EP0157920B2 - Roll for a roller grate, for example for a refuse burning plant or the like - Google Patents

Description

The invention relates to a grate roller for a grate of a waste incineration plant or the like with a hollow shaft and a cylindrical support structure with grate bar supports on which arc-shaped grate bars are arranged with the outer web walls forming the combustion chamber-side roll shell, each grate bar having a cross section essentially T-shaped with a base bar and one Cross bar is formed, and wherein air gaps for the supply of primary air are formed in each case between the cross bars of two adjacent grate bars.

A waste incineration plant in which the invention can be implemented, for example, consists of a feed device with a reciprocating slide with which the waste is pushed into the combustion chamber through an opening in a filling shaft. In the firebox, the waste is exposed to intense flame radiation. Downstream of the feed device is a roller grate in the firebox, which is designed as a sloping grate and consists of five or six grate rollers of approximately 1.5 m in diameter arranged one behind the other in a plane inclined at approximately 30 ° in the transport direction, so-called pockets being formed between the grate rollers.

The most important design features of the grate roller are usually a hollow shaft mounted on both sides and a cylindrical support structure with radial walls for holding the axially extending grate bar supports, on which the circular-arc grate bars made of rust bar cast are lined up next to one another and one behind the other, with slots remaining free between adjacent bars. The grate bars form the jacket of the grate roller or the so-called grate covering. Due to the rotation of the grate roller, they are only temporarily exposed to fire and can cool down again in the air zones. Guide walls are arranged between the grate rollers, which seal the rollers from one another and, together with the grate rollers, form pockets in which the waste is turned.

The roller grate is embedded in a sheet metal housing divided for each grate roller. The air is supplied to these zones from the side in controllable quantities. From the zones, the air should pass through the grate and the fuel waste bed into the combustion chamber.

Before the garbage reaches the roller grate, the drying and ignition of the easily combustible components have started. During the reciprocating movement of the slide, the garbage falls into the pocket formed by the first guide wall and the first grate roller as a slice or chunk of low thickness until the slowly rotating grate roller removes the material adhering to its surface from below out of your pocket. It passes through the grate roller into the second pocket between the first and second rollers. This process is repeated from roller to roller and brings an intensive turn of the garbage, which soon leads to a good base fire.

The air distribution is adapted to this combustion pattern with the adjustable underwind zones. The amount of air added is low in the drying and ignition zone. It reaches its maximum in the main combustion zone and decays to a minimum in the burnout zone.

It has been shown that the increased proportions of plastics, white metals, roofing felt. Greases or similar substances form deposits due to their combustion inside the rollers in the so-called roller baskets and in the grate diarrhea funnels, which lead to smearing between the roller bars and blockages in the grate diarrhea funnels. However, the roller grate is designed so that the amount of air required for combustion is passed through the roller cage between the grate bars to the firing material lying on the roller. However, this structurally provided combustion process is hampered by the deposits and smears in the roller cage. In addition, it cannot be ruled out that the plastics, fats, oils or the like lie in concentrated form on a roller and, during partial combustion, get into the roller basket through the not yet smeared grate slots and continue combustion in the roller basket. This creates the risk that the roller will start to burn. During cleaning work on a roller it could already be determined that most of the roller basket area had burned down.

The grate bars of a known type of grate rollers consist of a relatively narrow, from the side, arcuate web with two side walls, a head and a foot wall and a fire-side outer web wall. In the area of the outer web wall projecting tooth-like projections are arranged on each side wall at a regular distance from each other parallel to the direction of the axis of the grate roller, each projection of one side wall being positioned diagonally to the projection of the other side wall and the projections of a grate bar into the gaps between the projections of a grips laterally adjacent other grate bar, leaving a gap between adjacent grate bars of about 5 mm in width. As described, this gap is intended for supplying air. In the top and bottom walls, the grate bars are shaped so that they can be placed one behind the other in the circumferential direction on the grate bar supports and stored there in a stationary manner. Apart from the fact that the shape of the known grate bars is relatively complicated, it means that the gaps between adjacent grate bars cannot be kept much narrower. The width of the gaps is in turn responsible for the fact that relatively thin, still unburned waste components can get through the gaps into the interior of the roller, which results in the effects described.

Another grate roller for a roller grate for waste incineration is known from DE-B-1 164 014. The problem is also addressed here. that when garbage is burned by fractions of easily melting metals, there is a slight blockage of the rust coating in the gaps between the grate bars. During the rotation of the rollers, the molten metal drips from the firing layer of the upper part through the grate gaps into the interior of the roller and thus onto the back of the lower grate bars passing through the cooling air space during the combustion process. This easily clogs the rust gap in the lower run, into which the metal flows and cools there. According to this publication, this falling through of molten metal through the inside of the roller onto the cool grate bars of the lower run is to be made impossible. This is achieved by collecting plates, which are arranged within the roller in such a way that the dripping metal hits the collecting plates immediately after passing through the grate gaps of the upper roller center and therefore cannot pass further through the inside of the roller into the grate rod gaps of the opposite, lower grate bars . However, as a result of the substances entering the interior of the roll, it is still possible for hooks to form in the area of the gap in the upper roll center, so that they clog over time. In the following, combustion air can then only be supplied to an insufficient extent.

In the older, unpublished European patent application EP-A-0 124 826, a roller grate consisting of grate rollers for waste incineration plants is described. Here too, each grate roller consists of a hollow shaft that has holders for grate bar supports. Cross-sectionally T-shaped grate bars are suspended between the grate bar supports in such a way that they form the casing of the grate roller. Furthermore, air slots are formed between the grate bars. For this purpose, the abutting side surfaces of two adjacent grate bars are kept at a distance by spacers. But this distance is obviously, i.e. the gap or slot width, so large that - as in the prior art described above - disadvantageously during combustion e.g. molten metals or the like can enter the louvers, which can lead to caking, through which the louvers gradually become clogged, so that frequent maintenance work is required. To solve this problem, it is proposed here to design the grate roller so that the grate bars can perform relative movements relative to one another during operation, thereby preventing material which has already entered the interior of the roll through the slots from becoming lodged between the grate bars.

On the basis of this prior art (in accordance with Art. 54 (3) EPC), the present invention is based on the object of completely preventing the penetration of any substances, in particular also thin substances, into the air gaps, so that downtimes due to repairs are also avoided .

According to the invention this is solved by claim 1. Advantageous embodiments of the invention are characterized in the subclaims 2 to 12.

• Fig. 1 schematisch eine Müllverbrennungsanlage,
• Fig. 2 schematisch einen Teil einer Rostwalze,
• Fig. 3 eine Seitenansicht eines Roststabes,
• Fig. 4 einen Schnitt entlang der Linie A-B in Fig. 3,
• Fig. 5 schematisch seitlich aneinandergereihte Roststäbe,
• Fig. 6 eine Ansicht auf eine erfindungsgemäße Walze mit Abstreifer.

The invention is explained in more detail below by way of example with reference to the drawing. Show:

• 1 schematically shows a waste incineration plant,
• 2 schematically shows a part of a grate roller,
• 3 is a side view of a grate bar,
• 4 shows a section along the line AB in FIG. 3,
• 5 shows schematically side-by-side grate bars,
• Fig. 6 is a view of a roller according to the invention with a scraper.

The waste incineration plant according to FIG. 1 has a feed device 1, through which the waste (not shown) is pushed onto a roller grate 2 inclined in the transport direction. The roller grate 2 is constructed from a plurality of rotatable grate rollers 3 arranged side by side in the transport direction, pockets 4 being formed between adjacent grate rollers. The roller grate 2 is embedded in a sheet metal housing 5 divided for each grate roller. Air is supplied to these zones from the side in controllable quantities. Since all other parts of the waste incineration plant are not related to the invention, they are not described because they are known. Each grate roller 3 is laterally supported by a hollow shaft 6 in the corresponding sheet metal housing 5 (FIG. 2). The cylindrical support structure of the grate roller is located between the bearings. It essentially consists of radially extending walls or support webs 7, which are arranged at a distance from one another on the hollow shaft and on which rest the grate bar supports 8, which extend axially and are spaced apart on the circumference of the roller. Roller baskets 9 are formed between the walls 7, in which, according to a feature of the invention, air baffles 10 are arranged obliquely to the longitudinal axis direction of the roller. On the grate bar supports 8 are grate bars 11. The lines 12 and arrows 13 in FIG. 2 indicate the air path that the air is to take from the sheet metal housing 5 through the grate roller 3 into the combustion chamber 14. The other parts of a grate roller are for the Invention is immaterial, which is why they are not mentioned in the context of this description.

A grate bar 11 according to the invention is essentially T-shaped in cross-section (FIG. 4) and consists of the transverse web 15 and the base web 16. It has the outer web wall 17 and the inner web wall 18 as well as the side walls 19 and 20, the head wall 21 and the foot wall 22, the transverse web being provided with side edge surfaces 23 and 24. The design of the head and foot walls is known and is insignificant to the invention, which is why it is not explained.

It is essential that the side edge surfaces 23 and 24 are flat and viewed in cross-section (FIG. 4) from the edge 26 on the combustion chamber side to the inner edge 27 in the direction of the base web 16. This results in the side-by-side arrangement of two grate bars (FIG. 5) towards the combustion chamber, wedge-shaped tapered slots 25.

It is also essential that, due to the straight design of the edges 26 of the transverse webs 15 in the plan view, adjacent grate bars can be placed very closely next to one another. Accordingly, a grate roller according to the invention is characterized in that it is equipped with grate bars according to the invention and the gap 25 between adjacent grate bars on the combustion chamber side at the edges 26 is approximately 2 millimeters, in particular 1 millimeter and less. It can be advantageous here if the individual rolls have different gap widths, depending on their position in the combustion zone. Here, the smallest gap width should be present in the roller, which is arranged in the main combustion zone, since there the slag is usually the most liquid, so that there is the greatest risk that the liquid slag can run into the interior. The rolls with the larger gap width have manufacturing advantages because they can be manufactured with greater tolerances.

It is also particularly advantageous that the side walls 19 and 20 lead in the upper third with an arc 28 to the edge 27, which creates a kind of pointed vault 29 between adjacent grate bars (FIG. 5). It is also advantageous if the base web 16 widens evenly upwards, the widening possibly extending to the edge 27 without an arc. The latter features support the action of the slots 25.

With the newly developed shape of the grate roller bars, the primary air supply can be carried out through the 2 mm wide and narrower grate gaps 25. This prevents dripping of white metals and plastics or the like into the interior of the roller. The nozzle-shaped gap 25 increases the air speed, in particular in combination with the arch shape 29, so that care is taken to ensure that the rust roller nips 25 remain free during operation for the supply of the primary air, which is one of the most important physical components for the combustion. A balanced distribution of the combustion air over the entire grate surface of the individual rollers is ensured by the invention. In particular, gap widths of less than or equal to 1 millimeter in width counteract the dripping of the melts due to the surface tension of light metal melts. According to the invention, a certain flow rate is reached which prevents it. that the liquid slag can clog the grates or penetrate the roller. This flow rate depends largely on the ratio of the gap width to the distance between the base webs 16. A ratio of 1/25 to 1150 [gap width / distance] is expedient here.

The shape of the new grate bars enables higher surface pressures so that the risk of breakage of a grate bar is minimized. Defective bars are known to block the rollers and cause an emergency shutdown of a system, which leads to considerable economic disadvantages. The width of the transverse webs 15 is preferably forty to forty-eight mm and the base webs 16 is approximately 18 mm, in particular twenty to twenty-five gaps being provided per meter of the roll length.

The prescribed cleaning intervals according to the manufacturer's instructions are approximately 4000 hours. With the new grate roller, self-cleaning takes place through primary air supply. The cleaning time of around 250 hours per roller required according to previous experience can be omitted.

As can be seen in particular from FIG. 6, there are wipers 30 made of steel bristles 31 between the adjacent rollers 3 in the pockets 4, which are fastened next to one another in a clamping rail 32. The length of the wipers corresponds to the length of the roller. The distance between the bristles 31 is preferably 10 to 15 mm, the diameter is in particular 20 to 25 mm. The distance between the free bristle ends and the roller surface is approximately 10 to 15 mm. The advantage achieved by using the bristle wipers over the known wipers formed from sheet metal is the flexibility achieved, since jamming of foreign bodies in the gap between the roller and wiper can practically no longer occur. This largely prevents damage to the roller grate bars and the roller drive. In addition, the greater permeability of the bristles also improves ventilation of the gusset space between the rollers.

The invention therefore takes a path that is opposite to that of the prior art. The previous teaching required the widest possible gaps between the grate bars so that sufficient air can be passed through. According to the invention, the gaps are narrowed, but the shape of the grate bars ensures that the primary air is forced through the gaps at high speed, so that substances from the garbage cannot penetrate into the interior of the roller through the gaps for long periods and also cannot smear the columns.

Claims (12)

1. Grate roller (3) for a roller grate (2) of a refuse incinerating plant or similar, having a hollow shaft (6) and a cylindrical supporting structure with grate bar bearers (8), on which arc-shaped grate bars (11) are arranged with external bar walls (17) forming the roller shell on the combustion chamber side, each grate bar (11) having an essentially T-shaped cross-section formed by a base bar (16) and a cross bar (15), and respective air gaps (25) for the supply of primary air being formed between the cross bars (15) of two adjacent grate bars (11), which air gaps have a cross-section in the shape of a nozzle such that the primary air supplied achieves a sufficiently high velocity of flow to prevent substances from penetrating the air gaps (25), wherein the air gaps (25) on the combustion chamber side have a gap width of ≦ 2 mm.
2. Grate roller according to Claim 1, characterized in that the cross bar (15) of each grate bar (11) has plane lateral edge surfaces (23, 24), which, starting from the external bar wall (17) on the combustion chamber side, run inclined in the direction of the base bar (16) such that the cross-sectionally nozzle-shaped air gaps (25) taper in a wedge shape towards the combustion chamber.
3. Grate roller according to Claim 1, characterized in that the cross bar (15) of each grate bar (11) has plane lateral edge surfaces (23,24) which run at right angles to the external bar wall (17) on the combustion chamber side and also run parallel to one another.
4. Grate roller according to Claim 2 or 3, characterized in that the air gaps (25) on the combustion chamber side have a gap width of ≦ 1 mm.
5. Grate roller according to one of Claims 1 to 3, characterized in that air-guiding baffles (10) are arranged in the supporting structure at an angle to the longitudinal axis of the roller (3).
6. Grate roller according to one of Claims 1 to 5, characterized in that an ogival air inlet chamber (29) formed by the grate bars (11) is arranged in front of the wedge-shaped or nozzle-shaped gaps (25).
7. Grate roller according to one of Claims 1 to 6, characterized in that the ratio of gap width to the spacing between the base bars (16) is 1/25 to 1/50.
8. Grate roller according to one of Claims 1 to 7, characterized in that there are 20 to 25 gaps (25) per meter of roller length.
9. Grate roller according to one of Claims 1 to 8, characterized by a scraper (30) formed of individual steel bristles (31).
10. Grate roller according to one of Claims 1 to 9, characterized in that the base bar (16) of each grate bar (11) has side walls (19, 20) which in their upper third merge into the cross bar (15) by way of an arch (28).
11. Grate roller according to one of Claims 1 to 10, characterized in that the base bar (16) of each grate bar (11) broadens out evenly towards the top.
12. Grate roller according to one of Claims 1 to 11, characterized in that the width of the cross bar (15) of each grate bar (11) is 40 to 48 mm and that of the base bar (16) is approx. 18 mm.

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