DE1071267B - Procedure for operating a combined pulverized fuel grate »furnace - Google Patents

Description

The invention relates to a method for operating a combined pulverized fuel grate furnace for high-performance _{radiant steam generators, in which the advance of the traveling grate provided with underwind zones, layer height:} regulating and rear ventilation closure devices largely, to full, in accordance with the ash removal Grate output for heat-up and low-load firing can be regulated and the pipe walls installed in the combustion chamber to enlarge the cooling surface are in vertical planes. This process is characterized in that the fly ash separated from the combustion gases outside the furnace is returned to the furnace and that the grate operation is carried out in such a way that the ash and slag deposited on the grate sinter ....,. "-

It is known to return fly ash to the combustion chamber of a grate furnace. The aim is to burn the coke in the air and the ash to fall on the grate ■■; ■ if it is not carried away again by the train. In the case of a combined fuel dust / grate furnace, in which the dust furnace takes over the load and the grate furnace only serves as a secondary furnace and slag discharge device, the greater part of the incombustible material occurs as fly ash outside the combustion chamber. Since this fly ash is well burned out, it becomes' weight in. -The. Combustion chamber returned. However, the removal and depositing of this fine ash causes so many difficulties that one would be inclined to return them to the combustion chamber if they were to be obtained in a coarser form after the passage. For this purpose, special fly ash melting furnaces have been created in which the ash is melted and drawn off in liquid form. When firing with an auxiliary grate, it is possible, without melting, to convert the ash into an easily transportable form, namely in a state of superficial to complete slagging; the one to distinguish. The formation of other slag forms should be called sintering, although the metallurgical phenomena of sintering do not occur or only occur incompletely. - ■ ■ < '

'To achieve this effect it is necessary to have the To bring fly ash onto the grate and to run the grate in such a way that under the influence of the irradiation from the combustion chamber and the heat generated by burning the coal on the grate sintering occurs. There can then even be quantities of fly ash from other furnaces on this one grate still to be processed. '

The most favorable mode of operation has shown that the grate is retracted with coal in a low layer height, depending on the grain size, about 3 to 6 cm, but with large feed, so that the large amount of slag. ■

a combined
Dust and grate firing

Applicant:

German
Babcöck & WilGOx-pampfkessel-Werke

Shares - company,
Oberhausen (RhId, j * (Duisburger Str. 375

Dipl.-Ing. Hubert * Seidl, Duisburg,
has been named as the inventor

transported wird..Wenn ^r die.Flugasche is applied to the carbon layer, 'it covers the fire. This is by no means undesirable, because the temperature at the boundary layer between burning coal and fly ash is so high that the slag partially melts and this results in a kind of sintering. This effect is supported / that doughy from the furnace. Slag particles fall onto the layer of fly ash and bake together with it. As long as the fly ash is still in the form of dust, it will offer less flow resistance to the fire gases coming from the coal layer than the sintered ash. As a result, craters will form in these places from which the fly ash will be thrown onto the adjacent sintered surface with which it will fuse. Finally, the air sealing device at the discharge end sets the slag still in motion, so that on the one hand large panels are broken up and on the other hand an encrustation of dust-like inclusions is achieved. .

However, the grate must be given the possibility that the layer of carbon lying on it is exposed to radiation from the firebox ignites before using Fly ash is covered. This can be achieved approximately by blowing the fly ash into the combustion chamber so that it is evenly distributed over the grate surface. Not all of them are here Slag particles exposed along the same length of time as the fire. The desired effect is more complete achieved when the fly ash is scattered on the coal layer at a point where it has already ignited Has. In the case of the traveling grate, this depends on the gas content

909 689/143

of coal about a fifth to half that Burning length should be the case, while the moving grate or another one with ignition from below Grate, the fly ash can already be abandoned at the coal inlet. The traveling grate is therefore 5 ■ not the cheapest solution in terms of ignition, he however, it has the advantage that it does not mix the coal with the fly ash and therefore the coal almost completely burns out and has constant temperature zones. ίο

The slag that falls out of the dust flame is liquid and supports when it hits the fly ash layer also the desired sintering effect. However, some of it also flows along the combustion chamber walls down and therefore gets in larger quantities on the lateral parts of the focal path. So that these Do not lead to rust problems due to caking of slag, it is advantageous to provide drip edges, from which the slag drips freely onto the grate.

It may happen that the ratio of rust '■: fuel to fly ash does not match or that the combustion properties of the fuel rust or not enough to achieve the sintering temperature but that the sintering of the fly ash is unfavorable. In these cases, an additional furnace for gas, oil or coal dust, the flame jet of which is directed towards the surface of the fly ash, can be used to improve the situation.

A furnace for carrying out the process is in

Fig. 1 in vertical symmetry section, in
Fig. 2 in a vertical longitudinal section through the axes of the nozzles and in

Fig. 3 shown in horizontal cross section through the axes of the burner nozzles.

In the illustration according to Fig. 1, 2, 3, the combustion chamber 1 goes from a rectangular cross-section at the bottom into a Funnel 2, which is completed by a traveling grate 3 built underneath. The side walls of the focal ' chamber are provided with cooling tubes, which are connected at their ends by distributors and collectors which are also connected to one another by non-heated return pipes.

The cooling tube wall of the combustion chamber front wall consists of a distributor 4, the cooling tubes 5 and the collector 6, which is connected to the distributor 4 again by unheated return pipes 7. From the collector 6, the steam-water mixture is passed through pipes 8, which continue to run along the combustion chamber wall, to the separation drum 9. From it the water flows through the connecting pipes 10 and the steam through the connecting pipes 11 to the boiler drum 12. From it the saturated steam is passed through pipes 13 to the superheater 14, while the water flows back through downpipes 15 to the distributor 4. In a similar way, the cooling pipes of the combustion chamber rear wall with distributor 17, collector 18, return pipes 19 and riser pipes 20 are included in the water circuit, as are the distributors 21, 22 with cooling pipes 23, 24, collectors 25, 26, return pipes 27, 28 and risers 29, 30.

From the segregation drum 9, which hangs approximately over the middle of the combustion chamber 1, the pipe panels 31, 32 go in vertical planes, the pipes of which first run vertically downwards in front of the gas outlet 33 of the combustion chamber and are then bent in groups forwards and backwards and in Vertical distributors 34, 35 end, which are connected to the boiler drum 12 by downpipes (not shown).

This steam generator is fired with fuel dust, which is processed in the mills 40, 41, 42, 43 using the grinding-drying process. The raw fuel is fed from the bunker 36 through chutes 37 to the magnetic separators 38 and passed on by the conveyor belts 39 or fed directly to the mills which are set up at the edges of the combustion chamber and supply the burners 44, 45, 46, 47.

The burners are arranged so that their axes are inclined slightly downwards and are imaginary Tangent circular cylinder, which is coaxial with the combustion chamber and whose diameter is only a fraction is the combustion chamber width. The training and working methods of the so-called mill firing Processing is assumed to be known. Hot air is supplied to the mills, and suction is also applied fire gases from the combustion chamber.

The traveling grate 3 is provided with internals which form chambers 48, 49, 50, 51, which the combustion air from the fan 52 through duct 53. In the supply lines to the individual chambers control flaps are built in, which can be adjusted independently of each other. The grate is with a double funnel 54, 55 and provided with an air seal box 56 and at the end of the grate with a Air closure device 57. The drive device, not shown, allows the grate belt with several to move widely different feed speeds. With the help of the adjustable weir 58 the layer thickness of the fuel on the grate is regulated.

The fly ash is conveyed through the channels 59 by means of conveying air and blown in through the nozzles 60 transversely to the direction of advance of the traveling grate 3 and at such a low speed that most of it will be deposited on the grate. The nozzles are located after the first third of the grate's burn length. The lateral funnel slopes 61, 62 end in drip edges 63, 64, which extend beyond the distributors 21, 22 and which act as heat sinks.

Claims (1)

Patent claims: 1. Method for operating a combined dust and grate furnace for radiant steam generators high performance, at which the feed of the underwind zone, layer height control and rear air closure devices provided traveling grate largely, namely According to the ash removal, damped feed up to full grate output for heating and Low-load firing, which is controllable and which increases the cooling surface in the combustion chamber attached pipe walls lie in vertical planes, characterized in that the outside The fly ash separated from the combustion gases in the furnace is returned to the furnace is and that the grate operation is carried out so that the ash deposited on the grate and Slag sinters. 2. The method according to claim 1, characterized in that the grate with a thin layer of fuel and the greater the amount of slag that occurs, the greater the feed rate is. 3. The method according to claim 1, characterized in that the fly ash directly on the Grate is scattered at a point which is so far away from the grate inlet that the inlet fende fuel by radiation from the The combustion chamber has already ignited before it is covered by the fly ash. 4. Device for performing the method according to claim 1, characterized in that that the funnel slopes of the side walls of the combustion chamber above the grate with drip edges are provided. 5. Device for performing the method according to claim 1, characterized in that that burner nozzles are arranged above the grate, their flame obliquely against the grate surface is directed. Considered publications:
German patent specification No. 815 319. 1 sheet of drawings 1909.689 / 1 «12.59