Patent Application
20130171575
The present application relates to grate bars for use in furnaces.
In particular, the present application relates to improved grate bars for a thrust grate and especially for a reverse feed thrust grate that comprises a grate with a reciprocating motion. Therein, rows of grate bars are stacked on top of each other.
FR2599125 describes a grate bar in which interconnection between neighbouring grate bars is at the distal end.
DE3049086, U.S. Pat. No. 4,239,029 and DE3610819A1 describe arrangements of interconnected grate bars in which no relative movement between neighbouring bars is possible.
FR2599125 describes an arrangement of interconnected grate bars which is only located at the distal end of the bars.
DE1783200 describes an arrangement of interconnected grate bars in which the coupling means is integrated with ribs disposed on the underside of the grate bars.
DE911317 describes an arrangement of interconnected grate bars in which neighbouring bars can move longitudinally relative to one another, the side of the grate bars being modified to form engaging hooked lips. However, there is only a relatively small longitudinal area of interconnection.
U.S. Pat. No. 4,239,029 describes an arrangement of interconnected grate bars in which there is one interconnection along the longitudinal axis. Likewise, DE911317 discloses an arrangement in which the interconnection means is at one location along the longitudinal axis of the grate bar.
DE 2805712 describes an arrangement of interconnected grate bars, each having two coupling means at proximal and distal ends of the grate bar, however only one of the coupling means has an elongated groove to allow longitudinal movement of one bar with respect to its neighbour.
U.S. Pat. No. 4,240,402 describes an arrangement in which an interconnection between neighbouring grate bars allows pivotal movement of one grate bar with respect to the other, but not longitudinal planar movement.
DE 20 2007 018 707 U1 describes a roller grate with stationary grate elements that form the cylindrical surface of the roller grate.
Among others, the present application relates to an improved arrangement of interconnected grate bars and to improved grate bars
The grate bars according to the application comprise a coupling means with an elongated recess on the side of one grate bar and an engaging element on the abutting side of a neighbouring grate bar, which limits or prevents the lifting up relative to neighbouring grate bars and the tilting and falling down of broken grate bar pieces.
According to the application, neighbouring grate bars are able to move relative to each. In particular, the elongated recess and the corresponding engaging element of the neighbouring grate bar, which engages into the elongated recess, are formed such that the engaging element can move within the elongated recess along a longitudinal direction of the grate bars.
The relative movement of neighbouring grate bars improves mixing and comminution of combustible material and also provides a better gas supply for an improved combustion.
Furthermore, the grate bars according to the application comprise an arrangement of two interconnections, one at the proximal end and the other at the distal end of the grate bar, to prevent a broken grate bar from falling onto the base. It is advantageous if the parts of a broken grate bar, that are still moving, do not protrude too much from a row of grate bars in order to avoid damage to the frame of a grate.
It is an object of the application to provide improved grate bars for use in a furnace.
The application discloses a grate bar for a furnace that comprises an elongated recess at a first side of the grate bar. The elongated recess can be located at a proximal side of the grate bar. Herein “proximal” refers to the driven side, which is driven either directly via a moving step frame or indirectly via another grate bar at a first side of the grate bar.
The elongated recess comprises two parallel sliding surfaces which are oriented in longitudinal direction of the grate bar. The elongated recess may have a closed shape or may also be provided by just two longitudinal projections with parallel sliding surfaces that are facing each other to form a groove.
The elongated recess is provided in a longitudinal direction of the grate bar such that a corresponding neighbouring engaging element of a first neighbouring part is movable within the elongated recess in the longitudinal direction relative to the grate bar. The elongated recess is shaped such that a corresponding neighbouring engaging element of a first neighbouring part is movable within the elongated recess in the longitudinal direction relative to the grate bar.
The distance between the parallel sliding surfaces of the elongated recess is slightly larger than the distance between parallel sliding surfaces of an elongated recess of a further neighbouring part.
The elongated recess and the parallel sliding surfaces of the elongated recess can be seen, for example, on the second elongated recess 45 of
The grate bar further comprises an engaging element at a second side of the grate bar which is opposite to the first side. In particular, the engaging element may be located at the proximal side of the grate bar. The engaging element comprises two parallel sliding surfaces which are oriented in longitudinal direction of the grate bar.
The two parallel sliding surfaces of the engaging element can be seen for example, in
The neighbouring part may belong to a neighbouring grate bar or to a step frame. The longitudinal direction of the grate bar is the direction in which the grate bar has the longest extension.
Two “ends” of an engaging element are defined by two opposing points where the engaging member first touches the elongated recess when one is rotated relative to the other.
According to the application, the engaging element can be provided as an exchangeable part, for example by machining a bore into a main body of the grate bar such that the engaging element can be inserted into the bore. In addition, the bore may comprise a threading.
By providing predetermined longitudinal dimensions of the engaging element and the elongated recess of a grate bar, the grate bar is guided against tilting more than a predetermined relative. A longitudinal dimension of the elongated recess is can be made least as large as a longitudinal dimension of a neighbouring engaging part.
To provide for a relative movement between neighbouring grate bars it is furthermore advantageous to make a longitudinal dimension of the elongated recess at least as large as a large as the sum of a longitudinal dimension of a neighbouring engaging part, which engages into the elongated recess, and a maximum relative longitudinal displacement between neighbouring grate bars. Herein, the maximum longitudinal displacement is determined by a distance between the actuating surfaces of the grate bar and by a lateral dimension of an engaging member of a reciprocating grate that engages into the space between the actuating surfaces. Herein, it is understood, that the engaging member of the reciprocating grate can be itself fixed or reciprocating and that a reciprocating grate may comprise a fixed sub-grate.
Furthermore, the grate bar comprises two actuating surfaces at a bottom side of the grate bar for taking up a protrusion of a reciprocating grate such that the grate bar can be moved back and forth by an underlying reciprocating gate.
The proximal engaging element has a longitudinal shape with a first end and a second end, wherein the height of the proximal engaging element at the first end and at the second end is slightly smaller than the height of a corresponding proximal elongated recess of a further neighbouring part. More specifically, the further neighbouring part can be provided at opposite sides of the first neighbouring part.
A relative tilt angle between neighbouring grate bars is determined by the height difference of elongated recess and the engaging element and the geometrical shape of the engaging element. Advantageously, the tilt angle is such that a broken piece of a grate bar does not contact the underlying grate frame, for example less than 45° degrees.
The grate bar according to the application may furthermore comprise a distal elongated recess and a distal engaging element. “Distal” refers to a location close to the opposite side to the proximal side of the grate bar where the grate bar slides freely on a further grate bar. Preferably, the distal elongated recess is provided also at the first side of the grate bar and the distal engaging element is preferably also located at the second side of the grate bar. The distal engaging element can have the same shape as the proximal engaging element and the distal elongated recess can have the same shape as the proximal elongated recess. Preferentially, the engaging elements are fixed with respect to grate bar in order to prevent tilting and uplifting of the grate bar. The elongated recesses may be cast as part of a side of the grate bar.
In a further modification, at least one coupling element is adapted to the corresponding engaging element of the first neighbouring grate part such that the elongated recess can only tilt relative to the engaging element of the first neighbouring part by a tilt angle that does not exceed a maximum tilt angle. Furthermore, at least one engaging element is adapted to the corresponding coupling element of the second neighbouring part such that the engaging element can only tilt relative to the elongated recess of the second neighbouring part by a tilt angle that does not exceed the maximum tilt angle.
In a more specific embodiment, a height of the rectangular cross section of the engaging element is slightly smaller than the height of the corresponding elongated recess of the neighbouring part and a width of the rectangular cross section—or a longitudinal distance between the first end and the second end—is greater than the height of the corresponding elongated recess. By making the height slightly smaller, the engaging element can move within the elongated recess and by making the width greater than the height of the elongated recess the engaging element can lock at a tilting angle.
In a further embodiment, at least one of the engaging elements has an octagonal cross section and a height of the octagonal cross section is slightly smaller than the height of the corresponding elongated recess of the neighbouring part and a width of a longitudinally aligned surface of the engaging element that is parallel to a longitudinal axis of the engaging element is greater than the height of the corresponding elongated recess.
More generally, the engaging element may have two parallel horizontal faces and at least one oblique face, that is at an angle to the parallel faces. Waste particles are cut by movement against the oblique face and the parallel faces provide alignment of neighbouring grate bars.
In a further modification, at least one of the engaging elements has a bone shaped cross section, the bone shaped cross section comprising two widened ends, wherein a height of the widened ends is slightly smaller than the height of the corresponding elongated recess of the neighbouring part and a maximum distance of the widened ends is greater than the height of the corresponding elongated recess.
In a further embodiment, the proximal engaging element is provided next to a proximal end of the grate bar and the distal engaging element is placed next to a distal end of the grate bar. Furthermore, the proximal end of the grate bar is in contact with a supporting element that may be driven or fixed and the distal end of the grate bar is in contact with an upper surface of a further grate bar.
Especially, the abovementioned elongated recesses may be formed out as a gap between two longitudinal protrusions that extend along the grate bar. Alternatively, the elongated recesses are formed out as a proximal elongated recess and a distal elongated recess which have an O-shaped cross section or which have a rectangular cross section. Thereby, less material is needed, reducing the overall weight.
Especially, the recess or recesses may be formed out as protrusions of a main body of the grate. At least one engaging element may comprise a bolt to fix the engaging element to the grate bar. Slanted grooves or air ducts may be provided next to at least one elongated recess. More specifically, the proximal engaging element may be provided at a distance of about 40 cm from the distal engaging element which provides a good support for a typical length of a grate bar of about 70-80 cm.
The application further discloses a grate arrangement for a furnace which comprises an arrangement of grate bars that are either fixed or movable relative to a supporting member. The fixed and movable grate bars comprise longitudinal recesses and engaging elements and the engaging elements of a grate bar engage into the longitudinal recesses of a neighbouring part. More specifically, the arrangement of fixed and movable grate bars comprises rows of fixed and movable grate bars, wherein the fixed and movable grate bars are alternated. The rows of fixed and movable grate bars are provided on either fixed or movable step frames.
In a further development according to the application, the grate bars according to the application comprise engaging elements which engage with coupling means of horizontally adjacent grate bars to provide a relative movement of the grate bars for the improved transport of waste material and for the comminution of material that has fallen between the grate bars. The engaging elements may comprise sharp edges for an improved comminution of material that has been trapped between adjacent grate bars. Furthermore, lateral aeration grooves of the grate bars may have opposing inclinations between horizontally adjacent grate bars to provide a scissor effect for the comminution of trapped material.
In a further aspect, the sides of the grate bar are adapted with lateral grooves, that may be inclined for cutting and disposal of combusted material, and for self-cleaning of the lateral grate bar surface. U.S. Pat. No. 4,520,792 describes an arrangement of two or more grate bars having sides adapted to have teeth and tooth spaces for comminution of material resting on the upper surface of the grate bars as one grate bar moves longitudinally in relation to the neighbouring grate bar. Here and in the following, the term “comminution” refers to mechanical shredding or pulverizing of waste, as for example in solid and waste water treatment.
DE634810 describes an arrangement of stationary and movable grate bars such that gaps between sides of neighbouring stationary and movable grate bars vary in configuration as the movable grate bar moves relative to the stationary grate bar, thereby effecting cutting of material which falls into the gaps.
According to a further aspect, the application discloses a grate bar having a modification to improve air flow in the region beneath and between neighbouring grate bars, (see especially
DE102004034322 describes an arrangement, which allows for air flow between grate bars.
DE19648128 and EP1315936B1 describe a grate bar having internal channels within the grate bar for circulation of a coolant liquid.
WO06117478, DE9309198 and DE102004032291 describe a grate bar with fins integrated underneath the upper side to define one or more paths for air flow within the grate bar.
In a further aspect, the distal end of a grate bar is fitted with a removable end-cap to eliminate the need for grate bar replacement when the grate bar end wears.
U.S. Pat. No. 812,071, CH663266A5, FR2694376 and FR2530319 all describe arrangements of removable grate bar end caps.
In a further modification, the frame comprises engaging elements which mate with elongated recesses of grate bars that are adjacent to the frame. In another modification, the frame comprises elongated recesses which mate with engaging elements of adjacent grate bars. The application further discloses a waste incineration plant with the abovementioned arrangement of fixed and movable grate bars. A cutting effect in lateral air ducts of the grate bars supports self-cleaning and reduces lateral forces on the grate bars.
Furthermore, the application discloses a use of a plurality of grate bars in an incineration plant for the assisting the burning of material during an incineration. A reciprocating grate is used to move a grate bar of the plurality of grate bars relative to a neighbouring grate bar of the plurality of grate bars. The moving of the grate bar comprises a movement of an engaging element with two parallel sliding surfaces of the grate bar in a longitudinal recess with to parallel sliding surfaces of the neighbouring grate bar. The parallel surfaces are for guiding the movement as well as for preventing a tilting of the grate bar by more than a predetermined tilting angle.
In a further aspect, the application provides a grate bar for a furnace that comprises a first air duct or groove at a first side of the grate bar, the first air duct that is provided at an angle other than 90 degrees with respect to a longitudinal axis of the grate bar, which is approximately the direction of relative movement of neighbouring grate bars. The inclination of at least one neighbouring groove against the vertical is made such that an edge of the first air duct together with an edge of a corresponding neighbouring air duct of a neighbouring part forms a cutting arrangement for particles that are caught in the area of the first air duct and the neighbouring air duct. In a specific embodiment, an inclination relative to the vertical is about 30°.
In a further modification, the grate bar comprises further air ducts at the first side of the grate bar which have substantially the same inclination as the first air duct and which extend over the entire length of the first side. In a further embodiment, the grate bar also comprises a second air duct at a second side of the grate bar which is opposite to the first side. The second air duct has an inclination which is substantially different from the inclination of the first air duct. In an alternative embodiment, the inclination of the grooves on the second side may also be substantially the same as the inclination of the first air duct. As for the first side, the second side may also comprise further air ducts which have substantially the same inclination as the second air duct and which extend over the entire length of the second side.
To achieve a good cutting effect, the air duct or at least one of the air ducts may be provided with a rectangular cross section or also a straight or a rounded saw tooth shaped cross section.
The application also discloses a grate arrangement for a furnace with an arrangement of fixed and movable grate bars which comprise the abovementioned air ducts, especially one in which the fixed and movable grate bars are alternated within horizontal rows and wherein the horizontal rows of fixed and movable grate bars are provided on fixed and movable step frames.
In a more specific embodiment of a grate according to the application, at least two neighbouring grate bars of the arrangement comprise lateral air ducts such that there is a cutting angle between the air ducts of one of the neighbouring grate bars and the air ducts of the other one of the neighbouring grate bars. Especially, the air ducts may be provided at an inclination of about 60° against the horizontal, which gives a good compromise between cutting action and air transport. The surfaces in which the air ducts are provided may be smoothed such that the grates can be placed close together and less waste is trapped.
Furthermore, the application also discloses a furnace with the abovementioned grate. The furnace may be fuelled with coal, biologic material, or other combustion material with a high heating value and the heat may be used to for power generation and/or teleheating. Furthermore, the application discloses a waste incineration plant with the above-mentioned grate.
A grate according to the application is used in the following way. A movable step frame and a fixed step frame are provided. Furthermore, an array of alternating fixed and movable grate bars is provided on the movable step frame and the fixed step frame, wherein horizontally adjacent grate bars are movably connected via engaging members that engage into elongated recesses and. The grate bars are also provided with lateral air ducts that are slanted differently between adjacent sides of horizontally adjacent grate bars.
An alternating movement between neighboring grate bars is generated and the movement is used to move supporting members of the movable step frame. Fixed grate bars are moved with the supporting members of the movable step frame. A supporting member engages into a space between a downwardly extending hook and a proximal modified region of a fixed grate bar
Movable grate bars are moved relative to supporting members of the movable step frame, wherein a supporting member engages into a space between a downwardly extending portion and a nose of the movable grate bar. Material particles in a region between the neighboring grate bars are cut by edges of corresponding air ducts.
In a further aspect, the application discloses a grate bar for a furnace, the grate bar comprising at least one but preferentially a plurality of air ducts which extends along at least one longitudinal side of the grate bar from its low-er surface to its upper surface such that combustion gas can stream from underneath the grate bar to above it. Different from the prior art, the air ducts are provided in a side face of the grate bar which is facing towards a side face of a neighbouring grate bar. Moreover, the air ducts may be formed straight to enable a good airflow and removal of trapped material.
According to a modification the air ducts are essentially evenly distributed along the at least one side. The air ducts may form groups of equidistant air ducts which are essentially evenly distributed along the at least one side.
In one embodiment, the grate bar comprises at least eight air ducts on one side of the grate bar. Ventilation is also possible with less air ducts but with eight air ducts or more than that, for example in three groups of three air ducts, there is an improved ventilation.
The air ducts may extend from below the upper surface of the grate bar to an upper surface of the grate bar. The upper layer of the grate bar is relatively thin. This provides short air ducts that are less likely to be choked by combustion material. In one embodiment, the air ducts are also inclined against the longitudinal axis of the grate bar to generate a cutting effect between neighboring grate bars.
The application moreover discloses a grate of several grate bars which comprise the aforementioned grooves wherein at least two neighboring surfaces of neighboring grate bars comprise air ducts with differing inclination. Air or combustion gas is injected into a combustion material on top of a grate of a furnace by blowing the air or combustion gas into a space below the grate and conducting the air to the upper side of grate bars along side faces of grate bars of the grate. Provided that obstructions in and above the ducts are substantially equal the air flow can be adjusted such that there is a substantially equal airflow through air ducts of a grate bar.
In a further aspect, the application discloses a grate bar for a furnace, comprising an exchangeable head at a distal end of the grate bar, the exchangeable head being fixed to the grate bar with at least two bolts. The bolts comprising bolt heads which engage into a first and a second T-shaped slit that are provided in the exchangeable head. The exchangeable head is provided between a first step and a second step of a receiving area of the grate bar. Thereby, the first and second steps take up thrust forces and the bolts are subjected to less strain. The slit may also take on a slightly modified form such as a Y-shape, for example.
The exchangeable head may be provided within an indentation formed out of a main body of the grate bar which has an H-shaped profile at its distal end. The at least two bolts may be provided in the form of at least one front bolt and at least one rear bolt wherein the front bolt is shorter than the rear bolt and the front bolt engages into the first T-shaped slit and the rear bolt engages into the second T-shaped slit. The bolts may be spot welded to the grate bar for fast manufacture and durable connection.
The exchangeable head may further be provided with a thrust element at a sloping surface of the exchangeable head, especially a thrust element with a triangular cross section. Furthermore, the exchangeable head may be provided with a clearing element at a horizontal surface of the exchangeable head, especially a clearing element has a triangular cross section.
Alternatively or in addition, the exchangeable head may also comprise a pyramidal portion. The bolts are provided in bores of the grate bar such that a clearance is left between the bolts and the bores.
In the following description, details are provided to describe the embodiments of the application. It shall be apparent to one skilled in the art, however, that the embodiments may be practised without such details.
Figures in the figure descriptions below have similar parts. The similar parts have the same names or similar part numbers. For the sake of brevity, the description of the similar parts is not repeated every time.
The front face 65 comprises a lower vertical part 67 and an upper oblique part 68. An end cap 70 comprises two upwards-facing portions, one horizontal portion 71 and one parallel portion 72 to the oblique part 68 of the front face 65.
The end cap 70 is secured to the grate bar 62 or 63 by bolts 74, 75 inserted from the underside of the upper part 16, as illustrated in
As can be best seen in
In use, the end cap 70 is removable from grate bar 62 or 63 by removing bolts 74 and 75. Further embodiments of the end cap 70 are provided by the end caps 70′, 70″ or 70″′ of
The lateral grooves 66 serve to remove jammed material between the grate bars 62, 63 to beneath the grate bars 62, 63.
This removal is achieved by the lateral grooves 66 of neighbouring grate bars 62, 63 moving in opposing directions. The relative movement cooperates to transport and comminute the waste material. The lateral grooves 46, 47 then channel the comminuted material below the grate bars 10. In addition, the lateral grooves 66 also allow air flow from underneath the grate bar 62, 63 to above the upper part 16 for providing combustion gas to the material to be combusted.
The distance between grooves 66 and the width of the grooves 66 are adapted such that any material received by the grooves 66 would be cut into pieces as the grate bars 62, 63 move relative to each other. The lateral grooves are provided along the whole length of the grate bars 62, 63 for providing combustion gas to the whole area of the grate 60.
As can be seen in
As shown in
In a further embodiment of an end cap 70, which is not shown in
At the distal end 14 of the movable grate bar 10, the upper part 16 and the longitudinal projection 17 extend to the front face 13 disposed at an angle to the upper part 16. The front face 13 has a retaining hole 20. The underside of the front end, not shown, has a flat, step-like groove 21. A first end cap 22 or a second end cap 23 may be removably affixed to front face 13 by means of an affixing means 24.
The first end cap 22 is approximately L-shaped in side elevation, having a left side comprising a lower face 48 and an upper face 49 and a lower side, not shown. The lower side has an upwardly projecting engaging lip 26 at the end of the lower side proximal to the lower face 48. The first end cap 22 has an attachment hole 27 extending from its upper face 49 to the underside of its upper face. The lower face 48 of first end cap 22 is oriented perpendicular to the upper side 16 of the movable grate bar 10 when it is mounted on the front face 13. The upper face 49 is disposed at an angle to the lower face 48.
The second end cap 23, which can be used as an alternative to the first end cap 22, is approximately L-shaped in side elevation, having a left side 25 and a lower side, not shown. The lower side has an upwardly projecting engaging lip 26 at the end of the lower side, not shown, proximal to the left side 25. Second end cap 23 has an attachment hole 27 extending from its left side 25 to the underside of its front end. The left side 25 of the second end cap 23 is flat and is perpendicular to the upper side 16 of the movable grate bar 10 when mounted on the front face 13.
The longitudinal projection 17 has six modified regions, a left proximal modified region 28, a left central modified region 29, a left distal modified region 30, a right proximal modified region 31, a right central modified region 32, and a right distal modified region 33. The left proximal modified region 28, the left central modified region 29, the left distal modified region 30, the right proximal modified region 31, the right central modified region 32 and the right distal modified region 33 are shaped as rips whose cross-sectional thickness is lower than the thickness of the other parts of the longitudinal projection 17. The surfaces of the regions 28, 29, 30, 31, 33, which serve to enhance the stability and which counteract bending under load, are unmachined. In contrast, the surfaces of the left side 11, the right side 12, and the longitudinal side 17 are smoothened.
The left and right proximal modified regions 28, 31 of the longitudinal projection 17 comprise a first protrusion 34 and a second protrusion 35 both extending downwardly from the lower side, not shown, of the longitudinal projection 17. The first protrusion 34 and second protrusion 35 have identical shape and form the left side 36 and back side, not shown, of the left and right proximal modified regions 28, 31. The left and right proximal modified regions 28, 31 further comprise an attaching hole 37 extending from the left proximal modified region 28 to the right proximal modified region 31. The front end 36 of both the first protrusion 34 and second protrusion 35 is disposed perpendicularly to the upper part 16 of the movable grate bar 10 and faces towards the front face 13.
A first engaging element 38 is disposed on the left side 11 of the longitudinal projection 17 situated longitudinally between the left proximal modified region 28 and left central modified region 29. The first engaging element 38 has a hole 39 extending in an axis between the distal end 14 and the proximal end 15 of the movable grate bar 10.
A second engaging element 40 is disposed on the left side 11 of the longitudinal projection 17 situated longitudinally between the left central modified region 29 and the left distal modified region 30. The second engaging element 40 has a hole 41 extending in an axis from the distal end 14 to the proximal end 15 of the movable grate bar 10.
A first grate bar coupling means 42 is disposed on the right side 12 of the longitudinal projection 17 situated longitudinally between the right distal modified region 31 and the right central modified region 32. The first grate bar coupling means 42 has a first elongated recess 43 with the axis of elongation from the distal end 14 to the proximal end 15 of the movable grate bar 10.
A second grate bar coupling means 44 is disposed on the right side 12 of the longitudinal projection 17 situated longitudinally between the right distal modified region 33 and the right central modified region 32. The second grate bar coupling means 44 has a second elongated recess 45 with the axis of elongation from the distal end 14 to the proximal end 15 of the movable grate bar 10.
A first set of three lateral grooves 46 extend from the left side 11 of the upper part 16 to the left central modified region 29. The first set of lateral grooves 46 has an angle of inclination to the vertical.
A second set of lateral grooves 47 extends from the left side 11 of the upper part 16 to the left proximal modified region 30. The second set of lateral grooves 47 has the same angle of inclination to the vertical as the first set of lateral grooves 46.
The lateral grooves 46 and 47 of
In use, several movable grate bars 10 are used in an incinerator for combusting material. In an arrangement of grate bars, each movable grate bar 10 is aligned with a horizontally adjacent fixed grate bar such that its left side 11, 17 abuts the right side 12, 17 of the neighbouring fixed grate bar. There is relative movement of one movable grate bar 10 with respect to the adjacent fixed grate bars. Herein, “fixed” refers to a movement relative to a step frame or supporting member, which means that a fixed grate bar moves together with the supporting member when the supporting member moves.
The pyramidal element 50 is used for improving the mixing of the material to be combusted and its transport velocity. It is designed such that it can be replaced without replacing the entire movable grate bar 10.
The first engaging element 38 engages the first elongated recess 43 and the second engaging element 40 engages the second elongated recess 45. Moreover, the first and second engaging elements 38, 40 can move within the first and second elongated recesses 43, 45 respectively in the axis of elongation of the elongated recesses 43, 45. In this arrangement of interconnected grate bars, relative movement of neighbouring grate bars in a longitudinal axis is possible. In the event that a movable grate bar 10 suffers a breakage, the engagement between the engaging elements and the coupling means enables the broken grate bar to continue to move relative to its neighbour and, therefore, prevent jamming of the system.
The upper part 16 is used for receiving material to be combusted and for aggravating the material to be combusted.
The left and right central modified regions 29, 32 allow combustion gas such as air from below the grate bar to access the upper part 16. Furthermore, the left and right central modified regions 29, 32 act as cooling fins for the upper part 16 via transferring heat from the upper part 16 to the left and right central modified regions 29, 32.
The left and right central modified regions 29, 32 enable the moving grate bar 10 to benefit from gas circulation in the region below the grate bar 10. This provides efficient heat transfer, thus increasing the lifespan of the grate bar 10.
The lateral grooves 46, 47 serve to let the combustion air pass via the grate bars 10 to the fuel in the furnace and to transport material that is jammed between the grate bars to beneath the grate bars 10.
The lateral grooves 46, 47 provide benefits of self-cleaning of jammed material from the upper part 16 and of providing gas to the upper part 16 of the grate bar 10. The lateral grooves 46, 47 are advantageously provided at the left central modified region 11, 17 and at the distal modified region 12, 17 respectively. This enables flow of air between the upper part 16 and beneath the grate bar 10.
The first end cap 22 or second end cap 23 is used to urge the received material for combusting forward. The first end cap 22 or second end cap 23 are also designed for removal from the front face 13 of the grate bar 10 for easy maintenance.
According to
The removability of the end cap 22, 23 has the advantage that the whole grate bar need not be replaced when only the front face is worn out. This reduces material cost and system downtime. The front end of the grate bar 10 often suffers wear. The removability of the end cap 22, 23 also allows to use end caps of different types.
To improve securing of first end cap 22 or second end cap 23, the engaging lip 26 engages the groove 21. Further, affixing means 24 is inserted through attachment hole 27 of either the first end cap 22 or second end cap 23 and engages retaining hole 20.
A bore 194 is provided in the main body 190 for taking up a bolt 191. At the bottom side of the pyramidal element 50, a slit 192 is provided. The slit 192 has an enlarged upper portion 193. A head of the bolt 191 is provided in the enlarged upper portion 193 of the slit 192 and a nut 160 is provided at the bottom of the main body 190. A bolt 191 is provided in the bore 194 of the main body 190 and in the slit 192 of the pyramidal element 50 such that the bolt 191 passes through the nut 160. The nut 160 is spot welded to the bolt 191.
At its proximal end, the upper part 81 is modified to form a downwardly extending hook 85. The longitudinal projection 83, 93, 94 has on one of its longitudinal sides three modified regions in which the thickness of the longitudinal projection 83 is reduced. These are a proximal modified region 86, a central modified region 87 and a distal modified region 88. These regions 86, 87 and 88 of reduced thickness extend from the lower side 89 of the longitudinal projection 83, 93, 94 to a point between the lower side of the longitudinal projection 89 and the upper part 81 such that the thickness of the upper part 81 is not reduced.
The supporting member 84 has a horizontally extending portion 90 and a vertically extending portion 91. One end of the horizontally extending portion 90 extends from a middle part of the vertically extending portion 91. An upper part 92 of the vertically extending portion 91 is adapted to support the proximal end of the fixed grate bar 80. The supporting member 84 may be provided by the cross section of a carrier beam.
A left side 93 of the fixed grate bar 80 has a left external surface 94, which extends from the proximal end to the distal end of the fixed grate bar 80. The left external surface 94 has a plurality of lateral inclined grooves 95. The lateral inclined grooves 95 extend from the upper surface 96 of the fixed grate bar 80 to the lower surface 98 of the fixed grate bar 80. The left external surface 94 has a first engaging element 100 disposed between the proximal modified region 86 and the central modified region 87 and second engaging element 101 disposed between the central modified region 87 and the distal modified region 88.
Similarly, a right side, which is not shown, of the fixed grate bar 80 has a right external surface which extends from the proximal end to the distal end of the fixed grate bar 80. The right external surface has a plurality of lateral inclined grooves 126 which have an opposite inclination to the grooves 95. These lateral inclined grooves 126 extend from the upper surface 96 of the fixed grate bar 80 to the lower surface 98 of the fixed grate bar 80.
The right external surface, not shown, has a first coupling means, not shown, disposed between the proximal modified region 86 and the central modified region 87 and second coupling means, not shown, disposed between the central modified region 87 and the distal modified region 88.
On the side of the grate bar, which is not shown in
In the embodiment of
The upper part 81 of grate bar 120 is modified at its proximal end to form a downwardly extending portion 122. Further, a protrusion 124 is downwardly disposed at the proximal end of the grate bar 120 extending downwardly from a lower side of the longitudinal projection 83.
The downwardly extending portion 122 and a vertical part of the protrusion 124 define a space such that the upper part 92 of the vertically extending portion 91 of the supporting member 84 can move within the space. The movement 196 is such that the upper part 92 can abut either with the protrusion 124, as illustrated in
According to the application and as shown in
For a fixed grate bar, the distance of the actuating surfaces is such that a member of a moving grate has little or essentially no leeway to move between the two sliding surfaces, as shown in
In
The movable grate bars may furthermore comprise a pushing nose, which is provided by the protrusion 124 at the lower side of the grate bar in
The distal actuating surface is provided at proximal side of the pushing nose. The pushing nose further comprises a grate pushing surface which is provided opposite to the distal actuation surface. The pushing nose is provided for pushing an adjacent movable grate bar. The adjacent grate bar is a member of an adjacent row of grate bars and is not shown in
Similar to the fixed grate bar 80 of
Likewise, a right side, not shown, of the grate bar 120 has a right external surface, not shown, which extends from the proximal end to the distal end of the grate bar 120. The right external surface has a plurality of lateral inclined grooves 126, not shown. These lateral inclined grooves 126 extend from the upper surface 96 of the movable grate bar 120 to the lower surface 98 of the movable grate bar 120.
As mentioned before, the lateral inclined grooves 95 or 126 are inclined at an angle to the vertical such that the lateral inclined grooves 95 at both sides of the grate bar 80 or of the grate bar 120 are inclined in the same direction, respectively. The lateral inclined grooves 126 of the grate bar 120 of
In general, the movable grate bar 120 can have two identical protrusions 124 for lateral stability, as illustrated in
In use, each supporting member 84 is intended for supporting a plurality of the grate bars 80 and 120. The plurality of the grate bars 80 and 120 are arranged such that one fixed grate bar 80 is placed horizontally adjacent to a movable grate bar 120, as illustrated in
The supporting member 84 serves to move the grate bars 80 or 120 back and forth in a longitudinal direction of the grate bar 80 or 120, respectively. The back and forth movement is used for stirring material that is placed on the upper part 96 of the grate bar 80, 120 for combustion.
In a forward movement step, the supporting member 84 moves from a first end to a second end. The upper part 92 of the vertically extending portion 91 of the supporting member 84 then abuts the longitudinal projection 83 of the movable grate bar 120 to move the movable grate bar 120 in the same direction as the supporting member 84. The upper part 92 also abuts the protrusion 124 of the fixed grate bar 80 to move in the same direction, as illustrated in
In a backward movement step, the supporting member 84 moves from the second end to the first end. The upper part 92 of the vertically extending portion 91 of the supporting member 84 abuts the downwardly extending hook 85 of the fixed grate bar 80 to move the fixed grate bar 80 in the same direction as the supporting member 84. The upper part 92 also abuts the downwardly extending portion of the movable grate bar 120 to move in the same direction at a later time, as illustrated in
In other words, in the backward movement step, the movable grate bar 120 will start to move after the fixed grate bar 80. Similarly, in the subsequent forward movement step the movable grate bar 120 will start to move after the fixed grate bar 80. The forward and backward steps are repeated. This arrangement achieves comminution and transport of the waste material.
The left lateral inclined grooves 95 of the fixed grate bar 80 are intended to cooperate with the right lateral inclined grooves 126 of the grate bar 120 to receive and to comminute combustion material, as the grate bars 80 and 120 move relative to each in the manner described above.
Receiving of the combusted material can occur in a first position, when the upper end of the right lateral inclined grooves 126 and the upper end of the left lateral inclined grooves 95 align or coincide with each other, as illustrated in
As shown in
The cutting of material which is caught in the grooves 95, 126 occurs when the side edges of the adjacent grooves 95, 126 move towards each other. The relative movement of two adjacent grooves 95, 126 provides an increase of the cutting forces due to the angular relationship between the cutting forces and the inclination of the grooves 95, 126. A corresponding cutting angle β is indicated in
The cross section of one groove is calculated according to a formula as follows. A gas flow model is used to compute the sum of all cross sections of grooves of a grate bar such that the total cross section is large enough to provide enough combustion air according to the gas flow model. The single cross section is obtained by division of the total cross section by the number of grooves and multiplication times a correaction factor of 1/0.6-1/0.85 or of 1/0.7-1/0.85 that takes into account the resistance of the groove which depends on the shape of the groove.
In the cross section shown, all grate bars are fixed grate bars 80. Horizontally adjacent grate bars, which are located in a cross section in front of the shown cross section and in a cross section behind the shown cross section, are designed as movable grate bars 120 as can be best seen in
In operation, the driven set of fixed grate bars is moved forwards and backwards by the T-shaped supporting members 84 of the movable step frames 170 whilst the non-driven set of fixed grate bars is kept in position by the T-shaped supporting members 84 of the fixed step frames 171.
Likewise, the horizontally adjacent grate bars, three of which can be seen in
In operation, the driven set of movable grate bars 120 is moved forwards and backwards by the T-shaped supporting members 84 whilst the non-driven set of movable grate bars 120 is moved back and forth by the nose shaped protrusions 124 of the driven set of movable grate bars 120 and by the weight of the grate bars 120. The movable grate bars 120 of the non-driven set of movable grate bars 120 are movable between an upper and a lower end position that is determined by the space between the downwardly extending portion 122 and the nose shaped protrusion 124 in which the T-shaped supporting member 84 engages.
The supporting members 84 of the driven sets of grate bars are connected to a driving beam 172 which is connected to a push rod 162. The push rod 162 is in turn connected to a motor (not shown) which generates a reciprocating motion via the lever 173.
In use, the engaging elements 150, 152 can move within the elongated recesses 146, 148 of the coupling means 142, 144.
According to
The engaging elements 150, 152 are formed as protrusions of the grate bar. The engaging elements can be provided as separate parts which can be exchanged in the case of wear and tear. Moreover, the casting of the grate bar can be simplified by providing the engaging elements as separate parts.
The sliding surfaces of the engaging element 150, 152 fit into a gap between the sliding surfaces of the coupling means.
By designing the sliding surfaces of the coupling means 142, 146 as well as the sliding surfaces of the engaging elements 150, 152 as surfaces which are parallel to each other, a maximum tilting angle as well as a minimum tilting angle can be adjusted by providing a predetermined height difference between the parallel sliding surfaces of the coupling means and the parallel sliding surfaces of the engaging elements. This stands in contrast to the prior art known from U.S. Pat. No. 4,240,402, wherein round bars are provided which do not have parallel abutment surfaces to prevent tilting.
Moreover, by providing the sliding surfaces as parallel surfaces, the maximum and minimum tilting angles are essentially independent of the distance between neighbouring grate bars. This stands in contrast to the prior art known from DE 20 2007 018 707, in which surfaces of overlapping elements are not parallel but are tapered or diverging. Thereby, the maximum and minimum tilting angles increases with the distance between neighbouring grate bars.
A length of the coupling means is adjusted so as to provide guiding of the engaging elements from a first abutment position to a second abutment position of the grate bar relative to a neighbouring grate bar. The length of the coupling means in a longitudinal direction of the grate bar is at least as long as the maximum relative displacement in the longitudinal direction of a grate bar relative to a neighbouring grate bar. Thereby, the engaging element is guided in the coupling means during a relative motion of the grate bar relative to a neighbouring grate bar.
In use, the engaging element 155 experiences shear forces as it engages with a corresponding coupling means. The octagonal protrusion 157 provides a larger contact area with the coupling means such that wear due to the shear forces is reduced.
As neighbouring grate bars move relative to each other, material which is trapped between the grate bars is moved against the octagonal protrusion 157. The edges of the octagon provide a cutting effect. Furthermore, the four sides of the octagonal protrusion 157 that are slanted against the horizontal deflect the material towards the top and towards the bottom as it moves against the octagonal protrusion 157. This provides an improved self-cleaning of the elongated recess 146.
The mounting process is essentially the same for movable step frames and for fixed step frames. For mounting, one of the side bars 105, 106 is bend outwards with a lever that is not shown here. In the example of
In a modification of the embodiment of
Similar to the octagonal element 150 shown in
It can be shown through geometrical considerations that for a rectangular shape of an engaging element, the maximum angle of inclination α is approximately given by the relation H=l*sin(α)+h*cos(α), wherein l is the width of the rectangle and h is the height of the rectangle. It is desirable, to have a small angle of maximum inclination. This can be achieved by making l greater than H. A similar consideration applies for the octagonal shape of
Although the above description contains much specificity, this should not be construed as limiting the scope of the embodiments but merely providing illustration to the embodiments. The above stated advantages of the embodiments should not be construed as limiting the scope of the embodiments but merely to explain possible achievements if the described embodiments are put into practise. Thus, the scope of the embodiments should be determined by the claims and their equivalents, rather than by the examples given.
Further aspects and objects of the present application are disclosed in the below mentioned item list.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1014974.8 | Sep 2010 | GB | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IB2011/053942 | 9/9/2011 | WO | 00 | 3/8/2013 |
