Iron-molybdenum method formaldehyde safety production process and system based on DCS-SIS cooperative control

Abstract

The invention discloses a DCS-SIS cooperative control-based safe production process and system for formaldehyde by an iron-molybdenum method. The DCS-SIS cooperative control-based safe production process comprises the steps of raw material gas preparation, reaction, heat recovery and product absorption, DCS-SIS cooperative control, DCS real-time monitoring and adjustment of process parameters and maintenance of stable production. The SIS independently monitors key safety parameters, and when the key safety parameters exceed a threshold value, interlocking is triggered and the DCS is linked. The system comprises a feed gas preparation unit, a reaction unit, a heat recovery and absorption unit, a DCS control unit and an SIS safety unit. Through cooperation of the two systems, the production safety, stability and efficiency are improved, the system reliability is enhanced, production optimization is facilitated, and the method is suitable for safe production of formaldehyde through the iron-molybdenum method.

Description

Technical Field

[0001] The present invention relates to the technical field of formaldehyde production, and in particular to a safe production process and system of formaldehyde using an iron-molybdenum method based on DCS-SIS collaborative control. Background Art

[0002] In the traditional iron-molybdenum formaldehyde production process, there are many safety and control issues. On the one hand, the control of the production process mostly relies on a single control system, which makes it difficult to achieve accurate and comprehensive control of complex process parameters, easily leading to unstable production processes and affecting product quality and production efficiency. On the other hand, safety monitoring and control are often integrated into the same control system. When the system fails, the safety assurance mechanism may also be affected, and it is impossible to respond to sudden safety incidents in a timely and reliable manner. For example, abnormal temperature increases and sudden pressure increases in the reactor can easily lead to safety accidents and pose a serious threat to the safety of production equipment and operators. In addition, the coordination between various links such as raw gas preparation, reaction process, heat recovery and product absorption is poor, and information transmission is not timely, further reducing the safety and stability of production.

[0003] Therefore, a safe production process and system of formaldehyde using the iron-molybdenum method based on DCS-SIS collaborative control was proposed. Summary of the Invention

[0004] The purpose of the present invention is to provide a safe production process and system of formaldehyde by the iron-molybdenum method based on DCS-SIS collaborative control, so as to solve the technical problems of difficult control of complex process and poor coordination of various links in the traditional iron-molybdenum method formaldehyde production process.

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

[0006] The iron-molybdenum formaldehyde production safety process based on DCS-SIS collaborative control includes the following steps:

[0007] Raw gas preparation: refined methanol is pumped into the methanol evaporator through a methanol pump, where it is vaporized using saturated water vapor in the steam drum. Simultaneously, fresh air is mixed with part of the recycled absorber tail gas to form a mixed gas, which is then heat-exchanged with the vaporized methanol in a gas cooler.

[0008] Reaction process: The raw gas after heat exchange enters the methanol reactor and undergoes an oxidation reaction to produce formaldehyde under the action of an iron-molybdenum catalyst. The temperature of the catalyst bed in the reactor is maintained by the high-speed flow of heat-conducting molten salt in the gaps between the tubes. The temperature of the heat-conducting molten salt is controlled by vaporizing the desalted water in the serpentine coil heat exchanger located in the center of the reactor to remove heat. The desalted water is supplied by a high-pressure water supply pump, and the generated medium-pressure steam is directed to the steam drum.

[0009] Heat recovery and product absorption: the high-temperature mixed gas after reaction enters the waste heat recovery boiler and the gas cooler in turn for heat recovery, the cooled mixed gas enters the concentrated formaldehyde scrubber and is absorbed by the high-concentration formaldehyde solution circulating therein, and then the mixed gas containing lower concentration formaldehyde enters the absorption tower system and is absorbed by the low-concentration formaldehyde solution circulating in each section in countercurrent contact, and the desalted water of the absorbent is added from the top of the absorption tower;

[0010] DCS-SIS collaborative control: the DCS system monitors the process parameters in real time, such as the methanol flow, the water vapor pressure of the methanol evaporator, the temperature of the heat-conducting molten salt, the water inlet flow at the top of the absorption tower, the liquid level in the steam drum, and the formaldehyde solution level at the bottom of the absorption tower, and adjusts according to the preset control strategy; the SIS system independently monitors the key safety parameters, such as the pressure, temperature, and oxygen content in the reactor, and the methanol concentration in the raw material gas, and when the key safety parameters exceed the safety threshold, the SIS system immediately triggers the safety interlock action, including but not limited to cutting off the raw material supply, starting the emergency cooling system, opening the safety relief device, etc., and sends a safety signal to the DCS system, and the DCS system adjusts the control strategy according to the signal to ensure that the production process continues to run or safely stops under safe conditions.

[0011] As a preferred scheme of the present application, in the raw material gas preparation step, the flow of the methanol pump is accurately controlled by the DCS system to match the vaporization amount of the methanol with the flow of the mixed gas, and the flow of the steam into the methanol evaporator in the steam drum is adjusted according to the temperature and pressure of the mixed gas to ensure that the methanol vaporization temperature is stable within the preset range.

[0012] As a preferred scheme of the present application, in the reaction process, the DCS system adjusts the flow of the high-pressure water supply pump according to the temperature change of the heat-conducting molten salt, and then controls the vaporization amount of the desalted water in the snake-shaped coil heat exchanger to stabilize the temperature of the heat-conducting molten salt within the suitable working temperature range of the catalyst; the SIS system continuously monitors the temperature gradient of the catalyst bed in the reactor, and when the temperature gradient exceeds the preset safety value, it is judged that there may be local deactivation of the catalyst or abnormal reaction, and the safety interlock is immediately triggered to prevent the reaction from getting out of control.

[0013] As a preferred scheme of the present application, in the heat recovery and product absorption step, the DCS system adjusts the flow of the cooling medium according to the temperature of the mixed gas at the outlet of the waste heat recovery boiler and the gas cooler to achieve efficient heat recovery; at the same time, according to the concentration and temperature of the circulating solution in each section of the absorption tower, the addition amount of the desalted water of the absorbent and the circulating flow of the circulating solution are adjusted to ensure the stability of the formaldehyde absorption efficiency and product concentration; the SIS system monitors the pressure and liquid level in the absorption tower, and when the pressure is too high or the liquid level is abnormal, the corresponding safety interlock is started, such as opening the safety valve of the absorption tower or adjusting the operating state of the circulating pump.

[0014] As a preferred scheme of the present application, the DCS system and the SIS system interact with each other through a redundant communication link to ensure the reliability and real-time performance of data transmission; the communication link adopts an industrial Ethernet and is equipped with a network security protection device to prevent external network attacks from causing safety hazards to the production process.

[0015] As a preferred scheme of the present application, after triggering a safety interlock action, the SIS system automatically records detailed information of the safety event, including the time of the event, the parameter triggering the interlock, the content of the interlock action, etc., and transmits these information to the DCS system in real time, and the DCS system stores the safety event information in a historical database and generates a safety event report for accident analysis and production improvement by the operators and managers.

[0016] The present application also provides an iron-molybdenum method formaldehyde safety production system based on DCS-SIS collaborative control, which is used to realize the above-mentioned iron-molybdenum method formaldehyde safety production process based on DCS-SIS collaborative control, and comprises:

[0017] A raw gas preparation unit, comprising a methanol evaporator, a gas mixer and a gas cooler, which is used to vaporize refined methanol and mix and heat exchange with air and recycled tail gas to obtain raw gas;

[0018] A reaction unit, comprising a methanol reactor, a heat-conducting molten salt circulation system, a snake-shaped coil heat exchanger, a high-pressure water supply pump and a steam drum, which is used to generate formaldehyde by methanol oxidation reaction under the action of iron-molybdenum catalyst and control the reaction temperature to recover reaction heat to generate steam;

[0019] A heat recovery and product absorption unit, which is composed of a waste heat recovery boiler, a concentrated formaldehyde scrubber and an absorption tower system, and is used to recover heat of the mixed gas after reaction and absorb formaldehyde to obtain products;

[0020] A DCS control unit, which collects process parameters of each unit in real time through sensors, outputs control signals according to a preset control strategy, adjusts the equipment of each unit, and realizes stable operation of the production process;

[0021] An SIS safety unit, which independently sets up sensors to monitor key safety parameters, triggers a safety interlock action immediately when the parameters exceed a safety threshold, ensures production safety, and interacts with the DCS control unit.

[0022] As a preferred scheme of the present application, a steam flow regulating valve is installed on the methanol evaporator in the raw gas preparation unit, the regulating valve is connected with the DCS control unit, and the DCS control unit adjusts the opening degree of the steam flow regulating valve according to the temperature and pressure feedback signals in the methanol evaporator to control the amount of steam entering.

[0023] As a preferred scheme of the present application, a plurality of temperature sensors and pressure sensors are arranged in the methanol reactor of the reaction unit, which are connected with a DCS control unit and a SIS safety unit respectively, the DCS control unit is used for monitoring the distribution of temperature and pressure in the reactor and adjusting the process, and the SIS safety unit is used for judging whether the reactor is in a safe operation state, and triggering a safety interlock when the temperature or pressure is abnormal.

[0024] As a preferred scheme of the present application, a plurality of temperature sensors and pressure sensors are arranged in the methanol reactor of the reaction unit, which are connected with a DCS control unit and a SIS safety unit respectively, the DCS control unit is used for monitoring the distribution of temperature and pressure in the reactor and adjusting the process, and the SIS safety unit is used for judging whether the reactor is in a safe operation state, and triggering a safety interlock when the temperature or pressure is abnormal.

[0025] Compared with the prior art, the present application has the following beneficial effects:

[0026] 1. Improve production safety: through the independent monitoring of key safety parameters by the SIS system and the timely triggering of interlocking action when abnormal, the occurrence of dangerous accidents can be effectively prevented; at the same time, the cooperation of DCS and SIS can make the production process orderly adjusted or safely parked under the premise of safety, greatly reducing the probability of safety accidents, and providing reliable safety protection for production equipment and operating personnel.

[0027] 2. Improve production stability and efficiency: the accurate monitoring and adjustment of each process parameter by the DCS system ensure that the raw gas preparation, reaction process, heat recovery and product absorption and other links run stably according to the set process requirements, reduce the production interruption caused by parameter fluctuation, and improve the continuity of production. At the same time, stable process conditions are conducive to improving reaction efficiency and product quality, and improving overall production efficiency.

[0028] 3. Enhance system reliability: DCS and SIS systems use redundant communication links for data interaction, and are equipped with network security protection equipment, which ensures the reliability and real-time performance of data transmission, and avoids the problem of coordination failure caused by communication failure. In addition, the independent operation design of the SIS system makes it not affected by the failure of the DCS system, further enhancing the reliability of the whole system.

[0029] 4. Facilitate production optimization and improvement: the SIS system records safety event information and transmits it to the DCS system for storage and report generation, providing detailed accident analysis data for operating personnel and management personnel, which is helpful for summarizing production experience and improving production process and safety strategy, continuously improving the safety and process rationality of production. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings described in the following only represent the embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative effort.

[0031] Figure 1 The process flow diagram of the embodiment of the present application;

[0032] Figure 2 The system diagram of the embodiment of the present application. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the following will further describe the embodiments of the present application in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0034] In the description of the embodiments of the present application, it should be understood that the terms "upper", "lower", "front", "back", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, and are only used to facilitate the description of the embodiments of the present application and simplify the description, and are not intended to indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0035] In the description of the embodiments of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting" should be understood in a broad sense, for example, it can be fixedly connected, integrally connected, or detachably connected; it can be the communication inside two elements; it can be directly connected, or indirectly connected through an intermediate medium; for those skilled in the art, the specific meaning of the above terms in the embodiments of the present application should be understood according to the specific circumstances.

[0036] Referring to Figure 1 The iron-molybdenum method formaldehyde safe production process based on DCS-SIS collaborative control provided by the embodiment includes the following steps:

[0037] S1, raw material gas preparation: the refined methanol is pumped into a methanol evaporator by a methanol pump, and saturated water vapor in a steam drum is used to vaporize the methanol; at the same time, fresh air is mixed with part of the circulating absorption tower tail gas to form a mixed gas, and the mixed gas is heat exchanged with the vaporized methanol in a gas cooler;

[0038] S2, reaction process: after heat exchange, the raw material gas enters the methanol reactor, and under the action of iron-molybdenum catalyst, the oxidation reaction is carried out to generate formaldehyde, the temperature of the catalyst bed in the reactor is maintained by the high-speed flowing heat-conducting molten salt in the inter-tube gap, the temperature of the heat-conducting molten salt is controlled by the vaporization of the desalted water in the desalted water vaporization heat exchanger in the center of the reactor, the desalted water is supplied by a high-pressure water supply pump, and the generated medium-pressure steam is led to the steam drum;

[0039] S3, heat recovery and product absorption: the reacted high-temperature mixed gas enters the waste heat recovery boiler and the gas cooler in turn for heat recovery, the cooled mixed gas enters the concentrated formaldehyde scrubber and is absorbed by the continuously circulating high-concentration formaldehyde solution, and then the mixed gas containing lower concentration formaldehyde enters the absorption tower system and is in countercurrent contact with the circulating low-concentration formaldehyde solution for absorption, and the desalted water is added from the top of the absorption tower;

[0040] S4, DCS-SIS collaborative control: the DCS system monitors the process parameters such as methanol flow, methanol evaporator water vapor pressure, heat-conducting molten salt temperature, absorption tower top water inlet, steam drum liquid level, and absorption tower bottom formaldehyde solution liquid level in real time, and adjusts according to the preset control strategy; the SIS system independently monitors key safety parameters such as reactor pressure, temperature, oxygen content, and methanol concentration in raw material gas, and when the key safety parameters exceed the safety threshold, the SIS system immediately triggers the safety interlock action, including but not limited to cutting off the raw material supply, starting the emergency cooling system, opening the safety pressure relief device, etc., and sends a safety signal to the DCS system, and the DCS system adjusts the control strategy according to the signal to ensure that the production process continues to run or safely stops in a safe state.

[0041] The above technical solution combines the iron-molybdenum method formaldehyde production process with DCS-SIS collaborative control, the DCS system adjusts the process parameters in real time to ensure stable production, the SIS system independently monitors the key safety parameters and triggers interlocking when abnormal, and the two systems work together to make the production stable and efficient and run within the safety boundary, greatly reducing the risk of safety accidents and improving the safety and reliability of the production process.

[0042] In the raw material gas preparation step, the DCS system accurately controls the flow of the methanol pump to match the amount of methanol vaporization with the flow of the mixed gas, and adjusts the amount of steam entering the methanol evaporator according to the temperature and pressure of the mixed gas to ensure that the methanol vaporization temperature is stable within the preset range.

[0043] The DCS system accurately controls the flow of the methanol pump and the amount of steam entering to match the amount of methanol vaporization with the flow of the mixed gas and stabilize the vaporization temperature, ensuring that the raw material gas ratio and state are suitable, providing a stable raw material basis for subsequent reactions, which is beneficial to improve the reaction efficiency and product quality stability.

[0044] During the reaction process, the DCS system adjusts the flow of the high-pressure water supply pump according to the temperature change of the heat-conducting molten salt, and then controls the vaporization amount of the desalted water in the snake-shaped coil heat exchanger, so that the temperature of the heat-conducting molten salt is stabilized in the appropriate working temperature range of the catalyst; the SIS system continuously monitors the temperature gradient of the catalyst bed in the reactor, and when the temperature gradient exceeds the preset safety value, it is judged that there may be local deactivation of the catalyst or abnormal reaction, and the safety interlock is triggered immediately to prevent the reaction from getting out of control.

[0045] The DCS system controls the temperature of the heat-conducting molten salt by adjusting the flow of the high-pressure water supply pump to maintain the catalyst at an appropriate working temperature, ensuring efficient reaction; the SIS system monitors the temperature gradient of the catalyst bed to detect local deactivation of the catalyst or abnormal reaction and trigger interlocking in time to avoid reaction out of control and ensure safe and stable operation of the reaction unit.

[0046] In the heat recovery and product absorption step, the DCS system adjusts the flow of the cooling medium according to the temperature of the mixed gas at the outlet of the waste heat recovery boiler and the gas cooler to achieve efficient heat recovery; at the same time, according to the concentration and temperature of the circulating solution in each section of the absorption tower, the addition amount of the desalted water of the absorbent and the circulation flow of the circulating solution are adjusted to ensure the stability of the formaldehyde absorption efficiency and product concentration; the SIS system monitors the pressure and liquid level in the absorption tower, and when the pressure is too high or the liquid level is abnormal, the corresponding safety interlock is started, such as opening the safety valve of the absorption tower or adjusting the operating state of the circulating pump.

[0047] The DCS system adjusts the flow of the cooling medium and the relevant parameters of the absorbent according to temperature, concentration and other parameters to improve the heat recovery efficiency and formaldehyde absorption effect, and ensure the stability of the product concentration; the SIS system monitors the pressure and liquid level of the absorption tower and triggers the interlock when abnormal to prevent safety problems in the absorption tower and ensure the safety and efficiency of the absorption process.

[0048] The DCS system and the SIS system interact with each other through a redundant communication link to ensure the reliability and real-time performance of data transmission; the communication link uses industrial Ethernet and is equipped with network security protection equipment to prevent external network attacks from causing safety hazards to the production process. The DCS and SIS systems interact with each other through a redundant communication link and industrial Ethernet, and are equipped with network security protection equipment, which not only ensures the reliability and real-time performance of data transmission, ensures smooth collaborative control, but also prevents external network attacks, ensures the safety of the control system, and improves the stability and safety of the entire control system.

[0049] After triggering the safety interlock action, the SIS system automatically records detailed information of the safety event, including the time of event occurrence, the parameters triggering the interlock, the content of interlock action, etc., and transmits these information to the DCS system in real time. The DCS system stores the safety event information in the historical database and generates a safety event report, which is provided to the operators and managers for accident analysis and production improvement. The SIS system records the safety event information and transmits it to the DCS system, which stores the information and generates a report, providing the basis for accident analysis for operators and managers, which helps to summarize experience, improve production process and safety strategy, and continuously improve the safety and rationality of production process.

[0050] Referring to Figure 2 The embodiment also provides an iron-molybdenum method formaldehyde safety production system based on DCS-SIS collaborative control, which is used for realizing the iron-molybdenum method formaldehyde safety production process based on DCS-SIS collaborative control, and includes a raw gas preparation unit, a reaction unit, a heat recovery and product absorption unit, a DCS control unit and an SIS safety unit.

[0051] The raw gas preparation unit includes a methanol evaporator, a gas mixer and a gas cooler, which are used for vaporizing refined methanol and mixing and heat exchanging with air and circulating tail gas to obtain raw gas;

[0052] The reaction unit includes a methanol reactor, a heat-conducting molten salt circulation system, a snake-shaped coil heat exchanger, a high-pressure water supply pump and a steam drum, which are used for generating formaldehyde by methanol oxidation reaction under the action of iron-molybdenum catalyst and controlling the reaction temperature to recover reaction heat to generate steam;

[0053] The heat recovery and product absorption unit is composed of a waste heat recovery boiler, a concentrated formaldehyde scrubber and an absorption tower system, which are used for recovering heat of the mixed gas after reaction and absorbing formaldehyde to obtain products;

[0054] The DCS control unit collects process parameters of each unit in real time through sensors, outputs control signals according to a preset control strategy, adjusts the equipment of each unit, and realizes stable operation of the production process;

[0055] The SIS safety unit is used for independently setting sensors to monitor key safety parameters, triggering a safety interlock action immediately when the parameters exceed a safety threshold, ensuring production safety, and interacting with the DCS control unit.

[0056] The system integrates the raw gas preparation unit, the reaction unit, the heat recovery and product absorption unit and the like, is equipped with the DCS control unit and the SIS safety unit, and each unit cooperates to realize the whole formaldehyde production process. The cooperation of the DCS and the SIS enables the system to be stable in production while having reliable safety guarantee, forming an integrated, safe and efficient production system.

[0057] The methanol evaporator in the raw gas preparation unit is provided with a steam flow regulating valve connected with the DCS control unit, which adjusts the opening of the steam flow regulating valve according to the temperature and pressure feedback signals in the methanol evaporator to control the steam entering amount. The steam flow regulating valve on the methanol evaporator is connected with the DCS control unit, which adjusts the valve opening according to the temperature and pressure feedback to accurately control the steam entering amount, thereby stabilizing the working condition in the methanol evaporator and ensuring the stable methanol vaporization effect to provide reliable conditions for raw gas preparation.

[0058] The methanol reactor in the reaction unit is provided with multiple layers of temperature sensors and pressure sensors connected with the DCS control unit and the SIS safety unit respectively. The DCS control unit is used to monitor the temperature and pressure distribution in the reactor for process adjustment, and the SIS safety unit is used to determine whether the reactor is in a safe operating state and trigger safety interlocking when the temperature or pressure is abnormal.

[0059] The multiple layers of sensors in the methanol reactor are connected with the DCS and SIS systems respectively. The DCS can comprehensively monitor the temperature and pressure distribution and adjust it to ensure uniform and stable reaction. The SIS can determine the safety state of the reactor in time and trigger interlocking when abnormal, which provides double protection for the safe and stable operation of the reaction unit.

[0060] The concentration sensor and the liquid level sensor are provided in the absorption tower system. The concentration sensor is connected with the DCS control unit to monitor the formaldehyde concentration of the circulating solution in each section of the absorption tower, and the DCS control unit adjusts the amount of absorbent added and the circulating solution flow according to the concentration signal. The liquid level sensor is connected with the SIS safety unit, which triggers interlocking when the liquid level exceeds the safe range to prevent overflow or dry tower accidents in the absorption tower.

[0061] In the absorption tower system, the concentration sensor is connected with the DCS to accurately adjust the absorption-related parameters and ensure the absorption efficiency and product concentration. The liquid level sensor is connected with the SIS to trigger interlocking when the liquid level is abnormal to prevent overflow or dry tower in the absorption tower, ensuring the safe and stable operation of the absorption tower and improving the reliability of the product absorption process.

[0062] Working principle:

[0063] The iron-molybdenum method formaldehyde safe production process and system based on DCS-SIS collaborative control realizes precise control and reliable safety protection of the whole process of iron-molybdenum method formaldehyde production through the collaborative work of DCS system and SIS system.

[0064] The DCS system is responsible for real-time monitoring of various process parameters in the production process, such as methanol flow, methanol evaporator water vapor pressure, heat-conducting molten salt temperature, and absorption tower overhead water intake, and adjusting related equipment according to the pre-set control strategy to ensure that each production link operates stably according to the set process requirements, maintaining the continuity and efficiency of the production process.

[0065] The SIS system is independent of the DCS system and focuses on monitoring key safety parameters such as pressure, temperature, oxygen content in the reactor, and methanol concentration in the raw material gas. When these key safety parameters exceed the pre-set safety threshold, the SIS system can quickly trigger safety interlocking actions such as cutting off the raw material supply, starting the emergency cooling system, etc., to prevent further development of dangerous situations. At the same time, the SIS system interacts with the DCS system to enable the DCS system to adjust the control strategy according to the safety state, realizing the coordinated work of the two systems and ensuring the production under the premise of safety.

[0066] Method for use:

[0067] 1. System startup: First, start the DCS system and the SIS system to ensure that both are running normally and establish a communication connection. Then, start the related equipment of the raw material gas preparation unit, the reaction unit, and the heat recovery and product absorption unit, such as the methanol pump, the fan, and the circulating pump, in sequence.

[0068] 2. Production operation: During the production process, the DCS system collects real-time process parameters from each unit and automatically adjusts the operating state of related equipment according to the control strategy, such as controlling the methanol content in the raw material gas by adjusting the flow of the methanol pump and maintaining the temperature stability in the reactor by controlling the flow of the high-pressure water supply pump. The SIS system continuously monitors key safety parameters and is in standby state.

[0069] 3. Safety handling: When the SIS system detects abnormal key safety parameters, it immediately triggers safety interlocking actions and sends safety state signals to the DCS system. After receiving the signals, the DCS system adjusts the control strategy to cooperate with the actions of the SIS system, such as adjusting the related valves to close and stopping the feeding of subsequent links after cutting off the raw material supply.

[0070] 4. System stop: When normal shutdown occurs, gradually reduce the operating load of each device through the DCS system, stop the raw material supply, the reaction unit operation, and the product absorption unit operation in sequence, and finally shut down the DCS system and the SIS system. In case of emergency, the SIS system triggers an emergency shutdown interlock to quickly stop the operation of the entire production system.

[0071] In summary, the iron-molybdenum method formaldehyde safe production process and system based on DCS-SIS collaborative control provided by the embodiment has the following advantages:

[0072] 1. Enhancing production safety: By independently monitoring key safety parameters and triggering interlocking actions in time of abnormalities, SIS system can effectively prevent dangerous accidents from happening; meanwhile, the cooperation between DCS and SIS ensures the orderly adjustment or safe shutdown of the production process under the premise of safety, greatly reducing the probability of safety accidents and providing reliable safety protection for production equipment and operators.

[0073] 2. Improving production stability and efficiency: The precise monitoring and adjustment of DCS system on various process parameters ensure the stable operation of raw gas preparation, reaction process, heat recovery and product absorption in each link according to the set process requirements, reduce the production interruption caused by parameter fluctuation, and improve the continuity of production. At the same time, stable process conditions are conducive to improving reaction efficiency and product quality, and enhancing overall production efficiency.

[0074] 3. Enhancing system reliability: DCS and SIS systems use redundant communication links for data interaction and are equipped with network security protection equipment, ensuring the reliability and real-time performance of data transmission and avoiding the problem of coordination failure caused by communication failure. In addition, the independent operation design of SIS system makes it not affected by DCS system failure, further enhancing the reliability of the whole system.

[0075] 4. Facilitating production optimization and improvement: SIS system records safety event information and transmits it to DCS system for storage and report generation, providing detailed accident analysis data for operators and managers, which helps to summarize production experience and improve production process and safety strategy, continuously improving the safety and process rationality of production.

[0076] The above shows and describes the basic principles of the present invention, and the above is only the preferred embodiment of the present invention, and does not limit the present invention. The above examples and descriptions in the specification only illustrate the principles of the present invention. Any modification, equivalent replacement and improvement within the scope of the present invention shall be included in the protection scope of the present invention.

Claims

1. The iron-molybdenum formaldehyde production safety process based on DCS-SIS collaborative control is characterized by: The following steps are involved: Raw gas preparation: refined methanol is pumped into the methanol evaporator through a methanol pump, where it is vaporized using saturated water vapor in the steam drum. Simultaneously, fresh air is mixed with part of the recycled absorber tail gas to form a mixed gas, which is then heat-exchanged with the vaporized methanol in a gas cooler. Reaction process: The raw gas after heat exchange enters the methanol reactor and undergoes an oxidation reaction to produce formaldehyde under the action of an iron-molybdenum catalyst. The temperature of the catalyst bed in the reactor is maintained by the high-speed flow of heat-conducting molten salt in the gaps between the tubes. The temperature of the heat-conducting molten salt is controlled by vaporizing the desalted water in the serpentine coil heat exchanger located in the center of the reactor to remove heat. The desalted water is supplied by a high-pressure water supply pump, and the generated medium-pressure steam is directed to the steam drum. Heat recovery and product absorption: The high-temperature mixed gas after the reaction enters the waste heat recovery boiler and gas cooler in sequence for heat recovery. The cooled mixed gas enters the concentrated formaldehyde scrubber and is absorbed by the continuously circulating high-concentration formaldehyde solution. The mixed gas containing lower concentration formaldehyde then enters the absorption tower system and is countercurrently contacted with the circulating low-concentration formaldehyde solution in each section for absorption. The absorbent, desalted water, is added from the top of the absorption tower. DCS-SIS collaborative control: The DCS system monitors process parameters such as methanol flow, water vapor pressure of the methanol evaporator, molten salt temperature, water inlet to the top of the absorption tower, liquid level in the steam drum, and formaldehyde solution level at the bottom of the absorption tower in real time, and adjusts them according to the preset control strategy; the SIS system independently monitors key safety parameters such as pressure, temperature, oxygen content in the reactor and methanol concentration in the raw gas. When key safety parameters exceed the safety threshold, the SIS system immediately triggers safety interlock actions, including but not limited to cutting off the raw material supply, starting the emergency cooling system, opening the safety pressure relief device, etc., and simultaneously sends a safety status signal to the DCS system. The DCS system adjusts the control strategy based on the signal to ensure that the production process continues to operate in a safe state or is safely shut down.

2. The iron-molybdenum method formaldehyde safety production process based on DCS-SIS coordinated control according to claim 1 is characterized in that: During the raw gas preparation step, the flow of the methanol pump is precisely controlled by the DCS system to match the vaporization amount of methanol with the flow of the mixed gas. At the same time, the flow of steam in the steam drum entering the methanol evaporator is adjusted according to the temperature and pressure of the mixed gas to ensure that the methanol vaporization temperature is stable within the preset range.

3. The iron-molybdenum method formaldehyde safety production process based on DCS-SIS coordinated control according to claim 1 is characterized in that: During the reaction process, the DCS system adjusts the flow of the high-pressure water supply pump according to the temperature change of the heat-conducting molten salt, thereby controlling the vaporization amount of the desalted water in the serpentine coil heat exchanger, so that the temperature of the heat-conducting molten salt is stable within the suitable operating temperature range of the catalyst; The SIS system continuously monitors the temperature gradient of the catalyst bed in the reactor. When the temperature gradient exceeds the preset safety value, it determines that there may be local deactivation of the catalyst or abnormal reaction, and immediately triggers the safety interlock to prevent the reaction from getting out of control.

4. The iron-molybdenum method formaldehyde safety production process based on DCS-SIS coordinated control according to claim 1 is characterized in that: During the heat recovery and product absorption steps, the DCS system adjusts the flow of the cooling medium according to the temperature of the mixed gas at the outlet of the waste heat recovery boiler and the gas cooler to achieve efficient heat recovery. At the same time, the amount of absorbent desalted water added and the circulation flow of the circulating solution are adjusted according to the concentration and temperature of the circulating solution in each section of the absorption tower to ensure the formaldehyde absorption efficiency and stable product concentration. The SIS system monitors the pressure and liquid level in the absorption tower. When the pressure is too high or the liquid level is abnormal, the corresponding safety interlock is activated, such as opening the safety valve of the absorption tower or adjusting the operating status of the circulation pump.

5. The iron-molybdenum method formaldehyde safety production process based on DCS-SIS coordinated control according to claim 1 is characterized in that: The DCS system and the SIS system exchange data via redundant communication links to ensure the reliability and real-time performance of data transmission; The communication link uses industrial Ethernet and is equipped with network security protection equipment to prevent external network attacks from causing safety hazards to the production process.

6. The iron-molybdenum method formaldehyde safety production process based on DCS-SIS coordinated control according to claim 1 is characterized in that: After triggering the safety interlock action, the SIS system automatically records detailed information about the safety event, including the time of the event, the parameters that triggered the interlock, the content of the interlock action, etc., and transmits this information to the DCS system in real time. The DCS system stores the safety event information in a historical database and generates a safety event report for operators and managers to conduct accident analysis and production improvements.

7. The iron-molybdenum formaldehyde production safety system based on DCS-SIS collaborative control is characterized by: The method for realizing the safe production process of formaldehyde by the iron-molybdenum method based on DCS-SIS coordinated control according to any one of claims 1 to 6 comprises: The raw gas preparation unit includes a methanol evaporator, a gas mixer, and a gas cooler, which are used to vaporize refined methanol, mix it with air and recycled tail gas, and exchange heat to obtain raw gas; The reaction unit includes a methanol reactor, a heat-conducting molten salt circulation system, a serpentine coil heat exchanger, a high-pressure water supply pump, and a steam drum. It is used to oxidize methanol to form formaldehyde under the action of an iron-molybdenum catalyst, control the reaction temperature, and recover the reaction heat to generate steam. The heat recovery and product absorption unit consists of a waste heat recovery boiler, a concentrated formaldehyde scrubber, and an absorption tower system. It is used to recover the heat of the mixed gas after the reaction and absorb formaldehyde to obtain the product. The DCS control unit collects the process parameters of each unit in real time through sensors, outputs control signals according to the preset control strategy, and adjusts the equipment of each unit to achieve stable operation of the production process; The SIS safety unit independently sets sensors to monitor key safety parameters. When the parameters exceed the safety threshold, the safety interlock action is immediately triggered to ensure production safety and exchange data with the DCS control unit.

8. The iron-molybdenum process formaldehyde safety production system based on DCS-SIS coordinated control according to claim 7 is characterized in that: A steam flow regulating valve is installed on the methanol evaporator in the raw gas preparation unit, and the regulating valve is connected to the DCS control unit. The DCS control unit adjusts the opening of the steam flow regulating valve according to the temperature and pressure feedback signals in the methanol evaporator to control the amount of steam entering.

9. The iron-molybdenum process formaldehyde safety production system based on DCS-SIS coordinated control according to claim 7 is characterized in that: The methanol reactor of the reaction unit is equipped with multiple layers of temperature sensors and pressure sensors, which are respectively connected to the DCS control unit and the SIS safety unit. The DCS control unit is used to monitor the distribution of temperature and pressure in the reactor and perform process adjustments; the SIS safety unit is used to determine whether the reactor is in a safe operating state and trigger a safety interlock when the temperature or pressure is abnormal.

10. The iron-molybdenum process formaldehyde safety production system based on DCS-SIS coordinated control according to claim 7 is characterized in that: The absorption tower system is equipped with a concentration sensor and a liquid level sensor. The concentration sensor is connected to the DCS control unit to monitor the formaldehyde concentration of the circulating solution in each section of the absorption tower. The DCS control unit adjusts the amount of absorbent added and the flow rate of the circulating solution according to the concentration signal; the liquid level sensor is connected to the SIS safety unit. When the liquid level exceeds the safety range, the SIS safety unit triggers an interlock to prevent safety accidents such as overflow or dry tower in the absorption tower.

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