US2155927A - Apparatus for charging furnaces - Google Patents

Description

'PY 25, 1939- A. .1'. BOYNTON APPARATUS FOR CHARGING FURNACES Filed May 23, 1936 Inl/enf@ 7:-

Patented Apr. 1939 UNITED STATES YPATENT oFFicE d: Company, Chicago tionoflllinols Application my za, use, seran No. c1325 z claim (ci. zii-ss) 'I'his invention relates to a new and improved apparatus forcharging furnaces and particularly fori charging shaft furnaces, such, for example. as blast furnaces for the manufacture of pig iron.

In my prior Patent No. 1,815,897, the high degree of permeability of the stock column at and near the center of the blast furnace has been discussed. With the furnaces having moderate top diameters as formerly built, the circumstances of distribution of ore were approximately as required to intercept to the best advantage the currents of ascending' gases which form the media for reduction and preheating of the furnace charge. A furnace having a diameter at the stock line of 17 feet, which was a dimension formerly much in use, was customarily provided with a charging bell 13 feetl in diameter. The result of these dimensions and of the size of charge usually employed was the placing of ore within the furnace in the form of an annulus, the outer periphery of which coincided with the walls of the furnace while the inner diameter was from 4 feet to 5 feet. 'I'he central core of 4 or 5 feet in di ameter contained but little ore, but was composed of coke, for the most part of a size above the average of the charge. The permeability of this central core was reduced byits slow motion tc which reference is made hereafter, andit is probable that the permeability was not excessive so long as the furnace retained the 17 foot diameter at the stock line. This dimension was originally related to a maximum diameter at the boshof the furnace of 22 feet. This latter diameter has since been increased to nearly 28 feet which would result in a stock line diameter of 23 feet if the original dierential between the two diameters were preserved. Furnace designers have, however, refrained from making such an extreme change in stock line diameter which, today, has in no case exceeded feet. The relative constriction of this dimension has resulted in a high velocity of gases through the furnace top and a disposition to increase the ue dust production. Furnace designers have realized that when charging by means of an ordinary bell, an increased stock line diameter involved either an open center of large diameter or a failure to so distribute the charge laterally as to seal the walls with ore. The development in large furnace design to date has, therefore, been characterized by a stock line diameter smaller than would be preferable if the limitations of charging were removed.`

A blast furnace always received its air of combustion through a plurality of tuyres spaced about the periphery of the hearth. Investigation has proved that the union of this air with the coke of the furnace charge is complete within 42 inches Asslnning a nominal hearth diameter of.26 feet,` and a projection r of the tuyre beyond the hearth wall of 9 inches. the distance between opposite tuyre noses would be 24'6" and the inert circle of charged material inside the limit of combustion activity at the tuyre would be approximately 17 feet.

The causes of the .descent oi' the blast furnace 10 charge are first, the gasification of coke, and second, the shrinkage in volume d ue to melting of iron and slag. 'Since the ore is charged into the furnace in the form of an annulus next the wall these two causes of shrinkage affect the same porl5 tions of the furnace charge. Descent is more rapid above the tuyres. while in the center of the furnace at the-bottom the only movement is. that caused by absorption of carbon by pig iron in the hearth. This movement may conceivably 20 amount to'nothing if carburization of pig iron is complete by the time the iron reaches the hearth.

Movement of stock in the upper levels is also at a maximum next the walls and'a -minimum at the center. Thiscentral movement, although 25 relatively slow is a maximum at the stock line and a minimum in the hearth.

Observations made under the'auspices of the United States Bureau of Mines and published in Technical Papers No. 442 and No. 459 of the Bureau show the results of ordinary charging in a furnace too wide for usual methods tp give a perfect result. These researches indicate that speed of gas passage, grs pressure, content of carbon monoxide and gas temperature are all at a maximum in the center oi' the furnace and a minimum inthe annulus between an assumed central cylinder and the outer wallof the furnace. There is a disposltinnalso for these quantities to increase at points quite close to the wall, 40 a fact which indicates that any attempt to seal the center by reduction in the diameter of the bell will result in hard working of the gases on the walls of the furnace. with'consequent rapid deterioration of the lining. The width of the 45 annulus which can be covered by ore discharged from a bell, depends in some measure on the size -of the charge relative to the diameter of bell and stock line, but within the limits of the size of charge capable of being held on a bell of practical size at one time, and of the distance between bell and stock line its maximum width is between 6 and 7 feet. Thus with a 13 foot bell in a 17 foot stock line, the inner circle of the ore annulus will have a diameter of 4 feet. If the diii'erence 55 between inner and outer circles of the annulus is assumed to be constant, the inner circle of the ore annulus will have a diameter of 6 feet in a 19 foot stock line, and of 8 feet with a 21 foot stock line. These figures presuppose an increase of bell diameter which maintains a constant dinerence between diameter of bell and of stock line.

Under these conditions the central circle within which little or no ore is present is not only absolutely but relatively larger as the stock line increases. With an increase in stock line diameter from 17 feet to 23 feet, the area of the top increases 85.5%, that ofthe ore annulus 56.8% and that of the central ore-free circle 626.5%', while the ratio of area of ore-free area to that of ore annulus increases from 5.85% to 23.35% a relative increase to 4.05 times the original percentage.

With regard to means available for reducing the flow of gas through the center it is evident that ore placed within the central area, while it will be rapidly reduced by ascending gases will not experience contact with gases at the high temperatures which exist in front of and immediately above the tuyres. It is in the latter locality that final reduction and superheating above the melting temperature takes place. Experience shows the amount of ore which may be usefully placed at the center of the furnace to be very small.

On the other hand the placing of relatively small sizes of coke in the center of the furnace involves no such difficulties as does the similar placing of ore. The coke does not require to be reduced or smelted, but merely to be heated to a temperature which it limited by its position in the furnace. The size of coke so placed should be suii'iciently small to produce the desired reduction in amount of gas: passed, but sufficiently great to permit the passage of an adequate supply of gas to heat the central column.

It is an object of the present invention to pro' vide a new and improved method for charging shaft furnaces such as blast furnaces.

It is an additional object to provide a method of this character which is especially adapted for use in connection with blast furnaces of relatively large diameter.

It is also` an object to provide a method in which the larger material may be charged in an annulus adjacent the furnace walls and the finer material in the center of the annulus.

It is a further object to provide a method in which the center charge of nner material consists largely or entirely of c oke.

It is another object to provide means for carrying out these improved charging methods.

It is an additional objlect to provide furnace top mechanism including separately operable means for charging material toward the sides or center of the furnace.

It is also an object to provide a top construction including a primary charging hopper and secondary inner and outer distributing hoppers.

It is a further object to provide means for selectively transferring material from the primary hopper to either of the secondary hoppers.

It is another object to provide a construction which is simple in design and construction and adapted for commercial installation and use.

Other and further objects will appear as the description proceeds.

I have shown certain preferredembodiments of my invention in the accompanying drawing, in which- Figure 1 is a vertical section of a furance top and charging mechanism; and

I5, but it will be understood that this hopper and the associatedV portions may be supported by means of the usual structural framework which is not shown. The receiving hopper Il is supported above the rotating hopper I4 and is adapted to receive the material from the `cars and carry it into the rotating hopper.

The rotating hopper I4 is provided with the gear ring I1 and is supported upon rollers I8. The flange I9 effects a substantially gas-tight closure with the upper fixed ring 20 of the furnace structure. The rotating hopper I4 is closed by the upper bell 2I which is supported upon the tubular rod 22, which may be raised and lowered by any usual mechanism. The movable intermediate hopper 23 surrounds the lower end of the rotating hopper I4 and is provided with a plurality of extended arms 24 connected by means of rods 25. The rod 25, shown in Figure 1, is connected to a' chain 26which passes over pulley 21 xedly secured to shaft 28. 'I'he shaft 28 is rotated by means of a motor 23 having a sm'all gear 30 meshing with the large gear 3l suitably secured to the shaft 28. The endsl of the shaft 28 carry the pulleys 32 and 33 to which are connected the chains 34 and 35, passing over idler pulleys 38 and 31. These idler pulleys 33 and 31 are supported independently of the yshaft 28. The ends of chains 34 and 35 connect to similar supporting rods not shown.

The intermediate wall 38 separates the outer secondary hopper I2 and the innersecondary hopper 39.. This member 33 has an outwardly flared lower portion 40 which forms the bottom of the outer secondary hopper. inwardly extending lower portion 4I which serves to form a portion of the bottom of the inner secondary hopper 33. The intermediate member 38 is supported by means of a spider 42 which is connected by universal connection 43 to the tubular supporting rod 44 which may be raised and lowered by any suitable mechanism, not shown. The remainder of the lower portion of .the inner secondary hopper 39 is closed by the small bell 45 which is heldin position by means of the supporting rod 46. 'Ihe bell 45 normally rests on the inwardly extending portion. 4I of the intermediate member 384 and is held down by means of springs 41 which bear against the member 48 secured to the rod 46 and against the abutment 48, and thus contact is maintained between the bell 45 and the portion 4I.

, In order Ito discharge material from the inner .secondary hopper 39, the intermediate member 38 is lowered away from the bell 45, which is, limited in its downward movement by the-stop 50 which engages the abutment 49.

In the operation of the form of construction shown to carry out my improved method, a

mixed charge of large coke, flux material, such as limestone, and ore may be introduced into the receiving hopper I6 from which they pass into the rotating hopper I4. It will be understood IthasalsoanA that these materials may be mixed or the charge may comprise only one or two of the materials. In order to discharge these materials toward the outer wali of the blast furnace, the bell 2l is lowered and the material passes from the lower edge of the bell into the outer secondary hopper betweenv the walls i3 and 38. To discharge this material into the furnace, the intermediate member 38 is lowered so that the lower edge of theA portion di) clears the lower edge of the xed wall I3. The material is then discharged from the sloping wall fl@ against the stock line of the furnace and falls adjacent the walls. lt will be understood that the small bell 2l is closed before the intermediate member 38 is lowered, so as to prevent passage of gases from the furnace. In order to charge material such-as fine coke rtoward the center of the furnace, this material is passed in the receiving hopper i6 to the rotating hopper Ml. The intermediate hopper 23 is then lowered by rotating the shaft 28 until it reaches a position such as shown in broken lines in Figure l. The small bell 2i is then lowered to the broken line position of Figure l, in which position the fine material passes from the bell 2l against the inner wall of the member 23 and then Hows down into the inner secondary hopper 39. The small bell 2l is closed after the material has been discharged from the rotating hopper M. The intermediate member 38 is then lowered and the material in the inner secondary hopper 39 flows from the inwardly sloping bottom wall 4l the apparatus shown may be used for selectively charging any material to the center or to the outer portion of the furnace. -While I have described certain methods and illustrated certain preferred forms of construction, these are to be understood as illustrative only, as I contemplate such changes and modifications as come within the spirit and scope of the appended claims.

I claim:y 1. 'In-a blast furnace top, a primary hopper, a bellv for closing said hopper, and inner and outer secondary hoppers including a fixed outer wall for the outer secondary hopper, a movable intermediate member comprising the inner wall and bottom closure for the outer secondary hopper and the outer wall of the inner secondary hopper, a bell .for closing the inner secondary hopper, the primary hopper `bell normally discharging material into the outer secondaryhopper, and movable rmeans adapted to selectively deilectA material discharged from the primary hopper bell into the inner secondary hopper.

2..In a blast furnace top, a primary hopper, a bell for closing said hopper, and inner and outer secondary hoppers including a xed outer wall for the outer secondaryI hopper, a movable intermediate member comprising the inner wall .and bottom closure for the outer secondary hopper and the outer wall of the inner secondary hopper, a bell for closing the inner secondaryA hopper, the primary hopper bell normally discharging material into the outer secondary hopper, and a vertically movable transfer hopper normally out of the path of material owing from the primary hopper, said transfer hopper being movable down adjacent the movable intermediate member and there adapted to selectively deflect materialdischarged from the primary hopper bell into the inner secondary hopper.

ARTHUR. J. BOYNTON.

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