US1887891A - Pulverized fuel furnace - Google Patents

Description

Nov. 15, 1932. R. ROOSEN PULVERIZED FUEL FUiNACE Filed Sept. 20, 1930 Patented Nov. 15, 1932 UNITED STATES PATENT orrlcs.

RICHARD ROOSEN, OF CASSEL, GERMANY, ASSIGNOR TO STUG KOHLENSTAUBFEUEBUNG PATENTVERWERTUNG G. M. 3. IL, 01 CASSEL, GERMANY PULVERIZED FUEL FURNACE Application filed September 20, 1930,,Seria1 No. 483,385, and in Germany October 9, 1928.

The invention relates to a method of and means for operating pulverized fuel furnaces with secondary air of combustion, more particularly with locomotives.

With furnaces of this class the supply'of secondary air of combustion is well-known; the usual manner ofsupplying the secondary air however, suffers from several drawbacks. So, despite of a pressure below atmospheric prevailing in the firebox that would suflice to suck in the secondary air, incomplete combustion is to be observed, from which fact an unsatisfactory supply of the secondary air is to be inferred. The reason therefor is, that due to wrong guidance of the gases of combustion, damming-up of these gases takes place at the very places of entrance of the secondary air, and thus an unsatisfactory supply of the latter results. Furthermore, the walls of the firebox and its liner are in jured or entirely destroyed after a short time, because of the fact that due to this Wrong guidance of the fire gases, the hot products of combustion immediately strike these walls and liner, as the latter are not cooled by the secondary air.

Now the invention has for its object to eliminate these drawbacks. Moreover, the method of supplying the secondary air according to the invention and the means therefor, cause better mixing of pulverized fuel and air, and thus a reduction of the time of combustion. Therefore certain sorts of pulverized fuel can be used which hitherto could not be employed in pulverized fuel furnaces, such as pulverized pit coal, which has the tendency to form coke or the like.

The invention consists in the fact that the secondary air of combustion is supplied to the combustible mixture of air and pulverized fuel in a quantity adequate to the required quantity of this mixture, and subdivided in such a manner that a separate partial currentof secondary air is supplied at the following places of the path of the flame: at the zone of distillation of the pulverized fuel, in the range of the first combustion of the fuel after distillation, in the range of the main combustion, in the range of the final combustion, and in the cooling zone of the residues of combustion.

The invention further provides means for carrying out with particular advantage the indicated method of supplying the secondary air of combustion.

In order that the invention can be more readily understood, some preferred embodiments of the same are diagrammatically illustrated by way of example in the accompanying drawing in which Figure 1 is a central longitudinal section through the rear portion ofa pulverized fuelfired locomotive designed according to the invention, I

Figure 2 is a fragmentar similar section showing a modification of t e secondary air 811M215, Figure 3 1s a cross section through a modlfied firebox, seen toward the fire bridge, and Figure 4 is a section similarto Figure 3 showing another modification.

Referring first to Figure 1 of the drawing, 2 denotes the firebox of the locomotive boiler 3 in the lower portion 1 of which, where otherwise is arranged the ash pan, is disposed above the pulverized fuel burner'or burners 4 a short bridge 5 containing a secondary air passage 6 opening into the combustion chamber. In the bottom 7 of the firebox 2 are provid ed further secondary air feeding passages 8, 9, 10 which open into the firebox in parallel or approximately in parallel to the way A of the combustion flame, indicated by a dot and dash line. The path of the secondary air supplied is marked in all figures by full arrow lines. The air passages 8, 9, 10 on their outer end are in communication with a common chamber 11 to which the secondary air is supplied in a quantity that can be regulated by a damper 12. To prevent choking, a protective projection 13 is provided above each of the passages 8, 9, 10. On the lowermost place of bottom 7 is arranged anash an 14 from which the residues of combustlon collecting therein can be removed by opening a damper 15. Between the wall 16 bounding the firebox on the front end, andthe ash pan 14 there is provided a further secondary air passage 17 which extends into the firebox in an inclined upward direction.

In front of the front wall 16 of the firebox is disposed a further secondary air passage 18 extending in upward direction, the inlet of which passage opens into the free air and can be regulated by a damper 19. A portion of the secondary air supplied through pas sage 18 enters the firebox 2 through a passage 20 which is formed between an auxiliary stub fire bridge 22 and the main fire bridge 21. The remaining portion of the secondary air supplied through passage 18 is added to the current of the combustion gases through a passage provided in the fire bridge 21 itself and leaves it on its front edge at .23. In order to have the air more uniformly distributed on these two passages a baflle plate 24 may be arranged or the two passages may be completely separated from one another if required. To obtain-a satisfactory flow of the fire gases, the auxiliary bridge 22 is suitably rounded-ofl' on its underside at 25. If required, branch passages 26 may be provided that lead from the passage in the bridge 21 to the underside of the latter. The openings 20, 23 and 26 may extend either on the entire width of the combustion chamber or may be subdivided as illustrated in Figures 3 and 4. In this connection it is of advantage for instance to achieve a subdivided a1r supply through the main fire bridge 21 by means of pipes embedded therein which at the same time impart to the bridge a greater strength.

-Finally, small passages 30 provided in the base of bridge 21 and communicating with passage 18 serve to supply secondary air in Ehe vicinity of the tube wall 29 of the fireox. Y

In the embodiment illustrated in Figures 2 and 4 the air passage 18 merely opens into the space existing between the auxiliary bridge 22 and main bridge 21, the portion of the air escaping through the upper passage 27 that undividedly extends on the entire width of the bridge, serving to cool the main bridge 21 while the air escaping through the lower individual openings 28 forms the proper air of combustion for the flame. To increase the effect, the openings 27 and 28 as well as all other air outlets may be designed as nozzles.

The described appliances operate as follows and have the following effect.

The flame passes through the firebox on the S-shaped way marked by a dot and dash line A and comes into contact first with the secondary air entering through the passages 6 and 8 in the zone of distillation of the pulverized fuel. Further secondary air is then supplied in the range of the primary combustion through the passages 9 and 10 so that at once a brisk combustion takes place. The secondary air further supplied through 17 and that added through 20 and 27, 28, and 26 improvethe combustion in the zone of main combustion. This comparatively cool air at the same time protects the fire bridge and the lining as itprevents the bricks from directly being struck by the flame. Owing to the secondary air that enters through passages 28, Figures 3 a11d 4, being subdivided into several jets, the current of the combustion gas is loosened so that the surface of reaction is increased and a quick combustion obtained. The secondary air entering through 23 meets the gas current in the range of the last stage of combustion, while secondary air in the 'cooling zone of theresidues of combustion,

that is close to the tube wall 29 of the firebox, is supplied through the passages 30. It may still be noted that the secondary air current entering through passage 6 besides adding air in the zone of distillation still has the effect of urging the flame down below the fire bridge so that it comes into intimate contact with the secondary air entering there. A satisfactory guidance of the flame without shocks is obtained both by the respective faces of the combustion chamber being rounded off at the places of deflection, such as 25, and by the secondary air being supplied in currents which as far as possible extend in parallel to the gas flame everywhere they enter the firebox. so that no damming is caused anywhere by the fire gases and the supply of the secondary air is not impeded. This causes in turn, a quick combustion which is of great importance with regard to the comparatively small combustion chambers of locomotives.

Without deviating from the essence of the invention the individual elements thereof may be combined with one another as desired thermore, the number and situation of the secondary air supply passages may be varied according to the 'fuel employed'and to the length of the path at disposal for the flame. Finally, the passages'8, 9, 10 may open into the riser of every step of a stepped bottom of the firebox, whereby choking of these openings is prevented still in a higher degree.

What I claim is:

- 1. A pulverized fuel furnace having a firebox. a fire bridgetherein, apowdered fuel burner mounted to direct fuel towards said fire bridge, secondary air supply passages arranged in the bottom of said firebox at least approximately in parallel with the entrance path of the fuel, an auxiliary fire bridge spacedly arranged below said fire bridge, and another secondary air supply passage opening into the space existing between said fire bridge and auxiliary fire bridge.

2. A pulverized fuel furnace having a firebox, a fire bridge therein, a powdered fuel burner mounted to direct fuel towards said fire bridge, secondary air supply passages arranged in the bottom of said firebox at least approximately in parallel withthe entrance path of the fuel, an auxiliary fire bridge spacedly arranged below said fire bridge, and another secondary air supply passage open ing into the space existing between said fire bridge and auxiliary fire bridge, the latter being rounded off on its edge facing said burner.

3. A pulverized fuel furnace having a firebox, a fire bridge therein, a powdered fuel burner mounted to direct fuel towards said fire bridge, secondary air supply passages arranged in the bottom of said firebox at least approximately in parallel with the entrance path of the fuel, an auxiliary fire bridge spacedly arranged below said fire bridge, a secondary air supply passage opening into the space existing between said two fire bridges, and another secondary'air supply passage through said auxiliary fire bridge.

4. A pulverized fuel furnace having a firebox, a fire bridge therein, a powdered fuel burner mounted to direct fuel towards said fire bridge, secondary air supply passages arranged in the bottom of said firebox at least approximately in parallel with the entrance path of the fuel, an auxiliary fire bridge spacedly arranged below said fire bridge, a secondary air supply passage opening into the space existing between said two fire bridges, and a subdivided secondary air supply passage through said auxiliary fire bridge.

5. A pulverized fuel furnace having a firebox, a fire bridge therein, a powdered fuel burner mounted to direct fuel towards said fire bridge, secondary air supply passages arranged in the bottom of said firebox at least approximately in parallel with the entrance path of the fuel, other secondary air supply passages arranged in said fire bridge and opening into the front edge of the latter, passages branching off from said fire bridge passagesand opening at the underside of said fire bridge, and an upwardly directed secondary air supply passage in said fire bridge in its base.

6. A pulverized fuel furnace having a fire box, a fire bridge therein, a powdered fuel burner mounted to direct fuel towards said fire bridge, secondary air supply assages arranged in the bottom of said fire ox at least approximately in parallel with the entrance path of the fuel, an auxiliary fire bridge spacedly arranged below said fire bridge, another secondary air supply passage opening into the space existing between said fire bridge and auxiliary fire bridge, and subdivided into several individual passages.

7. A pulverized fuel furnace having a firebox, a fire bridge therein, a powdered fuel burner mounted todirect fuel towards said fire bridge, secondary air supply passages arranged in the bottom of said fire box at least for protecting said first mentioned passages from being choked by the residues of the combustion. I

The foregoing specification signed at Frankfort-on-the-Rhine, Germany, this 4th day of September, 1930.

- RICHARD ROOSEN.

Images