EP2143998B1 - Burner unit for pulverulent fuel - Google Patents

Description

The invention relates to a burner unit for dusty solid fuel having a first tube for conveying the solid fuel in a first conveying direction, wherein a deflecting body for deflecting the emerging from the first tube solid fuel jet is arranged in extension of the first tube. Furthermore, the invention relates to a burner assembly for a furnace, in particular for a ring-shaft furnace for burning limestone.

Burner units of the type mentioned are known from the prior art. They are preferably used in shaft furnace systems, for example in annular shaft furnaces for burning limestone. Here, the particular procedural challenge is to achieve the fullest possible implementation of the dusty fuel - this can be, for example, petroleum coke dust - in hot gases in order to use the energy content of the dusty solid fuel as completely as possible.

From the prior art is also known, the pneumatically, ie in an air flow, transported through the first tube dusty solid fuel deflected by an extension of the tube arranged deflecting in a substantially opposite direction to the burner inlet. The deflected fuel stream then mixes with another oncoming air stream, so that an approximately complete mixing of rod-shaped solid fuel and combustion air and thus a complete combustion of the fuel is ensured. Such with a deflecting body in extension of the transport tube for the fuel-air mixture is for example from the DE 10 2006 035 174 A1and the FR 2 842 584 A1 known. In the burners described here, a mixture of petroleum coke dust and primary air is deflected after exiting the burner lance at a cross-sectionally C-shaped flow deflector and mixed with tangentially injected into the burner chamber secondary air, wherein the thereby adjusting mixture of tangential blowing verdrallter secondary air, petcoke dust and primary air is transported in the direction of the exit of the combustion chamber, whereby it is completely converted into hot gases.

From practice, a further burner construction is known in which the first tube for conveying the solid fuel is surrounded by a second coaxially arranged tube through which secondary air is transported parallel to the fuel, which is intense when hitting the deflected by the deflecting solid fuel jet with this mixed. In particular, in this burner design has been shown in practice that the redirected from the deflecting solid fuel jet often strikes back into the surrounding pipe and there leads to deposits that lead in the long term to a closure of this tube.

The present invention is therefore based on the object to provide a burner unit for dusty solid fuel of the type mentioned, the complete implementation of the dusty fuel in hot gases ensures. Furthermore, the burner unit should be able to be operated with reduced maintenance costs, for example, by constructively avoiding the known from the prior art problem of buildup of the deflected dust-like fuel.

The task is solved with a burner unit for dust-like solid fuel according to the preamble of claim 1, characterized in that the first tube surrounding the first tube baffle body, which deflects the deflected by the deflecting solid fuel jet substantially in the first conveying direction again.

The particular advantage of the burner unit according to the invention is that on the one hand the principle of the deflection of the fuel jet can be maintained, which has proven to be extremely effective with respect to an intensive mixing of the dust-like fuel with the combustion air. On the other hand, it is ensured by the use of the impact tube surrounding the first tube, that the fuel jet undergoes the desired renewed change of direction, but without the risk that parts of the fuel jet strikes back into the burner unit and settle there, which is associated with the known problem.

The baffle body can assume all geometric shapes which ensure that the solid fuel jet initially deflected by the deflecting body is deflected again in the first conveying direction, without the overall aerodynamics of the construction being changed significantly overall, particularly when installed in a corresponding burner housing.

In particular, when using a first tube with a circular cross-section of the baffle body is preferably annular.

According to a further advantageous embodiment of the invention, the first tube is coaxially surrounded by at least one second tube to form an annular channel for conveying combustion air, wherein the free end of the second tube is set back axially relative to the free end of the first tube, wherein the impact body to is arranged opposite the free end of the second tube projecting pipe section of the first tube. This arrangement creates a combustion air cone surrounding the fuel jet emerging from the first tube, which on the one hand initially permits spatial separation of the solid fuel jet from the lining surrounding the combustion chamber in which the burner unit is arranged, wherein in the further course intensive mixing takes place second tube exiting combustion air with the solid fuel jet, which is a prerequisite for a complete implementation of the dusty solid fuel in hot gases takes place.

Characterized in that the free end of the second tube is set back axially relative to the free end of the first tube and the baffle body is disposed on the opposite the free end of the second tube projecting pipe section of the first tube, in particular the repelling of the emerging from the first tube solid fuel in the second tube, which would lead to the known formation of deposits, effectively avoided.

The combustion air can be introduced, for example, via a substantially radial feed line into the second tube.

According to a further advantageous embodiment of the invention, a combustion chamber is provided in the flow direction in front of the second tube, in which a gas-operated pilot burner is arranged. By means of this pilot burner, additional thermal energy, which is necessary to enable ignition of the pulverulent solid fuel entering a combustion chamber, can be provided during start-up of the furnace-fired furnace. The combustion chamber, in which the pilot burner is arranged, this can be fed through a line opening into the combustion chamber primary combustion air, wherein in the conduit a throttle valve is arranged to the combustion of the gas also supplied, for example propane, and thus indirectly the temperature of dust-like solid fuel to be able to control exactly.

If a stable burner flame has formed in which the dusty solid fuel is completely converted into hot gases, the pilot burner can be switched off since the flame itself as well as the heat radiation of the refractory furnace lining provide enough thermal energy for stable burner operation.

The exhaust gases of the pilot burner are preferably derived from the second tube surrounding the first tube from the combustion chamber. Accordingly, the combustion chamber is connected according to a further embodiment of the invention with the second tube, so that the burner gases into the second tube can be initiated and exit from this together with the combustion air in a combustion chamber.

Another aspect of the present invention relates to a burner assembly for an oven, in particular for a ring-shaft furnace for burning limestone, with a combustion chamber defining a burner housing and a burner unit according to one of claims 1 to 7.

For the advantages of such a burner arrangement, the above applies accordingly. In particular, a powerful and efficiently operating burner assembly is provided which ensures trouble-free continuous operation in an oven, in particular in a ring-shaft furnace for burning limestone.

The combustion chamber of the burner assembly can assume a wide variety of geometries. However, it is preferably substantially cylindrical, wherein the burner unit is arranged substantially coaxially in the combustion chamber.

According to a further embodiment of the invention, the burner housing comprises a screw housing into which a combustion air duct opens tangentially. This in the flow direction of the dust-like solid fuel and the combustion air preferably arranged in front of the combustion chamber screw housing causes the combustion air introduced there is twisted and enters the combustion chamber in this form, where it intensely mixed due to their spin with the dusty solid fuel and any existing combustion air , In this context can also be provided that the screw housing is arranged back in the propagation direction of the burner flame relative to the free end of the first tube of the burner unit.

Fig. 1

eine aus dem Stand der Technik bekannte Brenneranordnung,

Fig. 2

eine Brenneranordnung für einen Ringschachtofen zum Brennen von Kalkstein und

Fig. 3

einen Ringschachtofen zum Brennen von Kalkstein mit Brenneranordnungen gemäß Fig. 2.

In the following the invention will be explained in more detail with reference to an embodiment. Show it:

Fig. 1

a burner arrangement known from the prior art,

Fig. 2

a burner assembly for a ring shaft furnace for burning limestone and

Fig. 3

a ring shaft furnace for burning limestone with burner arrangements according to Fig. 2 ,

In Fig. 1 a burner arrangement known from the prior art is shown. The burner assembly comprises a burner housing 100 with a rotationally symmetrical combustion chamber 200, which initially widens conically in the transport direction of the fuel or in the direction of propagation of the flame and then tapers conically in the form of a nozzle up to the burner exit. By a coaxial with the combustion chamber 200 arranged central tube 300 dust-like solid fuel is pneumatically conveyed and exits at the free end 300 a of the central tube 300 from this. Subsequently, the dust-like solid fuel strikes a flow deflector 400, through which the fuel jet is deflected substantially 180 ° from its original flow direction.

The secondary combustion air blown into the combustion space 200 at its closed end via a feed 500 arranged tangentially to the combustion chamber 200 is twisted in the combustion chamber 200, as indicated by the spiral line S. The twisted secondary combustion air then mixes with the recirculated fuel jet, with a targeted mixing takes place, so that a strong air-enriched amount of dust flows through the burner chamber 200 in the direction of its output and passes into the burner flame B. In addition to the secondary combustion air 600 tertiary combustion air is still stepped through several tangentially arranged nozzles introduced into the combustion chamber 200 to support the swirl flow in the combustion chamber 200.

In this known from the prior art construction, it often happens that the deflected by the flow deflector 400 fuel jet is not completely detected by the twisted secondary air flow and directed back towards the burner output, but leads to deposits in the combustion chamber 200, resulting in regular cleaning requires.

In Fig. 2 In contrast, an improved burner arrangement X is shown, which can be used, for example, in a ring-shaft furnace for burning limestone. The burner assembly X in turn comprises a housing 1 which encloses a presently cylindrical combustion chamber 2. In the cylindrical combustion chamber 2 extends substantially coaxially a first tube 3 for the promotion of a dust-like solid fuel, in this case petcoke dust. In extension of the first tube 3 is a deflecting 4 for deflecting the Arranged from the first tube 3 solid fuel jet, which in the present case has approximately the shape of a mirrored "E". Other geometrical shapes of the deflecting body are also conceivable, for example those of a mirrored "C" or the like.

The first tube 3 is in the burner assembly of Fig. 2 Coaxially surrounded by a second tube 6 over a certain length. By means of the ring channel 6a forming in this case, combustion air, so-called secondary air, can be conducted, which is supplied to the pipe via a radial supply line 6b.

Again Fig. 2 can be seen, the free end of the second tube 6 is set back relative to the free end of the first tube 3. At the corresponding projecting portion of the first tube 3, a present annular baffle body 7 is arranged in relative proximity to the deflection body 4, whose function will be explained in more detail below.

The burner assembly X of Fig. 2 further comprises a arranged in the flow direction of the fuel in front of the burner housing combustion chamber 8, in which a pilot burner 8a is arranged for gaseous fuel, such as propane gas. Accordingly, supply lines 8b are provided for the supply of gaseous fuel as well as a combustion air supply line 8c, in which the volume flow can be adjusted by means of a throttle flap 8c *.

The combustion chamber 8 is connected to the second tube 6 at the end such that the exhaust gases of the pilot burner 8a can flow directly into the annular channel of the second tube and so with the introduced via the feed line 6b in the second pipe combustion air flow into the combustion chamber 2.

At the rear end of the burner housing 1 seen in the transport direction of the dust-like solid fuel, a screw housing 5 is arranged, via which a mixture of combustion air and recirculating exhaust gas can be introduced tangentially with a very high volume flow.

The operation of the burner assembly X according to Fig. 2 is the following:

In the first tube 3, a mixture of the dust-like solid fuel and a transport air flow is introduced via its rear end and conveyed through the first tube 3 into the combustion chamber 2. The dust-like solid fuel then exits at the free end of the tube 3 and bounces against the deflection body 4, whereby it is deflected by approximately 180 ° in the opposite direction. The thus deflected fuel jet is now on the baffle 7, which is arranged on the opposite to the second pipe 6 projecting pipe section of the first tube 3, again deflected, so that it flows substantially back in the original conveying direction, but it has a highly divergent flow profile ,

The combustion air flow introduced via the radial supply line 6b into the annular channel 6a of the second tube 6 enters the combustion chamber 2 in a conically divergent flow initially enclosing the twice deflected solid fuel jet. In the start-up operation of the furnace, the gas ignition burner 8a arranged in the combustion chamber 8 becomes additional operated to provide the necessary for the ignition of the solid fuel thermal energy. The hot gases of the pilot burner 8a then flow together with the combustion air into the combustion chamber 2. In stationary operation of the burner assembly X, the pilot burner 8a can be switched off again.

The volume flow of the combustion air emerging from the second tube is only a fraction of the injection air flowing in tangentially via the screw housing 5, which consists of a mixture of preheated blowing air and recirculating kiln exhaust gas, as in connection with FIG Fig. 3 will be explained in more detail. As a result of the geometric configuration of the screw housing 5, the injection air enters the combustion chamber 2 in a highly twisted manner, as indicated by the spiral line D. In the combustion chamber 2, the twisted injection air, the exiting from the second tube 6 (secondary) combustion air and emerging from the first tube 3 dusty solid fuel after its double deflection to the open end of the combustion chamber 2, not shown, intensively mixed, with the dust-shaped Solid fuel is ignited and completely converted to hot gases.

The integration of such a burner assembly in a ring shaft furnace for burning limestone is in the Fig. 3 shown. The ring shaft furnace of Fig. 3 is constructed according to the type "Beckenbach" and shall be briefly described below for the purpose of understanding the principle.

The oven has a cylindrical outer shell, which is divided into a top shaft 20 and a main shaft 10. The inner shaft wall of the main shaft 10 is formed by a lower inner cylinder 30, the upper shaft 20 by an upper inner cylinder 40. In the combustion zone BZ are a plurality of burner assemblies X associated with Fig. 2 described type arranged in a lower burner level, one of which is visible in the present sectional drawing.

During operation of the annular shaft furnace, the granular material G to be fired is introduced into the annular shaft furnace and, due to gravity, initially moves through the preheating zone VZ, where it is heated in countercurrent by exhaust gases rising from the combustion zone BZ. As soon as the firing material G has passed the upper inner cylinder 40, it enters the combustion zone BZ and is first burned there in countercurrent and below the lower burner plane in direct current. Subsequently, the now fired Good G * enters the cooling zone KZ, where it is again cooled in countercurrent. Finally, the good G * is discharged from the ring shaft furnace.

As in Fig. 3 recognizable flows in the preheating zone VZ of the upper shaft 20, a partial exhaust gas flow into the upper inner cylinder 40 and from there into a recuperator unit 70, where it heats a motive air flow. This feeds to the burner assemblies X connected, so-called injectors 50 together with a partial exhaust gas stream, which in turn flows through the lower inner cylinder 30 and one in the injectors 50. As a result, the required high volume flows and temperatures for the supply of the burner assemblies X are achieved.

Claims (11)

1. Combustion unit for powdery solid fuel with a first tube (3) for conveying the solid fuel in a first direction of conveyance, wherein a deflecting body (4) for deflecting the jet of solid fuel exiting out of the first tube (3) is arranged in the extension of the first tube (3), characterised in that the first tube (3) comprises an impact body (7) surrounding the first tube, which impact body (7) again deflects the jet of solid fuel deflected by the deflecting body (4) substantially in the first direction of conveyance.
2. Combustion unit according to Claim 1, characterised in that the impact body (7) is formed in the shape of a ring.
3. Combustion unit according to Claim 1 or 2, characterised in that the first tube (3) is coaxially surrounded by at least one second tube (6) to form an annular channel (6a) for conveying combustion air, wherein the free end of the second tube (6) is set back axially compared to the free end of the first tube (3) wherein the impact body (7) is arranged on the tube section of the first tube (3) projecting opposite the free end of the second tube (6).
4. Combustion unit according to Claim 3, characterised in that the second tube (6) comprises a substantially radial supply line (6b) for introducing the combustion air into the second tube (6).
5. Combustion unit according to Claim 3 or 4, characterised in that a combustion chamber (8) is provided before the second tube (6) in the direction of flow, in which combustion chamber (8) a gaspowered pilot burner (8a) is arranged.
6. Combustion unit according to Claim 5, characterised in that a pipe (8c) for combustion air for the pilot burner (8a) opens into the combustion chamber, wherein a butterfly valve (8c *) is arranged inside the pipe (8c).
7. Combustion unit according to Claim 5 or 6, characterised in that the combustion chamber (8) is connected to the second tube (6) for introducing the burner exhaust gases into the second tube (6).
8. Burner assembly (X) for a kiln, in particular for an annual shaft kiln for burning limestone, having a burner housing (1) defining a combustion space (2) and a combustion unit according to any one of Claims 1 to 7.
9. Burner assembly according to Claim 8, characterised in that the combustion space (2) is substantially cylindrical, wherein the combustion unit is arranged substantially coaxially in the combustion space (2).
10. Burner assembly according to Claim 8 or 9, characterised in that the burner housing (1) comprises a worm casing (5) into which a combustion air line tangentially opens.
11. Burner assembly according to Claim 10, characterised in that the worm casing (5) is arranged before the combustion space (2)in the direction of flow of the powdery solid fuel.

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