CN116293449A

CN116293449A - Air supply device for recycling maleic anhydride reaction tail gas, preparation system using same and operation method of preparation system

Info

Publication number: CN116293449A
Application number: CN202211576645.0A
Authority: CN
Inventors: 黄斌; 陈余平; 张智军; 孙鸿声; 周根标; 张立; 韩宏林; 李震; 张�林; 申振; 徐孟健; 陈军
Original assignee: Xian Shaangu Power Co Ltd
Current assignee: Xian Shaangu Power Co Ltd
Priority date: 2022-12-08
Filing date: 2022-12-08
Publication date: 2023-06-23

Abstract

The invention provides an air supply device for recycling tail gas of maleic anhydride reaction, which comprises: an axial flow air compressor provided with an anti-surge valve; an air inlet pipe, the air inlet end of which is in fluid communication with an air source, and the air outlet end of which is in fluid communication with the air inlet pipe of the air compressor; the tail gas recovery pipeline, the air inlet end of the tail gas recovery pipeline is in fluid communication with the downstream of the maleic anhydride reactor, and the air outlet end of the tail gas recovery pipeline is in fluid communication with the air inlet pipeline of the air compressor; and the air compressor is provided with a shaft end sealing structure. The invention can realize the mixed feeding of the tail gas of the maleic anhydride and the air through the same air compressor.

Description

Air supply device for recycling maleic anhydride reaction tail gas, preparation system using same and operation method of preparation system

Technical Field

The present invention relates to the field of maleic anhydride production, and more particularly, to an air supply device for maleic anhydride reaction tail gas recovery, a preparation system using the same, and an operation method thereof.

Background

Maleic anhydride is an important basic organic chemical raw material and is widely applied to the production of various chemicals. Currently, the main industrial processes for maleic anhydride include benzene and n-butane. The benzene method is to oxidize benzene and convert the benzene into maleic anhydride under the action of a catalyst by taking mixed gas of benzene and air as a raw material. The n-butane method is to oxidize and convert n-butane into maleic anhydride under the action of a catalyst by taking mixed gas of n-butane and air as a raw material. Maleic anhydride in China is mainly produced by a benzene method, but the productivity of maleic anhydride produced by the normal butane method in China is continuously increased in recent years due to the advantages of the normal butane method in the aspects of raw materials, environmental protection, efficiency, cost and the like.

Both the benzene process and the n-butane process use air as one of the starting materials. In the maleic anhydride plant, air is pressurized using an air compressor and then supplied to the maleic anhydride reactor for oxidation.

The most widely used maleic anhydride reactors, both in benzene and n-butane processes, are axial tube array fixed bed reactors. The axial column type fixed bed reactor consists of a large number of tubes and uses molten salt to effect heat exchange. Since the maleic anhydride formation reaction is a reaction having high sensitivity to changes in reaction conditions, the smooth progress of maleic anhydride production and product quality are highly dependent on the radial uniformity of materials and temperature in the reactor. However, as the diameter of the reactor increases, the difficulty in controlling the uniformity of the material and the uniformity of the temperature in the radial direction of the reactor increases. Therefore, in order to ensure that the reaction proceeds smoothly and the quality of maleic anhydride, the diameter of the maleic anhydride reactor is limited, and it is difficult to further expand.

Since the maximum diameter of a single maleic anhydride reactor is limited, the flow area of the fluid through the reactor is also limited, thereby placing higher demands on the bed height of the catalyst. The catalyst bed of the commercial maleic anhydride reactor has a large aspect ratio and the pressure drop of the reaction fluid flowing through the catalyst bed is high, thus requiring a higher air compressor outlet pressure. Because of the high sensitivity described above, the supply air (also referred to as blow) of the air compressor needs to remain very stable while maintaining high pressure, which may otherwise lead to reaction anomalies or even termination. The above-described air supply requirements place high demands on the air supply for the maleic anhydride reactor.

Downstream of the maleic anhydride reactor, a tail gas from the maleic anhydride production process may be obtained, which contains a certain amount of starting materials, such as benzene or n-butane. Typically, the tail gas comes from the top of the absorber column downstream of the maleic anhydride reactor. The feed material in the tail gas may be recovered and reused as a feed to the reactor.

There is also a need for an improved process for recycling maleic anhydride reactor off-gas.

Disclosure of Invention

In one aspect, the present invention provides an air supply device for maleic anhydride reaction tail gas recovery, the air supply device comprising:

An axial flow air compressor provided with an anti-surge valve;

an air inlet conduit having an inlet end in fluid communication with an air source and an outlet end in fluid communication with an inlet conduit of the air compressor;

an air inlet end of the tail gas recovery pipeline is in fluid communication with the downstream of the maleic anhydride reactor, and an air outlet end of the tail gas recovery pipeline is in fluid communication with an air inlet pipeline of the air compressor; and

an anti-surge valve bleed air return conduit, an air inlet end of the anti-surge valve bleed air return conduit being in fluid communication with an air outlet of the anti-surge valve, an air outlet end being in fluid communication with an air inlet conduit of the air compressor,

and the air compressor is provided with a shaft end sealing structure.

Optionally, the shaft end sealing structure adopts a combination seal of carbon ring sealing and Lawster sealing.

Optionally, at least part of the blade surface of the air compressor is acid-resistant treated.

In another aspect, the present invention provides a maleic anhydride preparation system comprising:

maleic anhydride reactor, and

the air supply device.

Optionally, the maleic anhydride preparation system further comprises:

an absorber column downstream of the maleic anhydride reactor,

Wherein the inlet end of the tail gas recovery pipeline is in fluid communication with the top of the absorption tower.

Optionally, the maleic anhydride preparation system comprises a plurality of reactors, the axial flow air compressor is provided with stationary vanes,

the air supply device includes:

a vane controller that feedback-controls vane angle based on a target exhaust pressure and/or flow;

an anti-surge valve controller that feedback-controls an anti-surge valve opening based on an anti-surge line of the air compressor; and

a feed forward performance controller configured to initiate a trip emergency control upon receipt of a trip signal from the maleic anhydride reactor, and to end the trip emergency control upon closing of the anti-surge valve,

wherein, jump car emergency control includes: feedforward controls the anti-surge valve opening, and changes the target exhaust pressure and/or flow of the vane controller.

In yet another aspect, the present invention provides a method of operating the above-described maleic anhydride production system comprising a plurality of reactors, the method of operating comprising:

introducing a tail gas comprising benzene or n-butane from a maleic anhydride reactor into the air compressor through the tail gas recovery line and an air intake line of the air compressor, and

And enabling the bleed air of the anti-surge valve to enter the air compressor through the bleed air backflow pipeline of the anti-surge valve.

Optionally, the maleic anhydride production system comprising a multi-reactor is the maleic anhydride production system comprising a feed forward performance controller described above, the method further comprising:

when the plurality of maleic anhydride reactors are operated, the stator blade controller feedback-controls the stator blade angle based on the target exhaust pressure and/or flow and according to the measured value, and the anti-surge valve controller feedback-controls the anti-surge valve opening based on the anti-surge line of the air compressor and according to the measured value;

when at least one of the plurality of maleic anhydride reactors jumps, the feedforward performance controller starts the jump emergency control after receiving a jump signal of the maleic anhydride reactor, and ends the jump emergency control after the anti-surge valve is closed, wherein the jump emergency control comprises:

i) According to the number of the residual running maleic anhydride reactors, rapidly opening the anti-surge valve to a first opening degree, and changing the target exhaust pressure and/or flow of the stationary blade controller;

ii) reducing the anti-surge valve from the first opening degree, and then waiting for the vane angle to stabilize;

iii) Repeating operation ii) until the anti-surge valve is closed.

Drawings

Fig. 1 shows a schematic view of an air supply device comprising an exhaust gas recovery conduit according to an embodiment of the invention.

Fig. 2 shows a combination of a lazuer seal and a carbocyclic seal.

Fig. 3 shows a typical air compressor anti-surge map.

Fig. 4 shows a schematic diagram of a feed forward control connection principle according to an embodiment of the invention.

Detailed description of the preferred embodiments

The air supply device for recycling the tail gas of the maleic anhydride reaction can recycle the tail gas in the preparation process of maleic anhydride.

Downstream of the maleic anhydride reactor, a tail gas from the maleic anhydride production process may be obtained, which contains a certain amount of starting materials, such as benzene or n-butane. Typically, the tail gas comes from the top of the absorber column downstream of the maleic anhydride reactor. The feed material in the tail gas may be recovered and reused as a feed to the reactor. The inventors have found that the direct use of the tail gas is cost-effective compared to the separation and purification of the raw materials in the tail gas, which are then incorporated into the raw material stream for recycling. Furthermore, it is cost-effective to let the tail gas into the reactor with the air feed, as compared to providing a separate tail gas feed line for the reactor. The location of the tail gas incorporation into the air feed may be selected upstream of the air compressor in the air supply or between the air compressor and the reactor. The inventors have found that incorporating the tail gas into the air feed downstream of the air compressor can destabilize the inlet flow and pressure to the maleic anhydride reactor, which is detrimental to the production of maleic anhydride.

Therefore, the tail gas of the maleic anhydride preparation process is returned to the upstream of the air compressor, and is mixed with fresh air and then sent to the reactor by the air compressor, so that the recycling of raw materials in the tail gas is realized. However, the inventors have found in practice that merely connecting the recycled tail gas directly upstream of the air compressor of the present invention does not enable safe production operation of the maleic anhydride reactor system.

When an axial flow air compressor encounters anti-surge control, the anti-surge valve will open and discharge a portion of the air feed into the environment. This is not a problem for air feeds that are not mixed with tail gas. However, when tail gas is mixed in the air feed, the opening of the anti-surge valve will allow the flammable and explosive and toxic and harmful benzene or n-butane in the tail gas to leak untreated into the environment, which should be avoided.

In order to recycle the tail gas of the maleic anhydride preparation process, the present invention provides an air supply device for recovering the tail gas of the maleic anhydride reaction, the air supply device comprising:

an axial flow air compressor provided with an anti-surge valve;

and the air compressor is provided with a shaft end sealing structure.

The air supply device of the invention comprises an axial flow type air compressor as a basic component thereof. The axial flow air compressor is provided with an anti-surge valve.

The anti-surge valve may be disposed on an exhaust duct of the air compressor, for example, on a branch line branched from the exhaust duct of the air compressor, and may be fully opened or opened by a certain opening degree, so that the exhaust duct is deflated, and the air pressure therein is reduced. The valve is classified according to the specific regulation mode of the anti-asthma valve, and the valve has equal percentage regulation, linear regulation and the like. The corresponding opening degree under different flow rates can be checked through the inherent characteristic curve of the anti-surge valve. Typically, it is required that the anti-surge valve can be opened quickly within 1.5 seconds, from fully closed to fully open (0% to 100%) within 3 seconds. When the air compressor normally operates, the anti-surge valve is in a closed state.

The air inlet pipeline of the air compressor is simultaneously communicated with the air inlet pipeline and the tail gas recovery pipeline, and the air inlet pipeline and the tail gas recovery pipeline are respectively communicated with the air source and the downstream of the reactor, so that the air compressor can simultaneously obtain air raw materials from the air source and recovered tail gas from the downstream of the reactor. For example, the tail gas recovery line may be in communication with the top of the absorber column downstream of the maleic anhydride reactor.

The air inlet pipeline of the air compressor is also communicated with the anti-surge valve air discharge backflow pipeline. That is, in the present invention, when the anti-surge valve is opened, all of the gas discharged therefrom does not enter ambient air, but returns upstream of the air compressor and reenters the air compressor with the air and exhaust gas.

The invention returns the gas discharged from the anti-surge valve to the inlet of the air compressor again, so as to avoid adverse effect on the environment. The inventors have found that directing the exhaust gas of an anti-surge valve upstream of an air compressor to achieve a closed cycle is significantly advantageous in terms of cost and process, as compared to innocuous treatment of the exhaust gas and eventual release into ambient air.

The introduction of the exhaust gas of the anti-surge valve into the air feed does not adversely affect the subsequent maleic anhydride reactor inlet pressure and flow. Although the gas with certain pressure discharged by the anti-surge valve enters the air inlet pipeline of the air compressor and possibly changes the pressure of the air compressor air inlet mixture to a certain extent, as the exhaust flow and the pressure of the air compressor can be regulated by the static vanes, the pressure change of the feed gas reaching the air compressor can be counteracted by the feedback control static vanes, so that the control of the exhaust flow and the pressure of the air compressor is maintained.

Thus, the problem of leakage of harmful gas of the anti-surge valve is solved by adding a bleed air return pipeline of the anti-surge valve.

In addition to the potential for leakage at the anti-surge valve, the air compressor itself may also be subject to leakage. Therefore, the axial-flow air compressor also has a shaft end sealing structure so as to avoid leakage of tail gas from the shaft end. The air supply device of the present invention can thus supply the exhaust gas while supplying air to the plurality of maleic anhydride reactors, and does not cause pollution to the environment.

Fig. 1 shows a schematic view of an air supply device comprising an exhaust gas recovery conduit according to an embodiment of the invention. In the figure, 1 is an air compressor, 2 is an air filter, 3 is an anti-surge valve, 4 is a backflow filter, 5 is an outlet check valve, 6 is a flowmeter, 7 is an outlet air supply valve, 8 is a start-up air release regulating valve, 9 is a tail gas inlet regulating valve, 10 is an air release muffler, and 11 is an air compressor shaft end seal. The tail gas and the bleed air from the anti-surge valve enter the air compressor together with the air raw material, so that the pollution to the environment is avoided. The start-up air release control valve can be used for air release control when no tail gas is input during start-up. However, when the air compressor inlet contains tail gas, the start-up vent regulating valve is closed, so that no tail gas leakage is ensured.

In one embodiment, a method of operating an air supply device may include:

1) In the starting stage of the air compressor unit, as no tail gas exists in the rear system, the tail inlet regulating valve 9 is closed, the outlet check valve 5 is closed, the outlet air supply valve 7 is closed, the anti-surge valve 3 is closed, the starting air supply regulating valve 8 is opened, the air compressor is started, air enters the air compressor unit 1 through the air filter 2 to be compressed, the angle of the static blade of the air compressor is regulated to be gradually loaded, the technological process is switched through the starting air supply regulating valve 8 and the outlet air supply valve 7, and finally the starting air supply regulating valve 8 is fully closed, the outlet air supply valve 7 and the outlet check valve 5 are fully opened;

2) In the normal operation stage of the air compressor, circulating tail gas from a process system is sent to an air compressor inlet, a tail gas inlet regulating valve 9 is controlled to be slowly opened and is integrated into the air compressor inlet, the flow is regulated according to the requirement of the system, the mixed gas is mixed with air and then enters the air compressor 1 to be compressed, the mixed gas is sent to a subsequent process system after passing through an outlet check valve 5, an outlet flowmeter 6 and an outlet air supply valve 7 which are arranged at an outlet, at the moment, a start-up blow-down regulating valve 8 is manually closed, a unit system anti-surge valve 3 is closed, and automatic control is applied;

3) When the surge phenomenon occurs in the air compressor unit, the anti-surge valve 3 is opened, and the mixed gas is cooled to a set temperature through the anti-surge reflux cooler 4 and then returned to the air compressor inlet, so that the working condition of the air compressor unit is maintained stable;

4) When the air compressor unit has a countercurrent working condition, the anti-surge valve 3 is fully opened, the outlet check valve 5 is closed, the outlet air supply valve 7 is closed, the mixed gas is cooled to a set temperature by the anti-surge reflux cooler 4 and then returns to the air compressor inlet, the angle of the static blade of the air compressor is reduced to 22 degrees, and the unit maintains a safe running state.

In a preferred embodiment, the shaft end seal arrangement employs a combination of a carbon ring seal and a Lawster seal. The Lapin seal is located on the inside and the carbocycle seal is located on the outside. The carbon ring is provided with an air charging port. Since the gas entering the air compressor includes air and exhaust gas, and the substances required to prevent leakage are only a portion of the exhaust gas, the combination of the selective draw seal and the carbocyclic seal may provide adequate tightness at a reasonable cost. Fig. 2 shows a combination of a lazuer seal and a carbocyclic seal. The left side in the figure is the process medium side, and the right side is the atmosphere side. The outer periphery of the end part of the main shaft 3 of the air compressor is provided with a draw-off seal 1, and besides the draw-off seal, a carbocycle seal 2 is also arranged, and a carbocycle seal inflation inlet 4 is arranged in the carbocycle seal. The combined sealing mode can ensure that harmful substances in the tail gas of the maleic anhydride recovery are fully sealed at the end part of the air compressor.

In a preferred embodiment, at least part of the blade surface of the air compressor is acid-resistant treated. The tail gas discharged from the absorber downstream of the maleic anhydride reactor contains a small amount of maleic anhydride in addition to the main gases such as benzene/n-butane, carbon monoxide, carbon dioxide, etc. These materials are not corrosive to metals without generating an acidic solution. Therefore, the vane surface of the air compressor is theoretically not required to be specially treated for these substances.

However, the inventors have unexpectedly found that maleic anhydride, when mixed with an air intake, may combine with water vapor in the air to form maleic acid. Particularly, in the initial stage of compression, such as the first three or four stages of the air compressor, water vapor in the air may be separated out, and an acidic liquid is easily formed with carbon dioxide, maleic anhydride, and the like. This is particularly evident in maleic anhydride plants in air-wet areas. This can cause some erosion to the air compressor blade, affecting the strength of the blade. Therefore, the present invention performs acid-proof treatment on the blades of the compressor. However, as the feed gas is compressed through the air compressor, the temperature increases significantly as the compression progresses. The water vapor in the air is in an overheat state, and no water is separated out in the compression process, so the invention can perform acid-resistant treatment on the dynamic and static blades of the first few stages (such as the first three stages or four stages) of the compressor.

In other words, the inventors found that, unlike pure air feed, the air feed mixed with maleic anhydride and having a certain humidity in the present invention, acidic liquid is generated during compression by the air compressor, if water in the air is separated out, and damage to the air compressor blades is caused. For this purpose, at least part of the blade surfaces of the air compressor are acid-resistant treated. Preferably, the acid-resistant treatment is carried out on the front three-stage movable and static blades of the air compressor. Or preferably, the acid-resistant treatment is carried out on the first four stages of movable and static blades of the air compressor. After a certain compression, the temperature of the mixed gas is continuously increased, the water vapor is in a superheated state, no water is separated out, and no acid liquid is formed, so that acid-resistant coatings are not needed for subsequent blades and pipelines.

The acid-resistant treatment may be an acid-resistant coating treatment, i.e., an acid-resistant layer is formed on a surface to be acid-resistant. The acid resistant layer may be formed by suitable coating, deposition, electroplating, and the like. It should be noted that the acid resistant layer cannot be a coating that is reactive with the starting benzene or cyclobutane. The surface can also be directly subjected to acid resistance treatment by adopting methods such as surface modification and the like. The present invention is not particularly limited thereto.

By the mode, the air supply device can safely recycle the tail gas in the maleic anhydride preparation process.

In one embodiment, the present invention provides a maleic anhydride production system comprising:

maleic anhydride reactor, and

the invention relates to an air supply device.

The maleic anhydride preparation system can realize the reutilization of tail gas and avoid environmental pollution.

Preferably, the maleic anhydride production system further comprises:

an absorber column downstream of the maleic anhydride reactor,

Absorption columns downstream of the maleic anhydride reactor are well known in the art of maleic anhydride preparation. The gas at the top of the absorption tower is rich in unreacted raw materials and has less harmful impurities, and is suitable for being introduced into an air compressor as tail gas for recycling. Therefore, it is preferable to fluidly connect the inlet end of the tail gas recovery conduit with the top of the absorber tower.

The air supply device is particularly suitable for a maleic anhydride preparation system comprising a plurality of reactors, wherein the maleic anhydride preparation system comprising the plurality of reactors is configured to respond to abnormal running conditions of the reactors through the cooperation of an anti-surge valve and a static blade.

In one embodiment, the maleic anhydride production system comprises a multi-reactor, the axial flow air compressor is provided with vanes,

The air supply device includes:

With the continuous improvement and development of air compressors in terms of supply air pressure and stability, it is possible to use a single air compressor to simultaneously supply air to a plurality of maleic anhydride reactors. However, the inventors have found in practice that connecting the exhaust port of an air compressor directly to the air inlet ports of two or more parallel maleic anhydride reactors makes it difficult to achieve safe production operation of a maleic anhydride production system comprising multiple reactors.

The maleic anhydride reactor is characterized by the fact that the stability of the air feed inlet is of great importance for its smooth operation. It can be said that the stabilization of the air supply quantity of the air compressor is a precondition for the smooth operation of the maleic anhydride reactor. Therefore, the air compressor for the maleic anhydride reactor needs to provide not only a sufficient pressure and flow rate, but also to maintain stable air supply to each maleic anhydride reactor working properly under various complex working conditions faced in practice as much as possible, otherwise, it is difficult to successfully and truly realize a design that a plurality of maleic anhydride reactors share one air compressor.

When one air compressor is used for providing pressurized air for a plurality of maleic anhydride reactors, the air inlet pipeline of each maleic anhydride reactor is directly communicated with the exhaust port of the same air compressor, so that the plurality of maleic anhydride reactors are connected in parallel at the downstream of the same air compressor. However, the inventors have unexpectedly found in practice that: it is difficult to meet the practical application requirements to directly connect such pipelines only downstream of a conventional air compressor. In this connection, although the air can be supplied stably for each reactor when all the maleic anhydride reactors are working normally, when some of the plurality of maleic anhydride reactors are in sudden abnormal conditions, other maleic anhydride reactors in the system are adversely affected, and even interlocking skip occurs unequivocally. This results in an arrangement of the above kind which is not practical. Without being bound by any theory, the inventors have found that the reason for these results is that the hysteresis of vane and anti-surge valve feedback control results in an inability to stabilize the discharge pressure and flow in a timely manner.

One sudden abnormal condition of a maleic anhydride reactor is an abnormal shutdown (also known as a skip) due to some unexpected conditions. At this point, to avoid damaging the reactor, the feed gas line to the reactor would be closed as soon as possible to stop receiving air. For a plurality of maleic anhydride reactor designs independent of one another, this does not cause problems, since with the feed gas line closed, the air compressors supplying the respective reactors are also shut down or the vent valves are opened. However, for a plurality of parallel maleic anhydride reactors sharing the same air compressor, if the air compressor is shut down or vented because one of the reactors is tripped, the air supply to all of the maleic anhydride reactors will be stopped, resulting in a reactor that does not have a trip, and has to be shut down. This is very uneconomical from a practical production point of view. Therefore, it is desirable that the air compressor can continue to supply air to the remaining reactors when a sudden jump occurs in one reactor.

The maleic anhydride reactor after the jump will gradually stop receiving air to avoid damaging the reactor. For example, the inlet air flow regulator valve in the reactor inlet line to the skip reactor is closed. The operation mode can be to close the corresponding air inlet flow regulating valve when the reactor jumps, so that the air compressor keeps working continuously to supply air for the rest reactors. However, the inventors have found through practice that in a maleic anhydride system that remains operating in this manner, the air intake of the remaining reactors can be affected, resulting in unstable operation, and also the possibility of interlocking trips. Without being bound by any theory, the inventors found that the reason is as follows. The total air supply required by the maleic anhydride preparation system is related to the number of reactors in operation, so that when one or more of the maleic anhydride reactors suddenly jump, the air supply flow requirement of the air compressor suddenly changes greatly, i.e. the larger air quantity is suddenly reduced in a shorter time. However, the performance adjustment (maintenance of the supply air pressure/flow rate) of the conventional axial flow air compressor is mainly completed by the static blades, and the adjustment of the supply air volume of the outlet of the air compressor cannot be completed rapidly and effectively when the rear system suddenly and greatly fluctuates. Therefore, the operation state of the air compressor cannot be immediately switched to a low air supply state suitable for a small number of reactors, but still maintains a relatively high air supply state. In this case, when the pressure in the air supply duct of the air compressor increases rapidly due to the incompatibility of the high air supply condition and the low air supply demand, the operating point of the air compressor is affected, and the response of the anti-surge system of the air compressor is further induced. The anti-surge system of the air compressor also needs a long time to finish the adjustment and stabilization of the working point, and the outlet pressure of the air compressor cannot be quickly stabilized, so that the air inlet of the running reactor is influenced. In other words, both conventional feedback performance regulation and feedback anti-surge regulation have difficulty in quickly regulating the supply air flow and pressure to a low supply air flow condition. Further, the anti-surge valve of the air compressor performs a full-open air bleeding operation when the pressure suddenly increases sharply (i.e., large disturbance), which causes a sudden drop in the supply air pressure. Although the air compressor is protected, the air supply to the maleic anhydride reactor becomes insufficient. As mentioned previously, maleic anhydride reactors have high requirements for blow stability. Therefore, if the air compressor does not perform related adjustment in advance but continues to perform feedback adjustment, the air supply rate may be excessively high, insufficient or severely fluctuated, and these conditions will affect the operation of the residual maleic anhydride reactor quickly, if the product quality is fluctuated, if the product quality is light, the reactor is stopped, so that the interlocking skip is caused, and the production efficiency is greatly reduced.

Therefore, the mode of simply connecting a plurality of maleic anhydride reactors in parallel at the downstream of the conventional air compressor cannot properly cope with the abnormal conditions of the reactor trip, and it is difficult to realize a practical maleic anhydride preparation system comprising a plurality of reactors.

In view of the above problems, the present invention proposes an air supply device for a maleic anhydride production system including a plurality of reactors, wherein the air supply device includes:

an axial flow air compressor provided with stationary vanes and an anti-surge valve;

a feed forward performance controller configured to initiate a trip emergency control upon receipt of a trip signal from the reactor, and to end the trip emergency control upon closing of the anti-surge valve,

The air supply device of the invention comprises an axial flow type air compressor as a basic component thereof. The axial flow air compressor needs to provide a stable supply of air to at least two maleic anhydride reactors simultaneously. An appropriate air compressor can be selected according to the air supply pressure and flow required by the maleic anhydride reactor and the number of the reactors. In one embodiment, the individual maleic anhydride reactors operate at a pressure of between 0.29 and 0.35MPaA and a required supply air flow of between 1000 and 4000Nm ³ /min。

The axial flow air compressor is provided with stationary vanes and an anti-surge valve. These components may all be conventional components in an axial flow air compressor.

The angle of the static blade is adjustable, so that the air inlet flow of the air compressor is changed. The angle adjustment range of the static blade of the conventional air compressor is 22-79 degrees.

The air supply device of the present invention further includes a vane controller for changing the vane angle. The vane controller may be connected to or include a vane angle adjustment mechanism. The vane controller is a controller having a feedback control function that realizes feedback control based on a difference between a set value and a current value (measured value). For example, the vane controller may be a controller employing a proportional-integral-derivative (PID) control algorithm. The controller has a Set Value (SV) receiving end and a current value (PV) receiving end. The set value of the exhaust pressure and/or flow of the air compressor is input to the controller through the SV receiving end, and the measured value of the exhaust pressure and/or flow of the air compressor is input to the controller through the PV receiving end as the current value. After calculation by PID algorithm, the control device sends the control device for increasing the angle of the stator blade or reducing the angle of the stator blade to the stator blade angle adjusting mechanism through an Output (OUT) end. In this way, the vane controller can perform feedback control on the vane angle based on the deviation of the current value of the exhaust pressure and/or flow rate of the air compressor from the set value, so as to maintain the exhaust pressure and/or flow rate near the set value. This ensures a stable supply of air to the downstream maleic anhydride reactor. It should be noted that such feedback control of vane controllers is slow to take effect and does not have sufficient reactive regulation capability for sudden and sudden fluctuations in pressure or flow.

The air supply device of the present invention further comprises an anti-surge valve controller. The anti-surge valve controller is used for controlling the anti-surge valve, and is also a controller with a feedback control function. The anti-surge valve feedback control is based on an anti-surge line. The operating point is adjusted by controlling the opening of the anti-surge valve by comparing the relative positions of the operating point and the anti-surge line. Likewise, the anti-surge valve controller may be a controller employing a PID algorithm, for example. The SV receiving end of the anti-surge valve controller receives the anti-surge line information, the PV receiving end receives the measuring result of the working point of the air compressor, and the OUT outputs an anti-surge valve control signal. When the working point passes over the anti-surge line and approaches the surge line, the anti-surge valve is selected to be opened at a proper angle based on the measuring result of the working point, so that the pressure is reduced, the working point is returned to a normal working area, and the surge phenomenon of the air compressor is prevented. It should be noted that such feedback control of the anti-surge valve controller is also relatively slow to take effect and is not very responsive to sudden and violent fluctuations in pressure or flow.

Operating points, surge lines and surge lines are well known in the air compressor art. For example, the status points, surge lines, and surge lines may be plotted in an anti-surge map with the differential throat pressure of the air compressor on the abscissa and the exhaust pressure of the air compressor on the ordinate. Fig. 3 shows a typical air compressor anti-surge diagram, wherein a surge line 1 and a surge line 2 are shown. In the anti-surge map, each point corresponds to a state point representing the throat differential pressure and the exhaust pressure of the air compressor. According to the on-site actual surge experiment of the air compressor, the surge points of the air compressor under different stator blade angles can be measured. These surge points are connected to obtain the actual surge line of the air compressor. At a state point in the region below the surge line to the right (the throat differential pressure is larger and the exhaust pressure is lower), the air compressor does not surge. At the surge line and its upper left (too small throat differential pressure, too high exhaust pressure) the air compressor will surge. Further, a certain safety margin (for example, 10%) is reserved as the surge line at the right lower part of the surge line. When the exhaust pressure of the air compressor increases to cause the working point to cross the surge line, the air compressor can reduce the exhaust pressure by opening the anti-surge valve by a certain opening degree, so that the working point is far away from the surge line, and surging is avoided. The anti-surge valve is gradually closed as the operating conditions causing the surge fluctuate. This process can be accomplished by the anti-surge valve controller through feedback control. In one embodiment, after temperature and pressure compensation calculation and calculation according to a broken line function are performed on the throat differential pressure in the control system, the throat differential pressure is used as a set value SV of the anti-surge valve controller, the exhaust pressure measured value of the air compressor is used as a current value PV of the anti-surge valve controller, the opening degree required by the anti-surge valve is calculated (for example, PID algorithm is used), and the opening degree of the anti-surge valve is correspondingly controlled to avoid surging. It will be appreciated that other suitable feedback algorithms may be used in addition to the PID algorithm.

Feedback control of the anti-surge valve is suitable for the case where the disturbance is small, i.e. the operating point crosses the surge line slowly and with a small amplitude. In this case, the operating point can be adjusted by gradually opening the anti-surge valve. However, when the pressure rises rapidly and greatly or the disturbance is large, the operating point may rapidly reach the surge region through the surge line and the safety margin region between the surge lines, and the hysteresis of the above feedback control will be difficult to ensure that the surge is prevented from occurring. Therefore, in the case that the working point may or has entered the surge region due to a large disturbance, in order to simply protect the air compressor, the conventional air compressor adopts an operation of opening the anti-surge valve to the maximum (i.e., full-open) discharge air immediately, so as to rapidly reduce the exhaust pressure, make the working point leave the surge region, and eliminate the surge phenomenon. As described above, the inventors found that this seriously affects the stability of the air supply to the remaining maleic anhydride reactor, and that the reactor may be interlocked to skip due to too low an air flow rate.

The invention sets a feedforward performance controller in the air supply device and properly handles the jump condition of the reactor. More specifically, the invention utilizes a feedforward performance controller to cooperatively regulate the anti-surge valve and the stationary blade to control the exhaust pressure and flow of the air compressor under the condition of reactor jump.

The feed-forward performance controller is configured to initiate a skip emergency control upon receipt of a skip signal from the maleic anhydride reactor and to terminate the skip emergency control upon closure of the anti-surge valve, the skip emergency control comprising: feedforward controls the anti-surge valve opening, and changes the target exhaust pressure and/or flow of the vane controller.

In other words, the present invention is directed to a case where a part of maleic anhydride reactors suddenly jumps as occurs in a maleic anhydride production system including a plurality of reactors, and a feedforward performance controller for emergency handling of the jump is exclusively provided in an air supply device.

The feed forward performance controller does not operate when a multi-reactor in the maleic anhydride production system is not jumping. When each reactor works normally, the exhaust pressure of the air compressor is controlled by the static blade controller and the anti-surge valve controller in a feedback way. The feedforward performance controller participates in the control of the air supply device only when an abnormal condition such as a skip occurs. The feed forward performance controller does not operate even if the discharge pressure of the air compressor suddenly rises for other reasons.

As shown in the drawing, in case that no jump of the reactor occurs, the vane controller feedback-controls the vane angle through the output terminal OUT according to the set value of the SV1 terminal and the measured value or the actual value of the PV terminal, and the anti-surge valve controller feedback-controls the anti-surge valve opening through the output terminal OUT according to the actual operating point positions of the anti-surge line input from the SV1 and the PV output when the operating point of the air compressor crosses the anti-surge line to eliminate a possible surge phenomenon.

The maleic anhydride production system may generate and send a trip signal when the maleic anhydride reactor trips. The maleic anhydride preparation system can send various reactor running state signals or simply running state signals, and the jump signal is one of the running state signals. The signal type of the operational status signal may be a digital quantity dry access point signal. The operating state signal may be automatically generated by a control system of the reactor (e.g., a decentralized control system, DCS). The control system of the reactor judges whether the reactor is operating normally or not by measuring parameters of the reactor. If the control system determines that the reactor is operating properly, it outputs a dry junction signal indicative of proper operation as a normal operating status signal, which may be, for example, a closed signal. When the reactor jumps due to a fault or the like, it outputs a jump operation state signal, for example, an off signal. The system operator can also actively send out a skip signal when the skip is found to occur.

The feed forward performance controller is configured to receive a trip signal from the maleic anhydride reactor and initiate a trip emergency control in response to the trip signal. As shown in fig. 4, the feed forward performance controller may receive the skip signals for reactors 1, 2, and 3. According to the emergency control method, according to the air quantity lost after the reactor jumps, the anti-surge valve and the air compressor stationary blade are coordinated and controlled in advance, so that the air compressor is ensured not to surge, and the air supply to the remaining non-jump reactors is ensured to be stable. As shown in fig. 4, the feedforward performance controller performs operation control through the output terminals OUT1 and OUT 2.

The emergency control includes feedforward control of the opening degree of the anti-surge valve. As described above, when feedback controlled by the anti-surge valve controller, the anti-surge valve is gradually opened in small disturbances and fully opened in large disturbances based on the increased exhaust pressure measurements. In contrast, the feedforward performance controller of the present invention is activated in response to a trip signal and controls the anti-surge valve in advance. That is, instead of performing feedback control after pressure rise due to a skip and subsequent closing of the air intake flow rate adjusting valve of the reactor, control is performed in advance according to the need for air supply after the skip using a feed-forward performance controller. According to the skip signal, the number of the skip reactors can be known, so that the air supply quantity required to be reduced under the corresponding working condition and the air supply quantity required to continue to operate the residual reactors can be known in advance. For example, in a three-reactor system, when the feedforward performance controller receives a skip signal, it can be known that one reactor is skip and the other two reactors are still running. The feedforward performance controller can calculate a proper anti-surge valve opening according to the required air supply quantity and the performance curve of the anti-surge valve. The feed forward performance controller opens (or quickly opens) the anti-surge valve directly to that opening. At this anti-surge valve opening, the bleed air from the anti-surge valve is not fed back to be gradually opened, nor is it fully opened, but is controlled to be opened quickly. The gas flow is adapted to the desired flow of the remaining maleic anhydride reactor by means of the anti-surge valve, so that the flow of air to the remaining reactor does not substantially fluctuate. In the process, the working point of the air compressor cannot reach the surge line, and no surge occurs.

The feedforward performance controller may control the opening of the anti-surge valve by the anti-surge valve controller. That is, the feedforward performance controller transmits a control signal to the anti-surge valve controller, and further controls the anti-surge valve by a signal output from the OUT terminal of the anti-surge valve controller. As shown in fig. 4, the anti-surge valve controller feedback-controls the anti-surge valve opening according to the operating point position received from the surge line and PV terminals received from the SV1 terminal in a normal state, but receives the feedforward signal output from the OUT1 output terminal of the feedforward performance controller from the SEL SV2 terminal when the feedforward performance controller is active.

Meanwhile, the feedforward performance controller calculates the exhaust pressure and flow rate required to be provided by the air compressor when the anti-surge valve is opened according to the known required air supply amount, and sends the required values as target exhaust pressure and/or flow rate to the stator blade controller. As shown in fig. 4, the OUT2 output through the feed-forward performance controller is output to the SEL SV2 terminal of the vane controller. The vane controller obtains the changed target exhaust pressure and/or flow from the feedforward performance controller in place of the set point previously received from the SV1 end. The modified target exhaust gas pressure and/or flow is suitable for operation of the remaining reactors at the aforementioned anti-surge valve opening. The vane controller feedback controls the vane angle based on the changed target exhaust pressure and/or flow, still based on the test values received from the PV end, such that the actual exhaust pressure and/or flow remains substantially stable.

And stable exhaust pressure and flow are obtained through feedforward control of the feedforward controller on the opening degree of the anti-surge valve and feedback control of the angle of the static blade matched with the feedforward controller, so that the rest reactor can still normally operate.

However, the state in which the anti-surge valve is kept open cannot be continued for a long time in consideration of the stability of the normal operation of the system, and this state also causes a large amount of unnecessary compressed air to be discharged from the anti-surge valve, wasting energy. Thus, the feedforward performance controller continues to operate, closing the anti-surge valve stepwise in small steps. For example, in one embodiment, the opening is first reduced to some extent, such as by 2% -5%. When the opening degree of the anti-surge valve is reduced to a small extent, the exhaust pressure and the flow rate are slightly changed correspondingly, but are not changed drastically. However, since the vane controller is still performing feedback control, the air compressor exhaust pressure and flow are coordinated and stabilized by the variation of the vane angle.

After the exhaust pressure stabilizes, i.e., the vane angle remains substantially unchanged, the feedforward performance controller continues to reduce the opening and repeats the above-described operations. By thus gradually and slowly decreasing the opening of the anti-surge valve, the surge valve will eventually be completely closed. During this process, a stable air supply to the remaining maleic anhydride reactors can be maintained at all times so that they can function properly.

When the surge valve is fully closed, the multi-reactor maleic anhydride production system has safely been relieved of sudden trip conditions and a new steady state operating condition has been reached as compared to before, wherein the number of reactors operating has been reduced and the target exhaust pressure and/or flow has been correspondingly altered. At this time, the angle of the stator blade is reduced, so that the inlet air flow is reduced, the throat differential pressure is reduced, and the air compressor is operated at a new working point. Accordingly, the skip emergency control of the feedforward performance control ends.

As described above, in one embodiment, to be able to receive signals from the feed forward performance controller, the vane controller may have another setpoint receiver. The original set value receiving end is SV1, and the new set value receiving end is SEL SV2.SEL SV2 is connected to one signal output OUT2 of the feed-forward performance controller. When the SEL SV2 receiver receives the changed target exhaust pressure and/or flow from the feedforward performance controller, the original SV1 target exhaust pressure and/or flow input values fail.

As described above, in one embodiment, the anti-surge valve controller may also have another set value receiving terminal SEL SV2 and be connected to another signal output terminal OUT1 of the feedforward performance controller. When the SEL SV2 receiving end of the anti-surge valve controller receives a control signal from the feedforward performance controller, it will directly change the anti-surge valve opening through the OUT end. The feedforward performance controller controls the anti-surge valve through the anti-surge valve controller has the advantage that all control signals for the anti-surge valve are sent out by the anti-surge valve controller, so that control conflicts are avoided. When the feedforward performance controller performs emergency control, the feedback control of the anti-surge valve controller is temporarily disabled because the feedforward performance controller can ensure that no surge occurs.

The feedforward performance controller takes the jump signal of the maleic anhydride reactor as a precondition for starting the jump emergency control, and decides a corresponding feedforward control strategy. According to the number of the received reactor jump signals, the number of the remaining reactors still working can be known, and the air supply quantity required by keeping the reactors working normally is correspondingly obtained. For example, for a three reactor system, if a skip signal is received, it is indicated that there are still two reactors that need to remain in operation. The feedforward performance controller can give the required control strategy and corresponding control signals for the number of skip signals.

The following description will be given by taking a reactor trip in a three-reactor system as an example. When one reactor jumps, it immediately sends a jump signal to the feed forward performance controller. The feed forward performance controller thus determines that the maleic anhydride system should be subsequently operated in a two reactor mode. The feedforward performance controller calculates the air supply quantity required by the operation of the two reactors. Based on the inherent characteristic curve of the anti-surge valve, the feedforward performance controller sends an opening control signal to the anti-surge valve controller according to the air supply amount, so that the anti-surge valve is quickly opened to the preset opening.

The principle of selecting the preset opening degree of the anti-surge valve is that firstly, the exhaust pressure is ensured to be in a non-surge region in an anti-surge graph, preferably in a safety region below and right of an anti-surge line under the current throat differential pressure; secondly, at this opening, the air flow and pressure to the maleic anhydride reactor without skip are made substantially unchanged, for example, with a fluctuation of not more than 20%, more preferably 10%, more preferably 5%, more preferably 2%.

The ultimate goal of emergency control is to achieve the desired supply air pressure and flow rate for the two reactors to operate. For this purpose, the feed forward performance controller inputs the target exhaust pressure and/or flow to the vane controller in place of its original exhaust pressure/flow set point. In other words, after the feed forward performance controller initiates emergency control, the vane controller's exhaust pressure and/or flow set point is converted to a value suitable for both reactors. Then, the vane controller stabilizes the supply air pressure and flow rate by adjusting the vanes based on the new set value, thereby ensuring substantially stable operation of the remaining reactors.

At this time, the anti-surge valve is still in a state of opening by a predetermined opening degree, and needs to be gradually closed to return to a normal operation state so as to continue to exert an anti-surge effect. To this end, the performance controller continues to send a feed forward control signal to the anti-surge valve controller. The control signal causes the anti-surge valve to gradually close. In a preferred embodiment, the control signal may be to reduce the opening of the anti-surge valve by 2% -5% at a time. After the opening degree is reduced, the feedback control of the stator blade controller enables the exhaust pressure and the flow to be restored and stabilized by adjusting the stator blade. The opening of 2% -5% can be reduced by the stride scope to get good balance between closing anti-surge valve and waiting for the stator blade to adjust in time as soon as possible. After the stationary blade is stabilized, the opening of the anti-surge valve is reduced next time. This is repeated until the anti-surge valve is fully closed. At this time, the feedforward performance controller ends the emergency control.

Thus, from the time of receiving the reactor trip signal, the feedforward performance controller adjusts the air intake and the air discharge of the air compressor in advance by matching the anti-surge valve with the static blade control, and adjusts the outlet pressure and the flow (namely, the anti-surge valve-performance control input) to obtain the required air supply. Because it is the feedforward control that responds to the jump signal, so unlike feedback control, it can be in advance to the effective intervention of air supply device before system pipe network change causes the air compressor machine to adjust more influence behind the air compressor machine. In the process, the air compressor is not damaged, and the work of the residual reactor is not influenced. By the control of the feedforward performance controller, the fluctuation caused by the reactor jump is effectively controlled under the cooperative adjustment of the static blade and the anti-surge valve, and the risk and probability of the device interlocking stop are reduced.

The air supply device combines the anti-surge control regulation, the static blade control regulation and the running state signal of the maleic anhydride reactor and forms a brand new air supply regulation system of the air compressor together with the additionally arranged feedforward performance controller, thereby ensuring the stability of air supply to the residual reactor.

In a multi-reactor maleic anhydride production system, the tail gas from each reactor may be returned to the air compressor.

In addition, in the maleic anhydride preparation system, when the reactor jump working condition is met, the emergency control can quickly open the anti-surge valve to a certain opening degree and gradually close the anti-surge valve. In this process, unlike the short-term small amount of exhaust gas of an anti-surge valve in a general anti-surge process, the system of the present invention continuously emits a large amount of exhaust gas to the environment. This will result in considerable amounts of flammable and explosive and toxic and hazardous benzene or n-butane being discharged untreated into the environment, which must be avoided. The tail gas recovery design of the invention is particularly suitable for a maleic anhydride preparation system for implementing the emergency control.

Therefore, the air supply device for recycling the tail gas of the maleic anhydride reaction is particularly suitable for the emergency control of the multi-reactor maleic anhydride preparation system, and can safely realize the safe and efficient operation of the reactor maleic anhydride preparation system.

The present invention is described in more detail below by way of examples.

Example 1

The production was performed using a maleic anhydride preparation system with one air compressor and one maleic anhydride reactor supplied with air. The reaction raw material is n-butane.

An exhaust gas recovery line in communication with the top of the absorber column downstream of the maleic anhydride reactor is in fluid communication with the intake line of the air compressor. The air supply device further includes a surge bleed air return conduit that fluidly communicates an exhaust port of the anti-surge valve with an intake conduit of the air compressor. The air compressor adopts a combined seal of carbon ring seal and Laganmao seal as a shaft end seal structure. The Lapin seal is located on the inside and the carbocycle seal is located on the outside. The carbon ring is provided with an air charging port.

The maleic anhydride production system was run and the air in the air compressor environment was checked and no n-butane was found to be present.

However, after 1000 hours of operation, the air compressor blade surface was inspected and corrosion was observed.

Example 2

The test was performed in the same manner as in example 1, except that the surface of the front three stage blade of the air compressor was subjected to acid-resistant treatment.

After 1000 hours of operation, the air compressor blade surface was inspected and no corrosion was observed.

Example 3

The production was performed using a maleic anhydride preparation system with one air compressor and one maleic anhydride reactor supplied with air. The reaction raw material is benzene.

The maleic anhydride production system was run and the air in the air compressor environment was checked and no benzene was found to be present.

After 1000 hours of operation, the surface of the air compressor blade was inspected and corrosion was observed.

Example 4

The test was performed in the same manner as in example 3, except that the surface of the front three stage blade of the air compressor was subjected to acid-resistant treatment.

Example 5

The production is carried out by using a maleic anhydride preparation system which uses an air compressor to simultaneously supply air for three parallel maleic anhydride reactors. The three maleic anhydride reactors are respectively called a No. 1 reactor, a No. 2 reactor and a No. 3 reactor. The reaction raw material is n-butane. Each reactor has a respective off-gas recovery conduit.

And setting a static blade controller and embedding a PID algorithm. The output end OUT of the device is connected with a stationary blade adjusting mechanism to control the angle of the stationary blade. The first set point receiving end SV1 obtains a target exhaust pressure set point of the reactor during normal operation from a control system. Its current value receiving end PV receives real-time exhaust pressure measurement values from the exhaust pressure sensor.

An anti-surge controller is arranged, and a PID algorithm is embedded. The output end OUT of the valve is connected with an anti-surge valve to control the opening degree of the anti-surge valve. The first set point receiving end SV1 obtains an anti-surge map from the control system, including a surge line and an anti-surge line. Its current value receiving end PV receives real-time operating point parameters from the exhaust pressure sensor and the differential throat pressure sensor.

A feed-forward performance controller is provided, three signal inputs of which receive operating signals from the reactors 1-3. The second output terminal OUT1 thereof is connected to a second set value receiving terminal SEL SV2 of the anti-surge valve controller. The first output end OUT2 of the first control device is connected with a second set value receiving end SEL SV2 of the stationary blade controller.

As shown in fig. 4, the reactor, anti-surge controller, anti-surge valve, vane controller, vane, and feed forward performance controller are connected together.

First, the reactors 1 to 3 were operated in a normal state. At this point, the feedforward performance controller is not operating. The vane controller performs feedback control on the vane angle based on the target exhaust pressure set value obtained by SV1 and the measured value obtained by PV. The anti-surge valve controller performs feedback control on the opening of the anti-surge valve according to the operating point parameters obtained by PV based on the anti-surge line obtained by SV 1.

To simulate a reactor trip, reactor number 1 is shut down and then the inlet air flow regulator valve to reactor number 1 is closed while a trip signal is sent to the feedforward performance controller.

The jump signal of the reactor 1 enables the feed-forward performance controller to start and starts jump emergency control. According to the jump signal of 1, the expected air flow rate is changed into two thirds of the original air flow rate, and the pressure is unchanged. For this purpose, the feedforward performance controller sends a feedforward signal to SEL SV2 of the anti-surge valve to quickly open the opening of the anti-surge valve to the first opening (not fully open), and exhaust gas. Under the first opening degree, the exhaust flow of the air which is led to the downstream is two thirds of the previous pressure under the current static blade angle and the working state of the air compressor. The working point is positioned at the right lower part of the surge prevention line, so that the surge can be avoided.

At the same time, the feed forward performance controller sends this target exhaust pressure and/or flow to SEL SV2 of the vane controller. The vane controller performs feedback control therefrom based on the changed target exhaust pressure and/or flow. Since the flow and pressure are now about the target values, the vane controller fine-tunes the vane angle based solely on the measured value feedback.

Subsequently, the feedforward performance controller reduced the anti-surge valve opening by 2%. At this point, both the exhaust pressure and flow rise, the vane controller will receive the increased pressure/flow measurement and feedback control the vanes to reduce the vane angle so that the exhaust pressure and flow drop back to the target values.

After the exhaust pressure and flow stabilize around the target values (i.e., after the vane angle is no longer continuously reduced), the feedforward performance controller reduces the anti-surge valve opening by 2% again. The above process is repeated until the anti-surge valve is completely closed.

After the anti-surge valve is completely closed, the feedforward performance controller is closed, and the emergency control of the vehicle jump is finished. The anti-surge valve controller takes over feedback control of the anti-surge valve.

During this process, the air inlet pressure and flow rate in the reactors No. 2 and No. 3 were monitored, and the operating state of the reactors was checked. As a result, the air inlet pressure and flow of the No. 2 and No. 3 reactors have small fluctuation, the reactors work stably, the product yield and quality are stable, and the influence of the jump of the No. 1 reactor is avoided.

In addition, although the anti-surge valve is opened for a long time during emergency control, n-butane is not found in the air of the air compressor environment.

Example 6

The test was performed in the same manner as in example 5, except that the reactors No. 1 and No. 2 of the three reactors were subjected to simulated skip.

Accordingly, the feedforward performance controller opens the anti-surge valve quickly and the changed target exhaust gas flow sent to the vane controller is one third of the previous, with unchanged pressure. Because the opening degree is large, the anti-surge valve opening degree per reduction is increased to 5% during the feedforward control.

During this process, the air inlet pressure and flow rate in reactor No. 3 were monitored, and the operating state of the reactor was checked. As a result, it was found that the fluctuation in the air intake pressure and flow rate of reactor No. 3 was not large. The reactor works stably, and the output and quality of the product are stable and are not influenced by the jump of the No. 1 and No. 2 reactors.

Comparative example 1:

the maleic anhydride reactor was supplied with air in the same apparatus as in example 5, except that a feedforward controller was not provided.

After the reactor No. 1 is bounced, the measured value of the exhaust pressure rises very fast, and the feedback control of the anti-surge controller is triggered, so that the anti-surge valve is fully opened. And after the anti-surge valve is fully opened, the reactors No. 2 and No. 3 are locked and jumped due to insufficient air supply, and the operation is stopped.

Comparative example 2:

the maleic anhydride reactor was supplied with air in the same apparatus as in example 6, except that a feedforward controller was not provided.

After the reactors 1 and 2 are simulated to jump, the measured value of the exhaust pressure rises very fast, and the feedback control of the anti-surge controller is triggered, so that the anti-surge valve is fully opened. After the anti-surge valve is fully opened, the reactor No. 3 quickly locks and jumps due to insufficient air supply, and stops running.

Therefore, when one or a plurality of maleic anhydride reactors are suddenly stopped, the air compressor is ensured not to be damaged due to surge, and the rest reactors are ensured not to work abnormally or stop in an interlocking way due to the sudden reduction of air supply.

The foregoing is merely illustrative of the present invention, and the present invention is not limited thereto, and any person skilled in the art will readily recognize that variations or substitutions are within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. An air supply device for maleic anhydride reaction tail gas recovery, characterized in that the air supply device comprises:

an axial flow air compressor provided with an anti-surge valve;

and the air compressor is provided with a shaft end sealing structure.

2. The air supply of claim 1, wherein the shaft end seal structure is a combination of a carbon ring seal and a pull seal.

3. The air supply device of claim 1, wherein at least a portion of a vane surface of the air compressor is acid resistant treated.

4. A maleic anhydride production system, characterized in that the maleic anhydride production system comprises:

Maleic anhydride reactor, and

an air supply device according to any one of claims 1-3.

5. The maleic anhydride production system of claim 4, further comprising:

an absorber column downstream of the maleic anhydride reactor,

6. The maleic anhydride production system according to claim 4, characterized in that the maleic anhydride production system comprises a multi-reactor, the axial flow air compressor is provided with vanes,

the air supply device includes:

7. A method of operating a maleic anhydride production system comprising a multi-reactor according to any one of claims 4-6, wherein the method of operating comprises:

8. The method of claim 7, wherein the step of determining the position of the probe is performed,

the maleic anhydride production system comprising multiple reactors is the maleic anhydride production system comprising multiple reactors according to claim 6, and the method further comprises:

iii) Repeating operation ii) until the anti-surge valve is closed.