GB2049894A - Tuyère base construction - Google Patents

Abstract

A self-supporting ceramic tuyère base or distributor plate made of refractory compressed material with tuyères (17, 18) disposed therein, the base being braced by refractory walls and being subdivided into lower support plates (10, 11) having an expansion joint (21) therebetween and, lying thereon, cover plates (1,2) having an expansion joint (22) therebetween, the lower support plates (10,11) and the cover plates (1,2) being arranged offset providing staggering of the expansion joints (21,22). Heat-resistant imbricate sheets (14,15) may be arranged between the plates (10,11) and the plates (1,2) and the tuyères (17,18) may have sheet-metal plates (19,20) fitted over them. The tuyère base is particularly useful in a fluidised-bed furnace. <IMAGE>

Description

SPECIFICATION Self-supporting ceramic tuyère bases The invention relates to self-supporting ceramic tuyère bases made of refractory compressed material with tuyères disposed therein, and particularly those for covering and delimiting fluidised-bed furnaces towards the bottom and for producing a definite passage of air through the tuyère bases into a fluidised bed, the tuyère bases braced by refractory walls.

Tuyère bases of this type are necessary in fluidised-bed furnaces which have to be operated at high undergrate temperatures, for example such as sewage sludge incinerators and the like. In these furnaces it is not possible to use steel plates for the load-bearing function. The load-bearing function can be satisfactorily undertaken at high temperatures only by self-supporting ceramic tuyère bases which are braced and supported in suitable manner by refractory walls.

It is known that ceramic refractory materials do not retain a constant volume. Depending on the heat stress, they are subject to contraction or expansion and are very liable to crack as a result of their sensitivity to sudden changes in temperature.

In addition to ceramic tuyère bases, there are also known tuyère bases made of heat-resistant steel in convex or concave shape, with or without a refractory support. Furthermore, it is known to produce a tuyere base from a flat, load-bearing standard steel grate and a sheet-metal covering resting thereon with welded-in tuyères, a monolithic lining of refractory compressed material being arranged on the sheet-metal covering.

Ceramic tuyère bases are incorporated in fluidised-bed furnaces which can be used for different processes. These tuyère bases have the purpose of delimiting the actual fluidised-bed furnace towards the bottom so that the hot gases required for the operation are directed at the necessary pressures according to the process, upwards through a plurality of tuyères into the fluidised-bed. The fluidised-bed itself consists of a more or less thick layer of quartz sand or other fine-grained ballast, depending on the process.

Now in order to prevent the occurrence of uncontrolled cracking, it is known to anticipate cracking, during the installation of the refractory tuyère base, by the provision of staggered working or expansion joints. This is achieved in that the contiguous abutting faces of the individuai tuyère bases are profiled and thus lie in different planes.

In this case it is assumed that the expansion and contraction movements are to take place within the design areas. However, experience has shown that these measures are unable to prevent finegrained turbulent matter from creeping through open expansion joints and directiy through fine cracks between the tuyères and the refractory material and thus accumulating under the tuyère base. Accordingly, a stoppage in operation may occur relatively quickly.

According to the present invention there is provided a self-supporting ceramic tuyère base made of refractory compressed material with tuyères disposed therein, said base being braced by refractory walls and being subdivided into lower support plates having an expansion joint therebetween and, lying thereon, cover plates having an expansion joint therebetween, said lower support plates and said cover plates being arranged offset providing staggering of said expansion joints.

In an embodiment of the invention heat resistant imbricate sheets are disposed between the lower support plates and the upper cover plates, in which case the imbricate sheets of adjacent tuyère rows overlap one another. In this way an additional increase in tightness is achieved by arranging imbricate sheets once more between the two plates of the tuyère base, which sheets in addition overlap one another. Accordingly, in practice, open expansion joints do not occur; furthermore, the contraction or expansion of the ceramic tuyère bases is rendered less criticai thereby.

In a further embodiment, an accurately fitting sheet-metal plate, which is preferably square, is fitted over each of the tuyères.

Using a tuyère base according to the invention fine-grained turbulent matter cannot even creep through fine cracks which may occur between the tuyères and the refractory material, and any uncontrolled leakage is prevented.

The invention is described in more detail in the following description with a reference to an embodiment thereof illustrated in the accompanying drawings in which: Figure 1 shows a plan view of a cutaway portion of a tuyère base with two rows of tuyères.

Figure 2 shows a cross-section along the line A-B in Figures 1, and Figure 3 shows a section along the line EF in Figure 2 to give a plan view of the lower support plates.

The self-supporting ceramic tuyère bases according to the invention made of refractory compressed material with tuyères arranged therein comprise, in accordance with Figures 1 and 2, cover plates 1, 2 which are contiguously arranged, in which case according to the crosssection in Figure 2 it is evident that the contiguous end faces of two adjacent cover plates are profiled so as to produce a non-planar expansion joint 22 or abutting face.

These cover plates 1, 2 are held by lower support plates 10,11 according to Figure 2, in which case contiguous end faces of two adjacent support plates are likewise profiled so that a nonplanar expansion joint 21 or non-planar abutting face is formed. In addition, the expansion joints 21 and 22 are mutually staggered.

Both the cover plates 1,2 and the support plates 10,11 have holes in which the tuyères 17,18 are arranged.

Furthermore, imbricate sheets 14,15 are arranged between the cover plates 1,2 and the support plates 10,11 in which case two adjacent imbricate sheets overlap one another as illustrated in Figure 2. In the vicinity of the tuyères these imbricate sheets 14,15 are provided towards the tuyères with a clearance which, for example, is 10 mm, so that the differential expansions between the sheets and the tuyère grate can be readily taken up. This clearance is covered by the sheet metal strips 19,20, which is likewise evident from Figure 2.

Claims (6)

1. A self-supporting ceramic tuyère base made of refractory compressed material with tuyères disposed therein, said base being braced by refractory walls and being subdivided into lower support plates having an expansion joint therebetween and, lying thereon, cqver plates having an expansion joint therebetween, said lower support plates and said cover plates being arranged offset providing staggering of said expansion joints.

2. A self-supporting ceramic tuyere base as claimed in claim 1, wherein between said lower support plates and said upper cover plates there are arranged heat-resistant imbricate sheets.

3. A self-supporting ceramic tuyère base as claimed in claim 2, with adjacent rows of tuyères disposed therein, and wherein said imbricate sheets of said adjacent rows of tuyères overlap one another.

4. A self-supporting ceramic tuyère base as claimed in any one of the preceding claims, having an accurately fitting sheet-metal plate fitted over each of the tuyères.

5. A self-supporting ceramic tuyère base as claimed in claim 1 substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

6. A fluidised-bed furnace incorporating a selfsupporting ceramic tuyère base as claimed in any one of the preceding claims.