US2571749A - Fluid heating - Google Patents

Description

Oct 16, 1951 c. NORTON, JR

FLUID HEATING 5 Sheets-Sheet 1 Filed July 4, 1944 INVENTOR. CYmr/e: L Norton] A TI'ORNE Y Get. 16, 1951 c. L. NGRTON, JR 9 9 FLUID HEATING Filed July 4, 1944' 5 Sheets-Sheet 2 huvmwummnnl lw [liIHHH-HhLh I I Y m M Q m m 5. r mv C Oct. 16, 1951 c. NORTON, JR ,7

FLUID HEATING Filed July 4, 1944 5 Sheets-Sheet 3 [Z/EL N i I 5/75 I 86 5 1 IN VEN TOR.

Char/e5 L. Norton, Jr:

Oct. 16, 1951 c. NORTON, JR

FLUID HEATING 5 Sheets-Sheet 4 Filed July 4, 1944 q M Q H H w f n, .l a ma l A H m w QQ .IQQ a s9 W I L m r. m U m Mm Y B m NR &

ATTORNEY Oct. 16, 1951 C. L. NORTON, JR

FLUID HEATING 5 Sheet s-Sheet 5 Filed July 4, 1944 INVENTOR Char/e51. Norton Jr ATTORNEY Patented a. 16, 1951 FLUID HEATING Charles L. Norton, Jr., New York, N. Y., assignor to The Babcock & Wilcox Company, Rockleigh, N. J a corporation of New Jersey Application July 4, 1944, Serial No. 543,442

12 Claims.

My present invention relates to the construction and operation of fluid heating apparatus of the general type disclosed in a copending application of E. G. Bailey et al., Serial No. 502,580, filed September 16, 1943, which has issued as Patent No. 2,447,306, in which a fluent mass or column of refractory heat transfer material is substantially continuously circulated downwardtransfer materials other than pebbles can be used therein.

Apparatus of the character described has been i found especially suitable for continuously heat- I ing fluids to final temperatures considerably higher than the fluid heating temperatures for which ordinary steel or even alloy steel tubes can be safely and economically used. In such apparatus the final temperature of the heated fluid is mainly dependent upon the maximum temperature of the heat transfer material in the cooling zone and the time of heat transfer contact of the fluid'to be heated with the heat transfer material. High capacity operation depends upon the maximum flow velocity permissible of the fluid to be heated through the mass of heat transfer material without excessive lifting and carryover of the heat transfer material with the outgoing heated fluid. The heat transfer material discharging from the cooling zone should be at a temperature at which it is not subjected to a thermal shock sufilcientto crack or rupture the pieces of heat transfer material and at which the heat transfer material can be safely handled by metallic feeding and elevating means without causing binding and seizing of such metal parts due to excessive thermal expansion. I counterflow of the fluid to be heated in the cooling chamber is therefore normally required to insure a suitable discharge temperature of the heat transfer material and a high thermal efllciency for the apparatus and process.

The general object of my invention is the pro vision of an improved method and apparatus of A low entrance temperature and the character described which are further characterized by the continuous heating of a fluid at relatively high capacities to a substantially uniform final temperature in a range, the upper limit of which is substantially higher than obtainable in a single unit of similar, size of the type and operating as disclosed in said prior copending application. A further and more specific object is the provision of a method and apparatus of the character described in which a fluid combustion constituent .is heated in the cooling zone to a high temperature and utilized in controlled amounts for the generation of heating gases for. the heating zone, whereby the temperature of the heat transfer material discharged from the heating zone and of the heated fluid discharged from the cooling zone can be progressively increased in a cyclic eflect to final temperatures limited only by the allowable use temperatures of the refractories in the apparatus. A further specific object is the provision of a pebble heater construction and operation of the character described in which any fluid flow restriction between the heating and cooling sections can be substantially decreased and the necessity of control mechanism responsive to the pressure differential between the sections eliminated. A further object is the provision of an improved method and apparatus for the high temperature heating of material in an oxidizing atmosphere. A further object is the provision of an improved method and apparatus for the high temperature heating of material in a reducing atmosphere.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described preferred embodiments of my invention.

Of the drawings:

Fig. l is a partly diagrammatic sectional elevation of a pebble heater unit embodying the invention;

Figs. 2 and 3 are horizontal sections taken on thelines 22 and 33 respectively of Fig. 1;

Fig.4 is a view similar to Fig. 1 of a modified pebble heater construction;

Fig. 5 is afragmentary horizontal section taken on the line 5-5 of Fig. 4;

Fig. 6 is a partly diagrammatic sectional elevation of material heating apparatus incorporating a modified pebble heater construction;

Fig. 7 is a view similar to Fig. 6 of a second form of material heating apparatus;

Fig. 8 is a vertical section taken on the line 8-8 of Fig. 9;

Fig. 9 is a vertical section taken on the line 39 of Fig. 8; and

Fig. 10 is a view similar to Fig. 6 of another heating apparatus arrangement.

In the fluid heater construction illustrated in Figs. 1-3 the pebble heater unit comprises a vertically elongated gas-tight metal casing ID of circular cross-section lined with an annular wall of suitable high temperature refractory H. The casing interior is divided into anupper chamber 12 and a lower chamber l3 connected by a vertically elongated uninterrupted throat passage M of substantially reduced horizontal crosssection. The chambers 12 and i3 and'throat M are normally filled to the level indicated with a continuous fluent mass or column of refractory heat transfer material i5 of the character hereinafter described.

A heat transfer material inlet pipe I6 is connected to the upper part of chamber l2, and a heating gas outlet pipe I! controlled by a valve I8 opens from the top of the chamber. A substantially annular combustion chamber is formed by an enlarged section of the casing I0 around the lower part of the upper chamber I2. As shown in Figs. 1 and 2, the combustion chamber has an inner annular bridge wall 25, over which the heating gases generated in the combustion chamber flow. One or more ports 21 are tangentially arranged at spaced points around the chamber 25 for the entrance of a combustible fluid mixture under a positive pressure. The heating gases generated flow over the bridge wall 26 and through a circular series of inwardly tapering gas inlet ports 32 formed between wedge shaped firebrick 33 and opening into the lower part of the chamber [2. The chamber l2 has an inverted conical bottom section extending from the ports 32 to the throat passage [4.

The lower chamber I3 is of substantially uniform circular cross-section from its upper end to a downwardly tapered lower end portion defined by an inverted frusto-conical metal screen 35. The corresponding portion 36 of the casing I0 is also downwardly tapered to a discharge opening 31 below the cone 35. The spaced cones 35 and 36 define an annular fluid inlet chamber 38 to which one or more fluid supply pipes 39 having regulating valves 34 are connected for the admission of a fluid to be heated under a positive pressure. The upper end of the chamber 13 has a flat refractory arch 40 through which a circular series of radial outlet slots 4! open into an annular outlet duct 42 around the throat H. One orv more refractory-lined fluid discharge pipes 43 are connected to the duct 42.

A relatively wide range of refractory materials can be used as the heat transfer material IS, the material chosen depending upon the operating conditions to be maintained. In general the material selected should have a high stren th and hardness, substantial resistance to thermal shock. and a high softeningtemperature. Such materials may be ceramic refractories or corrosion resistant alloys and alloy steels, in small pieces of regular or irregular sha e. such as sized grog, pebbles or crystals or crystalline aggregates of mullite, silicon carbide, alumina, or other refractories. As disclosed in said prim 99-:

kaolin and a binder, fired to 2850-3000 F. have been successfully used. The pellets are made of a diameter small enough to minimize thermal shocks and impact stresses, and to provide a large amount of heat transfer surface, and yet large enough to withstand the desired fluid velocities through the pellet mass without lifting. Pebble diameters and have been found suitable.

The downward flow of the fluent mass of heat transfer pellets through the upper chamber l2, throat l4, and lower chamber l3 can be controlled by a suitable discharge mechanism receiving pellets from the pellet outlet 31 while maintaining a fluid seal on the lower end of the chamber [3. A variable speed rotary pocket feeder 45, as

shown in said prior application, is located in a discharge pipe leading to a box 5| at the foot of an elevator casing 52. The box 5| has openings for the addition or removal of pellets from the system. The elevator casing 52 is of gastight construction and encloses an endless bucket elevator 53 driven by an electric motor 5|.

contact with the descending pellets, which reach I their maximum temperature approximately at the level of the heating gas inlets. The heated pellets continue their descent through the throatpassage ll into the lower chamber I3. The fluid to be heated, such as air, steam, or other gas or vapor, enters at a predetermined temperature and under a positive pressure through the supply pipe 39 and inlet chamber 38 and flows through the screen 35 into the lower end of the pellet mass in the chamber l3, passing upwardly through the interstices in the mass in intimate counterflow contact with the descending pellets. The entering fluid is preferably at a relatively low temperature, such as room temperature, to insure a low discharge temperature for the pellets at the outlet 31. The fluid to be heated reaches its maximum temperature at the top of the chamber i3, from which it passes out through the slots 4| and duct 42 to the discharge pipe 43. As disclosed in said prior pending application, mixing of the fluid atmospheres in the chambers 12 and 13 can be avoided by maintaining predetermined relative pressure conditions in the two chambers to provide a zero fluid flow through the throat H. Pressure taps 51 and 58 are conventional y indicated for transmitting the pressure difierential across the throat I throu h T5 pebble heater unit described is further construc- -view of the substantially greater combustion air requirements, it is more efficient to. preheat the combustion air than the fuel. With air supplied under pressure through the inlet pipe .39, the heated air outlet pipes 43 are each connected to a refractory-lined air casing 41 surrounding a water-cooled fluid fuel burner nozzle 48 and opening to the corresponding combustion chamber port 21. A valve-controlled fuel line 49 supplies a suitable fluid fuel to the nozzle 48. The

' fluid fuel and high temperature air streams intimately mix and a rapid and intense combustion takes place in the combustion chamber 25 andthe high temperature heating gases generated flow over the bridge wall- 28 and into the upper chamber II. A branch outlet pipe 59 controlled by a valve 60 connects the fluid outlet pipe 43 to a point of use of high temperature air. With this piping arrangement all or a portion of the air heated in the lower chamber can be supplied directly to the combustion chamber at a high temperature, and the remaining portion of the heated air bled off through the branch 59 to another point of use.

In starting up the unit after a normal shutdown, fluid fuel is supplied through the pipe 49 and air through the pipe 39 in a predetermined ratio. Combustion takes place in the chamber 25 and the heating gases generated heat the descending pellets which enter the chamber IS. The combustion air is then preheated on passing through the chamber l3 and its sensible heat correspondingly increases the combustion chamber temperature. An increase in pellet temperature results, causing a further increase in the air outlet temperature. This cycle building-up of the temperatures in the combustion chamber and of the heated air continues in gradually decreasing increments. The temperatures in the unit increase so rapidly that a reduction in the fuel sup-' ply is usually necessary to avoid destruction of the refractory lining or fusing of the pellets. The desired maximum pellet temperature is maintained by establishing a rate of supply of the combustion constituents at a fuel-air ratio at which the heat input will provide the desired pellet temperature and balance the heat losses of the unit and the sensible heat in the air bled oil through the branch pipe 59. As the air supply to the pipe 39 will normally be about 200-500% of the theoretical combustion air requirements to maintain a high thermal efliciency and a low pebble discharge temperature, there will be a substantial amount of high temperature air available for bleeding on for process use. A further control to prevent excessive temperature conditions in the unit is obtained by the provision of a regulable supply of low temperature air under pressure through an auxiliary supply pipe ii to the burner air casing 41. With this heater construction and method of operation, combustion chamber temperatures in excess of il0 F. and heated fluid outlet temperatures over 3000 6 F. can be attained. In view of the low exit temperatures of the pellets and heating gases, the fuel input is effectively used and a high thermal efliciency results.

Apparatus of the character described can also be used for the preheating of a gaseous fuel to a high temperature and utilization of the high temperature fuel partly for combustion in the chamber 25 and partly for process use. In such operation, for example, a predetermined amount of natural gas at a low-temperature and under pressure is introduced into the fluid inlet chamber 38 and passes upwardly through the downwardly moving high temperature pellet mass in the lower chamber l3. As the fuel gas reaches a cracking temperature in the pellet mass, a certain amount of thermal cracking will occur, causing the deposition of carbon on the descending pellets. The main constituent of thehigh temperature gases leaving the chamber I! through the outlet pipe 43 will then be hydrogen. For such operation, the connections of the pipes 43 and 49 to the burner casing 41 will be transposed and air at room temperature and under pressure is supplied through the pipe 49 and the highly preheated fuel gas through the pipe 43. Intense combustion takes place in the combustion chamber 25 and the gaseous products pass upwardly through the descending pellet mass in the chamber H. A secondary combustion effect is obtained in the chamber II by the burning of! of the deposited-carbon on the pellets, furnishing a substantial part of the heat requirements of the unit. The cyclic temperature boosting action previously described takes place at starting-up, but to a somewhat lesser degree with this mode of operation. The amount of fuel gas supplied to the inlet chamber 38 is proportioned to permit the bleeding-off of a portion of the high temperature outlet gases through the pipe 59 for process use.

While the construction and operations described provide for the continuous heating of one combustion constitutent to a substantially uniform high temperature and the utilization of the preheated constituent for combustion purposes for heating the pellets in the upper chamber permits the cyclic temperature-boosting effect to take place, resulting in combustion chamber temperatures in the range. of 3500-4000 F., even higher combustion chamber temperatures are obtainable if the second combustion constituent is also preheated before being introduced into the combustion chamber 25. For example, with air introduced into and preheated in the chamberv l3 as previously described, the fuel supply to the pipe 49 can be a high temperature gaseous fuel bled-oil? from a second pebble heater unit of simi lar construction in which the fuel constituent is preheated in the lower chamber. Combustion chamber temperatures well in excess of 4000 F. are obtainable with this mode of operation and are limited mainly by the use temperature limits of the refractory materials used in the pellets and chamber walls.

- In the construction shown in Figs. 1-3, the presence of the small diameter throat passage 14 connecting the upper and lower chambers, even though unobstructed and downwardly flaring, provides one potential source of operating trouble. The substantial reduction in flow area however greatly aids in minimizing fluid flow between the chambers. With the described high temperatures of the heating gases entering the upper chamber, some of the pellets may be fused into clusters due to a local hot spot or lower fusing temperature of some of the pellets, and such pellet clusters would tend to obstruct the flow of material through the throat passage. Furthermore,

control of the relative gas pressure conditions in the chambers I2 and I3 by the measurement of the pressure difierential across the throat passage is rendered difiicult it either the pressure. tap 51 or 88 is obstructed or closed. The modified construction shown in Figs. 4 and 5 eliminates the need for both of these features of the Figs. 1-3; construction. In the modified construction the upper chamber I2 and lower chamber I3 are connected by an unobstructed passage ll of smaller cross-sectional flow area than the chambers I2 and I3 but much greater than the flow area of the throat passage I 4 of Figs. 1-3. The passage I4 is proportioned to provide a flow area providing substantially the same mass flow conditions as in the chamber I3 under the designed normal operating condition, thereby maintaining a uniform pressure gradient throughout the chamber I3 and passage I4. In the construction shown the passage I4 has a diameter approximately one-half the diameter of the chambers I2 and I3. In this construction the portion of the cooling chamber I3 below the passage I4 is flared outwardly as indicated at 55 to provide an inclined bottom for radially arranged outlet slots 66 into which the mass of pellets extends. At the outlet side of the slots 88 is a common annular duct 81 containing an annular bridge wall 68. 'An outlet pipe 69 containing a control valve I0 connects the duct 61 to another point of use.

For extreme temperatures a refractory orifice of the desired flow area is substituted for the valve ll.

With this heater construction, one of the fluid combustion constituents is introduced through the pipe 39 and inlet chamber 38 and passes 40 upwardly through the screen 35 and mass of descending pellets in the chamber I3. The preheated fluid divides at the upper end of the chamber I3, with one portion passing directly upwardly through the passage I4 into the cham- 5 fluid combustion constituent flowing upwardly so through the passage it mixes in the lower part of the chamber I2 with a complementary fluid combustlonponstituent supplied thereto through a series of inclined burner orts I2, and a rapid and intense combustion takes place in the lower part of the pellet mass in the chamber l2. The gaseous products 0t combustion pass upwardly through the remainder of the pellet mass and out through the gas outlet I I. The second fluid combustion constituent is sup ed under pressure to the ports 12 through pipes I3 connected to a common annular duct I4 and a valve-controlled supply pipe, 15. An auxiliary compressed air inlet I6 is connected to the duct I4 for supplying part 01' the combustion air requirements when air is preheated in the chamber I3 and it is desired to reduce temperature.

The various modes oi operation described in connection with the Figs. 1-3 construction are equally applicable in the modified construction shown in Figs. 4 and 5. For example, air at room temperature and under pressure can be sunplied to the pipe 39 and preheated to a high temperature in the chamber I3. A portion of the highly preheated air can be withdrawn for process use through the duct 69, while the remaining portion flows upwardly through the passage I4 and mixes with the entering liquid or gaseous fuel streams from the pipes 13 with resulting high temperature combustion. With the described proportions of the passage I4 and chamber I3 and proper adjustment of the valves I8 and ID, about one-quarter oi the preheated constituent from chamber I3 will flow through the passage I4 at thedesigned normal operating condition and with substantially equal mass flows through the chamber and passage. The cyclic temperature-boosting eflect takes place at starting-up as previously described, permitting the maintenance of temperature conditions of the same order as those previously described for the heater unit.

In Figs. 6-9 I have illustrated pebble heater units of the general type illustrated in Figs. 4 and 5 in special industrial applications for which they are particularly suitable. In the Fig. 6 as- 7 sembly, the pebble heater unit is used for supplying high temperature air to an industrial furnace requiring a high temperature oxidizing atmosphere, such as a continuous tunnel kiln 88 used for theglaze-firing of ceramic War of approximately 1800" F. Heretofore this operation has usually been carried out by passing through the kiln a mixture of high temperature products of combustion and sufiicient air to render the kiln atmosphere oxidizing at the desired temperature. This method of glaze-firing is not wholly satisfactorybecause of the disadvantageous efiect certain' constituents of the com-bustion products. such as sulphur, have on the glaze. Muflie kilns and electrically heated kilns have also been used.

' but are more expensive to operate. My invention makes available a continuous supply of air at a uniform high temperature and uncontaminated by products of combustion. As shown in Fig. 6, air at room temperatur and under pressure is introduced into the pebble heater unit through the pipe 39, preheated in the lower chamber I3. and the preheated air divided at the upper end of the chamber I3, one portion passing upwardly through the passage I 4' for combustion in the chamber I2, and the remaining portion passing.

through the duct 69 to the tunnel ki n 80. The war is moved thorugh the kiln on cars 8| and the high temperature air is distributed along the length of the kiln through branch ducts 82 discharging into one end of longitudinally extending side chambers 83 and through a perforated wall 84. The air is withdrawn from the kiln through ducts 85 opening to the kiln at points spaced beyond the opposite end of the chambers 83. With this firing method the ware is contacted only by clean high temperature air, resulting in the highest quailty laze colors.

The air leaving the kiln is still at a substantial temperature, and the efliciency of the apparatus is substantially increased by the recirculation of the air through the pebble heaterchamber I3. For this purpose the ducts 85 are connected to a duct 86 leading to a recirculatin fan 81. A heat exchanger 88 is advantageously incorporated in the duct 86 to reduce the temperature of the air entering the fan 81. This heat exchange is advantageously used for preheating the fuel gas in the pipe 15. The discharge duct 89 from the fan 81 is connected to a fluid inlet chamber 90 intermediate the height of the chamber I3 and preferably at a level at which the pellets in the chamber I3 are at least at the same temperature as the recirculated air, whereby the pellets are cooled to the desired low temperature before leaving the chamber I3, and the recirculated air is reheated to the desired temperature before leaving the chamber I3. With this construction and arrangement of the parts and a substantially constant amount of air circulated through the tunnel kiln, the amount of low temperature air supplied through the pipe 39 will correspond to the amount required for combustion purposes in the chamber I2 plus any air losses in the system.-

The arrangement illustrated has a high overall thermal efficiency and effects the glaze-firing of ceramic ware under the most advantageous conditions.

The apparatus shown in Figs. 7-9 illustrates my invention as utilized with an industrial furnace requiring a high temperature reducin atmosphere, such as is desirable for the bright annealing of copper sheets. The pebble heater illustrated is generally similar to that shown in Fig. 6 except that a fuel gas is introduced through the pipe 39 and heated to a temperature within the thermal cracking range, as previously described. The portion of the high temperature gases leaving the chamber I3 through the pipe 92 is circulated through periodic annealing furnaces 93. Each furnace 93 has a stationary bottom section 94 and a removable top section 95, the joints therebetween being fluid sealed by a sand or fluid seal 96. Th bottom section 94 has a gas inlet conduit 91 and a pair of outlet conduits 98 connected by valve-controlled branch pipes 99 and I to the supply pipe 92 and a return pipe IIII respectively. A bleed-off connection I02 regulates the amount of gas in the return line. As shown in Figs. 8 and 9, each furnace has a refractory platform I03 on which a charge of sheets I04 is placed by raising the top section by corner hooks, I95 and inserting the charge. The top section is restored to its operating position and the furnace atmosphere purged by admitting a flow of natural gas through a separate supply line I01 to the inlet branch 99. The furnace is vented to atmosphere during this period through vent pipes I06. The high temperature reducing gas is then introduced from the supply pipe 92 through branch 99 and inlet conduit 91, and flow throughout the furnace, passing out through wall passages I08 to the conduits 98 and return pipe IN. A series of furnaces 93 are connected to the pipes 92 and IIII, and periodically operated to provide a continuous demand on the pebble heater unit.

The sensible heat in the reducing gases in the return line IN is partly utilized in preheating the air for combustion in a heat exchanger 0, the preheated air being introduced into the lower part of the chamber I2. The reducing gases leaving the heat exchanger I III pass to a recirculating fan 81 and are discharged through a valve controlled conduit 89 to a fluid inlet 90 intermediate the height of the chamber I3, in the same manner as the recirculated air in Fig. 6. The thermal efficiency of the apparatus is thus maintained at a high value and the amount of fuel gas introduced through the pipe 39 at a minimum. The sheet annealing operation with a high temperature substantially pure reducing atmosphere minimizes discoloring'of the sheets and permits simplification of th annealing furnace construction and mode of operation.

While in the constructions illustrated in Figs. 1-5, the fluid combustion constituent preheated in the lower chamber is divided into two portions, one of which is supplied for combustion combustion constituent with a complementary combustion constituent and burning of the mixture, either in a process furnace or a combustion chamber communicating with the upper chamber, for heating the heat transfer material in the upper chamber to the desired temperature.

In Fig. 10 I have illustrated an installation of this type in which a pebble heater unit of the general character shown in Figs. 1-3 is arranged to deliver all of the high temperature fluid combustion constituent from the outlet pipe 43 to a fluid fuel burner I20 mounted in a material melting pot I2I. As shown, air is preheated in the lower chamber I3 of the pebble heater unit and a liquid or gaseous fuel supplied to the burner I29 through a supply pipe I23. Extremely high temperatures are maintained in the melting pot under these conditions and the heating gases generated exit through the gas outlet pipe I24 leading to an annular chamber I26 surrounding and opening to the lower part of the upper chamber I2. The heating gases flow upwardly through the pellet mass to the gas outlet I'I as previously described.

I claim:

1. Heating apparatus comprising walls defining a vertically elongated chamber having a heating gas outlet and an inlet for solid material at its upper end and a solid material outlet at its lower end, means for moving a fluent mass of incombustible solid material downwardly through said chamber to said solid material outlet, and means for heating said solid material while in the upper part of said chamber including means for supplying a, combustion constituent directly to said chamber at a point intermediate the height thereof, and means for supplying a complementary fluid combustion constituent to said chamber at a point substantially below the point of admission of the first combustion constituent and in a. position to flow upwardly therein to the point of admission of the first combustion constituent in heat absorbing relation with the descending solid material.

2. A fluid heater comprising walls defining a vertically elongated chamber having a heating gas outletand an inlet for solid material at its upper end and a solid material outlet at its lower end. means for moving a fluent mass of incombustible solid material moving downwardly through said chamber to said solid material outlet, means for heating said solid material while in the upper part of said chamber including means for supplying a combustion constituent directly to said chamber at a point intermediate the height thereof, means for supplying a complementary fluid combustion constituent to said chamber at a point substantially below the point of admission of the first combustion constituent and in a position to flow upwardly therein to the point of admission of the first combustion constituent in heat absorbing relation with the descending solid material, means for withdrawing a regulable portion of said complementary fluid combustion constituent from said chamber, and external elevating means for returning solid material from said solid material outlet to said solid material inlet.

3. Heating apparatus comprising in combination a fluid heating unit including upper and chamber, means for passing a fluid combustion tion a fluid heating unit including upper and lower chambers, an unobstructed passage of reduced cross-section connecting said chambers, a continuous fluent mass of solid heat transfer material in said chambers and passage, means for effecting a flow of said heat transfer material downwardly through said chambers and passage and returning said material to said upper chamber, means for passing a fluid combustion constituent upwardly through said lower chamber in heat absorbing relation with the heat transfer material therein, means for supplying a complementary combustion constituent to said upper chamber, a separate heating chamber, means for passing at least a portion of said heated fluid combustion constituent through said separate heating chamber, means for passing another portion of said heated fluid combustion constituent into said upper chamber and mixing the same with said complementary combustion constituent, and means for recirculating said fluid combustion constituent from said separate heating chamber through at least a portion of said lower chamber.

5. Heating apparatus comprising in combination a fluid heating unit including upper and lower chambers, an unobstructed passage of reduced cross-section connecting said chambers, a continuous fluent mass of solid heat transfer material in said chambers and passage, means for effecting a flow of said heat transfer material downwardly through said chambers and passage and returning said material to said upper chamber, means for passing a fluid combustion constituent upwardly through said lower chamber in heat absorbing relation with the heat transfer material therein, means for supplying a complementary combustion constituent to said upper chamber, a separate material heating chamber, means for passing at least a portion of said heated fluid combustion constituent through said separate heating chamber, means for recirculating said fluid combustion constituent from said separate heating chamber through at least a portion of said lower chamber, and means for preheating said complementary combustion constituent by heat absorption from said recirculated fluid combustion constituent.

6. The method of heating a fluid combustion constituent to a high temperature which comprises moving a fluent mass of solid heat transl2 fer material downwardly through superposed heating and cooling zones, supplying a com- -bustion constituent directly to said heating zone in heat transfer relation with the descending solid material, supplying a complementary fluid combustion constituent to the lower part of the cooling zone in heat absorbing relation with the descending solid material therein and in position to flow upwardly therethrough to the point of admission of said first combustion constituent, and withdrawing the combustion gases generated by the mixing and burning of said, combustion constituents in the heating zone upwardly through said heating zone in heat transfer relation with the solid material descending therethrough.

7. The method of heating a fluid combustion constituent to a high temperature which comprises maintaining a substantially continuous flow of a fluent mass of solid heat transfer material downwardly through superposed heating and cooling zones, supplying a combustion constituent directly to said heating zone in heat transfer relation with the descending solid material, supplying a complementary fluid combustion constituent to the lower part of the cooling zone in heat absorbing relation with the descending solid material therein and in position to flow upwardly therethrough to the point of admission of said first combustion constituent, withdrawing a portion of said heated fluid combustion constituent before mixing with said first combustion constituent, and withdrawing the combustion gases generated by the mixing and burning of said combustion constituents in the heating zone upwardly through said heating zone in heat transfer relation with the solid material descending therethrough.

8. The method of heat transfer with circulated solid material which comprises substantially continuously moving a fluent mass of incombustible solid material in a continuous column of substantially uniform height downwardly through superposed heating and cooling zones, heating said mass of solid material to a high temperature while in said heating zone, continuously supplying a fluid combustion constituent to said cooling zone in an amount substantially in excess of the heating requirements of said heating zone and heating the fluid combustion constituent so supplied to a substantially uniform high temperature by direct contact with said heated mass of solid material while in said cooling zone, mixing a portion of said heated fluid combustion constituent with a complementary combustion constituent and burning the combustible mixture to heat said solid material in said heating zone, utilizing the remaining portion of said heated fluid combustion constituent independently of said solid material heating, and returning the cooled solid material from said cooling zone to said heating zone for reheating to repeat the cycle.

9. The method of heat transfer with circulated solid material which comprises substantially continuously moving a fluent mass of incombustible solid material in a continuous column of substantially uniform height downwardly through superposed heating and cooling zones, heating said mass of solid material to a high temperature while in said heating zone, continuously supplying air to said cooling zone in an amount substantially in excess of the combustion air requirements of said heating zone and heating the air so supplied to a high temperature by direct contact with said heated mass of solid material while in said cooling zone, mixing a portion of said heated air with a fluid fuel and burning the combustible mixture so formed to heat said solid material in said heating zone, returning the cooled solid material from said cooling zone to said heating zone for reheating to repeat the cycle and heat the air to a progressively higher temperature, reducing the amount of fluid fuel supplied as the temperature to which the air is heated increases, and separately utilizing the remaining portion of said heated air independently of said solid material heating.

10. The method of heating material in a high temperature oxidizing atmosphere which comprises maintaining a substantially continuous flow of a fluent mass of solid heat transfer material in a continuous column of substantially uniform height downwardly through superposed heating and cooling zones, heating said heat transfer material while in said heating zone to a high temperature, preheating an oxidizing gas to a high temperature by heat absorption from the heat transfer material in said cooling zone, passing at least a portion of the preheated oxidizing gas from said cooling zone while at a high temperature through a material heating chamber independent of said heating and cooling zones in direct contact with the material to be heated in an oxidizing atmosphere, separately utilizing the remaining portion of said high temperature oxidizing gas, recirculating the oxidizing gas from said independent material heating chamber to said cooling zone for reheating to a high temperature, and returning the cooled solid heat transfer material from said cooling zone to said heating zone for reheating to repeat the cycle..

11. The method of heating material in a high temperature reducing atmosphere which comprises maintaining a Substantially continuous flow of a fluent mass of solid heat transfer material in a continuous column of. substantially uniform height downwardly through superposed heating and cooling zones, heating said heat transfer material while in said heating zone to a high temperature, preheating a reducing gas to a high temperature by heat absorption from the heat transfer material in said cooling zone, passing at least a portion of the preheated reducing gas from saidcooling zone while at a high temperature through a material heating chamber independent of said heating and cooling zones in direct contact with the material to be heated in a. reducing atmosphere, separately utilizing the remaining portion of said high temperature reducing gas, recirculating the reducing gas from said independent material heating chamber to said cooling zone for reheating to a high-temperature, and returningthecooled solid heat transiegmateriaLfromhaidpooling zone to said heating zone for reheating to repeat the cycle.

12. Process of heat transfer in a shaft furnace using discrete fluent bodies of solid material, which comprises: establishing a gravitationally descending continuous column of the fluent bodies, said column consisting of two gas travabove and contiguous with upper free surfaces of said masses; charging the bodies onto the top surface of the upper mass and discharging a similar volume of the bodies from the bottom of the lower mass thereby maintaining the height of 15 said column; passing a current of initially substantially unheated air through the lower mass from the lower open space thereof to and through the gas-collecting space thereof andinto a combustion space separate from said column thereby effecting heat exchange between the initially substantially unheated air and the bodies constituting said lower mass; mixing the preheated air and a fluid fuel in said combustion space and burning the mixture to produce heating gases below but approaching the incipient fusion temperature of said bodies; passing the heating gases from the combustion space to and through the upper mass from the lower open space thereof to the gas-collecting space thereof thereby effecting heat exchange between the initially high temperature heating gases and the bodies constituting said upper mass; so controlling the rate of flow of the heating gases that the same passes into the gas-collecting space above the upper mass at a relatively low temperature; so controlling the rate of discharge'of the bodies from the bottom of the lower mass that the bodies are substantially cool as discharged; and so adjusting the amount of fuel introduced into the combustion space with 4 respect to changes in the rate of flow of the heating gases and in the rate of descent of the bodies that the temperature of the heating gases passing into the lower open space of the upper mass is maintained at the aforesaid temperature.

, CHARLES L. NORTON, JR.

REFERENCES CITED The following references-are of record in the file of this patent;

UNITED STATES PATENTS Number Name Date 1,148,331 Olsson -..---.,.-July 27, 1915 1,203,944 Weber Nov. '7, 1918 55 1,738,890 Goodrich; Dec. 10, 1929 1,904,153 Lucke Apr. 18, 1983 M 2,345,067 Osann Mar. 28, 1944 2,399,450 Ramseyer Apr. 30, 1946 FOREIGN PATENTS Number Country Date 212,671 Great Britain Mar. 20, 1924i 525,197 great'B'ritain 'Aug.'28. mo

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