USRE17908E - arrowood - Google Patents

Description

' Dec. 23, 1930. M. WQARROWOOD Re. 17,908

' manger: AND lETI-IOD OF BURNING FlimjzzaenZZrr- Reis aued Dee-23, 1930;

4 UNITED STAT MILTON W. ARROWOOD, OF GREENWICH,

ENGINEERS, 1Nc.,"or' WORCESTER, MASSACHUSETTS, a conroaa-rroN i 4 PATENT- o nc-i;

coNNEc'rIcU'r, ASSIGNOR *ro UNIVERSAL l FURNACE AND ME'rnon or BURNING- FUEL Original No. 1,617,510, dated February 15, 1927, Serial No. 490,529, filed August 8, 1921.

' reissue filed February 14,

'This invention relates in general to a mthd of and means for burning fuel, operating furnaces, and treating metals in furnaces, and while I have shown it in the present drawings as embodied in one of the preferred forms in a melting furnace, itshould be understood that the principles thereof are capable of embodiment in furnaces used'for other purposes, such as annealing orheating furnaces, or furnaces as used for smelting metals for instance.

My present invention may naturally be used I in all that general class of furnaces where the conditions ar'eless exacting than in the treatment of metals, in fact, the invention is not only desirable, but a real necessity in any furnace for whatever. purpose, where .com-

minuted, pulverized, atomized, or diffused fuels are burned in free suspension. It is obviously not feasible, and is not considered necessary, to illustrate all possible types of such furnaces where my invention is useful and necessary for-efficiency. Y

It should be observed that while the invention herein relates, in general, to a method and means for-treating metals in furnaces,

. it is, nevertheless true that certain of the features of my invention, as herein disclosed, particularly as relating to the regulation of the total quantity and of relative proportions of fuel'and air, and the even diffusion of the fuel throughout the air, and also as to the metals.

regulation of the static, pressure and draft in" the furnaces, apply equally well to furnaces ,1 in general, irrespective of whether the furnace at the time maybe used fortreating These featuresare, in fact, vital to. the proper regulation and control of fur naces when firing. comminuted,, pulverized, atomized, or diffused fuel, all of which may be fired and burned in free suspension. My invention relates to the control of firing and burning ofany fuel fired into the fur-.. naces. The regulatoryfeatures of myinvent-ion, as herein disclosed,'have'not been understood as applied to fuels burned-in a finely divided and diffused state in free suspension. My invention relates particularly to the method and means of establishing and n'ulinta-ining accurate control, under all de- Application for 1929- Serial N0- 339,964. I H

sired operatingconditions with all such fuels,

when burned, either-severally or collectively with two ormore saidfuels in an evenly diffused condition -in free suspension in combination with 'the correctly. proportioned combustion air delivered to the combustion chamber with the said fuel or fuels as an evenly diffused combustible mixture.

Both the quantity and relative proportions, as well as the evenness of diffusion ,of the fuel or fuels throughout the combustible are at all times underdefinite control when fed to furnaces, either severally or collectively, on the improved method herein outlined,.and

it is'this method of securin and maintaining definite control of all theji ring and burning conditions which is the essence of my present invention. When the total quantities of fuel or fuels and air, as wellas therelative proportions of the same, and the diffusion of the fuel or fuels throughout the air volume are regulated'and controlled asin my present invention, the various operating conditions of the furnace are also brought under control, with the result that my invention brings about a great improvement in the burning of all fuels in the state of adiflused mixture in free suspension. v I f M present invention brings about a Imar (ed increase in the efficiency of such firing operations where comminuted, 'pulver- I ized, atomized, or diffused fuels are fed and burned in free suspension within the said furnaces. For example, the total quantity of combustion gases produced under close regulation and, hence, the velocity of flow through the furnace, is"likewise closely controlled.

All of this, it is readily understod, is a distinct advantage in the operation of furnaces burning diffused fuelmixtures in free suspension,--as herein described 1 Prior to my invention these principles have not heretofore been at all understood in obnnection withfurnaces using such fuels burned in, free suspensionin the treatment of metals and, in'fact, these correct principles, which are the essence of my present invention, have not previously been understood or applied in any form of urnace ,,former1y used and fired with fuels burned in free suspension, either for metallurgical'orother purposes. 7 Owing to the intense heating conditions required in the treatment of metals and the necessity for relatively high temperatures, as well as the restrictions to particular types of'furnace construction customarily used in the metals industries, it has not been possible. heretofore successfully to treat metals with these fuels fired and burned in free suspension. One purpose of my invention, therefore, is to make possible the eflicient treatment of metals when fired with such fuels by estab lishing the aforementioned control conditions-which make possible eflic'ient combus-' tion and application of the resultingheat to the metals being treated. J I Without these control conditions it would be impossible to secure the desired te1npera- .tures in the furnace, in view of the large amount of heat'lost up the stacks, exceptby the consumption of a prohibitive amount of fuel.

It will be recognized that these principles operating so effectively under the exacting conditions existing in the metals industries will be equally effective in the operation of furnaces 1n general where it is desired to fire such comminuted, pulirerized, atomized, orv diffused fuel, or fuels, severally or two or more collectively, to furnaces. In other lines of activity operating conditions are not so exacting, and there is 'no limitation as to the necessity of maintaining temperatures on the order of the maximum possible temperatures obtainable from fuel combustion. 1y, others have been able to operate such furnaces with-steam generating equipment andfor other similarly less exacting industrial applications by resorting to specially desigried furnaces at considerable sacrifice in first cost, and, in many cases, also a material sacrifice in the efliciency of combustion and heat application. I

It has previously beenthe necessary custom in general for the operators of such furnaces to rely upon special and elaborate furnace designs and,'in most cases, they lrave had to employ furnaces of unusually large dimensions. One of the primary purposes. of the present invention is to avoid the necessity .of using siich specialand largevcumbersome furnaces and, in fact, to bring the firing and operating conditions under such close regu-r lation and control that fuels, whether comminuted, pulverized, atomized,. or in the gaseous forms, may be readily and efiiciently.

. fired, severally or two or more fired collectively, and burned in free suspension, irrespectiveof the articular form or construction of the given mace. In other words, it is the urpose of the present invention to make the ring of all the hereinbefore described'fuels oranyfuels burned in freesuspension, independent of particular or special furnace con- 659 struction-{relying solely upon the hereiendis- Formerclosed regulation control of the firing and furnace conditions to secure the desired results that-iscomplete combustion'of the fuel, or fuels, under the conditions mostfavorable for utilizing the liberated heat most efficiently."

In certain kinds of furnaces of this general character, andparticularly in meltin'g furnaces, it' has been customary heretofore to provide a' hearth which is sloped to a depressed point where the taphole is located.

As the result of this shape of hearth, the

solid charge of pig iron and scrap iron which n is piled upon the bottom of the hearth for melting purposes, is concentrated over the depressed portion of the hearth where'it assumes considerable depth, forming a barrier for the flame of burning fuel. It follows therefore that the flame cannot penetrate to any considerable distance into the base of the charge and becomes concentrated to "a large degree upon and against the forward portion of the charge, while the remaining portions are subjected to very little heat; The result 1 is that the melting of the charge takes place very slowly and requires the expenditure of a greatamount of fuel; F urtherinore, the moltenl.metalrforms a deep pool in the deressed portioh, the bottom of which tends to ecome cooled'so that in practice, it becomes necessary torun the furnace for a considerable period after the metal is all melted before it is all heated sufficiently for pouring purposes. 1 One of the primar ent invention as relating particularly to melting furnaces is to provide a furnace, the hearth of which will. be substantially level fromend to end and devoid of-depressions so ,as to provide a relatively shallow bath of substantially uniform depth. This construc-. tion permits of a more even distribution of the solid charge'over' the area of the hearth, with the result-that a large area of the charge is exposed to the action of the flames, thusma terially facilitating and expediting the melting of the charge and reducing the amount of fuel required for the melting. Manifestly, the molten metal in a shallow bath having a large top'surface" exposed to theheat in 'the fifrnace can be thoroughly heated much more expeditiously than the same quantity of metal in a deep ool. Consequently, with my improved shallow bath furnace, the pouring may be begun soon after the actual melting has been completed, thereby effecting amaterial economy both in time and in :fuel.

To insure the flow of the molten metal from the hearth through the tap holes, the hearth is preferably slightly inclined 'tran'sversely either from one side to the other,'or pref erably as herein shown, is slightly arched transversely so'that'the moltenmetal will flowto both sides thereof, where it may be purposes of my pres-- the furnace in controlled proportions at low velocity and-under low pressure, and the communicating opening between the furnace, and the stack is so located and so proportioned with respect to the fuel pressure and the size of the stack is so proportioned that the furnace chambenis usually maintained under a slight static pressure and the products of combustion leave the chamber and are delivered from the stack at a low velocity. Instead therefore of drawing enormousrquantities of heat up the stack, the fuel is practically completely consumed in the furnace chamber so that its heat units become effective upon the charge to be heated or melted and a minimum of heat is lostthrough the, stack, thereby greatly increasing the efficiency of the furnace. This draftcontr'ol is equally desirable in the. operation of furnaces imgeneral,

whether or not the furnacesmay be used-for the treatment of metals.' The stack and the draft opening betweemthe furnace and the stack are'so designed as to favor a slight static pressure in the furnace, but by varying the fuel delivery pressure, this fstatic'pressure may be changed to a substantially balanced draft or to an appreciable outlet draft i if desired. My invent-ion therefore provides for a wide range of flexibility in its opera:

tion to successfully meet various conditions to which it may be subjected.

Another feature of ny invention resides in the provision of means for delivering the romminuted, pulverized, atomized, or dif fused fuel or fuels mix-ed with air and evenly diffused throughout the air to the furnace in a turbulent condition, so that it or they swirl as a mass of slow moving mixture over the surface of the charge so as to-more readily distribute its heat thereto. The effectiveness of the burning mixture is further increased in the caseofn eltiiig furnaces by delivering it downwardly .or in a downwardly inclined direction from the nozzle against the bath which results 'in a penetration of the flame into the mass of loosely piled material forming'the charge on the hearth, thereby causing the flame to continue along the hearth at the base of the charge while the charge is in solid state, and also causing it to nnpmge against the adjacent margin of the bath when .melted, thus producing a most effective heatmgaction.

Another object of" this invention is to in sure-that the fuel, whether comminuted, pulverized, atomized, or diffused, is delivered to the furnace in a {completely atomized difa fused condition, being evenly distributed throughout all ofthe necessary combustion air and the entire diffused mixture. of the comminutefd, pulverized, atomized, or diffused fuel or fuels, severally or two or more collectively, being delivered in'a swirling turbulent condition to the furnace; while at the same time complete control is maintained of the quantity and relative proportions of the fuel. and air as well as control of the static pressure and other furnace operating conditions hereiii described. Itshould be particularly noted that the essential nature of the novelty of the invention in this patent is the main tai ning' of a definite control of all factors relating both to-the firing and chemical control of the gaseous andslag deposits in the furnace.

This includes not only the control of the v quantities of fuel or fuels, together with the control of the quantity of air, butsalso includes the governing of velocity and static pressure in the furnace as well as the chemical control of the ingredients in the burning mixture or mixtures which, in turn, gives control 'of-the chemical ingredients in the finished product; provided, of course, that the initial quantities of the desired. ingredients in the product are proportioned properly when making up the. raw batch of material going into the furnace.

v l Vhile it is apparent that the chemial control of metals is a desirable and novel feature resulting from thef accurate control of the quantity and relative proportions of fuel and air, it should not be understood that it is the purpose to limit this invention to metallurgical processes alone. The desirable gas c'ondit'onsestablished'by accurate control of the quantity and relative proportions of comminuted, pulverized; atomized, or diffused fuel or fuels, and combustion airdelivered in turbulent condition at low velocity are fully as effective in many other industrial applications as they are in "metallurgical furnaces. It is obvious that such regulation is highly desirable in any furnace as tending to conserve the total quantity of heat' and control the rate of heat liberation so as to secure maximum efliciency.

A further object of my invention is to provide a" furnace in which the front bridge wall isspaced a limited distance from the front Wall of the furnace chamber, the for'-' ward end of the hearth between these walls being provided with a masonry floor inclined downwardly from the front wall to the bridge wall sothatany slag deposited on this portion of the hearth will drain freely into the bath. In-order however to relieve the bath from an accumulation of as much slag as possible, this floor is provided adjacent the front wall and immediately beneath the point of delivery of the fuel into the furnace with a depressed pocket. Since the fuel is delivered at-low velocity, the flame formation pocket.

occurs near the front wall and that slag which results from the initial flame forma tion drops immediately intothis pocket from which it may be removed at intervals through cleaning doors communicating with the This construction eliminates to a large extent that portion of the-slag which is particularly in urious to the brick work ofthe bath and thereby materially reduces the cutting in of the side walls of the furnace at the slag line which has heretofore been a principal cause of brick repairs. The

corrosive action upon the brick walls is further reduced by the factthat the combustion in my improved furnace is rapid and complete instead of progressive throughout the length of the furnace, thereby causing an improved gas condition within the furnace which diminishes the deteriorative effects upon the brick work and reduces the chemical activity of the walls.

Another and important feature of my in- 'vention resides in the fact that where the" proportions of the several ingredients of a charge are substantially correct, by mixing with the comminu-ted, pulverized, atomized,

or'difi'used fuel or fuels just sufficient air to support complete combustion, or, in other words, providing a neutral flame; by delivei'ing this mixture at low velocity into the, furnace so that the combustion is speedy and complete; by directing the burning mixture downwardly against the bath; and by controlling the pressure withinthe'furnace, an extremely high, intense and penetrating heat is produced, which quickly melts the charge Without burning out as large a. percentage of the silicon and manganese as has heretofore been burnt out with other methods of firing. The result is that the furnace chargemay contain a much larger proportion of cheap scrap metal and a correspondingly less amount of expensive iron than customary,

thereby reducing the cost of the charge while still producing malleable metal of the desired composition.

The control of the combustion conditions which may be done so as to produce a neutral or oxidizing, or a reducing flame, as desired,

is obviously a vital factor in the operation of all furnaces in general where a fuel-or fuels are to be burned in free suspension, as herein described. Even in the case of V furnaces under boilers or steam generators, for example, these control features arestill 'of vital importance, as they make possible the inost efficient combustion of the fuel, and tend to protect and conserve the furnace linings and heating surfaces. r

And it obviously follows as a corollary of thereby be modulated to meet the requirethe relative bath slag upon the furnace f the matter of the foregoing paragraphs that regulation of the relative proportions of fuel and air admitted through the burners will vary the character of the flame which may 'ments of the charge. For instance, if the proportions of the carbon and silicon, manganese and sulplnirconstituents be too high,the proportion of air in relation to the fuel may be increased to produce an oxidizing flame.

On the other hand, by decreasing the propertion of air a reducing flame'can be secured,

While, asabove, if the batch is properly proportioned, as it should be, a neutral flame is used which will neither reduce norincrease proportions of the charge in-' gredi'ents. I

Still another object'of the invention is the provision of means whereby the direction of dischargeof thefuel mixture into the furnace may be regulated and controlled so that it may be directed downwardly upon the masonry floor in front of the bridge wall, or may be directed over the bridge wall into the forward end of the bath, or may be directed toward a 'point in the bath more remote from its front end, as desired, thus providing for flexibility in the furnace operation so that it may be accommodated to various requirements and rendered highly efficient under all conditions.

It will be seen that this flexibility in con-- trolling not only the chemical character, but the direction in which the flame is projected into the furnace, is desirable in furnaces in general, where, for example, it may be necessary or advisable to deflect the flame in a downward or otherwise specified. direction in order to. avoid impingement against'refractory walls, radiant heat superheaters, or for other necessary and sufficient reasons.

Vhile in many cases it is desirable to point I thdflame in a downward direction and to control the angularity of discharge with reference to the horizontal axis of the furnace, it should be-understood that the numerous other desirable features of my present invention, and the inherent advantages ofits operation are not to be limited solely to the downward projection ofthe flame. It is obvious that ion liq

all those features. of the invention'relating to the control of the total quantity and relative proportions of fuel and air and the resulting control ,of' the chemical condition of the gases inthe' furnace are present in the i operation of my improved furnace, irrespective of the angularity at which the flame is discharged. These and other similar advantages, t-herefore,are not to be in any sense restricted to the use of a flame discharged at a downward angle. 7

On theother hand, it is equally obvious that in many operations and especially in the melting of malleable iron, and also to some I extent in the smelting of metals the downward direction the fiame and its impingement' on the bath .must necessarily involve decided operating. advantages which are equally as essential parts of my present invention as is the other chain of advantages relating to and hinging about the control of the quantity and relative proportions of fuel and air and, hence, the chemistry control and gas velocity control of the furnace.

It will be observed that one class of improvementsin the present invention relates and is applicable to all that class o'f furnaces in general wherein the specified control conditions as to quantity, proportions, chemical constituents of' the gases, velocity and controlled draft pressure are always of necessity present when and wherever there is employed a burner capable of delivering acompletely and evenly diffused mixture in a turbulent condition at relatively low velocity, ahd in all respects under complete control, such as is had when using one of the preferred forms ofburners illustrated and described herein. While the preferred burners; as-illustrated, are entirely capable of establishing the conditions precedent to the successful working of this invention, it is entirely possible that burners of other types may also be capable of establishing the necessary conditions of turbulent firing under control, as herein described. It is not desired, therefore, to restrict the invention to any particular burner structure, but it should be understood that any burner or feed device capable of establishing the conditions of operation as described may be satisfactorily employed in carrying out the improved method of furnace operation as embodied in the present invention.

Another class of advantages of the present invention relates more particularly to the control of chemical ingredients in the metal or metals where same arebeing. melted or where ores are being smelted in order to pro duce metals. It is readily seen that the herein described advantages resulting from the condition wherein the; chemistry of the furnaces is at all times under accurate control, both as to the combustion gas es andvthe slag or ash produced, while reacting variously'in different types of furnaces, nevertheless at all times make possible a definite improvement in operation. As pointed out elsewhere, one improved result has to do with the avpiding of rapid deterioration on the refractories. This result, of course, is equally desirable in any and all types of furnaces, part ofthe containing Walls of which consist of refractories and this, in effect, means practically all furnaces, inasmuch as few, if any, furnaces or combustion chambers are properly constructed Without the use of refractories, at least to some extent.

Another manner in' which the advantages I inherent in complete chemical control of operations are made manifest is in the control of chemical ingredients necessarily required in certain metals when melted or, smelted in order to produce the desired character of product. Again, for example, in the case of steam boilers this same desirable complete chemical control of gases and slag formation manifests its decided advantage in such mat-1 siderable percentages -of sulphur can beburned with immunity when the methods and means constituting the present invention are brought into play. Thus, for example, the sulphur is so completely. and instanteously burned that the usualdeleterious efiect's experienced on heating surfaces and uptakes of the boilers are almost entirely eliminated. It is manifestly impracticable to catalogue all of the operating advantages resulting from the decided improvements of method involved in the present invention, but it is be-\ lieved that these examples sufficiently illustrate the very decided improvement in operation that is possible where full chemical control isestablished. It should be understood that such control is only possible Where the.

so operated in conjunction with the furnace form and draft regulation as to bring about,

through the combined operation of a suitable burner and furnace, the conditions of velocity, draft, and chemical control herein described.

Other objects and many of the inherent advantages of my invention should be readily appreciated as the same becomes better understood by reference to the following descri tion, when considered in connection witht e accompanying drawings. 7

Referring to the drawings: Fig. 1 is a longitudinal sectional View through a furnace embodying my invention; Fig. 2 is a transverse sectional view through the line 2-2 of Fig. 1 ;'and. I Fig. 3 is an enlarged sectional view through the delivery end of the mixer burner;

Referring now to the drawings more in del tail, it will be observed that my improved furnace comprises an enlongated chamber uninterrupted from end to end but comprising two portions, namely: the rear portion in which the material to be heated 1s placed, and which may be considered asa heating cham- --ber, and the forward portion where initial combustion of the fuel begins and is prac tically completed and which may be considered as a combustion chamber. The furnace chamber as a whole comprises the front wall 5, rear wall 6, and the roof 7 all of which are constructed of fire brick in & well known or preferred manner and bound together by I suitable tie rods 8 cooperating with buck stays 9. The bottom of'the chamber is provided with. a bridge wall 11 extending upwardly into the chamber a limited distancc,-this bridge wall being spaced alimitcd distance from the front wall -5 and the space between these walls being filled in and provided with a masonry floor 12 which is inclined downwardly from its front edgetothe top of the bridge wall, The foundation 13 of the I furnace disposed rearwardly of this bridge wall may be of suitable construction suitably covered in annealing or other heating furnacesgbut'for melting furnaces, such as I have hereinillustrated, this'foundation is covered by a sand bedlt forming the hearth which is substantially levelfrom end to end instead of having a' deep depression between its ends, as has'heretofore been customary.

This bed is-adapted toaccommodate a bath? 15 of molten metal which is relatively shallow andof substantiallyequal depth from for a considerable distance to facilitate end .to end, although in practice the rear portion is slightly sloped from rear to front of metal to thetap openings a-nd'to decrease the depth of the bath toward the rear of the furnace where the heat .is less high. This substantially level hearth permits a substantially even distribution of the solid charge over the area of the hearth and consequently the melting flame, instead of encountering a deep barrier to the bottom" of which it would be unable to penetrate, is caused to impinge against a large area and .to penetrate the charge of loosely piled solid material and swirl along the bottom ,of the charge so as to most effectively deliver its heat units" to the charge and reduce the melting time to is scarcely apparent in Fig. 1.

a minimum. 'In practice the material will be piled somewhat igher at the;front end of the pile than it is in the rear of the chamber so that a larger quantity will be subjected'to the maximum lieat'mea-r the forward end of the hearth. The decrease 'in depth of the bath toward therea-r end cor-' responds approximately to, the decrease in temperature and pressure of the products.

of combustion as they approach the rear end I of the chamber. Because of the reduced scale I of the drawings, this-decrease of bath depth For the urpose of holding the hot prodnets of combustion down against the bath, the

roof 7 is inclined downwardly toward its rear end, vand furthermore, the outlet opening from the furnace to the stack and also the top of the rear bridge wall are disposed only slightly above the level of the bath. The entirestructure therefore, is conducive to the most complete transference of heat from the products of combustion to the bath and to a high degree of furnace efficiency.

.In order to facilitate the withdrawal of the molten inetalfrom the bath, the floor thereof is preferably 7 slightly convex 1ntransverse cross section, as will be apparent from Fig. 2. This upward arching" of the floor is adapted to causethe metal to flow to the sides of the bath from which it may be drawn of: through one or Inore tap holes 16 located at each side of the furnace. Should.

it be preferable to draw the entire charge from one side of the furnace, the lmthfioor, instead of being transversely arched, nlay be slightly inclined from one side to the other so as to deliver the molten, metal to one side of the furnace.

The furnace may be charged through doors oropenings formed in the side wall or through the roof, which may be equipped with removable bungs, as is customary in reverberatory furnaces. In this instance, I

have shown for purposes of illustration, the

side wall provided with a plurality of charging doors 18, such as are customarily em ployed in open hearth furnaces and through Which the pig and scrap 1ron and other 1ngredients of the charge may be introduced, flOW unto the chamber and distributed over the hearth.

In certain smelting furnaces it is necessary to control the temperature within rather narrowly restricted limits, and also the character .of gases must be under control of the operato r,

as otherwise with excess temperature and perhaps, at the same time an excess of oxygenin the gases, theretwill be a-large loss of metal by oxidization and under certain conditions vthe smelting action, or melting of the metal from the ore may be greatly impeded, due to the possible excess formation of slag and lack of fl idity in same.

- T en again, in the case of smelting certain metals, a relatively slight inc'reaseof temperature may, as 1n the case of zinc, for-example, cause a vaporization of the metal and a very large loss by waste due to such vaporized metal escaping with the stack gases. It

is believed that without further explanation or illustration sufficient has "been stated to make plain the fact that very close control is necessary, in all smelting furnace ,opera; tlons, so that the improved features of my present'inventlon are most practicable to all sueh furnaces,.and indeed may be said to be almost a prerequisite to nomic'al operation.

successful. and eco- I Where the furnace is used merely for heating ingotsor bundles of metal, as in the furn ace commonly known as pile and board fu1'- nace, the 'wall may be-eliminated and, if -desired, thefloor may be' nade practically level.

This floor may be constructed of specialrei'ractory-sand, asin thecase offthe'melting furnaces or other convenient refractories may be used, if desired. In'case the floor is made level, it will be necessary to clean out the slag accumulation at perlodic intervals. It 1s,

therefore, generally preferable to slightly incl ine the floor in these heating furnaces in the manner already explained for melting furnaces in order that the slag may flow along the incline to the tap holes, which may be located on one or both sides of the furnace in the same manner as for the melting furnaces. ()ne of the distinct advantages of my invention in this respect lies in the fact that the flame produced under the conditions of con trol embodied in the present invention is of such character and intensity as makes possiproducedat the point of flame formation, it

willlbe apparent that this slag will drop directly into the pocket 19 where it. is collected and procluded from entering the bath. 1

have found that the separation of the slag produced at the point of flame formation of ble the formation of high oxide slag compounds, which are more fluid than the low oxide compounds generally formed under less favorable conditions and, hence, it is pos-- sible to remove the bulk of the slag from the. furnace floor through the tap holes. In the previous operation there has always been considerable difiiculty owing to the stiff natill - embodied ture of the low oxide slags, and the temperature and chemical conditions setup in carrying out mypresent invention overcome this serious operating condition. It will be seen, therefore, that the construction, as illustrated in Figures 1 to 3, is entirely suitable for all such heating or reheating furnaces, but it, will readily be seen that the improved principles of my inventioh may furnaces" having various modifications from the structure illustrated, and it is not the intention to restrict the method of this invention to the particular structure.-

\Vhere it is desired to anneal metals directly, as in the heat treatment of billets, rods, sheets, plates, etc.', the furnace as shown is entirely suitable, but again the principles of .my'invention are broadly capable of being in furnaces of modified structure.

If the metals that are to be-subjected to annealing treatment are packed in large metal pots,.as is commonly done in the case of tin plates, and/or malleable castings, the furnace as illustrated in Figures 1 to 3, may still be employed, but as a matter of convenience in charging the furnace a'modified construction is preferred. Special charging machines capable of carrying large pots full of material are mostconveniently placed in these ovens where the entire end consists of removable doors.

Referring again to the melting operation,

'it will be observed from Fig. 1 that the level of the bath is below the top of the, masonry floor 12 and the upper edge of the bridge wall, so that any slag which is deposited on this floor, above the level of the bath will drain freely into the bath. Adjacent the frontwall 5 the floor 12 is provided'with a pocket 19 disposed immediately beneath the delivery openings 21 through which the likewise be applied in gases and the fuel mixture, and the elimination of this speedy and complete combustion of the-fuel which improves the gas condition in the fun nace changes the chemical character of the. bath slag as well as reduces its quantity, with the result that the corrosion of the brick work at the slag line is materially reduced, thereby' diminishing the necessity for repairs to the furnace. The slag collected in the pocket 19 may be cleaned out at intervals through cleaning doors 22 located in the side walls of the furnace at each end ofthe pocket. With controlled combustion conditions as embodied in this invention the duantityncharacter and chemical composition of the combustion gases is maintained practically constant on a given furnace. Since-combustion. is complete and the resulting gases are. inert the chemical conditionsin the gases' are highly favorable to avoiding contamination or FIZ- jury to the product or to to the heating surfaces, or to the metal surfaces of pots, as in annealing processes. In previous practice there has always been considerable loss or damage in these varions directions, due to irregular operation and 'iilso due to varying temperaportion from the bath coupled with the.

the furnace walls or as in steamboilers,

tunes and varying chemical conditions in the slag on the surfaces of refractories,

and especially in many cases due to excess oxygen owing to unbalanced combustion conditions. This oxygen not only combines or burns out a considerable part of themetal,

but is also an active agent which, it may be said, is seeking to destroy whatever chemical elements it may encounter, and in the smelting of metals, for example, thc oxidizing of metals may even be a more serious loss than that encountered in the above described melting operations. Without further explanm tion, it is complete chemical control of gases and slag conditions inthe furnace as established in my present invention is of the greatest importance;

I have shown in the present installation somewhat. diagrammatically, a preferred type of burner mixer, the general construction of which is disclosed in U. S. Patent No. 1,855,444, granted October-12,1920, and the preferred specific construction in. my cobelieved that the attainment of It.

, pending application,Serial'No. 299,833, filed May 26, 1919, now Patent No, 1,474,613. In

this type of burner, thepowde'red coalis de-. livered from a hopper 23tl1rough a worm screw easing into a mining cylinder 25 to which air under pressure is delivered through a supply pipe 26. The fuel under pressure mixed with-air is then conducted through a connection 27 to the mixer proper 28 to which additional air under pressure is supplied through a pipe 29. q

After being thormxghly mixed with air in this mixer, the fuel is delivered through. a tapered downwardly inclined conduit 31 into the forward end of the furnace chamber. The shape of this conduit causes the mixture I of fuel and air to be delivered in a turbulent;

swirling condition and since the mixer is of,

the low velocity type, this turbulent supply of fuel continues after ignition in a swirling .mass'through the furnace in a -condition which is-most favorableto the transference of its heat tothe charge in the furnace.

It'will be noted that the delivery of the combustible mixture is in 'a downwardly oblique direction, but the vertical direction of discharge may be varied'and controlled by means of a controlling plate ordamper 32 located in the nozzle 33.0f the burner. This"controllingplate,which may be made of sheet iron or suitable material, is pivotally supported upon a transverse bearing rod 34 which may be equipped at one end with a handle 35 or other means by which the position of the plate may be adjusted to any point intermediate the full open position shown'in fulllinesin Fig. 3 and the full closed position shown in dotted linesin aid figure.

Any intermediate position bet een the two positions shown will vary the direction of' discharge ofthe combustible mixture spthat it may be diverteddownwardly upon the floor 12 or -over the edgezof the bridge wall into the bath or into the bath at 'a point more. remote .from the bridge wall depending. on

the position. of the plate which is, of course,

adjusted 'to metthe requirements of. the

most instances be suificient charge and the condition under which the furnace is being used. For purposes of bolding the plate in anyadjusted position, I have. provided a sector member 36 having provi- "sion'sffor cooperativelyengaging the handle 35to hold it inanyfiiadjustedposition.-

l \Vhileone or a series; of bur11ers for-.f supplying fuel to the furnace may be employed, depending on the size of the furnace and the size of the burners, I have/shown in the pres entinstance; as will apparent from Fig. 2 two burners having theirdelivery nozzles located in spaced relation in the front.

wall 5. 1 p

The manipulation of the plate $2 will in to cause the de- --livery of the fuel at the requisite'point in the'bath, and the sloping top wall 7, together in the furnace chamber.

the heat units fro the charge and insures a practically complete withthe location and size of the outlet opening and the proper proportion of the stack and proper regulation of the fuel pressure causesthe flame to hug the bath closely throughout its length to most effectively heat the bath. In some instances, however, it. maybe preferable to;employ a top blast to augment the'downward delivery of the flame and I have therefore made provision in my improvement for the employment of such a blast when required. With this en'dgin view, the top Wallof the chamber may be depressed, as indicatedat 37, directly above or just rearwardly of the bridge wall 11 and v this depressed portion is equipped. with a plurality of downwardly directed blast nozzles 37 through which air under pressure is delivered from the transversely extending supply pipe 38. As previously stated, the top blast may be used if desired, but I have found that with iny method, the flame is sufliciently controlled and depressed and a high degree of efliciency is obtained without the employment of this blast, which has heretofore been considered indispensable, but has i K I nevertheless been a source of trouble in cansing oxidization of metal and interfering with proper control of the relative proportions of fuel and air. troubles is one of the marked advantages resulting from my present invention.

The elimination of these The rear end -of the furnace chamber is connected with a properly constructed stack 39 through which the products of combustion are discharged and communication is we established betweenlthe chamber and this stackpreferably immediately above the reari bridge wall 41 through an opening 42 which 1s proportioned according to 'size'of the furnace and the pressure under which the fuel 5 is delivered by the burner nozzles.

It has heretofore been the practice to em-. ploy a large communicating opening between the furnace chamber and the stack and to induce strong draft through this opening. result hasbeen that an enormous quantity of the. heat units of '"the combustible fuel has "been carried from the furnace and delivered' to thestack so as to-be lost for effective use.

1 3 y employing a low pressure at the fuel dehvery nozzles, the veloci y of the flame through the furnace is reduced so that its heat' 2 units may be transferred-to the charge.- This desirableefl'ect isfurther increased by pro- {port-ioning the connectingopening 42 to the stack and proportioning the stack itself so that astatic pressure is normally maintained This pressure? is dist nguished from a partial vacuum which has heretoforebeeirmaintained'in these fur- 12h naces, greatly facilitates the transference .of

the burning mixture :to

combustion of the fuel particles before they leave the chamber,

w he. res lt theat r;

of the furnace.

ifany, unburned fuel particles are wasted through the stack. Obviously, this feature fireatly enhances the efliciency of the furnace.

y regulation of the feed pressure, this static ,pressure maybe controlled and may be reduced to. a balanced draft or even to an appreciable u draft if desired.

It wil be obvious from theforegoing that in my improved method, thecomminuted, pulverized, atomized, or diffused fuel or fuels, severally. ortwo' or. more collectively, thoroughl mixed with suflicient air tosupp t comp in 'an obliquely downward direction ,and at low velocity that ignition and combustion take place close tot e deliver ,nozzle. It

shouldbe observed, however, t at the igniv ete combustion, is delivered in a tur-' bulent, swirling condition'into the furnace establishes two very desirable factors viz: 1.) complete chemically balanced combustion, and (2) inert gases which cannot do damage to product, furnaces, or heating sur- I faces. 1

Furthermore, a considerable proportion of the slag resulting from flame formation isimmediately deposited in the front pocket beneath the burner so that it does not mingle with the bath slag, and consequently, not .only ,thequantity of bath slag is reduced,

materially but the character of the slag 1s improved. The flame directed against the.

bath being ina turbulent and swirl1ng'condition tends, by reason of its point and dlrection' v vof delivery into the bath, and by reason of the flat character of the bath' floor, to pene trate. the .charge of loosely piled solid mation and combustion takes place close to the terial upon the hearth and'to travel along nozzle, irrespective of the angular position at which the nozzle is directed intothe fur- .'nace, and it is not the purpose to limit or restrict this invention in respect of the vari- 1 'ous control features to the combination feature of discharge in an .angular direction. Indeed, it is obvious that the complete perfect combustion is due to other conditions than the angularity, among these controlling factors being the control ofquantity and delivery of the evenly diffused mixture. of the fuel or. fuels in a turbulent condition. This is irrespective of the angular-ityof delivery with reference, to the horizontal axis Theangui'ar delivery is of special value in certain particular processes and is an added feature of advantage in the present invention, wherein the process or operatin conditions make its use advisable.

5o ture is, one of the vital improved features in is known as the resent invention. .a c emical compound immediately after being released from a former existing combination is in.- a highly active state which nascent and, therefore, most and complete recombinasusceptible to quick tion. In this case it is desired to bind the fuel constituents existing as, nascent hydrocarbons with the oxygen'in chemically balanced proportions, so that the resulting. new

that is the combustion gases, are

mp u s,

possible inert and, hence-inactive as to any chemical reaction while passing through the was hati This invention,

1 furnace inv contact with product, walls or therefore,

-of fuel and air and the It 1s well known that the hearth beneath the'charge so as to expedite the melting of the same. en the charge is surface and because of the fact that the melted, the flame impingesupon its bath is shallow, and of substantially uniform depth, it becomes quickly and uniformly heated and pouring without prolonged operation of the furnace, vas is required where the bath floor is deepl depressed so'that the molten metal accumui ates in a des pool. The ra idity of the heating in the urnace' is furt er augmented by the fact that the flame is caused to closely hug thebath throughout its length. This condition is produced not only by the direction, velocity and manner of the fuel delivery into the furnace, but also by the fact that the rear portions-of the furnace chamber in which the 'products of combustion are coolest is of progressivel reduced cross sectional area by reason of t roof, andfurthermore by the fact that the rear bridge wall is low and the communicat-. ing-opening with the stack is also low and is so proportioned as is also the stack, that by regulationof the fuel pressure, a slight static pressure may be maintained in the furnace, which is conducive toward com .tion of the most effective trans delivery. with the pulverized fuelitself of sufli'cient' air to support complete combustion. Consequently, an auxiliarysupply'of combustion a1r through the walls of the fur- I n'ace is unnecessary, and

of auxiliary cold air into the furnace is not reduced to a condition suitable for e downwardly sloping lete combus rence of heat Y t0 the charge. My method contemplates the in fact, the delivery a c desirable since it tends to reduce the temperature thereof. The top blast may therefore be and preferably is entirely eliminated, but

since some types of work seem to be slightly more effectively-performed by additionally depressing the flame through the instrumen-i tality of, a top blast, I have illustrated the application of a top blast to the furnaceherer in shown.

By the practice of the method above'dia Q fined in t efollowing claims. 7

closed, Ianinot only able to reduce the :fuel consumption {and to expedite the melting, heatin and pouring of the, char e, but also to .em oy -in the composition oft e charge a 'duction of m'etalof a redetermined 0 ar-.

acts; and composition.

1 A nace charge. In practice, I

"betoolow inone bee-regulated to hold the molten mass in staconsi erably greater proportion-of scrap iron than has heretofore been possible in the rohis feature is manifestly of significant importance since the proportion .of ig iron required may be diminished, there '37 decreasing the cost of the furhave found that with my novel method, I am able to utilize, instead of over 60%.expensive'pig iron, high in silicon and. manganese to of scrap which is low in silicon and manganese,-as has heretofore been customary, considerably more scrap than ig iron in a -charge,-and still obtain a resu tant malleable iron of superior quality containing the reqnisitepredetermined pro rtions of silicon, manga- 'nese, carbon an sulphur manganese. I

Should a test of the molten metal show it to ingredient the flame may tus quo with respect to the other ingredients while the requisite quantity of thelow ingre-' dient is added to the charge to produce the desired analysis. My invention therefore, af

. ,workof the furnace and the cost of'repairsis serviceable for prolonged I It is believed that my invention, of its inherent advantages, ja nd appreciated from further description, and while and described a ,the me fords, a 'wide range offlexibility in its operation aud t-he results which may be secured thereby." v v Furthermore, by reason of the elimination fromth'e-bath of alar'ge portion of the slag character of the bath slag, asthe result of improved gas conditions f and by improving the in the furnace, thedeterioration of the brick is materially decreased,

roportionately diering the furnace periods of time.

and many minished, aswell as ren the fore oing. without have shown for cariging it into e'flect, obviously, both t od andapparatus' may be varied .within considerable limits without departing from the scopeof the invention vas defI claim: i.-

IZ 1; Ida furnace, the combination of a heat-a tion and and means for deliveringa combustible mix-i ing ing chamber. provided with a hearth, sa d hearth being substantially level from end to end, arched slightly'upwardly in cross secadapted to contain a shallow bath,

are oi eomminuted fuel and air to said cham- 2; In a furnace, the combination of a heat chamber, '-comp'risinga hearth substanproviding a relatially'level from end to end :ji gly shallowbath, an outlet stack'comm'u i5 jjca'ting with said chamber, and a rear bridge.

will beunderstood" pre rred methodandmeans b wall between saidbath and stack, the I communion-tin her and stack lation-to the stack and thefeed pressure as to maintain a bar. I v r 3. In a furnace,'the combination of a heatstatic pressure insaid 'cham Q ning between said chaming proportioned with re- .in chamber, comprising a hearth substantia 1y level from end to end, an outlet stack? communicating" with said chamber, and a rear bridge wall between said bath and "said r stack; the communicating opening between I said chamber and stack being so to Ortioned with relation to the stack and the eedjpressure as to maintain a static-pressure in said chamber. I

.4. In a furnace, the combination of a heating chamber, comprising a-hearth substan-' tially level from end to end and adapted to receive a charge'to be heated, an outlet stack communicating with said chamber, and a rear'bridge wall between said bath and said I stack; the communicating opening between I said chamber and stack being so with relation to the stack and t e eed pressure asto maintain a static pressure in said chamber. f

5. In a furnace, the combination of a heating chamber, comprisin a shallow bath, an out at stack and a rear wall between-said chamber and stack' ropro or'tioned a hearth providing" I vided witha restricted opening adapt to maintain a static pressure in saidchamber. 6.121 a furnace-,the combination of'a heat ing chamber, including a hearth, means for chamber, an outlet stack, and 'a -rear;wall between said chamber and with a restricted opening adapted to main, tain a static pressurein said chamber? I I 7.;-In a furnace, the combination of a heating chamber, an outlet stack communicating said chamber, sa' chamber and .stack'so proportioned as to maintain a static r. 8.113 a furnace,thecombii'iationof a heating chamber, means for'feedin a air and fuel into'saidbhampressure in the said chamso proportioned new ure in the said chamber.

stack provided I I I I o ceding a mixture ofair and fuel into said and an opening between r I mixture of a 1' II v an voutlet "stack communicating" with said chamber, and i an opening between said chamber and stack tain a. static pres- 9. In a'fur'nace, the combination are iia i' ing chamber,

air and fuel into said chamber, meana for controlling the fuel and ai'r fed, an outlet means for; feeding .a mixtureof stack communicating with saidcharnber, and

an opening between said chamber and stack so proportlonedas to maintain a static pres-c sure in the said chamber. f; f I

' 10. A furnace, comprising ac'hamber hav; ing front and-rear walls, a hearth, abridge wall spaced from s ai'df I I I clined lipwardly from said -bfiage "wa11; m:

' taining 11 static pressure in ward said front wall and provided adjacent the front wall. with a pocket, and means for delivering a mixture of air and comminuted fuel to said .chamber directly over said pocket.

11. In a furnace, the combination with a chamber provided with a health and a floor sloping upwardl' and forwardly of said hearth, of means for delivering to said chamher at low velocity a mixture of comminuted fuel and air in a turbulent condition, and a pocket in said floor immediately beneath the point of entrance of the mixture into the chamber adaptedto receive the slag produced at the point of flame formation in'said mixture. I v

12. In a furnace, 'the combination of a. chamber comprising front and rear walls,

a hearth, means formaintaining a static pressure in the chamber, means for supplying to said chamber in turbulent condition a mixture of comminuted fuel and'air, means for varying the direction of discharge to said mixture into said chamber, and a slag pocket "disposed adjacent to and beneath the point of entrance of said mixture into'the chamber. 13. The herein described method, which cons'istsin deliveringto a furnace containing a charge ofmaterial to be treated, a supply of plulverized fuel thoroughly mixed with sufcient air to support complete combustion, causing the delivery of such fuel in aturbu-- lent condition and 1n a downwardly inclined direction, separating a portion of the slag resulting from flame formation'and collecting the same at a point remote from the'bath, causing the flame to hug the bath, and maintaining a static pressure in the heating chamber of the furnace.

consists in delivering to-a furnace a supply of fuel thoroughl mixed with'sufficient air to support comp ete combustion, said fuel being)atomized and diffused and delivered in a tur ulent condition, separating a portion of the sla resulting from combustion at the; place flame formation and maintaining astatic pressure in the heating chamber of the furnace. 3 5 The herein described method, which consists in delivering to a furnace a supply of fuel thoroughly mixed with sufficient air to;

' support com lete combustion, said fuel being atomized an diffused and delivered in a turbulent condition at lowiv'elocit separating a portion of the sla resulting fiom combustion' at the point of ame formation and mainthe heating chamber of the furnace. 1 k

" m 16. Theyherein described method, which consists indelivering to 'a furnace a supply of f fuel thoroughly mixed with sufficient air to support complete co'mbustiom'said fuel being atomized and diffused and delivered in a i turbulentcondition withcontrolledjvelocity,

14.'The herein described method, which b separatin a portion of the slag resulting from com ustlon at the point of flame formation and maintaining a static pressurein the heating chamber of the furnace.

- 17. The herein described method which consists in delivering to a furnace controlled total quantities and controlled relative proportions of air and fuel in a mixture, the said fuel being atomized and diffused and in free suspension, said mixture being in a turbulent condition with controlled velocity, separating a portion of the slag resulting from combustion at or near the point of flame formation in the said mixture, and maintaining and controlling a static pressure in the heat- ,80

ing chamber. a

18. The herein described method, which consists in delivering in turbulent condition to a chamber containing a charge of material" to be treated,v a supply of pulverized combustible material at low velocity 'thoroughly mixed with suflicient air to. support combustion, causing'the flame from said combustible material to travel in proximity to v the bottom of the char e, and regulating the 0 pressure within said c amber. Y I 19. The herein described method, which consists in delivering in turbulent condition to a furnace chamber, a supply of pulverized combustible material at low velocity thoroughly mixed with suflicient airrto support combustion, and regulating the pressure Within said chamber. p 20. r The herein described method, which consists in delivering in turbulent condition to a furnace chamber, a suppl of pulverized combustible material thoroug ly mixed with suflicient air to support combustion and regulating the static pressure within said cham- 21. The herein described method, which consists in delivering controlled quantities and controlled relative proportions of fuel in a turbulent condition to a furnace chamber, I said fuel beingin free suspension at low-ivelocity, the said'fuel being thoroughly mixed with suflicient air; to support combustion, and regulating the static pressure within said chamber. a q

'22. The "herein described method which consists in producinga 'malleable -metalo predeterminedcompositionby charging a fur nace with pig iron and scrap, the quantity of scrap being in excess of t e pig iron, and reducing the chargefto malleable iron of a predetermined com ition. by subjecting the charge to-a flameo such quality and intensityas will reduce the charge without losing an appreciable portion o the silicon and manganese contained in the charge. j v

' 23. The herein described meth d which consists in producing amalleable metal' of predetermined composition by charging a urnace with pig iron and scrap, the quantity of scrap being n excess. of. the pig ironand I I I reducing-the charge to malleable iron of a 7 predetermined composition by subjecti'ngthe duced.

charge to a flame of such quality and inten-' sity as will reduce the charge and at the same time maintain control of the carbon, silicon and manganese contained'in the charge.'

24. The herein described method which c'onsistsin producing a malleable metal of predetermined composition by charging a furnace with pig iron and scrap, the quantity of scrap being in excess of the pig iron, and reducing the charge to malleable iron' of a predetermined composition by subject ing'the charge to a flame of such qualit and intensity as will reduce the charge withoutso alterlng' the content of carbon, silicon and manganese and other ingredients, as to impair the quality. of the malleable iron pro- 25. The herein described method =whiih consist in producing a malleable metal f predetermined composition by charging a scrapiron 'and subjecting to the act onof a flame of suc intensity as will reduce the charge without produces flame which will have the desired; I

' flame both as to-mtens tyand chemical comurnace with pig iron and scrap, the quantity of scrap being in excess of the "pig iron, and reducing the charge to malleable iron of a predetermined composition by subjecting the charge to a flame of suchv uality and intensity as will reduce the c ar ge without losing such portion of. the carbon, silicon,

manganese, and other ingredients contained.

in the charge as will impair-the quality of the finished product. I

26. The method which consists in deposit-. ing in a furnace a charge of metal consisting of less than 50% pig iron and more than said charge quality and appreciable loss 'of: silicon and manganese thereby producing a high grademalleable' iron. I a

27. The method of treating metals which-1 consists in subjectinga charge of'metal in a furnace to the action of a'burning turbulent mixture ,of pulverized fuel and air .deliv ered at low velocity, and controlling'the relative proportions of fuel and air so. as to effect u nthe 'cha r o 28. e method of treating. metals which consists in subjecting a charge of metal in' a furnace to the action of a burning turbulent mixtureof pulverizedfuel and air de-- livered at low velocity, controllingthe veiocit of the ,niixture delivered, and con- 5 trolling the relative proportions of fuel and air so as to produce a flamewhich will have I ll thequantity relative proportions of ,fuel

the desired efiect upon'the charge.

29. The method. of treating metals,1which' consists in subje cti nga charge of metal in a. furnace to the action of a burning'..tur- 'bulent mixture of'pulverized fuel and air delivered. at. low velocity, and controlling furnace to the action of aburnin and air so as to produce a flame which will have the desired effect upon thechar'ge.

a furnace to the action of a burning turbulent mixture of pulverized fuel and air delivered at low velocity, regulating the relative proportions of fuel and air and maintaining a static pressure in the furnace.

' 32. The method of firing which consists in delivering to a furnace a burning'turbuentmixture. or mixtures of fuel and air,

said fuel being diffused in a1r', said fuel being delivered at low velocity, regulating the rel- I ative proportions of fuel'and air and maintaining a static pressurein the'furnace.

33 The method of treatipg'metals', which consists in subjecting a charge of metal in a furnace to the action of a burning turbulent mixture of pulverized fuel and air, and. regulat' the static pressure 'in the furnace.

. '34l lhe method of treating metals, which consists in subjecting a charge of metal. in a furnace to the action f a burning turbulent mixture ofpulverized, fuel and air, and regulating the proportions of fuel and airto a neutral flame at 35. The method of treating metals, which consists in subjecting a charge of metal in a g turbulent mixture of pulverized fuel and air, and regulating the flame to cause the production in the metal when poured of the requisite propplrtlilons of carbon, silicon, manganese and s p v in to a furnacea burning turbulent mixture thereby produce an oxidizing, a reducing or no 36. The method which'consists in deliver a o pulverized fueland air and regulating the I position of'the' gases so as, to control the "cheinical reaction of the on any but in'g surfaces that ma be exposed to the' turbulent notion of v 2 consistsin placinga charge of material in. the suhi s M0 the? action 'of a burning garb- 15 mixture "of pulv r zedfuel. gnaw-an ulating the asf-Jflii' ihtensitjz 17,9os i i 13 chemicalcomposition of its constituent gases so 'as to have the desired chemical effect on the material beingtreated.

39. The combination with a heating cham- ,ber provided with a hearth constructed to contain a shallow bath, ofmeans for delivering at relatively low velocity to said chamher a swirling turbulent combustible mixtui'e comprising air with fuel uniformly lo diffused therethrough.

40. The combination with a heating chamber provided with a hearth constructed to contain a shallow bath, of means for delivering at relatively low velocity to said cham- 15 ber a swirling turbulent combustible mix-- ture com rismg air with fuel uniformly difi'used t erethrough and means including an adjustable damper for controlling the delivery of said mixture. T

2o 41. The herein disclosedmethod comprising, producing outside 'a-combustion chamber a combustible mixture of fuel uniformly diflused throughout suificient air to support complete combustion of said fuel, delivering said mixture in a turbulent condition at low velocity to the combustion chamber, and regulating the combustion of said mixture within a range including oxidizing and re-i ducing frames. 1 v V 1 an In witness of the foregoing I aflix my sig-.

nature. I .MILTON W. ARROWOOD.

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