CN112023839A - Gas pre-distributor of fluidized bed reactor - Google Patents

Abstract

The invention discloses a gas pre-distributor of a fluidized bed reactor, belonging to the field of fluidized bed design. The pre-distributor can improve the uniformity of gas distribution and liquid phase distribution and the stability of the operation of the fluidized bed reactor.

Description

A gas pre-distributor for a fluidized bed reactor

technical field

The present invention relates to a gas predistributor for a fluidized bed reactor.

Background technique

The fluidized bed reactor has the characteristics of high mass transfer and heat transfer efficiency, relatively uniform temperature distribution, and wide operating range. With the development of fluidized bed reactors in various industrial fields and the expansion of device scale, the uniform distribution of gas and liquid in fluidized bed reactors has become one of the key issues in its large-scale industrial design.

In industrial fluidized bed reactors, pre-distributors are often set above the gas inlet at the bottom of the reactor to improve the gas flow distribution at the bottom of the reactor and avoid direct impact of gas on the gas distribution plate, resulting in uneven distribution of gas and liquid below the distribution plate. The uniformity of the gas flow distribution under the distribution plate directly affects the fluidization quality and normal operation in the fluidized bed reactor. In the actual production process, a high liquid content area is often formed under the distribution plate, and then serious particle deposition and particle agglomeration occur, resulting in the blockage of the distributor by the polymer, which directly threatens the stable operation of the device.

The structure of the gas pre-distributor used in the fluidized bed in the prior art is relatively simple, and is mainly composed of a gas guide pipe and a flow guide. Among them, the deflector can be a general cap type, a conical ring, an annular baffle or a conical cap. For example, the pre-distributor used in CN102350275B is in the form of a conical cap and a guide tube. The gas pre-distributor adopted by CN102847491A combines a cylindrical structure and a conical structure. CN205517661U adopts a special annular flow deflector. However, the operation results of the industrial device show that the existing pre-distributor cannot achieve uniform distribution of the gas-liquid two phases under the condition of high liquid content, resulting in agglomeration and blockage of the distribution plate. Therefore, it is necessary to develop a new type of pre-distributor that has a wider operating range and can ensure the uniform distribution of gas and liquid even under the condition of high liquid content, so as to improve the operation stability of the fluidized bed reactor.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a gas pre-distributor for a fluidized bed reactor, which can make the inlet gas or gas-liquid mixture diffuse and the gas or gas-liquid mixture reaching the distribution plate to be more uniformly distributed to ensure the fluidized bed The liquid phase distribution under the reactor distribution plate can be relatively uniform, thereby ensuring the fluidization quality of the fluidized bed reactor, reducing the sticking wall and clogging of the gas pre-distributor, and ensuring the long-term stable operation of the device.

A fluidized-bed reactor gas pre-distributor, comprising horizontal annular baffles and a multi-layer conical table guide structure independently and coaxially arranged in sequence along the central axis of a gas inlet pipe of the fluidized-bed reactor, the The horizontal annular baffle and the multi-layer conical table guide structure are both located in the area between the gas inlet and the gas distribution plate of the fluidized bed reactor, and the horizontal annular baffle is close to the gas inlet; One end of the layered cone-shaped channel guide structure is close to the horizontal annular baffle and at the same height, and the other end is far away from the horizontal annular baffle.

When the gas or gas-liquid mixture enters the interior of the pre-distributor through the gas inlet pipe, the gas is first channeled through the multi-layer conical table diversion structure. Therefore, gas or gas-liquid mixture will pass through the outer side of the multi-layer cone-shaped trough guide structure. In order to make the gas or gas-liquid mixture distributed evenly outside the multi-layer cone-shaped trough guide structure, a horizontal annular baffle is added. At the same time, to prevent the inlet gas from directly rushing into the distribution plate, thereby causing uneven distribution of the liquid phase under the distribution plate, the multi-layer conical truncated flow guiding structure is set as a conical cap structure.

The horizontal annular baffle plate and the multi-layer conical table guide structure are both located in the area between the gas inlet of the fluidized bed reactor and the gas distribution plate;

The described horizontal annular baffle is close to the gas inlet, and there is a circular hole with a diameter D _i0 in the middle, and the outer diameter is D _O0 ;

The bottom end of the multi-layer cone-shaped table flow guiding structure is at the same level as the horizontal annular baffle;

The multi-layer cone-shaped truncated flow guiding structure has at least two layers inside, the inner and outer structures are parallel to the conical surfaces and there is a gap between the two, and the bottom end and the top of the multi-layer cone-shaped truncated flow guiding structure are provided with circular holes. , wherein the diameter of the bottom circular hole is D _bi , the diameter of the top circular hole is D _ui , i=1,2,...,n, n≥2.

The diameter relationship of the circular hole at the bottom of the multi-layer conical table guide structure is D _i0 >D _b1 >D _b2 >...>D _bn , and the diameter relationship of the top circular hole is D _u1 >D _u2 >... >D _un .

In order to allow the gas or gas-liquid mixture from the bottom inlet to pass through the gap between the horizontal annular baffle and the multi-layer conical table guide structure, and diffuse around the reactor to ensure that the gas or gas-liquid mixture reaching the distribution plate is evenly distributed, so The value range of the diameter of the circular hole at the bottom end of the first-layer cone-shaped truncated truncated diversion structure described above is: D _i0 ≥ D _b1 , and the value range of the top circular hole diameter D _u1 is: D _i0 ≤D _u1 ≤D _O0 .

The angle between the conical surface of the multi-layer cone-shaped trough guide structure and the central axis of the gas inlet pipe is 15°-75°, preferably 15°-60°, which can ensure that the gas or gas-liquid mixture is subjected to the diversion effect spread around the reactor.

The vertical distance between the outer side of the horizontal annular baffle and the bottom of the fluidized-bed reactor is h, and the area is S ₁ =hπD _O0 ; S ₁ represents the distance between the outer side of the horizontal annular baffle and the bottom of the fluidized-bed reactor The side area of the vertical cylinder is S ₂ =π(D _i0 ² -D _b1 ² )/4, and the annular area between the horizontal annular baffle and the bottom of the first-layer conical table diversion structure is The area of the circular hole at the bottom end of the conical table diversion structure is S ₃ =πD _b1 ² /4, and the relationship between S ₁ , S ₂ , and S ₃ is S ₃ ≤ S ₂ ≤ S ₁ , which can reduce the low pressure under the distribution plate. Liquid phase content zone to achieve uniform distribution of liquid phase.

When the number of layers of the conical truncated diversion structure is n=2, the area of the bottom ring between the first layer and the second layer is S ₄ =π(D _b1 ² -D _b2 ² )/4, and the second layer The area of the circular hole at the bottom end of the conical truncated diversion structure is S ₅ =πD _b2 ² /4, and the bottom annular area between the first layer of the conical truncated diversion structure and the second layer of the conical truncated diversion structure is S ₄ ≥ The circular hole area S ₅ at the bottom of the second-layer conical truncated flow guiding structure, wherein preferably 1.5≤S ₄ /S ₅ ≤10, ensures that the gas passing through the second-layer conical truncated flow guiding structure and the two-layer conical truncated guiding structure The amount of gas is evenly distributed between the flow structures.

The number of layers of the conical frustum diversion structure is n≥3, and the area of the bottom ring between the conical frustum diversion structure of the first layer and the conical frustum diversion structure of the second layer S ₄ ≥ the conical frustum of the second layer The bottom circular area S ₅ between the diversion structure and the third-layer conical truncated diversion structure is ≥...≥ the bottom circular hole area S _n+3 of the n-th conical truncated diversion structure.

For different sizes of reactors, different sizes of gas pre-distributors should be used. The specific dimensions can be simulated and optimized by the computational fluid dynamics software Fluent.

Compared with the existing pre-distributor, the gas pre-distributor provided by the present invention can improve the distribution of the gas phase, especially the liquid phase, under the distribution plate by setting a horizontal annular baffle plate and a multi-layer conical table guide structure to change the gas flow field. The uneven phenomenon reduces the impact of the fluid on the local part of the distribution plate and improves the stability of the fluidized bed reactor operation.

Description of drawings

1 is a schematic diagram of a fluidized bed reactor gas pre-distributor with a two-layer conical table guide structure provided by the present invention; wherein, 1 is a gas distribution plate, 2 is a second-layer conical table guide structure, 3 is the first-layer conical table diversion structure, 4 is the horizontal annular baffle, and 5 is the gas inlet pipe;

2 is a schematic diagram of the structural parameters of a fluidized-bed reactor gas pre-distributor with a two-layer conical stage guide structure provided by the present invention;

Figure 3 is the liquid phase distribution cloud diagram under the distribution plate of the fluidized bed reactor using the pre-distributor shown in Figure 1; the upper figure is the liquid phase distribution cloud diagram of the side section, and the lower figure is the liquid phase distribution cloud diagram under the distribution plate.

Figure 4 is a cloud diagram of liquid phase distribution under the distribution plate of a fluidized bed reactor using a predistributor with a single conical cap; the upper image is a side profile liquid distribution image, and the lower image is a liquid phase distribution image below the distribution plate.

FIG. 5 is a graph of the liquid phase volume fraction distribution under the distribution plate of the fluidized bed reactor using the pre-distributor shown in FIG. 1 .

Detailed ways

Example 1

As shown in Figure 1, the fluidized bed reactor gas pre-distributor of the present invention includes horizontal annular baffles 4 and multi-layer conical table guides that are independently arranged in sequence along the central axis of the gas inlet pipe of the fluidized bed reactor Structure (outer layer 3 and inner layer 2), the horizontal annular baffle 4 and the multi-layer two-layer conical truncated guide structure are all located between the gas inlet 5 and the gas distribution plate 1 of the fluidized bed reactor. area, the horizontal annular baffle 4 is close to the gas inlet 5; one end of the multi-layer cone-shaped truncated guide structure is close to the horizontal annular baffle 4 and at the same height, and the other end is far away from the horizontal annular baffle 4 . Rib plates are used to connect the conical table guide structures, between the conical table guide structures and the annular plate, and between the annular plate and the bottom head of the fluidized bed reactor.

For the reactor with an inner diameter of 3000m, the optimized structure of the gas pre-distributor is selected: the structural parameters of the horizontal horizontal annular baffle 4 are respectively D _i0 =700mm, and D _O0 : D _i0 is 2-2.5. A two-layer cone-shaped trough guide structure is selected, the height of the outer layer 2 is 280mm, and the included angle between the two-layer cone-shaped trough guide structure 2 and 3 and the central axis of the gas inlet pipe 4 is 15°-60°. The diameters D _u1 and D _u2 of the top circular holes of the two-layer conical truncated diversion structures 2 and 3 away from the horizontal annular baffle 4 are the largest, and the gap area S ₃ of the two-layer conical truncated diversion structures 2 and 3 is close to the inner layer. The ratio of the area S5 of the bottom circular holes of the horizontal annular baffle ₄ is 1.5-10, and the ratio of the diameters of the bottom circular holes D _b2 : D _b1 of the two-layer conical truncated diversion structures 2 and 3 close to the horizontal annular baffle 4 is 1.5-2, and the ratio of the diameters of the circular holes D _ui : D _bi at the bottom and the top of the two-layer conical truncated guide structures 2 and 3 near and far away from the horizontal annular baffle 4 is 2-5.

Example 2

In a gas-solid fluidized bed reactor with a diameter of 3039mm, air is used as the gas-phase fluidized phase, the apparent operating gas velocity of the fluidized bed is 0.6489m/s, and the inlet gas velocity is 17.7m/s. Fluent fluid mechanics simulation software is used. Do a simulation. The form of the gas pre-distributor is shown in Figure 1: Among them, the inner and outer diameters of the horizontal annular baffle 4 are 700mm and 1500mm respectively, and the distance from the gas inlet is 140mm; The inner and outer diameters of one end port of the diversion structure 2 and 3 close to the gas inlet pipe 1 are 200mm and 395mm respectively. The gap between the two-layer conical table diversion structure 2 and 3 is 50mm. 3. The inner and outer diameters of one end port away from the gas inlet pipe 1 are 800mm and 995mm respectively. The angle between the two-layer cone-shaped truncated flow guiding structures 2 and 3 and the central axis of the gas inlet pipe 5 is 45°, and the height of the cone-shaped truncated flow guiding structure is 282.84 mm.

Comparative Example 1

In a gas-solid fluidized bed reactor with a diameter of 3039mm, air is used as the gas-phase fluidized phase, the apparent operating gas velocity of the fluidized bed is 0.6489m/s, and the inlet gas velocity is 17.7m/s. Fluent fluid mechanics simulation software is used. Do a simulation. The gas pre-distributor with a single-layer conical cap is used as a comparative example, wherein the inner and outer diameters of the horizontal annular baffle 4 are 500 mm and 1500 mm, respectively, and the distance from the gas inlet is 140 mm; the conical cap structure is close to and far from the gas inlet. The diameters of the pipes are 395mm and 700mm respectively; the angle between the conical cap and the central axis is 24°, and the height of the conical frustum guide structure is 369.72mm.

Fig. 3 is the liquid phase distribution cloud diagram of the fluidized bed reactor of Example 2 under the condition of producing DGDA6098 brand high-density polyethylene plastics, and the liquid phase volume fraction is between 0.007-0.01. As can be seen from Figure 3, the horizontal annular baffle 4 at the bottom of the fluidized-bed reactor presses the inlet air flow to the wall of the head, and the two-layer conical table guide structures 2 and 3 with a 45° inclination angle press the inlet air flow to the wall. The horizontal annular baffle plate 4, the outer layer 2 and the inner layer 3 of the two-layer conical table guide structure avoid the direct impact of the inlet airflow on the gas distribution plate 1. The gas velocity distribution in the entire gas pre-distributor is relatively uniform, so the liquid phase distribution driven by the gas phase is relatively uniform and reasonable. At the same time, Figure 4 is the liquid phase distribution cloud diagram of the comparative fluidized bed reactor under the condition of producing the DGDA6098 high-density polyethylene plastic using the combination of the horizontal guide vane, the guide tube and the conical cap designed in CN102350275B, The liquid phase volume fraction is between 0.007-0.01. It can be seen from Figure 4 that the design of a single conical cap will lead to poor liquid distribution uniformity, and local low-velocity areas and areas with high liquid content will appear. However, the liquid phase distribution obtained in the form of the horizontal annular baffle combined with the multi-layer conical table diversion structure is more uniform and reasonable, and there will be no local low-velocity areas and areas with high liquid content.

Fig. 5 is the liquid phase volume fraction distribution under the distribution plate after the gas pre-distributor of Example 2 is used in the fluidized bed reactor. Under the action of the two-layer cone-shaped truncated guide structures 2 and 3 and the horizontal annular baffle 4, the gas-liquid distribution is relatively reasonable. Therefore, the direct impact of the inlet gas on the distribution plate 1 is avoided, and the obtained liquid phase volume fraction under the distribution plate is between 0.0097-0.0099, and the distribution is relatively uniform.

The above-mentioned embodiment is only a preferred solution of the present invention, but it is not intended to limit the present invention. Various changes and modifications can also be made by those of ordinary skill in the relevant technical field without departing from the spirit and scope of the present invention. Therefore, all technical solutions obtained by means of equivalent replacement or equivalent transformation fall within the protection scope of the present invention.

Claims (10)

1. a gas pre-distributor of a fluidized-bed reactor, comprising a horizontal annular baffle and a multi-layer conical table guide structure independently and coaxially arranged successively along the central axis of the gas inlet pipe of the fluidized-bed reactor , which is characterized by: The horizontal annular baffle plate and the multi-layer conical table guide structure are both located in the area between the gas inlet of the fluidized bed reactor and the gas distribution plate; The horizontal annular baffle is close to the gas inlet, and a circular hole is opened in the middle; The number of layers of the multi-layer cone-shaped truncated flow guiding structure is at least two, and the bottom end of each layer of the cone-shaped truncated flow guiding structure is at the same level as the flat annular baffle; The bottom end and the top end of each layer of the conical table guide structure are provided with circular holes. 2 . The gas pre-distributor of the fluidized bed reactor according to claim 1 , wherein the tops of the conical table guide structures of each layer are located above the horizontal annular baffle and at the same height. 3 . 3. the gas pre-distributor of the fluidized-bed reactor according to claim 1 and 2, is characterized in that, the diameter of the bottom circular hole of each layer of conical platform guide structure is D _bi , and the diameter of the top circular hole is D _ui , the layer number i=1,2,...,n, n≥2, the outer diameter of the horizontal annular baffle is D _O0 , the diameter of the circular hole opened on it is D _i0 , then D _i0 >D _b1 > D _b2 >…>D _bn , D _u1 >D _u2 >…>D _un . 4. The gas pre-distributor of the fluidized bed reactor according to claim 3, characterized in that, the value range of the diameter D _u1 of the top circular hole of the first-layer conical table guide structure is: D _{i0 ≤} D _u1 ≤D _O0 . 5 . The gas pre-distributor for a fluidized bed reactor according to claim 1 , wherein the conical surfaces of the conical truncated flow guiding structures of each layer are parallel and there is a gap between them. 6 . 6. The gas pre-distributor of the fluidized bed reactor according to any one of claims 1-5, wherein the conical surface of the multi-layer conical table guide structure is in the middle of the gas inlet pipe The included angle of the axis is 15°～75°. 7. The gas pre-distributor of the fluidized bed reactor according to any one of claims 1-6, characterized in that: The vertical distance between the outside of the horizontal annular baffle and the bottom of the fluidized-bed reactor is h, denoted area S ₁ =hπD _O0 ; The annular area between the horizontal annular baffle and the bottom of the first-layer conical-stage flow guiding structure is S ₂ =π(D _i0 ² -D _b1 ² )/4; The area of the circular hole at the bottom end of the first-layer conical table flow guiding structure is S ₃ =πD _b1 ² /4; The relationship between S ₁ , S ₂ , and S ₃ is S ₃ ≤S ₂ ≤S ₁ . 8. The gas pre-distributor of the fluidized bed reactor according to any one of claims 1-7, wherein the number of layers of the conical truncated flow guiding structure is n=2, and the first layer of the conical truncated The bottom annular area S ₄ between the diversion structure and the second-layer conical truncated diversion structure ≥ the bottom circular hole area S ₅ of the second-layer conical truncated diversion structure. 9 . The gas pre-distributor of the fluidized bed reactor according to claim 8 , wherein 1.5≦S ₄ /S ₅ ≦10. 10 . 10. The gas pre-distributor for a fluidized bed reactor according to any one of claims 1-7, wherein the number of layers of the conical trough flow guiding structure is n≥3, and the first layer of the conical trough Bottom annular area S ₄ between the diversion structure and the second-layer conical truncated diversion structure ≥ The bottom annular area S between the second-layer conical truncated diversion structure and the third-layer conical truncated diversion structure ₅ ≥...≥The area of the circular hole at the bottom of the n-th conical truncated diversion structure S _n+3 .

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