Patent application title: BACK-VENTILATED REFRACTORY WALL FOR AN INCINERATOR
Andreas Kern (Basel, CH)
Karl-Ulrich Martin (Ludwigsburg, DE)
IPC8 Class: AF22B3736FI
Class name: Liquid heaters and vaporizers casings
Publication date: 2011-06-23
Patent application number: 20110146596
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.
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.
CROSS-REFERENCE TO RELATED APPLICATION
 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.
 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.
 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.
BRIEF DESCRIPTION OF THE FIGURES
 FIG. 1 shows a first exemplary embodiment of the wall according to the invention in a view onto the protective lining,
 FIG. 2 is a section along line II-II in FIG. 1,
 FIG. 3 is a section along line in FIG. 1,
 FIG. 4 shows a detail from FIG. 3 in an enlarged representation,
 FIG. 5 is a view similar to FIG. 1 of a version of the wall,
 FIG. 6 is a perspective oblique view of a tile of the protective lining,
 FIG. 7 is a sectional representation similar to FIG. 3 of a second exemplary embodiment of the wall according to the invention,
 FIG. 8 is a schematic view of an incinerating plant with a refractory wall according to the invention,
 FIG. 9 is a perspective oblique view similar to FIG. 6 of a version of a tile of the protective lining,
 FIG. 10 is a view of the tile in the direction of the arrow X of FIG. 9,
 FIG. 11 is a section through the tile along line XI-XI of FIG. 10 and
 FIG. 12 is a section through the tile along line XII-XII of FIG. 10.
 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.
 The first exemplary embodiment of the refractory wall according to the invention designated W as a whole shown as in FIGS. 1-4 includes a tube wall 1 (see FIGS. 2-4) as a boiler wall and a protective lining 2 put in front of and spaced from the tube wall, where between the tube wall 1 and the protective lining 2 an intermediate space 3 is defined. The tube wall 1 has a multiplicity of, in practical use, vertical tubes 11, which are held together and mutually spaced by webs 12. The tubes 11 and the webs 12 commonly are of steel. The protective lining 2 consists of a multiplicity of refractory tiles 21 arranged next to one another and on top of one another, which engage with one another through complementary shaping of their edges and in this manner are mutually sealed to a certain degree. The separating joints between the tiles 21 are designated 23. The tiles for example are ceramic SiC tiles, preferentially SiC 90 tiles with a SiC content of approximately 90%, which are fire-resistant to above 1000° C. Each tile 21 is fastened to the tube wall 1 by, for example, four tile mountings 22. The tile mountings are of heat-resistant steel, e.g., steel number 310 according to AISI standard or material number 1.4845 according to DIN 17440. The tile mountings 22 include a square bolt 22a welded to a web 12 with an internal thread and flattened lateral surfaces 22b and a screw 22c (see FIG. 4) screwed into the squared bolt 22a. The tile mountings 22 engage in continuous vertical, open grooves 22a widened towards the inside of the tiles 21 and determine the spacing of the tiles 21 from the tube wall. In the vertical direction of the protective lining 2 the tiles 21 are movable to a certain degree so as to allow thermally-related expansion or contraction movement. On their side facing the tube wall, the tiles 21 are adapted in shape to the tubes 11 (cylindrical channels 21c, see FIG. 6) so that the clear width or gap width d of the intermediate space 3 between tube wall 1 and protective lining 2 is substantially roughly constant over the entire wall.
 The tiles 21 of the protective lining 2 may be mutually sealed in two ways. As is evident from FIGS. 3 and 7, the tile joints 23 of the protective lining 2 are z-shaped and are sealed by inserted ceramic sealing strips 23a of refractory material and through an additional grout 23b. The ceramic sealing strips 23a provide a certain flexibility, but do not provide absolute sealing. The latter is achieved through the additional grout sealing 23b.
 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 FIGS. 2 and 3). The protective gas or air feed is effected from the side of the boiler wall, where the inlet openings 31 penetrate the boiler wall, in this case the tube wall 1, in the region of its webs 12 (see FIGS. 3 and 4). The outlet openings 32 (see FIG. 1) penetrate the protective lining 2, as a result of which the protective gas flowing through the intermediate space 3 is discharged into the boiler.
 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 FIG. 4, but instead of the inlet opening 31 shown there, a corresponding outlet opening with reversed protective gas flow direction). The protective gas discharged to the outside is preferentially sucked into a comb box 33a (see FIG. 8) arranged on the outside of the boiler wall, in which for this purpose a vacuum is established. In this manner, the waste gas quantity in the boiler is not unnecessarily increased by protective gas so that the exhaust gas cleaning plant is not subject to additional load. In addition, the protective gas discharged to the outside can be analyzed for pollutants if required.
 FIG. 8 shows how the refractory wall W is used in an incinerating plant. The incinerating plant designated 100 as a whole includes a material input chamber 110 and a fire chamber 120 in a known manner. The refractory wall W is arranged in the region of the fire chamber 100 and forms a part of its wall. The feed of protective gas or air is effected in the lower region of the wall W via the already mentioned comb box 33. In the upper wall region, the comb box or manifold 33a is arranged, via which the protective gas or air is again discharged from the refractory wall W. The discharged protective gas or the discharged air can either be fed back into the refractory wall W (arrow 113) via the lower comb box 33 or fed to the incinerating plant 100. Feeding into the incinerating plant can be effected into the input chamber 110 as primary gas or air (arrow 111) and/or as secondary gas or air (arrow 112) at the lower end of the fire chamber 120.
 The outlet openings 32 are preferentially arranged in the region of the upper edge of the refractory wall, as schematically indicated in FIG. 1. The outlet openings 32 can be formed through regions of the tile joints 23 which are not sealed or alternatively, as explained above, through openings in the webs 12 of the tube wall 1. The inlet openings 31 can be arranged at the base of the wall, i.e. in the vicinity of its lower edge, as shown in FIG. 2. The inlet openings 31 however can also be distributed over the entire wall surface or individual regions of the latter.
 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 FIGS. 3 and 4. In FIG. 4 the fed-in air is symbolized by arrow L. The inlet openings 31 are arranged in the webs 12 in the region of the open grooves 21a. The fed-in gas or the air primarily enters the open grooves 21 a and in the process spreads over the entire wall without major flow resistance because of the grooves relatively large cross section. This allows one to greatly reduce the intermediate space 3 between the boiler wall or in this case the tube wall 1 and the protective lining 2 suspended in front, wherein the gap width d (see FIG. 4) in practice only amounts to 1 to 5 mm, preferentially 1 to 3 mm. The tube wall 1 can also touch the tiles 21 in some areas without damage. By utilizing the grooves 21a as protective gas or air distribution channels within the wall and the reduced clear spacing d between tube wall 1 and protective lining 2, lower gas or air volumes suffice and extremely low pressure losses occur. The required pressures compared with the boiler inner pressure can be reduced to 1 to 10 mbar, preferentially even 1 to 5 mbar. This in turn produces significant energy savings in practical operation. In addition, the smaller spacing between tube wall and protective lining substantially increases the heat transfer.
 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 FIGS. 5 and 6. This is important particularly if the wall in practical operation comprises installations, for example a burner or a window, which locally interrupt the vertical grooves so that the wall parts located above or with an alternative embodiment version--with feeding of protective gas or air from the top--below the installation can not be directly supplied with protective gas or air. FIG. 5 shows detail of a wall with an installation 40. It is evident that the grooves 21a are interrupted in the region of the installation 40. In order to be able to supply wall parts or tiles 21 located above the installation 40 with air, the tiles 21 of the tile row located immediately above the installation are equipped with transverse channels 21b, which connect the vertically running grooves 21a of the tiles 21 of the tile row in a communicating manner. In this manner protective gas or air can flow out of the laterally neighbouring grooves 21 a which are not interrupted transversely into the grooves 21 a of the tiles 21 located above the installation 40 as shown in FIG. 5 by the unmarked flow arrows.
 FIG. 6 shows a tile 21 in which a transverse channel 21b is defined. As evident, the transverse channel 21b is open on both sides of the tile 21 so that the transverse channels of neighbouring tiles define a continuous flow path.
 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 FIGS. 9 to 12 in a purely exemplary manner.
 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. FIG. 7 shows schematically a second exemplary embodiment wherein the boiler wall is designed as such a flat metal wall 1'. With this exemplary embodiment, too, the feeding of the air into the grooves 21a of the tiles 21 and the reduction of the gap width of the intermediate space 3 achieved by this also brings about the above mentioned advantages.