EP0628768B1 - Rotary furnace burner - Google Patents

Description

The invention relates to a burner for a rotary kiln, with an annularly arranged channel for the pneumatic transport of fine-grained solid fuel (coal dust) and with at least one concentrically arranged further channel, at the mouth of which an annular nozzle disk is fastened with a plurality of nozzles distributed around the circumference, through which primary air exits at increased speed.

Rotary kiln burners of this type are usually designed as so-called three-channel burners (US Pat. No. 4,428,727), ie the pneumatically transported coal dust flows through the central burner channel and it exits through an annular gap nozzle, the coal dust flowing out being surrounded by radially inner as well as radially outer primary air. In the known coal dust burner, the radially outer primary air, also known as jet air, is divided by means of a plurality of individual nozzles arranged in the annular jet air duct into many individual high-speed primary air jets which create a negative pressure area in their environment, i.e. the many high-speed primary air jets serve as propulsion jets according to the injector principle , through which the large mass of the practically still hot secondary air surrounding the rotary kiln burner is sucked in from approx. 800 ° C inwards towards the core of the burner flame, where the hot secondary air is intensively mixed with the coal dust escaping through the annular gap nozzle this way burns quickly and completely to form a short hot flame, as is required in the sintering zone of a rotary kiln for sintering the calcined cement raw material to cement clinker. To this It is possible to draw as much hot secondary air (e.g. approx. 95% by volume) as possible into the core of the burner flame with as little cold primary air as possible (e.g. approx. 5% by volume) for the purpose of quick and complete combustion of coal dust .

In the known burner, the jet air nozzles are fastened in an annular nozzle disk which is welded to the end opening of the outer burner support tube (jet air tube). Replacing such a nozzle disk is time-consuming inasmuch as the front area of the refractory jacket of the burner and part of the burner support tube have to be removed, and after replacing the nozzle disk the refractory jacket to be applied must dry out well before the burner is put back into operation. At the same time, the radially inner end face of the nozzle disk must be securely sealed against the annularly shaped coal dust nozzle of the coal dust duct so that the functionality of the burner is not endangered. Before the entire nozzle disk including the nozzles is replaced, there is often also a need to adjust or replace only one or more of the jet air nozzles attached to the nozzle disk, but this is difficult if the jet air nozzles are screwed into the nozzle disk because the thread in the thermally highly stressed Zone of the burner is and therefore only has a limited functionality.

The invention has for its object to provide a rotary kiln of the type mentioned, with a jet disk closing the jet disc, which is easy to replace without destroying / renewing the refractory material of the burner support tube and whose jet air nozzles are conveniently and reliably adjustable or replaceable.

This object is achieved with the measures of the characterizing part of claim 1. Advantageous refinements are specified in the subclaims.

In the rotary kiln according to the invention, the ring-shaped nozzle disc that closes the jet air duct with the jet air nozzles is not directly on the burner support tube (jet air tube), for. B. attached by welding, but the nozzle disc is fitted leaving the end-face annular expansion joints in the jet air duct and releasably and interchangeably attached to spacers accessible from the burner mouth front, which are fastened to maintain the concentricity of the jet air pipe and fuel pipe in the jet air duct. The spacers between the jet air pipe and the fuel pipe can consist of a one-part or multi-part ring which is arranged in the jet air duct as seen from the burner mouth at a distance behind the nozzle disk. The spacer ring has a plurality of openings, windows etc. distributed around the circumference for the passage of the jet air flow to the nozzles of the nozzle disk. Particularly advantageously, the nozzle disk can be pressed against the spacer ring via a radially inner sealing ring and via a radially outer sealing ring, and the fastening means for releasably fastening the nozzle disk ring to the spacer ring and for tightening the seals are screw bolts distributed around the circumference of the ring, the axes of which are parallel to the burner axis lie. Jet bolts flow around the bolts and their threads so that they can withstand thermal loads. In any case, after loosening the screw bolts from the burner mouth side, the nozzle disk can be easily detached from the spacer ring and thus the nozzle disk can be replaced quickly and easily, without having to destroy / replace the refractory casing of the burner support tube. As a result of the sealing rings between the nozzle disk and the spacer ring, the jet air of the jet air duct is prevented from emerging radially or laterally from the air duct in an undesirable manner.

The nozzles of the ring-shaped nozzle disk consist of cylindrical nozzle bodies which can be rotated without threads in corresponding bores arranged over the circumference of the nozzle disk, but can each be axially fixed by means of a circumferential ring groove. In this way, the jet air nozzles can be safely installed in the nozzle disc from the front of the burner and also interchangeable and rotatable into the desired position in order to be able to set a specific deflection angle or divergence angle of the jet air jets with respect to the longitudinal axis of the burner, possibly with a swirl flow component superimposed.

The invention and its further features and advantages are explained in more detail with reference to the exemplary embodiments shown schematically in the figures.

Fig. 1:

einen Axiallängsschnitt durch einen erfindungsgemäßen Drehofenbrenner, wobei der Schnitt in der oberen Figurenhälfte durch eine Jetluftdüse und in der unteren Figurenhälfte durch eine Brennermündungsstelle zwischen zwei benachbarten Jetluftdüsen gelegt ist,

Fig. 2:

ausschnittsweise die Brennermündung mit einer Variante einer Jetluftdüse, und

Fig. 3:

ausschnittsweise die Mündung eines Drehofenbrenners mit einer Düsenscheibe, in der außer Jetluftdüsen auch noch Brenngasdüsen eingesetzt sind.

It shows

Fig. 1:

3 shows an axial longitudinal section through a rotary kiln burner according to the invention, the section being made in the upper half of the figure through a jet air nozzle and in the lower half through a burner orifice point between two adjacent jet air nozzles,

Fig. 2:

sections of the burner mouth with a variant of a jet air nozzle, and

Fig. 3:

sections of the mouth of a rotary kiln burner with a nozzle disc, in which fuel gas nozzles are also used in addition to jet air nozzles.

The rotary kiln burner of FIG. 1 has an annular channel (10) for the pneumatic transport of fine-grained coal dust, enclosed by the fuel pipe (11). The coal dust primary air suspension (12) occurs at a speed of z. B. 28 m / s from an annular gap nozzle (13), which diverges with a small angle to the outside. A ring channel (14) is arranged concentrically around the coal dust channel (10), through which primary air flows, which flows at high speed, e.g. B. 140 to 420 m / s in the form of jet streams (15) emerges from individual burner nozzles (16) distributed around the circumference of the burner mouth. The primary air flowing in the ring channel (14), encompassed by the burner support tube (17), is also called jet air. The high-speed jet air jets (15) or high-speed driving jets are able to remove as much hot secondary air (18) as possible from the rotary kiln burner. B. 800 ° C in the core of the burner flame for the purpose of faster and suck in complete coal dust combustion. On the outside, the rotary kiln burner is protected against thermal overload by a casing (19) made of refractory material, only shown in the upper half of the drawing in FIG. 1. A further primary air duct (20) can be arranged concentrically within the coal dust duct (10) and can be equipped with a swirl generator (21) at its mouth. In the center of the burner there is also a tube (22) into which a central pilot burner can be inserted.

The distributed around the circumference jet air nozzles (16) are arranged in an annular nozzle disc (23) which is not welded to the burner orifice on the support tube (17), but which is fitted into the annular jet air duct (14) while leaving gap-shaped expansion joints at the front and over Fastening means accessible from the front of the burner orifice, in FIG. 1 releasably and interchangeably fastened via the screw bolts (24) to spacers which are fastened in the jet air duct (14) in order to maintain the concentricity of the burner support tube (17) or jet air tube and fuel tube (11) . According to the exemplary embodiments in FIGS. 1 and 2, the spacers between the jet air pipe (17) and the fuel pipe (11) consist of a two-part or three-part ring (26) screwed together with screws (25), which is seen in the jet air duct (14) from the combustion mouth is arranged a short distance behind the nozzle disk (23). The fact that the nozzle disk (23) is fitted into the annular jet air duct (14) while observing annular gap-shaped expansion joints prevents jamming of the nozzle disk (23) during its installation and removal. The heads of the screw bolts (24), which are located in the burner area cooled by the jet air, are protected in the recesses in the end face of the nozzle disk (23). When the screw bolts (24) are tightened, the nozzle disk (23) can be pressed against the spacer ring (26) via a radially inner sealing ring (27) and via a radially outer sealing ring (28), so that a perfect one Sealing of the jet air duct (14) is guaranteed. From Fig. 1 it can still be seen that the spacer ring (26) z. B. in circumferential areas between the bolts (24) has a plurality of openings or windows (29) etc. distributed around the circumference for the passage of the jet air flow to the nozzles (16) of the nozzle disk (23).

The jet air nozzles (16) of the annular nozzle disk (23) consist of cylindrical nozzle bodies which can be rotated without threads in corresponding bores arranged around the circumference of the nozzle disk, but can be axially fixed by inserting a pin by means of a circumferential annular groove (30). To remove a jet air nozzle (16), it is rotated until a longitudinal groove (31) reaches the area of the holding pin, after which the nozzle (16) can be pulled outwards. Depending on the rotational position of the jet air nozzle (16), the nozzle bore (32) can be changed with regard to its divergence from the longitudinal axis of the burner and, if applicable, its swirl flow component.

In the embodiment of FIG. 2, the rotatable jet air nozzle (16) with circumferential ring groove (30) can be fixed via a pin (33) which is accessible from the burner mouth and whose axis is parallel to the longitudinal axis of the burner.

In the embodiment of Fig. 3 it can be seen that the interchangeable and adjustable jet air nozzles (16) are arranged in the annular nozzle disk (23) on the outside on the periphery, while fuel gas nozzles (34), which are distributed radially further inward, are also arranged as additional fuel nozzles can be arranged.

Claims (5)

1. A burner for a rotary furnace, comprising a duct (10) disposed in a ring for pneumatic conveyance of fine-grained solid fuel, e.g. coal dust, and with at least one additional annular jet air duct (14) disposed concentrically therewith and having an annular nozzle plate (23) secured to its mouth and comprising a number of peripherally distributed nozzles (16) through which primary air is discharged at high speed, characterised in that the nozzle plate (23) is fitted into the annular jet air duct (14), leaving annular expansion joints at the ends, and is releasably and interchangeably secured by securing means (24) accessible from the front of the burner mouth to spacers (26) which are secured in the jet air duct (14) so as to keep the jet air pipe (17) concentric with the fuel pipe (11).
2. A burner according to claim 1, characterised in that the spacers between the jet air pipe (17) and the fuel pipe (11) comprise a one-part or multi-part ring (26) disposed in the jet air duct (14) at a slight distance behind the nozzle plate (23), as seen from the burner mouth.
3. A burner according to claim 2, characterised in that the spacer (23) comprises a number of peripherally distributed openings, windows (29) or the like for admitting the jet air flow to the nozzles (16) in the nozzle plate (23).
4. A burner according to any of claims 1 to 3, characterised in that the nozzle disc (23) can be pressed via a radially inner sealing ring (27) and a radially outer sealing ring (28) against the spacer ring (26), and the securing means for releasably securing the nozzle plate ring to the spacer ring are bolts (24) distributed around the ring periphery and having their axes parallel to the burner axis.
5. A burner according to any of claims 1 to 4, characterised in that the nozzles (16) in the annular nozzle plate (23) comprise cylindrical nozzle members which, without a thread, are rotatable in respective corresponding bores distributed around the nozzle-plate periphery, but can each be axially secured via a peripheral annular groove (30).

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