Partition plate tower for separating water through methanol extractive distillation and method for separating water through methanol extractive distillation
By designing a diaphragm tower and using extractant separation technology, the problems of high energy consumption and large equipment investment in methanol-water separation have been solved, achieving efficient and low-cost methanol recovery and water separation, which is suitable for the biodiesel industry.
Patent Information
- Application Number
- CN202411648412.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-18
- Publication Date
- 2026-05-19
AI Technical Summary
Existing methanol-water separation technologies suffer from high energy consumption and large investment costs. Furthermore, the introduction of azeotropic agents in extractive distillation methods increases the separation challenges, making it difficult to meet the needs of excess methanol recycling in the biodiesel industry.
Methanol extraction and distillation is carried out using a partitioned column. The column cavity is divided into a methanol recovery zone, a dehydration zone, and an extractant recovery zone by vertical and horizontal partitions. Extractant is used for extraction and distillation separation, which simplifies the process and reduces equipment investment.
It achieves the separation of high-purity methanol and water, reduces separation costs and energy consumption, simplifies the process, and reduces equipment investment and waste liquid treatment costs.
Smart Images
Figure CN122057249A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a baffled column for methanol extraction distillation to separate water and a method for methanol extraction distillation to separate water, belonging to the field of separation and purification technology, particularly the field of methanol distillation to separate water. Background Technology
[0002] Methanol is an important organic solvent and synthetic raw material, widely used in energy, chemical and other fields, and has a very large market demand.
[0003] In recent years, the biodiesel industry has developed rapidly. The two fundamental reactions in the production of biodiesel from oils—the esterification of fatty acids with methanol and the transesterification of fatty acid glycerides with methanol—are both reversible equilibrium reactions. Typically, the conversion rate of oil feedstocks is improved by increasing the alcohol-to-oil molar ratio, and excess methanol needs to be recycled. However, oil feedstocks usually contain a certain amount of free fatty acids, necessitating thorough separation of water entrained in the feedstock and water produced as a byproduct of the esterification reaction to prevent its accumulation in the methanol cycle.
[0004] In the industrial production of methanol or the recycling of methanol in processes, the refining and separation of methanol containing water is a crucial issue for methanol-related industries. The separation and recovery of methanol-water systems has been extensively studied in both academia and industry. Current methods for separating methanol-water mixtures include conventional distillation, azeotropic distillation, extractive distillation, and membrane separation.
[0005] Methanol has a boiling point of approximately 64°C at atmospheric pressure, while water has a boiling point of approximately 100°C at atmospheric pressure. Utilizing this difference in volatility, methanol and water can be separated by distillation. Industrial practice has evolved from conventional single-tower distillation to double-tower, triple-tower, and even multi-tower distillation technologies for methanol and water separation. For example, CN101084176A discloses a method for recovering methanol using 3-5 evaporation stages to recover methanol from wastewater, ultimately obtaining 95 wt% methanol. Depending on the separation requirements, distillation can yield methanol with a purity of over 99.9 wt%, but distillation typically involves higher energy consumption and investment costs.
[0006] A methanol-water azeotropic distillation separation method has been developed by utilizing the property that water forms azeotropes with some organic solvents. For example, methanol-water-ethyl acetate and methanol-water-benzene ternary azeotropic dehydration are commonly used in the purification of organic reagents. This method can obtain 99.9% methanol, but the introduction of azeotropic agents such as ethyl acetate increases the separation problem of the ternary system. Taking advantage of the characteristic that the azeotropic composition of azeotropes changes with pressure, CN113149838A discloses a method and control structure for separating ethyl acetate-methanol-water by dual-tower pressure-swinging batch distillation. Through the operation of a low-pressure column (LPC) and a high-pressure column (HPC), the ternary mixture is separated. After separation, the contents of ethyl acetate and water are both greater than 99.9 wt%, and the content of methanol is greater than 99.5 wt%. CN114939283A discloses a method for separating and purifying a ternary azeotropic mixture of ethyl acetate, methanol, and water. It uses dimethyl sulfoxide as the extraction solvent and a double-plate extractive distillation column as the separation and purification device. The double-plate extractive distillation column is divided from left to right into a dehydration and solvent recovery column, an extractive distillation column, and a methanol recovery column, directly separating the ethyl acetate-methanol-water ternary system. While azeotropic distillation can separate methanol and water, it also increases the difficulty of separating the azeotropic system.
[0007] Based on the colligative properties of solutions, a method for separating methanol-water by extractive distillation was developed by introducing high-boiling-point substances to alter the relative volatility of the system. CN100488931C discloses a method for separating methyl acetal-methanol-water by salt-added composite extractive distillation, which uses a salt-containing ethylene glycol extractant for distillation separation. Approximately 8 wt% methanol wastewater can be separated to obtain 99.8 wt% methanol, and the water separated by the salt-containing mixed extractant is recycled. Extractive distillation can also utilize multi-tower distillation to reduce energy consumption. For example, CN110903167A discloses a method for separating acetonitrile-methanol-water mixtures by thermally integrated three-tower vacuum extractive distillation, which reduces energy consumption through thermal integration.
[0008] To reduce energy consumption in methanol-water separation, several combined technologies have been developed. For example, CN103435444A discloses a method for separating methanol-water mixtures. This method first concentrates the methanol-water mixture to over 90 wt% in a distillation column, then dehydrates it using a superabsorbent resin, ultimately obtaining a methanol product with a purity of over 99.95 wt%. The superabsorbent resin is then dehydrated, regenerated, and recycled. CN114011108A discloses a system and method for separating methanol-water using a distillation-coupled membrane. This method feeds a methanol-water mixture into a distillation column, where most of the water is separated from the bottom of the column. The residual water and methanol mixture distilled from the top of the column are condensed and sent to a membrane separator. The methanol and water are further separated by a unipolar pervaporation membrane, increasing the methanol concentration in the permeate to over 99.9 wt%. This technology can achieve the stepwise separation of methanol at different concentrations.
[0009] Efficient methanol-water separation still faces challenges such as process simplification and energy consumption reduction. This invention addresses the problem of excess methanol recycling and water separation in the oil-to-biodiesel production industry by providing a baffled column and method for methanol extraction and distillation to separate water, aiming to reduce energy consumption and increase efficiency in the oil-to-biodiesel production industry. Summary of the Invention
[0010] To address the aforementioned shortcomings and deficiencies, the present invention aims to provide a baffled column for methanol extractive distillation and water separation, as well as a method for methanol extractive distillation and water separation. This method simplifies the process, reduces investment, lowers separation and recovery costs, and improves the purity of the separated product.
[0011] To achieve the above objectives, on the one hand, the present invention provides a partitioned column for methanol extraction distillation and water separation, comprising a column body, wherein a vertical partition and a horizontal partition are disposed within the column body, the horizontal partition being disposed between the top of the vertical partition and the right side wall of the column body; the vertical partition divides the inner cavity of the column body from top to bottom into a methanol recovery zone, a dehydration zone, and an extractant recovery zone.
[0012] The tower body is provided with an aqueous methanol inlet, a recovered methanol outlet, a produced water outlet, an extractant outlet, and an extractant inlet. The height of the aqueous methanol inlet is not lower than the lower end of the vertical partition, the height of the recovered methanol outlet is higher than the upper end of the vertical partition, the height of the produced water outlet is not higher than the upper end of the vertical partition, the extractant outlet is lower than the lower end of the vertical partition, and the extractant inlet is located above the aqueous methanol inlet.
[0013] In the partitioned tower described above, the upper and lower ends of the vertical partitions within the tower body are at a certain distance from the top and bottom of the tower. These vertical partitions divide the inner cavity of the tower body into three functional zones from top to bottom: a methanol recovery zone, a dehydration zone, and an extractant recovery zone. Specifically, the methanol recovery zone extends from the top of the tower to the upper end of the vertical partition; the dehydration zone (also called the water separation zone) is located between the upper and lower ends of the vertical partition; and the extractant recovery zone extends from the lower end of the vertical partition to the bottom of the tower. The methanol recovery zone primarily performs methanol-water extraction and distillation separation, yielding high-purity methanol from the recovered methanol outlet. The dehydration zone primarily separates water from the extractant, yielding high-purity water from the extracted water outlet. The extractant recovery zone primarily regenerates the extractant by separating water from it, yielding the extractant from the extractant outlet. The vertical and horizontal partitions divide the dehydration zone into left and right areas: the left area is a distillation separation zone containing methanol and water, while the right area is a distillation separation zone primarily containing water.
[0014] In the partition tower described above in this invention, the methanol recovery outlet is located at the top of the tower body, and the extractant outlet is located at the bottom of the tower body.
[0015] The structure of the baffle tower described above is not limited to having the five material inlets and outlets mentioned above. Depending on the needs, other material inlets and outlets can be added to the structure of the baffle tower. For example, the tower body may also be equipped with a methanol reflux port, a water reflux port, and a reboiling steam reflux port in the methanol recovery zone, dehydration zone, and extractant recovery zone, respectively.
[0016] In the plate column described above in this invention, the theoretical number of plates in the methanol recovery zone, dehydration zone, and extractant recovery zone are 10-40, 5-20, and 3-10, respectively. Increasing the number of plates is beneficial for improving separation purity, but it also increases equipment costs.
[0017] On the other hand, the present invention provides a method for methanol extraction distillation to separate water, wherein the method is implemented using the aforementioned baffled column for methanol extraction distillation to separate water, and includes the following steps:
[0018] Aqueous methanol and extractant are continuously fed into a baffled tower from the aqueous methanol inlet and the extractant inlet, respectively. In the methanol recovery zone, methanol and water vapor are separated by liquid distillation, and high-purity methanol is obtained from the recovered methanol outlet. The water separated by the extractant enters the extractant recovery zone, where the extractant is concentrated and separated from the extractant outlet. The water vapor enters the dehydration zone and is finally separated from the tower body from the produced water outlet.
[0019] The extractant separated from the extractant outlet is then introduced into the baffle column through the extractant feed inlet.
[0020] In the method described above in this invention, regardless of whether the aqueous methanol contains glycerol, the aqueous methanol and the extractant (which can be glycerol or other extractants containing glycerol) can be continuously fed into the baffle column from the aqueous methanol inlet and the extractant inlet, respectively, and then the subsequent separation operation can be carried out.
[0021] In the method described above by the present invention, preferably, when the aqueous methanol contains glycerol, the method includes:
[0022] Aqueous methanol is continuously fed into the baffle tower from the aqueous methanol inlet. In the methanol recovery zone, methanol and water vapor are separated by distillation, and high-purity methanol is obtained from the recovered methanol outlet. The water separated by the extractant enters the extractant recovery zone, where the extractant is concentrated and separated from the extractant outlet. The water vapor enters the dehydration zone and is finally separated from the tower body from the produced water outlet.
[0023] The extractant separated from the extractant outlet is fed into a baffled column through the extractant inlet, wherein the extractant is glycerol. This invention improves separation degree and separation efficiency by recycling the extractant separated from the extractant outlet into the baffled column through the extractant inlet.
[0024] In the method described above in this invention, when the aqueous methanol does not contain glycerol, the total weight of the aqueous methanol is 100%, wherein the methanol content is greater than or equal to 20 wt% and the water content is less than or equal to 80 wt%.
[0025] When the aqueous methanol contains glycerol, it shall be calculated as 100% of the total weight of the aqueous methanol, wherein the methanol content is greater than or equal to 20 wt%, the glycerol content is less than or equal to 50 wt%, and the balance is water. A high water content in the aqueous methanol necessitates an increase in the amount of extractant, which also increases operating energy consumption and workload. In systems involving oils and fats, the content of oils and fats and their derivatives in the aqueous methanol should be less than 5 wt%.
[0026] In the method described above in this invention, the mass ratio of the aqueous methanol to the extractant is 5:1 to 1:3.
[0027] In the methods described above in this invention, the extractant comprises glycerol and / or polyglycerol with a molecular weight less than 1000. Preferably, the glycerol content in the extractant is greater than 80 wt%, that is, the extractant is preferably glycerol, and when the extractant is a mixture of glycerol and polyglycerol with a molecular weight less than 1000, the glycerol content is greater than 80 wt%.
[0028] In the method described above, the pressure of the extractive distillation operation performed in the partition column is atmospheric pressure to 2 MPa. The composition of the aqueous methanol, the material temperature, and the heat recovery requirements are all important factors affecting the operating pressure. If the water content in the aqueous methanol is low, the temperature is less than 120°C, and the heat recovery requirements are low, atmospheric pressure extractive distillation can be used for separation. Increasing the operating pressure will improve the steam heat grade, but it also requires increasing the reboiling temperature.
[0029] The method described above in this invention further includes: condensing and refluxing the methanol recovered from the methanol recovery outlet, and / or condensing and refluxing the water vapor flowing out from the extracted water outlet, and / or reboiling the extractant separated from the extractant outlet in a reboiler and sending the resulting steam into the baffle tower through the reboiler steam reflux port.
[0030] In the method described above in this invention, depending on the operating pressure, the feed temperature of aqueous methanol and extractant is room temperature to 200°C, the temperature for condensing methanol is 60-170°C, and / or the temperature for condensing water vapor is 90-210°C, and / or the reboiling temperature is 120-260°C.
[0031] In the method described above, the reflux ratio for methanol recovery in the plate column extractive distillation operation is no greater than 3 (a reflux ratio of 0 indicates that methanol reflux is not required), and the reflux ratio for the collected water is no greater than 2 (a reflux ratio of 0 indicates that water reflux is not required). The temperature and pressure conditions, the number of plates, and the purity of recovered methanol, water, and extractant in the extractive distillation operation affect the reflux ratio. Increasing the number of plates and decreasing the purity can reduce the reflux ratio; increasing the reflux ratio will increase the purity of methanol and water, but will increase energy consumption.
[0032] The method provided by this invention uses an extractant to extract and distill aqueous methanol in a partitioned column to separate methanol and water, and then recovers the extractant. The purity of the separation can be controlled according to the intended use and requirements. In some embodiments of this invention, after extraction and distillation, the water content in the extractant is less than 25 wt%, the methanol content in the collected water is less than 0.1 wt%, the water content in the recovered methanol is less than or equal to 1 wt%, and the recovered methanol content is greater than 99 wt%. To obtain a product with higher purity, operating conditions can be optimized or further separation can be performed.
[0033] Compared with the prior art, the beneficial technical effects achieved by the present invention include:
[0034] 1. The extractant used in this invention is inexpensive and readily available, and can be derived from byproducts of biodiesel production, making it convenient to source materials locally and significantly reducing raw material costs;
[0035] 2. This invention uses a partitioned column distillation, which can reduce the number of equipment, simplify the distillation process, and reduce equipment investment;
[0036] 3. This invention performs distillation separation of aqueous methanol, directly recovering methanol and separating water, which can reduce waste liquid treatment costs;
[0037] 4. This invention uses a partitioned column for extraction and distillation to efficiently separate aqueous methanol, which can reduce separation costs.
[0038] In summary, the method for separating water by partition tower and methanol extraction distillation provided by this invention can simplify the process, reduce investment, reduce separation and recovery costs, and improve the purity of the separated products. Attached Figure Description
[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0040] Figure 1This is a schematic diagram of the structure of a partition column for methanol extraction distillation and water separation provided in Embodiment 1 of the present invention.
[0041] Explanation of main icon numbers:
[0042] 1. Tower body;
[0043] 11. Water-containing methanol inlet, 12. Recovered methanol outlet, 13. Methanol reflux outlet, 14. Produced water outlet, 15. Water reflux outlet, 16. Extractant outlet, 17. Reboiler steam reflux outlet and 18. Extractant inlet.
[0044] 2. Vertical partitions;
[0045] 3. Horizontal partitions;
[0046] 4. First condenser;
[0047] 5. Second condenser;
[0048] 6. Reboiler. Detailed Implementation
[0049] It should be noted that the term "comprising" and any variations thereof in the specification, claims, and accompanying drawings of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or devices.
[0050] In this invention, the terms "upper," "lower," "inner," "outer," "middle," "left," "right," "top," and "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing the invention and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.
[0051] Furthermore, some of the aforementioned terms, besides indicating direction or positional relationships, may also have other meanings. For example, the term "above" may, in certain circumstances, indicate a dependency or connection. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.
[0052] Furthermore, the terms "setup" and "connection" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.
[0053] The "range" disclosed in this invention is given in the form of a lower limit and an upper limit. It can be one or more lower limits and one or more upper limits, respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower and upper limits define the boundaries of the particular range. All ranges defined in this way are composable, meaning that any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for specific parameters, it is also expected that ranges of 60-110 and 80-120 are also expected. Furthermore, if the listed minimum range values are 1 and 2, and the listed maximum range values are 3, 4, and 5, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5.
[0054] In this invention, unless otherwise specified, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this invention, and "0-5" is simply a shortened representation of these numerical combinations.
[0055] In this invention, unless otherwise specified, all embodiments and preferred embodiments mentioned in this invention can be combined with each other to form new technical solutions.
[0056] In this invention, unless otherwise specified, all technical features and preferred features mentioned in this invention can be combined with each other to form new technical solutions.
[0057] In this invention, unless otherwise specified, all steps mentioned herein may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.
[0058] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying tables, drawings, and embodiments. The embodiments described below are some, but not all, embodiments of this invention, and are only used to illustrate the invention, and should not be considered as limiting the scope of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.
[0059] Example 1
[0060] This embodiment provides a baffle column for methanol extraction distillation and water separation, as shown in the schematic diagram below. Figure 1 As shown, from Figure 1 As can be seen from the diagram, the partition tower includes a tower body 1, wherein a vertical partition 2 and a horizontal partition 3 are provided inside the tower body 1. The horizontal partition 3 is located between the top of the vertical partition 2 and the right side wall of the tower body 1. The vertical partition 2 divides the inner cavity of the tower body 1 into a methanol recovery zone, a dehydration zone, and an extractant recovery zone from top to bottom. That is, the area from the top of the tower to the upper end of the vertical partition 2 is the methanol recovery zone, the area between the upper and lower ends of the vertical partition 2 is the dehydration zone (also called the water separation zone), and the area from the lower end of the vertical partition 2 to the bottom of the tower is the extractant recovery zone.
[0061] The tower body 1 is equipped with a water-containing methanol inlet 11, a recovered methanol outlet 12, a methanol reflux outlet 13, a produced water outlet 14, a water reflux outlet 15, an extractant outlet 16, a reboiler steam reflux outlet 17, and an extractant inlet 18. The water-containing methanol inlet 11 is located in the middle of the tower body 1, and its height is not lower than the lower end of the vertical partition 2. The recovered methanol outlet 12 is located at the top of the tower body 1, and the methanol reflux outlet 13 is located in the upper part of the tower body 1, near the top. The recovered methanol outlet 12 is connected to the methanol reflux outlet 13 via a pipeline through the first condenser 4. The produced water outlet 14 is located at... The height is not higher than the upper end of the vertical partition. The water reflux port 15 is located below the produced water outlet 14, and the produced water outlet 14 is connected to the produced water outlet 14 through a pipeline via the second condenser 5. The extractant outlet 16 is located at the bottom of the tower body 1. The reboiler steam reflux port 17 is located at the lower part of the tower body 1 and near the bottom of the tower. The extractant outlet 16 is connected to the reboiler steam reflux port 17 through a pipeline via the reboiler 6. The extractant inlet 18 is located above the aqueous methanol inlet 11, and the extractant outlet 16 is also connected to the extractant inlet 18 through a pipeline.
[0062] Example 2
[0063] This embodiment provides a method for separating water from an aqueous methanol solution (composed of 50 wt% methanol, 30 wt% water, and 20 wt% glycerol after separation) from a biodiesel company. This method utilizes the partitioned column provided in Example 1. The partitioned column used in this embodiment has 40, 20, and 10 plates in its methanol recovery zone, dehydration zone, and extractant recovery zone, respectively. The method includes the following specific steps:
[0064] The aqueous methanol solution is heated to 100°C and then continuously fed into the partition column from the aqueous methanol inlet (located horizontally at the 10th tray in the dehydration zone). In the methanol recovery zone, methanol and water vapor are separated by distillation (methanol is concentrated upwards, while water is separated downwards). The water separated by the extractant enters the extractant recovery zone, where the extractant is concentrated and separated from the extractant outlet at the bottom of the partition column. The water vapor enters the dehydration zone and is finally separated from the column body from the produced water outlet. Methanol, water, and extractant (glycerol) are continuously extracted in proportion to their composition from the recovered methanol outlet, the produced water outlet, and the extractant outlet, respectively. Methanol is obtained from the recovered methanol outlet, and the recovered methanol is condensed, refluxed, and extracted. Water vapor flowing from the produced water outlet is condensed, refluxed, and extracted. A portion of the extractant separated from the extractant outlet (denoted as regenerated extractant) enters the diaphragm column through the extractant feed inlet. The portion of the extractant separated from the extractant outlet is reboiled in the reboiler, and the resulting steam is sent back to the diaphragm column through the reboiler steam reflux port. The extractive distillation operation in the diaphragm column is performed at atmospheric pressure. The methanol is condensed at a temperature of 64°C with a reflux ratio of 2. The water vapor is condensed at a temperature of 100°C with a reflux ratio of 1. The glycerol extractant is reboiled at a temperature of 140°C. The reboiler steam is returned from the 9th tray of the extractant recovery zone. The regenerated extractant (with a mass ratio of 1:5 to the aqueous methanol solution) is returned from the 5th tray of the methanol recovery zone.
[0065] After extraction and distillation, the water content in methanol was 0.5 wt%, the methanol content in water was 0.01 wt%, the water content in the extractant (glycerol) was 10.5 wt%, and no methanol was detected.
[0066] Example 3
[0067] This embodiment provides a method for separating water from an aqueous methanol solution (composed of 20 wt% methanol, 60 wt% water, and 20 wt% glycerol after separation) from a biodiesel company. This method utilizes the partitioned column provided in Example 1. The partitioned column used in this embodiment has 40, 10, and 5 plates in its methanol recovery zone, dehydration zone, and extractant recovery zone, respectively. The method includes the following specific steps:
[0068] The aqueous methanol solution is heated to 150°C and then continuously fed into the partition column from the aqueous methanol inlet (located horizontally at the 5th tray in the dehydration zone). In the methanol recovery zone, methanol and water vapor are separated by distillation (methanol is concentrated upwards, while water is separated downwards). The water separated by the extractant enters the extractant recovery zone, where the extractant is concentrated and separated from the extractant outlet at the bottom of the partition column. The water vapor enters the dehydration zone and is finally separated from the column body from the produced water outlet. Methanol, water, and extractant (glycerol) are continuously extracted in proportion to their composition from the recovered methanol outlet, the produced water outlet, and the extractant outlet, respectively. Methanol is obtained from the recovered methanol outlet, and the recovered methanol is condensed, refluxed, and extracted. Water vapor flowing out from the produced water outlet is condensed, refluxed, and extracted. A portion of the extractant separated from the extractant outlet (referred to as the regenerated extractant) is fed into the baffled tower through the extractant inlet. The portion of the extractant separated from the extractant outlet is reboiled in the reboiler, and the resulting steam is sent to the baffled tower through the reboiler steam reflux port. The pressure of the extractive distillation operation in the partition column is 1 MPa, the temperature for condensing methanol is 138°C with a reflux ratio of 0.5, the temperature for condensing water vapor is 180°C with a reflux ratio of 1, the temperature for reboiling the glycerol extractant is 220°C, the reboiling steam is returned from the 5th tray of the extractant recovery zone, and the regenerated extractant (with a mass ratio of 1:1 to the aqueous methanol solution) is returned from the 10th tray of the methanol recovery zone.
[0069] After extraction and distillation, the water content in methanol was 1 wt%, the methanol content in water was 0.01 wt%, the water content in the extractant (glycerol) was 12 wt%, and methanol was not detected.
[0070] Example 4
[0071] This embodiment provides a method for separating water from an aqueous methanol solution (composed of 80 wt% methanol and 20 wt% water after separation) from a biodiesel company using methanol extraction distillation. This method utilizes the partitioned column provided in Example 1. The partitioned column used in this embodiment has 25, 20, and 10 plates in its methanol recovery zone, dehydration zone, and extractant recovery zone, respectively. The method includes the following specific steps:
[0072] The aqueous methanol solution is heated to 160°C and then continuously fed into the partition column from the aqueous methanol inlet (located horizontally on the 10th tray in the dehydration zone). The extractant is a glycerol solution containing 8 wt% diglycerol and 3 wt% triglycerol, with a water content of less than 0.1 wt%, fed into the partition column from the 4th tray in the methanol recovery zone. The mass ratio of extractant to aqueous methanol is 3:1. In the methanol recovery zone, methanol and water vapor are separated by distillation (methanol is concentrated upwards, while water is separated downwards). The water separated by the extractant enters the extractant recovery zone, where the extractant is concentrated and separated from the extractant outlet at the bottom of the partition column. The water vapor portion enters the dehydration zone and is finally separated from the column body from the produced water outlet. Methanol, water, and extractant (glycerol) are continuously extracted in proportion to their composition from the recovered methanol outlet, the produced water outlet, and the extractant outlet, respectively. Methanol is obtained from the recovered methanol outlet, and the recovered methanol is condensed, refluxed, and extracted. Water vapor flowing out from the produced water outlet is condensed, refluxed, and extracted. A portion of the extractant separated from the extractant outlet (referred to as the regenerated extractant) is fed into the baffled tower through the extractant inlet. The portion of the extractant separated from the extractant outlet is reboiled in the reboiler, and the resulting steam is sent to the baffled tower through the reboiler steam reflux port. The pressure of the extractive distillation operation in the partition column is 2 MPa, the temperature for condensing methanol is 166°C with a reflux ratio of 3, the temperature for condensing water vapor is 210°C with a reflux ratio of 0.3, the temperature for reboiling the glycerol extractant is 260°C, the reboiling steam is returned from the 9th tray of the extractant recovery zone, and the regenerated extractant (with a mass ratio of 3:1 to the aqueous methanol solution) is returned from the 4th tray of the methanol recovery zone.
[0073] After extraction and distillation separation, the water content in methanol was 0.01 wt%, the methanol content in water was 0.01 wt%, the water content in the extractant was 16 wt%, and no methanol was detected.
[0074] Example 5
[0075] This embodiment provides a method for separating water from an aqueous methanol solution (composed of 60 wt% methanol, 20 wt% water, and 20 wt% glycerol after separation) from a biodiesel company. This method utilizes the partitioned column provided in Example 1. The partitioned column used in this embodiment has 25, 20, and 10 plates in its methanol recovery zone, dehydration zone, and extractant recovery zone, respectively. The method includes the following specific steps:
[0076] The aqueous methanol solution is heated to 100°C and then continuously fed into the partition column from the aqueous methanol inlet (located horizontally at the 10th tray in the dehydration zone). In the methanol recovery zone, methanol and water vapor are separated by distillation (methanol is concentrated upwards, while water is separated downwards). The water separated by the extractant enters the extractant recovery zone, where the extractant is concentrated and separated from the extractant outlet at the bottom of the partition column. The water vapor enters the dehydration zone and is finally separated from the column body from the produced water outlet. Methanol, water, and extractant (glycerol) are continuously extracted in proportion to their composition from the recovered methanol outlet, the produced water outlet, and the extractant outlet, respectively. Methanol is obtained from the recovered methanol outlet, and the recovered methanol is condensed, refluxed, and extracted. Water vapor flowing out from the produced water outlet is condensed, refluxed, and extracted. A portion of the extractant separated from the extractant outlet (referred to as the regenerated extractant) is fed into the baffled tower through the extractant inlet. The portion of the extractant separated from the extractant outlet is reboiled in the reboiler, and the resulting steam is sent to the baffled tower through the reboiler steam reflux port. The extractive distillation operation in the partitioned column is carried out at atmospheric pressure. The temperature for condensing methanol is 64°C with a reflux ratio of 3. The temperature for condensing water vapor is 100°C with a reflux ratio of 2.5. The temperature for reboiling the glycerol extractant is 200°C. The reboiling vapor is returned from the 9th tray in the extractant recovery zone. The regenerated extractant (with a mass ratio of 1:2 to the aqueous methanol solution) is returned from the 20th tray in the methanol recovery zone.
[0077] After extraction and distillation, the water content in methanol was 0.1 wt%, the methanol content in water was 0.01 wt%, the water content in the extractant (glycerol) was 5 wt%, and methanol was not detected.
[0078] Example 6
[0079] This embodiment provides a method for separating water from an aqueous methanol solution (composed of 60 wt% methanol, 5 wt% water, and 35 wt% glycerol after separation) from a biodiesel company. This method utilizes the partitioned column provided in Example 1. The partitioned column used in this embodiment has 40, 20, and 10 plates in its methanol recovery zone, dehydration zone, and extractant recovery zone, respectively. The method includes the following specific steps:
[0080] The aqueous methanol solution is heated to 130°C and then continuously fed into the partition column from the aqueous methanol inlet (located horizontally at the 10th tray in the dehydration zone). In the methanol recovery zone, methanol and water vapor are separated by distillation (methanol is concentrated upwards, while water is separated downwards). The water separated by the extractant enters the extractant recovery zone, where the extractant is concentrated and separated from the extractant outlet at the bottom of the partition column. The water vapor enters the dehydration zone and is finally separated from the column body from the produced water outlet. Methanol, water, and extractant (glycerol) are continuously extracted in proportion to their composition from the recovered methanol outlet, the produced water outlet, and the extractant outlet, respectively. Methanol is obtained from the recovered methanol outlet, and the recovered methanol is condensed, refluxed, and extracted. Water vapor flowing out from the produced water outlet is condensed, refluxed, and extracted. A portion of the extractant separated from the extractant outlet (referred to as the regenerated extractant) is fed into the baffled tower through the extractant inlet. The portion of the extractant separated from the extractant outlet is reboiled in the reboiler, and the resulting steam is sent to the baffled tower through the reboiler steam reflux port. The pressure of the extractive distillation operation in the partition column is 0.5 MPa, the temperature for methanol condensation is 112℃ with a reflux ratio of 1.5, the temperature for water vapor condensation is 154℃ with a reflux ratio of 1.5, the temperature for reboiling the glycerol extractant is 200℃, the reboiling steam is returned from the 8th tray of the extractant recovery zone, and the regenerated extractant (with a mass ratio of 1:3 to the aqueous methanol solution) is returned from the 20th tray of the methanol recovery zone.
[0081] After extraction and distillation, the water content in methanol was 0.02 wt%, the methanol content in water was 0.01 wt%, the water content in the extractant (glycerol) was 6 wt%, and no methanol was detected.
[0082] Comparative Example 1
[0083] This comparative example provides a method for separating methanol and water by distillation. The aqueous methanol solution used is the same as in Example 3, i.e., after separation, the aqueous methanol solution has the composition of 20 wt% methanol, 60 wt% water, and 20 wt% glycerol. This method uses two distillation columns (i.e., a methanol separation column and a water separation column) to perform conventional ternary separation of methanol, water, and glycerol from the aqueous methanol solution. First, the methanol separation column (operating conditions: 1 MPa, 40 trays) is used for separation. The ternary components are heated to 150°C and continuously fed into the methanol separation column from the 10th tray. The methanol condensation temperature is 138°C, and the reflux ratio is 0.5. The heavy component is collected after reboiling at 190°C and fed into the water separation column (operating conditions: 1 MPa, 20 trays) from the 10th tray. The water condensation temperature is 180°C, the reflux ratio is 1, and the glycerol reboiling temperature is 220°C.
[0084] After distillation, the methanol contained 1 wt% water, the water contained 0.3 wt% methanol, and the glycerol contained 15 wt% water. Comparing the experimental data of Example 3 and Comparative Example 1, it can be seen that compared with Example 3, the methanol content in the water and the water content in the glycerol in this comparative example are both increased, that is, the purity of the extracted water and the separated glycerol are significantly reduced.
[0085] Comparative Example 2
[0086] This comparative example provides a method for separating methanol and water by distillation. The aqueous methanol solution used is the same as in Example 4, i.e., the composition of the aqueous methanol solution after separation is 80 wt% methanol and 20 wt% water. This method separates the aqueous methanol solution in a distillation column using conventional methanol and water distillation separation methods. The operating conditions are 2 MPa, 25 trays, methanol condensation temperature of 166°C, reflux ratio of 3, and water reboiling temperature of 210°C. The aqueous methanol solution is heated to 160°C and continuously fed into the distillation column from the 10th tray. Methanol and water are continuously collected in the specified composition ratio.
[0087] After distillation, the methanol contained 1.5 wt% water, and the water contained 0.6 wt% methanol. Comparing the experimental data from Example 4 and Comparative Example 2, it can be seen that the purity of methanol and water in this comparative example is significantly lower than that in Example 4.
[0088] Comparative Example 3
[0089] This comparative example provides a method for separating water by methanol extraction and distillation, which differs from Example 3 only in that: a portion of the extractant separated from the extractant outlet (denoted as the regenerated extractant) is not allowed to enter the baffle column through the extractant inlet.
[0090] After extractive distillation, the methanol contained 2 wt% water, the water contained 0.5 wt% methanol, and the extractant (glycerol) contained 16 wt% water. No methanol was detected. Comparing the experimental data of Example 3 and Comparative Example 3, it can be seen that, compared with Comparative Example 3, the extraction of extractant separated from the extractant outlet and recycled into the baffle column through the extractant inlet in Example 3 of this invention can improve the separation degree and separation effect.
[0091] Comparative Example 4
[0092] This comparative example provides a method for separating water by methanol extraction and distillation, which differs from Example 4 only in that: a portion of the extractant separated from the extractant outlet (denoted as the regenerated extractant) is not allowed to enter the baffle column through the extractant inlet.
[0093] After extractive distillation separation, the methanol contained 1.3 wt% water, the water contained 0.8 wt% methanol, and the extractant contained 19 wt% water. No methanol was detected. Comparing the experimental data in Example 4 and Comparative Example 4, it can be seen that, compared with Comparative Example 4, the extraction of extractant separated from the extractant outlet and recycled into the baffle column through the extractant inlet in Example 4 of this invention can improve the separation degree and separation effect.
[0094] The above description is merely a specific embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any substitution of equivalent components or equivalent changes and modifications made within the scope of protection of this patent should still fall within the scope of this patent. Furthermore, the technical features, technical features and technical inventions, and technical inventions in this invention can be freely combined and used.
Claims
1. A baffle column for methanol extractive distillation and water separation, comprising a column body, characterized in that, The tower body is provided with vertical baffles and horizontal baffles. The horizontal baffles are located between the top of the vertical baffles and the right side wall of the tower body. The vertical baffles divide the inner cavity of the tower body from top to bottom into a methanol recovery zone, a dehydration zone and an extractant recovery zone. The tower body is provided with an aqueous methanol inlet, a recovered methanol outlet, a produced water outlet, an extractant outlet, and an extractant inlet. The height of the aqueous methanol inlet is not lower than the lower end of the vertical partition, the height of the recovered methanol outlet is higher than the upper end of the vertical partition, the height of the produced water outlet is not higher than the upper end of the vertical partition, the extractant outlet is lower than the lower end of the vertical partition, and the extractant inlet is located above the aqueous methanol inlet.
2. The diaphragm tower according to claim 1, characterized in that, The recovered methanol outlet is located at the top of the tower, and the extractant outlet is located at the bottom of the tower.
3. The diaphragm tower according to claim 1 or 2, characterized in that, The tower body is also equipped with methanol reflux port, water reflux port and reboil steam reflux port in the methanol recovery zone, dehydration zone and extractant recovery zone respectively.
4. The diaphragm tower according to claim 1 or 2, characterized in that, The theoretical plate numbers for the methanol recovery zone, dehydration zone, and extractant recovery zone are 10-40, 5-20, and 3-10, respectively.
5. A method for separating water by methanol extraction and distillation, characterized in that, The method is implemented using the baffle column for methanol extractive distillation and water separation as described in any one of claims 1-4, and includes the following steps: Aqueous methanol and extractant are continuously fed into a baffled tower from the aqueous methanol inlet and the extractant inlet, respectively. In the methanol recovery zone, methanol and water vapor are separated by liquid distillation, and high-purity methanol is obtained from the recovered methanol outlet. The water separated by the extractant enters the extractant recovery zone, where the extractant is concentrated and separated from the extractant outlet. The water vapor enters the dehydration zone and is finally separated from the tower body from the produced water outlet. The extractant separated from the extractant outlet is then introduced into the baffle column through the extractant feed inlet.
6. The method according to claim 5, characterized in that, When the aqueous methanol contains glycerol, the method includes: Aqueous methanol is continuously fed into the baffle tower from the aqueous methanol inlet. In the methanol recovery zone, methanol and water vapor are separated by distillation, and high-purity methanol is obtained from the recovered methanol outlet. The water separated by the extractant enters the extractant recovery zone, where the extractant is concentrated and separated from the extractant outlet. The water vapor enters the dehydration zone and is finally separated from the tower body from the produced water outlet. The extractant obtained from the extractant outlet is introduced into the baffled tower through the extractant feed inlet, wherein the extractant is glycerol.
7. The method according to claim 5 or 6, characterized in that, When the aqueous methanol does not contain glycerol, the total weight of the aqueous methanol is 100%, wherein the methanol content is greater than or equal to 20 wt% and the water content is less than or equal to 80 wt%. When the aqueous methanol contains glycerol, the total weight of the aqueous methanol is 100%, wherein the methanol content is greater than or equal to 20 wt%, the glycerol content is less than or equal to 50 wt%, and the water content is the balance.
8. The method according to claim 5 or 6, characterized in that, The mass ratio of the aqueous methanol to the extractant is 5:1 to 1:
3.
9. The method according to claim 5, characterized in that, The extractant includes glycerol and / or polyglycerol with a molecular weight of less than 1000.
10. The method according to claim 5 or 6, characterized in that, The pressure of the extractive distillation operation carried out in the partition column is from atmospheric pressure to 2 MPa.
11. The method according to claim 5 or 6, characterized in that, The feed temperature for aqueous methanol and extractant is room temperature to 200°C.
12. The method according to claim 5 or 6, characterized in that, The method further includes: condensing and refluxing the methanol recovered from the methanol recovery outlet, and / or condensing and refluxing the water vapor flowing out from the water extraction outlet, and / or reboiling the extractant separated from the extractant outlet in the reboiler and sending the resulting steam into the baffle tower through the reboiler steam reflux port.
13. The method according to claim 12, characterized in that, The temperature for condensing methanol is 60-170°C, and / or the temperature for condensing water vapor is 90-210°C, and / or the temperature for reboiling is 120-260°C.
14. The method according to claim 12, characterized in that, The reflux ratio of methanol is no greater than 3, and / or the reflux ratio of produced water is no greater than 2.