Porous medium burner and low-heating-value fuel gas treatment method

Abstract

The invention discloses a porous medium combustor and a low-heating-value fuel gas treatment method. The porous medium combustor comprises a combustion chamber, a small-pore porous medium, a large-pore porous medium, an igniter and an electrode. Low-calorific-value fuel gas and air are mixed and then injected into a combustion chamber, a small-pore porous medium and a large-pore porous medium are arranged in the combustion chamber at intervals, and electrodes are connected with the two ends of the large-pore porous medium. The mixed gas flows to the macropore porous medium through the small-pore porous medium and is ignited through the igniter, the mixed gas can be fully combusted in the macropore porous medium, generated heat preheats the unreacted mixed gas through heat radiation and heat conduction effects, efficient combustion of low-heating-value fuel gas is achieved, the macropore porous medium generates an electric field through the electrodes, and the low-heating-value fuel gas is combusted through the igniter. Free electrons and active particles move in a combustion area, the mixed gas is catalyzed and activated, and therefore the problems that a combustor is large in size, complex in operation and high in cost are solved. And the small-pore porous medium serves as a flame blocking area, so that gas tempering is prevented, and combustion safety is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of gas burners, in particular to a porous medium burner and a low-calorific value gas treatment method. BACKGROUND

[0002] In recent years, the industrial and energy fields have put forward urgent demands for efficient and clean utilization of low-calorific value gas. For example, in emerging power generation technologies, 8% to 12% of combustible gas exists in the anode tail gas during the operation of solid oxide fuel cells. Due to the characteristics of low heat value and high content of non-combustible components in the composition of such gas, it is difficult to ignite and maintain combustion, and if not utilized or utilized incompletely, not only the gas resources are wasted, but also the atmospheric environment is polluted.

[0003] At present, the combustion technology for low-calorific value gas faces great challenges: on the one hand, in order to maintain flame stability, the combustion air often needs to be preheated to a very high temperature, or the burner needs to be designed to be extremely large, which significantly increases the system complexity and operating cost. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application provides a porous medium burner and a low-calorific value gas treatment method, which solves the problems of large volume, complex operation and high cost of the existing burners suitable for low-calorific value gas, and the specific technical solutions are as follows: In a first aspect, a porous medium burner is provided, and in a first implementation manner of the first aspect, the burner comprises: a combustion chamber comprising a mixed gas inlet end and a flue gas discharge end; a small-pore porous medium and a large-pore porous medium, which are sequentially and spacedly embedded in the combustion chamber in the direction from the mixed gas inlet end to the flue gas discharge end; an igniter arranged in the gap between the small-pore porous medium and the large-pore porous medium; an electrode electrically connected to the large-pore porous medium through the wall of the combustion chamber, wherein the large-pore porous medium is made of an electrically conductive material.

[0005] In a second implementation manner of the first aspect, in combination with the first implementation manner of the first aspect, the electrically conductive material comprises silicon carbide foam or conductive metal foam.

[0006] In a third implementation manner of the first aspect, in combination with the first implementation manner of the first aspect, an insulating layer is arranged on the inner wall of the combustion chamber.

[0007] In a fourth implementation manner of the first aspect, in combination with the third implementation manner of the first aspect, the insulating layer is made of an insulating material, and the insulating material comprises quartz or ceramic.

[0008] In a fifth implementation form of the first aspect, in the first implementation form of the first aspect, the small-pore porous medium is made of high-thermal-resistance insulating material.

[0009] In a sixth implementation form of the first aspect, in the first implementation form of the first aspect, the outer wall of the combustion chamber is provided with a heat preservation layer.

[0010] In a seventh implementation form of the first aspect, in the sixth implementation form of the first aspect, the heat preservation layer is made of heat preservation material, and the heat preservation material includes ceramic fiber.

[0011] In a second aspect, a low-calorific-value gas treatment method is provided, including: treating the low-calorific-value gas by using the porous medium burner in any one of the first to seventh implementation forms of the first aspect.

[0012] The porous medium burner and the low-calorific-value gas treatment method can utilize the combustion and heat exchange characteristics of the porous medium, so that the low-calorific-value gas and the air injected into the combustion chamber can be fully mixed and combusted in the large-pore porous medium, the heat generated by the combustion can preheat the unreacted mixed gas through heat radiation and heat conduction, and efficient combustion of the low-calorific-value gas is achieved. Meanwhile, the power supply can be connected to the large-pore porous medium through the electrodes, so that the large-pore porous medium region periodically generates a programmable electric field, the large-pore porous medium region can generate a programmed Joule heating effect under the action of the electric field, the temperature of the large-pore porous medium region is increased, and the combustion is strengthened. The free movement of free electrons and active particles in the large-pore porous medium region is promoted, the unreacted mixed gas is strengthened, catalyzed and activated, and the flow field mixing effect is also improved. In this way, the defects of difficult ignition and poor combustion stability of the low-calorific-value gas can be solved. The traditional heat exchange equipment is not needed, the volume of the burner is greatly reduced, and the problems of large volume, complex operation and high cost of the existing burners suitable for low-calorific-value gas are solved. Moreover, the small-pore porous medium can act as a flame blocking area in the combustion process, prevent the backfire of the combustion gas, ignite the mixed gas in the premixing chamber, and ensure the safety of the low-calorific-value gas combustion. BRIEF DESCRIPTION OF DRAWINGS

[0013] In order to more clearly illustrate the specific embodiments of the present application, the drawings required to be used in the specific embodiments will be briefly introduced below. In all the drawings, the elements or parts are not necessarily drawn according to the actual proportions.

[0014] Figure 1 A structural schematic diagram of the porous medium burner provided by an embodiment of the present application is shown in FIG. 1. Figure 2 A structural schematic diagram of the combustion chamber provided by an embodiment of the present application is shown in FIG. 2. Figure 3 Figure 1 is a schematic diagram of the distribution of large and small pore porous media; Reference signs: 1 - premixing chamber, 2 - combustion chamber, 3 - small pore porous medium, 4 - large pore porous medium, 5 - igniter, 6 - electrode, 7 - insulation layer, 8 - heat preservation layer, 9 - flow regulating valve, 10 - mixed gas inlet end, 11 - flue gas discharge end. DETAILED DESCRIPTION

[0015] The embodiments of the technical solutions of the present application will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and therefore only serve as examples, but cannot limit the protection scope of the present application.

[0016] As Figure 1 shown in the structural schematic diagram of the porous medium burner, the burner comprises: a combustion chamber 2 comprising a mixed gas inlet end 10 and a flue gas discharge end 11; a small pore porous medium 3 and a large pore porous medium 4, which are sequentially and spacedly arranged in the combustion chamber 2 along the direction from the mixed gas inlet end 10 to the flue gas discharge end 11; an igniter 5 arranged in the gap between the small pore porous medium 3 and the large pore porous medium 4.

[0017] Specifically, the burner comprises a premixing chamber 1, a combustion chamber 2, a small pore porous medium 3, a large pore porous medium 4 and an igniter 5. The premixing chamber 1 is communicated with a fan and a gas pipe, low-calorific value gas can be injected into the premixing chamber 1 through the gas pipe, and the fan can inject air into the premixing chamber 1 and preliminarily mix with the low-calorific value gas under the action of the fan. The premixing chamber 1 is communicated with the mixed gas inlet end 10 of the combustion chamber 2, and the preliminarily mixed mixed gas can be injected into the combustion chamber 2 under the action of the fan. The small pore porous medium 3 and the large pore porous medium 4 are sequentially and spacedly arranged in the combustion chamber 2 along the direction from the mixed gas inlet end 10 to the flue gas discharge end 11. The mixed gas injected into the combustion chamber 2 is preliminarily mixed by the small pore porous medium 3 and then fully mixed in the large pore porous medium 4.

[0018] The igniter 5 arranged between the small pore porous medium 3 and the large pore porous medium 4 can ignite the mixed gas, and the mixed gas can be fully mixed and combusted in the large pore porous medium 4. At the same time, the heat generated by the combustion can preheat the unreacted mixed gas through heat radiation and heat conduction, realizing efficient combustion of low-calorific value gas, without the need for traditional heat exchange equipment, greatly reducing the volume of the burner, and thus solving the problems of large volume, complex operation and high cost of the existing burners suitable for low-calorific value gas.

[0019] And in the combustion process, the small-pore porous medium 3 can be used as a flame block area to prevent the backfire of the combustion gas igniting the mixture in the premixing chamber 1, ensuring the safe combustion of low-calorific value gas. According to the Peclce number, it can be determined that the small-pore porous medium is more conducive to preventing backfire than the large-pore porous medium. The specific calculation formula of the Peclce number is as follows: ; wherein, is the laminar flame speed, is the equivalent diameter, is the specific heat capacity of the mixture, is the density of the mixture, is the thermal conductivity of the mixture.

[0020] It can be seen that the larger the pore diameter of the porous medium, the larger the Peclce number. When the Peclce number is , the flame propagates, and when the Peclce number is , the flame is extinguished. The small-pore porous medium is more conducive to preventing backfire. Therefore, the small-pore porous medium 3 is selected as the flame block area in the embodiment.

[0021] In the embodiment, optionally, the premixing chamber 1 further comprises: electrodes 6 electrically connected to the large-pore porous medium 4 through the wall of the combustion chamber 2, and the large-pore porous medium 4 is made of an electrically conductive material.

[0022] Specifically, the large-pore porous medium 4 can be made of an electrically conductive material with low thermal resistance and strong electrical conductivity. The wall of the combustion chamber 2 is provided with positive and negative electrodes 6, and the positive and negative electrodes 6 are electrically connected to the two sides of the large-pore porous medium 4, respectively. The positive and negative electrodes 6 can be connected to the positive and negative poles of the power supply, respectively, so as to periodically form a programmable electric field at the large-pore porous medium 4. Under the action of the electric field, not only the free electrons and active particles existing in the combustion zone move freely, but also the unreacted low-calorific value gas is catalyzed and activated, and the Joule heating effect is also programmed, and the mixing effect of the flow field is also improved to a certain extent. The defects of difficult ignition and poor combustion stability of low-calorific value gas are solved.

[0023] For improving the mixing effect of the flow field, specifically, under the action of the electric field, there is an ion wind effect, and a large number of positive and negative ions migrate along the direction of the electric field, so that the mass transfer and heat transfer of the unburned zone are enhanced. Under the action of the programmable power supply, the ion wind effect of the programmable change is more significant than the continuous power supply in improving the efficiency of turbulent mixing. And the electrohydrodynamic effect of the electric field on the electrofluid also promotes the mixing of the flow field.

[0024] If the electrode 6 is arranged at the mixture inlet of the combustion chamber 2, the plasma generated in the electric field will collide and recombine due to the vortex of the gas flow during the mixture enters the large-pore porous medium 4, resulting in the decrease of the plasma concentration, weakening the catalysis and activation of the low-calorific-value fuel gas, and not affecting the flow field of the combustion zone.

[0025] In the embodiment, the electrically conductive material can be silicon carbide foam or conductive metal foam, but is not limited to such materials.

[0026] Specifically, the large-pore porous medium 4 can be made of low-thermal-resistance and high-conductivity silicon carbide foam or conductive metal foam, but is not limited to such materials, and a material with low thermal resistance and high conductivity can be used.

[0027] Specifically, the silicon carbide foam has extremely high high-temperature resistance, low thermal resistance, and is not easy to oxidize. Moreover, it has good electrical conductivity at high temperatures. The conductive metal foam can be stainless steel foam, which has low cost, good electrical conductivity and thermal conductivity, and high cost performance.

[0028] In the embodiment, the inner wall of the combustion chamber 2 is provided with an insulating layer 7.

[0029] Specifically, the small-pore porous medium 3 prevents backfire from igniting the mixture in the premixing chamber 1. To avoid the electrification of the small-pore porous medium 3 due to the electrification of the large-pore porous medium 4, an insulating layer 7 is arranged on the inner wall of the combustion chamber 2, so that the current of the large-pore porous medium 4 is not transmitted to the small-pore porous medium 3, and the small-pore porous medium 3 is electrified. At the same time, the space between the small-pore porous medium 3 and the large-pore porous medium 4 provides space for the installation of the igniter 5.

[0030] In the embodiment, the insulating layer 7 can be made of quartz or ceramic, but is not limited to such materials.

[0031] Specifically, the insulating layer 7 arranged on the inner wall of the combustion chamber 2 can be made of quartz or ceramic. Quartz or ceramic has the characteristics of high temperature resistance and high insulation. While insulating the current conduction, it can withstand the high temperature environment formed by the combustion of low-calorific-value fuel gas. Materials with high temperature resistance and high insulation can be used.

[0032] In the embodiment, the small-pore porous medium 3 is made of high-thermal-resistance insulating material.

[0033] Specifically, the small-pore porous medium 3 can adopt high-thermal-resistance insulating material, which can slow down the heat transfer to the mixed gas in the upstream pre-mixing chamber, and protect the gas mixture from backfire caused by high-temperature impact. Therefore, the small-pore porous medium 3 made of small pores and high-thermal-resistance material can play a double role in preventing backfire.

[0034] The high-thermal-resistance insulating material can be alumina ceramic foam or zirconia ceramic foam, which have low thermal conductivity and good insulation effect, effectively preventing backfire and short circuit. High-thermal-resistance and insulating materials can be used, not limited to the above materials.

[0035] In this embodiment, optionally, a flow regulating valve 9 can be arranged on the communicating gas pipe of the pre-mixing chamber 1. The flow of low-calorific value gas injected into the pre-mixing chamber 1 can be adjusted by the flow regulating valve 9 to adjust the proportion of low-calorific value gas in the mixed gas.

[0036] In this embodiment, optionally, the outer wall of the combustion chamber 2 is provided with a heat preservation layer 8.

[0037] Specifically, a heat preservation layer 8 can be wrapped on the outer wall of the combustion chamber 2, which can effectively prevent the heat generated by combustion from being lost to the outside through the wall, reduce heat loss, and improve combustion efficiency. At the same time, the heat preservation layer 8 can prevent the temperature of the outer wall of the combustion chamber from being too high, protecting the safety of the operator.

[0038] In this embodiment, optionally, the heat preservation layer 8 can be made of ceramic fiber, but is not limited to such materials.

[0039] Specifically, the heat preservation layer 8 wrapped on the outer wall of the combustion chamber 2 can be made of ceramic fiber, which has the advantages of high-temperature resistance, low thermal conductivity, lightweight, plasticity, strong heat shock resistance, good heat preservation effect, and can be wrapped on the outer wall of a complex-shaped burner with low cost. Materials with the above advantages can be used, not limited to specific materials such as ceramic fiber.

[0040] A low-calorific value gas treatment method, comprising: treating the low-calorific value gas by using the porous medium burner described above.

[0041] The above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent substitutions for part or all of the technical features; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should be covered in the scope of the claims and the description of the present application.

Claims

1. A porous media burner, characterized in that, include: The combustion chamber includes the gas mixture inlet and the flue gas outlet. Small-pore porous media and large-pore porous media are sequentially and intermittently embedded in the combustion chamber along the direction from the inlet end of the mixed gas to the exhaust end of the flue gas; An igniter is disposed in the gap between the small-pore porous medium and the large-pore porous medium; An electrode passes through the combustion chamber wall and is electrically connected to a macroporous medium made of a conductive material.

2. The porous media burner according to claim 1, characterized in that, The conductive material includes silicon carbide foam or conductive metal foam.

3. The porous medium burner according to claim 1, characterized in that, The combustion chamber wall is provided with an insulating layer.

4. The porous medium burner according to claim 3, characterized in that, The insulating layer is made of an insulating material, including quartz or ceramic.

5. The porous media burner according to claim 1, characterized in that, The porous medium with small pores is made of a high thermal resistance insulating material.

6. The porous media burner according to claim 1, characterized in that, The outer wall of the combustion chamber is provided with a heat insulation layer.

7. The porous medium burner according to claim 6, characterized in that, The insulation layer is made of insulation material, including ceramic fiber.

8. A method for treating low-calorific-value fuel gas, characterized in that, include: Low-calorific-value gas is treated using a porous media burner as described in any one of claims 1-7.

Images