Device for separating and purifying isocyanate and production method thereof

Abstract

The invention relates to a device for separating and purifying isocyanate and a production method thereof.The device comprises a phosgene removal tower and a desolventizing tower, a tower kettle of the phosgene removal tower is communicated with the desolventizing tower, and a side line of the desolventizing tower is communicated with the phosgene removal tower; a phosgene removal tower primary condenser and a phosgene removal tower secondary condenser which are connected in sequence are arranged at the top of the phosgene removal tower, and the phosgene removal tower primary condenser is circularly communicated with the top of the phosgene removal tower; a phosgene removal tower and a desolventizing tower form a coupling system, namely materials in a tower kettle of the phosgene removal tower directly enter the desolventizing tower for solvent removal, gas-phase materials extracted from a side line of the desolventizing tower flow back to the tower kettle of the phosgene removal tower, and a secondary condenser is additionally arranged at the top of the phosgene removal tower; compared with the traditional process, the whole coupling system has the advantages that the number of reboilers at the bottom of the phosgene removal tower is reduced, the thermal load of the whole system is reduced, and 10-30% of energy consumption is saved; the device is simple in structure and scientific in principle, and has the remarkable advantages of energy conservation, low energy consumption and high efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical recycling, and particularly relates to a device for separating and purifying isocyanates and a production method thereof. Background Art

[0002] Toluene diisocyanate (TDI) is an important isocyanate compound. Since its first preparation in the early 20th century, it has rapidly become one of the key raw materials in the chemical industry. First developed by German chemists in the 1930s, with the rise of the polyurethane industry, TDI has become a key raw material for producing polyurethane foams, elastomers, coatings, etc. due to its excellent reactivity and wide application fields. With technological progress, significant progress has been made in improving catalysts and optimizing process conditions in the TDI production process, and the reaction efficiency and selectivity have been enhanced. However, the high energy consumption problem remains a major challenge restricting TDI production. Therefore, researching and designing new energy-saving methods to reduce energy consumption and improve the greenness and economy of the process have become the core objectives of current production process optimization.

[0003] The traditional phosgenation method is still the mainstream process for TDI preparation and is widely used in industrial production. This process generates TDI from phosgene and toluene diamine, with high production efficiency and a wide application basis. However, the phosgenation method also faces problems such as high energy consumption, large solvent usage, and difficult waste treatment, resulting in high energy consumption. Therefore, to achieve green and efficient TDI preparation, it is urgent to optimize the process based on the phosgenation method and explore new solutions to reduce energy consumption, reduce waste, and improve resource utilization efficiency. Summary of the Invention

[0004] To solve the above problems, the present invention provides a device for separating and purifying isocyanates and a production method thereof, aiming to optimize the process flow and improve energy efficiency.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A device for separating and purifying isocyanates includes a phosgene removal tower for introducing the phosgenation reaction material of isocyanates and a stripping tower for receiving the phosgene, solvent, and isocyanates produced in the phosgene removal tower. The bottom of the phosgene removal tower is connected to the stripping tower, and the side line of the stripping tower is connected to the phosgene removal tower. The top of the phosgene removal tower is provided with a phosgene removal tower primary condenser and a phosgene removal tower secondary condenser connected in sequence, and the phosgene removal tower secondary condenser is connected in a cycle with the top of the phosgene removal tower.

[0007] Preferably, a separator is provided on the connecting pipeline between the phosgene removal tower secondary condenser and the phosgene removal tower, and the phosgene removal tower primary condenser is connected to the separator.

[0008] Preferably, a stripping column condenser is provided at the top of the stripping column, and a stripping column reboiler is provided at the bottom of the stripping column. The stripping column condenser and the stripping column reboiler are both connected to the stripping column in a circulating manner.

[0009] Preferably, the phosgene removal column and the stripping column, the phosgene removal column condenser and the phosgene removal column, the stripping column and the stripping column condenser, and the stripping column and the stripping column reboiler are all connected by pipelines.

[0010] Preferably, the solvent includes one or more of benzene, toluene, xylene, chlorobenzene, and orthodichlorobenzene.

[0011] A method for separating and purifying isocyanate, characterized in that the operating pressure in the phosgene removal column is controlled at 3 bara, and the temperature is controlled at 170 - 180 °C. The phosgene removal column condenser condenses the rising steam to 40 °C. Part of the condensate is refluxed into the phosgene removal column, and the rest is used as an absorbent for the phosgene recovery system. The isocyanate solution after phosgene removal obtained at the bottom of the column directly enters the stripping column. The weight percentage concentration of the solvent in the condensate is 9 - 10%.

[0012] Preferably, the operating pressure in the phosgene removal column is controlled at 3 bara, and the temperature is controlled at 170 - 180 °C. The phosgene removal column condenser condenses the rising steam to 40 °C. Part of the condensate is refluxed into the phosgene removal column, and the rest is used as an absorbent for the phosgene recovery system. The isocyanate solution after phosgene removal obtained at the bottom of the column directly enters the stripping column. The weight percentage concentration of the solvent in the condensate is 9 - 10%.

[0013] Preferably, the operating pressure and temperature of the stripping column are the same as those of the phosgene removal column.

[0014] The present invention has achieved the following technical effects compared with the prior art:

[0015] Compared with the prior art, the phosgene removal column and the stripping column in the present invention form a coupled system, that is, the bottom material of the phosgene removal column directly enters the stripping column for solvent removal. The gas-phase material drawn from the side line of the stripping column is refluxed to the bottom of the phosgene removal column, and a secondary condensation is added to the top of the phosgene removal column; compared with the traditional process, the entire coupled system reduces the reboiler at the bottom of the phosgene removal column, reduces the heat load of the entire system, and saves 10 - 30% of the energy consumption; its device structure is simple, the principle is scientific, and it has the significant advantages of energy saving, low energy consumption, and high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] To more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0017] Attached Figure 1 is a schematic structural diagram of the present invention;

[0018] Among them, 1. Phosgene removal tower; 2. Primary condenser of phosgene removal tower; 3. Secondary condenser of phosgene removal tower; 4. Separator; 5. Desolventizing tower; 6. Condenser of desolventizing tower; 7. Reboiler of desolventizing tower. Specific embodiments

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0020] To solve the above problems, the present invention provides a device and a production method for separating and purifying isocyanate, aiming to optimize the process flow and improve energy efficiency.

[0021] To make the above objects, features and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

[0022] Refer to Figure 1 , a device for separating and purifying isocyanate, including a phosgene removal tower for introducing the phosgene reaction material of isocyanate and a desolventizing tower for receiving the phosgene, solvent and isocyanate produced in the phosgene removal tower. The bottom of the phosgene removal tower is connected to the desolventizing tower, and the side line of the desolventizing tower is connected to the phosgene removal tower. The top of the phosgene removal tower is provided with a primary condenser of the phosgene removal tower and a secondary condenser of the phosgene removal tower connected in sequence, and the secondary condenser of the phosgene removal tower is connected to the top of the phosgene removal tower in a circulating manner; in the present invention, the phosgene removal tower and the desolventizing tower form a coupling system, that is, the material at the bottom of the phosgene removal tower directly enters the desolventizing tower for solvent removal, the gas-phase material is taken out from the side line of the desolventizing tower and refluxed to the bottom of the phosgene removal tower, and a secondary condensation is added to the top of the phosgene removal tower; compared with the traditional process, the entire coupling system reduces the reboiler at the bottom of the phosgene removal tower, reduces the heat load of the entire system, and saves 10-30% of the energy consumption; its device structure is simple, the principle is scientific, and it has the significant advantages of energy saving, low energy consumption and high efficiency.

[0023] Reference Figure 1 A separator is provided on the connecting pipeline between the secondary condenser of the phosgene removal tower and the phosgene removal tower, and the primary condenser of the phosgene removal tower is connected to the separator.

[0024] Reference Figure 1 A condenser for the stripping tower is provided at the top of the stripping tower, and a reboiler for the stripping tower is provided at the bottom of the stripping tower. The condenser for the stripping tower and the reboiler for the stripping tower are both connected to the stripping tower in a circulating manner.

[0025] Reference Figure 1 The phosgene removal tower and the stripping tower, between the condenser of the phosgene removal tower and the phosgene removal tower, between the stripping tower and the condenser of the stripping tower, and between the stripping tower and the reboiler of the stripping tower are all connected by pipelines.

[0026] Further, the solvent includes one or more of benzene, toluene, xylene, chlorobenzene, and ortho-dichlorobenzene.

[0027] The following uses two examples to illustrate the method for separating and purifying TDI:

[0028] Example 1

[0029] (1) Phosgene removal: Continuously introduce the TDI solution containing phosgene into the phosgene removal tower, where the TDI concentration is 15.7%, the phosgene concentration is 41.3%, the solvent concentration is 42.96%, and the operating pressure is 3 bara; the gas phase at the top of the tower enters the primary condenser of the phosgene removal tower. The condensation temperature is 90 °C. The gas phase extracted from the primary condenser of the phosgene removal tower enters the secondary condenser of the phosgene removal tower to further condense the steam to 40 °C. Part of the condensate is refluxed into the phosgene removal tower, and the rest is used as an absorbent for the phosgene recovery system. The weight percentage concentration of the solvent in the condensate is 9.5%; the TDI solution after phosgene removal is obtained at the bottom of the tower. The solvent content in the TDI solution is 69.3% (mass content), and the TDI content is 27.8% (mass content);

[0030] (2) Stripping: Directly introduce the TDI solution after phosgene removal into the stripping tower. The operating pressure is the same as that of the phosgene removal tower, both being 3 bara, and the temperature is controlled at 170 - 180 °C; the gas phase at the top of the stripping tower enters the condenser of the stripping tower. The condensation temperature is 108 °C. The stripped solvent enters the solvent refining tower to further remove impurities. The gas-phase material extracted from the side line is refluxed to the bottom of the phosgene removal tower. The TDI solution separated at the bottom of the tower enters the next process. The weight percentage concentration of TDI in the solvent at the top of the solvent stripping tower is 9.5 ppm; the weight percentage concentration of TDI in the remaining TDI solution is 60%.

[0031] Example 2

[0032] (1) Phosgene removal: Continuously introduce the TDI solution containing phosgene into the phosgene removal tower. Among them, the TDI concentration is 15%, the phosgene concentration is 42.54%, the solvent concentration is 43.75%, and the operating pressure is 2.8 bara; the gas phase at the top of the tower enters the first condenser of the phosgene removal tower. The condensation temperature is 93 °C. The gas phase extracted from the first condenser of the phosgene removal tower enters the second condenser of the phosgene removal tower to further condense the steam to 38.57 °C. Part of the condensate is refluxed into the phosgene removal tower, and the rest is used as an absorbent for the phosgene recovery system. The weight percentage concentration of the solvent in the condensate is 10%; the TDI solution after phosgene removal is obtained at the bottom of the tower. The solvent content in the TDI solution is 68.5% (mass content), and the TDI content is 28.5% (mass content);

[0033] (2) Solvent removal: Directly introduce the TDI solution after phosgene removal into the solvent removal tower. The operating pressure is the same as that of the phosgene removal tower, both being 2.8 bara, and the temperature is controlled at 170 - 180 °C; the gas phase at the top of the solvent removal tower enters the condenser 6 of the solvent removal tower. The condensation temperature is 100 °C. The removed solvent enters the solvent refining tower to further remove impurities. The gas-phase material extracted from the side line is refluxed to the bottom of the phosgene removal tower. The TDI solution separated at the bottom of the tower enters the next process. The weight percentage concentration of TDI in the solvent at the top of the solvent removal tower is 9 ppm; the weight percentage concentration of TDI in the remaining TDI solution is 65%.

[0034] Adaptations made according to actual needs are all within the protection scope of the present invention.

[0035] It should be noted that for those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the invention. Any reference signs in the claims should not be regarded as limiting the claimed rights.

Claims

1. A device for separating and purifying isocyanate, characterized in that: It comprises a phosgene removal tower for introducing isocyanate photochemical reaction materials and a desolventizing tower for receiving phosgene, solvent and isocyanate produced in the phosgene removal tower, the bottom of the phosgene removal tower is connected to the desolventizing tower, the side line of the desolventizing tower is connected to the phosgene removal tower, the top of the phosgene removal tower is provided with a first-stage condenser of the phosgene removal tower and a second-stage condenser of the phosgene removal tower which are connected in sequence, and the earphone condenser of the phosgene removal tower is cyclically connected to the top of the phosgene removal tower.

2. The device for separating and purifying isocyanate according to claim 1, characterized in that: A separator is provided on the connecting pipeline between the secondary condenser of the phosgene removal tower and the phosgene removal tower, and the primary condenser of the phosgene removal tower is connected to the separator.

3. The device for separating and purifying isocyanate according to claim 2, characterized in that: A desolventizing tower condenser is arranged at the top of the desolventizing tower, and a desolventizing tower reboiler is arranged at the bottom of the desolventizing tower. Both the desolventizing tower condenser and the desolventizing tower reboiler are cyclically connected to the desolventizing tower.

4. The device for separating and purifying isocyanate according to claim 3, characterized in that: The phosgene removal tower and the desolventizing tower, the phosgene removal tower condenser and the phosgene removal tower, the desolventizing tower and the desolventizing tower condenser, and the desolventizing tower and the desolventizing tower reboiler are all connected by pipelines.

5. The device for separating and purifying isocyanate according to claim 1, characterized in that: The solvent includes one or more of benzene, toluene, xylene, chlorobenzene and o-dichlorobenzene.

6. A method for separating and purifying isocyanate, characterized in that: The device for separating and purifying isocyanate according to any one of claims 1 to 5 comprises the following steps: The isocyanate solution containing phosgene is continuously passed into the phosgene removal tower, and the rising steam at the top of the tower enters the primary condenser and the secondary condenser of the phosgene removal tower in turn for condensation; part of the condensate is refluxed into the phosgene removal tower, and the rest is used as an absorbent in the phosgene recovery system, and the isocyanate solution obtained in the bottom of the tower after the phosgene is removed directly enters the desolventizing tower; The desolventizing tower removes the solvent from the isocyanate solution after the phosgene is removed. The removed solvent enters the solvent refining tower to further remove impurities. The gaseous material taken out from the side line flows back to the phosgene removal tower kettle, and the isocyanate solution is separated in the kettle and enters the next process.

7. A method for separating and purifying isocyanate according to claim 6, characterized in that: The operating pressure in the phosgene removal tower is controlled at 3 bara, and the temperature is controlled at 170-180°C. The condenser of the phosgene removal tower condenses the rising steam to 40°C. Part of the condensate is refluxed into the phosgene removal tower, and the rest is used as an absorbent in the phosgene recovery system. The isocyanate solution from which the phosgene is removed in the bottom of the tower directly enters the desolventizing tower, and the weight percentage concentration of the solvent in the condensate is 9-10%.

8. The method for separating and purifying isocyanate according to claim 7, characterized in that: The operating pressure and temperature of the desolventizing tower are consistent with those of the phosgene removing tower.

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