Cracking method and cracking device

Abstract

The invention relates to the technical field of petrochemical cracking furnaces, in particular to a cracking method and a cracking device. A raw material flow and a diluted steam flow are heated and mixed in a convection section of a cracking furnace and then fed into a radiation section of the cracking furnace for cracking reaction to obtain cracking gas, the cracking gas is cooled by a quench cooler to obtain a product, and the cracking method comprises the following steps: a rotating unit of the cracking furnace is completely or partially driven by a motor; the heat of the pyrolysis gas is recycled through the raw material flow and / or the diluted steam flow; and / or the heat of the convection section is recovered by adopting the feeding material flow of the radiation section. According to the invention, a rotating unit of the cracking furnace is completely or partially changed to be driven by the motor to rotate, so that the demand quantity of high-pressure steam originally used for driving the rotating unit can be reduced. By changing the technological process and the connecting mode of the cracking furnace, the yield of high-pressure steam is reduced, and the energy utilization efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of petrochemical cracking furnaces, and in particular to a cracking method and a cracking device. Background Art

[0002] Traditional ethylene steam crackers produce high-temperature flue gas. The cracker recovers the waste heat from this flue gas to produce high-pressure steam. This high-quality high-pressure steam is then used to drive the large rotating units in the steam cracker (cracked gas compressor, ethylene compressor, and propylene compressor).

[0003] To produce qualified high-pressure steam, the boiler feedwater supplied to the drum must be heated to ensure sufficient heat within the drum. Conventional technology typically involves installing an economizer in the convection section of the cracking furnace. The boiler feedwater stream, heated by the economizer, is then passed through the shell side of a quench cooler, further heating the boiler feedwater stream and cooling the cracked gas within the quench cooler. Furthermore, the high-pressure steam generated by the drum needs to be passed through the convection section of the cracking furnace for superheating and temperature control before it can be used to drive the steam turbine, ultimately driving the turbine unit.

[0004] This makes the entire device more complicated and makes it inconvenient to accurately control the rotating unit.

[0005] With the increasing electrification rate, replacing traditional turbines with electric motors is a viable approach to increasing electrification rates. However, the significant reduction in steam usage associated with adopting electric motors for rotating units has a significant impact on the overall steam balance. Continuing with the existing process would waste resources and negatively impact energy savings and investment. Summary of the Invention

[0006] The purpose of the present invention is to overcome the problem of decreased energy utilization caused by the electrification transformation of the cracking furnace in the prior art, and to provide a cracking method and a cracking device that can avoid steam consumption imbalance and effectively reduce high-pressure steam generation after the rotating unit is driven by an electric motor.

[0007] To achieve the above object, the present invention provides a cracking method in one aspect, wherein a feed stream and a dilution steam stream are heated and mixed in a convection section of a cracking furnace, and then fed into a radiant section of the cracking furnace for cracking reaction to obtain cracked gas, and the cracked gas is cooled by a quencher to obtain a product, the cracking method comprising: all or part of the rotating unit of the cracking furnace is driven by a motor;

[0008] Recovering heat from the cracked gas using a feed stream and / or a dilution steam stream; and / or

[0009] The feed stream of the radiant section is used to recover the heat of the convection section for preheating before being fed into the radiant section for combustion. In this way, the degree of electrification is improved while energy consumption is reduced and energy utilization efficiency is improved.

[0010] In some embodiments, the feed stream and / or the dilution steam stream may be fed directly into the convection section.

[0011] In some embodiments, the feed stream and / or dilution steam stream are first passed through a quench cooler to recover heat from the cracked gas before entering the convection section, cooling the cracked gas stream and preheating the reactants entering the cracking furnace. In the present invention, a quench cooler is a heat exchanger whose primary purpose is to cool the cracked gas. Therefore, the shell side of the quench cooler allows the reactants (dilution steam stream and / or feed stream) entering the cracking furnace to be passed through. This reactants cool the cracked gas while also heating the reactants, thereby improving energy efficiency.

[0012] In some embodiments, multiple quench coolers are generally provided, and the cracking gas flow generated by the cracking furnace passes through the first quench cooler and the second quench cooler in sequence, and the raw material flow and / or dilution steam flow enters the second quench cooler, and enters the convection section after recovering the heat of the cracking gas; for example, the shell side of the first quench cooler is connected to the steam drum through a pipeline to heat the water in the steam drum, the shell side of the second quench cooler is passed through the raw material flow and / or dilution steam flow, and the cracking gas is passed through the pipe side of the first quench cooler and the second quench cooler.

[0013] In some embodiments, the feedstock stream and / or the dilution steam stream are first sent to the convection section for preheating and mixing, then passed into a quench cooler to recover the heat of the cracked gas, and then returned to the convection section.

[0014] In some embodiments, the cracking gas flow generated by the cracking furnace passes through a first quench cooler and a second quench cooler in sequence, wherein the raw material flow and the dilution steam flow are first sent into the convection section for preheating and mixing, and then passed into the second quench cooler to recover the heat of the cracking gas and then returned to the convection section.

[0015] In some embodiments, the cracking gas flow generated by the cracking furnace passes through a first quench cooler and a second quench cooler in sequence, wherein the raw material flow and the dilution steam flow are first sent into the convection section for preheating and mixing, and then passed into the second quench cooler to recover the heat of the cracking gas and then returned to the convection section.

[0016] In some embodiments, the cracking gas flow generated by the cracking furnace passes through a first quench cooler, a second quench cooler, and a third quench cooler in sequence, wherein the raw material flow is passed into the third quench cooler to recover the heat of the cracking gas and then enters the convection section, and the dilution steam is passed into the second quench cooler to recover the heat of the cracking gas and then enters the convection section.

[0017] In some embodiments, the feed flow of the radiant section includes fuel gas and air. The fuel gas and / or air are introduced into the convection section for preheating and then sent into the radiant section for combustion.

[0018] In some embodiments, the boiler feed water stream is fed directly into the steam drum or is fed into the steam drum after being preheated in an economizer.

[0019] In some embodiments, when the boiler feedwater stream is fed directly into the drum, the fuel gas and / or air is preheated in the convection section before being fed into the radiant section for combustion. Directly feeding the boiler feedwater stream into the drum eliminates the need for an economizer, wasting the heat originally used to heat the economizer in the convection section. Therefore, preheating the fuel gas and / or air in the convection section can reduce fuel usage by utilizing this energy.

[0020] In some embodiments, if the economizer is removed from the convection section, the boiler feedwater stream is directly fed into the steam drum without undergoing convection section heating or quencher heat exchange. This reduces the total heat input to the steam drum and reduces high-pressure steam production. Simultaneously, preheating the fuel gas and / or air within the convection section fully utilizes excess heat after the economizer is removed. Preheating the fuel gas and / or air also reduces fuel gas consumption.

[0021] Based on the cracking method proposed in the present invention, the present invention also provides a cracking device comprising a cracking furnace and a rotating unit. The cracking furnace includes a connected radiant section and a convection section. The cracking gas outlet of the cracking furnace is connected to a quench cooler. Part or all of the rotating unit of the cracking device is driven by a motor. A feedstock channel for circulating a feed stream and / or a steam channel for circulating a dilution steam stream passes through the quench cooler to recover heat from the cracked gas. For example, the feedstock channel and / or the steam channel are connected to the shell side of the quench cooler. The feed line connecting the radiant section is configured to pass through the convection section. This device implements the cracking method proposed in the second aspect and therefore has the same effect.

[0022] In some embodiments, the feedstock channel includes a connected feedstock feed pipe and a feedstock preheating section disposed in a convection section of the cracking furnace.

[0023] In some embodiments, the steam channel includes a connected dilution steam feed pipe and a steam preheating section disposed in the convection section.

[0024] In some embodiments, when no economizer is provided in the convection section of the cracking furnace, the boiler feed water line is connected to the water inlet of the steam drum.

[0025] In some embodiments, when an economizer is installed within the convection section of the cracking furnace, the economizer is connected to the boiler feedwater line, with the economizer outlet directly connected to the steam drum inlet. A steam preheating section is also installed within the convection section of the cracking furnace, with the dilution steam feed pipe connected to the shell side of the quench cooler, which in turn is connected to the steam preheating section. By allowing the boiler feedwater stream from the economizer to enter the steam drum directly, and allowing the dilution steam stream to enter the quench cooler for preheating, heat originally carried into the steam drum by the boiler feedwater stream is transferred to the dilution steam stream, reducing the pressure in the convection section and improving energy efficiency.

[0026] In some embodiments, the cracked gas flow generated by the cracking furnace passes through multiple quench coolers in sequence, and the raw material channel or the steam channel includes the shell side of the quench cooler. The raw material flow and / or the dilution steam flow are heat exchanged with the cracked gas flow generated by the cracking furnace to cool the cracked gas flow and preheat the raw material flow and / or the dilution steam flow, and then pass into the convection section for heating. The quench cooler is used to preheat the raw material flow and the dilution steam flow, thereby reducing the heat consumption of the convection section, thereby further reducing the fuel consumption.

[0027] In some embodiments, the quench cooler includes a first quench cooler and a second quench cooler connected in series at the cracking gas outlet of the cracking furnace along the cracking gas feed flow direction; the feedstock feed pipe and / or the steam feed pipe are connected to the shell side of the second quench cooler. The cracking gas passes through the tube side of the first and second quench coolers, and the shell side of the first quench cooler is connected to the steam drum via a pipe to heat the boiler water in the steam drum, achieving energy conservation. The inventors have found that the dilution steam stream has weak heat exchange capacity, so it is passed to the second quench cooler.

[0028] In some embodiments, the raw material feed pipe and the dilution steam feed pipe can also be directly connected to the raw material preheating section and the steam preheating section of the convection section. The raw material flow and the dilution steam flow are mixed in the raw material and dilution steam mixing section I in the convection section. An external circulation pipe is provided between the raw material and dilution steam mixing section I and the second quench cooler. Thus, the raw material flow and the dilution steam flow are first sent into the convection section for preheating and mixing, and then passed into the second quench cooler to recover the heat of the cracking gas and then return to the convection section.

[0029] In some embodiments, passing the feedstock stream and the dilution steam stream into separate quenchers can, on the one hand, cool the cracked gas. On the other hand, it can preheat the feedstock stream and the dilution steam stream, reducing heat consumption in the convection section. This can further reduce fuel consumption. Specifically, the quenchers include a first quencher, a second quencher, and a third quencher connected in series along the cracked gas material flow at the cracking gas outlet of the cracking furnace. The feedstock feed pipe passes through the third quencher, and the steam feed pipe passes through the second quencher. Specifically, the steam feed pipe is connected to the shell side of the second quencher; the feedstock feed pipe is connected to the shell side of the third quencher. As described above, the first quencher and the steam drum establish a circulation through the pipeline to heat the water in the drum.

[0030] In some embodiments, no economizer is provided in the convection section of the cracking furnace, and the boiler feed water line is connected to the water inlet of the steam drum.

[0031] In some embodiments, an economizer connected to the boiler feed water line is provided in the convection section of the cracking furnace, and the water outlet of the economizer is directly connected to the water inlet of the steam drum.

[0032] In some embodiments, a radiant feed preheating section is installed above the feed preheating section. The feed pipeline of the radiant section passes through the radiant feed preheating section, and a blower is installed on the feed pipeline of the radiant section. Because the heating effect of the air preheating section on the fuel gas or air does not affect the overall cracking process, even if the air or fuel gas is not preheated enough, it can be solved by simply adding more fuel gas or air. Therefore, the air preheating section is placed above the convection section.

[0033] Through the above technical solution, all or part of the rotating units of the cracking furnace, such as the cracked gas compressor, ethylene compressor, and propylene compressor, are converted to motor-driven rotation. This reduces the demand for high-pressure steam originally used to drive the rotating units. This application reduces the production of high-pressure steam and improves energy efficiency by changing the process flow and connection method of the cracking furnace. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a process flow chart of a traditional steam cracking furnace;

[0035] Figure 2 is a process flow diagram of the steam cracking furnace of Example 1;

[0036] Figure 3 is a process flow chart of the steam cracking furnace of Example 2;

[0037] Figure 4 is a process flow diagram of a steam cracking furnace in Example 3; DETAILED DESCRIPTION

[0038] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0039] In the present invention, unless otherwise specified, the directional terms "inside" and "outside" refer to the inside-outside relationship of the device itself.

[0040] Glossary

[0041] Cracking unit: The core component of the cracking unit is the cracking furnace. The entire cracking unit includes the cracking furnace and other surrounding auxiliary structures including boilers, steam drums, various material pipelines and rotating units. The rotating unit uses a mixer used by the compressor to mix materials, etc.

[0042] Radiant section: refers to the location in the cracking furnace where the cracking reaction occurs. The 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 crack and produce cracking gas.

[0043] Convection Section: This section is where the high-temperature flue gas is recovered after the fuel is burned in the cracking furnace. Within this section, multiple independent pipes are installed from top to bottom. Materials that need to be heated or preheated are passed through these pipes. The high-temperature flue gas heats the materials as it flows through. This divides the convection section into several functionally distinct areas.

[0044] Raw material logistics: including but not limited to hydrotreated tail oil, diesel, naphtha, light hydrocarbons, LPG, propane, ethane and other raw materials.

[0045] It should be noted that the temperature of the radiation furnace A is 900-1300°C, the temperature of the raw material preheating section I B is 60-300°C, the temperature of the raw material preheating section II D is 200-400°C, the temperature of the raw material and dilution steam mixing section I E is 300-500°C, the temperature of the dilution steam preheating section F is 200-550°C, the temperature of the high-pressure steam superheating section I G is 300-470°C, the temperature of the high-pressure steam superheating section II H is 400-500°C, and the temperature of the raw material and dilution steam mixing section II I is 350-700°C.

[0046] In the following examples and comparative examples, the heat exchange efficiency of the first quencher K, the second quencher L, and the third quencher O is 0.875±0.075, and the fuel and air introduced into the radiant section of the cracking furnace are at room temperature, 25°C. The fuel is conventional methane and hydrogen in the art, and the mass ratio of methane to hydrogen is 1:1. The electrification rate in the present invention is calculated as follows:

[0047] Comparative Example

[0048] The process flow diagram of traditional steam cracking furnace is attached. Figure 1.

[0049] Attachment Figure 1 Device marking instructions:

[0050] 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.

[0051] Attachment Figure 1 Logistics marking instructions:

[0052] 1. Raw material logistics; 2. Raw material logistics after raw material preheating stage I; 3. Raw material logistics after raw material preheating stage II; 4. Raw material\dilution mixed logistics; 5. Logistics after raw material and dilution steam mixing stage I; 6. Total dilution steam logistics; 7. Superheated dilution steam logistics; 8. Logistics after raw material and dilution steam mixing stage II; 9. Cracked gas logistics; 10. Cracked gas logistics after passing through the first quencher; 11. Cracked gas logistics after passing through the second quencher; 12. Boiler feed water logistics; 13. Boiler feed water logistics after economizer; 14. Boiler feed water logistics after passing through the second quencher; 15 High-pressure steam logistics; 16. Logistics after high-pressure steam superheating stage I; 17. Cooling logistics after desuperheater; 18 High-pressure boiler feed water logistics; 19. Logistics after high-pressure steam superheating stage II; 20. Air logistics; 21. Fuel gas logistics.

[0053] from Figure 1 As can be seen in the figure, the radiation section is located below the convection section, and the high-temperature flue gas generated by the combustion of fuel in the radiation section flows through the convection section from bottom to top.

[0054] The convection section 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, and I raw material and dilution steam mixing section II.

[0055] The process of the existing technology side:

[0056] like Figure 1 As shown in the figure, the raw material flow 1 first enters the raw material preheating section I B for preheating, then enters the raw material preheating section II D for further preheating, and then enters the raw material\dilution steam mixer M to be mixed with the dilution steam.

[0057] At the same time, the dilution steam flow first enters the dilution steam preheating section F, and then enters the raw material\dilution steam mixer M to mix with the raw material.

[0058] The mixed raw material / diluted mixture first enters the raw material and dilution steam mixing section I E for heating, then enters the raw material and dilution steam mixing section II I for superheating, and then enters the radiant section A for cracking, producing cracked gas for delivery. The cracked gas passes through the first quench cooler K and the second quench cooler L before being fed into subsequent processes.

[0059] At the same time, the existing technology sets an economizer section C in the convection section. The boiler feed water flow sent to the steam drum N is first preheated by the economizer, and then enters the shell side of the second quencher L. In the second quencher L, the boiler feed water absorbs the heat of the cracked gas and is heated before being sent to the steam drum N.

[0060] To produce high-quality high-pressure steam, steam drum N produces high-pressure steam. This steam then enters high-pressure steam superheater I (G), where it undergoes temperature control in desuperheater J, before entering high-pressure steam superheater II (H) to achieve high-quality steam. These two sections, G and H, are located within the convection section and consume a significant amount of heat from that section.

[0061] The temperature of the raw material flow 1 is 120°C, the temperature of the dilution steam flow 6 is 200°C, the flow rate of the dilution steam flow 6 is 4wt% of the raw material 1, the raw material flow 1 is ethane, and the yield of the product ethylene is 45%; the cracked gas is cooled to 490°C at the outlet of the first quench cooler K; the cracked gas is cooled to 305°C at the outlet of the second quench cooler L and then sent out of the system, the boiler feed water 12 has a temperature of 100°C and a pressure of 13MPa, and the temperature of the high-pressure steam superheated II section flow 19 (high-quality high-pressure steam) is 490°C and a pressure of 13MPa.

[0062] The fuel gas methane and hydrogen consumption for producing 1 ton of ethylene is 0.52 tons, wherein the overall ethylene unit electrification rate is 9.5%, and the output of high-pressure steam superheated II stage logistics 20 (high-quality high-pressure steam) is 5 tons / ton of ethylene.

[0063] Example 1

[0064] The process flow diagram of the steam cracking furnace of Example 1 is shown in the attached Figure 2 .

[0065] Attachment Figure 2 Device marking instructions:

[0066] 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.

[0067] Attachment Figure 2Logistics marking instructions:

[0068] 1. Raw material logistics; 2. Raw material logistics after raw material preheating stage I; 3. Raw material logistics after raw material preheating stage II; 4. Raw material\dilution mixed logistics; 5. Logistics after raw material and dilution steam mixing stage I; 6. Total dilution steam logistics; 7. Superheated dilution steam logistics after the second quencher; 8. Logistics after dilution steam superheating stage; 9. Logistics after raw material and dilution steam mixing stage II; 10. Cracked gas logistics; 11. Cracked gas logistics after passing through the first quencher; 12. Cracked gas logistics after passing through the second quencher; 13. Boiler feed water logistics; 14. Boiler feed water logistics after economizer; 15 High-pressure steam logistics; 16. Logistics after high-pressure steam superheating stage I; 17. Cooling logistics after desuperheater; 18 High-pressure boiler feed water logistics; 19. Logistics after high-pressure steam superheating stage II; 20. Air logistics; 21. Fuel gas logistics.

[0069] In this embodiment, the arrangement of the cracking furnace itself and the convection section of the cracking furnace includes, from top to bottom, as in the prior art: 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, and I raw material and dilution steam mixing section II.

[0070] Unlike the comparative example, all rotating units used in the cracking method and cracking apparatus are driven by electric motors, reducing the demand for high-pressure steam. Therefore, the boiler feedwater stream, after passing through the economizer, is directly fed into the steam drum N. The boiler feedwater stream no longer needs to enter the second quencher L to cool the cracked gas. Therefore, the dilution steam stream, which is directly fed into the convection section for heating, is fed into the shell side of the second quencher L. Through the above arrangement, the temperature of the boiler feedwater stream is lowered without wasting heat or reducing thermal efficiency, and the amount of heat fed into the steam drum is reduced. This reduces the generation of ultra-high-pressure steam, preheats the dilution steam stream, and reduces the demand for high-temperature flue gas in the convection section.

[0071] After the process flow was modified, the accompanying cracking unit was also adapted. Specifically, the cracking unit includes a cracking furnace, the cracked gas outlet of which is connected in series with a first quench cooler and a second quench cooler. All rotating units of the cracking unit are driven by electric motors. The water outlet of the economizer is directly connected to the water inlet of the steam drum N, and the dilution steam feed pipe is connected in series to the shell side of the second quench cooler L and the dilution steam preheating section F.

[0072] In this embodiment, the temperature of the raw material stream 1 is 120°C, the temperature of the dilution steam stream 6 is 200°C, the flow rate of the dilution steam stream 6 is 4wt% of the raw material 1, the raw material stream 1 is ethane, and the yield of the product ethylene is 45.5%; the cracked gas is cooled to 493°C at the outlet of the first quencher K; the cracked gas is cooled to 298°C at the outlet of the second quencher L and then sent out of the system, the boiler feed water 13 temperature is 100°C, the pressure is 13MPa, and the temperature of the high-pressure steam superheated II section stream 19 (high-quality high-pressure steam) is 496°C and the pressure is 13.2MPa.

[0073] The rest of the present embodiment is the same as the comparative example. For every ton of ethylene produced, 0.493 tons of fuel gas, methane and hydrogen are consumed. The overall electrification rate of the ethylene plant is 12.6%, and the output of the high-pressure steam superheated II stage stream 20 (high-quality high-pressure steam) is 4.5 tons / ton of ethylene.

[0074] Example 2

[0075] The process flow diagram of the steam cracking furnace of Example 2 is shown in the attached Figure 3 .

[0076] Attachment Figure 3 Device marking instructions:

[0077] A. Radiation section; B. Raw material preheating section I; 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; O. Third quench heat exchanger; P. Air preheating section; Q. Blower.

[0078] Attachment Figure 3 Logistics marking instructions:

[0079] 1. Raw material logistics; 2. Raw material logistics preheated by the third quench heat exchanger; 3. Raw material logistics after raw material preheating section I; 4. Raw material logistics after raw material preheating section II; 5. Raw material\dilution mixed logistics; 6. Total dilution steam logistics; 7. Superheated dilution steam logistics after the second quench cooler; 8. Logistics after the dilution steam superheating section; 9. Logistics after raw material and dilution steam mixed section I; 10. Logistics after raw material and dilution steam mixed section II; 11. Cracked gas logistics; 12. Cracked gas logistics after the first quench cooler; 13. Cracked gas logistics after the second quench cooler; 14. Cracked gas logistics after the third quench cooler; 15. Boiler feed water logistics; 16 High-pressure steam logistics; 17. Logistics after high-pressure steam superheating section I; 18. Logistics cooled by the desuperheater; 19 High-pressure boiler feed water logistics; 20. Logistics after high-pressure steam superheating section II; 21. Air logistics; 22. Logistics after the air preheating section; 23. Fuel gas logistics.

[0080] The convection section includes from top to bottom: P air preheating 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.

[0081] Unlike the comparative example, in this embodiment, the rotating unit in the cracking method and the associated cracking device is first changed to a motor-driven unit. Therefore, the demand for high-pressure steam is reduced. In order to avoid energy waste:

[0082] 1. Direct Boiler Feedwater to the Steam Drum: This solution eliminates the economizer section C in the convection section. Boiler feedwater stream 15 is fed directly to the steam drum N without preheating in the economizer or heating the shell side of the secondary quench cooler. Consequently, the heat input to the steam drum is significantly reduced, lowering high-pressure steam production. Consequently, the secondary quench cooler, previously used to heat the boiler feedwater stream, is now used to heat the dilution steam stream.

[0083] 2. Fuel gas and / or air are preheated in the convection section before being fed into the radiant section for combustion. Without an economizer in the convection section, the heat from the high-temperature flue gas cannot be fully utilized. Therefore, an air preheating section P is installed above the convection section. The heat from this flue gas is used to heat the fuel gas or air. The air here refers to the oxidant used in the radiant section, which can be pure oxygen.

[0084] Because the fuel gas is preheated, less fuel is used to achieve the same heating effect in the radiant section A, saving fuel. However, this also presents a problem: the production of high-temperature flue gas is reduced. The total energy consumption of the convection section is reduced, and the shell side of the second quench cooler L, which originally used boiler feedwater, is now fed with dilution steam. This reduces heat exchange capacity and reduces the cooling effect of the cracked gas.

[0085] Therefore, a third quencher O is installed after the second quencher. The feedstock first enters the shell side of the third quencher O for heat exchange with the cracked gas before being fed into the convection section. This compensates for the deterioration of cracked gas cooling efficiency and preheats the feedstock, addressing the reduction in total heat in the convection section after the high-temperature flue gas is reduced.

[0086] A cracking device according to supporting embodiment 2 includes a cracking furnace, which includes a radiation section and a convection section. All rotating units of the cracking device are driven by motors; a pipeline for boiler feed water logistics is connected to the water inlet of the steam drum N, the convection section is not provided with an economizer section C, an air preheating section P is arranged above the raw material preheating section I B, a blower is provided on the air duct and is connected to the inlet of the air preheating section P, and the outlet of the air preheating section P is connected to the air inlet of the radiation section A.

[0087] The cracking gas outlet of the cracking furnace is connected in series with the first quench cooler K, the second quench cooler L and the third quench cooler O; the dilution steam feed pipe is connected in series with the shell side of the second quench cooler L and the dilution steam preheating section F; the raw material feed pipe is connected in series with the shell side of the third quench cooler O and the raw material preheating section I B.

[0088] Process side flow:

[0089] 1. Raw material stream 1 enters the third quench cooler O and then enters the raw material preheating section B for preliminary preheating to obtain stream 3;

[0090] 2. Logistics 3 is further sent to the raw material preheating section II D for preheating. Example 2 ( Figure 3 ) Since the economizer section C is eliminated, the raw material preheating sections I and II can also be combined.

[0091] 3. The dilution steam flow 6 is first superheated by the second quench cooler L and then passed into the dilution steam preheating section F, which reduces the heat exchange load of the dilution steam preheating section F.

[0092] 4. The preheated feedstock stream and the dilution steam stream enter the feedstock / dilution steam mixer M for thorough mixing to obtain a feedstock / dilution mixed stream, which is then fed into the feedstock and dilution steam mixing section I E. The stream is further superheated in the feedstock and dilution steam mixing section II I and fed into the radiant section of the cracking furnace for cracking reaction, ultimately obtaining a cracked gas stream 10.

[0093] 5. The cracked gas stream is further cooled by heat exchange in the first quencher K, the second quencher L, and the third quencher O. The resulting product is then sent to the downstream separation device. The product is cracked to form a mixture of various small molecules, which are then cooled and sent to the downstream process for separation.

[0094] Utility engineering side process:

[0095] 1. The boiler feed water stream 15 is directly fed into the steam drum N, which reduces the load of the convection section.

[0096] 2. The boiler feed water in the drum N is vaporized through heat exchange in the first quench cooler K and then returns to the drum, forming a thermosiphon system.

[0097] 3. The high-pressure steam flow produced from the steam drum N is sent to the high-pressure steam superheating section I G and the high-pressure steam superheating section II H for superheating and then sent to the high-pressure steam pipeline network.

[0098] In this embodiment, the temperature of the raw material stream 1 is 120°C, the temperature of the dilution steam stream 6 is 200°C, the flow rate of the dilution steam stream 6 is 4wt% of the raw material 1, the raw material stream 1 is ethane, and the yield of the product ethylene is 46.4%; the cracked gas is cooled to 485°C at the outlet of the first quencher K; the cracked gas is cooled to 280°C at the outlet of the second quencher L, and is sent out of the system after being cooled to 205°C by the third quencher O. The boiler feed water 15 has a temperature of 100°C and a pressure of 13MPa. The temperature of the high-pressure steam superheated II section stream 20 (high-quality high-pressure steam) is 510°C and a pressure of 14MPa.

[0099] The rest of the present embodiment is the same as the comparative example. For every ton of ethylene produced, 0.41 tons of fuel gas, methane and hydrogen are consumed. The overall electrification rate of the ethylene plant is 15.7%. The output of the high-pressure steam superheated II stage stream 20 (high-quality high-pressure steam) is 2.5 tons / ton of ethylene.

[0100] Example 3

[0101] The process flow diagram of the steam cracking furnace of Example 3 is shown in the attached Figure 4 .

[0102] Attachment Figure 4 Device marking instructions:

[0103] A. Radiation section; B. Raw material preheating section I; 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; P. Air preheating section; Q. Blower.

[0104] Attachment Figure 3 Logistics marking instructions:

[0105] 2. Raw material logistics; 3. Raw material logistics after raw material preheating section I; 4. Raw material logistics after raw material preheating section II; 5. Raw material\dilution mixture flow to the second quencher; 6. Dilution steam logistics; 7. Logistics after dilution steam superheating section; 8. Raw material\dilution steam mixture flow after the second quencher; 9. Logistics after raw material and dilution steam mixing section I; 10. Logistics after raw material and dilution steam mixing section II; 11. Cracking gas logistics; 12. Cracking gas logistics after passing through the first quencher; 13. Cracking gas logistics after passing through the second quencher; 15. Boiler feed water logistics; 16 High-pressure steam logistics; 17. Logistics after high-pressure steam superheating section I; 18. Cooling logistics after desuperheater; 19 High-pressure boiler feed water logistics; 20. Logistics after high-pressure steam superheating section II; 21. Air logistics; 22. Logistics after passing through the air preheating section; 23. Fuel gas logistics.

[0106] The convection section includes, from top to bottom: P air preheating section; B raw material preheating section I; 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.

[0107] Different from the comparative example, in this embodiment, firstly, the rotating unit in the cracking method and the supporting cracking device is changed to be driven by a motor.

[0108] The boiler feedwater stream is fed directly into the steam drum. This scheme eliminates the economizer section C in the convection section. Instead, the boiler feedwater stream 15 is fed directly into the steam drum N, without preheating in the economizer or heating the shell side of the second quench cooler. Consequently, the heat input to the steam drum is significantly reduced, reducing high-pressure steam production. Consequently, the second quench cooler, originally used to heat the boiler feedwater stream, is now used to heat the dilution steam stream.

[0109] Air is preheated in the convection section before being sent to the radiant section for combustion. Without an economizer in the convection section, the heat from the high-temperature flue gas cannot be fully utilized. Therefore, an air preheating section P is installed at the top of the convection section. The heat from this flue gas is used to heat the air.

[0110] Raw material flow 2 first enters raw material preheating section I B for preheating, then enters raw material preheating section II D for further preheating, and then enters raw material\dilution steam mixer M to mix with dilution steam.

[0111] At the same time, the dilution steam flow first enters the dilution steam preheating section F, and then enters the raw material\dilution steam mixer M to mix with the raw material.

[0112] The mixed raw material / diluted mixture flow first enters the raw material and dilution steam mixing section I E for heating, and then is sent to the shell side of the second quench cooler L to recover the heat of the cracked gas. It then returns to the raw material and dilution steam mixing section I E and enters the raw material and dilution steam mixing section II I for superheating. It is then sent to the radiation section A for cracking to obtain cracked gas for delivery.

[0113] After the process flow is modified, the supporting cracking device is adaptively modified. Specifically, the cracking gas outlet of the cracking furnace is connected in series with the first quench cooler K and the second quench cooler L. All rotating units of the cracking device are driven by motors. The pipeline of the boiler feed water flow is connected to the water inlet of the steam drum N. The convection section is not provided with an economizer section C. An air preheating section P is arranged above the raw material preheating section I B. A blower is provided on the air pipe and connected to the inlet of the air preheating section P. The outlet of the air preheating section P is connected to the air inlet of the radiation section A; the raw material and dilution steam mixing section I E is connected to the shell side of the second quench cooler L through an external circulation pipe. The mixed flow of the dilution steam mixing section I E is sent to the shell side of the second quench cooler L to recover the heat of the cracked gas, and then returned to the raw material and dilution steam mixing section I E.

[0114] In this embodiment, the temperature of the raw material stream 2 is 120°C, the temperature of the dilution steam stream 6 is 200°C, the flow rate of the dilution steam stream 6 is 4wt% of the raw material 1, the raw material stream 1 is ethane, and the yield of the product ethylene is 45.2%; the cracked gas is cooled to 498°C at the outlet of the first quencher K; the cracked gas is cooled to 300°C at the outlet of the second quencher L and then sent out of the system, the boiler feed water 15 temperature is 100°C, the pressure is 13MPa, and the temperature of the high-pressure steam superheated II section stream 20 (high-quality high-pressure steam) is 504°C and the pressure is 13.7MPa.

[0115] The rest of the present embodiment is the same as the comparative example. For every ton of ethylene produced, 0.36 tons of fuel gas, methane and hydrogen are consumed. The overall electrification rate of the ethylene plant is 21.5%, and the output of the high-pressure steam superheated II stage stream 20 (high-quality high-pressure steam) is 1.8 tons / ton of ethylene.

[0116] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention may be subjected to various simple modifications, including combining the specific technical features in any suitable manner. To avoid unnecessary repetition, the present invention will not further describe various possible combinations. However, these simple modifications and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A cracking method, wherein a feed stream and a dilution steam stream are heated and mixed in a convection section of a cracking furnace, and then fed into a radiant section of the cracking furnace for cracking to obtain cracked gas, and the cracked gas is cooled in a quench cooler to obtain a product, characterized in that: The cracking method comprises: The rotating unit of the cracking furnace is driven entirely or partially by a motor; the heat of the cracking gas is recovered by using a raw material stream and / or a dilution steam stream; and / or Heat is recovered from the convection section using the feed stream from the radiant section.

2. The cracking method according to claim 1, characterized in that The raw material flow and / or the dilution steam flow are first passed into the quench cooler to recover the heat of the cracked gas and then enter the convection section.

3. The cracking method according to claim 2, characterized in that The cracked gas stream generated by the cracking furnace passes through the first quench cooler and the second quench cooler in sequence, wherein the raw material stream and / or dilution steam is first passed into the second quench cooler to recover the heat of the cracked gas and then enters the convection section.

4. The cracking method according to claim 1, characterized in that The raw material flow and / or the dilution steam flow are first fed into the convection section, then fed into a quench cooler to recover the heat of the cracked gas, and then returned to the convection section; The cracked gas flow generated by the cracking furnace passes through the first quench cooler and the second quench cooler in sequence, wherein the raw material flow and the dilution steam flow are first sent to the convection section for preheating and mixing, and then passed into the second quench cooler to recover the heat of the cracked gas and then returned to the convection section.

5. The cracking method according to claim 1, characterized in that The cracking gas flow generated by the cracking furnace passes through the first quench cooler, the second quench cooler and the third quench cooler in sequence, wherein the raw material flow is passed into the third quench cooler to recover the heat of the cracking gas and then enters the convection section, and the dilution steam is passed into the second quench cooler to recover the heat of the cracking gas and then enters the convection section.

6. The cracking method according to claim 1, characterized in that The boiler feedwater stream is fed directly into the steam drum or preheated in the economizer before being fed into the steam drum; and / or The feed flow of the radiant section includes fuel gas and air. The fuel gas and / or air are introduced into the convection section for preheating and then sent into the radiant section for combustion.

7. The cracking method according to claim 6, characterized in that When the boiler feed water flow enters the steam drum directly, the fuel gas and / or air is introduced into the convection section for preheating and then sent to the radiation section for combustion.

8. A cracking device comprising a cracking furnace and a rotating unit, wherein the cracking furnace comprises a radiant section and a convection section connected to each other, and the cracked gas outlet of the cracking furnace is connected to a quench cooler, characterized in that: Part or all of the rotating units of the cracking device are driven by motors; A feedstock channel for circulating a feedstock stream and / or a steam channel for circulating a dilution steam stream passes through the quench cooler to recover heat from the cracked gas; and / or The feed line connecting the radiant section is arranged to pass through the convection section.

9. The cracking device according to claim 8, characterized in that The raw material channel includes a connected raw material feed pipe and a raw material preheating section arranged in the convection section; and / or The steam channel includes a connected dilution steam feed pipe and a steam preheating section arranged in a convection section.

10. The cracking device according to claim 9, characterized in that The quench cooler comprises a first quench cooler and a second quench cooler which are sequentially arranged along the flow direction of the cracked gas material; The raw material feed pipe and / or the steam feed pipe passes through the second quench cooler; or The raw material channel and the steam channel are combined in the raw material and dilution steam mixing section I in the convection section. The raw material and dilution steam mixing section I is provided with an external circulation pipe, and the external circulation pipe passes through the second quench cooler.

11. The cracking device according to claim 10, characterized in that The quench cooler includes a first quench cooler, a second quench cooler and a third quench cooler which are sequentially arranged along the flow direction of the cracked gas material; The raw material feed pipe passes through the third quench cooler, and the steam feed pipe passes through the second quench cooler.

12. The cracking device according to claim 8, characterized in that There is no economizer in the convection section of the cracking furnace, and the boiler feed water line is connected to the water inlet of the steam drum; or An economizer connected to the boiler feed water pipeline is provided in the convection section of the cracking furnace, and the water outlet of the economizer is directly connected to the water inlet of the steam drum.

13. The cracking device according to claim 9, characterized in that A radiation section feed preheating section is provided on the raw material preheating section, and a feed pipeline of the radiation section passes through the radiation section feed preheating section.

Images