Dual dense phase circulating fluidized bed with prevention of bidirectional channeling

Abstract

This invention discloses a dual-dense-phase circulating fluidized bed for preventing bidirectional gas leakage, mainly comprising an ascending bed, an overflow pipe, a descending bed, and a return valve. The upper part of the ascending bed and the upper-middle part of the descending bed are connected by the overflow pipe, and the lower parts of both are connected by the return valve. During normal operation, both the ascending and descending beds are in a dense-phase fluidized state, but the operating gas velocity of the ascending bed is higher than that of the descending bed. The density difference between the two beds drives the particle circulation. In the upper part of the ascending bed, particles enter the descending bed through the overflow pipe, and the material seal in the overflow pipe prevents gas leakage between the upper parts of the two beds. In the lower part of the descending bed, particles enter the ascending bed through the return valve, and the return valve prevents gas leakage between the lower parts of the two beds. This equipment has a compact structure and flexible operation, effectively avoiding the gas leakage problem between the ascending and descending beds. The two beds can perform gas-solid contact operations completely independently, and the gases discharged from the two beds will not "contaminate" each other, eliminating the need for subsequent additional separation.

Description

Technical Field

[0001] This invention relates to the field of fluidized bed reactors, specifically a dual-dense-phase circulating fluidized bed that prevents bidirectional gas leakage. Background Technology

[0002] Bubbling fluidized bed reactors are commonly used for handling contact operations between gases and particulate matter. Specifically, when used for processes such as catalytic conversion, adsorption separation, and filtration, the particles in the bed gradually become deactivated or saturated. To ensure continuous gas processing, the deactivated / saturated particles need to be removed from the bed for regeneration, and the regenerated particles returned to the bubbling fluidized bed.

[0003] A circulating fluidized bed consists of an upward-flowing fluidized bed and a downward-flowing fluidized bed, with particles circulating between the two beds. This provides a good solution to the above problem: the downward-flowing bed can continuously process gas A, while the upward-flowing bed can regenerate the particles using gas B; the circulating flow of particles can continuously transport deactivated / saturated particles from the downward-flowing bed to the upward-flowing bed, while simultaneously returning regenerated particles from the upward-flowing bed to the downward-flowing bed.

[0004] Currently, two types of circulating fluidized beds have been proposed to solve the problem of continuous extraction, regeneration, and return of particles in bubbling fluidized beds.

[0005] The first type is based on dilute-dense phase circulating fluidization processes, which is the traditional circulating fluidized bed. For example... Figure 1 As shown, this type of circulating fluidized bed mainly consists of four parts: riser 1 (particles ascending), cyclone separator 2, vertical pipe 3 (particles descending), and return valve 4 (Guo Musun et al., Fluidization Handbook, 2007, Chemical Industry Press, pp. 240). This circulating fluidized bed can effectively avoid the problem of gas leakage between riser 1 and vertical pipe 3, so the gas-solid contact operation in the two beds can be carried out completely independently without interference. In addition, the gases discharged from the two beds will not "contaminate" each other, have high purity, and do not require additional separation. However, the disadvantages of the dilute-dense phase circulating fluidized bed are also very significant: 1) the equipment is large, the investment is high, and the operation is complex; 2) the wear between particles and equipment is severe, which is not conducive to long-term operation; 3) the fine powder generated by wear will contaminate the gas, resulting in a high dust removal load.

[0006] The second type is based on dense-dense phase circulating fluidization or dual-dense phase circulating fluidization processes. Currently, this type of circulating fluidization process is generally achieved by setting baffles or guide tubes inside the bubbling fluidized bed, commonly referred to as an internal circulating fluidized bed, such as the devices constructed in Chinese patents CN2487738Y, CN1096715A, CN106914192A, and 202210484133.5. Figure 2As shown, this type of circulating fluidized bed consists of an upward bed 1, an intermediate partition 2, and a downward bed 4. Gaps or orifices 3 and 5 are provided at the bottom and top of the partition 2 as channels for particle circulation. On both the upward and downward sides of the internal circulating fluidized bed, the particles are in a dense-phase fluidized state, but due to different operating gas velocities, they have different bed densities. This density difference drives the particles to circulate on both sides of the partition. Although the internal circulating fluidized bed overcomes the disadvantages of large-scale traditional dilute-dense phase circulating fluidized beds and maintains the advantage of a compact bubbling fluidized bed structure, it also has significant drawbacks. Severe gas leakage occurs between the upward and downward beds, preventing independent gas-solid contact operation on both sides. Furthermore, the gases discharged from both sides are mutually contaminated, resulting in low purity and requiring additional separation methods.

[0007] In conclusion, to date, no circulating fluidized bed has been able to effectively avoid the gas leakage problem between the ascending and descending beds while maintaining a compact equipment structure. Summary of the Invention

[0008] The purpose of this invention is to solve the above-mentioned technical problems by proposing a compact dual-density phase circulating fluidized bed, in which particles can circulate between the ascending and descending beds without the problem of bidirectional gas leakage. Different gas-solid contact operations can be carried out completely independently in the two beds, and the outlet gases will not contaminate each other.

[0009] A dual-dense phase circulating fluidized bed for preventing bidirectional gas leakage includes an upward bed, an overflow pipe, a downward bed, and a return valve.

[0010] Both the ascending and descending beds are in a dense-phase fluidization state, such as bubbling or turbulent fluidization.

[0011] The operating gas velocity in the ascending bed is greater than that in the descending bed, and the bed density of the ascending bed is less than that of the descending bed. This density difference is the original driving force that enables the particles to circulate.

[0012] The upper part of the ascending bed and the upper part of the descending bed are connected by an overflow pipe, and the material in the ascending bed enters the overflow pipe in the form of overflow.

[0013] The material seal in the overflow pipe can prevent air leakage between the upper part of the upper and lower beds.

[0014] The lower part of the descending bed and the lower part of the ascending bed are connected by a return valve.

[0015] The aforementioned return valve can prevent air leakage between the lower part of the descending bed and the lower part of the ascending bed, and can also adjust the particle circulation rate to a certain extent.

[0016] Preferably, the inclination angle of the overflow pipe is generally greater than the angle of repose of the particles to ensure that the particles can flow down smoothly.

[0017] Preferably, the return valve can be a pneumatic valve or a mechanically driven valve.

[0018] The beneficial effects of this invention are as follows: It provides a novel dual-dense-phase circulating fluidized bed, in which particles can circulate between the ascending and descending beds, and the cross-flow problem between the ascending and descending beds can be effectively avoided. Compared with the existing technical solutions, the solution proposed in this invention has the following advantages: (1) The equipment structure is compact, the investment cost is small, and the operation is simple and flexible; (2) The wear between the particles and the inner wall of the fluidized bed is small, and it is easy to achieve long-term operation; (3) The fine powder generated by particle loss is small, and the subsequent dust removal load of the gas is small; (4) There is no cross-flow problem between the lower parts of the ascending and descending beds, and the gas-solid contact operation can be carried out completely independently in the two beds without interfering with each other; (5) There is no cross-flow problem between the upper part of the ascending bed and the upper part of the descending bed, and the discharged gas will not "contaminate" each other, and no additional separation means are required afterward; (6) In addition to the operating gas velocity of the two beds, the return valve can also assist in adjusting the particle circulation rate. Attached Figure Description

[0019] Figure 1 It is a traditional rare-dense phase circulating fluidized bed.

[0020] Figure 2 It is a traditional dual-dense phase circulating fluidized bed.

[0021] Figure 3 This is a dual-close-phase circulating fluidized bed using a pneumatic return valve.

[0022] Figure 4 This is a dual-close-phase circulating fluidized bed using a mechanical return valve. Detailed Implementation

[0023] Implementation Method 1

[0024] The following is in conjunction with the appendix Figure 3 The apparatus of the present invention will be further described as follows:

[0025] See Figure 3 1 is the gas outlet of the moving bed, 2 is the moving bed, 3 is the air chamber of the moving bed, 4 is the gas inlet of the moving bed, 5 and 6 are the gas inlets of the pneumatic return valve, 7 is the gas inlet of the moving bed, 8 is the air chamber of the moving bed, 9 is the gas distribution plate, 10 is the pneumatic return valve, 11 is the moving bed, 12 is the overflow pipe, and 13 is the gas outlet of the moving bed.

[0026] During operation, gas is introduced into both the ascending bed 2 and the descending bed 11, both operating in a dense-phase fluidized state. However, the operating gas velocity of the ascending bed 2 is higher than that of the descending bed 11. Therefore, the bed density of the ascending bed 2 is lower than that of the descending bed 11, while the material level in the ascending bed 2 is higher than that in the descending bed 11. In the upper part of the ascending bed 2, particles carried up by air bubbles first fall into the overflow pipe 12 and eventually enter the descending bed 11 by gravity. In the descending bed 11, the particles are macroscopically in a dense-phase fluidized state, but move downwards overall. The pressure at the bottom of the descending bed 11 is greater than that at the bottom of the ascending bed 2. Driven by this pressure difference, the particles first enter the pneumatic return valve 10 and eventually return to the bottom of the ascending bed 2. In this way, the particles can continuously circulate between the ascending and descending beds.

[0027] During the particle circulation process, a certain amount of particles will accumulate in the overflow pipe 12. These particles can play an effective material sealing role, thereby avoiding the problem of gas leakage between the upper part of the ascending bed 2 and the lower bed 11. Finally, the gas discharged from the ascending bed 2 and the lower bed 11 will not "contaminate" each other, and no additional separation is required afterward.

[0028] A large number of particles will also accumulate in the pneumatic return valve 10, which can avoid the problem of air leakage between the lower parts of the upper bed 2 and the lower bed 11. Ultimately, the upper bed 2 and the lower bed 11 can perform gas-solid contact operation completely independently without interfering with each other.

[0029] A certain amount of loosening gas needs to be introduced into the pneumatic return valve 10. Inert and easily separable gases (such as water vapor) can be used to minimize the load required for subsequent separation, while not affecting the gas-solid contact operation in the ascending bed 2 and descending bed 11. In addition to the ascending bed gas velocity and the descending bed gas velocity, the pneumatic return valve 10 can also assist in adjusting the particle circulation rate.

[0030] Implementation Method 2

[0031] The following is in conjunction with the appendix Figure 4 The apparatus of the present invention will be further described as follows:

[0032] See Figure 4 1 is the gas outlet of the moving bed, 2 is the moving bed, 3 is the gas distribution plate, 4 is the air chamber of the moving bed, 5 is the gas inlet of the moving bed, 6 is the gas inlet of the moving bed, 7 is the air chamber of the moving bed, 8 is the mechanical return valve, 9 is the drive motor of the mechanical return valve, 10 is the moving bed, 11 is the overflow pipe, and 12 is the gas outlet of the moving bed.

[0033] During operation, gas is introduced into both the ascending bed 2 and the descending bed 10, both operating in a dense-phase fluidized state. However, the operating gas velocity of the ascending bed 2 is higher than that of the descending bed 10. Therefore, the bed density of the ascending bed 2 is lower than that of the descending bed 10, while the material level in the ascending bed 2 is higher than that in the descending bed 10. In the upper part of the ascending bed 2, particles carried up by air bubbles first fall into the overflow pipe 11 and eventually enter the descending bed 10 by gravity. In the descending bed 10, the particles are macroscopically in a dense-phase fluidized state, but move downwards overall. The pressure at the bottom of the descending bed 10 is greater than that at the bottom of the ascending bed 2. Driven by this pressure difference, the particles first enter the mechanical return valve 8 and eventually return to the bottom of the ascending bed 2. In this way, the particles can continuously circulate between the ascending and descending beds.

[0034] During the particle circulation process, a certain amount of particles will accumulate in the overflow pipe 11. These particles can play an effective material sealing role, thereby avoiding the problem of gas leakage between the upper part of the ascending bed 2 and the lower bed 10. Finally, the gas discharged from the ascending bed 2 and the lower bed 10 will not "contaminate" each other, and no additional separation is required afterward.

[0035] A large number of particles will also accumulate in the mechanical return valve 8, which can avoid the problem of air leakage between the lower parts of the upper bed 2 and the lower bed 10. Ultimately, the upper bed 2 and the lower bed 10 can perform gas-solid contact transmission operations completely independently, without mutual interference.

[0036] The mechanical return valve 8 is driven by a motor 9, which can effectively regulate the circulation rate of the particles.

[0037] The above descriptions are merely two specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A dual-dense-phase circulating fluidized bed for preventing bidirectional gas leakage, characterized in that, It includes the following components: an ascending bed, an overflow pipe, a descending bed, and a return valve. The upper part of the ascending bed and the upper-middle part of the descending bed are connected by the overflow pipe, and the lower parts of the two are connected by the return valve. During normal operation, both the ascending and descending beds are in a dense phase fluidization state, but the operating gas velocity of the ascending bed is higher than that of the descending bed, and the bed density of the ascending bed is lower than that of the descending bed. The difference in density between the two beds drives the particle circulation. The material level in the ascending bed is higher than that in the descending bed. In the upper part of the ascending bed, particles enter the descending bed through the overflow pipe. The material seal in the overflow pipe can prevent air leakage between the upper parts of the two beds. In the lower part of the descending bed, particles enter the ascending bed through the return valve. The return valve can prevent air leakage between the lower parts of the two beds and can also effectively regulate the particle circulation rate. The particles in the upward bed overflow into the downward bed through the overflow pipe.

2. A dual-dense-phase circulating fluidized bed for preventing bidirectional gas leakage as described in claim 1, characterized in that, The difference in bed density between ascending and descending bed beds is due to the different operating gas velocities of the two beds.

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