US2395231A

US2395231A - Cupola furnace

Info

Publication number: US2395231A
Application number: US411504A
Authority: US
Inventors: William M Mcneil
Original assignee: United States Gypsum Co
Current assignee: United States Gypsum Co
Priority date: 1941-09-19
Filing date: 1941-09-19
Publication date: 1946-02-19
Anticipated expiration: 1963-02-19

Description

Feb. 19, 1946. w. M. McNl-:IL

CUPOLA FURNACE A Filed sept'. 19, 1941 2 Sheets-Sheet 2 2z 26M M h.

retenait-en 19, i946` CUPOLA FURNACE William M. McNeil, Wheaton, Ill., assigner to United States Gypsum Company, Chicago, Ill., a corporation of Illinois Application September 19, 1941, Serial No. 411,504

14 Claims.

This invention relates to methods of and apparatus for the production of mineral melt, and has reference more `particularly to a combination steam generating furnace and cupola which is useful for the production of mineral wool.

In the production of mineral wool by the blowing of molten mineral matter with steam or other gas, it is customary to charge a mixture of coke and mineral matter into a cupola and to effect the melting of the mineral matter by the combustion of the coke in the cupola. The coke and mineral matter are charged into the cupola in rather large pieces in order to enable combustion gases readily to passthrough the fuel bed. It has in the past been impractical to use cheap coal as a fuel since, on heating, the coal has a tendency to become plastic and packs within the cupola so that air and combustion gases will not pass through the fuel bed. Also coal usually contains a high percentage of volatile matter and a large portion of the heat in the coal is not eectively utilized in the cupola because the combustible volatile matter has a tendency to distill off and to pass up the stack. Also, the cupolas of the prior art have generally been charged by hand shoveling thereby materially increasing the labor cost of operating the same.

An object of this invention, therefore, is to provide a combination cupola and furnace which will successfully burn coal as a fuel.

Another object of this invention is to provide a furnace cupola in which fine or coarse mineral matter may be melted to form a molten slag for blowing into mineral wool.

Another object of this invention is to provide a furnace cupola in which the volatile matter is completely burned with ther liberation of heat which is utilized to produce steam for blowing molten slag into mineral wool or for other purposes.

Another object of the invention is to provide a furnace cupola in which the coal is preheated to distill off the volatile matter and to produce pieces or chunks of coke and sintered mineral matter which may be discharged into a cupola thereby permitting free passage of air and cornbustion gases through the fuel bed in the cupola.

A further object of the invention is to provide a furnace cupola in which a mixture of coal and mineral matter'is fed automatically into the furr provide a two stage process of producing mineral wool which is simple and economical.

Further and additional objects will appear from the following description, the accompanying drawings, and the appended claims.

In accordance with one embodiment of this invention, an apparatus has been provided, (1) for subjecting a mixture of carbonaceous material, such as coal, and mineral matter, to a preliminary heating step in order to drive off the combustible volatile matter from the carbonaceous material and to cause a coalescence of the carbonaceous material and mineral matter, (2) for discharging the resulting lumps of consolidated carbonaceous material and mineral matter into a cupola whereby the mineral matter is melted, and (3) for finally discharging the mineral melt from the cupola in a continuous stream. The cupola is provided with steam generating tubes in association with a steam boiler positioned in a combustion chamber above the cupola for providing high pressure steam for disintegrating the molten stream of mineral matter into mineral wool. The volatiles distilled from the mixture of carbonaceous material and mineral matter are burned in the combustion chamber above the 7 provided for the preparation of a melt of mineral matter from a mixture of finely divided mineral matter and carbonaceous material, such as slack coal. This melt may be blown by a high pressure steam jet into a mineral wool product. However, if desired, other products may be prepared from th melt, such as deiluorinated phosphate rock which is suitable for use as a fertilizer. rination may be effected by passing a quantity of steam over the mixture of a fluorine-containing phosphate and a carbonaceous material undergoing combustion before introduction into the cupola. Alternative or supplementary deuorination may also be effected by treating the phosphate melt discharged from the cupola with steam at low pressure to form pellets of a deiluorinated phosphate which latter may be used as a fertilizer.

For a more complete understanding of this invention, reference will now be had to the drawings .forming a part of this specification, in which Defluothe pit I2 and delivering the mixture to a hopper |6 positioned above a moving chain grate stoker I8 positioned adjacent the lower oor of a combustion chamber 20. Air ducts 22, controlled by dampers 24, are positioned below the upper reach of the chain grate stoker I8 and a manifold 26 connects a blower 28 to the ducts 22 for supplying air for combustion purposes to and through the mixture of slack coal and mineral matter on the chain grate stoker I8. The chain grate stoker I8 moves in the direction indicated by the arrow in Fig. 1 towards a chute 30 which is positioned above a cupola 32 and is so arranged that the material deposited on the stoker I8 from .the bin I6 will be discharged into the top of the cupola 32.

The cupola 32 comprises an elongated upright chamber having an oval cross-section which is provided with side walls lined with a plurality of vertically extending steam generator tubes 34 connected to an upper manifold 38 and a lower manifold 38. As most clearly shown in Fig. 3, refractory cement 40 extends between the tubes 34, and a layer of mineral wool 42 extends between a metal shell 44 and the refractory cement 40.

As shown most clearly in Fig. 1, the upper end of the cupola 32 opens into the combustion chamber 20 so that gases from the cupola and air from the ducts 22 passing through the grate stoker I8 may be combined. In the upper portion of the combustion chamber 20 is positioned a boiler 45 mounted within a setting 48. A plurality of boiler tubes 50 extend longitudinally through the boiler 46 and provide passageways between the combustion chamber 20 and a stack 52, thereby providing means for discharging hot combustion gases from the combustion chamber. Surroundlng the stack 52 are preheating jackets 54, 56, and 58 (see Fig. 2), having a blower 60 associated therewith for forcing intake air through a duct 62, which is connected to the jacket 54, and ducts 64 and 66 which are connected to jackets 54, 56 and 58 in seriesl A duct 68 extends from the jacket 58 to a bustle box 10 which surrounds a medial portion of the cupola 32. Tuyres 'I2 are provided for injecting preheated air from the bustle box to the lower portion of the cupola 32 to accelerate the combustion of the coke therein, whereby the mineral matter associated therewith is fused. Adjacent a lower edge of the oor of the cupola 32 is located a spout or port 14 through which the melt is discharged to a point near a steam blowing nozzle 'I6 which disintegrates the mineral melt into mineral wool. The nozzle 18 is positioned to discharge the blown fibers to a blow chamber .18 through an opening 80 whereby the fibers are deposited on a conveyor 82 to form a mat 84 of mineral wool.

In order to provide cold make-up Water for the steam generating system of the apparatus, an intake water pipe 88 connects with pipes 88 passing in series through a refractory arch 80 which extends obliquely into the combustion chamber 20 above the cupola 32, .This arch serves not only to carry the pipes 88 for preheating the make-up water but also lengthens the path of travel of the gases of combustion from thecupola into the combustion chamber so as to make the combustion more complete. A pipe 82 is provided for removing the preheated water from the pipes 88 within the arch 80 and connects with a cylinder 94 of a water pump which is operated by a steam cylinder 98. A pipe 98 having a check valve |00 extends between the cylinder 94 and a circulating pipe |02 for discharging the preheated water into the lower manifold 38 surrounding the cupola 32. A blow-oil valve |04 is provided in the manifold 38 to discharge sludge from the system' when necessary. A steam pipe |08 connects the upper manifold 38 of the cupola 32 and the boiler 48. Water is withdrawn from the boiler 46 by a pump |08 through a line ||0 and circulated through the line |02 to the lower manifold 38 of the cupola 32. As shown, a. steam drumr I2 is provided in the top of the boiler 48 and a steam pipe ||4 leads therefrom for conducting high pressure steam to the wool blowing nozzle 16. A branch steam pipe 6 leads from the pipe ||4 to the steam cylinder 96, the flow of steam through said pipe I6 being controlled by a valve II8. A branch pipe |20 controlled by valve |22 leads from the steam pipe ||4 to the duct 88 so that steam, if desired, may be introduced into the cupola 32 through the tuyres 'I2 in order to assist in certain chemlca1 reactions such as the deuorination of phosphate rock.

A charging door |24 is provided in the furnace setting 48 above the cupola 32 so that fuel may be manually added to said cupola if desired. A clean-out door |26 is also provided in the setting 48 above the arch 90.

In th'e operation of the above described apparatus, coal slack and mineral matter are dumped into the pit I2 and the mixture is carried by the bucket conveyor I4 to the hopper I5 and is discharged through a suitable gate onto the chain grate stoker I8. The mineral matter mixed with the coal slack may be granulated slag, small size rock, coarse sand or gravel, clay, ph'osphate rock, or similar material. Other forms of carbonaceous material may be substituted for the slack coal if desired. For example, under certain conditions it may be desirable to employ petroleum coke or a heavy petroleum pitch. The relative amounts of mineral matter and carbonaceous material may be adjusted so that the combination of the charged mineral matter combined with v the ash of th'e carbonaceous material produces a melt having the desired composition. The mixture of carbonaceous material and mineral matter on the chain grate stoker I8 is continuously advanced toward the chute 30. The high temperature within th'e combustion chamber causes the volatile matter to be distilled from the slack coal or other carbonaceous material on the stoker surface and the volatile matter admixed with air passed through the stoker from the ducts 22 burns within the combustion ch'amber 20. These hot products of combustion pass through the tubes'50 of the tube boiler 46 to generate steam therein and they thereafter pass out through the stack 52. 'I'h'eheating and partial distillation of the material on the chain grate stoker I8 causes the slack coal or other carbonaceous material to carbonize to form a coke which coalesces with the mineral matter to form relatively large pieces 2,398,231 or chunks of a mixture of coke and mineral matair passing into the cupola through the tuyresl 'I2 from the bustle box l0, this air having been preheated in th'e stack jackets 54, 56 and 58 that are connected thereto as hereinbefore described. The fused mineral matter flows in a stream through the port I4 and is blown into mineral wool by the steam nozzle 16. 'I'he mineral wool sintered mixture of .coke and mineral matter, and

fra second stage in which the pieces of this mixture deposits on the conveyor 82 in the blow chamber I8 in the form of amat 84. Y u

Hot water under pressure circulates in the system from .the boiler 46 through the pipe IIII, the circulating pump -I08, the pipe |82, the manifold 38, the steam generating tubes 34, the manifold 36 and the pipe I 86. Cold make-up water is supplied as needed through the pipe 86, th'e preheating pipes 88 ln the arch 90, the pipe 92, the water pump 94, and 1 the pipe 88, into the pipe |82. Steam passes from the steam drum I I2 associated with the boiler 46 through' the pipe II4 to the nozzle 'I6 and through the pipe H6 to the steam cylinder 96. The steam generated in the steam generating tubes 34 of the cupola 32 passes through the pipe'IIl6 to th'eboiler 46 along with the-circulating water.

YThe carbonaceous mixture that is deposited on the stoker ,I8 from the bin I6 should be spread in a relatively thin layer over the upper surface of the stoker to permit the free passage of air -th'erethrough from the ducts 22, and to permit conveying systems may be employed t0 effect this result.

As most clearly indicated in Fig. 3, the melting chamber* within the cupola 32 has an oval crosssection and the cupola is disposed with respect I to the stoker so that the maximum diameter of the cupola extends transversely to the direction of movement/of the stoker. The sintered mass of carbonaceous material and mineral matter is thus more readily deposited within the cupola and a more even temperature within the cupola is. obtainable than would be the case if the cross section thereof were circular.

From the above description it will appear that a process' and apparatus have been described for producing a stream of mineral melt the flow of which from the cupola remains substantially constant or may be regulated as desired. The rate of flow of the melt may be controlled by regulating the speed ofA the belt conveyor I4 and the chain grate stoker I8, the mineral matter in the mixture being supplied to the top of the cupola. at substantially the same rate as it is desired to withdraw the melt from the bottom thereof through the spout 14.

It is apparent that'the cupola furnace of this invention carries out a two stage process, viz: an initial stage in which the volatile matter is distilled from the coal to produce large pieces of a into mineral wool.

are completely burned'at a high temperature to produce moltenv mineral matter which is blown The coking step is carried out with the c'oal lying on the stoker in a shallow layer so that it can be readily heated and coalesced and so that air for combustion can readily pass through the sintering mixture. The second or melting stepis carried out while the large pieces are maintained in a comparatively deep column. lIn the second step, the fuel is in the form of pieces of coke which readily permitthe passage of the preheated air and combustiongases therethrough and the carbonaceous material has passed the plastic stage Where it will tend to coalesce within the cupola. Thus fusion of the mineral matter is more readily` effected in the cupola. 'I'he process is especially advantageous because of the low cost of the materials which may be usted including coal fines, or even slack coal having a high ash content, and fine mineral matter which is ordinarily discarded as waste. The cupola furnace also produces its own'steam for blowing purposes, and utilizes most of the waste heat so that stack gases are discharged at the lowest possible temperature. The mixture of coal and mineral matter is automatically fed to the furnace thus greatly reducing the labor of operation incident to hand firing heretofore used.

The apparatus is suited for a variety of uses other than the production of mineral Wool. For instance, it may be used for the smelting of ores, such as iron ore. As another example, gypsum might be included in the mineral mixture so that sulfur dioxide and sulfuric acid becomes one of the by-products. 'I'he apparatus might also be used for the defluorination of phosphate rock in the production of phosphate fertilizer or even elemental phosphorus. In this type of reaction, the steam introduced into the cupola enters into the reaction to accomplish the deiluorination of the rock. Low temperature steam maybe used' at the nozzle 'I6 in defiuorination so that pellets of fused phosphate rock are produced instead 0f wool. Deuorination may also be effected by mixing steam with the air which is passed through the mixture of mineral matter and carbonaceous material on the stoker I8.`

It will be recognized that the fuel and mineral matter may be thoroughly mixed before it is initially charged into the receiving pit. This mixing may be effected in any type of mixing machine (not shown) such as one which is useful for mixing concrete. In such case, the fuel and mineral matter may be stored in separate storage bins (not shown) and withdrawn in desired quantities and supplied to the mixer. The resulting mixture having a predetermined composition may then be charged to the receiving pit I2 and thereafter passed through the cupola furnace as hereinbefore described.

While a particular embodiment of this invention is shown above, it will be understood, of course, thatthe invention is not to be limited thereto, since many modifications may be made, and it is contemplated, therefore, by the appended claims, to cover any such modifications as fall within the true spirit and scope of this invention.

I claim: l

l. The process of producing fused mineral matter by a continuous process which comprises admixing mineral matter with a carbonaceous fuel containing volatile matter in substantial quan titles, passing the resulting mixture on a conveyor through an enclosed combustion zone wherein assumez Stoker within said setting and spaced from said said volatile matterA is burned from the fuel and a sintered mass of mineral matter and coke-like material is formed, discharging the resulting sintered mass in lump form into a separate high temperature melting and oxidizing zone wherein said coke-like material is burned thereby fusing said mineral matter, and substantially continuously removing said fused mineral matter from said oxidizing zone.

2. The method of producing a stream of molten mineral matter, which comprises moving a mixture of solid carbonaceous fuel initially containing volatile matter in substantial quantities and solid mineral mattei' in a shallow layer through an enclosed combustion zone, heating said layer therein under oxidizing conditions so as to distill and burn the volatile matter from said fuel and to produce substantially large pieces of a sintered mixture of coke-like material and mineral matter, introducing said pieces into a vertial combustion chamber provided with means for forcing combustion-supporting gases therethrough, completlng the combustion of the carbonaceous fuel in said chamber whereby to produce gaseous products of combustion and fused mineral matter, and withdrawing said fused mineral matter in a stream from the bottom ofA said chamber.

3. The method of continuously producing a melt suitable for blowing into mineral wool which comprises continuously moving a mixture of coal and potentially fusible mineral matter in a shallow layer in an enclosed combustion zone, heating said layer under oxidizing conditions therein so as rto distill and burn volatile matter from said coal and to produce substantially large pieces of a sintered mixture of coke and mineral matter, continuously introducing said pieces into a combustion chamber yprovided with positive means for forcing combustion supporting gases therethrough, and completing the combustion of the coke in said chamber to produce gaseous products of combustion and fused mineral matter.

4. The process of producing fused mineral matter by a continuous process which comprises admixing a finely divided carbonaceous fuel containing volatile matter in substantial quantities with finely divided mineral matter, continuously advancing the resulting mixture on a conveyor through a primary combustion and heating chamber whereby the fuel is incompletely burned to distill off the volatile matter and a sintered mass of mineral matter and coke-like material is formed, continuously discharging said sintered mass in lump form into a separate high temperature melting cupola wherein said coke-like material is burned thereby fusing said mineral matter, and continuously removing said fused mineral matter from said cupola.

5. The method of heat treating a substance, which comprises continuously moving a mixture of carbonaceous fuel and mineral matter in a shallow layer, subjecting said layer to oxidizing conditions so as to distill and burn volatile matter from said mixture and to produce a sintered mixture of coke and mineral matter, assembling said sintered mixture in a combustion chamber,

passing preheated air through said assembled mixture whereby to burn said coke and continuously to produce a mass of fused mineral matter, and continuously withdrawing said fused mineral matter from said combustion chamber.

6. In an apparatus of the class described, a furnace setting, a boiler within said setting, a

boiler, a cupola associated with said stoker,

`means for supplying a mixture of solid fuel and mineral matter to said stoker to be sintered and incompletely burned, means for supplying a combustion-supporting gas to the mixture on said stoker, means for removing said sintered mixture from said stoker into said cupola, said cupola having Walls comprising a series of vertically arranged water tubes, means for completing the combustion of carbon in said mixture within said cupola to form fused mineral matter, and means for circulating water between said boiler and the water tubes of said cupola whereby to generate steam.

7. In an apparatus of the class described, a housing, a chain grate stoker in said housing, a receiving pit, a feed hopper associated with said stoker, conveyor means for delivering a mixture of solid. fuel and mineral matter from said pit to said hopper, said hopper being arranged to deliver a shallow layer of said mixture on said Stoker, means for sintering and partially burning the mixture on said stoker, a cupola, means for delivering said mixture to said cupola to be completely burned to form molten mineral matter, and means for withdrawing said fused mineral matter from said cupola.

8. An apparatus of the character described which comprises a first combustion chamber, a conveyor within said chamber, means for supplying a mixture of solid fuel and mineral matter to said conveyor, means for supplying combustion-supporting gases to the mixture on said conveyor whereby said mixture is sintered and the fuel therein is incompletely burned, a second combustion chamber opening into said first combustion chamber for receiving the sintered mixture from said conveyor, means for supplying additional combustion-supporting gases to said second combustion chamber completely to burn the fuel in the sintered mixture therein whereby to melt said mineral matter, and means for discharging the molten mineral matter from said second combustion chamber.

9. An apparatus of the character described which comprises a first combustion chamber, a stoker within said chamber, means for supplying a mixture of solid fuel and mineral matter to said stoker whereby said mixture is advanced within said chamber, means for supplying combustion-supporting gases to the mixture on said Stoker whereby to sinter the mixture and incompletely to burn the fuel in said mixture thereby liberating hot combustion gases, a second combustion chamber positioned adjacent the discharge end of said stoker communicating with said rst .combustion chamber, means for supplying additional combustion-supporting gases to said second combustion chamber completely to burn the fuel in said mixture therein whereby to melt said mineral matter, means for withdrawing combustion gases from said apparatus, an`d means for discharging the molten mineral matter from said second combustion chamber.

10. An apparatus of the character described which comprises a first combustion chamber, a boiler positioned in the upper reaches of said chamber, a stoker within said chamber spaced from said boiler, means for supplying a mixture of solid fuel and mineral matter to said stoker `whereby said mixture is advanced within said chamber, means for supplying combustion-supporting gases to the mixture on said stoker whereby to sinter the mixture and incompletely to burn the fuel in said mixture thereby liberating hot combustion gases, a second combustion chamber positioned adjacent the discharge end of said stoker communicating with said first com- 'bustion chamber, means for supplying additional combustion-supporting gases to said second combustion chamber completely to burn the fuel in V 11. An apparatus of the character described' which comprises a first combustion chamber, a boiler positioned in the upper reaches of said chamber, a stoker Within said chamber spaced jacent the discharge end of said stoker adapted to receive said lumps, means for supplying a combustion-supporting gas to said melting chamber whereby said fuel in themixture is burned to melt said mineral matter and to produce hot combustion gases, said melting chamber being open to said primary chamber whereby the hot combustion gases pass to the latter lto assist in from said boiler, means for supplying a mixture of solid fuel and mineral matter to said stoker whereby said mixture is advanced within said chamber, means for supplying combustion-supporting gases to the mixture on said stoker whereby to sinter the mixture and incompletely to burn the fuel in said mixture thereby liberating hot combustion gases, a, second combustion chamber positioned adjacent the discharge end of said stoker communicating with said rstcombustion chamber, means for supplying additional combustion-supporting gasesto said second combustion chamber completely to burn the fuel in the sintered mixture whereby to melt said mineral matter and to form additional hot combustion gases, means for admixing the hot combustion gases from each combustion chamber, means for passing the combined hot combustion gases into heat exchange relationship withsa/id boiler prior-to discharge from the apparatus, means for discharging the molten mineral matter from said second combustion chamber, steam-generating tubes associated with said second combustion chamber, means for circulating Water and steam from. said boiler to said steam-generating tubes, and means for dischargingV generated steam from said boiler.

12. An apparatus for the continuous production of a melt suitable for blowing into mineral wool, from mineral matter and a nely divided carbonaceous fuel containing volatile matter in substantial quantities, which comprises, a primary sintering and combustion chamber, a stoker for continuously passing a mixture of said min'- eral matter and said fuel in a shallow layer through said sintering and combustion chamber whereby the mixture is sintered to form large lumps, a vertical melting chamber'positicned adthe sintering operation, and means for continuously discharging molten mineral matter in a stream from the melting chamber 'as rapidly as it is formed. l

13. An apparatus for the continuous production of a melt lsuitable for blowing into mineral wool, from minerall matter and finely divided coal which comprises, a primary sintering and combustion chamber, a steam boiler within said chamber, a, stoker for continuously advancing a mixture of said mineral matter and said coil in a shallow layer through said chamber whereby said mixture is sintered to form large lumps of a mixture of coke-like material and mineral matter, a

supporting gas to said melting chamber whereby said coke-like material in the mixture is burned open to said primary chamber whereby the hot combustion gases pass to the latter t0 assist in the sintering operation, means for circulating water and steam from the steam-generating tubes to the boiler, means for supplying make-up water to the boiler, and means for continuously discharging molten mineral matter in a stream from the melting chamber as rapidly as it is'formed.I

14. The method of heat-treating a mixture containing a. finely divided4 fuel and a fusible material by a continuous method which comprises advancing the mixture in a shallow layer on a conveyor through a first combustion zone under conditions controlled to permit said fuel to be incompletely burned to produce sintered lumps of a mixture of coke-like matter and fusible material, dischargingv said lumps as rapidly as they are formed from the conveyor into a second combustion zone, passing a combustion-supporting gas into said second zone to burn the coke-like zone.

' WILLIAM M. McNEIL.

Certificate of Correction Patent No. 2,395,231. Februarylg, 1946. I

WILLIAM M. MCNEIL It is hereby certified that errors appear in the printed specification. of the above numbered patent requiring correction as follows:` Page 1, second column, line 41, for th melt read the melt; page 5, second column, line 19, claim 13, for coil read coal; and that the said Letters Patent should be read with these corrections therein i that the lsame may conform to the record. of the case in the Patent Ofiice.

Signed and sealed this 14th day of May, A. D. 1946.

[SEAL] LESLIE FRAZER,

Ffirs Assiste/ni Commissioner of Patents.