Supercritical carbon dioxide catalytic cracking slurry mixing system

Abstract

This invention discloses a supercritical carbon dioxide catalytic cracking slurry mixing system, comprising a vertical tank, a supercritical carbon dioxide inlet, a supercritical carbon dioxide dispersion chamber, a dispersion tube, an oil slurry dispersion chamber, an oil slurry inlet, a mixing tube, a supercritical carbon dioxide outlet, and a mixture outlet. A vertical dispersion tube is mounted on the bottom plate of the supercritical carbon dioxide dispersion chamber, with dispersion holes on its wall and a closed lower end. The oil slurry dispersion chamber is located below the supercritical carbon dioxide dispersion chamber, and a vertical mixing tube is mounted on its bottom plate, with an open lower end. The dispersion tube is inserted into the mixing tube and coaxially arranged with it. A spiral guide vane is provided in the annular space between the dispersion tube and the mixing tube. The supercritical carbon dioxide outlet is located on the tank wall of the vertical tank below the oil slurry dispersion chamber, and the mixture outlet is located at the bottom of the vertical tank. This invention overcomes the mixing difficulties caused by the high viscosity and poor fluidity of the oil slurry, achieving thorough mixing of the oil slurry and supercritical carbon dioxide.

Description

Technical Field

[0001] This invention belongs to the field of mixer technology, specifically relating to a supercritical carbon dioxide catalytic cracking slurry mixing system. Background Technology

[0002] Catalytic cracking slurry contains a large amount of aromatics and alkanes. Using it to produce high-value-added products such as needle coke, carbon black, carbon fiber, rubber fillers, plasticizers, and heat transfer oils can significantly increase the added value of the slurry. However, the presence of a large number of solid catalyst particles in the slurry severely limits its high-value utilization. For example, slurry used to produce carbon black or rubber fillers requires a solid content of no more than 500 ppm; slurry used to produce needle coke requires a solid content of no more than 100 ppm; and the requirements for producing carbon fiber are even more stringent, requiring a solid content of less than 20 ppm. Since the content of solid catalyst powder in catalytic cracking slurry is generally between 2000 and 9000 ppm, the removal of solid particles from the slurry is a prerequisite for high-value utilization.

[0003] The high viscosity, poor fluidity, difficulty in dispersion, and easy solidification at room temperature of oil slurry severely limit the ability to achieve continuous solid-phase separation. Supercritical carbon dioxide has a very low viscosity, close to that of a gas, and a large diffusion coefficient. Mixing supercritical carbon dioxide with oil slurry significantly reduces the viscosity of the slurry, making liquid-solid separation easier. A mixer is required when mixing oil slurry and supercritical carbon dioxide. Chinese patent CN 211514352 U discloses a dynamic mixer for high-viscosity media, which extrudes the medium in the upper chamber in a spiral shape into the inner cylinder to mix with other media. This can thoroughly and evenly mix the media and solve the problem of dead zones in the stirring device. However, since carbon dioxide only reaches a supercritical state at pressures above 7.38 MPa, the dynamic seal of the mixer suffers severe wear under high pressure, making long-term continuous operation difficult. Chinese patent CN211216214U discloses a static mixer for high-viscosity liquid materials. By adding mixing sections and flow guide sections inside the mixer, the mixing times of the liquid materials are effectively increased. However, due to the poor fluidity of the oil slurry, the flow is difficult and the pressure drop is large during mixing. Summary of the Invention

[0004] To address the problems of flow difficulties, large pressure drop, and difficulty in long-term continuous operation in existing mixing systems when mixing oil slurry and supercritical carbon dioxide, this invention provides a supercritical carbon dioxide catalytic cracking oil slurry mixing system.

[0005] The supercritical carbon dioxide catalytic cracking slurry mixing system provided by this invention includes a vertical tank and, arranged sequentially from top to bottom along the vertical tank, a supercritical carbon dioxide inlet, a supercritical carbon dioxide dispersion chamber, a dispersion pipe, a slurry dispersion chamber, a slurry inlet, a mixing pipe, a supercritical carbon dioxide outlet, and a mixture outlet. The supercritical carbon dioxide inlet is located at the top of the vertical tank and communicates with the supercritical carbon dioxide dispersion chamber. The supercritical carbon dioxide dispersion chamber is a closed cavity, and its bottom plate is provided with a vertical dispersion pipe communicating with the supercritical carbon dioxide dispersion chamber. The dispersion pipe wall is provided with dispersion holes. The system is characterized by: a closed end; an oil slurry dispersion chamber located below the supercritical carbon dioxide dispersion chamber; a vertical mixing pipe connected to the oil slurry dispersion chamber on its bottom plate; an open lower end of the mixing pipe; an oil slurry inlet located on the wall of the vertical tank containing the oil slurry dispersion chamber; a dispersion pipe inserted into the mixing pipe and coaxially arranged with it; a spiral guide vane surrounding the dispersion pipe within the annular space between the outer wall of the dispersion pipe and the inner wall of the mixing pipe; a supercritical carbon dioxide outlet located on the wall of the vertical tank below the oil slurry dispersion chamber; and a mixture outlet located at the bottom of the vertical tank.

[0006] The dispersion holes can be round holes, slits, or square holes. From a manufacturing perspective, round holes are preferable, with a diameter of 2–50 mm. Slits have a width of 2–20 mm and a length of 5–50 mm. As a recommended approach, to reduce the resistance of the slurry in the dispersion chamber and to ensure smoother flow and lower pressure drop, dispersion holes are not provided on the wall of the dispersion tube within the dispersion chamber area. Instead, the dispersion holes are located on the wall of the dispersion tube at the overlapping portion of the dispersion tube and the mixing tube.

[0007] The mixing tube has a diameter larger than the dispersion tube diameter, preferably 1.1 to 3 times the dispersion tube diameter. One end is connected to the oil slurry dispersion chamber, allowing the oil slurry entering from the dispersion chamber to enter the mixing tube, while the other end allows the mixture to exit the mixing tube. The mixing tube contains the mixing space for the oil slurry and supercritical carbon dioxide, where the supercritical carbon dioxide flowing out of the dispersion tube mixes with the oil slurry. As a preferred embodiment, to provide space for the expansion of the oil slurry and supercritical carbon dioxide after mixing, the mixing tube can be a conical tube with a smaller upper end and a larger lower end, allowing for smoother flow.

[0008] The spiral guide vane is spiral-shaped, and the pitch of the spiral guide vane is preferably 0.5 to 3 times the diameter of the dispersion tube. The spiral guide vane forms a spiral channel in the annular space between the outer wall of the dispersion tube and the inner wall of the mixing tube. After the oil slurry enters the mixing tube from the oil slurry dispersion chamber, it enters the spiral channel under the action of gravity. On the spiral guide vane, the oil slurry continuously swirls around the dispersion tube from top to bottom, constantly contacting the supercritical carbon dioxide entering from the dispersion hole. During the spiral motion, the oil slurry and supercritical carbon dioxide collide and change direction continuously, greatly enhancing the mixing time and mixing intensity of the oil slurry in the vertical tank, ensuring the mixing effect and effectively reducing the viscosity of the mixture.

[0009] As an optimization solution, to make full use of the spiral guide vanes in the mixing tube, the connection between the upper end of the mixing tube and the oil slurry dispersion chamber is partially open rather than completely open. The partial opening is located at the starting point of the spiral guide vanes, and the opening angle is one-eighth to one-quarter of the circumference of the upper end of the mixing tube. This allows more oil slurry to flow on the spiral guide vanes, improving the utilization rate of the spiral guide vanes and extending the time of the oil slurry in the mixing tube. On the other hand, it also helps the oil slurry enter the spiral guide vanes more smoothly.

[0010] As a further improvement, considering that the mixing of oil slurry and supercritical carbon dioxide requires a certain amount of time, the concentrated entry of supercritical carbon dioxide will cause local over-dissolved carbon dioxide, resulting in poor actual mixing effect. To further improve the mixing effect, the release of supercritical carbon dioxide can be controlled by the location and number of dispersion holes on the wall of the dispersion tube. The specific scheme is as follows: the dispersion holes on the dispersion tube are spirally distributed along the spiral direction of the spiral guide vane and located above the spiral guide vane, generally at a position of 10-100 mm above the spiral guide vane; the opening of the dispersion holes faces the direction of the spiral guide vane, and the supercritical carbon dioxide enters in the direction of oil slurry flow, which will promote the flow of oil slurry.

[0011] As a further solution, to further improve the space utilization within the vertical tank and enhance mixing intensity, the pitch of the spiral guide vanes should be set to gradually decrease from top to bottom. This is because in the first half of the process, the dissolved carbon dioxide in the slurry is less, resulting in poor fluidity; a larger pitch can increase the fluidity of the slurry. In the second half, as supercritical carbon dioxide gradually dissolves, the fluidity of the slurry improves, allowing the pitch to be reduced. This better utilizes the internal space of the vertical tank, increases the contact time between the slurry and supercritical carbon dioxide, and achieves a better mixing effect.

[0012] The supercritical carbon dioxide outlet is located below the oil slurry dispersion chamber, allowing supercritical carbon dioxide that has not been completely dissolved in the oil slurry to overflow. After overflowing, it can be directly discharged into the air, or it can be pressurized and circulated back to the supercritical carbon dioxide inlet through pipeline to continue dissolving into the oil slurry.

[0013] As a further solution, given the high temperature of the oil slurry and the potentially low temperature of the supercritical carbon dioxide, a heating chamber can be installed below the oil slurry dispersion chamber and above the supercritical carbon dioxide outlet to prevent excessive temperature drop and reduced fluidity of the mixture after mixing. The heating chamber is a closed cavity, formed by the outer wall of the mixing pipe, the bottom plate of the oil slurry dispersion chamber, the inner wall of the vertical tank, and the bottom plate of the heating chamber. The bottom plate of the heating chamber is a perforated plate located below the oil slurry dispersion chamber, through which the mixing pipe passes. The outer wall of the mixing pipe is fixedly and tightly connected to the opening in the bottom plate of the heating chamber. The vertical tank containing the heating chamber has an inlet and an outlet for a heat-insulating medium. The inlet is located in the lower part of the heating chamber, and the outlet is higher than the inlet. A heat-insulating medium can be introduced into the heating chamber, or a heater or heating coil can be installed to maintain the oil slurry, supercritical carbon dioxide, and their mixture at a suitable temperature.

[0014] As a further solution, an enhanced mixing element can be installed below the outlet of the mixing pipe. The purpose of using the enhanced mixing element is to further promote the mixing of oil slurry and supercritical carbon dioxide. The enhanced mixing element can be a multi-layer wire mesh, a multi-layer staggered grid, or a support-supported packing material with an increased specific surface area. The purpose is to use the large specific surface area to disperse the oil slurry and mix it with supercritical carbon dioxide, thereby enhancing the mixing effect.

[0015] The mixture outlet is located at the bottom of the vertical tank, either at the bottom of the side wall or at the bottom cap, allowing for further utilization of the mixed and viscosity-reduced slurry.

[0016] As an improvement, the bottom of the vertical tank can be set to be conical, and the liquid mixture is stored in the conical hopper under the action of gravity, making it easy for the mixture to leave from the mixture outlet.

[0017] The present invention has the following beneficial effects:

[0018] 1) By dispersing and mixing oil slurry and supercritical carbon dioxide separately, and under the guiding action of the spiral guide vanes in the annular space, the gravity of the oil slurry and the impact force of supercritical carbon dioxide are fully utilized to increase the fluidity of the oil slurry and improve the mixing effect, thus overcoming the shortcomings of high viscosity and poor fluidity of oil slurry and achieving the effect of mixing and reducing viscosity.

[0019] 2) The use of spiral blades increases the contact time and contact intensity between the oil slurry and supercritical carbon dioxide; when the mixing tube is a conical tube, the gradually increasing annular space can provide space for the mixture of oil slurry and supercritical carbon dioxide to expand, resulting in smooth flow and low flow pressure drop.

[0020] 3) The mixing system has no moving parts such as stirring elements, which reduces the energy consumption of the system, makes it suitable for high-pressure mixing conditions, and enables long-cycle operation of the mixing system. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the hybrid system of the present invention;

[0022] Figure 2 yes Figure 1 A schematic diagram of the radial cross-sectional structure at the location of the central heating cavity;

[0023] Figure 3 This is a diagram showing the arrangement of the dispersion holes on the dispersion tube.

[0024] In the diagram: 1-Supercritical carbon dioxide inlet, 2-Vertical tank, 3-Supercritical carbon dioxide dispersion chamber, 4-Dispersion pipe, 5-Oil slurry dispersion chamber, 6-Oil slurry inlet, 7-Mixing pipe, 8-Spiral guide vane, 9-Heating chamber, 10-Insulation medium inlet, 11-Insulation medium outlet, 12-Heating chamber bottom plate, 13-Supercritical carbon dioxide outlet, 14-Enhanced mixing element, 15-Mixed mixture outlet, 16-Dispersion hole. Detailed Implementation

[0025] The invention will now be further described with reference to the accompanying drawings.

[0026] like Figures 1-3 As shown, the supercritical carbon dioxide catalytic cracking slurry mixing system of the present invention includes a vertical tank 2 and, arranged sequentially from top to bottom along the vertical tank 2, a supercritical carbon dioxide inlet 1, a supercritical carbon dioxide dispersion chamber 3, a dispersion pipe 4, a slurry dispersion chamber 5, a slurry inlet 6, a mixing pipe 7, a spiral guide vane 8, a heating chamber 9, a heat-insulating medium inlet 10, a heat-insulating medium outlet 11, a heating chamber bottom plate 12, a supercritical carbon dioxide outlet 13, a strengthening mixing element 14, and a mixture outlet 15.

[0027] The supercritical carbon dioxide inlet 1 is located at the top of the vertical tank 2 and communicates with the supercritical carbon dioxide dispersion chamber 3. The supercritical carbon dioxide dispersion chamber 3 is a closed cavity on all four sides, and a vertical dispersion tube 4 communicating with the supercritical carbon dioxide dispersion chamber 3 is provided on its bottom plate. The dispersion tube 4 has dispersion holes 16 on its wall and is closed at the lower end. The oil slurry dispersion chamber 5 is located below the supercritical carbon dioxide dispersion chamber 3. The oil slurry dispersion chamber 5 is a closed cavity on all four sides, and a vertical mixing tube 7 communicating with the oil slurry dispersion chamber 5 is provided on its bottom plate. The mixing tube 7 is open at the lower end and is a conical tube with a smaller upper end and a larger lower end. The oil slurry inlet 6 is located on the wall of the vertical tank 2 where the oil slurry dispersion chamber 5 is located and communicates with the oil slurry dispersion chamber 5. The dispersion tube 4 is inserted into the mixing tube 7 and is coaxially arranged with the mixing tube 7. A spiral guide vane 8 is provided around the dispersion tube 4 in the annular space between the outer wall of the dispersion tube 4 and the inner wall of the mixing tube 7. A heating chamber 9 is located below the dispersion chamber 5 and above the supercritical carbon dioxide outlet 13. The heating chamber is a closed cavity, which is surrounded by the outer wall of the mixing pipe 7, the bottom plate of the oil slurry dispersion chamber 5, the inner wall of the vertical tank 2, and the bottom plate 12 of the heating chamber. The bottom plate 12 of the heating chamber is a perforated plate located below the oil slurry dispersion chamber 5. The mixing pipe 7 passes through the opening on it, and the outer wall of the mixing pipe 7 is fixedly and tightly connected to the opening of the bottom plate 12 of the heating chamber. The wall of the vertical tank 2, where the heating chamber 9 is located, is provided with a heat-insulating medium inlet 10 and a heat-insulating medium outlet 11. The heat-insulating medium inlet 10 is located in the lower part of the heating chamber 9, and the position of the heat-insulating medium outlet 11 is higher than the position of the heat-insulating medium inlet 10. A strengthening mixing element 14 is provided below the outlet of the mixing pipe 7. The strengthening mixing element 14 is a multi-layer wire mesh. The supercritical carbon dioxide outlet 13 is located on the wall of the vertical tank 2 below the heating chamber 9, and the mixture outlet 15 is located at the bottom of the vertical tank 2.

[0028] The pitch of the spiral guide vane 8 is 0.5 to 3 times the diameter of the dispersion tube 4. The spiral guide vane forms a spiral channel in the annular space between the outer wall of the dispersion tube 4 and the inner wall of the mixing tube 7. The pitch of the spiral guide vane 8 is set to gradually decrease from top to bottom.

[0029] like Figure 3 As shown, the dispersion holes 16 on the dispersion tube 4 are distributed in a spiral shape along the spiral direction of the spiral guide vane, and the openings of the dispersion holes 16 are oriented along the spiral direction of the spiral guide vane.

[0030] Figures 1-3The working process of the mixing system shown is as follows: Supercritical carbon dioxide enters the supercritical carbon dioxide dispersion chamber 3 through the supercritical carbon dioxide inlet 1, and after being evenly distributed in the supercritical carbon dioxide dispersion chamber 3, it enters the dispersion tube 4, and then enters the mixing tube 7 where the spiral guide vane 8 is located through the dispersion holes 16 on the wall of the dispersion tube 4; the oil slurry enters the oil slurry dispersion chamber 5 through the oil slurry inlet 6, and after being evenly distributed in the oil slurry dispersion chamber 5, it enters the mixing tube 7 to mix with the supercritical carbon dioxide. Under the action of gravity, the oil slurry continuously swirls around the dispersion tube 4 from top to bottom on the spiral guide vane, mixing with the supercritical carbon dioxide entering from the dispersion holes 16. As carbon continuously contacts the supercritical carbon dioxide and the oil slurry collide and change direction during the spiral motion, the mixing time and mixing intensity of the oil slurry in the vertical tank are greatly enhanced, ensuring the mixing effect and effectively reducing the viscosity of the mixture. The oil slurry mixture leaving the mixing pipe 7 is further mixed by the enhanced mixing element 14 and then discharged from the mixture outlet 15. The supercritical carbon dioxide that has not dissolved into the oil slurry is discharged through the supercritical carbon dioxide outlet 13. The heat preservation medium enters the heating chamber 9 through the heat preservation medium inlet 10, heats the oil slurry mixture in the mixing pipe 7, and then leaves the heating chamber 9 through the heat preservation medium outlet 11.

Claims

1. A supercritical carbon dioxide catalytic cracking slurry mixing system, characterized in that: The system includes a vertical tank and, arranged sequentially from top to bottom along the tank, a supercritical carbon dioxide inlet, a supercritical carbon dioxide dispersion chamber, a dispersion pipe, an oil slurry dispersion chamber, an oil slurry inlet, a mixing pipe, a supercritical carbon dioxide outlet, and a mixture outlet. The supercritical carbon dioxide inlet is located at the top of the vertical tank and communicates with the supercritical carbon dioxide dispersion chamber. The supercritical carbon dioxide dispersion chamber is a closed cavity with a vertical dispersion pipe on its bottom plate communicating with it. The dispersion pipe has dispersion holes on its wall and is closed at its lower end. The oil slurry dispersion chamber is located within the supercritical carbon dioxide dispersion chamber. Below the slurry dispersion chamber, the slurry dispersion chamber is a closed cavity on all four sides. A vertical mixing pipe communicating with the slurry dispersion chamber is provided on its bottom plate. The lower end of the mixing pipe is open. The slurry inlet is located on the tank wall of the vertical tank where the slurry dispersion chamber is located and communicates with the slurry dispersion chamber. The dispersion pipe is inserted into the mixing pipe and is coaxially arranged with the mixing pipe. A spiral guide vane is provided in the annular space between the outer wall of the dispersion pipe and the inner wall of the mixing pipe. The supercritical carbon dioxide outlet is located on the tank wall of the vertical tank below the slurry dispersion chamber. The mixture outlet is located at the bottom of the vertical tank. The mixing pipe is a conical pipe with a smaller upper end and a larger lower end.

2. The hybrid system according to claim 1, characterized in that: The pitch of the spiral guide vane should gradually decrease from top to bottom.

3. The hybrid system according to claim 1, characterized in that: The opening of the dispersion hole is oriented in the direction of the spiral guide vane, and the supercritical carbon dioxide enters in the direction of the oil slurry flow, thus promoting the flow of the oil slurry.

4. The hybrid system according to claim 1, characterized in that: The dispersion holes are all located on the wall of the dispersion tube in the overlapping part of the dispersion tube and the mixing tube.

5. The hybrid system according to claim 1, characterized in that: The upper end of the mixing tube is partially open at the connection point with the oil slurry dispersion chamber, and the open point is located at the starting point of the spiral guide vane.

6. The hybrid system according to claim 4, characterized in that: The pitch of the spiral guide vane should gradually decrease from top to bottom.

7. The hybrid system according to any one of claims 1 to 6, characterized in that: Below the oil slurry dispersion chamber is a heating chamber, which is a closed cavity formed by the outer wall of the mixing pipe, the bottom plate of the oil slurry dispersion chamber, the inner wall of the vertical tank, and the bottom plate of the heating chamber. The bottom plate of the heating chamber is a perforated plate located below the oil slurry dispersion chamber, through which the mixing pipe passes. The outer wall of the mixing pipe is fixedly and tightly connected to the opening of the bottom plate of the heating chamber. The vertical tank wall where the heating chamber is located has an inlet and an outlet for the insulating medium. The inlet for the insulating medium is located in the lower part of the heating chamber, and the outlet for the insulating medium is located higher than the inlet. The supercritical carbon dioxide outlet is located on the tank wall of the vertical tank below the heating chamber.

8. The hybrid system according to any one of claims 1 to 6, characterized in that: A mixing enhancement element is provided below the outlet of the mixing pipe.

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