US2386336A - Combustion apparatus - Google Patents

Description

Gd. 9, i945 D. J. MOSSHART 235,336

COMBUSTION APPARATUS Y y Filed June l2, 3,941

0 a l d' ATTORNEY www vPatented Oct. 9, 1945 y oi-'FicE coMnUs'rroN APPARATUS Y,

Donald '.r. Masami, Ardmore,

Pa.. asslxnor to Westinghouse Electric Corporation, East Pittsbur-gh, Pa., a corporation of Pennsylvania Application June 12, 1941, Serial No. 397,670

2 Claims. (Ci. 110-40) The invention relates to a furnace and method of operating the same, wherein the fuel is fed to a progressive feed sto'kerby means loi a spreader or sprinkler.

An object of the invention isto so control theA heating and combustion of the sprinkled fuel during its travel from the feeder to the grate that the fuel is deposited on the grate in a spongy. loose. lightly agglutinated which air will readily flow but which will, because of its partial agglutination, resist being carried away by the air flowing through the grate in the latter stages of combustion.

Another object of the invention is to limit the deposition of the fuel on the fuel bed to a limited first portion thereof, and restricting the flow of air to that portion to an extent sumcient to prevent the fuel being lifted from the fuel bed and to prevent the particles of the fuel being sprinkled thereon from beingcarried away in the gases rising from the fuel bed.

Yet another object of the invention is to so operate a chain or traveling grate stoker that the fuel is deposited on a limited portion thereof by a spreading or sprinkling device in such manner that the fuel bed tapers nothing at the extreme front encl'to a maximum at the rear end of the fuel-sprinkling portion, and then tapers to nothing at the rear or ashdischarge end thereof,

A further object of the invention is the provision, in a spreader-fed chain grate Stoker of pressure-responsive means for maintaining a predetermined ratio between rate of feed of fuel to the grate and rate of flow of air to the fuel-fed portion of the grate.

These and other objects are edected by the invention as will be apparent from the following description and claims taken in connection with the accompanying drawing, forminga part of this application, in which the single figure is a vertical sectional view taken through a furnace and Stoker installation constructed in accordance with the present invention.

Referring now to the drawing more in detail, there is shown at i a furnace comprising front and rear walls li and i2, respectively, and side walls i3. A suitable progressive feed stoker i5 is provided in the lower portion of the furnace, which, in the arrangement herein illustrated, is a chain grate st oker, of conventional construction. Fuel is fed to thegrate l5 from a hopper i8 located externally of the furnace l by means such as the ram il and spreader i8, both driven from a suitable source of power, such as the bed or mass throughl in thickness from variable-speed motor i9, by belts 20 and 2i, respectively. A conventional ash pit 23 is provided beneath the rear or discharge end of the stoker for reception of ash and other refuse discharged fromy the traveling grate.

In accordance with the present invention, the usual plenum chamber 25 is divided by a partition structure 26 and 21' into a first compartment at 28 and a second compartment at 29. Air under pressure is supplied to 30, by way of the passages 3i and 32, respectively. In order to control the supply of air to the compartment 28, there is provided a metering orifice 3d followed by a damper 35. Pressure-responsive apparatus, at 36, provides for variation in the flow of air to the compartment 28 in direct proportion to variations in the quantity of fuel fed to the grate.

To this end, the motor i9 is directly connected a tachometer blower 3l which supplies air under pressure to a bellows 3d, the latter being connected through the compression spring t@ to one end of a lever te, pivotally mounted intermediate its ends on a fixed support at ll. The compression spring 3d. whose tension may be adjusted by the screw di, urges the right-hand end of the lever lll upwardly with respect to the bellows 3d. The left-hand end ofthe lever d@ is connected through the rod l5 to a pair of spaced bellows 13B and tl, the former being in communication with the upstream side of the metering orifice 343 and the latter being in communication with the downstream side thereof. The lever d@ is also connected through the stem 5i with the valve 52 controlling flow of pressure medium through the conduit 53, the latter being in communication with the expansible chamber 5t. One wall of this chamber is defined by the movable piston 55, which is connected by the rod 56 with the bellcrank 5l, xedly secured to the damper 35 in the passage 3i. A compression coil spring 59 urges the movable wall 55 of the chamber 5t into contracted or collapsed position.

The partition structure 2B and 2l, which divides the plenum chamber 25 into the compartments 28 and 2t.' is so disposed as to, in effect,

divide the grate surface and the atmosphere thereabout into first and second zones, A and B, respectively. The particular percentage of the grate surface occupied by each of these two zones will be dependent up'on varying conditions of operation, particularly the type of fuel being burned. With a number of fuels, the first zone A would constitute approximately Y40% of the fuel-supthe compartments 28 and 29 from any suitable source, such as the blower porting surface, and the zone B would make up the remaining 60% of the surface, However, under other conditions, the first zone A might vary from 30 to 60% of the total grate surface.

According to the improved method of operation, it is proposed to project the fuel onto the first zone of the grate through the hot atmos- I phere above that zone, with the result that lthe fuel is partially ignited and deposited upon the grate as a light, spongy and partly agglutinated mass. In order to obtain this result, it is found necessary to limit the supply of air fed to this first zone to such an extent that the tendency for particles of fuel to be carried off the fuel bed is minimized and so thatv the air rising from this section of the bed is of insufficient velocity to prevent the sprinkled fuel from falling therethrough to the bed rather than for the lighter portions thereof to be caught and carried away in suspension by the rising gases. Thus, by operating the first zone A with a deficiency of air, the latter operates, in effect, as a gas producer or coking portion. 4

Substantially complete combustion of this partially-coked fuel is completed in the second zone B of' the grate. In the event that insufficient air is supplied to this second zone B to produce complete combustion of the fuel thereon, secondary air may be supplied to the atmosphere immediately overlying the second zone through ducts 60 and conduits 6I associated with the rear wall I2 of the furnace.`

If it is found that, due to improper operation, any considerable quantity of fuel particles are carried into the boiler structure by the combustion gases, means, such as the hopper 62, may be provided for returning the particles to the combustion chamber. To this end, there is provided a conduit 63 from the secondary air duct 6D, which terminates in an ejector nozzle G4, aligned with the inlet end of the conduit Bi. It will be apparent that, with this arrangement, the secondary air from the duct 60 will serve to convey the fuel particles from the hopper 62 to the combustion chamber. Preferably, this secondary air is supplied under sufficient force to carry the fuel particles across the zone B and into the atmosphere of zone A, where the restricted flow of air will permit these particles to settle for normal consumption upon the fuel bed.

If desired, further means for supplying secondary air may be provided in the form of a second duct 66 and delivery ducts 61 associated with the front wall l l of the furnace.

While the invention has been shown in but one assenso form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof, and it is desired,

Itherefore, that only such limitations shall be placed thereupon as are specifically set forth in the appended claims.

What is claimed is:

1. A progressive feed stoker providing a fuelsupporting surface having a receiving and nokmg first zone and a combustion and discharging second zone, considered in the direction of fuel feed; means of the sprinkler or spreader type spaced a material distance above the fuel-supporting surface and adjacent an edge of the receiving zone, said means spreading the fuel uniformly over the first zone only of the fuel-supporting surface through the hot atmosphere above said first zone only, to heat and ignite said fuel before it is deposited on the surface; a plenum chamber below the stoker for conducting ail to the latter; a partition dividing said chamber into a first space communicating with the first zone and a second space communicating with the second zone; and pressure-responsive means for maintaining a, predetermined ratio of rate of flow of fuel to rateof flow of air to the first zone, whereby there may be provided on said first zone a loose, partially coked and ignited fuel bed adapted to be consumed on the second zone.

2. A progressive feed stoker providing a fuelsupporting surface extending from front to rear thereof and having a front fuel-receiving and coking zone and a rear fuel-consuming and discharging zone; fuel-feeding means of the sprinkler or spreader type spaced a material distance above the fuel-supporting surface and adjacent the front edge of the front fuel-receiving and coking zone, said means spreading the fuel uniformly over the first zone only through the atmosphere above said first zone only, whereby said fuel is heated and at least partially ignited before being deposited on said first zone; a plenum chamber below the Stoker for conducting air to the latter: a partition dividing said chamber into a first space communicating with the front zone and a second space communicatingwith the rear zone; and pressure-responsive means for maintaining a predetermined ratio of rate of flow of 'fuel to rate of -ow of air to the front zone,

whereby there may be provided on said front zone a partially coked and ignited fuel bed adapted to be consumed on the rear zone.

DONALD J. MOSSHART.

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