US1682328A - Furnace structure - Google Patents

Description

Aug. 2s, 1922 1,682,328

. R. A.I FORESMAN l Funmca sTRucTunE Filed April 12,V 1925` mvENToR ATTORNEY CAD Patented Aug. 28, 1928.

UNITED STATES PATENT OFFICE.'

ROBERT A. FORESMAN, OF MOORE, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA,

EURNACE STRUCTURE.

Application filed April 12,

This invention relates to underfeed stoker furnaces and has for its object to provide a furnace of the character designated which shall economically burn low grade fuels such as lignite and coke braize. It has for a further object the ready ignition of t-he green entering fuel and the maintenance of uniform combustion conditions throughout the fuel bed by the employment of a refractory arch overlying the fuel bed for the purpose of radiating heat to and causing a portion of the heated gases from the high temperature sections of the fuel bed to pass over the green fuel, and at the same time permitting a major portion of the furnace gases to pass directly to the heat absorbing s urfaces of the boiler or other units utilizing the heat of the furnace.

These and other objects of my invention which are made more manifest in the further description thereof, may be attained by the employment of the apparatus illustrated in the accompanying drawing in which Iilig. l is a diagrammatic sectional representation of an underfeed furnace equipped with a refractory arch in accordance with the present invention; and F ig. 2 is a view in section on line IIII of Fig. 1.

It has heretofore been considered impracticable. to burn lignites or coke braizes successfully on an underfeed stoker, for the reason that these fuels ignite with difficulty and tend to drift toward the rear of the fire boX, resulting in a failure to maintain a sufficiently uniform combustion condition throughout the entire fuel bed for the economical combustion of these fuels. I have found that in practice these low grade, drifting fuels can be burned satisfactorily by disposing an arch above the fuel bedand spaced from the front wall and the bridge wall, the resulting passages being so proportioned that a sufficient quantity of the heated furnace gases sweeps forwardly over the entering fuel to assist in the maintef nance of active combustion on forward portions of the stoker grate. I have also found it to be desirable when burning these low grade fuels to admit air or steam, or both.v in regulatable quantities over the fuel bed at the bridge wall of the furnace. This 1923. Serial No. 631,665.

serves to retard the rearward drifting of the fuel to mixthe gases and secure a more complete combustion of their combustible constituents. In some installations, it niav be desirable also to adiiiit air at the front walls of the furnace.

Referring to the drawing I show a furnace 10 housing an underfeed stoker 11 and a boiler 12 of the Stirling type. The furnace comprises a front wall 14, a bridge wall 15, and side walls 16 of usual construction. The underfeed Stoker is of the well known multiple retort type and comprises a hopper 20, retorts 21, twyer banks 22, and dump grates 23. The normal contour of the fuel bed is designated by the line 25.

The baffle member or refractory arch extends the full width of the furnace, and is spaced from the front wall 14 and the fuel bed 25 a sufficient distance to permit a portion of the heated furnace gases from zones of most active combustion'to pass forwardly under the arch and over the incoming fuel and then upwardly between the front wall of the furnace and the arch.

.As illustrated, the arch is of a hollow, air-cooled construction, built in the following manner: Two pairs of channel beanis 31 are supported in the side walls of the furnace, each pair having the flanges of the beams inwardly directed to provide a slot 3Q in which T-hangers 33 are suspended. The base of the arch is formed of a plurality of rows of refractory tile 35 supported by T-beams 36 which lock into an undercut groove 37 in the upper portion of eacli tile. The several rows of tiles are assenibled transversely to the channel beams 31 and are suspended therefrom by a detachable connection 38, which secures the T- beams 36 to the lower ends of the hangers 33. Side walls 10 of the` arch are carried by the end tiles 35 and are preferably of refractory brick cobbled inwardly toward the top of therv arch. The top wall of the arch is supported upon lintelsl lwhich rest on the beams 31, a fire brick 43 being interposed to cut down the heat transfer between the beamsv 31 and the lintels.

Tiles 45 are carried by the lintels 42 and one or more layers of fire brick are laid upon the tiles 45. Openings 46 in the side walls 16 lead into the interior of the baffle and permit the circulation of air therethrough for cooling the arch structure. The 'air thus heated may advantageously feed to the furnace grate. l

It is to be understood, however, that the above described arch structure is merely illustrative of one form of baffle member adapted for carrying out my invention, and that my invention is not limited to the specilic arch structure employed.

Twyers are provided in the front wall of the furnace and twyers 51 in the bridge wall, through which twyers, air or steam under pressure may be directed above the fuel bed to assist in the combustion of the furnace gases. lThe air or steam is supplied to the tuyere 50 by means of a conduit 52 formed in the front wall lll, and is supplied to the tuyres 5l by a conduit 53 formed in the bridge wall l5.

From the foregoing description the 1nanner in which my invention is practiced is apparent. In brief, assuming that the furnace is in operation and that coke braize, or other low grade fuel, is being fed into the retorts 21 from the hopper 20, the entering green fuel, which normally would travel a considerable distance toward the rear of the furnace, due to the drifting character of these fuels, before being fully ignited,`s subjected to the heat of a continuous stream of heated gases from the zones of active combustion. These highly heated gases, together with'radiated heat from the arch, quickly ignite the incoming fuel, and as a result a more nearly uniform combustion condition prevails throughout the fuel bed than has been possible to attain heretofore. The air or steam flowing through the tuyres 5l will force the lighter particles of fuel towards the front of the fuel bed and will thus overcome the tendency of this fuel to drift towards the rear of the furnace. It is to be noted that in some instances the coke braise or other low-grade fuel is mixed with a bituminous coal. In such a case my improved construction has an additional advantage in that the colring of the fuel will commence at a point closer to the front wall of the furnace and will thus aid in retarding the objectionable shifting of the fuel tewards the rear, before it is in condition to be ignited.

A circulation of air through the arch 30 can be maintained by induced or by force draft mechanism. Thus, the air for combustion may be drawn through the arch to the air blower which supplies air to the furnace grate, or the air from the blower may be passed in whole or in part through the arch prior to delivery to the furnace grate.

While it is not essential to good operation in the furnace above described, jets of modifications, without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claim is:

1. In a furnace having the usual front, side and bridge walls, the combination with an underfeed Stoker of the multiple retort type having a generally inclined fuel bed from the front wall to the bridge wall, of a refractory baille spaced from the fuel bed, the front wall and the bridge wall in such manner that the furnace gases are directed from the fuel bed in two distinct paths of travel, one path extending forwardly and upwardly between the frontwall and the baille, and the other path extending upwardly between the bridge wall and the baffle and means for injecting ets of oxygenbeaing fluid into the gases in the said other pat 2. In a furnace having the usual front, side and bridge walls, the combination with an underfeed Stoker of the multiple retort type having a generally inclined fuel bed from the front wall to the bridge wall, of a refractory baffle spaced from the fuel bed, the front wall and the bridge wall in such manner that the furnace gases are directed from the fuel bed in two distinct paths of travel, one path extending forwardly and upwardly between the front wall and the baffle, and the other path extending upwardly between the bridge wall and the baille, means for injecting jets of oxygenbearing fluid into the gases in the said one path, and means for injecting jets of oxygen-bearing fluid into the gases in the said other path.

3. In a furnace having the usual front, side and bridge walls, the combination with an underfced stolrer of the multiple retort type having a generally inclined fuel bed from the front wall to the bridge wall, of a refractory baffle spaced from the fuel bed, the front wall and the bridge wall in such manner that the furnace gases are directed from the fuel bed in two distinct paths of travel, one path extending forwardly and upwardly between the front wall and the baille, and the' other path extending upwardly between the bridge wall and the4 baflle and means associated with the bridge wall for injecting jets of oxygen-bearing uid into the gases immediately over the fuel bed in a direction counter to the travel of the fuel through the furnace.

4. In a furnace, the combination with a progressive feed grate on Which fuel is fed at the front of the furnace and then rear- Wardly and downwardly to discharge, of a refractory baille arranged directly above and adjacent to the fuel bed, and means associated With the furnace for injecting oxygen- 10 In testimony whereof, I have hereunto 15 subscribed my name this 9th day of April, 1928.

ROBERT A. FORESMAN.

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