Combustion grate for an incinerator of a waste incineration plant

Abstract

A combustion grate comprising a tensioning device (30) for a row (16) of grate blocks (18) arranged in the combustion grate (10), the tensioning device (30) being designed to maintain the alignment of the row of grate blocks. The tensioning device comprises a cable (70) having a cable first end region (70a) and a cable second end region (70b) opposed to the cable first end region (70a), a first connecting means (40) for connecting the cable first end region (70a) to a side wall (14a) of a first border region of the combustion grate bordering laterally the combustion grate, and a second connecting means (50) for connecting the cable second end region (70b) to a side wall (14b) of a second border region opposed to the first border region and bordering laterally the combustion grate.

Description

[0001] Combustion grate for an incinerator of a waste incineration plant

[0002] The present invention relates to a combustion grate for an incinerator of a waste incineration plant in which waste is used as a fuel source to typically generate steam for electrical power generation .

[0003] The combustion grate provides the necessary support for waste while being transported through the combustion sequence . Typically, the combustion grate can be of a forward moving reciprocating-type with grate blocks each inclined at an angle and with alternating transverse rows , as seen relative to the direction of waste flow, also referred to as direction of conveyance , of stationary and reciprocating grate blocks . Each row of grate blocks overlaps the row ahead of it to provide the combustion grate . The alternate rows which move in a reciprocating manner are supported by a moving structure providing the reciprocating motion . Attachment to either a fixed or moving guide is made at the back part of the grate blocks which is located below the prior overlapping block .

[0004] Combustion grates are usually made up of rows of grate blocks and comprise press plates defining lateral sides of the combustion grate , the press plates being arranged on each side of the rows .

[0005] Maintaining the alignment of each row of grate blocks , i . e . keeping the grate blocks aligned in a direction perpendicular to the direction of conveyance , requires that the grate blocks fit tightly side by side . The tight fit also contributes to proper air distribution by avoiding gaps between the grate blocks so that air supplied is forced only into the air supply channels configured for supplying air to the waste bed . The tight fit is usually accomplished by at least one tension rod located below each row of grate blocks . In reciprocating rows , the tension rod is attached at each end to the corresponding side grate block in such rows . In stationary rows , each end of the tension rod is attached to a corresponding one of the two press plates which define the lateral sides relative to waste flow of the combustion grate . Alternatively, each end of the tension rod can be attached to the corresponding side grate block in such rows , wherein the side grate blocks can be screwed to the press plates .

[0006] The tension rod is essentially a solid metallic rod with a turnbuckle at the other end thereof . Preferably, the tension rod is located about midway in each row of grate blocks to allow tightening to a pre-determined torque to provide the desired tension during operating conditions . However, the tension rod is manually fixed to the pre-determined tension while the combustion grate is in the cold condition . During operation, the tension rod is cooled by combustion air flowing beneath the combustion grate , while the combustion grate is subj ected to temperatures relative to the fire above . Therefore , the tension rods can still reach temperatures of up to 400 ° C or more . Accordingly, the tension rods exhibit great sensitivity to the various conditions present during operation, for example expanding during operation or retracting during shutdown of the furnace . Defining the appropriate tension for mounting tension rods remains a di f ficult task, especially because failure of a tension rod would cause the entire row of grate blocks to li ft and require a shutdown to repair it .

[0007] US5377663A discloses grate blocks which alleviate or eliminate plugging of air holes in the leading face of the grate blocks . The grate blocks are tightened by a tension rod comprising two sections . A first section comprises a head end inserted through a hole in a side of a side grate block of a row of grate blocks and an opposite end opposed to the head end . The opposite end has a threaded portion which engages a turnbuckle . A second section comprises a further head end inserted through a hole in a side of a further side grate block arranged at the opposed end of the row of grate blocks and an opposite end opposed to the further head end, the opposite end having also a threaded portion which engages the turnbuckle . In a mounted state , the turnbuckle is turned to increase or decrease the tension across the tension rod . Each section of the tension rod further comprises a mid-section that is replaced by a spring-section to better accommodate tensions in the tension rod and varying conditions in plant operations which may slowly or abruptly change the tension on the tension rod . The tension rod comprises multiple components that need to be adj usted to each other because they are made of di f ferent material expanding di f ferently under the influence of heat . Speci fically, the spring-sections can lose their elasticity over time and require maintenance of the combustion grate . The components can also react di f ferently to corrosion which in turn can entail more maintenance work .

[0008] WO 2011 / 063912A1 discloses a waste disposal plant in which waste laid on a combustion grate are burnt , said combustion grate comprising at least a handling group formed by a plurality of grate blocks or plates which move alternatively one with respect to the other by advancing the waste on the grate . The grate blocks are kept mutually aligned in the plane of the grate by way of lateral plates on both sides of the grate that can be pressed against the grate blocks by way of a grate block approaching system . The approaching system comprises a tie-rod having an abutment disc at its opposing ends resting on a supporting saddle of the lateral plates . At a first end of the approaching system, the first abutment disc is connected by a thread to a coil spring which is in turn connected to the tie-rod . At the other end, the tie-rod is threaded and connected to the second abutment disc through which it inserted and maintained by a nut . The contact pressure between the abutment discs on the lateral plates and thereby on the grate blocks can be set by screwing the nut in an appropriate manner .

[0009] US 4 , 018 , 168 discloses a furnace feed grate of an incinerator comprises transverse rows of grate blocks , the blocks of alternate rows being movable to feed refuse along the grate . Clamping devices at the underside of the grate resiliently urge together the grate blocks of the respective rows together to prevent gaps between them . A clamping shoe is arranged in a lower part of each of the two external blocks of a row and is provided with a spring barrel which is arranged securely on the clamping shoe . A clamping bar is held in the two spring barrels and is provided at its two ends with abutments for receiving the clamping pressure . The clamping bar with its two abutments forms a rigid unit and the two clamping springs are in each case elastically compressed between the associated bar abutments . The axial displacement of the spring barrels accommodates expansion of the grate blocks due to heat when the incinerator is in use . As an alternative to the helically wound clamping springs , the use of cup springs is also mentioned .

[0010] Tension rods in the form of solid rods of metal attached at both ends to a row of grate blocks have been known as a mean to keep grate blocks aligned in combustion grate for decades . A solid metallic rod has been generally accepted as a solution supporting the heavy mechanical constraints present in an incinerator and ful filling the main technical requirements . For this reason, little ef forts have been made to optimi ze the role of this mostly hidden component in the assembly of a combustion grate .

[0011] However, there is a growing interest in improving the ef ficiency of incinerators to trans form waste into energy, which depends also on potential improvements in the air supply to the waste bed . Further, there is still a need to simpli fy the maintenance of incinerators . In addition, the development of wider combustion grates is limited by the mechanical characteristics of the solid metallic rods that are used to keep the grate blocks aligned . The longer the metallic rod, the larger the expansion under the ef fect of temperature variations so that either threads breakaway or grate blocks are li fting .

[0012] In summary, in the past it was common to build smaller incinerators with lower calori fic value and therefore less thermal stres s on the combustion grate . The resulting thermal expansion could be absorbed by a well-known steel rod acting as a tension rod . Due to the requirement of ever larger incinerators and the resulting ever greater thermal stress on the combustion grate , the steel rod is no longer satis fying because failures are more likely .

[0013] A need exists to further improve combustion grates in which tensioning devices designed to maintain the alignment of each row of grate blocks of the combustion grate so that the grate blocks fit tightly side by side , to allow the development of wider combustion grates .

[0014] Accordingly, the obj ect of the present invention is to provide a combustion grate having an improved tensioning device to maintain the alignment of each row of grate blocks of the combustion grate , the tensioning device requiring low maintenance ef fort and having a cost ef fective , simple construction . It is also an obj ective of the present invention to provide a combustion grate that can be wider than combustion grates presently commercially available .

[0015] This obj ect is achieved by the combustion grate defined in independent claim 1 .

[0016] Preferred embodiments of the combustion grate according to the invention are reflected in the dependent claims .

[0017] In an incinerator of a waste incineration plant , a combustion grate or a plurality of combustion grates arranged next to each other can be present . The combustion grate can be sloped downwards in a direction of conveyance of a waste bed for combustion .

[0018] The combustion grate has a first border region and a second border region opposed to the first border region that border laterally the combustion grate in a direction parallel to the direction of conveyance of the combustion grate .

[0019] The combustion grate comprises rows of grate blocks aligned perpendicular to the direction of conveyance . Each row of grate blocks overlaps the row ahead of it to form the combustion grate . The grate blocks of a row are attached to either a fixed or a moving guide at the back part of the grate blocks which is located below the prior overlapping grate blocks . Alternate rows of grate blocks can be moved in a reciprocating manner by a moving structure including the guide and providing the reciprocating motion .

[0020] A grate block comprises a block body which is usually configured as a casting and substantially in the form of an elongated hollow cuboid with a longitudinal axis . The grate block comprises an upper wall which forms a bearing face along which the incinerator charge is to be conveyed, a front wall closing the grate block perpendicularly to the longitudinal axis and side walls closing the sides of the grate block .

[0021] The combustion grate comprises a tensioning device for a row of grate blocks arranged in the combustion grate that is designed to maintain the alignment of the row of grate blocks perpendicular to the direction of conveyance . The tensioning device extends along a longitudinal axis defining a longitudinal direction that is perpendicular or substantially perpendicular, i . e . within the angular tolerance limits to keep an alignment of the row of grate blocks , to the direction of conveyance . The grate blocks are stably connected in a row to each other by the tensioning device that extends under the upper walls of the grate blocks , perpendicular to the direction of conveyance and across the inside width between the first border region and the second border region .

[0022] According to the invention, the tensioning device comprises a cable having a cable first end region and a cable second end region opposed to the cable first end region, a first connecting means for connecting the cable first end region to a side wall of the first border region, and a second connecting means for connecting the cable second end region to a side wall of the second border region .

[0023] A cable in the meaning of the present invention is made of a group of metallic strands that are twisted or braided together into a larger and stronger form . Each strand can in turn be made of several wires twisted together .

[0024] Various studies have shown that cables , in particular steel cables , have an ideal elasticity range to meet the requirements of a combustion grate in a large incinerator . The behavior comparison under stress is best illustrated by the graphic represented in Fig . 8 . Cables have a tensile strength and can withstand larger longitudinal stress while being stretched or pulled before breaking than a metallic rod known in the prior art . Further, in contrary to a metallic rod that breaks all at once , a cable is less critical in this regard because strands making up the cable can easily take up the load in case some other strands are damaged . It follows that the tensioning device exhibits less sensitivity to the various conditions present during operation of the incinerator, for example less sensitivity to expanding during operation or to retracting during shutdown of the incinerator . Further, the wear control of the tensioning device becomes easier because failures of the cable can be anticipated when some strands are visibly damaged, acting as a warning signal . In this case , the cable can be replaced before complete rupture . In contrary, the wear control of a tension rod is more di f ficult to estimate and the risk of having an entire row of grate blocks li fting because of tension rod rupture is accordingly more di f ficult to anticipate .

[0025] In addition, the cable can be dimensioned such that its elastic modulus allows a cable tension that maintain the alignment of the row of grate blocks in the mounted state of the row of blocks and during operation of the incinerator . For this purpose , the tensioning device can be mounted for example by means of a cable tensioning clamp for pulling the cable to fix it to the side wall of the first border region or, as the case may be , of the second border region . This arrangement without a separate tensioning means included in the tensioning device is advantageous for its simple and economical conception .

[0026] In a preferred embodiment , the first border region and the second border region are formed by press plates of the combustion grate that extend parallel to the direction of conveyance . The lateral sides or side walls formed by the press plates extend parallel to the direction of conveyance . In a row, the grate blocks are stably maintained aligned by the tensioning device extending perpendicular to the direction of conveyance and across the inside width between the press plates . The tension applied by the tensioning device presses the press plates on both side of the row of grate block . This embodiment reinforces the stability of the combustion grate . In another preferred embodiment , the first border region and the second border region are formed by a first side grate block and a second side grate block, respectively, the first side grate block forming a first end of the row and the second side grate block forming a second end of the row opposed to the first end of the row . The first side grate block and the second side grate block are arranged adj acent to the corresponding side walls formed by press plates . The first side grate block and the second side grate block can be fixed to press plates to form a robust structure . However, the first side grate block and the second side grate block can also be free to move relatively to the press plates i f the raw of grate blocks is a moving row of the combustion grate . In a row, the grate blocks are stably connected to each other by the tensioning device extending perpendicular to the direction of conveyance and across the inside width between the first side grate block and the second side grate block .

[0027] In a preferred embodiment , an end of the first connecting means that faces away from the cable and / or an end of the second connecting means that faces away from the cable is formed as a foot plate , the foot plate being configured to be inserted in a similar shaped hole in the side wall of the first border region and / or the side wall of the second border region, respectively, and to be subsequently rotated by an angle , preferably of 90 ° , so as to rest on the surface of the side wall facing away from the cable and to be retained in the mounted state of the row o f grate blocks .

[0028] In an embodiment in which the first border region is formed by the first side grate block, the end of the first connecting means facing away from the cable can be formed as a foot plate that can be used as a locking means of the tensioning device to the first side grate block . The foot plate is formed as plate having a geometry from which a shaft proj ects for a direct or indirect , i . e . by way of intermediary components , connection to the cable . To lock the tensioning device , the side wall of the first side grate block facing in the direction to the cable has a hole having a similar shape as the plate to allow the insertion of the foot plate into the side wall . In the mounted state of the row of grate blocks , the first connecting means is positioned such that the foot plate extends beyond the side wall in the interior of the first side grate block . In this manner, the plate , after the foot plate has been subsequently rotated by an angle , can rest on the surface of the s ide wall facing the interior of the grate block . This arrangement has the advantage of an easy assembly for the installation and, conversely, disassembly for maintenance . Preferably, the foot plate and the shaft are made into a single piece for a better resistance .

[0029] Preferably the plate of the foot plate has a rectangular shape that is simple to manufacture . However, other shapes can be considered that allow the same principle of locking, for example elliptical shapes . on the opposed side of the tensioning device , the second connecting means and the second side grate block can be formed in the same manner as j ust described . This has the advantage of a simpli fied mounting of the tensioning device . However, it is also possible that the opposed side of the tensioning device is fixed by other means known in the art that does not include a foot plate . The same principle can be applied mutatis mutandis to the case in which the first border region and the second border region are formed by press plates . To lock the tensioning device , the side wall formed by the press plate has a hole having a similar shape as the plate to allow the insertion of the foot plate into the side wall .

[0030] In a preferred embodiment , the end of the first connecting means and of the second connecting means are formed as foot plate . This embodiment can be assembled simply because both ends are formed in the same manner .

[0031] More generally, connection means configured to removably fix at least one of the first connection means or the second connecting means to the first border region or the second border region, respectively, can be chosen to retain the tensioning device .

[0032] In a preferred embodiment , the first connecting means or the second connecting means is welded to the side wall of the first border region or the side wall of the second border region, respectively . Advantageously, welding simpli fies the assembly .

[0033] In a preferred embodiment , the first connecting means and / or the second connecting means comprise a cable fitting configured to be connected in the mounted state with the cable first end region and / or the cable second end region, respectively . A cable fitting provides an inexpensive interface between cable and first or second connecting means that can be fixed permanently to the cable first and / or second end regions with widespread and economical techniques . For example , the cable fitting can comprise a sleeve extending longitudinally in which a cable end region is loosely inserted and a mechanical or hydraulic tool compress and deforms the sleeve , creating a permanent j oint between the cable and the cable fitting .

[0034] In a more preferred embodiment , the cable fitting comprises a threaded section formed at the end of the cable fitting opposed to the cable , and the first connecting means and / or the second connection means comprises a receiving threaded section corresponding to the threaded section to attach the cable fitting . This arrangement provides a simple connection interface between the cable and the first and / or second connecting means in case it is necessary to replace the cable . Preferably, the receiving threaded section is in the form of a rod having a threaded longitudinal hole .

[0035] In a preferred embodiment , the end of the first connecting means and / or of the second connecting means that face away from the cable are formed as foot plate , wherein the foot plate is formed as plate having a geometry from which a shaft proj ects , an end region of the shaft facing in the direction of the cable being configured as the cable fitting . The cable fitting can be formed as a blind hole extending longitudinally in the shaft designed to receive the corresponding cable end region .

[0036] In a preferred embodiment , the cable fitting has two parallel surfaces arranged diametrically opposed with respect to the longitudinal axis for torque transmission . Preferably, the two surfaces are at the same radial distance to the longitudinal axis . The two surfaces are preferably at a distance from each other that allows torquing by a wrench of the corresponding si ze . The surfaces can also be used for keeping the cable fitting in a fixed rotational position . This feature is helpful during assembly and disassembly of the tensioning device to hold the cable fitting in fixed position or to apply a torque .

[0037] In a preferred embodiment , the tensioning device comprises a tensioning means to adj ust the tension of the cable in the mounted state of the row of grate blocks . The tensioning means has the advantage that the tension range that can be applied to the tensioning device is wider than the tension range available based on the elastic modulus of the cable alone . This can be advantageous in case the temperature to which the tensioning device is submitted has a large variation range , thereby submitting the tensioning device to large expansion .

[0038] In a preferred embodiment , the tensioning means is a turnbuckle which is well known means to apply a tension in a tensioning device . In a preferred embodiment , the turnbuckle can be formed as a rod having a first threaded hole extending longitudinally from a first end of the rod, the threaded hole being configured to receive a threaded segment of the first connecting means or the second connection means . Further, the rod has a second threaded hole extending longitudinally from a second end of the rod opposed to the first end of the rod, the second threaded hole being configured to receive a threaded section formed at the end of the corresponding cable fitting, wherein the thread of the second threaded hole runs in a direction opposed to the thread of the first threaded hole .

[0039] In a preferred embodiment , the first connecting means or the second connecting means comprises a main body distinct from the cable fitting and connected in the mounted state to the side wall of the first border region or to the side wall of the second border region, respectively, and the tensioning means is arranged between the cable fitting and the main body . Preferably, the tensioning means is configured to be connected at a first end to the main body and at a second end opposed to the first end to the cable fitting . In this embodiment , the tensioning means is embedded in the first connecting means or of the second connecting means between the main body and the cable fitting, thereby forming a compact arrangement .

[0040] It is also conceivable to arrange the tensioning means in an intermediate position of the cable between two segments of the cable . The connections to the cable can be ensured by further cable fittings as described previously .

[0041] In a preferred embodiment characteri zed by at least one of the cable fittings having a threaded section formed at the end of the cable fitting opposed to the cable , and by the tensioning means being arranged between the cable fitting and the main body of the first connecting means or of the second connecting means , the threaded section of the cable fitting can be configured to be screwed directly in the tensioning means . This embodiment is also compact and requires less distinct parts .

[0042] In another preferred embodiment , the tensioning means is formed as a threaded portion formed in an end region of the first connecting means that faces away from the cable or in an end region of the second connecting means that faces away from the cable , wherein the threaded portion extends in the mounted state of the row of grate blocks through an opening in the side wall of the first border region or an opening in the side wall of the second border region, respectively, and the threaded portion is retained by at least one nut screwed on each side of the side wall . Preferably, the threaded portion is arranged at the end of the first connecting means or the second connecting means facing the first border region or of the second border region, respectively, to form a compact arrangement .

[0043] In a preferred embodiment , the cable has a diameter of at least 6 . 0 mm, more preferably between 8 . 0 mm and 25 . 0 mm, most preferably between 10 . 0 mm and 15 . 0 mm . These ranges cover the main temperature ranges that can be found in the incinerator while allowing a suf ficient tensioning of the rows of grate blocks .

[0044] In a preferred embodiment , the cable is made of steel , preferably stainless steel to reduce the risk of corrosion and withstand the temperature range present in the incinerator .

[0045] In a preferred embodiment , the cable has at least three strands to provide for a minimum elasticity modulus .

[0046] In a preferred embodiment , the cable extends continuously from the cable first end region to the cable second end region . In other words , the cable is free from an interruption from the cable first end region to the cable second end region . This embodiment avoid the use of connection parts that are necessary i f the cable is provided in several sections , thereby reducing the production costs .

[0047] The invention will be illustrated by means of the appended figures , in which :

[0048] Fig . 1 shows a perspective view of a combustion grate comprising a tensioning device according to the invention; Fig. 2 shows a perspective view of a tensioning device according to the invention;

[0049] Fig. 3A shows a front view of a portion of the tensioning device according to Fig. 2 including a first connecting means;

[0050] Fig. 3B shows a front view of the first connecting means of Fig. 3A;

[0051] Fig. 3C shows a front view of the cable fitting of Fig. 3A;

[0052] Fig. 4 shows a perspective view of the first connecting means of Fig. 3B;

[0053] Fig. 5 shows a perspective view of the turnbuckle of Fig. 2;

[0054] Fig. 6 shows a perspective view of a portion of the second connecting means of Fig. 2;

[0055] Fig. 7A shows a front view of a cable according to a further embodiment of the tensioning device;

[0056] Fig. 7B shows a front view of a first cable fitting of Fig. 7 A;

[0057] Fig. 7C shows a front view of a second cable fitting arranged at the end of the cable of Fig. 7A opposed to the first cable fitting; and

[0058] Fig. 8 illustrates the behavior of a steel rod and of two different steel cables under the effect of a tensile force . The basic structure of a combustion grate 10 with its essential elements is illustrated in a perspective view in Fig . 1 . In an incinerator of a waste incineration plant , a plurality of such combustion grates 10 can be arranged next to each other as represented in Fig . 1 in which a portion of combustion grates arranged laterally on both side of the combustion grate 10 are also shown .

[0059] The combustion grate 10 is sloped downwards in the direction of conveyance , as represented by an arrow 12 . The combustion grate 10 is delimited laterally by a pair of side walls 14a, 14b formed by press plates 15a, 15b .

[0060] The combustion grate comprises rows 16 of grate blocks 18 aligned perpendicular to the direction of conveyance 12 . Each row of grate blocks overlaps the row ahead of it to provide the combustion grate . In Fig . 1 the grate blocks are removed in the two rows at the back of the combustion grate to show the attachment to either a fixed or moving guide 20 at the back part of the grate blocks which is located below the prior overlapping grate blocks . The alternate rows which move in a reciprocating manner are supported by a moving structure including the guide 20 , said moving structure providing the reciprocating motion .

[0061] Each row of grate blocks has a first side grate block 22a forming a first end of the row and a second side grate block 22b forming a second end of the row opposed to the first end of the row . The first side grate block 22a and the second side grate block 22b are arranged adj acent to the corresponding side wall 14a, 14b and form a first border region and a second border region, respectively . In a row 16 the grate blocks 18 are stably connected to each other by a tensioning device . The tensioning device 30 extends perpendicular to the direction of conveyance 12 and across the inside width between the first side grate block 22a and the second side grate block 22b .

[0062] The tensioning device 30 comprises first connecting means 40 for connecting a cable first end region 70a to a side wall of the first side grate block 22a, and second connecting means 50 for connecting a cable second end region 70b to a side wall of the second side grate block 22b . In the embodiment represented the side wall of the first side grate block facing the interior of the row and the side wall of the second side grate block facing the interior of the row have each an opening 54 through which the first connecting means and the second connecting means extend, respectively, for securing to the side walls for example by nuts on threaded ends of the first connecting means and the second connecting means . Further possible embodiments for securing the first connecting means and the second connecting means are discussed below .

[0063] The tensioning device also comprises a tensioning means in the form of a turnbuckle 60 arranged in the first connecting means and configured to tension the tensioning rod to keep the alignment of the grate blocks in a row .

[0064] The tensioning device 30 itsel f is represented in Fig . 2 . The tensioning device 30 for a row of grate blocks arranged in a combustion grate is designed to maintain the alignment of the rows 16 of grate blocks 18 .

[0065] The tensioning device 30 comprises a cable 70 having a cable first end region 70a and a cable second end region 70b opposed to the cable first end region, first connecting means 40 designed for connecting the cable first end region 70a to a side wall of the first side grate block 22a, and second connecting means 50 designed for connecting the cable second end region 70b to a side wall of the second side grate block 22b .

[0066] The cable 70 has suitably a diameter of at least 12 . 0 mm comprising at least three strands and is made of stainless steel .

[0067] The second connecting means 50 , also represented in Fig . 4 and in the mounted state in Fig . 3B, comprises a foot plate 80 having a rectangular shape arranged at the end of the second connecting means facing away from the cable . A second cable fitting 82 in the form of a hollow cylindrical shaft proj ects in the longitudinal direction perpendicularly from the foot plate , delimiting a blind hole extending longitudinally . The foot plate 80 and the second cable fitting 82 are made into a single piece . The foot plate is configured to be inserted in a similar shaped hole in the side wall of the second side grate block 22b . The second connecting means extends through the side wall so that the second connecting means can be subsequently rotated by an angle , for example 90 ° , to rest on the surface of the side wall facing away from the cable 70 and secure the tensioning device in the mounted state of the row of grate blocks . The blind hole is designed to receive the cable second end region 70b which is fixed in the blind hole preferably by swaging .

[0068] As shown in Fig . 3A, at the cable first end region 70a a first cable fitting 86 is arranged, having the form of a hollow cylindrical shaft extending longitudinally and forming a blind hole in the direction facing the cable . The blind hole is designed to receive the cable first end region . The cable fitting extends longitudinally in the direction opposed to the cable in the form of an externally threaded rod 88 as represented in Fig . 3C . The first connecting means has two parallel surfaces 90 , only one which is visible in Fig . 3C, formed on the first cable fitting 86 and designed for torque transmission by positive locking .

[0069] The turnbuckle 60 used as tensioning means to adj ust the tension of the cable is formed as a rod having a hexagonal cross section, as shown in Fig . 5 , to allow tightening with a wrench . The rod has a first threaded hole extending longitudinally from a first end of the rod 60a, the threaded hole being configured to receive a threaded segment 100 of the first connecting means 40 .

[0070] The rod has a second threaded hole extending longitudinally from a second end of the rod 60b opposed to the first end of the rod, the second threaded hole being configured to receive the external ly threaded rod of the first connecting means 40 , wherein the thread of the second threaded hole runs in a direction opposed to the thread of the first threaded hole . A marking 62 is present at the second end of the rod to identi fy the orientation of the turnbuckle and the corresponding thread directions in the mounted state of the tensioning device .

[0071] The first connection means comprises further a foot plate 102 having a rectangular shape arranged at the end of the first connecting means facing away from the cable . A cylindrical shaft 104 proj ects in the longitudinal direction perpendicularly from the foot plate . The foot plate 102 is configured to be inserted in a similar shaped hole in the side wall of the first side grate block 22a . The first connecting means extends through the side wall so that the first connecting means can be subsequently rotated by an angle , for example 90 ° , to rest on the surface of the side wall facing away from the cable 70 and secure the tensioning device in the mounted state of the row of grate blocks . The shaft 104 ends with the threaded segment 100 configured to be screwed in the first threaded hole of the turnbuckle 60 .

[0072] A further embodiment illustrated in Fig . 7 is also conceivable in which a first cable fitting 86 is arranged at the cable first end region 70a, the cable fitting having the same embodiment as the first cable fitting described above and being designed to receive the cable first end region . The first cable fitting extends longitudinally in the direction opposed to the cable in the form of an externally threaded rod 88 as represented in Fig . 7C . A second cable fitting 86 ' having the same embodiment as the first cable fitting 86 is arranged at the cable second end region 70b .

[0073] The graphic of Fig . 8 shows the elongation of a steel rod ( reference A) and of two di f ferent steel cables ( reference B, reference C ) measured on the X-axis ( from 0 mm to 200 mm) under the ef fect of a tensile force represented on the Y-axis ( from 0 N to 90000 N) . Reference A is a known steel rod used in combustion grate to keep the grate blocks aligned . Reference B is a cable of 19 strands made of stainless steel A4 1 . 4401 AIS I 316 , rigidity of 1260- 1570 N / mm . Reference C is a cable of 7x7 strands made of stainless steel A4 1 . 4401 AIS I 316 , rigidity of 1570 N / mm . The thermal expansion of the combustion grate in all directions , in particular in the direction along the rows of grate blocks , is the source of the tensile force acting on the steel rod or on the steel cables .

[0074] For the same initial length of 2 . 75 m and diameter of 10 mm, the failure of the steel rod ( reference A) occurs after only an elongation of approximately 10 mm, whereas the steel cables resist up to an elongation of 120 mm to 180 mm for the cables of reference B and reference C, respectively .

[0075] List of reference signs

[0076] Combustion grate 10 direction of conveyance 12 side walls of the combustion grate 14a, 14b press plates 15a, 15b rows of grate blocks 16 grate blocks 18 guide of grate blocks 20 first and second side grate block 22a, 22b tensioning device 30 first connecting means 40 second connecting means 50 opening in the side wall o f grate block 54 turnbuckle 60 first and second end of the rod 60a, 60b marking 62 cable 70 cable first and second end region 70a, 70b foot plate of second connection means 80 second cable fitting 82 first cable fitting 86 externally threaded rod 88 surfaces for torque transmission 90 threaded segment 100 foot plate of first connection means 102 shaft of first connection means 104

Claims

Claims1. Combustion grate (10) for an incinerator of a waste incineration plant, the combustion grate (10) having a first border region and a second border region opposed to the first border region, said first border region and second border region bordering laterally the combustion grate (10) and extending in a direction parallel to a direction of conveyance (12) of the combustion grate, a row of grate blocks extending between the first border region and the second border region, the combustion grate comprising a tensioning device (30) for the row (16) of grate blocks (18) arranged in the combustion grate (10) , the tensioning device (30) extending in a longitudinal direction and being designed to maintain the alignment of the row of grate blocks, characterized in that the tensioning device comprises a cable (70) having a cable first end region (70a) and a cable second end region (70b) opposed to the cable first end region (70a) , a first connecting means (40) for connecting the cable first end region (70a) to a side wall (14a) of the first border region, and a second connecting means (50) for connecting the cable second end region (70b) to a side wall (14b) of the second border region.

2. Combustion grate (10) according to claim 1, characterized in that the first border region and the second border region are formed by press plates (15a, 15b) of thecombustion grate that extend parallel to the direction of conveyance (12) , or in that the first border region and the second border region are formed by a first side grate block (20a) and a second side grate block (20b) , respectively, the first side grate block (20a) forming a first end of the row and the second side grate block (20b) forming a second end of the row opposed to the first end of the row.

3. Combustion grate (10) according to claim 1 or 2, characterized in that an end of the first connecting means (40) that faces away from the cable and / or an end of the second connecting means (50) that faces away from the cable is formed as a foot plate, the foot plate being configured to be inserted in a similar shaped hole in the side wall of the first border region and / or the side wall of the second border region, respectively, and to be subsequently rotated by an angle, preferably of 90°, so as to rest on the surface of the side wall facing away from the cable (70) and to be retained in a mounted state of the row (16) of grate blocks (18) .

4. Combustion grate (10) according to any one of claims 1 or2, characterized in that the first connecting means (40) or the second connecting means (50) is welded to the side wall of the first border region or the side wall of the second border region, respectively.

5. Combustion grate (10) according to any one of claims 1 to4, characterized in that the first connecting means (40) and / or the second connecting means (50) comprise a cable fitting (82, 86) configured to be connected in the mountedstate with the cable first end region (70a) and / or the cable second end region (70b) , respectively.

6. Combustion grate (10) according to claim 5, characterized in that the cable fitting (82, 86) comprises a threaded section formed at the end of the cable fitting opposed to the cable, and in that the first connecting means (40) and / or the second connection (50) means comprises a receiving threaded section corresponding to the threaded section to attach the cable fitting (82, 86) , the receiving threaded section being preferably in the form of a rod having a threaded longitudinal hole.

7. Combustion grate (10) according to any one of claims 5 to6, characterized in that the cable fitting (82, 86) has two parallel surfaces (90) arranged diametrically opposed with respect to a longitudinal axis of the tensioning device for torque transmission.

8. Combustion grate (10) according to any one of claims 1 to7, characterized by a tensioning means to adjust the tension of the cable (70) in the mounted state of the row of grate blocks (18) .

9. Combustion grate (10) according to claim 8, characterized in that the tensioning means is a turnbuckle (60) .

10. Combustion grate (10) according to any one of claims 5 to 7 and any one of claims 8 to 9, characterized in that the first connecting means or the second connecting means comprises a main body distinct from the cable fitting and connected in the mounted state to the side wall (14a) of the first border region or to the side wall (14b) of thesecond border region, respectively, and the tensioning means is arranged between the cable fitting and the main body .

11. Combustion grate (10) according to claim 8, characterized in that the tensioning means is formed as a threaded portion formed in an end region of the first connecting means (40) that faces away from the cable (70) or in an end region of the second connecting means (50) that faces away from the cable (70) , wherein the threaded portion extends in the mounted state of the row of grate blocks (18) through an opening in the side wall (14a) of the first border region or an opening in the side wall (14b) of the second border region, respectively, and the threaded portion is retained by at least one nut on each side of the side wall.

12. Combustion grate (10) according to any one of claims 1 to 11, characterized in that the cable (70) has a diameter of at least 6.0 mm, more preferably between 8.0 mm and 25.0 mm, most preferably between 10.0 mm and 15.0 mm.

13. Combustion grate (10) according to any one of claims 1 to12, characterized in that the cable (70) is made of stainless steel.

14. Combustion grate (10) according to any one of claims 1 to13, characterized in that the cable (70) has at least three strands.

15. Combustion grate (10) according to any one of claims 1 to14, characterized in that the cable (70) extendscontinuously from the cable first end region (70a) to the cable second end region (70b) .

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