Carbon dioxide emission reduction method in catalyst regeneration process

Abstract

The invention discloses a method for realizing carbon dioxide emission reduction in a catalyst regeneration process, regenerated flue gas is subjected to dust removal and pressure reduction to obtain low-pressure flue gas, the low-pressure flue gas is divided into a first flue gas material flow and a second flue gas material flow, the first flue gas material flow is subjected to heat exchange, denitration and desulfurization dust removal treatment to obtain desulfurized flue gas, and the desulfurized flue gas is subjected to heat exchange, denitration and desulfurization dust removal treatment to obtain a second flue gas material flow; water vapor in the desulfurized flue gas is removed to obtain low-humidity flue gas, part of the low-humidity flue gas serves as circulating flue gas to participate in catalyst regeneration, part of the low-humidity flue gas and hydrogen are subjected to a combustion reaction, deoxidized flue gas is obtained, and high-concentration carbon dioxide is obtained after the deoxidized flue gas is dehydrated; the second flue gas material flow is subjected to heat exchange with the circulating flue gas or is returned together with the circulating flue gas to participate in catalyst regeneration or is mixed with the first flue gas material flow in the denitration process, and heat exchange, desulfurization and dust removal are continued to obtain desulfurized flue gas. The method solves the problems of large total carbon dioxide emission, low carbon dioxide concentration and high trapping cost of a hydrocarbon processing device in the prior art.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon dioxide emission reduction, and in particular to a method for reducing carbon dioxide emission in a catalyst regeneration process. Background Art

[0002] As the most important secondary processing method for oil processing in my country, the catalytic cracking process undertakes the production tasks of 70% of gasoline, 35% of diesel and 40% of propylene in my country. It is an important means of heavy oil processing and occupies a pivotal position in my country's oil refining industry. By 2021, PetroChina will start operation of about 40 catalytic cracking units, with an annual processing capacity of nearly 60 million tons, and emit about 17 million tons of carbon dioxide into the atmosphere each year, accounting for about 31% of the refinery's carbon emissions. Taking vacuum distillate as raw oil, the catalytic cracking unit with an annual processing capacity of about 2.5 million tons is taken as an example. The carbon dioxide generated by coking alone is as high as 400-500kt per year, which has a significant impact on the environment. At the same time, as the slag blending ratio of the catalytic cracking unit gradually increases, the contradiction between the coke yield and the processing capacity and carbon emissions of the unit becomes more acute. At present, the carbon emission reduction means of the catalytic cracking unit are mainly to develop low-coking catalysts, reduce the coking amount of the unit and thus reduce the carbon emissions of the unit. However, due to the heat balance characteristics of the catalytic cracking unit, the heat generated by the burning of the regeneration part provides the heat required by the reaction part through the catalyst circulation, so the degree of reducing the carbon emissions of the catalytic unit by reducing the amount of coke is limited. On the other hand, the current oil refining industry is facing the pressure of "reducing oil and increasing chemicals". The catalytic cracking unit also needs to increase the production of "trienes, triphenyls" and other chemical raw materials by means of increasing the reaction temperature, and the corresponding coke yield and carbon emissions will also increase accordingly, further exacerbating the contradiction between the future production of catalytic cracking units and carbon emission reduction.

[0003] At present, driven by the policy and situation of green and low-carbon development, some industries with high carbon emissions (such as thermal power generation and steel industry) have launched carbon dioxide capture projects to reduce carbon emissions in the industry. Through the practice of these carbon emission reduction projects in the industry, it can be concluded that the capture cost of carbon dioxide is proportional to the concentration of carbon dioxide in the exhaust gas. However, the concentration of carbon dioxide in the flue gas of catalytic cracking regeneration is low, generally 10-20v%, and the energy consumption of direct capture and utilization is large. Higher carbon dioxide concentration usually means lower carbon dioxide capture cost. Therefore, increasing the carbon dioxide concentration or even directly increasing the carbon dioxide concentration in the flue gas to a usable level (such as carbon dioxide concentration ≥95v% for oil recovery and underground storage carbon dioxide concentration ≥90v%) will be an effective way to reduce the cost of carbon dioxide capture. Based on this background, a catalyst regeneration method that can significantly increase the carbon dioxide concentration is developed for FCC units. Reducing carbon dioxide emissions from FCC units is particularly important for the realization of the "dual carbon goals" of the refining industry.

[0004] Patent CN103725309A discloses a catalyst regeneration method for reducing carbon dioxide emissions. The carbon-bearing catalyst is first partially regenerated in a coke burner with pure oxygen, and then enters the dense phase bed of the regeneration device through a dilute phase pipe to burn the remaining coke. A heat collector is set on the dense phase bed to control the temperature of the dense phase bed. The flue gas is separated by a cyclone and then enters the flue gas energy recovery system and the carbon dioxide separation system in turn to separate the carbon dioxide and capture it. The regenerated catalyst is directly returned to the reactor for recycling. This method can not only completely regenerate the catalyst, but also make the catalyst activity more evenly distributed, thereby reducing the yield of coke and dry gas byproducts of catalytic cracking; it can also significantly reduce carbon emissions, even to zero carbon emissions.

[0005] Patent CN103721766A discloses a catalyst regeneration method for reducing carbon dioxide emissions and improving selectivity. The carbon-bearing catalyst is first partially regenerated in the first regenerator with pure oxygen, and then enters the second regenerator located below the first regenerator through an external circulation pipe to burn the remaining coke with pure oxygen. The catalyst coming out of the first regenerator enters the external heat exchanger, and returns to the second regenerator after cooling. Most of the flue gas enters the flue gas energy recovery system and the carbon dioxide separation system in turn after separating carbon dioxide and capturing it. A small amount of flue gas is circulated to the bottom of the second regenerator. The regenerated catalyst enters the reactor for recycling after the catalyst is cooled and activated. This method can not only completely regenerate the catalyst, but also make the catalyst activity more evenly distributed, thereby reducing the yield of coke and dry gas byproducts of catalytic cracking; it can also greatly reduce carbon emissions, and even achieve zero carbon emissions.

[0006] Patent CN103721763A discloses a catalyst regeneration method for reducing carbon dioxide emissions and improving selectivity. The carbon-carrying catalyst first ascends in a charring tube under the influence of pure oxygen gas, and a coke combustion reaction occurs. The charring ratio in the charring tube is 30-50%. The catalyst coming out of the charring tube burns the remaining coke with pure oxygen. The flue gas is separated by a cyclone and then enters the flue gas energy recovery system and the carbon dioxide separation system in turn to separate carbon dioxide and capture it. The regenerated catalyst enters the reactor for recycling after the catalyst is cooled and activated. This method can not only completely regenerate the catalyst, but also make the catalyst activity more evenly distributed, thereby reducing the yield of coke and dry gas as byproducts of catalytic cracking; it can also significantly reduce carbon emissions, and even achieve zero carbon emissions.

[0007] Patent CN103725311A discloses a catalyst regeneration method for reducing carbon dioxide emissions and improving selectivity. The carbon-bearing catalyst is first regenerated in the first regenerator with pure oxygen, and then enters the second regenerator through a U-shaped conveying pipe to burn the remaining coke with pure oxygen. The flue gas from the first regenerator is divided into three parts, wherein the first part of the flue gas is circulated and supplemented to the bottom of the second regenerator; the second part sends the semi-regenerated catalyst from the first regenerator to the second regenerator; the third part enters the flue gas energy recovery system; the flue gas from the second regenerator and the flue gas from the first regenerator from the flue gas energy recovery system are combined and then enter the carbon dioxide separation system, and the carbon dioxide is separated and captured. The regenerated catalyst enters the reactor for recycling after the catalyst is cooled and activated. This method can not only completely regenerate the catalyst, but also make the catalyst activity more evenly distributed, thereby reducing the yield of catalytic cracking byproducts coke and dry gas; it can also greatly reduce carbon emissions, and even achieve zero carbon emissions.

[0008] Patent CN113582179B discloses a process for fully recovering carbon dioxide emitted from a catalytic cracking regeneration unit, and the system required for the process includes a catalytic cracking regeneration unit, a flue gas recovery unit, a high-temperature flue gas fan, an oxygen production unit, and a carbon-based gas mixer. The present invention circulates the flue gas of the catalytic cracking regeneration unit, and the concentration of carbon dioxide is increased, making it easier to capture carbon dioxide, creating favorable conditions for low-cost CCUS, reducing carbon dioxide emissions, and reducing the greenhouse effect. At the same time, the circulating flue gas and oxygen are mixed to produce carbon-based gas, and the carbon-based gas is used as the combustion-supporting gas of the catalytic cracking regeneration unit. Carbon dioxide replaces nitrogen, avoids the generation of nitrogen oxides during the combustion process, reduces environmental pollution, and greatly reduces the cost of denitrification. After carbon dioxide replaces nitrogen, the radiation intensity in the catalytic cracking regeneration unit is greatly improved, promoting the reaction of C+CO2→CO, greatly enhancing the combustion effect, and the reaction is more complete, achieving a significant effect of energy saving and consumption reduction.

[0009] In the above technologies, the oxygen content of the flue gas is relatively high, and the total amount of oxygen used is large, which will increase the risk of secondary combustion in the regenerator and the cost of the catalyst regeneration process; the flue gas enters the regenerator cycle without being treated, and the content of sulfur oxides, nitrogen oxides, water vapor and other substances in the flue gas will gradually increase during the circulation process, which will have an adverse effect on the physical and chemical properties of the catalyst in the regenerator.

[0010] Patent CN113877371A discloses a catalytic cracking regeneration method with zero carbon dioxide emission. It includes the following steps: air is compressed and separated, and the oxygen obtained is used for catalyst regeneration, and then the regenerated flue gas is separated from the catalyst to recover the flue gas pressure energy and heat energy; the regenerated flue gas heats the desorption tower bottom material to become low-temperature flue gas; the low-temperature flue gas is separated and desulfurized to remove water vapor to obtain dry flue gas, part of which is sent to the flue gas circulation compressor for pressurization and circulation, and the other part is used to absorb and enrich the carbon dioxide to obtain lean gas and rich liquid; the rich liquid enters the desorption tower for desorption, and the alcohol amine solution and carbon dioxide are recovered; a part of the alcohol amine solution is heat-exchanged with the flue gas discharged from the waste heat boiler and then returned to the desorption tower, and the other part is heat-exchanged with the fresh alcohol amine solution after the desorption tower feed heater is mixed and entered into the absorption tower; the recovered carbon dioxide is used for storage or oil recovery. The present invention is a catalytic cracking regeneration method that effectively reduces carbon emissions from the source.

[0011] Patent CN113877397A discloses a non-complete regeneration method for catalytic cracking with zero emission of carbon dioxide. It includes the following steps: air compression; air separation to obtain pure oxygen; pure oxygen and carbon dioxide pressurized by the circulating compressor are mixed, the catalyst is charred and regenerated to obtain regenerated flue gas; the regenerated flue gas separates the catalyst fine powder in the flue gas; the regenerated flue gas without catalyst fine powder is subjected to pressure energy recovery, and then the flue gas heat energy is recovered to obtain low-temperature flue gas discharged from the waste heat boiler; the low-temperature flue gas is desulfurized and water vapor is removed to obtain dry flue gas; the dry flue gas enters the pressure swing adsorption device for gas separation to obtain waste gas, high-concentration carbon monoxide and high-concentration carbon dioxide respectively; the waste gas is directly discharged, and the high-concentration carbon monoxide is used as a chemical raw material or fuel; a part of the high-concentration carbon dioxide is used as circulating carbon dioxide, and the other part is directly used for storage or oil recovery. On the basis of the existing catalytic cracking regeneration process, the present invention realizes the effective reduction of carbon emissions from the source.

[0012] The above technologies use alcohol amine solution or pressure swing adsorption to purify carbon dioxide, and the energy consumption is relatively high. The low-temperature dehydration equipment has high energy consumption. The corrosion of the main fan caused by flue gas circulation under long-term working conditions is not considered, and the impact of circulating flue gas / oxygen regeneration on the regeneration temperature is not considered.

[0013] Patent CN101497811A provides a method for heating an FCC unit having a regenerator and a reactor for overall CO2 reduction. The method comprises compressing a syngas to obtain a compressed syngas. A first gas stream containing CO2 is separated from the compressed syngas. A second gas stream containing O2 is expanded with the first gas stream to obtain a feed gas. The feed gas is introduced into the regenerator, and the regenerator burns coke on a severely coked spent catalyst from the reactor under gasification conditions, thereby generating syngas and heat for operating the reactor at a reaction temperature.

[0014] Patent CN101538475A provides a method for heating a fluidized catalytic cracking unit having a reactor and a regenerator for overall carbon dioxide reduction. The method includes compressing synthesis gas to obtain compressed synthesis gas. CO2 is separated from the compressed synthesis gas to provide a first gas stream containing CO2. The first gas stream is expanded with a second gas stream containing O2 to obtain a feed gas. The feed gas and the injected hydrocarbon feed are introduced into a regenerator containing a spent catalyst from the reactor. The regenerator burns the injected hydrocarbon feed and coke from the spent catalyst under gasification conditions to produce synthesis gas and heat for operating the reactor at a reaction temperature.

[0015] The above technology injects solvent deasphalting asphalt into the regenerator to burn and supplement heat. The heavy metal content in asphalt is high, which easily leads to heavy metal pollution and deactivation of the catalyst. In addition, the uneven distribution of asphalt will cause local overheating of the catalyst during combustion, which will also destroy the catalyst activity. Summary of the invention

[0016] The object of the present invention is to provide a method for reducing carbon dioxide emissions during catalyst regeneration to solve the problem in the prior art that hydrocarbon processing equipment has a large total carbon dioxide emission but a low carbon dioxide concentration and high capture cost.

[0017] To achieve the above-mentioned purpose, the present invention provides a method for reducing carbon dioxide emissions during a catalyst regeneration process, wherein the regenerated flue gas is subjected to dust removal and pressure reduction to obtain low-pressure flue gas, and the low-pressure flue gas is divided into a first flue gas flow and a second flue gas flow, wherein the first flue gas flow is subjected to heat exchange, denitrification and desulfurization and dust removal to obtain desulfurized flue gas, and water vapor in the desulfurized flue gas is removed to obtain low-humidity flue gas, part of the low-humidity flue gas is used as circulating flue gas to participate in catalyst regeneration, and part of the low-humidity flue gas undergoes a combustion reaction with hydrogen to obtain deoxygenated flue gas, and the deoxygenated flue gas is dehydrated to obtain high-concentration carbon dioxide; the second flue gas flow is subjected to heat exchange with the circulating flue gas or is returned together with the circulating flue gas to participate in catalyst regeneration or is mixed with the first flue gas flow in the denitrification process, and continues to undergo heat exchange, desulfurization and dust removal to obtain desulfurized flue gas.

[0018] In the method for reducing carbon dioxide emissions during catalyst regeneration of the present invention, when the circulating flue gas returns to participate in catalyst regeneration, oxygen-containing gas needs to be supplemented as the regeneration main air, and the oxygen concentration in the regeneration main air is 20v%-25v%, preferably 21vol%-24vol%.

[0019] The method for reducing carbon dioxide emissions during catalyst regeneration of the present invention first stores the obtained desulfurized flue gas and then removes water vapor. The storage device has a venting pipeline and a sealing device to maintain system pressure and prevent external air from entering.

[0020] The method for achieving carbon dioxide emission reduction during catalyst regeneration described in the present invention, the operating pressure of the storage device is 5-30kPa (G), preferably 10-25kPa (G), and the amount of stored flue gas is greater than or equal to 2-5 times the regeneration main air volume required for burning per second during the catalyst regeneration process.

[0021] In the method of the present invention, the hydrogen and oxygen used can be produced by electrolysis of pure water, the energy of the water electrolysis device can come from photovoltaic power generation and / or wind power generation and / or hydropower generation, and the purity of the oxygen and hydrogen is not less than 99 vol%. When the low-humidity flue gas and hydrogen undergo combustion reaction, palladium or platinum can be used as a catalyst, and the hydrogen introduced reacts with the excess oxygen in the low-humidity flue gas to generate water, wherein the amount of hydrogen introduced is determined according to the excess oxygen amount.

[0022] In the method for reducing carbon dioxide emissions during catalyst regeneration of the present invention, the oxygen concentration in the regeneration flue gas is not higher than 8 vol%, preferably not higher than 5 vol%, and the low-pressure flue gas temperature is 400-650°C, preferably 450-600°C.

[0023] The method for achieving carbon dioxide emission reduction during the catalyst regeneration process described in the present invention is as follows: if the second flue gas flow is returned for catalyst regeneration, direct contact heat exchange is adopted when exchanging heat with the circulating flue gas; if the second flue gas flow is mixed with the first flue gas flow in the denitrification process, a partition wall heat exchanger is adopted when exchanging heat with the circulating flue gas.

[0024] In the method for reducing carbon dioxide emissions during catalyst regeneration of the present invention, the volume flow rate of the second flue gas stream accounts for 0-30% of the low-pressure flue gas.

[0025] In the method for reducing carbon dioxide emissions during catalyst regeneration of the present invention, the temperature of the circulating flue gas after heat exchange with the second flue gas flow is 40-150°C, preferably 60-120°C.

[0026] In the method for reducing carbon dioxide emissions during catalyst regeneration of the present invention, high-concentration carbon dioxide is used as a diluent gas during the denitration process.

[0027] The method for achieving carbon dioxide emission reduction during the catalyst regeneration process described in the present invention adopts a flue gas cooling device to remove water vapor in the desulfurized flue gas, wherein the flue gas cooling device includes a partition-type water-cooled heat exchanger and a gas-liquid separation tank, wherein the operating temperature of the gas-liquid separation tank is 10-40°C, and the water vapor content in the low-humidity flue gas is not higher than 4vol%, preferably not higher than 3vol%.

[0028] In the method for reducing carbon dioxide emissions during catalyst regeneration of the present invention, the volume flow of low-humidity flue gas that undergoes combustion reaction with hydrogen is 10%-30% of the total low-humidity flue gas.

[0029] The method for reducing carbon dioxide emissions during catalyst regeneration of the present invention uses triethylene glycol dehydration or solid adsorption dehydration to dehydrate the deoxygenated flue gas.

[0030] In the method for reducing carbon dioxide emissions during catalyst regeneration of the present invention, the concentration of the high-concentration carbon dioxide is not less than 99 vol%.

[0031] The method for reducing carbon dioxide emissions during catalyst regeneration of the present invention introduces circulating flue gas into the catalyst regeneration device through a main fan, and the main fan is provided with an air inlet and a circulating flue gas inlet.

[0032] The method for reducing carbon dioxide emissions during catalyst regeneration of the present invention also includes the step of preparing methanol by reacting high-concentration carbon dioxide with hydrogen.

[0033] Beneficial effects of the present invention:

[0034] 1. In the process of regeneration of coking catalyst, circulating flue gas / oxygen mixed gas is used as the main air to enter the regenerator for coking regeneration. The concentration of carbon dioxide in the flue gas is further increased by coking. Part of the flue gas rich in carbon dioxide is circulated back to the regenerator, and the other part is used to capture and store carbon dioxide, thereby achieving a significant reduction in carbon dioxide emissions and reducing the cost of carbon dioxide capture, helping refining and chemical companies achieve their carbon emission reduction goals.

[0035] 2. The water vapor contained in the circulating flue gas causes the dew point of the flue gas to increase. If it enters the main fan directly without heating, it will condense in the main fan. The circulating flue gas also contains sulfur oxides that have not been removed. Long-term operation will cause serious corrosion to the internal steel structure of the main fan. Heat exchange and heating of the circulating flue gas can make its temperature higher than the flue gas dew point, avoid corrosion, and ensure long-term operation of the device. Since the specific heat capacity of carbon dioxide is greater than that of nitrogen, using circulating flue gas / oxygen as the regeneration main air will take away more heat in the regenerator. Heat exchange of the circulating flue gas can also make up for this part of the heat loss, avoiding the regeneration temperature from dropping and affecting the charring efficiency.

[0036] 3. This method sets up a flue gas buffer tank and a venting pipeline, which can prevent abnormal pressure fluctuations during the flue gas circulation process from causing adverse effects on the entire device. The venting pipeline combined with the water seal tank can prevent the system from overpressure and avoid the entry of external air, thereby fundamentally ensuring the safety of the system.

[0037] 4. In this method, circulating flue gas / oxygen is used as the main regeneration air. The composition of the regenerated flue gas is carbon dioxide, water vapor, oxygen and a small amount of nitrogen oxides, sulfur oxides and catalyst dust. After desulfurization and denitrification treatment, the captured flue gas mainly contains carbon dioxide and excess oxygen. High-concentration carbon dioxide gas can be obtained by dehydration treatment after catalytic combustion, without the need for purification by chemical absorption, gas distillation and other methods. Therefore, the flue gas cooling device can use conventional water-cooled heat exchange without the need to add a refrigeration device. The captured flue gas uses catalytic combustion to remove excess oxygen. The high-concentration carbon dioxide concentration after dehydration can reach more than 99 vol%, which greatly reduces the energy consumption of the carbon dioxide capture process.

[0038] 5. In this method, the main fan is provided with air inlet and circulating flue gas inlet respectively. Air regeneration is adopted when starting the operation, and the generated flue gas is discharged through the chimney. After the device runs smoothly, the water seal tank is filled with water for liquid sealing. After the pressure of the flue gas buffer tank reaches the set value, the corresponding valve of the flue gas circulation pipeline is gradually opened, and the air inlet valve is gradually closed to realize the switching from air regeneration to circulating flue gas / oxygen regeneration. This method is compatible with air regeneration and circulating flue gas / oxygen regeneration, and improves the flexibility of the catalyst regeneration process. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A schematic flow chart of a method for reducing carbon dioxide emissions in a catalyst regeneration process provided by the present invention.

[0040] Wherein, the reference numerals are:

[0041] 1. Crude oil; 2. Riser reactor; 3. Stripping settler; 4. Oil and gas products; 5. Waiting inclined pipe; 6. Regeneration inclined pipe; 7. Regenerator; 8. Regeneration flue gas; 9. Three-stage cyclone separator; 10. Regeneration flue gas with catalyst dust removed; 11. Smoke machine; 12. First flue gas logistics; 13. Second flue gas logistics; 14. Second flue gas logistics after heat exchange; 15. Flue gas heat exchanger; 16. Hot cycle flue gas; 17. Waste heat boiler; 18. Water vapor generated by waste heat boiler; 19. Flue gas denitrification device; 20. Low-temperature flue gas; 21. Alkali liquid; 22. Sulfur-containing wastewater; 23. Flue gas desulfurization and dust removal tower; 24. Desulfurized flue gas; 25. Induced draft fan; 26. Flue gas buffer tank; 27. Wastewater outlet; 28. Venting pipeline; 29. ​​Sealed water seal tank; 30 chimney; 31 flue gas logistics at the outlet of the buffer tank; 32 cooling water; 33 partition-type water-cooled heat exchanger; 34 gas-liquid separation tank; 35 waste water; 36 low-humidity flue gas; 37 circulating flue gas; 38 captured flue gas; 39 hydrogen; 40 flue gas catalytic combustion reactor; 41 deoxygenated flue gas; 42 triethylene glycol; 43 triethylene glycol dehydration unit; 44 aqueous triethylene glycol solution; 45 high-concentration carbon dioxide; 46 carbon dioxide hydrogenation unit; 47 methanol product; 48 hydrogen; 49 hydrogen storage tank; 50 hydrogen produced by the water electrolysis unit; 51 water electrolysis unit; 52 pure water; 53 oxygen produced by the water electrolysis unit; 54 oxygen storage tank; 55 oxygen; 56 regenerated main air; 57 main fan; 58 air. DETAILED DESCRIPTION

[0042] The present invention is described in detail below by way of examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Those skilled in the art in this field can make some non-essential improvements and adjustments to the present invention based on the above content of the present invention.

[0043] Please refer to Figure 1First, the crude oil 1 contacts the regenerated catalyst from the regeneration inclined pipe 6 in the riser reactor 2 to undergo a catalytic cracking reaction, and then enters the stripping settler 3 for gas-solid separation to obtain an oil and gas product 4. The generated catalyst to be regenerated passes through the regeneration inclined pipe 5 and enters the regenerator 7 to undergo a charring regeneration reaction with the regeneration main air 56 to obtain a regenerated flue gas 8. The regenerated flue gas 8 passes through the three-stage cyclone separator 9 to remove the catalyst dust carried, and then obtains the regenerated flue gas 10 with the catalyst dust removed, and then enters the smoke exhaust fan 11 to recover the pressure energy. The flue gas at the outlet of the smoke exhaust fan 11 is divided into a flue gas flow 1 12 and a flue gas flow 2 13. The flue gas flow 1 12 enters the waste heat boiler 17 to generate water vapor 18, and the flue gas flow 2 13 enters the partition-type flue gas heat exchanger 15 to exchange heat with the circulating flue gas 37, and then passes through the flue gas denitrification device 19 to return to the waste heat boiler 17, or exchanges heat with the direct contact flue gas heat exchanger 15 and then enters the main air blower 57 to participate in catalyst regeneration. The low-temperature flue gas 20 from the waste heat boiler 17 enters the flue gas desulfurization and dust removal tower 23 and contacts with the alkaline solution 21 in countercurrent desulfurization and dust removal to obtain desulfurized flue gas 24, and generates sulfur-containing wastewater 22. The desulfurized flue gas 24 from the flue gas desulfurization and dust removal tower 23 is guided by the induced draft fan 25 into the flue gas buffer tank 26. A wastewater outlet 27 is provided at the bottom of the flue gas buffer tank 26. A venting pipeline 28 is provided at the top of the flue gas buffer tank 26 and is successively connected to a sealed water seal tank 29 and a chimney 30. The flue gas flow 31 from the flue gas buffer tank 26 enters the partition-type water-cooled heat exchanger 33, is cooled by cooling water 32, enters the gas-liquid separation tank 34, and obtains wastewater 35 and low-humidity flue gas 36 after gas-liquid separation. The low-humidity flue gas 36 is divided into circulating flue gas 37 and captured flue gas 38, wherein the circulating flue gas 37 enters the flue gas heat exchanger 15 and exchanges heat with the flue gas flow 2 13 to obtain hot circulating flue gas 16, and then the hot circulating flue gas 16 enters the main fan 57 for pressurization and mixes with the oxygen 55 from the oxygen storage tank 54 to obtain the regeneration main wind 56 to participate in the catalyst regeneration; the other captured flue gas 38 enters the flue gas catalytic combustion reactor 40 and reacts with hydrogen 39 under the action of the metal catalyst to obtain waste water 35 and deoxygenated flue gas 41, and then the deoxygenated flue gas 41 enters the triethylene glycol dehydration device 43 for further dehydration to obtain high-concentration carbon dioxide 45. The high-concentration carbon dioxide 45 and the hydrogen 48 from the hydrogen storage tank 49 enter the carbon dioxide hydrogenation device 46 to react to generate methanol 47. Pure water 52 enters the water electrolysis device 51 for electrolysis to generate hydrogen 50 and oxygen 53 for use in the entire process.

[0044] The present invention will be further described in the following examples, but the present invention is not limited thereto.

[0045] Start-up plan: According to Figure 1As shown in the process flow, the catalytic cracking unit adopts the traditional catalytic cracking start-up method when starting up, closes the valves on the second flue gas logistics pipeline 13, the heat cycle flue gas pipeline 16, the buffer tank outlet flue gas logistics pipeline 31, and the oxygen 55 pipeline, opens the valve on the air pipeline 58, does not inject water into the water seal tank 29, and the air is pressurized by the compressor 57 and enters the regenerator 7 to participate in the charring. The generated flue gas passes through the three-stage cyclone separator 9, the smoke exhaust fan 11, the waste heat boiler 17, the desulfurization and dust removal tower 23, the induced draft fan 25, the flue gas buffer tank 26, and the water seal tank 29 in turn, and is discharged through the chimney 30. The water electrolysis device 51 produces oxygen 53 and hydrogen 50, which are stored for standby use, so as to achieve stable operation of the device.

[0046] Air regeneration and circulating flue gas / oxygen switching: according to Figure 1 In the process flow shown, after the device is started and runs smoothly, cooling water is introduced into the partition-type water-cooled heat exchanger 33, water is injected into the water seal tank 29, and the triethylene glycol dehydration device 43 is opened. Then, the valve on the flue gas flow 31 pipeline at the outlet of the buffer tank is opened, and the circulating flue gas 37 is set to account for 80%. The valve on the oxygen 55 pipeline is gradually opened and adjusted, the valve on the hot circulating flue gas 16 pipeline is gradually opened and adjusted, the valve on the air 58 pipeline is gradually closed, and the valve on the second flue gas flow 13 pipeline is gradually opened and adjusted until the circulating flue gas / oxygen regeneration is completely adopted. Then, hydrogen 39 is introduced into the flue gas catalytic combustion reactor 40. As the flue gas circulates in the device, the residual nitrogen in the flue gas is gradually replaced by carbon dioxide. When the concentration of the high-concentration carbon dioxide 45 to be produced reaches 98 vol% or more, the carbon dioxide hydrogenation device 46 is opened to produce methanol. It should be noted that the use of carbon dioxide hydrogenation to produce methanol in the attached figure is only one of the ways to utilize carbon dioxide, and does not limit the use of carbon dioxide.

[0047] Source of raw materials or equipment: The raw material oil used in the embodiments and comparative examples is catalytic cracking raw material oil, and its properties are listed in Table 1. The catalyst is produced by the Catalyst Plant of Lanzhou Petrochemical Company of China National Petroleum Corporation, with the product number LDC-200, and its properties are listed in Table 2. 0.5% carbon monoxide combustion improver is added to the catalyst.

[0048] Evaluation and analysis methods:

[0049] Example:

[0050] The embodiments are carried out on a catalytic cracking riser pilot plant, such as Figure 1 The pilot plant only includes the reaction-regeneration part. Figure 1The rest of the process is simulated and calculated using process simulation software, wherein the ratio of the first / second regenerated flue gas is 1:1, the circulating flue gas adopts a partition heat exchange, the ratio of the captured flue gas / circulating flue gas is 1:4, the operating temperature of the gas-liquid separation tank is 20°C, and the main conditions of the process flue gas are listed in Table 4. The catalyst is regenerated according to the regeneration method provided by the present invention, and a circulating flue gas / oxygen mixed gas is introduced into the bottom of the regenerator, wherein the oxygen content is 21v%, and the circulating flue gas temperature is 150°C. The regenerated catalyst enters the reactor and contacts with the feedstock oil listed in Table 1 for catalytic cracking reaction. The regeneration conditions, reaction conditions, reaction product composition, regenerated catalyst carbon content and flue gas composition are all listed in Table 3.

[0051] Comparative Example 1

[0052] Comparative Example 1 was carried out on the same catalytic cracking riser pilot plant. The catalyst to be regenerated as in Example 1 was regenerated according to a conventional regeneration method, and air was introduced into the bottom of the regenerator, wherein the oxygen content was 21% by volume and the air temperature was 20°C. The regenerated catalyst entered the reactor and contacted with the feedstock oil listed in Table 1 to carry out catalytic cracking reaction. The regeneration conditions, reaction conditions, carbon content of the regenerated catalyst and flue gas composition are all listed in Table 3.

[0053] Comparative Example 2

[0054] Comparative Example 2 was carried out on a catalytic cracking riser pilot plant. Figure 1 The pilot plant only includes the reaction-regeneration part. Figure 1 The rest of the process is simulated and calculated using process simulation software, wherein the second flue gas flow does not enter the flue gas heat exchanger but enters the waste heat boiler together with the first regenerated flue gas, the circulating flue gas does not undergo flue gas heat exchange, the ratio of captured flue gas / circulating flue gas is 1:4, the operating temperature of the gas-liquid separation tank is 40°C, and the main conditions of the process flue gas are listed in Table 5. The catalyst is regenerated according to the regeneration method provided by the present invention, and a circulating flue gas / oxygen mixed gas is introduced into the bottom of the regenerator, wherein the oxygen content is 21v%, and the circulating flue gas temperature is 40°C. The regenerated catalyst enters the reactor and contacts with the feedstock oil listed in Table 1 for catalytic cracking reaction, and the regeneration conditions, reaction conditions, reaction product composition, regenerated catalyst carbon content and flue gas composition are all listed in Table 3.

[0055] From the comparison of the operating conditions and the results in Table 3, it can be seen that, compared with Comparative Example 1, the regeneration temperature is reduced less by adopting the regeneration method proposed in the present invention, the carbon content on the regenerated catalyst is basically the same as that in the traditional regeneration, the carbon dioxide content in the regenerated flue gas is as high as 88.6 vol%, and the carbon dioxide concentration of the product after further purification of the regenerated flue gas reaches 99 vol%, achieving the effect of reducing carbon dioxide emissions during catalyst regeneration; in Comparative Example 2, the regeneration temperature is reduced by 30°C, and the charring effect is slightly inferior to that in the embodiment.

[0056] Table 1

[0057] Raw oil name Catalytic cracking feedstock Molecular weight, g / mol 437 Carbon residue, m% 3.63 Heavy metals, μg / g Ca 2.2 Cu 0.08 Pb <0.01 Ni 4.42 V 4.69 Fe 4.28 Hydrocarbon composition, m% Saturated hydrocarbons 63.2 Aromatics 33.2 Gel 3.6 Asphaltene /

[0058] Table 2

[0059] Catalyst Product Number LDC-200 Chemical composition, w% Alumina 50.9 Sodium Oxide 0.273 <![CDATA[Apparent density, kg / m 3 > 700 Specific surface area 227 Sieving composition, w% 0-40μm 16.7 40-80μm 51.2 >80μm 32.1

[0060] Table 3

[0061]

[0062] Table 4

[0063]

[0064] Table 5

[0065]

[0066] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, technicians familiar with the field may make various corresponding changes and deformations based on the present invention, but these corresponding changes and deformations should all fall within the scope of protection of the claims of the present invention.

Claims

1. A method for reducing carbon dioxide emissions during catalyst regeneration, characterized in that: The regenerated flue gas is subjected to dust removal and pressure reduction to obtain low-pressure flue gas, and the low-pressure flue gas is divided into a first flue gas flow and a second flue gas flow. The first flue gas flow is subjected to heat exchange, denitrification, desulfurization and dust removal to obtain desulfurized flue gas, and water vapor in the desulfurized flue gas is removed to obtain low-humidity flue gas. Part of the low-humidity flue gas is used as circulating flue gas to participate in catalyst regeneration, and part of it undergoes combustion reaction with hydrogen to obtain deoxygenated flue gas. The deoxygenated flue gas is dehydrated to obtain high-concentration carbon dioxide; the second flue gas flow is subjected to heat exchange with the circulating flue gas or returned together with the circulating flue gas to participate in catalyst regeneration or mixed with the first flue gas flow in the denitrification process, and continues to undergo heat exchange, desulfurization and dust removal to obtain desulfurized flue gas.

2. The method for reducing carbon dioxide emissions during catalyst regeneration according to claim 1, characterized in that: When the circulating flue gas returns to participate in the catalyst regeneration, it needs to supplement oxygen-containing gas as the regeneration main air, and the oxygen concentration in the regeneration main air is 20v%-25v%, preferably 21vol%-24vol%.

3. The method for reducing carbon dioxide emissions during catalyst regeneration according to claim 2, characterized in that: The desulfurized flue gas is first stored and then the water vapor is removed. The storage device is equipped with a venting pipeline and a sealing device to maintain the system pressure and prevent the entry of external air.

4. The method for reducing carbon dioxide emissions during catalyst regeneration according to claim 3, characterized in that: The operating pressure of the storage device is 5-30 kPa (G), preferably 10-25 kPa (G), and the amount of stored flue gas is greater than or equal to 2-5 times the regeneration main air volume required for burning per second during the catalyst regeneration process.

5. The method for reducing carbon dioxide emissions during catalyst regeneration according to claim 1, characterized in that: The oxygen concentration in the regeneration flue gas is not higher than 8 vol%, preferably not higher than 5 vol%, and the temperature of the low-pressure flue gas is 400-650°C, preferably 450-600°C.

6. The method for reducing carbon dioxide emissions during catalyst regeneration according to claim 1, characterized in that: If the second flue gas flow is returned for catalyst regeneration, direct contact heat exchange is used for heat exchange with the circulating flue gas; if the second flue gas flow is mixed with the first flue gas flow in the denitrification process, a partition heat exchanger is used for heat exchange with the circulating flue gas.

7. The method for reducing carbon dioxide emissions during catalyst regeneration according to claim 1, characterized in that: The volume flow rate of the second flue gas flow accounts for 0-30% of the low-pressure flue gas.

8. The method for reducing carbon dioxide emissions during catalyst regeneration according to claim 1, characterized in that: The temperature of the circulating flue gas after heat exchange with the second flue gas flow is 40-150°C, preferably 60-120°C.

9. The method for reducing carbon dioxide emissions during catalyst regeneration according to claim 1, characterized in that: High concentration carbon dioxide is used as a diluent gas in the denitrification process.

10. The method for reducing carbon dioxide emissions during catalyst regeneration according to claim 1, characterized in that: A flue gas cooling device is used to remove water vapor from the desulfurized flue gas, and the flue gas cooling device includes a partition-type water-cooled heat exchanger and a gas-liquid separation tank, wherein the operating temperature of the gas-liquid separation tank is 10-40°C, and the water vapor content in the low-humidity flue gas is not higher than 4vol%, preferably not higher than 3vol%.

11. The method for reducing carbon dioxide emissions during catalyst regeneration according to claim 1, characterized in that: The volume flow rate of the low-humidity flue gas that undergoes combustion reaction with hydrogen is 10%-30% of the total low-humidity flue gas.

12. The method for reducing carbon dioxide emissions during catalyst regeneration according to claim 1, characterized in that: The deoxygenated flue gas is dehydrated by triethylene glycol dehydration or solid adsorption dehydration.

13. The method for reducing carbon dioxide emissions during catalyst regeneration according to claim 1, characterized in that: The concentration of the high-concentration carbon dioxide is not less than 99 vol%.

14. The method for reducing carbon dioxide emissions during catalyst regeneration according to claim 1, characterized in that: The circulating flue gas is introduced into the catalyst regeneration device through a main fan, and the main fan is provided with an air inlet and a circulating flue gas inlet.

15. The method for reducing carbon dioxide emissions during catalyst regeneration according to claim 1, characterized in that: The method also includes the step of preparing methanol by reacting high-concentration carbon dioxide with hydrogen.

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