Hot-state circulating standby method for methanol-to-light olefin reaction-regeneration device

Abstract

This invention discloses a hot-state circulating feed method for a methanol-to-olefins (MTO) reactor-regenerator, belonging to the field of fluidized bed MTO technology. During normal production, when the MTO reactor-regenerator needs to be shut down briefly, the hot-state circulating feed method provided by this invention can maintain the hot circulation of the reactor and regenerator without unloading or restarting the catalyst, reducing the risks of shutdown / startup operations and catalyst loss during unloading / reloading. The shutdown waiting time can be long or short, and a rapid restart within 4 hours is achieved. The hot-state circulating feed method provided by this invention is simple to operate, allows for rapid production recovery, and significantly improves production efficiency. Furthermore, by controlling appropriate reactor and regenerator temperatures, bed linear velocity, and bed density to maintain circulation, this invention reduces energy consumption and catalyst activity loss during the waiting period. Even with hot-state circulating feed lasting more than 15 days, the catalyst activity remains largely unaffected.

Description

Technical Field

[0001] This invention belongs to the field of fluidized bed methanol-to-olefins technology, specifically relating to a hot-state circulating feed method for a methanol-to-low-carbon olefins reaction-regeneration device. Background Technology

[0002] The methanol-to-olefins (MTO) reaction-regeneration unit is a device that uses MTO-grade methanol as feedstock to produce ethylene, propylene, and other low-carbon olefins. During operation, the methanol conversion reaction and catalyst regeneration / coke burning occur continuously. The reactor is replenished with regenerated catalyst after coke burning to ensure appropriate catalyst activity and ethylene / propylene selectivity, allowing the conversion reaction to proceed smoothly. For the MTO reaction-regeneration unit, when the unit load drops to a certain level, the heat of reaction and the heat generated by coke burning cannot be balanced; or after the unit cuts the methanol feedstock, the reaction and regeneration temperatures will drop rapidly. When the temperature drops below 250℃, there is a risk of catalyst sludge formation.

[0003] Because the reaction and coking characteristics in the methanol-to-olefins reaction-regeneration unit are different from those in the catalytic cracking unit, the methanol-to-olefins conversion produces less coking. Therefore, the unit is a typical example of "large reaction, small regeneration". The catalyst in the reactor cannot be transferred to the regenerator to achieve single-container fluidization after feed cut-off, and the combustion oil is injected to maintain the regeneration temperature, as is the case in the catalytic cracking unit.

[0004] Patent CN 102295503 B discloses a methanol-to-olefins reaction-regeneration device, which includes a reactor auxiliary combustion chamber, an auxiliary combustion chamber, and an auxiliary heater, employing a combination of two auxiliary combustion chambers and one auxiliary heater. During production, if the reactor and regenerator are abnormally shut down, the catalyst in the reactor faces the risk of "mudification" as the reactor temperature decreases. Furthermore, if steam is used as the fluidizing medium during catalyst unloading, the same risk of "mudification" exists after catalyst discharge. Therefore, the reactor auxiliary combustion chamber is essential. Although it is shut down under normal operating conditions, in an emergency, the auxiliary combustion chamber serves as a heat source for catalyst unloading, ensuring the safe discharge of catalyst from the reactor to the catalyst storage tank, avoiding the risk of catalyst "mudification," and effectively reducing catalyst loss. With the reactor and regenerator shut off, the auxiliary heater is activated, and heated steam enters the reactor to displace residual raw materials and products. Then, the reactor's auxiliary combustion chamber is activated to heat air, which is then introduced into the reactor to displace residual steam while maintaining the reactor temperature above 300°C. Once the steam has been completely displaced, the catalyst is safely discharged from the reactor unloading line. The regenerator receives heat through its auxiliary combustion chamber, and the catalyst is discharged from the regenerator unloading line. This process effectively avoids the "mud-like" phenomenon during catalyst discharge from the reactor, reducing catalyst loss. The patent employs devices such as an auxiliary combustion chamber, an auxiliary combustion chamber, and an auxiliary heating furnace, that is, a combination of two auxiliary combustion chambers and one auxiliary heating furnace. According to the above method, it takes 2-3 days to unload the catalyst, about 5 days to open the manhole to inspect and clean the unloaded catalyst, and at least 5 days to start up the unit, heat up the temperature, and reload the catalyst until methanol is fed. Therefore, if there is a problem with the unit, the whole process takes more than 12 days, which is difficult to operate and time-consuming. In addition, since it is necessary to stop production to unload the catalyst and restart the unit to reload the catalyst, the risks of shutdown / startup and the losses of unloading / loading catalyst are both relatively large. Summary of the Invention

[0005] To address the shortcomings and operational risks of existing methods, the present invention aims to provide a hot-state circulating feedstock method for a methanol-to-olefins (MTO) reaction-regeneration unit. This method eliminates the need for an auxiliary combustion chamber in the reactor, employing instead a combination of an auxiliary combustion chamber and a start-up steam superheater. By utilizing the start-up steam superheater and auxiliary calcination chamber, and through process and operational parameter settings, a hot-state circulation of the reactor and regenerator is maintained. This eliminates the need to stop production to unload and restart catalyst loading, reducing the risks of shutdown / start-up operations and catalyst losses during unloading / loading, and enabling rapid start-up recovery. This method has significant potential for widespread application in methanol-to-olefins (MTO) production.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A hot-state circulating feed method for a methanol-to-olefins (MTO) reaction-regeneration unit, comprising a reactor, an external heat exchanger, a regenerator, an external heat exchanger for the regenerated catalyst, a degassing tank for the regenerated catalyst, and a degassing tank for the regenerated catalyst. The reactor is connected to a start-up steam superheater via a high-temperature steam pipeline and to a methanol feed system via a methanol feed pipeline. The regenerator is connected to an auxiliary combustion chamber and a regenerator combustion oil supply pipeline. The auxiliary combustion chamber is connected to a fuel gas supply pipeline, an air supply pipeline, and a combustion oil supply pipeline. When the MTO reaction-regeneration unit needs to temporarily stop production due to its own reasons or reasons related to upstream or downstream units, it is brought into a hot-state circulating feed state through the following steps:

[0008] The auxiliary combustion chamber uses ignition fuel gas, which, after passing analysis, is ignited and heated.

[0009] The superheated steam furnace is started by introducing fuel gas. After the analysis is qualified, it is ignited and heated. The steam generated is dehydrated and superheated and then fed into the reactor. The methanol feed is reduced proportionally according to the amount of superheated steam entering the reactor until the reaction is completely stopped. The methanol feed system is kept in a hot cycle.

[0010] Based on the reduction in methanol feed to the reactor and the reduction in coke production, the heat output of the external heat exchangers of the reactor and the regenerator should be reduced accordingly.

[0011] After all methanol feed is discharged, the reactor temperature is provided by the superheated steam generated by the start-up superheater; the regenerator temperature is provided by the auxiliary combustion chamber, and if necessary, a small amount of regenerator combustion oil can be added to the regenerator through the regenerator combustion oil supply pipeline to maintain the temperature. Through the above operations, the methanol-to-low-carbon olefins reaction-regeneration unit enters a hot-cycle waiting state. During the hot-cycle waiting state, the reactor temperature is controlled at 300-380℃, and the regenerator temperature is controlled at 320-400℃, maintaining normal circulation for both the reactor and the regenerator. Further, the superheated steam flow rate of the start-up superheater and the main air flow rate of the regenerator are adjusted, the reactor rapid bed linear velocity is 0.9-1.2 m / s, and the bed density is not greater than 400 kg / m³. 3 The linear velocity of the regenerator coke burner is 1.0-1.3 m / s, and the bed density is no more than 450 kg / m³. 3 The bed linear velocity in the reactor and regenerator is kept low to reduce catalyst loss.

[0012] When the waiting time for materials in the hot cycle exceeds 2 days, the methanol feeding system is switched from hot cycle to cold cycle back to the tank area or the cycle is stopped.

[0013] When the hot-cycle waiting state ends, restoring the methanol-to-olefins reaction-regeneration unit to normal production involves the following steps: restoring the methanol feed system to hot circulation; gradually raising the temperature inside the regenerator to 640°C and the reactor to 480°C using the auxiliary combustion chamber, regenerator combustion oil, and start-up steam superheater; gradually introducing methanol into the reactor according to normal start-up procedures, while gradually reducing the superheated steam volume of the start-up steam superheater; adjusting the load of the auxiliary combustion chamber and the amount of regenerator combustion oil based on the coking situation; and restoring all operating parameters to normal after the methanol feed is restored. During normal operation, the auxiliary combustion chamber is shut down. The main air supplied from the main air duct enters the regenerator through the auxiliary combustion chamber, providing sufficient combustion air for catalyst regeneration. At this time, the auxiliary combustion chamber only functions as a main air duct.

[0014] The beneficial effects of this invention are as follows:

[0015] When a methanol-to-olefins (MTO) reactor-regenerator needs to temporarily shut down due to its own internal issues or problems with its upstream or downstream units, the hot-state circulation method provided by this invention can maintain the hot-state circulation of the reactor and regenerator during short-term shutdowns. This eliminates the need for catalyst unloading and restarting, reducing the risks of shutdown / startup operations and catalyst loss. Furthermore, regardless of whether the shutdown is for 1, 5, 10, or 15 days, rapid restart is possible at any time. From hot-state circulation to methanol feeding takes only 4 hours. The hot-state circulation method provided by this invention is simple to operate, allows for rapid production recovery, and enables quick methanol feeding and restart. By controlling the appropriate reactor and regenerator temperatures to maintain circulation, even with hot-state circulation exceeding 15 days, catalyst activity (dienene selectivity) remains largely unaffected. In addition, during the hot-state circulation of the reactor and regenerator, the reaction and regeneration bed linear velocity is low, resulting in minimal catalyst loss. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a methanol-to-low-carbon olefins reaction-regeneration unit.

[0017] Figure reference numerals: 1-Reactor; 2-Start-up steam superheater; 3-Regenerator; 4-Regenerator external heat exchanger; 5-Reactor external heat exchanger; 6-Degassing tank for awaiting catalyst; 7-Degassing tank for regenerated catalyst; 8-Auxiliary combustion chamber; 9-Methanol feed line; 10-Superheated steam line; 11-Main air line; 12-Methanol feed system; 13-Regenerator combustion oil conveying line; 14-Combustion oil conveying line; 15-Air conveying line; 16-Fuel gas conveying line; 17-Sulfurization medium conveying line. Detailed Implementation

[0018] The present invention will be further described below with reference to embodiments, so that those skilled in the art can better understand and implement the present invention, but the embodiments are not intended to limit the present invention.

[0019] refer to Figure 1 The methanol-to-olefins reaction-regeneration unit includes a reactor 1, a regenerator 3, an external heat exchanger 5, an external heat exchanger 4, a start-up steam superheater 2, a degassing tank for the spent catalyst 6, a degassing tank for the regenerated catalyst 7, and an auxiliary combustion chamber 8. The reactor 1 is connected to a methanol feed system 12 via a methanol feed pipeline 9, and gaseous methanol enters the reactor 1 through the methanol feed pipeline 9. Start-up superheated steam enters the bottom of the reactor 1 from a superheated steam pipeline 10. The regenerator 3 is connected to the auxiliary combustion chamber 8, and both the regenerator 3 and the auxiliary combustion chamber 8 are connected to the main air pipeline 11. The external heat exchanger 4 is connected to a sulfurizing medium conveying pipeline 17. The auxiliary combustion chamber 8 is connected to a fuel gas conveying pipeline 16, an air conveying pipeline 15, and a combustion oil conveying pipeline 14. The regenerator 3 is also connected to a regenerator combustion oil conveying pipeline 13.

[0020] Reaction-Regeneration Process: Superheated gaseous methanol (0.6MPa, 200℃) from the methanol feed line is fully mixed and reacted (480℃) with the regenerated catalyst (after degassing from the regenerated catalyst degassing tank), the catalyst from the external heat exchanger, and the catalyst from the reactor circulation inclined tube in the lower part of the reactor. Then, it enters the upper part of the reactor. The upper part of the reactor is mainly used to separate the process gas from the catalyst. The separated catalyst passes through the upper part of the reactor in a double-density bed, and most of it is returned to the lower part through the regeneration circulation inclined tube, which increases the catalyst flow rate in the lower part of the reactor and meets the requirements of space velocity, residence time, temperature rise, and catalyst carbonization required for the reaction.

[0021] The temperature at the bottom outlet of the reactor is controlled by heat recovery from an external heat exchanger. The external heat exchanger utilizes the excess heat generated by the methanol conversion reaction to produce high-pressure saturated steam.

[0022] The hydrocarbons entrained in the spent catalyst are stripped out in the spent catalyst stripper, and the stripped spent catalyst is then sent to the regenerator through the spent catalyst inclined tube. The heat generated by coke combustion is utilized by the external heat exchanger of the regenerator to produce high-pressure saturated steam. The heat exchange is controlled by adjusting the opening of the sliding valve of the heat exchanger or the amount of fluidizing nitrogen, thereby controlling the temperature of the regenerator. The coked catalyst is returned to the lower part of the reactor through the regenerated catalyst degassing tank and the regeneration inclined tube.

[0023] The high-temperature flue gas from the regenerator first enters the third-stage flue gas cyclone separator, where most of the fine catalyst powder is separated. After passing through the flue gas turbine, the flue gas enters the waste heat boiler to recover the sensible heat of the flue gas and generate high-pressure saturated steam, and then superheats the low-pressure saturated steam. After passing through the waste heat boiler, the temperature of the flue gas drops to 150°C, and after dust removal treatment, it is discharged into the chimney.

[0024] The air used for burn-off in the regenerator is supplied by the main fan through the main air pipeline; the fluidizing medium of the external heat exchanger of the regenerator is low-pressure nitrogen, which is transported through the sulfurization medium transport pipeline.

[0025] The reactor outlet material (468℃, 0.136MPa) is subjected to a third-stage process gas cyclone separator to remove the fine powder of the catalyst to be produced. Then, it is cooled down to 220℃ before entering the subsequent product separation unit.

[0026] During unit startup, the auxiliary combustion chamber heats the main blower's air supply at approximately 180°C to 600–800°C before it enters the regenerator, achieving the effect of preheating and heating the reactor and regenerator systems. During normal unit operation, the auxiliary combustion chamber is shut down. The main air supplied from the main air pipeline passes through the auxiliary combustion chamber into the regenerator, providing sufficient combustion air for catalyst regeneration. At this time, the auxiliary combustion chamber only serves as a main air duct. The start-up steam superheater superheats the 1.3MPa, 250°C steam from the pipeline to 550°C for heating the reaction system during the startup phase.

[0027] This invention provides a hot-state circulating feed waiting method for a methanol-to-olefins reaction-regeneration unit. When the methanol-to-olefins reaction-regeneration unit needs to temporarily stop production in normal operation due to its own reasons or reasons of its upstream and downstream units, the following operation steps are used to put it into a hot-state circulating feed waiting state:

[0028] The auxiliary combustion chamber uses ignition fuel gas, which, after passing analysis, is ignited and heated.

[0029] The start-up steam superheater furnace is ignited with fuel gas. After the gas passes the analysis, it is ignited and heated. The steam generated is dehydrated and superheated and then fed into the reactor through the superheated steam pipeline. The methanol feed is reduced proportionally according to the amount of superheated steam entering the reactor until the reaction is completely stopped. The methanol feed system is kept in a hot cycle.

[0030] Based on the reduction in methanol feed to the reactor and the reduction in coke production, the heat output of the external heat exchangers of the reactor and the regenerator should be reduced accordingly.

[0031] After all methanol feed is discharged, the reactor temperature is supplied by the superheated steam generated by the start-up superheater; the regenerator temperature is supplied by the auxiliary combustion chamber, and if necessary, a small amount of regenerator combustion oil can be added to the regenerator through the regenerator combustion oil supply pipeline to maintain the temperature. Through the above operations, the methanol-to-olefins reaction-regeneration unit enters a hot-cycle waiting state. During the hot-cycle waiting state, the reactor temperature is controlled at 300-380℃, and the regenerator temperature is controlled at 320-400℃, maintaining normal circulation for both the reactor and the regenerator. By adjusting the superheated steam flow rate of the start-up superheater and the main air flow rate of the regenerator, the rapid bed velocity of the reactor is controlled at 0.9-1.2 m / s, and the bed density is not greater than 400 kg / m³. 3 The linear velocity of the regenerator coke burner is 1.0-1.3 m / s, and the bed density is no more than 450 kg / m³. 3 The bed linear velocity in the reactor and regenerator is relatively low, which reduces catalyst loss.

[0032] Example 1

[0033] Due to a downstream unit of the methanol-to-olefins reaction-regeneration unit requiring a short-term shutdown, the hot-state circulation waiting method described in this invention is employed. During the hot-state circulation waiting period, the reactor temperature is controlled at 320°C, and the regenerator temperature is controlled at 360°C, with both units maintaining normal circulation. The superheated steam flow rate of the start-up steam superheater is 110 t / h, and the main air flow rate of the regenerator is 50,000 Nm³. 3 After circulating the feed for 25 days, methanol was fed in to resume production. The catalyst activity (diene selectivity) was tested and found to be around 87%.

[0034] Example 2

[0035] Due to an upstream unit issue in the methanol-to-olefins reaction-regeneration unit, a short-term production shutdown is required. A hot-state circulation waiting-for-feed method will be adopted. During the hot-state circulation waiting-for-feed period, the reactor temperature will be controlled at 330℃, and the regenerator temperature at 380℃. Both units will maintain normal circulation. The superheated steam flow rate of the start-up steam superheater is 120 t / h, and the main air flow rate of the regenerator is 52000 Nm³. 3 After circulating the feed for 14 days, methanol was fed in to resume production. The catalyst activity (diene selectivity) was tested and found to be around 86.8%.

[0036] Example 3

[0037] Due to an upstream unit issue in the methanol-to-olefins reaction-regeneration unit, a short-term production shutdown is required. A hot-state circulation waiting-for-feed method will be adopted. During the hot-state circulation waiting-for-feed period, the reactor temperature will be controlled at 325℃, and the regenerator temperature at 370℃. Both units will maintain normal circulation. The superheated steam flow rate of the start-up steam superheater is 115 t / h, and the main air flow rate of the regenerator is 50,000 Nm³. 3After circulating the feed for 2 days, methanol was fed in to resume production. The catalyst activity (diene selectivity) was tested and found to be around 87.0%.

[0038] As can be seen from the above embodiments, the hot-state circulation feeding method provided by the present invention can maintain the hot-state circulation of the reactor and regenerator when methanol-to-olefins production is stopped for a short time. It does not require stopping production to unload the catalyst and restarting the equipment, reducing the risks of shutdown / startup operations and catalyst unloading / addition, and ensuring that the catalyst activity (diene selectivity) is basically unaffected.

[0039] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A hot-state circulating feed method for a methanol-to-low-carbon olefins reaction-regeneration unit, wherein the methanol-to-low-carbon olefins reaction-regeneration unit comprises a reactor, an external heat exchanger for the reactor, a regenerator, an external heat exchanger for the regenerator, a degassing tank for the spent catalyst, and a degassing tank for the regenerated catalyst, characterized in that: The reactor is connected to a start-up steam superheater via a high-temperature steam pipeline, and is also connected to a methanol feed system via a methanol feed pipeline. The regenerator is connected to an auxiliary combustion chamber. When the methanol-to-olefins reaction-regeneration unit needs to be shut down during normal production, it is brought into a hot-cycle, waiting-for-feed state through the following steps: The auxiliary combustion chamber uses ignition fuel gas, which, after passing analysis, is ignited and heated. The superheated steam furnace is started by introducing fuel gas. After the analysis is qualified, it is ignited and heated. The steam generated is dehydrated and superheated and then fed into the reactor. The methanol feed is reduced proportionally according to the amount of superheated steam entering the reactor until the reaction is completely stopped. The methanol feed system is kept in a hot cycle. Based on the reduction in methanol feed to the reactor and the reduction in coke production, the heat output of the external heat exchangers of the reactor and the regenerator should be reduced accordingly. After all the methanol feed is cut off, the temperature of the reactor is provided by the superheated steam generated by the start-up steam superheater, and the temperature of the regenerator is provided by the auxiliary combustion chamber, so that the methanol-to-low-carbon olefins reaction-regeneration unit enters the hot-state circulation waiting state; during the hot-state circulation waiting state, the temperature of the reactor is controlled at 300-380℃, the temperature of the regenerator is controlled at 320-400℃, and the reactor and regenerator maintain normal circulation; During the hot-cycle waiting state, the reactor's rapid bed linear velocity is 0.9-1.2 m / s, and the bed density is no more than 400 kg / m³. 3 The linear velocity of the regenerator coke burner is 1.0-1.3 m / s, and the bed density is no more than 450 kg / m³. 3 ; The auxiliary combustion chamber is connected to a fuel gas supply pipeline for supplying fuel gas, a combustion oil supply pipeline for supplying combustion oil, and an air supply pipeline for supplying air. The temperature in the regenerator is maintained by supplying fuel gas and combustion oil into the auxiliary combustion chamber. The regenerator is connected to a regenerator combustion oil supply pipeline for supplying combustion oil into it, which helps to adjust the temperature in the regenerator. When the hot-cycle waiting state ends, restoring the methanol-to-olefins reaction-regeneration unit to normal production includes the following steps: restoring the methanol feed system to hot circulation; gradually raising the temperature inside the regenerator to 640°C and the temperature inside the reactor to 480°C using the auxiliary combustion chamber, regenerator combustion oil, and start-up steam superheater; gradually introducing methanol into the reactor according to the normal start-up procedure, and gradually reducing the amount of superheated steam in the start-up steam superheater; adjusting the load of the auxiliary combustion chamber and the amount of combustion oil in the regenerator according to the coking situation; after the methanol feed is restored, all operating parameters return to normal; during normal operation, the auxiliary combustion chamber is shut down, and the main air supplied from the main air pipeline enters the regenerator through the auxiliary combustion chamber to provide sufficient combustion air for catalyst regeneration. At this time, the auxiliary combustion chamber only serves as a main air passage.

2. The hot-state circulating feed method for the methanol-to-low-carbon olefins reaction-regeneration unit according to claim 1, characterized in that: When the waiting time for materials in the hot cycle exceeds 2 days, the methanol feeding system is switched from hot cycle to cold cycle back to the tank area or the cycle is stopped.

3. The hot-state circulating feed method for the methanol-to-low-carbon olefins reaction-regeneration unit according to claim 1 or 2, characterized in that: The auxiliary combustion chamber is connected to a fuel gas delivery pipeline, an air delivery pipeline, and a combustion oil delivery pipeline.

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