Nylon 66 polymerizer salt liquid feed metering device
The metering device, which combines a metering tank with a control system, enables precise metering and circulation of the brine solution during the production of nylon 66. This solves the problems of inaccurate metering and crystallization blockage, thereby improving production efficiency and product quality.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- SHANDONG LONGHUA POLYMER MATERIALS CO LTD
- Filing Date
- 2026-02-11
- Publication Date
- 2026-04-21
AI Technical Summary
In the existing technology, the salt solution metering during the production of nylon 66 is inaccurate, which easily crystallizes and clogs valves and pipelines, affecting product quality stability and production efficiency.
A metering device combining a metering tank and a control system is used to achieve accurate metering and circulation of the brine through an overflow pipe and a level gauge. The device is combined with an insulation jacket to maintain the temperature and prevent crystallization. The volatilized hexamethylenediamine is recovered through a gas phase balance pipe to ensure the stability of the feeding process.
It improved the accuracy of salt solution metering, prevented crystallization blockage, reduced material waste, and enhanced production efficiency and product quality stability.
Smart Images
Figure CN224142183U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of chemical equipment technology, specifically relating to a metering device for feeding brine into a nylon 66 polymerization reactor. Background Technology
[0002] Nylon 66 is a major product in the nylon series. Its raw materials are adipic acid and hexamethylenediamine. The process involves the equimolar reaction of hexamethylenediamine and adipic acid to form a nylon 66 salt solution. After concentration and polymerization, the water in the system is continuously removed to form a large molecular molten polymer. The finished product is then obtained through processes such as melt casting, cooling, pelletizing, drying, sieving, and packaging. The main production processes of Nylon 66 include salt formation, concentration, polymerization, pelleting, drying, and sieving. Among these, the salt formation process is the initial step in production. It requires mixing hexamethylenediamine, adipic acid, and water to form a 50-55% salt solution. The core purpose is to control the salt formation reaction between hexamethylenediamine and adipic acid in an equimolar ratio of 1:1. This is crucial for ensuring the regularity of the molecular weight of the synthesized polymer. Typically, the pH of the salt solution needs to be adjusted to 7.3-7.8 to ensure a slight excess of hexamethylenediamine, thereby balancing the amine loss during the polymerization and dehydration process. The quality and metering accuracy of the salt solution are key factors in controlling the polymerization quality of Nylon 66, directly determining key indicators such as viscosity, terminal amines, and molecular weight of the product. Therefore, it must be given high priority during the production process.
[0003] Qualified brine solutions are stored in tanks, and to prevent crystallization, the temperature of the brine solution must not be lower than 80℃. Currently, the industry mainly uses the traditional control mode of flow meters and regulating valve groups to directly feed the solution into the concentration tank. After feeding is completed, the regulating valve is closed, and the solution is discharged into the polymerization tank after concentration. This mode has many problems: First, the brine solution is fed in batches. After feeding is completed, the regulating valve is closed, and the brine solution stops flowing. When the temperature is lower than 80℃, it is easy to crystallize and solidify, clogging the valve and feed pipeline, causing feeding to stop, and the subsequent cleaning of the pipeline is a huge workload; Second, there is a risk of gas in the feed pipeline. Issues such as liquid entrainment and insufficient instrument accuracy lead to deviations in material metering, especially significant batch-to-batch metering deviations, which in turn affect the accuracy of subsequent additions of various additives and seriously impact product quality. Thirdly, the concentration kettle maintains a high temperature of nearly 155°C during the salt solution concentration stage. After the salt solution enters the kettle, it rapidly vaporizes, and the system directly depressurizes to discharge the vaporized material into the condensation system. During this process, hexamethylenediamine-like substances in the salt solution will volatilize along with the vaporization, causing material loss and disrupting the original salt solution ratio, thereby affecting the product quality stability of subsequent polymerization reactions. Utility Model Content
[0004] To address the shortcomings of existing technologies, the present invention aims to provide a metering device for feeding brine into a nylon 66 polymerization reactor. This device improves metering accuracy, reducing product quality fluctuations at the source, and enables brine circulation, effectively preventing crystallization and blockage of valves and pipelines, thus enhancing production efficiency. Simultaneously, the device can recover volatile hexamethylenediamine, avoiding pH deviations and reducing material waste and emissions while ensuring quality stability.
[0005] This utility model is achieved using the following technical solution:
[0006] The aforementioned nylon 66 polymerization reactor brine feeding and metering device includes a metering tank. At least two overflow pipes at different heights are provided on the side wall of the metering tank. The outlet of each overflow pipe is connected to the inlet of a storage tank. The outlet of the storage tank is connected to the inlet of the metering tank via an inlet pipe. The outlet of the metering tank is connected to the inlet of a concentration reactor via a discharge pipe. The gas outlet of the concentration reactor is connected to the top of the metering tank via a gas phase balance pipe. The metering tank is installed at a higher height than the concentration reactor. The device also includes a control system.
[0007] The feed pipe is equipped with a shut-off valve and a mass flow meter, which are electrically connected to the control system.
[0008] The metering tank is equipped with a level gauge, and overflow valves are installed on overflow pipes at different heights. The level gauge and each overflow valve are electrically connected to the control system.
[0009] The concentration vessel is equipped with a pressure gauge, and the gas phase balance pipeline is equipped with an exhaust valve. The pressure gauge and the exhaust valve are electrically connected to the control system.
[0010] The discharge pipe is equipped with a discharge valve, which is electrically connected to the control system.
[0011] The metering tank is equipped with an insulation jacket on its outer wall, and the concentration vessel is equipped with a steam heating jacket on its outer wall.
[0012] The working principle of the nylon 66 polymerization reactor brine feeding metering device is as follows:
[0013] Firstly, by utilizing overflow pipes at different heights installed on the side wall of the metering tank, and combining this with the electrical connection between the level gauge and the control system, the appropriate overflow pipe height can be selected based on the required feed volume of the concentration vessel. Before commissioning, the brine mass at each overflow pipe height was calibrated to ensure that the feed volume accurately matches production needs. The shut-off valve and mass flow meter on the feed pipe are electrically connected to the control system, enabling real-time monitoring of the brine inflow and precise control of the feed start and stop. The metering tank is installed at a higher height than the concentration vessel, allowing for smooth discharge of the brine by gravity. Its outer insulation jacket maintains the brine temperature at approximately 80°C, preventing crystallization. Simultaneously, after the brine flows into the metering tank through the feed pipe, any excess flows back to the storage tank via the overflow pipe, creating a circulating flow and preventing blockages caused by stagnant brine. The pressure gauge on the concentration vessel and the vent valve on the gas phase balance pipeline are both electrically connected to the control system. Before feeding, the vent valve is opened, and the gas phase balance pipeline connects the outlet of the concentration vessel to the top of the metering tank to achieve pressure balance, ensuring a stable and orderly brine discharge process. The discharge valve on the discharge pipeline is electrically connected to the control system, allowing precise control of the brine discharge into the concentration vessel. After the brine enters the concentration vessel, the steam heating jacket on the outer wall of the concentration vessel heats the brine. During this process, the volatilized hexamethylenediamine enters the metering tank through the gas phase balance pipeline for temporary storage. During the next feeding, it is fully mixed and absorbed with the new brine flowing from the storage tank through the feed pipeline, achieving hexamethylenediamine recovery and avoiding material loss and pH deviation caused by pressure relief discharge. The entire process, through the coordinated control of all components by the control system, ensures accurate brine metering, a stable and efficient process, and guarantees product quality.
[0014] Compared with the prior art, the beneficial effects of this utility model are as follows:
[0015] (1) The nylon 66 polymerization reactor salt solution feeding metering device described in this utility model solves the problem of large batch metering deviation of traditional flow meters, avoids the situation that the subsequent addition metering of additives is affected by the inaccurate metering of salt solution, reduces the problem of product quality fluctuation between batches from the source, and ensures the stability of product quality.
[0016] (2) The nylon 66 polymerization reactor salt solution feeding metering device described in this utility model realizes the circulation of salt solution, completely solves the problem of frequent crystallization and blockage of valves and pipelines due to stagnation and non-flow of salt solution in the traditional mode, reduces the downtime of production line cleaning and significantly improves production efficiency.
[0017] (3) The nylon 66 polymerization reactor salt solution feeding metering device described in this utility model can recover and utilize the hexamethylenediamine volatilized during the salt solution feeding process, avoid the pH value deviation of the salt solution caused by the volatilization of hexamethylenediamine, solve the problem of unstable product quality, and also reduce material waste and emissions. Attached Figure Description
[0018] Figure 1 This is a schematic diagram of the overall structure of the nylon 66 polymerization reactor brine feeding and metering device described in this utility model;
[0019] In the diagram: 1. Metering tank; 2. Overflow pipe; 3. Storage tank; 4. Feed pipe; 5. Discharge pipe; 6. Concentrator; 7. Gas phase balance pipe; 8. Shut-off valve; 9. Mass flow meter; 10. Level gauge; 11. Overflow valve; 12. Pressure gauge; 13. Exhaust valve; 14. Discharge valve; 15. Insulation jacket; 16. Steam heating jacket. Detailed Implementation
[0020] To make the objectives and technical solutions of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings.
[0021] Example 1
[0022] like Figure 1 As shown, the nylon 66 polymerization reactor brine feeding metering device includes a metering tank 1. Two overflow pipes 2 at different heights are provided on the side wall of the metering tank 1. The outlet of each overflow pipe 2 is connected to the inlet of a storage tank 3. The outlet of the storage tank 3 is connected to the inlet of the metering tank 1 via an inlet pipe 4. The outlet of the metering tank 1 is connected to the inlet of a concentration reactor 6 via a discharge pipe 5. The outlet of the concentration reactor 6 is connected to the top of the metering tank 1 via a gas phase balance pipe 7. The metering tank 1 is installed at a higher height than the concentration reactor 6. The device also includes a control system.
[0023] The feed pipe 4 is equipped with a shut-off valve 8 and a mass flow meter 9, which are electrically connected to the control system.
[0024] The metering tank 1 is equipped with a level gauge 10, and overflow valves 11 are respectively installed on the overflow pipes 2 at different heights. The level gauge 10 and each overflow valve 11 are electrically connected to the control system.
[0025] The concentration vessel 6 is equipped with a pressure gauge 12, and the gas phase balance pipeline 7 is equipped with an exhaust valve 13. The pressure gauge 12 and the exhaust valve 13 are electrically connected to the control system.
[0026] The discharge pipe 5 is equipped with a discharge valve 14, which is electrically connected to the control system.
[0027] The outer wall of the metering tank 1 is provided with a heat-insulating jacket 15, and the outer wall of the concentration vessel 6 is provided with a steam heating jacket 16.
[0028] The specific steps for doing this are as follows:
[0029] The control system first determines the required brine feed rate based on the feeding requirements of the concentration vessel 6, then selects the overflow pipe 2 at the corresponding height on the side wall of the metering tank 1. Subsequently, the control system opens the shut-off valve 8 on the feed pipe 4, allowing the brine in the storage tank 3 to flow into the metering tank 1 through the feed pipe 4. Simultaneously, the control system opens the overflow valve 11 on the selected overflow pipe 2, allowing excess brine in the metering tank 1 to flow back to the storage tank 3 through the overflow pipe 2, forming a circulating flow. During this period, the insulation jacket 15 on the outer wall of the metering tank 1 continuously operates, maintaining the brine temperature stably at 80℃ to prevent brine crystallization. When the mass flow meter 9 on the feed pipe 4 shows a stable reading, and the level gauge 10 indicates that the brine in the metering tank 1 has reached the preset feed rate, the control system issues a command to close the shut-off valve 8 and the overflow valve 11, completing the accurate metering of the brine. Next, the control system opens the exhaust valve 13 on the gas phase balance pipeline 7, achieving pressure balance between the metering tank 1 and the concentration vessel 6. The operator can monitor pressure changes in real time using the pressure gauge 12 on the concentration vessel 6. Once the pressure gauge 12 reading stabilizes, the control system opens the discharge valve 14 on the discharge pipeline 5. Because the metering tank 1 is installed at a higher height than the concentration vessel 6, the brine in the metering tank 1 flows smoothly into the concentration vessel 6 through the discharge pipeline 5 under gravity. When the level gauge 10 shows that the brine level in the metering tank 1 is 0, it indicates that feeding is complete, and the control system immediately closes the discharge valve 14 and the exhaust valve 13. Next, the steam heating jacket 16 on the outer wall of the concentration vessel 6 begins operation, raising the temperature of the brine in the concentration vessel 6 to 155°C. After concentration is complete, the material is discharged into the polymerization vessel for the next polymerization operation. The hexamethylenediamine produced by the volatilization of the brine during the heating process in the concentration vessel 6 is temporarily stored in the metering tank 1 through the gas phase balance pipe 7. When the next feeding process is started, the remaining volatilized hexamethylenediamine will be fully mixed and absorbed with the new brine entering the metering tank 1 from the storage tank 3 through the feeding pipe 4. No pressure relief or discharge is carried out throughout the process, thus realizing the recovery and utilization of hexamethylenediamine.
Claims
1. A metering device for feeding brine into a nylon 66 polymerization reactor, characterized in that, The system includes a metering tank (1), which has at least two overflow pipes (2) at different heights on its side wall. The outlet of each overflow pipe (2) is connected to the inlet of a storage tank (3). The outlet of the storage tank (3) is connected to the inlet of the metering tank (1) through a feed pipe (4). The outlet of the metering tank (1) is connected to the inlet of a concentration vessel (6) through a discharge pipe (5). The outlet of the concentration vessel (6) is connected to the top of the metering tank (1) through a gas phase balance pipe (7). The metering tank (1) is installed at a height higher than the concentration vessel (6). The system also includes a control system.
2. The nylon 66 polymerizer salt solution feed metering device of claim 1 wherein, The feed pipe (4) is equipped with a shut-off valve (8) and a mass flow meter (9), which are electrically connected to the control system.
3. The nylon 66 polymerizer salt feed metering device of claim 1 wherein, The metering tank (1) is equipped with a level gauge (10), and overflow valves (11) are respectively installed on the overflow pipes (2) at different heights. The level gauge (10) and each overflow valve (11) are electrically connected to the control system.
4. The nylon 66 polymerizer salt feed metering device of claim 1 wherein, The concentration vessel (6) is equipped with a pressure gauge (12), and the gas phase balance pipeline (7) is equipped with an exhaust valve (13). The pressure gauge (12) and the exhaust valve (13) are electrically connected to the control system.
5. The nylon 66 polymerizer salt solution feed metering device of claim 1 wherein, The discharge pipe (5) is equipped with a discharge valve (14), which is electrically connected to the control system.
6. The nylon 66 polymerizer salt solution feed metering device of claim 1 wherein, The outer wall of the metering tank (1) is provided with a heat insulation jacket (15), and the outer wall of the concentration vessel (6) is provided with a steam heating jacket (16).