US3544096A - Cross-current blast furnace - Google Patents

Description

References Cited UNITED STATES PATENTS 485,392 11/1892 Koncman............. 1,895,284 l/1933 Hay............. 2,078,747 4/1937 Via1..............

2/1938 Greenawalt .II S am .mM 1 tu m hmc awn M m m d OS nfi c a g eemhgem t nn .1 .1a mm m wM hem 0 k dd.m.hl. ae wa d up .10 u vCnl Mm .WI 9.0. d dn U .m m .1 d is mk nfl O e a fit liSeW tau n b dw nmw eo m OVClVWI Primary Examiner-J. Spencer Overholser Assistant Examiner.lohn S. Brown Attorney-Singer, Stern & Carlberg ABSTRACT: A crosscurrent blast furnace for the combustion [21 Appl. No.

[22] Filed [54] CROSS-CURRENT BLAST FURNACE wzom 3 [51] Int. [50] Field 11,17, 25, 27, 20, 24, 30; 263/29, 30; 75/34, 35,

CROSS-CURRENT BLAST FURNACE The invention relates to a crosscurrent blast furnace for the combustion or sintering of limestone, dolomite or magnesite in a stack with preferably rectangular cross section and with gas chambers arranged at opposite sides, in which furnace the combustion material passes from top to bottom consecutively through a preheating zone, at least two combustion zones and a cooling zone as well as sealing zones disposed between these zones. Furnaces of such type are known, for example the German Pat. No. 976,930 discloses a furnace, in which the combustible heating gas flows consecutively through several combustion zones disposed superimposed and with mutiple partial addition of preheated combustion air and gradually is burned along this path. With this type of construction, the control of the temperature conditions in the individual combustion zones requires great care and skill, as every change in the feed of combustion air takes effect on all combustion zones following in the gas flow direction. The speed of the gas in the combustion zones is relatively low and accordingly, the temperature drop between the inflow side and the outflow side of each combustion zone is greater than is desirable in the interest ofa quality end product.

For the simple control of the combustion temperatures, also arrangements with several firing devices independent of one another were suggested previously. Furthermore, arrangements are known, in which the furnace yield is to be increased by means of two driving nozzles for the circulation of the heating gases, said nozzles being connected consecutively in the gas flow direction (German Pat. No. 1,034,090,) and another in which a more uniform temperature distribution is attempted over the cross-sectional area of the stack by means of a periodic change ofthe direction of flow of the heating gases.

Up to now, however, no crosscurrent blast furnace of the above indicated type has become known, which combines the advantages of high uniformity of the end product with a simple servicing as well as high furnace yield and economy. This invention has the object of coming closer to this aim.

In accordance with the present invention each combustion zone has a heating gas circulation, closed per se, which is provided with its own individual means for introducing fresh air, fuel and energy, and there is also provided at least one gas channel discharging into the preheating zone. Since a furnace of this type may be so operated that at a sealing zone disposed between two combustion zones no noteworthy drop in gas pressure exists, it is possible to provide channels from the illustrated gas chamber floors to the adjacent sealing zone or to a feed device and thus to obtain areturn of the combustion material dragged along by the heating gas in the stack or its discharge without manual effort.

For the supervision and adjustment, respectively, necessary for the operation, of the combustion air supply and fuel supply, as well as of the gas pressure in each heating gas circuit, means known per se, are provided, such as measuring instruments, valves, slide members and throttle valves, which also may be in operative connection with a regulating device.

The drawing illustrates by way of example a crosscurrent blast furnace in accordance with the invention.

Referring to the drawing, the furnace stack 1 extends over the entire height of the furnace. The combustible material is introduced at the upper end of the stack, which in known manner is provided with a charging gear installation not shown in the drawing. The stack 1 is divided into a preheating zone 2, a sealing zone 3a, an upper combustion zone 40, a second sealing zone 3b, a lower combustion zone 4b, a third sealing zone 3c and a cooling zone 5. At the lower end 6 of the stack 1 is disposed a device, not shown in the drawing, for the continuous discharge and withdrawal of the burnt material with a speed which corresponds to that of the combustion process.

Before the burnt material leaves the stack, it is traversed by a stream of fresh air in the cooling zone and thereby is cooled. The heated cooling air passes through a preheater 7 for use as combustion air. The preheated combustion air is conducted by pipe conduits 8 into jet blower 9. Each combustion zone is associated with at least one jet blower. In this manner, each combustion zone is provided with a heating gas circuit in which both the required quantity of preheated combustion air as well as also the necessary kinetic energy for the multiple revolution of the heating gases in the heating gas circuit is introduced. The circulation of the heating gases in each combustion zone 4a, 4b is produced by the jet blower 9 from the combustion chamber 10, through the infeeding gas chamber 11, the associated combustion zone, the discharging gas chamber 12 and a circulation channel 13 and back to the jet blower 9, as indicated by arrows in the drawing. The fuel is introduced by the burner 14 into the combustion chamber 10. The excess gas forming during the combustion process is conducted by the exhaust gas channels 15, above the upper sealing zone 3a into the preheating zone 2 and after it has transferred the heat to the fresh charging material, it is discharged into a flue or chimney 16.

In the described arrangement, the heating gases flow openings 17 in the walls of the stack, horizontally, namely, in a crosscurrent, through the combustible material disposed in the stack. In order to prevent that the gases flow through the stack in a vertical direction, there are arranged above and below each combustion zone, sealing zones, which consist of suitably dimensioned sections of height of the combustible material column. The sealing effect is insured in sufficient degree by means of the densely layered combustible material. Deviating from the example shown, a desired number of combustion zones may be provided, so that it is always possible and advantageous for uniformity of the end product when the direction of the heating gas flow through the stack alternates from combustion zone to combustion zone. Even if the temperature gradient between the inflow and outflow side of the combustion zone, on account of the repeated circulation of the gas and high circulation speeds is very small, so that thereby alone a very uniform burning is attained over the entire cross section of the stack, the alternating direction of the gas flow ties in with different sinking decreasing speed at the beginning of nonuniformly burnt portions of the combustion material.

The flow of the heating gases during the operation causes the finer grains of the combustible material to be dragged along. They collect for the most part on the floors of the gas chambers. Owing to the inclined position of the gas chamber floors l8 and its transition into a channel 19 communicating with the next adjacent sealing zone, the material divided out under action of specific gravity comes again into the stack 1 for further treatment. Because the individual heating gas circuits are completely independent of one another, the sealing zones may be kept free from gas flow and pressure differences, so that the passage downwardly of the separated material is not affected. Since, under certain circumstances it is not desired to return the deposits in the lowermost gas chamber into the stack 1, there are provided mechanical conveyor devices 20 which remove the deposits continuously.

The high economy of the furnace according to the invention rests, in addition to the full utilization of the waste heat in the cooling zone 5 and the preheating zones 2 on the intensive circulation of the heating gas in connection with the possibility of influencing independently the air and fuel feed in each heating gas circuit and therewith is insured the desired quality of the end product in each combustion zone, whereby the values of the temperature of the gas speed and the gas pressure permit an adjustment of the quality of the gas or a maintenance of the same by means of regulating apparatus according to prescribed values, without that by means of an adjusting or regulating operation the other combustion zones are affected. In this manner, a stable furnace operation is insured.

As adjusting member, may be employed any desired flaps, slide members, valves and ejectors known in the art but not shown in the drawings. The adjusting members are arranged in the conduits for air and fuel 8, 14, as well as in the exhaust gas channels 15 or in other suitable and accessible places, and if need be may be brought into operative connection with measuring and regulating members likewise of known kind.

I claim:

1. ln acrosscurrent shaft: furnace for burning and sintering material such as limestone, dolomite and magnesite, avertical stack through which said material is passed from atop supply end to a bottom discharge end, a first sealingzone in said stack adjacently below said'top supply end, a second-sealing zone,in

said stack adjacently above said bottom discharge end, at least two superposed combustion .zones in said stack-between said first and second sealing zones, at least one additionalsealing zone in said stack separating said combustion zonesfrom each other, wallmeansspaced outwardlyfrom saidflstackand extendingfrom top-to bottom of each said combustion zone-to form at one side of each combustion zone a-f rstseparate chamber and at theopposite side of each said combustion zone a second separate chamber, said first and second separatechambershaving top and bottom walls, a combustion chamber at the bottom of said first separate chamber and communicating therewith, a circulation channel at the top of said second separate chamber and communicating therewith, fuel supply means for supplying fuel separately toeach said' combustion chamber, at least one jet blower opening-into each said combustion chamber, means for supplying compressed air to each said jet blower through saidcirculatioh,

channel, means .for preheating said compressed air, and conduit means connecting said circulation channel with a com bustion gas exhaust opening, whereby a circuit is provided through which'combustion gas passes from said combustion chamber tosaid first separate chamber, through the material bers may be returned to the downwardly moving material within said stack;

33 The.crosscurrentshaft'furnace as set forth-in claim 1, in which said first and second separate chambers nearest the bottom'ofthe stack are in communication with'mechanical conveyor means disposed below said first and second separate chambers.

4. The crosscurrent shaft furnace as set forth in claim 1, includinglcontrol means for regulating the fuel supply, the compressed air supply and the exhaust gas discharge,

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