EP0834040A1 - COMBUSTION DEVICE AND METHOD FOR OPERATING A COMBUSTION DEVICE FOR LOW-NO x? AND LOW-CO COMBUSTION - Google Patents

Abstract

A low NOx and CO emission heating apparatus provides for substantially separate fuel and combustion air feeds into a combustion chamber provided at one end with an exhaust gas opening and, at an opposite end with an elongated porous air distributor through which air is fed into the combustion chamber and into jets of fuel directed into the space between the air distributor and the side wall of the combustion chamber. Both air and fuel may be subjected to swirl to improve the combustion, by adjusting the inclination of the fuel nozzles.

Description

description

Burner means and method for operating a burner device for an NO _x - and CO-lean combustion

The invention relates to a burner device and a corresponding method for an NO _x - and CO-combustion with predominantly separate supply of fuel and combustion air to the combustion chamber, wherein all or most of the combustion air at a plurality of points in space continuously promoted and the combustion chamber is supplied.

Fuel is to be understood here to mean substances which react exothermically with oxygen and which are in gaseous or vapor form at ambient temperature and / or when fed into the combustion chamber. Fuel should also be understood to mean liquid or dusty substances with air, steam and / or exhaust gas as carrier gas. Combustion air here is to be understood as meaning gases and / or vapors with an oxygen content which ensures stable combustion with respect to the selected fuel that the combustion air can also contain exhaust gas The combustion zone is to be understood here as the area in which the combustion takes place

In burners known from (DE OS 4 419 345, DE OS 4 231 788) with predominantly separate supply of fuel and combustion air to the combustion chamber, the combustion air is usually introduced coaxially with the introduction of the fuel. For this purpose, a fuel jet is generated in the area of the burner mouth. The combustion air is supplied on the outside of the fuel jet and outside the flame area via a mostly ring-shaped distributor, which is positioned near the fuel nozzle, usually coaxially to the fuel nozzle. Because of the considerable spatial distance of the combustion air distributor from the flame area, especially from the flame core, it becomes practical Operation with such burners a uniform mixing of fuel and combustion air or a staged mixture taking place according to predetermined proportions is not achieved. To alleviate this disadvantage, the combustion air is divided into primary and secondary air, so that locally limited Peak values of the oxygen concentration can be reduced and the stochiometric conditions during combustion can be regulated somewhat better. The fundamental disadvantage of this type of burner, namely the unsatisfactory controllability of the stochiometric ratios of fuel and combustion air, which are decisive for the formation of pollutants such as nitrogen oxides and carbon monoxide However, it can only be reduced with a relatively high outlay. The reason for this disadvantage can be that the supply of the combustion air extends only to a relatively small area of the combustion zone, so that the stochiometric conditions during the combustion essentially depend only on the relatively difficult to control convection conditions in the combustion zone are determined By means of special internals, which ensure a more intensive swirling of fuel and combustion air, attempts are made to reduce this disadvantage, but this is due to increased pressure loss is associated with high energy expenditure

Another way to reduce the NO _x formation in the combustion chamber in the case of burners without partial premixing is to inject the combustion air and the fuel at high speed into the combustion zone preheated to approx. 950 ° C. However, this is an energetically and structurally very complex Solution and not interesting from a firing point of view, since it leads to long flames and does not result in an optimal mixture

In the case of burners without premixing, a multi-stage supply of combustion air is often implemented to improve burnout and reduce pollutant emissions. Such a solution is used, for example, in the burner according to DE OS 4 041 360. This burner with a horizontal burner tube, which has a large number of gas outlet openings on its top, contains additional openings above the primary air supply for the supply of secondary air within so-called radiation rods , which are used for flame cooling The thermal stress of such radiation rod is very high, so that only high-temperature resistant material can be used.At the same time, optimal regulation of the burner with regard to pollutant emissions at different load levels is considerably more difficult because the ratio of Pπmar and secondary air quantities is only narrow Limits can be changed In particular in the area of full load, the secondary air supply to the upper flame zone is insufficient Attempts are made to reduce these disadvantages by means of a separately controllable secondary air supply or by means of partial premixing, the two-stage air supply possibly being expanded to a three- or four-stage air supply. A burner operated by such a method is described, for example, in DE OS 4 142 401. The burner, which in this case works with premixing, is operated in a strongly sub-stoichiometric manner. The oxygen that is missing for combustion is only supplied at a significant distance from the burner mouth at one or more points, whereby the direction of the oxygen injection must not be parallel to the main flow direction of the combustion gases. This process provides for the operation of large-format industrial ovens such as rotary kilns and. Like. undoubtedly an improvement, although it is relatively difficult to control because of the complicated and the flow of the combustion air to be adapted to the geometry of the furnace walls for the operation of compact burners with smaller heating outputs, however, it is too expensive. In addition, this method has the general disadvantage that the Combustion air is introduced essentially selectively into areas of the combustion zone with a relatively high flame temperature

The advantages of multi-stage air supply are also used in a special variant of burners without premixing, which have a combustion chamber that widens conically in the direction of the flame, which forms a diffuser and ensures more intensive mixing of fuel and combustion air in burners of this type (cf. DE OS 3 600 784), fuel and primary combustion air are introduced into the center of the diffuser and burned there. Secondary combustion air is additionally fed in the radial direction of the flame via wall openings in the diffuser. However, the length of the diffuser cannot be increased arbitrarily, because otherwise the diffuser would shield the flame too much, which would result in heat emission to the furnace or boiler wall impaired Since the flame length at higher heating outputs can significantly exceed the diffuser length, this means that, especially at higher heating outputs, the area of the flame tip is insufficiently supplied with secondary combustion air has an adverse effect on the pollutant emissions of the burner

In combustion processes using this method, the hottest flame zones are always inside the diffuser and cause the wall to glow. This is disadvantageous for two reasons. On the one hand, the glow leads to an intensification due to the elevated temperature The formation of the environmentally harmful nitrogen oxides and, secondly, special temperature-resistant materials are required for the diffuser wall. Overall, even with this type of burner, the introduction of the combustion air is restricted to relatively small areas of the combustion zone, which also have a very high flame temperature.

Another type of air distribution according to US Pat. No. 1,247,740 is used to improve the mixing of combustion air and fuel. The combustion air is led into the mixing space via a plurality of openings on this wall via an elongated round wall positioned within the furnace space. This space is delimited by a second elongated round wall surrounding the first wall and closed by a tight connection of both walls in the head part. In the foot section, the hollow double-walled cylindrical ring space thus created remains open and is connected to an annular opening for the fuel supply in this area. The second (outer) wall of this double-walled cylinder ring also has openings at which the air-gas mixture is ignited. The combustion takes place directly in these openings as well as on the surface of the outer wall, and there are many single flames. A major disadvantage of such burns is the costly materials required for this, which have to withstand high temperatures and thermal stresses and are nevertheless limited in their service life

Although the multi-stage spatial air grading provides a sub-stoichiometric mixing in the foot area, which gradually changes to superstoichiometry with increasing air ratio, no control of the mixing ratios can be guaranteed with the double-walled burner structure of this state of the art, since the double-walled enclosed space of the cylinder ring quickly becomes complete Mixing of fuel and combustion air sets before ignition occurs at the openings in the outer wall. Combustion also has the disadvantages of premixed flames. The reduction effect important for reducing nitrogen oxide emissions is therefore not given

In addition, the manner in which the exhaust gas is conveyed from the furnace space does not permit the use of such combustion technologies in heating boilers and industrial furnaces, since no effective heat transfer to the hot material is guaranteed Other disadvantages of this double-walled burner structure, in addition to its complicated structure, are its positioning within the furnace space

Another way to improve the mixing state is to connect an additional mixing chamber upstream of the combustion chamber, which creates a burner with larger dimensions, which now also has the disadvantages of this type of burner as a burner with premixing. Such a burner with a very intensive premixing is for example in DE OS 3 915 704, which, however, has an extremely complex construction. The multi-part mixing channels used there require a high amount of energy in order to compensate for the pressure loss caused by them. The mixing channels are also difficult to access and therefore difficult to clean

In summary, the following can be stated regarding the prior art

In burner construction, there is a tendency to use a multi-stage supply of combustion air to the combustion chamber in order to be able to influence the stoichiometric conditions during combustion better and thus to meet the current high requirements of the legislator for economic and ecological combustion. However, the consistent continuation of such solution approaches has been achieved lead to relatively complicated burner designs with a large number of combustion air distribution lines which are guided in the combustion zone or penetrate furnace or boiler walls and additional radiation rods for flame cooling. Such solutions are neither reliable nor suitable for compact construction

Another development trend uses the principle of surface combustion in order to achieve good mixing, full burnout and low pollutant emissions.With this principle, the air-gas mixture is applied to the entire surface of the burner body which protrudes into the furnace chamber or is positioned within the furnace chamber by means of a large number divided by openings and ignited there The combustion takes place directly on the surface and leads to its glow.The combustion air is either completely mixed with the fuel before entering the burner body, or it is double-walled by means of a large number of openings on the inner wall cylindrical burner structure in the enclosed between the inner and outer wall cylindrical ring space and mixed there with the fuel. The mixture is then ignited on the surface of the outer burner wall. All surface burners working according to this principle require the use of expensive materials and have particular difficulties when installing the burner in the furnace chamber. In addition, their service life and field of application are limited to small output ranges and gaseous fuels

Another line of development in burner construction uses the negative pressure generated by the flow velocity of the flame gases in order to draw in secondary, tertiary, etc. combustion air. However, this principle requires that the flame gases flow past a diffuser wall provided with suction openings for the combustion air at a predetermined speed. Therefore, the combustion air volume sucked in per unit of time cannot be changed independently of the flame parameters. In the interest of a compact design, it is advantageous to limit the space available for flame formation, as is done by the diffuser wall, so this indicates The following significant disadvantage is the construction. The intake openings for the combustion air are located in a zone with a very high flame temperature, which leads to the increased formation of the environmentally harmful nitrogen oxides

The invention is therefore based on the object _x with the aim of NO - and CO-lean combustion, and an intensification of heat transfer between the flame / gas and the wall of the heat sink, a structurally simple and suitable for a compact structure in burner means with predominantly separate supply of fuel and combustion air to create the combustion chamber in which the combustion air is fed in as many stages as possible into larger flame areas. This task results in the following subtasks in particular

• Dosage of the amount of combustion air supplied per unit of time in such a way that predeterminable λ number ranges of the fuel / combustion air mixture are approximately realized • Reduction of the thermal load on the assemblies for supplying combustion air and flame cooling and ensuring the use of inexpensive materials for these assemblies

• Elimination of impairments in the heat transfer between the flame and the wall of the heat sink as a result of diffusers or other means for mixing the fuel / combustion air streams

• Design of the combustion and exhaust gas zone with a geometry adapted to the walls of the heat sink

According to the invention, this object is achieved by a burner device according to the characterizing part of claims 1 and 13 and by an associated method for operating this burner device according to independent method claim 1 1

The basic concept of the invention, which also relates to the claimed method for operating the burner device, consists in the following Ca 70 to 100 vol% of the total amount of combustion air supplied is by means of one or more combustion air distribution body in a mainly radial direction in the space filled by the flame between the outer wall of the combustion chamber and the contour of the combustion air distribution body fed along the entire or large part of the flame length. This results in a large-scale distribution of the combustion air over the entire flame area or over large parts of the flame area.For this purpose, a large number of openings for the combustion air outlet are distributed on the contour of the combustion air distributor body.The number per unit area and the cross-section of these on the contour of the Combustion air distributing bodies are selected so that a predetermined volume flow of combustion air enters the combustion zone. As a result, the stochiometric conditions in the fuel / combustion air mixture can be better controlled. Furthermore, a predetermined course of the λ number range between the flame base and the flame tip can be realized at the metering point

In contrast to the combustion air supply, the fuel is fed into the combustion zone exclusively in the area of the combustion air Distributor located flame base by means of one or more rows of nozzles arranged around the combustion air distributor

At an air flow rate of less than 100%, the remaining part of the combustion air required for the combustion, ie. h 0 to approx. 30 vol%, admixed The admixture of this part of the combustion air increases the momentum of the fuel, improves the mixing of fuel and combustion air and leads to the ignition limit being reached more quickly. The NO _x values drop drastically

The advantages of this concept are that the combustion is initially sub-stoichiometric and, with a gradually increasing air supply, it changes to stoichiometry or over-stoichiometry shortly before the flame tip, where complete burnout is achieved _x and CO) drastically reduced This type of feeding the combustion air also has the advantageous effect that the flame is blown away from the combustion air distributor body, so that no direct combustion takes place on the surface of this combustion air distributor body. This lowers the thermal load on the combustion air distributor body , especially since they are additionally cooled by the combustion air flowing through them

Another advantageous effect of the combustion air supply according to the invention, in particular in the case of large-area combustion air distribution bodies, is that they simultaneously lead to cooling the flame, thereby reducing the formation of NO _x . In addition, when using large-area combustion air distribution bodies with suitable shaping, it can be achieved that The geometry of the combustion zone is largely determined by the geometry of this combustion air distribution body. A function of the combustion air distribution body that is essential to the invention is therefore seen in that the size of the combustion chamber is decisively influenced by the choice of its dimensions. Overall, even with different burner outputs, there is a low thermal output Load on the combustion air distribution body, since the cooling effect increases with increasing burner output due to the then increasing combustion air throughput Various advantageous embodiments of the burner device according to the invention result from the associated subclaims

There is a large variety of variants for the design of the contour of the combustion air distribution body. Depending on the furnace or boiler room geometry, the choice of a suitable form of combustion air distribution body can optimize the NO _x and CO emissions and heat transfer

Further advantageous embodiments of the invention relate to the configuration of the nozzle rows for the fuel supply. It has proven to be particularly effective for optimally maintaining predetermined value ranges of the air ratio λ if the jet direction of the fuel nozzles within the same nozzle row and / or the jet direction of the fuel nozzles of adjacent nozzle rows over different length ranges aim the combustion air distribution body In order to give the fuel flow an additional twist, the jet directions mentioned are at least partially skewed. Furthermore, the combustion air distribution body and / or the fuel nozzles can be designed to be interchangeable in order to optimally adapt their parameters to a predetermined burner output

The solution according to the invention, including its mode of operation, is explained in more detail below on the basis of exemplary embodiments

1 a is a schematic representation of a first variant of a low-CO and NO _x burner device with a conical combustion air distribution body for heating purposes,

1 b is a schematic representation of a second variant of a low-CO and NO _x burner device with a conical combustion air distribution body for industrial purposes,

2 a is a schematic representation of a selection of different geometrical

Variants of the combustion air distribution body in side view and top view, 2 b is a schematic representation of the interchangeability of the combustion air distribution body,

3 a is a schematic representation of variants of the jet directions of the fuel nozzles,

3 b is a schematic representation of the interchangeability of the fuel nozzles,

3 c is a schematic representation of the oblique fuel holes,

3 d is a schematic representation of the fuel annular gap with an internal swirl generator,

4 a is a graphical representation of the dependence of the NO _x emission values in the exhaust gas on the burner output for a selected variant of a combustion air distribution body, with no premixing of combustion air to the fuel,

4 b is a graphical representation of the dependence of the NO _x emission values in the exhaust gas on the burner output for a selected variant of a combustion air distribution body, with premixing of combustion air to the fuel being used (increased fuel nozzle pulse),

5 a is a graphical representation of the dependency of the CO emission values in the exhaust gas on the burner output for a selected variant of a combustion air distribution body, work being carried out without premixing combustion air to the fuel,

5 b shows a graphical representation of the dependence of the CO emission values in the exhaust gas on the burner output for a selected variant of a combustion air distribution body, with premixing of combustion air to the fuel being used (increased fuel nozzle pulse). According to FIG. 1 a, a cylindrical fire or combustion chamber (2) with a longitudinal central axis (34) of a burner device is delimited by a conical combustion air distribution body (7) and an outer wall (3) enclosing steel. The outer wall (3) consists of a cylindrical one Shell wall (3a), a top wall (3b) and a bottom wall (3c) Not shown in the schematic drawing are combustion chamber details such as viewing openings for visual observation of the flame development in the combustion chamber, openings for the ignition of the gas-air mixture and for temperature measurement in the Lower part of the combustion chamber Also not shown are a UV probe for monitoring the flame and a suction probe for exhaust gas extraction to carry out the concentration analysis of the exhaust gas emerging at the exhaust gas outlet (6). The exhaust gas outlet (6) is arranged in the cover wall (3b) of the combustion chamber Fire or combustion chamber (2) can also be polygonal as a prism, has he always has a horizontal or vertical longitudinal central axis (34)

For the flame formation there is essentially an empty space (1) between the outer wall (3) and a combustion air distribution body (7). This empty space (1) is the part of the combustion chamber (2) that lies below an imaginary level (10) , which sits on the end of the head part (9) of the frustoconical combustion air distribution body (7), the base (15) of which lies on the lower bottom wall (3c) of the combustion chamber (2)

For heating purposes, the heat is removed from the outer wall (3) via cooling water, which flows around the outer wall (3) either in coils (16) and / or in water chambers (17)

The combustion air distribution body (7) consists of simple sheet steel with a large number of openings (1 1) for the exit of the combustion air into the combustion zone. While the almost horizontal head part (9) of the combustion air distribution body is closed, its foot part (8) remains open and is screwed into the air supply pipe (18) The entire combustion air or most of it (> 70 vol% of the total combustion air throughput required for the combustion of 100%) is via the inner pipe (18) of a coaxial pipe into the interior of the combustion air distribution body (7) by means of a blower (19) provided with a motor (20) The lower end of the inner tube (18) of the coaxial tube flows into the combustion air supply (5)

The entire fuel is separated or with the remaining part of the combustion air (<30 vol% of the total combustion air throughput of 100%) via a cylinder ring (21) arranged perpendicular to the longitudinal central axis (34) between the inner tube (18) and outer tube (22) of the coaxial tube Combustion zone fed The lower end of the outer tube (22) of the coaxial tube flows into the fuel feed (4). This admixture of the combustion air throughput to the fuel takes place in particular to increase the fuel's momentum

The cylinder ring (21) is provided directly at the foot of the combustion air distribution body (7) with a row of nozzles (12). This row of nozzles (12) has a large number of fuel nozzles (13) arranged around the combustion air distribution body (7) for distribution of the fuel into the combustion zone in jet directions (14) which can be set as desired in two mutually perpendicular planes crossing the longitudinal center axis (34) (see FIGS. 3a-3d)

Investigations were carried out with natural gas H as fuel. All the forms of combustion air distribution body shown in side view and top view in FIG. 2a were used, the number of openings (1 1) for the combustion air outlet into the combustion zone or their diameter along the Contour of the combustion air distribution body were varied so that the mixing ratios can be changed to control the combustion process

The burner output was at relatively small combustion air distribution bodies (length 25-30 cm, width at the foot part 2-3 cm and at the head part 0-10 cm, with a length of the fire or combustion chamber of 80 cm) to values between 10 and 22 kW set and the air ratio varies between 1, 1 and 1, 5 This does not represent a fundamental limitation. The distribution body shown in Fig. la, to which the measured values in Fig. 4 and 5 refer, was approx. 30 cm long at the foot section 2.5 cm wide In all test series, a thin, dimly glowing oil, depending on the operating variant, also showed a barely or invisible) stable turbulent flame around the combustion air distribution body (7), and a complete burnout was just above the head part level (10) of the combustion air distribution body ( 7) to be recorded The flame did not touch the surface of the combustion air distribution body, it filled the empty space (1) over a large area. Intensive heat transfer to the outer wall (3) of the combustion chamber was the result. This inevitably leads to an improved and more intensive heat exchange with the the arm transfer medium arranged in or around the combustion chamber walls (3a, 3b, 3c) in the coils (16) or in the water chambers (17)

The contour of the combustion air distribution body did not glow and remained relatively cold (below 300 ° C.) in all designs according to FIG. 2 a. The exhaust gas analysis showed, in particular, as the measurement data in FIGS. 4 a, 4 b, 5 a and 5 b show with an increased fuel nozzle pulse, extremely low NO _x and CO emission values, which are far below the legal limit values for industrial burners and even fall short of the proposed revision of the limit values for boiler furnaces

A major advantage of the invention is therefore the possibility of building an energy-saving and environmentally friendly incinerator with a compact burner and combustion chamber shape, which is used for generating heat at smaller outputs up to 100 kW (such as in household appliances, wall-mounted heaters and boilers) medium outputs,> 100 kW to 1 MW (such as in heating centers, thermal power stations and biomass combustion) and also with larger outputs> 1 MW (such as in power plant furnaces and rotary kilns) is suitable. The combustion chamber of such systems will be compared to the previously usual Significantly reduce the combustion space due to the better heat transfer conditions to the hot material and the short burn-out distance. In conclusion, the new burner device is more ecological and economical than conventional firing technology

1b shows a schematic arrangement of several burner devices for industrial purposes in power plant technology. The combustion chamber (2) has a square cross section, the burner devices shown have the same features as in FIG 1 a and are installed on the lower wall (3c), as explained above. The heat is dissipated via the water pipes (23) installed in the outer wall and via the evaporator and superheater heating surfaces (24) and (25) Air preheater, which preheats the combustion air of the burner, reached in the exhaust duct, which is not shown in the schematic drawing

Fig. 2 a shows a schematic representation of different geometric variants of the combustion air distribution body. These can have a square, cylindrical, cone, polygon prism or pyramid shape or their contour can be ellipsoidal or hyperbolic. Further geometric designs are possible. In principle, all combustion air has - Distribution body an internal cavity for the supply of the combustion air, a thin perforated or porous wall surrounding the cavity, a closed head part and an open foot part on The dimensions of the combustion air distribution body and the number and geometry of the openings on their circumference should be chosen so that they ensure a controlled combustion process around the combustion air distribution body. That means that with the choice of these parameters the air delivery to the combustion area depending on the burner output according to the specific requirements of an Fe The control process is to be controlled in such a way that substochiometric combustion takes place over a larger combustion area and full burnout is only completed near the top of the combustion air distribution body. Measurements showed that different dimensions of the combustion air distribution body are required for different burner outputs. Therefore, the combustion air distribution body is for To make certain load ranges separately and to design them interchangeably, this can be done as follows, as schematically illustrated in FIG. 2b. The foot part (8) of the combustion air distribution body (7) is connected to an external thread (26) and the air supply pipe (18) at the pipe outlet provided with an internal thread The combustion air distribution body (7) is screwed into the air supply pipe (18) In principle, the measurements have confirmed that, in order to achieve a stable, low-pollution and perfect combustion, the following data on the combustion air distribution body should be adjusted (see Fig. 1 a) The length (A) of the combustion air distribution body (7) is> 40 - 85% of the combustion chamber length (B), the diameter (C) of the combustion air distribution body (7) at the foot part (8) is> 10% of the combustion chamber diameter (D), and the porosity of the combustion air distribution body is <20%

3 a shows a schematic representation of variants of the jet directions of the fuel nozzles (13), which are positioned in a row of nozzles (12) or several rows of nozzles at the foot part of the combustion air distribution body (7) and are arranged around them. A row of nozzles (12) contains a large number of nozzles, the jet direction (14) of which can be changed both in the longitudinal central axis and at an angle to it.On the one hand, this allows the fuel to be distributed over different contour areas of the combustion air distribution body, which contributes to the targeted control of the mixing ratios and favors the ignition a fuel swirl is generated in the jet direction, which leads to more intensive mixing of fuel and combustion air and to the longer residence time of the fuel particles in the flame area. Both fuel nozzle settings (axial and tangential inclination) ensure together in conjunction with of the continuously flowing air from the openings of the combustion air Verteilkoφer _x a NO - and CO-lean combustion In the tests carried out it has been found that the optimum range of the axial and tangential inclination angle of the Brennstoffdusen of about - 45 ° to + 45 ° with respect to the longitudinal direction of the combustion zone The angle setting depends on the shape of the combustion air distribution body and has a major influence on the quality of the combustion The addition of small amounts of air (<30% of the combustion air volume flow) with the fuel leads to improved results due to the increased impulse Mixing of fuel and combustion air and for reaching the ignition limit faster The NO _x values drop drastically

The rows of nozzles are to be manufactured for different load ranges and should be interchangeable, this can be done, for example, as shown in FIG. 3 b. The coaxial ring 21 is closed directly before the fuel enters the combustion chamber and is connected to the fuel supply by connecting channels (32) provide the combustion chamber, the channels (32) have internal threads (33) and the fuel nozzles (13) have external threads (28). The fuel nozzles (13) are screwed into the connecting channels (32) Instead of the fuel nozzles (13) within a row of nozzles (12), oblique bores (29) or an annular gap (30) with an inner swirl generator (31) can be used, as shown in FIGS. 3 c and 3 d

The variety of design options for fuel nozzles makes it possible to use liquid, gaseous or dusty fuels

The graphs in FIGS. 4 a and 5 a show the NO _x and CO emission values measured in the exhaust gas as a function of the burner output at different air ratios for the variant shown in FIG. 1 a with the conical combustion air distribution body. Natural gas H was fed in as fuel by means of a single row of nozzles, the nozzles being set in such a way that every second nozzle was provided with a weak swirl. While the burner output for the relatively small pilot plant was varied between 10 and 22 kW, the air figures for that in combustion plants are The usual and interesting range from 1.2 to 1.5 has been set. The NO _x and CO emission values shown have been converted to 3 vol% O ₂ in the exhaust gas so that a comparison with the limit values of the TA-Luft is possible

From Fig. 4 a it can be clearly seen that the NO _x emission values in this variant of the combustion air distribution body increase slightly with the burner load due to increasing combustion temperatures. However, since the flame temperature remains below 1200 ° C for all examined load ranges, the NO _x emission values tend to remain constant at higher outputs. An increase in the air ratio leads to a drastic reduction in the NO _x emission values, for example, its maximum with the air ratio 1.2 and the power 22 kW drops from 31 ppm to 19.5 ppm with the air ratio 1.5 and the same load

The decisive factor for the further reduction of the NO _x emission values is the influence of the increase in momentum through the fuel nozzles, so a slight addition of air with the fuel leads to strong turbulence and a better mixture between fuel and combustion air. The ignition limit is rather reached. Furthermore, the flame becomes thinner, larger and burns in the present example with an admixture of approx. 20% Combustion air to the fuel hardly or not visible Fig. 4 b shows an admixture of approx. 20% combustion air to the fuel and otherwise the same settings as in Fig. 4 a extremely low NO _x emission values for all air ratios and for all examined load ranges

If one looks at the corresponding CO emission values in FIG. 5 a, one finds that these are generally very low and tend to disappear completely (zero values) with increasing burner load and air ratio. The increase in momentum of the fuel nozzles through the addition of approx. 20% combustion air to the fuel leads, as shown in FIG. 5b, to complete combustion. The exhaust gases are at air ratios greater than 1.05 and are CO-free for all the powers examined. This behavior with regard to CO emissions is also typical for all other forms of combustion air distribution bodies. The experimental investigations show that the zero values of CO emissions can occur very quickly if the fuel nozzles are set appropriately

The axial and tangential setting of the fuel nozzles has a special influence on the NO _x and CO formation, but depending on the combustion air distribution body used there are different optimal angular positions

Overall, it can be stated that the NO _x and CO emission values of the new burner device are significantly below the limit values of TA-Luft (NO 1 14 ppm, CO. 93 ppm) and the new BIm Seh V (NO 45 ppm, CO 55 ppm) ) and that even the production of CO-free exhaust gas from combustion processes is possible

The individual elements of the individual figures of the different embodiment variants can be combined with one another as desired without departing from the essence of the invention and the scope of protection of the patent claims

Claims

claims l. Burner device for an NO _x - and CO-combustion with predominantly separate supply of fuel and combustion air to a combustion space, wherein all or most of the combustion air is continuously staged at a plurality of points in space and the combustion chamber is supplied, characterized in that • The burner device consists of a coaxial tube, at one end the inner tube (18) into one or more feed lines (5) for the combustion air supply and the outer tube (22) to one or more feed lines (4) for the supply of fuel or .Open fuel-combustion air mixture; and at the other end of which a combustion air distribution body (7) is tightly connected to the inner tube (18) and at least one row of nozzles (12) consisting of several fuel nozzles (13) tightly closes the cylinder ring between the inner and outer tubes, • the combustion air distribution body (7) consists of an elongated inner cavity which is enclosed by a thin perforated or porous wall and a closed head part (9), an open foot part (8) and a plurality of distributed openings (11) for the exit of combustion air into the combustion zone, • The combustion air distributor body (7) is tightly connected with its open foot part (8) to the inner tube (18) of the coaxial tube, • The length ratio (A / B) of the longitudinal expansion of the combustion air distribution body (7) to the longitudinal expansion of the combustion chamber (2) and the diameter ratio (C / D) from the cross section of the combustion air distribution body (7) at the foot part (8) to the equivalent cross section of the Combustion chamber (2) are dimensioned in such a way that an ignitable mixture is formed and stable combustion occurs, The fuel nozzles (13) are open on both sides and ensure the supply of fuel or fuel-air mixture from the cylinder (21) enclosed between the inner tube (18) and outer tube (22) of the coaxial tube into the combustion zone, • The fuel nozzles (13) are arranged in the area of the foot parts (8) of the combustion air distribution body (7) around this combustion air distribution body, The jet direction (14) of the fuel nozzles within the same row of nozzles (12) and / or the jet direction (14) of the fuel nozzles of adjacent rows of nozzles (12) can be set separately, • The burner device is installed in the combustion chamber (2) so that the end of the coaxial tube with the feed lines for combustion air and fuel supply (5) and (4) remains outside the combustion chamber (2), the entire length of the combustion air distribution body (7 ) is in the combustion chamber (2) and the fuel nozzles (13) protrude into the combustion chamber (2), but do not exceed the distance from the foot section (8) of the combustion air distribution body (7) until the openings (11) begin. One or more burner devices are installed in the combustion chamber (2) in such a way that they penetrate the outer wall (3) surrounding it and have a tight connection with it, The combustion zone in the combustion chamber (2) is at the same time the zone for the complete mixing of the combustion air from the openings (11) with the fuel or fuel-air mixture from the fuel nozzles (13), • The volume and geometry of the combustion zone essentially corresponds to the volume and geometry of that empty space (1) which has an outer wall (3) surrounding a combustion chamber (2), the openings in particular the installation of the burner device and the exhaust gas outlet (6) , and from the Outer contour of one or more combustion air distribution bodies (7), each of which is arranged entirely within the combustion chamber (2) and one within the combustion chamber (2) and located on the end of the head part (9) of the combustion air distribution body (7) , imaginary level (10) is limited. 2. Burner device according to claim 1, characterized in that • only the combustion air from the elongated combustion air distribution body (7) is spatially distributed into the combustion zone (1) by means of the many openings (1 1), where it mixes with the fuel or fuel-air mixture from the fuel nozzles (13) , The mixture formed in the combustion zone (1) is ignited in the vicinity of the fuel nozzles (13) and burns out in the same zone without further division, The flame forms in the entire area of the combustion zone (1) and the combustion exhaust gases flow through the imaginary plane (10) without obstruction and leave the combustion chamber through the exhaust gas opening (6), the porosity of the combustion air distribution body (7) is dimensioned such that predetermined ranges of values for the air ratio λ in the combustion zone approximately set from the substoichiometric range in the vicinity of the foot parts (8) to the overstoichiometric range in the vicinity of the head parts (9) , the arrangement and the number of openings (1 1) on the contour of the combustion air distributor (7) are chosen so that the pulse of the combustion air flows from the openings (1 1) blows the flame away from the combustion air distributor (7), so that there is no combustion on the wall of the combustion air distributor body (7) and this wall has no glow Burner device according to Claims 1 and 2, characterized in that the inner cavity of the combustion air distribution body (7) is enclosed by a single wall which has a square, cylindrical, cylindrical, conical, polygonal prism or pyramidal shape or its contour is ellipsoidal or hyperbolic is trained Burner device according to at least one of the preceding claims, characterized in that the wall of the combustion air distribution body (7) consists of porous ceramic materials or of metallic materials which are designed as a sieve, perforated plate, wire mesh, grid or metal mesh, or that the combustion air Distribution body (7) is designed as a wire body or sintered body Burner device according to at least one of the preceding claims, characterized in that the combustion air distribution body (7) has guide devices for generating a swirl flow of the combustion air Burner device according to at least one of the preceding claims, characterized in that the combustion air distribution bodies (7) are designed to be exchangeable Burner device according to at least one of the preceding claims, characterized in that the nozzles (13) or nozzle rows (12) are designed to be exchangeable Burner device according to at least one of the preceding claims, characterized in that the jet direction (14) of the fuel nozzles (13) within the same row of nozzles (12) and / or the jet direction (14) of the fuel nozzles of adjacent row of nozzles (12) onto different length regions of the combustion air - Distributor (7) aims Burner device according to at least one of the preceding claims, characterized in that the fuel nozzles (13) within the same nozzle row (12) and / or the fuel nozzles (13) of adjacent rows of nozzles (12) are arranged at an incline such that a swirl is imparted to the fuel flow, 10. Burner device according to at least one of the preceding claims, characterized in that the fuel nozzles (13) within a row of nozzles (12) as oblique bores (29) or as an annular gap (30) with an inner swirl generator (31) are executable 11 Method for operating a burner device for a low NO _x and CO Combustion with predominantly separate supply of fuel and combustion air to a combustion chamber, all or most of the combustion air being continuously graded at several points in the room and fed to the combustion chamber, characterized in that Approx. 70 to 100% by volume of the total combustion air throughput fed in by means of one or more elongated combustion air distribution bodies (7) in a mainly radial direction into the combustion zone filled by the flame along the entire or large part of the flame length, • The fuel in the combustion zone exclusively by means of the fuel nozzles (13) of one or more rows of nozzles (12), the oblique bores (29) or the annular gap (30) in the area of the flame base at the foot part of the combustion air distribution body (7) and around it is fed, The fuel is mixed with the remaining volume fraction of the combustion air required for the combustion before entering the combustion zone, • Depending on the operating parameters and fuel type, a certain angle setting of the fuel nozzles (13), the bores (29) or the swirl generator (3 l) in Combination with a certain mixture ratio of the combustion air in the fuel flow leads to a visible or an invisible flame • Depending on the operating parameters and type of fuel, a certain angle setting of the fuel nozzles (13), the bores (29) or the swirl generator (31) in combination with a certain mixture ratio of the combustion air in the fuel flow leads to a minimum of the NO _x and CO emission values in the exhaust gas Method for operating a burner device according to claim 1 1, characterized in that The fuel or the fuel-air mixture is fed in from the fuel nozzles (13) essentially in the direction of an angular range of approximately - 45 ° to + 45 °, based on the longitudinal direction of the combustion zone, • The proportion of the combustion air in the fuel stream emerging from the fuel nozzles (13) is in a range from 0 to approx. 30 vol.% Of the total combustion air throughput supplied Burner with a supply of fluid fuel and an oxygen carrier which is arranged on a combustion chamber which has a wall for heat dissipation, characterized in that the supplies of the fuel are arranged on a ring (35) which has outlets into the combustion chamber That within the ring (35) a distribution body (7) for the oxygen carrier is arranged, which extends with its longitudinal extension essentially in the main blow-out direction of the fuel and has oxygen carrier blow-out openings (1 1), the blow-out direction of which crosses with that of the fuel outlets Burner according to claim 13, characterized in that the combustion chamber is cylindrical and that the fuel outlets are arranged on an end face of the cylinder Burner according to Claim 13, characterized in that the length of the distributor body (7) is between 30% and 85% of the length of the combustion chamber Burner according to claim 13, characterized in that the diameter of the distribution body (7) in the area of the fuel outlets is between 10% and 60% of the inside diameter of the combustion chamber wall Burner according to one of claims 1 to 10 and 13 to 16, characterized in that a further heat exchanger (24) is provided in the combustion chamber downstream of the distribution body (7) Burner according to claim 1 or 13, characterized in that the fuel nozzles (13) are arranged parallel to one another and inclined to the cylinder ring (21), so that there is an annular swirl Burner according to claim 1 or 13, characterized in that the fuel nozzles (13) are arranged diverging or converging to the nozzle circle (35) on the cylinder ring (21), so that there is an expanding or contracting flow Burner according to claim 18 and 19, characterized in that the fuel nozzles (13) are arranged inclined in both directions on the cylinder ring (21)