FR2715459A3 - Atmospheric burner. - Google Patents

Abstract

The invention relates to an atmospheric burner for the combustion of a pre-prepared rich mixture of air and fuel gas on the perforated surface of one or more burner tubes equipped with integrated Venturi tubes. Said burner has one or more openings (4) made in the wall of each Venturi tube (2) for the recirculation of a partial stream of the mixture from the annular space (3) between the burner tube (1) and the Venturi tube (2) in the mixture which passes through said Venturi tube (2). The burner according to the invention makes it possible to adjust, without an external adjustment device, the supply of primary air P by adjusting the recirculation of the gas mixture, in order to avoid a rising of the flame accompanied by an increased formation of CO. , as well as a support of the flame accompanied by an increased formation of NOx.

Description

Atmospheric burner The invention relates to an atmospheric burner for

  the combustion of a pre-prepared rich mixture of air and combustible gas at the perforated surface of one or more burner tubes equipped with venturi tubes integrated within said burner tubes. The problem of rich-atmosphere atmospheric burners is that, when low-calorific gases, ie low-Wobbe-index gases are used, the fl uids deviate from the burner tube. For a constant nozzle diameter and a constant gas pressure in the nozzle, it is in the presence of an excess of primary air which has the effect of lifting the flamne and, more particularly during the

  cold deboning, to increase the formation of CO.

  In the case of higher Wobbe gas, the opposite effect is obtained with a 2C-based gas. burner tube. This results in high temperatures on the surface of the burner tubes, accompanied by emissions

increased NOx.

  It has already been sought to regulate the supply of primary air as a function of the temperature of the flume or another suitable adjustment quantity. To do this, it is necessary to use a measuring device that sends the corresponding signals to a blower installed in the primary air stream, as for example described in DE-39 18 855 A1. This not only requires corresponding expenditures for regulation, but still does not solve the problem of safe operation and proper combustion during an accidental shutdown of the

  wind tunnel, which can not be excluded.

  The object of the invention is to vary the primary air supply of the mixture of combustible gas and air, intended for a rich mixture atmospheric burner, without particular regulation arrangement, so that one prevents a Flame heave and increased CO formation as well as flaume support with training

increased NOx.

  According to the invention, the atmospheric burner is characterized by one or more openings in the wall of each Venturi tube for the recirculation of a partial flow of the mixture of the annular space of the burner, which surrounds the Venturi tube, in the mixture that passes through said Venturi tube. The wall of each venturi tube has one or more openings. In this way, a partial stream of the gas mixture can be recycled from the space

  ring of the burner tube that surrounds the Venturi.

  Since the quantity of gas supplied is determined by the diameter of the gas nozzle and by the pressure at the gas nozzle, more or less significant recycling necessarily entails a modification of the sucked primary air. In order to counter burner tube flame lift, the primary air flow must be reduced. This is achieved by a greater recirculation of the gas mixture from the annular space of burner tubes into the Venturi tube. In order to act against the support of the flame on the burner tube, there is, instead, to increase the primary air flow. To do this, it reduces or completely interrupts the circulation. The recirculation openings are advantageously arranged in the intake zone of the Venturi tube so as to be able to act directly on admission to the primary air intake. The openings advantageously have a variable passage section. This makes it possible to vary the recirculation

  and, therefore, the primary air suction.

  Bimetallic valves permit the variation of the passage cross section of the openings in a continuous manner, as a function of the temperature of the burner tube; this also makes it possible to vary the recirculation and the primary air intake continuously. In the case of low burner tube temperatures, i.e., as the flame rises and upon increased CO formation, the openings are fully open. High recirculation reduces primary air suction. The temperature of the burner tube increases. As the temperature of the burner tubes increases, the openings are closed partially and then from a

  determined surface temperature, completely.

  Primary air intake increases and temperature

  burner tubes decreases again.

  It is therefore possible to adjust the temperature of the burner tubes accurately and appropriately by modifying the primary air suction, by means of a more or less substantial recirculation of the combustible gas-air mixture in the burner tube and the Venturi tube. This eliminates defects due to high temperatures or

too low.

  The drawings show an embodiment of the invention: - Figure 1 is a longitudinal section through a burner tube, which shows the principle of the invention; - Figure 2 is a partial longitudinal section through a burner tube; - Figure 3 is a section along the line A - A of Figure 2; and - Figure 4 is a plan view of the burner tube

of Figure 2.

  A Venturi tube 2 is integrated in a burner tube 1. The gas G is ejected out of a gas nozzle in the Venturi tube 2 and sucks in the necessary primary air P. After deflection at the end of the Venturi tube 2 , the combustible gas-air mixture enters the annular space 3 between the Venturi tube 2 and the burner tube 1. The gas mixture ignites at the

  perforated surface of the burner tubes and is burned.

  The suction of the primary air P is influenced by the fact that a partial stream of the mixture enters the Venturi tube 2 again through the openings 4. This recirculation acts on the quantity of primary air P sucked. Recirculation can be varied by means of temperature-adjustable bimetallic valves. These are fixed via a

  stirrup 6 at the inner wall of the burner tube 1.

  Said valves can completely release (FIG. 3, left) the opening 4 in the event of a high burner tube temperature, or completely close (FIG. 3, right) the opening 4, in the case of low burner tube temperatures. All intermediate steps

can also be set.

Claims (4)

  1. Atmospheric burner for the combustion of a rich mixture prepared beforehand of air and combustible gas, to the perforated surface of one or more burner tubes equipped with venturi tubes integrated inside said burner tubes, characterized by one or more openings (4) in the wall of each Venturi tube (2) for recirculating a partial flow of the mixture of the annular space (3) of the burner (1), which surrounds the Venturi tube ( 2) in the mixture passing through the said Venturi tube (2).   2. Atmospheric burner according to claim 1, characterized in that the openings (4) are arranged in the zone of the inlet of the Venturi tube.   (2) and have a variable passage section.   3. Atmospheric burner according to claims 1 and 2,   characterized in that the passage section of the openings (4) is continuously variable as a function of the temperature and with valves bimetallic.   4. Atmospheric burner according to claims 1 to 3,   characterized in that the passage section of the openings (4) is completely released at low temperatures of the burner tube and in that it is completely sealed off from a defined temperature of the surface of the burner tube (1 ).