GAS-FIRED BURNER, IN PARTICULAR FOR A DRYING DRUM OF AN ASPHALT MIXING PLANT

Abstract

A gas-fired burner for a drying drum of an asphalt mixing plant, such that the burner preferably has a central primary air duct (6), which opens into a combustion zone (4) via a swirl body (2). The burner has gas supply openings (9) in the area of the circumferential boundaries of the swirl body (2) for supplying fuel gas to the primary air for firing the burner. It has been shown that a stable and well-developed flame can be produced over a very large load range with such burners according to the disclosure.

Description

TECHNICAL FIELD

The present invention relates to a gas-fired burner, in particular for a drying drum of an asphalt mixing plant, and to the use of the burner for heating a drying drum of an asphalt mixing plant according to the preambles of the independent patent claims.

BACKGROUND

For the production of hot gas in industry, and in particular for drying drums in asphalt mixing plants, it is desirable to provide burners that produce a stable and well-developed flame over the widest possible load range. In this way, different applications can be covered with one and the same burner type, which reduces product diversity and simplifies component and spare parts management.

There is still a clear need for improvement in this respect in the gas-fired burners known today. In these burners, the fuel gas is introduced into the primary air upstream of the primary air swirl body and/or introduced into the combustion zone with a secondary air flow.

SUMMARY

The task here is to provide a gas-fired burner that produces a stable and well-developed flame over a very large load range.

This problem is solved by the burner according to claim 1.

According to this, the invention relates to a gas-fired burner, preferably for a drying drum of an asphalt mixing plant.

The burner preferably has a central primary air duct, which opens into a combustion zone via a swirler. The burner has gas supply openings in the area of the circumferential boundaries of the swirl body for supplying fuel gas to the primary air for firing the burner.

It has been shown that a stable and well-developed flame can be produced over a very large load range with such burners according to the invention.

In a first preferred embodiment of the burner according to the invention, the swirl body has gas supply openings in the area of its circumferential boundaries for supplying fuel gas into the primary air for firing the burner.

The gas supply openings are preferably designed as radial holes in the circumferential boundaries of the swirler. This has the advantage that the flow of primary air in the swirler is practically unaffected by the gas supply openings.

It is also preferred that the gas supply openings are arranged between the blades of the swirler, preferably in the area of the negative pressure sides of the swirler blades and preferably in the area of the outlet edges of the swirler blades. This favors a particularly good mixing of fuel gas and primary air.

In a second preferred embodiment of the burner according to the invention, the swirl body is surrounded on its outlet side by a plurality of gas supply openings for supplying fuel gas into the primary air for firing the burner.

The circumferential boundaries of the swirl body of the burner according to the invention are preferably formed as a cone that widens towards the combustion zone. Such designs have proven to be particularly suitable.

In a preferred embodiment, the burner comprises a secondary air duct arranged concentrically around the primary air duct, which opens into the combustion zone.

Particularly in the event that the ratio of primary air to secondary air is adjustable, which is preferred, this has the advantage that the flame pattern or flame shape can be optimally adjusted for each load range.

It has proven to be particularly advantageous if, in the area in which the secondary air duct opens into the combustion zone, an edge projecting radially outwards from an inner boundary wall of the secondary air duct is arranged, which forms a “tripping edge” for the secondary air flow when entering the combustion zone, for the turbulence of the secondary air.

In a further preferred embodiment of the invention, the burner comprises a fuel gas supply arranged concentrically around the primary air guide, which flows into the gas supply openings of the swirl body and which is advantageously arranged concentrically between the primary air guide and the secondary air guide. Such designs of the burner according to the invention allow a very uniform introduction of the fuel gas and the primary and secondary air into the combustion zone.

In yet another preferred embodiment, the burner according to the invention comprises a feed for liquid fuel arranged in the center of the primary air duct, which opens into the combustion zone via a nozzle, for feeding atomized liquid fuel into the primary air emerging from the swirl body. Such burners can be used in a variety of ways as combination burners.

In the burner according to the invention, the combustion zone is advantageously surrounded by a flame tube that widens conically in the direction of the flame. Such designs of the combustion zone have proven to be particularly suitable.

Furthermore, the burner according to the invention is preferably designed in such a way that the entire quantity of fuel gas used to fire the burner can be supplied, preferably exclusively, via the appropriate gas supply openings.

BRIEF DESCRIPTION OF THE DRAWINGS

Further preferred embodiments of the invention are apparent from the dependent claims and from the now following description with reference to the figures. Therein show:

FIG. 1 a longitudinal section through a burner according to the invention;

FIG. 2 a perspective section of the front part of the burner according to FIG. 1; and

FIG. 3 a representation like FIG. 2 of a variant of the burner.

DETAILED DESCRIPTION

FIGS. 1 and 2 show sectional views of a first combination burner according to the invention for the optional combustion of fuel gas or liquid fuel for heating a drying drum of an asphalt mixing plant. FIG. 1 shows a vertical longitudinal section through the entire burner and FIG. 2 shows a perspective vertical section through the front part of the burner.

As can be seen, the burner has a central burner lance 1 for the liquid fuel, which opens into the combustion zone 4 of the burner in the center of a swirl body 2 for primary air via a fuel nozzle 3, for feeding atomized liquid fuel into the primary air emerging from the swirl body 2. The burner lance 1 is concentrically surrounded by a primary air pipe 5 which, together with the outer boundaries of the burner lance 1, forms a central primary air supply 6 with an essentially circular cross-section, which opens into the combustion zone 4 via the swirl body 2. A pilot burner 17 is arranged inside the primary air supply 6, which generates a pilot flame to ignite the burner.

In the front area of the burner, the primary air pipe 5 is concentrically surrounded by a fuel gas pipe 7 which, together with the outer boundaries of the primary air pipe 5, forms a fuel gas supply 8 arranged concentrically around the primary air guide 6, which is supplied with fuel gas via a radial gas supply line 18 and opens into gas supply openings 9 in the circumferential boundaries of the swirl body 2. The burner is designed in such a way that the entire quantity of fuel gas used to fire the burner is fed into the primary air exclusively via the gas supply openings.

The primary air tube 5 and the fuel gas tube 7 are concentrically surrounded by a secondary air tube 10, which forms the housing of the burner and, together with the outer boundaries of the primary air tube 5 and the fuel gas tube 7, forms a secondary air duct 11 with an essentially circular cross-section, which opens into the combustion zone 4.

The combustion zone 4 is surrounded by a conical flame tube 13.

As can be seen in FIG. 2, the gas supply openings 9 are designed as radial holes in the circumferential boundaries of the swirler 2 and arranged between the vanes of the swirler 2, in each case in the area of the vacuum sides of the swirler vanes and in the area of their outlet edges.

The circumferential boundaries of the swirler 2, which form the gas supply openings 9, are designed as a cone that widens towards the combustion zone.

As can also be seen, in the area where the secondary air duct 11 opens into the combustion zone 4, there is an edge 12 projecting radially outwards into the secondary air flow from the fuel gas pipe 7, which forms the inner boundary wall of the secondary air duct 11, which causes the flow cross-section of the secondary air at the outlet area from the secondary air duct to be abruptly reduced.

At its end facing away from the combustion zone 4, the burner is connected to an air supply line 14, via which it receives the combustion air from an associated fan (not shown). The total combustion air flow provided by the air supply line 14 is divided into four partial combustion air flows 15a, 15b, 15c, 15d in the inlet area of the burner by means of partitions, of which the two front air flows 15a, 15b flow into the secondary air duct 11 and the two rear air flows 15c, 15d flow into the primary air duct 6. The four partial combustion air flows 15a, 15b, 15c, 15d can be adjusted individually or in pairs by means of associated throttle valves 16 (for the sake of clarity, only one throttle valve is provided with the reference number 16), so that the ratio of primary air and secondary air can be adjusted.

FIG. 3 shows an illustration like FIG. 2 of a variant of the burner according to the invention described above.

This variant differs from the burner described above only in that the gas supply openings 9 are not arranged in the circumferential boundaries of the swirl body 2. Here, the swirl body 2 is surrounded on its outlet side by a large number of gas supply openings 9, which are supplied with fuel gas from the fuel gas supply 8. Otherwise, the structure of this second burner according to the invention is identical to that of the first burner according to the invention, which is why reference can be made to the preceding description of FIGS. 1 and 2.

While preferred embodiments of the invention are described in the present application, it should be clearly noted that the invention is not limited thereto and may also be practiced in other ways within the scope of the following claims.

Claims

1. A gas-fired burner, in particular for a drying drum of an asphalt mixing plant, having a primary air duct, in particular a central primary air duct, which flows via a swirl body into a combustion zone, the burner having gas supply openings in the region of the circumferential boundaries of the swirl body for supplying fuel gas into the primary air for firing the burner.

2. The burner according to claim 1, wherein the swirl body has gas supply openings in its circumferential boundaries for supplying fuel gas into the primary air for firing the burner.

3. The burner according to claim 2, wherein the gas supply openings are formed as radial bores in the circumferential boundaries of the swirl body, in particular with regular spacings in the circumferential direction.

4. The burner according to claim 1, wherein the gas supply openings are arranged between the vanes of the swirler, in particular between all the vanes.

5. The burner according to claim 4, wherein the gas supply openings are each arranged in the region of the lower pressure sides of the swirl body vanes.

6. The burner according to claim 4, wherein the gas supply openings are each arranged in the region of the outlet edges of the swirl body vanes.

7. The burner according to claim 1, wherein the swirl body is surrounded on its outlet side by a plurality of gas supply openings for supplying fuel gas for firing the burner into the primary air.

8. The burner according to claim 1, wherein the circumferential boundaries of the swirl body are designed as a cone widening towards the combustion zone.

9. The burner according to claim 1, further comprising a secondary air duct arranged concentrically around the primary air duct, which opens into the combustion zone.

10. The burner according to claim 7, wherein in the region in which the secondary air duct opens into the combustion zone, an edge projecting radially outwards into the secondary air flow from an inner boundary wall of the secondary air duct is arranged.

11. The burner according to claim 7, wherein the burner is designed in such a way that the ratio of primary air and secondary air is adjustable, in particular individually and differently for variable load stages.

12. The burner according to claim 1, comprising a fuel gas supply which is arranged concentrically around the primary air guide and opens into the gas supply openings.

13. The burner according to claim 10, wherein the combustion gas supply is arranged concentrically between the primary air duct and the secondary air duct.

14. The burner according to claim 1, further comprising a supply for liquid fuel, which is arranged in the center of the primary air duct and opens into the combustion zone via a nozzle, for supplying atomized liquid fuel into the primary air emerging from the swirl body.

15. The burner according to claim 1, wherein the combustion zone is surrounded by a conical flame tube

16. The burner according to claim 1, wherein the burner is designed such that the entire quantity of fuel gas used for firing the burner can be supplied in particular exclusively via the gas supply openings.

17. Use of the burner according to claim 1 for heating a drying drum of an asphalt mixing plant.