Catalyst grid for radial reactor and radial reactor

Abstract

A catalyst grid for a radial reactor and a radial reactor, belonging to the field of catalyst support and fixation in petrochemical reactions, comprises a cylindrical structure formed by rolling a Johnson mesh formed by woven metal wire strips. Along the axial direction of the grid tube and in accordance with the flow direction of the reactants, the grid tube is divided into an upper region near the reactant inlet of the radial reactor, a middle region, and a lower region near the reactant outlet of the radial reactor. The cross-section of the metal wire strips in the upper region is a special shape formed by splicing an isosceles triangle and an isosceles trapezoid, the cross-section of the metal wire strips in the middle region is an ellipse, and the cross-section of the metal wire strips in the lower region is a circle. This invention changes the flow parameters of the catalyst particles, significantly reducing the wear between the catalyst particles and the wear between the catalyst particles and the Johnson mesh during flow.

Description

Technical Field

[0001] The present invention relates to the field of catalyst support and fixation in petrochemical reactions, in particular to a catalyst grid for a radial reactor and a radial reactor. Background Art

[0002] In the petrochemical production process, reactants are introduced into a reactor and react under the catalytic action of the catalyst within the reactor. To ensure sufficient contact between the reactants and the catalyst, existing fixed-bed reactors typically use a Johnson mesh grid to secure the catalyst layer within the reactor. Because the Johnson mesh is a mesh structure, the reactants will pass through it to contact the catalyst without affecting the flow of the reactants within the reactor.

[0003] During the reaction process, friction, erosion and collision occur continuously between the catalysts, between the catalysts and the reaction materials, and between the catalysts and the grid, causing the catalysts to be worn and damaged, which in turn leads to problems such as increased reaction pressure, uneven reaction temperature, and reduced reaction efficiency, which is not conducive to the control of the reaction process.

[0004] In order to solve the problem of catalyst wear and damage, the commonly adopted measure at present is to increase the catalyst strength. However, after a period of operation, the catalyst will inevitably wear out, especially under abnormal operating conditions, the catalyst wear phenomenon is more obvious; and increasing the catalyst strength is generally achieved by changing the manufacturing process or changing the catalyst composition, which will inevitably increase the cost of the catalyst. Summary of the Invention

[0005] The purpose of the present invention is to provide a catalyst grid for a radial reactor and a radial reactor. By improving the structure of the Johnson mesh, the flow parameters of the catalyst particles are changed, and the wear between the catalyst particles and the wear between the catalyst particles and the Johnson mesh during flow is greatly reduced. At the same time, it can also improve the distribution uniformity of the reaction materials after passing through the catalyst layer to a certain extent.

[0006] The technical solution adopted by the present invention to achieve the above technical objectives is: a catalyst grid tube for a radial reactor, the grid tube being a cylindrical structure formed by rolling a Johnson mesh formed by woven metal wire strips. Along the axial direction of the grid tube and in accordance with the flow direction of the reactants, the grid tube is divided into an upper region near the reactant inlet of the radial reactor, a middle region, and a lower region near the reactant outlet of the radial reactor;

[0007] The cross-sectional shape of the metal wire strips in the upper region is a special shape formed by splicing an isosceles triangle and an isosceles trapezoid. When the two are spliced ​​together, the base of the isosceles triangle is connected to the short base of the isosceles trapezoid as a whole, and the long base of the isosceles trapezoid forms a planar contact surface with the catalyst, and gap channels are formed on both sides of the planar contact surface.

[0008] The cross-section of the metal wire strip in the middle region is elliptical, and the arc corresponding to the long axis of the ellipse forms an arc-shaped contact surface in contact with the catalyst, and gap channels are also formed on both sides of the arc-shaped contact surface;

[0009] The cross section of the metal wire strip in the lower area is circular, forming an arc-shaped contact surface in contact with the catalyst, and gap channels are also formed on both sides of the arc-shaped contact surface.

[0010] As an optimization solution for the catalyst grid for the radial reactor, the slit channel width in the upper region is smaller than that in the middle region, and the slit channel width in the middle region is smaller than that in the lower region.

[0011] As another optimization solution for the catalyst grid for the radial reactor, the width of the upper region is 20-30% of the axial length of the grid tube, the width of the middle region is 20-30% of the axial length of the grid tube, and the rest is the lower region.

[0012] As another optimization solution for the catalyst grid for the radial reactor, the metal wire strips with special-shaped cross-sections in the upper region are chamfered at the corners of the cross-sections to form arc-shaped transitions.

[0013] As another optimization scheme for the catalyst grid for the above-mentioned radial reactor, during the chamfering treatment, the chamfer radian is determined according to the particle shape of the catalyst, and when the catalyst is spherical, the chamfer radian is not less than the diameter of the spherical catalyst, and when the catalyst is strip-shaped, the chamfer radian is not less than 5 times the catalyst diameter.

[0014] As another optimization scheme for the catalyst grid for the above-mentioned radial reactor, the metal wire strips with special-shaped cross-section in the upper area form an isosceles triangle with a special-shaped cross-section, and the angle formed by the two sides is greater than the angle formed by the extension lines of the two sides of the isosceles trapezoid, so that the width of the gap channel in the upper area forms two variable diameter areas with different slopes.

[0015] As another optimization solution for the catalyst grid for the radial reactor, the angle formed by the extension lines of the two sides of the isosceles trapezoid is 20-40°, and the angle formed by the two sides of the isosceles triangle is 30-50°.

[0016] As another optimization solution for the catalyst grid for the radial reactor, the metal wire strips with special-shaped cross-sections in the upper region form an isosceles triangle with a height ratio of 2-3:1 to an isosceles trapezoid with a special-shaped cross-section.

[0017] As another optimization solution for the catalyst grid for the radial reactor, the slit channels in the upper, middle and lower regions gradually increase in width along the line from the reactant inlet to the reactant outlet of the radial reactor.

[0018] As another optimization scheme for the catalyst grid for the above-mentioned radial reactor, in the upper region, the ratio of the width of the planar contact surface to the width of the slit channel openings on both sides thereof is 0.5-5; the ratio of the maximum width to the minimum width of the slit channel in the middle region is 0.5-2; and the ratio of the maximum width to the minimum width of the slit channel in the lower region is 0.5-2.

[0019] A radial reactor comprises two layers of inner and outer catalyst grid tubes arranged in a reactor cylinder, wherein a catalyst bed is sandwiched between the two layers of catalyst grid tubes, and the grids are the grids mentioned above.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention divides the grid tube of a radial reactor into three areas, upper, middle and lower, along the direction of reactant flow. Each area is woven into a Johnson mesh using different metal wire strips, thereby forming contact surfaces and gap channels of different shapes that contact the catalyst layer, thereby changing the flow parameters of the catalyst particles and significantly reducing the wear between the catalyst particles and the wear between the catalyst particles and the Johnson mesh during flow. Experiments have shown that compared with the existing Johnson mesh with a circular cross-section, the use of the Johnson mesh of the present invention to make a grid tube structure in a radial reactor can effectively reduce the wear of the catalyst particles by more than about 50%. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the cross-sectional shape of the Johnson net in the upper region (a special shape formed by splicing an isosceles trapezoid and an isosceles triangle);

[0023] Figure 2 Schematic diagram of the cross-sectional shape of the Johnson net in the middle region (ellipse);

[0024] Figure 3 Schematic diagram of the cross-sectional shape of the Johnson net in the lower region (circle);

[0025] Figure 4 Schematic diagram of the structure of the radial reactor. DETAILED DESCRIPTION

[0026] The technical solutions of the present invention are further described in detail below with reference to specific embodiments. Any portions of the present invention not described in detail in the following embodiments should be understood as prior art known or should be known to those skilled in the art, such as how to weave a Johnson mesh with metal wire strips, how to fabricate the Johnson mesh into a grid tube to hold a catalyst, and how to secure the Johnson mesh within a radial reactor.

[0027] Example 1

[0028] A catalyst grid tube for a radial reactor. The grid tube is a cylindrical structure formed by rolling a Johnson mesh formed by woven metal wire strips. Along the axial direction of the grid tube and in accordance with the flow direction of the reactants, the grid tube is divided from top to bottom into an upper area near the reactant inlet of the radial reactor, a middle area, and a lower area near the reactant outlet of the radial reactor.

[0029] The upper area is cylindrical, the width of the cylinder (ie, the axial length) is 20-30% of the axial length of the grid tube, and the cross-section of the metal wire strips in this area is a special shape formed by splicing an isosceles triangle and an isosceles trapezoid, such as Figure 1 As shown, when the two are spliced ​​together, the base of the isosceles triangle is connected to the short base of the isosceles trapezoid as a whole, and the long base of the isosceles trapezoid forms a planar contact surface with the catalyst, and gap channels are formed on both sides of the planar contact surface; at this time, the width of the gap channel in the upper area gradually increases from the side in contact with the catalyst to the other side, forming a trumpet-shaped gap channel;

[0030] In the upper region, the ratio of the width of the planar contact surface to the width of the slot channel openings on both sides thereof is 1.5-4:1;

[0031] The middle area is also cylindrical and connected to the upper area. The width of the cylinder (i.e., the axial length) is 20-30% of the axial length of the grid tube. The cross-section of the metal wire strips in this area is elliptical, and the arc corresponding to the long axis of the ellipse forms an arc-shaped contact surface with the catalyst, such as Figure 2 As shown, slit channels are also formed on both sides of the arc-shaped contact surface; at this time, the width of the slit channel in the middle area gradually decreases from the side in contact with the catalyst to the other side, and then gradually increases, forming a hyperbolic slit channel;

[0032] In the middle region, the ratio of the maximum width to the minimum width of the slit channel is 2–5:1;

[0033] The rest of the grid tube except the upper and middle areas is the lower area, which is also cylindrical. The cross section of the metal wire strips in this area is circular, forming an arc-shaped contact surface with the catalyst, such as Figure 3As shown, slit channels are also formed on both sides of the arc-shaped contact surface; at this time, the width of the slit channel in the lower area gradually decreases from the side in contact with the catalyst to the other side, and then gradually increases, forming a hyperbolic slit channel;

[0034] In the lower region, the ratio of the maximum width to the minimum width of the slit channel is 3-6:1.

[0035] In this embodiment, the width of the slit channel in the upper area is smaller than the width of the slit channel in the middle area, and the width of the slit channel in the middle area is smaller than the width of the slit channel in the lower area. The most preferred embodiment is that the width of the slit channels in the upper area, the middle area and the lower area gradually increases along the radial direction of the reactor from the reactant inlet to the reactant outlet. From the overall direction of the grid tube, the upper part of the grid tube is close to the reactant inlet of the reactor, and the lower part is close to the reactant outlet of the reactor. From top to bottom, the width of the slit channels of the grid tube becomes larger and larger.

[0036] The above is a basic implementation of the present invention, and further improvements, optimizations and limitations can be made on the above basis to obtain the following embodiments:

[0037] Example 2

[0038] This embodiment is an optimized solution based on the embodiment 1. Its main structure is the same as that of the embodiment 1. The improvement is that: the metal wire strips with special cross-sections in the upper region are chamfered at the corners of the metal wire strip cross-section to form an arc-shaped transition.

[0039] In this embodiment, during the chamfering treatment, the chamfer radius is determined according to the particle shape of the catalyst, and when the catalyst is spherical, the chamfer radius is not less than the diameter of the spherical catalyst, and when the catalyst is strip-shaped, the chamfer radius is not less than 5 times the catalyst diameter.

[0040] Example 3

[0041] This embodiment is another optimization scheme based on Example 1. Its main structure is the same as that of Example 1. The improvement lies in that: as another optimization scheme for the catalyst grid for the above-mentioned radial reactor, the metal wire strips with special-shaped cross-sections in the upper area form an isosceles triangle with a special-shaped cross-section, and the angle formed by the two sides is greater than the angle formed by the extension lines of the two sides of the isosceles trapezoid, so that the width of the gap channel in the upper area forms two variable diameter areas with different slopes.

[0042] In this embodiment, the angle formed by the extension lines of the two sides of the isosceles trapezoid is 20-40°, and the angle formed by the two sides of the isosceles triangle is 30-50°.

[0043] In this embodiment, the metal wire strips with special-shaped cross-sections in the upper region form a special-shaped cross-section, and the height ratio of the isosceles triangle to the isosceles trapezoid is 2-3:1.

[0044] Example 4

[0045] A radial reactor comprises two layers of inner and outer catalyst grid tubes arranged in a reactor cylinder, wherein a catalyst bed is sandwiched between the two layers of catalyst grid tubes, and the grids are the grids mentioned above.

[0046] In order to verify the effect of the present invention, the following comparative experiments were performed:

[0047] Experimental Example 1

[0048] In a fixed-bed reactor, three catalyst units are arranged along the direction of reactant flow. Each catalyst unit includes a catalyst bed and two layers of grids that clamp the fixed catalyst bed. The grid is a Johnson mesh woven from metal wire strips. The center of the grid is used as a reference to divide the center area and the center area into a central area and a guide area surrounding the central area. The central area is circular, and its area accounts for 30% of the surface area of ​​the grid. The cross-section of the metal wire strips in the central area is an isosceles triangle, and the bottom edge serves as a planar contact surface contacting the catalyst layer. Slit channels are formed on both sides of the planar contact surface, and the width of the slit channel gradually increases from one side of the planar contact surface to the other side; the cross-section of the metal wire strips in the guide area is elliptical, thereby forming an arc-shaped contact surface that contacts the catalyst and bulges toward the catalyst. Slit channels are also formed on both sides of each arc-shaped contact surface, and the curvature of the arc-shaped contact surface gradually decreases from the center to the edge.

[0049] Experimental Example 2

[0050] The structure of the fixed bed reactor is basically the same as that of Experimental Example 1, with the only difference being that the cross section of the metal wire strips in the central area is an isosceles triangle, and the corners are chamfered to form an arc-shaped transition.

[0051] Comparative Example 1

[0052] The structure of the fixed bed reactor is basically the same as that of Example 1, except that the central area and the guide area are not designed, and the cross section of the metal wire strips in the Johnson mesh woven from the metal wire strips forming the grid is circular.

[0053] Comparative Example 2

[0054] The structure of the fixed bed reactor is basically the same as that of Example 1, except that the central area and the guide area are not designed, and the cross section of the metal wire strips in the Johnson mesh woven to form the grid is elliptical.

[0055] Experimental methods:

[0056] Experiments were conducted in a 400mm diameter radial bed reactor using different catalyst grids. Air and water, respectively, were introduced simultaneously from the reactor top. The gas and liquid flow rates were converted to those of a diesel hydrotreating fixed-bed reactor at a refinery, maintaining the same superficial gas-liquid velocity and a gas-liquid ratio of 8.8. The reactor contained only one catalyst bed, a strip-shaped catalyst. The catalyst was enclosed in a cylindrical grid, with the grid tube 1m from the reactor top and the catalyst bed height 1m.

[0057] Six cubic meters of catalyst were prepared to accommodate repeated experiments. After each test, fresh catalyst was replaced. Experiments were conducted using the catalyst grids used in Experimental Examples 1 and 2, and the grids used in Comparative Examples 1 and 2. The gas and liquid phases entered the reactor from the top, traversed the bed, and exited from the bottom, circulating for 5 hours. After replacing the catalyst grid, the experiment was repeated for the same duration, maintaining the same gas and liquid flow rates.

[0058] After the gas-liquid two-phase circulation is completed, the catalyst is unloaded and sieved with a mesh of the same diameter as the catalyst strips. The sieved catalyst dust is weighed and compared. The impact of the screen on the catalyst wear is compared based on the crushed catalyst dust. The experimental results are as follows:

[0059] project Experimental Example 1 Experimental Example 2 Comparative Example 1 Comparative Example 2 Wear amount (g) 188 106 310 365

[0060] According to the experimental results, it can be concluded that the catalyst grid of the present invention can effectively improve the catalyst wear phenomenon in the radial reactor and maintain the stable progress of the reaction.

Claims

1. A catalyst grid tube for a radial reactor, the grid tube being a cylindrical structure formed by rolling a Johnson mesh formed by weaving metal wire strips, characterized by: Along the axial direction of the grid tube and according to the flow direction of the reactants, the grid tube is divided into an upper area close to the reactant inlet of the radial reactor, a middle area and a lower area close to the reactant outlet of the radial reactor; The cross-sectional shape of the metal wire strips in the upper region is a special shape formed by splicing an isosceles triangle and an isosceles trapezoid. When the two are spliced ​​together, the base of the isosceles triangle is connected to the short base of the isosceles trapezoid as a whole, and the long base of the isosceles trapezoid forms a planar contact surface with the catalyst, and gap channels are formed on both sides of the planar contact surface. The cross-section of the metal wire strip in the middle region is elliptical, and the arc corresponding to the long axis of the ellipse forms an arc-shaped contact surface in contact with the catalyst, and gap channels are also formed on both sides of the arc-shaped contact surface; The cross section of the metal wire strip in the lower area is circular, forming an arc-shaped contact surface in contact with the catalyst, and gap channels are also formed on both sides of the arc-shaped contact surface.

2. The catalyst grid tube for a radial reactor according to claim 1, characterized in that: The slit channel width in the upper region is smaller than that in the middle region, and the slit channel width in the middle region is smaller than that in the lower region.

3. The catalyst grid tube for a radial reactor according to claim 1, characterized in that: The width of the upper region is 20-30% of the axial length of the grid tube, the width of the middle region is 20-30% of the axial length of the grid tube, and the rest is the lower region.

4. The catalyst grid tube for a radial reactor according to claim 1, characterized in that: The metal wire strips with special-shaped cross-sections in the upper region are chamfered at the corners of the cross-sections of the metal wire strips to form arc-shaped transitions.

5. The catalyst grid tube for a radial reactor according to claim 4, characterized in that: During the chamfering treatment, the chamfer radian is determined according to the particle shape of the catalyst, and when the catalyst is spherical, the chamfer radian is not less than the diameter of the spherical catalyst, and when the catalyst is strip-shaped, the chamfer radian is not less than 5 times the catalyst diameter.

6. The catalyst grid tube for a radial reactor according to claim 1, characterized in that: The metal wire strips with special cross-sections in the upper area form an isosceles triangle with a special cross-section, and the angle formed by the two sides is greater than the angle formed by the extension lines of the two sides of the isosceles trapezoid, so that the width of the gap channel in the upper area forms two diameter-changing areas with different slopes.

7. A catalyst grid tube for a radial reactor according to claim 1 or 6, characterized in that: The angle formed by the extension lines of the two sides of the isosceles trapezoid is 20-40°, and the angle formed by the two sides of the isosceles triangle is 30-50°.

8. The catalyst grid tube for a radial reactor according to claim 1, characterized in that: The metal wire strips with special-shaped cross-sections in the upper region form an isosceles triangle with a height ratio of 2-3:1 to an isosceles trapezoid with a special-shaped cross-section.

9. The catalyst grid tube for a radial reactor according to claim 1, characterized in that: The widths of the slit channels in the upper region, the middle region and the lower region gradually increase along the direction of the line connecting the reactant inlet to the reactant outlet of the radial reactor.

10. The catalyst grid tube for a radial reactor according to claim 1, characterized in that: In the upper region, the ratio of the width of the planar contact surface to the width of the slit channel openings on both sides thereof is 0.5-5; the ratio of the maximum width to the minimum width of the slit channel in the middle region is 0.5-2; and the ratio of the maximum width to the minimum width of the slit channel in the lower region is 0.5-2.

11. A radial reactor comprising inner and outer catalyst grid tubes disposed within a reactor cylinder, with a catalyst bed sandwiched between the two catalyst grid tubes, characterized in that: The grid tube adopts the grid tube according to any one of claims 1 to 10.

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