Catalytic cracking device with ultra-large catalyst-oil ratio for inferior heavy oil

Abstract

A catalytic cracking device with an ultra-large catalyst-oil ratio for inferior heavy oil relates to the technical field of heavy oil catalytic cracking, and comprises a regenerator and a downer reactor which are coaxially and vertically arranged, and a catalyst flow controller, a regenerant distributor and a regenerant distribution pipe are sequentially and downwards connected between the regenerator and the downer reactor; a quick separator is arranged at the bottom of the downer reactor, a reaction cyclone separator is arranged in a settler, an outlet of the reaction cyclone separator is connected with a switchable parallel filter arranged outside the settler, reaction oil gas subjected to three-time gas-solid separation is separated by an oil-gas separation system, and a part of dry gas is returned to the downer reactor from a dry gas distributor after being pressurized by a circulating compressor. According to the utility model, the problems that the concentration of catalyst particles in the reactor is too low, the adaptability to inferior heavy oil is poor, the treatment capacity is low and the target product yield is low in the existing downer catalytic cracking device are solved, and the application range of the downer reactor in the field of catalytic lightening of heavy inferior raw oil is widened.

Description

TECHNICAL FIELD

[0001] The utility model relates to heavy oil catalytic cracking technical field especially to a kind of super large catalyst oil ratio catalytic cracking device of inferior heavy oil. BACKGROUND

[0002] Catalytic cracking device is very important heavy oil lightening equipment in refinery, and is also the core device for measuring refinery heavy oil conversion capacity and economic benefit. However, with the continuous heavy and inferior quality of crude oil resources, the traditional catalyst oil parallel flow upflowing riser reactor exposes many drawbacks in the operation process. Main problems include: the secondary reaction is serious due to the too long riser reaction time, and the coking rate is high; catalyst slides and backmixes due to gravity in the upflowing process; catalyst upflowing process due to the existence of choke problem leads to catalyst oil ratio cannot be too large; heat removal load limit and the existence of coking blockage risk in riser feed site make that feedstock oil carbon residue value cannot be too high, so heavy inferior feedstock oil cannot be processed.

[0003] Compared with traditional riser reactor, the feed and catalyst of downflow bed reactor move downward along the direction of gravity field in nearly plug flow manner, with the following advantages: feedstock and catalyst contact well, particle concentration and gas-solid velocity distribution are uniform, axial backmixing is small, gas-solid contact time is short, and secondary reaction is less. These characteristics make downflow bed reactor show good application prospect in petroleum chemical industry, coal chemical industry and biomass pyrolysis fields. However, due to the limitation of its own structure, the existing downflow bed reactor has low catalyst particle concentration in bed, and it is difficult to operate under super large catalyst oil ratio. This defect largely limits the processing capacity and adaptability to heavy inferior feedstock of downflow bed reactor, and also restricts its industrial application in heavy inferior oil catalytic cracking field. Therefore, it is particularly necessary to develop a super large catalyst oil ratio catalytic cracking device suitable for inferior heavy oil.

[0004] A Chinese invention patent (CN114410344B) discloses a method for catalytic conversion of inferior oil, which can directly use heavy inferior crude oil to produce low-carbon olefins and aromatic hydrocarbons. The method sprays the preheated crude oil into the first down-flow bed reactor to contact with the catalyst for the first reaction, then introduces the first reaction product and catalyst stream into the reactor with an expanded diameter for the second reaction, and then introduces the oil gas and catalyst in the expanded diameter reactor into the second down-flow bed reactor for the third reaction. The quenching agent is introduced at the outlet of the second down-flow bed reactor, and after the reaction is completed, the oil gas product and the coked deactivated spent catalyst are obtained by oil agent separation. The oil gas product enters the fractionating column, and the spent catalyst is recycled after regeneration. After separation of the reaction product, low-carbon olefins and aromatic hydrocarbons are obtained, and part of the light components are introduced into the riser reactor to contact with the catalyst for the fourth reaction, and the semi-spent catalyst of the fourth reactor is sent to the expanded diameter reactor. The invention is suitable for catalytic conversion of inferior intermediate base crude oil with low hydrogen content, high asphaltene, heavy metal and high carbon residue to produce low-carbon olefins and aromatic hydrocarbons, and has the characteristics of strong raw material adaptability and high yield of low-carbon olefins and aromatic hydrocarbons. However, the oil catalyst ratio of the operation process of the invention is low (the maximum oil catalyst ratio is 30), which cannot provide a large number of active centers for catalytic cracking reaction, resulting in a complex process and low reaction efficiency.

[0005] A Chinese invention patent (CN114410340B) discloses a method for maximizing the production of low-carbon olefins and aromatic hydrocarbons from raw oil, which sprays the preheated raw oil into the first expanded diameter reaction section of the down-flow reaction bed to contact with the catalytic cracking catalyst for mild catalytic cracking reaction, then introduces the oil agent obtained from the first expanded diameter reaction section of the down-flow reaction bed into the second expanded diameter reaction section for moderate catalytic cracking reaction, and then introduces the product oil agent into the third expanded diameter reaction section of the down-flow reaction bed for deep catalytic cracking reaction to obtain oil gas product and regenerated catalyst. The oil gas product is separated into high-value chemical raw materials, and the regenerated catalyst is sent to the coke-burning regenerator for catalyst regeneration after washing with steam to remove the remaining oil gas product. The regenerated catalyst is recycled. The method is suitable for processing various properties of crude oil, vacuum gas oil, atmospheric residue and vacuum residue, etc. It can maximize the production of low-carbon olefins and aromatic hydrocarbons, has high selectivity of low-carbon olefins and low-carbon aromatic hydrocarbons, low dry gas and coke yield, almost no fuel oil, simple process flow, and low production cost. However, its shortcomings are the same as those of the invention patent CN114410344B described above.

[0006] A Chinese invention patent (CN116769506A) discloses a catalytic cracking downflow bed reaction system and method, which comprises a downflow bed reactor and a fast separation device located at the outlet of the downflow bed reactor. The downflow bed reactor comprises a turnaround cylinder, a straight cylinder body and a booster. The inlet of the straight cylinder body is located in the turnaround cylinder for receiving the catalyst output from the turnaround cylinder, and the outlet of the straight cylinder body is located outside the turnaround cylinder for outputting the catalyst and oil gas after catalytic cracking reaction in the straight cylinder body. The outlet of the booster extends through the top of the turnaround cylinder to the inlet of the straight cylinder body for inputting booster gas flow to push the catalyst from the turnaround cylinder to the straight cylinder body. The utility model realizes high-throughput operation of catalyst particles in the downflow bed, and improves the production capacity of the downflow bed reaction system. However, in order to improve the catalyst particle concentration in the downflow bed reactor, a large amount of fluidizing steam and booster gas / steam is introduced, which will correspondingly reduce the feed amount of raw oil and reduce the processing capacity of the downflow bed reactor, and also reduce the temperature of the catalyst entering the downflow bed reactor, further reducing the reaction efficiency.

[0007] A Chinese invention patent (CN1390916A) discloses a method for catalytic thermal cracking of hydrocarbons using a downflow bed reactor. After the raw oil is heated to 350°C, it is sprayed into the downflow bed reactor under the action of atomizing steam, and contacts with the catalyst uniformly entering the top of the reactor in the oil agent mixing zone for cracking reaction under concurrent downflow at 600-800°C. The weight ratio of catalyst to raw oil is 10-40. After the gas-solid mixture is rapidly separated in the gas-solid rapid separation device at the end of the downflow bed reactor, the gas and liquid products are obtained by cooling, and the deactivated catalyst is reused after regeneration. The invention can process heavy raw materials, and adjust the ratio of ethylene and propylene by adjusting the process conditions. However, the invention does not specify how to achieve uniform distribution of catalyst in the downflow bed, nor does it involve solutions to overcome the low catalyst density in the downflow bed reactor and the adaptability to poor quality raw materials.

[0008] In summary, the existing catalytic cracking device has many deficiencies in processing heavy and poor quality raw oil, and it is of great practical significance to develop a super large catalyst / oil ratio catalytic cracking device suitable for poor heavy oil. By optimizing the arrangement and connection mode of the regenerator and the reactor, setting a positive displacement catalyst flow controller, using circulating dry gas to realize short-range rectification of the catalyst, and improving the separation efficiency of gas-solid two-phase flow, the circulation efficiency of the catalyst and the catalyst concentration in the reactor can be significantly improved, the secondary reaction and coke generation can be reduced, the yield of target products can be improved, and the application of the downflow bed reactor in the field of catalytic lightening of heavy and poor quality raw oil can be broadened. SUMMARY

[0009] In order to overcome the shortcomings of the prior art, this utility model discloses a high-capacity catalyst-to-oil ratio catalytic cracking device for inferior heavy oil.

[0010] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0011] A high-capacity catalytic cracking unit for low-quality heavy oil, characterized by: a regenerator and a descending bed reactor arranged coaxially and vertically; a nozzle for introducing feedstock oil into the upper section of the descending bed reactor, with an upward-sweeping dry gas distributor above the nozzle, the dry gas distributor having an annular tubular structure; a lower section of the descending bed reactor sealed within a reaction settling tank, with a fast separator at the outlet of the lower section including a funnel-shaped fast separator expansion section, the larger end of the fast separator expansion section connected to an ellipsoidal fast separator head via connecting ribs, the spherical surface of the ellipsoidal fast separator head pointing towards the smaller end of the funnel opening of the fast separator; a feedstock riser connected to the bottom of the reaction settling tank via a feedstock inclined pipe, the outlet end of the feedstock riser connected to the regenerator; a filter located on the outside of the reaction settling tank, the bottom solid outlet line of the filter connected to a waste feedstock tank, and the top gas phase outlet line connected to an oil-gas separation system; the oil-gas separation system connected to a dry gas recirculation compressor, the dry gas recirculation compressor connected to the dry gas distributor.

[0012] Preferably, the regenerator includes a regenerator settling section, a regenerator coking section, and a regenerator gas stripping section connected from top to bottom; the outlet end of the regenerator riser pipe is connected to the regenerator settling section; the regenerator gas stripping section is connected to a regenerator distributor through a regenerator flow controller, and the bottom of the regenerator distributor is provided with multiple regenerator distribution pipes at intervals along the circumference for corresponding communication with the downward bed reactor, and the outlet end of the regenerator distribution pipe is higher than the outlet of the dry gas distributor.

[0013] Preferably, the regenerant distribution pipe has an arc-shaped structure, with its inlet and outlet ends evenly arranged along the outer side of the lower cone of the regenerant distributor and the upper outer side of the descending bed reactor, respectively; the number of regenerant distribution pipes is not less than two.

[0014] Preferably, the inner ring surface of the dry gas distributor, with an angle of 50 to 85 degrees between the horizontal plane and the central axis of the downward-flowing bed reactor, has several gas distribution holes with a diameter of 1 to 6 mm.

[0015] Preferably, the reaction settling device includes a reaction settling section and a reaction stripping section connected from top to bottom; a reaction vortex separator is installed in the reaction settling section;

[0016] Preferably, the reaction filter includes a reaction filter a and a reaction filter b installed in parallel, and the lateral air inlets of both reaction filter a and reaction filter b are connected to the gas phase outlet of the reaction vortex.

[0017] Preferably, the reaction filter a and the reaction filter b can be a single filter or a set of filters connected in parallel. Each set of filters is connected to the backflush air H. Valves are provided on the gas phase inlet and outlet lines and the solid phase outlet lines of each set of filters. When one set of filters is working, the other set of filters can switch to backflush. Filtration and backflush can be performed alternately.

[0018] Preferably, the pore size of the reaction filter a and the reaction filter b is no greater than 5µm.

[0019] Preferably, the lower outlet of the reaction stripping section is connected to the pre-regenerated inclined tube via a pre-regenerated catalyst flow controller; the pre-regenerated catalyst flow controller and the regenerator flow controller rely on an externally driven volumetric solid fine powder flow control device, and control the amount of catalyst fine powder passing through the controller by changing the rotation speed of its internal volumetric metering component. The rotation speeds of the two are respectively cascaded with the regenerated catalyst level in the regenerator stripping section and the pre-regenerated catalyst level in the pre-regenerated catalyst stripping section.

[0020] Preferably, the dry gas circulating compressor has two gas paths, one of which is connected to the dry gas distributor, and the other serves as an external dry gas discharge device.

[0021] By adopting the technical solution described above, this utility model has the following beneficial effects:

[0022] This invention significantly improves the catalyst circulation efficiency and catalyst concentration within the reactor by optimizing the arrangement and connection of the regenerator and the downward-flowing bed reactor. Simultaneously, it achieves short-path rectification of the catalyst through circulating dry gas, improving the uniformity of oil-catalyst contact, suppressing excessive cracking and coking reactions, and increasing the yield of the target product. Specific beneficial effects are as follows:

[0023] (1) Optimize the layout of the regenerator and reactor:

[0024] Height difference design: The regenerator is coaxially arranged directly above the downward bed reactor, forming a sufficient height difference, which increases the downward driving force and flow rate of the catalyst, creating conditions for achieving ultra-high catalyst-to-oil ratio operation.

[0025] Catalyst flow control: A volumetric regenerated catalyst flow controller is installed, which avoids the problem of poor downward flow caused by catalyst particle flow resistance and bridging, such as traditional slide valves and L valves, and increases the catalyst delivery rate.

[0026] Catalyst distribution: The regenerated catalyst is rapidly and evenly distributed in different quadrants of the descending bed reactor through the regenerator distributor and regenerator distribution pipe, avoiding coking and blockage caused by catalyst flow deviation.

[0027] Catalyst flow control: A catalyst flow controller is installed between the catalyst stripping section and the catalyst inclined tube to achieve rapid and accurate catalyst transfer between the regenerator and the downward bed reactor, ensuring the relative stability of the catalyst reserves in the reaction and regeneration systems.

[0028] (2) Using circulating dry gas to achieve catalyst short-path rectification:

[0029] Dry gas recirculation: The dry gas generated in the downflow bed catalytic cracking process is separated, and after being pressurized by the dry gas recirculation compressor, part of it is used in the low-pressure gas system, and the other part is introduced into the downflow bed reactor from the dry gas distributor to achieve short-path rectification of the catalyst.

[0030] Rectification effect: Through the dispersion effect of dry gas, the regenerated catalyst is evenly distributed in the bed space, improving the uniformity of oil-agent contact, reducing coke formation, and increasing the yield of the target product.

[0031] Chemical equilibrium adjustment: The introduction of recycled dry gas alters the chemical equilibrium of the catalytic cracking reaction, reducing the yield of low-value-added dry gas components and making the reaction more conducive to the production of high-value-added liquefied products.

[0032] (3) Improve the separation efficiency of gas-solid two-phase streams:

[0033] Fast separator design: A fast separator with simple structure and good separation effect is used to perform primary gas-solid separation, suppress the occurrence of secondary reactions, and reduce coking.

[0034] Cyclone separation: The reaction oil and gas and stripped oil and gas that have undergone primary separation enter the reaction cyclone separator for secondary separation, further improving the separation efficiency.

[0035] Filtration and separation: The oil and gas after secondary separation enter two sets of parallel filters that can be switched between each other, so as to achieve precise separation of ultrafine catalyst, extend the service life of the filters and the operating cycle of the equipment. Attached Figure Description

[0036] Fig. 1 This is a schematic diagram of the frame structure of this utility model;

[0037] Fig. 2 This is a schematic diagram of the fast divider.

[0038] In the diagram: 1. Regenerator; 101. Regenerator settling section; 102. Regenerator reaction section; 103. Regenerator stripping section; 2. Regenerant flow controller; 3. Regenerant distributor; 4. Regenerant distribution pipe; 5. Nozzle; 6. Downward bed reactor; 61. Dry gas distributor; 62. Fast separator; 621. Fast separator expansion section; 622. Ellipsoidal fast separator head; 623. Connecting rib; 7. Reaction settling tank; 701. Reaction stripping section; 702. Reaction settling section; 703. Reaction stripping section; 704. Reaction Filter a; 705. Reaction Filter b; 706. Waste Agent Tank; 8. Oil-Gas Separation System; 9. Dry Gas Circulation Compressor; 10. Regenerator Flow Controller; 11. Regenerator Inclined Pipe; 12. Regenerator Riser Pipe; A. Additive Dosing Line; B. Regeneration Main Air; C. Regenerator Stripping Gas; D. Atomized Steam; E. Raw Material Oil; F. Regenerator Stripping Gas; G. Regenerator Riser Air; H. Backflush Air; J. Liquefied Products; K. Exhaust Dry Gas; L. Regeneration Flue Gas Line. Detailed Implementation

[0039] The present invention will be explained in detail through the following embodiments. The purpose of disclosing the present invention is to protect all technical improvements within the scope of the present invention. In the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "front", "rear", "left", "right" indicating the orientation or positional relationship, they are only corresponding to the drawings of this application for the convenience of describing the present invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation.

[0040] Example 1, in conjunction with Appendix Figs. 1-2 A catalytic cracking unit for inferior heavy oil with an ultra-high catalyst-to-oil ratio and its usage method, wherein the regenerator 1 is arranged coaxially and is located directly above the descending bed reactor 6.

[0041] It is important to note that traditional riser catalytic cracking units and downflow bed catalytic cracking units generally employ two arrangements for the regenerator and reactor: a parallel high-low configuration and a coaxial configuration. In the parallel high-low configuration, the two units are arranged laterally parallel, with a relatively small vertical height difference between them. In the coaxial configuration, the settling section of the reactor is partially inserted into the regenerator, and the height difference between the two units is also limited. Therefore, the driving force for catalyst circulation between the two units primarily comes from the operating pressure difference rather than the height difference.

[0042] In this invention, the regenerator 1 is coaxially arranged directly above the descending bed reactor 6, and the two are completely separated in the vertical direction. This creates a sufficient height difference between the regenerator and the reactor. In addition to the traditional operating pressure difference between the two reactors, the catalyst circulation driving force is also increased by the catalyst static pressure difference formed by the height difference. Under the same operating pressure, more downward driving force can be provided for the catalyst. In other words, under the same operating conditions and flow area, more catalyst flow can be provided for the descending bed reactor, creating favorable conditions for achieving ultra-high catalyst-to-oil ratio operation.

[0043] The top of the regenerator 1 is equipped with a fresh catalyst addition line A and a regenerated flue gas line L to facilitate the addition of fresh catalyst and the discharge of flue gas. The regenerator 1 is divided into three parts from top to bottom: the regenerator settling section 101, the regenerator regeneration section 102, and the regenerator gas lift section 103. The catalyst flows smoothly between the parts through a connecting structure.

[0044] At the bottom of the regenerator stripping section 103, from top to bottom, are connected a regenerator flow controller 2, a regenerator distributor 3, and a regenerator distribution pipe 4. These components are designed to precisely control the flow rate of the regenerated catalyst and distribute it evenly throughout the descending bed reactor 6. The downward flow rate of the catalyst is proportional to the rotational speed of the controller. Additionally, a reaction settling tank 7, a regenerator flow controller 10, and a regenerator inclined tube 11 are also connected. The outlet of the regenerator inclined tube 11 is connected to the regenerator settling section 101 via a riser pipe 12, forming a circulation channel that allows for controllable catalyst flow, ensuring efficient catalyst circulation within the system.

[0045] It is worth noting that since the rotation of the flow controller 2 is driven by external power, the problem of poor downward flow caused by catalyst particle flow resistance and bridging, which occurs in traditional slide valves and L valves, is avoided, thus increasing the amount of catalyst delivered from the regenerator 1 to the moving bed reactor 6.

[0046] Catalyst recycling process:

[0047] When the unit starts up or needs to be replenished with fresh catalyst, the fresh catalyst enters the settling section 101 of the regenerator through the addition line A. Here, it mixes with the spent catalyst returning from the spent catalyst riser 12 and falls together into the regeneration section 102 of the regenerator. In the regeneration section 102, the catalyst comes into counter-current contact with the preheated regeneration main air B at a certain temperature, undergoing coking treatment in a fluidized state. This process effectively removes coke deposits from the surface and pores of the spent catalyst, fully restoring its activity and preparing it for subsequent catalytic reactions.

[0048] The regenerated catalyst, after being coked, flows out of the regenerator stripping section 103 and flows downward through the regenerator flow controller 2 into the regenerator distributor 3. To ensure effective isolation between the oxygen-containing environment of the regeneration system and the hydrocarbon-containing environment of the reaction system, the regenerator stripping section 103 needs to maintain a sufficient catalyst level. Cascade control between the catalyst level in the regenerator stripping section and the regenerator flow control valve ensures a sufficient catalyst level in the regenerator stripping section, effectively isolating the oxygen-containing environment of the regenerator from the hydrocarbon-containing environment of the downward-flowing bed reactor.

[0049] Multiple arc-shaped regenerant distribution pipes 4 are evenly arranged on the outer side of the lower cone of the regenerant distributor 3 and the outer side of the upper part of the descending bed reactor 6. By adjusting the number and cross-sectional area of ​​the regenerant distribution pipes 4, the regenerated catalyst can flow rapidly and evenly from the regenerant distributor 3 into different quadrants of the descending bed reactor 6. This design not only improves the uniformity of catalyst distribution but also enhances the catalyst concentration within the reactor, providing more active centers for the catalytic cracking reaction; it also avoids coking and blockage at the feed nozzles of the descending bed reactor due to catalyst flow deviation, which would affect catalyst flow.

[0050] Setting of dry air distributor and feed nozzle:

[0051] The connection point between the regenerant distribution pipe 4 and the downward-flowing bed reactor 6 should be appropriately higher than the installation position of the dry gas distributor 61, and the number should be no less than two. The dry gas distributor 61 is a circular hollow tube installed close to the inner wall of the downward-flowing bed reactor 6. Several gas distribution holes with a diameter of 1-6 mm are opened on its inner annular surface, where the angle between its horizontal plane and the reactor's central axis is 50-85 degrees. Preferably, the opening angle is 60-75 degrees, and the diameter of the distribution holes is 2-4 mm. Its installation position should be between the regenerant distribution pipe 4 and the lower outlet of the feed nozzle 5.

[0052] The feed nozzle 5 passes through the center of the top cover of the descending bed reactor 6 and extends downwards to the installation position of the dry gas distributor 61. Through the combination of the structure, relative position, and operating process of the regenerator distribution pipe 4, dry gas distributor 61, and feed nozzle 5, the following four objectives can be achieved: First, to provide multiple high-flow-rate descending channels for the regenerated catalyst, preventing catalyst bridging and blockage; second, to evenly distribute the regenerated catalyst in different quadrants of the descending bed reactor 6, increasing the average concentration of catalyst particles within the reactor; third, to utilize the dispersing effect of the circulating dry gas to blow the regenerated catalyst entering the descending bed obliquely upwards towards the top of the reactor, achieving short-path rectification after rebound, creating favorable conditions for thorough mixing of the oil and catalyst; and fourth, to improve the oil-catalyst mixing effect, providing more active centers for the catalytic cracking reaction of the feedstock, reducing secondary reactions and coke yield, and improving the adaptability to heavy and inferior feedstocks and the stability of the unit operation.

[0053] Cracking reaction and oil-gas separation of feedstock:

[0054] Preheated heavy, low-quality feedstock oil E is mixed with atomized steam D and then injected downwards into the descending bed reactor 6 through nozzle 5. Here, the feedstock oil comes into full contact with the regenerated catalyst, which enters from the regenerator distribution pipe 4 and is then rectified by the circulating dry gas distributor 61, undergoing a short-path rectification process as it descends. When the catalyst and the oil-gas mixture descend to the fast separator 62 located at the bottom outlet of the descending bed reactor 6, the descending catalyst is significantly decelerated through collision, achieving the first rapid separation of the catalyst and the oil-gas. This process effectively suppresses the occurrence of secondary reactions and prevents the separated catalyst from fluidizing again.

[0055] The rapid separator 62 is located inside the reaction settling tank 7 and consists of a rapid separator expansion section 621, an ellipsoidal rapid separator head 622, and connecting ribs 623. The connecting ribs 623 fix the ellipsoidal rapid separator head 622 to the inner wall of the rapid separator expansion section 621, which has a trumpet-shaped structure that is smaller at the top and larger at the bottom. The ellipsoidal rapid separator head 622 is a horizontally placed semi-ellipsoid, located at the bottom center of the rapid separator expansion section 621, with its spherical surface pointing towards the smaller end of the trumpet opening of the rapid separator 62. The major axis diameter d2 of the ellipsoidal rapid separator head 622 is smaller than the inner diameter d3 of the rapid separator expansion section 621, but larger than the inner diameter d1 of the descending bed reactor 6. The relationships between d1, d2, and d3 satisfy… Preferred .

[0056] After initial separation, the reacted catalyst slides downwards into the stripping section 702. Here, the catalyst comes into counter-current contact with the stripping gas F entering from the lower part of the stripping section 702, stripping the catalyst particles and oil / gas in the channels. The stripped oil / gas, the reacted oil / gas, and a small amount of entrained catalyst powder enter the reaction cyclone separator 703 for secondary gas-solid separation. The separated catalyst particles enter the stripping section 701 along the feed leg of the reaction cyclone separator 703, maximizing the recovery of usable catalyst.

[0057] The oil and gas flowing out of the gas phase outlet line of reaction cyclone separator 703 continues to rise and enter one of the parallel reaction filters a704 or b705 for three-stage gas-solid filtration separation. Reaction filters a704 and b705 are switched based on the pressure differential. For example, when reaction filter a704 is in operation and reaction filter b705 is in standby mode, if the operating pressure differential of reaction filter a704 is greater than 5 kPa, the gas phase flowing out of reaction cyclone separator 703 can be switched into reaction filter b705 by opening and closing the corresponding valve. Backflush air H is used to remove the catalyst adhering to the filter cartridge of reaction filter a704, reducing its pressure differential to below 0.1 kPa for standby. Similarly, when the operating pressure differential of reaction filter b705 reaches 5 kPa, a similar operation is performed to achieve backflush standby for reaction filter b705. This process is repeated to achieve continuous operation of the reaction filters.

[0058] It is worth noting that when the mixture of reactant oil and gas and catalyst flows down to the fast separator 62, it collides with the ellipsoidal fast separator head 622. The downward velocity of the solid catalyst particles is significantly reduced, and they slide down along the ellipsoidal fast separator head 622 into the reaction settling tank 7. The velocity of the gas phase products does not change much, and they continue to flow out along the annular gap between the enlarged section and the ellipsoidal fast separator head 622. The gas and solid phases are rapidly separated, suppressing the occurrence of secondary reactions. Because the catalyst sliding down from the ellipsoidal fast separator head 622 has a low velocity, it can avoid secondary fluidization in the reaction settling tank 7, greatly reducing the impact on subsequent gas-solid separation. The impact on the facility; to further improve the separation degree of the reaction oil and gas and the catalyst, the reaction oil and gas, which are separated in the first stage and carry a small amount of fine catalyst powder, enter the reaction cyclone separator for secondary separation to recover as much catalyst as possible; the oil and gas after secondary separation is led out of the reaction settling tank 7 and enters two sets of parallel and interchangeable filters to achieve precise separation of ultrafine catalyst. The separated catalyst, due to its small particle size, belongs to Class C particles and is not suitable for fluidized catalytic cracking reaction, so it is collected as waste catalyst in the waste tank 706; thus achieving precise separation of ultrafine catalyst. The filter cartridge pore size of reaction filter a704 and reaction filter b705 is no greater than 5µm, preferably no greater than 3µm. The oil and gas after three separations is introduced into the oil and gas separation system to ensure the stable operation of the separation system and the dry gas circulation compressor; in addition, since the filter is located outside the reaction settling tank 7, it is convenient to reduce the temperature of the reaction oil and gas, further reducing the secondary reaction of unstable components; at the same time, it is convenient to perform non-stop maintenance and replacement of the filter, extending the service life of the filter and the operating cycle of the unit.

[0059] Oil and gas separation and recycling:

[0060] The oil and gas passing through reaction filter a704 or reaction filter b705 enters the oil-gas separation system 8 for gas-liquid separation. The separated liquefied product J is led out of the extraction device, while the non-liquefied dry gas is introduced into the dry gas recirculation compressor 9. After pressurization, part of the dry gas is led out of the exhaust dry gas K extraction device, and the other part is introduced into the dry gas distributor 61 for short-range rectification of the regenerated catalyst entering the downflow bed reactor 6 and to suppress excessive cracking reaction. Since the recirculating dry gas contains a large amount of hydrogen and methane, its introduction changes the chemical equilibrium and product distribution of the catalytic cracking reaction, significantly reducing the yield of low-value-added dry gas such as hydrogen and methane, increasing the yield of high-value-added liquefied products, and reducing coke formation in the downflow bed catalytic cracking process, thus creating favorable conditions for the heavy and degraded quality of the feedstock.

[0061] It is important to note that the catalytic cracking process, due to factors such as catalyst contamination, feedstock degradation, poor oil-catalyst contact, and harsh operating conditions, generates dry gas equivalent to 3%–5% of the total feed and varying amounts of coke. These are undesirable low-value-added products of the catalytic cracking process. This invention separates the dry gas generated during the downward-flowing bed catalytic cracking reaction. After being pressurized by the dry gas recirculation compressor 9, a portion is desulfurized and enters the low-pressure gas system, while the other portion is introduced into the downward-flowing bed reactor from the dry gas distributor 61 installed between the regenerator distribution pipe 4 and the feed nozzle 5 outlet. This dry gas is then sprayed upwards at an angle of 50–85 degrees to the reactor's central axis, blowing the regenerated catalyst flowing into the downward-flowing bed reactor 6 along the regenerator distribution pipe 4 towards the top of the reactor. After being bounced off the inner side of the top cover, the catalyst falls evenly along the bed cross-section, thus achieving the purpose of rectifying the downward-flowing catalyst within a relatively short bed space. Because the rectified catalyst is evenly distributed throughout the entire bed space… The heavy, low-quality feedstock droplets ejected from the atomizing nozzle can come into uniform contact with the catalyst and undergo cracking, increasing the number of reactive sites and correspondingly improving the yield of the target product while reducing coke formation. Simultaneously, the introduction of circulating dry gas into the reaction system alters the chemical equilibrium of the catalytic cracking reaction, significantly reducing the yield of low-value-added dry gas components such as hydrogen and methane, thus guiding the catalytic cracking reaction towards a direction more conducive to the production of high-value-added liquefied products. Furthermore, the increased catalyst particle concentration in the downflow reactor also prevents feedstock from being sprayed onto the reactor walls, thus preventing coking and blockage and creating favorable conditions for the refining and deterioration of the feedstock.

[0062] Catalyst flow control and circulation:

[0063] The catalyst stripped in the stripping section 701 descends and is metered by the catalyst flow controller 10 before sliding along the inclined tube 11 to the junction of the inclined tube 11 and the catalyst riser tube 12. Here, under the action of the catalyst riser air G, the catalyst rises along the catalyst riser tube 12 into the settling section 101 of the regenerator 1. The catalyst flow controller 10 is an externally driven rotating volumetric catalyst powder metering device, and its flow rate is proportional to the rotational speed. The higher the rotational speed, the greater the catalyst flow rate, and vice versa. In order to achieve catalyst inflow and outflow balance in the descending bed reactor 6, and to isolate the hydrocarbon zone reaction separation system from the oxygen zone catalyst riser and regeneration system, the catalyst bed in the stripping section 701 must maintain a sufficient height, i.e., the material level. This material level is cascadedly regulated with respect to the rotational speed of the catalyst flow controller 10.

[0064] This completes the catalyst recycling and regeneration process within the entire downflow bed catalytic cracking unit, as well as the catalytic cracking reaction process of heavy, low-quality feedstock. This process not only improves catalyst utilization efficiency but also provides a strong guarantee for the efficient conversion of heavy, low-quality feedstock.

[0065] Example 2, in conjunction with Appendix Figs. 1-2 A high-capacity catalytic cracking device for low-quality heavy oil, which differs from Example 1 in that, based on Example 1, the high-capacity catalytic cracking device described in this utility model is used as a pilot plant, with a catalyst storage capacity of 150 kg.

[0066] During the test, the catalyst balancer or aging agent is added to the regenerator 1 along the catalyst addition line A, and the corresponding fluidizing medium is turned on to allow the catalyst entering the regenerator to circulate and preheat within the device.

[0067] The specific implementation process is as follows:

[0068] Turn on the heaters in each part to preheat the equipment, raw materials, and main air.

[0069] The regenerator 1, regenerator flow controller 2, regenerator distributor 3, and regenerator distribution pipe 4 are all preheated to 650℃, and the pressure at the top of the regenerator is 0.175MPa; the descending bed reactor 6 is preheated to 520℃; the reaction settling tank 7, regenerator flow controller 10, regenerator inclined pipe 11, and regenerator riser pipe 12 are all preheated to 490℃, and the pressure at the top of the reaction settling tank is 0.150MPa; the reaction filters a704 and 705 and their auxiliary systems are preheated to 350℃, and the filter backflush pressure difference is set to 5KPa. When the pressure difference exceeds this set value, the two filters will automatically switch to backflush; the outlet pressure of the circulating dry gas compressor is set to 0.50MPa; the fluidizing air B and regenerator riser air G are all preheated to 200℃; the regenerated gas stripping gas C, atomized steam D, feed oil E, and regenerator stripping gas F are all preheated to 350℃.

[0070] During the preheating process, the catalyst entering the regenerator flows downwards along the settling section 101 of regenerator 1, sequentially passing through the regeneration section 102, the regeneration stripping section 103, the regenerator flow controller 2, the regeneration distributor 3, the regeneration distributor 4, the descending bed reactor 6, the fast separator 62, the reaction settling tank 7, the regenerator flow controller 10, and the regenerator inclined tube 11. Then, under the action of the regenerator lift air G, it rises along the regenerator lift pipe 12 and enters regenerator 1 from the regenerator settling section 101, completing the catalyst circulation within the unit. During the catalyst circulation heating process, the regeneration stripping gas C, atomized steam D, feed oil E, regenerator stripping gas F, regenerator lift air G, backflushing air H, and circulating dry gas are all replaced with air, and its pressure and quantity are adjusted at any time according to the unit's operating conditions.

[0071] Once the feedstock, process media, and all parts of the unit have reached the set temperatures, the regenerated stripping gas C, the pre-regenerating agent lifting air G, and the backflushing air H are switched to nitrogen, and the atomizing steam D and the pre-regenerating agent stripping gas F are switched to steam. This replacement process takes at least 10 minutes. After the hydrocarbon-contaminated area is essentially free of oxygen, the feedstock E is switched from air to feedstock oil. The atomizing steam usage is 5% of the feedstock oil mass. The feedstock oil is vacuum residue with a density of 0.985 g / cm³. 3 The residual carbon value was 22.7%, and the feed rate was 1.0 kg / h. The micro-reaction activity of the catalyst used in the experiment was 66. The catalyst flow rates of both the regenerator flow controller 2 and the feedstock flow controller 10 were set to 50 kg / h, i.e., the catalyst-to-oil ratio was set to 50. The conversion rate of the raw material in this experimental process was 56.62%, and the light oil yield was 59.33%.

[0072] Example 3, in conjunction with Appendix Figs. 1-2A high-capacity catalytic cracking unit for low-quality heavy oil, based on Example 1 or 2, involves preheating the regenerator 1, regenerator flow controller 2, regenerator distributor 3, and regenerator distribution pipe 4 to 680°C, and preheating the descending bed reactor 6 to 540°C; the feed oil is atmospheric residue with a density of 0.962 g / cm³. 3 The residual carbon value was 9.3%, and the feed rate was 1.2 kg / h. The micro-reaction activity of the catalyst used in the experiment was 62. The catalyst flow rates of both the regenerator flow controller 2 and the feedstock flow controller 10 were set to 150 kg / h, i.e., the catalyst-to-oil ratio was set to 125. The conversion rate of this experimental process was 68.47 m%, and the light oil yield was 71.06 m%. Other conditions and processes were the same as in Example 1.

[0073] Example 4, in conjunction with Appendix Figs. 1-2 A high-capacity catalytic cracking unit for low-quality heavy oil, based on any of the embodiments in Examples 1 to 3, involves preheating the regenerator 1, regenerator flow controller 2, regenerator distributor 3, and regenerator distribution pipe 4 to 670°C, and preheating the downflow bed reactor 6 to 525°C; the feed oil is recycled oil with a density of 1.10 g / cm³. 3 The residual carbon value was 11.4%, and the feed rate was 1.5 kg / h. The micro-reaction activity of the catalyst used in the experiment was 60. The catalyst flow rates of both the regenerator flow controller 2 and the feedstock flow controller 10 were set to 100 kg / h, i.e., the catalyst-to-oil ratio was set to 66.7. The conversion rate of this experimental process was 44.18 m%, and the light oil yield was 55.20 m%. Other conditions and processes were the same as in Example 1.

[0074] The parts of this utility model not described in detail are prior art. It is obvious to those skilled in the art that this utility model is not limited to the details of the above exemplary embodiments, and that this utility model can be implemented in other specific forms without departing from the spirit or basic characteristics of this utility model. Therefore, the embodiments should be regarded as exemplary and non-limiting in all respects, and are intended to include all changes that fall within the meaning and scope of equivalents within this utility model.

Claims

1. A high-capacity catalyst-to-oil ratio catalytic cracking unit for low-quality heavy oil, characterized in that: The reactor comprises a regenerator and a descending bed reactor arranged coaxially and vertically. The upper section of the descending bed reactor has a nozzle at its top for introducing feedstock oil. Above the nozzle is an inclined, upward-spraying dry gas distributor in a ring-shaped tubular structure. The lower section of the descending bed reactor is sealed within a reaction settling tank. At the outlet of the lower section is a fast separator including a funnel-shaped fast separator expansion section. The larger end of the expansion section is connected to an ellipsoidal fast separator head via connecting ribs, with the spherical surface of the ellipsoidal fast separator head pointing towards the smaller end of the funnel opening. The bottom of the reaction settling tank is connected to a pre-regenerating agent riser via a pre-regenerating inclined pipe. The outlet end of the pre-regenerating agent riser is connected to the regenerator. A filter is located on the outside of the reaction settling tank. The bottom solid outlet line of the filter is connected to a waste agent tank, and the top gas phase outlet line is connected to an oil-gas separation system. The oil-gas separation system is connected to a dry gas recirculation compressor, which is connected to the dry gas distributor.

2. The ultra-high catalyst-to-oil ratio catalytic cracking unit for inferior heavy oil as described in claim 1, characterized in that: The regenerator includes a regenerator settling section, a regenerator coking section, and a regenerator gas stripping section connected from top to bottom; the outlet end of the regenerator riser pipe is connected to the regenerator settling section; the regenerator gas stripping section is connected to a regenerator distributor through a regenerator flow controller, and the bottom of the regenerator distributor is provided with multiple regenerator distribution pipes at intervals along the circumference for corresponding communication with the downward bed reactor, and the outlet end of the regenerator distribution pipe is higher than the outlet of the dry gas distributor.

3. The ultra-high catalyst-to-oil ratio catalytic cracking unit for inferior heavy oil as described in claim 2, characterized in that: The regenerant distribution pipe has an arc-shaped structure, with its inlet and outlet ends evenly arranged along the outer side of the lower cone of the regenerant distributor and the outer side of the upper part of the descending bed reactor, respectively. The number of regenerant distribution pipes shall not be less than two.

4. The ultra-high catalyst-to-oil ratio catalytic cracking unit for inferior heavy oil as described in claim 1, characterized in that: The dry gas distributor has several gas distribution holes with a diameter of 1 to 6 mm on its inner ring surface, which has an angle of 50 to 85 degrees between the horizontal plane and the central axis of the downward-flowing bed reactor.

5. The ultra-high catalyst-to-oil ratio catalytic cracking unit for inferior heavy oil as described in claim 1, characterized in that: The aforementioned reaction settling device includes a reaction settling section and a reaction stripping section connected from top to bottom; a reaction vortex separator is installed in the reaction settling section.

6. The ultra-high catalyst-to-oil ratio catalytic cracking unit for inferior heavy oil as described in claim 5, characterized in that: It also includes a reaction filter, which comprises a reaction filter a and a reaction filter b installed in parallel, and the lateral air inlets of both reaction filter a and reaction filter b are connected to the gas phase outlet of the reaction vortex.

7. The ultra-high catalyst-to-oil ratio catalytic cracking unit for inferior heavy oil as described in claim 6, characterized in that: The reaction filter a and reaction filter b can be a single filter or a set of filters connected in parallel. Each set of filters is connected to the backflush air H. Valves are provided on the gas phase inlet and outlet lines and the solid phase outlet lines of each set of filters. When one set of filters is working, the other set of filters can switch to backflush. Filtration and backflush can be performed alternately.

8. The ultra-high catalyst-to-oil ratio catalytic cracking unit for inferior heavy oil as described in claim 7, characterized in that: The pore sizes of the reaction filters a and b are no greater than 5µm.

9. The ultra-high catalyst-to-oil ratio catalytic cracking unit for inferior heavy oil as described in claim 8, characterized in that: The lower outlet of the reaction stripping section is connected to the pre-regenerated inclined tube through a pre-regenerated catalyst flow controller. The pre-regenerated catalyst flow controller and the regenerator flow controller rely on an externally driven volumetric solid fine powder flow control device. By changing the rotation speed of the internal volumetric metering component, the amount of catalyst fine powder passing through the controller is controlled. The rotation speeds of the two controllers are respectively cascaded with the regenerated catalyst level in the regenerator stripping section and the pre-regenerated catalyst level in the pre-regenerated catalyst stripping section.

10. The ultra-high catalyst-to-oil ratio catalytic cracking unit for inferior heavy oil as described in claim 8, characterized in that: The dry gas circulating compressor has two gas paths, one of which is connected to the dry gas distributor, and the other serves as the dry gas discharge outlet device.

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