DE3915992A1 - Process for the reduction of nitrogen oxides - Google Patents

Abstract

In order, during the combustion of a combustion material (1, 5) which is conducted along a combustion section (3) during the combustion process, to reduce the content of nitrogen oxides in the resulting exhaust gas, the amount of oxygen is varied locally by means of the combustion air fed along the combustion section (3) in such a way that the combustion temperature does not at any point of the section essentially exceed a maximum value at which the formation of nitrogen oxides occurs. The amount of oxygen can be varied locally along the combustion section (3) by varying the oxygen content or the local feed rate of the combustion air. The variation of the oxygen content in the fed combustion air is preferably performed by adding a gas mixture lower in oxygen in comparison to air, for example returned flue gases (18). <IMAGE>

Description

The present invention is concerned with a Process for reducing the nitrogen content oxides in exhaust gases, which are produced when burning a burner good emerge that during the combustion process it is guided along a combustion path, a plant for burning a combustible material, wel ches when burning along a combustion stretch over at least one air distribution device a waste incineration plant, a coal power plant and with applications of the method.

Nitrogen oxides, or also called NO _x or nitrogen oxides, are essentially formed in the most diverse types of combustion processes and operations and can be found in the exhaust gases or. so-called flue gases from these processes. These include NO, NO ₂ , N ₂ O ₄ , NO ₃ , N ₂ O ₃ and N ₂ O ₅ . These compounds, especially the mixtures of NO and NO ₂ , also called red mixtures or nitrous gases, are enormously toxic and can lead to breathing difficulties even in low concentrations. Furthermore, the nitrogen oxides combine with the air humidity and form in water dissolves both nitrous acid and nitric acid. These acids then lead to acid rain on the one hand and enormous corrosion damage to buildings, roads, vehicles etc. on the other.

To this enormous environmental pollution caused by nitrogen To contain oxides from exhaust gases, the various  developed most techniques and processes. It han on the one hand, there are treatment methods the exhaust gases themselves, with the nitrogen oxides Wash out or spray absorption from the exhaust gases be removed. There is also the possibility of Reduction of nitrogen oxides in nitrogen what can be obtained by means of suitable catalysts. This latter method in particular is described in the so-called auto-catalysts performed.

In contrast, using so-called primary measure already increased the formation of nitrogen oxides the combustion is not even allowed by for example the combustion nozzle of an oil burner ners instead of pure air as so-called combustion air an exhaust gas / air mixture is supplied to the Burning intensity and thus the combustion temperature reduce tur. This reduction in combustion temperature can also be caused by water injection, steam injection or by adding additives to the Combustion nozzle can be reached.

With regard to this reduction in combustion temperature one has to know that the formation of nitrogen oxides is only possible at very high temperatures, because nitrogen oxides are formed strongly endothermic reactions.

According to Van't Hoff's equation, it is found that in endothermic reactions (ie chemical reactions that absorb energy) the equilibrium constant increases with increasing ambient temperature, ie that this reaction becomes more likely with increasing ambient temperature. The formation of NO _x , such as NO, NO ₂ , N ₂ O ₃ etc., is enormously endothermic, so that these reactions do not set in at room temperature or even at slightly elevated temperatures. For example, the production of 1 mole of NO ₂ at 25 ° C from oxygen and nitrogen requires 11'570 cal. The formation of one mole of NO even requires 20'850 cal. From these numbers it is immediately clear that the formation of nitrogen oxides is only possible with very high temperatures is possible. For example, it was found that the yield of NO when merging nitrogen and oxygen at 1500 ° C is only 0.4%, but at 3000 ° C already 5%. (Information from K. Denbigh, principles of chemical equilibrium).

From the above it is now clear that upper half a certain threshold temperature the bil formation of nitrogen oxides from nitrogen and acid substance that comes from the combustion air, strong increases. Especially with larger waste incinerators plants or coal-fired power plants, some of which at Use of firing goods with a high firing worth combustion temperatures of more than 1700 ° C to be reached in the flame tips is education of these nitrogen oxides significantly. With these mentioned plant types, it has been shown that the above-mentioned measures to reduce the stick oxide emissions either very expensive or not are realizable. On the one hand there are washing processes and Absorption with the enormous amounts of exhaust gas very expensive  and affect the economy of such Large systems crucial.

On the other hand, the so-called primary measures, such as with mixing exhaust gases to combustion air, injection from water to fuel, because of the way how they were used, not to the desired one Success led. Especially with waste incineration plants with very different firing materials This primary measure became the most diverse calorific values used in such a way that the facilities within soot in the steam registers the exhaust flues caused severe afterburns and ultimately the attack of ashes due to insufficient Burning the garbage was great.

It has been shown that these primary measures, which in the case of burners and gas turbines with ge targeted short-term or explosive ver combustion within a limited combustion chamber are full of excitement on large systems with an ent along a route incineration which also expires over a longer period of time, not are readily transferable.

Nevertheless, the nitrogen oxide content in gases, especially in large incineration plants, such as waste incineration plants or coal-fired power plants, must be greatly reduced without significantly affecting the economic viability of these plants. Legislators are always demanding lower nitrogen oxide or NO _x values in the exhaust gases in order to further reduce the environmental impact.

It is therefore a task of the present inventor dung, a process for the reduction of nitrogen propose oxides in exhaust gases, by means of which the nitrogen oxide content especially in plants redu is adorned where a firing material of the most varied types composition and with different calorific values during the combustion process, which has a Time span and does not explode, ent is led along a combustion path.

According to the invention, this object is achieved by a method according to the wording, preferably after at least one of the claims, in particular according to claim 1, solved.

To reduce the nitrogen oxides in exhaust gases proposed that when burning a Brenngu tes, which ent during the combustion process along the combustion route, the Sauer amount of substance through along the combustion route Combustion air supplied varies locally in such a way is that at no point on the route is the cremation temperature essentially a maximum value at which the formation of nitrogen uses oxides.

Basically, this variation is the oxygen quantity possible through two measures. For one, can this can be achieved by the oxygen content in the supplied along the combustion route Combustion air is varied locally. To change can the combustion supplied per unit of time  Local air volume along the combustion path can be varied, which means that the composition of the combustion air the oxygen amount is varied.

According to the invention, the first dimension is reached proposed that the oxygen content in of the supplied combustion air locally by Bei mix a gas with less oxygen than air mixture or gas along the combustion path is reduced to high combustion at this location prevent temperatures as much as possible and thus the formation of nitrogen oxides largely prevent. The one with less oxygen than air The gas mixture is preferably back guided smoke gases, which arise during combustion.

It is proposed according to the invention that the Combustion temperature at no point of combustion distance essentially the value of approx. 1300 ° C in the flame tips. It is preferred wisely ensured that the combustion temperature at least along part of the combustion distance is kept almost constant.

Because the kiln at the start of the combustion process has a relatively high calorific value, is preferred the Beauf at the beginning of the combustion section Beat the combustion air with recirculated Flue gases held up and along the cremation distance is reduced.  

If the combustion material is, for example, moist waste or cold combustion material, the flue gases are preferably fed to the combustion zone at an initial zone for drying and / or heating the combustion material. It has been shown that when using warm, pure fresh air to dry a wet firing product, the combustion suddenly begins after drying at a certain point due to the high oxygen content of the fresh air, which immediately leads to very high temperatures due to the high calorific value of the product become and thus there is a risk of formation of NO _x . Wei ter advantageous in the use of recirculated flue gases is the fact that this is already heated and is therefore ideal for drying.

But around the kiln along the combustion path Burning completely is suggested gene that at an end zone of the combustion section the combustion air essentially consists of pure air with a correspondingly high oxygen content stands. Since the kiln only in this end zone includes a greatly reduced calorific value no more danger of too high temperatures in the Flame tips. Essentially, the kiln burns up only in this end zone.

To ensure the best possible and efficient implementation to guarantee the combustion air through the firing material afford, it is further proposed that the Brenn  well along the combustion route over one or several air distribution devices, such as one or more combustion grates or nozzle bases for fluidized bed. Here is further provided that the combustion path in min at least two combustion zones is divided, whereby the combustion air through each combustion zone at least one separate air zone is supplied. The composition of the combustion air can be in each air zone can be selected individually, whereby then the combustion air with the desired Zu composition, resp. with the desired oxygen contained in the kiln by the air distribution device is well managed, which is in the corresponding Combustion zone of the combustion section is located.

It is also proposed that the Ver sub-devices at least partially along the Combustion section side walls arranged who by which combustion air as so-called primary air into the firing material or as so-called secondary air in the flue gases leaving the kiln are fed becomes.

It is further proposed that this too the combustion air supplied in the side walls their composition along the combustion route can be varied locally, preferably essentially correspond to the composition of the corresponds to the combustion air on the same Place the combustion air through the grate in the Firing material is guided.  

To control the composition of the combustion air, respectively. of the oxygen content in the combustion air is further proposed that the combustion temperatures of the material to be measured along the combustion path. This can be done on the one hand by thermal measuring elements which are arranged along the combustion path, or optically by measuring the brightness of the flame, respectively. the flame tips from which the respective temperatures in the flame or in the flame tips can be deduced. If too high a combustion temperature is measured at one point in the combustion zone, the oxygen content of the combustion air, which is supplied to the combustion zone in which this point is located, is reduced to such an extent that the temperature drops below the required maximum value. As a result, it is sufficient that the possible formation of NO _x gases used at this point is essentially impossible again.

Another procedure proposes that the flue gases leaving the fuel in one Furnace or in a mixing section by secondary air from one or more first inlet nozzles is mixed and / or swirled. This is how it came about The air / flue gas mixture is in a fire space and / or gas following the mixing section burnout zone by supplying additional secondary air almost from one or more second inlet nozzles completely burned out. This burning out the smoke gases is necessary that no afterburns in the  subsequent pipe runs arise to damage to avoid in the pipe runs.

It is proposed that the secondary air out the first inlet nozzles preferably at least partially as consists of recirculated flue gases and that the secondary air from the second inlet nozzles is almost pure air. Because of the high oxygen content of the secondary air from the second inlet The smoke will completely burn out gases guaranteed.

According to the method of the invention a plant for burning a combustible is featured in which when burning a burner good along a combustion route over minde least an air distribution device, such as a combustion grate, exhaust gases are formed are essentially free of nitrogen oxides. The System is characterized in that the supply the combustion air through the device the route in at least two separate sections Air zones and mixing device in each air zone lines are arranged to fresh air and zurückge led to smoke gases generated during combustion to mix any ratio, whereby due to the different together setting of the combustion air, respectively. the difference Liche oxygen content in the combustion air, the Combustion temperature over each air zone separately can be controlled. So that the combustion temperature along the whole route under one  critical value is kept, which for the Formation of nitrogen oxides is decisive. In a Design variant of the system according to the invention it is further proposed that laterally to the Ver partial devices, respectively. to the combustion grate, sides walls are arranged, being in the Seitenwan air supply or air nozzles for the in blowing combustion air are arranged. In turn are provided mixing devices through which the composition of the through the side walls imported combustion air can be varied locally can.

In a further embodiment of the invention According plant is proposed that at the through passage zone from the combustion chamber into a gas burnout zone, which is essentially a round cross-section points and which essentially by a so-called Mixing section is formed along the periphery the cross section of the first inlet nozzles for secondary air can be arranged. These first inlet nozzles can either be almost horizontal in one plane can be arranged horizontally or helically offset against each other along the wall on ver different levels. The inlet direction of the inlet nozzles are pointing in the same circumferential direction angles to the respective tangent of the curve to pass through blowing the secondary air tangentially into a vortex flow into the smoke escaping the combustion chamber to produce gases. These are preferably the first Nozzles arranged in a plane if the firebox is low, and preferably then  arranged in a spiral if it is a high combustion chamber.

It is further proposed that in an analogous manner another second inlet above the first nozzles nozzles for secondary air are arranged through which essentially oxygen-rich combustion air into the vortex generated by the first nozzles leads to an almost complete burnout to allow the flue gases. This second inlet nozzles can either lie in one plane offset or offset in a spiral be ordered, the direction of their blowing advantageous in the same direction as the one already created Vertebra points.

It is advantageous to generate this vortex flow stuck when the cross section at the exit of the fire room, in the mixing section and at the beginning of the first Zug is almost round.

It is also proposed that, after the first train switched, a cyclone filter is arranged in which coarse, weakly toxic solid particles from the Flue gases are excreted. The cyclone filter is preferably arranged such that the vortex flow generated in the mixing section in the cyclone filter continues, causing the elimination the solid particle is favored. It has happened shows that the toxic substances in flue gases, such as heavy metals, nitrogen oxides etc., adhere to the finest particles and not to the coarse  share. These relatively non-toxic coarse parts can then be fed back to the kiln.

For excreting the highly toxic fine particles will continue the arrangement of another cyclone Filters suggested which preferably the tube trains will follow in an area where the Flue gases only have a heat of approx. 300 ° C. By these equipment measures can be achieved that the accumulation of highly toxic substances is reduced to a minimum.

The processes and systems mentioned above are suitable especially in waste incineration plants or in coal power plants.

The methods and systems according to the invention remain but do not apply to these two areas of application limits, but can be used wherever a kiln is not stationary locally within a small, limited firebox is burned, but led along a combustion route and is burned.

The invention is then followed, for example hand use in waste incineration plants Further explained with reference to figures.

Show:

Fig. 1 is illustrated schematically in the longitudinal direction of a combustion according to the invention route a waste incineration plant,

Fig. 2 shows schematically a Müllverbren drying plant according to the invention with the supply of the combustion air,

Fig. 3-5 graphically illustrated the mixing recirculated flue gases combustion air in the Ver.

Fig. 6 shows the combustion distance in the cross section of the supply line of the combustion air by side walls,

Fig. 7 schematically space a further embodiment of the invention a combustion path with fire and first train Müllverbren a drying plant with the supply of the combustion air,

Figure 8 is approximately variant. Exporting a further invention, shown in more detail,

Fig. 9 shows the cross section of the mixing section along line AA of Fig. 8 and

Fig. 10 shows schematically the cyclone filter downstream of the first train according to the invention.

In Fig. 1 is shown schematically in the longitudinal direction a combustion route equipped according to the invention of a waste incineration plant. In this case, garbage 1 , which may be municipal or industrial, moist or dry waste, for example, is fed into a supply zone 2 and placed on a combustion path 3 consisting of a combustion grate. The garbage now passes through the combustion zone 3 as a burning material 5 and leaves it at the end in the form of ash 7 , which is collected in a collecting vessel in a deashing zone 8 and carried away.

The combustion air responsible for the combustion is fed from below through the grate 3 , namely through the independent air zones 11-16 , which are each formed by a collecting funnel for the ashes 4 , in which the ash falling through the grate is collected . The air zones 11-16 are each fed by a supply line from a mixing valve 19 with combustion air, in which mixing of fresh air 17 and returning smoke gases 18 takes place. The mixing setting in the valves 19 can be selected individually.

If the garbage 1 is now on the combustion grate 3 ge, it is first dried in the area above the air zone 11 , degassed and then, depending on the oxygen supply, gasified or burned ver. Depending on the calorific value of the waste or of the now burning material 5 can use the combustion very intensively, as a result of which strong and very bright flames 6 develop. The combustion temperature is highest, especially in the flames where the flame is brightest, almost white. Accordingly, the greatest danger here is the formation of nitrogen oxides. By throttling the oxygen content in the supplied combustion air, in which more recirculated flue gases 18 are admixed, the fire can be throttled and thus also the maximum temperatures in the flame tips. This largely prevents the formation of nitrogen oxides.

The combustible 5 then passes through the combustion section over the other air zones 12-16 , where the composition of the combustion air in the individual zones depending on the burning intensity, respectively. flame formation during combustion. Due to the still high calorific value of the firing material 5 above air zone 12 , the smoke gas content is still high here, while in the end area, because of the already low calorific value, fewer flue gases in zones 15 and 16 of the combustion air are added. Here it is even important that as much oxygen as possible is supplied to the firing material so that it burns completely.

The throttling of oxygen along the combustion route 3 can also be achieved in that the supply quantity of the combustion air is reduced. However, it has been shown that if the combustion air throughput is too small, the cooling of the grate is too low due to the combustion grate. Due to excessive temperatures on the grate, the kiln or slag begins to melt and penetrates the grate, which is undesirable. The high combustion air throughput thus required can, however, be maintained with pre-proposed, variable admixing of flue gases 18 to the combustion air on the entire combustion route 3 .

In Fig. 2, a waste incineration plant with the supply of combustion air according to the invention is shown schematically. The supply of garbage 1 in a feed zone 2 , the passage of the combustible material 5 along the combustion route 3 , and the feed of the combustion air through the air zones 11 - 16 roughly correspond to the illustration in FIG. 1. A difference is that that the combustion section is subdivided into three combustion grates 3 which are graded from one another.

The combustion chamber 21 is arranged above the combustion zone 3 , through which the flue gases leaving the flames 6 are guided into a so-called mixing zone 22 a . Peripherally in the wall of this mixing section 22 a , two groups of feed nozzles 31 and 32 are arranged, for the supply of secondary air. The cross section of this mixing section 22 a is preferably circular. Connected to the mixing section 22 a is a gas burnout zone or first train 22 , in which the flue gases mixed with secondary air are still completely burned out. Along the further trains arranged after the first train, shown in the form of a heat exchanger 23 , the flue gases are guided to a filter or deduster 24 , where solid particles and fly ash are filtered out of the flue gases. The flue gases leaving the deduster, or now also called exhaust gases, can also be used for heating so-called district heating, or leave the waste incineration plant, for example, by means of a chimney (not shown).

Part of the smoke or exhaust gases leaving the deduster are drawn off via a line 25 and guided via a flue gas blower 18 a into the pipes 18 , where the recirculated flue gases are used for admixing in primary combustion air or in the secondary air for the nozzles 31 and 32 . The admixture in the primary combustion air for the air zones 11-16 takes place in the valves 19 . The admixture of the returned flue gases in the secondary air for the nozzles 31 and 32 takes place in the mixing valve 33 , which is fed further by fresh air 34 via a fresh air blower 34 a .

The combustion air supplied through the air zones 11-16 during the combustion of the combustion material 5 is acted upon with recycled flue gases 18 analogously to that described in FIG. 1. The composition of the secondary air in the nozzles 31 and 32 is of the type selected that a complete burnout of the flue gases leaving the flame zone 6 in the mixing and a 22 is ensured in the Gasausbrandzone 22nd It is necessary that the flue gases leaving the combustion chamber still have at least a temperature of approx. 800 ° C. The oxygen content and thus the proportion of fresh air 34 in the nozzles 31 and 32 is then selected so that the combustion temperatures hardly ever exceed the maximum range of approximately 1100 ° C. to 1300 ° C. when the flue gases are burned out. The pipes possibly already arranged in the first train 22 for the heat absorption from the flue gases are not shown in FIG. 2. The returned through line 25 flue gases could also be deducted before the deduster 24 , but it has been shown that fly ash and solid particles in the flue gases can lead to blockages in the blower 18 a .

In the Figs. 3 to 5 show three possible examples the percentages are of the recirculated flue gases into the combustion air in the air zones 11-16 illustrated. It is assumed that the supply of combustion air is constant along the six air zones.

It should also be noted that the three Darge provided examples show a snapshot since the composition of the garbage is constantly changing and thus the composition of the combustion air in the individual air zones vary constantly can. So it's more about illustrative examples games to the inventive idea of the Variie along the composition of the combustion air to illustrate the combustion route.

Fig. 3 shows a typical exposure to flue gases to be returned when burning waste with a relatively high calorific value.

Fig. 4 shows, in contrast, a typical exposure with recirculated flue gases when burning waste with a relatively low calorific value.

Fig. 5 finally shows the exposure of the combustion air with recirculated flue gases when burning wet waste.

All three figures show that the Beauf striking along the combustion route is decreasing, but that is definitely the case that can come in a subsequent burning air supply zone, the exposure to be higher can than in the previous one.

To Fig. 5 is also to be noted that the humid combustible material therefore preferably is dried with recirculated flue gases, because the one hand have increased to recirculated flue gas temperature, and also does not use any uncontrolled fire development in the drying of the firing point.

In Fig. 6 the combustion section is shown in cross section with the supply of secondary air through side walls. The two side walls 41 are arranged laterally to the combustion grate 3 . Arranged in the two side walls 41 are upper and lower inlet nozzles 42 and 43 , through which the secondary air can be blown in. The advantage of attaching side walls is on the one hand in that the burning material 5 can not drop laterally from the grate and also the lateral radiation losses can be reduced. The supply of secondary air through the side walls 41 has the advantage, on the one hand, that less slag or ash particles adhere to the walls, and there is also the possibility of partially influencing the combustion and the composition of the flue gases lying above the flame.

The composition of the secondary air introduced through the inlet nozzles 42 and 43 can either be kept constant along the entire combustion path 3 , or else it can also be varied in zones by more or less admixing of recirculated flue gases.

In Fig. 7 is also a combus tion 3 a waste incineration plant with the overlying combustion chamber 21 and a gas fire zone 22nd In Fig. 7 the Seitenwandun are now shown gen 41 in the longitudinal scheme, along the track above the combustion air zones 11 - 14 results. Side walls 41 are advantageously arranged along that part of the combustion section 3 where high flame development is possible. Wei ter recognizable in the longitudinal direction, schematically represented by a dash, the two A laßdüsen 42 and 43rd The longitudinally extended inlet nozzles 42 and 43 are each fed by a metering valve 48 with secondary air. The metering valves 48 in turn are fed by a mixing valve device 46 , to which fresh air 45 on the one hand and flue gases 18 which are returned on the other hand are supplied.

Next arranged in Fig. 7, two temperature sensors 47, namely a in the region above the two air supply zones 11 and 12 and the other upper half of the air supply zones 13 and 14. Due to the temperatures measured by the two sensors 47 , on the one hand the composition of the combustion air in the supply zones 11-16 is set by varying the settings of the mixing devices 19 and on the other hand the composition of the secondary air which flows through the side walls 41 via the nozzles 42 and 43 is blown. Depending on the temperature, the setting of the Doier valves 48 is also variable.

It is entirely possible to arrange a temperature sensor for each air supply zone in order to achieve the most exact possible control of the combustion air composition. On the other hand, it has been shown that, based on two measured temperatures, a typical temperature profile along the entire combustion path 3 can be concluded. It essentially depends on how different the composition of the waste to be incinerated is. It is also possible to arrange a further temperature sensor in the region of the mixing section 22 a in order to vary the setting of the mixing device 33 and thus to control the composition of the secondary air which is blown in through the nozzles 31 and 32 .

In Fig. 8 the same section of a waste incineration plant shown in Fig. 7 is again shown.

Fig. 8 is, however, in particular with regard to essential features for waste incineration plants designed in more detail, and in addition, other inventive design options for supplying the combustion air are shown.

The feed zone 2 consists essentially of a funnel 2 a , a gate valve 2 b and a För dereinheit 2 c . The waste supplied through the supply zone 2 (not shown) is now placed on the incineration line, consisting of several grates 3 . The grids 3 are mounted, shown in a step-like manner, whereby they generate a conveying movement of the material to be burned along the combustion path by movements, for example displaceable relative to one another in the longitudinal direction. Arranged underneath the combustion grates 3 are the funnel-shaped air supply zones 11-16 , which at the same time each form an ash funnel 4 . The ash funnel 4 are each immersed in a water basin 4 a , which ensures that no air supply from below is possible in the ash funnel. The supply of fresh air 17 , respectively. recirculated flue gases 18 into the air supply zones 11-16 take place via the two metering valves 19 a and 19 b . In the air supply zones 11 , 13 and 15 so-called hold-up zones 49 are further provided, whereby the combustion air of these air supply zones can also be blown in at the beginning of the corresponding combustion path in the longitudinal direction to the combustion path.

Further arranged are side walls 41 , with the corresponding longitudinally formed inlet nozzles 42 , 43 . In the embodiment shown in FIG. 8, the composition of the secondary air in the inlet nozzles 42 and 43 is also set via the metering valves 19 a and 19 b , where in the side walls the composition of the secondary air of the composition of the primary air in the corresponding, below Corresponds to driving zones. By further arranged Doier valves 48 , the supply amount of secondary air can be controlled. Shown above the feed zones 11 and 12 , a temperature sensor 47 is arranged, whereby the composition of the combustion air can be adjusted in each feed zone on the basis of the temperature measured over this zone.

On the representation of the other four temperature sensor was omitted for reasons of clarity.

The supply of the inlet nozzles 31 and 32 arranged at the mixing section 22 a with secondary air, in contrast to the illustration in FIG. 7, can be set individually. The composition of the secondary air 35 a for the nozzles 31 is set via the mixing device 33 a and the composition of the secondary air 35 b via the mixing device 33 b . The main task of the nozzles 31 is to generate a swirling flow 51 into the flue gases leaving the combustion chamber. For this reason, the secondary air 35 a for the nozzles 31 is largely from recirculated flue gases 18th In contrast, the task of the nozzles 32 consists largely in introducing secondary combustion air into the vortex 51 in order to achieve a complete combustion of the flue gases. For this reason, the secondary air 35 b for the nozzles 32 largely consists of pure fresh air 34 .

In Fig. 8 is shown schematically in elevation, the cross section 22 b of the mixing section 22 a , respectively. of the first train 22 , which is advantageously round.

The ash (not shown) leaving the combustion zone 3 falls into a collecting vessel in the ash removal zone 8 . Likewise, the ash collected in the water of the ash 4 a is exhausted by conveyor devices and leads to the ash removal zone 8 . In the ash removal zone 8 , the ashes obtained are fed, for example, via conveyors to an ash bunker not shown.

In FIG. 9, the cross section of the mixing section 22 a is shown in a cross section along the line AA from FIG. 8. The inlet nozzles 31 lying almost in one plane are fed with secondary air via a line 35 a . The Einblasrich device of the nozzles 31 extends, pointing in the same direction, tangentially angled, so that in the mixing section 22 a, a vortex flow 51 is generated. The arrangement of the nozzles 31 does not have to be compulsory in one plane, but it can also be spiral-shaped, the nozzles being arranged helically against one another. The latter arrangement is always advantageous when there is a high combustion chamber.

The arrangement of the nozzles 32 for blowing in preferably fresh air, for burning the flue gases, is analogous to that of the arrangement of the nozzles 31 shown in FIG. 9.

Fig. 10 shows a schematic representation of the arrangement of two cyclone filters for separating solid particles and fly ash from the flue gases leaving the first train 22 .

Directly downstream of the first train 22 is a cyclone filter 55 , in which coarse solid particles 53 are separated out. Via a Rückführvorrich device 54 , these coarse solid particles can be returned to the combustion chamber 21 . The Festparti keln 53 are largely non-toxic substances, since the highly toxic heavy metals, nitrogen oxides, hydrogen sulfide, etc. on fine particles, respectively. the so-called fly ash, adhere and continue with the flue gases escaping the cyclone.

The cyclone filter 55 is preferably connected to the first train 22 in such a way that the route 22 a in the mixing, respectively. in the first train 22 generated vortex flow 51 can also be used in the cyclone 55 .

The other trains 23 is followed by a white tere cyclone filter 56 , in which the highly toxic fine particles, respectively. the fly ash 57 are excreted. This highly toxic failure 57 can be discharged via a discharge device 58 for disposal. The flue gases escaping from the cyclone 56 are finally fed to the deduster 24 .

By arranging these two cyclone filters 55 and 56 can be achieved that the accumulation of highly toxic waste from waste gases from waste incineration plants is reduced to a minimum. Of course, this also reduces the disposal costs of the highly toxic waste.

The execution variants of the invention shown in FIGS . 1 to 10 using a combustion route, respectively. on the basis of diagrams of a waste incineration plant are not limited to these, but can be transferred to any combustion processes where any kind of combustible material is guided along a combustion path. He thinks it is only a coal-fired power station where coal is gasified or burned along a combustion path. is burned.

Claims (27)

1. The method, preferably according to at least one of the claims, for reducing the content of nitrogen oxides in exhaust gases which arise during the combustion of a combustible material ( 1 , 5 ) which is guided along a combustion path ( 3 ) during the combustion process, characterized in that that the quantity of oxygen is locally varied by the combustion air supplied along the combustion path ( 3 ) in such a way that at no point on the path does the combustion temperature essentially exceed a maximum value at which the formation of nitrogen oxides begins. 2. The method, preferably according to at least one of the claims, characterized in that the oxygen content in the combustion air supplied along the combustion path ( 3 ) is locally varied. 3. The method, preferably according to at least one of the claims, characterized in that the supply of combustion air along the combustion route ( 3 ) is varied locally. 4. The method, preferably according to at least one of the claims, for reducing the formation of nitrogen oxides when burning a combustible material ( 1 , 5 ), which is guided during the combustion process along a combustion path ( 3 ), characterized in that the oxygen content in the to localized combustion air is reduced locally by admixing a gas mixture ( 18 ) or gas with less oxygen than air along the combustion path ( 3 ) in order to largely prevent high combustion temperatures at this location and thus largely to prevent the formation of nitrogen oxides. 5. The method, preferably according to at least one of the claims, as claimed in one of claims 1 to 4, characterized in that the oxygen content in the combustion air or the amount of oxygen supplied by admixing returned flue gases ( 18 ) which arise during combustion varies or . is reduced. 6. The method, preferably according to at least one of the claims, as claimed in one of claims 1 to 5, characterized in that the combustion temperature at kei ner point of the combustion path ( 3 ) essentially the value of approx. By the local variation of the oxygen content of the supplied combustion air . Exceeds 1300 ° C in the flame tips. 7. The method, preferably according to at least one of the claims, such as according to one of claims 1 to 6, characterized in that the combustion temperature at kei ner point of the combustion path ( 3 ) substantially the value of approx. By the local variation of the oxygen content of the supplied combustion air . Exceeds 1100 ° C in the flame tips. 8. The method, preferably according to at least one of the claims, as claimed in one of claims 1 to 7, characterized in that the combustion temperature is kept almost constant at least along part of the combustion path ( 3 ). 9. The method, preferably according to at least one of the claims, as claimed in one of claims 5 to 8, characterized in that the exposure of the combustion air to recirculated flue gases ( 18 ) is high at the beginning of the combustion path and that it runs along the combustion path ( 3 ) significantly decreases. 10. The method, preferably according to at least one of the claims, as claimed in one of claims 5 to 9, characterized in that the flue gases ( 18 ) at an initial zone of the combustion section ( 3 ) for drying and / or heating the combustion material ( 1 ) fed to the latter will. 11. The method, preferably according to at least one of the claims, as claimed in one of claims 1 to 10, characterized in that the material to be burned ( 1 , 5 ) is burned at an end zone of the combustion section ( 3 ) essentially with pure air ( 17 ). 12. The method, preferably according to at least one of the claims, as claimed in one of claims 1 to 11, characterized in that the firing material ( 1 , 5 ) via one or more air distribution devices, such as combustion grates ( 3 ) or nozzle plates for fluidized bed, out and the combustion route ( 3 ) is divided into at least two combustion zones, the combustion air being fed through at least one separate air zone to each combustion zone. 13. The method, preferably according to at least one of the claims, as claimed in one of claims 11 or 12, characterized in that at least partially along the combustion path ( 3 ) on both sides of the or the distribution devices ( 3 ) side walls ( 41 ) are arranged , through which Ver combustion air is fed as so-called primary air into the fuel ( 5 ) or as so-called secondary air to the flue gases. 14. The method, preferably according to at least one of the claims, as claimed in claim 13, characterized in that the oxygen content of the combustion air supplied through the side walls ( 41 ) as primary air or secondary air preferably speaks ent essentially to that of the combustion air which is in the same place the combustion route ( 3 ) through the grate into the firing material ( 5 ) leads ge. 15. The method, preferably by at least one of claims, as in one of claims 1 to 14, characterized in that the combustion temperature optically by measuring the brightness of the  Flame or thermal by temperature measurement is averaged and the oxygen content in the ver Combustion air at locally determined, too high ver combustion temperatures at this point of the route is reduced. 16. The method, preferably according to at least one of the claims, for reducing the content of nitrogen oxides in flue gases which arise during the combustion of a combustible material ( 5 ) which is guided along a combustion path ( 3 ) during the combustion process, characterized in that the Flue gases in a combustion chamber ( 21 ) or a mixing section ( 22 a ) are mixed and / or swirled by secondary air from one or more first inlet nozzles ( 31 ) and the resulting air / smoke gas mixture in one of the combustion chamber ( 21 ) or mixing section (22 a) following Gasausbrandzone (22) further, by supplying secondary air from one or more second inlet nozzle (32) is almost completely burnt out. 17. The method, preferably according to at least one of the claims, as claimed in claim 16, characterized in that the secondary air from the first inlet nozzles ( 31 ) preferably contains recirculated smoke gases ( 18 ) and that the secondary air from the second inlet nozzles ( 32 ) almost is pure air ( 34 ). 18. Plant, preferably according to at least one of the claims, for burning a material to be burned ( 1 , 5 ) which is guided along a combustion path during combustion via at least one air distribution device, such as a combustion grate ( 3 ), the exhaust gases formed during the combustion in are essentially free of nitrogen oxides, characterized in that the supply of combustion air through the device ( 3 ) along the route is divided into at least two separate air zones and mixing devices ( 19 ) are arranged in each air zone to supply fresh air ( 17 ) and recirculated flue gases ( 18 ) formed during combustion to mix with each other in any ratio to separately control the combustion temperature over each air zone by varying the oxygen content of the combustion air, so that the temperature along a critical value for nitrogen oxide formation along essentially does not exceed the entire route. 19. Plant, preferably according to at least one of the claims, as claimed in claim 18, characterized in that side walls ( 41 ) are arranged at least partially along the combustion path ( 3 ) to the side of the combustion grate, air feeds ( 42 , 43 ) on the side walls. for combustion air, as primary air in the firing material or as secondary air in the escaping flue gas, which are at least partially connected to mixing devices ( 19 , 46 ) of the combustion air supply in which the oxygen content by mixing fresh air ( 17 , 45 ) can be varied with recirculated flue gases ( 18 ). 20. Plant, preferably according to at least one of the claims, as claimed in one of claims 18 or 19, characterized in that at the passage zone from the combustion chamber ( 21 ) into a gas burnout zone ( 22 ), which is essentially formed by a mixing section ( 22 a ) is and which is essentially a round cross-section ( 22 b ), at least two peripheral first inlet nozzles ( 31 ) for secondary air lying in an almost horizontal plane or offset spirally from one another, the inlet directions of which are angled pointing in the same circumferential direction to the respective tangent of the curve are arranged to generate a vortex flow ( 51 ) into the combustion chamber ( 21 ) evacuating flue gases by tangential injection and thus achieve a good mixing of the flue gases. 21. Plant, preferably according to at least one of the claims, as claimed in claim 20, characterized in that above the first nozzles ( 31 ), just in case almost lying in a horizontal plane or offset spirally offset, at least two further second inlet nozzles ( 32 ) are arranged for secondary air in order to introduce oxygen-rich combustion air into the vortex ( 51 ) generated by the first nozzles ( 31 ) and to allow the flue gases to be almost completely burned out. 22. Plant, preferably according to at least one of the claims, as claimed in one of claims 18 to 21, characterized in that the passage from the combustion chamber ( 21 ) into the gas burnout zone ( 22 ) or. in the first turn has almost a round cross-section ( 22 b ). 23.The system, preferably according to at least one of the claims, for burning a combustible material which is guided along a combustion path during combustion, the exhaust gases formed during combustion and leaving the system being essentially free of highly toxic solid particles, characterized in that the gas burnout zone ( 22 ) resp. downstream of the first train a cyclone filter ( 55 ) is arranged, in which weakly toxic coarse solid particles ( 53 ) are excreted from the flue gases, and that the other trains ( 23 ) for heat removal from the flue gases are followed by a further cyclone filter ( 56 ) is arranged for the excretion of highly toxic fine solid particles respectively. the fly ash ( 57 ) from the flue gases. 24. Waste incineration plant with a plant, in front preferably according to at least one of the claims. 25. Coal-fired power plant with one plant, preferably according to at least one of the claims. 26. Application of the method, preferably after at least one of the claims in a garbage incinerator.   27. Application of the method, preferably after at least one of the claims in a coal power plant.