An ethylene cracking system and an ethylene cracking method

Abstract

The application provides an ethylene cracking system and an ethylene cracking method. The ethylene cracking system and the ethylene cracking method couple a CO combustion boiler and an ethylene cracking furnace, utilize CO combustion in catalytic cracking regeneration flue gas to provide heat for cracking reactions in a radiation furnace tube group, reduce fuel consumption of an ethylene cracking device, and recover waste heat of CO combustion in multiple ways, thereby effectively reducing energy consumption and carbon emissions of the ethylene cracking system.

Description

Technical Field

[0001] This invention belongs to the field of petrochemical technology, and particularly relates to an ethylene cracking system and an ethylene cracking method. Background Technology

[0002] The ethylene cracking furnace is the core of an ethylene plant. Petroleum hydrocarbons undergo high-temperature cracking reactions in tubular cracking furnaces to produce ethylene. This technology is the most mature technology for ethylene production. The main energy consumption of ethylene cracking is concentrated in the cracking furnace, typically accounting for 50%-80% of the total energy consumption of an ethylene plant. This portion of energy consumption is mainly generated by the flue gas produced when fuel combustion supplies heat to the cracking furnace.

[0003] Catalytic cracking units are among the most important secondary processing units in oil refineries. With the increasing quality and weight of feedstocks, the coking rate in the reactors of catalytic cracking units reaches 6%-12%. The coke adheres to the unregenerated catalyst and is sent to the regenerator for burning. To reduce energy consumption, the regenerators in heavy oil catalytic cracking units generally employ incomplete regeneration. The flue gas at the regenerator outlet contains a large amount of CO. This CO is further burned in a CO combustion boiler to become CO2, releasing heat used for superheated steam, generator steam, and preheating deoxygenated water. The radiant section temperature of the CO combustion boiler reaches 800℃-1000℃, which can meet the requirements of ethylene cracking. Summary of the Invention

[0004] To address the issue of high energy consumption in existing ethylene cracking units, the present invention aims to provide an ethylene cracking system and method that couples a CO combustion boiler from a catalytic cracking unit to an ethylene cracking furnace. The CO combustion boiler burns flue gas from the regenerator outlet of the catalytic cracking unit, and the heat released is used for ethylene cracking. This process recovers heat from the flue gas from the regenerator outlet of the catalytic cracking unit while reducing the energy consumption of the ethylene cracking furnace.

[0005] To achieve the above objectives, one aspect of the present invention provides an ethylene cracking system, the ethylene cracking system comprising a catalytic cracking regeneration unit and an ethylene cracking unit; wherein,

[0006] The catalytic cracking regeneration unit is used for the coking and regeneration of the spent catalyst to generate catalytic cracking regeneration flue gas, which is then transported to the ethylene cracking unit.

[0007] The ethylene cracking unit is used to carry out a cracking reaction by utilizing the heat generated by the combustion of CO in the catalytic cracking regeneration flue gas, and to recover the waste heat from the CO combustion.

[0008] According to the present invention, the ethylene cracking unit includes a CO combustion cracking furnace 1 and a steam drum 2;

[0009] The CO combustion pyrolysis furnace 1 includes a radiant section 11, an ultra-high pressure steam superheating section 12, an SCR denitrification section 13, a high pressure steam superheating section 14, an evaporation section 15, an economizing section 16, and a pyrolysis feedstock preheating section 17; wherein...

[0010] The radiation section 11 is used to burn CO in the catalytic cracking regeneration flue gas, and to use the heat generated by the CO combustion for the cracking reaction; the ultra-high pressure steam superheating section 12, the high pressure steam superheating section 14, the evaporation section 15, the coal-saving section 16, the cracking feedstock preheating section 17 and the steam drum 2 are used to recover the waste heat of CO combustion in the radiation section 11; the SCR denitrification section 13 is used to remove NOx from the catalytic cracking regeneration flue gas.

[0011] According to the present invention, the catalytic cracking regeneration unit includes a first regenerator 3, a second regenerator 4, a third-stage cyclone separator 5, and a flue gas turbine 6; wherein,

[0012] Both the first regenerator 3 and the second regenerator 4 are used to regenerate the catalyst to be recycled by coking, thereby generating the catalytic cracking regeneration flue gas; the outlet of the second regenerator 4 is connected to the inlet of the first regenerator 3, and is used to transport the catalytic cracking regeneration flue gas generated by the second regenerator 4 to the first regenerator 3.

[0013] The outlet of the first regenerator 3 is connected to the inlet of the third-stage cyclone separator 5, the outlet of the third-stage cyclone separator 5 is connected to the inlet of the flue gas turbine 6, and the outlet of the flue gas turbine 6 is connected to the inlet of the CO combustion cracking furnace 1. This is used to transport the catalytic cracking regeneration flue gas generated by the first regenerator 3 and the second regenerator 4 after preliminary dust removal and purification to the CO combustion cracking furnace 1 for combustion, thereby providing heat for the cracking reaction.

[0014] According to the present invention, a low NOx burner 18 is provided at the inlet of the radiation section 11. The low NOx burner 18 is connected to the fuel gas network of the device through a supplementary combustion gas pipeline 101 and is used to burn supplementary fuel to supplement the heat of the pyrolysis reaction.

[0015] According to the present invention, the radiant section 11, the ultra-high pressure steam superheating section 12, the high pressure steam superheating section 14, the evaporation section 15, the coal-saving section 16, and the pyrolysis feedstock preheating section 17 are respectively equipped with radiant furnace tube group 102, ultra-high pressure steam superheating tube group 103, high pressure steam superheating tube group 104, steam generating tube group 105, boiler feedwater preheating tube group 106, and pyrolysis feedstock preheating tube group 107; the SCR denitrification section 13 is equipped with a denitrification catalyst bed.

[0016] According to the present invention, the inlet of the radiant furnace tube assembly 102 is connected to the outlet of the pyrolysis feedstock preheating tube assembly 107 and the dilution steam line 108. The inlet of the pyrolysis feedstock preheating tube assembly 107 is connected to the cold pyrolysis feedstock line 109, and the outlet of the radiant furnace tube assembly 102 is connected to the pyrolysis gas line 110. This is used to preheat the pyrolysis feedstock using the waste heat from the CO combustion, and then the hot pyrolysis feedstock and dilution steam are transported to the radiant furnace tube assembly 102 to carry out the pyrolysis reaction. The generated pyrolysis gas is transported downstream to recover low-carbon olefins.

[0017] According to the present invention, the inlet and outlet of the ultra-high pressure steam superheated tube assembly 103 are respectively connected to the ultra-high pressure saturated steam outlet of the steam drum 2 and the ultra-high pressure superheated steam pipeline 111, for generating ultra-high pressure superheated steam to recover the waste heat of the CO combustion.

[0018] The denitrification catalyst bed inlet is connected to the denitrification agent pipeline 112, which is used to introduce the denitrification agent into the denitrification catalyst bed to react with NOx in the catalytic cracking regeneration flue gas, thereby achieving NOx removal;

[0019] Preferably, the inlet of the ultra-high pressure steam superheated pipe assembly 103 is also connected to an external ultra-high pressure saturated steam pipeline 113 to supplement the ultra-high pressure saturated steam for the generation of ultra-high pressure superheated steam.

[0020] According to the present invention, the inlet and outlet of the high-pressure steam superheated tube assembly 104 are respectively connected to the high-pressure saturated steam pipeline 114 and the high-pressure superheated steam pipeline 115; for generating high-pressure superheated steam to recover the waste heat of the CO combustion.

[0021] According to the present invention, the inlet and outlet of the steam generating tube assembly 105 are respectively connected to the circulating hot water outlet and the steam-water mixture inlet of the steam drum 2, for recovering the waste heat of the CO combustion to heat the circulating hot water from the steam drum 2, and providing the steam-water mixture to the steam drum 2 to generate the ultra-high pressure saturated steam;

[0022] The inlet and outlet of the boiler feedwater preheating pipe assembly 106 are respectively connected to the deoxygenated water pipeline 116 and the water inlet of the steam drum 2; it is used to recover the waste heat of CO combustion to heat the deoxygenated water and provide boiler feedwater for the steam drum 2.

[0023] According to the present invention, the ethylene cracking system further includes a flue gas desulfurization and dust removal unit; the flue gas desulfurization and dust removal unit is connected to the ethylene cracking unit and is used to purify the catalytic cracking regeneration flue gas discharged from the ethylene cracking unit after CO combustion, waste heat recovery and NOx removal by means of desulfurization and dust removal.

[0024] According to the present invention, the dry volume of the catalytic cracking regeneration flue gas generated by the catalytic cracking regeneration unit is 100%, wherein the CO content is 1 Vol%-15 Vol.

[0025] The second invention provides an ethylene cracking method, implemented according to the ethylene cracking system of the first invention, comprising:

[0026] The catalytic cracking regeneration flue gas generated by the catalytic cracking regeneration unit is fed into the ethylene cracking unit for combustion. The heat generated by the combustion of CO in the catalytic cracking regeneration flue gas is used for cracking reaction to produce cracked gas. The cracked gas is then fed into the product separation system of the catalytic cracking unit to recover low-carbon olefins.

[0027] In the ethylene cracking unit, the waste heat from CO combustion is recovered by generating ultra-high pressure superheated steam, ultra-high pressure saturated steam and high pressure superheated steam, preheating boiler feedwater and preheating cracking feedstock.

[0028] The beneficial effects of this invention are:

[0029] To address the issue of high energy consumption in existing ethylene cracking units, this invention provides an ethylene cracking system and an ethylene cracking method. The ethylene cracking system includes a catalytic cracking regeneration unit and an ethylene cracking unit. The catalytic cracking regeneration unit is used for the coking and regeneration of spent catalyst, generating catalytic cracking regeneration flue gas, which is then transported to the ethylene cracking unit. The ethylene cracking unit utilizes the heat generated from the combustion of CO in the catalytic cracking regeneration flue gas for a cracking reaction and recovers the waste heat from the CO combustion. The ethylene cracking method, implemented according to the ethylene cracking system, includes transporting the catalytic cracking regeneration flue gas generated by the catalytic cracking regeneration unit to the ethylene cracking unit for combustion, utilizing the heat generated from the combustion of CO in the catalytic cracking regeneration flue gas for a cracking reaction to generate cracked gas; transporting the cracked gas to the product separation system of the catalytic cracking unit to recover low-carbon olefins; and recovering the waste heat from the CO combustion in the ethylene cracking unit by generating ultra-high pressure superheated steam, ultra-high pressure saturated steam, and high pressure superheated steam, preheating boiler feedwater, and preheating cracking feedstock. Compared with the prior art, this invention has at least the following advantages:

[0030] 1) This invention creatively couples a CO combustion boiler and an ethylene cracking furnace. The catalytic cracking regeneration flue gas generated after the catalytic cracking regeneration unit regenerates the spent catalyst from the catalytic cracking unit is transported to the radiant section of the CO combustion ethylene cracking furnace for combustion. The heat released by the CO combustion in the catalytic cracking regeneration flue gas is used to heat the cracking reaction in the radiant furnace tube group. Under this design, unlike conventional ethylene cracking systems and methods that use a large amount of fuel combustion to provide heat for the cracking reaction, this invention only needs to introduce a small amount of fuel through the supplementary combustion gas pipeline and use a low-NOx burner for low-NOx combustion to supplement a small amount of heat for the cracking reaction in the radiant section. The fuel consumption is greatly reduced, thereby effectively reducing the energy consumption and carbon emissions of the ethylene cracking system.

[0031] 2) Based on 1), the present invention further includes an ultra-high pressure steam superheating section, a high pressure steam superheating section, a steam generation section, a coal-saving section, and a pyrolysis feedstock preheating section in the CO combustion pyrolysis furnace. In conjunction with the steam drum, the waste heat of CO combustion is further recovered by generating ultra-high pressure superheated steam, ultra-high pressure saturated steam, and high pressure superheated steam, preheating deoxygenated water, and cooling pyrolysis feedstock, thereby improving the energy utilization efficiency of the system.

[0032] 3) Based on 1) and 2), the present invention sets up an SCR denitrification section between the ultra-high pressure steam superheating section and the high pressure steam superheating section in the CO combustion cracking furnace to remove NOx from the catalytic cracking regeneration flue gas; and sets up a desulfurization and dust removal unit after the ethylene cracking unit to remove SOx and dust and other pollutants from the catalytic cracking regeneration flue gas after CO combustion and denitrification, so that the purified flue gas discharged from the ethylene cracking system meets the environmental protection emission standards.

[0033] 4) This invention utilizes the product separation system of a catalytic cracking unit to perform rapid cooling, fractionation, absorption stabilization, dual desulfurization, gas separation, and C2 recovery on the cracked gas generated in the radiation section, thereby achieving the recovery of low-carbon ethylene. There is no need to set up a rapid cooling boiler, which greatly simplifies the cracked gas separation system and helps to significantly reduce the investment, land area, and energy consumption of the cracked gas rapid cooling separation system.

[0034] 5) The ethylene cracking system and ethylene cracking method provided by the present invention can not only process external oil and gas feedstocks, but also directly process by-products such as ethane, propane, C4 hydrocarbons, and light gasoline separated by the product separation unit of the catalytic cracking unit. This is beneficial to improving the yield of low-carbon olefins and aromatics such as ethylene, propylene, butene, and BTX (i.e., benzene-toluene-xylene mixture) in the catalytic cracking unit, thereby increasing economic benefits. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the ethylene cracking system provided in Example 1.

[0036] Figure 2 A schematic diagram of the existing conventional ethylene cracking system provided for Comparative Example 1.

[0037] The meanings of the reference numerals in the figure are as follows:

[0038] 1-CO combustion pyrolysis furnace; 2-Steam drum; 3-First regenerator; 4-Second regenerator; 5-Third-stage cyclone separator; 6-Flue gas turbine;

[0039] 11-Radiation section; 12-Ultra-high pressure steam superheating section; 13-SCR denitrification section; 14-High pressure steam superheating section; 15-Evaporation section; 16-Economy section; 17-Pyrolysis feedstock preheating section; 18-Low NOx burner;

[0040] 101-Refueling gas pipeline; 102-Radiant furnace tube assembly; 103-Ultra-high pressure steam superheater tube assembly; 104-High pressure steam superheater tube assembly; 105-Steam generator tube assembly; 106-Boiler feedwater preheater tube assembly; 107-Pyrolysis feedstock preheater tube assembly; 108-Dilution steam pipeline; 109-Cold pyrolysis feedstock pipeline; 110-Pyrolysis gas pipeline; 111-Ultra-high pressure superheated steam pipeline; 112-Denitrification agent pipeline; 113-External ultra-high pressure saturated steam pipeline; 114-High pressure saturated steam pipeline; 115-High pressure superheated steam pipeline; 116-Deoxygenated water pipeline; 117-External boiler feedwater pipeline; 118-Purified flue;

[0041] 7-Conventional ethylene cracking furnace; 71-Radiant section of cracking furnace; 72-Convection section of cracking furnace; 8-Quick cooling boiler; 701-Radiant furnace tube; 702-Cracking feedstock; 703-Cracking gas.

[0042] The above figures are not drawn to the actual size and scale. Detailed Implementation

[0043] To make the technical solutions and advantages of the present invention clearer, exemplary embodiments of the present invention will be described in further detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not an exhaustive list of all embodiments. Furthermore, without conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0044] Existing ethylene plants are centered around ethylene cracking furnaces, which use tubular cracking furnaces to produce ethylene through high-temperature cracking of petroleum hydrocarbons. The energy consumption from the flue gas generated by fuel combustion in the cracking furnace, which provides heat for the high-temperature cracking, is significant, accounting for approximately 50%-80% of the total energy consumption of the ethylene plant. Therefore, the energy consumption generated by the ethylene cracking furnace in the process of producing ethylene from petroleum hydrocarbons is too high and urgently needs improvement.

[0045] In catalytic cracking units, the deterioration and heavier nature of feedstocks lead to a significant increase in the coking rate of the reactor, consequently increasing the energy consumption of the regenerator used for catalyst coking regeneration. To reduce energy consumption, the regenerator typically employs incomplete regeneration, resulting in a large amount of CO in the regenerator outlet flue gas. To address this, catalytic cracking units generally utilize a CO combustion boiler to further combust the CO in the regenerator outlet flue gas, converting it into CO2 and releasing heat. This heat is used for superheated steam, generator steam, and preheating deoxygenated water. The inventors noted that the radiant section of the CO combustion boiler has a high temperature, reaching 800°C to 1000°C, which meets the temperature requirements for high-temperature cracking of petroleum hydrocarbons to produce ethylene in an ethylene cracking furnace. If the heat from the radiant section of the CO combustion boiler could be introduced into the ethylene cracking furnace, replacing the existing fuel combustion to provide heat for ethylene cracking, the energy consumption of the ethylene cracking furnace could be significantly reduced, thereby lowering the overall energy consumption of the ethylene plant.

[0046] The first aspect of this invention provides an ethylene cracking system, such as... Figure 1 As shown, the ethylene cracking system includes a catalytic cracking regeneration unit and an ethylene cracking unit. The catalytic cracking regeneration unit is used for the coking and regeneration of the spent catalyst, generating catalytic cracking regeneration flue gas, which is then transported to the ethylene cracking unit. The ethylene cracking unit utilizes the heat generated by the combustion of CO in the catalytic cracking regeneration flue gas for a cracking reaction and recovers the waste heat from the CO combustion. The catalytic cracking regeneration flue gas referred to in this invention is the outlet flue gas generated during the coking and regeneration of the catalyst in the regenerator of the catalytic cracking unit. Its components (mainly referring to non-solid components other than dust and particles) include CO, N2, CO2, and H2O. Therefore, this invention utilizes the heat generated by the combustion of CO in the catalytic cracking regeneration flue gas for a cracking reaction. The ethylene cracking system provided in this embodiment of the invention couples a CO combustion boiler to an ethylene cracking furnace. The catalytic cracking regeneration flue gas, generated from the coking and regeneration of the spent catalyst from the catalytic cracking unit, is transported to the ethylene cracking unit for combustion. The heat generated from the CO combustion in the catalytic cracking regeneration flue gas provides the necessary heat for the high-temperature cracking of petroleum hydrocarbons to produce ethylene. Furthermore, the heat generated from CO combustion is recovered within the ethylene cracking unit. This invention abandons the traditional approach of primarily utilizing additional fuel combustion to provide heat for ethylene cracking, thereby reducing the energy consumption of the ethylene cracking process.

[0047] In one specific embodiment of the present invention, the ethylene cracking unit includes a CO combustion cracking furnace 1 and a steam drum 2, wherein the CO combustion cracking furnace 1 includes a radiation section 11, an ultra-high pressure steam superheating section 12, an SCR denitrification section 13, a high pressure steam superheating section 14, an evaporation section 15, a coal-saving section 16 and a cracking feedstock preheating section 17.

[0048] The catalytic cracking regeneration unit includes a first regenerator 3, a second regenerator 4, a third-stage cyclone separator 5, and a flue gas turbine 6.

[0049] In one specific embodiment of the present invention, the first regenerator 3 and the second regenerator 4 are both used to regenerate the spent catalyst from the catalytic cracking unit by burning coke, thereby generating the catalytic cracking regeneration flue gas; wherein, the first regenerator 3 and the second regenerator 4 are arranged overlappingly or side by side, and the outlet of the second regenerator 4 is connected to the inlet of the first regenerator 3, for conveying the catalytic cracking regeneration flue gas generated by the second regenerator 4 to the first regenerator 3.

[0050] The outlet of the first regenerator 3 is connected to the inlet of the third-stage cyclone separator 5 (e.g., by setting up a regeneration flue), the outlet of the third-stage cyclone separator 5 is connected to the inlet of the flue gas turbine 6 (e.g., by setting up a three-cyclone outlet flue), and the outlet of the flue gas turbine 6 is connected to the inlet of the CO combustion cracking furnace 1. This is used to collect the catalytic cracking regeneration flue gas generated by the first regenerator 3 and the second regenerator 4 from the outlet of the first regenerator 3 and transport it to the third-stage cyclone separator 5 for preliminary dust removal and purification. Then, the catalytic cracking regeneration flue gas is transported to the CO combustion cracking furnace 1 (specifically, the radiation section 11 of the CO combustion cracking furnace 1) for combustion through the flue gas turbine 6, using the heat generated by the combustion of CO in the catalytic cracking regeneration flue gas to provide heat for the cracking reaction.

[0051] In one specific embodiment of the present invention, the dry basis volume of the catalytic cracking regeneration flue gas generated by the catalytic cracking regeneration unit is 100%, wherein the CO content is 1 Vol%-15 Vol.

[0052] In a preferred embodiment of the present invention, the dry basis volume of the catalytic cracking regeneration flue gas generated by the catalytic cracking regeneration unit is 100%, wherein the CO content is 2 Vol%-10 Vol.

[0053] In a preferred embodiment of the present invention, the dry basis volume of the catalytic cracking regeneration flue gas generated by the catalytic cracking regeneration unit is 100%, wherein the CO content is 4-8 vol%.

[0054] In a more preferred embodiment of the present invention, the dry basis volume of the catalytic cracking regeneration flue gas generated by the catalytic cracking regeneration unit is 100%, wherein the CO content is 5-6 vol%.

[0055] It should be noted that in the embodiments that limit the CO content in the catalytic cracking regeneration flue gas described above, the dry basis volume of the catalytic cracking regeneration flue gas refers to the dry basis volume of the catalytic cracking regeneration flue gas before CO combustion.

[0056] In one specific embodiment of the present invention, the radiation section 11 is used to burn CO in the catalytic cracking regeneration flue gas, and to use the heat generated by the combustion of CO to carry out a cracking reaction.

[0057] In a preferred embodiment of the present invention, a low-NOx burner 18 is provided at the inlet of the radiation section 11. The low-NOx burner 18 is connected to the fuel gas network of the device through a supplementary combustion gas pipeline 101 for burning supplementary fuel, increasing the temperature of the catalytic cracking regeneration flue gas, ensuring complete combustion of CO, and supplementing heat for the cracking reaction.

[0058] In one specific embodiment of the present invention, a radiant furnace tube assembly 102 is provided in the radiant section 11, and a pyrolysis feedstock preheating tube assembly 107 is provided in the pyrolysis feedstock preheating section 17. The inlet of the radiant furnace tube assembly 102 is connected to the outlet of the pyrolysis feedstock preheating tube assembly 107 (e.g., by providing a thermal pyrolysis feedstock pipeline). The inlet of the radiant furnace tube assembly 102 is connected to a dilution steam pipeline 108 (e.g., by connecting the dilution steam pipeline 108 to the thermal pyrolysis feedstock pipeline). The inlet of the pyrolysis feedstock preheating tube assembly 107 is connected to a cold pyrolysis feedstock pipeline 109. This is used to input cold pyrolysis feedstock into the pyrolysis feedstock preheating tube assembly 107, using the waste heat from the CO combustion in the catalytic cracking regeneration flue gas in the radiant section 11 to preheat the cold pyrolysis feedstock, and to preheat the thermal pyrolysis feedstock. The feedstock and the dilution steam are transported to the radiant furnace tube group 102 for the cracking reaction to produce cracked gas. The introduction of the dilution steam can reduce the partial pressure of oil and gas and increase the ethylene yield. Furthermore, the outlet of the radiant furnace tube group 102 is connected to the cracked gas pipeline 110. The cracked gas produced is transported downstream through the cracked gas pipeline 110 to recover low-carbon olefins. For example, the cracked gas pipeline 110 transports the cracked gas to the product separation system of the catalytic cracking unit for rapid cooling, fractionation, absorption stabilization (mainly including liquefied gas absorption, desorption and gasoline stabilization), dual desulfurization (i.e., desulfurization and desulfurization of dry gas and liquefied gas), gas separation (i.e., separation of liquefied gas to obtain propane, propylene and C4 components), and C2 recovery (i.e., recovery of ethane and ethylene from dry gas) to recover low-carbon olefins.

[0059] In one specific embodiment of the present invention, the ultra-high pressure steam superheating section 12, the high pressure steam superheating section 14, the evaporation section 15, the coal-saving section 16, the pyrolysis feedstock preheating section 17 and the steam drum 2 are used to recover the waste heat of CO combustion in the radiation section 11.

[0060] Specifically, an ultra-high pressure steam superheating section 12 is provided with an ultra-high pressure steam superheating tube assembly 103. The inlet and outlet of the ultra-high pressure steam superheating tube assembly 103 are respectively connected to the ultra-high pressure saturated steam outlet of the steam drum 2 and the ultra-high pressure superheated steam pipeline 111 (for example, by setting an ultra-high pressure saturated steam pipeline at the inlet of the ultra-high pressure steam superheating tube assembly 103 and a steam drum ultra-high pressure saturated steam pipeline at the ultra-high pressure saturated steam outlet of the steam drum 2, thereby connecting the ultra-high pressure saturated steam pipeline and the steam drum ultra-high pressure saturated steam pipeline); used to transfer ultra-high pressure saturated steam from the steam drum 2... Steam is transported to the ultra-high pressure steam superheater tube group 103, and heated by the waste heat from the combustion of CO in the catalytic cracking regeneration flue gas in the radiant section 11 to obtain ultra-high pressure superheated steam. That is, the waste heat from the combustion of CO in the radiant section 11 is recovered by generating ultra-high pressure superheated steam. The inlet of the ultra-high pressure steam superheater tube group 103 is preferably connected to an external ultra-high pressure saturated steam pipeline 113 (for example, by connecting the ultra-high pressure saturated steam pipeline and the external ultra-high pressure saturated steam pipeline 113) to supplement the ultra-high pressure saturated steam for the generation of ultra-high pressure superheated steam.

[0061] The high-pressure steam superheating section 14 is equipped with a high-pressure steam superheating tube assembly 104. The inlet and outlet of the high-pressure steam superheating tube assembly 104 are connected to the high-pressure saturated steam pipeline 114 and the high-pressure superheated steam pipeline 115, respectively, for conveying high-pressure saturated steam to the high-pressure steam superheating tube assembly 104. After heating with the waste heat from the combustion of CO in the catalytic cracking regeneration flue gas in the radiation section 11, high-pressure superheated steam is obtained. That is, the waste heat from the combustion of CO in the radiation section 11 is recovered by generating high-pressure superheated steam.

[0062] A steam generating pipe assembly 105 is installed within the evaporation section 15. The inlet and outlet of the steam generating pipe assembly 105 are connected to the circulating hot water outlet and the steam-water mixture inlet of the steam drum 2, respectively (for example, by installing a circulating hot water pipeline between the inlet of the steam generating pipe assembly 105 and the circulating hot water outlet of the steam drum 2, and a steam-water mixture pipeline between the outlet of the steam generating pipe assembly 105 and the steam-water mixture inlet of the steam drum 2). This assembly is used to transport the circulating hot water in the steam drum 2 to the steam generating pipe assembly 105. After heating with the waste heat from the CO combustion in the catalytic cracking regeneration flue gas in the radiation section 11, a steam-water mixture is obtained. This mixture is then transported to the steam drum 2 through the steam-water mixture pipeline for the generation of ultra-high pressure saturated steam. In other words, the waste heat from the CO combustion in the radiation section 11 is recovered to heat the circulating hot water from the steam drum 2, providing the steam-water mixture to the steam drum 2 for the generation of ultra-high pressure saturated steam.

[0063] A boiler feedwater preheating pipe assembly 106 is installed within the coal-saving section 16. The inlet and outlet of the boiler feedwater preheating pipe assembly 106 are connected to the deoxygenated water pipeline 116 and the water inlet of the steam drum 2, respectively (for example, by installing a boiler feedwater main pipe at the outlet of the boiler feedwater preheating pipe assembly 106 and a steam drum water inlet pipeline at the water inlet of the steam drum 2, thus connecting the boiler feedwater main pipe and the steam drum water inlet pipeline). This assembly is used to transport deoxygenated water to the boiler feedwater preheating pipe assembly 106, utilizing the waste heat from the combustion of CO in the catalytic cracking regeneration flue gas in the radiation section 11. After heating, boiler feedwater is obtained and used to supply boiler feedwater to the steam drum 2. That is, the waste heat from CO combustion in the radiant section 11 is recovered to heat the deoxygenated water and supply boiler feedwater to the steam drum 2. Furthermore, the outlet of the boiler feedwater preheating pipe group 106 is also connected to the external boiler feedwater pipeline 117 (for example, by connecting the boiler feedwater main pipe and the external boiler feedwater pipeline 117) to supply boiler feedwater to external boiler feedwater users. That is, the waste heat from CO combustion in the radiant section 11 is recovered to heat the deoxygenated water and supply boiler feedwater to the external boiler feedwater users.

[0064] In one specific embodiment of the present invention, the number of the radiant furnace tube group 102, the ultra-high pressure steam superheating tube group 103, the high pressure steam superheating tube group 104, the steam generating tube group 105, the boiler feedwater preheating tube group 106, and the pyrolysis raw material preheating tube group 107 is independently one or more.

[0065] Preferably, each of the radiant furnace tube groups 102 includes one or more radiant furnace tubes; and / or

[0066] Each of the ultra-high pressure steam superheater tube groups 103 includes one or more ultra-high pressure steam superheater tubes; and / or

[0067] Each of the high-pressure steam superheater tube assemblies 104 includes one or more high-pressure steam superheater tubes; and / or

[0068] Each of the steam generating pipe groups 105 includes one or more steam generating pipes; and / or

[0069] Each of the aforementioned boiler feedwater preheating tube bundles 106 includes one or more boiler feedwater preheating tubes; and / or

[0070] Each of the pyrolysis feedstock preheating tube groups 107 includes one or more pyrolysis feedstock preheating tubes.

[0071] In one specific embodiment of the present invention, the SCR denitrification section 13 is used to remove NOx from the catalytic cracking regeneration flue gas; wherein, the SCR denitrification section 13 is provided with a denitrification catalyst bed, preferably a plurality of denitrification catalyst beds; the inlet of the denitrification catalyst bed is connected to a denitrification agent pipeline 112, for introducing the denitrification agent into the denitrification catalyst bed, where it undergoes a reduction reaction with NOx in the catalytic cracking regeneration flue gas to remove NOx. In the present invention, NOx represents nitrogen oxides.

[0072] In a preferred embodiment of the present invention, the ethylene cracking system further includes a flue gas desulfurization and dust removal unit; the flue gas desulfurization and dust removal unit is connected to the ethylene cracking unit and is used to purify the catalytic cracking regeneration flue gas discharged from the ethylene cracking unit after CO combustion, waste heat recovery and NOx removal by means of desulfurization and dust removal.

[0073] Specifically, the inlet of the flue gas desulfurization and dust removal unit is connected to the outlet of the CO combustion pyrolysis furnace 1 (for example, by setting up a pyrolysis furnace outlet flue). The outlet of the flue gas desulfurization and dust removal unit is also connected to a purification flue 118, which is used to transport the catalytic cracking regeneration flue gas discharged from the outlet of the CO combustion pyrolysis furnace 1 after CO combustion, waste heat recovery and NOx removal to the flue gas desulfurization and dust removal unit for desulfurization and dust removal treatment to obtain purified flue gas. The purified flue gas is discharged from the system through the purification flue 118.

[0074] A second aspect of the present invention provides an ethylene cracking method, implemented according to the ethylene cracking system of the first aspect of the present invention, comprising: conveying the catalytic cracking regeneration flue gas generated by the catalytic cracking regeneration unit to the ethylene cracking unit for combustion, utilizing the heat generated by the combustion of CO in the catalytic cracking regeneration flue gas for a cracking reaction to generate cracked gas; conveying the cracked gas to the product separation system of the catalytic cracking unit to recover low-carbon olefins; and recovering the waste heat of the CO combustion in the ethylene cracking unit by generating ultra-high pressure superheated steam, ultra-high pressure saturated steam and high pressure superheated steam, preheating boiler feedwater and preheating cracking feedstock.

[0075] In one specific embodiment of the present invention, the ethylene cracking method includes:

[0076] The catalytic cracking regeneration flue gas discharged from the outlet of the first regenerator 3 (including the catalytic cracking regeneration flue gas generated by the second regenerator 4 and transported to the first regenerator 3) is transported to the third-stage cyclone separator 5 for preliminary dust removal and purification, and then transported to the flue gas turbine 6. The flue gas turbine 6 transports the catalytic cracking regeneration flue gas to the radiation section 11, where CO combustion releases heat.

[0077] The cold pyrolysis feedstock is fed to the pyrolysis feedstock preheating section 17 for preheating. The resulting hot pyrolysis feedstock is mixed with dilution steam and then fed into the radiation section 11 for pyrolysis reaction to produce pyrolysis gas. After the pyrolysis gas is discharged from the radiation section 11, it is transported to the catalytic cracking fractionation tower for rapid cooling via the pyrolysis gas pipeline 110. Low-carbon olefins are further recovered using units such as catalytic cracking fractionation, absorption stabilization, dual desulfurization, gas separation, and C2 recovery.

[0078] The waste heat from CO combustion in the radiation section 11 is further recovered by generating ultra-high pressure superheated steam, ultra-high pressure saturated steam, and high pressure superheated steam, preheating boiler feedwater, and preheating pyrolysis feedstock. Furthermore, the SCR denitrification section 13 and the flue gas desulfurization and dust removal unit remove pollutants such as NOx, SOx, and dust from the catalytic cracking regeneration flue gas to meet environmental emission standards. In this invention, SOx represents sulfur oxides.

[0079] It should be noted that the cracking reaction referred to in this invention refers to the production of ethylene from petroleum hydrocarbon steam cracking.

[0080] The ethylene cracking system and ethylene cracking method provided by the present invention will be further described in detail below through embodiments.

[0081] Example 1

[0082] Part 1: Ethylene Cracking System

[0083] like Figure 1 As shown, the ethylene cracking system provided in this embodiment includes a catalytic cracking regeneration unit, an ethylene cracking unit, and a flue gas desulfurization and dust removal unit connected in sequence. The catalytic cracking regeneration unit includes a first regenerator 3, a second regenerator 4, a third-stage cyclone separator 5, and a flue gas turbine 6. The ethylene cracking unit includes a CO combustion cracking furnace 1 and a steam drum 2. The CO combustion cracking furnace 1 includes a radiation section 11, an ultra-high pressure steam superheating section 12, an SCR denitrification section 13, a high pressure steam superheating section 14, an evaporation section 15, an economizing section 16, and a cracking feedstock preheating section 17.

[0084] The first regenerator 3 and the second regenerator 4 are arranged in an overlapping manner. The catalytic cracking regeneration flue gas produced by the second regenerator 4 enters the first regenerator 3. The CO content in the catalytic cracking regeneration flue gas emitted from the outlet of the first regenerator 3 is 5-6 vol% (dry basis). The outlet of the first regenerator 3 passes through a regeneration flue ( Figure 1 (Not marked in the text) is connected to the inlet of the third-stage cyclone separator 5; the outlet of the third-stage cyclone separator 5 is connected to the flue gas three-cyclone outlet flue ( Figure 1 (Not marked in the text) is connected to the inlet of the flue gas turbine 6; the outlet flue of the flue gas turbine 6 ( Figure 1 (Not marked in the text) Connects to the inlet of CO combustion pyrolysis furnace 1; the outlet of CO combustion pyrolysis furnace 1 is connected to the pyrolysis furnace outlet flue ( Figure 1 (Not marked in the text) is connected to the inlet of the flue gas desulfurization and dust removal unit; the outlet of the flue gas desulfurization and dust removal unit is connected to the purification flue duct 118.

[0085] Four radiant furnace tube groups 102 are arranged within the radiant section 11, each group comprising 400 radiant furnace tubes; four low-NOx burners 18 are also installed at the inlet of the radiant section 11; eight ultra-high pressure steam superheating tube groups 103 are arranged within the ultra-high pressure steam superheating section 12, each group comprising 100 ultra-high pressure steam superheating tubes; four high-pressure steam superheating tube groups 104 are arranged within the high-pressure steam superheating section 14, each group comprising 100 high-pressure steam superheating tubes. The steam superheater tubes; the evaporation section 15 has 4 steam generating tube groups 105, each steam generating tube group 105 including 100 steam generating tubes; the economizing section 16 has 2 boiler feedwater preheating tube groups 106, each boiler feedwater preheating tube group 106 including 50 boiler feedwater preheating tubes; the cracking feedstock preheating section 17 has 2 cracking feedstock preheating tube groups 107, each cracking feedstock preheating tube group 107 including 100 cracking feedstock preheating tubes; the SCR denitrification section 13 has 3 denitrification catalyst beds.

[0086] The inlet of the radiant furnace tube assembly 102 is connected to the outlet of the pyrolysis feedstock preheating tube assembly 107 and the dilution steam line 108. The inlet of the pyrolysis feedstock preheating tube assembly 107 is connected to the cold pyrolysis feedstock line 109. The outlet of the radiant furnace tube assembly 102 is connected to the pyrolysis gas line 110. The inlet and outlet of the ultra-high pressure steam superheating tube assembly 103 are respectively connected to the ultra-high pressure saturated steam outlet of the steam drum 2. Figure 1 (Not marked in the text) and ultra-high pressure superheated steam pipeline 111; the inlet of ultra-high pressure steam superheated pipe assembly 103 is also connected to an external ultra-high pressure saturated steam pipeline 113; the inlet and outlet of high pressure steam superheated pipe assembly 104 are connected to high pressure saturated steam pipeline 114 and high pressure superheated steam pipeline 115 respectively; the inlet and outlet of steam generating pipe assembly 105 are connected to the circulating hot water outlet of steam drum 2 (not marked in the text) Figure 1 (not marked in the text) and the soft drink mixture inlet ( Figure 1 (Not marked in the text) Connections; the inlet and outlet of the boiler feedwater preheating pipe assembly 106 are respectively connected to the deaerator water pipeline 116 and the water inlet of the steam drum 2. Figure 1 (Not marked in the text) Connections; The outlet of the boiler feedwater preheating tube group 106 is also connected to the external boiler feedwater pipeline 117; The denitrification catalyst bed is connected to the denitrification agent pipeline 112;

[0087] The inlet of the radiant furnace tube group 102 and the outlet of the pyrolysis feedstock preheating tube group 107 are connected by a pyrolysis feedstock pipeline. Figure 1 (Not marked in the text) connection; dilution steam pipeline 108 is connected to the pyrolysis raw material pipeline ( Figure 1(Not marked) to achieve connection with the inlet of the radiant furnace tube group 102; an ultra-high pressure saturated steam pipeline is installed at the inlet of the ultra-high pressure steam superheated tube group 103. Figure 1 (Not marked in the text) An ultra-high pressure saturated steam pipeline is installed at the ultra-high pressure saturated steam outlet of steam drum 2. Figure 1 (Not shown in the text) This connects the ultra-high pressure saturated steam pipeline and the ultra-high pressure saturated steam pipeline of the steam drum, thus connecting the inlet of the ultra-high pressure steam superheater tube group 103 and the ultra-high pressure saturated steam outlet of the steam drum 2; the external ultra-high pressure saturated steam pipeline 113 connects to the ultra-high pressure saturated steam superheater tube group 103 by connecting the ultra-high pressure saturated steam pipeline; a circulating hot water pipeline is installed between the inlet of the steam generating tube group 105 and the circulating hot water outlet of the steam drum 2. Figure 1 (Not shown in the diagram) A steam-water mixing pipeline is installed between the outlet of the steam generator assembly 105 and the steam-water mixture inlet of the steam drum 2. Figure 1 (Not shown in the text) Connects the inlet and outlet of the steam generating tube assembly 105 to the circulating hot water outlet and steam-water mixture inlet of the steam drum 2, respectively; and installs a boiler feedwater main pipe at the outlet of the boiler feedwater preheating tube assembly 106. Figure 1 (Not shown in the diagram), a steam drum water supply pipeline is installed at the water inlet of steam drum 2. Figure 1 (Not marked in the text) connects the boiler feedwater main and the steam drum water supply line to connect the outlet of the boiler feedwater preheating tube group 106 and the water inlet of the steam drum 2; the external boiler feedwater line 117 connects to the outlet of the boiler feedwater preheating tube group 106 by connecting to the boiler feedwater main; the inlet of the flue gas desulfurization and dust removal unit and the outlet of the CO combustion cracking furnace 1 are connected by setting a cracking furnace outlet flue ( Figure 1 (Connections not marked in the text)

[0088] Part Two: Ethylene Cracking Methods

[0089] Utilize Figure 1 The ethylene cracking system shown in the diagram delivers the catalytic cracking regeneration flue gas generated by the catalytic cracking regeneration unit to the ethylene cracking unit for combustion. The heat generated from the combustion of CO in the catalytic cracking regeneration flue gas is used for the cracking reaction to produce cracked gas. The cracked gas is then delivered to the product separation system of the catalytic cracking unit. Figure 1 (Not shown in the image) Low-carbon olefins are recovered; in the ethylene cracking unit, the waste heat of CO combustion is recovered by generating ultra-high pressure superheated steam, ultra-high pressure saturated steam and high pressure superheated steam, preheating boiler feedwater and preheating cracking feedstock.

[0090] Specifically: the catalytic cracking regeneration flue gas discharged from the outlet of the first regenerator 3 is transported to the third-stage cyclone separator 5 for preliminary dust removal and purification, and then transported to the flue gas turbine 6. The flue gas turbine 6 transports the catalytic cracking regeneration flue gas to the radiation section 11, where CO combustion releases heat.

[0091] The cold cracking feedstock is transported to the cracking feedstock preheating section 17 for preheating. The resulting hot cracking feedstock is mixed with dilution steam and then fed into the radiation section 11 for cracking reaction to produce cracked gas. After being discharged from the radiation section 11, the cracked gas is transported to the catalytic cracking fractionation tower for rapid cooling via the cracked gas pipeline 110. Low-carbon olefins are further recovered using units such as catalytic cracking fractionation, absorption stabilization, dual desulfurization, gas separation, and C2 recovery.

[0092] The waste heat from CO combustion in the radiation section 11 is further recovered by generating ultra-high pressure superheated steam, ultra-high pressure saturated steam and high pressure superheated steam, preheating boiler feedwater and preheating pyrolysis feedstock; and the SCR denitrification section 13 and flue gas desulfurization and dust removal unit remove pollutants such as NOx, SOx and dust from the catalytic cracking regeneration flue gas, turning it into purified flue gas, which is discharged from the system through the purified flue duct 118 to achieve emissions that meet environmental protection standards.

[0093] Comparative Example 1

[0094] Part 1: Conventional Ethylene Cracking System

[0095] like Figure 2 As shown, the conventional ethylene cracking system includes a conventional ethylene cracking furnace 7, a quench boiler 8, and a steam drum 2. The conventional ethylene cracking furnace 7 is equipped with a radiant section 71 and a convection section 72. However, [the following is unclear and likely refers to a separate section:] ... Figure 2 As shown, the convection section 72 of the pyrolysis furnace is equipped with a pyrolysis feedstock preheater, a boiler feedwater preheater, a dilution steam preheater, and an ultra-high pressure steam superheater.

[0096] A radiant furnace tube 701 is installed in the radiant section 71 of the pyrolysis furnace; low NOx burners 18 are arranged at multiple inlets of the radiant section 71 of the pyrolysis furnace, and the low NOx burners 18 are all connected to the fuel gas network of the unit through the supplementary combustion gas pipeline 101.

[0097] Part Two: Conventional Ethylene Cracking Methods

[0098] Utilize Figure 2 The conventional ethylene cracking system shown introduces cracking feedstock 702 into radiant furnace tube 701, where a cracking reaction occurs at high temperature to produce cracked gas 703. The heat required for the cracking reaction is provided by low-NOx burner 18 burning fuel supplied by supplementary combustion gas pipeline 101.

[0099] The cracked gas 703 is sent to the quench boiler 8 for quenching, and then sent to the subsequent separation system to recover low-carbon olefins.

[0100] Practical application evaluation and comparison

[0101] The conventional ethylene cracking furnace provided in Comparative Example 1 requires a large amount of fuel gas, which accounts for 50%-80% of the energy consumption of the entire ethylene plant. In contrast, the ethylene cracking system and method provided in Example 1, using a CO combustion cracking furnace, only requires a small amount of fuel gas for CO supplementary combustion in the catalytic cracking regeneration flue gas. Compared to Comparative Example 1, this significantly reduces fuel gas consumption and substantially lowers ethylene cracking energy consumption, carbon emissions, and operating costs. It also further saves on investment, land use, and energy consumption in the separation system. A detailed comparison is provided below using a 1.8 million tons / year high-yield ethylene-propylene catalytic cracking unit as an example.

[0102] For a catalytic cracking unit with a capacity of 1.8 million tons / year producing more ethylene and propylene:

[0103] When using the conventional ethylene cracking system and method provided in Comparative Example 1, two separate cracking furnaces are required to process the ethane, propane, and C4 alkylates produced by the high-yield ethylene-propylene catalytic cracking unit. In this case, it is calculated that 22 t / h of fuel gas is needed to provide heat for the two cracking furnaces.

[0104] Using the ethylene cracking system and method provided in Example 1, when the heat generated by the combustion of CO in the catalytic cracking regeneration flue gas is used to provide heat for the cracking reaction, only 2t / h of fuel gas needs to be consumed to supplement the heat to meet the heat requirements of the cracking reaction in the CO combustion cracking furnace.

[0105] As can be seen, compared with conventional ethylene cracking systems and methods, the ethylene cracking system and method provided by this invention reduce fuel gas consumption, fuel operating costs, and carbon dioxide emissions by more than 90%. At the same time, this invention combines the cracking furnace and the original CO combustion boiler of the unit into a CO combustion cracking furnace, which can reduce the investment in two cracking furnaces and supporting equipment, pipelines, instruments, structures, etc., thereby reducing the investment in the entire multi-yield ethylene and propylene catalytic cracking unit by more than 10%.

[0106] It should be understood that the embodiments disclosed herein are not limited to the specific structures, processing steps, or materials disclosed herein, but should be extended to equivalent substitutions of these features as understood by those skilled in the art. It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

[0107] In the description of this invention, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," "tail," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0108] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0109] Certain terms are used throughout this application to refer to specific system components. As those skilled in the art will recognize, the same components may often be referred to by different names, and therefore this application is not intended to distinguish components that differ only in name and not in function. The terms "an embodiment" or "embodiment" used in the specification mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Therefore, the phrase "an embodiment" or "embodiment" appearing throughout the specification does not necessarily refer to the same embodiment.

[0110] The embodiments of the present invention are given for illustrative and descriptive purposes only, and are not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention, and to enable those skilled in the art to understand the invention and to design various embodiments with various modifications suitable for a particular purpose.

[0111] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and / or modifications falling within the scope of the invention, and all changes and / or modifications made according to embodiments of the invention should be covered within the protection scope of the invention.

Claims

1. An ethylene cracking system, characterized in that, The ethylene cracking system includes a catalytic cracking regeneration unit and an ethylene cracking unit; wherein... The catalytic cracking regeneration unit is used for the coking and regeneration of the spent catalyst to generate catalytic cracking regeneration flue gas, which is then transported to the ethylene cracking unit. The ethylene cracking unit is used to carry out a cracking reaction by utilizing the heat generated by the combustion of CO in the catalytic cracking regeneration flue gas, and to recover the waste heat from the CO combustion.

2. The ethylene cracking system according to claim 1, characterized in that, The ethylene cracking unit includes a CO combustion cracking furnace (1) and a steam drum (2); The CO combustion pyrolysis furnace (1) includes a radiation section (11), an ultra-high pressure steam superheating section (12), an SCR denitrification section (13), a high pressure steam superheating section (14), an evaporation section (15), an economizing section (16), and a pyrolysis feedstock preheating section (17); wherein, The radiation section (11) is used to burn CO in the catalytic cracking regeneration flue gas and use the heat generated by CO combustion for cracking reaction; the ultra-high pressure steam superheating section (12), high pressure steam superheating section (14), evaporation section (15), coal saving section (16), cracking feedstock preheating section (17) and steam drum (2) are used to recover the waste heat of CO combustion in the radiation section (11); the SCR denitrification section (13) is used to remove NOx in the catalytic cracking regeneration flue gas.

3. The ethylene cracking system according to claim 2, characterized in that, The catalytic cracking regeneration unit includes a first regenerator (3), a second regenerator (4), a third-stage cyclone separator (5), and a flue gas turbine (6); wherein, The first regenerator (3) and the second regenerator (4) are both used for the coking and regeneration of the catalyst to be generated, producing the catalytic cracking regeneration flue gas; the outlet of the second regenerator (4) is connected to the inlet of the first regenerator (3), and is used to transport the catalytic cracking regeneration flue gas generated by the second regenerator (4) to the first regenerator (3). The outlet of the first regenerator (3) is connected to the inlet of the third-stage cyclone separator (5), the outlet of the third-stage cyclone separator (5) is connected to the inlet of the flue gas turbine (6), and the outlet of the flue gas turbine (6) is connected to the inlet of the CO combustion cracking furnace (1). This is used to transport the catalytic cracking regeneration flue gas generated by the first regenerator (3) and the second regenerator (4) to the CO combustion cracking furnace (1) for combustion after preliminary dust removal and purification, so as to provide heat for the cracking reaction.

4. The ethylene cracking system according to claim 2, characterized in that, A low-NOx burner (18) is installed at the entrance of the radiation section (11). The low-NOx burner (18) is connected to the fuel gas network of the device through a supplementary combustion gas pipeline (101) and is used to burn supplementary fuel to supplement the heat of the cracking reaction.

5. The ethylene cracking system according to claim 2, characterized in that, The radiation section (11), ultra-high pressure steam superheating section (12), high pressure steam superheating section (14), evaporation section (15), coal-saving section (16), and cracking feedstock preheating section (17) are respectively equipped with radiation furnace tube group (102), ultra-high pressure steam superheating tube group (103), high pressure steam superheating tube group (104), steam generation tube group (105), boiler feedwater preheating tube group (106), and cracking feedstock preheating tube group (107); the SCR denitrification section (13) is equipped with a denitrification catalyst bed.

6. The ethylene cracking system according to claim 5, characterized in that, The inlet of the radiant furnace tube assembly (102) is connected to the outlet of the cracking feedstock preheating tube assembly (107) and the dilution steam line (108). The inlet of the cracking feedstock preheating tube assembly (107) is connected to the cold cracking feedstock line (109), and the outlet of the radiant furnace tube assembly (102) is connected to the cracking gas line (110). This is used to preheat the cracking feedstock using the waste heat from the CO combustion, and then transport the hot cracking feedstock and dilution steam to the radiant furnace tube assembly (102) for the cracking reaction. The resulting cracked gas is transported downstream to recover low-carbon olefins.

7. The ethylene cracking system according to claim 5, characterized in that, The inlet and outlet of the ultra-high pressure steam superheated tube group (103) are respectively connected to the ultra-high pressure saturated steam outlet and the ultra-high pressure superheated steam pipeline (111) of the steam drum (2), and are used to generate ultra-high pressure superheated steam to recover the waste heat of the CO combustion. The denitrification catalyst bed inlet is connected to a denitrification agent pipeline (112), which is used to introduce denitrification agent into the denitrification catalyst bed to react with NOx in the catalytic cracking regeneration flue gas, thereby achieving NOx removal; Preferably, the inlet of the ultra-high pressure steam superheated pipe group (103) is also connected to an external ultra-high pressure saturated steam pipeline (113) to supplement ultra-high pressure saturated steam for the generation of ultra-high pressure superheated steam.

8. The ethylene cracking system according to claim 5, characterized in that, The inlet and outlet of the high-pressure steam superheated pipe assembly (104) are connected to the high-pressure saturated steam pipeline (114) and the high-pressure superheated steam pipeline (115), respectively, for generating high-pressure superheated steam to recover the waste heat from the combustion of CO.

9. The ethylene cracking system according to claim 5, characterized in that, The inlet and outlet of the steam generating pipe assembly (105) are respectively connected to the circulating hot water outlet and the steam-water mixture inlet of the steam drum (2) to recover the waste heat from the CO combustion to heat the circulating hot water from the steam drum (2) and provide the steam-water mixture to the steam drum (2) to generate the ultra-high pressure saturated steam. The inlet and outlet of the boiler feedwater preheating pipe assembly (106) are respectively connected to the deoxygenated water pipeline (116) and the water inlet of the steam drum (2); the deoxygenated water is heated by recovering the waste heat from the combustion of CO, and the boiler feedwater is provided to the steam drum (2).

10. The ethylene cracking system according to claim 1, characterized in that, The ethylene cracking system also includes a flue gas desulfurization and dust removal unit; the flue gas desulfurization and dust removal unit is connected to the ethylene cracking unit and is used to purify the catalytic cracking regeneration flue gas discharged from the ethylene cracking unit after CO combustion, waste heat recovery and NOx removal by means of desulfurization and dust removal.

11. The ethylene cracking system according to any one of claims 1 to 10, characterized in that, The catalytic cracking regeneration flue gas generated by the catalytic cracking regeneration unit is 100% on a dry basis, and the CO content is 1-15 vol.

12. A method for ethylene cracking, characterized in that, The ethylene cracking system according to any one of claims 1 to 11 comprises: The catalytic cracking regeneration flue gas generated by the catalytic cracking regeneration unit is fed into the ethylene cracking unit for combustion. The heat generated by the combustion of CO in the catalytic cracking regeneration flue gas is used for cracking reaction to produce cracked gas. The cracked gas is then fed into the product separation system of the catalytic cracking unit to recover low-carbon olefins. In the ethylene cracking unit, the waste heat from CO combustion is recovered by generating ultra-high pressure superheated steam, ultra-high pressure saturated steam and high pressure superheated steam, preheating boiler feedwater and preheating cracking feedstock.

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