US2493960A - Method and apparatus for burning fine solids - Google Patents

Description

Jan. 10, 1950 c. s. GLADDEN METHOD AND APPARATUS FOR BURNINGFINE sou s 3 Sheets-Sheet 1 Filed Dec.

NVENTOR.

CHARLES 5. GLADDE/V A TTOP/VEYS Jan. 10, 1950 c. s. GLADDEN METHOD AND APPARATUS FOR BURNING FINE SOLIDS 3 Sheets-Sheet 2 Filed Dec. 11, l945 /7 INVENTOR. CHARLES aaz/woav ATTORNEYS Jan. 10, 1950 c. s. GLADDEN METHOD AND APPARATUS FOR BURNING FINE SOLIDS 3 Sheets-Sheet 3 Filed Dec. 11, 1945 INVENTOR. CHA EL ES 5. GLADDEN Patented Jan. 10, 1950 METHOD AND APPARATUSFOR BURNING ,FINESOLIDS Charles s. Gladden, Brooklyn, N. Y;

Application December 11, 1945, Serial No'. 634 281 2 Claims; 01. 110-165) This invention relates generally to the art of solid fuel combustion and particularly to a new method of, andnew apparatus for, burn-ingthe carbon in the fly-ash collected from the gases of a stoker fired furnace.

A serious problem has long existed in the operation of stoker fired furnaces with respect to the collection and burning-of finely-divided solid-s commonly known as fly-ash; which is carried out of the combustion chamber of the furnace by the ases. hoppers in the rear passes of the boiler setting or at the base of the stack of the furnace. This fly-ash contains considerable quantities of combustible carbon. The fiy-ash which collects in the forward passes of the boiler may contain fromabout 80% to about 90% of combustible carbon,

while the fly-ash which is collected in the rear Passes of the boiler and that collected adjacent to the stack base may contain combustible carbon from about 60% to about 75%. Generally speaking, the percentage of carbon content in the flyash increases with the rate of combustion-and-inv creases as the size of the coal decreases. In all cases, however, the quantity of the fiy-ash and the carbon content of the fiy-ash are so reat that marked inefliciency results if the carbon content of the fiy-ash is not burned in the combustion chamber. 7

Many efforts have been made by highly skilled workers in the art heretofore to burn the fly-ash and various proposals have been made to the end of accomplishing that result. However, so far as I know, none of these efforts-or proposals has been entirely satisfactory.

The present invention is predicated on a new mode of operation and on the use of a new apparatus. According to the present concept the fly-ash is continuously withdrawn from collecting hoppers and moved toward the combustion chamber and isvcontinuously mixed with sufficient air for substantially complete combustion of the carbon contentof the fiy-ash and the mixture is delivered into the combustion chamber under the rear arch where combustion is most active and the temperatures-are highest, and delivery of this mixture is directed forwardly over the fire in the general direction of traveler the fur- Apparatus is provided for continu ously feeding fly-ash toward the combustion nace gases.

chamber for mixing the ash with air for combustion, preferably preheated air, and for .dis-

charging this mixture vforwardly in the hottest portion'of the combustion chamber in the gen- Much of this fly-ash can be collected in eral direction of the travel of the furnace gases. 56

both as regards the utilization of large quantiw ties of the carbon content ofv the fly-ash and in the maintenance of uniform operating conditions and high efficiency of the furnace and boiler.

In the drawings which accompany and. form a part of this vspecification;

Figure 1 is a fragmentary rear elevational View, partly in section, talien on line 1-1 of 2 andshowing astoker fired furnace embodying the present invention} Figure'2 isalongitudihal view, partly in section, -taken on -11'ne2'-2 of 1'; v

Figure 3 is .a fragmentary plan view, partly in section, 'takenon line 3-3 of Fig. I;

Figure lis a side elevational View, partly in section, of one of the traps of Figs. 1 and 2;]

Figure 5 is an end elevational View, partly in section, of the trap of Fig. 4 with the associated conduits; and,

Figure 6 is a diagrammatic partly sectional View of conventional apparatus with which the apparatus of- Figs. l to 5 may be used.

The furnace of Figs. 1 and 2 may be ofconventional construction. As shown, it comprises a conventional chain grate stoker'l, the upper grate of which constitutes the base'of combustion chamber '2 of the furnace having arear end wall indicated at 3 and .a-front .end wall indicated at 4. The rear arch of the furnace 5 extends from the rear wall 3.to the furnace throat 8 and.

tations of the combustion chamber 2.. The icon-.-

struction of the rear arch .5 and rear wall 9 and front wall 10 may be 0f :solid refractory or of .re-

fractory blocks suspended from structural supporting steel, or they may be provided with the conventional water tubes: along the inner stir-,- faces which are connected with headers and through which boiler water circulates to reduce.

the temperature and protect-the refractory from excessively high temperature.

.I-iopper 15 :at the front of the furnace is {151 vided to receive coal from .a storage hopper (not shown). The lower end of this hopper is ad-H jacent to the -top-of moving grate. =.l which travels. under the .fuel .hepper from the front toward .the rear and thus coal which forms the fuel bed F6 Two Vertical sidewalls f2,"

is supplied to the grate as the latter enters combustion chamber 2. It will be understood that air for combustion of the coal on the grate is blown into forced draft compartments I1 beneath the coal ladened, rearwardly moving reach of the grate l and flows up thru the bed of fuel affording oxygen for combustion of the fuel on the grate.

Fig. 6 shows, partly diagrammatically and partly in section, conventional apparatus with which the apparatus of Figs. 1 to 5 may be is discharged into the combustion chamber the air will not tend to exert any material cooling effect on the gases in the combustion chamber.

used. This Fig. 6 shows part of the combustion;

I80 and below a duct leading upward to an air- Fig. 6 also shows an induced preheater 2|. draft fan 22 which causes furnace gases to flow around baflies l8a, I81) and |8c through air. heater 2| and propels those gases through duct 23to the base of stack 24. The baseof the stack is provided with a hopper 2 4a 'which'is connected by a downwardly extending conduit 25b to hopper 201) into which fly-ash from the stack may be delivered. A forced draft fan Madischarges air through preheater 2i and thence into housing 39, presently to be described, whence such air is delivered through conduits 38 and thence into conduits 34.

In installations where induceddraft fans are present and where there is' a greater negative draft'in one of the rear passes-of the boiler than at the base of the stack, the fiy ash whichis collected in a hopper at the base of the stack may be continuously discharged by gravity directly into the fly-ash hoppers of such 'rear passes of the boiler, and thence delivered into the'rev'olving traps.

From the lower portion of each hopper25 comprising hoppers 29a and 2012 a conduit 26 extends downwardly and opens into a trap 21 (see Figs. fand 5).. Each'trap .Z'lhasa shaft 28 extending axially carries. blades 38 spaced therearound' at "intervals, for example, 90 degrees apart. The shaft and blades constitute a rotatable feeder in trap 21 for continuously receivingfly-ash from hopper 25 and delivering it in successive quantities to conduit 3! leading downwardly from the bottom portion of the trap. The diametrical dimensions of Wings 39 are suchthat there is a small clearance between the outer edges of the wings and the This clearancepermits inner surface of trap 21. w free rotation of the shaft and blades and preventsany substantial flow of gases from the low negative pressure region in the combustion chamher up to the much lower pressure region inthe fly-ash collecting-hoppers. conduit 3| is connected toa conduit 32 extending at an angleto conduit3l and conduit 32 is connected thru swivel'joint 33 toconduit'M which extends thru arch 5 into the top portion of combustion chamber]. A header 36 communicates with the upper endof conduit 3?. thru can;

therethru and mounted inbearings 29jon the outer sides of the trap. Shaft 28 The lower end of It will be noted that conduits 32 and 34 are inclined downwardly toward the throat end of the combustion chamber and that by reason of this inclination the mixture of air and fiy-ash is projected into the combustion chamber in the general direction of travel of the gases toward the front of the furnace, as illustrated in Fig. 2. The general travel of the furnace gases is indicated by broken arrows and the entering fly-ash is indicated by solid arrows interminging with the broken arrows and flowing in the same general direction toward the throat 8 of the combustion chamber. It will be noted that certain solid arrows, indicating the heavier particles of carbon and fiy-ash drop to the stoker grate in a zone where combustion is most actively taking plate. As indicated, conduits 34' extend thru the roof or arch 5 of the furnace over the region of the fuel bed where the combustion is most rapid and the temperatures of the gases are highest. Preferably, sufficient air is admitted into conduits 32 to supply the oxygen required for substantially complete combustion of the carbon in the fly-ash with which it mixes. In this manner the finer particles 0f fly-ash cinders are surrounded with air when they enter the combustion chamber and burn almost immediately, while the larger particles of fly-ash cinders, which do not burn in suspension may fall onto the burning'fuel bed where their burning will be completed.

As is shown in Fig. 1, the rotating elements of two adjacent traps 21 may be connected to-f gether for simultaneous operation by a single geared motor. Such a motor is shown at 40 and is directly connected to shaft 41 which in turn is connected to shaft 28 of the adjacent trap 21. The shaftof that trap may be coupled by shaft 42 to the shaft of'an adjacent trap.

As is better shown in Fig. 3, shaft 4| may be connected as by sprocket wheels and chain belt 45 to adjacent trap 21, and the shaft from this latter trap may be connected by shaft 5% to another trap 21. In that manner one motor may drive the revolving elements of four traps. It

will be obvious that additional traps may be actuated'in a similar manner if desired. 1

The operation of the above described apparatus is substantially as follows: With stoker l in operation and fuel burning thereon, gases flow up thru throat 8 around the boiler tubes in the first pass thence over the first baffle and around the boiler tubes in the second pass. Under the lower edge of baffle 181) where the furnace gases change direction from a downward movement through the second pass to an upward 'movethrown down into therear fly-ash hopper 2% when the gases again change direction from a downward to an upward movement'before pass-' ing on to the suction of the induced draft fan-f 22. The induced draft fan discharges the gases 2' into the base of the stack thence to the atmosphere from the top of the stack. The fly ash delivered into hoppers 25 is continuouslyf'fed 5 thru traps ill by rotation of shafts 28 and blades 1 30 into conduits 3| where the fiy-ash is mixed with air which preferably has been preheated and the mixture passes thru conduits 34 into the hottest part of the combustion chamber. The inclination of conduits 34 directs the mixtures into the combustion chamber in the direction of travel of the gases above the stoker. The carbon in the lighter particles burns while they are mixing with the gases. The larger particles which are too heavy to remain suspended in the gases fall onto the burning fuel on the stoker grate and the carbon in these larger particles burns partly while the particles are in the gases and partly while the particles are on the ignited fuel. The courses of travel of the large and small particles are indicated by the arrows in Fig. 2.

One important function of the revolving trap is to prevent back draft from interfering with the continuous gravity flow of fly-ash from hoppers 25 into the combustion chamber. Since there is a higher gas pressure in the combustion chamber than in hoppers 25, or in the fly-ash hoppers which communicate with those hoppers, there would be a tendency for gases to flow from the combustion chamber up thru conduits 34 and hoppers 25. This tendency, however, is overcome by the small clearance between the traps and their revolving portions and thus furnace gases are prevented from imposing any noticeable resistance to the free gravity flow of fly-ash from traps 21 into the combustion chamber.

Having thus described my invention so that others skilled in the art may be able to understand and practice the same, I state that what I desire to secure by Letters Patent is defined in what is claimed.

What is claimed is:

1. The method of recovering and burning flyash which comprises the steps of removing flyash from furnace gases while on their way from the throat of a combustion chamber to a stack and depositing such ash in a hopper, feeding ash continuously from the hopper in a restricted stream by gravity while mechanically preventing opposed flow of furnace gases toward said hopper, continuously mixing with said flowing stream of ash an amount of air approximately suflicient for substantially complete combustion of the carbon contained in the ash in said stream, and continuously discharging the resulting mixture of ash and air into the furnace combustion chambet at a place remote from said throat and on 8 a line directed downwardly at a substantially acute angle to the horizontal and toward said throat.

2. Apparatus for recovering and burning flyash comprising a furnace having a combustion chamber defined in part by a front wall, a rear wall, side walls, and a roof sloping upwardly from the rear wall toward the front wall, a substantially horizontal stoker extending from the front wall toward the rear wall and beneath said roof, a stack, a fly-ash collecting hopper between the chamber and stack, a conduit extending downwardly from said hopper at such an angle that fly-ash will flow freely along it, said conduit projecting through the sloping roof over the stoker at a substantial acute angle to the top of said stoker and in a direction opposed to the direction of travel of the stoker, a rotatable trap in said conduit for feeding fly-ash from the hopper into said conduit while preventing counterflow of furnace gases from the conduit into the hopper, and inlet means for admitting air under pressure into the conduit to mix with and propel fly-ash therealong and into said chamber.

CHARLES S. GLADDEN.

REFERENCES orrEn The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 264,905 Spear et al. Sept. 26, 1882 738,132 Weaver Sept. 1, 1903 759,357 Edison May 10, 1904 806,127 Field Dec. 5, 1905 867,068 McClave Sept. 24, 1907 1,747,676 Kerr Feb. 18, 1930 1,898,479 Coghlan et a1. Feb. 21, 1933 1,943,949 Coghlan et al Jan. 16, 1934 2,029,285 Bennett Feb. 4, 1936 2,386,336 Mosshart Oct. 9, 1945 2,400,797 Webb May 21, 1946 FOREIGN PATENTS Number Country Date 127,062 Austria Feb. 25, 1932 384,877 Great Britain Dec. 15, 1932 690,650

France June 24, 1930

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