EP0378821B1 - Pusher grate installation for the heat treatment of bulk material - Google Patents

Abstract

The heat treatment of solids by combustion, cooling, or the like with the aid of gas may take place on a grate conveying such solids while the gas is passed through openings in the surface of the grate. In order to provide lateral clearances of such grates with the same order of narrowness as the majority of the grate's openings, the mobile framework of the grate is suspended by tension elements inclined at an angle of at least 3 degrees relative to the perpendicular. If the mobile frame deviates from a straight course, the inclined suspension creates a centering force guiding the mobile frame without mechanical contact and wear. As a result, the lateral clearances for thermal expansion and building tolerances are reduced from about 20 to 2 mm.

Description

Field of the Invention

The invention relates to a moving grate device for the heat treatment of unspecific fine-grained bulk goods, comprising an upper and a lower housing, which is under the pressure of the cooling medium, a plurality of grate rows which are at least partially movable transversely to a predetermined conveying direction of the bulk goods and overlapping one another in a scale-like manner Supporting structure made of side members and cross members for the movably arranged rows of grates and elongated tension elements for suspending the supporting structure, and deals in general with the lateral guidance of such sliding gratings and, above all, their improvement.

State of the art

In the case of sliding gratings which are customary in practice, the supporting structure is mounted either on rollers and axes or on axes of rotation with races for receiving the conveying movement. Due to the resulting wear problems described below, a grate of the type described above was used, in which the structure is suspended from long tension elements parallel to the vertical grate longitudinal plane. Although the wear problem of the rollers or races could be eliminated, this solution was abandoned due to problems in the lateral guidance of the structure.

In general, the supporting structure of such sliding grates consists of longitudinal beams which, together with the movable rows of grates themselves and with further struts, form an overall frame are stiffened. In order to convey the bulk material, it carries out so-called thrusts, from which the term "sliding grate" originates. These are 3 to 30 batches per minute, usually 70 to 150 mm in length, coordinated with the length of the overlap of the grate plates of the successive grate rows. The thrusts are generated by mechanical cranks or hydraulic cylinders and directed onto the frame.

Either the side of the frame is guided by wheel flanges on the rollers that roll on permanently installed rail sections, or vice versa by rail sections on the side members that run back and forth on wheels equipped with wheel flanges. Or the crossbeams receive steel plates on their underside when they are suspended from long traction elements, which rub on fixed counter plates.

These solutions based on the principle of positive locking for the lateral guidance of the sliding grids by means of wheel flanges or friction plates are subject to wear and require a specification of this wear path in the edge gaps of the movable grate rows. These specifications add up to the specifications for the thermal expansion of the grate girders and lead to correspondingly wide, open marginal gaps.

According to the prior art, the quality of a sliding grate lies in its resistance to the gas permeability in order to achieve a uniform gas flow in the bulk material to be treated (see K. von Wedel and R. Wagner "Are cooling gratings clinker coolers or heat recuperators?", Cement-lime gypsum , 37th year, No. 5/1984, pp. 244-247). This resistance can be achieved by appropriately fine and evenly distributed openings in the grate floor. For this purpose, a grate to be referred to as a resistance grate has become known (EP-A-0 167 658), in which box-like grate plates and hollow supports are provided as grate supports as essential components. However, they have no significant influence marginal gaps to be avoided between fixed side plates and the grate plates of movable grate rows, as of course wear can also affect the procedural behavior of such a resistance grate as well as other types of sliding grates.

Slatted frames generally suffer from marginal mobility for both the gas and the goods. In the case of cooling grates for cement clinker, the passage of the cooling air to the edges leads to wear on the side masonry due to sandblasting effects. The limitation of the service life of the sliding grates due to wear often starts from the marginal gaps, especially if after wear of the wheel flanges of the rollers or the friction plates made of steel, the positive side guidance on one side of the grate changes to a frictional connection between the fixed side board and the movable grate plate. This frictional engagement is one-sided because of uneven introduction of the drawers into the frame or uneven counter-forces from the bulk material. To the extent that the abrasive material pair wears out, the opposite side becomes more accessible.

If the oscillating frame is driven by a hydraulic cylinder on each side of the grate, the uneven application of force can be so great without complicated control devices for distributing the force to the cylinders that only one of the two cylinders does the pushing work while the other cylinder runs without pressure. Since only the one with the lower counterforce does the work with free distribution of the oil flow to the two cylinders, the friction from the side guide must be applied via the frame by the opposite cylinder force. Because of the limited rigidity of the frame, particularly large forces act on one side on the side guide of the grate.

Task

The invention has for its object to form the edge gaps of sliding grates so tight that they meet the quality requirements for a resistance grate. In addition, the invention aims to ensure, by the formation of sliding grates, that the procedural behavior cannot deteriorate due to wear, in the knowledge that this depends not insignificantly on changing marginal gaps and, incidentally, also on the sliding gaps and is therefore subject to wear Solution is not allowed.

Solution and advantages

According to the invention, this object is achieved in a sliding grate of the type described in the introduction by tension elements which form an angle of attack of more than 3 degrees against the vertical grate longitudinal plane. Depending on the angle of attack, the own weight of the grate results in horizontal tensile forces according to the parallelogram of the forces in the cross member, which cancel each other out in the central position of rest. If there is a deviation from the central position, an unequal pair of forces arises, the resulting force of which, as a centering force, counteracts disturbing forces from the thrust movement directed sideways. Depending on the angle of attack, even with small deflections from the central position, such a large centering force acts on the movable grate that it is guided laterally only by forces and without a frictional positive fit. This also makes it possible, in the case of a so-called resistance grate (EP-AO 167 658), to set the flat shear gaps above the movable grate rows to the fixed grate rows or fixed side rims and the vertical edge gaps between movable grate rows and fixed side rims in the long term, too, and thus to improve its function over time.

In an advantageous development of the invention, the inclined traction elements can be designed as firmly clamped leaf springs arranged transversely to the conveying direction. While the leaf springs deform slightly in the direction of thrust, in the transverse direction they form a rigid system together with the cross beams. The forces from this stiffness add up to the transverse forces from the inclined position of the tension elements, which means that the swing frame is also guided in the center. The forces for the lateral guidance are so large overall that a one-way hydraulic drive would be permissible - as described above.

According to a further embodiment of the invention, the tension elements can be arranged in oblique, gas-tight protuberances of the lower housing. The lower housing takes on an unusual shape with these protuberances. However, by forming the protuberances according to a further embodiment of the invention as channels for the supply of the cooling medium to the lower housing, at least some of the usual fans for the cooling medium can advantageously be set up on the furnace platform, which is usually located above the sliding grate. The advantage in terms of the task is then that the tension elements are arranged in the inflow of the cooling medium. As a result, temperature influences caused by the hot bulk material and changes in length of the tension elements caused thereby can be excluded in a particularly favorable manner.

Embodiments of the invention

Fig. 1

einen Querschnitt durch einen Schubrost nach dem Stand der Technik,

Fig. 2

einen Querschnitt durch einen anderen Schubrost nach dem Stand der Technik,

Fig. 3

einen Querschnitt durch einen erfindungsgemäßen Schubrost und

Fig. 4

im Detail gemäß IV der Fig. 1 bis 3 eine im Maßstab vergrößerte Darstellung der Spaltverhältnisse im Seitenwandbereich der Roste.

Further advantages and embodiments or possibilities of the invention emerge from the following description of the exemplary embodiments shown in the schematic drawings, which are not drawn to scale with respect to one another. It shows

Fig. 1

a cross section through a sliding grate according to the prior art,

Fig. 2

a cross section through another sliding grate according to the prior art,

Fig. 3

a cross section through a sliding grate according to the invention and

Fig. 4

in detail according to IV of FIGS. 1 to 3 an enlarged representation of the gap ratios in the side wall area of the grids.

In the known type of sliding grate shown in FIG. 1, the working and usable space is determined by a housing, the upper housing being formed by grate plates 12 and masonry 10, while the lower housing extends between side walls with supports 11 up to the grate plates 12 . The structure for movable grate beams 1 of the sliding grate comprises longitudinal beams 2 and running axles 6 with rollers 5 fastened thereon, which have wheel flanges and which represent the lateral guide. Fig. 4 shows the detail IV of FIGS. 1 to 3, namely the masonry 10, a fixed side board 13 and a movable grate plate 12, which forms a thrust gap 15 and an edge gap 14 with the fixed side board 13. The gaps 14, 15 are dimensioned so that they accommodate the dimensional tolerances, thermal expansion and wear paths. The gap widths in this arrangement of the prior art are therefore 6 mm for the shear gap 15 and 20 mm for the edge gap 14.

In contrast, the known embodiment of FIG. 2 already represents an improvement. It shows a sliding grate, the side members 2 of which rest on cross members 3 which are suspended from long traction elements 4. The upper fastenings of the tension elements 4 are not shown. The side guidance is done by friction plates 7. Additionally can be tensioned diagonally tension chains 8 between the supports 11 and the cross members 3.

In contrast, the sliding grate of FIG. 3 designed according to the invention has tension elements 4 set at an angle α of (here) 15 degrees. Depending on the desired force ratios as well as weight and dimensions, the angle α can vary between 3 and 45 degrees. The tensile forces arising in the cross member 3 take over the function of the friction plates 7 or pull chains 8. By designing the tension elements 4 as firmly clamped leaf springs which are advantageously arranged in a package and which deform as a result of the pushing movement, both the pushing gap 15 and the edge gap 14 are independent of wear . The thrust gap 15 and the edge gap 14 are, for example, only 2 mm each in this construction and maintain this quality without the influence of wearing components of the movable supporting structure. The edge and shear gaps thus have the same order of magnitude as the air openings in the area of the grate plates 12 when the grate is constructed as a resistance grate according to EP-A-0 167 658.

Fig. 3 also shows protuberances 16 of the lower housing, in which the tension elements 4 are arranged, and the connection of these protuberances to an air supply line 17. As a result, the tension elements 4 are in the cold air flow. This also eliminates changes in length of the tension elements, which could occur due to thermal expansion at different temperatures of the masonry 10 or due to heat build-up from the lower housing.

Claims (4)

1. Pusher grate arrangement for the heat treatment of particularly fine-grained bulk material, including

   a) an upper and a lower housing charged with a pressurised cooling medium

   b) a plurality of grate rows arranged transversely with respect to a predetermined direction of transport of the bulk material, said grate rows being at least partially mobile and overlapping each other,

   c) a supporting frame structure of longitudinal and transverse beams for the mobile grate rows, and

   d) elongated tension elements for suspending the supporting frame structure,
   characterized in that

   e) the tension elements (4) are arranged at an angle of attack (α) of more than 3 degrees relative to the perpendicular longitudinal plane of the grate.
2. Arrangement as claimed in claim 1, characterized in that the tension elements (4) are designed as plate-springs, which are firmly fixed and arranged transversely to the direction of transport.
3. Arrangement as claimed in any one of claims 1 or 2, characterized in that the tension elements (4) are arranged in inclined, airtight protuberances (16) of the lower housing.
4. Arrangement as claimed in claim 3, characterized in that the protuberances (16) are designed as conduits for supplying the cooling medium to the lower housing.

Images