A start-up method for an oil refinery catalytic cracking unit

Abstract

The present application provides a kind of start-up method of oil refining catalytic cracking unit, comprising the following steps: 1) cut off regenerator and settler;With steam, air is discharged into oil column;2) single vessel fluidization: when the regeneration temperature reaches the second temperature, open the booster, and introduce the plenum wind into the external heat exchanger, and the external heat exchanger starts to produce steam;When the regeneration temperature reaches the third temperature, the steam produced by the external heat exchanger warms up the steam turbine;By adjusting the injection amount of combustion oil, when the regeneration temperature reaches the fourth temperature, the steam produced by the external heat exchanger first increases the speed of the steam turbine;3) double vessel fluidization;4) reaction oil injection: the injection amount gradually increases, the steam temperature and pressure produced by the external heat exchanger gradually increase, the steam turbine gradually increases the speed, and then the air compressor motor is opened.The start-up method solves the problem of oil and gas waste caused by oil injection and fire at the initial stage of the start-up of the oil refining catalytic cracking unit, the impact on the downstream flare device, environmental pollution and social influence.

Description

Technical Field

[0001] This invention relates to the field of catalytic cracking technology in oil refining, and in particular to a start-up method for an oil refining catalytic cracking unit. Background Technology

[0002] The catalytic converter complex includes a catalytic cracking unit, a gas refining unit, and a gas fractionation unit. The catalytic cracking unit mainly consists of a reaction regeneration system, a fractionation system, an absorption stabilization system, and a generator system. Feedstock is injected into the lower part of the riser reactor, where it mixes with, vaporizes, and reacts with the high-temperature catalyst. The reactant oil and gas are separated from the catalyst in a settling tank and a cyclone separator (referred to as a cyclone separator), and then enter a fractionation tower to separate gasoline, diesel, and recycled oil. The cracked gas is compressed and sent to the gas separation system. Coked catalyst is recycled after the coke is burned off with air in the regenerator. During the initial start-up phase, due to insufficient oil and gas load, the compressor is generally started only after normal injection to prevent compressor surge and reaction pressure fluctuations. At this time, the reaction pressure is controlled by the flare at the compressor inlet. A large amount of oil and gas enters the flare system, affecting the environmental and economic benefits of the unit and significantly impacting the operation of the downstream flare recovery unit. If the discharge volume is too large, the flare unit needs to be ignited, further causing energy waste and adverse social impacts. Summary of the Invention

[0003] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a start-up method for a catalytic cracking unit in oil refining, which solves the problems of oil and gas waste caused by the oil injection flare torque during the initial start-up of the catalytic cracking unit, the impact on downstream flare units, environmental pollution, and social impact.

[0004] To achieve the above and other related objectives, the present invention provides a start-up method for a petroleum refining catalytic cracking unit, comprising the following steps:

[0005] 1) Cut off the regenerator and settler, and control the first negative differential pressure of the regenerator and settler; after purging the air in the reactor, settler and fractionation tower with steam, feed oil into the fractionation tower;

[0006] 2) Single-container fluidization: Control the regenerator and settler to the second negative differential pressure, and add a balancing catalyst to the regenerator; when the regeneration temperature reaches the first temperature, start injecting combustion oil; when the regeneration temperature reaches the second temperature, start the booster compressor and introduce booster air into the external heat exchanger, which begins to generate steam; when the regeneration temperature reaches the third temperature, the steam generated by the external heat exchanger warms up the turbine; add supplementary catalyst to the regenerator; by adjusting the amount of combustion oil injected, when the regeneration temperature reaches the fourth temperature, the steam generated by the external heat exchanger accelerates the turbine for the first time.

[0007] 3) Dual-container fluidization: The regenerator and settling tank are controlled at the first positive differential pressure, and the catalyst is circulated in the reactor, settling tank and regenerator;

[0008] 4) Reaction oil injection: Control the regenerator and settler to the second positive differential pressure. During the reaction oil injection stage, the oil injection volume gradually increases, the steam temperature and pressure generated by the external heat exchanger gradually increase, the turbine speed is gradually increased, and then the air compressor motor is started.

[0009] Preferably, in step 1), the first negative differential pressure is 10–30 kPa, such as 10–20 kPa or 20–30 kPa. The pressure of the regenerator is ≤0.01 MPa; the pressure of the settling device is 0.01–0.03 MPa higher than the pressure of the regenerator.

[0010] Preferably, in step 2), the second negative differential pressure is 10-30 kPa, such as 10-20 kPa or 20-30 kPa.

[0011] Preferably, step 2) further includes at least one of the following technical features:

[0012] 21) The first temperature is 380–400℃, such as 380–390℃ or 390–400℃;

[0013] 22) The second temperature is 500-520℃, such as 500-510℃ or 510-520℃.

[0014] Preferably, in step 2), the steam generated by the external heat exchanger is incorporated into the medium-pressure steam pipeline network and then fed into the steam turbine.

[0015] Preferably, step 2) further includes at least one of the following technical features:

[0016] 23) The third temperature is 650–670℃, such as 650–660℃ or 660–670℃;

[0017] 24) When warming up the steam turbine, the steam pressure generated by the external heat exchanger is 0.9 to 1.1 MPa, such as 0.9 to 1.0 MPa or 1.0 to 1.1 MPa;

[0018] 25) When warming up the steam turbine, the steam temperature generated by the external heat exchanger is 190-210℃, such as 190-200℃ or 200-210℃;

[0019] 26) When warming up the steam turbine, the turbine speed is 1450-1550 rpm, such as 1450-1500 rpm or 1500-1550 rpm.

[0020] Preferably, step 2) further includes at least one of the following technical features:

[0021] 27) The fourth temperature is 675-685℃, such as 675-680℃ or 680-685℃;

[0022] 28) When the steam turbine is first accelerated, the steam pressure generated by the external heat exchanger is 1.9 to 2.1 MPa, such as 1.9 to 2.1 MPa or 2.0 to 2.1 MPa;

[0023] 29) When the steam turbine is first accelerated, the steam temperature generated by the external heat exchanger is 290-310℃, such as 290-300℃ or 300-310℃;

[0024] 210) When the turbine is first accelerated, the turbine speed is 2450-2550 rpm, such as 2450-2500 rpm or 2500-2550 rpm.

[0025] Preferably, in step 3), the first positive differential pressure is 10-30 kPa, such as 10-20 kPa or 20-30 kPa.

[0026] Preferably, step 4) further includes at least one of the following technical features:

[0027] 41) The second positive differential pressure is 10-30 kPa, such as 10-20 kPa or 20-30 kPa;

[0028] 42) When the air compressor motor is turned on, the steam pressure generated by the external heat exchanger is 2.6-2.8 MPa, such as 2.6-2.7 MPa or 2.7-2.8 MPa;

[0029] 43) When the air compressor motor is turned on, the steam temperature generated by the external heat exchanger is 370-390℃, such as 370-380℃ or 380-390℃;

[0030] 44) When the air compressor motor is turned on, the turbine speed is 7500-7600 rpm, such as 7500-7550 rpm or 7550-7600 rpm.

[0031] Preferably, the air compressor speed is increased to 9840-9940 rpm, such as 9840-9890 rpm or 9890-9940 rpm, and the air compressor is put into normal operation.

[0032] As described above, the present invention starts the booster in advance during single-container fluidization, introduces the booster air into the external heat exchanger, and the external heat exchanger starts to generate steam. The steam generated by the external heat exchanger warms up the turbine in advance, which solves the problems of oil and gas waste caused by the oil injection flare torque in the early stage of operation of the oil refining catalytic cracking unit, impact on downstream flare units, environmental pollution and social impact. Attached Figure Description

[0033] Figure 1 This is a system diagram of a petroleum refining catalytic cracking unit.

[0034] Figure Labels

[0035] 1. Settling device

[0036] 2 Regenerator

[0037] 3. Reactor

[0038] 4. Distillation Tower

[0039] 5. External Heat Exchanger

[0040] 6 Main fan units

[0041] 7 Pneumatic compressor units

[0042] 8. Intensifier Detailed Implementation

[0043] The present invention is further illustrated below with reference to the embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods and reagents not specified in the following embodiments, unless otherwise stated, were performed or prepared under conventional conditions or conditions recommended by the manufacturer.

[0044] Figure 1 The existing oil refining catalytic cracking unit mainly includes a settling tank 1, a regenerator 2, a reactor 3, a fractionation tower 4, an external heat exchanger 5, a main blower unit 6, a gas compressor unit 7, and a booster compressor 8.

[0045] The feedstock is injected into reactor 3, which is located at the bottom of the riser reactor. Here, it mixes with, vaporizes, and reacts with the high-temperature catalyst. The reactant oil and gas are separated from the catalyst in settling tank 1 and cyclone separator (referred to as cyclone separator), and then enter fractionation tower 4 to separate gasoline, diesel, and heavy recycled oil. The coked catalyst is recycled after the coke is burned off by air in regenerator 3.

[0046] The coke-covered catalyst, after exiting the coarse vortex, flows to the overflow hopper and undergoes simple stripping. It then merges with the catalyst recovered from the single-stage cyclone separation in the settling tank and enters the stripping section. Here, it comes into countercurrent contact with steam to strip the oil and gas carried by the catalyst. The stripped catalyst flows down the regenerator riser, passes through the regenerator plug valve, and then enters the upper part of the dense phase bed of the regenerator through the distributor at the outlet of the regenerator plug valve sleeve. It undergoes complete countercurrent regeneration at a regeneration temperature of approximately 700°C, under oxygen-enriched (3% v) and CO combustion-supporting conditions. Excess heat generated during the coking process is removed by the external heat exchanger 5. The regenerated catalyst, after regeneration in the regenerator 3, enters the bottom of the riser reactor through the regeneration riser and regeneration single-acting slide valve. Under the lifting of dry gas and steam, the catalyst undergoes acceleration and dispersion, and then comes into contact with the atomized feedstock.

[0047] The main air required for coke burning in the regenerator is supplied by the main fan in the main fan unit 6. The main air from the main fan enters the regenerator as coke burning air, while the booster air from the booster compressor 8 serves as the fluidizing air, lifting air, and sleeve fluidizing air for the external heat exchanger 5. The flue gas generated by the regenerator 2 can be separated from the catalyst and then enter the flue gas turbine in the main fan unit 6 for expansion and work, driving the main fan. The flue gas exiting the flue gas turbine can enter the waste heat boiler to further recover the heat energy of the flue gas, reducing the flue gas temperature to about 280℃, and finally being discharged into the atmosphere after purification by the desulfurization and denitrification system.

[0048] The main fan unit 6 includes a flue gas turbine, a main fan, a gearbox, and a motor / generator. It can be a single-stage cantilevered flue gas turbine, or simply a flue gas turbine. Its working principle is that high-temperature flue gas at a certain pressure drives the flue gas turbine impeller to rotate, which in turn drives the main fan to perform work. Alternatively, if there is surplus energy after the main fan has performed work, it drives the motor / generator to generate electricity, thus achieving energy recovery. The main fan used can be an axial flow main fan. Its working principle is that after the airflow passes through the inlet guide vane, a velocity field is formed in front of the first-stage moving blades of the compressor. When the airflow passes through the high-speed rotating moving blades, it receives mechanical work and converts it into kinetic energy, increasing the absolute velocity of the airflow. In the stationary blades, the high-speed airflow flowing in from the moving blade outlet gradually decelerates, thereby achieving pressurization. Furthermore, it ensures that the airflow enters the next stage of the moving blades with the necessary velocity field to achieve the required outlet pressure. Outlet flow control can be achieved simply by changing the stationary blade angle. Under normal operating conditions, the power output of the three units exceeds the power required by the axial flow main fan. The excess power is then generated by an electric motor / generator and connected to the grid. When the smoke generator is operating at low load or is disconnected from the grid, the electric motor / generator performs work to drive the axial flow main fan.

[0049] The pneumatic compressor unit 7 includes a steam turbine, a pneumatic compressor, a gearbox, and an electric motor / generator. The steam turbine works by utilizing the expansion of steam, converting some of its thermal and static pressure energy into a high-speed steam flow. This steam drives the impeller, converting it into mechanical energy to power the pneumatic compressor. The pneumatic compressor compresses gas using the centrifugal force generated by the high-speed rotating impeller. The gas moves radially perpendicular to the compressor shaft. As the gas flows through the impeller, the centrifugal force creates pressure, and the gas gains velocity. The diffuser further slows the gas, increasing its pressure, before it is sent to the absorption and stabilization system. The electric motor / generator operates as follows: Under normal operating conditions, the steam turbine's power output exceeds that of the pneumatic compressor. The excess power is generated by the electric motor / generator and connected to the grid. In case of turbine failure or low-load operation, the electric motor / generator powers the pneumatic compressor.

[0050] The working principle of the booster compressor 8 is as follows: It relies on the centrifugal force generated by the high-speed rotating impeller to compress air. The air moves in the impeller in a radial direction perpendicular to the booster compressor shaft. When the air flows through the impeller, the air is subjected to centrifugal force due to the rotation of the impeller, which generates pressure. At the same time, the air also gains speed. Then, the air speed is slowed down by the diffuser, which further increases the air pressure, and then it is sent to the regenerator 2 and the external heat exchanger 5.

[0051] Example 1

[0052] A method for starting up an oil refining catalytic cracking unit includes the following steps:

[0053] 1) Cut off the regenerator and settler, and control the first negative differential pressure of the regenerator and settler; after venting the air in the reactor, settler and fractionation tower with steam, feed oil into the fractionation tower; wherein, the first negative differential pressure is 10 kPa;

[0054] 2) Single-Container Fluidized Regeneration: The regenerator and settling tank are controlled at a negative differential pressure; a balancing catalyst is added to the regenerator. When the regeneration temperature reaches the first temperature, fuel oil injection begins. When the regeneration temperature reaches the second temperature, the booster compressor is started, introducing booster air into the external heat exchanger, which begins to generate steam. When the regeneration temperature reaches the third temperature, the steam generated by the external heat exchanger warms up the turbine. Supplementary catalyst is added to the regenerator. By adjusting the fuel oil injection rate, when the regeneration temperature reaches the fourth temperature, the steam generated by the external heat exchanger provides the first speed-up to the turbine. The second negative differential pressure... The pressure is 10 kPa; the first temperature is 380°C; the second temperature is 500°C; the steam generated by the external heat exchanger is incorporated into the medium-pressure steam pipeline network and then fed into the steam turbine; the third temperature is 650°C; when warming up the steam turbine, the steam pressure generated by the external heat exchanger is 1.0 MPa, the steam temperature is 200°C, and the steam turbine speed is 1500 rpm; the fourth temperature is 680°C; when the steam turbine is first accelerated, the steam pressure generated by the external heat exchanger is 2.0 MPa, the steam temperature is 300°C, and the steam turbine speed is 2500 rpm;

[0055] 3) Dual-container fluidization: The regenerator and settling tank are controlled at a first positive differential pressure, and the catalyst is circulated in the reactor, settling tank and regenerator; wherein, the first positive differential pressure is 10 kPa;

[0056] 4) Reaction Injection: The regenerator and settler are controlled at a second positive differential pressure. During the reaction injection stage, the injection rate gradually increases, leading to a gradual increase in the steam temperature and pressure generated by the external heat exchanger, which in turn gradually increases the turbine speed. Then, the air compressor motor is started. The second positive differential pressure is 10 kPa. When the air compressor motor is started, the steam pressure generated by the external heat exchanger is 2.7 MPa, the steam temperature is 380°C, and the turbine speed is 7550 rpm. The air compressor speed increases to 9890 rpm, and the air compressor is operating normally.

[0057] Based on an initial plant capacity of 80 t / h and a dry gas capacity of 100 Nm³, 3 / min (based on DCS metering data), liquefied petroleum gas (LPG) 13.6t / h (based on a 17% yield), the last start-up flare duration was 1 hour, and the internal settlement prices for dry gas and LPG were RMB 3980 / ton and RMB 6101 / ton respectively. The economic benefits of this saving are as follows:

[0058] 100 * 0.8 * 60 / 1000 * 3980 + 80 * 17% * 6101 = 102077 (yuan)

[0059] As can be seen, this embodiment solves the problem of a large amount of gas flaring out of the compressor inlet during the initial stage of catalytic reaction injection, which would cause a huge impact on the flare recovery system. It avoids the pollution to the surrounding environment caused by a large amount of rich gas breaking through the water seal and igniting the flare. At the same time, it avoids the combustion of large amounts of rich gas (dry gas + liquefied gas) in the flare, saving the unit 100,000 yuan in economic benefits.

[0060] Example 2

[0061] A method for starting up an oil refining catalytic cracking unit includes the following steps:

[0062] 1) Cut off the regenerator and settler, and control the first negative differential pressure of the regenerator and settler; after venting the air in the reactor, settler and fractionation tower with steam, feed oil into the fractionation tower; wherein, the first negative differential pressure is 20 kPa;

[0063] 2) Single-Container Fluidized Regeneration: The regenerator and settling tank are controlled at a negative differential pressure; a balancing catalyst is added to the regenerator. When the regeneration temperature reaches the first temperature, fuel oil injection begins. When the regeneration temperature reaches the second temperature, the booster compressor is started, introducing booster air into the external heat exchanger, which begins to generate steam. When the regeneration temperature reaches the third temperature, the steam generated by the external heat exchanger warms up the turbine. Supplementary catalyst is added to the regenerator. By adjusting the fuel oil injection rate, when the regeneration temperature reaches the fourth temperature, the steam generated by the external heat exchanger provides the first speed-up to the turbine. The second negative differential pressure... The pressure is 20 kPa; the first temperature is 390°C; the second temperature is 510°C; the steam generated by the external heat exchanger is incorporated into the medium-pressure steam pipeline network and then fed into the steam turbine; the third temperature is 660°C; when warming up the steam turbine, the steam pressure generated by the external heat exchanger is 0.9 MPa, the steam temperature is 190°C, and the steam turbine speed is 1500 rpm; the fourth temperature is 675°C; when the steam turbine is first accelerated, the steam pressure generated by the external heat exchanger is 1.9 MPa, the steam temperature is 290°C, and the steam turbine speed is 2500 rpm;

[0064] 3) Dual-container fluidization: The regenerator and settling tank are controlled at a first positive differential pressure, and the catalyst is circulated in the reactor, settling tank and regenerator; wherein, the first positive differential pressure is 20 kPa;

[0065] 4) Reaction Injection: The regenerator and settler are controlled at a second positive differential pressure. During the reaction injection stage, the injection rate gradually increases, leading to a gradual increase in the steam temperature and pressure generated by the external heat exchanger, which in turn gradually increases the turbine speed. Then, the air compressor motor is started. The second positive differential pressure is 20 kPa. When the air compressor motor is started, the steam pressure generated by the external heat exchanger is 2.6 MPa, the steam temperature is 370°C, and the turbine speed is 7550 rpm. The air compressor speed increases to 9890 rpm, and the air compressor is operating normally.

[0066] This embodiment solves the problem of a large amount of gas released into the compressor inlet during the initial stage of catalytic reaction injection, which can cause a significant impact on the flare recovery system. It avoids the pollution to the surrounding environment caused by a large amount of rich gas breaking through the water seal and igniting the flare. Simultaneously, it avoids the combustion of large amounts of rich gas (dry gas + liquefied petroleum gas) in the flare, saving the unit 100,000 yuan in economic benefits (initial unit processing capacity 80t / h).

[0067] Example 3

[0068] A method for starting up an oil refining catalytic cracking unit includes the following steps:

[0069] 1) Cut off the regenerator and settler, and control the first negative differential pressure of the regenerator and settler; after venting the air in the reactor, settler and fractionation tower with steam, feed oil into the fractionation tower; wherein, the first negative differential pressure is 30 kPa;

[0070] 2) Single-Container Fluidized Regeneration: The regenerator and settling tank are controlled at a negative differential pressure; a balancing catalyst is added to the regenerator. When the regeneration temperature reaches the first temperature, fuel oil injection begins. When the regeneration temperature reaches the second temperature, the booster compressor is started, introducing booster air into the external heat exchanger, which begins to generate steam. When the regeneration temperature reaches the third temperature, the steam generated by the external heat exchanger warms up the turbine. Supplementary catalyst is added to the regenerator. By adjusting the fuel oil injection rate, when the regeneration temperature reaches the fourth temperature, the steam generated by the external heat exchanger provides the first speed-up to the turbine. The second negative differential pressure... The pressure is 30 kPa; the first temperature is 400°C; the second temperature is 520°C; the steam generated by the external heat exchanger is incorporated into the medium-pressure steam pipeline network and then fed into the steam turbine; the third temperature is 670°C; when warming up the steam turbine, the steam pressure generated by the external heat exchanger is 1.1 MPa, the steam temperature is 210°C, and the steam turbine speed is 1500 rpm; the fourth temperature is 685°C; when the steam turbine is first accelerated, the steam pressure generated by the external heat exchanger is 2.1 MPa, the steam temperature is 310°C, and the steam turbine speed is 2500 rpm;

[0071] 3) Dual-container fluidization: The regenerator and settling tank are controlled at a second positive differential pressure, and the catalyst is circulated in the reactor, settling tank and regenerator; wherein, the second positive differential pressure is 30 kPa;

[0072] 4) Reaction Injection: The regenerator and settler are controlled at a second positive differential pressure. During the reaction injection stage, the injection rate gradually increases, leading to a gradual increase in the steam temperature and pressure generated by the external heat exchanger, which in turn gradually increases the turbine speed. Then, the air compressor motor is started. The second positive differential pressure is 30 kPa. When the air compressor motor is started, the steam pressure generated by the external heat exchanger is 2.8 MPa, the steam temperature is 390°C, and the turbine speed is 7550 rpm. The air compressor speed increases to 9890 rpm, and the air compressor is operating normally.

[0073] This embodiment solves the problem of a large amount of gas flaring out of the compressor inlet during the initial stage of catalytic reaction injection, which can severely impact the flare recovery system. It avoids the pollution to the surrounding environment caused by a large amount of rich gas breaking through the water seal and igniting the flare. Simultaneously, it avoids the combustion of large amounts of rich gas (dry gas + liquefied petroleum gas) in the flare, saving the unit 100,000 yuan in economic benefits.

[0074] The above embodiments are for illustrating the implementation schemes disclosed in this invention and should not be construed as limiting the invention. Furthermore, various modifications listed herein, as well as variations in the methods and compositions of the invention, will be apparent to those skilled in the art without departing from the scope and spirit of the invention. Although the invention has been specifically described in conjunction with various specific preferred embodiments, it should be understood that the invention should not be limited to these specific embodiments. In fact, various modifications as described above that are obvious to those skilled in the art to obtain the invention should be included within the scope of this invention.

Claims

1. A method for starting up an oil refining catalytic cracking unit, characterized in that, Includes the following steps: 1) Cut off the regenerator and settling tank, and control the regenerator and settling tank to the first negative differential pressure; after purging the air in the reactor, settling tank and fractionation tower with steam, feed oil into the fractionation tower; 2) Single-container fluidization: Control the regenerator and settling tank to a second negative differential pressure, and add a balanced catalyst to the regenerator; Once the regeneration temperature reaches the first temperature, combustion oil injection begins. When the regeneration temperature reaches the second temperature, the booster compressor is turned on to introduce the booster air into the external heat exchanger, which begins to generate steam. When the regeneration temperature reaches the third temperature, the steam generated by the external heat exchanger warms up the turbine. A supplementary catalyst is added to the regenerator. By adjusting the amount of fuel oil injected, when the regeneration temperature reaches the fourth temperature, the steam generated by the external heat exchanger accelerates the turbine for the first time. 3) Dual-container fluidization: The regenerator and settling tank are controlled at the first positive differential pressure, and the catalyst is circulated in the reactor, settling tank and regenerator; 4) Reaction oil injection: Control the regenerator and settler to the second positive differential pressure. During the reaction oil injection stage, the oil injection volume gradually increases, the steam temperature and pressure generated by the external heat exchanger gradually increase, the turbine speed is gradually increased, and then the air compressor motor is started. The heat for generating steam in the external heat exchanger comes from the excess heat generated by the burner in the regenerator. The first temperature is 380~400℃; The second temperature is 500~520℃; The third temperature is 650~670℃; When warming up the steam turbine, the steam pressure generated by the external heat exchanger is 0.9~1.1MPa; When the steam turbine is warmed up, the steam temperature generated by the external heat exchanger is 190~210℃; When warming up the steam turbine, the turbine speed is 1450~1550 rpm; The fourth temperature is 675~685℃; When the steam turbine is first accelerated, the steam pressure generated by the external heat exchanger is 1.9~2.1 MPa; When the turbine is first accelerated, the steam temperature generated by the external heat exchanger is 290~310℃. When the turbine is first accelerated, the turbine speed is 2450~2550 rpm.

2. The start-up method of the oil refining catalytic cracking unit as described in claim 1, characterized in that, In step 1), the first negative differential pressure is 10~30 kPa.

3. The start-up method of the oil refining catalytic cracking unit as described in claim 1, characterized in that, In step 2), the second negative differential pressure is 10~20 kPa.

4. The start-up method of the oil refining catalytic cracking unit as described in claim 1, characterized in that, In step 2), the steam generated by the external heat exchanger is incorporated into the medium-pressure steam pipeline network and then fed into the steam turbine.

5. The start-up method for a catalytic cracking unit in oil refining as described in claim 1, characterized in that, In step 3), the first positive differential pressure is 10~30 kPa.

6. The start-up method for a petroleum refining catalytic cracking unit as described in claim 1, characterized in that, In step 4): 41) The second positive differential pressure is 10~30 kPa; 42) When the air compressor motor is turned on, the steam pressure generated by the external heat exchanger is 2.6~2.8MPa; 43) When the air compressor motor is turned on, the steam temperature generated by the external heat exchanger is 370~390℃; 44) When the air compressor motor is turned on, the turbine speed is 7500~7600 rpm.

7. The start-up method for a petroleum refining catalytic cracking unit as described in claim 1, characterized in that, The air compressor speed increased to 9840~9940 rpm, and the air compressor was put into normal operation.

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