In the light component removal distillation column 2, low-boiling-point light component impurities are vaporized and discharged from the top of the column. After being condensed by the first condenser 6, they enter the first reflux tank 7, where part is refluxed and part is discharged as waste liquid into the light component collection tank 8. The material after the light components have been removed flows out from the bottom of the light component removal distillation column 2 and is sent to the main distillation column 3 by the first intermediate transfer pump.

[0027] The material entering the main distillation column 3 is evenly distributed on the structured packing layer 9 by the tray-type liquid distributor 10. Rising vapor and falling droplets undergo intense mass and heat exchange on the corrugated packing surface. The purity of the main component solvent continuously increases during the ascent, while near-boiling point impurities are enriched in the liquid phase and flow downwards. A temperature sensor at the top of the column monitors changes in vapor composition in real time, and a constant reflux ratio is maintained by adjusting the opening of the three-way regulating valve 5 to ensure the separation accuracy of the main component. The material purified by the main distillation column 3 is then pumped into the de-heavy distillation column 4 by the second intermediate transfer pump.

[0028] In the deweighting distillation column 4, the material undergoes a final deweighting process. As the rising solvent vapor passes through the baffle demister, high-boiling-point heavy component droplets are physically intercepted. Finally, the pure solvent vapor is completely condensed in the third condenser 13 and collected in the third reflux tank 14, eventually entering the finished product storage tank 15. The heavy components enriched at the bottom of the column (such as polymers, heavy metal salts, etc.) are discharged as waste liquid and contribute residual heat to the preheating of the feedstock as they flow through the shell-and-tube heat exchanger.

[0029] To enable those skilled in the art to fully understand this invention, the following section provides further supplementation on the specific implementation principles of this utility model in conjunction with a specific application scenario.

[0030] Step 1, during raw material preheating and preliminary light component removal, begins by starting the raw material pump via an external control terminal. The pump forces crude methyl ethyl carbonate (MEC) containing trace amounts of moisture, light component impurities, and high-boiling-point heavy components into the preheating feed pipe 1. As the material flows through the preheating feed pipe 1, a shell-and-tube heat exchanger is installed on its outer side. The shell side of this heat exchanger carries high-temperature heavy component waste liquid discharged from the bottom of the heavy component removal distillation column 4, raising the raw material temperature to near its azeotropic point before it enters the light component removal distillation column 2. Subsequently, the material enters the light component removal distillation column 2. Driven by rising steam provided by the bottom reboiler, low-boiling-point impurities vaporize and are discharged from the top of the column, entering the first condenser 6. The condensed liquid phase collects in the first reflux tank 7. By adjusting the valve on the outlet pipe of the first reflux tank 7, a portion of the liquid is refluxed back to the top of the light component removal distillation column 2, where the liquid film and rising steam achieve preliminary component separation.

[0031] Step 2: During the deep distillation of the main component, the material after the removal of light components flows out from the bottom of the light component removal distillation column 2, is pressurized by the first intermediate transfer pump, and then sent to the middle of the main distillation column 3. After entering the main distillation column 3, the material first falls into the central tank of the tray-type liquid distributor 10 and is quickly distributed to each sub-tank. Under the action of gravity, the liquid enters the liquid guide pipe through the liquid distribution holes at the bottom of the sub-tank and is evenly distributed on the surface of the uppermost structured packing layer 9 in a multi-point dripping manner. Since the structured packing layer 9 is composed of stainless steel wire mesh corrugated packing blocks stacked at 90-degree angles, the falling droplets form an extremely thin liquid film on the wire mesh surface, while the rising vapor generated by the bottom reboiler is forced to continuously change its flow direction when passing through the corrugated gaps, and physically collides with the liquid film in a turbulent state. This complex geometric path forces the gas and liquid phases to undergo intense momentum and mass exchange in a limited space, causing the purity of the main component solvent to increase stepwise as it flows upward.

[0032] Step 3: During dynamic adjustment of the reflux ratio, the vapor at the top of the main distillation column 3 enters the second condenser 11 for condensation, and then flows into the second reflux tank 12. A temperature sensor installed at the top of the main distillation column 3 collects the vapor phase temperature signal in real time and transmits the signal to the actuator of the electronic three-way regulating valve 5. When fluctuations in the feed composition cause a large amount of near-boiling-point impurities to be mixed into the vapor at the top of the column, the vapor temperature will deviate. At this time, the three-way regulating valve 5 automatically increases the opening of the reflux port according to the temperature feedback signal, increasing the amount of condensate refluxed to the top of the main distillation column 3. The increased reflux liquid physically washes and cools the rising vapor during its descent, condensing high-boiling-point impurities and carrying them back to the bottom of the column. This maintains the purity of the solvent produced at the top of the column within the set range by changing the gas-liquid load ratio within the column.

[0033] Step 4, Removal of Heavy Components and Collection of Finished Product: The intermediate material purified by the main distillation column 3 is pumped into the heavy component removal distillation column 4 by the second intermediate transfer pump. Inside the heavy component removal distillation column 4, the main component solvent vaporizes again and rises, while the high-boiling-point heavy component impurities accumulate at the bottom of the column. Before reaching the top outlet, the rising steam must pass through a baffle demister. As the steam flows through the S-shaped airflow channel formed by the baffles, the tiny heavy component droplets entrained in it, due to their large inertia, cannot quickly change direction with the airflow, thus impacting the serrated baffle wall and condensing and falling. The purified steam after droplet removal enters the third condenser 13 for complete condensation, and finally flows into the third reflux tank 14 and into the finished product storage tank 15. The level gauge on the side wall of the finished product storage tank 15 is used to monitor the storage level, and the breather valve is used to balance the pressure difference inside and outside the tank, ensuring that the internal pressure of the system remains stable when the finished product is sampled at the sampling port.

[0034] All contents not described in detail in the specification are existing technologies known to those skilled in the art, and the model parameters of each electrical appliance and valve are not specifically limited. Conventional equipment can be used. Electrical control components (such as valves) not mentioned in this technical solution are not shown in the figure because they are existing technologies, and will not be described here.

[0035] Although the present invention has been described with reference to preferred embodiments, various modifications can be made to it and components can be replaced with equivalents without departing from the scope of the present invention. In particular, the technical features mentioned in the various embodiments can be combined in any manner as long as there is no structural conflict. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

[0036] In the description of this utility model, terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," which indicate direction or positional relationships, are based on the direction or positional relationships shown in the accompanying drawings. These are used merely for ease of description and do not indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on this utility model. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0037] Furthermore, it should be noted that, in the description of this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0038] The term "comprising" or any other similar term is intended to cover non-exclusive inclusion, such that a process, article, or apparatus / device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to those processes, articles, or apparatus / devices.

[0039] The technical solution of this utility model has been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the protection scope of this utility model is obviously not limited to these specific embodiments. Without departing from the principle of this utility model, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the protection scope of this utility model.

Claims

1. A multi-stage distillation purification system for the production of methyl ethyl carbonate, comprising multiple distillation columns, characterized in that: The multiple distillation columns include a light-weight removal distillation column (2), a main distillation column (3), and a heavy-weight removal distillation column (4) installed sequentially from left to right. A preheating feed pipe (1) is fixedly connected to the middle side wall of the light-weight removal distillation column (2). The top of the light-weight removal distillation column (2) is connected to a first condenser (6) via a steam pipe. The bottom outlet of the first condenser (6) is connected to a first reflux tank (7). The bottom of the first reflux tank (7) is divided into two paths by a pipe. One path is connected to the reflux port at the top of the light-weight removal distillation column (2), and the other path is connected to... The light component collection tank (8) is connected to the bottom outlet of the light component removal distillation column (2) and the middle inlet of the main distillation column (3) via a first intermediate transfer pump; the main distillation column (3) is provided with multiple layers of structured packing (9), and a tray-type liquid distributor (10) is provided above the structured packing (9); the top of the main distillation column (3) is connected to a second condenser (11) via a gas phase pipe; the liquid phase outlet of the second condenser (11) is connected to a second reflux tank (12); the second reflux tank (12) The bottom outlet of 12) is connected to the middle feed port of the de-heavy distillation column (4) via a second intermediate transfer pump; the top of the de-heavy distillation column (4) is connected to a third condenser (13) via a pipe, the outlet of the third condenser (13) is connected to a third reflux tank (14), the bottom outlet of the third reflux tank (14) is connected to a finished product storage tank (15), the bottom of the de-heavy distillation column (4) is provided with a heavy component discharge outlet, and a shell-and-tube heat exchanger is sleeved on the outside of the preheating feed pipe (1), the heat medium of the shell-and-tube heat exchanger The mass inlet is connected to the heavy component outlet at the bottom of the de-heavy distillation column (4) via a pump-connected pipeline. The heat medium outlet of the shell-and-tube heat exchanger is connected to a waste tank (16). A three-way regulating valve (5) is installed on the connecting pipeline between the second condenser (11) and the second reflux tank (12). The other two ports of the three-way regulating valve (5) are connected to the reflux port of the second reflux tank (12) and the main distillation column (3), respectively. The control end of the three-way regulating valve (5) is electrically connected to a temperature sensor located at the top of the main distillation column (3).

2. The multi-stage distillation and purification system for the production of methyl ethyl carbonate according to claim 1, characterized in that: The light distillation column (2), the main distillation column (3), and the heavy distillation column (4) are all externally connected to reboilers.

3. The multi-stage distillation and purification system for the production of methyl ethyl carbonate according to claim 1, characterized in that: The structured packing layer (9) of the main distillation column (3) includes packing blocks and grid-type packing support plates, the periphery of which is welded to the inner wall of the main distillation column (3).

4. A multi-stage distillation and purification system for the production of methyl ethyl carbonate according to claim 1, characterized in that: The tray-type liquid distributor (10) includes a central tank and multiple sub-tanks arranged perpendicular to the central tank. Liquid distribution holes are provided at the bottom of the central tank and the sub-tanks. A liquid guide pipe is provided below the liquid distribution hole, and the bottom end of the liquid guide pipe extends above the regular packing layer (9).

5. A multi-stage distillation and purification system for the production of methyl ethyl carbonate according to claim 1, characterized in that: The lower end of the de-heavy distillation column (4) is provided with a baffle demister. The baffle demister is located above the heavy component discharge outlet. The baffle demister includes multiple baffles arranged in a sawtooth pattern, and an S-shaped airflow channel is formed between the baffles.

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