US1904128A - Method of burning fuel - Google Patents

Description

METHOD 0F BURNING FUEL Original Filed March 19. 1924 lNVE. TOR wie@ if f Mufmw /uATToRNEYJ ently Patented Apr. 18, 1933 UNITED STATES PATENT OFFICE JAMES W. FULLER, 0F OATASA'UQUA, PENNSYLVANIA, ASSIONOB, BY MESNE ASSIGN- KENTS, T0 FULLER LEHIGH COHPAN'Y, A CORPORATION 0F DELAWARE METHOD 0F BURNING FUEL Application med March 19, 1924, Serial This invention relates to the art of burning ulverulent fuel, and more particularly to t e use of a finely divided fuel of low volatile content for heating chambers of considerable length through or along which the products of combustion pass to a stack. The principles of the invention y are capable of utilization in various ways, but are of especial importance in connection with the burning of cement in rotar kilns, such as are in general use, althou li the ap lication of these principles to the eating of) dryers and other similar devices is also advantageous. In order that the invention may be clearly understood, its use in connection with the production of Portland cement will presbc explained although it is tol be understood that the description of that adaptation is merely typical of various applications.

It is Well known that considera le saving in the cost of the production of Portland cement could be made if it Were possible to use low volatile fuels for firin the kilns. Attempts have been made heretofore to make use of fuel such as anthracite, culm or cokebreeze, but when the ordinary burning equipment is used for this purpose it has been found that the ca acity of the kiln is materially reduced. n such kilns .the three zones of dehydration, sintering, and clinkering must have a definite relation to each other in order to produce cement at the greatest kiln efficiency and when such fuels as above referred to are used without alteration in the burning e uipment, it has been found that the zone o high temperature is thrown far back into the kiln. This, of course, reduces the length of the zones of lower temperature and necessitates that the kiln be run at a low speed. Also the fuel is not used to the best advantage, since the stack gases leave at unusually high tempera tures. Various attempts have heretofore been made to solve the problems involved but without renounced success. For instance, it has n proposed to make use of a mixture of bituminous coal with a small pro on of low volatile fuel. The result of urning this mixture is to some extent satisfactory, but the practice is not commer- NO. 700,199. Renewed August 22, 1931.

cially useful because of the inconvenience and labor involved in producing the mixture and also because of the relatively small savin which is secured.

e present invention, however, provides a method and apparatus by which fuel having a low volatile content may be used in such kilns in the pulverulent condition without admixture, and according to this method, the first stage of the combustion of the fuel takes place in a preliminary combustion chamber rom `which the ignited stream passes into the kiln. This chamber is located at the discharge end of the kiln and partially encloses the latter. The clinker dischar ed from the kiln passes into the chamber w ich ma be provided with an inclined wall over w ich the clinker moves by gravity, or else with a traveling grate which serves to continuously remove the clinker discharged into the chamber. One of the great diliiculties involved in making use of this low volatile material is the ignition of the entering fuel and the maintenance of combustion, and in the present instance `this difficulty is overcome by directing the entering jet of fuel into the chamber in such a direction that the ignited stream leaving the chamber and entering the kiln makes an abrupt change of direction, resulting in a partial counterflow of the ignited stream. This returning jet or flame gives up heat to the entering fuel jet thus serving to ignite it, and also assisting in its combustion. A part of the air necessary. for combustion enters with the fuel but the greater part enters the chamber along that surface over which the clinker discharged from the kiln L moves. The air so entering is led close to the surface of the clinker so as to preliminarily raise the air to a high temperature and the air'thus preheated mingling with the fuel in the chamber supports combustion and is carried into the kiln with the ignited stream. The turning back of the jet .upon itself occurs in proximity to the clinker which is, of course, at an extremely high temperature and the entering fuel jet not only takes up heat from the i ited stream but also receives heat radiate from the moving bed of clinkers. This arrangement of the apparatus not only increases the speed of combustion so that its first stage takes place before the gases enter the kiln proper but it further insures that the entering fuel will be continuously ignited and combustion maintained. Furthermore, the zone of highest temperature is now maintained just within the discharge end of the kiln so that continuous operation `with low volatile fuels is carried on without reducin the capacit of the kiln, the zones of whic have the re ative length required for efficient operation.

In one form of apparatus which I have devised for the practice of the method, I make use of a combustion chamber having a floor sloping downwardly away from the Y discharge end of the kiln so that the discharged clinker will pass over this floor by gravity. The fuel is projected into the chamber by means of a vertical nozzle directing a jet of fuel downwardly along the side of the chamber farthest from the end of the kiln. The fuel so introduced in the chamber travels along a path which brings it close to the surface of the bed of clinker and then causes it to turn upwardly and travel with a partial counterflow into the open end of the kiln. In this partial counterflow, heat is transferred from the ignited stream to the entering jet which also receives heat radiated from the bed of clinker. The chamber has an air inlet located just above the floor over which the clinker is passing in the wall opposite to that into which the end of the kiln projects, and the air entering the chamber is, therefore,

reheated and raised to a high temperature Ey means of the heat contained in the clinker. Air may be introduced with the fuel both by projecting into the chamber mingled fuel and air through the nozzle and also by introducing air into the chamber around the outside of the nozzle, this air bein drawn into the chamber by the induction e ect of the enterin fuel.

n another form of the apparatus I provide a similar chamber having a fuel jet similarly placed. The fioor of the chamber, however, consists of a travelin grate which serves to positively remove t e clinker and permits of making use of the apparatus under conditions where space would not be available to permit of inclining the floor of the chamber at a sufficient angle to secure the desired rate of flow of the clinker. In addition to the vertical jet I provide one or more horizontal jets the nozzles for which are adjustable so that the point of impingement of the several jets may be located as may be desired with reference to the end of the kiln. These several jets are located out of line vertically and preferably the jets will not iminge until just before entering the kiln. gihen a horizontal burner is used the amount of fuel admitted by the two burners will be varied so as to obtain the best results, the

vertical jet serving as a pilot flame for the horizontal jet. It 1s also possible to make use of a low volatile fuel in one and a hi h volatile fuel in the other, the high volati e flame again serving as a pilot for the low volatile fuel. In this case, as before, the vertical jet 1s so directed into the chamber as to necessitate its partial counterflow in passing into the end of the kiln and the ignited stream in this partial return gives up a part of its heat and assists in igniting and maintaining the combustion of the entering fuel.

0 It will also be seen that in directing the jet downwardly in the manner described, its full force is not directed against any sin le surface of the combustion chamber. lthough the jet is directed toward the bed of clinker, it does not impinge a ainst this bed with full force on account o the counterflow before it enters the kiln. This jet, therefore, can do little injury to the combustion chamber and when the horizontal jets are used they are adjusted so that the fuel is projected from them directly toward the open end of the kiln.

In the accompanying drawing there is illust-rated that embodiment of the invention which is now preferred, together with a modification.

Fig. 1 is a vertical cross-sectional view, mainly diagrammatic, showing the end of the kiln and the combustion chamber in which a single fuel jet is employed,

Fig. 2 is a view similar to Fig. l but showingrthe use of vertical and horlzontal jets,

ig. 3 is a horizontal cross-sectional view on the line 3-3 of Fig. `2.

Referring now to this drawing the kiln l with which this apparatus is illustrated is of the usual cylindrlcal type, consisting of a steel cylinder suitably lined with a refractory material. This cylinder is mounted so as to have a slight downward pitch and -is mounted on bearings so that it may be rotated, thus causing the gradual movement of the material from one end to the other. The mounting and driving mechanism of the kiln is not illustrated and is of the wellknown form ordinarily used for this purpose. At the discharge end of the kiln there is constructed a preliminary combustion. chamber 5 which is preferably built of fire brick in any convenient manner. This chamber has an openin 6 in one side through which the end of t e kiln rojects and the chamber is given a slo ing oor 7 so that the clinker 8 discharged rom the kiln into the chamber will low by gravity over this iioory and eventually be discharged into a trough 9, whence it is removed by a traveling bucket elevator 10. The discharge end of the kiln enters the chamber at some distance above the adjacent end of the sloping floor, so that the material discharged may acquire initial velocity before it strikes the inclined surface. The wall 11 of the chamber opposite the end of the kiln has an inlet port 12 through which air may be admitted, and this port is so located that the air enters the chamber close to the surface of the clinker so as to be preliminaril heated thereby, the admission of air throu h this port being con trolled by slides 13 w ich may be operated from the platform 14. The front wall of the chamber is also provided with additional air ports 15 and 16, which may be controlled by slides and the slide 15 is provided with an observation door so that conditions within the chamber ma be readily ascertained. In the top wall of t e chamber is an aperture 17 into which projects a burner nozzle 18. The aperture 17 is located near the front wall and air may be admitted to the chamber through the aperture around the nozzle the amount of air so admitted being controlled by a slide 19 encircling the4 nozzle. The jet of fuel projected into the chamber by means of the nozzle passes downward vertically along the front wall, as indicated at 20, and then returns upon itself as at 21 to enter the kiln. It will be noted that at its lowest point the jet flows in proximity with the bed of clinker and ignition of the entering fuel is brought about and the combustion of the jet is maintained in part by heat transferred from the ignited stream 21 in its partial counteriiow and in part by heat given oif by the bed of clinker.

With this arrangement low volatile fuel may be used in connection with the usual type f rotary kiln without reducing its eilieiency since the fuel passes through its first stage of combustion in the chamber and by the heat absorbed from the ignited stream and also from the moving bed of clinker its ignition and combustion are continuously maintained. The zone of high temperature in the kiln lies close to its discharge end and does not extend an undesirable distance into the kiln, thus permitting of the maintenance of sintering and dehydration zones of the proper relative length and also cutting down the temperature of the stack gases.

In Fig. 2 there is illustrated a somewhat modified form of the apparatus, utilizing the principles of this invention; this is particularly suitable under conditions where lack of space prevents the use of a chamber having an inclined ioor over which the bed of clinker moves by gravity alone. In this form the chamber 5 has the aperture 6, as before, into which the end of the kiln 4 projects. The inclined floor of the kiln as used in Fig. 1, however, is now replaced by a traveling grate 22, which may be of any convenient form, preferably of the endless type so that on its return to the kiln it may pass through a body of water asat 23 and be cooled so as to prevent its rapid deterioration. This grate discharges the clinker, as before, into a horizontal trough 9.

The chamber has a vertical burner 18 extending through an aperture 17 provided with alr control slides 19, and is also rovided, as before, with an air inlet 12, w ich causes the air to be admitted to the chamber in proximity to the bed of clinker traveling alone on the grate. The front wall of the chamber is also provided with an intake 15 as before, which is provided with a control slide and a similar slide 13 is provided for use in connection with the intake 12.

Located in the front wall of the chamber l1 are horizontal burners 24 here illustrated as being two in number and disposed to either side of the vertical burner 18. These horizontal burners are mounted to extend through apertures 25 provided with air control slides 26 as in the case of the vertical burner, and are adjustablymounted so that the horizontal jets may be caused to mpinge on the vertical jet at any desired point. Y

In Fig. 3 this lmpingement is shown to take place just before the jets enter the kiln and this is the desired arrangement when low volatile fuel is being used in all the jets. With the jets so arranged the vertical jet is, as before, caused to counterflow partially and it gives up heat to the fuel entering through the vertical burner as well as through the horizontal burners, thus bringing about igiition and maintaining combustion of the fuel so introduced. The fuel entering from the horizontal burners also takes up heat radiated from the traveling bed of clinker, a part of which heat is also absorbed by the fuel projected into the chamber by means of the vertical jet.

The arrangement above described is the one preferred when low volatile fuel is being used in both horizontal and vertical burners, and the division of fuel between the burners may be varied at will to obtain the best results, the vertical jet serving as a pilot flame for the horizontal jet. If desired, however, low volatile fuel may be used through one burner and high volatile fuel in the other, in which case the high volatile flame acts as a pilot for the low volatile jet. It will be seen that the use of a separate pilot jet of high volatile fuel differs from the processes previously attempted since the two fuels are not mixed together, but are simply used in separate burners with the jets so projected into the chamber as to bring about the ignition and t0 maintain the combustion of the low volatile material being used. It is, therefore, not necessary to determine accurately the relative amounts of high and low 'volatile fuels to be burned prior to their ignition, but a sufficient quantity of the high volatile material will be employed so as to produce a pilot flame which is effective and this adjustment may be made without diliiculty.

It will be seen then, that I have provided a method and apparatus for the burning of low volatile fuel in the finely divided state which offers many advantages and economies. By the application of the principles of the invention, I may heat cement kilns or other similar devices at little expense, since I may use low cost materials heretofore found unsatisfactory for such use. Furthermore, the combustion of th`ese materials is brought about under such conditions that the efficiency of the kiln is not reduced by reducing the length of the various zones init, this being a result ofthe arrangement of the apparatus such that the preliminary stages of the combustion occur before the ignited stream enters the kiln. This latter feature promotes economy by reason of the fact that the temperature of the stack gases is kept low so that the amount of heat so lost is reduced. Also, since the air admitted to the combustion chamber is assed over the bed of clinker in proximity t ereto, the air is preheated before it mingles with the stream of fuel, and a part of the heat absorbed b the clinker is thus made to serve a usefu purpose. Another part of this heat radiates from the clinker and helps to ignite and maintain the combustion of the entering fuel stream. Since no part of the ignited stream impinges directly on a wall of the combustion chamber, the frequency with which the refractory material of the chamber need be replaced is lessened and this cuts down the cost of maiutenance.

I claim:

1. The method of burning fuel forheating non-combustible material in a kiln having an inlet end for the material to be trea ed and a discharge end, and a primary com ustion chamber in direct communication with the discharge end, which comprises passing the material through the kiln and through the primary combustion chamber and during such movement of the material heating it by the combustion of pulverulent fuel of low volatile content, the combustion taking place partly in the chamber and partly in the kiln as the gases flow from the chamber into the kiln, and confining the zone of highest temperature to a relatively restricted region within and adjacent the discharge end of the kiln by projecting the fuel into the chamber in the form of a jet so directed that the fuel stream passes through the chamber along a circuitous path such that ignition of the fuel particles entering the chamber is brought about and combustion is maintained by radiant heat from the ignited fuel particles and also by radiant heat given off by the hot dischar 'ng material.

2. e method of burning fuel for heating non-combustible material in a kiln having an inlet end for the material to be treated and a discharge end, and a primary combustion chamber in direct communication with the discharge end, which comprises passing the material dischargin from the kiln through the chamber, admitting air into the chamber and during such admission raising the temperature of the air by heat radiated from the discharging material, projecting a jet of fuel of low volatile content into the chamber at an angle to the longitudinal agis of.,the kiln, and bringin about ignition of the entering fuel and assisting the maintenance of combustion thereof by causing the fuel stream to pass from its point of admission into the chamber to its point of admission into the kiln along a circuitous path such that the entering fuel stream receives heat radiated by the ignited portion thereof and also given off by discharging material.

3. The method of burning fuel for heating non-combustible material in a kiln having an inlet end.for the material to be treated and a discharge end, and a primary combustion chamber in direct communication with the discharge end, which comprises passing the material discharging from the kiln through the chamber, projecting a jet of pulverulent fuel of low volatile content into the chamber at an angle to cause the'fuel stream to oav through the chamber along a circuitous path in which the stream turns upon itself in proximity to the discharging material and in contact therewith and thus bringing about ignition of the entering fuel and assisting the maintenance of combustion thereof by heat given off by the ignited portion of the fuel stream and by the dischargin material, and admitting air to the combustion chamber in proximity to the point at which the fue stream turns upon itself.

4. In a method of burning fuel for heating non-combustible material uin a kiln having an inlet end for the material to be treated and a discharge end, and a primary combustion chamber in direct communication with the discharge end, the steps of burning pulverulent fuel of low volatile content artly in the combustion chamber and partly in the kiln, and confining the zone of highest temperature to a relatively restricted re 'on Within and adjacent the discharge end o the kiln by projecting the fuel into the chamber in the form of two jets diffusing into each other, one of these jets being projected into the combustion chamber directly toward the discharge end of the kiln and the other being so directed into the combustion `chamber that its fuel stream turns upon itself within the chamber in such manner that the entering portion of the fuel stream in both jets receives heat radiated from the ignited portion of the second jet.

5. In a method of burning fuel for heatling non-combustiblematerial in a having an inlet end for the material to be treated and a discharge end, and a primary combustion chamber in direct communication with the discharge end, the steps of projecting a jet of fuel of low volatile content into the combustion chamber in such manner as to pass for only a portion of its path within Such chamber immediately prior to its entry into the kiln in countercurrent to and in contact with the material discharging from the kiln, and projectin a second jet of said fuel throu h said comustion chamber directly towar the discharge end of the kiln and in such manner as to diffuse into the first jet at points within that portion of the latters path within the combustion chamber in which it moves countercurrent to the material being discharged from the kiln.

6. In a method of burning fuel for heating non-combustible material in a kiln having an inlet end for the material to be treated and a discharge end, and a primary combustion chamber in direct vcommunication with the discharge end, the steps of projecting a jet of fuel of low volatile content into the primary combustion chamber downwardly and causing the fuel so admitted to pass from its point of admission into the chamber to its point of admission into the kiln alon a circuitous ath, projecting a second jet of uel of low vo atile content into the chamber to diffuse into the first, the ignition and maintenance of combustion of the fuel in both jets being brought about in part by heat radiated from the ignited portion of the first jet, passing the material discharging from the kiln through the primary combustion chamber, and admitting the major portion of the air required to support comustion to the chamber in proximity to the said discharging material, whereby the air is preheated by heat radiated from the materlal.

7. In a method of burning fuel for heating non-combustible material in a kiln having an inlet end for the material to, be treated and a discharge end, and a primary combustion chamber in direct communication with the discharge end, the steps of projecting a jet of pulverulent fuel o low volatile content downwardly into the rimary Vcombustion chamber to {iow theret rough along a circuitous path to enter the discharge en of the kiln, projecting a pair of jets of said fuel at an angle to and out of alignment with the first jet, the said first jet being so projected that the unignited fuel entering the chamber in all three jets is ignited and its combustion maintained in part by heat radiated from the ignited portion of the first jet, assing the material discharging from the 'ln through the chamber in proximity to portions of the several jets so that heat given oi by the discharging material is in part absorbed by the entering fuel introend or the introduction of the material to be heated and an outlet end through which the material is discharged, a primary combustion chamber havin an opening in one wall through which the c amber is in direct communication with the kiln, the material discharging from the kiln passing through the opening into the chamber, means for projecting a jet of pulverulent fuel and air downwardly into the chamber, a fiat elon ated discharge opening in the wall of the c amber opposite to that through which the material enters the chamber, this opening permitting the entrance of air for combustion into the chamber over the surface of the discharging material to be heated thereby, and means in the bottom of the chamber for bringing about movement of the material from its point of entrance into the chamber and out of the discharge openin 9. The combination o a rotary kiln adapted to convey material therealong by its rotation from an inlet end to a discharge end, a primar combustion chamber through one wall o which direct communication is provided with the discharge end of the kiln, 100

' means disposed in the lower end of the combustion c amber for con-ducting the material dischar ed from the kiln across the chamber an out through an opening in the wall opposite to that through which the material enters, means for rojecting a jet of fuel vertically downwardly into the combustion chamber, and means for admitting re latin quantities of air into the combustlon cham er in counterflow to the discharging material and over the surface thereof, whereby the air is preheated by the radiant heat from the said material.

10. The combination of a rotary kiln havin an inlet end and a discharge end, this kiln being adapted to convey material from one end to the other by its rotation, a primary combustion chamber into which the discharge end of the kiln projects, means in the bottom of the chamber for conducting material discharging from the kiln out of the chamber, a nozzle for projecting a stream of fuel downwardly into the chamber, this nozzle being disposed at a distance from the end of the kiln, `whereby the stream from the nozzle Hows through the chamber and into the kiln along a circuitous path, a portion of which is in proximity to the material passing through the chamber, and a pair of nozzles for projecting jets of fuel into the chamber in sub- 30 JAMES W. FULLER.

CERTIFICATE OF CORRECTION.

Patent No. 1,904,128. April 18, 1933.

JAMES W. FULER.

lt is hereby certified that error appears in the printed specification of the above numbered patent requiring correction ne follows: Page 4, line 95, claim 3, for "et en enfle" reed "in such manner as": and the! the uid Lettere Patent should be read with. this correction therein that the seme my contorni to the record of the cese in the Patent Office.

Signed and sealed this 22nd day oi August, A. D. 1933.

M. J. Moore.-

(Seel) Acting Commissioner ol Patente.

JAMES W. FULLER.

CERTIFICATE OF CORRECTION.

Patent No. 1,904,128. April 18, 1933.

JAMES W. FULER.

lt is hereby certified that error appears in the printed specification of the above numbered patent requiring correction ne follows: Page 4, line 95, claim 3, for "et en enfle" reed "in such manner as": and the! the uid Lettere Patent should be read with. this correction therein that the seme my contorni to the record of the cese in the Patent Office.

Signed and sealed this 22nd day oi August, A. D. 1933.

M. J. Moore.-

(Seel) Acting Commissioner ol Patente.

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