Method for operating an air supply device of a gas and electric dual drive for a maleic anhydride production system

Abstract

The application provides a running method of a steam-electric dual-drive air supply device for a maleic anhydride preparation system, the air supply device comprising an air compressor, an electric motor, a steam turbine, a gear box and a clutch, the rotating shaft of the electric motor is coupled with the rotating shaft of the air compressor through the gear box, the rotating shaft of the steam turbine is uncouplably coupled with the rotating shaft of the air compressor through the clutch, the running method comprises: reducing the rotating speed of the steam turbine in a rotating speed control mode, judging whether the cut-out is successful by detecting the holding time of the clutch engagement switch and the power of the electric motor, and closing the steam turbine if the cut-out is successful; and increasing the rotating speed of the steam turbine in the rotating speed control mode, judging whether the cut-in is successful by detecting the holding time of the clutch engagement switch and the power of the electric motor, and changing the rotating speed control mode into a load loading control mode if the cut-in is successful. The application can realize the arbitrary cut-in / cut-out of the steam turbine in the maleic anhydride preparation process.

Description

Technical Field

[0001] This invention relates to the field of maleic anhydride production, and more specifically, to a method for operating a dual-drive (gas and electric) air supply device for a maleic anhydride preparation system. Background Technology

[0002] Maleic anhydride is an important basic organic chemical raw material, widely used in the production of various chemicals. Currently, the main industrial production methods for maleic anhydride include the benzene process and the n-butane process. The benzene process uses a mixture of benzene and air as raw material, oxidizing benzene to maleic anhydride in the presence of a catalyst. The n-butane process uses a mixture of n-butane and air as raw material, oxidizing n-butane to maleic anhydride in the presence of a catalyst. Previously, my country mainly used the benzene process to produce maleic anhydride, but due to the advantages of the n-butane process in terms of raw materials, environmental protection, efficiency, and cost, my country's production capacity for maleic anhydride using the n-butane process has been continuously increasing in recent years.

[0003] Both the benzene process and the n-butane process use air as one of the raw materials. In maleic anhydride plants, an air compressor is used to pressurize the air and send it to the maleic anhydride reactor for the oxidation reaction.

[0004] In both the benzene and n-butane processes, the most widely used maleic anhydride reactor is the axial-tube fixed-bed reactor. This reactor consists of numerous tubes and uses molten salt for heat exchange. Because the maleic anhydride formation reaction is highly sensitive to changes in reaction conditions, the smooth progress of maleic anhydride production and product quality are heavily dependent on the radial homogeneity of the material and temperature within the reactor. However, as the reactor diameter increases, controlling the radial homogeneity of the material and temperature within the reactor becomes increasingly difficult. Therefore, to ensure smooth reaction progress and the quality of maleic anhydride, the diameter of the maleic anhydride reactor is limited and cannot be further increased.

[0005] Because the maximum diameter of a single maleic anhydride reactor is limited, the surface area of ​​the fluid flowing through the reactor is also limited, which in turn places higher demands on the catalyst bed height. Industrial maleic anhydride reactors have a large height-to-diameter ratio of the catalyst bed, resulting in a high pressure drop as the reaction fluid flows through the catalyst bed, thus requiring higher air compressor outlet pressures. Due to this high sensitivity, the air supply (also known as air delivery) from the air compressor must maintain both high pressure and very stable operation; otherwise, it may lead to abnormal reactions or even termination of the reaction. These air supply requirements place high demands on the air supply system used in maleic anhydride reactors.

[0006] The core of the air supply system for supplying air to the maleic anhydride reactor is the air compressor. Typically, the air compressor can be driven by an electric motor, or by a combination of a steam turbine and an electric motor.

[0007] There is still a need for improvement in the air supply device used in the maleic anhydride preparation system. Summary of the Invention

[0008] In one aspect, the present invention provides a method for operating a dual-drive (steam and electric) air supply device for a maleic anhydride preparation system. The air supply device includes an air compressor, an electric motor, a steam turbine, a gearbox, and a clutch. The shaft of the electric motor is coupled to the shaft of the air compressor via the gearbox, and the shaft of the steam turbine is disengaged from the shaft of the air compressor via the clutch.

[0009] The operating method includes:

[0010] The turbine speed is reduced using a speed control mode. The success of the disengagement is determined by detecting the clutch engagement switch holding time and the motor power. If the disengagement is successful, the turbine is shut down.

[0011] The turbine speed is increased by adopting a speed control mode. The engagement success is determined by detecting the clutch engagement switch holding time and the motor power. If the engagement is successful, the speed control mode is changed to a load loading control mode.

[0012] Optionally, the maleic anhydride preparation system is a multi-reactor system, and the power of the electric motor is insufficient to drive the air compressor load when all maleic anhydride reactors are running.

[0013] Optionally, the maleic anhydride preparation system is a multi-reactor system and includes a steam generation device.

[0014] The steam generating device is configured to supply steam to the steam turbine.

[0015] Optionally, the steam generating device is a molten salt heat exchanger and steam boiler of a maleic anhydride reactor, and the operating method further includes:

[0016] Water is fed into the molten salt heat exchanger, and the water is heated to form steam in the steam package.

[0017] Optionally, the steam generating device is a waste gas incinerator of a maleic anhydride reactor, and the operating method further includes:

[0018] The heat from the waste gas incinerator is used to heat water to form steam.

[0019] Optionally, the steam generating device is a molten salt heat exchanger, a steam drum, and a waste gas incinerator connected in series for a maleic anhydride reactor, and the operating method further includes:

[0020] Water is fed into the molten salt heat exchanger, heated to form steam in the steam package, and further heated in the waste gas incinerator.

[0021] Optionally, the maleic anhydride preparation system is a system comprising multiple reactors.

[0022] The air compressor is an axial flow air compressor, which is equipped with stator vanes and anti-surge valve;

[0023] The air supply device of the air compressor also includes:

[0024] A stator vane controller that controls the stator vane angle based on target exhaust pressure and / or flow feedback;

[0025] An anti-surge valve controller, which controls the opening degree of the anti-surge valve based on the anti-surge line feedback of the air compressor; and

[0026] The feedforward performance controller is configured to initiate emergency trip control upon receiving a reactor trip signal, and to terminate the emergency trip control after the anti-surge valve closes.

[0027] The emergency control for vehicle slump includes: feedforward control of the anti-surge valve opening, and changing the target exhaust pressure and / or flow rate of the stator vane controller.

[0028] The operating method includes:

[0029] When the plurality of maleic anhydride reactors are running, the stationary vane controller controls the stationary vane angle based on the target exhaust pressure and / or flow rate and feedback from the measured value, and the anti-surge valve controller controls the anti-surge valve opening based on the anti-surge line of the air compressor and feedback from the measured value.

[0030] When at least one of the plurality of maleic anhydride reactors trips, the feedforward performance controller initiates the trip emergency control upon receiving a trip signal from the maleic anhydride reactor, and terminates the trip emergency control after the anti-surge valve closes, wherein the trip emergency control includes:

[0031] i) Based on the number of remaining operating maleic anhydride reactors, quickly open the anti-surge valve to the first opening degree and change the target exhaust pressure and / or flow rate of the stationary vane controller;

[0032] ii) Reduce the anti-surge valve opening from the first degree, and then wait for the stationary vane angle to stabilize;

[0033] iii) Repeat step ii) until the anti-surge valve is closed. Attached Figure Description

[0034] Figure 1A schematic diagram of an air compressor unit, including an air compressor and a drive source, is shown.

[0035] Figure 2 A schematic diagram of the connection between the steam-electric dual-drive air compressor unit and the reactor is shown in one embodiment.

[0036] Figure 3 A typical anti-surge diagram for an air compressor is shown.

[0037] Figure 4 A schematic diagram of the feedforward control connection principle according to an embodiment of the present invention is shown. Detailed Implementation Plan

[0038] In maleic anhydride plants, to save energy, a dual-drive (steam and electric) air compressor can be used, driven by both an electric motor and a steam turbine. The steam used to drive the turbine can be obtained from heat recovered from the maleic anhydride reactor or from other sources. For example, the maleic anhydride preparation system may include a steam bath for recovering heat from the maleic anhydride reactor. Steam can also be obtained from other sources within the maleic anhydride plant, such as a waste gas incinerator.

[0039] In practical operation, the power and load conditions of the air compressor are constantly changing. In some cases, the steam supplied to the maleic anhydride plant may be unstable; for example, problems may occur in the steam system. Furthermore, the turbine may malfunction and fail to operate normally. If a turbine malfunction causes large fluctuations in the air supply from the air compressor to the maleic anhydride reactor, the reaction results, which are highly sensitive to air supply stability, will deteriorate. Therefore, during air compressor operation, the turbine needs to be able to be switched on and off online at will to prevent turbine malfunctions from affecting the stable air supply to the maleic anhydride reactor.

[0040] During the operation of an air compressor, due to the instability of steam conditions, the operation of the steam turbine requires online start-up and shutdown.

[0041] In order to ensure that the normal operation of the motor-driven unit is not affected when there is a problem with the steam system or the steam turbine fails to operate normally, a clutch coupling the steam turbine and the air compressor is used in the air supply device of the present invention.

[0042] In one embodiment, the present invention provides a method for operating a dual-drive (steam and electric) air supply device for a maleic anhydride preparation system. The air supply device includes an air compressor, an electric motor, a steam turbine, a gearbox, and a clutch. The shaft of the electric motor is coupled to the shaft of the air compressor via the gearbox, and the shaft of the steam turbine is disengaged from the shaft of the air compressor via the clutch.

[0043] The operating method includes:

[0044] The turbine speed is reduced using a speed control mode. The success of the disengagement is determined by detecting the clutch engagement switch holding time and the motor power. If the disengagement is successful, the turbine is shut down.

[0045] The turbine speed is increased by adopting a speed control mode. The engagement success is determined by detecting the clutch engagement switch holding time and the motor power. If the engagement is successful, the speed control mode is changed to a load loading control mode.

[0046] The air supply unit includes an electric motor, a steam turbine, a gearbox, and a clutch. The shaft of the electric motor is coupled to the shaft of the air compressor via the gearbox, and the shaft of the steam turbine is disengaged from the shaft of the air compressor via the clutch.

[0047] The motor shaft and the air compressor shaft are coupled via a gearbox. The gearbox ensures that the air compressor is always coupled to the motor and can convert the motor shaft speed to a suitable air compressor shaft speed.

[0048] The clutch's input shaft is connected to the steam turbine, and its output shaft is connected to the air compressor. The clutch engages and disengages by comparing the input shaft speed with the output shaft speed. When the clutch's input shaft speed is greater than the output shaft speed (i.e., the steam turbine's shaft speed is greater than the air compressor's shaft speed), the clutch automatically engages, allowing the steam turbine to drive the air compressor. When the clutch's input shaft speed is less than the output shaft speed (i.e., the steam turbine's shaft speed is less than the air compressor's shaft speed), the clutch automatically disengages, allowing the steam turbine to disengage.

[0049] Figure 1 A schematic diagram of an air compressor unit including an air compressor and a drive source is shown. The shaft of the electric motor 2 is coupled to the shaft of the air compressor 1 via a gearbox 4, and the shaft of the steam turbine 3 is disengaged from the shaft of the air compressor 1 via a clutch 5.

[0050] Figure 2 A schematic diagram of the connection between the steam-electric dual-drive air compressor unit and the reactor is shown in one embodiment. In the diagram, the components corresponding to the numbers are: air compressor 1, electric motor 2, steam turbine 3, gearbox 4, clutch 5, air filter 6, vent silencer 7, anti-surge valve 8, check valve 9, flow meter 10, air supply valve 11, mixer 12, maleic anhydride reactor 13, molten salt heat exchanger 14, steam drum 15, and incinerator 16. Boiler feedwater enters the molten salt heat exchanger, is heated, and then passes through the steam drum. The generated steam is further heated in the incinerator to drive the steam turbine. The steam turbine can be disengaged from the air compressor via a clutch.

[0051] This invention enables a flexible combination of electric motor drive and steam turbine drive by incorporating a clutch between the steam turbine and the air compressor, and a gearbox between the electric motor and the air compressor. In conjunction with specific operations in the operating method, the steam turbine and electric motor can be flexibly combined to drive the air compressor according to different operating conditions, thereby maintaining a stable air supply to the maleic anhydride reactor.

[0052] As described above, the clutch engages and disengages by comparing the input shaft speed with the output shaft speed. However, this is only an ideal situation; during actual operation, it is necessary to ensure that the operation is completed and the air compressor is subsequently in the correct operating state. Therefore, in one embodiment, the operating method of the present invention performs a special detection operation to achieve engagement and disengagement.

[0053] During the cut-out operation, the holding time of the clutch engagement switch is monitored, and this is combined with changes in motor power to determine whether the turbine has successfully cut out. If the engagement switch holding time is within the limit and the motor power increases significantly, the cut-out is considered successful. If the engagement switch holding time exceeds the limit or the motor power does not increase significantly, the cut-out is considered unsuccessful. If the cut-out is successful, the turbine enters the shutdown process. All of the above judgments and controls can be executed automatically through a pre-set program.

[0054] During operation, the holding time of the clutch engagement switch is monitored and combined with changes in motor power to determine whether the turbine has been successfully engaged. If the engagement switch holding time is within the limit and the motor power decreases significantly, the engagement is considered successful. If the engagement switch holding time exceeds the limit or the motor power does not increase significantly, the engagement is considered unsuccessful. If the engagement is successful, the turbine switches from the pre-engagement speed control mode to the load loading control mode. All of the above judgments and controls can be executed automatically through a pre-set program.

[0055] Accordingly, the operating method of the present invention includes:

[0056] The turbine speed is reduced using a speed control mode. The success of the disengagement is determined by detecting the clutch engagement switch holding time and the motor power. If the disengagement is successful, the turbine is shut down.

[0057] The turbine speed is increased by adopting a speed control mode. The engagement success is determined by detecting the clutch engagement switch holding time and the motor power. If the engagement is successful, the speed control mode is changed to a load loading control mode.

[0058] The above judgment can be executed automatically through the control program.

[0059] In other words, in one implementation scheme, the online cut-in and cut-out operations of the steam turbine include:

[0060] 1. When the steam-electric dual-drive unit is running normally, if the steam turbine or steam system malfunctions and the steam turbine needs to be shut down, but the unit needs to continue running normally, the turbine speed can be reduced to be lower than the air compressor speed. At this time, the clutch input shaft speed is lower than the output shaft speed, the clutch automatically disengages, and the steam turbine can be disconnected from the unit's running shaft system and can be stopped and run independently by electric drive.

[0061] 2. Before the turbine is disconnected, the turbine speed is reduced. By measuring the disengagement holding time of the clutch engagement switch and the change in the main motor power, the control program automatically determines whether the turbine has successfully disconnected. After automatically determining that the turbine has successfully disengaged, the turbine automatically enters the shutdown operation.

[0062] 3. When the air compressor unit is running normally driven by the motor, if it is necessary to put the steam turbine into operation, the speed of the steam turbine can be increased to be higher than that of the air compressor. At this time, the speed of the clutch input shaft is greater than that of the output shaft, the clutch automatically engages, and the steam turbine can be put into the unit's shaft system, and the unit can operate under both steam and electric drive.

[0063] 4. The turbine engagement is mainly determined by the engagement and holding time of the clutch engagement switch and the change in the main motor power. The control program automatically determines whether the turbine engagement is successful. After determining that the turbine has completed online engagement, the turbine control mode changes from the speed control mode before engagement to the load loading control mode after engagement.

[0064] By setting up a clutch and providing the above-described operating method, the air supply device of the present invention can ensure the normal operation of the motor-driven unit when there is a problem with the maleic anhydride steam system or the turbine cannot operate normally, without causing significant impact on the user's process equipment or causing reactor shutdown, thus improving the uptime rate.

[0065] In one embodiment, the maleic anhydride preparation system is a multi-reactor system, and the power of the electric motor is insufficient to drive the air compressor load when all maleic anhydride reactors are running.

[0066] In current maleic anhydride plants, one air compressor supplies air to one reactor. For such air compressors, the steam turbine in a dual-drive (steam-electric) configuration serves as a beneficial supplement to the electric motor. That is, the electric motor's power can independently drive the air compressor to its maximum operating load. When the reactor is running, the steam turbine operates, allowing the electric motor to run at a lower power to save energy.

[0067] However, the inventors discovered that in maleic anhydride preparation systems comprising multiple reactors, each reactor requires a high supply pressure, placing high demands on the total power of the air compressors, while using a single high-power electric motor places high demands on the equipment. However, maleic anhydride preparation systems can generate a significant amount of usable waste heat. Therefore, in one embodiment, the power selection of the electric motor of the present invention cannot solely drive the air compressor to its maximum operating load, but only to a partial load. In other words, when the maleic anhydride preparation system is operating normally, both the turbine and the electric motor are required to drive the air compressor. This avoids the use of a single high-power electric motor and fully utilizes the waste heat in the plant, thus saving energy. However, this requires simultaneously finding appropriate operating methods to ensure the safe operation of the gas supply unit under various operating conditions. For such systems, the online commissioning and shutdown operation of the turbine of the present invention is particularly necessary.

[0068] In one embodiment, the maleic anhydride preparation system is a multi-reactor system and includes a steam generation device.

[0069] The steam generating device is configured to supply steam to the steam turbine.

[0070] When the maleic anhydride preparation system of the present invention includes a steam generating device and can drive a steam turbine, thermal energy can be fully utilized to convert it into driving force for an air compressor. The steam generating device can be a device utilizing the exothermic heat from a reactor, a device utilizing the exothermic heat from a waste gas incinerator, or an additional separate steam generating device, etc. The steam generating device can be, for example, a steam drum.

[0071] The inventors have discovered that the following components in the maleic anhydride preparation system are particularly suitable for providing a stable and sufficient steam drive for the steam turbine of an air compressor in production.

[0072] In one embodiment, the steam generating apparatus is a molten salt heat exchanger and a steam drum of a maleic anhydride reactor, and the operating method further includes: feeding water into the molten salt heat exchanger, heating the water, and then generating steam in the steam drum. Figure 2 As shown, boiler feedwater can pass through molten salt heat exchanger 14, utilizing the waste heat of the molten salt to raise the water temperature and generate steam in the steam drum. The molten salt in the maleic anhydride reactor can provide a large amount of heat that can convert water into steam. Utilizing the steam to recover waste heat from the molten salt used in the maleic anhydride reactor to drive the steam turbine can achieve significant energy savings.

[0073] In one embodiment, the steam generating device is a waste gas incinerator of a maleic anhydride reactor, and the operating method further includes heating water to generate steam using the heat from the waste gas incinerator. The waste gas incinerator of the maleic anhydride reactor can provide a large amount of energy that can be carried by steam, and using it to drive a steam turbine can achieve significant energy savings.

[0074] In a preferred embodiment, the steam generating apparatus comprises a molten salt heat exchanger, a steam drum, and a waste gas incinerator connected in series with a maleic anhydride reactor, and the operating method further includes: feeding water into the molten salt heat exchanger, heating the water to form steam in the steam drum, and further heating the steam in the waste gas incinerator. Figure 2 As shown, the steam generated using the waste heat of the molten salt can be further passed through an exhaust gas incinerator, and the heat generated from the incineration exhaust gas can be used to heat and pressurize the steam. This fully utilizes the heat in the molten salt that dissipates heat from the reactor, as well as the combustion heat contained in the exhaust gas, thereby providing a stronger drive for the steam turbine.

[0075] For maleic anhydride preparation systems containing multiple reactors, the preferred operating method of the present invention can also address abnormal reactor tripping conditions by using anti-surge valves in conjunction with stationary vanes.

[0076] In one embodiment, the maleic anhydride preparation system is a multi-reactor system.

[0077] The air compressor is an axial flow air compressor, which is equipped with stator vanes and anti-surge valve;

[0078] The air supply device of the air compressor also includes:

[0079] A stator vane controller that controls the stator vane angle based on target exhaust pressure and / or flow feedback;

[0080] An anti-surge valve controller, which controls the opening degree of the anti-surge valve based on the anti-surge line feedback of the air compressor; and

[0081] The feedforward performance controller is configured to initiate emergency trip control upon receiving a reactor trip signal, and to terminate the emergency trip control after the anti-surge valve closes.

[0082] The emergency control for vehicle slump includes: feedforward control of the anti-surge valve opening, and changing the target exhaust pressure and / or flow rate of the stator vane controller.

[0083] The operating method includes:

[0084] When the plurality of maleic anhydride reactors are running, the stationary vane controller controls the stationary vane angle based on the target exhaust pressure and / or flow rate and feedback from the measured value, and the anti-surge valve controller controls the anti-surge valve opening based on the anti-surge line of the air compressor and feedback from the measured value.

[0085] When at least one of the plurality of maleic anhydride reactors trips, the feedforward performance controller initiates the trip emergency control upon receiving a trip signal from the maleic anhydride reactor, and terminates the trip emergency control after the anti-surge valve closes, wherein the trip emergency control includes:

[0086] i) Based on the number of remaining operating maleic anhydride reactors, quickly open the anti-surge valve to the first opening degree and change the target exhaust pressure and / or flow rate of the stationary vane controller;

[0087] ii) Reduce the anti-surge valve opening from the first degree, and then wait for the stationary vane angle to stabilize;

[0088] iii) Repeat step ii) until the anti-surge valve is closed.

[0089] With continuous improvements and developments in air compressors regarding delivery pressure and stability, it has become possible to simultaneously supply air to multiple maleic anhydride reactors using a single air compressor. However, the inventors have discovered in practice that directly connecting the exhaust port of the air compressor to the air inlet of two or more parallel maleic anhydride reactors makes it difficult to achieve safe production operation of maleic anhydride preparation systems containing multiple reactors.

[0090] A key characteristic of maleic anhydride reactors is that the stability of the incoming air supply is crucial for their smooth operation. In essence, a stable airflow from the air compressor is a prerequisite for the stable operation of the maleic anhydride reactor. Therefore, the air compressor used in maleic anhydride reactors not only needs to provide sufficiently high pressure and flow rate, but also needs to maintain a stable air supply to each normally operating maleic anhydride reactor under various complex operating conditions. Otherwise, it is difficult to successfully implement a design where multiple maleic anhydride reactors share a single air compressor.

[0091] When using a single air compressor to supply pressurized air to multiple maleic anhydride reactors, the air inlet pipes of each reactor are directly connected to the exhaust port of the same air compressor, thus connecting multiple reactors in parallel downstream of the same compressor. However, the inventors unexpectedly discovered in practice that such direct pipe connections downstream of a conventional air compressor are insufficient for practical applications. While this connection method can provide stable air supply to each reactor when all reactors are operating normally, sudden abnormal conditions in some reactors can adversely affect other reactors in the system, even causing unexplained interlocking trips. This renders the aforementioned device impractical. Without relying on any theory, the inventors discovered that these results are caused by the lag in the feedback control of the stator vanes and anti-surge valve, which prevents timely stabilization of exhaust pressure and flow.

[0092] One type of sudden abnormal operation in a maleic anhydride reactor is an unnatural shutdown (also known as a trip) caused by unexpected circumstances. In this case, to avoid damaging the reactor, the feed gas pipeline to that reactor will be shut off as soon as possible to stop receiving air. For a design with multiple independent maleic anhydride reactors, this is not a problem because as the feed gas pipeline is shut down, the air compressor supplying air to the corresponding reactor will also stop or open its vent valve. However, for multiple maleic anhydride reactors connected in parallel sharing the same air compressor, if the air compressor is shut down or vented because one reactor trips, the air supply to all maleic anhydride reactors will be stopped, forcing even reactors that haven't tripped to shut down. This is highly uneconomical from a practical production perspective. Therefore, it is desirable for the air compressor to continue supplying air to the remaining reactors even if one reactor suddenly trips.

[0093] After a reactor trips, the maleic anhydride reactor gradually stops receiving air to avoid damaging it. For example, the inlet flow control valve in the reactor inlet pipe leading to the tripped reactor is closed. One operating mode is to close the corresponding inlet flow control valve when a reactor trips, allowing the air compressor to continue operating to supply air to the remaining reactors. However, the inventors discovered through practice that in a maleic anhydride system operating in this way, the air supply to the remaining reactors is affected, leading to operational instability and potentially interlocking trips. Without relying on any theory, the inventors found the following reason: The total air supply required by the maleic anhydride preparation system is related to the number of operating reactors. Therefore, when one or more of the maleic anhydride reactors suddenly trip, the air compressor's air supply flow requirement will experience a significant abrupt change, i.e., a sudden and large reduction in air volume within a short period of time. However, the performance regulation (maintaining air supply pressure / flow) of conventional axial air compressors is mainly accomplished by the stator vanes, which cannot quickly and effectively regulate the air supply volume at the compressor outlet when there are sudden and large fluctuations in the downstream system. Therefore, the air compressor cannot immediately switch to a low airflow rate state suitable for a smaller number of reactors, but instead maintains a relatively high airflow rate. In this situation, when the pressure in the air compressor's air duct rises sharply due to the incompatibility between the high airflow rate and the low airflow demand, it will affect the compressor's operating point, triggering the anti-surge system. The anti-surge system also requires a considerable amount of time to adjust and stabilize its operating point, and cannot quickly stabilize the compressor's outlet pressure, thus affecting the airflow to the operating reactors. In other words, conventional feedback performance regulation and feedback anti-surge regulation are insufficient to quickly adjust the airflow and pressure to a low airflow rate state. Furthermore, the compressor's anti-surge valve will fully open in the event of a sudden and sharp increase in pressure (i.e., a large disturbance), causing a sudden drop in airflow pressure. Although the compressor is protected, the airflow to the maleic anhydride reactor will become insufficient. As mentioned earlier, the maleic anhydride reactor has very high requirements for airflow stability. Therefore, if the air compressor does not make relevant adjustments in advance but continues to make feedback adjustments, the air supply volume may be continuously too high, continuously insufficient, or fluctuate drastically. These situations will quickly affect the operation of the remaining maleic anhydride reactor. At best, it will cause fluctuations in product quality; at worst, it will cause the reactor to stop working, causing interlocking trips and significantly reducing production efficiency.

[0094] Therefore, simply connecting multiple maleic anhydride reactors in parallel downstream of a conventional air compressor cannot adequately handle the aforementioned reactor tripping abnormalities, making it difficult to realize a practical maleic anhydride preparation system that includes multiple reactors.

[0095] To address the above problems, this invention proposes an air supply device and related operating method for a maleic anhydride preparation system comprising multiple reactors, wherein the air supply device includes:

[0096] Axial flow air compressor, which is equipped with stator vanes and anti-surge valve;

[0097] A stator vane controller that controls the stator vane angle based on target exhaust pressure and / or flow feedback;

[0098] An anti-surge valve controller, which controls the opening degree of the anti-surge valve based on the anti-surge line feedback of the air compressor; and

[0099] The feedforward performance controller is configured to initiate emergency trip control upon receiving a reactor trip signal, and to terminate the emergency trip control after the anti-surge valve closes.

[0100] The emergency control for vehicle scrambling includes: feedforward control of the opening of the anti-surge valve, and changing the target exhaust pressure and / or flow rate of the stationary vane controller.

[0101] The air supply system of this embodiment includes an axial flow air compressor as its basic component. The axial flow air compressor needs to provide a stable air supply to at least two maleic anhydride reactors simultaneously. A suitable air compressor can be selected based on the required air supply pressure and flow rate of the maleic anhydride reactors and the number of reactors. In one embodiment, the operating pressure of a single maleic anhydride reactor is between 0.29 and 0.35 MPaA, and the required air flow rate is between 1000 and 4000 Nm³. 3 / min.

[0102] Axial flow air compressors are equipped with stator vanes and anti-surge valves. These components can all be standard parts found in axial flow air compressors.

[0103] The stator vane angle is adjustable, thus changing the air intake flow of the air compressor. The stator vane angle adjustment range for conventional air compressors is from 22° to 79°.

[0104] Anti-surge valves can be installed on the air compressor's exhaust pipe, such as on a branch line extending from the exhaust pipe. They can be fully open or partially opened to release air from the exhaust pipe and reduce its pressure. Anti-surge valves are classified according to their adjustment methods, including equal percentage adjustment and linear adjustment. The opening degree at different flow rates can be found through the valve's inherent characteristic curve. Typically, the anti-surge valve is required to open rapidly within 1.5 seconds and fully open (0% to 100%) within 3 seconds. During normal operation of the air compressor, the anti-surge valve is in the closed state.

[0105] The air supply unit of this embodiment also includes a stator vane controller for changing the stator vane angle. The stator vane controller may be connected to or include a stator vane angle adjustment mechanism. The stator vane controller is a controller with feedback control functionality, which achieves feedback control based on the difference between a setpoint and a current value (measured value). For example, the stator vane controller may be a controller employing a proportional-integral-derivative (PID) control algorithm. This type of controller has a setpoint (SV) receiver and a current value (PV) receiver. The setpoint for the air compressor exhaust pressure and / or flow rate is input to the controller via the SV receiver, and the measured value of the air compressor exhaust pressure and / or flow rate is input to the controller as the current value via the PV receiver. After calculation by the PID algorithm, a control signal to increase or decrease the stator vane angle is sent to the stator vane angle adjustment mechanism via the output (OUT) terminal. In this way, the stator vane controller can perform feedback control of the stator vane angle based on the deviation between the current value and the setpoint of the air compressor exhaust pressure and / or flow rate, thereby maintaining the exhaust pressure and / or flow rate near the setpoint. This ensures a stable air supply to the downstream maleic anhydride reactor. It should be noted that this type of feedback control in the stationary vane controller is slow to take effect and does not have sufficient ability to respond to sudden and drastic fluctuations in pressure or flow.

[0106] The air supply unit in this implementation also includes an anti-surge valve controller. This controller, which controls the anti-surge valve, is a type of controller with feedback control functionality. The anti-surge valve feedback control is based on the anti-surge line. By comparing the relative position of the operating point to the anti-surge line, the operating point is adjusted by controlling the opening of the anti-surge valve. Similarly, the anti-surge valve controller can also be, for example, a controller employing a PID algorithm. The SV receiver of the anti-surge valve controller receives anti-surge line information, the PV receiver receives the air compressor operating point measurement results, and the OUT outputs the anti-surge valve control signal. When the operating point crosses the anti-surge line and approaches the surge line, based on the operating point measurement results, the anti-surge valve is opened at an appropriate angle, thereby reducing the pressure and returning the operating point to the normal operating range, preventing surge in the air compressor. It should be noted that this feedback control of the anti-surge valve controller is relatively slow to take effect and its ability to respond to sudden and drastic fluctuations in pressure or flow is not very strong.

[0107] Operating point, surge line, and anti-surge line are well-known concepts in the air compressor industry. For example, state point, surge line, and anti-surge line can be plotted on an anti-surge diagram with the throat differential pressure of the air compressor on the horizontal axis and the exhaust pressure of the air compressor on the vertical axis. Figure 3A typical anti-surge diagram for an air compressor is shown, including surge line 1 and anti-surge line 2. In the anti-surge diagram, each point corresponds to a state point representing the throat differential pressure and exhaust pressure of the air compressor. Based on actual surge tests of the air compressor in the field, surge points at different stator vane angles can be measured. Connecting these surge points yields the actual surge line of the air compressor. State points in the area below and to the right of this surge line (larger throat differential pressure, lower exhaust pressure) do not experience surge. Surge will occur on the surge line and above and to the left of it (too small throat differential pressure, too high exhaust pressure). Therefore, a certain safety margin (e.g., 10%) is reserved below and to the right of the surge line as an anti-surge line. When the air compressor's exhaust pressure increases, causing the operating point to cross the anti-surge line, the air compressor can reduce the exhaust pressure by opening the anti-surge valve to a certain degree, thus moving the operating point away from the surge line and preventing surge. As the operating conditions causing surge gradually fluctuate, the anti-surge valve gradually closes. This process can be achieved through feedback control by an anti-surge valve controller. In one implementation, the throat differential pressure, after temperature and pressure compensation calculations and calculations based on a piecewise linear function within the control system, becomes the setpoint SV of the anti-surge valve controller. The measured exhaust pressure of the air compressor becomes the current value PV of the anti-surge valve controller. The required opening degree of the anti-surge valve is calculated (e.g., using a PID algorithm), and the opening degree of the anti-surge valve is controlled accordingly to prevent surge. It is understood that other suitable feedback algorithms can also be used besides the PID algorithm.

[0108] Feedback control of the anti-surge valve is suitable for situations with small disturbances, i.e., when the operating point slowly and slightly crosses the anti-surge line. In this case, the operating point can be adjusted by gradually opening the anti-surge valve. However, when the pressure rises rapidly or the disturbance is large, the operating point may quickly cross the safety margin between the anti-surge line and the surge line to reach the surge zone. The lag in the above feedback control will make it difficult to guarantee that surge will not occur. Therefore, when a large disturbance causes the operating point to potentially or already enter the surge zone, conventional air compressors, in order to simply protect the air compressor, immediately open the anti-surge valve to its maximum opening (i.e., fully open) to release air, thereby rapidly reducing the exhaust pressure, causing the operating point to leave the surge zone, and eliminating the surge phenomenon. As mentioned above, the inventors found that this seriously affects the stability of the air supply to the remaining maleic anhydride reactor, and in severe cases, the reactor may trip due to excessively low air flow.

[0109] This invention incorporates a feedforward performance controller in the air supply unit to appropriately handle reactor tripping conditions. More specifically, in the event of a reactor trip, this invention utilizes the feedforward performance controller to coordinate the adjustment of the anti-surge valve and the stationary vane to control the air compressor's exhaust pressure and flow rate.

[0110] The feedforward performance controller is configured to initiate trip emergency control upon receiving a trip signal from the maleic anhydride reactor, and terminate the trip emergency control after the anti-surge valve is closed. The trip emergency control includes: feedforward control of the opening degree of the anti-surge valve, and changing the target exhaust pressure and / or flow rate of the stationary vane controller.

[0111] In other words, this invention addresses the issue of some maleic anhydride reactors suddenly tripping in a maleic anhydride preparation system containing multiple reactors by specifically incorporating a feedforward performance controller in the air supply unit for emergency handling of such trips.

[0112] The feedforward performance controller does not operate in the maleic anhydride preparation system unless a trip occurs in the multiple reactors. When each reactor is operating normally, the air compressor's exhaust pressure is controlled by feedback from the stator vane controller and anti-surge valve controller. This feedforward performance controller only participates in the control of the air supply system in the event of a trip, an abnormal operating condition. Even if the air compressor's exhaust pressure suddenly rises for other reasons, this feedforward performance controller will not operate.

[0113] Figure 4 A schematic diagram of the feedforward control connection principle according to an embodiment of the present invention is shown.

[0114] As shown in the figure, when the reactor does not trip, the stationary vane controller controls the stationary vane angle through feedback from the output terminal OUT based on the set value at the SV1 terminal and the measured or actual value at the PV terminal. When the air compressor operating point crosses the anti-surge line, the anti-surge valve controller controls the opening of the anti-surge valve through feedback from the output terminal OUT based on the anti-surge line input from SV1 and the actual operating point position output from PV to eliminate possible surge phenomena.

[0115] The maleic anhydride preparation system can generate and send a trip signal when the maleic anhydride reactor trips. The system can send various reactor operating status signals, or simply operating status signals, with the trip signal being one of them. The operating status signal can be a digital dry contact signal. This signal can be automatically generated by the reactor's control system (e.g., a distributed control system, DCS). The control system measures reactor parameters to determine if the reactor is operating normally. If the control system determines that the reactor is operating normally, it outputs a dry contact signal indicating normal operation as the normal operating status signal, such as a closed signal. When the reactor trips due to a malfunction or other factors, it outputs a trip operating status signal, such as an open signal. Alternatively, a trip signal can be actively issued by the system operator upon detecting a trip.

[0116] The feedforward performance controller is configured to receive a trip signal from the maleic anhydride reactor and, in response to this signal, initiate emergency trip control. For example... Figure 4As shown, the feedforward performance controller can receive trip signals from reactors 1, 2, and 3. The emergency control in this implementation scheme, based on the air volume loss after a reactor trip, coordinates the control of the anti-surge valve and the air compressor stator vanes in advance, ensuring stable air supply to the remaining reactors while preventing air compressor surge. Figure 4 As shown, the feedforward performance controller controls operation through output terminals OUT1 and OUT2.

[0117] Emergency control includes feedforward control of the anti-surge valve opening. As mentioned above, when controlled by the anti-surge valve controller, the anti-surge valve gradually opens under small disturbances and fully opens under large disturbances based on the increased exhaust pressure measurement. In contrast, this implementation's feedforward performance controller responds to a trip signal and controls the anti-surge valve in advance. That is, instead of feedback control after the pressure rise due to the trip and subsequent closure of the reactor's inlet flow regulating valve, control is initiated in advance based on the air supply needs after the trip. The number of tripped reactors can be determined from the trip signal, thus allowing for advance prediction of the required reduction in air supply for the corresponding operating condition and the air supply required for the remaining reactors to continue operating. For example, in a three-reactor system, when the feedforward performance controller receives a trip signal, it indicates that one reactor has tripped, while the other two reactors are still operating. The feedforward performance controller can calculate an appropriate anti-surge valve opening based on the required air supply and the anti-surge valve's performance curve. The feedforward performance controller directly opens (or quickly opens) the anti-surge valve to this opening degree. At this valve opening, the venting from the anti-surge valve is not a gradual feedback opening, nor is it a fully open flow, but rather a controlled, rapid opening. Venting through the anti-surge valve ensures that the gas flow rate adapts to the needs of the remaining maleic anhydride reactor, thus maintaining minimal fluctuations in the air flow to the remaining reactor. During this process, the air compressor's operating point does not reach the surge line, and surge does not occur.

[0118] The feedforward performance controller can control the opening of the anti-surge valve through the anti-surge valve controller. That is, the feedforward performance controller sends a control signal to the anti-surge valve controller, which then controls the anti-surge valve through the signal output from the OUT terminal of the anti-surge valve controller. For example... Figure 4 As shown, the anti-surge valve controller controls the opening degree of the anti-surge valve based on the anti-surge line received from the SV1 terminal and the operating point position received from the PV terminal under normal conditions. However, when the feedforward performance controller is in operation, it receives the feedforward signal output from the OUT1 output terminal of the feedforward performance controller from the SELSV2 terminal.

[0119] Simultaneously, the feedforward performance controller calculates the required exhaust pressure and flow rate of the air compressor at the anti-surge valve opening based on the known required air volume, and sends these required values ​​as target exhaust pressure and / or flow rate to the stationary vane controller. For example... Figure 4 As shown, the output is sent from the OUT2 output terminal of the feedforward performance controller to the SEL SV2 terminal of the stator vane controller. The stator vane controller receives the changed target exhaust pressure and / or flow rate from the feedforward performance controller, replacing the previously received setpoint from the SV1 terminal. This changed target exhaust pressure and / or flow rate applies to the operation of the remaining reactor under the aforementioned anti-surge valve opening. Based on this changed target exhaust pressure and / or flow rate, the stator vane controller still controls the stator vane angle based on the test value received from the PV terminal, so that the actual exhaust pressure and / or flow rate remain substantially stable.

[0120] By using a feedforward controller to control the opening of the anti-surge valve and, in conjunction with the feedback control of the stationary vane angle, stable exhaust pressure and flow rate are obtained, ensuring that the remaining reactors can still operate normally.

[0121] However, considering the stability of the system's normal operation, the anti-surge valve cannot remain open for an extended period, as this would cause a large amount of unnecessary compressed air to be discharged from the valve, wasting energy. Therefore, the feedforward performance controller continues to operate, gradually closing the anti-surge valve in small increments. For example, in one implementation, the opening is initially reduced by a certain amount, such as 2%-5%. As the anti-surge valve opening decreases slightly, the discharge pressure and flow rate change accordingly, but not drastically. However, since the stator vane controller is still performing feedback control, the change in the stator vane angle coordinates and stabilizes the compressor's discharge pressure and flow rate.

[0122] Once the exhaust pressure stabilizes, i.e., the stator vane angle remains essentially constant, the feedforward performance controller continues to reduce the opening and repeats the above operation. By gradually and slowly reducing the anti-surge valve opening in this way, the surge valve will eventually close completely. Throughout this process, a stable air supply can be maintained to the remaining maleic anhydride reactors, allowing them to operate normally.

[0123] Once the surge valve is fully closed, the multi-reactor maleic anhydride preparation system has safely recovered from the sudden shutdown and reached a new steady-state operation compared to before, in which the number of operating reactors has decreased, and the target exhaust pressure and / or flow rate have changed accordingly. At this point, the stator vane angle decreases, resulting in a lower intake flow rate and a lower throat differential pressure, and the air compressor will operate at a new operating point. Accordingly, the emergency shutdown control of the feedforward performance control ends.

[0124] As described above, in one embodiment, the stator controller may have another setpoint receiver to receive signals from the feedforward performance controller. The original setpoint receiver is SV1, and the new setpoint receiver is SEL SV2. SEL SV2 is connected to a signal output terminal OUT2 of the feedforward performance controller. When the SEL SV2 receiver receives the changed target exhaust pressure and / or flow rate from the feedforward performance controller, the original target exhaust pressure and / or flow rate input values ​​of SV1 become invalid.

[0125] As described above, in one embodiment, the anti-surge valve controller may also have another setpoint receiver, SELSV2, connected to another signal output, OUT1, of the feedforward performance controller. When the SELSV2 receiver of the anti-surge valve controller receives a control signal from the feedforward performance controller, it will directly change the opening degree of the anti-surge valve through the OUT terminal. The advantage of the feedforward performance controller controlling the anti-surge valve through the anti-surge valve controller is that all control signals for the anti-surge valve are issued by the anti-surge valve controller, avoiding control conflicts. When the feedforward performance controller performs emergency control, the feedback control of the anti-surge valve controller temporarily fails because the feedforward performance controller has already ensured that surge does not occur.

[0126] The feedforward performance controller uses the receipt of a trip signal from the maleic anhydride reactor as a prerequisite for initiating its emergency trip control and determines the corresponding feedforward control strategy. Based on the number of received reactor trip signals, the number of reactors still operating can be determined, along with the required airflow to maintain their normal operation. For example, in a three-reactor system, receiving one trip signal indicates that two reactors still need to remain operational. The feedforward performance controller can provide the necessary control strategy and corresponding control signals based on the number of trip signals.

[0127] Continuing with the example of a reactor tripping in a three-reactor system, when a reactor trips, it immediately sends a trip signal to the feedforward performance controller. The feedforward performance controller then determines that the maleic anhydride system should subsequently be operated in two-reactor mode. The feedforward performance controller calculates the required airflow for both reactors. Based on the inherent characteristic curve of the anti-surge valve, and according to this airflow requirement, the feedforward performance controller sends an opening control signal to the anti-surge valve controller, causing the anti-surge valve to quickly open to the predetermined opening.

[0128] The principle for selecting the predetermined opening degree of the anti-surge valve is to first ensure that the exhaust pressure is in the non-surge zone of the anti-surge diagram under the current throat differential pressure, preferably in the safe zone below the right of the anti-surge line; secondly, to ensure that the air flow and pressure to the maleic anhydride reactor that has not tripped remain basically unchanged under this opening degree, for example, the fluctuation does not exceed 20%, more preferably 10%, more preferably 5%, and more preferably 2%.

[0129] The ultimate goal of emergency control is to achieve the required supply air pressure and flow rate for both reactors to operate. To this end, the feedforward performance controller inputs the target exhaust pressure and / or flow rate into the stator controller, replacing its original exhaust pressure / flow rate setpoints. In other words, after the feedforward performance controller initiates emergency control, the stator controller's exhaust pressure and / or flow rate setpoints are changed to values ​​applicable to both reactors. Subsequently, based on these new setpoints, the stator controller adjusts the stator blades to stabilize the supply air pressure and flow rate, thereby ensuring the basic stable operation of the remaining reactors.

[0130] At this point, the anti-surge valve is still open to its predetermined degree and needs to be gradually closed to return to normal operation and continue its anti-surge function. To this end, the performance controller continues to send feedforward control signals to the anti-surge valve controller. This control signal causes the anti-surge valve to gradually close. In a preferred embodiment, the control signal can be to reduce the opening of the anti-surge valve by 2%-5% at a time. After the opening is reduced, the feedback control of the stator vane controller adjusts the stator vanes to restore stable exhaust pressure and flow. A 2%-5% reduction range strikes a good balance between quickly closing the anti-surge valve and waiting for the stator vanes to adjust in time. After the stator vanes stabilize, the anti-surge valve opening is reduced again. This process is repeated until the anti-surge valve is completely closed. At this point, the feedforward performance controller terminates emergency control.

[0131] Therefore, upon receiving a reactor trip signal, the feedforward performance controller, in conjunction with the anti-surge valve and stator vane control, preemptively adjusts the air compressor's intake and exhaust, regulating the outlet pressure and flow rate (i.e., anti-surge valve performance control activation) to obtain the required air supply. Because it is a feedforward control responding to the trip signal, unlike feedback control, it can effectively intervene in the air supply system before changes in the downstream piping network significantly impact compressor regulation. This process avoids damage to the air compressor and does not affect the operation of the remaining reactors. Through the control of the feedforward performance controller, fluctuations caused by reactor trips are effectively controlled through the coordinated regulation of the stator vanes and anti-surge valve, reducing the risk and probability of system interlock shutdowns.

[0132] The air supply device in this implementation combines the anti-surge control and regulation of the air compressor, the static vane control and regulation, with the operating status signal of the maleic anhydride reactor, and together with the added feedforward performance controller, forms a brand-new air compressor air supply regulation system, thereby ensuring the stability of the air supply to the remaining reactor.

[0133] The present invention will be described in more detail below through examples.

[0134] Example 1:

[0135] Production is carried out using a maleic anhydride preparation system that simultaneously supplies air to three parallel maleic anhydride reactors using one air compressor of this invention. The reactant is n-butane.

[0136] Perform the following tests to cut off / put on the steam turbine during the operation of the preparation system.

[0137] 1. Testing the situation where a fault occurs in the steam turbine or steam system, requiring the turbine to be shut down, but the unit needs to continue operating normally.

[0138] First, the air compressor is driven by both the electric motor and the steam turbine.

[0139] To shut down the steam turbine, the following operations must be performed:

[0140] Reduce the speed of the steam turbine to be lower than that of the air compressor, so that the speed of the clutch input shaft is lower than that of the output shaft.

[0141] The control program measures the disengagement holding time of the clutch engagement switch and the change in motor power to determine whether the clutch has disengaged, i.e. whether the turbine has successfully disengaged from the unit's running shaft system.

[0142] Once it is determined that the turbine has successfully disengaged, the turbine will be shut down, because successful disengagement indicates that the turbine shaft is no longer linked to the air compressor shaft.

[0143] 2. Test the situation where the steam turbine needs to be put into operation during the normal operation of the air compressor unit.

[0144] First, the air compressor is made to run solely driven by the electric motor.

[0145] In order to put the steam turbine into operation, the following operations are performed:

[0146] Increase the speed of the steam turbine to be higher than that of the air compressor, so that the speed of the clutch input shaft is greater than that of the output shaft;

[0147] The control program measures the disengagement holding time of the clutch engagement switch and the change in motor power to determine whether the clutch is engaged, i.e. whether the turbine is successfully connected to the unit's operating shaft system.

[0148] Once it is determined that the steam turbine has been successfully put into operation, the steam turbine will be switched from speed control mode to load loading control mode.

[0149] Test results show that the steam turbine can be safely engaged / disengaged from the air compressor drive system using the above operating methods.

[0150] Example 2

[0151] Based on Example 1, a maleic anhydride preparation system was used, employing the same air compressor to simultaneously supply air to three parallel maleic anhydride reactors. The three maleic anhydride reactors were designated Reactor No. 1, No. 2, and No. 3. The reactant was n-butane. Each of the three reactors had a steam drum and supplied steam to a turbine. During operation, the air compressor was driven by both an electric motor and the turbine.

[0152] A stator vane controller with an embedded PID algorithm is installed. Its output terminal OUT is connected to the stator vane adjustment mechanism to control the stator vane angle. Its first setpoint receiver SV1 obtains the target exhaust pressure setpoint for normal reactor operation from the control system. Its current value receiver PV receives the real-time exhaust pressure measurement value from the exhaust pressure sensor.

[0153] An anti-surge controller with an embedded PID algorithm is installed. Its output terminal OUT is connected to the anti-surge valve to control the valve opening. Its first setpoint receiver SV1 obtains the anti-surge graph, including the surge line and the anti-surge line, from the control system. Its current value receiver PV receives real-time operating point parameters from the exhaust pressure sensor and the throat differential pressure sensor.

[0154] A feedforward performance controller is installed, with three signal input terminals receiving operating signals from reactors 1-3. Its second output terminal OUT1 is connected to the second setpoint receiver SEL SV2 of the anti-surge valve controller. Its first output terminal OUT2 is connected to the second setpoint receiver SEL SV2 of the stationary vane controller.

[0155] like Figure 4 As shown, the reactor, anti-surge controller, anti-surge valve, stationary vane controller, stationary vane, and feedforward performance controller are connected together.

[0156] First, reactors 1-3 are operated under normal conditions. At this time, the feedforward performance controller is not operational. The stator vane controller, based on the target exhaust pressure setpoint obtained from SV1, performs feedback control on the stator vane angle according to the measured value obtained from PV. The anti-surge valve controller, based on the anti-surge line obtained from SV1, performs feedback control on the anti-surge valve opening according to the operating point parameters obtained from PV.

[0157] To simulate a reactor trip, reactor 1 was shut down, and the airflow control valve leading to reactor 1 was immediately closed, while a trip signal was sent to the feedforward performance controller.

[0158] The trip signal of reactor No. 1 triggered the feedforward performance controller, initiating emergency trip control. Based on the single trip signal, the expected gas flow rate would decrease to two-thirds of its original value, while the pressure remained unchanged. Therefore, the feedforward performance controller sent a feedforward signal to the anti-surge valve's SEL SV2, rapidly opening the valve to its first opening degree (not fully open), releasing gas. At this first opening degree, under the current stator vane angle and compressor operating conditions, the exhaust air flow rate downstream is two-thirds of its previous value, while the pressure remains unchanged. This operating point is located to the lower right of the anti-surge line, preventing surge from occurring.

[0159] Simultaneously, the feedforward performance controller sends this target exhaust pressure and / or flow rate to the stator vane controller's SELSV2. The stator vane controller then performs feedback control based on the changed target exhaust pressure and / or flow rate. Since the flow rate and pressure are now approximately at the target values, the stator vane controller only makes fine adjustments to the stator vane angle based on the measured feedback.

[0160] Subsequently, the feedforward performance controller reduces the anti-surge valve opening by 2%. At this point, both the exhaust pressure and flow rate increase. The stator controller receives the increased pressure / flow rate measurements and performs feedback control on the stator, reducing the stator angle so that the exhaust pressure and flow rate drop back to the target values.

[0161] Once the exhaust pressure and flow rate stabilize around the target value (i.e., the stator angle no longer decreases), the feedforward performance controller reduces the anti-surge valve opening by 2% again. Repeat the above process until the anti-surge valve is completely closed.

[0162] After the anti-surge valve is fully closed, the feedforward performance controller shuts down, ending the emergency trip control. The anti-surge valve controller then takes over the feedback control of the anti-surge valve.

[0163] During this process, the air inlet pressure and flow rate in reactors 2 and 3 were monitored, and the operating status of the reactors was checked. The results showed that the air inlet pressure and flow rate in reactors 2 and 3 fluctuated little, the reactors operated smoothly, and the product yield and quality remained stable, unaffected by the trip of reactor 1.

[0164] Example 3

[0165] The test was conducted in the same manner as in Example 2, except that reactors 1 and 2 of the three reactors underwent a simulated trip.

[0166] Accordingly, the feedforward performance controller quickly opens the anti-surge valve and sends a modified target exhaust flow rate to the stator controller, which is one-third of the previous rate, while the pressure remains unchanged. Due to the larger opening, the reduction in the anti-surge valve opening is increased to 5% each time during feedforward control.

[0167] During this process, the air inlet pressure and flow rate in reactor No. 3 were monitored, and the reactor's operating status was checked. The results showed that the air inlet pressure and flow rate in reactor No. 3 fluctuated only slightly. The reactor operated smoothly, with stable product yield and quality, unaffected by the shutdowns of reactors No. 1 and No. 2.

[0168] Meanwhile, due to the shutdown of reactors 1 and 2, the steam supply to the turbines has changed significantly, allowing the turbines to be temporarily shut down. A speed control mode is used to reduce the turbine speed, disconnecting the turbines from the air compressor, and the turbines are then shut down after successful disconnection. An electric motor drives the air compressor to supply air to the remaining reactors.

[0169] Comparative Example 1:

[0170] Except for the absence of a feedforward controller, the maleic anhydride reactor is supplied with air using the same apparatus as in Example 2.

[0171] After the simulated reactor No. 1 tripped, the exhaust pressure measurement rose rapidly, triggering the feedback control of the anti-surge controller, and the anti-surge valve opened fully. Shortly after the anti-surge valve opened fully, reactors No. 2 and No. 3 tripped due to insufficient gas supply and stopped operating.

[0172] Comparative Example 2:

[0173] Except for the absence of a feedforward controller, the maleic anhydride reactor is supplied with air using the same apparatus as in Example 3.

[0174] After reactors 1 and 2 tripped, the exhaust pressure readings rose rapidly, triggering the feedback control of the anti-surge controller, which fully opened the anti-surge valve. Once the anti-surge valve was fully open, reactor 3 quickly tripped due to insufficient gas supply and stopped operating.

[0175] Therefore, when one or more of the maleic anhydride reactors suddenly stop, the apparatus and method of the present invention ensure that the air compressor is not damaged due to surge, while also ensuring that the remaining reactors do not experience abnormal operation or interlock shutdown due to a sudden reduction in air supply.

[0176] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for operating a dual-drive (steam and electric) air supply device for a maleic anhydride preparation system, the air supply device comprising an air compressor, an electric motor, a steam turbine, a gearbox, and a clutch, wherein the shaft of the electric motor is coupled to the shaft of the air compressor via the gearbox, and the shaft of the steam turbine is disengaged from the shaft of the air compressor via the clutch. Its features are, The operating method includes: The turbine speed is reduced using a speed control mode. The success of the disengagement is determined by detecting the clutch engagement switch holding time and the motor power. If the disengagement is successful, the turbine is shut down. The turbine speed is increased by using a speed control mode. The success of the engagement is determined by detecting the clutch engagement switch holding time and the motor power. If the engagement is successful, the speed control mode is switched to a load loading control mode. in, The maleic anhydride preparation system is a system comprising multiple maleic anhydride reactors. The air compressor is an axial flow air compressor, which is equipped with stator vanes and anti-surge valve; The air supply device of the air compressor also includes: A stator vane controller that controls the stator vane angle based on target exhaust pressure and / or flow feedback; An anti-surge valve controller, which controls the opening degree of the anti-surge valve based on the anti-surge line feedback of the air compressor; and The feedforward performance controller is configured to initiate emergency trip control upon receiving a reactor trip signal, and to terminate the emergency trip control after the anti-surge valve closes. The emergency control for vehicle slump includes: feedforward control of the anti-surge valve opening, and changing the target exhaust pressure and / or flow rate of the stator vane controller. The operating method includes: When the plurality of maleic anhydride reactors are running, the stationary vane controller controls the stationary vane angle based on the target exhaust pressure and / or flow rate and feedback from the measured value, and the anti-surge valve controller controls the anti-surge valve opening based on the anti-surge line of the air compressor and feedback from the measured value. When at least one of the plurality of maleic anhydride reactors trips, the feedforward performance controller initiates the trip emergency control upon receiving a trip signal from the maleic anhydride reactor, and terminates the trip emergency control after the anti-surge valve closes, wherein the trip emergency control includes: i) Based on the number of remaining operating maleic anhydride reactors, quickly open the anti-surge valve to the first opening degree and change the target exhaust pressure and / or flow rate of the stationary vane controller; ii) Reduce the anti-surge valve opening from the first degree, and then wait for the stationary vane angle to stabilize; iii) Repeat step ii) until the anti-surge valve is closed.

2. The operating method according to claim 1, characterized in that, The maleic anhydride preparation system is a multi-reactor system, and the power of the electric motor is insufficient to drive the air compressor load when all maleic anhydride reactors are running.

3. The operating method according to claim 1, characterized in that, The maleic anhydride preparation system is a multi-reactor system and includes a steam generation device. The steam generating device is configured to supply steam to the steam turbine.

4. The operating method according to claim 3, characterized in that, The steam generating apparatus consists of a molten salt heat exchanger and a steam boiler for the maleic anhydride reactor, and the operating method further includes: Water is fed into the molten salt heat exchanger, and the water is heated to form steam in the steam package.

5. The operating method according to claim 3, characterized in that, The steam generating device is a waste gas incinerator for a maleic anhydride reactor, and the operating method further includes: The heat from the waste gas incinerator is used to heat water to form steam.

6. The operating method according to claim 3, characterized in that, The steam generating unit consists of a maleic anhydride reactor, a molten salt heat exchanger, a steam drum, and a waste gas incinerator connected in series, and the operating method further includes: Water is fed into the molten salt heat exchanger, heated to form steam in the steam package, and further heated in the waste gas incinerator.

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