Method and device for refining high-purity methylpyridine from crude pyridine

Abstract

The present invention discloses a method and apparatus for refining high-purity methylpyridine from crude pyridine. On the one hand, the present invention adopts an integrated de-heavy fractionation device, which simplifies the process flow, reduces the floor area of equipment, and lowers the investment cost of the device; on the other hand, it adopts a heat pump distillation technology. After compressing and heating the gas at the top of the distillation column, it is directly used as the heat source of the reboiler at the bottom of the column, fully utilizing the condensation latent heat of the gas at the top of the column. Compared with the traditional distillation system, the energy consumption is reduced by about 70%, and the operating cost is greatly reduced. At the same time, the present invention adopts the atmospheric and vacuum distillation technology to finally obtain a high-purity methylpyridine product with a purity not less than 97%, which has great industrial application value.

Description

Technical Field

[0001] The present invention belongs to the field of production of coal chemical products, and particularly relates to a method and device for refining crude pyridine into high-purity methylpyridine. Background Art

[0002] As an important chemical raw material and intermediate, methylpyridine is widely used in the production of pharmaceuticals, pesticides, fragrances, feed additives, daily chemicals, etc. At present, methylpyridine is mainly prepared by catalytic synthesis of formaldehyde, acetaldehyde and ammonia. This process belongs to a chemical synthesis process, which consumes a large amount of raw materials during production and causes great harm to the environment. China is rich in coal tar resources. Among them, medium and low temperature coal tar contains a certain amount of crude pyridine and crude phenolic compounds, which can be used to extract high-value fine chemical products such as pyridine, methylpyridine, phenol, etc. If these coal tar resources can be fully utilized, a large amount of environmental costs and economic costs will be saved.

[0003] CN104893750 discloses a method for separating phenolic and pyridine components from coal tar and then obtaining related pyridine products through refining, but does not give the specific refining process.

[0004] CN109912500A discloses a method for refining crude pyridine into high-purity pyridine series products. After dehydrating and deslagging pretreatment of the crude pyridine raw material from medium and low temperature coal tar, azeotropic distillation, atmospheric and vacuum distillation and heat integration technology are further used to separate high-value pyridine series products, so that the purity of pyridine, o-methylpyridine, methylpyridine, dimethylpyridine and trimethylpyridine reaches more than 96wt%. However, from the single-line process of obtaining pure methylpyridine from crude pyridine, the required equipment occupies a large area, has low heat transfer efficiency and high cost investment.

[0005] Therefore, it is of great significance to develop a technology for separating and purifying methylpyridine products with high efficiency and low energy consumption using the crude pyridine component in medium and low temperature coal tar as the raw material. Summary of the Invention

[0006] The purpose of the present invention is to provide a method and device for refining crude pyridine into high-purity methylpyridine in view of the deficiencies of the prior art, including the following steps:

[0007] (1) Introduce the crude pyridine raw material into the crude pyridine deweight fractionation column (T-01). The crude pyridine deweight fractionation column (T-01) consists of a lower deweight falling film evaporator and an upper crude pyridine fractionation column. The crude pyridine raw material first enters the lower falling film evaporator, the heavy components are discharged from the bottom of the unit, and the light components are taken out from the side line of the falling film evaporator and sent to the upper fractionation column; the gas-phase pyridine and o-cresol mixed components at the top of the fractionation column are condensed by the condenser (EW01), and a part is taken out, and the other part is refluxed. A part of the crude pyridine components at the bottom of the column is refluxed after being reboiled by the thermosyphon reboiler (E-01) of the crude pyridine fractionation column, and the other part is sent to the methylpyridine rectification column (T-02);

[0008] (2) The methylpyridine rectification system adopts heat pump rectification technology. In the methylpyridine rectification column (T-02), the gas-phase methylpyridine at the top of the column is heated and pressurized by the compressor (C-03) after being heated by the compressor inlet preheater (E-03). The heated material is introduced into the bottom reboiler (E-02) as the heat source of the bottom reboiler (E-02); the methylpyridine discharged from the thermosyphon reboiler (E-02) of the methylpyridine rectification column is first heated by the compressor inlet preheater (E-03) and then condensed by the methylpyridine rectification column top condenser (EW-02). A part of the condensed material is refluxed to the methylpyridine rectification column, and the other part is taken out as a high-purity methylpyridine product and sent to the product storage tank; the crude dimethylpyridine components at the bottom of the column are taken out and subjected to other treatments.

[0009] Among them, the crude pyridine raw material comes from medium and low temperature coal tar. Preferably, its water content is less than 0.1 wt%.

[0010] The operating conditions of the falling film evaporator are: the operating pressure is 0.04 - 0.05 MpaG, and the operating temperature is 150 - 170 °C.

[0011] The fractionation column operating conditions of the crude pyridine deweight fractionation column are: the top temperature is 110 - 120 °C, the pressure is 0.001 - 0.005 MPaG, the bottom temperature is 150 - 170 °C, the pressure is 0.02 - 0.03 MpaG, and the top reflux ratio is 0.8 - 1.6. Increasing the reflux ratio can improve the purity of methylpyridine.

[0012] Preferably, the fractionation column is a plate column or a packed column, the number of theoretical plates is 15 - 25, and the feed position is the 8th - 13th theoretical plate from the bottom up.

[0013] The operating conditions of the methylpyridine rectification column are as follows: the top temperature is 120 - 150 °C, the pressure is -0.055 - -0.065 MPaG, the bottom temperature is 140 - 160 °C, the pressure is -0.06 - -0.07 MPaG, and the top reflux ratio is 1.1 - 1.8. Increasing the reflux ratio can improve the purity of methylpyridine. The gas phase at the top of the column is preheated to 125 - 135 °C in a heat exchanger, then adiabatically compressed by a compressor to a temperature of 170 °C, and sent to the bottom reboiler as a heat source, so that the bottom temperature is 140 - 160 °C and the pressure is -0.06 - -0.07 MPaG. After passing through the bottom reboiler, it enters the top preheater, and finally is condensed by a condenser. Part of it is refluxed into the methylpyridine rectification column, and part is directly taken out as a product.

[0014] Preferably, the methylpyridine rectification column is a plate column or a packed column, with 20 - 30 theoretical plates, and the feed position is the 10th - 15th theoretical plate from the bottom up. When the content of methylpyridine in the raw material is low, the product purity can be improved by moving the feed position downward.

[0015] Preferably, the outlet temperature of the compressor is 160 - 170 °C and the pressure is 0.13 - 0.18 MPaG.

[0016] The present invention further provides a device for refining high-purity methylpyridine from crude pyridine, including a crude pyridine deweighting fractionation column, a methylpyridine rectification column, and a methylpyridine product storage tank. The crude pyridine deweighting fractionation column consists of a lower deweighting falling-film evaporator and an upper crude pyridine fractionation column, and the two parts are connected by an external side line. The upper end of the fractionation column is provided with a top condenser EW-01 of the crude pyridine fractionation column, and the lower end is provided with a thermosyphon reboiler E-01 of the crude pyridine fractionation column. The bottom of the fractionation column is connected to the feed end of the methylpyridine rectification column T-02;

[0017] At the top of the methylpyridine rectification column T-02, a compressor inlet preheater E-03 and a compressor C-03 are successively arranged. The compressor C-03 is connected to the bottom reboiler E-02. The high-temperature gas compressed by the compressor C-03 is used as the heat source for the methylpyridine rectification column thermosyphon reboiler E-02. The methylpyridine rectification column thermosyphon reboiler E-02 is successively connected to the compressor inlet preheater E-03 and the methylpyridine rectification column top condenser EW-02. The high-temperature gas from the methylpyridine rectification column thermosyphon reboiler E-02 is condensed by the methylpyridine rectification column top condenser EW-02 after heat exchange through the compressor inlet preheater E-03. Part of it is refluxed into the methylpyridine rectification column T-02, and the other part is taken out as a product to the product storage tank.

[0018] Beneficial effects: The present invention adopts a deweighting and fractionation integrated device, which simplifies the process flow, reduces the floor area of equipment, and lowers the investment cost of the device; the bottom of the device uses a falling film evaporator, which has the advantages of short residence time, high heat transfer efficiency, and small pressure drop, reducing the production and operation cost; the methylpyridine rectification system adopts a heat pump rectification technology. By compressing the gas at the top of the rectification tower, the pressure and condensation temperature of the gas at the top are increased, and it is directly used as the heat source of the reboiler of the rectification tower, making full use of the condensation latent heat of the gas at the top. Compared with the traditional rectification system, the energy consumption is reduced by about 70%, and the operating cost is greatly reduced. At the same time, the present invention adopts the atmospheric and vacuum rectification technology to finally obtain a high-purity methylpyridine product with a purity of not less than 97%. Brief Description of the Drawings

[0019] Figure 1 It is the process flow diagram of a specific implementation scheme of the present invention, where T-01 is the crude pyridine deweighting and fractionation tower, E-01 is the thermosyphon reboiler of the crude pyridine fractionation tower, EW-01 is the overhead condenser of the crude pyridine fractionation tower, T-02 is the methylpyridine rectification tower, E-02 is the thermosyphon reboiler of the methylpyridine rectification tower, E-03 is the preheater at the compressor inlet; EW-02 is the overhead condenser of the methylpyridine rectification tower, P-01 is the bottom transfer pump of the crude pyridine fractionation tower, P-02 is the bottom circulation pump of the methylpyridine rectification tower, and V-01 is the methylpyridine product storage tank. Detailed Embodiments

[0020] The technical solution of the present invention will be elaborated in detail below in conjunction with the drawings and specific embodiments, but the protection scope of the present invention is not limited to the following embodiments.

[0021] As Figure 1 shown, it is the process flow diagram of the implementation scheme of the present application, and the following embodiments are all carried out according to the following process. The device of the embodiment of the present application includes a crude pyridine deweighting and fractionation tower, a methylpyridine rectification tower, and a methylpyridine product storage tank. The crude pyridine deweighting and fractionation tower consists of a lower deweighting falling film evaporator and an upper crude pyridine fractionation tower. The two parts are connected through an external side line. The upper end of the fractionation tower is provided with an overhead condenser EW-01 of the crude pyridine fractionation tower, and the lower end is provided with a thermosyphon reboiler E-01 of the crude pyridine fractionation tower. The bottom of the fractionation tower is connected to the feed end of the methylpyridine rectification tower T-02.

[0022] At the top of the methylpyridine rectification column T-02, a preheater E-03 for the compressor inlet and a compressor C-03 are successively arranged. The compressor C-03 is connected to the reboiler E-02 at the bottom of the column. The high-temperature gas compressed by the compressor C-03 serves as the heat source for the methylpyridine rectification column thermosiphon reboiler E-02. The methylpyridine rectification column thermosiphon reboiler E-02 is successively connected to the compressor inlet preheater E-03 and the methylpyridine rectification column top condenser EW-02. The high-temperature gas from the methylpyridine rectification column thermosiphon reboiler E-02 is condensed by the methylpyridine rectification column top condenser EW-02 after heat exchange through the compressor inlet preheater E-03. Part of it flows back into the methylpyridine rectification column T-02, and the other part is taken out as a product to the product storage tank.

[0023] Example 1

[0024] The crude pyridine raw material is fed into the falling film evaporator at the lower part of the crude pyridine deweight fractionation column. The crude pyridine raw material comes from medium and low temperature coal tar, with a feed flow rate of 5500 kg / h, a pressure of 0.3 MPa, and a temperature of 45°C. The composition of the crude pyridine raw material is: water 0.07%, benzene 18.13%, pyridine 41.5%, o-methylpyridine 3.7%, 2,6-dimethylpyridine 3.6%, m-methylpyridine 9.2%, 2,4-dimethylpyridine 6.8%, 2,3,6-trimethylpyridine 6.2%, aniline 5.7% and other components 5.1%. The light components are sent to the upper crude pyridine fractionation column through the side line.

[0025] The fractionation column at the upper part of the crude pyridine deweight fractionation column is a plate column with a total of 20 theoretical plates. The feed is at the position of the 13th theoretical plate from top to bottom. The operating conditions are a top temperature of 115°C, a pressure of 0.001 - 0.005 MPaG, a bottom temperature of 160°C, a pressure of 0.02 - 0.03 MPaG, and a top reflux ratio of 1.2. The pyridine and o-cresol components at the top of the column are taken out, and the crude methylpyridine components (including m-methylpyridine and p-methylpyridine) at the bottom enter the methylpyridine rectification column.

[0026] The methylpyridine rectification column is a plate column with a total of 25 theoretical plates. The feed is at the position of the 12th theoretical plate from top to bottom. A methylpyridine rectification column thermosiphon reboiler is attached to the bottom of the column. The operating conditions of this column are under negative pressure, with a top temperature of 130°C, a pressure of -0.055 - -0.065 MPaG. The top gas phase is preheated to 125 - 135°C through a heat exchanger, and then adiabatically compressed by a compressor to a temperature of 170°C and sent to the reboiler at the bottom of the column as a heat source, making the bottom temperature 150°C and its pressure -0.06 - -0.07 MPaG. After passing through the reboiler at the bottom of the column, it enters the top preheater and finally is condensed by the condenser. Part of it flows back into the methylpyridine rectification column, and the top reflux ratio is 1.3. Part of it is directly taken out as a product. The operating conditions of the compressor are: an outlet temperature of 160 - 170°C and a pressure of 0.15 MPaG.

[0027] Finally, a high-purity methylpyridine component with a purity of 98.2% (including m-methylpyridine and p-methylpyridine) is obtained at the top of the tower and drawn into the product storage tank. The recovery rate of methylpyridine is about 98.2%. The crude dimethylpyridine component at the bottom of the tower is drawn out for other treatments.

[0028] The methylpyridine rectification system adopts the heat pump rectification technology. By compressing the gas at the top of the rectification tower, the pressure and condensation temperature of the gas at the top of the tower are increased, which is directly used as the heat source of the reboiler of the rectification tower. The condensation latent heat of the gas at the top of the tower is fully utilized. Compared with the traditional rectification system, the energy consumption is reduced by about 70%. As shown in Table 1, the operating cost is significantly reduced.

[0029] Table 1 Comparison of energy consumption indicators

[0030] Traditional distillation Heat pump distillation Heat source 0.5 MPa steam Electricity Heat source consumption ( / h) 0.5t 45 kW Energy conversion value (kg standard oil) 33 9.9 Energy saving rate (%) 70

[0031] Note: The compressor efficiency is calculated at 80%, and the energy conversion value is calculated in accordance with GB / T 50441-2016 "Calculation Standard for Energy Consumption in Petrochemical Design".

[0032] Example 2

[0033] Replace the heavy component fractionation tower of crude pyridine in this process system with two devices, namely a kettle evaporator and a rectification tower. The feeding conditions are the same as those in Example 1, and the heat load of the evaporator is kept consistent with that of the falling film evaporator. The top pressure of the rectification tower is 0.001 - 0.005 MPaG, the bottom pressure is 0.02 - 0.03 MPaG, and the top reflux ratio is 1.2; the pyridine and o-cresol components at the top of the tower are drawn out, and the crude methylpyridine component (including m-methylpyridine and p-methylpyridine) at the bottom of the tower enters the methylpyridine rectification tower;

[0034] The methylpyridine rectification tower is a plate tower. Both the equipment conditions and operating conditions are kept consistent with those in Example 1. A high-purity methylpyridine component with a purity of 97.3% (including m-methylpyridine and p-methylpyridine) is obtained at the top of the tower and drawn into the product storage tank. The recovery rate of methylpyridine is about 96.5%. The crude dimethylpyridine component at the bottom of the tower is drawn out for other treatments.

[0035] Example 3

[0036] Feed the crude pyridine raw material into the falling film evaporator at the lower part of the heavy component fractionation tower of crude pyridine. The feeding flow rate is 5500 kg / h, the pressure is 0.3 MPa, and the temperature is 45°C. The composition of the crude pyridine raw material is: water 0.04%, benzene 17.56%, pyridine 40.9%, o-methylpyridine 3.7%, 2,6-dimethylpyridine 3.6%, m-methylpyridine 10.3%, 2,4-dimethylpyridine 6.8%, 2,3,6-trimethylpyridine 6.3%, aniline 5.7% and other components 5.1%. The light components are sent to the upper crude pyridine fractionation tower through the side line.

[0037] The crude pyridine fractionation tower is of tray type, with a total of 20 theoretical plates. The feed is introduced at the position of the 8th theoretical plate counted from the top downwards. The operating conditions are: the top temperature is 110 - 120 °C, the pressure is 0.001 - 0.005 MPaG, the bottom temperature is 150 - 170 °C, the pressure is 0.02 - 0.03 MPaG, and the top reflux ratio is 1.2; the pyridine and o-cresol components at the top are drawn off, and the crude methylpyridine component at the bottom enters the methylpyridine rectification tower.

[0038] The methylpyridine rectification tower is a plate column, with a total of 25 theoretical plates. The feed is introduced at the position of the 12th theoretical plate counted from the top downwards. There is a thermosyphon reboiler attached to the bottom of the tower. The operating conditions of this tower are under negative pressure. The top temperature is 130 °C, the pressure is -0.055 - -0.065 MPaG. The top gas phase is preheated to 125 - 135 °C by a heat exchanger, and then adiabatically compressed by a compressor to a temperature of 170 °C and sent to the bottom reboiler as a heat source. The bottom temperature is 150 °C, the pressure is -0.06 - -0.07 MPaG. After passing through the bottom reboiler, it enters the top preheater and finally is condensed by a condenser. Part of it is refluxed into the methylpyridine rectification tower, and the top reflux ratio is 1.2; high-purity methylpyridine component with a purity of 98.32% is obtained at the top and drawn off to the product storage tank. The methylpyridine recovery rate is about 98.4%. The crude dimethylpyridine component at the bottom is drawn off for other treatments.

[0039] Example 4

[0040] The crude pyridine raw material is fed into the lower falling film evaporator of the crude pyridine deheavy fractionation tower. The feed flow rate is 5500 kg / h, the pressure is 0.3 MPa, and the temperature is 45 °C. The crude pyridine raw material is the same as that in Example 3. The light components are sent to the upper crude pyridine fractionation tower through the side line.

[0041] The crude pyridine fractionation tower is of tray type or packed tower, with a total of 20 theoretical plates. The feed is introduced at the position of the 8th theoretical plate counted from the top downwards. The operating conditions are: the top temperature is 115 °C, the pressure is 0.001 - 0.005 MPaG, the bottom temperature is 165 °C, the pressure is 0.02 - 0.03 MPaG, and the top reflux ratio is 1.3; the pyridine and o-cresol components at the top are drawn off, and the crude methylpyridine component at the bottom enters the methylpyridine rectification tower.

[0042] The methylpyridine rectification column is a tray column or a packed column, with a total of 25 theoretical plates. The feed is introduced at the position of the 12th theoretical plate from top to bottom. A thermosyphon reboiler is attached to the bottom of the column. The operating conditions of this column are under negative pressure, with a top temperature of 140 °C, a pressure of -0.055 to -0.065 MPaG. The top gas phase is preheated to 125 - 135 °C by a heat exchanger, then adiabatically compressed by a compressor to a temperature of 170 °C and sent to the bottom reboiler as a heat source. The bottom temperature is 150 °C, and the pressure is -0.06 to -0.07 MPaG. After passing through the bottom reboiler, it enters the top preheater and is finally condensed by a condenser, with part of it refluxed into the methylpyridine rectification column. The top reflux ratio is 1.3. A high-purity methylpyridine component with a purity of 98.41% is obtained at the top and withdrawn to the product storage tank. The methylpyridine recovery rate is approximately 98.4%. The crude dimethylpyridine component at the bottom is withdrawn for other treatments.

[0043] Example 5

[0044] The crude pyridine raw material is fed into the falling film evaporator at the lower part of the crude pyridine de-heavy fractionation column. The feed flow rate is 5500 kg / h, the pressure is 0.3 MPa, and the temperature is 45 °C. The composition of the crude pyridine raw material is: water 6.2%, benzene 15.5%, pyridine 38.9%, o-methylpyridine 3.7%, 2,6-dimethylpyridine 3.6%, m-methylpyridine 8.2%, 2,4-dimethylpyridine 6.8%, 2,3,6-trimethylpyridine 6.2%, aniline 5.7%, and other components 5.2%. The light components are sent to the upper crude pyridine fractionation column through the side line.

[0045] The crude pyridine fractionation column is a tray column or a packed column, with a total of 20 theoretical plates. The feed is introduced at the position of the 6th theoretical plate from top to bottom. The operating conditions are a top temperature of 115 °C, a pressure of 0.001 - 0.005 MPaG, a bottom temperature of 165 °C, and a pressure of 0.02 - 0.03 MPaG. The top reflux ratio is 1.3. The pyridine and o-cresol components are withdrawn from the top, and the crude methylpyridine component at the bottom enters the methylpyridine rectification column.

[0046] The methylpyridine rectification column is a tray column or a packed column, with a total of 25 theoretical plates. The feed is introduced at the position of the 12th theoretical plate from top to bottom. A thermosyphon reboiler is attached to the bottom of the column. The operating conditions of this column are under negative pressure, with a top temperature of 140 °C, a pressure of -0.055 to -0.065 MPaG. The top gas phase is preheated to 125 - 135 °C by a heat exchanger, then adiabatically compressed by a compressor to a temperature of 170 °C and sent to the bottom reboiler as a heat source. The bottom temperature is 150 °C, and the pressure is -0.06 to -0.07 MPaG. After passing through the bottom reboiler, it enters the top preheater and is finally condensed by a condenser, with part of it refluxed into the methylpyridine rectification column. The top reflux ratio is 1.4. A high-purity methylpyridine component with a purity of 98.31% is obtained at the top and withdrawn to the product storage tank. The methylpyridine recovery rate is approximately 98.2%. The crude dimethylpyridine component at the bottom is withdrawn for other treatments.

[0047] By comparing Example 1 and Example 2, it can be found that under the same heat load, the heat transfer efficiency of the integrated device for heavy component removal and crude pyridine rectification is higher, and the product purity and recovery rate obtained are also higher. By comparing Example 1, Example 3, Example 4 and Example 5, it can be found that the method of the present invention has a certain operating flexibility for the crude pyridine raw material, and the separation and purification effect can be adjusted by changing the operating conditions (reflux ratio, feed position, operating temperature, etc.). By appropriately increasing the reflux ratio, raising the operating temperature, and changing the side-line feed position of the integrated device for heavy component removal and fractionation, the product purity and recovery rate can be improved to a certain extent.

[0048] The above is the description of a technical method and device for refining high-purity methylpyridine products from crude pyridine provided by the present invention. For professionals in this industry, according to the idea of the embodiments of the present invention, there will be changes or improvements in the specific implementation manner and application scope. Therefore, the content of this specification should not be regarded as a limitation to the present invention.

Claims

1. A method for refining high-purity methylpyridine from crude pyridine, characterized in that, The steps are as follows: (1) Introduce the crude pyridine raw material into the crude pyridine heavy component removal fractionating column (T-01). The crude pyridine heavy component removal fractionating column (T-01) consists of a lower heavy component removal falling film evaporator and an upper crude pyridine fractionating column. The crude pyridine raw material first enters the lower falling film evaporator, and the heavy components are discharged from the bottom of the device. The light components are taken out from the side line of the falling film evaporator and sent to the upper fractionating column. The gas-phase pyridine and o-cresol mixed components at the top of the fractionating column are condensed by a condenser (EW01), and a part of the condensed components is taken out, and the other part is refluxed. A part of the crude pyridine components at the bottom of the column is refluxed after being reboiled by the crude pyridine fractionating column thermosyphon reboiler (E-01), and the other part is sent to the methylpyridine rectifying column (T-02); (2) The methylpyridine rectifying system adopts heat pump rectification technology. In the methylpyridine rectifying column (T-02), the gas-phase methylpyridine at the top of the column is preheated by the compressor inlet preheater (E-03) and then pressurized and heated by a compressor (C-03). The heated material is introduced into the bottom reboiler (E-02) as the heat source of the bottom reboiler (E-02). The methylpyridine discharged from the methylpyridine rectifying column thermosyphon reboiler (E-02) is first heated by the compressor inlet preheater (E-03) and then condensed by the methylpyridine rectifying column top condenser (EW-02). A part of the condensed material is refluxed to the methylpyridine rectifying column, and the other part is taken out as a high-purity methylpyridine product and sent to the product storage tank. The crude 2,6-lutidine components at the bottom of the column are taken out and subjected to other treatments after being taken out; 2. The method according to claim 1, characterized in that The crude pyridine raw material comes from medium and low-temperature coal tar, and its water content is less than 0.1 wt%.

3. The method according to claim 1, wherein The operating conditions of the falling film evaporator are: the operating pressure is 0.04~0.05 MpaG, and the operating temperature is 150~170°C.

4. The method according to claim 1, wherein The fractionating column operating conditions of the crude pyridine heavy component removal fractionating column are: the top temperature is 110 - 120°C, the pressure is 0.001~0.005 MPaG, the bottom temperature is 150 - 170°C, the pressure is 0.02~0.03 MpaG, and the top reflux ratio is 0.8~1.

6.

5. The method according to claim 1, characterized in that The fractionating column is a plate column or a packed column, the number of theoretical plates is 15~25, and the feed position is the 8th to 13th theoretical plate from the bottom up.

6. The method according to claim 2, wherein The operating conditions of the methylpyridine rectifying column are: the top temperature is 120~150°C, the pressure is -0.055~-0.065 MPaG, the bottom temperature is 140 - 160°C, the pressure is -0.06~-0.07 MPaG, and the top reflux ratio is 1.1~1.

8.

7. The method according to claim 2, characterized in that, The methylpyridine rectifying column is a plate column or a packed column, the number of theoretical plates is 20~30, and the feed position is the 10th to 15th theoretical plate from the bottom up.

8. The method according to claim 1, characterized in that The outlet temperature of the compressor (C-03) is 160 - 170°C, and the pressure is 0.13 - 0.18 MPaG.

9. An apparatus for refining high-purity methylpyridine from crude pyridine, characterized in that, It includes a heavy pyridine removal fractionation column, a methylpyridine rectification column and a methylpyridine product storage tank. The heavy pyridine removal fractionation column consists of a lower heavy pyridine removal falling film evaporator and an upper heavy pyridine fractionation column. The two parts are connected through an external side line. At the upper end of the fractionation column, a top condenser (EW-01) of the heavy pyridine fractionation column is provided, and at the lower end, a thermosyphon reboiler (E-01) of the heavy pyridine fractionation column is provided. The bottom of the fractionation column is connected to the feed end of the methylpyridine rectification column (T-02). At the top of the methylpyridine rectification column (T-02), a compressor inlet preheater (E-03) and a compressor (C-03) are successively arranged. The compressor (C-03) is connected to the reboiler (E-02) at the bottom of the column. The high-temperature gas compressed by the compressor (C-03) serves as the heat source for the methylpyridine rectification column thermosyphon reboiler (E-02). The methylpyridine rectification column thermosyphon reboiler (E-02) is successively connected to the compressor inlet preheater (E-03) and the top condenser (EW-02) of the methylpyridine rectification column. The high-temperature gas from the methylpyridine rectification column thermosyphon reboiler (E-02) is condensed by the top condenser (EW-02) of the methylpyridine rectification column after heat exchange through the compressor inlet preheater (E-03). Part of it flows back into the methylpyridine rectification column (T-02), and the other part is taken out as a product to the product storage tank.

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