The invention relates to an arrangement in furnaces com¬ prising a combustion chamber having a non-perforated, flat bottom surface for supporting the solid or paste-like fuel and at least one rod which extends through the side wall of the furnace substantially parallel with and close to the bottom surface, and which is adapted for reciprocal movement in its longitudinal direction.

If the fuel used in such furnaces has a low calorific value, the combustion can take place slowly and the temperature in the combustion chamber is correspondingly low. This can also happen in connection with furnaces having grates with water cooled portions which can cool the fuel to such a degree that the combustion takes place slowly and at a low temperature. Further, easily fusible constituents of the fuel may melt and flow down through the grate, whereby it will not burn completely. The latter is especially unfortunate when these constituents contain infectious or poisonous materials. However, if the calorific value of the fuel is sufficient for the temperature to be very high, the rods of the grate may be burnt through or covered by slag.

The object of the invention is to provide an arrangement in furnaces in which the above drawbacks are avoided.

The characteristic features of the arrangement appear from the features defined in the characteristic clause of the claims.

In the following the invention will be described in detail, with reference to the drawing which shows an embodiment of the arrangement according to the invention.

Figure 1 shows a vertical section along the line I-I in

Figure 2 through a furnace having an arrangement according to the invention, portions of the furnace being cut away.

Figure 2 shows a section along the line II-II in Figure 1.

Figure 3 shows a section along the line III-III in Figure 2.

Figure 4 shows a section along the line IV- V in Figure 2.

As seen from Figure 1, a furnace 1 comprises a bottom surface

2 and a side wall 3 which may be made of steel and which is lined with a refractory material 4. As best seen from Figures

3 and 4, a plurality of spaced guide rails in the form of elongated boxes 6 made of e.g. steel, are fastened to the steel frame of the furnace on bottom surface portions 5 having no lining, said boxes extending substantially perpendi¬ cular to the wall 3, one end portion of said boxes being located adjacent thereto. The rails may for instance be fastened by welding. Their upper wall or roof 7 extends parallel to the bottom surface 2, while their side walls 8 extend perpendicularly to the bottom surface 2.

Slidable relative to the -rails and above" each respective rail there is provided an elongated, hollow, box-shaped rod 9, the bottom 10 of..which rests upon the rail, whereas its side walls 11 continue somewhat downwards and extend outside and along the side walls 8 of the rail 9 with a small clear¬ ance relative thereto. In this manner the rod 9 will be guided when sliding on the rail 6.

The rods 9 extend with a small clearance through respective openings 12 which are is formed in the wall 3 of the furnace, the shape thereof substantially corresponding to the outer contour of the rod section.

In the following the distal end of the rod with respect to the side wall 3 will be referred to as the forward end of the rod.

Parallel to the bottom 10 of the rod and at some distance therefrom two mutually spaced partitions 13, 14 extend the total length of the rod. In the portion which constitutes approximately the forward half of the rod, the upper of these partitions forms the roof of the box-shaped rod, wherea the side walls 11 in the rear half of the rod continue upward and are connected to a horizontally extending plate 19 here constituting the roof of the rod. At the forward end of the portion of the side walls 11 above the partition 14 there is arranged a vertical end plate 15, and at its forward end the rod 9 terminates in an end plate 17. At the rear end or the end projecting from the furnace the rod 9 is provided with an end plate 18. Thus, three separate channels 21, 22, 23 are thus provided in the rod 9. In the side walls 11 of the upper and the lower channel 21 and 23, respectively, and in the roof 19 of the upper channel there are formed through- going openings 25, 26 and 27, respectively, and in the rear end portion of the upper channel 21 and the lower channel 23 there are provided pipe sockets 28, 29. In the central channel 22 there is provided a pipe 30 which sealingly extend through the end wall, through which is also extending a pipe socket 21.

A plurality of barb-like carriers 32 are fastened to the side walls 11 of the rod 9.

In addition to the above-mentioned parts there is provided a means (not shown) for reciprocating the rods 9 sliding on the rails 6, and means for supplying air to the channels 21 and 23 through the pipe sockets 28 and 29, respectively, as well as means for supplying a cooling fluid, e.g. water, to the channel 22 through the pipe 30.

The function of the device according to the invention is as follows.

When there is fuel in the combustion chamber 16 of the fur¬ nace, air is supplied through the upper and lower channels 21, 23, as indicated by the arrows A and B. The air flows through these channels, out through the openings 25 and into the fuel, and contributes to a vigorous burning thereof. Some of the heat of combustion is led through the walls of these channels and heats the air flowing therein, which air thus contributes to a cooling of the channel walls and pre¬ vents overheating thereof. The amount of heat transferred to the air is thus returned to the combustion chamber, so that the temperature therein remains high, which is advan¬ tageous for obtaining good burning of the fuel.

As indicated by the arrow E a cooling fluid, e.g. water or air, is supplied to the pipe 30, which cooling fluid flows through the pipe 30 to the forward end of the channel, and then in the opposite direction along the outside thereof, leaving the channel 22 through the pipe socket 31. Thereupon the cooling fluid may flow to a cooling device and be reintro- duced into the pipe 30. On the forward portion of the rod, where the channel 22 for the cooling fluid is not covered by the air channel 21, the cooling fluid will provide a powerful cooling of the fuel. Such an uncovered design of the channel for the ^" cooling fluid will therefore be used for portions where the combustion temperature is expected to become especi¬ ally high, intensive cooling therefore being required. Additionally, the portion of the channels for the cooling fluid covered by the air channel 21 will constitute a reserve providing the required cooling if the air cooling should be insufficient or fail completely. In such a case the roof 19 and the walls 11 of the rod will be heated so strongly that a large amount of heat will be transferred to the cooling fluid by radiation.

By being moved the rods will provide a desired mixing of the fuel, and during this movement the carriers 32 will cause fuel, slag and ashes to be moved away from the wall 3

of the furnace. If the rods are moved out of time a very good mixture of the fuel can be obtained.

Above a rod is described wherein the air channels partly surround the cooling channel. However, it may be advantageous for the air channels completely to surround the cooling channels, or that the air channel is surrounded by the latter The last-mentioned arrangement can be advantageous if the fuel has a very high calorific value and the temperature within the furnace becomes very high, so that a larger amount of heat has to be carried off in order to prevent the rods from being destroyed. In this case there must be provided e.g. transverse ducts connecting the air-channel to the combustion chamber and extending through the surrounding cooling channel.

In addition to the channels formed in the rods 9, cooling channels should also be formed in the bottom surface 2 in order to prevent sintering of slag and ashes.