Patent ID: 12196416

FIG.1schematically shows a first embodiment of a burner10according to the invention, based on which the essential features of the invention are to be explained. However, the structure of the burner is not to be understood to be limiting, andFIG.1presents, in particular, only a schematic representation of the components and component dimensions. The same also applies to theFIGS.3and4that show further embodiments. Designs without a recuperator are also included.

The burner10is built into a furnace wall20and generates a flame56with which a heating space55is to be heated. In this embodiment, this is an open flame directly heating the heating space55. However, other embodiments with indirect heating are possible, in which a radiant tube is used.FIG.4shows such an embodiment.

The burner10has a mixing and combustion chamber54which is formed by an air feed30in the form of an air feed pipe. Combustion air is introduced (not shown) into this air feed30and flows into the mixing and combustion chamber54as a first partial air flow L1. An igniting and mixing device51connected to a fuel feed50through which fuel is fed to the igniting and mixing device51is secured within this air feed pipe30. The fuel is natural gas, for instance.

The igniting and mixing device51is configured in a suitable manner such that the fuel exits it in such a way that a stable flame56can be produced by igniting the mixture of the fuel flow B and the first partial air flow L1. In the schematic representation ofFIG.1, several fuel flows exit the igniting and mixing device51laterally at an angle for this purpose, but this is not to be understood as limiting. Any other suitable igniting and mixing device51may also be used.

In this embodiment, the burner further includes a recuperator40surrounding the air feed pipe30. Hot waste gases A1are drawn from the heating space55into the recuperator40, and a second partial air flow L2is heated in the counter flow. Optionally, the first partial air flow L1may also have been preheated in the recuperator40. The second preheated partial air flow L2is fed to the heating space55. This takes place in the region of an elongated flame56, this flame56having different flame zones. A first flame zone56ais located within the mixing and combustion chamber54, wherein the air feed pipe30forms a combustion chamber opening53through which the flame56extends from the igniting and mixing device51. A second flame zone56bis formed in the heating space55in front of the combustion chamber opening53. The second preheated partial air flow L2is fed to the flame zone56bfrom the recuperator40. At the same time, hot waste gases A2are suctioned from the heating space55into the flame zone56b.

In this burner configuration, the cross-section of the combustion chamber opening53relative to the burner output is in the range of between 1.5 mm2/kW and 5 mm2/kW, particularly preferably between 2.5 mm2/kW and 3.5 mm2/kW, for instance. This leads to high exit speeds at the combustion chamber opening53, which cause low NOx values in the flame zone56b. Together with the NOx formation of the flame56within the mixing and combustion chamber, low NOx values, on the whole, in the range of 5 to 100 mg/Nm3relative to 3% O2in dry waste gas can be obtained with direct firing. Moreover, the flame56is easily monitored, wherein an ionization bar52, with which the presence of the flame56can be detected, is provided in the mixing and combustion chamber54for this purpose.

In order to bring the burner into the operating state ofFIG.1, a heating-up phase with a certain control of the fuel flow B and the partial air flows L1, L2preferably takes place in order to be able to generate a stable flame56even in the case of a cold burner10. Control means60, whose configuration can be gathered by way of example fromFIG.2, are provided for this purpose. A burner10is equipped with control means60that enable the burner10to be supplied with fuel and air. Hereinafter, the fuel is simply referred to as gas. Starting from the burner10, a series of an adjusting valve61, a gas valve63, a compensator64and a spherical valve65for connection to a gas supply (not shown) is provided for the gas flow. Starting from the burner10, a series of an adjusting valve66, an air valve67, a compensator68and a gate valve69for connection to an air supply (not shown) is provided for the air flow. A balanced pressure regulator62with a gas valve and a further gas valve62ain a bypass are provided in a parallel connection between the adjusting valve61and the gas valve63. Between the adjusting valve66and the air valve67, an impulse line70branches off towards the balanced pressure regulator62with the gas valve.

With these control means the burner can be started up, at first in a cold state, with a fuel-to-air ratio of about 1:20, which enables the formation of a stable flame56. In the process, the full amount of air is already made available, whereas the fuel flow is at first reduced by means of the valve62a. Depending on the configuration of the burner10and the ambient conditions in a furnace, the fuel flow may be increased from a predetermined temperature, because the flame56now stabilizes even at a higher fuel percentage. From this temperature on, a switch is made for the fuel flow from the valve62ato the valve62, the fuel flow is thus increased, and a fuel-to-air ratio of approximately 1:10 is set in the process, for example.

FIG.3shows an alternative embodiment of the burner11according to the invention, in which, however, the recuperator40forms the combustion chamber opening53′. Thus, the second partial air flow L2′ preheated in the recuperator40′ leads into the mixing and combustion chamber54′ together with the first partial air flow L1. However, the flame56with the two flame zones56aand56bis formed in an analogous manner, and the other components also correspond to the embodiment ofFIG.1. Only the cross-section of the combustion chamber opening53′ relative to the burner output is in this case in the range of between 3 mm2/kW and 10 mm2/kW, particularly preferably between 3 mm2/kW and 6 mm2/kW.

FIG.4shows a burner12according to the embodiment ofFIG.3, in which a heating space55′ to be heated is disposed within a flame tube42. The flame tube42is surrounded by a radiant tube41which protrudes from the furnace wall20into a furnace interior space for indirect heating. The flame tube42within the radiant tube41permits the flow of hot waste gases A3back to the burner12, wherein they are either fed as waste gases A1to the recuperator, or suctioned in as waste gases A2by the flame zone56b. If an SER radiant tube is used, for example, NOx values in the range of 50 to 150 mg/Nm3relative to 3% O2in dry waste gas can be obtained with the invention.

LIST OF REFERENCE NUMERALS

10,11,12Burner20Furnace wall30,30′ Air feed, air feed pipe40,40′ Recuperator41Radiant tube42Flame tube50Fuel feed51Mixing and igniting device52Flame monitoring means, ionization bar53Burner chamber opening54,54′ Mixing and combustion chamber55,55′ Heating space56Flame56a,56bFlame zone60Control means61Adjusting valve gas62Balanced pressure regulator with gas valve V262aGas valve bypass63Gas valve V164Compensator65Spherical valve66Adjusting valve air67Air valve68Compensator69Gate valve70Impulse lineL1Partial air flowL2Partial air flow, preheatedB Fuel flowA1Waste gas flow in recuperatorA2Waste gas flow in flameA3Waste gas flow return feed