EP1301442A1

EP1301442A1 - Nitrogen oxide reduced introduction of fuel in combustion air ports of a glass furnace

Info

Publication number: EP1301442A1
Application number: EP01951653A
Authority: EP
Inventors: Frank Hegewald; Peter Hemmann; Helmut Heelemann
Original assignee: Software & Technologie Glas Cottbus GmbH
Current assignee: Software & Technologie Glas Cottbus GmbH
Priority date: 2000-07-05
Filing date: 2001-07-05
Publication date: 2003-04-16
Also published as: CZ2003318A3; KR20030023693A; AU2001272523A1; PL359243A1; WO2002002468A1; US20040099011A1; CN1449364A

Abstract

The invention relates to an NOx reduced firing of glass furnaces, with preferably lateral fuel introduction by means of the combustion air ports thereof, whereby, by means of wall segments arranged in the combustion air port, cross-currents of combustion air and fuel gas are reduced. Air turbulence on the wall sections is reduced, by means of exhaust filling of low pressure regions and a primary turbulence-free flame root is generated by means of a free-stream injection of fuel gas. Wall segment and exhaust filling together form a so-called flame root shield. Furthermore, the free-stream is maintained, whereby the fuel gas stream is introduced in the core shadow of the flame root shield. The wall segment preferably has the form of the idealised projection of a free-stream of gas, viewed in the direction of the incoming combustion air. The exhaust filling in the turbulent volume is achieved by means of introduction of exhaust gas or fuel gas, preferably by means of a displacement lance and forms a gas dynamic exhaust gas spoiler in front of the wall segment, which lifts the incoming combustion air over the wall segment and reduces turbulence. The displacement lance preferably comprises at least one axial gas exit slot, lies horizontally on the air inlet side at the foot of the wall segment and may be positioned radially and axially relative to the wall segment.

Description

NITROGEN-REDUCED COMBUSTION GAS INLAY IN COMBUSTION AIR PORTS

FROM GLASS MELTING TUBS

The invention relates to a so-called primary measure for NOx reduction, in particular methods and associated devices for NOx reduction on flames from fossil-heated glass melting tanks.

As primary measures, simplification and in the narrower sense are measures that are used within the furnace to reduce the formation of NOx. To put it more narrowly, the invention relates to fire control measures for NOx reduction.

Compared to secondary measures, primary measures are usually associated with less effort. However, primary measures often do not achieve the desired reduction potential. Cross-flame glass melting furnaces with a burner arrangement on the side are particularly problematic because they have a particularly high starting level of NOx and the known pri- measures are not very effective. For example, when using NOx-reducing burners, which are highly effective in applications with underport-fired trays, no significant effect is achieved on these trays.

With regard to thermal NOx, the suppression of NOx formation is essentially based on the fact that the combustion of atmospheric nitrogen and atmospheric oxygen to NOx that begins at high temperatures is reduced. The local concentration product of oxygen and nitrogen, with which the NOx formation increases, is materially important. Thermally, the temperature of the flame is essential, especially at the flame root. Starting points of the NOx reduction for the first aspect are the air preheating temperature of the combustion air, the cold "secondary air", the (local) fuel-air ratio, and the composition of the air, ie its exhaust gas, N2 and O2 content. In this regard, a number developed by processes such as the oxyfuel process, in which the combustion air is replaced by almost pure oxygen, or the near-stoichiometric furnace operation, inter alia according to WO 98/02386, in which all excess air is avoided.

Other measures include technical changes to the furnace, such as the arrangement of sealing plates on nozzle stones to avoid injector air from the environment, or sealing against ingress of false air on the furnace. An "air grading method" according to DE 43 01 664 A1 avoids locally high concentration products at the critical flame root.

Modifications to burners or new types of burners are also used for the purpose of NOx reduction.

Exhaust gas recirculation also lowers the local concentration product of oxygen and nitrogen. At the same time, as with other processes, the second reduction aspect is used and the ignition is slowed down, which has a temperature-reducing influence. For example, is intended to avoid flameless oxidation in the burner NOx and only the exhaust gas is to provide heat transfer.

The purpose of cooling the flame root is also pursued by processes in which the mixture of fuel and air is delayed. These are as Solutions especially the "cascade firing" according to DE 34 41 675 A1 and DE 44 15902 C1 and carburization stages have become known.

Generally the ignition of the flame or the main flame is delayed. Exhaust gas is added to the combustion air or the fuel jet is enveloped. The flame root is cooled with water vapor. The geometric design of the introduction of air into the furnace for low-turbulent air flow was known as the "free jet port". This reduces turbulence in the air and premature random mixing of fuel and air. For heating oil, burners have been known which avoid very fine droplets during oil atomization. Avoid hot flame roots also gas burners that bring the fuel gas into the furnace with a low-turbulent jet, which have become known as free-jet burners.

Similar threshold solutions have also been known and used for energy saving in the USA for a long time, see e.g. "Melting Furnace Design in the Glass Industry", Alexis G. Pincus, 1976. But the same problems also occur here. The "cascade firing" differs positively from this solution in that a small pre-flame causes a 02-depleted gas stream over the main burner arranged in the under bench lighting is placed, whereby this risk is less.

Recently, in the case of a further development of the cascade method, the arrangement of a threshold in the port is used similarly to the aforementioned method. This became known as: "Second generation cascade lighting with integrated bufflewall technology" (glass engineer 5/98). The disadvantage of this is that the exhaust gas layer to be formed by the cascade injection is first produced by a flame itself and this itself becomes a strong emission source for NOx This reduces the effectiveness of the reduction, and the method cannot be used for tubs with side-fired ports.

The carburizing stage and cascade firing of the second generation have in common that fuel gas is introduced into the space of an air flow shadow of steps or thresholds, which is arranged on the step facing away from the air inflow side. The level is marked as a negative Level jump of the port floor in the direction of air flow. The main difference between the carburization stage and the second generation cascade is that all or only some of the fuel gas is used behind this threshold / stage.

Firing under bench with an increased distance between fuel and air intake is a professional measure that has been created by comparing different furnace designs. The number of flames is often reduced, which proportionally reduces the space of particularly hot or even adiabatic flame zones, which are a major source of NOx.

The state of the art which is closest to the inventive concern has been realized on a U-flame trough for container glass for several years. This solution essentially consists in the arrangement of a carburizing stage in the combustion air port, the fuel being introduced in the flow shadows of the combustion air from both port side walls, each with a conventional gas burner, so that the impulses of the two gas jets directed towards one another are at least partially compensated for. The decisive idea for the application of this NOx reduction solution was based on a calculation of the NOx formation for this arrangement on the basis of the improvement in the heat radiation behavior of the flames by carburization of fuel gases, with internal and external carburization, which is known from old literature and own experiments given to the subsequent user and their use was then recommended. During the risk assessment, attention was drawn to the extremely changed flame pattern and soot formation. However, measurement results for NOx formation were not available, since carburization stages were used for energy management purposes long before the ecological upgrading of the NOx problem. In the following practical application of the NOx reduction process by a German glass furnace construction company, the calculation has also been confirmed quantitatively over several years. The operator describes the arrangement and method, in particular with regard to NOx reduction, as being successful in comparison with the above-mentioned prior art. The problem of the formation of carbon deposits in the port is not mastered and can easily become critical in other cases. Then unproductive compensation measures are such as high combustion air factors. The shape of the flame and the position of the flames in the furnace chamber depend almost exclusively on the design of the threshold and the port. Burner control actions have too little influence, both within the scope of common, as well as innovative and technologically sensible target parameters. The device, once carried out by furnace construction, is not very flexible. For example, the slant flame method according to DE 195 20 649 A1, which is effective for NOx reduction and increased performance, cannot be transferred to systems equipped in this way.

The problem now is that many of the methods mentioned can only be applied with great effort, are not suitable for certain furnace designs or can only be used there with little effect. An example of this is the frequently used design of a cross flame trough with a burner arrangement on the side of the combustion air port. Combustion air and fuel are mixed with one another in cross flow immediately after fuel emerges from the nozzle block. The result is high NOx formation. All of the above-mentioned methods, including the promising port stage for gas carburizing, do not solve this fundamental problem or have negative side effects. The carburization stage, which is effective in terms of NOx reduction, requires a large overall height for a significant NOx reduction, which, as a side effect, results in an undesirably strong restriction of the combustion air supply. In addition, if only some of the existing ports are equipped in this way, flue gas and air are relatively strongly redistributed to other ports on cross-flame tanks. The structural modification of the ports to take these effects into account also has negative side effects, since the size of the ports has to be increased, at least in a very complex manner.

However, the application of the process for tanks with high quality requirements is very significantly restricted by the fact that the formation of elemental carbon, which is the mandatory process basis of the carburization stage, cannot be limited to the fine distribution of the carbon particles, but rather that larger graphite deposits occur in the shadow of the stage that can also get into the glass. This is a high risk potential for glass production. The object of the invention is therefore to develop methods and devices for an effective nitrogen oxide-reduced introduction of fuel gas into combustion air ports of glass melting furnaces, which largely solve the problems associated with the above-mentioned methods and devices and essentially for all types of furnaces, in particular also those relating to the NOx reduction critical cross flame pan with side burner arrangement are suitable and can be used effectively.

Surprisingly, it was found that by retrofitting a combustion air port with a wall segment according to the invention, which is combined with a gas-dynamic combustion air lift according to the invention, as main components of flame root shielding, all side effects of carburization stages can be substantially avoided or suppressed and effective NOx reduction can be achieved.

The object is achieved according to the invention by the method according to claim 1, 2 or 3 and associated devices according to claim 6, 15 and 20.

A gas jet is preferably introduced into the foot zone of a flow barrier or a flow obstacle exposed to the air flow in an amount that is between 1 and 5% of the fuel flow of the combustion air port in question.

A device according to the invention relates to a protective device against combustion air flow in the immediate area of the introduction of fuel within a combustion air port of glass melting tanks, designed as a so-called flame root screen, and is characterized by a wall segment which blocks the air path and forms a solid angle closed on three sides with the port floor and a port side wall. The wall segment according to the invention has a length which is significantly shorter than half the width of the port base, is arranged essentially perpendicular to the port side wall and points into the combustion air port, and its greatest height compared to the lower mat line of the idealized fuel gas free jet is approximately equal to or greater than the sum of the diameter of the fuel gas inlet and 1/3 the length of the wall segment. The Wall segment is advantageously formed with a large wall thickness, the wide wall crown of the air segment blocking wall segment having a flat rise of approximately 10 °, which is measured in the air flow direction against the plane of the port floor.

In a further preferred embodiment of the invention, the apex of the crown of the wall segment is modeled in the flow direction of the combustion air of a vertically flat projection of a gas free jet. The apex preferably has a continuous or stepped increase of approximately 20 ° from the port side wall to its distal end.

Furthermore, the vertical end face of the wall segment facing the center of the port can have a calming surface at least over the greater part of its width, which is angled in the air flow direction by approximately 10 °, so that it forms a constriction with the equally angled end face of the opposite wall segment.

In a further embodiment, a gas-dynamic increase in the combustion air over the wall segment is achieved by refitting the side of the wall segment facing the air flow with refractory material, so that the incoming air initially rises by approximately 10 ° to 30 ° and on the way over the ramp in the end an increase of about 10 ° is forced. The port floor can have a shaft that drops approximately 10 ° in the direction of flow of the combustion air and ends approximately at the wall segment.

The property right is also claimed for flame root shielding with gas-dynamic, turbulence-reducing raising of combustion air via a wall-shaped airway obstructing installation in the form of a wall segment within a combustion air port, which is characterized by the injection of recirculated or afterburned exhaust gas, preferably by means of a displacement lance according to the invention, into the Solid angle of the flame root screen formed by means of a wall segment on the side of the wall segment facing the air flow, in particular from the port side wall, the starting point of the injection being close to the spatial angle corner point, which is formed by the wall segment, port floor and port side wall on the combustion air flow side of the wall segment.

After the rising wall crown, this exhaust gas injection forms the second gas dynamic component of the flame root shield according to the invention.

A preferred device for the turbulence-reducing raising of the combustion air via the combustion air flow barrier is characterized in that a displacement lance is arranged at the foot of the air flow side of the combustion air flow barrier.

In one embodiment, the displacement lance is designed as a cylindrical lance lying approximately parallel to the port base, which has a feed for a gas mixture or a combustible gas on one end face and the other end face of which is closed and which is provided with at least one axial longitudinal slot for gas discharge. The displacement lance and its gas discharge slots can be positioned and adjusted with respect to the combustion air flow barrier by means of axial displacement and radial rotation.

In another embodiment, the displacement lance is a multi-walled tubular steel lance which is guided approximately perpendicularly through the port base, at least one coolant layer of circulating coolant being formed between two tubes of the lance, which has an outer gas supply jacket which is shortened compared to the lance and closed at the front and which is at the front closed end face has at least a radially oriented and radially widening gas outlet slot where the tubing of the coolant layer is interrupted. It is oriented and arranged essentially vertically through the port base in such a way that the fuel gas jet emerging from the lance emanates from the base of the combustion air flow barrier where the front edge of its end face in the air flow direction is directly exposed to the combustion air flow, the jet near the port base and is directed near the combustion air flow barrier to the port side wall to which the combustion air flow barrier has a connection. The fuel is introduced within the combustion air port in the air-away flow shadow of the wall segment, in particular in the solid angle of the flame root screen, such that the fuel outlet is positioned so close to the origin of the space that starts from the flame root screen, that is open on three sides, that the circumference of the fuel jet is aligned Approximately touch the wall segment and the port floor.

A preferred device for the low-turbulence introduction of fuel gas to suppress intensive mixing of combustion air and fuel gas at the fuel gas inlet within the combustion air port is a gas burner, through which the gas jet is introduced into the combustion air port as a low-turbulence gas jet in itself by the outlet opening of the gas from the burner and / or burner nozzle block is designed in the form of a natural free jet, the burner and / or burner nozzle block continuously having the shape of a diffuser with an opening angle of approximately 20 ° as the gas outlet.

The outlet opening of the fuel in the solid angle lying in the flow shadow is preferably positioned and aligned in such a way that the circumferential line of the fuel jet at the entry into the combustion air port and / or the extended circumferential line of the outlet opening of the burner and / or burner nozzle block approximately affect the alignments of the wall segment and the port floor but do not overlap.

Suitable gas burners are preferably used to generate a free jet. These can be pure free-jet burners or gas burners which can be configured as free-jet or turbulence burners through actuating actions.

The latter gas burners are characterized in that the burner is provided with a cooling jacket and, in connection with a cylindrical gas supply pipe and forming the connection to the burner mouth, a long diffuser is arranged which has a free jet opening angle of 20 °, the burner having a minimum burner mouth diameter of approximately 50 mm open points, which is therefore much larger than the conventional burner, the burner is not followed by a nozzle block, but the direct fuel gas outlet into the furnace chamber is formed by the burner mouth itself. The burner is preferably further characterized in that the gas supply to the long diffuser over a length of about five diameters of the gas supply pipe does not contain any fixtures or fittings introduced into this position by manipulations which would in particular impair the axis of the gas flow in the pipe.

The shield according to the invention is implemented in the most preferred embodiment by three elements. The first is the mechanical flow protection through the wall segment, which radially completely covers the flame root, which in the axial course of the flame at the end of the wall segment abruptly releases the entire fuel jet for air mixing. The second is the gas-dynamic elevation of the wall segment and the resulting horizontal leveling of the underside of the continuous air flow due to the preferably 10 ° increasing wall crown design. The third is the turbulence suppression and turbulence-reducing increase of the combustion air by means of ramp-shaped wall segment components or exhaust gas filling of the vacuum chamber, which is formed by the solid angle on the air-flowing side of the wall segment, as a result of which the combustion air is smoothly and gas-dynamically lifted over the segment wall by the mechanically forced flow or by expanding exhaust gas , This exhaust gas can be supplied cold from the outside or formed in the port by fuel gas and air or exhaust gas.

The commercial application of the invention is particularly advantageous for those glass melting furnaces which have a lateral introduction of the fuel into the combustion air ports. Such stoves certainly have advantages in their design, but have recently been put at risk because of their inferiority in primary NOx reduction as a promising solution. The invention of the flame root screen is able to compensate for this disadvantage and also to make the advantages of the smaller number of burners of this type of furnace effective as a benefit of NOx reduction compared to the previously superior under bench-fired trays. The operators of such stoves are able to To be able to maintain the furnace type that has been tried and tested for glass production, not to be forced to undertake complex non-system secondary measures or “3R” according to PL 922 48 52 and to be able to switch the furnace type during operation to the best NOx reduction values.

If carried out properly, there are positive side effects: energy saving, lowering the furnace chamber temperature, increasing the output and extending the furnace runtime. The arrangement of the device according to the invention close to the burner mouth of the combustion air port has an advantageous effect on the adjustability of the position of the flames.

In contrast to thresholds or steps, there is no disadvantage in going a long way from gas injection to the burner mouth, so that changing the burner angle has a significant influence on the position of the flame and the fire control is therefore technologically flexible.

The device according to the invention has numerous advantages over the known prior art.

Although the carburizing effect of the flame root shielding according to the invention is small in comparison with carburization levels, a comparatively higher NOx reduction is achieved by the fact that the wall segment, which is kept small in terms of the design concept, for shielding the flame root in its construction without major side effects in all dimensions in a size appropriate to the needs, in particular higher, so that the shape of the flame root, which is understood as a free jet, is completely covered against direct air inflow. The start reaction and mixing with air is only allowed completely at the end of the screen and not already partially in the upper areas of the flame root. There, however, the fuel flow forms a sufficiently wide front, which is capable of exchanging enough heat by means of radiant heat to the environment due to the large surface area that the adiabatic temperatures usually caused by heat build-up are always avoided by conventional flame roots. The wall crown rising according to the invention in the air flow direction forms an essential part Gas-dynamic contribution, because the air's demolition map favors its progressively horizontal plane spread.

In contrast to this, with a carburization step on the bank that runs horizontally parallel to the port floor and ends with the tear-off edge, the spreading of the combustion air is then promoted at a descending angle of approximately 10 °, which means that the carburization steps (including the cascade steps) that have become known become the function of flow in terms of flow technology erroneously fulfill only to a limited extent and, in the course of the flame development, subject the port floor lying behind the threshold to a random and strong thermal load.

In comparison with carburizing stages, the flame root shielding according to the invention at the root of the flame means that the construction of the flame is complete, but not complex, including the core of the flame, but at the same time only incompletely shielding, the mixing of fuel with air is effectively reduced and thereby Formation of a particularly hot or adiabatic temperature zone of the flame at the flame root is suppressed. Adverse turbulence of the rise of air on the upstream side of the wall segment, which is initially associated with the design of the wall as a result of the need to be retrofittable, becomes gas-dynamic through the introduction of recirculated, low-O2 exhaust gas or fuel gas in combination with exhaust gas or air into the upstream Vacuum area greatly reduced, so that the problem of this newly created second flow dead zone on the screen is mitigated by exhaust gas expanding there. The amounts of fuel that may be used in advance for the purpose of exhaust gas production and air lifting, on the other hand, are small and advantageously just large enough that the exhaust gas entrained by the air flow is continuously replaced in the vacuum chamber, which can be recognized by a minimum of NOx emissions. The problem of heat build-up and adiabatic temperatures does not arise here, since the amount of fuel supplied burns predominantly or preferably completely externally, with the addition of exhaust gas and, due to the locality, colder than usual in the furnace. An additional source of NOx from fuel gas residues carried into the furnace remains imperceptibly small. The flame root shield is a primary measure z. B. Easily retrofitted compared to carburization levels, has a functionally optimized size and can be optimized both in terms of fluid dynamics and gas dynamics.

An advantageous side effect of the third functional element is that exhaust gas is mixed in from the space in front of the wall segment by the suction effect of the air flowing over it into the lower layers of the combustion air before the air enters the reaction space after the screen. In the upper area of the flame or more precisely at the interface between fuel and air, the starting reaction is additionally reduced. An increased introduction of fuels, with the aim of producing a strong exhaust gas separation layer, as is known from cascade firing, is unproductive on the flame root screen, since the known disadvantage of forming a new NOx source at the pre-fire is also disadvantageous due to exhaust gas filling with excess fuel can be. The exhaust gas filling of the inflow area at the flame root shield expediently only remedies a fluidic error in the already complete geometric protection of the entire flame root, which consists in the upstream, structurally caused, turbulence-causing inflow of the wall segment by continuously filling up the vacuum zone there and its gas dynamic influence Air flow diminishes.

The advantageous design of the displacement lance with axial gas outlet slots always ensures, even if it is operated with a small amount of fuel gas, relatively large and thus cold flame areas, so that little NOx is formed. The low-pulse supply of exhaust gas takes place through the radial gas bursts directly into the vacuum zone in the foot area of the wall segment in a geometrically adapted form.

The short overall length of the wall segments, which are usually arranged symmetrically opposite one another, leaves a large section on the port floor free of internals that obstruct air flow. As a result, this section, which is particularly characterized by carbon deposits in thresholds or steps, is kept free of carbon deposits by an intensified combustion air flow. There is therefore no quality risk for the melt goes beyond that of conventional ports that have no flow restricting internals.

In an advantageous embodiment, the fuel is injected by means of a free-jet burner in accordance with the invention at the flame root screen and turned away from the three space-forming walls at least about 10 ° in each case, the largest being the turning away from the port wall. Fluidically random ignitions at the flame root are particularly effectively avoided. It is advantageous that the wall segment does not require any ongoing operating expenses and that the flame root screen is functional even with this simple structure.

Further advantages are that the device can be retrofitted to existing systems with little effort and that after its commissioning, additional NOx primary measures can also be used effectively for tubs with an intensive cross-mixing between fuel and combustion air. For example, in addition to the preferably usable free-jet burners, other burners with a small gas pulse also have their NOx-reducing effect. Nozzle stone and burner are better thermally protected by the flame root shield.

The invention will be explained in more detail below on the basis of exemplary embodiments with reference to the accompanying drawings, in which:

1 is a perspective view of a preferred embodiment of the mechanical flame root shield according to the invention;

Figure 2 is a perspective view of another preferred embodiment of the full flame root shield of the invention;

3 shows the mechanical flame root shielding according to the invention with a combustion air lift with turbulence-reducing facing stone; 4 shows the introduction of exhaust gas into a wall segment according to the invention;

5 shows an embodiment of a displacement lance according to the invention with a radially oriented fuel and air outlet;

6 shows another embodiment of a displacement lance with radial gas discharge and its arrangement on the wall segment;

7 shows an advantageous air-cooled free jet gas burner.

FIG. 1 shows a schematic perspective view of a combustion air port 1 of a float glass trough with the burners 3 arranged on the side. The combustion air port 1 was equipped with a flame root shield according to the invention during operation. For this purpose, stackable building blocks were arranged as wall segment 4 on the port floor 5 adjacent to the port side wall 11, which have a form-fitting profile on the inner bearing surfaces, transversely to the direction of the air flow 2 and in the air flow direction in front of the burner nozzle stones or the burner mouth 3a. The burner 3 is arranged behind the wall segment 4 in the direction of combustion air flow. The elongated axis of the burner nozzle stones or burner orifice 3a is turned away from the wall 4b of the wall segment 4, which is at the rear in the flow direction, in such a way that the plane angle is approximately 10 °, measured horizontally in the direction of the combustion air flow 2 against the wall 4b of the wall segment 4. The same axis has a vertical rise of 10 °, measured against the level of the port floor 5.

So-called free jet gas burners can be used as the burner type, as disclosed in DE 19520650, or gas burners whose mouth itself forms the mouth instead of the burner nozzle bricks which are conventionally used subsequently on the burners. Such a burner is shown in Fig. 7 and will be described in more detail below.

In the latter case, the diameter of the opening 3a of the fuel is thus the opening of the burner. In the example, its dimension is 95 mm, the width of the port is 1.5 m. The dimensions of the wall segment 4 of the flame root shielding according to the invention are in the example: length 500 mm, width 250 mm, height 300 mm. The height was accordingly determined as the sum of the diameter of the burner orifice 3a and 1/3 of the length of the wall segment 4, in the present case the elevated position of the burner orifice 3a had to be taken into account when calculating the height of the wall segment 4, that is, in terms of construction to compensate for any errors in the position of the burner mouth 3a with respect to the origin 10 of the wall segment 4, since in the example the fuel jet 8 does not affect the port base 5, in contrast to the preferred positioning according to the invention.

In the example, the lower edge of the burner mouth is 40 mm above the port base 5 and the lower surface line of the successive beam, which is assumed to be a free jet, is parallel to the port base 5, raised by this amount, above it. The area at the upper surface line of the fuel jet 8 would otherwise be exposed to premature air mixing. The wall segment 4 was therefore expediently made 40 mm higher.

The wall segment 4 has over its entire width a wall crown 4c which rises by 10 ° in relation to the port base 5 in the direction of the air flow 2.

The short overall length of the wall segments 4 arranged symmetrically opposite one another leaves a large section on the port base 5 free of internals which obstruct air flow. This section is kept free of carbon deposits by an intensified combustion air flow. There is therefore no quality risk for the melt that goes beyond that of conventional ports that have no flow restricting internals. At the distal end of the wall segment 4, the entire fuel jet at the combustion air passage 7 is abruptly released for the combustion air to be mixed in.

Two methods have proven to be practical for installing the wall segment 4 according to the invention. In the first case, the side wall 11 of the port is opened laterally next to the burner nozzle block or the burner mouth 3a, in order to insert the components from the side and by stacking them Add layers to port 1. In the second method, the port base 5 is sawn from below. The floor cutout is then lowered, cleared and discarded using a lifting platform. A new floor segment is built up with the wall segment 4 of the flame root screen on the lifting platform and with the help of it is lifted back into port 1 slightly below the level of the old port floor 5, or sunk into the new port floor segment, in order to prevent the wall segment from slipping on the Avoid port bottom 5 safely. The process of sawing up the port floor is advantageous in terms of labor costs and labor difficulties.

As a result of the exemplary embodiment described, the NOx formation is reduced by approximately 50%. At the same time, there are other advantageous side effects for the furnace operation. In particular, the fuel consumption is reduced, the vaulting temperature of the furnace is reduced, and thus less corrosion of the refractory material is achieved. An increase in the melting capacity of the tub is also significant.

FIG. 2 shows a further advantageous embodiment of the flame root shield and, in comparison with FIG. 1, additionally equipped with the second gas dynamic component of the flame root shield in the form of turbulence-reducing combustion air elevation by introducing gas in front of the wall segment 4. To simplify the drawing, only one wall segment is shown, the wall segment located on the opposite port side wall has been omitted. In addition, in this embodiment of the wall segment according to the invention, special components are used which, in contrast to conventional stone formats, form an additional increase in the wall crown 4c of the wall segment 4 from the port side wall 11 to the distal end of the wall segment 4 located towards the center of the port by approximately 20 ° and thus the external geometry of the wall segment 4 of the gas jet shape 8 of a natural free jet better adapt and with further improved shielding of the flame root because of their smaller size have at the same time little blocking effect in the exhaust gas period and little air distribution side effects in transverse flame troughs. The NOx effective maximum height of the wall segment according to claim 7 is retained. As a burner-technical device for introducing exhaust gas, a known burner for flameless oxidation is proposed in the present example, which previously could not be used for heating glass melting tanks. Its application restriction is based on the exhaust gas temperature being too low and the complete combustion in the burner, which is advantageous here, however, because only exhaust gas is now introduced into the furnace and the effect of an additional NOx source known from additional flames no longer occurs. The burner is inserted from the port side wall 11 and its jet 9 is guided obliquely upwards along the wall segment 4, on the side of the front wall surface 4a, towards the center of the port. The required amounts of exhaust gas are in the order of one to a few percent of the total amount of exhaust gas. The device is expertly supplemented by a facing stone 13 on the lower layer of the wall segment 4, which is intended to reduce exhaust gas which draws off deeply and ineffectively and redirects it to the more effective upper paths. Furthermore, the firing jet side on the rear wall alignment 4b of the wall segment 4 is carried out in a professional manner.

In Figure 3 a wall segment 4 is shown, in which the combustion air lift instead of the gas dynamic component by means of a mechanical device, e.g. turbulence-reducing facing stones 12 is realized, which are arranged in the flow direction of the air from the port base 5 continuously and continuously increasing by about 10 ° to the crown 4c of the wall segment 4. However, compared to the gas-dynamic component, this solution has the disadvantages that no cheap concept or simple technology has yet been found for retrofitting the ports during operation, which means that it can only be used when the tub is new or cold repaired and is hardly accessible for simple repairs is.

FIG. 4 shows the introduction of exhaust gas into the wall segment 4 for the inventive gas dynamic combustion air lift. The wall segment 4 is formed from suitably shaped wall segment modules 14, the upper wall segment module 14 being modified in such a way that its support web 14a is shortened on the side of the front wall surface 4a and does not rest positively on the lower wall segment module 14 and thus one Forms gas outlet slot 15 for the exhaust gas introduced through the wall through an exhaust gas supply 6. The internal structure can be seen in FIG. 4 through a section of the wall segment 4, but the refractory layer of the wall segment 4 which closes at the end is not shown. The exhaust gas is introduced into the upper wall segment module 14 of the wall segment 4 from the port side wall 11 by means of a configuration known per se, consisting of exhaust gas supply 6 and a known burner for flameless oxidation (not shown) with a ceramic burner tube. An alternative to this is not shown, in which a compact wall segment is provided with a blind hole which has a lateral slot in a similar position to that shown in FIG. 4. During the fire period, fuel gas, exhaust gas or a combustible gas mixture is injected into the blind hole.

FIG. 5 shows the possible and advantageous embodiment of a displacement lance according to the invention with a radially oriented fuel and air discharge in a sectional view, the cold end 27 being shown rotated clockwise by 90 degrees in relation to the hot end 26 which is essential for the implementation of the method and the device. An outer water circuit is fed via a cooling water inlet 20, which near the end plate 22 at the hot end 26 has a semi-cylindrical outer interruption in the tubing of the water cooling jacket. This interruption releases a radial fuel gas outlet 16 and a radial air outlet 17. In a plan view, not shown, these exits would be approximately semicircular. The cooling water circuit is separated from the fuel gas outlet 16 by the jacket of a truncated cone segment 23, which at the same time characterizes the upper flank of the gas jet by deflecting the axial flow in the radial direction by approximately 50 °. Together with a diffuser segment 24, which in turn has a radial deflection of approximately 70 °, an exit angle is forced on the gas jet at the fuel gas outlet, which has an increase of 30 ° against the radial plane. The slit-shaped opening itself has an opening angle of 20 ° and thus, if only partially, fulfills the criteria for forming a natural free jet in a section plane. The radial air outlet 17 is also shaped according to the partial free jet criterion mentioned above through the underside of the diffuser segment 24 and a disk segment 25 downwards. As a result, an air-free jet is layered under the gas-free jet, the lower jacket of which is parallel to the radial plane runs. This is essential for the process because in the installation situation the port floor also runs parallel to the radial plane and so the air is not directed against the port floor. The flame that forms is calmed as best as possible by both free jets and at the same time is as close as possible to the port floor without being directed against it. The cold end 27 has the fuel gas connection 18, the air connection 19, the cooling water supply 20 and the cooling water return 21 as media connections. Cooling water supply and return are designed in the form of a half-shell in order to avoid high construction costs, which is disadvantageous in the case of an alternatively multi-jacket design. The lance is preferably operated with similar gas pressures for fuel gas and atomizing air. For reasons of clarity of the functional principle, the air outlet in the example is shown to be of a similar size relative to the gas outlet. It is customary for carrying out the method that the smallest slit dimension of the air, which determines the passage, is several times larger than that of the fuel gas.

FIG. 6 shows the simple and descriptive illustration of a displacement lance 28 with axial slots 30 in a horizontal installation situation in the solid angle of the foot of a wall segment 4 on its side 4a exposed to the flow of combustion air 2.

In the example, the displacement lance 28 has two axial slots 30, which are directed against the incoming combustion air in such a way that the exhaust gas emerging from the slots 30 forms a gas-dynamic exhaust gas spoiler through the input pulse and the thermal gas expansion, which reduces the combustion air via the flow obstacle in the form of the turbulence Wall segment 4 lifts. The setting of the lance position is simple because the lance is arranged so that it can be moved and rotated through the wall bore 29 on the cold side of the port side wall 11 (not shown).

FIG. 7 shows a possible embodiment of a burner for generating a fuel gas free jet, as is preferably used. The technology of the combustion process also has a major impact on product quality, energy economy, life expectancy and the production capacity of industrial furnaces. However, this influence is particularly strong on the formation of NOx. A particularly effective method for gas burners for glass melting furnaces has been named free jet gas burner, in which there is a very high reduction in nitrogen oxide formation.

The burner used according to the invention is preferably a configuration-modifiable burner that does not require a nozzle block, but is designed to be completely metallic and cooled, with a long diffuser forming the gas flow space externally and an axially displaceable cylindrical gas supply pipe being arranged therein and the cooling air having an adjustable cooling air current redirection of the burner mouth can be supplied as an enveloping combustion primary air stream. As a result, the flame can largely be adjusted in the range of the characteristics of conventional burner designs. In the case of quality disturbances with an unclear cause, old experience of quality assurance can be used with known means and attitudes. All that is then required is the adjustment of the burner with positioning of the central nozzle in the vicinity of the diffuser root. A well-known, highly turbulent flame is formed in this way, which can optionally be modified further by means of primary air by a quick start reaction. Old notes on quality-assuring kiln procedures can thus be used. The effective burner mode of operation in free jet mode can thus be set step by step, starting from the conventional flame jet.

In the following, the burner is described in its configuration as a free jet burner, as it is preferably used in combination with the wall segments according to the invention and the gas dynamic combustion air lift.

For this purpose, the cylindrical central nozzle pipe 35 was completely withdrawn from the long diffuser 33 and positioned in the gas supply pipe 32 with the nozzle orifice 36 of the central nozzle pipe 35 five times the diameter of the cylindrical gas supply pipe 32 from the root 37 of the long diffuser 33. The cooling air flow deflection 41 blocks the path of the combustion primary air flow 40 between the cooling jacket 31 and the burner receiving stone 39 into the free space of the burner insert bore 38. A low-turbulent gas-free jet emerges at the burner mouth 34. The weakened interference of air from the environment, the subsequent carbonation of the Fuel gas with high proportions of carbon particles and the ignition of the flame only in an area with a large surface area of the flame, i.e. with good heat radiation conditions, are the causes of the low NOx emission of the burner in this setting, in which the usual high or even adiabatic flame temperatures are reliably avoided ,

List of the reference symbols used

1 combustion air port

2 combustion air

3 burners

3a burner nozzle / burner mouth

4 wall segment

4a front wall surface 4b rear wall surface 4c wall crown

5 port floor

6 exhaust gas supply

7 combustion air outlet

8 fuel jet

9 exhaust gas jet

10 point of origin

11 port side wall

12 Turbulence-reducing facing stone

13 facing stone

14 wall segment block 14a support web.

15 gas outlet slot

16 Radial fuel gas outlet

17 Radial air outlet

18 Fuel gas connection

19 air connection

20 cooling water flow

21 Cooling water return

22 end plate

23 Mantle of the truncated cone segment

24 diffuser segment

25 slice segment

26 Hot ends

27 Cold ends

28 Displacement lance with axial slots Wall bore Axial slot Cooling jacket Gas supply pipe Long diffuser Mouth of the burner Central nozzle pipe Mouth of the central nozzle pipe Root of the long diffuser Burner insert hole Burner receiving stone Combustion primary air flow Cooling air flow deflection

Claims

claims

1. A method for nitrogen oxide reduction in combustion air ports of glass melting tanks, characterized in that a flow shadow is formed to protect against combustion air flow through the immediate area of the confluence of the fuel jet within the combustion air port by means of a mechanical combustion air flow barrier that completely radially covers this area continues in the air flow direction following the combustion air flow barrier as a flow shadow essentially parallel to the port base, the entire fuel jet at the distal end of the combustion air flow barrier at the combustion air passage being abruptly released for air mixing

2. A method for reducing nitrogen oxide in combustion air ports of glass melting tanks, characterized in that at least one gas jet is injected into the swirling space in front of flow obstacles in such a way that the vacuum space located there is actively and dynamically filled with gas in such a large quantity that including the thermal gas expansion therein The area predominantly has a slight overpressure.

3. A method for nitrogen oxide reduction in combustion air ports of glass melting tanks, characterized by the combination of the method according to claim 1 and 2.

4. The method according to claim 2 or 3, characterized in that the gas jet is preferably entered as a gas layer in the exposed to the air flow foot zone of the flow barrier / the flow obstacle in an amount that is between 1 and 5% of the fuel flow of the combustion air port in question.

5. The method according to any one of claims 1 to 4, characterized in that the fuel gas is injected as a preformed natural free jet into the three-sided solid angle downstream of the combustion air flow barrier.

6. Device for forming a flow shadow for protection against combustion air flow through the immediate area of the fuel jet within a combustion air port for carrying out the method according to claim 1, 3, 4 or 5, characterized by an air-blocking wall segment (4) which with the port floor (5) and a port side wall (11) forms a solid angle closed on three sides.

7. The device according to claim 6, characterized in that the wall segment (4) has a length which is significantly shorter than half the width of the port base (5), the wall segment (4) substantially perpendicular to the port side wall (11) in the combustion air port (1) is arranged facing inwards and its greatest height compared to the lower surface line of the idealized free jet (8) is approximately equal to or greater than the sum of the diameter of the fuel gas inlet (3a) and 1/3 the length of the wall segment (4).

8. The device according to claim 6 or 7, characterized in that the crown (4c) of the wall segment (4) at least over part of its length and at least over the greater part of its width with a flat in the direction of flow of the combustion air (2) rising air guide surface sharp tear-off edge is provided.

9. The device according to claim 8, characterized in that the flat rise is formed at an angle of about 10 ° with respect to the subsequent port floor.

10. The device according to one or more of claims 6 to 9, characterized in that the apex of the crown (4c) of the wall segment (4) in the flow direction of the combustion air (2) is simulated a vertically flat projection of a gas jet.

11. The device according to claim 10, characterized in that the crown of the crown (4c) from the port side wall (11) to its distal end has a continuous or stepped increase of approximately 20 °.

12. Device according to one of claims 6 to 11, characterized in that the vertical end face of the wall segment (4) facing the center of the port has at least over the greater part of its width a calming surface which is angled in the air flow direction by approximately 10 °, so that it forms a constriction with the equally angled end face of an opposite wall segment (4).

13. The device according to one or more of claims 6 to 12, characterized in that the side facing the air flow side of the combustion air flow barrier is equipped in a ramp-like manner with refractory material (12) that the incoming air on the way over the ramp initially has an increase of about 10 ° to 30 ° and in the end an increase of about 10 ° is forced.

14. The apparatus according to claim 13, characterized in that the ramp is horizontally flat and that the length of the ramp and subsequently the port floor drops approximately 10 ° against the horizontal plane in the air flow direction.

15. Device for injecting a gas jet for carrying out the method according to claim 2, 3 or 4, characterized in that a displacement lance for supplying at least one gas jet is arranged on the air-flowed side of the combustion air flow barrier at its foot.

16. The apparatus according to claim 15, characterized in that the displacement lance is designed as a cylindrical lance lying approximately parallel to the port bottom, which has at least one inlet for a gas mixture or a combustible gas on its one end and the other end of which is closed, and which is closed with at least one axial longitudinal slot is provided for gas discharge.

17. The apparatus according to claim 16, characterized in that the displacement lance and its gas discharge slots can be positioned and adjusted by means of axial displacement and radial rotation with respect to the combustion air flow barrier, in that it is in through a bore in the port side wall the port protrudes approximately horizontally and outside the port the shaft of the displacement lance is received in at least one pipe clamp.

18. The apparatus according to claim 15, characterized in that the displacement lance is a multi-walled steel tube lance which is guided approximately perpendicularly through the port base, wherein between two tubes of the lance at least one coolant layer of circulating coolant is formed, which shortened an outer, opposite the lance and has a gas supply jacket which is closed on the end face and which has a radially oriented and radially widening gas outlet slot on the closed end face at least where the piping around the coolant layer is interrupted.

19. The apparatus according to claim 18, characterized in that the displacement lance is oriented and arranged essentially vertically through the port base in such a way that the fuel gas jet emerging from the lance preferably emanates from the base of the combustion air flow barrier where it is in the air flow direction leading edge of its end face is directly exposed to the flow of combustion air, the jet being directed near the port bottom and near the combustion air flow barrier to the port side wall to which the combustion air flow barrier has a connection.

20. Device for the low-turbulence introduction of fuel gas in combustion air ports of furnace furnaces to suppress intensive mixing of combustion air and fuel gas at the fuel gas inlet within the combustion air port for carrying out the method according to claim 5, characterized in that the gas jet of the fuel gas-carrying burner into a combustion air port is itself less turbulent Gas jet is introduced into the combustion air port by designing the outlet opening of the gas from the burner and / or burner nozzle block in the form of a natural free jet, the burner and / or burner nozzle block continuously having the shape of a diffuser with an opening angle of approximately 20 ° as the gas outlet , and the length of the diffuser is greater than its smallest diameter.

21. The apparatus according to claim 20, characterized in that the outlet opening of the fuel in the space lying in the flow shadow is positioned and aligned in such a way that the circumferential line of the fuel jet at the entry into the combustion air port and / or the extended circumferential line of the outlet opening of the burner and / or burner nozzle block affect the alignments of the wall segment and the port base approximately, but do not overlap.