BACK-VENTILATED REFRACTORY WALL FOR AN INCINERATOR
A fire-resistant wall intended in particular for use in an incinerator has a tube wall, composed of tubes connected by webs, and, placed in front and at a distance from the tube wall, a fire-resistant protective cladding composed of a plurality of fire-resistant tiles which are arranged next to and above one another and which are fastened to the webs of the tube wall via in each case at least one tile holder. The tiles are provided with continuous open grooves into which the tile holders engage. In the tube wall are provided inlet openings via which air can be introduced into the gap between the tube wall and the protective cladding. Also provided are outlet openings through which air can be removed from the wall. The air supply openings are arranged in the region of the open grooves of the tiles, with the result that the supplied air flows directly into the grooves and is distributed through these grooves over the entire wall. By incorporating the grooves into the air distribution system within the wall, the gap width between the tube wall and the protective cladding can be reduced to 5 mm, thereby considerably improving the heat transfer. It is possible at the same time to manage with relatively small air volumes and the pressure loss is considerably reduced, making possible considerable energy savings.
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This application is a continuation of International Patent Application No. PCT/CH2009/000277 filed on Aug. 21, 2009 the contents of which are hereby incorporated by reference in their entirety.FIELD OF THE INVENTION
The invention relates to a back-ventilated refractory wall for, e.g., an incinerator.BACKGROUND
Such refractory walls are used for instance in fire chambers of incinerating plants. Frequently the boiler wall is designed as metal tube wall and as a rule consists of tubes connected by webs. The refractory protective lining suspended in front of and spaced from the tube wall is to protect the tube wall from corrosion through smoke gasses. Refractory walls are for instance also used with fluidized bed furnaces, wherein the boiler wall consists of a simple metal wall of greater or lesser thickness. Here, too, the boiler wall or metal wall is to be protected from corrosion.
The boiler walls and protective linings in today's incinerating plants are often exposed to temperatures of more than 1000° C. and are subjected to expansions and contractions because of the large temperature differentials of the individual operating states even with suitable choice of material. Temperature differentials are generally greater with the protective linings than with the boiler walls proper, which has to be considered when selecting the material and/or designing the protective linings, so that the protective linings are not destroyed through expansions and contractions greater than the boiler walls. As a rule, the protective linings or the tiles of these are therefore not rigidly attached to the boiler wall but are attached with play, so that offsetting movements parallel to the boiler walls are possible to a limited extent.
The selection of a suitable material for the protective lining makes it possible that the protective lining is matched to the boiler wall for any operating state. For boiler walls of steel, protective linings of ceramic materials, in particular SiC, have proved suitable, while the SiC content can vary greatly. In practice, SiC compounds or SiC tiles with SiC content of 30% to 90% are employed.
The tiles of the protective lining are generally sealed against one another to a certain degree through various measures in order to prevent the passage of smoke gasses. In practice, however, this does not entirely prevent corrosive smoke gasses from penetrating the protective lining and attacking the boiler wall.
So-called back-ventilated wall systems combat this problem in that a protective gas—generally air—is pumped through the intermediate space between the boiler wall and the protective lining put in front. The gas or the air is subjected to slight overpressure relative to the fire chamber, as a result of which it is prevented that the smoke gasses from the fire chamber can enter the wall intermediate space and attack the boiler wall or other metal parts. Conventional wall systems of this type have a relatively large air requirement and require an undesirably high pumping rate.
From German Patent document DE 198 16 059 C2, a back-ventilated refractory wall with a tube wall and a spaced protective lining of a multiplicity of refractory tiles (plates) located in front is known, where the intermediate space between the tube wall and the protective lining is designed as at least one closed pressure chamber, where each pressure chamber is charged with pressurized protective gas. The overpressure of the protective gas is so great that no smoke gas from the incinerator can enter through the protective lining. Although a relatively good corrosion protection effect is achieved by this, the insulating effect of the protective gas hinders the heat transfer between the protective lining and the tube wall, so that depending on the use insufficient heat is removed.SUMMARY
The invention has the goal of improving a refractory wall in that the boiler wall on the one hand is reliably protected from corrosion through smoke gasses and that on the other hand a process-optimized heat transfer between the protective lining and the boiler wall is guaranteed and the protective gas pumping rate minimized.
In accordance with the invention a refractory wall is a back-ventilated system and has a gas feeding port for feeding a protective gas, generally air, into the intermediate space between the boiler wall and the protective lining. Through the protective gas flowing through the wall, the entry of smoke gasses in the wall is prevented. The gas or the air is fed through the boiler wall in the region of continuous vertical grooves present in the tiles via which the gas or the air can spread over the entire wall with minimal pressure drop. Because of this, the spacing between boiler wall and protective lining can be reduced to a few millimetres and relatively small protective gas or air volumes are sufficient, which in turn has the advantage that little additional waste gas is produced. Through the small spacing between the boiler wall and the protective lining, heat transfer is substantially increased. The low pressure drop in the grooves results in considerable energy saving.
In one embodiment, the grooves of neighbouring tiles located on top of one another are in alignment and connected in a communicating manner.
The gas feeding port advantageously includes inlet openings arranged in the region of the grooves in the boiler wall. The inlet openings are preferentially arranged in the lower region of the boiler wall or distributed over the boiler wall surface.
According to an exemplary embodiment, the boiler wall is a tube wall of tubes connected by webs and the inlet openings are arranged in the region of the webs and not limited to use in a boiler.
The gap width of the intermediate space is advantageously less than or equal to 5 mm, preferentially less than or equal to 3 mm.
Advantageously, the wall discharges the protective gas from the intermediate space and the grooves. The port for discharging the protective gas advantageously includes outlet openings penetrating the protective lining or the boiler wall which are preferentially arranged in the uppermost region of the wall.
According to an exemplary embodiment, tile joints are present between the refractory tiles which are sealed by inserted ceramic sealing strips of refractory material and by an additional grout.
The outlet openings are advantageously formed by regions of the tile joints that have not been sealed.
Advantageously the tile mountings each comprise a bolt fastened to the boiler wall, preferentially welded on, with an internal thread and a flat tile contact surface, and a screw screwed into the bolt by which the spacing of the tile from the boiler wall can be varied.
According to one embodiment, the tiles of at least one horizontal tile row are arranged at a slightly greater spacing from the boiler wall relative to the remaining tiles and consequently define a transverse channel through which protective gas, in particular air, can spread over the wall width.
According to one embodiment, at least some laterally neighbouring tiles define a continuous transverse channel substantially running horizontally, which joins the vertical grooves of these tiles with one another in a communicating manner. Here, the tiles having the transverse channel are arranged above or below wall installations and/or in tile rows located spaced on top of one another.
According to a further embodiment, the tiles are provided with swirling elements, which generate vortices in the protective gas flowing between the tiles and the boiler wall and because of this increase the heat transfer between the tiles and the boiler wall. The swirling elements are advantageously formed through raised and/or sunken regions of the tiles facing the boiler wall.
The protective gas or the air discharged from the refractory wall is preferentially returned into the refractory wall and/or fed into the incinerating plant as primary gas or air and/or secondary gas or air.
In the following, the refractory wall according to the invention is described in more detail by means of exemplary embodiments making reference to the drawings.
The position and directional designations such as top, bottom, width, height, vertical, horizontal, transverse, on top of one another, next to one another etc. in the following refer to the usual orientation of the wall in practice.DETAILED DESCRIPTION
The first exemplary embodiment of the refractory wall according to the invention designated W as a whole shown as in
The tiles 21 of the protective lining 2 may be mutually sealed in two ways. As is evident from
The refractory wall W here is a back-ventilated system. This means that the intermediate space 3 between the protective lining 2 and the boiler wall, in the first exemplary embodiment the tube wall 1, is subjected to a through-flow of a protective gas—generally air—in operation. The gas (or the air) in the intermediate space is slightly pressurized relative to the fire chamber of the incinerator. Because of this it is avoided that corrosive smoke gasses can enter the intermediate space 3 from the fire chamber through leaking areas of the protective lining and attack the tube wall 1.
For feeding and discharging the protective gas in or from the intermediate space 3 of the wall, inlet openings 31 and outlet openings 32 are defined in the wall, where the inlet openings 31 are connected to a feed channel or a plurality of feed channels 33 and are fed by the channel or channels (see
Alternatively, the outlet openings are arranged in the boiler wall, in particular in webs 12 of the tube wall 1, instead of the protective lining 2, and the protective gas discharged to the outside by that route (similar to
The outlet openings 32 are preferentially arranged in the region of the upper edge of the refractory wall, as schematically indicated in
An aspect of the invention is that the feeding of the protective gas or the air is effected directly in the region of the continuous open grooves 21a of the tiles 21, as is particularly evident from
Further improvement of the protective gas or air distribution within the wall according to an advantageous further development in accordance with the invention can be achieved in that some horizontal tile rows of the protective lining at certain vertical spacings, e.g. 2 to 4 m each, are arranged at a slightly greater spacing from the tube wall than the remaining tiles, so that horizontal transverse channels are formed via which the air can spread over the width of the wall.
In addition or alternatively, transverse channels which substantially run horizontally can also be formed in the or some tiles according to a particularly advantageous further configuration of the invention as shown in
The transverse channels 21b need not extend through the entire tile row located above the installation 40. In practice it is sufficient if the tiles located above the installation are connected at least on one side, preferentially however on both sides, with at least one neighbouring tile of the tile row located laterally outside the installation in a communicating manner. Even if the vertical protective gas or air flow is not interrupted by any installations it can be advantageous in the interest of better flow distribution to arrange tile rows with transverse channels at certain intervals or even equip all tiles with transverse channels.
According to an aspect of the invention, heat transfer between the tiles of the protected lining 2 and the tube wall 1 can be increased in that in the flow path of the protective gas or the air swirling elements are arranged, as is shown in
In one embodiment, the swirling elements are formed by raised bent ribs 21d in the region of the cylindrical channels 21c of the tiles 21. Alternatively or additionally, the swirling elements are defined by depressions 21e in the region of the flow paths of the protective gas or the air. Finally, the swirling elements can also include pin-like elements 21f which protrude into the open grooves 21a.
As already mentioned, the protective gas or air feed is effected via one feeding channel or a plurality of feeding channels 33 which are preferentially formed as a comb box. The blower required for conducting the air is for example driven by a frequency-controlled motor, wherein the overpressure in the grooves 21a measured at one or a plurality of points is utilized for controlling the blower. In this manner, the energy requirement can be optimized or minimized.
As mentioned above, the boiler wall of the refractory wall according to the invention need not be a tube wall, but can for example also be a conventional metal wall.
1. A back-ventilated refractory wall comprising:
- a boiler wall,
- a refractory protective lining spaced from the boiler wall, having a plurality of refractory tiles arranged next to and on one another, and each fastened to the boiler wall by at least one tile mounting, whereby between the boiler wall and the protective lining at least partially is an intermediate space, and
- a port for feeding gas into the intermediate space between the boiler wall and the protective lining,
- wherein the tiles define continuous grooves substantially running vertically and open toward the boiler wall and the grooves in the interior of the tiles have an expanded cross section, in which grooves the tile mountings engage, and the gas feeding port feeds the gas into the grooves or in the region of the grooves into the intermediate space.
2. A wall according to claim 1, wherein the grooves of neighbouring tiles located on one another are in alignment and communicate.
3. A wall according to claim 1, wherein the gas feeding port comprises a plurality of inlet openings arranged in the region of the grooves in the boiler wall.
4. A wall according to claim 3, wherein the inlet openings are arranged in a lower region of the boiler wall or distributed over the boiler wall surface.
5. A wall according to claim 3, wherein the boiler wall comprises a plurality of tubes connected by webs and the inlet openings are arranged in the region of the webs.
6. A wall according to claim 1, wherein the width of the intermediate space is less than or equal to 5 mm.
7. A wall according to claim 1, further comprising a port for discharging the gas from the intermediate space and the grooves.
8. A wall according to claim 7, wherein the discharging port comprises a plurality of outlet openings penetrating the protective lining or the boiler wall and arranged in an uppermost region of the wall.
9. A wall according to claim 1, wherein tile joints between the refractory tiles are sealed by ceramic strips of refractory material and a grout.
10. A wall according to claim 1, wherein the tile mountings each comprise a bolt fastened to the boiler wall and having an internal thread and a flat tile support surface and a screw screwed into the bolt by which the spacing of the tile from the boiler wall is variable.
11. A wall according to claim 1, wherein the tiles of at least one horizontal row of the tiles are arranged at a greater spacing from the boiler wall relative to the remaining tiles and thereby define a transverse channel through which the gas spreads over a width of the boiler wall.
12. A wall according to claim 1, wherein at least some laterally neighbouring tiles define a continuous transverse channel substantially running horizontally, and which connects the vertical grooves of neighbouring tiles.
13. A wall according to claim 12, wherein the tiles define a transverse channel arranged above or below an installation in the boiler wall.
14. A wall according to claim 12, wherein the tiles having the transverse channel are arranged in rows spaced on one another.
15. A wall according to claim 1, further comprising swirling elements for the gas flowing between the boiler wall and the protective lining.
International Classification: F22B 37/36 (20060101);