Dual-column rectification method and dual-column rectification system

Abstract

The application discloses a double-tower rectification method and a double-tower rectification system, which comprises the following steps: feeding a material to be separated into a first rectification tower through the middle part of the first rectification tower to perform first rectification treatment, so as to form a first rectification tower top product and a first rectification tower bottom product, and the mass content of a light key component in the first rectification tower top product is 5%-10%; feeding the first rectification tower top product into a second rectification tower through the middle part of the second rectification tower from the top of the first rectification tower through a transmission channel after discharging heat through a second reboiler, so as to perform second rectification treatment, and thus forming a second rectification tower top product and a second rectification tower bottom product. The method can realize excellent separation results while reducing energy consumption.

Description

Technical Field

[0001] This invention relates to a dual-tower distillation method and a dual-tower distillation system. Background Technology

[0002] The traditional single-tower process for pyridine benzene removal is the most energy-intensive in the product distillation system. Because the reboiler uses steam heating, steam consumption is high, resulting in high costs. The top product of the traditional benzene removal tower is benzene and light components, while the bottom product is pyridine and heavy components. Benzene's atmospheric boiling point is 80℃, while pyridine's is 115℃, a significant difference. The tower operates at a pressure of 60 kPa·G to 80 kPa·G, with a top temperature of 95℃ to 100℃ and a bottom temperature of 145℃ to 155℃. This large temperature difference between the top and bottom makes it difficult to achieve double-effect distillation using differential pressure distillation.

[0003] The prior art CN102351634A discloses a new energy-saving process for benzene separation that integrates dual-effect distillation and heat. Although it uses multi-stage distillation columns for the system of aromatics and benzene, the separation capacity and results of each stage of distillation column are consistent. However, if applied to the system of pyridine and benzene, the large temperature difference between the top and bottom of the column leads to a large difference in the operating pressure between the first and second columns, making it difficult or impossible to achieve. Therefore, it is impossible to achieve the effect of reducing energy consumption while obtaining excellent separation results.

[0004] Therefore, a purification method for pyridine is needed to achieve excellent separation results while reducing energy consumption. Summary of the Invention

[0005] To address the issue that existing separation methods for pyridine and benzene systems cannot achieve both excellent separation results and reduced energy consumption, this invention provides a dual-tower distillation method and system that can reduce energy consumption while achieving excellent separation results.

[0006] The present invention solves the above-mentioned technical problems through the following technical solutions.

[0007] This invention provides a dual-tower distillation method for separating light critical components and heavy critical components from a material to be separated. The difference in atmospheric boiling points between the heavy critical components and the light critical components is 20-100°C. The mass content of the heavy critical components is 10%-30%, and the mass content of the light critical components is 50%-80%. The method includes the following steps:

[0008] S1. A first distillation column and a second distillation column are provided, wherein the top of the first distillation column forms a transfer channel through a second reboiler and the middle of the second distillation column;

[0009] S2. The first distillation column is heated by connecting a first reboiler to the bottom of the first distillation column;

[0010] S3. The second distillation column is heated by the second reboiler connected to the bottom of the second distillation column;

[0011] S4. The material to be separated is passed through the middle of the first distillation column and then into the first distillation column for first distillation treatment to form the top product and the bottom product of the first distillation column. The mass content of the light key components in the top product of the first distillation column is 5%-10%.

[0012] S5. After the top product of the first distillation column releases heat through the second reboiler, it enters the second distillation column from the top of the first distillation column through the transmission channel from the middle of the second distillation column for second distillation treatment, forming the top product of the second distillation column and the bottom product of the second distillation column.

[0013] In this invention, the mass content of the heavy key component means the percentage of the mass of the heavy key component relative to the mass of the material to be separated, and the mass content of the light key component means the percentage of the mass of the light key component relative to the mass of the material to be separated.

[0014] In this invention, preferably, the heavy key component is benzene and the light key component is pyridine;

[0015] Wherein, the pressure at the top of the first distillation treatment column is 100-160 kPa.G, and the temperature at the top of the first distillation treatment column is 100-120℃;

[0016] The temperature of the bottom of the second distillation treatment column is 70-100℃.

[0017] In existing technologies, due to the special properties of pyridine and benzene, a single-column separation is typically used, but this often results in very high energy consumption. While multi-stage distillation is employed for other separation systems (such as the aromatic hydrocarbons and benzene disclosed in CN102351634A), the physicochemical properties of the mixture formed by pyridine and benzene differ significantly from those of the mixture formed by aromatic hydrocarbons and benzene. For example, toluene has a normal boiling point of 110°C, which is closer to benzene's boiling point than pyridine's 115°C. More importantly, the aromatic hydrocarbon and benzene system disclosed in CN102351634A does not contain any high-boiling-point unknown heavy impurities, allowing for effective multi-stage distillation with conventional parallel feed. However, existing pyridine and benzene systems generally contain high-boiling-point unknown heavy impurities, which would cause higher reboiler temperatures in the distillation column, making it impossible to directly apply the existing multi-stage distillation systems (such as the system disclosed in CN102351634A).

[0018] In the separation system of pyridine and benzene, this invention adopts a series feeding method, that is, the total feed only enters the middle of the first distillation column, while the feed of the second distillation column comes from the top of the first distillation column. This results in the top temperature of the first distillation column being 100-120℃ and the bottom temperature of the second distillation column being 70-100℃, thus achieving a temperature difference of more than 20℃ between the two. This overcomes the limitations of traditional temperature mismatch and successfully realizes a double-effect process. The top temperature of the first distillation column can perfectly match the heat source temperature requirements of the second reboiler, which can further reduce the steam consumption of the reboiler. This not only reduces the difficulty of realizing the double-effect process but also maximizes energy saving; at the same time, it can also obtain high-purity products.

[0019] In this invention, the temperatures of the top and bottom of the first and second distillation processes can be controlled by the temperatures of the first and second reboilers, and the pressures of the top and bottom of the first and second distillation processes can be controlled by a pressure control system. For example, the pressure of the first distillation process can be controlled by a pressure regulating valve system, and the pressure of the second distillation process can be controlled by a combination of a vacuum pump and a pressure regulator.

[0020] In this invention, preferably, the mass content of pyridine in the material to be separated is 10%-30%.

[0021] In this invention, preferably, the benzene content in the material to be separated is 50%-80%, for example, 77%.

[0022] In this invention, the material to be separated can be the material obtained after benzene extraction. The material to be separated is mostly benzene, followed by pyridine, and contains about 10%-20% pyridine homologues and heavy impurities. Heavy impurities are compounds with a molecular weight more than 5 times that of pyridine homologues.

[0023] Optionally, the pyridine homologues include 2-methylpyridine, 3-methylpyridine, 3,5-dimethylpyridine, and 2,3,5-trimethylpyridine.

[0024] Optionally, the mass content of the pyridine homologue is 9%-17%.

[0025] In some specific embodiments, the pyridine homologues include 2-methylpyridine, and the mass content of 2-methylpyridine in the material to be separated is 1%-5%.

[0026] In some specific embodiments, the pyridine homologues include 3-methylpyridine, and the mass content of 3-methylpyridine in the material to be separated is 5%-15%.

[0027] In some specific embodiments, the pyridine homologues include 3,5-dimethylpyridine, and the mass content of 3,5-dimethylpyridine in the material to be separated is 1%-5%.

[0028] In some specific embodiments, the pyridine homologues include 2,3,5-trimethylpyridine, and the mass content of 2,3,5-trimethylpyridine in the material to be separated is 1%-3%.

[0029] Optionally, the heavy impurities include unknown substances such as tar generated in the upstream reaction, and the mass content of the heavy impurities is 1%-3%.

[0030] In one specific embodiment of the present invention, the pyridine homologues include 2-methylpyridine, 3-methylpyridine, 3,5-dimethylpyridine, and 2,3,5-trimethylpyridine. The mass content of 2-methylpyridine in the material to be separated is 2%, the mass content of 3-methylpyridine in the material to be separated is 6%, the mass content of 3,5-dimethylpyridine in the material to be separated is 2%, and the mass content of 2,3,5-trimethylpyridine in the material to be separated is 1%.

[0031] In this invention, preferably, the top pressure of the first distillation treatment column is 120-160 kPa.G, more preferably 140-160 kPa.G.

[0032] In this invention, preferably, the top temperature of the first distillation treatment column is 110-120°C, more preferably 113-120°C, for example 116°C.

[0033] In this invention, preferably, the reboiler temperature of the first distillation treatment is 163-173°C, for example, 168°C.

[0034] In this invention, preferably, the pressure of the reboiler in the first distillation process is 155-185 kPa.G, for example, 165 kPa.G.

[0035] In this invention, preferably, the mass content of pyridine in the top product of the first distillation column is 5%-10%, for example, 6%.

[0036] In this invention, preferably, the benzene content of the bottom product of the first distillation column is less than 0.1%.

[0037] In this invention, preferably, the reboiler temperature of the second distillation treatment is 70-90°C, more preferably 78-90°C, for example 81°C.

[0038] In this invention, preferably, the reboiler pressure of the second distillation treatment is -48 kPa.G to -15 kPa.G, for example -37 kPa.G.

[0039] In this invention, preferably, the top temperature of the second distillation treatment column is 58-72°C, for example, 64°C.

[0040] In this invention, preferably, the top pressure of the second distillation treatment column is -50 kPa.G to -20 kPa.G, for example -40 kPa.G.

[0041] In this invention, preferably, the benzene content in the bottom product of the second distillation column is 40%-60%, for example, 50% or 55%.

[0042] In this invention, preferably, the mass content of pyridine in the top product of the second distillation column is less than 0.1%.

[0043] In this invention, the top reflux ratio is the ratio of the mass flow rate of the reflux liquid returning from the top of the distillation column to the mass flow rate of the top product.

[0044] In this invention, preferably, the top reflux ratio of the first distillation column is 0.1-0.2, for example, 0.123, 0.126, 0.129 or 0.187.

[0045] In this invention, preferably, the top reflux ratio of the second distillation column is 0.43-0.55, for example, 0.455, 0.456, 0.485 or 0.51.

[0046] In this invention, preferably, the bottom product of the second distillation column is recycled to the middle of the first distillation column as part of the material to be separated.

[0047] In this invention, preferably, the ratio of the flow rate of the material to be separated into the first distillation column to the flow rate of the top product of the first distillation column into the second distillation column is (1.1-1.5):1, for example, 1.17:1.

[0048] In this invention, preferably, the flow rate of the material to be separated into the first distillation column is 50-60 t / h, for example, 55.8 t / h.

[0049] In this invention, preferably, the flow rate of the top product of the first distillation column into the second distillation column is 40-50 t / h, for example, 47.73 t / h.

[0050] The present invention also provides a dual-tower distillation system for the above-described dual-tower distillation method, comprising a first distillation column and a second distillation column in sequence; a first reboiler is externally connected to the bottom of the first distillation column, the first reboiler being used to heat the bottom product of the first distillation column before it is refluxed into the bottom of the first distillation column; a second reboiler is externally connected to the bottom of the second distillation column, the second reboiler being used to heat the bottom product of the second distillation column before it is refluxed into the bottom of the second distillation column.

[0051] The first distillation column includes a feed inlet, a top outlet, and a bottom outlet.

[0052] The second distillation column includes a feed inlet, a top outlet, and a bottom outlet.

[0053] The top outlet of the first distillation column is connected to the feed inlet of the second distillation column through the second reboiler, forming a transmission channel.

[0054] In this invention, preferably, the first distillation column is further provided with a top reflux path and a top feed inlet, and the top discharge outlet and the top feed inlet of the first distillation column are connected through the top reflux path.

[0055] In this invention, preferably, the second distillation column is further provided with a top reflux path and a top feed inlet of the second distillation column, and the top discharge outlet and the top feed inlet of the second distillation column are connected through the top reflux path of the second distillation column.

[0056] Preferably, the dual-tower distillation system further includes a second reflux tank and a second condenser. The top outlet of the second distillation column is connected to the top inlet of the second distillation column in sequence through the second condenser and the second reflux tank, forming the top reflux path of the second distillation column.

[0057] In this invention, preferably, the bottom outlet of the second distillation column is connected to the inlet of the first distillation column.

[0058] In this invention, preferably, the dual-tower distillation system further includes a first reflux tank and a first condenser, wherein the top outlet of the first distillation column is connected to the feed inlet of the second distillation column in sequence through the second reboiler, the first condenser, and the first reflux tank.

[0059] In this invention, preferably, the first distillation column is provided with structured packing above the feed inlet, and with anti-clogging trays below the feed inlet. The structured packing and anti-clogging trays can be conventional structures and trays used in the art. This application's arrangement of structured packing above the feed inlet and anti-clogging trays below the feed inlet further improves product separation accuracy and reduces clogging issues.

[0060] The structured packing material is of the type MellapakPlus. TM .

[0061] The anti-clogging tower tray is a Sulzer anti-clogging tower tray.

[0062] In this invention, preferably, the second distillation column is provided with structured packing.

[0063] The structured packing material is of the type MellapakPlus. TM .

[0064] In this invention, preferably, the dual-tower distillation system further includes a first reflux tank and a first condenser. The top outlet of the first distillation column passes sequentially through the second reboiler, the first condenser, and the first reflux tank, and then splits into two paths: one path connects to the feed inlet of the second distillation column, and the other path connects to the top feed inlet of the first distillation column; wherein the top feed inlet of the first distillation column is connected to the heat medium connection port of the second reboiler.

[0065] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0066] The reagents and raw materials used in this invention are all commercially available.

[0067] The positive and progressive effects of this invention are as follows:

[0068] The dual-tower distillation method of the present invention overcomes the limitations of traditional temperature mismatch by selecting parameters and successfully realizes a double-effect process. The top temperature of the first distillation column can be perfectly matched with the heat source temperature requirements of the second reboiler, which can further reduce the steam consumption of the reboiler. This not only reduces the difficulty of realizing the double-effect process, but also maximizes energy saving; at the same time, it can also obtain high-purity products. Attached Figure Description

[0069] Figure 1 This is a schematic diagram of the dual-tower distillation system of Example 1.

[0070] The attached figures are labeled as follows:

[0071] 1-First distillation column; 2-Second distillation column; 3-First reboiler; 4-Second reboiler; 5-First condenser; 6-First reflux tank; 7-Second condenser; 8-Second reflux tank;

[0072] 101-Structured packing; 102-Anti-clogging tray. Detailed Implementation

[0073] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0074] Example 1

[0075] A schematic diagram of the dual-tower distillation system is shown below. Figure 1 As shown, it sequentially includes a first distillation column 1 and a second distillation column 2; the bottom of the first distillation column 1 is connected to a first reboiler 3, which is used to heat the bottom product of the first distillation column before it flows back into the bottom of the first distillation column 1; the bottom of the second distillation column 2 is connected to a second reboiler 4, which is used to heat the bottom product of the second distillation column 2 before it flows back into the bottom of the second distillation column 2.

[0076] The first distillation column 1 includes a feed inlet, a top outlet, and a bottom outlet.

[0077] The second distillation column 2 includes a feed inlet, a top outlet, and a bottom outlet.

[0078] The top outlet of the first distillation column 1 is connected to the second reboiler 4 and the feed inlet of the second distillation column 2 to form a transmission channel.

[0079] The first distillation column 1 is also provided with a top reflux path and a top feed inlet of the first distillation column 1. The top discharge outlet of the first distillation column 1 and the top feed inlet of 11 are connected through the top reflux path of the first distillation column.

[0080] The dual-tower distillation system also includes a first reflux tank 6 and a first condenser 5. The top outlet of the first distillation column passes through the second reboiler 4, the first condenser 5, and the first reflux tank 6 in sequence, and then splits into two paths: one path connects to the feed inlet of the second distillation column 2, and the other path connects to the top feed inlet of the first distillation column 1, forming the aforementioned top reflux path of the first distillation column; wherein, the top feed inlet of the first distillation column 1 is connected to the heat medium connection port of the second reboiler 4;

[0081] The second distillation column 2 is also provided with a top reflux path and a top feed inlet of the second distillation column 2. The dual-column distillation system also includes a second reflux tank 8 and a second condenser 7. The top discharge port of the second distillation column 2 is connected to the top feed inlet of the second distillation column 2 in sequence through the second condenser 7 and the second reflux tank 8, forming the top reflux path of the second distillation column 2.

[0082] The bottom outlet of the second distillation column 2 is connected to the feed inlet of the first distillation column 1;

[0083] The first distillation column 1 is equipped with structured packing 101 (Sulzer Mellapak Plus) above the first feed inlet. TM The first distillation column 1 is equipped with an anti-clogging tray 102 (Sulzer anti-clogging tray) below the first feed inlet, and the second distillation column 2 is equipped with structured packing (Sulzer Mellapak Plus). TM ).

[0084] The dual-tower distillation method includes the following steps:

[0085] S1. The material to be separated (the light key component is pyridine, the heavy key component is benzene, the difference in their atmospheric boiling points is 35℃, the mass content of pyridine is 10%, the mass content of benzene is 77%, the mass content of pyridine homologues (2-methylpyridine 2%, 3-methylpyridine 6%, 3,5-dimethylpyridine 2%, and 2,3,5-trimethylpyridine 1%) and heavy impurities (2% mass content of unknown substances such as tar generated from upstream reactions, which can be ignored) are fed into the first distillation column at a flow rate of 55800 kg / h for first distillation treatment, forming the top product of the first distillation column (pyridine mass content of 5%) and the bottom product of the first distillation column (benzene mass content of less than 0.1%); the reflux ratio at the top of the first distillation column is 0.129;

[0086] The pressure at the top of the first distillation column is 140 kPa.G, and the temperature at the top of the first distillation column is 113℃; the temperature at the bottom of the first distillation column is 168℃, and the pressure at the bottom of the first distillation column is 165 kPa.G.

[0087] S2. After absorbing heat in the second reboiler, the top product of the first distillation column is fed into the second distillation column through the first feed inlet (the flow rate of the top product of the first distillation column into the second distillation column is 47730 kg / h) and undergoes second distillation to form the top product of the second distillation column (pyridine mass content is less than 0.1%) and the bottom product of the second distillation column (benzene mass content is 55%); the reflux ratio at the top of the second distillation column is 0.455.

[0088] The temperature of the bottom of the second distillation column is 81℃, the pressure of the bottom column is -37kPa.G, the temperature of the top column is 64℃, and the pressure of the top column is -40kPa.G.

[0089] The bottom product of the second distillation column is recycled to the first feed inlet of the first distillation column as part of the material to be separated.

[0090] In this embodiment, the processing capacity is 40,000 tons of pyridine / year, the annual operating time is 7,200 hours, the mass content of pyridine in the bottom product of the first distillation column is 45.9%, the mass content of benzene is less than 0.1% (the rest are mainly pyridine homologues and unknown heavy impurities); the mass content of benzene in the top product of the second distillation column is 99%, the mass content of pyridine is less than 0.1%, the rest are mainly small amounts of light impurities), the energy consumption is 7.89MW, and the steam consumption is 13,915kg / h.

[0091] Example 2

[0092] The first distillation column is equipped with structured packing (Sulzer Mellapak Plus) in both the portion above and below the first feed inlet. TM The process produces a first distillation column top product (pyridine content of 5%) and a first distillation column bottom product (benzene content of 0.1%), a second distillation column top product (pyridine content of 0.1%) and a second distillation column bottom product (benzene content of 40%). The reflux ratio at the top of the first distillation column is 0.187, and the reflux ratio at the top of the second distillation column is 0.485. The remaining conditions are the same as in Example 1.

[0093] In this embodiment, the mass content of pyridine in the bottom product of the first distillation column is 45.9%, and the mass content of benzene is 0.1%; the mass content of benzene in the top product of the second distillation column is 99%, and the mass content of pyridine is 0.1%; the energy consumption is 8.17MW, and the steam consumption is 14409kg / h.

[0094] In this embodiment, the first distillation column is equipped with structured packing. The heavier components in the material to be separated will affect the distribution performance of the structured packing surface. Compared with Example 1, the separation efficiency will decrease and energy consumption will increase.

[0095] Example 3

[0096] The top pressure of the first distillation treatment column is 160 kPa.G, the top temperature of the first distillation treatment column is 116℃, and the bottom pressure of the first distillation treatment column is 185 kPa.G; the bottom temperature of the second distillation treatment column is 78℃.

[0097] The first distillation column produces a top product (pyridine content of 5%) and a bottom product (benzene content of 0.1%), and the second distillation column produces a top product (pyridine content of 0.1%) and a bottom product (benzene content of 50%). The reflux ratio at the top of the first distillation column is 0.126, and the reflux ratio at the top of the second distillation column is 0.456. The remaining conditions are the same as in Example 1.

[0098] In this embodiment, the mass content of pyridine in the bottom product of the first distillation column is 45.9%, and the mass content of benzene is 0.1%; the mass content of benzene in the top product of the second distillation column is 99%, and the mass content of pyridine is 0.1%; the energy consumption is 8.09 MW, and the steam consumption is 14268 kg / h.

[0099] Example 4

[0100] The temperature of the bottom of the second distillation column is 90℃, the pressure of the bottom column is -15kPa.G, the temperature of the top column is 72℃, and the pressure of the top column is -20kPa.G.

[0101] The first distillation column produces a top product (pyridine content of 6%) and a bottom product (benzene content of 0.1%), and the second distillation column produces a top product (pyridine content of 0.1%) and a bottom product (benzene content of 40%). The reflux ratio at the top of the first distillation column is 0.123, and the reflux ratio at the top of the second distillation column is 0.51. The remaining conditions are the same as in Example 1.

[0102] In this embodiment, the mass content of pyridine in the bottom product of the first distillation column is 45.9%, and the mass content of benzene is 0.1%; the mass content of benzene in the top product of the second distillation column is 99%, and the mass content of pyridine is 0.1%; the energy consumption is 7.98MW, and the steam consumption is 14074kg / h.

[0103] Example 5

[0104] The pressure at the top of the first distillation column is 100 kPa·G, the temperature at the top of the first distillation column is 106°C, the pressure at the bottom of the first distillation column is 125 kPa·G, and the temperature at the bottom of the first distillation column is 161°C. The pressure at the top of the second distillation column is -20 kPa·G, the temperature at the top of the second distillation column is 72°C, the pressure at the bottom of the second distillation column is -15 kPa·G, and the temperature at the bottom of the second distillation column is 90°C. The top product of the first distillation column (pyridine mass content of 6%) and the bottom product of the second distillation column (benzene mass content of 0.1%) are formed. The top product of the second distillation column (pyridine mass content of 0.1%) and the bottom product of the second distillation column (benzene mass content of 40%) are formed. The reflux ratio at the top of the first distillation column is 0.144, and the reflux ratio at the top of the second distillation column is 0.51. The remaining conditions are the same as in Example 1.

[0105] In this comparative example, the mass content of pyridine in the bottom product of the first distillation column was 45.9%, and the mass content of benzene was 0.1%; the mass content of benzene in the top product of the second distillation column was 99%, and the mass content of pyridine was 0.1%. The energy consumption was 7.93 MW, and the steam consumption was 13986 kg / h. Compared with Example 1, reducing the top pressure of the first distillation column leads to a decrease in the heat transfer temperature difference between the top of the first distillation column and the bottom of the second distillation column, thereby increasing the design difficulty of the reboiler and requiring an increase in the heat exchange area.

[0106] Example 6

[0107] The reboiler temperature of the second distillation treatment is 100°C, the top pressure of the second distillation treatment is 10 kPa·G, the top temperature of the second distillation treatment is 82°C, and the reboiler pressure of the second distillation treatment is 13 kPa·G. This forms the top product of the first distillation column (pyridine mass content of 5%) and the bottom product of the first distillation column (benzene mass content of 0.1%). It also forms the top product of the second distillation column (pyridine mass content of 0.1%) and the bottom product of the second distillation column (benzene mass content of 40%). The reflux ratio at the top of the first distillation column is 0.131, and the reflux ratio at the top of the second distillation column is 0.54. The remaining conditions are the same as in Example 1.

[0108] In this comparative example, the mass content of pyridine in the bottom product of the first distillation column was 45.9%, and the mass content of benzene was 0.1%; the mass content of benzene in the top product of the second distillation column was 99%, and the mass content of pyridine was 0.1%. The energy consumption was 7.86 MW, and the steam consumption was 13862 kg / h. Compared with Example 1, increasing the reboiler temperature of the second distillation column also leads to a decrease in the heat transfer temperature difference between the top of the first distillation column and the reboiler of the second distillation column, thereby increasing the design difficulty of the reboiler and requiring an increase in the heat exchange area.

[0109] Comparative Example 1

[0110] This comparative example uses a separate distillation column to separate the materials to be separated in Example 1. The specific operating conditions are as follows:

[0111] The temperature at the top of the column is 97℃; the pressure at the top of the column is 70 kPa.G; the temperature at the bottom of the column is 151℃; and the pressure at the bottom of the column is 80 kPa.G.

[0112] In this comparative example, the pyridine product contained 45.9% pyridine by mass and 0.3% benzene by mass; the benzene product contained 99% benzene by mass and 0.3% pyridine by mass, with an energy consumption of 10.77 MW and a steam consumption of 18995 kg / h.

[0113] Based on the results of the above embodiments and comparative examples, the dual-tower distillation system and method of the present invention can obtain the bottom product of the first distillation column with a pyridine mass content of more than 45.9% and the top product of the second distillation column with a benzene mass content of more than 99%; indicating that the embodiments can obtain products with high purity.

[0114] Based on this, the energy consumption of the embodiment is only less than 8.17MW and the steam consumption is only less than 14409kg / h.

[0115] In contrast, Comparative Example 1 uses a separate distillation column. Compared with Comparative Example 1, the pyridine content in the benzene product is reduced from about 0.3 wt% to below 0.1 wt%, and the benzene content in the pyridine-debenzened product is reduced from about 0.3 wt% to below 0.1 wt%. At the same time, energy consumption is significantly reduced. Comparative Example 1 requires as much as 10.77 MW of energy and as much as 18,995 kg / h of steam. This example can reduce energy consumption by more than 25%, which can save about 36,600 tons of steam per year based on 1.0 MPa.G saturated steam, which is very considerable.

Claims

1. A dual-tower distillation method for separating a light critical component and a heavy critical component from a material to be separated, wherein the difference in atmospheric boiling points between the heavy critical component and the light critical component is 20-100°C, the mass content of the heavy critical component is 10%-30%, and the mass content of the light critical component is 50%-80%, characterized in that... It includes the following steps: S1. A first distillation column and a second distillation column are set up. The top outlet of the first distillation column passes through the second reboiler, the first condenser and the first reflux tank in sequence, and then splits into two paths. One path is connected to the feed inlet of the second distillation column to form a transmission channel, and the other path is connected to the top feed inlet of the first distillation column to form the top reflux path of the first distillation column. S2. The first distillation column is heated by connecting a first reboiler to the bottom of the first distillation column; S3. The second distillation column is heated by the second reboiler connected to the bottom of the second distillation column; S4. The material to be separated is passed through the middle of the first distillation column and then into the first distillation column for first distillation treatment to form the top product and the bottom product of the first distillation column. The mass content of the light key components in the top product of the first distillation column is 5%-10%. S5. After the top product of the first distillation column releases heat through the second reboiler, it enters the second distillation column from the top of the first distillation column through the transmission channel from the middle of the second distillation column for second distillation treatment, forming the top product of the second distillation column and the bottom product of the second distillation column. Wherein, the heavy key component is benzene, and the light key component is pyridine; Wherein, the pressure at the top of the first distillation treatment column is 100-160 kPa.G, and the temperature at the top of the first distillation treatment column is 100-120℃; The temperature of the bottom of the second distillation treatment column is 70-100℃.

2. The dual-tower distillation method as described in claim 1, characterized in that, It meets one or more of the following conditions: (a) The top pressure of the first distillation treatment column is 120-160 kPa·G; (b) The top temperature of the first distillation treatment column is 110-120°C; (c) The temperature of the reboiler in the first distillation process is 163-173°C; (d) The pressure of the bottom column of the first distillation treatment is 155-185 kPa.G.

3. The dual-tower distillation method as described in claim 1, characterized in that, It meets one or more of the following conditions: (a) The pyridine content in the top product of the first distillation column is 6% by mass; (b) The benzene content of the bottom product of the first distillation column is less than 0.1%.

4. The dual-tower distillation method as described in claim 1, characterized in that, It meets one or more of the following conditions: (a) The bottom temperature of the second distillation treatment column is 70-90°C; (b) The reboiler pressure of the second distillation treatment is from -48 kPa.G to -15 kPa.G; (c) The top temperature of the second distillation treatment column is 58-72℃; (d) The top pressure of the second distillation treatment column is from -50 kPa.G to -20 kPa.G.

5. The dual-tower distillation method as described in claim 1, characterized in that, It meets one or more of the following conditions: (a) The benzene content in the bottom product of the second distillation column is 40%-60% by mass; (b) The mass content of pyridine in the top product of the second distillation column is less than 0.1%.

6. The dual-tower distillation method as described in claim 1, characterized in that, It meets one or more of the following conditions: (a) The reflux ratio at the top of the first distillation column is 0.1-0.2; (b) The reflux ratio at the top of the second distillation column is 0.43-0.

55.

7. The dual-tower distillation method as described in claim 1, characterized in that, It meets one or more of the following conditions: (a) The bottom product of the second distillation column is recycled to the middle of the first distillation column as part of the material to be separated; (b) The ratio of the flow rate of the material to be separated into the first distillation column to the flow rate of the top product of the first distillation column into the second distillation column is (1.1-1.5):1.

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