Cooler for cooling hot bulk material, in particular cement clinker

Abstract

A device for cooling hot bulk material, in particular cement clinker, by means of a cooling gas (80). A cooling grate (3) conveys a layer of the bulk material (9) and is flowed through by cooling gas. The cooling grate comprises a number of bars (4) which are alternately moved forwards and back in the conveying direction and on which the bulk material (9) lies. Adjacent bars (4) are moved at the same time in the forward stroke and at different times in the return stroke. According to the invention, at least one bar is formed as a hybrid bar (4*) with a varying configuration of the bar surface (60), having a middle portion (42) with a smooth bar covering (6) and also a beginning portion (41) and / or end portion (42) comprising a protective layer (5) of bulk material (90) located on the bar surface (60). This provides protection from wear. This produces an increased friction coefficient for the bulk material as compared with the middle portion. Omitting the protective layer in the middle portion, which extends over at least half the length of the hybrid bar, has the effect of reducing the pressure loss for the cooling gas and reducing problematic compacting of the bulk material in the return stroke. Along with decreasing operating expenditure, the cooling effect is improved.

Description

[0001] Device for cooling hot bulk material, in particular cement clinker

[0002] The invention relates to a device for cooling hot bulk material, in particular cement clinker, by means of a cooling gas. The device comprises a cooling grate which conveys a layer of the bulk material from a feed end in a conveying direction to a discharge end and through which cooling gas flows, the bulk material to be cooled lying on said grate. The cooling grate comprises a plurality of planks which are moved forwards and backwards in the conveying direction alternately by a stroke length, the drive of which planks is controlled such that at least two adjacent planks are moved simultaneously in the forward stroke and non-simultaneously in the return stroke.

[0003] Cooling devices of this type are used to cool bulk material using gas. The bulk material is placed as a bed on a cooling grate and transported along this, while gas is supplied from below the cooling grate for cooling. The cooling gas, which is typically cooling air from the space below the grate, rises through the cooling grate into the bed of bulk material and cools it in the process. In cooling devices of this type, the cooling grate has three functions with regard to the bulk material. One function is to support the bulk material to form a bed of material, another is to provide a surface for the introduction of cooling air, and a further function is to transport the bulk material from one feed end to a discharge end. Various basic designs have become known for implementing these functions. Of interest here is the design with several planks extending in the conveying direction which are moved alternately back and forth.One difficulty with this conveying principle is that the planks' surfaces are subjected to considerable stress, namely due to the high temperature of the material being cooled, at least initially or temporarily, as well as due to abrasion, particularly with sharp-edged material such as clinker. This high stress leads to considerable wear on the planks.

[0004] It is known to form the surface of the planks using grate plates, which are relatively easy to replace. However, it is complex to design appropriate cooling gas passages in the grate plate, on whose surface the material bed to be cooled rests, to ensure a sufficient supply of cooling gas, as well as to offer sufficient protection against problematic grate penetration through the cooling gas passages, and also to manufacture them efficiently. Furthermore, replacing the grate plates is complex, since this requires shutting down the cooler.

[0005] For efficient operation, on the one hand, a high cooling effect is important, which is determined, among other things, by the cooling gas throughput through the cooling grate with its cooling gas passage openings and, on the other hand, an efficient and low-wear conveying along the cooling grate by means of the movement of the planks.

[0006] A design of the cooler with planks that have a smooth surface for supporting the bulk material is known from DE 10 2007 019 530 A1. Ventilation slots that extend the entire length of the plank are arranged in the space between them. They act as air passages for the cooling gas. They are provided with a special side-blow profile in order to minimize unwanted ingress of bulk material and thus grate penetration into the space below the grate. The surface of the planks is swept over by the escaping cooling gas.To protect the plank surface from thermal and abrasive stress caused by the bulk material, which is particularly relevant when hot clinker material is used as bulk material emerging from a kiln immediately upstream, it is known from EP 1509737 B1 to guide the planks of such a cooling grate with a large number of retaining troughs on the surface of the planks. During operation, bulk material is deposited in the troughs, forming an autogenous protective layer that protects the sensitive plank surface from the high thermal and abrasive stress caused by the hot clinker material.

[0007] The provision of a protective layer on the planks has the advantage that it offers good protection for the surface of the planks. In particular with hot, aggressive bulk material, such as clinker, this can reduce wear on the surface of the planks. However, the protective layer has the disadvantages that it creates a flow resistance for the cooling gas flowing upwards from below through the cooling grate and that it generates a disruptively high frictional force on the bulk material, at least during the return stroke. The latter requires different dimensioning of the steel structure and a more powerful drive. This also leads to compaction of the bulk material during the return stroke, which creates additional flow resistance for the cooling gas flowing through the cooling grate, thereby increasing the inherent pressure losses in the cooling gas supply.

[0008] A smooth design of the planks without a protective layer offers the advantage that only a low return stroke force is required and, due to the lack of a protective layer, only a low pressure loss occurs. However, this is offset by the disadvantage of increased wear due to the aggressive stress caused by abrasive bulk material. This disadvantage can be mitigated by special materials, but this is costly. Another disadvantage is that, due to the lack of a protective layer, the plank surface is more sensitive to thermal stress from the hot bulk material bed. This becomes a particular risk in the event of a failure of the cooling gas supply, which then leads to thermal damage to the planks very quickly due to the direct thermal contact between the planks and the hot bulk material.Finally, rust perforation can also be a problem, which can be counteracted by high gas velocity, but this leads to a quadratic increase in the inherent pressure losses.

[0009] A further design is known (DE 10 2010 055 825 B4) in which the planks are designed with zones of rough surface formed by an autogenous wear protection layer along their length and zones of smooth surface, with the zones alternating several times. In the smooth zones the average coefficient of friction between the bulk material to be cooled and the upper side of the plank is smaller than in the zone with the autogenous wear protection layer on the plank. These different coefficients of friction lead to alternating compression and extension in the bulk material bed when the bulk material is conveyed along the conveying direction. The continuous, repeatedly alternating extension and compacting compression results in a flexing movement which leads to vertical mixing of the bulk material bed starting from the bottom of the planks and moving upwards.In this case, compacting compression occurs several times, namely in the return stroke at the change points from smooth to rough zone (seen in the conveying direction).

[0010] The object of the invention is to provide an improved cooling device that offers greater efficiency and high wear protection. The solution according to the invention lies in the features of the independent claim. Advantageous further developments are the subject of the dependent claims.

[0011] In a device for cooling hot bulk material, in particular cement clinker, by means of a cooling gas, which has a cooling grate which conveys a layer of the bulk material from a feed end in a conveying direction to a discharge end and through which cooling gas flows, wherein the cooling grate comprises several planks which are moved forwards and backwards in the conveying direction alternately by a stroke length, the drive of which is controlled in such a way that at least two adjacent planks are moved simultaneously in the forward stroke and non-simultaneously in the return stroke, wherein the planks form a substantially flat support surface for the bulk material, it is provided according to the invention that at least one plank is designed as a hybrid plank with a different design of the plank surface, which

[0012] - a central section with smooth plate covering, the central section extending over at least half the length of the hybrid plank, and

[0013] - immediately adjacent to the central section, a starting section and / or end section comprising a protective layer of loose material arranged on the plank surface, whereby an increased coefficient of friction with the loose material is formed compared to the central section.

[0014] The core of the invention lies in the idea of ​​not providing the planks of the cooling grate with a uniform surface, but rather providing their main section (which comprises at least the middle section of the plank) with a plate covering with a smooth, essentially flat surface for supporting the bulk material (this is also referred to as a flat plate covering) and providing the planks with a receptacle for a protective layer of bulk material only at another specific location, namely outside the middle section which extends at least over half the length of the plank. This specific location can be a start section of the plank, or an end section of the plank, or a combination of both, i.e. the start and end section of the plank. The plate covering has a smooth surface and is therefore not provided with a protective layer of bulk material according to the invention (smooth plate covering).The surface serving to support the bulk material is thus formed either by the panel covering, which according to the invention does not have a protective layer of bulk material, or by such a protective layer. The friction coefficient between this smooth panel covering and the bulk material is smaller than that between the protective layer and the bulk material. Such a hybrid surface design of the planks, which can also be briefly referred to as "smooth or with a protective layer," offers significant advantages.

[0015] The initial section , which is arranged immediately in front of the middle section in the conveying direction , the middle section with its exclusively smooth plate covering and the final section , which is arranged immediately after the middle section in the conveying direction , form the entire length of the hybrid plank .

[0016] The central section extends over a large part (at least half) of the longitudinal extent of the plank, thus forming a main section. It is continuously covered with a smooth plate covering. Due to the smooth plate covering, no protective layer is formed on the central section; it is free of any protective layer. Since the cooling gas does not have to pass through a protective layer and consequently its flow resistance is eliminated, the pressure loss for conducting the cooling gas from the lower grate space through the plank into the bulk material to be cooled is minimized.

[0017] Furthermore, since the middle section has no protective layer, only a lower force is required in the return stroke compared to a moving floor with a continuous protective layer, i.e. where the protective layer also exists in the middle section.

[0018] Just as the pressure loss caused by the protective layer is avoided, compaction of the bulk material caused by the protective layer is also avoided, which led to an additional pressure loss and thus to an increase in the inherent pressure losses in the prior art for planks with a protective layer (see the further explanation above in the introduction to the prior art).

[0019] The risk of damage to the planks due to thermal stress is minimized because, according to the invention, a protective layer is provided in the critical beginning / end section. This means that the stress and therefore the wear on the planks at these highly stressed points can be minimized. Additional armoring of the plank surface, for example, to protect against thermal and abrasive stress is not required, thus avoiding expense. Although there is a local increase in pressure loss at these points due to the protective layer, this is considerably reduced compared to previous designs with a continuous protective layer in accordance with the state of the art.

[0020] Due to the smooth design of the surface of the planks in the middle section, the drive force required for the return stroke is reduced, which also makes it possible to make the drive, in particular the hydraulic cylinder and the corresponding hydraulic unit, smaller and to make the steel structure required to accommodate the cooling grate with its drive lighter.

[0021] Since the smooth central section dominates at least half of the total length of the hybrid plank, its low coefficient of friction is also dominant and leads to a considerable reduction of friction losses during operation.

[0022] Compaction of the bulk material lying on top, particularly as a result of the return stroke movement, is reduced with the design according to the invention. In the initial area, a "rough" section with a protective layer is followed in the conveying direction by the smooth main section, which in principle does not lead to compression / compaction. The opposite of compression, namely "stretching", does not occur there either, since due to a higher coefficient of friction in the "rough" initial section with the protective layer, loosened areas in the material at the transition to the smooth main section are immediately filled with newly thrown-up bulk material. This is all the more true since in the area where the material is fed onto the cooling grate (feed end), a constant bed height of the bulk material has not yet developed anyway.- In the final section, no compaction / compression can occur during the return stroke, since the bulk material there slides off the end of the plank under the influence of the driving force resulting from the angle of repose. Stretching is also ruled out in the final section, since, viewed in the conveying direction, the rough end section is reached (and thus no smooth section follows). Thus, the inventive design of the planks not only reduces pressure losses but also harmonizes the transport movement with a constant average transport speed.

[0023] This harmonization is also based on the fact that, unlike in the prior art, there are no repeated alternations between smooth and rough zones starting from the central section, both forwards to the beginning of the plank and backwards to the end of the plank. Thus, the disadvantages of repeatedly alternating compression / extension, which reduce efficiency and occur in the prior art, can be avoided by the inventive design with a long, smooth central section and, starting from the central section, no repeated alternations between smooth and rough, either forwards or backwards.

[0024] The invention thus enables improved operating behavior, in particular a reduction in pressure losses, while simultaneously maintaining a high level of wear protection, whereby the requirements for the drive and steel construction are also reduced. The manufacture and operation of the cooling grate are considerably improved by the method according to the invention, namely the targeted arrangement of the protective layer such that the protective layer is arranged only in the beginning / end section, but not in the middle section, of the cooling grate planks.

[0025] Some of the terms used are explained below:

[0026] An initial section is understood to be a region of the cooling grate that is located upstream of the middle section in the conveying direction. Typically, this is the area where the bulk material is fed onto the cooling grate (feed end). An end section is understood to be a region of the cooling grate that is located downstream of the middle section in the conveying direction. Typically, this is the area where the bulk material is discharged from the cooling grate (discharge end).

[0027] The planks extend longitudinally in the conveying direction. They are equipped with cooling gas passages at the beginning, middle, and end sections to ventilate the bulk material with cooling gas.

[0028] The stroke length is the distance the planks are moved forward during a forward movement and backward during a return stroke. If the stroke length is adjustable, the largest stroke length is the maximum stroke length.

[0029] A smooth surface is defined as a flat, unroughened, homogeneously closed surface made of a material, in particular a metal surface without protruding structures. Technically necessary perforations, such as those for ventilation slots or fastening devices, are not taken into account. Thanks to this smoothness, it has a lower coefficient of friction with the bulk material than a rough surface, such as the protective layer against the bulk material.

[0030] The plate covering has such a smooth surface on its support surface for the bulk material and thus forms a smooth plate covering.

[0031] The start and / or end section with the protective layer are expediently designed so that they each have a length which is at least 0.5 times the maximum stroke length, preferably at least 0.9 times. The sections of the planks at the start and end which are particularly subject to high thermal stress are thus much better protected. In the end section, a relatively short protective layer is sufficient because when a plank is pulled back by a full stroke length, the bulk material from its neighbouring planks can flow off laterally into the gap created in this way, whereby this continues to happen in the end section of the neighbouring planks which is protected by the bulk material layer. Preferably, the protective layer in the area of ​​the start and / or end section is no longer than 6 times, more preferably no longer than 12 times the stroke length; in the case of an adjustable stroke length, this is related to the maximum possible.

[0032] If both the initial and final sections are designed for the protective layer, the initial section is preferably longer than the final section. This takes into account the fact that the thermal load in the initial section is very high and that the effective length of the protective layer is reduced during the return stroke, particularly when passing under a feed ramp.

[0033] It is advantageous to provide receiving troughs in the start and / or end section as receptacles for the protective layer. These are either filled in a targeted manner or material is deposited thereon to form the protective layer. The receiving troughs can be filled wholly or partly with loose material, for example a layer of gravel. It can also be provided that part of the loose material is collected in these receiving troughs during operation, thereby creating an autogenous protective layer. However, a combination can also be provided, in particular partial filling with a different loose material at the bottom of the receptacles and, if necessary, an autogenous protective layer made of the loose material on top. The receiving troughs are expediently provided with subdivisions in the longitudinal and / or transverse direction. This allows the protective layer to be held more effectively.It is advantageous if the subdivisions in the longitudinal and transverse directions are of the same height so that their respective upper edges are at the same level.

[0034] Advantageously, the plate surface in the middle section is level with the surface formed by the protective layer in the initial and / or final sections. In the case of an autogenous protective layer, this applies to the operating state when the autogenous protective layer is formed. Thanks to this level, conveying and cooling of the bulk material on the planks is achieved without any vertical offset.

[0035] Advantageously, a majority of the planks of the device are designed as hybrid planks. However, it is not mandatory that all planks of the cooling grate be designed as hybrid planks; however, in a preferred embodiment, all planks can be designed this way. The cooling grate can advantageously also have additional planks, in particular planks that are not hybrid planks. Such non-hybrid planks are advantageously provided with a continuously smooth plate covering to minimize the pressure loss for the cooling gas.

[0036] Optionally, additional planks can be provided which are continuously covered with a protective layer of bulk material. This can advantageously be provided specifically at locations where there is a risk of increased thermal stress on the respective plank. This applies in particular to edge-mounted planks (plank at the side edge of the cooling grate, edge plank), for example along at least one of the side edges. This preferably concerns the edge plank on which a higher proportion of the fine fraction of the bulk material lies during operation. The fine fraction is susceptible to fluidization by the cooling gas, which greatly increases the flow velocity and consequently the affected bulk material remains red-hot and stretches along the plank like a red-hot river (known in expert circles as the "red river" phenomenon).Such a phenomenon is extremely detrimental to reliable cooling operation and it is important to prevent it. The additional plank is particularly advantageous when it comes to fine fractions and the ever-present risk of localized cooling disruption. Although its continuous protective layer results in increased pressure loss for the cooling gas, this pressure loss also leads to reduced ventilation in the critical area, which reduces the fluidization of the bulk material and thus the flow velocity, which is higher in the "Red River" case. At the same time, the rough protective layer reduces the conveying velocity on this plank, resulting in slower advancement with reliable cooling of the bulk material.Since the bulk material on the edge plank is typically slowed down by friction on the side wall anyway, the slower transport there does not result in any relevant disadvantage.

[0037] Planks that are more prone to the formation of "red river" do not always need to be designed as additional planks with a continuous protective layer. Often a hybrid plank is sufficient for safe handling. It can therefore be expedient if at least one edge plank is designed as a hybrid plank. Preferably, at least one plank immediately adjacent to the edge plank can not be designed as a hybrid plank, but is provided with a continuous smooth plate covering. This allows safe and reliable cooling to be achieved with a minimum of friction and pressure losses due to the protective layer.

[0038] If the cooling device is arranged downstream of a rotary kiln which rotates in one direction, the plank on the edge furthest from the direction of rotation is preferably designed as an additional or hybrid plank. If the rotary kiln rotates to the right in the conveying direction, the left edge plank in the conveying direction is “far from the direction of rotation” and is designed as an additional or hybrid plank, and vice versa for a rotary kiln which rotates to the left. In certain designs it may be sufficient if only this edge plank is designed as an additional or hybrid plank and the other planks are designed as conventional smooth planks. This makes it possible to improve the prevention of “red river” while also largely reducing the pressure loss in the other planks.

[0039] Typically the bulk material is made up of particles of different sizes; the larger particles form a coarse fraction, the smaller particles a fine fraction. Frequently there is an asymmetrical distribution of coarse and fine fractions of the bulk material across the width of the cooling grate. Preferably the said additional or hybrid plank is expediently arranged on the lateral edge at which the fine fraction is most prevalent. In the case of an upstream rotary kiln this is usually the side furthest from the direction of rotation, as stated above. Preferably at least one immediately adjacent plank is not designed as a hybrid plank, but is provided with a continuously smooth plate covering. To better control the cooling effect on the edge planks it can be advantageous to provide an additional (separate) ventilation device there.

[0040] To form the smooth surface of the planks, it is expedient to provide, for example, replaceable grate plates which have a smooth cover plate with cooling gas passage openings, in particular (longitudinal) slots located in the conveying direction, for cooling gas to escape. This makes it possible to repair, in the event of wear to the plank surface, simply by replacing the grate plates. The slots can be produced efficiently using a casting process for the grate plate, either as transverse slots or as longitudinal slots. Compared to transverse slots, the design as longitudinal slots makes it possible to avoid disturbances in the material bed caused by the slots, in particular parasitic vertical mixing. Furthermore, the longitudinal slots are preferably arranged symmetrically to a center line of the grate plate, which results in a more uniform symmetrical cooling effect.Beneath the longitudinal slots, there are expediently arranged longitudinally extending collecting channels at a predetermined distance. They catch any material that falls through and ensure that it is caught again by the cooling gas flow and blown upwards out of the longitudinal slots back into the bulk material. The predetermined distance ensures that a desired cross-sectional width is maintained between the collecting channel and the wall of the grate plate in order to achieve predetermined flow conditions for the cooling gas flow. The collecting channels are advantageously designed as a single piece with the grate plate as a cast part, which simplifies manufacture and ensures that the predetermined distance is maintained at a reasonable cost. The grate plates and / or receiving troughs are advantageously designed as replaceable modular units for the planks. This enables particularly efficient replacement.

[0041] In a preferred embodiment, a replaceable extension bracket can be provided on the end section of each plank, which forms an extension of the support surface for the bulk material and is not ventilated. This means that no cooling gas is conducted through the extension bracket. The extension bracket thus forms an uncooled end section of the respective plank, from which the (at this point already largely) cooled bulk material slides down and is thus thrown off the cooling grate. The extension brackets preferably do not have a protective layer, but are provided with a smooth plate covering, which can in particular be implemented using grate plates. Since this sliding is particularly wear-intensive due to the abrasive bulk material, this wear occurs on the relatively easily replaceable extension brackets and not on the actual planks, which are thus protected.The extension brackets are preferably hardfacing at their free ends. Thermal spraying, spray fusion, and welding processes are typically used to apply the hardfacing layer. Commonly used materials include cobalt-based alloys (such as tungsten carbide), nickel-based alloys, chromium carbide alloys, etc. The extension brackets are preferably no longer than the initial or final sections, and preferably half as long.

[0042] According to a particularly advantageous development of the invention, which may deserve independent protection, the planks are designed differently when viewed transversely to the conveying direction with regard to the protective layer they are provided with. For example, planks with an increased coefficient of friction at least in some sections (e.g. hybrid or additional planks) can preferably be arranged on at least one of the side edges of the cooling grate, and planks with a consistently smooth surface can be arranged in the middle and / or on the other side edge. Hybrid planks with their increased coefficient of friction at least in some sections are preferably arranged on at least one of the side edges of the cooling grate, and planks without a protective layer, i.e. with a smooth surface, can be arranged in the middle and / or on the other side edge.In this way, an optimal cooling effect can be achieved across the width of the cooling grate by only arranging planks with an increased coefficient of friction, hybrid planks or planks with a continuous protective layer at points identified as critical (particularly near the edge).

[0043] The invention expediently also comprises a cooling arrangement with a plurality of at least two cooling grates arranged one behind the other in the conveying direction, each of which has planks. In this way, a cooling section is formed. The cooling grate at the start / end of the cooling section can be designed as described above and is in particular provided with planks, of which at least one is designed as a hybrid plank, as described above, or is provided with a protective layer throughout. In this case, at least one further cooling grate (or several), in particular a downstream cooling grate (i.e. in the middle or rear position of the cooling section), can preferably have exclusively smooth planks throughout, with the exception of edge planks, which can be provided with no protective layer of loose material or at least partially with it.Thus, a hybrid structure similar to a multi-part hybrid plank can be functionally realized along the cooling section by sequentially arranging cooling grates with different planks. To avoid repetition, reference is made to the above description, which should be applied accordingly.

[0044] The invention will be explained in more detail below with reference to the accompanying drawings using at least one advantageous embodiment as an example. Shown are:

[0045] Fig. 1 is a schematic longitudinal section through a cooling device;

[0046] Fig. 2 schematic partial plan views of a cooling grate of the device in different stages of a conveying movement;

[0047] Fig. 3 is a longitudinal section of a first embodiment of the cooling grate;

[0048] Fig. 4 is an enlarged partial longitudinal section of an initial section of the cooling grate according to Fig. 3;

[0049] Fig. 5 is an enlarged partial longitudinal section of an initial section of the cooling grate according to Fig. 3;

[0050] Fig. 6 is an enlarged partial longitudinal section of an initial section of a second embodiment of the cooling grate;

[0051] Fig . 7 an enlarged partial longitudinal section of a

[0052] End section of a third embodiment of the cooling grate;

[0053] Fig. 8 shows a longitudinal section of a fourth embodiment of the cooling grate; Figs. 9A-F show perspective views of various further embodiments of plank arrangements;

[0054] Fig. 10A, B each show a cross section through an end region of the plank arrangement according to Fig. 9D and 9E;

[0055] Fig. 11 shows a partial cross-section of a plank with a smooth surface;

[0056] Fig. 12 shows a partial cross-section of a plank with a protective layer;

[0057] Fig. 13A-C Detailed cross-sections of seals between planks and side walls;

[0058] Fig. 14A, B a perspective view and a plan view of a grate plate;

[0059] Fig. 15 is a longitudinal sectional view along line XV-XV of

[0060] Fig . 14B ) ;

[0061] Fig. 16 is a cross-sectional view along line XVI-XVI of

[0062] Fig . 14B ) ; and

[0063] Fig. 17 is a schematic longitudinal section of an arrangement comprising several cooling grates arranged in steps.

[0064] A schematic exemplary embodiment of a cooling device according to the invention is shown in Fig. 1. A housing 1 has, in the region of its front wall 11 at one end, a feed chute 12 at which a discharge opening of an upstream rotary kiln 2 opens. The bulk material to be cooled, which is also referred to below as cooling material for short, is thrown from the rotary kiln 2 and falls in the feed chute 12 onto a feed ramp 13 and from there onto a cooling grate 3 designed according to the invention. The feed ramp 13 has a ramp-like shape and extends almost over the entire width of the cooling grate 3 in order to initially ensure that the bulk material 9 is distributed as widely as possible onto the cooling grate 3.

[0065] The cooling grate 3 is essentially flat (installed horizontally or at an angle) and forms a support surface 30 for the material to be cooled 9 . Cooling gas 80, which is blown into a grate sub-chamber 38 by a cooling air supply 8, is supplied through the cooling grate 3 to the bulk material 9 to be cooled lying on the cooling grate 3. Furthermore, the bulk material 9 is transported from a feed end 31 in the region of the feed ramp 13 in a conveying direction 14 along the support surface 30 to a discharge end 32. Via an optionally provided discharge plate 16, the now largely cooled bulk material 9 is guided in a targeted manner to a downstream processing stage, for example a crusher 17. In this area, the housing 1 is delimited by a rear wall 18. Side walls 15 are provided along the long sides of the cooling grate 3, so that the cooling grate 3 is completely surrounded by the housing 1.

[0066] The cooling grate 3 is designed in such a way that it has a plurality of elongated planks 4 arranged parallel in the conveying direction 14. They are mounted on a plurality of grate bearings 36 (by means of bearing rollers) and can be moved individually back and forth over a stroke length 39. They are driven by a drive 37 with a movement control device 37 in such a way that the planks 4 (seen in the conveying direction 14) are pushed forward together (forward stroke) and moved back one after the other (return stroke). The mode of operation of the cooling grate 3 with its planks 4 is shown schematically in Fig. 2. The grate consists, as already explained, of a plurality of elongated planks 4 arranged next to one another, of which four are shown in Fig. 2 shows, by way of example, three planks 4', 4", 4"' which can each represent one or a group of adjacent planks 4.The functional principle carried out by the movement control device of the drive 37 is shown with its essential phases in the individual illustrations in Fig. 2. The basic principle is a cyclical movement sequence in which the planks 4', 4", 4"' move in the conveying direction 14. Fig. 2A shows a phase of the cycle in which the planks 4 are advanced essentially simultaneously in the conveying direction 14 by one stroke length until they reach their front end position. The next phase is shown in Fig. 2B. In the process, one of the planks 4, namely plank 4', is retracted by one stroke length until it reaches its rear end position. For the phase shown in Fig. 2C, plank 4"' moves back until it reaches its rear end position. Finally, plank 4" also moves to its rear end position, so that the plank 4" shown in Fig. 2D) is reached. The cycle then begins again.In this way, a movement pattern is created in which all of the planks are moved forward together, while they are retracted one after the other. During the joint advance, the planks 4 take the bed of bulk material 9 lying on them with them. When the planks 4 are then moved back one after the other, the bulk material 9 lying on the respective plank being moved back cannot for the most part follow because it is held in place by frictional forces exerted on it by the bulk material 9 lying on the adjacent planks or by the side walls 15. In short, one can therefore say that the bulk material 9 takes part in the joint forward stroke of the planks 4, but not in the return stroke of the individual planks. This is how the conveying effect is created. Even if some of the bulk material is moved along in the return stroke, this is no damage because this only affects a small part and a considerable net conveying effect remains.

[0067] Instead of individual planks, groups of planks can also be moved in this way if required; however, in the interests of high conveying efficiency, it is generally advantageous to carry out the retraction only over a small width, i.e. to retract the planks individually if possible. It should also be noted that the speed during the forward movement (forward stroke) does not necessarily have to be the same as the speed during the backward movement (return stroke). Furthermore, it is not absolutely necessary for all planks moving forward to have the same speed. In accordance with the speed profile of the bulk material 9 which usually occurs, it can also be provided in particular that the planks 4 adjacent to the side walls 15 are moved more slowly than planks arranged in the middle.

[0068] A first embodiment of the cooling grate 3 with a plank is shown in longitudinal section in Fig. 3. On the left in the figure, the feed ramp 13 on the front wall 11 of the housing 1 of the cooling device can be seen. Adjoining the feed ramp 13 in the conveying direction 14 is the cooling grate 3 with its planks arranged to move back and forth in the conveying direction 14. For this purpose, they rest with their guide rails 35 arranged on the underside on bearing rollers of the grate bearings 36.

[0069] The planks are divided into several sections, namely an initial section 41 located at the beginning as seen in the conveying direction 14, a middle section 42 immediately following this in the conveying direction 14, and an end section 43 immediately following this in the conveying direction 14. The middle section 42 extends over at least half the length of the plank (the length is seen in the conveying direction 14) and thus forms a main section.

[0070] The initial section 41 and the end section 43 are provided with a protective layer 5 made of loose material 90 arranged on the plank surface 40. Receiving troughs 45 are arranged on the upper side of the plank in the initial section 41 and the end section 43 to receive the loose material 90. In contrast, in the middle section 42 there is no protective layer 5 but rather a smooth plate covering 6 made in particular of a metallic material. The bulk material 9 to be cooled, which is applied to the cooling grate 3 by means of the feed ramp 13 and distributed in the conveying direction 14, lies on the plank in the manner already described. In the middle section 42 this bulk material directly touches the plank surface with its plate covering 6, whereas in the initial section 41 and the end section 43 there is a protective layer 5 made of loose material 90. The loose material 90 is preferably foreign material, e.g. Gravel that is added before commissioning .

[0071] Such a plank, which has at least one of the sections 41, 43 with a protective layer 5 and whose middle section 42 has no such protective layer, but a smooth, in particular metallic plate covering 6, is referred to as a hybrid plank 4*.

[0072] To effect cooling, a plurality of cooling gas passage openings for the cooling gas 80 (cooling air) are provided in the plank. In the exemplary embodiment of the hybrid plank 4 * shown in Fig. 3, cooling gas passage openings 47 are provided in the region of the initial section 41 and the end section 43 (each with a protective layer 5) and thus guide the cooling gas 80 from the grate sub-chamber 38 into the respective receiving trough 45. Enlarged partial longitudinal sections for the initial and end regions of the hybrid plank 4 * are shown in Fig. 4 and Fig. 5, which also show the design of the plate covering 6 by means of grate plates 7 (see Fig. 14A, B). The cooling gas 80 then continues to rise through the protective layer 5 and subsequently enters from below into the material bed formed by the bulk material 9 on the plank 4 *. Furthermore, in the central section 42 (without protective layer) in the plate covering 6 there, cooling gas passage openings 48 are provided (in Fig.3 is shown only symbolically). In the illustrated embodiment, they are implemented in the form of longitudinal slots 78 in the grate plates 7 (see Fig. 14A, B), which - as will be explained in more detail later - form the plate covering 6. The cooling gas 80 is guided in a corresponding manner through the air passage openings 48 from the lower grate space 38 through the plank and subsequently enters from below the material bed 9 formed by the bulk material lying on the plank surface 40.

[0073] Instead of directly ventilating the cooling grate 3 by overpressure in the grate subspace 38, the planks can also be connected, either entirely or in sections, to compressed air sources for supplying the cooling gas via flexible supply lines or ducts (not shown). This offers the additional advantage of being able to more precisely influence the distribution of the cooling gas 80. However, this has no influence on the inventive design of the planks with their different surfaces with protective layer 5 / without protective layer and with plate covering 6.

[0074] The hybrid plank 4* formed in this way therefore has a plank surface 40 with a different (hybrid) character: in its central section, which takes up at least half of the total length of the hybrid plank 4*, no protective layer 5 is provided, but the surface is formed by a plate covering 6 that is metallically smooth and thus has a low coefficient of friction with respect to the bulk material 9 located above it; in its initial section 41 and its end section 43, however, the plank surface 40 is formed by a protective layer 5 in which the bulk material 90 lies. The protective layer 5 has an irregular, rather rough surface and thus has a (significantly) higher coefficient of friction with respect to the bulk material 9 located above it compared to the surface of the plate covering 6.The dimensions of the plate covering 6, in particular of its upper plate surface 60, are adapted to the protective layer 5 occurring during operation in such a way that the plank surface 40 is essentially level over all sections 41, 42, 43.

[0075] For cement clinker as bulk material 9, the friction coefficient with respect to the metallic plate covering 6 is approximately p = 0.56, and with respect to the protective layer 5 made of clinker material, approximately p = 0.84. If this is applied to a cooling grate 3 with 24.2 m long planks 4*, with the initial section 41 having a length of 4.4 m and the end section 43 having a length of 2.2 m, and the middle section 43 correspondingly 17.6 m, only 6.6 m of 24.2 m have the higher friction coefficient of p = 0.84, while the 17.6 m of the middle section 42 have the low friction coefficient of the smooth metallic plate covering 6 of p = 0.56. This results in an average friction coefficient of only p = 0.636 over the entire length of the plank 4*, which is only slightly higher than that of a purely smooth plank at p = 0.56.The targeted arrangement of the protective layer 5 in sections 41, 43 achieves the same level of protection of the plank against thermal overload caused by the hot bulk material 9 as with a conventional plank according to the prior art, which is provided with a protective layer 5 throughout. With a friction coefficient of p = 0.84, such a conventional design has a good 30% more friction than the exemplary hybrid plank. Thanks to the design according to the invention, a significant reduction in friction is thus achieved during the return stroke. This not only results in a considerable reduction in undesirable compaction, but also, as a side effect, brings with it a noticeable reduction in the required drive power.Since the hybrid plank 4 *, just like conventional planks which are provided with a protective layer throughout, has cooling gas passage openings 47, 48 along its entire length, this results in an at least equivalent, if not even improved, supply of cooling gas 80 through the planks of the cooling grate 3 and, moreover, taking into account the reduced undesirable compaction, even an improvement in the cooling effect in the bulk material 9. This results in significant advantages in terms of more efficient conveying as well as better cooling effect.

[0076] In a second embodiment of the cooling grate 3, it is sufficient if the end section 43 is designed as described above with a protective layer 5. In this variant, however, in contrast to the first embodiment described above, the starting section 41 can also be designed with a plate covering 6, which is correspondingly provided with cooling gas passage openings 48, while the end section 43 is provided with a protective layer 5 as in the first embodiment. It is understood that the middle section 42 is still provided with the plate covering 6 according to the invention. Such an embodiment with a different design of the starting section is shown in Fig. 6. Alternatively, however, in a third embodiment it can be provided that, in contrast to the first embodiment described, the end section 43 is designed with a plate covering 6, as shown in Fig. 7.Here, the initial section 41 is provided with a protective layer 5, as in the first embodiment. Here, too, it goes without saying that the middle section 42 is still provided with the plate covering 6 according to the invention. Depending on the specific requirements of the bulk material 9 to be cooled, the second or third embodiment may be advantageous. What both have in common is that they lead to the reduction of the average coefficient of friction according to the invention.

[0077] In a fourth embodiment, which is based on the second embodiment, a plate covering 6 is provided in the initial section 41 (as well as in the middle section 42), so that a protective layer 5 is provided only in the end section 43. This embodiment, however, has the special feature that, in the area of ​​the discharge end 32 of the cooling grate 3, an extension bracket 49 is arranged on the end section 43 of the respective plank 4*. The extension bracket 49 is provided with a plate covering 6 similar to the end section 43, but unlike the latter, it is not ventilated, i.e. no cooling gas passes through it. Such an embodiment is shown in Fig. 8. It should be noted that an extension bracket 49 can also be provided in a corresponding manner in the other embodiments.The application of the continuation bracket 49 is not limited to hybrid planks 4 *, but can also be provided on the other planks, in particular with a continuous protective layer 5 or with a continuous plate covering 6.

[0078] Fig. 9A to 9G show perspective views of various exemplary embodiments of plank arrangements for cooling grates 3. What they all have in common is that the cooling grate 3 is of modular construction comprising several modular sections. For this purpose, an initial section I, one or more middle sections II and an end section III are provided. These modular sections I, II and III are typically dimensioned so that they are easily transportable and enable efficient assembly of the entire cooling grate. Each modular section I, II and III comprises a certain length of the planks 4 together with the required grate support with bearing rollers 36. For assembly, sections I, II and III are put together one behind the other and the individual lengths of the planks are connected to one another to create a continuous plank. Typical dimensions for such sections are, for example:

[0079] 2.2 m or 4.4 m. If a preferred length for a starting section 41 and / or an end section 43 is, for example, 2.2 m, the length of a modular section I, II and III is expediently an integer multiple of this, for example twice, i.e. 4.4 m. This enables an efficient modular construction, so that in the case of 4.4 m long sections I, II and III with only four sections, a cooling grate 3 with a plank length of 17.6 m can be constructed efficiently.

[0080] In Figs. 9A to 9G, the conveying direction runs from top left to bottom right. In the area of ​​the top left feed end 31, an outlet 22 of the rotary kiln 2 can be seen. The direction of rotation of the rotary kiln 2 is symbolized by a circulating arrow 21. In the illustrated embodiments, the rotary kiln 2 rotates clockwise in the conveying direction 14.

[0081] Fig. 9A shows a first exemplary embodiment in which hybrid planks 4* according to the first embodiment described above, as shown in Fig. 3, are provided across the entire width of the cooling grate 3. Fig. 9B shows a second exemplary embodiment with hybrid planks 4* in which only the end section is provided with a protective layer 5, as in the second embodiment shown in Fig. 6. In this case, almost the entire surface of the cooling grate is designed with a smooth, essentially flat plate covering 6, except for the said end section 43 of the planks. In the third exemplary embodiment shown in Fig. 9C, this concept of concentrating on the end section 43 is taken to the extreme, in that all the other planks, except for the end section of an edge-positioned hybrid plank 4*, are provided with a plate covering 6 throughout.

[0082] The fourth embodiment according to Fig. 9D shows the inverse case to the second embodiment. As in the third embodiment according to Fig. 7, a protective layer 5 is provided only in the initial section 41 of the hybrid planks 4*, while the remaining regions, namely the middle section 42 and the end section 43, are provided with the plate covering 6.

[0083] However, it is not necessary for the invention that all the planks are of the same design across the entire width of the cooling grate 3. For example, in the fifth exemplary embodiment shown in Fig. 9E, which is based on the fourth exemplary embodiment according to Fig. 9D, an additional edge plank with a continuous protective layer 5 can be provided as an additional plank 4 * *. The additional plank 4 * * is arranged on the left as seen in the conveying direction 14, i.e. is located at the end furthest from the direction of rotation with respect to the direction of rotation 21. This is the side on which bulk material 9 emerging from the mouth 22 of the rotary kiln typically has a higher proportion of fine fraction. This therefore collects primarily on the plank furthest from the direction of rotation, in the illustration in Fig. 9E therefore on the plank located on the left edge in the conveying direction. Since the fine fraction has special requirements, in particular to prevent the undesired formation of a so-calledTo avoid "Red River," an additional plank 4** provided with a continuous protective layer 5 is expediently provided at this location. This allows for slower conveying and, in this particular case, more reliable cooling. The remaining planks are designed as hybrid planks 4*, as in the fourth embodiment shown in Fig. 9D. A variant of this is shown in Fig. 9F as a sixth embodiment. Here, the protective layer 5 is provided in the end section of the hybrid planks 4* (instead of the initial section). It can also be provided that the hybrid planks 4* are provided with the protective layer 5 in both the initial and final sections.

[0084] A continuation of this concept is shown in a seventh embodiment in Fig. 9G. Here, both edge planks are designed as additional planks 4** with a continuous protective layer 5. It should be noted that this variant with additional planks 4** for both edge planks can also be provided with respect to the fifth embodiment according to Fig. 9E, i.e., with the protective layer 5 in the initial section (instead of the end section) or with the protective layer 5 in both the initial and end sections.

[0085] Fig. 10A and Fig. 10B each show a cross-sectional view of the cooling grates 3. These are cross-sections for the plank arrangement according to Fig. 9A and Fig. 9E, respectively, in the region of the central section 42 (in Fig. 9D and Fig. 9E in the modular sections II) looking in the conveying direction 14. The cooling grate 3, which in the illustrated embodiments comprises a total of five planks, is guided on its two longitudinal sides between two edge strips 19, each of which is arranged on one of the side walls 15 (see Fig. 2A). Referring to Fig. 10A, five hybrid planks 4 with the plate covering 6 are shown in their respective central section 42. The spaces between the planks are sealed by longitudinal seals 84. Edge seals 84' are provided for each of the edge strips 19. These seals 84, 84' prevent an uncontrolled outflow of the cooling gas 80 from the space below the cooling grate 3 upwards into the bed of bulk material 9. In Fig.10B shows the embodiment according to Fig. 9E, which has an additional plank 4** on one side (left in the conveying direction) that is continuously provided with a protective layer 5. Otherwise, the structure corresponds to that according to Fig. 10A; edge strips 19 are provided on the outer sides, and longitudinal seals 84 between the planks and edge seals 84' to the edge strips 19 are provided to prevent uncontrolled escape of the cooling gas 80.

[0086] The structure of the longitudinal seals is described below with reference to Figs. 11, 12, and 13. Figs. 11 and 12 show the arrangement of the respective seals 84, 84" with respect to planks with a flat plate covering 6 or with a protective layer 5.

[0087] Fig. 13A-C are detailed illustrations of longitudinal seals. The structure of the longitudinal seal 84 between two planks is shown in Fig. 13B and is described below as an example. Also shown there are partial views of a hybrid plank 4* and an additional plank 4**. However, the type of plank is largely irrelevant for the design of the seal 84. On the long sides of each plank there is a vertical wall 46, 46' extending vertically upwards and downwards. It extends upwards far enough to be approximately level with the panel surface 60 of the panel covering 6. This also applies to planks for which a protective layer 5 is provided, whereby the level here is determined by the design height of the protective layer 5.

[0088] The seal 84 is designed to seal the space between the two opposite vertical walls 46 of two adjacent planks against an undesired flow of cooling gas 80. For this purpose, an L-shaped spring plate 86 is arranged on an inner side of the vertical wall 46 facing the center of the plank, which is fastened with its shorter leg to the inner side of the vertical wall 46 such that the longer leg is oriented horizontally approximately plane-parallel to the plate surface 60. Doubled onto the top of the longer L-leg of the spring plate 86 is an elongated, flat sealing plate whose width is dimensioned such that it covers the opposite vertical wall 46 of the immediately adjacent plank.The free end of the sealing plate 87 rests on a sealing counterpart 88 which is arranged on the inside of the opposite vertical wall 46 and which, for this purpose, has an extensive horizontal sealing surface 89 on its upper side. The sealing effect lies in the fact that - under the effect of a downward pre-tensioning of the spring plate 86 - the free end of the sealing plate 87 rests with a downward force on the sealing surface 89 of the sealing counterpart 88. The space between the two opposite vertical walls 46 is thus sealed on one side by the angled spring plate 86 and on the other side by the sealing plate 87 resting on the sealing surface 89. The spring plate 46, the sealing plate 87 and the sealing counterpart 88 each extend continuously over the entire length of a plank and can each be designed in one or more parts.

[0089] A cover 85 is provided as mechanical protection for the seal 84 against stresses caused by the bulk material 9 lying on top. This cover is also L-shaped and is fastened to the vertical wall 46 by its shorter leg in the same way as the spring plate 86. The longer leg of the cover 85 completely overlaps the sealing plate 87 and rests with its outer end on the edge of the sealing counterpart 88 in order to also protect the latter from damage caused by the bulk material 9 lying on top.

[0090] Fig. 10C shows the design of a seal 84' which seals an edge strip 19 from the adjacent edge plank. In contrast to the design according to Fig. 10B, the spring plate 86 and the cover 85 are arranged on an upwardly projecting angle plate 19' of the edge strip 19, and the sealing counterpart 88 is arranged on the inside of the edge plank. Otherwise, the structure corresponds to that in Fig. 10B. Accordingly, Fig. 10A shows the design of the seal 84" for the other edge strip 19. This is basically a mirror image of the seal 84', so that the spring plate 86 and the cover 85 are again arranged on an upwardly projecting angle plate 19' and the sealing counterpart 88 is arranged on the inside of the edge plank.

[0091] A grate plate 7, of which the plank covering 6 is preferably made, is shown in a perspective view in Fig. 14A and in a plan view in Fig. 14B. The grate plate 7 has the shape of a flat cuboid. The upper side of the grate plate 7 is smooth and essentially flat, with two fastening holes 76 spaced apart from one another being countersunk in a center line 75. This serves for the easily detachable fastening of the grate plate 7 to the respective plank 4* to form the plank covering 6. Approximately centrally between the center line 78 and the longitudinal edges of the grate plate 7, a plurality of longitudinal slots 78 are arranged one behind the other. They are elongated and aligned parallel to the center line 78. They extend over a large part of the longitudinal extent of the grate plate 7, preferably over at least 60%, preferably at least 80% of the longitudinal extent.The longitudinal slots 78 are connected to the underside of the grate plate 7 so that cooling gas 80 can flow through them from a grate sub-chamber 38 through the grate plates 7 into the bulk material 9 to be cooled, which lies on the plank 4* or grate plate 7. This is also shown in Fig. 15 and 16, which each show a longitudinal section through the longitudinal slots 78 and a cross-section through the grate plate 7. The longitudinal section shows the longitudinal slots 78, each separated from one another by a separating web 79, as well as a collecting channel 73 arranged underneath and, furthermore, the design of the grate plate 7, which is essentially open at the bottom. The cross-section shows that the sub-chamber of the grate plate 7 is symmetrically divided into two areas by a separating web 74 running along the center line. In each of the areas a row of longitudinal slots 78 is arranged.Below this, in each of the two areas, the collecting channel 73 is arranged, extending over the respective longitudinal slots 78. On the one hand, it is designed to collect bulk material 90 falling through the longitudinal slots 78 so that it can be blown out again by the air stream 80. On the other hand, the collecting channel 73 serves to set a predetermined cross-section for the supply of the cooling gas 80 from the grate sub-chamber 38 to the longitudinal slots 78. The collecting channel 73, together with the longitudinal slots 78, thus forms the cooling gas passage openings 48, in order to bring about a defined passage of cooling gas 80 through the grate plate 7 into the bulk material 9 to be cooled, as shown by the dotted arrows in Fig. 16.

[0092] Fig. 17 shows a further expedient embodiment. It comprises not just one, but several cooling grates 3, which are arranged one behind the other in the conveying direction 14 and thus form a cooling section comprising several cooling grates 3, 3', 3". They are preferably arranged in stages, as shown in Fig. 17. Due to the staged arrangement, the bulk material 9 passes easily from the end of one of the cooling grates 3, 3' to the beginning of the respective subsequent cooling grate 3', 3". Each of these cooling grates 3, 3', 3" has planks that are movable over a stroke length 39, as described above. The planks of the various cooling grates can be designed differently with regard to the plate covering 6 or protective layer 5. In the illustrated embodiment, the cooling grate 3' has continuously smooth planks at the middle position of the cooling section, i.e., planks with a plate covering 6.In contrast, the cooling grate 3 at the beginning of the cooling section has planks in which at least the initial section is provided with a protective layer 5. The cooling grate 3" at the end of the cooling section has a plate covering 6 or can optionally also be provided with a protective layer 5 at least in its end section.

[0093] In this way, a hybrid structure corresponding to the hybrid planks can also be realized with cooling grates 3, 3', 3" arranged one behind the other, wherein this embodiment makes it possible for some or all of the individual cooling grates 3, 3', 3" to be uniformly provided with only one type of plank, either with a protective layer 5 or with a plate covering 6. This enables efficient production, which can be a considerable advantage, especially when creating long cooling sections. Furthermore, reference is made to the above description, in particular to the embodiments according to Fig. 3 and Fig. 8, which are to be applied accordingly.

Claims

Patent claims 1. Device for cooling hot bulk material (9), in particular cement clinker, by means of a cooling gas (80), which comprises a cooling grate (3) through which cooling gas flows, conveying a layer of the bulk material from a feed end (31) in a conveying direction (14) to a discharge end (32), wherein the cooling grate (3) comprises a plurality of planks (4) which are alternately moved forwards and backwards in the conveying direction by a stroke length, the drive (37) of which is controlled such that at least two adjacent planks (4) are moved simultaneously in the forward stroke and non-simultaneously in the return stroke, wherein the planks (4) form a substantially flat support surface (30) for the bulk material (9), characterized in that at least one plank is designed as a hybrid plank (4*) with a different design of the plank surface (60), which has - a central section (42) with a smooth plate covering (6), the central section (42) extending over at least half the length of the hybrid plank (4*), and - immediately adjacent to the central section (42) a starting section (41) and / or end section (42) comprising a protective layer (5) made of bulk material (90) arranged on the plank surface (60), whereby an increased coefficient of friction with the bulk material is formed compared to the central section (42).

2. Device according to claim 1, characterized in that the initial and / or the end section (41, 42) with the protective layer (5) each has a length which is at least 0.5 times the maximum stroke length (39), in particular at least 0.9 times, and preferably at most 12 times, in particular at most 6 times, the maximum stroke length (39).

3. Device according to claim 2, characterized in that the initial section (41) has a greater length than the end section (43).

4. Device according to one of the preceding claims, characterized in that receiving troughs (45) for the protective layer (5) made of loose material (90) are provided in the initial and / or final section (41, 42), which are preferably provided with subdivisions in the longitudinal and / or transverse direction.

5. Device according to one of the preceding claims, characterized in that the plate surface (60) in the middle section (42) is at the same level as the surface formed by the protective layer (5) in the initial and / or final section (41, 42).

6. Device according to one of the preceding claims, characterized in that planks (4) which are not hybrid planks have a smooth plate covering (6).

7. Device according to one of the preceding claims, characterized in that additional planks (4**) can be provided which are continuously provided with the protective layer (5), which are preferably arranged laterally at the edge.

8. Device according to one of the preceding claims, characterized in that at least one edge plank is designed as a hybrid plank (4*), wherein preferably at least one plank immediately adjacent to the edge plank is not designed as a hybrid plank, but is in particular provided with a continuously smooth panel covering.

9. Device according to claim 7 or 8, characterized in that the additional plank (4**) or the hybrid plank (4*) is arranged on that lateral edge which has an increased proportion of a fine fraction of the bulk material (5), wherein preferably at least one immediately adjacent plank is not designed as a hybrid plank, but is in particular provided with a continuously smooth plate covering.

10. Device according to one of claims 7 to 9, characterized in that when the cooling grate (3) is arranged downstream of a rotary kiln (2) which rotates in a direction of rotation (21), the plank of the cooling grate (3) on the edge remote from the direction of rotation is designed as an additional plank (4**) or hybrid plank, namely the left plank in the conveying direction (14) in the case of a rotary kiln (2) rotating clockwise in the conveying direction (14) or vice versa.

11. Device according to one of the preceding claims, characterized in that a majority of the planks of the device are designed as hybrid planks (4*), preferably all of them.

12. Device according to one of the preceding claims, characterized in that grate plates (7) are provided for the plank surface (40), which have a plurality of cooling gas passage openings, in particular longitudinal slots (78) located in the conveying direction, for a cooling gas outlet.

13. Device according to claim 4 or claim 12, characterized in that the grate plates (7) and / or receiving troughs (45) are designed as replaceable modular units for the planks.

14. Device according to one of the preceding claims, characterized in that the cooling grate (3) in the conveyor device (14) is divided into several modular sections (I, II, III), each of which comprises a longitudinal section of the planks with its substructure and can be arranged one behind the other to form the planks.

15. Device according to claim 14, characterized in that the length of the modular sections (I, II, III) is dimensioned such that it corresponds to the length of one of the start / end sections (41, 43) or an integer multiple thereof, in particular twice.

16. Device according to one of the preceding claims, characterized in that an interchangeable extension bracket (49) is provided on the end section (43) of the respective plank, which extension bracket forms an extension of the plank surface (40) for the bulk material (9) and is not ventilated.

17. Device according to one of the preceding claims, characterized in that, viewed transversely to the conveying direction (14), the planks are designed differently, preferably planks with an increased friction coefficient at least in sections on at least one of the side edges of the cooling grate (3) and planks with a smooth surface in the middle and / or on the other side edge.

18. Cooling arrangement for cooling hot bulk material (9), in particular cement clinker, by means of a cooling gas (80), which comprises a cooling section with at least two cooling grates (3, 3', 3") arranged one behind the other in a conveying direction, each of which conveys a layer of the bulk material (9) from a feed end (31) in a conveying direction (14) to a discharge end and through which cooling gas (80) flows, wherein the cooling grate (3, 3', 3") each has a plurality of planks (4) which are alternately moved forwards and backwards in the conveying direction by a stroke length, the drive (37) of which is controlled such that at least two adjacent planks (4) are moved simultaneously in the forward stroke and non-simultaneously in the return stroke, wherein the planks (4) form a substantially flat support surface (30) for the bulk material (9), characterized in that at least one of the cooling grates (3, 3', 3") at the beginning and / or end of the cooling section has at least one plank which is designed as a hybrid plank (4*) according to one of the preceding claims or which is continuously covered with a protective layer (5) made of loose material (90).

19. Arrangement according to claim 18, characterized in that at least one further of the cooling grates (3, 3', 3") has exclusively planks with a smooth plate covering (60) with the exception of edge planks, which can be provided without or at least partially with a protective layer (5) of loose material.

20. Arrangement according to claim 18 or 19, characterized in that the cooling grates are designed according to one of claims 1 to 17.

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