Cracking method of electrified cracking furnace and electrified cracking device

Abstract

The invention relates to the technical field of petrochemical cracking furnaces, in particular to a cracking method of an electrified cracking furnace and an electrified cracking device. The raw material flow is heated and then mixed with the diluted steam flow, the mixture is fed into a convection section of a cracking furnace to be overheated and then fed into a radiation section of the cracking furnace to be subjected to a cracking reaction to obtain cracked gas, the cracked gas is cooled by a quench cooler to obtain a product, and a rotating unit in the cracking method is driven by a motor; the steam pocket generates medium-pressure steam flow, and the medium-pressure steam flow is fed into the quench cooler to be subjected to heat exchange with cracking gas and then is fed into a medium-pressure steam pipe network. According to the technical scheme, a rotating unit of the cracking furnace is changed to be driven by the motor to rotate, so that the control is simpler. And the energy utilization efficiency is improved by changing the technological process and the connection mode of the cracking furnace.

Description

Technical Field

[0001] The present invention relates to the technical field of steam cracking processes, and more particularly to a cracking method for an electrified cracking furnace and an electrified cracking device. Background Art

[0002] In the cracking production activities of petrochemical industry, many large rotating machinery sets are used, such as cracking gas compressors, ethylene compressors, and propylene compressors. At the same time, the core component of the cracking process, the cracking furnace, generates high-temperature flue gas. Therefore, in the prior art, the high-temperature flue gas is recovered and utilized to preheat and produce high-quality ultra-high-pressure steam to drive the large rotating machinery sets in the steam cracking device.

[0003] To produce qualified high-pressure steam, on the one hand, the boiler feed water supplied to the steam drum needs to be heated so that there is enough heat in the steam drum. The most common method is to set a economizer in the convection section of the cracking furnace, and then the boiler feed water stream heated by the economizer is introduced into the shell side of the quench cooler. On the one hand, it further heats the boiler feed water stream, and on the other hand, it cools the cracking gas in the quench cooler. And the high-pressure steam stream generated by the steam drum also needs to be introduced into the convection section of the cracking furnace for superheating and temperature control. Then it can be used to drive the steam turbine and finally drive the rotating machinery set.

[0004] In this way, the whole device will be relatively complex, and it is not convenient to precisely control the rotating machinery set.

[0005] Now, with the improvement of electrification level, replacing the traditional turbine drive with an electric motor is a practical way to improve the electrification rate. The structure and control of the rotating machinery set driven by an electric motor will be simpler. However, after the rotating machinery set is driven by an electric motor, the significant reduction in steam consumption has a major impact on the overall plant steam balance. Continuing with the original process flow will cause waste of resources and have an adverse impact on plant energy conservation, investment, etc. Summary of the Invention

[0006] The purpose of the present invention is to overcome the problem of the decline in energy utilization rate caused by the electrification transformation of the cracking furnace in the prior art, and to provide a cracking method for an electrified cracking furnace and an electrified cracking device, which can effectively reduce the generation of high-pressure steam and recover and utilize the energy used to generate high-pressure steam to avoid waste.

[0007] The present invention provides a cracking method for an electrified cracking furnace. The cracking method includes heating a raw material stream, mixing it with a dilution steam stream, and sending it into the convection section of the cracking furnace for superheating, and then sending it into the radiation section of the cracking furnace for cracking reaction to obtain cracked gas. The cracked gas is cooled by a quench cooler to obtain a product. All or part of the rotating machinery sets in the cracking method are driven by electric motors. If some sets are changed to be driven by electric motors, then the rotating machinery sets that have not been changed to be driven by electric motors and are still driven by steam turbines need to be supplied with high-pressure steam from the high-pressure steam network.

[0008] The steam drum generates a medium-pressure steam stream, which is sent to a quench cooler for heat exchange with the pyrolysis gas, and then sent to a desuperheater. After that, the medium-pressure steam stream is sent to the medium-pressure steam pipe network, and medium-pressure boiler feed water stream is introduced into the desuperheater for heat exchange with the medium-pressure steam. Medium-pressure steam is an important raw material in the entire petrochemical production. After the generated medium-pressure steam is incorporated into the medium-pressure steam pipe network, it is used by other equipment.

[0009] In this solution, the steam drum no longer produces high-pressure steam but instead produces medium-pressure steam. The pressure and temperature of the medium-pressure steam directly produced by the steam drum are not appropriate and need further fine adjustment. Therefore, the medium-pressure steam produced by the steam drum is sent to the shell side of the quench cooler for further heating, then enters the desuperheater to control its temperature, and then can be sent to the medium-pressure steam pipe network. The desuperheater is essentially also a heat exchanger. Therefore, while medium-pressure steam is introduced into the desuperheater, medium-pressure boiler feed water stream is also introduced for heat exchange with the medium-pressure steam.

[0010] After such modification, there is no need to superheat high-pressure steam in the convection section anymore, and the high-pressure steam superheat section can be cancelled. This saves the use of high-temperature flue gas in the convection section, which can be used more for heating raw materials. This greatly reduces the fuel demand and improves the energy utilization efficiency.

[0011] Since the steam drum no longer produces high-pressure steam but instead produces medium-pressure steam. First, the pressure level of the steam drum is reduced, making it safer, and at the same time, the heat demand is reduced. Therefore, the boiler feed water stream is directly sent into the steam drum. The boiler feed water stream no longer enters the economizer in the convection section for heating, nor does it need to enter the quench cooler for heating.

[0012] As described above, since the economizer is no longer needed, to avoid energy waste, fuel gas and / or air are introduced into the convection section for preheating and then sent to the radiation section for combustion. The heat originally used to heat the boiler feed water is changed to heat the fuel gas and / or air, and the pyrolysis gas stream generated by the pyrolysis furnace passes through multiple quench coolers in sequence.

[0013] Because the temperature control of the medium-pressure steam stream directly produced by the steam drum is difficult, and the temperature may not meet the standard, the medium-pressure steam stream is introduced into the shell side of some quench coolers, where the medium-pressure steam stream exchanges heat with the pyrolysis gas stream generated by the pyrolysis furnace, and then the medium-pressure steam stream is sent to the desuperheater. The quench cooler first heats the medium-pressure steam stream through heat exchange, and then the desuperheater is used to control the temperature.

[0014] And because the heat exchange capacity of the medium-pressure steam stream is poor, the temperature reduction of the pyrolysis gas is insufficient. After being cooled by the medium-pressure steam stream, the pyrolysis gas still has abundant residual heat. Therefore, this part of the heat can be used to heat the feed stream. Specifically, the feed stream is introduced into the shell side of another part of the quench cooler, where the feed stream exchanges heat with the pyrolysis gas stream generated by the pyrolysis furnace, cools the pyrolysis gas stream and preheats the dilution steam stream, and then the feed stream is introduced into the convection section for heating.

[0015] The pyrolysis gas stream generated by the pyrolysis furnace sequentially passes through the first quench cooler, the second quench cooler and the third quench cooler; the medium-pressure steam stream is introduced into the second quench cooler; the feed stream is introduced into the third quench cooler. The first quench cooler needs to be introduced with liquid, that is, the water in the steam drum. The second quench cooler is introduced with medium-pressure steam, and its main purpose is to heat the medium-pressure steam, and the secondary purpose is to reduce the temperature of the pyrolysis gas. Finally, the excess heat of the pyrolysis gas is transferred to the feed stream through the third quench cooler to save energy.

[0016] Based on the foregoing pyrolysis method proposed by the present invention, a pyrolysis device is proposed, which includes a pyrolysis furnace, a steam drum, a quench cooler and a desuperheater. The pyrolysis furnace includes a radiation section and a convection section. The pyrolysis gas outlet of the pyrolysis furnace is connected to the quench cooler. The rotating machine set of the pyrolysis furnace is driven by an electric motor. The steam outlet of the steam drum is communicated with the quench cooler; the quench cooler is communicated with the desuperheater, and the medium-pressure steam stream flows into the desuperheater after passing through the quench cooler; the medium-pressure boiler feed water stream pipeline is connected to the desuperheater, and the medium-pressure boiler feed water stream enters the desuperheater to exchange heat with the medium-pressure steam stream. In this scheme, the steam drum no longer produces high-pressure steam, but instead produces medium-pressure steam. The pressure and temperature of the medium-pressure steam directly produced by the steam drum are not suitable and need further fine adjustment. Therefore, the medium-pressure steam produced by the steam drum is sent to the shell side of the quench cooler for further heating, and then enters the desuperheater to control its temperature, and then can be sent to the medium-pressure steam pipe network. At the same time, the convection section no longer needs to superheat high-pressure steam, which can save the use of high-temperature flue gas in the convection section and be more used for heating raw materials. Greatly reducing the fuel demand and improving the energy utilization efficiency.

[0017] The boiler feed water stream pipeline is connected to the water inlet of the steam drum. In this way, the economizer can be removed, simplifying the device while reducing the heat of the steam drum. And an air preheating section is arranged in the convection section. The fuel gas pipeline and / or the air pipeline are connected to the inlet of the air preheating section, and the outlet of the air preheating section is connected to the radiation section. The energy that cannot be fully utilized after removing the economizer is utilized by setting the air preheating section.

[0018] A first quench cooler, a second quench cooler and a third quench cooler are sequentially connected in series on the pyrolysis gas discharge pipeline connected to the pyrolysis gas outlet.

[0019] The steam drum is connected to the shell side of the second quench cooler; the shell side of the second quench cooler is connected to the desuperheater. The shell side of the second quench cooler is used to further heat the medium-pressure steam, facilitating subsequent temperature control of the medium-pressure steam.

[0020] The raw material stream is connected to the shell side of the third quench cooler, and the shell side of the third quench cooler is connected to the convection section. The excess heat in the pyrolysis gas is recovered and utilized to heat the raw material stream.

[0021] Through the above technical solution, the rotating units of the pyrolysis furnace, such as the pyrolysis gas compressor, ethylene compressor, and propylene compressor, are changed to be driven by an electric motor to rotate. In this way, the demand for high-pressure steam originally used to drive the rotating units will decrease. This application changes the process flow and connection method of the pyrolysis furnace. The control of the rotating units is simpler, and high-pressure steam is no longer produced to avoid waste, improving the energy utilization efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is the process flow diagram of the traditional steam pyrolysis furnace;

[0023] Figure 2 is the process flow diagram of the steam pyrolysis furnace of Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0024] The following will describe in detail the specific embodiments of the present invention with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for the purpose of illustrating and explaining the present invention, and are not used to limit the present invention.

[0025] In the present invention, unless otherwise stated, the orientation terms "inside and outside" refer to the internal and external relationships of the contour of the equipment itself.

[0026] GLOSSARY

[0027] Pyrolysis device: The core component of the pyrolysis device is the pyrolysis furnace. The entire pyrolysis device includes the pyrolysis furnace and other surrounding auxiliary structures, including boilers, steam drums, various material pipelines, and rotating units. The rotating units use mixers for mixing materials, etc.

[0028] Radiation section: It refers to the location in the pyrolysis furnace where pyrolysis reactions occur. Fuel burns here to release heat, and then the heat is absorbed by the mixture of raw materials and steam, causing the raw materials to pyrolyze and produce pyrolysis gas.

[0029] Convection section: The convection section refers to the part where the high-temperature flue gas is recovered after the fuel in the pyrolysis furnace burns. Multiple sets of independent pipelines are arranged vertically in the convection section, and the materials that need to be heated or preheated are passed through these pipelines. When the high-temperature flue gas flows through, these materials will be heated. In this way, the convection section is divided into several regions with different functions.

[0030] Raw material logistics: including but not limited to feedstocks such as hydrocracking tail oil, diesel, naphtha, light hydrocarbons, LPG, propane, ethane, etc. During specific implementation, cracking can be carried out by selecting one according to the situation.

[0031] Prior art

[0032] The process flow diagram of the traditional steam cracking furnace is shown in the appendix Figure 1 .

[0033] Appendix Figure 1 Device marking description:

[0034] A, radiant section; B, raw material preheating section I; C, economizer section; D, raw material preheating section II; E, raw material and dilution steam mixing section I; F, dilution steam preheating section; G, high-pressure steam superheating section I; H, high-pressure steam superheating section II; I, raw material and dilution steam mixing section II; J, desuperheater; K, first quench cooler; L, second quench cooler; M, raw material / dilution steam mixer; N, steam drum.

[0035] Appendix Figure 1 Logistics marking description of

[0036] 1. Raw material logistics; 2. Raw material logistics after passing through raw material preheating section I; 3. Raw material logistics after passing through raw material preheating section II; 4. Raw material / dilution mixture logistics; 5. Logistics after passing through raw material and dilution steam mixing section I; 6. Total dilution steam logistics; 7. Superheated dilution steam logistics; 8. Logistics after passing through raw material and dilution steam mixing section II; 9. Pyrolysis gas logistics; 10. Pyrolysis gas logistics after passing through the first quench cooler; 11. Pyrolysis gas logistics after passing through the second quench cooler; 12. Boiler feed water logistics; 13. Boiler feed water logistics after passing through the economizer; 14. Boiler feed water logistics after passing through the second quench cooler; 15. High-pressure steam logistics; 16. Logistics after passing through high-pressure steam superheating section I; 17. Logistics after cooling down through the desuperheater; 18. High-pressure boiler feed water logistics; 19. Logistics after passing through high-pressure steam superheating section II; 20. Air logistics; 21. Fuel gas logistics.

[0037] From Figure 1 it can be seen that the radiant section A is located below the convection section, and the high-temperature flue gas generated by fuel combustion in the radiant section flows through the convection section from bottom to top.

[0038] The convection section sequentially includes, from top to bottom according to different functions: B raw material preheating section I, C economizer section, D raw material preheating section II, E raw material and dilution steam mixing section I, F dilution steam preheating section, G high-pressure steam superheating section I, H high-pressure steam superheating section II, I raw material and dilution steam mixing section II.

[0039] Such as Figure 1As shown in [figure], the raw material logistics first enter the raw material preheating section I (B) for preheating, then enter the raw material preheating section II (D) for further preheating, and then enter the raw material / dilution steam mixer (M) to be mixed with the dilution steam.

[0040] Meanwhile, the dilution steam logistics first enter the dilution steam preheating section (F), and then enter the raw material / dilution steam mixer (M) to be mixed with the raw materials.

[0041] The mixed raw material / dilution mixture first enters the raw material and dilution steam mixing section I (E) for heating, and then enters the raw material and dilution steam mixing section II (I) for superheating. Then it is sent to the radiant section (A) for cracking and becomes cracked gas to be sent out. The cracked gas is sent to the subsequent process flow after passing through the first quench cooler (K) and the second quench cooler (L).

[0042] At the same time, in the prior art, an economizer section (C) is provided in the convection section. The boiler feed water logistics 12 sent to the steam drum (N) first pass through the economizer for preheating, and then enter the shell side of the second quench cooler (L). In the second quench cooler (L), the boiler feed water absorbs the heat of the cracked gas and is heated and then sent into the steam drum (N).

[0043] And because high-quality high-pressure steam is required to drive the rotating units in the steam cracking device, the steam drum (N) will produce high-pressure steam. The high-pressure steam will enter the high-pressure steam superheating section I (G), then pass through the attemperator (J) for temperature control, and then enter the high-pressure steam superheating section II (H) to produce high-quality high-pressure steam. The high-pressure steam superheating section I (G) and the high-pressure steam superheating section II (H) are provided in the convection section, and a large amount of heat in the convection section is consumed itself.

[0044] Process side flow:

[0045] 1. The raw material logistics 1 enter the raw material preheating section I (B) for preliminary preheating to obtain logistics 2.

[0046] 2. The raw material logistics 1 are further sent to the raw material preheating section II (D) for preheating.

[0047] 3. At the same time, the dilution steam logistics 6 and 7 are superheated through the dilution steam preheating section (F).

[0048] 4. The preheated raw material logistics and dilution steam logistics enter the raw material / dilution steam mixer (M) for full mixing to obtain the raw material / dilution mixture, which is sent to the raw material and dilution steam mixing section I (E) and further superheated in the raw material and dilution steam mixing section II (I) and then sent into the radiant section of the cracking furnace for cracking reaction to finally obtain the cracked gas logistics 9.

[0049] 5. The cracked gas logistics are further cooled by heat exchange through the first and second quench coolers and sent to the downstream separation device. The products here are a mixture of various small molecules after cracking and enter the downstream process for separation after cooling.

[0050] Utility-side process:

[0051] 1. The boiler feed water stream is preheated through the economizer section C and then sent into the steam drum N after being heated by the second quench cooler L.

[0052] 2. The boiler feed water in the steam drum N is vaporized by heat exchange in the first quench cooler K and then returns to the steam drum, forming a thermosyphon system.

[0053] 3. The traditional process ( Figure 1 ) The high-pressure steam stream produced from the steam drum is sent into the high-pressure steam superheat section I, then into the desuperheater and then into the high-pressure steam superheat section II for superheating and finally sent into the high-pressure steam pipe network.

[0054] Example 1

[0055] The process flow diagram of the steam cracking furnace in this example is shown in the appendix Figure 2 .

[0056] Appendix Figure 2 Device marking description:

[0057] A. Radiation section; B. Raw material preheat section I; C. Economizer section; D. Raw material preheat section II; E. Raw material and dilution steam mixing section I; F. Dilution steam preheat section; I. Raw material and dilution steam mixing section II; J. Desuperheater; K. First quench cooler; L. Second quench cooler; M. Raw material / dilution steam mixer; N. Steam drum; O. Third quench heat exchanger; P. Air preheat section; Q. Blower.

[0058] Appendix Figure 2 Stream marking description:

[0059] 1. Raw material stream; 2. Raw material stream preheated through the third quench heat exchanger; 3. Raw material stream after passing through the raw material preheat section I; 4. Raw material stream after passing through the raw material preheat section II; 5. Raw material / dilution mixture stream; 6. Total dilution steam stream; 7. Superheated dilution steam stream after passing through the second quench cooler; 8. Stream after passing through the dilution steam superheat section; 9. Stream after passing through the raw material and dilution steam mixing section I; 10. Stream after passing through the raw material and dilution steam mixing section II; 11. Cracked gas stream; 12. Cracked gas stream after passing through the first quench cooler; 13. Cracked gas stream after passing through the second quench cooler; 14. Cracked gas stream after passing through the third quench cooler; 15. Boiler feed water stream; 16. Medium-pressure steam stream; 17. Medium-pressure steam stream after passing through the second quench heat exchanger; 18. Medium-pressure boiler feed water stream; 19. Medium-pressure steam stream cooled by the desuperheater; 21. Air stream; 22. Stream after passing through the air preheat section; 23. Fuel gas stream.

[0060] In the prior art, the steam drum N generates a high-pressure steam stream, which then enters the first stage G of high-pressure steam superheating, then passes through a desuperheater and enters the second stage H of high-pressure steam superheating before entering the steam turbine to drive the rotating unit to rotate.

[0061] In this embodiment, first, the rotating unit in the cracking method and the cracking device used in conjunction is changed to be driven by an electric motor. Therefore, the demand for high-pressure steam is reduced. To avoid heat waste, the steam drum N is changed to produce medium-pressure steam, which is then sent into the quench cooler to exchange heat with the cracked gas, and then the produced medium-pressure steam enters the medium-pressure steam pipe network.

[0062] Also, because the medium-pressure steam stream generated by the steam drum N enters the pipe network after passing through the quench cooler, the first stage G of high-pressure steam superheating and the second stage H of high-pressure steam superheating are removed from the convection section.

[0063] Such as Figure 2 , in this embodiment, the convection section from top to bottom sequentially includes B, the first stage of raw material preheating; C, the economizer section; D, the second stage of raw material preheating; E, the first stage of raw material and dilution steam mixing; F, the dilution steam preheating section; I, the second stage of raw material and dilution steam mixing.

[0064] Correspondingly, the boiler feed water stream is directly sent into the steam drum N; the economizer section C is no longer provided in the convection section of this scheme, and the boiler feed water stream 15 is directly sent into the steam drum N, neither preheated in the economizer nor heated on the shell side of the second quench cooler L. Therefore, the heat input into the steam drum N is greatly reduced, reducing the output of high-pressure steam. Instead, a medium-pressure steam stream is produced. In this way, the second quench cooler L that was originally used to heat the boiler feed water stream is changed to heat the medium-pressure steam stream.

[0065] Air is introduced into the convection section for preheating and then sent into the radiation section for combustion. The economizer section C, the first stage G of high-pressure steam superheating, and the second stage H of high-pressure steam superheating are no longer provided in the convection section, and the heat of the high-temperature flue gas cannot be fully utilized. Therefore, an air preheating section P is provided at the topmost part of the convection section. The heat of this part of the flue gas is used to heat the air. The air here refers to the oxidant used in the radiation section combustion, and the air can be pure oxygen.

[0066] Since the air is preheated in advance, less fuel is used to achieve the same heating effect in the radiation section, which can save fuel. However, there is also a problem that the output of high-temperature flue gas becomes less. The total energy of the convection section becomes less. And originally, the boiler feed water stream 15 was introduced into the shell side of the second quench cooler L, and now it is changed to a medium-pressure steam stream, so the heat exchange capacity decreases. The cooling effect of the cracked gas becomes worse.

[0067] Therefore, a third quench cooler O is also provided after the second quench cooler L. The raw material logistics 1 first enters the shell side of the third quench cooler O to exchange heat with the pyrolysis gas for preheating, and then is sent to the convection section. On the one hand, it compensates for the problem of the deteriorated cooling effect of the pyrolysis gas, and on the other hand, it preheats the raw material to solve the problem of the reduction of the total heat in the convection section after the reduction of the high-temperature flue gas.

[0068] The medium-pressure steam logistics is sent to the desuperheater J after passing through the quench cooler, and medium-pressure boiler feed water logistics is introduced into the desuperheater J to exchange heat with the medium-pressure steam logistics. The desuperheater J adjusts the temperature of the medium-pressure steam logistics and then sends it to the medium-pressure logistics pipe network.

[0069] The pyrolysis gas logistics generated by the pyrolysis furnace sequentially passes through multiple quench coolers; the pyrolysis gas logistics generated by the pyrolysis furnace sequentially passes through the first quench cooler K, the second quench cooler L, and the third quench cooler O; the medium-pressure steam logistics is introduced into the second quench cooler L; the raw material logistics is introduced into the third quench cooler O.

[0070] A pyrolysis device is also proposed in matching with the embodiment, such as Figure 2 , which includes a pyrolysis furnace and a steam drum N. The pyrolysis furnace includes a radiation section A and a convection section. The pyrolysis gas outlet of the pyrolysis furnace is connected to the quench cooler. All the rotating units of the pyrolysis furnace are driven by motors. The steam outlet of the steam drum N is communicated with the quench cooler. The quench cooler is communicated with the desuperheater J. The medium-pressure steam logistics flows into the desuperheater J after passing through the quench cooler; the medium-pressure boiler feed water logistics pipeline is connected to the desuperheater J, and the medium-pressure boiler feed water logistics 18 enters the desuperheater to exchange heat with the medium-pressure steam logistics.

[0071] The boiler feed water logistics pipeline is connected to the water inlet of the steam drum N. The pyrolysis gas logistics at the outlet of the pyrolysis furnace is sequentially provided with a first quench cooler K, a second quench cooler L, and a third quench cooler O in series; the steam drum N is communicated with the shell side of the second quench cooler L; the shell side of the second quench cooler L is connected to the desuperheater J; the raw material logistics 1 is communicated with the shell side of the third quench cooler O, and the shell side of the third quench cooler O is connected to the convection section.

[0072] An air preheating section P is arranged in the convection section. The air pipeline is connected to the inlet of the air preheating section P, and the outlet of the air preheating section P is connected to the radiation section A.

[0073] Process side flow:

[0074] 1. The raw material logistics 1 passes through the third quench cooler O and then enters the raw material preheating I section B for preliminary preheating to obtain the logistics 3.

[0075] 2. The raw material logistics 1 is further sent to the raw material preheating II section D for preheating, and since the economizer section C is cancelled, the raw material preheating I section and II can be combined.

[0076] 3. In the embodiment, the dilution steam logistics 7 is superheated through the dilution steam preheating section F.

[0077] 4. The preheated raw material stream and the dilution steam stream enter the raw material / dilution steam mixer M for full mixing to obtain a raw material / dilution mixed stream, which is sent to the first stage E of the raw material and dilution steam mixing and is further superheated in the second stage I of the raw material and dilution steam mixing to obtain stream 10.

[0078] 5. Stream 10 is sent into the radiant section of the cracking furnace for cracking reaction to finally obtain a cracked gas stream 11.

[0079] The cracked gas stream is further cooled by heat exchange through the first, second, and third quenchers and then sent to the downstream separation unit.

[0080] Utility side process:

[0081] 1. In the embodiment, the economizer section C is cancelled, and the boiler feed water stream is directly sent into the steam drum, reducing the convection section load. The boiler feed water stream is medium-pressure boiler feed water.

[0082] 2. The boiler feed water in the steam drum N is vaporized by heat exchange through the first quencher K and then returns to the steam drum to form a thermosyphon system.

[0083] 3. The medium-pressure steam produced by the steam drum is superheated through the second quencher L and the temperature is adjusted by the attemperator J and then sent into the medium-pressure steam network.

[0084] The preferred embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited thereto. Within the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any suitable combination of each specific technical feature. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods. But these simple modifications and combinations should also be regarded as the content disclosed by the present invention and all fall within the protection scope of the present invention.

Claims

1. A cracking method for an electrified cracking furnace, in which a raw material stream is heated, mixed with a dilution steam stream, and sent into the convection section of the cracking furnace for superheating, and then sent into the radiation section of the cracking furnace for cracking reaction to obtain cracked gas. The cracked gas is cooled by a quencher to obtain a product, and is characterized in that, The rotating machine set in the cracking method is driven by an electric motor; A medium-pressure steam stream is generated by a steam drum, and the medium-pressure steam stream is sent into the quencher for heat exchange with the cracked gas, and then sent into the medium-pressure steam pipe network.

2. The cracking method according to claim 1, characterized in that, The boiler feed water stream is directly sent into the steam drum.

3. The cracking method according to claim 1, wherein, Fuel gas and / or air are introduced into the convection section for preheating and then sent into the radiation section for combustion.

4. The cracking method according to claim 1, wherein After passing through the quencher, the medium-pressure steam stream is first sent into a desuperheater and then sent into the medium-pressure steam pipe network; and medium-pressure boiler feed water stream is introduced into the desuperheater for heat exchange with the medium-pressure steam stream.

5. The cracking method according to claim 1, characterized in that, The cracked gas stream generated by the cracking furnace sequentially passes through a plurality of quenchers.

6. The cracking method according to claim 5, wherein The medium-pressure steam stream is introduced into the shell side of some of the quenchers, and the medium-pressure steam stream exchanges heat with the cracked gas stream generated by the cracking furnace; The raw material stream is introduced into the shell side of some other quenchers, and the raw material stream exchanges heat with the cracked gas stream generated by the cracking furnace, cools the cracked gas stream and preheats the dilution steam stream, and then the raw material stream is sent into the convection section for heating.

7. The cracking method according to claim 6, characterized in that, The cracked gas stream generated by the cracking furnace sequentially passes through a first quencher, a second quencher and a third quencher; the medium-pressure steam stream is introduced into the second quencher; the raw material stream is introduced into the third quencher.

8. An electrified cracking device, characterized in that, It includes a cracking furnace, a steam drum, a quencher and a desuperheater. The cracking furnace includes a radiation section and a convection section. The cracked gas outlet of the cracking furnace is connected to the quencher. The rotating machine set of the cracking furnace is driven by an electric motor. The steam outlet of the steam drum is communicated with the quencher; the quencher is communicated with the desuperheater; The medium-pressure boiler feed water stream pipeline is connected to the desuperheater, so that the medium-pressure boiler feed water stream enters the desuperheater for heat exchange with the medium-pressure steam stream.

9. The electrification cracking device according to claim 8, characterized in that, The boiler feed water stream pipeline is connected to the water inlet of the steam drum.

10. The electrified cracking device according to claim 8, wherein, A first quencher, a second quencher and a third quencher are sequentially connected in series on the cracked gas discharge pipeline connected to the cracked gas outlet; The steam drum is communicated with the shell side of the second quencher; the shell side of the second quencher is connected to the desuperheater; The raw material stream pipeline is connected to the shell side of the third quencher, and the shell side of the third quencher is connected to the convection section.

11. The electrified cracking device according to claim 8, characterized in that, An air preheating section is arranged in the convection section. The fuel gas pipeline and / or the air pipeline are connected to the inlet of the air preheating section, and the outlet of the air preheating section is connected to the radiation section.

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