A waste heat recovery device and process for the production of long-chain nylon resin

Abstract

This invention provides a waste heat utilization device and process for the production of long-chain nylon resin. The waste heat utilization device includes a polymerization reactor, an evaporator, a steam manifold, and a hot water circulation system. The hot water circulation system includes a hot water storage tank and a hot water circulation pump. The polymerization reactor is connected to the inlet of the hot water storage tank via an exhaust pipe to the hot water storage tank and to the inlet of the evaporator via an exhaust pipe to the evaporator. The outlet of the evaporator is connected to the steam manifold via an inlet pipe. The steam manifold is connected to the steam user end via a steam pipeline to the steam network. The outlet of the hot water storage tank is connected to the hot water user end via the hot water circulation pump and a hot water pipeline. This invention uses the steam discharged during the polymerization process as a heat medium to heat deionized water to obtain saturated steam and hot water, which are then supplied to the factory's steam and hot water users. This fully utilizes the waste heat from the polymerization process, reduces the factory's steam consumption, and lowers production energy consumption.

Description

Technical Field

[0001] This invention relates to a device and process for utilizing waste heat during the production of long-chain nylon resin, belonging to the field of polymer material preparation and production applications. Background Technology

[0002] Long-chain nylons typically refer to nylons where the methylene groups in the chain segment have a length of 10 or more carbons, including nylon 11, nylon 12, nylon 1010, and nylon 1012. Looking at the chain structure of long-chain nylon resins, the methylene groups in the macromolecular chain are longer, and the amide group density is lower. Therefore, in addition to possessing most of the general properties of ordinary nylons, such as lubricity, wear resistance, pressure resistance, and ease of processing, long-chain nylons also possess characteristics not found in conventional nylon 6 and nylon 66, such as high toughness and flexibility, low water absorption, and good dimensional stability.

[0003] The main domestic long-chain nylon products are Nylon 1010 and Nylon 1012. Their production process generally employs batch polymerization, where long-chain diacids and diamines are added to a reactor, followed by the addition of an equivalent amount of deionized water to form a homogeneous solution. This improves mass and heat transfer during polymerization. As polymerization proceeds, the deionized water in the polymerization system evaporates into steam and is discharged from the reactor or released directly into the atmosphere as exhaust gas. This high-temperature steam carries away a significant amount of heat, resulting in energy waste. Therefore, it is necessary to utilize this energy.

[0004] In the continuous polymerization of nylon 66, the secondary steam generated by the reactor evaporation becomes the heat source for heating the second evaporator. The steam tail after heating the second evaporator is sent to the intermediate heat exchanger to keep the brine warm.

[0005] The steam generated by the first and second evaporators is sent to the salt preheater to preheat the 50% concentration raw material, raising the salt solution temperature from 45°C to 93°C. This method recovers and reuses the steam generated during polymerization, significantly reducing energy consumption and being highly environmentally friendly. (Ding Jianlong, “Analysis of Heat Consumption in Continuous Polymerization of Nylon 66,” *Synthetic Fiber Industry*, 2006, Vol. 29 (No. 3), pp. 54-56)

[0006] Chinese patent CN114147030A discloses a system for recovering and utilizing direct exhaust steam from a continuous nylon 66 polymerization reactor. This system converts superheated steam discharged from the continuous nylon 66 polymerization reactor into saturated steam, which is then supplied to the nylon 66 continuous polymerization concentration tank. However, this method of recovering steam from continuous nylon 66 polymerization is not suitable for batch nylon production processes. During batch nylon production, the amount and temperature of steam discharged are not constant and vary with the reaction progress.

[0007] Utility model patent CN217511845U discloses a device for recovering and utilizing waste heat in the production process of semi-aromatic polyamide. The steam generated during the semi-aromatic polyamide production process is directly introduced into the salt-forming kettle, or the liquid material in the kettle is heated via a heat exchanger. This allows the exhaust waste heat from the polymerization process to be used for heating the nylon salt formation process, promoting the salt-forming reaction and raising the temperature of the salt solution. Since the heat required for the salt-forming process is relatively small, only a portion of the heat from the steam discharged during polymerization is utilized for salt-forming heating. The heat required to heat the salt solution in a single kettle accounts for only 30-40% of the heat from the steam discharged during the polymerization reaction in a single kettle, leaving a significant amount of waste heat. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a waste heat utilization device and process for the production of long-chain nylon resin. This invention uses the steam discharged during polymerization as a heat medium to heat deionized water to obtain saturated steam and hot water, which are then supplied to the factory's steam and hot water users. This fully utilizes the waste heat from the polymerization process, reduces the factory's steam consumption, and lowers production energy consumption.

[0009] To achieve the above technical objectives, the technical solution adopted in the embodiments of the present invention is as follows:

[0010] In a first aspect, embodiments of the present invention provide a waste heat utilization device in the production process of long-chain nylon resin, comprising a polymerization reactor, an evaporator, a steam manifold, and a hot water circulation system. The hot water circulation system includes a hot water storage tank and a hot water circulation pump. The polymerization reactor is connected to the inlet end of the hot water storage tank via an exhaust pipe to the hot water storage tank and to the inlet end of the evaporator via an exhaust pipe to the evaporator. The outlet end of the evaporator is connected to the steam manifold via an air inlet pipe. The steam manifold is connected to the steam user end via a steam pipeline to the steam network. The outlet end of the hot water storage tank is connected to the hot water user end via the hot water circulation pump and the hot water pipeline.

[0011] Furthermore, the polymerization reactor is a vertical reactor equipped with a jacket, coils, and a stirring device, and a steam pressure regulating valve is installed on the exhaust pipe to the evaporator between the polymerization reactor and the evaporator.

[0012] Furthermore, the evaporator is a vertical cylindrical container with an internal coil. The evaporator is equipped with a level gauge and a water inlet pipe, and the water inlet pipe is equipped with a regulating valve.

[0013] Furthermore, the steam tank is a horizontal cylindrical container equipped with a supplementary steam pipe.

[0014] Furthermore, the hot water circulation system includes one or more hot water storage tanks and a hot water circulation pump, wherein the hot water storage tank is equipped with a coil, a hot water storage tank condensate pipe and a hot water return pipe.

[0015] Secondly, considering the characteristics of high steam pressure during the constant-pressure exhaust stage and the early stage of pressure-reducing exhaust in the polymerization reaction, and low steam pressure during the later stage of pressure-reducing exhaust in the polymerization reaction, this embodiment of the invention provides a waste heat utilization process in the production of long-chain nylon resin, including the following steps:

[0016] Step S1: Add the long-chain nylon salt obtained from long-chain diamine, long-chain dicarboxylic acid and deionized water into the polymerization reactor. Pass high-temperature heat transfer oil into the jacket and coil of the polymerization reactor to heat the long-chain nylon salt solution in the polymerization reactor. After reaching the set pressure, discharge steam to maintain a constant pressure in the polymerization reactor.

[0017] Step S2: When the polymerization process enters the constant pressure exhaust stage, the steam discharged from the polymerization reactor is introduced into the coil of the evaporator to heat the deionized water in the evaporator and generate saturated steam at a certain pressure.

[0018] Step S3: When the polymerization process enters the depressurization and steam exhaust stage, the steam discharged from the polymerization reactor continues to be fed into the evaporator to heat the deionized water in the evaporator and generate saturated steam at a certain pressure.

[0019] Step S4: During the pressure reduction and steam discharge stage, when the pressure of the polymerization reactor drops to the set pressure, the steam discharged from the polymerization reactor is introduced into the hot water storage tank to heat the hot water entering the hot water storage tank through the hot water return pipe. The hot water with a temperature of 80-95℃ is supplied to hot water users through the hot water circulation pump.

[0020] Step S5: The saturated steam generated in the evaporator is fed into a steam tank, and the steam in the steam tank is fed into the steam pipeline network to supply steam users.

[0021] Furthermore, the pressure set in step S1 is 1.0-2.0 MPa.

[0022] Furthermore, the pressure of the saturated water vapor in steps S2 and S3 is 0.3-0.5 MPa.

[0023] Furthermore, the pressure set in step S4 is 0.8-0.9 MPa.

[0024] Furthermore, the pressure of the steam tank in step S5 is 0.3-0.5 MPa, and the steam tank is equipped with a pressure regulation and control system. When the pressure of the steam tank is lower than 0.3 MPa, steam from other sources is introduced through the supplementary steam pipeline to maintain the pressure inside the steam tank.

[0025] Compared with the prior art, the technical solution of the embodiments of the present invention has the following beneficial effects:

[0026] The waste heat recovery process of this invention fully utilizes the steam discharged during the polymerization process as a heat transfer medium to recover heat, based on the different stages of the exhaust steam during the intermittent production of long-chain nylon. During the constant-pressure exhaust stage and the early stage of the pressure-reducing exhaust, the steam pressure is relatively high and used to generate saturated steam. In the later stage of the pressure-reducing exhaust, the steam pressure is relatively low and used to generate hot water. This invention can effectively reduce steam consumption in the plant, achieving emission reduction to a certain extent, and has positive significance for my country's goal of achieving carbon peaking and carbon neutrality. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the waste heat utilization device in the production process of long carbon chain nylon resin according to the present invention.

[0028] Explanation of reference numerals in the attached diagram: 1-Polymerization reactor; 2-Evaporator; 3-Steam manifold; 4-Hot water storage tank; 5-Hot water circulation pump; 6-Evaporator exhaust pipe; 7-Evaporator condensate pipe; 8-Water inlet pipe; 9-Air inlet pipe; 10-Supplementary steam pipe; 11-Steam network pipe; 12-Hot water storage tank exhaust pipe; 13-Hot water storage tank condensate pipe; 14-Hot water pipe; 15-Hot water return pipe; 16-Steam pressure regulating valve; 17-Level gauge; 18-Regulating valve. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0030] Example 1

[0031] like Figure 1 As shown, a waste heat utilization device in the production process of long-chain nylon resin includes a polymerization reactor 1, an evaporator 2, a steam tank 3, and a hot water circulation system. The hot water circulation system includes a hot water storage tank 4 and a hot water circulation pump 5. The polymerization reactor 1 is connected to the inlet end of the hot water storage tank 4 through an exhaust pipe 12 to the hot water storage tank, and is also connected to the inlet end of the evaporator 2 through an exhaust pipe 6 to the evaporator. The outlet end of the evaporator 2 is connected to the steam tank 3 through an air inlet pipe 9. The steam tank 3 is connected to the steam user end through a steam network pipe 11. The outlet end of the hot water storage tank 4 is connected to the hot water user end through the hot water circulation pump 5 and a hot water pipe 14.

[0032] The polymerization reactor 1 is a vertical reactor equipped with a jacket, coil and stirring device. A steam pressure regulating valve 16 is installed on the exhaust pipe 6 between the polymerization reactor 1 and the evaporator 2.

[0033] Evaporator 2 is a vertical cylindrical container with an internal coil. Evaporator 2 is equipped with a level gauge 17 and a water inlet pipe 8, and a regulating valve 18 is installed on the water inlet pipe 8.

[0034] The steam tank 3 is a horizontal cylindrical container with steam inlet and outlet and supplementary steam pipe 10.

[0035] The hot water circulation system includes one or more hot water storage tanks 4 and a hot water circulation pump 5. The hot water storage tank 4 is equipped with a coil, a hot water storage tank condensate pipe 13 and a hot water return pipe 15.

[0036] The batch polymerization process of long-chain nylon is mainly divided into four stages:

[0037] 1) During the heating and pressurization stage, the salt solution in the polymerization reactor is heated to evaporate the water and build up a certain pressure. Only a small amount of steam is discharged during this stage.

[0038] 2) Constant pressure exhaust stage: When the polymerization reactor reaches a certain pressure, the material inside the reactor continues to be heated, and the reactor continuously discharges steam to maintain a constant pressure inside the reactor. During this stage, 80-90% of the steam is discharged.

[0039] 3) Pressure Reduction and Steam Discharge Stage. Steam is continuously discharged from the polymerization reactor, gradually reducing the pressure to atmospheric pressure. During this stage, 10-20% of the steam is discharged.

[0040] 4) Atmospheric pressure stage. In this stage, a small amount of water produced by the polymerization reaction is discharged, and only a very small amount of steam is discharged.

[0041] To address the characteristics of high steam pressure during the constant-pressure exhaust stage and the early stage of the pressure-reducing exhaust phase of the polymerization reaction, and low steam pressure during the later stage of the pressure-reducing exhaust phase, this invention provides a waste heat utilization process in the production of long-chain nylon resin, comprising the following steps:

[0042] Step S1: Add the long-chain nylon salt obtained from long-chain diamine, long-chain dicarboxylic acid and deionized water to the polymerization reactor 1. Introduce high-temperature heat transfer oil into the jacket and coil of the polymerization reactor 1 to heat the long-chain nylon salt solution in the polymerization reactor 1. After reaching the set pressure of 1.0-2.0 MPa, discharge steam to maintain a constant pressure in the polymerization reactor 1.

[0043] Step S2: When the polymerization process enters the constant pressure exhaust stage, the steam discharged from the polymerization reactor 1 is introduced into the coil of the evaporator 2 to heat the deionized water in the evaporator 2 and generate saturated water steam with a pressure of 0.3-0.5 MPa.

[0044] Step S3: When the polymerization process enters the depressurization and steam exhaust stage, the steam discharged from the polymerization reactor 1 continues to be fed into the evaporator 2 to heat the deionized water in the evaporator 2 and generate saturated water steam with a pressure of 0.3-0.5 MPa.

[0045] Step S4: During the depressurization and steam exhaust stage, when the pressure of the polymerization reactor 1 drops to 0.8-0.9 MPa, the steam discharged from the polymerization reactor 1 is introduced into the hot water storage tank 4 to heat the hot water entering the hot water storage tank 4 through the hot water return pipe 15. The hot water with a temperature of 80-95℃ is supplied to the hot water users through the hot water circulation pump 5.

[0046] Step S5: The saturated steam generated in the evaporator 2 is introduced into the steam tank 3, and the steam in the steam tank 3 is introduced into the steam pipeline network to supply steam users.

[0047] In step S5, the pressure of the steam tank 3 is 0.3-0.5 MPa. The steam tank 3 is equipped with a pressure regulation and control system. When the pressure of the steam tank 3 is lower than 0.3 MPa, steam from other sources is introduced through the supplementary steam pipe 10 to maintain the pressure inside the steam tank 3.

[0048] The following example, in conjunction with Example 2, provides a detailed explanation of the waste heat utilization process during the production of long-chain nylon resin.

[0049] Example 2

[0050] A process for utilizing waste heat during the production of long-chain nylon resin includes the following steps:

[0051] Step S1: Add the long-chain nylon salt obtained from long-chain diamine, long-chain dicarboxylic acid and deionized water to the polymerization reactor 1. After the addition is completed, high-temperature heat transfer oil is introduced into the jacket and coil of the polymerization reactor 1 to raise the temperature and pressure of the polymerization reactor 1. When the pressure of the polymerization reactor 1 reaches 1.5MPa, open the steam pressure regulating valve 16 on the exhaust pipe 6 to the evaporator. The steam discharged from the polymerization reactor 1 enters the coil of the evaporator 2 through the exhaust pipe 6 to heat the deionized water in the evaporator 2. The condensate formed after the steam is cooled is discharged from the evaporator condensate pipe 7.

[0052] Step S2: When the polymerization process enters the constant pressure exhaust and reduced pressure exhaust stage, the steam discharged from the polymerization reactor 1 is introduced into the evaporator 2 to heat the deionized water in the evaporator 2. The deionized water in the evaporator 2 is heated and evaporated to form saturated steam at 0.3-0.5 MPa.

[0053] Step S3: After the polymerization process enters the depressurization and exhaust stage, when the pressure of the polymerization reactor 1 is lower than 0.8 MPa, the steam supply to the exhaust pipe 6 to the evaporator is stopped, and the valve on the exhaust pipe 12 to the hot water storage tank is opened. The steam discharged from the polymerization reactor 1 enters the coil of the hot water storage tank 4 through the exhaust pipe 12 to the hot water storage tank, heating the water in the hot water storage tank 4. The hot water heated to 80-95℃ in the hot water storage tank 4 is supplied to the factory's hot water users through the hot water circulation pump 5 and the hot water pipe 14. After being used by the hot water users, the lower-temperature hot water returns to the hot water storage tank 4 through the hot water return pipe 15. The condensate after the steam is cooled is discharged from the condensate pipe 13 of the hot water storage tank.

[0054] Step S4: The saturated steam generated in the evaporator 2 enters the steam tank 3 through the air inlet pipe 9, and water is added to the evaporator 2 through the water inlet pipe 8 to maintain a certain liquid level. The pressure inside the evaporator 2 is controlled by the regulating valve 18, and the liquid level of the evaporator 2 is monitored in real time by the liquid level gauge 17.

[0055] The saturated steam in the steam tank 3 is supplied to the factory steam users through the steam network pipeline 11. When the factory's steam consumption is large and the pressure of the steam tank 3 is lower than 0.3 MPa, commercial steam enters the steam tank 3 through the supplementary steam pipeline 10 to maintain the pressure of the steam tank 3 at 0.3 to 0.5 MPa.

[0056] Long-chain nylon resin refers to nylon with a methylene length of more than 10 carbons in the chain segment. Preferably, in the embodiments of the present invention, long-chain nylon resin refers to nylon with a methylene length of 10-16 carbons in the chain segment.

[0057] By applying the method of this invention, 75%-80% of the waste heat from polymerization steam can be recovered during the constant-pressure exhaust stage, and 8%-12% can be recovered during the depressurization exhaust stage. Compared with existing technologies, this invention can fully utilize the waste heat of polymerization steam, resulting in significant energy saving and emission reduction effects.

[0058] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A process for utilizing waste heat in a long carbon chain nylon resin production process, characterized by, The waste heat utilization process is carried out in the waste heat utilization device during the production of long carbon chain nylon resin. The waste heat utilization device includes a polymerization reactor (1), an evaporator (2), a steam tank (3) and a hot water circulation system. The hot water circulation system includes a hot water storage tank (4) and a hot water circulation pump (5). The polymerization reactor (1) is connected to the inlet end of the hot water storage tank (4) through the exhaust pipe (12) to the hot water storage tank, and is connected to the inlet end of the evaporator (2) through the exhaust pipe (6) to the evaporator. The outlet end of the evaporator (2) is connected to the steam tank (3) through the air inlet pipe (9). The steam tank (3) is connected to the steam user end through the steam network pipe (11). The outlet end of the hot water storage tank (4) is connected to the hot water user end through the hot water circulation pump (5) and the hot water pipe (14). The waste heat utilization process includes the following steps: Step S1: Add the long-chain nylon salt obtained from long-chain diamine, long-chain dicarboxylic acid and deionized water into the polymerization reactor (1), and introduce high-temperature heat transfer oil into the jacket and coil of the polymerization reactor (1) to heat the long-chain nylon salt solution in the polymerization reactor (1). After reaching the set pressure, discharge steam to maintain a constant pressure in the polymerization reactor (1). Step S2: When the polymerization process enters the constant pressure exhaust stage, the steam discharged from the polymerization reactor (1) is introduced into the coil of the evaporator (2) to heat the deionized water in the evaporator (2) and generate saturated water steam at a certain pressure. Step S3: When the polymerization process enters the depressurization and steam exhaust stage, the steam discharged from the polymerization reactor (1) continues to be fed into the evaporator (2) to heat the deionized water in the evaporator (2) and generate saturated water vapor at a certain pressure. Step S4: During the pressure reduction and steam discharge stage, when the pressure of the polymerization reactor (1) drops to the set pressure, the steam discharged from the polymerization reactor (1) is introduced into the hot water storage tank (4) to heat the hot water entering the hot water storage tank (4) through the hot water return pipe (15). The hot water with a temperature of 80-95℃ is supplied to the hot water user through the hot water circulation pump (5). Step S5: The saturated steam generated in the evaporator (2) is fed into the steam tank (3), and the steam in the steam tank (3) is fed into the steam pipeline network to supply steam users.

2. The waste heat utilization process in the production of long-chain nylon resin according to claim 1, characterized in that, The polymerization reactor (1) is a vertical reactor equipped with a jacket, coil and stirring device. A steam pressure regulating valve (16) is installed on the exhaust pipe (6) between the polymerization reactor (1) and the evaporator (2).

3. The waste heat utilization process in the production of long-chain nylon resin according to claim 1, characterized in that, The evaporator (2) is a vertical cylindrical container with a coil inside. The evaporator (2) is equipped with a level gauge (17) and a water inlet pipe (8). The water inlet pipe (8) is equipped with a regulating valve (18).

4. The waste heat utilization process in the production of long-chain nylon resin according to claim 1, characterized in that, The steam tank (3) is a horizontal cylindrical container with a supplementary steam pipe (10).

5. The waste heat utilization process in the production of long-chain nylon resin according to claim 1, characterized in that, The hot water circulation system includes one or more hot water storage tanks (4) and a hot water circulation pump (5). The hot water storage tank (4) is equipped with a coil, a hot water storage tank condensate pipe (13) and a hot water return pipe (15).

6. The waste heat utilization process in the production of long-chain nylon resin according to claim 1, characterized in that, The pressure set in step S1 is 1.0-2.0 MPa.

7. The waste heat utilization process in the production of long-chain nylon resin according to claim 1, characterized in that, The pressure of the saturated water vapor in steps S2 and S3 is 0.3-0.5 MPa.

8. The waste heat utilization process in the production of long-chain nylon resin according to claim 1, characterized in that, The pressure set in step S4 is 0.8-0.9 MPa.

9. The waste heat utilization process in the production of long-chain nylon resin according to claim 1, characterized in that, The pressure of the steam tank (3) in step S5 is 0.3-0.5 MPa. The steam tank (3) is equipped with a pressure regulation and control system. When the pressure of the steam tank (3) is lower than 0.3 MPa, steam from other sources is introduced through the supplementary steam pipe (10) to maintain the pressure inside the steam tank (3).

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