Radiant tube system structure and natural gas reformer comprising same

Abstract

A radiant tube system structure and a natural gas reformer comprising same. The radiant tube system structure comprises an inlet gas collection header (1), a gas delivery header (6), and a plurality of parallel radiant tube arrangements, wherein each parallel radiant tube arrangement includes an inlet distribution tube (2), outlet collection tubes and a plurality of parallel radiant tubes; each parallel radiant tube comprises an inlet pigtail tube (3), a reforming tube (4) and an outlet connection tube which are connected in sequence from top to bottom, and every two parallel radiant tubes are symmetrically distributed on two sides of an inlet distribution tube, the inlet pigtail tubes being horizontally connected perpendicular to the axis of the inlet distribution tube, and the outlet connection tube at an outlet of each parallel radiant tube being connected to an outlet collection tube, thereby forming one parallel radiant tube arrangement; and a plurality of parallel radiant tube arrangements are connected in parallel, a plurality of inlet distribution tubes at an inlet being connected to the inlet gas collection header, and outlet collection tubes at an outlet being connected to the gas delivery header, thereby forming a parallel radiant tube array. By means of symmetrical structures in which the inlet pigtail tubes are connected to two horizontal sides of each inlet distribution tube, and structural measures for reducing thermal differential stress, such as pre-biasing the installation of the top of each reforming tube, providing expansion holes in a base plate (10), and the outlet collection tubes, thermal stress in the entire tube system due to high-temperature expansion during operation can be effectively reduced.

Description

A radiant tube system structure and a natural gas reformer including the same Technical Field

[0001] The utility model belongs to the technical field of natural gas conversion, and mainly relates to a furnace pipe system structure of a radiation section of a natural gas conversion furnace. Background Art

[0002] The natural gas reformer is the main equipment in petrochemical plants (hydrogen production, synthetic ammonia, methanol, etc.). It mainly uses natural gas, oilfield gas and other raw materials to undergo conversion reactions under high temperature and a certain pressure (such as 4Mpa) through the action of catalysts to produce conversion gas with H2 and CO as the main components, which serves as the raw gas for downstream products.

[0003] The radiant section piping system of a reformer primarily consists of an inlet gas header, inlet distribution pipes, inlet pigtails, reformer tubes, outlet connecting pipes, and an outlet manifold. The piping system operates at high temperatures, with the inlet feed gas temperature typically ranging from 475°C to 650°C. The reformer tubes are directly heated by the flames within the furnace, reaching tube wall temperatures as high as 1000°C. The reforming reaction occurs within the tubes, and the outlet reformed gas temperature typically ranges from 750°C to 930°C. The piping system operates under high temperatures and pressures, and the various components must coordinate large expansion displacements, resulting in complex piping stresses. The most popular piping system features flexible pigtails between the inlet distribution pipe and the reformer to coordinate thermal expansion of the reformer tubes. The outlet connecting pipes can be connected using either a flexible pigtail combined with a hot-wall manifold to the outlet cold-wall manifold, or a hot-cold-wall connecting pipe directly to the outlet cold-wall manifold.

[0004] The investment in the converter is large, and its long-term operation requires continuous improvement of the design and use of optimizable content. Measures such as more coordinated deformation, smaller temperature differences, and more uniform force should be taken to avoid the impact of additional deformation and stress on high-temperature components.

[0005] Utility Model Content

[0006] The purpose of the present utility model is to address the shortcomings of the prior art and provide an improved radiant piping structure for a natural gas reformer, which can effectively reduce the thermal stress caused by thermal expansion of the radiant piping during actual operation, thereby ensuring the reliability and safety of the entire piping system, and to provide a natural gas reformer including the above-mentioned radiant piping structure.

[0007] To achieve the above-mentioned purpose, the present invention adopts the following technical solutions: a natural gas reformer radiant pipe system structure, comprising: an inlet gas collecting main pipe, a gas transmission main pipe and an array of parallel radiant tubes;

[0008] Each group of parallel radiant tubes includes an inlet distribution tube, an outlet collection tube, and multiple parallel radiant tubes; each parallel radiant tube includes an inlet pigtail tube, a conversion tube, and an outlet connecting tube connected in sequence from top to bottom. The two parallel radiant tubes are symmetrically distributed on both sides of the inlet distribution tube, and the inlet pigtail tubes are horizontally connected to the axis of the inlet distribution tube vertically. The outlet connecting tubes of the parallel radiant tubes are connected to the outlet collection tube, forming a group of parallel radiant tubes.

[0009] Several parallel radiant tubes are arranged and connected in parallel, several inlet distribution pipes at the inlet are connected to the inlet gas collecting main pipe, and the outlet collecting pipe at the outlet is connected to the gas transmission main pipe, forming a parallel radiant tube array.

[0010] Furthermore, the outlet manifold is a hot wall manifold or a cold wall manifold.

[0011] Furthermore, when the outlet collecting pipe is a hot wall collecting pipe, the outlet connecting pipe is an outlet pigtail pipe, and the number of inlet distribution pipes and hot wall collecting pipes in each group of parallel radiation tubes is the same. The outlet pigtail pipes at the outlets of the two parallel radiation tubes are symmetrically distributed on both sides of the hot wall collecting pipe, and the outlet pigtail pipes are horizontally connected to the axis of the hot wall collecting pipe perpendicularly.

[0012] Furthermore, when the outlet collecting pipe is a cold wall collecting pipe, the outlet connecting pipe is a rigid straight-connected pipe, the number of cold wall collecting pipes is twice that of the inlet distribution pipes, and in the two symmetrically distributed parallel radiant tubes, the rigid straight-connected pipe at the outlet of one side of the parallel radiant tube is connected to a cold wall collecting pipe.

[0013] Furthermore, heat dissipation fins are provided on the side of the cold wall manifold close to the conversion tube or on the rigid straight-connected pipe or the gas main pipe. The heat dissipation fins are arranged spirally, annularly or axially along the cold wall manifold and are of comb-tooth or corrugated plate structure.

[0014] Furthermore, a conical diffuser or a basket-type gas distributor is provided at the end of the inner process gas conduit of the rigid straight-connecting pipe.

[0015] Furthermore, the length of the rigid straight-connecting pipe is 600 to 1000 mm.

[0016] Furthermore, a saddle support is provided at the bottom of the cold wall manifold, and a stress relief groove is provided at the connection between the web of the saddle support and the manifold.

[0017] A natural gas reformer comprises the above-mentioned radiation tube system structure.

[0018] Furthermore, expansion holes 50 to 80 mm larger than the outer diameter of the conversion tube are provided at the positions where the conversion tube passes through the bottom plate and the top plate of the conversion furnace; a positioning ring 2 to 8 mm larger than the outer diameter of the conversion tube is provided above the hole through the top of the furnace; and an opening is provided at the top of the flue at the bottom of the radiation section of the conversion furnace.

[0019] The beneficial effect of the present invention is that the radiation piping structure can effectively reduce the high-temperature expansion thermal stress of the entire piping during operation.

[0020] (1) The structural symmetry of the inlet pigtail pipe and the inlet distribution pipe on both sides ensures that the force on the conversion tube is balanced during vertical expansion and displacement;

[0021] (2) An expansion hole 50 to 80 mm larger than the outer diameter of the converter tube is opened at the location where the converter tube passes through the furnace bottom, so that the converter tube will not be hindered by the furnace bottom plate when it expands and moves with the cold wall manifold. This effectively ensures the sealing of the furnace bottom plate and reduces the thermal stress of the joint between the converter tube and the cold wall manifold;

[0022] (3) Increase the heat dissipation of the upper part of the cold wall manifold by adding a heat dissipation fin structure on the upper part of the cold wall manifold. Adding a conical diffuser or a basket-type gas distributor at the process inlet of the cold wall manifold can not only prevent high-speed gas from directly eroding the castable, but also make the temperature of the upper and lower sides of the cold wall manifold close, reduce the temperature difference stress caused by the temperature difference between the upper and lower surfaces, avoid the "thermal arch" phenomenon of the cold wall manifold, and also reduce the impact of the deformation of the cold wall manifold on the uneven stress of the upper pipe system;

[0023] (4) On the saddle supports of the cold wall manifold and the gas main, stress relief grooves can be opened in the middle of the webs to effectively reduce the thermal stress of the cold wall pipes;

[0024] (5) If the rigid straight-connecting pipe is too short, it will lead to a large temperature gradient in the conversion tube, large temperature stress, and serious cold wall manifold arch phenomenon; if the rigid straight-connecting pipe is too long, it will lead to an excessively high furnace bottom and increase construction costs. According to the analysis of temperature field and stress field, the appropriate length of the cold and hot wall connecting pipe can be selected;

[0025] (6) The top of the converter tube is pre-biased during installation, so that the converter tube is in a slightly tilted state during installation. It can be restored to a vertical state under operating conditions, reducing the additional stress caused by the displacement difference between the converter tube and the cold wall manifold during operation; the converter tube is in a vertical state during operation (when the hanging point is in the normal position, the converter tube is pre-biased during installation, and when the converter tube is installed in the designed position, the hanging point is pre-biased). In order to make the converter tube temperature more uniform, a small number of openings are added to the top of the flue at the bottom of the radiation section to facilitate fine-tuning when necessary to make the flue gas flow field outside the converter tube more uniform. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG1 is a front view of the radiation tube system structure of Example 1.

[0027] FIG2 is a side view of the radiation tube system structure of Example 1.

[0028] FIG3 is a schematic structural diagram of the cold wall manifold, the gas main heat dissipation fins, the support stress relief grooves and the basket-type gas distributor in Example 1.

[0029] FIG4 is a diagram showing the spiral arrangement of the cooling fins of the cold wall manifold and the gas main pipe in Example 1.

[0030] FIG5 is a spiral groove structure of the cooling fins of the cold wall collecting pipe and the gas main pipe in Example 1.

[0031] FIG6 is a front view of the conversion tube in the pre-biased state of Example 2.

[0032] Figure 7 is a top view of the conversion tube passing through the furnace bottom plate in Example 2.

[0033] FIG8 is a schematic diagram showing the connection between the outlet pigtail pipe and the hot wall manifold in Example 3.

[0034] Figure 1: 1-inlet gas collecting main pipe; 2-inlet distribution pipe; 3-inlet pigtail pipe; 4-conversion pipe; 5-cold wall collecting pipe; 6-gas transmission main pipe; 7-outlet pigtail pipe; 8-hot wall collecting pipe; 9-furnace top plate; 10-furnace bottom plate; 11-annular heat dissipation fin (on rigid straight-connected pipe); 12-annular heat dissipation fin (on cold wall collecting pipe or gas transmission main pipe); 13-spiral heat dissipation fin; 14-stress relief groove; 15-basket-type gas distributor; 16-rigid straight-connected pipe; 17-positioning ring DETAILED DESCRIPTION

[0035] In order to enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of this application.

[0036] It should be noted that the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or are inherent to these processes, methods, products or apparatuses.

[0037] Example 1

[0038] As shown in Figures 1 and 2, a reformer radiant tube system comprises an inlet gas collecting main pipe 1, a gas transmission main pipe 6, and a plurality of parallel radiant tube arrangements. Each parallel radiant tube arrangement comprises an inlet distribution pipe 2, a cold wall manifold 5, and multiple parallel radiant tubes.

[0039] Each parallel radiant tube includes an inlet pigtail tube 3, a conversion tube 4 and a rigid straight-connecting tube 16 connected in sequence from top to bottom. The two parallel radiant tubes are symmetrically distributed on both sides of the inlet distribution tube. The inlet pigtail tube is horizontally connected to the axis of the inlet distribution tube vertically. The rigid straight-connecting tubes at the outlets of the parallel radiant tubes are connected to the cold wall manifold to form a group of parallel radiant tubes. The number of cold wall manifolds is twice that of the inlet distribution tubes. In the two symmetrically distributed parallel radiant tubes, the rigid straight-connecting tube at the outlet of one parallel radiant tube is connected to a cold wall manifold.

[0040] Several parallel radiant tubes are arranged in parallel and connected. Several inlet distribution pipes at the inlet are connected to the inlet gas collecting main pipe, and the outlet cold wall collecting pipe at the outlet is connected to the gas transmission main pipe to form a parallel radiant tube array.

[0041] As shown in Figures 3 and 4, a basket-type gas distributor 15 can be installed at the end of the process gas duct inside the rigid straight-connect pipe. Cooling fins are arranged on the side of the cold wall manifold facing the conversion tube. These fins can be arranged spirally, circumferentially, or axially along the cold wall manifold, and can have a comb-shaped or corrugated plate structure. The cooling fins can be made of the same material as the cold wall manifold or other materials with good thermal conductivity. Reference numeral 11 denotes the annular cooling fins on the rigid straight-connect pipe, 12 denotes the annular cooling fins on the cold wall manifold or gas main, and 13 denotes the spiral cooling fins.

[0042] As shown in Figure 3, stress relief grooves 14 can be provided on the webs of the saddle supports at the bottom of the cold wall manifold where they connect to the manifold. Figure 5 shows the spirally grooved structure of the cooling fins on the cold wall manifold and gas main. The cooling fins are comb-tooth or corrugated plate structures, with the groove spacing and depth determined by heat dissipation requirements.

[0043] The rigid straight-connecting pipe is preferably 600 to 1000 mm long.

[0044] Example 2

[0045] A natural gas reformer comprising the radiant tube system structure of Example 1. As shown in FIG6 , when the reformer tubes are connected to the cold wall manifold using rigid straight-connecting pipes, holes 50 to 80 mm larger than the outer diameter of the reformer tubes are provided on the furnace bottom plate 9 and furnace top plate 10 at the locations where the reformer tubes pass through. During installation, as shown in FIG7 , the reformer tubes are eccentric to the side of the furnace bottom or furnace top through-holes that are away from the direction of displacement during operation. A positioning ring 17 , which is only 2 to 8 mm larger than the outer diameter of the reformer tubes, is provided above the furnace top through-holes. After the reformer tubes are welded to the upper and lower portions, the positioning rings are used to offset and position the reformer tubes according to the displacement direction and expansion amount of the cold wall manifold during operation. The expansion amount varies at different points on the reformer tubes, with the largest at the far end. The aperture spacing can be varied individually or stepwise to minimize the open hole area.

[0046] The lifting point on the top of the conversion tube is pre-deflected by the displacement distance according to the displacement direction and expansion amount during the operation of the cold wall manifold.

[0047] Example 3

[0048] A reformer radiant tube system structure comprises: an inlet gas collecting main pipe 1, a gas transmission main pipe 6, and a plurality of parallel radiant tube arrangements. Each parallel radiant tube arrangement comprises an inlet distribution pipe 2, a hot wall collection pipe 8, and multiple parallel radiant tubes. Each parallel radiant tube arrangement comprises an inlet pigtail pipe 3, a reformer pipe 4, and an outlet pigtail pipe 7, connected sequentially from top to bottom. The two parallel radiant tubes are symmetrically distributed on either side of the inlet distribution pipe, with the inlet pigtails connected horizontally and perpendicularly to the axis of the inlet distribution pipe. The outlet pigtails at the outlets of the two parallel radiant tubes are symmetrically distributed on either side of the hot wall collection pipe, with the outlet pigtails connected horizontally and perpendicularly to the axis of the hot wall collection pipe (as shown in FIG8), forming a single parallel radiant tube arrangement.

[0049] Several parallel radiant tubes are arranged and connected in parallel, several inlet distribution pipes at the inlet are connected to the inlet gas collecting main pipe, and the outlet collecting pipe at the outlet is connected to the gas transmission main pipe, forming a parallel radiant tube array.

[0050] The above is a further detailed description of the present invention and should not be considered as a limitation on the specific implementation of the present invention. For those skilled in the art of the present invention, simple deductions or substitutions that do not depart from the concept of the present invention are within the scope of protection of the present invention.

Claims

1. A radiant tube system structure for a natural gas reforming furnace, characterized in that Comprising: An inlet gas collecting main pipe, a gas transmission main pipe, and an array of parallel radiation pipes arranged; Each group of parallel radiation pipes arranged includes an inlet distribution pipe, an outlet collecting pipe, and multiple parallel radiation pipes; each parallel radiation pipe includes an inlet pigtail pipe, a conversion pipe, and an outlet connecting pipe connected in sequence from top to bottom. Two parallel radiation pipes are symmetrically distributed on both sides of the inlet distribution pipe. The inlet pigtail pipe is horizontally and perpendicularly connected to the axis of the inlet distribution pipe. The outlet connecting pipe at the outlet of the parallel radiation pipe is connected to the outlet collecting pipe to form a group of parallel radiation pipes arranged. An array of parallel radiation pipes is formed by connecting multiple groups of parallel radiation pipes arranged in parallel. Several inlet distribution pipes at the inlet are connected to the inlet gas collecting main pipe, and the outlet collecting pipes at the outlet are connected to the gas transmission main pipe.

2. The radiant tube system structure of the natural gas reforming furnace according to claim 1, characterized in that: The outlet collecting pipe is a hot-wall collecting pipe or a cold-wall collecting pipe.

3. The radiant tube system structure of the natural gas reforming furnace according to claim 2, wherein: When the outlet collecting pipe is a hot-wall collecting pipe, the outlet connecting pipe is an outlet pigtail pipe. The number of inlet distribution pipes and hot-wall collecting pipes in each group of parallel radiation pipes arranged is the same. The outlet pigtail pipes at the outlets of the two parallel radiation pipes are symmetrically distributed on both sides of the hot-wall collecting pipe. The outlet pigtail pipe is horizontally and perpendicularly connected to the axis of the hot-wall collecting pipe.

4. The radiant tube system structure of the natural gas reforming furnace according to claim 2, wherein: When the outlet collecting pipe is a cold-wall collecting pipe, the outlet connecting pipe is a rigid direct connection pipe. The number of cold-wall collecting pipes is twice that of the inlet distribution pipes. Among the two symmetrically distributed parallel radiation pipes, the rigid direct connection pipe at the outlet of one side of the parallel radiation pipe is connected to one cold-wall collecting pipe.

5. The radiant tube system structure of the natural gas reforming furnace according to claim 4, characterized in that: Heat dissipation fins are provided on the side of the cold-wall collecting pipe close to the conversion pipe, or on the rigid direct connection pipe, or on the gas transmission main pipe. The heat dissipation fins are arranged spirally, circumferentially, or axially along the cold-wall collecting pipe. The heat dissipation fins are of a comb-tooth type or a corrugated plate structure.

6. The radiant tube system structure of the natural gas reforming furnace according to claim 4, characterized in that: A conical diffuser or a basket-type gas distributor is provided at the end of the process gas conduit inside the rigid direct connection pipe.

7. The radiant tube system structure of the natural gas reforming furnace according to claim 4, characterized in that: The length of the rigid direct connection pipe is 600 - 1000 mm.

8. The radiant tube system structure of the natural gas reforming furnace according to claim 4, characterized in that: A saddle support is provided at the bottom of the cold-wall collecting pipe. A stress relief groove is provided at the connection between the web of the saddle support and the collecting pipe.

9. A natural gas reforming furnace, characterized in that: Including the radiation pipe system structure according to any one of claims 1 to 8.

10. The natural gas reforming furnace according to claim 9, characterized in that: Expansion holes larger than the outer diameter of the conversion pipe by 50 - 80 mm are opened at the positions where the furnace bottom plate and the furnace top plate of the reforming furnace are penetrated by the conversion pipes; a positioning ring larger than the outer diameter of the conversion pipe by 2 - 8 mm is provided above the through-hole on the furnace top; openings are provided at the top of the bottom flue of the radiation section of the reforming furnace.

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