EP0913631A2 - 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 (NOx) emissions, especially for higher performances, with at least a centrally arranged 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.

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 equipment expenditure.

The invention has for its object an oil combustion system of the beginning 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 around the centrally arranged central atomizer nozzle around inside the flame tube the atomization chamber facing a number of further atomizer nozzles evenly spaced is arranged.

By arranging several atomizing nozzles around the central atomizing nozzle around it one reaches a core flame and an enveloping 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 at an overall reduced average temperature level in the flame, which in turn causes a good burnout in the entire flame area is achieved. The core flame is preferred through a central atomizing nozzle produced in combination with a mixing system of conventional design, which can be yellow at the core. In the area of the flame one reaches bluish Burnout and overall a slim flame shape without clouding of Fuel.

In a preferred embodiment, between the central atomizing nozzle or the mixing system and the atomizing nozzles surrounding it 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.

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 positions - in particular infinitely adjustable. This can adjust the air supply adjustment serve the amount of fuel when the load changes, otherwise can 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 °. Because of this narrow spray angle it is achieved that the combustion chamber wall is not wetted with oil. About that In addition, coking in the area of the flame tube mouth and the Avoid adjacent areas on the outer edges of the bluff body.

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 an in this direction projecting essay, preferably continuously is ring-shaped and in particular the annular inner edge of the annular disk bluff body arranged immediately afterwards is. The attachment can be formed in one piece on this bluff body ring disk be.

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 around the central pilot atomizer nozzle Main atomizer nozzles with radially inward bulges be provided.

The annular disk bluff body or physically considered the bluff body annular 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 caking 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 ring-shaped side atomizer nozzles. 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 intended 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 in operation, a constant as possible certain amount of fuel is supplied under predetermined pressure. On the In this respect, 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.

sternförmig" an Ölvorlauf- und Ölrücklaufleitung im Sinne einer Ölvorlaufdruckquelle und einer gemeinsamen Ölrückführung, die für alle Haupt-Zerstäuberdüsen speisend und abführend vorgesehen sind, anschließen. In bevorzugter Ausführung werden die Haupt-Zerstäuberdüsen hinsichtlich sowohl ihres Ölvorlaufes als auch ihres Ölrücklaufes in Form einer Ringleitung miteinander verbunden, d.h. sämtliche Haupt-Zerstäuberdüsen sind in ihrem Sockelbereich an diese Ringleitung angeschlossen, die ihrerseits zentral mit der Ölvorlaufdruckquelle und dem Ölrücklauf in Verbindung steht, vorzugsweise dergestalt, daß diese Ringleitungen zwischen zwei benachbarten Haupt-Zerstäuberdüsen eine Einspeisungs- bzw. Abführstelle für eine zentrale Ölvorlaufdruckleitung und eine Ölrücklaufleitung aufweisen.Basically, the main atomizer nozzles arranged in a ring around the central pilot atomizer nozzle can be used

Star-shaped "to the oil supply and oil return line in the sense of an oil supply pressure source and a common oil return, which are provided for all main atomizing nozzles feeding and discharging. In a preferred embodiment, the main atomizing nozzles are in the form of a ring line with regard to both their oil flow and their oil return connected to each other, i.e. all main atomizer nozzles are connected in their base area to this ring line, which in turn is centrally connected to the oil supply pressure source and the oil return line, preferably in such a way that these ring lines between two adjacent main atomizer nozzles provide a feed or discharge point for one have a central oil supply pressure line and an oil return line.

The prescribed central supply of the main atomizer nozzles arranged in a ring secures you - ultimately also by sufficient cross-section of the feed and 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 atomizing nozzles via a Loop. In a particularly preferred embodiment is therefore both in the course of Oil flow as well as in the course of the oil return of each main atomizer nozzle one valve each is provided which is actuated hydraulically. These valves work therefore under the influence of the oil pressure depending on the force assigned to springs. If, therefore, the cross section of the oil return line in the operating phases causes an excess pressure for the spraying of oil through the nozzle 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 supply line and from the oil return line Oil can drip through the nozzle into the combustion chamber.

Preferred embodiments of the invention result from the subclaims, in particular in relation 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, is in its tube axis - i.e. in the middle - a central atomizer nozzle 3 as part of a mixing system of the usual type arranged. Around this central atomizing nozzle 3 - pilot atomizing nozzle - there are several more on a concentric circle with radius r Atomizer nozzles 2 - main atomizer nozzles - arranged. The central nozzle 3 is used to supply fuel to a pilot flame, and concentrically the main part is supplied around these atomizing nozzles 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 direction of flow, 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 the 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 cross sections fed to the exit plane of the flame tube 1. These ring section cross sections result from the respective flame tube inner diameter, 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 Another disc damper is integrated coaxially into the annular disc bluff body 6. Both bluff bodies are through an annular gap for combustion air passage Cut. The central volume bluff body has adjustable combustion air inlet cross sections in a prechamber 7. The end of the prechamber 7, in Seen flow direction, is with a bluff body 8 with radial flushing slots, a center hole and one on the outside diameter, in the direction of flow standing collar, 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 8 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. Means 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 effects of heat in the combustion chamber.

Ignition of fuel from atomizers of a partial circle will Initially prevented to intensely recirculate 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. (Burning 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, focused 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 to 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 around the central pilot atomizing nozzle are connected to one another in their base region 18 by two parallel ring lines 14, 15, one 14 of which supplies the oil supply and the other 15 the oil return forms. These ring lines are intended to ensure that the pressure behavior is as equal as possible - constant oil supply pressure and controlled oil return pressure depending on the desired mode of operation. This can be achieved by appropriately dimensioning the diameter of the lines and thus negligible flow resistances. FIG. 5 shows that the connection of the ring lines 14 and 15 to the central oil supply, that is to say an oil pressure source relevant for all main atomizing nozzles on the one hand and oil return on the other hand, can be achieved in that the ring lines 14, 15 via T-shaped branch points are tapped ".

Of particular importance is that a valve device is provided in each of the main atomizing nozzles 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 to be set, i.e. in the event of 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 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 path for space or availability reasons.

Claims (19)

Oil combustion system for combustion with reduced nitrogen oxide emissions, in particular for higher outputs, with at least one centrally arranged atomizer nozzle and associated ignition device and a blower for the supply of combustion air which is fed to the atomization chamber downstream behind the nozzle through a flame tube surrounding the atomizer nozzle,
characterized,
that a number of further atomizing nozzles (2) are arranged evenly spaced around the centrally arranged central atomizing nozzle (3) within the flame tube (1) facing the atomizing space. Oil combustion plants according to claim 1,
characterized,
that the central atomizer nozzle (3) is that of a mixing system - atomizer nozzle, air supply, flame stabilizer, ignition device - of a conventional design. Oil burner system according to claim 1 or 2,
characterized,
that an annular disk baffle (4) is arranged between the central atomizing nozzle (3) or mixing system and the surrounding atomizing nozzles (2). Oil burner system according to claim 1 or 2,
characterized,
that the central atomizer nozzle (3) or mixing system with annular disk bluff body (4) in the longitudinal axis of the flame tube (1) in various displacement positions - in particular continuously - is adjustable. Oil burner system according to claim 4,
characterized,
that the bluff body (4) in the transition to the central atomizer nozzle (3) and / or the surrounding atomizer nozzles (2) is spaced apart with a gap formation - optionally adjustable gap width. Oil burner system according to one of claims 1 to 5,
characterized,
that the considerably lower proportion, for example 2-5% of the oil throughput on the central atomizing nozzle (3) is eliminated. Oil firing system according to one of claims 1 to 6,
characterized,
that the atomizing nozzles (2) surrounding the central atomizing nozzle (3) have a narrower spray angle than that of the central nozzle (3). Oil burner system according to claim 7,
characterized,
that the spray angle of the surrounding atomizing nozzles (2) is approximately 30 ° to 45 °. Oil firing system according to one of claims 1 to 8,
characterized,
that the supplied combustion air is accelerated before it enters the combustion chamber, ie when it flows out of the flame tube (12), for example through a conically tapered section (9). Oil firing system according to one of claims 1 to 9,
characterized,
that the annular disk bluff body (4) on its downstream side facing the combustion chamber (11) has a projecting in this direction (10), which is preferably ring-shaped and in particular is arranged immediately after the annular inner edge of the bluff body ring disk (4). Oil burner system according to claim 10,
characterized,
that the attachment (10) is integrally formed with the bluff ring (4). Oil firing system according to one of claims 1 to 11,
characterized,
that the bluff body washer (4) has on its ring-shaped outer edge an edge flange (12) projecting downstream of the combustion chamber. Oil firing system according to one of claims 1 to 12,
characterized,
that the bluff body washer (4) is provided with radially inwardly directed bulges (13) in the areas of the respective main atomizer nozzles (2) arranged in a ring around the central atomizer nozzle (3). Oil firing system according to one of claims 1 to 13,
characterized,
that the main atomizer nozzles (2) arranged in a ring around the central pilot atomizer nozzle (3) are each connected to an oil feed line and an oil return line (15), which are combined for all main atomizer nozzles and connected to a common oil feed pressure source and to a common oil return are. Oil burner system according to claim 14,
characterized,
that the oil supply and return lines (14, 15) connected to the main atomizing nozzles (2) are each combined to form a ring line. Oil burner system according to claim 14 or 15,
characterized,
that each of the main atomizing nozzles (2) is provided with a hydraulically actuated valve device both in the oil flow and in the oil return in front of the nozzle. Oil firing system according to one of claims 14 to 16,
characterized,
that the oil supply line (14) is kept at a constant oil pressure, while the oil return line is designed to be controllable with regard to its discharge cross-section for determining the amount of oil supplied to the nozzle (2). Oil burner system according to claim 17,
characterized,
that the cross-sectional control of the oil return line takes place centrally for all annularly arranged main atomizing nozzles (2). Oil firing system according to one of claims 14 to 18,
characterized,
that the connection of the common oil flow pressure source to the oil flow ring line (14) for all main atomizing nozzles (2) and the connection of the common oil return (15) to the associated ring line (14, 15) between two adjacent main atomizing nozzles (2) is.

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