CA2211124C - Burner, in particular for heating systems - Google Patents
Burner, in particular for heating systems Download PDFInfo
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- CA2211124C CA2211124C CA002211124A CA2211124A CA2211124C CA 2211124 C CA2211124 C CA 2211124C CA 002211124 A CA002211124 A CA 002211124A CA 2211124 A CA2211124 A CA 2211124A CA 2211124 C CA2211124 C CA 2211124C
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- burner
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- ordered packing
- porous body
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C99/00—Subject-matter not provided for in other groups of this subclass
- F23C99/006—Flameless combustion stabilised within a bed of porous heat-resistant material
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- Combustion & Propulsion (AREA)
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Abstract
A packing as a porous body for burners, in particular for heating systems, is provided with a housing (1) having an inlet (4) for a gas/air mixture as a combustable gas mixture, a combustion chamber (7), an ignition device (9) in the combustion chamber (7) and an exhaust gas outlet (13). The combustion chamber (7) is at least partly filled with a three-dimensional ordered packing (8) of heat resistant ceramic material, foil material, or sheet metal material having continuous hollow cavities for the formation of a defined flame zone.
Description
Burner, in particular for Heating Systems The invention relates to a burner, in particular for heating systems, with the features set forth in the preamble of claim 1.
Various concepts are known from the prior art for the reduc-tion of the noxious substances such as NOX or CO, which arise during combustion. Since the NOx production is large at high combustion temperatures, one attempts, for example, to keep the flame temperature low. For this purpose a heating boiler has been proposed, for example in EP 0 256 322 B1, in which a fuel gas is burned at a temperature of less than 700°C
through the use of a catalyst of the platinum group, whereby the creation of nitrogen oxides is prevented. However, such catalysts have only a relatively low working life and are, moreover, very costly. The essential disadvantage of cata-lytic combustion, however, lies in the fact that its flame temperature is too low, which does not permit any effective exploitation of the heat and thereby only allows the con-struction of a burner with a low power density.
In addition to this, there are burners which operate in ac-cordance with the process of exhaust gas recirculation. Here a part of the exhaust gas is returned into the flame, whereby an optimised, pollution reduced combustion is achieved. A
stable flame arises with the burner model "RotriX" of the Vi-essmann company through an intentional decay of the turbulent fuel/air mixture, which has been set into rotation. The ex-haust gas recirculation rate can be further increased by a flameless oxidation at a free surface. According to the spe-cialist paper by J.A. Wunning and J.G. Wunning: "Brenner fur __ _di~ flammlose Oxidation mit geringer NO-Bildung auch bei, 'hochster Luftvorwarmung" (Burner for the flameless oxidation with low NO-formation even with the highest air pre-heating), in GASWARME International, Vol. 41 (1992), No. 10, pages 438 to 444, the flameless oxidation is usable in burners with process temperatures over 850°C. This process, however, in-volves high constructional cost and complexity because auxil-iary burners are required, for example, for the heating up of the fuel/air mixture to ignition temperature.
A further concept is present in the form of the "Thermomax-Burner" of the company Ruhrgas AG, which is treated in the specialist paper by H. Berg and T. Jannemann "Entwicklung eines schadstoffarmen Vormischbrenners fur den Einsatz in Haushalts-Gaskesseln mit zylindrischer Brennkammer"
(Development of a low-pollution pre-mixing burner for use in domestic gas boilers with a cylindrical combustion chamber), in GASWARME International, Vol. 38 (1989), No. 1, pages 28 to 34. The combustion takes place there in a flameless manner at the surface of a metallic, apertured sheet, which transmits the heat energy produced out of the reaction zone principally by radiation. The combustion temperature is kept to approxi-mately 800°C through this giving off of heat, which in turn has the consequence of a reduction of the emission of pollu-tion. Burners of this type of construction typically have a thermal surface loading of 300 kW/mz.
An increase of the thermal loading to approximately 3000 kW/mz is achieved by a burner which is known from DE 43 22 109 A1. There, a part of the combustion chamber, in which a flame propagates, is completely filled with a porous material whose porosity changes along the flow direction of the fuel gas/air mixture in such a way that a critical Peclet number results at a boundary surface, or in a specific zone of the porous material, from which point on a flame can arise. Having regard to the Peclet number, the following ~should be explained: -' With a specific pore size of the porous material, the produc-tion of heat by chemical reactions in the flame and the dis-sipation of heat by the porous medium are of the size so that beneath this pore size no flame can arise but above it a free ignition occurs.
This condition is described with the aid of the Peclet num-ber, which recites the ratio of heat production to heat dis-sipation. In this way a critical Peclet number results for the flame propagation. A self-stabilising flame within the supercritical zone results through the provision of a sub-critical zone and a supercritical zone with respect to the Peclet number.
Through the arrangement set forth in DE 43 22 109 A1, the problem of the stability of a flame burning in a porous me-dium is solved under the side conditions of a low temperature and thus a low emission of pollution. Ceramic foams or bulk fillings of balls are proposed as porous material. These ma-terials have, however, a relatively low porosity, whereby combustion space is wasted and the gas/air mixture is exposed to a higher flow resistance. Moreover, these materials re-strict, as a result of their low optical permeability, the energy transport on the basis of the thermal transport mecha-nism of thermal radiation which dominates in the present tem-perature range. This leads to a situation - from a specific constructional size of a burner of this kind onwards - in which the heat produced cannot be dissipated sufficiently well outwardly from the inner region of the combustion space.
The local overheating in the porous material brought about in this way leads to material damage by thermal strains and an increased output of pollutants.
26380-24 ca o22iii24 2ooo-os-io The invention is thus based on the object of providing a porous medium for a burner which has a high porosity and thus a high optical permeability and which is also insensitive with respect to thermal strains. Moreover, it should be possible to manufacture the porous medium in a simple manner from the technical manufacturing viewpoint, at a favourable cost and with constant precision.
Therefore, this invention seeks to provide a burner comprising a combustion chamber in a housing that includes an inlet for air and gaseous fuel, an ignition device, and an exhaust gas outlet, the burner further comprising a porous body that at least partly fills out the combustion chamber, the porous body consisting of heat resistant material and having spatially connected, hollow cavities for the formation of a defined flame zone, a part of the porous body being provided as a flame zone and being formed as an ordered packing, the ordered packing being built up of layers of crossing webs and consisting of at least one of metallic and ceramic materials, said burner further comprising a second porous body being integrated at the inlet region of the ordered packing and having a peclet number that is subcritical.
Accordingly, the combustion space of the burner is at least partly filed by a three-dimensional ordered packing having connected cavities and consisting of ceramic material, foil material or sheet metal material for the formation of a defined flame zone.
Such ordered packings can basically be manufactured with the required high porosity of up to approximately 99%
and thus offer a larger combustion space than, for example, ceramic foams or bulk fillings of ceramic bodies. As a result of the high optical permeability of such packings, the 26380-24 CA o22iii24 Zooo-os-io 4a thermal transport by thermal radiation is not blocked so that a rapid and effective thermal dissipation to the thermal transfer medium is ensured. Furthermore, these packings have a low flow resistance as a result of the open structure.
Thus, the pressure loss of the gas flow when flowing through the combustion space can be reduced, which lowers the required energy input. The known manufacturing methods for such packings furthermore enable their production in a simple manner from a technical manufacturing viewpoint and at favourable cost, with invariable precision with respect to the dimensioning of the hollow cavities. The latter can be varied in their size without great complexity.
The packings have, as a result of their three-dimensional structure, the further advantage that they react resiliently to thermal or mechani-cal loading, whereby the danger of points of fracture, such as exists, for example, with the foam-like ceramic parts used in the prior art, is overcome.
Since the packings of the invention can be manufactured with much higher degrees of porosity when compared with the prior art, the proportion of material related to the total volume is very low. This leads to a considerable shortening of the response times of the burner in comparison to the previously known porous media. Moreover, such packings can be made vari-able with respect to their diameter, length, hydraulic diame-ter etc., whereby an ideal flow-mechanical design can be achieved.
Ordered packings which are used as static mixers have, in ad-dition to a low pressure drop and optical permeability, also other characteristics which have a positive benefit. The pro-nounced transverse mixing leads to homogenous concentration profiles and temperature profiles of the combustion gases, which favourably influences the combustion process and fur-ther reduces the production of pollution because no cold points and no so-called hot spots occur. Stagnating zones and also break-throughs of the flow media are prevented because of the low back mixing, and the combustion zone is addition-ally stabilised in the flow direction.
Furthermore, it can be of advantage to use two or more pack-ing elements, which are arranged rotated relative to one an-other. In this way a homogenous distribution of concentra-tion, temperature and flow speed is ensured over the entire flow cross section.
The above advantages are in particular achieved by a packing _ which consists of a material which is resistant to tempera-~tures in the range between 1200°C and 2000°C (claim 2).
Ordered packings such as, for example, static mixers, which are built up of layers of corrugated lamella, or lamella folded in zig-zag-like manner, which form channels have proved to be particularly suitable, with the channels of neighbouring layers crossing one another and with the lamella consisting of metallic and/or ceramic materials, whereby the packing can also be of monolithic construction (claim 3).
In accordance with claim 4 the lamella can be foils or metal sheets which are arranged loosely alongside another and which have a plurality of perforations.
Another type of ordered packing is made of webs which inter-sect cross-wise and have the same features as packings which are formed of corrugated lamella.
In accordance with claim 5 the packing can be built up of layers of webs which cross each other and consist of metallic and/or ceramic materials.
In accordance with claim 6 the packing can consist of ceramic materials, with the principal components being A1203, Zr02 or SiC. These materials have advantages with respect to tempera-ture resistance and corrosion resistance.
The advantages listed are in particular achieved by a packing which has a high hollow space component or proportion, i.e. a high porosity of at least 70 % and a wave height of the lay-ers, or a web width, of between 3 mm and 15 mm (claim 7).
With these geometrical data, low pressure losses and low emissions of pollutants can be realised.
In accordance with claim 8 the packing in the combustion chamber can be catalytically coated or can be manufactured of a catalytically active material, i.e. it is itself catalyti-cally active. In this way very low pollution emission values are achieved.
In accordance with claim 9 a porous body is placed in front of the inlet zone of the ordered packing. It functions as a flame holder or flame barrier in that it ensures that the Pe-clet number present there is subcritical, preferably smaller than 65. This porous body can be formed as an ordered packing (claim 10) .
Claims 9 and 10 characterise measures for the defined re-striction of the flame zone of the burner with the operation taking place in accordance with claim 9 with a flame holder of conventional construction known from the prior art; at the same time the mixing between the gaseous or vaporous fuel in the air is made more intense by the finely pored body. In this way conventional burners with free flame formation, which normally have such flame holders, can be retrospec-tively equipped with packings in accordance with the inven-tion. In this way a cost favourable possibility is provided for the reduction of pollution of burners which are already in use.
In the alternative set forth in claim 10, a finely porous ma-terial is arranged in the throughflow direction of the gas/air mixture upstream of the flame zone defined by the packing. No flame can form in this finely porous material be-cause of its subcritical Peclet number. Thus, the concept known from DE 43 22 109 A1 for flame stabilisation can be combined with the present invention.
The finely pored material, which can be produced without _ problems as an ordered packing with a porosity having a Pe-~clet number which is in particular smaller than 65, can be manufactured in analogous manner from temperature resistant ceramic material, foil material or sheet metal material, in the same way as the actual ordered packing in the combustion chamber.
In this arrangement this finely pored packing not only serves for the flame stabilisation but rather the combustion gases such as, for example, natural gas, methane or heating oil va-pour are homogenously mixed with air before the actual com-bustion chamber as a result of the transverse mixing charac-teristics. This additionally favourably influences the com-bustion process, in particular with respect to the emission of pollutants.
Further features, particulars and advantages of the invention can be seen from the following description, in which examples of the subject of the invention are explained in more detail with reference to the accompanying drawings. There are shown:
Fig. 1 an ordered packing of ceramic material, Fig. 2 a schematic longitudinal section through a burner in a first embodiment, Fig. 3 a schematic longitudinal section through a burner in a second embodiment, and Fig. 4 a typical axial temperature profile within the burner.
The ordered packing shown in Fig. 1 is put together from a plurality of corrugated ceramic plates. These ceramic plates are so arranged that the corrugations of two neighbouring corrugated plates form an angle of 60°. In this way open --channels result which cross each other.
The burner shown in Fig. 2 has a housing 1 comprising a cy-lindrical main portion 2 and a truncated, cone-like upper end part 3. The latter has at its upper side an inlet 4 for a gas/air mixture as the combustible gas mixture. In the throughflow direction D of the gas/air mixture the prechamber formed by he end part 3 is followed by a conventional flame holder or a perforated plate 6, through which the gas/air mixture enters into the subsequent combustion chamber 7. This combustion chamber is filled out with an ordered packing 8, which has, for example, the following specifica-tions:
diameter: 70 mm height: 90 mm porosity: ca. 95 0 corrugation height: 8 mm material: heat resistant ceramic The gas/air mixture entering into the ordered packing 8 is ignited by an ignition device 9 sitting at the side in the housing 1 at the level of the combustion chamber 7 and burns while forming a defined flame zone within the ordered packing 8 while producing thermal energy. The latter arises to a large part as thermal radiation which heats the main part 2 of the housing. The main part 2 is surrounded by a heat transmitting jacket 10 in which helically extending channels 11 are provided. A heat exchanger medium, such as for example water, which circulates through a heating system, flows through these channels.
After the combustion space in the passage direction D, there is further provided an exhaust gas space 12, in which tem-peratures between 700°C and 1300°C prevail at the inlet of -this zone and between 35°C and 150°C at the outlet of this region. The exhaust gas space 12 serves as a cooling zone, with the cooling coil of stainless steel 14 extracting heat from the exhaust gas, which can be used as useful heat. The cooling coil 14 is kept at temperatures below 200°C by the heat exchanger medium flowing through it so that other mate-rials, in particular aluminium, brass or copper are also pos-sible. The exhaust gas space 12 opens into the exhaust gas outlet 13 of the burner.
The burner shown in Fig. 3 is distinguished from the burner in Fig. 2 only in two details. To this extent components are provided which otherwise correspond with the same reference numerals as in Fig. 2 and do not require repeated explana-tion.
In distinction to Fig. 2, the burner of Fig. 3 has no conven-tional flame holder. On the contrary, a finely pored packing is arranged in front of the ordered packing when viewed in the throughflow direction D of the gas/air mixture, and is likewise formed from an ordered packing. The latter has a smaller pore size and porosity than the ordered packing 8, so that its Peclet number is smaller than 65 and is thus sub-critical. This signifies that no flame can form in the or-dered packing 15. The ordered packing 8 is so specified that the Peclet number is supercritical, so that a flame can form there in defined manner.
Moreover, a static mixer 16 is inserted in front of the burner (claim 11). It brings about a very homogenous gas/air mixture.
The temperature profile shown in Fig. 4 for a 6 kW natural gas burner with a power of 3 kW and an air number of 1.2 shows that the maximum temperatures arise shortly after the transition between the finely pored region A and the coarsely pored region C and can lie in the range of approximately 1400°C to 1500°C. In the region D which follows it, the tem-peratures lie at around 1100°C at the inlet and sink towards the outlet to temperatures which are of the same order of magnitude as those of the heat exchanger medium.
The gaseous fuel can, for example, also be vapourised heating oil or diesel oil.
Moreover, it should be pointed out that the flame which forms through the ignition of the gas/air mixture in the flame zone defined by the ordered packing 8 propagates in dependence on the ratio of gas to air and also of the quantities thereof.
To this extent the power of the burner can be regulated via the quantity of the gas and also of the gas/air mixture.
Various concepts are known from the prior art for the reduc-tion of the noxious substances such as NOX or CO, which arise during combustion. Since the NOx production is large at high combustion temperatures, one attempts, for example, to keep the flame temperature low. For this purpose a heating boiler has been proposed, for example in EP 0 256 322 B1, in which a fuel gas is burned at a temperature of less than 700°C
through the use of a catalyst of the platinum group, whereby the creation of nitrogen oxides is prevented. However, such catalysts have only a relatively low working life and are, moreover, very costly. The essential disadvantage of cata-lytic combustion, however, lies in the fact that its flame temperature is too low, which does not permit any effective exploitation of the heat and thereby only allows the con-struction of a burner with a low power density.
In addition to this, there are burners which operate in ac-cordance with the process of exhaust gas recirculation. Here a part of the exhaust gas is returned into the flame, whereby an optimised, pollution reduced combustion is achieved. A
stable flame arises with the burner model "RotriX" of the Vi-essmann company through an intentional decay of the turbulent fuel/air mixture, which has been set into rotation. The ex-haust gas recirculation rate can be further increased by a flameless oxidation at a free surface. According to the spe-cialist paper by J.A. Wunning and J.G. Wunning: "Brenner fur __ _di~ flammlose Oxidation mit geringer NO-Bildung auch bei, 'hochster Luftvorwarmung" (Burner for the flameless oxidation with low NO-formation even with the highest air pre-heating), in GASWARME International, Vol. 41 (1992), No. 10, pages 438 to 444, the flameless oxidation is usable in burners with process temperatures over 850°C. This process, however, in-volves high constructional cost and complexity because auxil-iary burners are required, for example, for the heating up of the fuel/air mixture to ignition temperature.
A further concept is present in the form of the "Thermomax-Burner" of the company Ruhrgas AG, which is treated in the specialist paper by H. Berg and T. Jannemann "Entwicklung eines schadstoffarmen Vormischbrenners fur den Einsatz in Haushalts-Gaskesseln mit zylindrischer Brennkammer"
(Development of a low-pollution pre-mixing burner for use in domestic gas boilers with a cylindrical combustion chamber), in GASWARME International, Vol. 38 (1989), No. 1, pages 28 to 34. The combustion takes place there in a flameless manner at the surface of a metallic, apertured sheet, which transmits the heat energy produced out of the reaction zone principally by radiation. The combustion temperature is kept to approxi-mately 800°C through this giving off of heat, which in turn has the consequence of a reduction of the emission of pollu-tion. Burners of this type of construction typically have a thermal surface loading of 300 kW/mz.
An increase of the thermal loading to approximately 3000 kW/mz is achieved by a burner which is known from DE 43 22 109 A1. There, a part of the combustion chamber, in which a flame propagates, is completely filled with a porous material whose porosity changes along the flow direction of the fuel gas/air mixture in such a way that a critical Peclet number results at a boundary surface, or in a specific zone of the porous material, from which point on a flame can arise. Having regard to the Peclet number, the following ~should be explained: -' With a specific pore size of the porous material, the produc-tion of heat by chemical reactions in the flame and the dis-sipation of heat by the porous medium are of the size so that beneath this pore size no flame can arise but above it a free ignition occurs.
This condition is described with the aid of the Peclet num-ber, which recites the ratio of heat production to heat dis-sipation. In this way a critical Peclet number results for the flame propagation. A self-stabilising flame within the supercritical zone results through the provision of a sub-critical zone and a supercritical zone with respect to the Peclet number.
Through the arrangement set forth in DE 43 22 109 A1, the problem of the stability of a flame burning in a porous me-dium is solved under the side conditions of a low temperature and thus a low emission of pollution. Ceramic foams or bulk fillings of balls are proposed as porous material. These ma-terials have, however, a relatively low porosity, whereby combustion space is wasted and the gas/air mixture is exposed to a higher flow resistance. Moreover, these materials re-strict, as a result of their low optical permeability, the energy transport on the basis of the thermal transport mecha-nism of thermal radiation which dominates in the present tem-perature range. This leads to a situation - from a specific constructional size of a burner of this kind onwards - in which the heat produced cannot be dissipated sufficiently well outwardly from the inner region of the combustion space.
The local overheating in the porous material brought about in this way leads to material damage by thermal strains and an increased output of pollutants.
26380-24 ca o22iii24 2ooo-os-io The invention is thus based on the object of providing a porous medium for a burner which has a high porosity and thus a high optical permeability and which is also insensitive with respect to thermal strains. Moreover, it should be possible to manufacture the porous medium in a simple manner from the technical manufacturing viewpoint, at a favourable cost and with constant precision.
Therefore, this invention seeks to provide a burner comprising a combustion chamber in a housing that includes an inlet for air and gaseous fuel, an ignition device, and an exhaust gas outlet, the burner further comprising a porous body that at least partly fills out the combustion chamber, the porous body consisting of heat resistant material and having spatially connected, hollow cavities for the formation of a defined flame zone, a part of the porous body being provided as a flame zone and being formed as an ordered packing, the ordered packing being built up of layers of crossing webs and consisting of at least one of metallic and ceramic materials, said burner further comprising a second porous body being integrated at the inlet region of the ordered packing and having a peclet number that is subcritical.
Accordingly, the combustion space of the burner is at least partly filed by a three-dimensional ordered packing having connected cavities and consisting of ceramic material, foil material or sheet metal material for the formation of a defined flame zone.
Such ordered packings can basically be manufactured with the required high porosity of up to approximately 99%
and thus offer a larger combustion space than, for example, ceramic foams or bulk fillings of ceramic bodies. As a result of the high optical permeability of such packings, the 26380-24 CA o22iii24 Zooo-os-io 4a thermal transport by thermal radiation is not blocked so that a rapid and effective thermal dissipation to the thermal transfer medium is ensured. Furthermore, these packings have a low flow resistance as a result of the open structure.
Thus, the pressure loss of the gas flow when flowing through the combustion space can be reduced, which lowers the required energy input. The known manufacturing methods for such packings furthermore enable their production in a simple manner from a technical manufacturing viewpoint and at favourable cost, with invariable precision with respect to the dimensioning of the hollow cavities. The latter can be varied in their size without great complexity.
The packings have, as a result of their three-dimensional structure, the further advantage that they react resiliently to thermal or mechani-cal loading, whereby the danger of points of fracture, such as exists, for example, with the foam-like ceramic parts used in the prior art, is overcome.
Since the packings of the invention can be manufactured with much higher degrees of porosity when compared with the prior art, the proportion of material related to the total volume is very low. This leads to a considerable shortening of the response times of the burner in comparison to the previously known porous media. Moreover, such packings can be made vari-able with respect to their diameter, length, hydraulic diame-ter etc., whereby an ideal flow-mechanical design can be achieved.
Ordered packings which are used as static mixers have, in ad-dition to a low pressure drop and optical permeability, also other characteristics which have a positive benefit. The pro-nounced transverse mixing leads to homogenous concentration profiles and temperature profiles of the combustion gases, which favourably influences the combustion process and fur-ther reduces the production of pollution because no cold points and no so-called hot spots occur. Stagnating zones and also break-throughs of the flow media are prevented because of the low back mixing, and the combustion zone is addition-ally stabilised in the flow direction.
Furthermore, it can be of advantage to use two or more pack-ing elements, which are arranged rotated relative to one an-other. In this way a homogenous distribution of concentra-tion, temperature and flow speed is ensured over the entire flow cross section.
The above advantages are in particular achieved by a packing _ which consists of a material which is resistant to tempera-~tures in the range between 1200°C and 2000°C (claim 2).
Ordered packings such as, for example, static mixers, which are built up of layers of corrugated lamella, or lamella folded in zig-zag-like manner, which form channels have proved to be particularly suitable, with the channels of neighbouring layers crossing one another and with the lamella consisting of metallic and/or ceramic materials, whereby the packing can also be of monolithic construction (claim 3).
In accordance with claim 4 the lamella can be foils or metal sheets which are arranged loosely alongside another and which have a plurality of perforations.
Another type of ordered packing is made of webs which inter-sect cross-wise and have the same features as packings which are formed of corrugated lamella.
In accordance with claim 5 the packing can be built up of layers of webs which cross each other and consist of metallic and/or ceramic materials.
In accordance with claim 6 the packing can consist of ceramic materials, with the principal components being A1203, Zr02 or SiC. These materials have advantages with respect to tempera-ture resistance and corrosion resistance.
The advantages listed are in particular achieved by a packing which has a high hollow space component or proportion, i.e. a high porosity of at least 70 % and a wave height of the lay-ers, or a web width, of between 3 mm and 15 mm (claim 7).
With these geometrical data, low pressure losses and low emissions of pollutants can be realised.
In accordance with claim 8 the packing in the combustion chamber can be catalytically coated or can be manufactured of a catalytically active material, i.e. it is itself catalyti-cally active. In this way very low pollution emission values are achieved.
In accordance with claim 9 a porous body is placed in front of the inlet zone of the ordered packing. It functions as a flame holder or flame barrier in that it ensures that the Pe-clet number present there is subcritical, preferably smaller than 65. This porous body can be formed as an ordered packing (claim 10) .
Claims 9 and 10 characterise measures for the defined re-striction of the flame zone of the burner with the operation taking place in accordance with claim 9 with a flame holder of conventional construction known from the prior art; at the same time the mixing between the gaseous or vaporous fuel in the air is made more intense by the finely pored body. In this way conventional burners with free flame formation, which normally have such flame holders, can be retrospec-tively equipped with packings in accordance with the inven-tion. In this way a cost favourable possibility is provided for the reduction of pollution of burners which are already in use.
In the alternative set forth in claim 10, a finely porous ma-terial is arranged in the throughflow direction of the gas/air mixture upstream of the flame zone defined by the packing. No flame can form in this finely porous material be-cause of its subcritical Peclet number. Thus, the concept known from DE 43 22 109 A1 for flame stabilisation can be combined with the present invention.
The finely pored material, which can be produced without _ problems as an ordered packing with a porosity having a Pe-~clet number which is in particular smaller than 65, can be manufactured in analogous manner from temperature resistant ceramic material, foil material or sheet metal material, in the same way as the actual ordered packing in the combustion chamber.
In this arrangement this finely pored packing not only serves for the flame stabilisation but rather the combustion gases such as, for example, natural gas, methane or heating oil va-pour are homogenously mixed with air before the actual com-bustion chamber as a result of the transverse mixing charac-teristics. This additionally favourably influences the com-bustion process, in particular with respect to the emission of pollutants.
Further features, particulars and advantages of the invention can be seen from the following description, in which examples of the subject of the invention are explained in more detail with reference to the accompanying drawings. There are shown:
Fig. 1 an ordered packing of ceramic material, Fig. 2 a schematic longitudinal section through a burner in a first embodiment, Fig. 3 a schematic longitudinal section through a burner in a second embodiment, and Fig. 4 a typical axial temperature profile within the burner.
The ordered packing shown in Fig. 1 is put together from a plurality of corrugated ceramic plates. These ceramic plates are so arranged that the corrugations of two neighbouring corrugated plates form an angle of 60°. In this way open --channels result which cross each other.
The burner shown in Fig. 2 has a housing 1 comprising a cy-lindrical main portion 2 and a truncated, cone-like upper end part 3. The latter has at its upper side an inlet 4 for a gas/air mixture as the combustible gas mixture. In the throughflow direction D of the gas/air mixture the prechamber formed by he end part 3 is followed by a conventional flame holder or a perforated plate 6, through which the gas/air mixture enters into the subsequent combustion chamber 7. This combustion chamber is filled out with an ordered packing 8, which has, for example, the following specifica-tions:
diameter: 70 mm height: 90 mm porosity: ca. 95 0 corrugation height: 8 mm material: heat resistant ceramic The gas/air mixture entering into the ordered packing 8 is ignited by an ignition device 9 sitting at the side in the housing 1 at the level of the combustion chamber 7 and burns while forming a defined flame zone within the ordered packing 8 while producing thermal energy. The latter arises to a large part as thermal radiation which heats the main part 2 of the housing. The main part 2 is surrounded by a heat transmitting jacket 10 in which helically extending channels 11 are provided. A heat exchanger medium, such as for example water, which circulates through a heating system, flows through these channels.
After the combustion space in the passage direction D, there is further provided an exhaust gas space 12, in which tem-peratures between 700°C and 1300°C prevail at the inlet of -this zone and between 35°C and 150°C at the outlet of this region. The exhaust gas space 12 serves as a cooling zone, with the cooling coil of stainless steel 14 extracting heat from the exhaust gas, which can be used as useful heat. The cooling coil 14 is kept at temperatures below 200°C by the heat exchanger medium flowing through it so that other mate-rials, in particular aluminium, brass or copper are also pos-sible. The exhaust gas space 12 opens into the exhaust gas outlet 13 of the burner.
The burner shown in Fig. 3 is distinguished from the burner in Fig. 2 only in two details. To this extent components are provided which otherwise correspond with the same reference numerals as in Fig. 2 and do not require repeated explana-tion.
In distinction to Fig. 2, the burner of Fig. 3 has no conven-tional flame holder. On the contrary, a finely pored packing is arranged in front of the ordered packing when viewed in the throughflow direction D of the gas/air mixture, and is likewise formed from an ordered packing. The latter has a smaller pore size and porosity than the ordered packing 8, so that its Peclet number is smaller than 65 and is thus sub-critical. This signifies that no flame can form in the or-dered packing 15. The ordered packing 8 is so specified that the Peclet number is supercritical, so that a flame can form there in defined manner.
Moreover, a static mixer 16 is inserted in front of the burner (claim 11). It brings about a very homogenous gas/air mixture.
The temperature profile shown in Fig. 4 for a 6 kW natural gas burner with a power of 3 kW and an air number of 1.2 shows that the maximum temperatures arise shortly after the transition between the finely pored region A and the coarsely pored region C and can lie in the range of approximately 1400°C to 1500°C. In the region D which follows it, the tem-peratures lie at around 1100°C at the inlet and sink towards the outlet to temperatures which are of the same order of magnitude as those of the heat exchanger medium.
The gaseous fuel can, for example, also be vapourised heating oil or diesel oil.
Moreover, it should be pointed out that the flame which forms through the ignition of the gas/air mixture in the flame zone defined by the ordered packing 8 propagates in dependence on the ratio of gas to air and also of the quantities thereof.
To this extent the power of the burner can be regulated via the quantity of the gas and also of the gas/air mixture.
Claims (17)
1. A burner comprising a combustion chamber in a housing that includes an inlet for air and gaseous fuel, an ignition device, and an exhaust gas outlet, the burner further comprising a porous body that at least partly fills out the combustion chamber, the porous body consisting of heat resistant material and having spatially connected, hollow cavities for the formation of a defined flame zone, a part of the porous body being provided as a flame zone and being formed as an ordered packing, the ordered packing being built up of layers of crossing webs and consisting of at least one of metallic and ceramic materials, said burner further comprising a second porous body being integrated at the inlet region of the ordered packing and having a peclet number that is subcritical.
2. A burner in accordance with claim 1 wherein the ordered packing consists of material that is resistant to a temperature of 1200°C to 2000°C.
3. A burner in accordance with claim 1 wherein the porosity of the ordered packing amounts to at least 70% and wherein one of either a wave height of the layers or a width of the webs have dimensions in a range between 3 millimeters and 15 millimeters.
4. A burner in accordance with claim 1 wherein the ordered packing has a catalytically active surface.
5. A burner in accordance with claim 1 wherein the porous body integrated at the inlet is formed as an ordered packing.
6. A burner in accordance with claim 1 wherein a static mixture is arranged in an inlet of the housing for production of an air/gas mixture.
7. A burner comprising a combustion chamber in a housing that includes an inlet for air and gaseous fuel, an ignition device, and an exhaust gas outlet, the burner further comprising a porous body that at least partly fills out the combustion chamber, the porous body consisting of heat resistant material and spatially connected, hollow cavities for the formation of a defined flame zone, a part of the porous body being provided as a flame zone and being formed as an ordered packing, wherein the ordered packing is built up of layers of corrugated lamella that form channels, the channels of adjacent layers crossing one another, the lamella consisting of at least one of metallic and ceramic materials, wherein a second porous body is integrated at the inlet region of the ordered packing and has a peclet number that is subcritical.
8. A burner in accordance with claim 7 wherein the lamella are foils or metal sheets that are loosely arranged along side one another and that have a plurality of perforations.
9. A burner in accordance with claim 7 wherein either Al2O3, ZrO2 or SiC is provided as the ceramic material.
10. A burner in accordance with claim 7 wherein the ordered packing includes a hallow cavity component having a porosity that amounts to at least 70%, and wherein a wave height of the layers has dimensions in a range between 3 millimeters and 15 millimeters.
11. A burner in accordance with claim 7 wherein the ordered packing has a catalytically active surface.
12. A burner in accordance with claim 7 wherein the porous body integrated at the inlet is formed as an ordered packing.
13. A burner in accordance with claim 7 wherein a static mixer is arranged in the inlet of the housing for production of an air/gas mixture.
14. A burner in accordance with claim 7 wherein the ordered packing is built up of lamella folded in a zigzag-like manner.
15. A burner in accordance with claim 7 wherein the ordered packing is of a monolithic design.
16. A burner in accordance with claim 7 wherein the peclet number of said second porous member is smaller than 65.
17. A burner is accordance with claim 1 wherein the peclet number of said second porous member is smaller than 65.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/897,800 US5890886A (en) | 1997-07-21 | 1997-07-21 | Burner for heating systems |
| CA002211124A CA2211124C (en) | 1997-07-21 | 1997-07-22 | Burner, in particular for heating systems |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/897,800 US5890886A (en) | 1997-07-21 | 1997-07-21 | Burner for heating systems |
| CA002211124A CA2211124C (en) | 1997-07-21 | 1997-07-22 | Burner, in particular for heating systems |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2211124A1 CA2211124A1 (en) | 1999-01-22 |
| CA2211124C true CA2211124C (en) | 2001-04-24 |
Family
ID=33419218
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002211124A Expired - Fee Related CA2211124C (en) | 1997-07-21 | 1997-07-22 | Burner, in particular for heating systems |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US5890886A (en) |
| CA (1) | CA2211124C (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102005004062A1 (en) * | 2005-01-21 | 2006-07-27 | Deutsches Zentrum für Luft- und Raumfahrt e.V. | Multilayer pore body arrangement for pore burner, comprises preheat zone area, gas supply area provided with recess for ignition and treated as burn zone and corrosion/oxidation protective ceramic layer formed on the both areas surfaces |
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| DE19646957B4 (en) * | 1996-11-13 | 2005-03-17 | Gvp Gesellschaft Zur Vermarktung Der Porenbrennertechnik Mbh | Method and apparatus for burning liquid fuel |
| DE19948203A1 (en) * | 1999-10-06 | 2001-04-12 | Solvay Fluor & Derivate | Thermal decomposition of halogenated carbon compounds |
| CN1279320C (en) * | 2001-06-26 | 2006-10-11 | 霓佳斯株式会社 | Method and device for cleaning air |
| JP2003202174A (en) * | 2002-01-09 | 2003-07-18 | Tadahiro Omi | Air cooling device |
| DE10230149B4 (en) * | 2002-07-04 | 2008-08-07 | Sgl Carbon Ag | Device for generating hydrogen |
| DE10246231A1 (en) * | 2002-10-04 | 2004-04-15 | Robert Bosch Gmbh | Automotive fuel cell has afterburner chamber void filled with open pored silicon carbide foam ceramic foam block with glow plug ignition with regulated input of combustion gases |
| WO2004092646A1 (en) * | 2003-04-16 | 2004-10-28 | Sgl Carbon Ag | Porous burner comprising a silicon-carbide porous body |
| DE102004006824B4 (en) * | 2003-04-18 | 2005-07-28 | Enginion Ag | Pore burner with silicon carbide pore body |
| CA2543470A1 (en) * | 2003-10-21 | 2005-05-12 | Petroleum Analyzer Company, Lp | An improved combustion apparatus and methods for making and using same |
| CN100394108C (en) * | 2006-01-20 | 2008-06-11 | 东北大学 | Flame length adjustable metal-ceramic porous medium gas fuel burner |
| AT504398B1 (en) * | 2006-10-24 | 2008-07-15 | Windhager Zentralheizung Techn | PORENBURNER, AND METHOD FOR OPERATING A PORN BURNER |
| CN101737778B (en) * | 2009-12-08 | 2011-08-17 | 东北大学 | Diffusion type porous medium gas fuel combustor |
| US9976740B2 (en) * | 2012-06-12 | 2018-05-22 | Board of Regents of the Nevada Systems of Higher Educations, on Behalf of the University of Nevada, Reno | Burner |
| US10458649B2 (en) | 2013-02-14 | 2019-10-29 | Clearsign Combustion Corporation | Horizontally fired burner with a perforated flame holder |
| US10571124B2 (en) | 2013-02-14 | 2020-02-25 | Clearsign Combustion Corporation | Selectable dilution low NOx burner |
| US10119704B2 (en) | 2013-02-14 | 2018-11-06 | Clearsign Combustion Corporation | Burner system including a non-planar perforated flame holder |
| WO2014127307A1 (en) | 2013-02-14 | 2014-08-21 | Clearsign Combustion Corporation | Perforated flame holder and burner including a perforated flame holder |
| EP3739263A1 (en) | 2013-02-14 | 2020-11-18 | ClearSign Technologies Corporation | Fuel combustion system with a perforated reaction holder |
| US10386062B2 (en) | 2013-02-14 | 2019-08-20 | Clearsign Combustion Corporation | Method for operating a combustion system including a perforated flame holder |
| WO2015044171A1 (en) * | 2013-09-26 | 2015-04-02 | Hans Larsson | Ir-emitter |
| EP3105173A1 (en) * | 2014-02-14 | 2016-12-21 | Clearsign Combustion Corporation | Down-fired burner with a perforated flame holder |
| US10514165B2 (en) | 2016-07-29 | 2019-12-24 | Clearsign Combustion Corporation | Perforated flame holder and system including protection from abrasive or corrosive fuel |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3088271A (en) * | 1961-02-06 | 1963-05-07 | Minnesota Mining & Mfg | Reaction milieu and afterburner incorporating same |
| US5306140A (en) * | 1976-04-07 | 1994-04-26 | Smith Thomas M | Infra-red generation |
| US5667374A (en) * | 1992-10-16 | 1997-09-16 | Process Combustion Corporation | Premix single stage low NOx burner |
| DE4322109C2 (en) * | 1993-07-02 | 2001-02-22 | Franz Durst | Burner for a gas / air mixture |
| US5441402A (en) * | 1993-10-28 | 1995-08-15 | Gas Research Institute | Emission reduction |
-
1997
- 1997-07-21 US US08/897,800 patent/US5890886A/en not_active Expired - Fee Related
- 1997-07-22 CA CA002211124A patent/CA2211124C/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102005004062A1 (en) * | 2005-01-21 | 2006-07-27 | Deutsches Zentrum für Luft- und Raumfahrt e.V. | Multilayer pore body arrangement for pore burner, comprises preheat zone area, gas supply area provided with recess for ignition and treated as burn zone and corrosion/oxidation protective ceramic layer formed on the both areas surfaces |
Also Published As
| Publication number | Publication date |
|---|---|
| CA2211124A1 (en) | 1999-01-22 |
| US5890886A (en) | 1999-04-06 |
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