US3373796A - Method and means for cooling a combustion chamber by means of a powderlike material - Google Patents

Description

March 19, 1968 VALLAK ETAL 3,373,796

METHOD AND MEANS FOR COOLING A COMBUSTION CHAMBER BY MEANS OF A POWDERLIKE MATERIAL Filed April 25, 1966 5 Sheets-Sheet 1 Fig .1 l

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March 19, 1968 E. VALLAK ETAL 3,373,796

METHOD AND MEANS FOR COOLING A COMBUSTION CHAMBER BY MEANS OF A POWDERLIKE MATERIAL Filed April 25, 1966 5 Sheets-Sheet 2 /NVtfNTORS. E/v/v VALLAK SVEA/ f/(ETOEP ATTORNEY.

March 19, 1968 E. VALLAK ETAL METHOD AND MEANS FOR COOLING A COMBUSTION CHAMBER BY MEANS OF A POWDERLIKE MATERIAL 5 Sheets-Sheet 3 Filed April 25, 1966 Si B-B l5rlvll lrrlralll I 74. I. l

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Mardl 1968 E. VALLAK ETAL METHOD AND MEANS FOR COOLING A COMBUSTION CHAMBER BY MEANS OF A POWDERLIKE MATERIAL Filed April 25, 1966 5 Sheets-$heet 4.-

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- LIN BUSTION CHAM METHOD AND MEANS FOR 000 G A COM MEANS OF A POWDERLIKE MATERIAL BER BY Filed April 25, 1966 A 5 Sheets-Sheet '5 /NVENTOR-S. a E/v/v VALL'AK S l/EN EKETORP ATTORNEY.

United States Patent f 3,373,796 METHOD AND MEANS FOR COOLING A COM- BUSTION CHAMBER BY MEANS OF A POW- DERLIKE MATERIAL Enn Vallak, 82 Rte. de Florissant, Geneva, Switzerland,

and Sven Eketorp, Bromma, Sweden; said Eketorp assignor to said Vallak Filed Apr. 25, 1966, Ser. No. 544,868 Claims priority, application Sweden, Apr. 23, 1965, 5,369/ 65 22 Claims. (Cl. 165-1) I The inventor has already described (see French patent specification 1,432,309) a method for cooling a combustion chamber used in the smelting reduction of metal oxides, wherein the metal oxide is supplied as a cooling means in the form of one or more curtains or the like between the furnace lining and a high temperature zone in the furnace.

The present invention represents a further development of this method of cooling to be used not only for cooling by the curtain effect but also direct cooling of the combustion zone. The invention may be applied also in other situations than smelting reactions and effects the cooling by supplying powder like material with various grain sizes to the high-temperature zone of the combustion chamber in such a way that coarser particles of the powder material are mainly located outside the finer particles in respect to the center of the high temperature zone. In this way the finer particles, which are most effective for cooling, are found nearest the area where the temperature is highest and thus they absorb the greatest amount of heat while the coarser particles act more as an accompanying shield inside the walls of the furnace.

A rather high speed is imparted to the particles forming the curtains between the combustion zone and the furnace lining so that these particles will obtain a determined direction of movement, e.g. from the middle part of the high temperature zone outward toward the furnace walls to be cooled. The particles having the greatest mass, i.e. the largest particles, are given the highest speed. The smaller the particles are, the more difficult it is to cause them to move along a given path. "In this way the above described distribution of coarse and fine particles is obtained.

The present invention may be used in all types of processes where it is desired to screen a high temperature zone from a furnace lining in order to thereby reduce the radiation of heat to the lining and also heat the powder material which is preferably a raw material used in the process itself. However the invention shall be described in the following in connection with its application to smelting for the production of pig iron from metal oxide or from scrap in the form of powder-like material. In the following, the metal oxide or scrap dressed ore.

According to one modification of the invention the powder material may be replaced by a liquid, e.g. melted pig iron, which, during the production of steel by supplying oxygen to a molten pool of pig iron, is supplied in one or more curtains in order to cool the walls of the furnace.

The accompanying drawing shows some embodiments of arrangements for carrying out the invention.

FIG. 1 shows in vertical section a skeleton diagram of a smelting furnace in which the invention is applied;

FIG. 2 is a vertical section showing more details of the furnace;

FIG. 3 shows an embodiment with cooling boxes which will be called rotate together with the disks for throwing the powder material outward;

3,373,796 Patented Mar. 19, 1968 'ice FIG. 4 shows a further embodiment in which the dressed ore is supplied through a central tube;

FIG. 5 shows an embodiment of a throwing arrangement for the dressed ore;

FIG. 6 is a vertical section of a converter for producing steel from pig iron;

FIG. 7 shows a modification of this converter.

According to FIG. 1 the dressed ore is supplied through a central supply duct 3 into a furnace with a furnace wall 1 and a molten pool 2 in the lower part of the furnace. At the center 4 a rapid, horizontal, radial motion toward all sides is imparted to the dressed ore and at 5 the particle stream is guided from a horizontal to a vertical direction. If the dressed ore comprises various sizes of particles, as is always the case in practice, the coarsest particles 6 will follow the outermost path, while the finer particles 7 distribute themselves inside the coarser particles, and the very finest particles 8 can hardly be induced to follow any well defined path. The result is that the stream of dressed ore will form a space in the furnace defined at its outer contour by the coarser particles 6 while the finer particles 7 and 8 are located within this boundary formed by the curtain of coarse particles.

A high temperature zone 9 is located in the center of the furnace. An object of the invention is the prevention of excessively strong heat radiation from this zone to the furnace walls 1. This is accomplished by the shielding effect of the larger, curtain forming ore particles 6 but to an even higher degree the high temperature zone is cooled or screened off by the finer particles 7 and 8. The cooling effect is proportional to the surface exposed to the heat and the finer particles represent the larger part of the total surface area contained in the ore particles. A dressed ore for this purpose may have a total surface area per weight of, for example, 550 cmP/gram. The coarse particles make up for example 50% of the total weight and have a specific surface area of for example 100 cmF/gram, while the finer particles (making up the remaining 50% by weight) have a specific surface area of 1000 cmfi/gram. Thus for 100 grams of ore having a total surface area of 55,000 cm. the finer particles contribute 50,000 cm. i.e. about In the production of iron, if a rich ore is used, about 15-00 kilograms of dressed ore are used per ton of raw iron and so the total exposed dressed ore surface, with the particle sizes given above, it about 83,000 m. ton of raw iron. It is easily seen that this large surface area has a great heat absorbing capacity.

The shielding effect for the furnace wall is influenced not only by the grain size of the dressed ore but also by the amount of ore per unit of time, the thickness of the layer of ore, and the speed of the curtain of ore. An additional factor, and thus an additional control opportunity, is the distance 13 between the dressed ore curtain and the furnace wall. This distance may, if desired, be very large, since the stream of ore, by its contact with the deflecting screen, serves as a means for delimting the furnace space.

The finer particles thus have a large heat absorbing ability due to the large surface area and can therefore quickly reduce an excessive temperature in the furnace while at the same time the particles themselves are being heated. Byadjusting the percent-age of fine particles the high temperature zone can be maintained at a desired temperature level. The heated, fine, dressed ore particles, like the coarser particles, move downward toward the bath 2 and react there during the reduction.

Quite generally one could consider supplying fine grained particles to a furnace space for absorbing the radiation heat from a high temperature zone. According to this a certain amount of the ore can be sprayed directly toward the high temperature zone. However if no other measures than this are taken, it is not possible to prevent the finest particles from accompanying the exhaust fumes out of the furnace and thus this method is excluded. The present invention solves this problem by placing the finer particles within a curtain of coarser particles as described above.

As mentioned above the finer particles have a greater propensity than the coarser particles to be drawn along by the gas stream. The invention has also solved this problem. The exhaust gases which at leave the furnace through opening 11 must pass through the ore curtain 12 in the area near the center of the furnace where the ore particles have their greatest speed. In this way even fine particles are not drawn along upward by the gas stream. The coarser particles have a certain injector effect and cause the finer grains to be caught in their backwater. In this way an effective filter action is achieved.

The above described method of placing the finer, heat absorbing ore particles inside a curtain of coarse particles at greater speed may be achieved with an arrangement which in principle operates so that the coarse particles are forced to follow a distinct path to form a well defined curtain with a spacing 13 from the furnace lining, while the finer grains are located within this curtain.

An embodiment of such an arrangement is shown in FIG. 2 where only the paths of the coarser ore particles are marked. The ore is introduced for example by a vibration feeder 14 into a chute 15 from which it enters a cavity 16 between a rotating, central, hollow shaft 17 and a cooling jacket 18. In the lower end of cavity 16 the ore encounters a rapidly rotating, substantially horizontal or slightly inclined disk 19 which is rigidly joined with shaft 17. By centrifugal force the ore is hurled outward along the upper surface of disk 19 and then encounters the lower surface of another rotating disk 20 which is rigidly joined with disk 19. The ore then follows the lower surface of disk 20 to the edge 21 where it leaves the disk in an approximately horizontal direction. The disk 20 should make a certain angle with the horizontal plane so that through friction a great speed will be imparted to the stream of ore. The stream of ore 22 encounters a deflection screen 23 placed at a certain distance from the throwing arrangement 19, 20 formed by the disks. This distance is chosen so that the velocity of exhaust gases through the opening is not too large. The stream of ore moves almost horizontally in its free passage and it is observed that the coarser particles are found at the streams upper side. Due to their greater kinetic energy the tzzaarser particles tend to lie nearest the underside of disk After its horizontal passage the stream of ore follows the inner surface of screen 23 which is designed to deflect the horizontal stream into an approximately vertical downward directed stream. The horizontal and vertical stream forms the ore curtain enclosed spaces described above. Deflecting screen 23 has a suitable curvature for this purpose. For a deflection of 90 the profile of the screen may for example be formed from a quarter of a circle with straight sections extending at 90 to each other. The deflection angle (measured on the inside) may however be greater, .e.g. up toward 135. Angles larger than 90 may be-used in larger furnaces when the space enclosed by the ore curtain is to be large. The vertical, or almost vertical ore stream 24 forms the ore curtain for the desired cooling effect.

The rotating shaft 17 is driven from a motor shaft 25 via a speed regulated transmission 26 with a drive pulley 27. The shaft is mounted on bearings 28 and 29.

Since the rotating arrangement is located in the hot exhaust fumes it must be cooled. The cooling may be arranged in the manner shown in FIG. 2. The exhaust fumes which pass through ore curtain 22 are collected in space 30 from which they are directed to a suitable exhaust duct. The space 30 is bordered partly by the horizontal curtain 22 and partly by a jacket with water cooled walls. The part of the drive shaft 17 which is located in the exhaust fume space 30 is surrounded by a water cooled, double jacket 31 whose lower part 32 protects the upper rotating disk 20 while the middle part protects the shaft 17. The cooling water is supplied through pipes 33a to the central upper part 33 and leaves through pipe 33b. The roof and sides of the exhaust fume space 30 are also cooled with double jacketed cooling boxes 34 and 35. The lower cooling section is built together with the deflection screen 23. A seal 36 is located between the cooling boxes for the central parts and the outer parts.

The lower rotating disk 19 is cooled by a double jacketed case 37 which, by means of tubes 38 and 39, communi-cates with a cooling system for the deflection screen 23. Inlet tube 38 is slimmer than the outlet tube 39. By means of inner walls 40 (see also the cross section AA shown at the bottom of FIG. 2) the cooling water is forced to traverse the entire coling box 37. The underside of the cooling box is, for example by means of ceramic material 41, well insulated from radiation to and from furnace space 9.

The invention also includes a simple adjusting arrangement for distributing the coarse and fine particles in the desired manner. This is accomplished by varying the speed of shaft 17 and thus also the speed of disks 19 and At low speeds a larger amount of fine particles will fill the space inside the curtain formed by coarser particles, while at high disk speeds a greater amount of the finer particles follow the ore curtain. This results in a respectively larger or smaller amount of cooling of the high temperature zone.

Powder material and especially iron ore is highly abrasive against the deflection screen. In order to counteract, and possibly prevent, wear and tear various measures may be taken. If the ore is magnetic, as in the case with Fe O or if it to a certain extent consists of magnetic material, a protective layer of the ore itself can be formed by placing a magnet on the backside of the screen. The screen need not necessarily be magnetic itself but if it is the magnetic force lines are better concentrated in the deflection screen. According to FIG. 2 magnets 42 are placed behind screen 23. The ore stream strikes against the screen at 43 where the magnetic particles are collected. By suitably adjusting the strength of the magnet and the distance between the screen and the magnet, it is possible to obtain the desired thickness .of the protective layer.

Another way of protecting the screen is to coat it with a wear resisting ceramic material. An additional method would be to continually or periodically mix a small amount of material with the ore which will cling or sinter fast to the screen and serve for a period as a Wear re sistant coating.

Also the parts of the rotating disks which come into contact with the ore at high speeds, and thus risk being Worn, may be protected in a corresponding way. Magnets 44 may be placed under the lower disk as well as above the upper disk. The other named protecitve methods may also be used on the rotating parts.

The arrangement including the rotating disks is fixed in a powerful frame construction 45. As a safety feature in case of possible explosions in the furnace, the entire arrangement may be swung around point 46 so that the space above the furnace is opened. The force necessary for this swinging may be reduced by adding a counter weight.

In the embodiment shown in FIG. 2 the cooling system is fixedly mounted around the rotating shaft and disks.

FIG. 3 shows an embodiment where the cooling boxes rotate together with shaft 17 and disks 19, 20. Shaft 17 is furnished with an axially located, cooling water channel 50 which at the top communicates with a cooling water connection 51 via a rotatable coupling 52. Shaft 17 is mounted in bearings 53. At the bottom channel 50 is widened into a cooling chamber 54 which cools disk 19 and, by means of a number of vertical channels 61, communicates with a jacket 55 which cools shaft 17 and at its upper end discharges at 56 to allow the cooling water to stream out into cooling space 57. This cooling space 57 surrounds the upper part of the furnace and the water leaves the space through rim outlet 58. The entire cooling is simple and very effective. Chamber 54 forms a cooling box which rotates with shaft 17. A seal is located at 59. The dressed ore is slung out through radial channels 60 between the disks 19, 20 which in this case are secured together.

FIG. 4 shows still another embodiment where the coling systemo rotates with shaft 17 and disks 19, 20, but where the ore is supplied in a central tube 62 in shaft 17 instead of in space 16 according to FIGURES 2 and 3. The ore is supplied from vibration feeder 14 and falls down into funnel 15 located at the upper end of tube 62. In principle the cooling system is similar to the embodiment according to FIG. 3 but the cooling water is supplied through a stationary inlet 63 which opens into an inner cooling jacket 64 surrounding shaft 17 and which at the bottom communicates with an outer cooling jacket 65 on the other side of a partition 66. This cooling jacket 65 is connected With outlet 56. In this case disk 19 has no cooling chamber of its own but is protected from below by a ceramic protective material 67.

The arrangements shown in FIGURES 2-4 are designed not only to form a heat absorbing ore curtain 24 but also to serve as a filter for the exhaust fumes which stream upward through the horizontal curtain 22 in order to leave through upper space 30. In the normal case curtain 22 is sufficient to ensure that the finer ore particles are not carried out of the furnace by the exhaust gases. If additional cleaning of the exhaust fumes is desired, an additional horizontal curtain may be arranged. This curtain may possibly be made of a material other than the iron ore, for example sand, which may be pretreated such as by sifting so that the finer grain fraction is removed. The sand may be circulated in the system.

FIG. shows how a throwing arrangement may be fitted into the upper part 68 of a furnace space. The gases pass at through ore curtain 22 up through channel 11 to the gas outlet. The additional curtain 69 is arranged in channel 11. The sand, or similar granular material, is fed via a chute 70 to a stationary double walled tube 17 and by the rotating disks 72 and 73 the sand is slung out in form of a curtain 69 against wall 74 of channel 11. Disks 72 and 73 are rigidly secured to each other and to the rotating hollow shaft 17 to which also the lower disks 19 and 20 are secured. The sand in curtain 69 is slung against the cupped wall 74 and thereby the stream is deflected vertically. The sand is collected in a groove 75 and leaves the system via a surface 76. Thereafter the sand may be returned to chute 70, possibly after having first passed through a channel 77.

The powdery raw material for the process may also be used for the secondary filter curtain 69. In that case the ore is supplied in the same way as shown in FIG. 5 and removed through channel 77 in the furnace lining. Thereafter the ore which may have been heated to about 500 C. is returned to the supply location 70. In addition several curtains 69 may be used.

In large furnaces the furnace may have an oblong horizontal cross-section with semi-circular ends. Several ore curtains may then be arranged horizontally beside each other. The outlet for the exhaust gases may be suitably located at ends of the extended furnace space.

Many modifications of the invention may be carried out within the scope of the invention. Oxygen or air may be supplied from a distributing conduit 78 (FIG. 1) through holes 79 in the walls of the combustion chamber, preferably at the lower part of this chamber above the molten pool 2.

It is clear from the above description that one may control the speed of the powder particles in order to thereby regulate the cooling effect. The powder material,

6. preferably the finer particles, may be blown directly into the high temperature zone in order to cool this zone.

Furthermore the described disks could be replaced by some other rotating throwing or blowing arrangement,

' e.g. in the form of one or more rotating nozzles.

If the major portion of the powder material is nonmagnetic a certain amount of magnetic powder material may be mixed in so that by means of a magnetic field a protective layer may be formed on the deflecting screen and possibly on the moving parts of the driving arrangement of the disk. In addition thereto, material which clings fast or sinters fast to the deflecting screen or the rotating disks, etc. may be used as coating for these parts. The rotation speed of the disks may be varied in order to regulate the distribution between the fine and coarse particles.

Difficulties with the furnace lining also often occur in other processes than in smelt reactions. The same principle as described above may for example be used in the production of steel from pig iron in a converter with oxygen injection. FIGURES 6 and 7 show an example of this application of the invention. In FIG. 6 the converter is indicated by 1 while 2 is a molten pool of pig iron against which oxygen is blown in through tube 78. Liquid pig iron and/or ore, scrap or other powder material is supplied through an outer tube 17 and by means of a stationary or rotating disk 79 thrown outward to form a curtain 80 which is deflected to a substantially vertical curtain enclosing the high temperature zone as can be seen in the drawing. In this way the converter wall is cooled. The liquid pig iron may be either thrown directly against the converter wall or the earlier mentioned screen may be used to form a curtain between the converter wall and the combustion zone. In most cases the spreading of material directly against the converter wall should be suitable. At the same time this curtain acts as a filter for the exhaust fumes. Simultaneously with the pig iron one may also supply a requisite amount of ore.

The oxygen may in a known way be blown in from the side or through the center of disk 79 as shown in FIG. 6. The disk and its central shaft may be coated with fire resistant material.

By spreading the pig iron in this way a large contact surface is obtained.

Also according to FIG. 7 the converter may be furnished around the top with a groove 81 into which pig iron is poured from a container 82 with bottom outlet 83 and stopper 84. When the groove is filled to a certain level the pig iron runs over the edge and downward to form a curtain enclosing the high temperature-zone and/ or downward along the converter wall which is thereby cooled.

What we claim is:

1. A method for cooling of a combustion chamber by means of powdery material with various grain sizes which in the form of at least one curtain is supplied between a wall of the combustion chamber and a high temperature zone therein, said method being characterized in that the coarse particles of said powder material are mainly sup plied outside the fine particles in relation to the central part of the high temperature zone.

2. The method according to claim 1 wherein a plurality of curtains are supplied at various distances from the furnace walls for regulating the cooling effect of the curtains.

3. The method according to claim .1 whereen the speed of the powder particles is varied in order to control the cooling elfect in respect to the furnace wall.

4. The method according to claim 1 wherein at least part of the powder material is supplied directly toward the high temperature zone in order to cool said zone directly.

5. The method according to claim 1 wherein exhaust gases from the combustion chamber .are cleaned by being passed through at least one particle curtain.

6. The method according to claim 5 wherein the gases are cleaned b being passed through at least a second particle curtain.

7. The method according to claim 1 wherein magnetic powder material'is mixed into a substantially non-magnetic powder material.

8. The method of cooling a combustion chamber by means of at least one curtain of liquid material supplied between the wall of the combustion chamber and a high temperature zone therein.

9. The method of claim 8 wherein the liquid material is liquid pig iron and the combustion chamber is a converter for producing steel from pig iron.

10. -An arrangment for cooling a combustion chamber by means of fluent material supplied in the form of at least one curtain characterized in that rotatable means are arranged to receive the filament material and force it against at least one deflecting screen arranged to deflect the coarser particles of the material stream into at least one curtain between the chamber wall and an inner high temperature zone while the finer particles form a particle layer near the center of the high temperature zone.

11. The arrangement according to claim 10 which include-s a device for supplying the powder material to the rotatable means through a cavity between an inner rotatable shaft for said rotatable means and an outer cooling Wall.

12. The arrangement according to claim 10 wherein the powder material is supplied to the rotatable means through a hollow shaft which rotates the rotatable means.

13. The arrangement of claim 10 wherein a cooling system is arranged for cooling the rotatable means.

14. The arrangement of claim 13 wherein the cooling system rotates together with the rotatable means.

15. The arrangement of claim 10 wherein said fluent material is magnetic and said arrangement includes means for producing a magnetic field to cause some of said magnetic material to form a fixed layer on said deflecting screen.

16. The arrangement of claim 10 wherein a layer of ceramic wear resistant material is located on the deflecting screen.

17. The arrangement of claim 10 wherein the exhaust gases from the combustion chamber pass through .at least one of said curtains so as tobe cleaned thereby.

1-8. The arrangement of claim 10 including means for controlling the distribution of the fine and coarse particles of the fluent material.

19. The arrangement according to claim 18 wherein the regulation is achieved by adjusting the rotation speed of the rotatable means.

20. The arranagement according to claim 10 wherein the rotatable means includes at least one nozzle for blowing the fluent material in a substantially horizontal direction.

21. The arrangement according to claim 10 wherein plural rotatable means are arranged beside each other in an oblong combustion chamber.

22. An arrangement for cooling a combustion chamber by means of fluent material in at least one curtain characterized in that said arrangement includes a groove at the top part of said combustion chamber and said fluent material is a liquid which overflows from said groove to form a curtain of liquid material inside said combustion chamber.

References Cited UNITED STATES PATENTS 2,769,618 11/1956 'Nettel 1 2,965,463 12/1960 Elliott 165l34 3,307,616 3/1967 Giger 1651 ROBERT A. OLEARY, Primary Examiner. C. SUKALO, Assistant Examiner.

Claims (1)

1. A METHOD FOR COOLING OF A COMBUSTION CHAMBER BY MEANS OF POWDERY MATERIAL WITH VARIOUS GRAIN SIZES WHICH IN THE FORM OF AT LEAST ONE CURTAIN IS SUPPLIED BETWEEN A WALL OF THE COMBUSTION CHAMBER AND A HIGH TEMPERATURE ZONE THEREIN, SAID METHOD BEING CHARACTERIZED IN THAT THE COARSE PARTICLES OF SAID POWDER MATERIAL ARE MAINLY SUP-

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