Porous medium combustor for stable combustion of gas with ultralow heat value

Abstract

The invention provides a porous medium combustor for stable combustion of ultralow-calorific-value gas, belongs to the technical field of combustors, and solves the problems that an existing combustor is low in heat recycling efficiency and air is not fully preheated before entering a combustion area. The combustor comprises a shell, a gradually-shrunk porous medium layer, a stable-combustion porous medium layer, a gradually-expanded porous medium layer, a premixing chamber, a fuel channel and an oxidizing agent channel, and the gradually-shrunk porous medium layer, the stable-combustion porous medium layer and the gradually-expanded porous medium layer are all located in the shell and are sequentially arranged from top to bottom; the premixing chamber is communicated with the lower part of the divergent porous medium layer; an outlet of the fuel channel is communicated with the premixing chamber; the oxidant channel surrounds the stable combustion porous medium layer and the divergent porous medium layer and is spirally arranged on the shell, an inlet of the oxidant channel is located above the stable combustion porous medium layer, and an outlet of the oxidant channel is communicated with the premixing chamber. The combustible limit of the low-heating-value fuel gas can be widened, stable and efficient utilization of the ultralow-heating-value fuel gas is achieved, and the heat recycling efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of burners, and in particular relates to a porous medium burner for stable combustion of ultra-low calorific value gas. Background Art

[0002] Gas fuels are generally divided into three categories according to their calorific value. 3 It is a high calorific value fuel with a calorific value of 6.28~15.07 MJ / Nm 3 The fuel in between is medium calorific value fuel, with calorific value less than 6.28 MJ / Nm 3 Low calorific value fuel, ultra-low calorific value gas fuel is generally defined as calorific value less than 3.35 MJ / Nm 3 of gas fuel.

[0003] There is a lot of room for recycling and utilizing ultra-low calorific value gases in the steel, petrochemical, and coal industries, but a large amount of ultra-low calorific value gases cannot be effectively utilized due to technical reasons and have to be discharged, seriously polluting the environment and wasting energy. The structures and internal materials used in existing technical solutions to solve this problem cannot fully meet the needs of low calorific value gas combustion in industrial scenarios. Patent application with patent publication number CN101737778A discloses a diffusion-type porous medium gas fuel burner, in which the gas does not pass through a rectifier to directly reach the diverter pipe and then reach the porous medium area. This method cannot ensure that the distribution and mixing of air and gas in the porous medium are sufficiently uniform, resulting in incomplete combustion and difficulty in adapting to the combustion of low calorific value gases. Patent application with patent publication number CN116379425A discloses a low calorific value preheating premixed porous medium burner. This device uses ceramic ball materials, has low heat recirculation efficiency, and the air is not fully preheated before entering the combustion zone, making it difficult for the flame to be immersed in the porous medium to achieve stable combustion.

[0004] Therefore, there is an urgent need for a porous medium burner for stable combustion of ultra-low calorific value gas, which can improve the heat recirculation efficiency, enhance the fuel activity, enable the ultra-low calorific value gas to achieve submerged stationary combustion, and realize safe preheating and sufficient heat exchange, thereby improving the stable combustion effect. Summary of the Invention

[0005] In view of this, in order to solve the problems that existing burners cannot burn completely, are difficult to adapt to the combustion of low calorific value gas, have low heat recirculation efficiency, and the air is not fully preheated before entering the combustion zone, making it difficult for the flame to be immersed in the porous medium to achieve stable combustion, the present invention proposes a porous medium burner for stable combustion of ultra-low calorific value gas.

[0006] To achieve the above object, the present invention adopts the following technical solutions: A porous medium burner for stable combustion of ultra-low calorific value gas, comprising: case; The gradually contracting porous medium layer, the combustion stabilizing porous medium layer and the gradually expanding porous medium layer are all located in the shell and are arranged in sequence from top to bottom; a premixing chamber, the premixing chamber being in communication with the lower portion of the gradually expanding porous medium layer; a fuel channel, wherein an outlet of the fuel channel is communicated with the premixing chamber; The oxidant channel is spirally arranged on the shell around the combustion stabilizing porous medium layer and the gradually expanding porous medium layer. The inlet of the oxidant channel is located above the combustion stabilizing porous medium layer, and the outlet of the oxidant channel is connected to the premixing chamber.

[0007] As a preferred solution of the above-mentioned porous medium burner for stable combustion of ultra-low calorific value gas, the inner surface of the shell is provided with a high-temperature resistant lining.

[0008] As a preferred solution of the above-mentioned porous media burner for stable combustion of ultra-low calorific value gas, the shell includes an upstream metal shell and a downstream metal shell, the upstream metal shell and the downstream metal shell are connected by a flange, the tapered porous media layer is located in the upstream metal shell, the stable combustion porous media layer and the gradually expanding porous media layer are located in the downstream metal shell, and the oxidant channel is arranged in the downstream metal shell.

[0009] As a preferred solution of the above-mentioned porous medium burner for stable combustion of ultra-low calorific value gas, the outlet of the fuel channel is arranged opposite to the outlet of the oxidant channel.

[0010] As a preferred solution of the porous medium burner for stable combustion of ultra-low calorific value gas, the stable combustion porous medium layer, the gradually contracting porous medium layer and the gradually expanding porous medium layer are all made of SiC foam ceramic material.

[0011] As a preferred solution of the above-mentioned porous medium burner for stable combustion of ultra-low calorific value gas, the high-temperature resistant liner is made of mullite material.

[0012] As a preferred solution of the above-mentioned porous medium burner for stable combustion of ultra-low calorific value gas, the number of spiral turns of the oxidant channel is 20.

[0013] As a preferred solution of the porous medium burner for stable combustion of ultra-low calorific value gas, the PPI of the gradually expanding porous medium layer is greater than 40 and the porosity is less than 0.7.

[0014] As a preferred solution of the porous medium burner for stable combustion of ultra-low calorific value gas, the PPI of the stable combustion porous medium layer is less than 10 and the porosity is greater than 0.85.

[0015] As a preferred solution of the porous medium burner for stable combustion of ultra-low calorific value gas, the PPI of the tapered porous medium layer is greater than 40 and the porosity is less than 0.7.

[0016] Compared with the prior art, the porous medium burner for stable combustion of ultra-low calorific value gas provided by the present invention has the following beneficial effects: The present invention provides a porous medium burner for the stable combustion of ultra-low calorific value gases. This porous medium burner for the stable combustion of ultra-low calorific value gases utilizes a porous medium structure that first gradually expands and then gradually converges, ensuring that the flame is localized in the stable combustion porous medium layer. Air fully absorbs the heat of combustion in the stable combustion porous medium layer, heating the fuel and enhancing fuel activity. The converging porous medium layer promotes gas phase recirculation and gas-solid surface heat exchange in the post-flame zone, improving heat recirculation efficiency. This burner can broaden the flammability limit of low-calorific value gases and achieve stable and efficient utilization of ultra-low calorific value gases. Furthermore, the fuel channel and oxidant channel are independent of each other. The fuel and oxidant enter the premixing chamber from the fuel channel and the oxidant channel, respectively, and then enter the gradually diverging porous medium layer from the premixing chamber, ensuring thorough mixing of the fuel and oxidant. Furthermore, the oxidant channel is spirally arranged in the housing, surrounding the stable combustion porous medium layer and the gradually diverging porous medium layer. The inlet of the oxidant channel is located above the stable combustion porous medium layer, and the outlet of the oxidant channel is connected to the premixing chamber. Before entering the premixing chamber, the oxidizer undergoes inter-wall heat exchange with the combustion-stabilizing porous media layer and the gradually expanding porous media layer in the oxidizer channel. The heated oxidizer then enters the premixing chamber to heat the fuel, where it is premixed with the fuel and then enters the gradually expanding porous media layer. This ensures safe preheating and sufficient heat exchange, reduces the risk of flashback, and improves combustion stabilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings: Figure 1 It is a structural schematic diagram of a porous medium burner for stable combustion of ultra-low calorific value gas provided by a specific embodiment of the present invention.

[0018] In the picture: 1. Oxidant channel; 2. Fuel channel; 3. Premixing chamber; 4. Upstream metal shell; 5. Downstream metal shell; 6. High-temperature resistant liner; 7. Gradual-converging porous medium layer; 8. Combustion-stabilizing porous medium layer; 9. Gradual-expanding porous medium layer; 10. Inlet of oxidant channel; 11. Outlet of oxidant channel. DETAILED DESCRIPTION

[0019] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely explain the technical solutions in the embodiments of the present invention. It should be noted that the embodiments of the present invention and the features therein can be combined with each other in the absence of conflict, and the embodiments described are only part of the embodiments of the present invention, not all of the embodiments.

[0020] In the description of the present invention, unless otherwise expressly specified or limited, the terms "connected," "connected," and "fixed" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention in specific circumstances.

[0021] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0022] In the description of this embodiment, terms such as "upper," "lower," and "right" are used to refer to positions or locations based on the positions or locations shown in the accompanying drawings. These terms are intended solely to facilitate description and simplify operation, and are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used solely for descriptive purposes and have no special meaning.

[0023] See also Figure 1To describe this embodiment, the present invention provides a porous medium burner for stable combustion of ultra-low calorific value gas, which includes a shell, a tapered porous medium layer 7, a stable combustion porous medium layer 8, a gradually expanding porous medium layer 9, a premixing chamber 3, a fuel channel 2, and an oxidant channel 1. The tapered porous medium layer 7, the stable combustion porous medium layer 8, and the gradually expanding porous medium layer 9 are all located in the shell and are arranged in sequence from top to bottom; the premixing chamber 3 is connected to the bottom of the gradually expanding porous medium layer 9; the outlet of the fuel channel 2 is connected to the premixing chamber 3; the oxidant channel 1 is spirally arranged in the shell around the stable combustion porous medium layer 8 and the gradually expanding porous medium layer 9, the inlet 10 of the oxidant channel is located above the stable combustion porous medium layer 8, and the outlet 11 of the oxidant channel is connected to the premixing chamber 3.

[0024] This porous medium burner for stable combustion of ultra-low calorific value gas adopts a porous medium structure that first gradually expands and then gradually contracts, which can ensure that the flame is destined to the stable combustion porous medium layer 8. The air in the stable combustion porous medium layer 8 fully absorbs the combustion heat, heats the fuel, and enhances the fuel activity. The gradually contracting porous medium layer 7 promotes gas phase reflux and gas-solid surface heat exchange in the post-flame zone, improving the heat recirculation efficiency. This burner can broaden the flammability limit of low calorific value gas and achieve stable and efficient utilization of ultra-low calorific value gas. In addition, the fuel channel 2 and the oxidant channel 1 are independent of each other. The fuel and oxidant enter the premixing chamber 3 from the fuel channel 2 and the oxidant channel 1 respectively, and then enter the gradually expanding porous medium layer 9 from the premixing chamber 3, which can fully mix the fuel and oxidant. In addition, the oxidant channel 1 is spirally arranged in the shell around the stable combustion porous medium layer 8 and the gradually expanding porous medium layer 9. The inlet 10 of the oxidant channel is located above the stable combustion porous medium layer 8, and the outlet 11 of the oxidant channel is connected to the premixing chamber 3. Before entering the premixing chamber 3, the oxidizer undergoes inter-wall heat exchange with the combustion-stabilizing porous medium layer 8 and the gradually expanding porous medium layer 9 in the oxidizer channel 1. After entering the premixing chamber 3, the heated oxidizer enters the premixing chamber 3 to heat the fuel, where it is premixed with the fuel and enters the gradually expanding porous medium layer 9. This achieves safe preheating and sufficient heat exchange, reduces the risk of flashback, and improves combustion stabilization.

[0025] Optionally, the inner surface of the shell is provided with a high-temperature resistant lining 6. The gradually expanding porous medium layer 9, the combustion-stabilizing porous medium layer 8, and the gradually converging porous medium layer 7 are all encased in the high-temperature resistant lining 6 to prevent the shell from exceeding its temperature limit. The high-temperature resistant lining 6 and the shell are secured using a nail-grabbing cast-in method. The high-temperature resistant lining 6 is 200 mm thick.

[0026] Optionally, the shell comprises an upstream metal shell 4 and a downstream metal shell 5, connected by flanges. A converging porous media layer 7 is located within the upstream metal shell 4, a combustion-stabilizing porous media layer 8 and a gradually diverging porous media layer 9 are located within the downstream metal shell 5, and the oxidizer channel 1 is provided within the downstream metal shell 5. The flange connection between the upstream and downstream metal shells 4 and 5 facilitates the removal and replacement of the porous media. Both the upstream and downstream metal shells 4 and 5 are made of 310 S material with a thickness of 10 mm. Both the upstream and downstream metal shells 4 and 5 have circular cross-sections.

[0027] In this embodiment, two fuel and oxidant channels are provided, with the outlet of the fuel channel 2 positioned opposite the outlet 11 of the oxidant channel. This enhances the premixing effect. In other embodiments, four fuel and oxidant channels are provided, each injected tangentially into the four corners of the premixing chamber 3.

[0028] Optionally, the number of spiral turns of the oxidant channel 1 is 20. The oxidant channel 1 is a jacket channel provided in the upstream metal shell 4 .

[0029] Optionally, the PPI of the gradually expanding porous medium layer 9 is greater than 40, and the porosity is less than 0.7. The gradually expanding porous medium layer 9 is made of a high thermal conductivity material, which absorbs heat from the stable combustion porous medium layer 8 and further preheats the fuel-oxidant mixture through gas-solid phase heat transfer (direct contact heat exchange). The gradually expanding porous medium layer 9 adopts a high PPI (average number of pores per unit foot length) and low porosity setting, and has a high specific surface area, so that the pore flow velocity is maintained at a high level, the convective heat transfer is enhanced, and the fuel-oxidant mixture is helped to preheat. Preferably, the gradually expanding porous medium layer 9 has a gradually expanding angle greater than 15 degrees. The gradually expanding angle is defined as the acute angle between the hypotenuse generatrix of the high-temperature resistant liner 6 and the axial centerline on the cross section of the burner axial centerline.

[0030] In this embodiment, the height of the gradually expanding porous medium layer 9 is 12.5 cm, the PPI is set to 30 PPI, the porosity is 0.65, and the gradually expanding angle is set to 30 degrees.

[0031] Optionally, the combustion-stabilizing porous medium layer 8 has a PPI less than 10 and a porosity greater than 0.85. The preheated fuel-oxidizer mixture combusts within the combustion-stabilizing porous medium layer 8. The combustion-stabilizing porous medium layer 8 is constructed of a high-thermal-conductivity material with a low PPI and high porosity. This results in a low pore Reynolds number for the fuel-oxidizer mixture within the combustion-stabilizing porous medium layer 8, maintaining a low pore flow velocity and increasing its residence time. This allows the fuel-oxidizer mixture to ignite and burn fully, resulting in a submerged and stationary flame.

[0032] In this embodiment, the height of the combustion-stabilizing porous medium layer 8 is 10 cm, the PPI is set to 5 PPI, and the porosity is 0.85.

[0033] Optionally, the PPI of the tapered porous medium layer 7 is greater than 40, and the porosity is less than 0.7. After combustion, the flue gas passes through the tapered porous medium layer 7 and is discharged. The tapered porous medium layer 7 is made of high thermal conductivity material, high PPI and low porosity, and has a high specific surface area, so that the pore flow velocity is maintained at a high level, the convection heat transfer is enhanced, and the heat of the flue gas is recovered to the solid phase of the porous medium. The tapered structure can create a recirculation zone for the flue gas. Preferably, the tapering angle is greater than 15 degrees. The tapering angle is defined as the acute angle between the hypotenuse generatrix of the high-temperature resistant bushing 6 and the axial centerline on the cross section of the burner axial centerline.

[0034] In this embodiment, the height of the tapered porous medium layer 7 is 12.5 cm, the PPI is set to 30 PPI, the porosity is 0.65, and the tapered angle is set to 30 degrees.

[0035] In this embodiment, the combustion-stabilizing porous medium layer 8, the gradually contracting porous medium layer 7 and the gradually expanding porous medium layer 9 are all made of SiC foam ceramic material. The high-temperature resistant bushing 6 is made of mullite material.

[0036]

[0037] The fuel composition is shown in Table 1. Air is used as the oxidizer. The fuel is drawn from a storage tank, and the air is taken from the environment. Air enters premixing chamber 3 through oxidizer channel 1, and fuel enters premixing chamber 3 through fuel channel 2. The fuel and oxidizer are injected in a counter-flow manner. Premixing chamber 3 is cylindrical with a diameter of 5 cm and a length of 5 cm. The air flow rate is set at 0.5 kg / h to 1 kg / h, and the fuel flow rate is set at 0.05 m 3 / h~0.5 m 3 / h, control the equivalence ratio range to <1.1, and the premixed adiabatic flame temperature to less than 1200 ℃.

[0038] The experiment began with top ignition, using conventional natural gas as the fuel. A high-energy igniter was used for ignition. After successful ignition, the flame retracted into the stable porous medium layer 8. After the temperature rose to above 1400°C and remained there for 5 minutes, the fuel was switched to ultra-low calorific value gas.

[0039] After switching the fuel to ultra-low calorific value gas, the equivalence ratio is maintained at 0.9 and the flue gas temperature is controlled below 1000 ℃.

[0040] Obviously, the embodiments of the present invention disclosed above are intended only to help illustrate the present invention. The embodiments do not describe all details in detail, nor do they limit the invention to the specific embodiments described. Numerous modifications and variations are possible based on the contents of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. It is not necessary and impossible to list all embodiments here.

Claims

1. A porous medium burner for stable combustion of ultra-low calorific value gas, characterized in that: include: case; The gradually contracting porous medium layer (7), the combustion stabilizing porous medium layer (8) and the gradually expanding porous medium layer (9) are all located in the shell and are arranged in sequence from top to bottom; A premixing chamber (3), the premixing chamber (3) is in communication with the lower portion of the gradually expanding porous medium layer (9); A fuel channel (2), wherein an outlet of the fuel channel (2) is in communication with a premixing chamber (3); The oxidant channel (1) is spirally arranged on the shell around the combustion stabilizing porous medium layer (8) and the gradually expanding porous medium layer (9), the inlet (10) of the oxidant channel is located above the combustion stabilizing porous medium layer (8), and the outlet (11) of the oxidant channel is connected to the premixing chamber (3).

2. The porous medium burner for stable combustion of ultra-low calorific value gas according to claim 1, characterized in that: The inner surface of the shell is provided with a high temperature resistant bushing (6).

3. The porous medium burner for stable combustion of ultra-low calorific value gas according to claim 1, characterized in that: The shell comprises an upstream metal shell (4) and a downstream metal shell (5), wherein the upstream metal shell (4) and the downstream metal shell (5) are connected via a flange, the tapered porous medium layer (7) is located in the upstream metal shell (4), the combustion stabilizing porous medium layer (8) and the gradually expanding porous medium layer (9) are located in the downstream metal shell (5), and the oxidant channel (1) is provided in the downstream metal shell (5).

4. The porous medium burner for stable combustion of ultra-low calorific value gas according to claim 1, characterized in that: The outlet of the fuel channel (2) is arranged opposite to the outlet (11) of the oxidant channel.

5. The porous medium burner for stable combustion of ultra-low calorific value gas according to claim 1, characterized in that: The combustion-stabilizing porous medium layer (8), the gradually shrinking porous medium layer (7) and the gradually expanding porous medium layer (9) are all made of SiC foam ceramic material.

6. The porous medium burner for stable combustion of ultra-low calorific value gas according to claim 1, characterized in that: The high temperature resistant bushing (6) is made of mullite material.

7. The porous medium burner for stable combustion of ultra-low calorific value gas according to claim 1, characterized in that: The number of spiral turns of the oxidant channel (1) is 20.

8. The porous medium burner for stable combustion of ultra-low calorific value gas according to claim 1, characterized in that: The PPI of the gradually expanding porous medium layer (9) is greater than 40, and the porosity is less than 0.

7.

9. The porous medium burner for stable combustion of ultra-low calorific value gas according to claim 1, characterized in that: The combustion-stabilizing porous medium layer (8) has a PPI of less than 10 and a porosity of greater than 0.

85.

10. The porous medium burner for stable combustion of ultra-low calorific value gas according to claim 1, characterized in that: The PPI of the tapered porous medium layer (7) is greater than 40, and the porosity is less than 0.7.

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