US1531648A - Method and apparatus for heating air for blast furnaces - Google Patents

Description

METHOD AND APPARATUS FOR HEATING AIR FOR BLAST FURNACES INVENTOR MLDEmARDr/ssE/v www ATTORNEY March 31, 1925. 1,531,648

w. DYRSSEN METHOD AND APPARATUS FOR HEATING AIR FOR BLAST FURNACES Filed Nov. 20 1922 5 sheets-sheet 2 H, l, l, Ill",

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March 31, 1925.

W. DYRSSEN METHOD AND APPARATUs FOR HEATING AIR Fon BLAST FURNACES Filed NOV. 20. 1922 5 Sheets-Sheet 3 INVENTOR. WALDEMAR yRssE/v.

BY I L5 A TTORNEY.

March 3l. 1925.

W. DYRSSEN METHOD AND APPARATUS FOR HEATING AIR FOR BLAST FURNACES Filed Nov, 20, 1922 5 Sheets-Sheet 4 V/g 'f s INVENTOR. MLDEMA/e DrRssE/m ATTORNEY.

5 Sheets-Sheet 5 W. DYRSSEN METHOD AND APPARATUS FOR HEATING AIR FOR BLAST FURNAcEs Filed Nov. 20, 1922 March 31. 1925.

. IN l//IV T( 7A MLDEMA Ry/TSJEM ,41 TURA/EV by burning Patented Mar. 31, 1925.

, A 1,531,648 UNITED STATES PATENT OFFICE.

WALDEMAR -D'YRSSEN, 0F 'TARRYTOWN, NEW YORK.

METHOD AND APPARATUS FOR HEATING AIR FOR BLAST FURNACIB.

Application led November 20, 1922. Serial No. 602,804.

To aZZ whom t may concern.' p

Re it known that I, WALDEMAR DYRssEN, a citizen of they United States, and resident of Tarrytown, New York, have in-vented certain new and useful Improvements in the Method and Apparatus for Heating Air for Blast Furnaces, of which the following is a specification.

This invention relates to an improved method and apparatus for heating the air blast supplied to blast furnaces and also to improvements in the construction of stoves used to heat the blast. 4

VHeretofore there have been two typical methods employed for heating the air ifor blast furnaces. The simplest and oldest method consisted briefly in passing air through iron pipes which were externally heated bythe combustion of blast furnace gas. Such method is not suitable for heat-- ving the blast' to a high temperature, i'equired in modern practice, as the iron pipes are quickly destroyed or cracked by the excessive heat. 'The use of iron pipes is not suitable where a high pressure-air blast is used on account of the liability to leakage, and in modern blast furnace practice the air blast is usually supplied at a high pressure. For these reasons the use ofiron pipes for heating the blast has been practically abandoned.

The second and more generally used method of heating the blast consists iii passing the air through stoves filled with bricks forming a checkerwork which has previously been heated to ahigh temperature blast furnace gas in the stove. Then heating the air blast in this way it is necessary tohave at least two stoves for each blast furnace as the checkerwork in one must be heated while the checkerwork in the other is giving up its heat to the air blast. In most modern plants five stoves are built for each blast furnace, one or two being used to heat the air blast and two oi' three being heated by the blast furnace gas for subsequent use. and the fifth stove being held in reserve for use inthe event of a breakdown or repairs to any of the other stoves. .These stoves are of large dimensions being approximately 100 feet in height and Q5 feet in diameter and each containing several million pounds of bricks. Suitable valves for part of the usual installation whereby one or more stoves can be alternately used to heat the blast, or be supplied With this method, the temperature of the blast is not constant because at the beginning the checker bricks are hotter and consequently heat the air blast toa. higher temperature at the beginning of a period, than at the end of a period after the bricks have( been cooled down by the blast. Such method of heating is rather inefficient and practical operation shows that only 50 to per cent of the heat in the blast furnace 'gas is effective for heating the checkerwork. This inetliciencyv is due partly to the large surface exposed to atmosphere by the several stoves and partly due to losses in changing the stoves over filom burning gas' to heating the blast.- vFurther losses are due to leaky hot blast valves, it being known to those skilled in the art that it 1s extremely diflicult to keep these valves tight because of the high ltemperatures andpressures in modern blast furnace'practice.

Myimproved method will overcome the above objections and I can secure a heating eiiciency as high as or more and only one stove is required for each blast furnace, and this stove is smaller than any one of the lfour or five heretofore provided to accomplish the same function. v It is possible to heat the air for'the blast furnace to a high enough temperature by direct heating by the use of brick pi s through which hot gases are passed. Brick pipes can stand a much higher temperature than iron pipes but it is difficult to use brick or tile pipes exclusively for heating the airblast because of the pressure used in modern blast furnace practice, it being apparent that brick or tile pipes would not withstand the high pressure without bursting or leaking at the joints.

According to my method, however, I can use brick pipes successfully as I compress the gas and air necessary for combustion in the stove 'or heating apparatus to substantially the sameV pressure as the blast and thereby eliminate any difference'in pressure between the hot gases within the pipes and the blast outside the pipes, or vice versa. I can use pipes in the stove constructed partly of refractory materia-l such as brick or tile and partly of iron or. other metal. Pref- Vbe damaged by the excessive heat.

erably I use iron pipes to heat the blast to about 70() degrees F. and brick pipes to heat the'blast from 700 degrees F. to the highest temperature required or to about 1300 degrees F. The use of iron pipes at the lower temperature is of particular advantage because the heat can be transferred through the walls of.iron pipes about two to five times faster than through brick pipes. I use brick or other refractory pipes in the hottestI zone of the stove as they will ppt Y method will be understood and the construe'- tion rofmy improved apparatus will be' clear from the following specification when read in' connection with the accompanymg drawings in which- Fig.y 1 is a diagrammatic view showing a blast furnace, a stove for heating the blast therefor and other associated apparatus Fig. 2 is a vertical longitudinal section through a stove illustrating features of my invention;

Fig. 3 is a section lon line 33 of Fig. 2;

Fig. 4 is a section on line 4-4 of Fig. 2;

Fig. 5 is a section on line ff-5 of Fig. 2;

Fig. 6 is an enlarged detail illustrating the construction Ofpipes formed partly of refractory material and partly of metal;

Fig. 7 is an inverted plan of a fitting used to couple the brick pipes to the metal. pipes and Fig. 8'is a modification of fitting illustrated 1n Fig. 7

Fig. 9 is an enlarged detail View; Fig. 10 illustrates a modification.

Referring first to Fig. 1 the blast furnace 10 is of the usual type and the blast furnace gas passes through downcomer 12 to lthe usual dust catcher 14 and from there to the usual scrubber 9 Where the gas 4is cleared and cooled to approximately atmospheric temperature. From the scrubber part of the gas passes by way of pipe 16 to a conipressor 18 and by pipe 20 and Y-fitting 22 to branches 24 and nozzles 26. These nozzles discharge the gas through ports 28 in a tangential direction as indicated in Fig.

5. The nozzles 26 project through openings ,Y

formed in extensions 30 which are connected with an air supply branch 32. The branches 32 communicate with an air supply pipe 34 which through a port 36 is in communication with the. heating chamber 38 of the hot blast stove indicated as a whole by the numeral 40. The stove is built `with an outer shelL 41 of suitable metal and islined with suitable insulating brickwork refractory lining 48. In addition to the heating chamber 38, the stove is provided with a combustion chamber 42 which is separated from the heating chamber by .a diaphragmor wall 44. At its lower end, the stove is formed with a waste gas chamber 46 which is separated from the heating chamber by a wall or diaphragm 48. The

of fittings 56 and said fittings are provided' with two or more branches 58 as shown in Figs. 6 to 8 which are adapted to engage suitable sockets formed in the ends of the pipes 54. In this way I can usetile pipes iron, stainless of generous dimensions and connect each A tile pipe with two or more metal pipes as will be understood.

The cold air blast is supplied through a pipe 60 by a suitable, blowing engine 62, thel air entering through ports 64 formed in the lower part of the heating chamber 38. The air circulates through the heating chamber around the pipes 54 and 52 and is heated by -contact with said pipes, it being understood that the blast furnace gas introduced through the nozzles 26 burns in the combustion chamber 42 with air supplied from the heating chamber 38 through port 36 and pipe 34 and that the products of combustion pass at approximately the same pressure as the air blast, through the pipes .2 and 54 into the waste gas chamber 46.

The cold blast is supplied to the pipe 60 by the blowing engine 62 at the usual pressure required in modern blastfiirnace practice of 15 to'20 pounds above atmosphere and the compressor 18 raises the-pressure of the blast furnace gas supplied to the combustion chamber 42 to slightly above the pressureof the blast. The pipes 34 and 32 supplying combustion air from the partly heated blast in heating cha1nber3S are of such generous dimensions as areF also the ports 28` that there is practically no fricv tional pressure loss, hence it is apparent that the pressure in the combustion chamber and inside and outside the pipes is equalized and there is no appreciable strain exerted upon the iping from the blast pressure. The slight y higher pressure of the gas 1s consumed in-nozzles 26 for effective mixing with the air in order to obtain perfect and vrapid combustion.

Suitable baffle plates 64 are placed at intervals in the heating chamber and these baflies are provided with openings 66 which. are arranged so that the openings in one plate are staggered with relation to those of the next so that the air blast is compelled to travel a circuitous path through the heating chamber and thereby come in intimate contact with the pipes heated by the blast furnace gas. The holes 66 at the inner zone of the plates 64 are preferably larger than lon will be provided with a butterfly valve 78 for either cutting off the supply therethrough or yfor controlling the volume lof air so supplied.

The waste gases or products of combustion which pass into the chamber 46 will contain an appreciably higher amount of mechanical energy than was used for the compression of the gas and air before combustion as their temperature is in the neighborhood'of from 400 to 500 degrees F. I propose to utilize this energy and to these ends I have' illustrated an outlet having a nozzle 82 the outlet orifice area of which can be controlled by valve 84 normally held in the wide open position by a spring, not shown, and adapted to be moved inwardly by any suitable means such as a thumb screw 86. This nozzle directs the jet of gas against the vanes of a turbine rotor 88 enclosed in a suitable casing 90, the spent gases escaping to. the atmosphere or being lead-to a stack from the outlet connection 92 formed inthe casing. The rotor 88 is coupled to an armature shaft 92 of a suitable electric generator delivers su cient energy to drive the compressor 18 and supply power to the electric power system of the plant.

From the foregoing it is clear that my invention contemplates compressing the blast furnace gas and supplying it to the4 combustion chamber 42 of the stove wherein it is mixed with part of the blast air. It is apparent that as the products of combustion pass downwardly through the pipes 52-54 y l .that they will be intensely heated and that the blast of air circulating through the chamber 38 around said pipes will be thoroughly heated. The hot blast willbe discharged through the pipe 72 and conveyed to the blast furnace l0. The metallic portions of the pipes as indicated at 54 are in the cooler zone of the stove, remote from the combustion chamber, while the pipes of refractory material are adjacent to the combustion chamber and hence in the hottest zone. This arrangement is advantageous as the metallic pipes in the cooler zone are capable of effecting a more rapid ,transfer of heat to the air flowing around them than pipes of brick l or other refractory material would be capable'of. Furthermore the refractory pipes in the upper zone are capable of withstandenerator 94 and saidV ing the excessive heat which often reaches a temperature of 2500 degrees F. and in this zone because of the high heat it is not necessary to use material capable of transmitting heat so rapidly. In view of the fact that the gas and the airused for combustion is raised to apres'sure substantially equal to that of the cold blast it is apparent'that the pressure on the inside and outside ofthe pipes is equalized, hence no undue strain from the blast pressure is exerted which would tend to fracture either the metal or refractory pipes.

In the above description I havedescribed the stove as being provided with a combustion chamber so arranged that the products of combustion are passed through pipes to heatv an air blast which circulates around the exterior of the pipes. It is to be understood, however, that if desired I may arrange the stoveso that the air blast will pass through the pipes and the products .of combustion pass around the exterior of the pipes orl any' .other equivalent arrangement or apparatus for the direct heat interchange between two gases separated from each other can be used.

In this description I have only referred to blast furnace gas as fuel. This is the natural fuel to uselas it-is alwaysv available as soon as the blast furnace is in operation. However I may also use any other kind of fuel such as tar or fuel oil. In such case I can substitute the -gas compressor 18 with a fuel pump. I can also use powdered coal, producer gas, coke-oven gas, or natural gas. The compressors 18 and 62 can be of any common type such as gas, steam or electrically driven cylinder engines or steam tu'rbine or4 electromotor driven 'turbine' comi pressors. The turbine 90 might also be substituted with a cylinder engine. This power unit does not form an essential part of the installation and under certain conditions it might not be -desirableto utilize the pressure energyof they waste gases and in such a case only a nozzle or valve is used. It is evident that regulating of the opening of the nozzle 82 influences the combustion of the gas in chamber 42. If it is open too much an excess amount of air will be drawn through pipes 34 and 32 and if the opening is too small the gas will not .be completely burnt. I propose to install a C()2 recorder in pipe 80 in order to manually or automatically regulatethe valve 84 so that I obtain ideal combustion in all cases. In order to regulate the temperature of the blast to the furnace I vary the amount of gas compressed in 18. Under ce1'- tain conditions I also waste gas motor 90, generator 94 and compressor 18 in one unit. It is also possible to make compressor 62 with its motor part of this unit in order to reduce the cost of the equipment. It is,obvious that it is desirable to install the usual mechanically and autopropose/ to arrange the A vvarious changes maybe made by'those skilled inthe art Without departing 'from the invention as defined in the appended IV hat I claim is:

l. rl`he method of heating the air blast for blast furnaces which consists in simultaneously passing the air blast and combustible gas or fuel in separate streams through a heating apparatus'and compressing the air blast and the combustible gas or fuel and burning said fuel in said heating apparatus under substantially the same pressure as the blast air to beheated in said heating apparatus. f l

.2. The "method of heating air for blast furnaces which consists in compressing blast furnaceA gas to substantially the same prcssure `as the cold blast/and burning said gas with air under substantially the same pressure and passing the products ofl combustion under substantially the same pressure through' a' heating apparatus counter-current to the airblast to heat the latter and conveying the heated air to the blast furnace. 3. The method of heating air for blast furnaces Which consists in conveying gas from-a blast furnace to a compresser' and raising the pressure thereof thereof'to substantially or approximately the same pressure as the air blast, conveying said gas to v a surface heating apparatus and mixing it with part of the cold air blast for combustion and burningth'e mixture under substantially or approximately the same pressure as the air blast, passing the products of combustion under the same pressure through pipes in one direction and passing the air blast around the pipes in the opposite direction to heat the air blast and conveying the heated blast to the blast furnace.

4. The method of heating air for blast furnaces which consists in supplying gas to a heating apparatus at a pressure above atmosphere, supplying an air blast to the apparatus at substantially or approximately the same pressure as the gas, gas With air, burning the mixture in said heating apparatus and passing the products of combustion through the heating aparatus counter-current to the air blast to heat the latter.

5. The method of heating air for blast furnaces which consists in supplying blast mixing said furnace gas under pressure to the combustion chamber of a heating apparatus,- supplying an air blast to said heating ap` paratus at substantially the same pressure as said blast furnace gas mixing part of the air from said blast with the gas to support combustion and passing the products of combustion through pipes in the heating ap paratus to heat the air blast.

6. An apparatus of the class described having a combustion chamber, means for supplying blast furnace gas under pressure to said combustion chamber, means for passingthe products of combustion under pressure from said chamber through the apparatus in one direction, and means for passing an air blast at'substantially the same pressure as `the products .of lcombustion through said apparatus in the opposite direction so'as to heat said air blast.

7. An apparatus of the class described having a combustion chamber, means for .supplying blast furnace gas under pressure 'to said combustion chamber, means for passing the products ofcombustion from said chamber through the apparatus in one direction, means for passing an air blast through the apparatus in the opposite direction so ,as to heat said air blast and means for supplying part of the air blast to the combustion chamber to support combustion of the blast furnace gas.l

8. In an apparatus of the class described, a structure having a combustion chamber, means for supply blast -furnace gas at pressure above atmosphere to said combustion chamber, a multiplicity of pipes for conveyingthe products of combustion from said chamberthrough the structure, and means for passing an air blast through the structure in contact with said pipes at substantially the same pressure as that of the blast furnace gas.

9. In an apparatus of the class described, a structure including a combustion chamber, means for supplying blast furnace gas under pressure to said combustion chamber, a multiplicity of pipes communicating with said combustion chamber and arranged to convey the products of combustion through the structure, said pipes being formed in sections of refractory material and of metal, the refractory sections being located in the hotter zone and the metallic sections being located in the cooler zone, and means for passing an air blast throughv the structure in such manner that it is heated' by coutact with said pipes. 10. In an apparatus of the class described means for heating the air supplied to a blast furnace, comprising a stove adapted to burn compressed blast furnace gas, said stove having a blast inlet and a hot blast outlet and a multiplicityof pipes arranged to convey the products of combustionV through the stove, said pipes being ofl sectional formation and having refractory and metallic sections, the metallic sections bcing located in the cooler zone of the stove and the refractory sections being located in the hotter zone.

11. An apparatus adapted to heat the air supplied to a blast furnace, including a combustion chamber adapted to receive blast furnace gas under pressure,` an inlet for the comparatively cold air blast, pipes communicating with said combustion chamber adapted to heat the cold air blast, a hot air blast outlet adjacent the combustion chamber, a Waste gas chamber remote from said combustionchamber and communicating therewith by means of said pipes and means for supplying air heated by said pipes to said combustion chamber to support combustion of the blast furnace gas supplied thereto.

.12. Anapparatus adapted to heat the air supplied to a blast furnace including a combustion chamber, a waste gas chamber, an air heating chamber between the combustionfend waste gas chamber, pipes connecting the combustion and waste gas chambers, means for supplying blast furnace gas under pressure to said combustion chamber, means ,for supplying air to said heating chamber at substantially the same pressure as the gas and means for equalizing the pressure of the blast furnace gas and the air blast to prevent leakage through said pipes.

13. In combination with a blast furnace, a single stove for continuously heating the air blast supplied to said furnace, means for continuously conveying gas from said blast furnace to a compressor and raising the pressure thereof, a combustion chamber in said stove, supplying air under pressure to said com bustion chamber to support combustion of said gas, pipes for conveying the hot products of combustion lthrough the stove and lmeans for continuously passing a blast ofy air through the stove in a circuitous path around said pipes to heat the blast.

In `"Witness lwhereof I` have hereunto signed my name.

WALDEMAR DYRSSEN.

means for continuously

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