Catalyst grid for fixed bed reactor and fixed bed reactor

Abstract

A catalyst grid for a fixed-bed reactor and a fixed-bed reactor, belonging to the field of catalyst support and fixation in petrochemical reactions, comprises a Johnson mesh woven from metal wire strips. The grid center is used as a reference to divide the grid into a central area and a flow guide area surrounding the central area. The metal wire strips in the central area have planar contact surfaces that contact the catalyst layer, with slit channels formed on both sides of each planar contact surface. The metal wire strips in the flow guide area have arcuate contact surfaces that contact the catalyst and protrude toward the catalyst, with slit channels also formed on both sides of each arcuate contact surface. The curvature of the arcuate contact surfaces gradually decreases from the center to the edge. By improving the structure of the Johnson mesh, the present 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, and also improving the distribution uniformity of the reaction materials to a certain extent.

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 fixed bed reactor and a fixed bed 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 fixed bed reactor and a fixed bed reactor. By improving the structure of the Johnson grid, the flow parameters of the catalyst particles are changed, the wear between the catalyst particles and the wear between the catalyst particles and the Johnson grid during flow are greatly reduced, and at the same time, the distribution uniformity of the reaction materials after passing through the catalyst layer can be improved to a certain extent.

[0006] The technical solution adopted by the present invention to achieve the above-mentioned technical objectives is: a catalyst grid for a fixed bed reactor, which is a Johnson mesh woven from metal wire strips, and is divided into a central area and a guide area surrounding the central area based on the center of the grid, wherein the metal wire strips in the central area have a planar contact surface contacting the catalyst layer, and gap channels are formed on both sides of each planar contact surface. The metal wire strips in the guide area have an arcuate contact surface that contacts the catalyst and protrudes toward the catalyst, and gap channels are also formed on both sides of each arcuate contact surface, and the curvature of the arcuate contact surface gradually decreases from the center to the edge.

[0007] As an optimized solution for the catalyst grid for the fixed bed reactor, the central area accounts for 20-30% of the surface area of the grid.

[0008] As another optimization solution for the catalyst grid for the fixed bed reactor, the width of the slit channel in the central area gradually increases from one side of the planar contact surface to the other side.

[0009] As another optimization solution for the catalyst grid for the fixed bed reactor, the ratio of the width of the slit channel opening of the Johnson mesh in the central area to the width of the flat contact surface is 0.5-2.

[0010] As another optimization scheme for the catalyst grid for the above-mentioned fixed bed reactor, the cross-sectional shape of the metal wire strips in the central area is an isosceles triangle, an isosceles trapezoid or an irregular shape formed by splicing the two, and when the two are spliced, the base of the isosceles triangle and the short base of the isosceles trapezoid are connected as one; the corners of the isosceles triangle, the isosceles trapezoid or the irregular shape formed by splicing the two are chamfered to form an arc-shaped transition.

[0011] As another optimization solution for the catalyst grid for the fixed bed reactor, the isosceles trapezoid or the special shape formed by splicing all uses the long bottom side as the flat contact surface.

[0012] As another optimization scheme for the catalyst grid for the above-mentioned fixed bed reactor, the angle between the side of the isosceles trapezoid or isosceles triangle and the vertical direction is 30-50°, and the width of the opening of the gap channel on both sides of the supporting plane is 0.5-5 times the width of the base of the isosceles triangle or the width of the short base of the isosceles trapezoid.

[0013] As another optimization scheme for the catalyst grid for the above-mentioned fixed bed 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 solution for the catalyst grid for the fixed bed reactor, the cross-section of the metal wire strips in the guide area is rectangular or elliptical, and the two end faces of the rectangle form an arc-shaped contact surface with the catalyst.

[0015] As another optimization scheme for the catalyst grid for the fixed bed reactor, the slit channel in the guide area is a variable diameter channel, and its width gradually decreases and then increases from one side of the arc-shaped contact surface to the other side, forming a necking section in the middle.

[0016] A fixed bed reactor comprises a plurality of catalyst units distributed along the flow direction of reactants, each catalyst unit comprises a catalyst bed and two layers of grids clamping the fixed catalyst bed, the grids being the above-mentioned grids.

[0017] As an optimization scheme for the above-mentioned fixed bed reactor, along the flow direction of the reactants, in the grids of two adjacent catalyst units, the ratio of the width of the planar contact surface of the metal wire strips in the central area to the width of the gap channel gradually increases; the ratio of the width of the arcuate contact surface of the metal wire strips at the same position in the guide area to the width of the gap channel gradually increases.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention divides a grid made of a Johnson mesh into two parts: a central area and a guide area at the edge. The wire strips of the Johnson mesh in the central area are shaped to have a flat contact surface with the catalyst, and the wire strips of the Johnson mesh in the guide area are shaped to have an arcuate contact surface with the catalyst, thereby changing the flow parameters of the catalyst particles, greatly reducing the wear between the catalyst particles and the wear between the catalyst particles and the Johnson mesh during flow, and 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. Experiments have shown that compared with the existing Johnson mesh with a cylindrical cross-section, the use of the Johnson mesh of the present invention to make a grid plate structure in a fixed bed reactor can effectively improve the uniformity of the gas-liquid two-phase passing through the grid plate by about 10%, and reduce the wear of the catalyst particles in the upflow fixed bed reactor by more than 50%. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the cross-sectional shape of the Johnson net in the central area (isosceles triangle);

[0021] Figure 2 Schematic diagram of the cross-sectional shape of the Johnson net in the central area (isosceles trapezoid);

[0022] Figure 3 The cross-sectional shape diagram of the Johnson net in the central area (a special shape formed by splicing an isosceles trapezoid and an isosceles triangle);

[0023] Figure 4 is a schematic diagram of the cross-sectional shape of the Johnson network in the diversion area (ellipse);

[0024] Figure 5 Schematic diagram of the cross-sectional shape of the Johnson net in the diversion area (rectangular with curved end faces);

[0025] Figure 6 Schematic diagram of the structure of a fixed bed 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 and how to fabricate the Johnson mesh into a grid and secure it within a fixed-bed reactor.

[0027] Example 1

[0028] A catalyst grid for a fixed-bed reactor comprises a Johnson mesh woven from metal wire strips. The diameter of the metal wire strips is determined based on actual conditions. The grid is generally circular, with the center of the grid serving as a reference to divide the grid into a central area and a guide area surrounding the central area. The reference refers to the central axis of the fixed-bed reactor or the central axis of the circular grid. The central area is generally arranged in a circular shape, and its area generally accounts for 20-30% of the surface area of the grid. The metal wire strips in the central area have a planar contact surface contacting the catalyst layer, with slit channels formed on both sides of each planar contact surface. The metal wire strips in the guide area have an arcuate contact surface contacting the catalyst and protruding toward the catalyst. Slit channels are also formed on both sides of each arcuate contact surface, and the curvature of the arcuate contact surface gradually decreases from the center to the edge.

[0029] In this embodiment, the guide area can effectively suppress the wall flow phenomenon of the fixed bed reactor and reduce the fluid flow rate at the edge of the grid, thereby playing a role in evenly distributing the fluid.

[0030] 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:

[0031] Example 2

[0032] This embodiment is an optimization solution based on embodiment 1. Its main structure is the same as that of embodiment 1. The improvement is as follows: Figure 1-3 As shown, the width of the slit channel in the central area gradually increases from one side of the planar contact surface to the other side. Such a structure enables the reactants to be more evenly distributed when passing through the slit channel.

[0033] In this embodiment, the ratio of the width of the slit channel opening of the central region Johnson mesh to the width of the planar contact surface is 0.5-2.

[0034] Example 3

[0035] This embodiment is another optimization solution based on the embodiment 1. Its main structure is the same as that of the embodiment 1. The improvement is that the cross-section of the metal wire strip in the central area is an isosceles triangle (such as Figure 1 As shown), isosceles trapezoid (as Figure 2 As shown) or the special shape formed by splicing the two (as shown Figure 3 As shown), and 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; the corners of the isosceles triangle, the isosceles trapezoid or the special shape formed by splicing the two are chamfered to form an arc transition;

[0036] In this embodiment, the isosceles trapezoid or the special shape formed by splicing all use the long base as the plane contact surface;

[0037] In this embodiment, the angle between the side of the isosceles trapezoid or the isosceles triangle and the vertical direction is 30-50°, and the width of the opening of the gap channel on both sides of the support plane is 0.5-5 times the width of the base of the isosceles triangle or the width of the short base of the isosceles trapezoid;

[0038] In this embodiment, when chamfering is performed, 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.

[0039] Example 4

[0040] This embodiment is another optimization solution based on embodiment 1. Its main structure is the same as that of embodiment 1. The improvement is that the cross section of the metal wire strip in the guide area is rectangular (such as Figure 5 as shown) or oval (as Figure 4 As shown), the two end faces of the rectangle form an arc-shaped contact surface with the catalyst (as shown Figure 5 As shown), the aspect ratio of the rectangle is preferably 2-3:1.

[0041] Example 5

[0042] This embodiment is another optimization solution based on embodiment 1. Its main structure is the same as that of embodiment 1, and the improvement is as follows: Figure 4 As shown in FIG5 , the slit channel in the guide area is a variable diameter channel, and its width gradually decreases from one side of the arc-shaped contact surface to the other side, and then gradually increases, and a necking section is formed in the middle;

[0043] In this embodiment, if Figure 4 As shown, the cross section of the metal wire forming the guide area is elliptical, and the gap channel between the metal wires is hyperbolic. From one side of the arc-shaped contact surface to the other side, the width gradually decreases to form a necking section, and then gradually increases.

[0044] like Figure 5 As shown, the cross section of the metal wire forming the guide area is a rectangle with an arc-shaped contact surface, the arc-shaped contact surfaces of adjacent metal wires form a gradually shrinking or gradually expanding interval, and the side edges of the rectangle form a necking section.

[0045] Example 6

[0046] A fixed bed reactor, such as Figure 6 As shown, it includes several catalyst units distributed along the flow direction of the reactants, each catalyst unit includes a catalyst bed and two layers of grids that clamp and fix the catalyst bed, and the grids are the grids in Examples 1-6.

[0047] Example 7

[0048] This embodiment is an optimized solution based on Example 6. Its main structure is the same as that of Example 6, with the following improvements: along the reactant flow direction, in the grids of two adjacent catalyst units, the ratio of the width of the planar contact surface of the metal wire strips in the central area to the width of the slit channel gradually increases; and the ratio of the width of the arcuate contact surface of the metal wire strips at the same position in the guide area to the width of the slit channel gradually increases;

[0049] In this embodiment, being at the same position in the guide area means that the projections of two positions in the grids of two adjacent catalyst units on the vertical plane overlap with each other, and these two positions are called the same position;

[0050] In this embodiment, the catalyst unit is composed of a grid group consisting of two grids, which sandwich a catalyst bed. Along the direction of reactant flow, the grid groups sandwiching the catalyst bed are numbered as grid group 1#, grid group 2#, grid group 3#, and grid group 4#. The upper and lower grid structures of the same grid group are completely symmetrical. The structures of the central area and the guide area are arranged according to the grid structures in Examples 1-6.

[0051] Among them, in the 1# grid group, the ratio of the width of the plane contact surface of the metal wire strips in the central area to the width of the gap channel is selected as 8:1, the ratio of the width of the plane contact surface of the 2# grid group to the width of the gap channel is selected as 8.5:1, the ratio of the width of the plane contact surface of the 3# grid group to the width of the gap channel is selected as 9.5:1, and the ratio of the width of the plane contact surface of the 4# grid group to the width of the gap channel is selected as 12:1;

[0052] Draw an imaginary line parallel to the axis of the fixed bed reactor. This imaginary line is located somewhere in the flow-guiding area, specifically at 2 / 3 of the radius of the circular grid plate from the center. At this point, the intersection of this imaginary line and the four grid groups are four identical positions, defined as points A, B, C, and D.

[0053] At this time, in the 1# grid group, the ratio of the width of the arc-shaped contact surface at point A to the width of the gap channel is selected as 7:1, in the 2# grid group, the ratio of the width of the arc-shaped contact surface at point B to the width of the gap channel is selected as 7.5:1, in the 3# grid group, the ratio of the width of the arc-shaped contact surface at point C to the width of the gap channel is selected as 8:1, and in the 4# grid group, the ratio of the width of the arc-shaped contact surface at point D to the width of the gap channel is selected as 9:1.

[0054] In order to verify the effect of the present invention, the following comparative experiments were performed:

[0055] Experimental Example 1

[0056] The fixed bed reactor is selected to have a diameter of 600 mm, and a catalyst unit is arranged along the flow direction of the reactants. The catalyst unit includes a catalyst bed and two layers of grids that clamp the fixed catalyst bed. The catalyst is a strip catalyst. The catalyst unit is 1 m away from the top of the reactor and the catalyst bed is 1 m high. The grid is a Johnson mesh woven from metal wire strips. The center of the grid is used as a reference to divide the central area and the 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.

[0057] Experimental Example 2

[0058] 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.

[0059] Comparative Example 1

[0060] 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.

[0061] Comparative Example 2

[0062] 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.

[0063] Experimental methods:

[0064] The gas and liquid phases are air and water respectively, which enter the reactor simultaneously from the top of the reactor. The gas-liquid flow rate is converted according to the diesel hydrogenation fixed-bed reactor of a refinery to keep the same apparent gas-liquid velocity and gas-liquid ratio of 8.8.

[0065] Catalyst preparation 1m 3 To meet the needs of repeated experiments, a new catalyst was replaced after each test. Experiments were conducted using the catalyst grids used in Experimental Examples 1 and 2 and the grids used in Comparative Examples 1 and 2, respectively. The gas and liquid phases entered the reactor from the top and exited the bottom, circulating for 5 hours. After replacing the catalyst grid, the experiment was repeated for the same duration, using the same gas and liquid flow rates.

[0066] After the gas-liquid two-phase circulation is completed, the catalyst is unloaded and sieved with a mesh with the same diameter as the catalyst strips. The sieved catalyst dust is weighed and compared. The wear effect of the grid on the catalyst is compared based on the crushed catalyst dust. The experimental results are as follows:

[0067] project Experimental Example 1 Experimental Example 2 Comparative Example 1 Comparative Example 2 Wear amount (g) 120 100 255 280

[0068] The measurement results clearly show that the catalyst grid with an improved structure can effectively improve the catalyst wear phenomenon in the fixed bed reactor and maintain the stable progress of the reaction.

Claims

1. A catalyst grid for a fixed bed reactor, the grid being a Johnson mesh woven from metal wire strips, characterized in that: The center of the grid is used as a reference to divide the central area and the diversion area surrounding the central area, wherein the central area accounts for 20-30% of the surface area of the grid, the metal wire strips in the central area have a planar contact surface contacting the catalyst layer, and gap channels are formed on both sides of each planar contact surface. The cross-sectional shape of the metal wire strips in the central area is an isosceles triangle, an isosceles trapezoid, or a special shape formed by splicing the two, and when the two are spliced, the base of the isosceles triangle is connected to the short base of the isosceles trapezoid as a whole; the corners of the isosceles triangle, the isosceles trapezoid, or the special shape formed by splicing the two are chamfered to form an arc transition; The metal wire strips in the guide area have an arc-shaped contact surface that contacts the catalyst and bulges toward the catalyst. Gap 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. The cross-section of the metal wire strips in the guide area is rectangular or elliptical, and the two end faces of the rectangle form an arc-shaped contact surface that contacts the catalyst.

2. The catalyst grid for a fixed bed reactor according to claim 1, characterized in that: The width of the slit channel in the central area gradually increases from one side of the planar contact surface to the other side.

3. The catalyst grid for a fixed bed reactor according to claim 1, characterized in that: The ratio of the width of the slit channel opening of the central region Johnson mesh to the width of the plane contact surface is 0.5-2.

4. The catalyst grid for a fixed bed reactor according to claim 1, characterized in that: In the isosceles trapezoid or the special shape formed by splicing, the long base is used as the plane contact surface.

5. The catalyst grid for a fixed bed reactor according to claim 1, characterized in that: The angle between the side of the isosceles trapezoid or isosceles triangle and the vertical direction is 30-50°, and the width of the opening of the gap channel on both sides of the supporting plane is 0.5-5 times the width of the base of the isosceles triangle or the short base of the isosceles trapezoid.

6. The catalyst grid for a fixed bed reactor according to claim 1, 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.

7. The catalyst grid for a fixed bed reactor according to claim 1, characterized in that: The slit channel in the guide area is a variable diameter channel, and its width gradually decreases and then increases from one side of the arc-shaped contact surface to the other side, and a necking section is formed in the middle.

8. A fixed bed reactor comprising a plurality of catalyst units distributed along the flow direction of reactants, each catalyst unit comprising a catalyst bed and two layers of grids sandwiching the fixed catalyst bed, characterized in that: The grid is the grid according to any one of claims 1 to 7.

9. The fixed bed reactor according to claim 8, characterized in that: Along the flow direction of the reactants, in the grids of two adjacent catalyst units, the ratio of the width of the planar contact surface of the metal wire strips in the central area to the width of the gap channel gradually increases; the ratio of the width of the arcuate contact surface of the metal wire strips at the same position in the guide area to the width of the gap channel gradually increases.

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