Natural gas converter

Abstract

The utility model discloses a natural gas reformer. A furnace chamber is divided into an upper convection area and a lower radiation area by an inner vault; a through hole is formed in the inner vault, the upper end of the conversion pipe is communicated with the feed gas bag and penetrates through the convection area, the through hole and the radiation area, and the lower end is communicated with the synthesis gas bag. The middle parts of the convection tube and the radiant tube of the conversion tube are spiral sections, and the spiral sections can provide a thermal expansion space, improve reaction kinetics, reduce the height of the conversion furnace and strengthen a thermal effect. Tail gas outlets are evenly distributed in the top of the converter and communicated with a tail gas pipe. And the tail gas pipe is communicated with a tail gas bag. Due to the design of the cavities and the through holes, energy can be saved, and the modular natural gas heat exchanger is suitable for modularization of large-scale natural gas equipment. The conversion pipe in the furnace has few welding seams and is safe to operate.

Description

Technical Field

[0001] The utility model is applied to the chemical industry field, relates to manufacturing syngas from natural gas, and specifically is a natural gas reforming furnace. Background Technique

[0002] China's chemical industry has first developed and successfully applied the heat exchange reforming process for synthesizing ammonia with natural gas as the raw material. Its main function is to add steam to the raw material natural gas, so that methane in the raw material gas undergoes a reforming reaction to synthesize gas under the action of a catalyst. This reaction is an endothermic reaction, and the key equipment is the heat exchange reforming furnace.

[0003] In the high-temperature working condition of the reforming tubes in the reforming furnace, there is thermal expansion. Most reforming furnaces use the deformation of the pigtail tubes to make up for thermal expansion, such as a heat exchange type primary reforming furnace in CN201598172U. The heat exchange reforming furnace disclosed in CN201980995U points out the deficiencies of the pigtail tubes in the background technique and adopts a sleeved reforming tube, but its disadvantage is that the gas flow resistance is relatively large. A natural gas reforming furnace disclosed in CN206646080U can prevent combustion sparks from entering the regenerative furnace and the reforming furnace, and solve the equipment operation safety problem. Content of the Utility Model

[0004] The technical problem solved by the utility model is: to provide a natural gas reforming furnace that does not use pigtail tubes to make up for thermal expansion, and the reforming tubes have as few welds as possible to ensure the safe operation of the reforming furnace.

[0005] The technical solution adopted by the utility model is: the furnace cavity of the natural gas reforming furnace is divided into an upper convection zone and a lower radiation zone by an inner arch roof; through holes are arranged on the inner arch roof, and the reforming tubes pass through the convection zone, the through holes and the radiation zone from top to bottom; the upper end of the reforming tube is communicated with the raw material gas header, and the lower end is communicated with the syngas header. The convection tubes of the reforming tubes in the convection zone are single branch tubes, and the middle part is a spiral section; Pb-Al 2 O 3 active catalyst or Ni-Al 2 O 3 active catalyst is placed in the spiral section. The radiation tubes of the reforming tubes in the radiation zone are single branch tubes or two branch tubes with an inverted U-shaped bifurcation, and the middle part is a spiral section; Ni-Al 2 O 3 active catalyst is placed in the spiral section.

[0006] Furthermore, the ventilation cross-sectional area of the radiation tubes is not less than that of the convection tubes.

[0007] Furthermore, tail gas outlets are evenly distributed on the furnace top of the reforming furnace, and the tail gas outlets are communicated with tail gas pipes. The tail gas pipes are communicated with a tail gas header.

[0008] Furthermore, a refractory layer is provided on the inner side of the furnace body of the reformer, and a heat insulation layer is preferably added between the furnace body and the refractory layer.

[0009] The beneficial effects of the present utility model are as follows: The present utility model utilizes the spiral section of the reforming tube to provide thermal expansion space, improve reaction kinetics, reduce the height of the reformer, strengthen the thermal effect, and promote the generation of synthesis gas in the reforming reaction. The cavity division and through-hole design of the reformer contribute to energy conservation. The present utility model adopts a modular alternating working mode to achieve non-conflict between continuous production and maintenance. The reforming tube has only one weld or no weld, ensuring safe operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is the front view schematic diagram of the structure of Embodiment 1;

[0011] Figure 2 is the side view schematic diagram of the structure of Embodiment 1;

[0012] Figure 3 is the schematic diagram of the top tail gas pipeline of Embodiment 2;

[0013] Figure 4 is the schematic diagram of the reforming tube of Embodiment 3;

[0014] In the figures: 1 - raw material gas gas drum, 2 - reforming tube, 3 - furnace body, 4 - refractory layer, 5 - inner arch top, 6 - burner, 7 - synthesis gas gas drum, 8 - radiation zone, 9 - through hole, 10 - convection zone, 11 - tail gas pipe, 12 - tail gas gas drum;

[0015] 21 - convection tube, 22 - radiation tube. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016] Embodiment

[0017] The structure of the natural gas reformer in this embodiment is as shown in the attached Figure 1 and the attached Figure 2 figures. The furnace cavity is divided by the inner arch top 5 in the middle into the upper convection zone 10 and the lower radiation zone 8. A through hole 9 is provided on the inner arch top 5, and the reforming tube 2 passes through the convection zone 10, the through hole 9, and the radiation zone 8 from top to bottom. The upper end of the reforming tube 2 is connected to the raw material gas gas drum 1, and the lower end is connected to the synthesis gas gas drum 7. The reforming tubes in the convection zone 10 are convection tubes 21, and the reforming tubes in the radiation zone 8 are radiation tubes 22. The convection tube 21 is a single branch tube with a spiral shape in the middle. The radiation tube 22 is a bifurcated two-branch tube in an inverted U shape, also with a spiral shape in the middle. The convection tube 21 is connected to the top of the radiation tube 22, and the gas passage cross-sectional area of the radiation tube 22 is not less than that of the convection tube 21.

[0018] Rh (rhodium)-TiO 2 (titanium dioxide) active catalyst is placed in the spiral section of the convection tube 21, and TiO 2Using [carrier] and noble metal Rh (rhodium) as the catalyst. Inside the spiral section of the radiant tube 22, Ni (nickel)-Al 2 O 3 active catalyst is placed, with Al 2 O 3 as the carrier and Ni (nickel) as the catalyst. Since the noble metal Rh (rhodium) is expensive and not suitable for industrial production, it is replaced with inexpensive Pb-Al 2 O 3 active catalyst or relatively inexpensive Ni-Al 2 O 3 active catalyst.

[0019] The cross-section of the reformer is rectangular, and the furnace top is arc-shaped. Tail gas outlets are evenly distributed on the furnace top, and the tail gas outlets are connected to the tail gas pipe 11. Burners 6 are arranged on the side walls of the radiant zone 8 of the reformer. Natural gas is used as the fuel gas, and air or oxygen is used as the combustion-supporting gas. The heat of the burners 6 heats the radiant zone 8 and the radiant tubes 22. The tail gas rises from the through-hole 9 to the convection zone 10 and is sent out through the tail gas outlet and the tail gas pipe 11. Since the convection tubes 21 are located directly above the through-hole 9, the rising high-temperature tail gas convectively heats the convection tubes 21.

[0020] The raw material gas header 1 temporarily stores the uniformly mixed raw material gas, which is a mixture of natural gas, steam, carbon dioxide, and carbon monoxide. The pressure of the raw material gas in the raw material gas header 1 is relatively stable, ensuring that the raw material gas passing through each reforming tube 2 is relatively balanced. When the raw material gas passes through the reforming tube 2, under the action of the active catalyst, a syngas reaction occurs, and the produced syngas is sent into the syngas header 7.

[0021] The spiral sections of the radiant tubes 22 and the convection tubes 21 can achieve the following functions: 1) Provide displacement for the thermal expansion of the reforming tubes. The temperatures of the radiant tubes 22 and the convection tubes 21 are different, and the expansion amounts are different. The pitch of the spiral section provides a displacement space for the deformation of the tubes due to thermal expansion, thus eliminating the use of pigtail tubes. 2) The gas flow inside the spiral section is turbulent, which is conducive to increasing the diffusion rate of the reaction raw material gas and fully contacting with the catalyst, thereby improving the reaction kinetics. 3) The spiral section increases the length of the reforming tubes in a small space. Under the same reaction time, the height dimension of the reformer can be reduced, saving the equipment investment of the reformer. 4) Strengthen the thermal effect. The spiral section of the convection tube is not parallel to the upward gas flow, eliminating the laminar flow of the gas layer with the wall attachment effect and strengthening the heat transfer; the spiral section of the radiant tube can absorb radiant heat from different angles, increasing the radiant heat absorption area and strengthening the radiant heating.

[0022] The inner arch roof 5 helps to prevent the heat radiation transfer from the radiant zone to the convection zone, concentrating the heat relatively on the radiant tubes, thereby saving energy.

[0023] To achieve heat preservation for the reformer, a refractory layer 4 is provided inside the furnace body 3, and a heat-insulating layer is preferably provided between the furnace body 3 and the refractory layer 4.

[0024] Embodiment

[0025] This embodiment is an improvement based on Embodiment 1. In Embodiment 1, the tail gas outlet of the reformer is connected to a tail gas pipe 11. The gas flow rate in each section of the tail gas pipe is uneven, resulting in uneven flow velocity and pressure, which in turn affects the gas flow in the convection zone. For this reason, in this embodiment, each tail gas outlet is connected to a tail gas pipe, and all the tail gas pipes are connected to a tail gas header 16, as shown in the attached... Figure 3 As shown. In this way, by using the pressure in the tail gas header 16, the gas flow rate in each tail gas pipe 11 is kept balanced, thereby ensuring the stability and balance of the gas flow in the convection zone.

[0026] Embodiment

[0027] In Embodiment 1, one convection tube 21 is connected to two radiant tubes 22. The purpose is to reduce the size of the radiant tubes, which is beneficial for the radiant heat to quickly heat the reaction gas in the tubes. The connection between the convection tube and the radiant tube is usually by welding, and there is only one weld seam on the reforming tube in the reformer. Due to the thermal expansion of the reforming tube, to ensure the safety of the weld seam, higher requirements are put forward for the welding quality at the welded joint, such as the selection of welding materials, welding process, welding inspection, etc. For this reason, in this embodiment, the radiant tube and the convection tube are made of a seamless tube, eliminating the weld seam of the reforming tube in the furnace, as shown in the attached... Figure 4 As shown. In this way, the reforming tube operates more smoothly and safely.

[0028] The spiral section of the present utility model can be bent on a special equipment with a seamless tube, and there is no weld seam on the spiral section.

[0029] The present utility model adopts a reforming tube with a spiral section. Its pitch provides thermal expansion space, does not use a pigtail tube, and meets the thermal expansion requirements; it promotes gas turbulent diffusion, improves reaction kinetics; reduces the height dimension of the reforming tube and shrinks the height of the reformer; strengthens convection and radiation heat transfer, and enhances the thermal effect. Therefore, the spiral section promotes the generation of synthesis gas for the reforming reaction from multiple angles. However, when the radiant tube is a single tube, there is no weld seam on the reforming tube in the reformer, and the production safety is improved. The cavity division and through-hole design of the reformer contribute to improving the thermal effect and saving energy.

[0030] The present utility model is preferably modular. Multiple such reformers can be used in large-scale natural gas reforming equipment, and the reformers work alternately to achieve the purpose of continuous production without conflict with maintenance.

Claims

1. A natural gas reformer, characterized in that: The furnace chamber of the reformer is divided into an upper convection zone (10) and a lower radiation zone (8) by an inner dome (5); the inner dome (5) is provided with a through hole (9); a reformer tube (2) passes through the convection zone (10), the through hole (9) and the radiation zone (8) from top to bottom; the upper end of the reformer tube (2) is connected to a raw gas bag (1), and the lower end is connected to a synthesis gas bag (7); the reformer tube (2) of the convection zone (10) is a convection tube (21), and the convection tube (21) is a single branch tube, and the middle part is a spiral section; the reformer tube (2) of the radiation zone (8) is a radiation tube (22), and the radiation tube (22) is a single branch tube or two branches bifurcated in an inverted U shape, and the middle part is a spiral section.

2. A natural gas reformer according to claim 1, characterized in that: A Pb-Al2O3 active catalyst or a Ni-Al2O3 active catalyst is placed in the spiral section of the convection tube (21).

3. A natural gas reformer according to claim 1, characterized in that: A Ni-Al2O3 active catalyst is placed in the spiral section of the radiation tube (22).

4. A natural gas reformer according to claim 1, characterized in that: The ventilation cross-sectional area of ​​the radiation tube (22) is not less than the ventilation cross-sectional area of ​​the convection tube (21).

5. The natural gas reformer according to claim 1, characterized in that: Tail gas outlets are evenly distributed on the top of the reforming furnace, and the tail gas outlets are connected to the tail gas pipe (11).

6. A natural gas reformer according to claim 5, characterized in that: The tail gas pipe (11) is connected to the tail gas bag (12).

7. The natural gas reformer according to claim 1, characterized in that: A refractory layer (4) is arranged inside the furnace body (3) of the converter, and a heat-insulating layer is arranged between the furnace body (3) and the refractory layer (4).

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