EP0913631B1 - Oil firing installation with reduced nitrogen oxide (NOx) - emissions - Google Patents

Abstract

The oil-fired burner assembly has at least one central spray jet and associated ignition, with a fan blower for the combustion air which is fed through the flame tube surrounding the spray zone downstream of the jet. Further spray jets (2) are at equal intervals round the central spray jet (3), within the flame tube (1). The central jet (3) is a mixing spray jet with an air feed, flame stabilizer and ignition. A ring disk body (4) is between the central jet (3) and the surrounding jets (2).

Description

The invention relates to an oil firing system for combustion under reduced Nitrogen oxide emissions, especially for higher outputs, with at least one centrally arranged pilot atomizer nozzle and associated ignition device as well as a fan for the supply of combustion air, which by a Flame tube surrounding atomizer nozzle downstream of the atomization chamber is fed to the nozzle, and with a number of other atomizing nozzles that around the centrally located central atomizer nozzle around inside the flame tube the atomization chamber are arranged evenly spaced.

Oil combustion plants of the type in question work for the purpose of reduction the thermal nitrogen oxides with exhaust gas recirculation designed in many ways. This leads in part to flame instabilities with a high level at the same time expenditure on equipment.

Oil firing systems of the type mentioned at the outset are in EP 0, among others 397 046 A, EP 0 478 305 A and approximately also GB 1 011 058 A. Thereby all atomizing nozzles are blocking or swirling discs assigned.

The invention is based, an oil firing system the task to provide the type mentioned in which the distribution is as homogeneous as possible of fuel, air and exhaust gas is given and at avoidance targeted or separate external exhaust gas recirculation the formation of thermal NOx is reduced.

This is achieved according to the invention in that between the central Atomizer nozzle (3) or mixing system and the surrounding An annular disk bluff body (4) is arranged in the atomizer nozzles (2).

By arranging several atomizing nozzles around the central atomizing nozzle around it you reach a core flame and a flame around it Core flame around, which is reliable regardless of the geometry of the firebox and burn stably. In the combustion chamber area after the central nozzle surrounding atomizing nozzles one reaches a fuel gasification and mixing zone. Here the components become more atomized Fuel, air and exhaust gases flowing back internally in the combustion chamber are premixed intensively. The heat emission from the core flame supports fuel gasification. The aim is a homogeneous mixture with the result of an equalization of the Flame temperature with an overall reduced average temperature level in the flame, which in turn causes a good burnout in the entire flame area is achieved. Between the central atomizer nozzle or Mixing system and the atomizing nozzles surrounding it is a Ring disk bluff body arranged to the central atomizer nozzle or the central mixing system can be arranged with gap formation. This gap formation is important for the air introduction to the central flame.

The core flame is preferred through a central atomizing nozzle in Combination with a mixing system of conventional design, which in the core yellow can be. In the area of the flame, bluish burnout and overall a slim flame shape without cloud of fuel.

In a further preferred embodiment, the central atomizer nozzle or Mixing system complete with the ring disk bluff body in the direction of Longitudinal axis of the flame tube in different displacement positions - in particular infinitely adjustable. This can adjust the air supply adjustment to serve the amount of fuel when the load changes, otherwise this shifting option enables the NOx values to be set or optimized to reach.

In another preferred embodiment, they have the central atomizing nozzle surrounding atomizer nozzles at a narrower spray angle than that the central nozzle. The spray angle is preferably the surrounding one Atomizer nozzles selected around 30 ° to 45 °. Through this narrow spray angle the combustion chamber wall is not wetted with oil. In addition, coking in the area of the flame tube mouth and the adjacent areas of the outer edges of the bluff body avoid.

In a particularly preferred embodiment, the annular disk bluff body is on it the outside facing the combustion chamber, i.e. the centrally located one Atomizer nozzle - pilot atomizer nozzle - side facing away, with one in this Provide direction projecting essay, preferably continuously is ring-shaped and in particular the annular In immediately afterwards is. The attachment can be formed in one piece on this bluff body ring disk his.

Furthermore, the bluff ring washer on its outer edge again with regard to the combustion air supplied downstream of the combustion chamber have facing projecting edge edging, which are related with the flame tube to improve airflow. To this Purposes can also be a tapered design of the flame tube on serve downstream end of the combustion air duct. To this combustion air duct To favor, the bluff ring washer in the areas the respective ring arranged around the central pilot atomizer nozzle Main atomizer nozzles with radially inward bulges be provided.

The ring disk bluff body or physically considered the bluff body ring disk of the kind described makes it possible in particular to use nozzles with large Spray angle - 60 ° - to use and even with this large one Spray angle an impact and baking of oil droplets on the front to prevent the bluff ring. If the Mixing device is moved back accordingly, there is also Danger of contamination of the annular atomizing nozzles. In addition, this measure further reduces NOx emissions and improves combustion overall, i.e. Soot formation is reduced, and the combustion approaches that of gas. It takes place a flow equalization with the result of higher flame stability.

Of particular importance is the supply of the ring around the central one Atomizer nozzle arranged as a pilot nozzle atomizer nozzles for the Load case deliver the majority of the atomized fuel, namely about 95% and more. These main atomizer nozzles are designed for a uniform burnout of the desired type according to the task, namely approximately at low NOx emissions Blue fire behavior, work as evenly and constantly as possible. To For this purpose, these main atomizing nozzles are in a manner known per se an oil supply connected, which provides an oil supply and an oil return, in such a way that, when the respective nozzle is operating, a constant as possible certain amount of fuel is supplied under predetermined pressure. On the To this extent, flow and return become an oversupply of what is to be sprayed through the nozzle Fuel supplied. The pressure in the oil feed line is preferred kept stable while the amount of fuel sprayed through the nozzle controlled by cross-sectional control (throttling) of the oil return line becomes.

Basically, you can arrange the ring around the central pilot atomizer nozzle Main atomizer nozzles "star-shaped" on oil supply and Oil return lines in the sense of an oil supply pressure source and a common one Oil return, which feeds and exhausts for all main atomizing nozzles are provided, connect. In a preferred embodiment, the main atomizer nozzles with regard to both their oil flow and their oil return connected together in the form of a ring line, i.e. all main atomizing nozzles are connected to this ring line in their base area, which in turn are centrally connected to the oil supply pressure source and the oil return stands, preferably such that these ring lines between two adjacent main atomizer nozzles a feed or discharge point for have a central oil supply pressure line and an oil return line.

The central supply described above for the main atomizer nozzles arranged in a ring secures you - ultimately also by sufficient cross-section of the feed Discharges - even operation of these nozzles, i.e. Ejection of the sprayed Oil under practically matching conditions.

In the event of a business interruption, there is the problem that the oil supply like also drain residual oil from the oil return lines into the combustion chamber, which is undesirable. This applies in particular to the preferred one described above Execution of the oil supply to the main atomizer nozzles via a ring line. In Particularly preferred execution is therefore both in the course of the oil flow as One valve each in the course of the oil return of each main atomizer nozzle provided that is hydraulically operated. These valves therefore work under Influence of the oil pressure depending on the force of the assigned springs. If accordingly, the cross section of the oil return line in the operating phases Excess pressure for spraying oil through the nozzle are the Valves against due to the pressure difference between flow and return their spring force more or less opened. However, if the cross section of the Oil return line in the sense of a business interruption opened accordingly, close the valves so that both from the oil feed line and from the oil return line no oil can drip through the nozzle into the combustion chamber.

Preferred embodiments of the invention result from the subclaims, in particular with respect to those shown schematically in the drawing Exemplary embodiments on the basis of which the invention is explained below:

Figur 1

einen schematischen Schnitt durch die Längsachse des Flammrohres eines ersten Ausführungsbeispieles einer erfindungsgemäßen Ölfeuerungsanlage;

Figuren 2 bis 4

perspektivische Darstellungen eines modifizierten Ausführungsbeispieles gemäß Figur 1;

Figur 5

ein Ausführungsbeispiel der Ausführung nach den Figuren 2 bis 4;

Figur 6

eine Schemaskizze der Ventilsteuerung für Vor- und Rücklauf des Öls als Brennstoff;

Show it:

Figure 1

a schematic section through the longitudinal axis of the flame tube of a first embodiment of an oil combustion system according to the invention;

Figures 2 to 4

perspective views of a modified embodiment according to Figure 1;

Figure 5

an embodiment of the embodiment according to Figures 2 to 4;

Figure 6

a schematic diagram of the valve control for supply and return of the oil as fuel;

Figure 1 shows a cylindrical flame tube 1, at the outlet of which the combustion air is accelerated, for example by moving in the direction of flow conically tapering section 9, in the tube axis - that is, in the middle - one central atomizing nozzle 3 as part of a mixing system of conventional design is arranged. Around this central atomizer nozzle 3-pilot atomizer nozzle - there are several more on a concentric circle with radius r Atomizer nozzles 2 - main atomizer nozzles - arranged. The central nozzle 3 serves to supply fuel to a pilot flame; and about the concentric the main part is supplied around these atomizer nozzles 2 of the liquid fuel in or with the main combustion air.

The number of atomizing nozzles evenly spaced on the pitch circle 2, the defined minimum radius 3 of the pitch circle to the central nozzle 3 and the nozzle outlet conditions depend on each other.

The nozzle outlet holes of all atomizers on the concentric pitch circle are in the flow direction in front of or in the air outlet plane of the Flame tube.

The ratio of the distribution of the total amount of fuel supplied for the Pilot flame to the atomizing nozzles 2 of the pitch circle is an essential one Criterion for combustion with low NOx emissions. (approx. 2- 5% of Total fuel quantity at high load is required for the central pilot flame).

The main combustion air is applied to the flame via the ring section cross sections fed to the exit plane of the flame tube 1. These ring section cross sections result from the respective inner diameter of the flame tube, one for Flame tube axis coaxially arranged bluff body 4, e.g. executed as Washer, and the atomizer nozzles 2 on the concentric pitch circle. in the Annular disk bluff body 4 is integrated coaxially Volume bluff body 6. Both bluff bodies are through an annular gap for Combustion air passage separated. The central volume bluff has adjustable combustion air inlet cross sections in a prechamber 7. Das End of the pre-chamber 7 is seen with a Bluff body 5 with radial flushing slots, a center hole and a Outside diameter, collar standing in the direction of flow, closed.

The annular disk bluff body 4 improves the operating behavior.

Part of the combustion air flow, according to the power distribution, the pilot flame over the bluff body 5 and the annular gap between the volume bluff body 6 and washer bluff body 4 supplied. In the antechamber 7 of the central volume accumulation body 6 is the central nozzle 3 with an electric one Ignition device arranged.

With the arrangement described, the following combustion process results. through the thermal energy emitted along a minimum path length of the constant, central pilot flame, the thermal energy from flue gases from the combustion chamber, the Atomization distribution over several nozzles and the pitch circle arrangement succeeds first of all a very good fuel preparation.

Parts of the fuel spray from the atomizer nozzles on the pitch circle start due to to gasify the heat in the combustion chamber.

Ignition of fuel from atomizers of a partial circle will initially prevented to intensely recirculated flue gas in the combustion chamber and to mix the supplied combustion air. This has a very homogeneous Mixture of fuel, combustion air and flue gas results. (Mixed phase).

The individual fuel-gas mixture partial flows mix completely with the pilot flame according to the minimum path length and ignite in the process - the main flame stabilizes. In this main flame there is a uniform, complete combustion of the individual partial mixture flows at reduced O ₂ partial pressure. (Internal phase).

As demonstrated by tests, the thermal NOx formation in the Flame significantly reduced, reduction 30-40%, with a good rating at the same time of the other operating parameters. The firing starts with the electric Ignite the pilot flame and switch on the atomizer on the pitch circle. It This creates a continuous slim, bundled flame. The flame burns with a yellow core and blue border areas.

Figures 2 and 3 show perspective views of the central mixing system with the central atomizer nozzle 3 and three arranged circumferentially to this Main atomizer nozzles 2. The in connection with the schematic embodiment Reference symbols used according to FIG. 1 are found in the same Way again in these drawings.

As can be seen in FIGS. 2 and 3 and in particular also 4, the three are Main atomizing nozzles arranged around the central pilot nozzle or the mixing system in a base area 18 via two ring pipes connected, one of which is the oil supply line under constant pressure 14 and the other symbolizes an oil return line 15. The care of Atomizing nozzles by means of a differential pressure between a supply pressure and a return pressure is generally known. Through the ring line training This oil flow and oil return system ensures that all of the Main atomizer nozzles work practically under the same operating conditions, so that the oil atomization around the pilot flame is stable.

Figures 2 and 3 leave a special design of the ring disk bluff body 4 recognize that it surrounds the central atomizing nozzle 3 Internal border has an attachment 10, which serves to ensure that the outside 11 of the bluff body 4 of sprayed oil particles and thus impending Deposits remains free. The outer circumference of this annular bluff body 4 is provided with a rim 12, which is interrupted by bulges 13 which are directed radially inwards and the reception of the main atomizing nozzles serve. In this way, the central pilot atomizer nozzle 3 or Mixing system together with the annular disk bluff body 4 opposite the ring around these arranged main atomizing nozzles 2 axially to the flame tube 1 be moved. The edging 12 and in particular the tapered Section 9 of the flame tube 1 is used to guide the combustion air in the combustion chamber.

As FIGS. 2 and 3 and in particular also FIG. 4 show, the main atomizing nozzles are all around the central pilot atomizer nozzle in their Base area 18 connected by two parallel ring lines 14, 15, one of which 14 the oil supply and the other 15 forms the oil return. By these ring lines should have the same pressure behavior as possible - constant oil supply pressure and controlled oil return pressure depending on the desired mode of operation - be ensured. This is achieved with the appropriate dimensioning of the diameter of the lines and thus negligible flow resistance. FIG. 5 shows that the ring lines 14 and 15 are connected to the central oil supply, i.e. one that is decisive for all main atomizing nozzles Oil pressure source, on the one hand, and oil return, on the other hand, thereby achieved can be that the ring lines 14, 15 via T-shaped branches are "tapped".

Of particular importance is that in each of the main atomizing nozzles there is a valve device is provided, both the oil supply line and the oil return line separates from the nozzle mouth when burner operation is interrupted becomes. This is of particular importance at the end of the operating intervals because then there is a tendency to drain oil through the nozzle into the combustion chamber, which leads to contamination etc. The valve device is basically hydraulic, i.e. depending on that by controlling the flow the oil return line actuated in such a way that are under spring tension Valves react according to the pressure conditions that arise, i.e. in the event of an interruption of the burning operation by pressure build-up in the closing direction Valves, however, in operation through their opening. Because of the structural Ratios or the common model sizes of such valves, it may be advisable per line - two for both the oil flow and the oil return Provide valves connected in parallel; such a valve arrangement is shown in FIG. 3 provided. In any case, the valve devices are located between the the ring lines of the oil flow and the oil return base of the respective nozzle lance of the main atomizing nozzles 2 and their nozzle head, such as this can be seen in particular in FIG. 2. The valve device arranged in this way each nozzle lance is surrounded by a jacket.

In Figure 6 is a circuit diagram for an oil firing system with three around a pilot nozzle main atomizer nozzles arranged around each, each in the oil supply as in the oil return with two spring-loaded, hydraulically connected in parallel actuated valves is provided, two for each oil route for space or availability reasons.

Claims (18)

1. Oil burning installation for combustion with reduced nitric oxide emission, particularly for higher outputs, having at least one centrally arranged pilot atomiser jet and an associated ignition device as well as a fan for supplying air for combustion which is fed into the atomiser chamber downstream of the atomiser jet through a flame tube surrounding the jet, and having a plurality of other atomiser jets (2) which are arranged at uniform spacings around the central atomiser jet (3) disposed in the middle inside the flame tube (1) facing the atomiser chamber, characterised in that a ring target baffle member (4) is arranged between the central atomiser jet (3) or mixing system and the atomiser jets (2) surrounding the latter.
2. Oil burning installation according to claim 1, characterised in that the central atomiser jet (3) is that of a mixing system - atomiser jet, air suipply, flame stabiliser, ignition means - of conventional construction.
3. Oil burning installation according to claim 1 or 2, characterised in that the central atomiser jet (3) or mixing system with a ring target baffle member (4) is adjustable, particularly smoothly adjustable, by sliding along the longitudinal axis of the flame tube (1) into various positions.
4. Oil burning installation according to claim 3, characterised in that the baffle member (4) is disposed at a spacing in the transition to the central atomiser jet (3) and/or the surrounding atomiser jets (2), forming a gap, optionally of adjustable width.
5. Oil burning installation according to one of claims 1 to 4, characterised in that a considerably smaller proportion, e.g. 2 to 5 % of the oil throughput, is apportioned to the central atomiser jet (3).
6. Oil burning installation according to one of claims 1 to 5, characterised in that the atomiser jets (2) surrounding the central atomiser jet (3) have a narrower spraying angle than the central jet (3).
7. Oil burning installation according to claim 6, characterised in that the spraying angle of the surrounding atomiser jets (2) is about 30° to 45°.
8. Oil burning installation according to one of claims 1 to 7, characterised in that the air fed in for combustion is accelerated before entering the combustion chamber, i.e. as it flows out of the flame tube (12), e.g. by means of a conically tapering section (9).
9. Oil burning installation according to one of claims 1 to 8, characterised in that the ring target baffle member (4) has an attachment (10) on its outer side (11) facing the combustion chamber downstream, the attachment preferably being annular in construction and being disposed immediately adjacent to the annular inner edge of the ring target baffle member (4).
10. Oil burning installation according to claim 9, characterised in that the attachment (10) is integrally formed with the ring target baffle member (4).
11. Oil burning installation according to one of claims 1 to 10, characterised in that the ring target baffle member (4) has, on its annular outer edge, a knurled rim (12) projecting towards the combustion chamber downstream.
12. Oil burning installation according to one of claims 1 to 11, characterised in that the ring target baffle member (4) is provided with radially inwardly directed concavities (13) in the regions of the main atomiser jets (2) disposed in a ring around the central atomiser jet (3).
13. Oil burning installation according to one of claims 1 to 12, characterised in that the main atomiser jets (2) disposed in a ring around the central pilot atomiser jet (3) are each connected to an oil flow line and an oil backflow line (15) which are combined for all the main atomiser jets and connected to a common oil flow pressure source and to a common oil return.
14. Oil burning installation according to claim 13, characterised in that the oil flow and backflow lines (14, 15) attached to the main atomiser jets (2) are combined to form an annular line.
15. Oil burning installation according to claim 13 or 14, characterised in that each of the main atomiser jets (2) is provided with a hydraulically operated valve device in the oil flow and in the oil backflow in front of the jet.
16. Oil burning installation according to one of claims 14 and 15, characterised in that the oil flow line (14) is maintained under a constant oil pressure, whereas the oil backflow line is constructed to be controllable in terms of its outflow cross section in order to determine the quantity of oil supplied to the jet (2).
17. Oil burning installation according to claim 16, characterised in that the cross section of the oil backflow line is controlled centrally for all the main atomiser jets (2) arranged in a ring.
18. Oil burning installation according to one of claims 14 to 17, characterised in that the connection of the common oil flow pressure source to the oil flow annular line (14) for all the main atomiser jets (2) and the connection of the common oil return (15) to the associated annular line (14, 15) is connected between two adjacent main atomiser jets (2).

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