US1194151A - doherty - Google Patents

Description

H. L. DOHERTY.

METHOD OF HEATING.

APPLICATION HLED JAN. 9. 1912.

1.1 M 151. Patented Aug. 8, 1916.

2 SHEETSSHEET I.

H. L. DOHERH.

METHOD OF HEATING.

APPLICATION FILED JAN. 9, 1912.

1,191,151.. Fzii-fehtedAug. 8,1916.

2 SHEETS-SHEET 2- 27 3:28 29} l I 85 Q 'l 25' 42 4a I I 4| 1 n I 45* A 7 u we Mo: 811 1 atlozueu HENRY Il- DOHERTY, OF NEW YORK, N. Y.

METHOD or HEATING.

Specification of Letters Patent.

Patented Aug. 8, 1916.

Original application filed November 15,- 1911, Serial No. 660,450. Divided and this application filed January 9, 1912. Serial No. 670,839.

' ing.

The object of my invention is to supply to the art animproved method of heating which will permit of the easy regulation of the temperature of the heating oven and the furnace, promote the rapidity of the heat transfer from the heating gases to the objects to be heated, by insuring a high vel o city of circulation of the heating gases and at'the same time secure a high degree of recuperation of the heat of the rejected Brieflystated, my invention comprisesthe maintaining of a continuous circulation of gases from a furnace to a heating oven and ack againto the furnacethe return cir culation to the furnace consisting of a balanced stream of completely burned and incompletely burned gas with the continuous re ection of completely burned gases from the circulation to an air recuperator to heat the air used in the combustion, the volume of the gases so rejected being that corresponding approximately to the increment in volume of the gaseous body due to the air used in the combustion.

In the accompanying drawings I have shown an embodiment of my invention. as applied to the heating of retorts for the carbonization of coal.

In the drawings, Figure 1 is a vertical longitudinal cross-section through the furnace and heating chamber or oven of the apparatus on the line 'IJ of Fig. 4., Fig. 2 is a horizontal cross-section of the same on the line A-B of Fig. 1. Fig. 3 is a horizontal cross-section on the line CD. of Fig. 1. Fig.4 is a horizontal cross-section on the line EF of Fig. 1, and Fig. 5 is a vertical cross-section through one of the recuperators on the line G--I-I of Fig. 2.

Fig. 6 is an elevation of the furnace end of two umts of the apparatus.

The ap lication is a division of my application er. No. 660,450, filed Nov. 15th, 1911, which describes my method of heating in detail without claimin the same.

My present invention is in the nature of an lmprovement upon the invention which is described and claimed in my copending appllcation Ser. No. 603093, filed Jan. 17th, 1911, in which the gas generator of a heatmg apparatus is run on a current of flue gases, alone, without the addition of extraneous air. In this present invention I have improved the process of said application by substituting a volume of IHCOIII- pletely burned gases as the principal vehicle for carrying heat to the generator in place of using an excess of flue gases (comprlsing combustion gases, alone, or combustion gases and air) as the heat carrier anddepending upon regulation of the velocity of passage of the gases through the fuel bed to control the temperature of the bed and the quantity of combustible gas made.

In the drawings, 1 refers to the furnace.

2 is a heating chamber or oven of the apparatus (in this case a retort oven).

. 4 and 4: refer to the two sections of the outer walls of the furnace which incloses the heat interchanger 21.

v 5 is a gasifying chamber of the furnace.

6 is a preheating chamber.

7 is the cooler.

8 is the fuel charging opening of the furnace.

9 indicates a movable fuel hopper below the cooler 7 of the furnace.

10 is the discharge door of the furnace, which is preferably opened and closed by a mechanical arrangement.

11 is the elevator which elevates the raw coal to the fuel bin 61.

12 is an ash and coal conveyor which, as shown, serves at the same time to convey away the fuel and ash withdrawn from the cooler 7 and to convey to the fuel bed atthetop of the furnace the mixture of raw fuel and carbonized fuel which constitutes the charge.

13 is a gas off-take from the top of the preheating chamber 6 of the furnace through which gas is drawn by the blower 14 and forced through the pipe 15 into the lower part of the cooler '7.

As shown in the drawings, the walls of the furnace at the gasifying chamber 5 are offset to permit the fuel in the same to form two free surfaces on its angle of repose. The upper of these spaces, which is designated 16 in the drawings, provides aspace for the distribution of theprimary current to the furnace, while the space 17 furnishes a free space over the fuel through which is drawn off the gases formed by the combustion taking place in the gasifying cham-- ber 5.

18, 18, etc., designate the nostrils through which the gas formed in the furnace is withdrawn from the space'17. These nostrils communicate with the upcast flue 19 of the heat interchanger 21.

20 is a diagram separating the upcast flue 19 from the downcast flue 24 of the heat interchanger21, while 23 isa blower which draws the gas from 19 through the aperture 22 in the diaphragm 20 and forces it through the downcast flue 24 and through the connecting flues to the lower combustion fiues 36v of the furnace. ,'The passages 25 connect the upper part of flue 19 with the stacks 26 of the recuperators.

26' indicates the dampers-on the stacks 26..

27 27 are valves on the connections 25.

28 1s a connection from the gas ofl'-take 1 3 to the atmosphere, and is provided with'a valve, 29.

30 is a valve on 13 between the atmospheric connection 28 and the preheater 6.

31 and 31 refer to gas off-take fiues which communicate with either side of the lower part of the downcast flue 24 of the heat in-- terchanger 21.

32 and 32 are dampers on 31 and 31, respectively.

33 and 33 indicate, respectively, connections from the off-take fiues 31 and 31' to the cross-flue 34.

35,- 35, etc., are gas nostrils permitting the discharge of the gas which enters flue 34 from both ends into the lower combustion flues 36 of the retort oven 2.

36, 36 etc., refer to'a second set of combustion flues which are located immediately above the flue 36.,

36" refers to a set of combustion fiues above 36, While 36 refers to the uppermost set of combustion fiues ofthe retort oven.

37 are the combustion gas off-take nostrils which establish communication between the uppermost combustion flues 36 and the cross-flue 38.

39 and 39 are fiues establishing communication between the cross-flue 38 and the combustion gas flue '40of the irespective recuperators 41 and 41'.

42 and 42' are the air dampers on the respective air recuperators, while 43 indicates the air fiues of these recuperators.

44 and44' indicate, respectively, the off take air passages from the flues 43 of the re spective recuperators.

45 and 45 are. connectionsfroni 44 to the gas flue 36", while 48 refers to the nostrils which establish communication between the lowermost cross-flue for air 46 and the lowest set of combustion fiues 36 of the retort oven. 1

49 and 49' are dampers on, respectively, 45 and 45.-

50 is the b'aflie which separates the lowest group of combustion flues 36 from the second tier of combustion flues 36.

50 refers to the baflle separating fiues 36 from'flues 36", while 50 refers to the set of baflies separating 36" from the uppermost combustion fiues 36".

51, 51, etc., refer to the gas ofi-take nostrils from the fiues 36 tothecross-flue for gas 52. I

. 53, 53' are connections from the ends of the cross flue 52 to the cross-flue 54 which conducts the gas to the primary inlet flue 55.

58', 58' are dampers on the fiues 53 and 53, operated by rods 537,53".

56 1s a flue establishing communication between the uppermost cross-flue for the combustion gases 38 to the primary air inlet flue 55.

56" is a damper on 56 which is operated by the rod 57.

- In starting operations either coarse cinder through the atmospheric connection 28 of p the pipe 13 by blower 14 which forces the air through the pipe 15 into the lower part of the cooler. At this .stage of operations the valve 29 on 28 is of course opened and the valve 30 between 29 andthe preheating chamber 6 is closed. When the kindling has been pro erly ignited, fuel is charged onto it from t e charging opening 8. vWhen this fuel has been pro erly ignited more fuel is gradually charge until a mass of ignited fuel has been built up through theshaft to the point of offset of the walls of the shaft; or, in other words, until the. asifying chamber 5 has been completely fil ed with a mass of ignited fuel. Fuel is now rapidly charged until the preheating chamber 6 has been completely filled.

During the'preliminary combustion the gases may be permitted to escape directly to the atmosphere through the charging opening 8 at the top of the preheating chamber 6. When the fuel bed in the furnace chamber 5 is in proper condition to establish normal operating conditions, the valve 29 on 28 is closed and valve on 13 is opened. The blower 14 now draws a part of the gases from the gasifying chamber 5 through the cold fuel occupying the preheating chamber 6 and forces the cold gases into the bottom of the cooler 7 through which they pass in contact with the fuel mass occupying the same and join the main draft current of the furnace.

As hereinafter explained, in this embodiment of my invention, I move the fuel mass through the furnace at a rate greater than the rate of combustion of the fuel therein. The material occupying the chamber 7 therefore consists of a mixture of fuel and ash. The cooled gases entering the lower part of 7 and passing up through the fuel therein, of course, take up heat from the material, being themselves raised in temperature. By properly proportioning the volume of the I cooling gases to the rate at which the material is drawn from 7 the mixture of fuel and ash may be cooled down to the temperature desired before it is withdrawn from 7 The normal gas circulation thus established in the apparatus under normal operating conditions is as follows: The gases drawn off from the gasifying chamber 5 pass ofl from the off-take space 17 through the gas nostrils 18 into the upcast flue 19 of heat interchanger 21 under the inductive action of the fan 23 and are forced down through the flue 24, thence through the flues 31 and 31' which communicate with either side of the bottom of the downcast flue 24 to the flues 33 and 33', respectively, which discharge into the cross-flue 34. From 34 the gases pass through the gas nostrils 35 into the lowermost set of combustion flues 36 of the furnace, where they are burned by air admitted from either or both the air nostrils 48 or 48.

The function of the heat interchanger 21 is the cooling of the gases approaching the enter the lower end of the flue 19. Discharging from the periphery of the fan, however, they are impelled down through the outer flue 24 and thus subjected to reheating by the hotter gases passing in the reverse direction through the flue 19. It is plain that a heat differential that has once been established between the two streams of gas will thereafter he maintained as long as no extraneous heating or cooling action is introduced. The amount of this heat differential will, in the absence of any extraneous influence, depend entirely upon the superficial area and heat transmitting power of the diaphragm 20 and upon the velocity of the draft. In any case, however, within certain limits, should the size of the flues. 19 and 24 be too small (or, rather, should the heat transferring surface of the diaphragm be too small) the normal differential may be increased by admitting to the upper part of flue 19 a portion of the relatively cool gases of complete combustion which are drawn from the stacks 26 through the flues 25. The volume ofth'bombustion gases which are thus drawn down into the flue 19 I regulate by means of the valves 27 on the connections 25. The addition of this relatively cold gas of course lowers the temperature of the gas mixture reaching the fan and thus permits the establishment of the required temperature difl'erence between the two currents. In this case the differential is further increased as the gas flows through the downcast flue 24 by the increased heat capacity of the current discharging from the fan due to the volume of gas which has been added at the top of flue 19. There is obviously no actual loss of heat from the gas save the small loss by conduction and radiation to the setting but simply a transfer of heat from the current approaching the fan to the current discharging from the same. By these features, therefore, I am able to move the hot gases with ordinary fan blowers with substantially no sacrifice of the heat of the gases. This-method of moving hot gases by ordi nary fan blowers I will claim specifically in another application.

In normal working only sufficient air is admitted through the nostrils 48 to burn somewhat more than one-half of the combustible constituents in the gases introduced through the gas nostrils 35, while at the air nostrils 48' sufficient air is introduced to insure the complete combustion of all the residual combustible constituents entering the flues 36" which were unburned by the air introduced through the nostrils 48. The combustion gases flow through the flues 36, 36, 36 and 36 in a serpentine course along the walls of the retorts 3. Discharg- &

combustion gases enter the cross-flue 38. In 38, the combustion gases divide into two separate streams, one stream flowing to the recuperators while the second stream joins the primary draft of the furnace 1. The. first of these streams is drawn off through.

the flues 39 and 39', respectively, in two sub-divisions to the combustion gas flues 40 of the recupera- tors 41 and 41. Passing through the combustion gas flues 40 of the recuperators the gases discharge to the atmosphere through the stacks 26. The second stream flows through the flue 56 to the primary draft inlet 55 of the furnace. The distribution of the combustion gases between these two streams is controlled by the dampers 56' and 26 on 56 and 26, respectively.

The air for supporting the combustion 1n the combustion flues 36 and 36 enters the recuperators 41 and 41' through the an dampers 42 and 42, respectively. Passing through the air flues 43 the air is heated by the heat of the hot combustion gases which are at the same time flowing in the opposite direction through the flues 40 of the recuperators. The heated air discharges from the flues 43 through the flues 44 and 44, which are connected, respectively, with the air flues of the respective recuperators 41 and 41. From 43 the hot air is distributedto either one or both of the cross-flues 46 and 46, respectively. By means of the dampers 49 and 49, respectively, on-the connections 45 and 45 between the cross flue 46 and the downcast air flues 44 and 44, the'distribution of the air between the cross-flues 46 and 46 may be regulated as desired. Since the inductive action on the stacks and the fans 23 is exerted to a greater extent on the higher combustion flues 36 than on the lower combustion-flues 36, the air will then by preference flow -to through the cross-flue 46 and thence into the combustion flues 36", when the connection to 46 is free for the passage ofthe air owing to the opening of the dampers on the flues 45 and 45. By partially closing these' dampers the flow of air may be diverted in part to the lower cross-flue 46, from which 50 it enters the lower combustion flues 36; or by entirely closing the dampers the entire volume of the secondary air may be forced to take the path through the flues 46 into the lower combustion flues. In operating the apparatus it is my object, however, to secure a diffused combustion of the gases through the four sets of combustion flues. To this end,.I so regulate the distribution of the air between the nostrils 48 and 48' as to main- 6 0 tain a fairly uniform combustion throughout the flues.

In the operation of the furnace, I support the combustion of the fuel in the gasifying chamber 5 by supplying thereto a highly c5 heated primary current. composed of parthe gas to introduce air through the nostrils '48 in excess of the volume which ,is required to completely burn the residual combustibleconstituents of the gas by the time it has reached the flues 38, there is usually more or less free oxygen in the combustion gases which are drawn from the flue 38. On the other hand, the gases withdrawn 5 from the combustion flues 36 usually contain a greater or less proportion of unburned gases. Since the two streams, however, are at a high temperature when they mingle in the primary inlet flue 55, any free oxygen in the'portion of the primary current thus drawn from the flue 38 will combine with some of the incompletely burned gas in the portion of the draft which is drawn from the flue 36. Since this limited combustion takes place, however, in close proximity to the gasifying chamber 5 practically all of the heat thus generated is available in the fuel bed in 5 for assisting in the dissociation of the carbon dioxid of the primary draft. In describing the method of carrying out the combustion in the chamber 5, therefore,

I will'assume that the two sub-divisions of the primary draft enter the gasifying cham her 5 without mingling; or, in other words, that such combustion as takes place between the two sub-divisions of the primary current will take place in the space 16 above the fuel bed. Since the carbon dioxid or water vapor which has been formed by this limited combustion between the two sub-divisions of the primary draft current is reduced to carbon monoxid in passing through the fuel bed by reaction wlth the carbon of the same at the expense of the heat which was formed in its combustion, this limited combustion exerts practically no effect on the tem erature conditions prevailing in the gasifying chamber 5.

Both the portion of the primary current drawn off from 36 and the portion drawn off from the flue 38 are at a comparatively high temperature-from 2200 to 2500 F. While the initial temperature of the primarycurrent is somewhat reduced by the time it 12 reaches the furnace, still it should enter the fuel bed in the latter at atemperature above 2000 F., and usually at about 2200 F. In passin through the fuel bed in 5 more or less 0 the carbon dioxid of the primary 1 0 wearer Supplied by the sensible heat carried by the primary current at its entrance into the fuel bed. Since, bymy method of combustion,

proximating 1800 F. and above, rapidly as the temperature falls.

.inore or less reaction takes lace even down to and below 1300 F. It is evident, therefore, that by regulating thequantity of CO the water vapor present in the gases is always exclusively the vapor derived from the air and the fuel, its action in the furnace is relatively unimportant. "We only. need, therefore,.to consider the action of the car- I 'the carbon of the fuel at temperatures apbon dioxid-" This reacts energetically with but less There is carried into the furnace and the quantity of heat accompanying the CO by regulating the draw of gases from 36' and 38, respectively, I am able to maintain the fuel bed in.

thechamber 5 of furnace 1 at any temperathe fiues from the nostrils 48', as already exture desired within the working range. ,In order to secure-complete combustion of 'thefgases in the combustion flues it is necessary to introduce a slight excess of air into plained. The portion of the primary draft drawn off from cross-flue 38 through flue 56, therefore, will usually contain a small proportion of free oxygen. As explained, this will burn any excess of unburned gases in theportion of the primary current which is drawn from the flues 36', but in its effect on the fuel in chamber 5 it will act as though it thence onto the conveyer 12, by which it is were. introduced separately; or, in other words, there will be a portion of thefuel burned in 5 to CO equivalentjto the. free; 1 oxygen in the main branch of the current. The result'is that there -wi 1 be derimary veloped inthe fuel itself an excess of heat which will go tohelp support the dissociation of the CO of'the accompanyin .draft current. Under normal work ng con itions, however, this excess of airis kept as low as possible. This portion of thedraft'current, therefore, has a strong netendothermic or heat absorbing effect. The portion of the primary draft withdrawn from 36,'on the other hand, carries under normal conditions more than enough sensible heat to dissociate its own ()0 .by. reaction '(a) and has thus a net exothermic or heating effect on the fuel I bed. By varying the actual volume of the primary current and properly proportioning the two separate streams of gas making of the screening device- 60.

and coke is discharge up the same I am able to control the temperature of the fuel bed in 5 and also the quantity ofcombustible gas generated. The volume of the gases drawn through the fuel bedis, of course, controlled by the speed of the fan 23 and the various dampers on the several conduits. This also serves to control the proportion of 00 of the primary draft which isdissociated, since by varying the volume of the primary draft I vary the speed at which the gas is passed through the fuel bed and therefore the time it is in contact with the hot fuel.

Contrary to the practice in producer firing, I do not aim to correct the maximum possible proportion of the CO of the draft current in the furnace. On the contrary, in normal working, the gases are circulated I through the fuel at such a velocity that the dissociation is usually less than 50 per cent. of the total CO that passes through the fuel. I am thus able to easily maintain the ternperature of the fuel at a point that insures I is burned, however,the proportion of ash in the mass is prevented from increasing to the degree at which it would offer objectional obstruction to the draft passing through the furnace. This movement of the fuel is effected by -withdrawing portions of the mass (which has been cooled in the manner described above) from the chamber 7, by

lowering the. door 10 by means of the mechanism provided for that purpose. The cold mixture of fuel, and ash falls intothe movable hopper 9, and is gradually fed from elevated and delivered into the; hopper 59 P ssin through 60, the fine'ash is separated from the mixture and is rejected while 'the screened coke discharges into the bin 61.

The properquantity of raw coal to form a fuel mixture of the composition desired is, at the same time, discharged into 61 by the elevator 11; By openin the gate 62 the coal from 61 onto the return 'flight of the conveyer 12, and transported to the charging doors 8 of the several furnaces as required. Coke from someother source may, of course, be substituted for the carbonized material withdrawn from the furnace itself. It is advantageous, however,

where a coking coal is economically available for use in the furnace, to simply make use of r the coke produced by the furnace itself.

The purpose. of thus adding the coke to its maintenance in an active gas making the charge is that I may utilize as fuel very inferior grades of bituminous coal which usually have more or less tendency to cake,

or an' actualcaking coal. By mixing the coked fuel with the bituminous coal I prevent the formation'of the fuel aggregates or clinkers in the combustion region of the furbodies the method of passing the fuel through the furnace at a rate greater than its rate'of combustion is designed, in the same manner, to preventthe formation of clinkers in the ash of the fuel. In preventing the formation of clinkers the coke acts in a manner similar to its action in preventing the formation of aggregates in the unburned fuel mass. It serves to prevent the ash formed from agglomerating, as it would in a combustion method in which the fuel is completely burned. Bythis method, therefore, I am able 'to burn fuels which have an easily fusible ash without the formation of clinkers and which, when burned entirely to ash, readily clinker.

In ordinary conditions of working I consider it advantageous to draw the fuel through at such a rate that. the mixture withdrawn at the bottom of cooler 7 will-not contain more than 10 per cent. of free ash.

In fact, I prefer, usually, to work at such a rate that the ash-fuel mixture will contain closer to 5 per cent. than 10 per cent. of ash. The most advantageous rate of passing the fuel through the furnace, however, will vary with almost every variety of fuel which is used. I cannot, therefore, prescribe any d'efinite rate which will be the most advantageous under all conditions, but this must be fixed by experiment with any particular fuel.

As pi'eviously stated, before withdrawing the mixture of fuel and ash from the cooler 7 it is cooled by the as which has been forced into. the cooler by the blower 14. As described, this cold gas is derived by drawing off from the cold fuel at the top of the preheating chamber of the furnace a portion of the gas produced in the combus tion region of the furnace. While this method of operation possesses marked advantages, Ido not limit myself to the use of a coohng current secured in this way. In- "stead of cold gases withdrawn from the furnace, it is possible to use either steam alone, a mixture of combustion gases and steam, or

furnace to the retort oven and back again to the furnace-the return circulation to the furnace consisting of a balanced stream of -completely and incompletely burned gases. A volume of completely burned gases corresponding to the air introduced into the combustion fines of the retort oven is continuously ejected from the circulation and sent through the air recuperator. By thus circulating a large volume of gases at high velocity through'the combustion fines and the fuel bed of the furnace, as well as by distributing the combustion through the fines, I am able to secure a proper heating of the retorts without the necessity of maintaining an excessively high temperature in the combustionflues, since, as is well known, the velocity of heat transmission through the retort walls varies with the velocity of the heating gases along the surface of the walls. No increased loss of heat in the rejected gases'is occasion'ed, since the volume rejected from the circulationcorresponds to the volume 'of air used, and the two currents in the recuperators are thus about balanced in their ther mal capacities.

Having described my invention, what I claim is:

1. The method of heating, which comprises, withdrawing hot heatinggases from a heating chamber before said gases have been entirely consumed, withdrawing completely burned gases from said chamber and mixing said incompletely burned and said completely burned gases, the said gases being withdrawn at such temperatures that. the resulting mixture will carry "sufficient heat to support the reaction of a regulated proportion of its combustion products with carbon, passing said hot gaseous mixture through a bed'of ignited fuel to convert a regulated portion ofthe combustion products of said mixtureinto combustible gases by reaction with the fuel of said fuel bed, conducting said gases after their passage through said fuel bed into said heating'chamber, and adding)air to said gases in said heating chamber to urn the combustible constituents of said gases.

2. The method of heating which comprises, igniting gases containin a propor tion of combustible constituents in a heating chamber, withdrawing from said chamber a portion of said gases before thesame ha e been completely consumed at a temperature at which said gases will carry sufficient sensible heat tosupport the reaction of a regulated proportion of their combustion products with carbon, passing the said gases through a fuel bed, whereby said regulated portion of the combustion products carried by the said gases is caused to react with the fuel in said fuel bed to regenerate combusti-. ble gases at the expense of the sensible heat of the said gases, and returning the effluent gases from said fuel. bed to' said heating chamber.

3. The method of heating which comprises, passing a mixture of combustible and combustion gases at a comparatively high temperature first through a fuel bed to generate a portion of combustible gases by reaction between the combustion products in the said gases and a portion of the fuel in said bed at the expense of the sensible heat of said gases and then through a heating chamber, adding air to the said gases in said chamber to support the combustion of the combustible constituents of said gases, and repassing a portion of the gases from such combustion before said gases have been entirely consumed through said fuel bed, whereby more or less of the fuel of the said fuel bed is burned by reaction with the products of the combustion carried into the said 7 fuel bed by the said stream of mixed gases.

'tible gases by reaction with the carbon of said fuel at the expense of the sensible heat of said withdrawn gases, returning the effluent gases from said fuel bed to said heating chamber, and passing through a recuperator to heat the air for sustaining the said combustion in said heating chamber, the portion of the completely burned eflluent gases from said heating chamber that is not passed through said fuel bed.

5. The method of heating which comprises, burning combustible constituents of a stream of circulating gases in a heating chamber by successive additions of heated air, whereby the said. stream, of circulating gases is subjected to gradual combustion,

withdrawing from said stream of gases a.

volume of completely burned gases equivalent to the volume of air added to said gaseous stream in said heating chamber, conducting said volume of completely burned gases through a recuperator to heat the air introduced into said heating chamber, withdrawing incompletely burned gases from said gaseous stream, passing the said incompletely burned gases together with the residue of said completely burned gases in admixture through a bed of carbonaceous fuel to convert a portion of the products of complete combustion in said gaseous mixture into combustible gas, and returning the efliuent gases from said fuel bed to said heating chamber.

6. The rocess of heating which comprises, maintaining a circulation of heating gases through a fuel bed and a heating chamber, sustaining the combustion of combustible constituents of said circulating gases in said heating chamber by successive additions thereto of heated air, withdrawing from said gaseous circulation a volume of completely burned gases approximately equivalent to the volume of air added to said gases in said heating chamber, passing the said completely burned gases through a recuperator to heat said air, withdrawing from said gaseous circulation a volume of said gases before the same have been completely burned, and repassing said incompletely burned gases and the remainder of said circulating gases through said fuel bed to generate combustible gas by reaction between completely burned constituents of said circulating gases and said carbonaceous fuel.

7. The process of heating which comprises, maintaining a circulation of heating gases through a fuel bed and a heating chamber, sustaining the combustion of combustible constituents of said circulating gases in said heating chamber by successive additions thereto of heated air, withdrawing from said gaseous circulation a volume of completely burned gases approximately equivalent to the volume of air added to said gases in said heating chamber, passing the said completely burned gases through a recuperator to heat said air, withdrawing from said gaseous circulation a volume of said gases before the same have been completely burned, and repassing said incompletely burned gases and the remainder of said circulating gases through said fuel bed to generate combustible gas by reaction between completely burned constituents of said circulating gases and said can bonaceous fuel at the expense of the sensible heat of said circulating gases.

8. The process of heating which comprises,'maintaining acirculation of heating gases through a fuel bed and a heating chamber, sustaining the combustion of combustible constituents of said circulating gases in said heating chamber by successive additions thereto of heated air, withdraw ing from said gaseous circulation a volume of completely burned gases approximately volume of said gases before the same havebeen completely bui ned, and repassing said incompletely burned. .gases and the remainder of said circulating gases through said fuel bed to generate combustible gas by reaction betweenthe completely burned constituents of said circulating gases and said carbonaceous fuel at the expense of the sensible heat of the volume of said circulating gases Withdrawn, the said circulating ases being withdrawn from said heating 0 amher at temperatures at which they bear sufficient available sensible heat to sustain the generation of the quantity of combustible gas desired.

9. The process of heating which comprises, passing through a fuel bed a balanced draft current of completely burned and incompletely burned gases in admixture, at a temperature above the temperature of the fuel in same, the proportion of said incompletely burned gases being regulated to that volume required to carry sufficient sensible heat, in addition to the heat carried by said completely burned gases, to maintain the heat of said fuel bed, whereby a portion of the carbon dioxid of the said draft current is caused to react with a portion of the carbon of the said fuel bed at the expense of the sensible heat of the said balanced draft current, and passmg the resulting gases througha heating chamber.

10. The process of heating which comprises, passing into an ignited fuel bed a regulated draft current of completely and incompletely burned gases in admixture and at a temperature above the temperature of the said fuel bed, the proportion of said incompletely burned gases in said admixture being regulated to that volume required to carry sufficient sensible heat, in addition to the heat carried by said completely burned gases, to maintain the temperature of said fuel bed to generate combustible gas from a portion of said gases of complete combustion, passing the said draft current through said fuel bed at a velocity such as will restrain the com bustible gases generated to the proportion desired, conducting the resulting gas to a heating chamber and subjecting combustible constituents of said gases in said chamber to a prolonged combustion by the successive addition thereto of a plurality of portions of air.

11. The process of heating which comprises, passing ,a balanced draft current of completely burned and incompletely burned gases through a fuel bed, the said incompletely burned gases being at a temperature such that their sensible heat above the temheating chamber, the volume of the said second portion of air being that required to completely burn the residual combustible gases from the first combustion,dividing the completely burned gases from thesecond combustion into two streams, passing one of said streams to a recuperator to heat a fresh portion of air, withdrawing the remainder of the gases of complete combustion from the said heating chamber and introducing them together withv the said portion of incom-.

pletely burned gases withdrawn from the said heating chamber into the said fuel bed to form afresh volume of combustible gas at the expense of the heat carried by the said gases out of said heating chamber.

12. The process of heating which comprises, subjecting a body of gas containing combustible constituents to successive combustion steps-by successive additions thereto of air, withdrawing hot gases comprising substantial proportions of unburned combustible gas from one of the earlier of said combustion steps, andpassing the hot gases withdrawn through a bed ofhot carbonaceous fuel to bring about reaction betweena portion of the carbon dioxid of the gases withdrawn and said hot fuel, the said gases being withdrawn from said combustion at a temperature such that their sensible heat will maintain the temperature of said fuel during said reaction.

'13. The process of heating which com-.

bustible gas and said completely burned.

gases through a bed of ignited fuel to generate fresh portions of combustible gases from a portion of said completely burned gases, the proportion of unconsumed combustible gases withdrawn being regulated to that volume required to carry sufficient heat, in addition to the heat carried by said completely burned gases to maintain the said meager fuel at a reactive temperature, withdrawing the gases from said fuel bed and returning the same to said combustion steps.

14. The process of heating which comprises, introducing a draft current containing a proportion of combustible constituents into a heating chamber, adding to the said draft current a volume of preheated air suflicient to burn a portion of the combustible constituents of the said draft current, withdrawing a portion ofthe resulting incompletely burned gas from the said heating chamber, burning the residual combustible constituents in said gas by the addition to the said draft current of a second volume of preheated air suflicient to completely bum said combustible constituents; withdrawing from the said completely burned gases a portion of the same, combining the incompletely burned gases and the completely burned gases withdrawn from the said heating chamber, and passing the combined current through a fuel bed toburn a portion of the fuel of the same and to generate a fresh volume of combustible gas, the volume of the the fuel bed will be suficient to support the pombustion of the desired proportion of the fuel of the said bed by reaction with a portion of the carbon dioxid of the said draft current, and passing the gases withdrawn from the said fuel bed back to the said heating chamber to heat the same.

Signed at New York city, in the county of New York and State of New York, this 8th day of Jan, A. D. 1912.

HENRY L. DOHEETY.

Witnesses:

H. A. MACKENZIE, JOHN J. MoCLone.

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