An apparatus for separating a binary azeotrope

Abstract

The utility model provides a device for separating binary azeotrope. The device comprises first rectifying tower, second rectifying tower and third rectifying tower which are connected in sequence, the middle part of first rectifying tower is provided with feed inlet, characterized by, the device still includes first reboiler which is connected with the tower kettle material export of first rectifying tower, second reboiler which is connected with the tower kettle material export of second rectifying tower, the overhead vapor export of second rectifying tower is connected with the heat source import of first reboiler, the heat source export of first reboiler is connected with the overhead stream import of second rectifying tower, the overhead vapor export of third rectifying tower is connected with the heat source import of second reboiler, and the heat source export of second reboiler is connected with the overhead stream import of third rectifying tower. The device of the utility model has the characteristics of low energy consumption, short flow and high heat exchange efficiency.

Description

Technical Field

[0001] This utility model relates to the field of binary azeotropic substance separation technology, specifically to a device for separating binary azeotropic substances. Background Technology

[0002] Tetrahydrofuran, also known as oxacyclopentane or 1,4-epoxybutane, is a heterocyclic organic compound with the chemical formula C4H8O. Belonging to the ether family, it is the fully hydrogenated product of furan, a colorless and transparent liquid, soluble in water, ethanol, diethyl ether, acetone, benzene, etc. It is mainly used as a solvent, chemical synthesis intermediate, and analytical reagent, and is widely applied in organic synthesis, biomedicine, and fine chemicals. Because tetrahydrofuran and liquid mixtures of water / methanol / ethanol form a minimum azeotrope, it is difficult to separate them using ordinary distillation. Special distillation methods such as extractive distillation and conventional pressure swing distillation can be used. However, extractive distillation requires a third substance to change the relative volatility between the components, complicating the process; while conventional pressure swing distillation is simple and does not introduce a third substance, it is still not energy-efficient. Therefore, an improved special distillation method is urgently needed to solve this problem.

[0003] Patent (CN103394209A) discloses a method for separating an azeotropic system of ethanol and tetrahydrofuran using a dual-tower pressure swing distillation system. The apparatus consists of an atmospheric distillation column and a pressurized distillation column, utilizing the characteristic that the azeotropic composition of ethanol and tetrahydrofuran changes significantly with pressure to effectively separate them. However, this method does not further consider energy consumption. The paper "Application of Aspen Plus in Simulated Separation of Tetrahydrofuran-Water Azeotropic Distillation" discloses a method for separating a mixture of tetrahydrofuran and water using a dual-tower distillation process with atmospheric and pressurized pressure. This study optimized the theoretical plate number, feed location, reflux ratio, and distillation ratio of the atmospheric and pressurized towers, considering both separation purity and production costs. The optimal process parameters for the dual-tower pressure-swing distillation simulation were obtained: 12 theoretical plates for the atmospheric tower, a reflux ratio of 1.767, a feed location of 9, and a distillation ratio of 0.6950; and 19 theoretical plates for the pressurized tower, a reflux ratio of 1.6, a feed location of 13, and a distillation ratio of 0.5531. Although efficient separation was considered, only tetrahydrofuran with a mass fraction ≥99.7% was obtained, resulting in low purity and high energy consumption of approximately 3000 kW, failing to achieve energy savings. The literature "Design and Thermal Integration of Tetrahydrofuran-Water High and Low Pressure Dual-Tower Azeotropic Distillation" investigated the effects of factors such as the number of trays, feed conditions, and reflux rate on heat load and product quality, and also performed thermal integration calculations for the dual-tower pressure swing distillation process. However, these methods are still not energy-efficient enough. Utility Model Content

[0004] In order to solve one of the above-mentioned technical problems in the prior art, the present invention provides a device for separating binary azeotropes, which has the characteristics of low energy consumption, short process and high heat exchange efficiency.

[0005] This invention provides an apparatus for separating binary azeotropic compounds, comprising a first distillation column, a second distillation column, and a third distillation column connected in sequence; a feed inlet is provided in the middle of the first distillation column; the apparatus further includes a first reboiler connected to the bottom material outlet of the first distillation column and a second reboiler connected to the bottom material outlet of the second distillation column; the top vapor outlet of the second distillation column is connected to the heat source inlet of the first reboiler, and the heat source outlet of the first reboiler is connected to the top stream inlet of the second distillation column; the top vapor outlet of the third distillation column is connected to the heat source inlet of the second reboiler, and the heat source outlet of the second reboiler is connected to the top stream inlet of the third distillation column.

[0006] Furthermore, the apparatus also includes a condenser and a first reflux tank. The inlet of the condenser is connected to the top vapor outlet of the first distillation column, the outlet of the condenser is connected to the top feed inlet of the first reflux tank, and the bottom outlet of the first reflux tank is connected to the top vapor inlet of the first distillation column and the top vapor inlet of the second distillation column, respectively.

[0007] Furthermore, the apparatus also includes a second reflux tank, the top inlet of which is connected to the heat source outlet of the first reboiler, and the bottom outlet of which is connected to the steam inlet at the top of the third distillation column.

[0008] Furthermore, the device also includes a third reflux tank, the top inlet of which is connected to the heat source outlet of the second reboiler, and the bottom outlet of which is connected to the middle inlet of the first distillation column.

[0009] Furthermore, the apparatus also includes a third reboiler for the bottom of the third distillation column, wherein the heat source inlet of the third reboiler is connected to the outlet of the bottom of the third distillation column, and the heat source outlet of the third reboiler is connected to the inlet of the bottom of the third distillation column.

[0010] Furthermore, the material conveying power in the device is provided by a conveying pump.

[0011] Furthermore, the device is connected via a pipe.

[0012] Furthermore, the theoretical number of plates in the first distillation column is 10-70.

[0013] Furthermore, the theoretical number of plates in the second distillation column is 10-70.

[0014] Furthermore, the third distillation column has a theoretical number of 10-70 plates.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] (1) The device provided by this utility model can effectively break the azeotropic reaction and obtain products with a mass fraction of more than 99.9%, and does not require the introduction of a third component into the system, thereby ensuring the reliability and stability of solvent recycling.

[0017] (2) This utility model reduces costs and saves energy by multi-effect distillation, while ensuring efficient separation of two systems. It is shorter in process, requires less equipment investment, and can effectively reduce energy consumption by more than 20% compared with other devices. Attached Figure Description

[0018] Figure 1 A flowchart according to one embodiment of the present invention is shown;

[0019] Figure 2 Flowcharts for Comparative Example 1 and Comparative Example 2 are shown;

[0020] The above figures include the following reference numerals:

[0021] 1. First distillation column; 2. First reboiler; 3. First reflux tank; 4. Condenser; 5. First transfer pump; 6. Second distillation column; 7. Second reflux tank; 8. Second reboiler; 9. Second transfer pump; 10. Third reboiler; 11. Third distillation column; 12. Third reflux tank; 13. Third transfer pump. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this utility model clearer, the following detailed description is provided in conjunction with the embodiments and accompanying drawings. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this utility model in any way.

[0023] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0024] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "connection" and "linked" 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 direct connection or an indirect connection through an intermediate medium; they can refer to abutment; they can refer to the internal communication of two components or the interaction between 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.

[0025] In the description of this utility model, it should be understood that the terms "upper," "lower," "front," "rear," "left," "right," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this utility model and for simplifying the description, and do not indicate or imply that the device or element referred to 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" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, features defined with "first" or "second" may explicitly or implicitly include one or more of the stated features.

[0026] This utility model provides an apparatus for separating binary azeotropic compounds, comprising a first distillation column, a second distillation column, and a third distillation column connected in sequence; a feed inlet is provided in the middle of the first distillation column; the apparatus further comprises a first reboiler connected to the bottom material outlet of the first distillation column and a second reboiler connected to the bottom material outlet of the second distillation column; the top vapor outlet of the second distillation column is connected to the heat source inlet of the first reboiler, and the heat source outlet of the first reboiler is connected to the top stream inlet of the second distillation column; the top vapor outlet of the third distillation column is connected to the heat source inlet of the second reboiler, and the heat source outlet of the second reboiler is connected to the top stream inlet of the third distillation column.

[0027] In some embodiments, the binary azeotrope includes a first component and a second component.

[0028] In some embodiments, the first component is selected from any one of ester solvents, water, alcohol solvents, acetonitrile, or amide solvents.

[0029] In some embodiments, the second component is selected from any one of alcohol solvents, tetrahydrofuran, or organic acid solvents.

[0030] In some embodiments, the binary azeotrope is selected from alcohol solvents and ester solvents, tetrahydrofuran and water, tetrahydrofuran and alcohol solvents, alcohol solvents and water, acetonitrile and water, organic acid solvents and amide solvents.

[0031] In some embodiments, the alcohol solvent is selected from one or more of methanol, ethanol, propanol, or isopropanol.

[0032] In some embodiments, the ester solvent is selected from methyl acetate.

[0033] In some embodiments, the organic acid solvent is selected from formic acid and / or acetic acid.

[0034] In some embodiments, the amide solvent is selected from N,N-dimethylacetamide and / or N,N-dimethylformamide.

[0035] In some embodiments, the first component is water and / or acetonitrile.

[0036] In some embodiments, the second component is tetrahydrofuran and / or methanol.

[0037] In some embodiments, the first component is selected from water, and the second component is selected from tetrahydrofuran.

[0038] In some embodiments, the first component is selected from methanol and the second component is selected from acetonitrile.

[0039] In some embodiments, the first distillation column is used to obtain a first component, such as methanol or water, by distillation separation.

[0040] In some embodiments, the second and third distillation columns are used to obtain a second component, such as acetonitrile or tetrahydrofuran, by distillation separation.

[0041] In some embodiments, the apparatus further includes a condenser and a first reflux tank, wherein the condenser inlet is connected to the top vapor outlet of the first distillation column, the condenser outlet is connected to the top feed inlet of the first reflux tank, and the bottom outlet of the first reflux tank is connected to the top vapor inlet of the first distillation column and the top vapor inlet of the second distillation column, respectively.

[0042] In some embodiments, the apparatus further includes a second reflux tank, the top inlet of which is connected to the heat source outlet of the first reboiler, and the bottom outlet of which is connected to the steam inlet at the top of the third distillation column.

[0043] In some embodiments, the apparatus further includes a third reflux tank, the top inlet of which is connected to the heat source outlet of the second reboiler, and the bottom outlet of which is connected to the middle inlet of the first distillation column.

[0044] In some embodiments, the apparatus further includes a third reboiler for the reboiler of the third distillation column, wherein the heat source inlet of the third reboiler is connected to the outlet of the reboiler of the third distillation column, and the heat source outlet of the third reboiler is connected to the inlet of the reboiler of the third distillation column.

[0045] In some embodiments, the power for material conveying in the device is provided by a conveying pump.

[0046] In some implementations, the device is connected via a pipe.

[0047] In some embodiments, the operating pressures of the first, second, and third distillation columns increase sequentially.

[0048] In some embodiments, the operating pressure of the first distillation column is -0.09 to 0.5 MPaG; the operating pressure of the second distillation column is 0.3 to 1.0 MPaG; and the operating pressure of the third distillation column is 0.6 to 2.0 MPaG.

[0049] In some implementations, the first distillation column has 10-70 theoretical plates.

[0050] In some embodiments, the second distillation column has 10-70 theoretical plates.

[0051] In some embodiments, the third distillation column has 10-70 theoretical plates.

[0052] In some embodiments, the reflux ratio of the first distillation column is 0.01-30.

[0053] According to a specific embodiment of this utility model, such as Figure 1 As shown, the method of using the apparatus for separating binary azeotropes includes the following steps:

[0054] (S1) The binary azeotropic feedstock is subjected to a first distillation in the first distillation column 1. The vapor stream I is collected from the top vapor outlet of the first distillation column 1, and the material I and the first component are collected from the bottom of the first distillation column 1.

[0055] (S2) The gaseous stream I is condensed by the condenser 4 and then flows into the first reflux tank 3. It is then divided into stream I and stream II. Stream I is sent to the top of the first distillation column 1 as reflux liquid by the first transfer pump 5 to form reflux. Stream II is sent to the top of the second distillation column 6 by the first transfer pump 5. Second distillation is carried out in the second distillation column 6. The vapor stream II is collected from the top vapor outlet of the second distillation column 6. The material II and the second component are collected from the bottom of the second distillation column. After the material I and the gaseous stream II are subjected to the first heat exchange treatment in the first reboiler 2, the gaseous stream II is condensed to obtain the liquid stream II. The material I is returned to the first distillation column 1.

[0056] (S3) The liquid stream II flows into the second reflux tank 7 and is sent to the top of the third distillation column 11 by the second transfer pump 9. The third distillation is carried out in the third distillation column 11. The vapor stream III is collected from the top vapor outlet of the third distillation column. The material III and the second component are collected from the bottom of the third distillation column. After the two streams of vapor stream III and material II undergo the second heat exchange treatment at the second reboiler 8, the vapor stream III is condensed to obtain liquid stream III. The liquid stream III enters the third reflux tank 12 and is sent to the top of the first distillation column 1 by the third transfer pump 13 to form a cycle. The material III is returned to the third distillation column 11 via the third reboiler 10.

[0057] In some embodiments, the first heat exchange process includes: allowing the gaseous stream II to enter the first reboiler and exchange heat with the material I collected from the bottom of the first distillation column, wherein the gaseous stream II is condensed to obtain liquid stream II, and the heat released by the heat exchange serves as the heat source for the first reboiler.

[0058] In some embodiments, the second heat exchange process includes: allowing the gaseous stream III to enter the second reboiler and exchange heat with the material II collected from the bottom of the second distillation column, wherein the gaseous stream III is condensed to obtain liquid stream III, and the heat released by the heat exchange serves as the heat source for the second reboiler.

[0059] In some embodiments, gas stream I, gas stream II and gas stream III are all binary azeotropic compositions at the corresponding temperatures, i.e., mixtures composed of different amounts of the first component and the second component.

[0060] In some implementations, the compositions of stream I and stream II are consistent with those of gas stream I, and are the azeotropic compositions of the binary components at the operating pressure of the first distillation column.

[0061] According to a specific embodiment of this utility model, when the binary azeotrope is tetrahydrofuran and water, the separation method includes:

[0062] (S1) The binary azeotropic feedstock is subjected to a first distillation in the first distillation column 1. The vapor stream I is collected from the top vapor outlet of the first distillation column 1, and the material I and high-purity water are collected from the bottom of the first distillation column 1.

[0063] (S2) The gaseous stream I is condensed by the condenser 4 and then flows into the first reflux tank 3. It is then divided into stream I and stream II. Stream I is sent to the top of the first distillation column 1 as reflux liquid by the first transfer pump 5 to form reflux. Stream II is sent to the top of the second distillation column 6 by the first transfer pump 5. Second distillation is carried out in the second distillation column 6. The vapor stream II is collected from the top vapor outlet of the second distillation column 6. The bottom of the second distillation column is collected from the material II and high-purity tetrahydrofuran. After the material I and the gaseous stream II are subjected to the first heat exchange treatment in the first reboiler 2, the gaseous stream II is condensed to obtain the liquid stream II. The material I is returned to the first distillation column 1.

[0064] (S3) The liquid stream II flows into the second reflux tank 7 and is sent to the top of the third distillation column 11 by the second transfer pump 9. The third distillation is carried out in the third distillation column 11. The vapor stream III is collected from the top vapor outlet of the third distillation column. The bottom of the third distillation column collects material III and high-purity tetrahydrofuran. After the two streams of vapor stream III and material II undergo the second heat exchange treatment at the second reboiler 8, vapor stream III is condensed to obtain liquid stream III. Liquid stream III enters the third reflux tank 12 and is sent to the top of the first distillation column 1 by the third transfer pump 13 to form a cycle. Material III is returned to the third distillation column 11 via the third reboiler 10.

[0065] In some implementations, the operating pressure of the first distillation is -0.05 to -0 MPaG.

[0066] In some implementations, the operating pressure of the first distillation is 0.2-0.5 MPaG.

[0067] In some implementations, the operating pressure of the first distillation is 0.7-1 MPaG.

[0068] According to a specific embodiment of this utility model, when the binary azeotrope is methanol and acetonitrile, the separation method includes:

[0069] (S1) The binary azeotropic feedstock is subjected to a first distillation in the first distillation column 1. The vapor stream I is collected from the top vapor outlet of the first distillation column 1, and the material I and high-purity acetonitrile are collected from the bottom of the first distillation column 1.

[0070] (S2) The gaseous stream I is condensed by the condenser 4 and then flows into the first reflux tank 3. It is then divided into stream I and stream II. Stream I is sent to the top of the first distillation column 1 as reflux liquid by the first transfer pump 5 to form reflux. Stream II is sent to the top of the second distillation column 6 by the first transfer pump 5. Second distillation is carried out in the second distillation column 6. The vapor stream II is collected from the top vapor outlet of the second distillation column 6. The bottom of the second distillation column collects material II and high-purity methanol. After the material I and the gaseous stream II are subjected to the first heat exchange treatment in the first reboiler 2, the gaseous stream II is condensed to obtain liquid stream II. The material I is returned to the first distillation column 1.

[0071] (S3) The liquid stream II flows into the second reflux tank 7 and is sent to the top of the third distillation column 11 by the second transfer pump 9. The third distillation is carried out in the third distillation column 11. The vapor stream III is collected from the top vapor outlet of the third distillation column. The bottom of the third distillation column collects material III and high-purity methanol. After the two streams of vapor stream III and material II undergo a second heat exchange treatment at the second reboiler 8, vapor stream III is condensed to obtain liquid stream III. Liquid stream III enters the third reflux tank 12 and is sent to the top of the first distillation column 1 by the third transfer pump 13 to form a cycle. Material III is returned to the third distillation column 11 via the third reboiler 10.

[0072] In some implementations, the operating pressure of the first distillation is 0-0.005 MPaG.

[0073] In some implementations, the operating pressure of the first distillation is 0.1-0.3 MPaG.

[0074] In some implementations, the operating pressure of the first distillation is 0.3-0.7 MPaG.

[0075] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0076] In this article, "azeotrope" refers to a mixture of two or more homogeneous solutions of different components that, when mixed in a specific ratio and under a fixed pressure, have only one boiling point. Azeotrope is a mixture of identical components that forms at gas-liquid equilibrium due to intermolecular interactions between the different chemical components.

[0077] In this article, "lowest azeotrope" and "lowest azeotrope" refer to the formation of the highest azeotrope when there is a large difference between molecules, and both attractive and repulsive forces exist. When the attractive force plays a major role at a certain temperature and significantly increases the vapor pressure of the components, the highest azeotrope is formed; otherwise, the lowest azeotrope is formed.

[0078] In this article, "azeotropic point" refers to the boiling temperature of an azeotrope. When the boiling temperature of an azeotrope is higher than the boiling points of the two pure components that make up the azeotrope, it is called the "highest azeotropic point"; when the boiling temperature of an azeotrope is lower than the boiling points of the two pure components that make up the azeotrope, it is called the "lowest azeotropic point".

[0079] The "pressure swing distillation" in this paper utilizes the characteristic that the composition of azeotropes changes with pressure, and separates azeotropes using two distillation columns with different pressures to achieve the separation purpose. The "multi-effect distillation" in this paper is an energy-saving operation process that utilizes the bond energy and temperature difference of different columns to connect several columns in series.

[0080] Unless otherwise specified, the operating pressure in the embodiments and comparative examples in this article refers to gauge pressure.

[0081] Unless otherwise specified, "%" in the embodiments and comparative examples in this article refers to mass percentage.

[0082] Example 1: The binary azeotrope used in this example is a mixed waste liquid of tetrahydrofuran and water from a chemical plant in Lu'an City. The composition is: 80wt% tetrahydrofuran and 20wt% water, with a feed rate of 2000 kg / h. Figure 1 The process shown involves the feedstock entering the first distillation column 1 for primary distillation. The operating pressure (gauge pressure) of the first distillation column 1 is -0.04 MPaG, the overall pressure drop is 0.004 MPaG, the top temperature is 49°C, the bottom temperature is 87°C, and the reflux ratio is 1. The bottom of the first distillation column 1 yields high-purity water (mass fraction ≥ 99.99%) and feed I (mass fraction ≥ 99.99% water). The top of the first distillation column 1 yields vapor stream I (97% tetrahydrofuran and 3% water).

[0083] The aforementioned gaseous stream I is condensed by condenser 4 and then enters the first reflux tank 3, where it is divided into two parts: stream I and stream II. Stream I (97% tetrahydrofuran and 3% water) is returned to the top of the first distillation column 1 via the first transfer pump 5 to form reflux. Stream II (97% tetrahydrofuran and 3% water) is pumped by the first transfer pump 5 to the top of the second distillation column 6 for second distillation. The operating pressure of the second distillation column 6 is 0.4 MPaG, the overall pressure drop is 0.004 MPaG, the top temperature is 119℃, and the bottom temperature is 126℃. The bottom of the second distillation column 6 yields high-purity tetrahydrofuran (tetrahydrofuran mass fraction ≥99.99%) and stream II (mass fraction ≥99.99% THF). The top of the second distillation column 6 yields gaseous stream II (91% THF and 9% water).

[0084] The vapor stream II collected from the top of the second distillation column 6 serves as the heat source for the first reboiler 2 of the first distillation column 1. After heat exchange between the two streams, material I collected from the bottom of the first distillation column 1 and vapor stream II, material I is returned to the first distillation column 1. Vapor stream II condenses to obtain liquid stream II, which enters the second reflux tank 7 and is then pumped by the second transfer pump 9 to the third distillation column 11 for third distillation. The operating pressure of the third distillation column 11 is 0.9 MPaG, the overall pressure drop is 0.004 MPaG, the top temperature is 144℃, and the bottom temperature is 159℃. The bottom product of the third distillation column 11 is material III (THF mass fraction ≥99.99%) and high-purity tetrahydrofuran (tetrahydrofuran mass fraction ≥99.99%). The top product of the third distillation column 11 is vapor stream III (88% THF and 12% water).

[0085] The vapor stream III collected from the top of the third distillation column 11 serves as the heat source for the second reboiler 8 at the bottom of the second distillation column 6. After heat exchange between the material II collected from the bottom of the second distillation column 6 and the vapor stream III at the second reboiler 8, the material II collected from the bottom of the second distillation column 6 returns to the second distillation column 6, and the vapor stream III is condensed to obtain the liquid stream III, which enters the third reflux tank 12 and is sent to the top of the first distillation column 1 via the third transfer pump 13. The material III collected from the bottom of the third distillation column 11 returns to the third distillation column 11 via the third reboiler 10.

[0086] In the above embodiment, the total heat load required by the first distillation column, the second distillation column, and the third distillation column is 458KW.

[0087] Example 2: The binary azeotrope used in this example is a mixed waste liquid of tetrahydrofuran and water from a chemical plant in Nantong City. The composition is: 90 wt% tetrahydrofuran and 10 wt% water, with a feed rate of 5000 kg / h. According to... Figure 1 The process shown involves the feedstock entering the first distillation column 1 for primary distillation. The operating pressure of the first distillation column 1 is -0.05 MPaG, the overall pressure drop is 0.004 MPaG, the top temperature is 44°C, the bottom temperature is 83°C, and the reflux ratio is 0.95. The bottom of the first distillation column 1 yields high-purity water (≥99.99% by mass) and feed I (≥99.99% water by mass). The top of the first distillation column 1 yields vapor stream I (96.5% THF and 3.5% water).

[0088] The aforementioned gaseous stream I is condensed by condenser 4 and then enters the first reflux tank 3, where it is divided into two parts: stream I and stream II (both stream I and stream II consist of 96.5% THF and 3.5% water). Stream I, as reflux liquid, is returned to the top of the first distillation column 1 via the first transfer pump 5 to form reflux. Stream II is transported by the first transfer pump 5 to the top of the second distillation column 6 for second distillation. The operating pressure of the second distillation column 6 is 0.3 MPaG, the overall pressure drop is 0.005 MPaG, the top temperature is 109℃, and the bottom temperature is 116℃. The bottom of the second distillation column 6 yields high-purity tetrahydrofuran (tetrahydrofuran mass fraction ≥99.99%) and stream II (mass fraction ≥99.99% THF). The top of the second distillation column 6 yields gaseous stream II (91.2% THF and 8.8% water).

[0089] The vapor stream II collected from the top of the second distillation column 6 serves as the heat source for the first reboiler 2 of the first distillation column 1. After heat exchange between the two streams, material I collected from the bottom of the first distillation column 1 and vapor stream II, material I is returned to the first distillation column 1. Vapor stream II condenses to obtain liquid stream II, which enters the second reflux tank 7 and is then pumped by the second transfer pump 9 to the third distillation column 11 for third distillation. The operating pressure of the third distillation column 11 is 0.8 MPaG, with a total pressure drop of 0.005 MPaG. The top temperature is 139°C, and the bottom temperature is 154°C. The bottom product of the third distillation column 11 is material III (≥99.99% THF by mass) and high-purity tetrahydrofuran (≥99.99% tetrahydrofuran by mass). The top product of the third distillation column 11 is vapor stream III (88.2% THF and 11.8% water).

[0090] The vapor stream III collected from the top of the third distillation column 11 serves as the heat source for the second reboiler 8 at the bottom of the second distillation column 6. After heat exchange between the material II collected from the bottom of the second distillation column 6 and the vapor stream III at the reboiler 8, the material II collected from the bottom of the second distillation column 6 returns to the second distillation column 6, and the vapor stream III condenses to obtain the liquid stream III, which enters the third reflux tank 12 and is sent to the top of the first distillation column 1 via the third distillation column transfer pump 13. The material III collected from the bottom of the third distillation column 11 returns to the third distillation column 11 via the third reboiler 10.

[0091] In the above embodiment, the total heat load required by the first distillation column, the second distillation column, and the third distillation column is 1196KW.

[0092] Example 3: The binary azeotrope used in this example is a mixed waste liquid of methanol and acetonitrile from a chemical plant in Shenyang City, with a composition of 85 wt% methanol and 15 wt% acetonitrile, and a feed rate of 1000 kg / h. According to... Figure 1The process shown involves the feedstock entering the first distillation column 1 for primary distillation. The operating pressure of the first distillation column 1 is 0.001 MPaG, the overall pressure drop is 0.004 MPaG, the top temperature is 64°C, the bottom temperature is 66°C, and the reflux ratio is 5. The bottom of the first distillation column 1 yields high-purity methanol (mass fraction ≥ 99.99%) and feed I (mass fraction ≥ 99.99% methanol). The top of the first distillation column 1 yields vapor stream I (77% methanol + 23% acetonitrile).

[0093] The vapor stream I collected from the top of the first distillation column 1 is condensed by condenser 4 and then enters the first reflux tank 3. It is then divided into two parts: stream I and stream II (both stream I and stream II consist of 77% methanol + 23% acetonitrile). Stream I, as reflux liquid, is returned to the top of the first distillation column 1 via the first transfer pump 5 to form reflux. Stream II is pumped by the first transfer pump 5 to the top of the second distillation column 6 for second distillation. The operating pressure of the second distillation column 6 is 0.2 MPaG, the overall pressure drop is 0.005 MPaG, the top temperature is 95℃, and the bottom temperature is 121℃. The bottom of the second distillation column 6 yields high-purity acetonitrile (acetonitrile mass fraction ≥ 99.99%) and stream II (acetonitrile mass fraction ≥ 99.99%). The top of the second distillation column 6 yields vapor stream II (88.4% methanol + 11.6% acetonitrile).

[0094] The vapor stream II collected from the top of the second distillation column 6 serves as the heat source for the first reboiler 2 of the first distillation column 1. After heat exchange between the two streams, material I collected from the bottom of the first distillation column 1 and vapor stream II, material I is returned to the first distillation column 1. Vapor stream II condenses to obtain liquid stream II, which enters the second reflux tank 7 and is then pumped by the second transfer pump 9 to the third distillation column 11 for third distillation. The operating pressure of the third distillation column 11 is 0.5 MPaG, with a total pressure drop of 0.005 MPaG. The top temperature is 118℃, and the bottom temperature is 151℃. The bottom of the third distillation column 11 produces material III (acetonitrile with a mass fraction ≥99.99%) and high-purity acetonitrile (acetonitrile mass fraction ≥99.99%). The top of the third distillation column 11 produces vapor stream III (97% methanol and 3% acetonitrile).

[0095] The vapor stream III collected from the top of the third distillation column 11 serves as the heat source for the second reboiler 8 at the bottom of the second distillation column 6. After heat exchange between the material II collected from the bottom of the second distillation column 6 and the vapor stream III at the second reboiler 8, the material II collected from the bottom of the second distillation column 6 returns to the second distillation column 6, and the vapor stream III is condensed to obtain the liquid stream III, which enters the third reflux tank 12 and is sent to the top of the first distillation column 1 via the third transfer pump 13. The material III collected from the bottom of the third distillation column 11 returns to the third distillation column 11 via the third reboiler 10.

[0096] In the above embodiment, the total heat load required by the first distillation column, the second distillation column, and the third distillation column is 1740KW.

[0097] Comparative Example 1

[0098] The binary azeotrope used in this comparative example was a mixed waste liquid of tetrahydrofuran and water from a chemical plant in Lu'an City, with a composition of 80 wt% tetrahydrofuran and 20 wt% water, and a feed rate of 2000 kg / h. Figure 2 The process shown involves the feedstock entering the first distillation column 1 for primary distillation. The operating pressure of the first distillation column 1 is -0.04 MPaG, the overall pressure drop is 0.004 MPaG, the top temperature is 49°C, the bottom temperature is 87°C, and the reflux ratio is 1. The bottom product of the first distillation column 1 is water (99.9% by mass) and feed I (99.9% by mass of water). The top product of the first distillation column 1 is vapor stream I (97% THF and 3% water).

[0099] The vapor stream I collected from the top of the first distillation column 1 is condensed by condenser 4 and then enters the first reflux tank 3. It is then divided into two parts: stream I and stream II. Stream I, as reflux liquid, is returned to the top of the first distillation column 1 via the first transfer pump 5. Stream II is pumped by the first transfer pump 5 to the top of the second distillation column 6 for second distillation. The operating pressure of the second distillation column 6 is 0.9 MPaG, the overall pressure drop is 0.004 MPaG, the top temperature is 144℃, and the bottom temperature is 159℃. The bottom of the second distillation column 6 yields tetrahydrofuran (tetrahydrofuran mass fraction ≥99.99%) and stream II (THF mass fraction ≥99.99%). The top of the second distillation column 6 yields vapor stream II (88% THF and 12% water).

[0100] The vapor stream II collected from the top of the second distillation column 6 serves as the heat source for the first reboiler 2 at the bottom of the first distillation column 1. After heat exchange between the material I collected from the bottom of the first distillation column 1 and the vapor stream II at the first reboiler 2, the material I collected from the bottom of the first distillation column 1 returns to the first distillation column 1, and the vapor stream II is condensed to obtain liquid stream II which enters the second reflux tank 7 and is sent to the top of the first distillation column 1 by the second distillation column transfer pump 9. The material II collected from the bottom of the second distillation column 6 returns to the second distillation column 6 via the second reboiler 8.

[0101] In the above comparative example, the total heat load required by the first and second distillation columns is 962KW.

[0102] As can be seen from the comparison between Example 1 and Comparative Example 1, the energy consumption of the three-tower process in Example 1 is reduced by 52.4% compared with the two-tower process in Comparative Example 1.

[0103] Comparative Example 2

[0104] The binary azeotrope used in this comparative example was a mixed waste liquid of tetrahydrofuran and water from a chemical plant in Nantong City. If it were a dual-tower distillation process, the composition would be: 90 wt% tetrahydrofuran and 10 wt% water, with a feed rate of 5000 kg / h. Figure 2 The process shown involves the feedstock entering the first distillation column 1 for primary distillation. The operating pressure of the first distillation column 1 is -0.05 MPaG, the overall pressure drop is 0.004 MPaG, the top temperature is 44°C, the bottom temperature is 83°C, and the reflux ratio is 0.95. The bottom product of the first distillation column 1 is water (99.99% by mass) and feed I (≥99.99% water by mass). The top product of the first distillation column 1 is vapor stream I (96.5% THF and 3.5% water).

[0105] The vapor stream I collected from the top of the first distillation column 1 is condensed by condenser 4 and then enters the first reflux tank 3. It is then divided into two parts: stream I and stream II. Stream I, as reflux liquid, is returned to the top of the first distillation column 1 via the first transfer pump 5. Stream II is pumped by the first transfer pump 5 to the top of the second distillation column 6 for second distillation. The operating pressure of the second distillation column 6 is 0.8 MPaG, the overall pressure drop is 0.005 MPaG, the top temperature is 139℃, and the bottom temperature is 154℃. The bottom of the second distillation column 6 yields tetrahydrofuran (tetrahydrofuran mass fraction ≥99.99%) and stream II (THF mass fraction ≥99.99%). The top of the second distillation column 6 yields vapor stream II (88.2% THF and 11.8% water).

[0106] The vapor stream II collected from the top of the second distillation column 6 serves as the heat source for the first reboiler 2 at the bottom of the first distillation column 1. After heat exchange between the material I collected from the bottom of the first distillation column 1 and the vapor stream II at the first reboiler 2, the material I collected from the bottom of the first distillation column 1 returns to the first distillation column 1, and the vapor stream II is condensed to obtain liquid stream II which enters the second reflux tank 7 and is sent to the top of the first distillation column 1 by the second distillation column transfer pump 9. The material II collected from the bottom of the second distillation column 6 returns to the second distillation column 6 via the second reboiler 8.

[0107] In the above comparative example, the total heat load required by the first and second distillation columns is 2632KW.

[0108] As can be seen from the comparison between Example 2 and Comparative Example 2, the energy consumption of the three-tower process in Example 2 is reduced by 54.6% compared with the two-tower process in Comparative Example 2.

[0109] Comparative Example 3

[0110] The binary azeotrope used in this comparative example was a mixed waste liquid of methanol and acetonitrile from a chemical plant in Shenyang City, with a composition of 85 wt% methanol and 15 wt% acetonitrile, and a feed rate of 1000 kg / h. Figure 2 The process shown involves the feedstock entering the first distillation column 1 for primary distillation. The operating pressure of the first distillation column 1 is 0.001 MPaG, the overall pressure drop is 0.004 MPaG, the top temperature is 64°C, the bottom temperature is 66°C, and the reflux ratio is 5. The bottom product of the first distillation column 1 is methanol (99.99% by mass) and feed I (99.99% methanol by mass). The top product of the first distillation column 1 is vapor stream I (77% methanol and 23% acetonitrile).

[0111] The vapor stream I collected from the top of the first distillation column 1 is condensed by condenser 4 and enters the first reflux tank 3. It then splits into two parts: stream I and stream II. Stream I, as reflux liquid, is returned to the top of the first distillation column 1 via the first transfer pump 5. Stream II is pumped by the first transfer pump 5 to the top of the second distillation column 6 for second distillation. The operating pressure of the second distillation column 6 is 0.5 MPaG, the overall pressure drop is 0.005 MPaG, the top temperature is 118℃, and the bottom temperature is 151℃. Acetonitrile (acetonitrile mass fraction ≥99.99%) and stream II (acetonitrile mass fraction ≥99.99%) are collected from the bottom of the second distillation column 6. The top of the second distillation column 6 collects vapor stream II (97% methanol and 3% acetonitrile).

[0112] The vapor stream II collected from the top of the second distillation column 6 serves as the heat source for the first reboiler 2 at the bottom of the first distillation column 1. After heat exchange between the material I collected from the bottom of the first distillation column 1 and the vapor stream II at the first reboiler 2, the material I collected from the bottom of the first distillation column 1 returns to the first distillation column 1, and the vapor stream II is condensed to obtain liquid stream II which enters the second reflux tank 7 and is sent to the top of the first distillation column 1 via the second transfer pump 9. The material II collected from the bottom of the second distillation column 6 returns to the second distillation column 6 via the second reboiler 8.

[0113] In the above comparative example, the total heat load required by the first and second distillation columns is 3520KW.

[0114] As can be seen from the data comparison between Example 3 and Comparative Example 3, the energy consumption of the three-tower process in Example 3 is reduced by 50.6% compared with the two-tower process in Comparative Example 3.

[0115] The technical solution of this utility model is not limited to the specific embodiments described above. All technical modifications made based on the technical solution of this utility model shall fall within the protection scope of this utility model.

Claims

1. An apparatus for separating a binary azeotrope, comprising a first rectifying column, a second rectifying column and a third rectifying column connected in sequence; a feed inlet is arranged in the middle of the first rectifying column, characterized in that, The apparatus further includes a first reboiler connected to the bottom material outlet of the first distillation column, and a second reboiler connected to the bottom material outlet of the second distillation column; the top vapor outlet of the second distillation column is connected to the heat source inlet of the first reboiler, and the heat source outlet of the first reboiler is connected to the top stream inlet of the second distillation column; the top vapor outlet of the third distillation column is connected to the heat source inlet of the second reboiler, and the heat source outlet of the second reboiler is connected to the top stream inlet of the third distillation column.

2. The apparatus of claim 1, wherein, The apparatus further includes a condenser and a first reflux tank. The inlet of the condenser is connected to the top vapor outlet of the first distillation column, and the outlet of the condenser is connected to the top feed inlet of the first reflux tank. The bottom outlet of the first reflux tank is connected to the top vapor inlet of the first distillation column and the top vapor inlet of the second distillation column, respectively.

3. The apparatus according to claim 1, characterized in that, The apparatus further includes a second reflux tank, the top inlet of which is connected to the heat source outlet of the first reboiler, and the bottom outlet of which is connected to the steam inlet at the top of the third distillation column.

4. The apparatus according to claim 1, characterized in that, The device also includes a third reflux tank, the top inlet of which is connected to the heat source outlet of the second reboiler, and the bottom outlet of which is connected to the middle inlet of the first distillation column.

5. The apparatus according to claim 1, characterized in that, The apparatus also includes a third reboiler for the bottom of the third distillation column, wherein the heat source inlet of the third reboiler is connected to the outlet of the bottom of the third distillation column, and the heat source outlet of the third reboiler is connected to the inlet of the bottom of the third distillation column.

6. The apparatus according to claim 1, characterized in that, The power for material conveying in the device is provided by a conveying pump.

7. The apparatus according to claim 1, characterized in that, The device is connected via a pipe.

8. The apparatus according to claim 1, characterized in that, The theoretical number of plates in the first distillation column is 10-70.

9. The apparatus according to claim 1, characterized in that, The theoretical number of plates in the second distillation column is 10-70.

10. The apparatus according to claim 1, characterized in that, The theoretical number of plates in the third distillation column is 10-70.

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