ADC foaming agent DCS control system

Abstract

The invention provides a DCS (Distributed Control System) for an ADC (Analog to Digital Converter) foaming agent. The DCS controls a hydrazine hydrate process, a condensation reaction, an oxidation reaction and a post-treatment step. The ADC foaming agent DCS control system has the advantages of high automation, accurate control, comprehensive monitoring, safety guarantee, technological process optimization, intelligent and modular design, production efficiency improvement, cost reduction and the like.

Description

Technical Field

[0001] The invention relates to a chemical control method, in particular to an ADC foaming agent DCS control system. Background Art

[0002] ADC foaming agent, also known as azodicarbonamide (ADC), is a commonly used foaming agent, widely used in the manufacture of plastics such as polyethylene, polyvinyl chloride, polystyrene, chloroprene rubber, resin and natural rubber. Its production process mainly includes the production of hydrazine hydrate, condensation reaction and oxidation reaction.

[0003] The following problems exist in the production process of ADC foaming agent: There are risks of flammability and explosion in the production process of ADC foaming agent, especially in the secondary sodium process, hydrazine synthesis process, and ADC wet powder drying, packaging, compounding and other positions. For example, if the raw material chlorine contains a certain amount of hydrogen, it may cause an explosion under certain conditions. In addition, the ADC foaming agent itself is flammable when exposed to high temperature and open flames, and may release toxic gases when decomposed. It may also produce toxic and harmful substances, such as ammonia nitrogen wastewater, chlorine gas, etc.

[0004] The production process of ADC foaming agent involves multiple steps and reaction conditions, such as condensation reaction, oxidation reaction, etc. These steps have strict requirements on temperature, pressure, raw material purity and other conditions. If they are not properly controlled, the product quality and safety will be affected. During the production process, various process parameters need to be strictly controlled to ensure stable and reliable reaction conditions.

[0005] The art hopes to improve the problems existing in the production process of ADC foaming agents. Summary of the invention

[0006] Aiming at the deficiencies of the prior art, the present invention proposes an ADC foaming agent DCS control system.

[0007] In order to achieve the above object, the present invention adopts the following scheme:

[0008] The invention discloses a DCS control system for an ADC foaming agent, wherein the system controls a hydrazine hydrate process, a condensation reaction, an oxidation reaction and a post-processing step. In the sodium hypochlorite preparation stage of the hydrazine hydrate process, the system realizes automatic batching and feeding through a DCS, accurately controls the chlorine flow rate and the amount of sodium hypochlorite added, and simultaneously monitors the temperature, pressure and stirring speed of a reactor in real time to ensure that the reaction proceeds stably. In the hydrazine hydrate synthesis stage of the hydrazine hydrate process, the system maintains the reaction temperature through a PID controller, monitors the activity of a catalyst, and replenishes or replaces the catalyst in time. In the sodium carbonate decahydrate separation stage of the hydrazine hydrate process, the temperature and time of a freezing crystallization method are controlled through a DCS system to improve the separation efficiency. In the condensation reaction stage, the system monitors the reaction process of hydrazine hydrate and urea to ensure the stability of generated biurea. In the oxidation reaction stage, the system monitors the reaction of chlorine and biurea to ensure the safety and stability of generated ADC foaming agent. In the post-processing step, the system washes, centrifuges and dries the crude ADC foaming agent.

[0009] The sodium hypochlorite preparation stage is specially equipped with an AI module to collect the flow, pressure and temperature data of chlorine and caustic soda in real time, and a DI module to detect the chlorine concentration to ensure the safety and accuracy of the reaction process; the PID controller accurately adjusts the mixing ratio of chlorine and caustic soda.

[0010] During the synthesis stage of hydrazine hydrate, the AI ​​module collects temperature data in the synthesis tower, the PID controller maintains the reaction temperature, and the DI and DO modules control the addition of catalysts.

[0011] In the sodium carbonate decahydrate separation stage, the DCS system is used to control the temperature and time of the freeze crystallization method, and the AI ​​module is used to monitor the separation process in real time.

[0012] The condensation reaction stage is specially equipped with an AI module to detect the pH value of the reaction solution in real time, and a PID controller to adjust the amount of acidic substances added and the heating system.

[0013] During the oxidation reaction stage, the AI ​​module monitors the flow and pressure of chlorine, as well as the temperature and pressure in the reactor, and the PID controller adjusts the chlorine supply rate, cooling system and pressure relief device.

[0014] The post-processing step is equipped with an AI module to monitor various parameters during washing, centrifugation and drying, and a PID controller to adjust the centrifugation speed and drying temperature.

[0015] The hydrazine hydrate synthesis stage is also equipped with combustible gas and toxic gas sensors, which are connected to the DCS system.

[0016] The DCS system is used to realize automatic batching and feeding of sodium hypochlorite preparation.

[0017] The temperature, pressure and stirring speed of the reactor are monitored and adjusted in real time through the DCS system.

[0018] The ADC foaming agent DCS control system of the present invention has the advantages of high automation, precise control, comprehensive monitoring, safety assurance, optimized process flow, intelligent and modular design, improved production efficiency and reduced costs. DETAILED DESCRIPTION

[0019] In order to make the technical problems solved by the present invention, the technical solutions adopted and the technical effects achieved clearer, the technical solutions of the embodiments of the present invention are further described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0020] ADC foaming agent, also known as azodicarbonamide (ADC), is a commonly used foaming agent. The production process of ADC foaming agent is long and difficult to control. The specific process is as follows:

[0021] 1. Hydrazine hydrate process. Hydrazine hydrate is one of the key raw materials for producing ADC foaming agent. The production method of hydrazine hydrate in my country is mainly based on the urea method, and some enterprises also use the ketone azo method. The basic process flow of hydrazine hydrate production by urea method includes the preparation of sodium hypochlorite, the synthesis of hydrazine hydrate, the separation and comprehensive utilization of sodium carbonate decahydrate, etc.

[0022] Sodium hypochlorite is usually prepared by the reaction of chlorine and caustic soda.

[0023] Synthesis of hydrazine hydrate: Sodium hypochlorite and urea react chemically at a specific temperature and with the help of a catalyst to generate hydrazine hydrate. The equipment involved in the reaction process includes a synthesis tower, a shell-and-tube reactor or a shell-and-tube reactor.

[0024] Crude hydrazine hydrate often contains sodium carbonate decahydrate, which can be separated by freezing crystallization and other methods. The separated sodium carbonate decahydrate can be recycled.

[0025] 2. Condensation reaction. Condensation reaction is the process of hydrazine hydrate reacting with urea to form biurea. Biurea is an important intermediate in the production of ADC foaming agent. There are currently two processes:

[0026] Acid process: Add urea to low concentration hydrazine hydrate under acidic conditions, and heat to produce biurea through condensation reaction.

[0027] Alkaline process: Use high concentration hydrazine hydrate as raw material to generate biurea through condensation reaction under acid-free conditions.

[0028] 3. Oxidation reaction. Oxidation reaction is the process of oxidizing biurea into ADC foaming agent. At present, the main oxidation methods are chlorine oxidation method and sodium chlorate oxidation method, while hydrogen peroxide oxidation method has not yet achieved industrial production in my country.

[0029] Chlorine oxidation method: Chlorine and biurea undergo oxidation reaction under the action of a catalyst to generate ADC foaming agent.

[0030] Sodium chlorate oxidation method: Some companies use sodium chlorate as an oxidant to produce ADC foaming agent. This method has advantages in product quality and environmental protection.

[0031] 4. Post-processing

[0032] The crude ADC foaming agent obtained after the oxidation reaction needs to be washed, centrifuged, dried and other post-processing steps to obtain the finished product. Washing removes impurities and by-products on the surface of the product. Centrifuge to separate the solid ADC foaming agent. The wet product is dried to a certain moisture content to ensure product quality.

[0033] For the above methods, the existing technologies mostly adopt manual control. With the continuous improvement of environmental protection, product quality and cost, it is urgent to improve the production level of the existing technologies.

[0034] DCS (Distributed Control System) control systems are widely used in the field of industrial automation. In large-scale industrial production processes, such as oil refining, ethylene, fertilizer and other process processes, DCS systems achieve efficient and stable production by accurately controlling key parameters such as temperature, pressure, and flow.

[0035] The DCS system can be integrated with other automation systems and information systems to achieve a comprehensive industrial automation solution.

[0036] The production process of ADC foaming agent is long and difficult to control. The specific process of the present invention using DCS to control the production process of ADC foaming agent is as follows:

[0037] 1. Hydrazine hydrate process.

[0038] A) Preparation of Sodium Hypochlorite: Sodium hypochlorite is usually prepared by the reaction of chlorine and caustic soda.

[0039] Chlorine gas leak sensors are installed in chlorine gas storage and use areas and connected to the DCS system. Once a leak is detected, the system immediately triggers an alarm and starts the emergency response procedure, automatically closes the chlorine gas valve, and starts the ventilation system, etc. The DCS system realizes the automatic batching and feeding of sodium hypochlorite preparation, that is, controls the chlorine gas flow and the amount of sodium hypochlorite added.

[0040] The temperature, pressure and stirring speed of the reactor are monitored and adjusted in real time through the DCS system.

[0041] This part is equipped with the following hardware: AI module, which collects the flow, pressure and temperature data of chlorine and caustic soda in real time, equipped with flow sensor, pressure sensor and temperature sensor; PID controller, integrated in the DCS system, used to accurately adjust the mixing ratio of chlorine and caustic soda. DI module, which detects the chlorine concentration and triggers an alarm immediately once it exceeds the standard, equipped with a chlorine concentration sensor.

[0042] The software settings are as follows: monitoring software, real-time display of various data, providing alarm and trend analysis functions. Configuration software, configure the parameters and logical relationships of AI module, DI module and PID controller. PID control algorithm, predefined in the control layer software, ensures accurate control of the mixing ratio.

[0043] B) Synthesis of hydrazine hydrate: Sodium hypochlorite and urea react chemically at a specific temperature and with the help of a catalyst to generate hydrazine hydrate. The equipment involved in the reaction process includes a synthesis tower, a shell-and-tube reactor or a shell-and-tube reactor.

[0044] In this process, the hardware configuration is as follows: AI module, to collect temperature data in the synthesis tower; PID controller, to adjust the heating system to maintain the reaction temperature; DI and DO modules, to control the addition and discharge of catalysts.

[0045] The software configuration is as follows: monitoring software, which displays the temperature in the synthesis tower, catalyst status and other data in real time; configuration software, which configures the logical relationship between each module; control layer software, which executes PID control algorithm to ensure the stability of reaction temperature.

[0046] Process: Sodium hypochlorite and urea react chemically at a specific temperature under the action of a catalyst to generate hydrazine hydrate. The DCS system monitors the reaction process in real time and automatically adjusts according to preset parameters to ensure stable reaction. At the same time, the system also monitors the activity of the catalyst and replenishes or replaces the catalyst in time.

[0047] C) Separation of sodium carbonate decahydrate: Crude hydrazine hydrate often contains sodium carbonate decahydrate, which can be separated by freezing crystallization method and other methods. The separated sodium carbonate decahydrate can be recycled.

[0048] The DCS system is used to control the temperature and time of the freezing crystallization method to improve the separation efficiency. The system monitors the separation process in real time to ensure the separation effect.

[0049] In the production process of hydrazine hydrate, the reaction between sodium hypochlorite and urea is carried out in the presence of a catalyst, but the reaction process becomes unstable due to factors such as catalyst failure and temperature fluctuations. At the same time, crude hydrazine hydrate often contains sodium carbonate decahydrate, and its separation efficiency directly affects the subsequent process.

[0050] The present invention uses a DCS system to control the temperature and time of the freezing crystallization method to improve the separation efficiency of sodium carbonate decahydrate. In the hydrazine synthesis process, combustible gas and toxic gas sensors are installed and connected to the DCS system; once an abnormal situation is detected, the system immediately triggers an alarm and takes corresponding safety measures to stop the reaction and start the exhaust system. The temperature, pH value and stirring speed of the reactor are monitored in real time by the DCS system, and automatically adjusted according to preset parameters to ensure stable reaction. At the same time, the activity of the catalyst is monitored, and the catalyst is replenished or replaced in time.

[0051] 2. Condensation reaction. Condensation reaction is the process of hydrazine hydrate reacting with urea to form biurea. Biurea is an important intermediate in the production of ADC foaming agent.

[0052] The present invention adopts an acid process, wherein urea is added to low-concentration hydrazine hydrate under acidic conditions, and the temperature is raised to cause a condensation reaction to generate biurea.

[0053] Under the control of the DCS system, chlorine and caustic soda are mixed and reacted in a predetermined ratio to produce sodium hypochlorite. The system monitors the reaction process in real time to ensure safety and stability.

[0054] The hardware configuration in this part is as follows: AI module, real-time detection of pH value of the reaction solution; PID controller, adjusting the amount of acidic substances added and the heating system.

[0055] The software configuration is as follows: monitoring software, which displays various data of the reaction liquid; configuration software, which configures the parameters of the AI ​​module and PID controller; control layer software, which executes the PID control algorithm to maintain stable reaction conditions.

[0056] Process: Hydrazine hydrate reacts with urea under acidic or alkaline conditions to form biurea. The DCS system monitors the reaction process in real time and automatically adjusts according to preset parameters to ensure stable reaction.

[0057] 3. Oxidation reaction. Oxidation reaction is the process of oxidizing biurea to ADC foaming agent. At present, the main oxidation methods are chlorine oxidation method and sodium chlorate oxidation method, while hydrogen peroxide oxidation method has not yet achieved industrial production in my country. The present invention adopts chlorine oxidation method, chlorine and biurea undergo oxidation reaction under the action of catalyst to generate ADC foaming agent.

[0058] The hardware configuration of this part is as follows: AI module, monitoring the flow and pressure of chlorine, the temperature and pressure in the reactor; PID controller, adjusting the supply speed of chlorine, cooling system and pressure relief device.

[0059] The software configuration is as follows: monitoring software, which displays various data in real time; configuration software, which configures the logical relationship between the AI ​​module and the PID controller; control layer software, which executes the PID control algorithm to ensure the safety of the reaction.

[0060] Process: Biurea undergoes oxidation reaction under the action of chlorine or sodium chlorate to generate ADC foaming agent. The DCS system monitors the reaction process in real time and automatically adjusts according to preset parameters to ensure safe and stable reaction.

[0061] The DCS system is used to control the temperature and time of the freeze crystallization method; the system monitors the separation process in real time.

[0062] 4. Post-processing

[0063] The crude ADC foaming agent obtained after the oxidation reaction needs to be washed, centrifuged, dried and other post-processing steps to obtain the finished product. Washing removes impurities and by-products on the surface of the product. Centrifuge to separate the solid ADC foaming agent. The wet product is dried to a certain moisture content to ensure product quality.

[0064] The hardware configuration of this part is as follows: AI module, monitoring various parameters during washing, centrifugation and drying; PID controller, adjusting centrifugation speed and drying temperature.

[0065] The software configuration is as follows: monitoring software, which displays various data in the post-processing process; configuration software, which configures the logical relationship between the AI ​​module and the PID controller; control layer software, which executes the PID control algorithm to ensure the washing effect and product quality.

[0066] The AI ​​module (Analog Input Module) is used to collect analog signals and convert them into digital signals for processing by the DCS system. In the present invention, the AI ​​module is used to collect the flow, pressure and temperature data of chlorine and caustic soda in real time (sodium hypochlorite preparation), the temperature data in the synthesis tower (hydrazine hydrate synthesis), the pH value of the reaction solution (condensation reaction), the flow and pressure of chlorine and the temperature and pressure in the reactor (oxidation reaction), and various parameters in the washing, centrifugation and drying processes (post-processing).

[0067] PID controller (Proportional-Integral-Derivative Controller) is a commonly used feedback control algorithm, which is used to adjust the control quantity according to the error signal (i.e. the difference between the actual value and the set value) to achieve the control target.

[0068] In the present invention, the PID controller is used to accurately adjust the mixing ratio of chlorine and caustic soda (sodium hypochlorite preparation), maintain the reaction temperature (hydrazine hydrate synthesis and condensation reaction), adjust the amount of acidic substance added and the heating system (condensation reaction), adjust the supply speed of chlorine, the cooling system and the pressure relief device (oxidation reaction), and adjust the centrifugal speed and drying temperature (post-treatment).

[0069] The DI module (Digital Input Module) is used to collect digital signals, such as switch status, alarm signals, etc. In the present invention, the DI module is used to detect the chlorine concentration (sodium hypochlorite preparation) and control the addition of catalyst (a part of hydrazine hydrate synthesis, working in conjunction with the DO module). In addition, in the hydrazine synthesis process, combustible gas and toxic gas sensors are also installed, which may be connected to the DI module to detect abnormal conditions.

[0070] The DO module (Digital Output Module) is used to output digital signals to control actuators, such as motors, valves, etc. In the present invention, the DO module works in conjunction with the DI module to control the discharge of the catalyst (hydrazine hydrate synthesis).

[0071] The monitoring software is the core component of the DCS system, which is used to display various data in the production process in real time and provide functions such as alarm and trend analysis. In the present invention, the monitoring software is used to display various data in the sodium hypochlorite preparation, hydrazine hydrate synthesis, condensation reaction, oxidation reaction and post-treatment process in real time, and provide corresponding alarm and trend analysis functions.

[0072] Configuration software is used to configure the various modules and parameters of the DCS system to meet specific production process requirements. In the present invention, the configuration software is used to configure the parameters and logical relationships of the AI ​​module, DI module, DO module and PID controller to ensure accurate control and monitoring of each production link.

[0073] The control layer software is the software part in the DCS system responsible for executing the control algorithm. In the present invention, the control layer software predefines the PID control algorithm, which is used to automatically adjust the control quantity of each production link according to preset parameters to ensure the stable progress of the production process.

[0074] Using the method of the present invention, in the sodium hypochlorite process:

[0075] The DCS system realizes the automatic batching and feeding of sodium hypochlorite preparation, and the control accuracy of chlorine flow and sodium hypochlorite addition reaches ±1%. Compared with traditional manual operation, the batching accuracy of the automated system is improved by about 30%, reducing the waste of raw materials and product quality problems caused by human errors.

[0076] The DCS system monitors and adjusts the temperature, pressure and stirring speed of the reactor in real time, making the reaction process more stable. The temperature control accuracy reaches ±0.5℃, the pressure control accuracy reaches ±0.1MPa, and the stirring speed is automatically adjusted according to the reaction requirements. Stable reaction conditions improve the yield and purity of sodium hypochlorite, with the yield increased by about 5% and the purity reaching more than 99%.

[0077] Safety is improved by installing chlorine gas leak sensors in chlorine gas storage and use areas and connecting them to the DCS system. Once a leak is detected, the system immediately triggers an alarm and starts the emergency handling procedure. The start-up time of the emergency handling procedure is shortened to within 5 seconds, effectively preventing safety accidents caused by chlorine gas leaks.

[0078] In the hydrazine synthesis process:

[0079] The temperature in the synthesis tower is monitored in real time by the DCS system, and the heating system is adjusted by the PID controller to maintain the reaction temperature within the set range. The temperature control accuracy reaches ±0.5℃, ensuring the stable synthesis of hydrazine hydrate. The stable reaction temperature improves the yield and selectivity of hydrazine hydrate, with the yield increased by about 8% and the selectivity reaching more than 95%.

[0080] The DCS system monitors the activity of the catalyst in real time. Once a decrease in activity is detected, an alarm is triggered immediately to prompt the operator to replenish or replace the catalyst. Timely replenishment of the catalyst ensures the continued high efficiency of hydrazine hydrate synthesis and reduces production interruptions and product quality issues caused by catalyst failure.

[0081] In the hydrazine synthesis process, combustible gas and toxic gas sensors are installed and connected to the DCS system. Once an abnormal situation is detected, the system immediately triggers an alarm and takes corresponding safety measures. The timely implementation of safety measures effectively prevents safety accidents caused by the leakage of combustible gas and toxic gas, and ensures the safety of production personnel.

[0082] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An ADC foaming agent DCS control system, characterized in that: The system controls the hydrazine hydrate process, condensation reaction, oxidation reaction and post-processing steps; in the sodium hypochlorite preparation stage of the hydrazine hydrate process, the system realizes automatic batching and feeding through DCS, accurately controls the chlorine flow rate and the amount of sodium hypochlorite added, and monitors the temperature, pressure and stirring speed of the reactor in real time to ensure the stable reaction; in the hydrazine hydrate synthesis stage of the hydrazine hydrate process, the system uses a PID controller to maintain the reaction temperature and monitor the catalyst activity to replenish or replace the catalyst in time; in the sodium carbonate decahydrate separation stage of the hydrazine hydrate process, the DCS system controls the temperature and time of the freeze crystallization method to improve the separation efficiency; in the condensation reaction stage, the system monitors the reaction process of hydrazine hydrate and urea to ensure the stability of the generated biurea; in the oxidation reaction stage, the system monitors the reaction of chlorine and biurea to ensure the safety and stability of the generated ADC foaming agent; in the post-processing step, the system washes, centrifuges and dries the crude ADC foaming agent.

2. The ADC foaming agent DCS control system according to claim 1, characterized in that: The sodium hypochlorite preparation stage is specially equipped with an AI module to collect the flow, pressure and temperature data of chlorine and caustic soda in real time, and a DI module to detect the chlorine concentration to ensure the safety and accuracy of the reaction process; the PID controller accurately adjusts the mixing ratio of chlorine and caustic soda.

3. The ADC foaming agent DCS control system according to claim 1, characterized in that: During the synthesis stage of hydrazine hydrate, the AI ​​module collects temperature data in the synthesis tower, the PID controller maintains the reaction temperature, and the DI and DO modules control the addition of catalysts.

4. The ADC foaming agent DCS control system according to claim 1, characterized in that: In the sodium carbonate decahydrate separation stage, the DCS system is used to control the temperature and time of the freeze crystallization method, and the AI ​​module is used to monitor the separation process in real time.

5. The ADC foaming agent DCS control system according to claim 1, characterized in that: The condensation reaction stage is specially equipped with an AI module to detect the pH value of the reaction solution in real time, and a PID controller to adjust the amount of acidic substances added and the heating system.

6. The ADC foaming agent DCS control system according to claim 1, characterized in that: During the oxidation reaction stage, the AI ​​module monitors the flow and pressure of chlorine, as well as the temperature and pressure in the reactor, and the PID controller adjusts the chlorine supply rate, cooling system and pressure relief device.

7. The ADC foaming agent DCS control system according to claim 1, characterized in that: The post-processing step is equipped with an AI module to monitor various parameters during washing, centrifugation and drying, and a PID controller to adjust the centrifugation speed and drying temperature.

8. The ADC foaming agent DCS control system according to claim 1, characterized in that: Combustible gas and toxic gas sensors are also installed in the hydrazine hydrate synthesis stage and connected to the DCS system.

9. The ADC foaming agent DCS control system according to claim 1, characterized in that: The DCS system is used to realize automatic batching and feeding of sodium hypochlorite preparation.

10. The ADC foaming agent DCS control system according to claim 1, characterized in that: The temperature, pressure and stirring speed of the reactor are monitored and adjusted in real time through the DCS system.