Grate covering

Inactive Publication Date: 2006-09-28
ALSTOM TECH LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0018] The advantages of the invention lie in the fact that, on the one hand, only the parts of the grate bar that are exposed to the corrosive and oxidizing atmospheres at high temperatures are provided with a high temperature-resistant, abrasion-resistant and corrosion-resistant non-metallic layer, so that the grate bar is relatively inexpensive and, on the other hand, weld build-ups on the grate bars are prevented in the critical areas as a result of which malfunctions in the course of the incineration, installation standstills and operational failures are all avoided.
[0019] It is advantageous for the layer to be applied or cemented in by means of an adhesive bond since this can be done quickly and inexpensively.
[0020] It is likewise advantageous for the layer to be applied to the surface of the grate bar by means of a mechanical joint, especially a countersunk screwed connection. The

Problems solved by technology

The marked fluctuation in the quality of the waste in terms of gross calorific value, density, flow resistance, moisture, etc. leads to enormous temperature fluctuations, and often to excessively high temperatures of the air-cooled cast grate bars, which cannot be tolerated.
The movement of the bars relative to each other and relative to the waste leads to a high wear and tear due to abrasion, a phenomenon that occurs at an accelerated rate at high temperatures.
The frequent temperature changes with large temperature gradients and temperature transients lead to the thermomechanical failure of individual grate bars.
The resultant changed flow conditions for the primary air ultimately damage larges sections of the grate.
On the one hand, they are technically much more complex than air-cooled grates since they require a separate cooling-water circulation system, in addition to which they are very damage-prone.
If leaks occur, they have to be shut down.
On the other hand, a detrimentally large amount of heat energy is withdrawn from the system at a low level, which reduces the thermal efficiency of the waste incineration plant.
In actual practice, in addition to the above-mentioned problems, so-called weld build-ups are encountered with the described grate bars.
Such weld build-ups on forward feed grates are especially detrimental when they occur in the zones where two grate bars come into contact with each other.
This leads to greater wear and tear of the contact areas and, in the case of water-cooled grate bars, can cause premature failure when leaks occur due to excessive material abrasion especially in this area.
In addition, the operation of the installation can be impaired if the weld build-up hinders or blocks the movement of the rows of grate bars.
The conse

Method used

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Examples

Experimental program
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Example

[0034] In the case of a forward feed grate of the type described in the first embodiment, the layer 5 on the grate bar 1 is applied only in the contact zone 6 with the adjacent grate bar 1. In FIG. 1, this area is indicated by the hatched depiction of the position of the upper grate bar 1. The material properties of the layer 5 are selected in such a way that the grate bar 1 and liquid material from the product being incinerated cannot fuse in this area and so that no weld build-ups can be formed that would impair the movement of the grate bar and so that little or no wear and tear occurs. Advantageously, ceramic material is used as the material for the layer 5 because of its good combination of properties.

[0035] Since the layer 5 is very thin, it can advantageously be applied or cemented in by means of an adhesive bond. However, application by means of a mechanical joint, for example, a countersunk screwed connection, is likewise possible. Then it can be detached from the grate co...

Example

[0036]FIGS. 2 and 3 show a second embodiment. FIG. 2 shows a longitudinal section through a schematically depicted grate covering according to the invention for a roller grate. FIG. 3 shows a section through two adjacent grate rollers and the stripping device of a roller grate.

[0037] The roller grate consists of a support construction (not shown in FIGS. 3 and 4) that is inclined with respect to the horizontal in the direction of the waste discharge. Several consecutive cylindrical grate rollers 7 are suspended in this support construction and they serve to transport the waste through the furnace as a result of a rotating movement. The grate rollers 7 are provided with a plurality of grate rods 1, usually made of gray cast iron. Strippers 8 are arranged behind each grate roller 7 and they strip off the waste lying on the grate roller 7 and feed it to the next grate roller 7. The strippers 8 have replaceable stripping plates 9 that are positioned close to the grate rollers 7 and are...

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Abstract

A grate covering for an incineration grate of an incineration furnace having a combustion chamber, includes a plurality of metal grate bars, each having a surface facing the combustion chamber that includes a layer made of a temperature-resistant, corrosion-resistant and abrasion-resistant non-metallic material, wherein a thickness of the layer is minimally sufficient to bear pressure and thrust loading. The thickness of the layer is about 10 mm to 15 mm. For a forward feed grate, the layer on each metal grate bar is present only in a zone of contact with an adjacent metal grate bar, and for a roller grate, and wherein the layer is present on the entire surface facing the combustion chamber.

Description

FIELD OF THE INVENTION [0001] The invention relates to the field of incineration technology. It pertains to a grate covering having a protective layer made of a temperature-resistant, corrosion-resistant and abrasion-resistant non-metallic material that can be used especially for a grate in an incineration furnace for burning waste. DESCRIPTION OF RELATED ART [0002] It is known from the state of the art to burn waste on an incineration grate, for example, a forward feed grate or roller grate, whose grate covering made up of air-cooled or water-cooled grate bars transports the waste through the combustion chamber by means of a defined movement. [0003] In the case of air-cooled grates, primary air flows through the grate, where it is first used to cool the grate bars and subsequently as a requisite reactant for the combustion. This system entails the following drawbacks: [0004] The marked fluctuation in the quality of the waste in terms of gross calorific value, density, flow resistan...

Claims

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Application Information

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IPC IPC(8): F23K3/08F23K3/18
CPCC21D9/0025F23G5/002F23H9/02F23H17/12F27D5/0006
InventorZIMMERMANN, BERNHARD
OwnerALSTOM TECH LTD