EP0167658B1 - Grate area element for the construction of a grate surface as well as heat treating process - Google Patents

Abstract

The combustion, cooling or other treatment of solids with the aid of gas may take place on a grate carrying or conveying said solids while the gas is passed through openings provided in the surface of the grate. In order to retain said solids entirely above said grate surface, to cool the grate surface sufficiently and to distribute the gas evenly in the solids to be treated, thin slots, inclined in the direction of transport, curved in the manner of a siphone and maintaining a high resistance to gas penetration are provided in grate plates composed to form a grate. The slots are formed between elements of such grate plates which can be manufactured by casting. The design of these grate plates avoids the necessity of handling dribblings passing said grates. The grate plates can be aerated through grate beams carrying them.

Description

The invention relates to a grate floor element for the construction of a grate surface or a grate floor for receiving solids during their combustion, cooling or other heat treatment, the grate floor element having a surface perforated by gas outlet openings for carrying the solids located on the grate, also to one a plurality of such grate floor elements, as well as a process for the combustion, cooling or other heat treatment of solids located and conveyed on a heat-resistant grate floor by means of gases such as, for example Air, these gases used for heat treatment first flowing through the grate and then the solids on it.

In practice, grate floors for the above-mentioned treatment purposes for solids are usually formed from grate bars, grate plates or grate blocks, which are dimensioned in such a way that they do not warp under thermal expansion. These grate floors carry the solids and promote them due to their inclination or movement. The funding can also be provided by scratches or by the gas used for treatment, usually air.

An essential feature of grate floors is openings for the gas to pass through. They are formed between the grate bars or incorporated into the grate plates or grate blocks. Special requirements for gas passage are met by inflow or nozzle plates. Such floors can be made of ceramic materials for use at high temperatures. Because of their low mechanical strength, however, they generally do not fulfill the conveying function of movable gratings.

Known grate floors meet the demand for good self-cooling and a defined resistance to uniform distribution of the gas in the solid to be treated above it in different ways.

Cooling fins or channels arranged on the gas side are described in DE-A-32 13 294.

In another way, DE-A-17 58 067 rotatably installed grate plates with an additional weight are described in order to counteract the buoyancy caused by the rust resistance, which can be greater than the dead weight of the grate element. A key figure for the resistance of the grate is the open grate surface. 5% open grate surface means that the gas supplied in the openings assumes 20 times the speed and causes a considerable lift.

The high exit velocity of the gas in the vertical direction can be disruptive.

The advantages of gas emerging horizontally from rust floors are described in US Pat. No. 3,304,619: the solid is conveyed by high outlet speeds and the heat transfer is improved. However, a heat-resistant grate floor that realizes these advantages is not described.

Slits arranged transversely and inclined to the conveying direction have so far been formed between individual grate bars. In contrast to grate plates installed directly on grate beams, they require longitudinally laid intermediate beams. The tight connection of the chambers for the gas supply, especially at high pressures for high rust resistance, and the transmission of the conveying movements to the grate surface is made more difficult by such intermediate supports.

It is also generally known that a small, open grate surface in connection with high gas velocity greatly reduces the grate diarrhea. Nevertheless, grids must have elaborate facilities for discharging fallen solid from the chambers and for removing them. It is only in the case of nozzle bottoms that an overlapping cover of the openings ensures, for example, that the solid does not get into the openings even when the gas supply is interrupted.

DE-A-20 05 869 describes a blind-like staircase wall in which a powder is conveyed transversely to the gas passage. The blind stairs run against gravity, so that no solid can run out.

The last two examples show that rust obstructions can be avoided by obstacles oriented in the direction of gravity. The blind solution, however, has the disadvantage that a sufficient resistance for gas distribution is not realized, while nozzle bottoms have so far not been able to be realized in a mechanically promoting grate.

The invention is based on the object to provide mechanically stressable grate floor elements for building up a grate surface and thus a grate, which combines the advantages known from the various above-mentioned constructions of grate bars, grate plates, grate blocks and nozzle plates with regard to self-cooling, gas distribution (including resistance) and freedom from diarrhea , wherein the grate floor elements should in particular be economically producible and, with regard to the method, to achieve improved and more economical conveyance of solids to be treated on grate floors.

According to the invention, this object is achieved in the case of the grate floor element in that it is box-shaped and has lateral support webs which determine its width and between which the surface spans, on which the surface-defining bodies are arranged, the support webs moving in the manner of cheeks from the surface below and the surface-defining bodies between the cheeks to form fine gas slots substantially transverse to the cheeks, and that the gas slots are dimensioned and arranged with respect to the surface in such a way that they have a high resistance to gas passage and an obstacle to penetration or fall through of the transported solids.

Such a box-like grate floor element is comparable in its function to ventilation boxes which are covered with semi-permeable fabrics or porous substances and are used in the area of low temperatures and fine powders. With the invention, the use of grate floor elements of such a function is now also possible for hot and coarse solids. The e.g. Casting grate flooring elements that can be produced economically can be laid directly on grate girders without creating any further openings between the supporting bars. As a result, only the formed gas slots determine the rust resistance and the gas outlet speed, which prevents the ingress of solid matter. If the gas supply is interrupted, the grate slots form an effective obstacle against grate diarrhea due to their dimensioning and arrangement, which are matched to the overall surface of the grate, so that devices for discharging and removing the grate diarrhea become superfluous.

The object on which the method is based is achieved in that the gases are fed to the solids essentially parallel to the grate bottom and in the conveying direction at high speed in the form of fine gas jets which are wide transversely to the conveying direction. This makes it possible to significantly support the conveying process of the solids to be treated, which are located on a grate, with the aid of the treatment medium, and above all the transport of the fine particles of such solids can be supported. A major and extremely important advantage is the additional cooling of the surface and the distribution of the gas from a layer parallel to the grate surface, regardless of the fineness of the slots. In other words, the gas emerging from the slots provided in the grate bottom elements can form the conveying means for the solids located on the grate. While the conveyance of the solids is supported by moving the grate or by means of an additional conveying device through the gas outlet from the slots inclined in the conveying direction, it is with fine solids, here in connection with a horizontal grate, or with coarse solids in connection with an inclination of the Grate surface in the conveying direction possible, to convey the solid only with the process gas. This is useful if the grate floor is rigid or the solid is too hot for mechanical conveying. With this conveyance of the heat treatment material, which is significantly supported or even carried out by the process gas, it can be advantageous for the conveying process if the gas supply is pulsating. It is also expedient for uniform and / or intermittent conveying to apply gas to adjacent gas jets in groups in the conveying direction, with groups of adjacent, jointly applied gas jets covering the entire area, for example to achieve a uniform movement across the grate width Extend width of the grate bottom and, if necessary, such gas jet groups can pulsate together. These various measures, which can be taken individually or in combination with one another, allow a wide variety of conditions to be set and achieved with regard to the conveyance and treatment of the materials processed on the grate floor.

In a preferred embodiment of the grate floor element, the supporting webs and bodies can be provided as parts that can be attached to one another to form a rigid grate floor element. This makes handling and laying easier, while the easy manufacture by casting is retained.

According to another advantageous embodiment of the grate floor elements, the supporting webs and the body can be positively plugged together. The advantage that can be achieved in this way is the mobility of the parts to one another as a result of the mechanical stress, which brings about or supports a self-cleaning effect.

Furthermore, the supporting webs and bodies can be provided in the form of two complementary basic components, each of which comprises a supporting web with a plurality of bodies extending transversely thereto. Such grate floor elements are easy to cast and embody particularly stable, closed boxes with any narrow, internal gas slots. Advantageously, the grate bottom element can have a bottom plate which extends between the two supporting webs and in which an opening for the gas supply into the interior of the box-like grate bottom element can be provided. As a result, the ventilation can preferably take place via grate supports, as will be described in more detail below as support elements for the grate floor elements according to the invention, and, as already explained, gas streams adjacent to each other in the conveying direction can be acted upon in groups together with gas, which has advantages are achievable in terms of both the design effort and the procedural process.

According to another possibility of designing the grate floor elements, the slots can be inclined towards the grate surface. The inclination in the direction of conveyance, which has a significant influence on the formation of an obstacle to rust diarrhea, preferably takes place in order to support the conveying process in accordance with the method according to the invention. Such conveyance of the fine fraction of solids to be treated on the grate is particularly advantageous when using a scraper conveyor or with a sliding grate, since the fine fraction is mechanically difficult to convey.

Appropriately, the inclination of the slits can be less than 40 ° relative to the surface, as a result of which the escaping gas flow rests on the surface and thus particularly in front contributes in part to the implementation of the method according to the invention.

According to a further embodiment, the slots are curved in a siphon-like manner at their gas inlet against gravity. This shape represents a particularly easy to manufacture and effective obstacle against rust diarrhea in connection with inclined slots.

The slots preferably have throttles and extensions. This further improves the internal cooling of the grate floor element through the Joule-Thomson effect. At the same time, resistance to gas passage is increased.

A majority of the grate floor elements designed according to the invention build up a grate in which the grate floor elements are arranged next to one another on grate supports in rows of grates and a plurality of such grate rows one behind the other, and in the further development of the invention the grate support hollow girders with connection to the gas supply and the grate floor elements sealing to the grate supports can be attached, openings for the gas supply from the grate carriers are provided in the interior of the grate floor elements and are in coverage with each other. While known air chambers for ventilation of grates always have to comprise several grate rows because of the device for discharging the grate diarrhea, this type of arrangement of the grate floor elements according to the invention enables grate ventilation to be divided into individual grate rows. Installation in the grate supports can further influence the air distribution.

The grate can expediently comprise a device for the pulsating supply of the gas (air) to the slots or a valve for the controlled interval supply of the gas to the slots. Both devices allow the gas speed required for the conveyance to be set independently of the amount of gas required for the process.

• Fig. 1 einen Teil eines Rostbodenelements im Längsschnitt,
• Fig. 2 eine Draufsicht auf ein Rostbodenelement der Fig. 1,
• Fig. 3 eine andere Ausführungsform eines Teils eines Rostbodenelements im Längsschnitt,
• Fig. 4 eine weitere Ausführungsform, ebenfalls im Längsschnitt,
• Fig. 5 eine weitere Ausführungsform eines Rostbodenelements im Längsschnitt,
• Fig. 6 eine Draufsicht auf das Rostbodenelement der Fig. 5,
• Fig. 7 eine abgewandelte Ausführungsform eines Rostbodenelements mit einem zur Belüftung vorgesehenen Rostträger in geschnittener Seitenansicht und
• Fig. 8 eine aus Rostbodenelementen nach der Erfindung aufgebaute Rostreihe in räumlicher Darstellung.

Further advantages and training possibilities of the invention emerge from the following description of the exemplary embodiments shown in the schematic drawings. In the drawings shows

• 1 shows a part of a grate floor element in longitudinal section,
• 2 is a plan view of a grate floor element of FIG. 1,
• 3 shows another embodiment of part of a grate floor element in longitudinal section,
• 4 shows a further embodiment, also in longitudinal section,
• 5 shows a further embodiment of a grate floor element in longitudinal section,
• 6 is a plan view of the grate floor element of FIG. 5,
• Fig. 7 shows a modified embodiment of a grate floor element with a grate support provided for ventilation in a sectional side view and
• 8 shows a row of grates constructed from grate floor elements according to the invention in a spatial representation.

A grate floor element 19, which forms part of a grate row 20 shown in FIG. 8 and explained further below, can be cast metal or ceramic and comprises, according to FIGS. 1 and 2, basic components 1 and 2 with main bodies 3 which form part of the effective grate surface or determine and are referred to in the text for simplicity only as "body". These bodies 3 are cast alternately on mutually opposite supporting webs 4 of the basic components 1 and 2 and form slots 5 between them due to their dimensions in the longitudinal direction of the grate floor element.

The grate surface, as can be seen from FIGS. 6 and 6, is formed from the bodies 3, the supporting webs 4 and the slots 5. The area ratio of bodies 3: supporting webs 4: slots 5 can range from 1: 5: 1 to 40: 1: 1. Due to the formation of casting cones on the bodies 3, the slots 5 can, however, also deviate from the 90 degree angular position shown relative to the supporting webs.

In Fig. 1 oblique slots 5 are shown, which are preferably inclined so that they emerge in the conveying direction. The inclination should not exceed an angle 23 (FIG. 5) of 40 ° in order to produce a flow of gas lying on the surface. Particularly favorable results can be achieved with angles of inclination of 30 to 35 °.

• Fig. 3 zeigt siphonartig an ihrem Gaseintritt 14 entgegen der Schwerkraft gekrümmte Luftschlitze 10 als Hindernis gegen Rostdurchfall.
• Fig. 4 zeigt Luftschlitze 11 mit Drosseln 12 und Erweiterungen 13 zur Erhöhung des Rostwiderstandes und zur inneren Kühlung nach dem Joule-Thomson-Effekt.

The slots 5 can be adapted to various requirements, for example with regard to inclination, curvature and conicity. Different slot shapes can also be realized within a grate floor element.

• Fig. 3 shows siphon-like at its gas inlet 14 against the gravity curved air slots 10 as an obstacle to rust diarrhea.
• Fig. 4 shows louvers 11 with throttles 12 and extensions 13 to increase the rust resistance and for internal cooling according to the Joule-Thomson effect.

The slot shapes 10 and 11 can also be combined.

5 and 6, the grate floor elements are formed from individual supporting webs 4 and bodies 3 by form-fitting assembly. For this purpose, the body 3 have pins 8, which are received by holes 9 in the supporting webs 4. Instead of the pins 8 and holes 9, for example, brackets (not shown) can be fastened to the supporting webs 4 for receiving the bodies 3. Such a simplified construction is preferred, for example, when using ceramic instead of metallic materials.

One or more of the grate floor elements of FIGS. 1 and 2 or FIGS. 5 and 6 are held together by tie rods 15 (FIG. 2) which are guided through bores 7. In addition to the body 3, the distance between the supporting webs 4 can also be ensured by spacers 6. Instead of the tie rods 15, the holding forces for the tight fit of the supporting webs 4 can also be applied to one another by pressure.

7 and 8 show the arrangement of grate floor elements 19, here with siphon-like slots 10 on a grate carrier 16 for building up a grate row 20. It is readily known to the person skilled in the art that several such grate rows one after the other to form a grate of some kind, not shown here the known types (thrust, moving grate, stationary grate) are put together. With such an arrangement, the supporting webs 4 are designed in such a way that they can be fastened in a form-fitting manner on a grate support 16 designed as a hollow support. The grate floor elements 19 are displaceable across the grate on the grate carrier 16 so that they can be changed during operation. The air or gas is supplied via the grate support 16, which is therefore well cooled. One of the two supporting webs 4 has a base plate 17 in order to ensure ventilation via the grate carrier 16. This type of ventilation enables a particularly narrow division of the air chambers under the grate floor. The grate supports can contain adjustable flaps 24 for further air distribution.

The base plate 17 can rest on the subsequent grate base element, not shown, whereby a step grate is formed. The promotion can take place in a known manner by the pushing movements of the rows of grates. Due to the air emerging from the slots 10, the frequency of this thrust movement necessary for the conveyance of solids is reduced in a manner which is more favorable for wear.

In the case of complete assumption of the conveyance of the solid matter by the gas or the air, which is dimensioned in a certain process from a process engineering point of view with respect to the amount of solid matter, it is necessary to make the speed necessary for the conveyance at the exit from the slots 5 and 10 independent of adjust the amount. The grate carrier 16 has a connection 21 for the gas supply. Devices 22 for pulsation or valves (not shown here) for controlled intake of the air are assigned to this.

Claims (18)

1. Grate element for forming a grate surface or a grate for receiving solid material during its combustion, cooling or other heat-treatment, the grate element having a working surface for carrying the solid material present on the grate, which surface is open through gas exit openings, characterized in that the grate element (19) is shaped in the form of a box and comprises lateral brackets (4) defining its width and spanning the surface therebetween, on which brackets bodies (3) defining the surface are provided, the brackets extending downwardly from the surface in the manner of cheeks and the surface defining bodies extending between the cheeks while forming fine gas slots (5, 10) extending essentially transverse to the cheeks, and that the gas slots are dimensioned and arranged such with respect to the surface that they constitute a high resistance to the passage of the gas and an impediment against the penetration or fall through of the transported solid material.

2. Grate element according to claim 1, characterized in that the brackets (4) and bodies (3) are provided as members to be attached to each other to form a rigid grate element (19).

3. Grate element according to claim 2, characterized in that the brackets (4) and bodies (3) are lockable positively to each other.

4. Grate element according to any of of claims 1 to 3, characterized in that the brackets (4) and bodies (3) are provided in the form of two complemental basic parts (1, 2), each of which comprises one of the brackets (4) with a plurality of bodies extending transversely thereto.

5. Grate element according to any one of claims 1 to 4, characterized in that the slots (5, 10) are inclined with respect to the surface.

6. Grate element according to claim 5, characterized in that the inclination of the slots (5, 10) with respect to the surface is less than 40°.

7. Grate element according to any one of claims 1 to 6, characterized in that the slots (5, 10) are curved in the manner of a siphon rising towards their gas inlet (14) with respect to gravity.

8. Grate element according to any one of claims 1 to 7, characterized in that the slots (5, 10) incorporate throttles (12) and enlargements (13).

9. Grate element according to any one of claims 1 to 8, characterized in that it has a bottom plate (17) extending between the two brackets (4) serving as a lower closing, in which bottom plate there ist provided an opening (18a) for the gas supply to the interior of the box-shaped grate element (19).

10. Grate composed of a plurality of grate elements according to any one of claims 1 to 9, the grate elements being arranged side by side in grate rows on grate beams and several of such rows being arranged in series, characterized in that the grate beams (16) are hollow carriers with a connection (21) to the gas supply and that the grate elements (19) are attached to the grate beams in a sealing manner, openings (18a, b) being provided for the gas supply from the grate beams (16) into the interior of the grate elements (19), and lying flush with each other.

11. Grate according to claim 10, characterized in that the gas emerging from the slots (5, 10) provided in the grate elements forms the conveying means for the solid material present on the grate.

12. Grate according to claim 10, characterized in that it comprises a device (22) for pulsatingly supplying the gas to the slots (5, 10).

13. Grate according to claim 10, characterized in that it comprises a valve for controlling an interval-manner supply of the gas to the slots (5, 10).

14. Method for the combustion, cooling or other heat treatment of solid material positioned and conveyed on a heat-resistant grate by means of gas such as e.g. air, such gas serving the heat treatment first passing the grate and then the solid material positioned thereon, characterized in that the gas is supplied to the solid material essentially parallelly to the grate and in the conveying direction at high velocity in the form of fine gas beams which have a distinct width extension transversely to the conveying direction.

15. Method according to claim 14, characterized in that the gas supply occurs pulsatingly.

16. Method according to claim 14 or 15, characterized in that gas beams which are positioned adjacent to each other when seen in the conveying direction are gas-charged commonly in groups.

17. Method according to claim 16, characterized in that such groups of adjacent, commonly charged gas beams extend over the whole width of the grate.

18. Method according to claim 16 or 17, characterized in that such gas beam groups pulsate commonly.

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