US3764027A - Blast furnace high top pressure charging system - Google Patents

Abstract

A blast furnace high top pressure charging system, and a method of operating such a system, in which burden materials are charged into a receiving hopper which is pressure isolated from the balance of the charging system, and thence into a small bell hopper from whence it is charged into the furnace. A conical revolving hopper is located within the furnace in lieu of the conventional bell system. The revolving hopper can be operated either during passage of burden materials into the furnace, or between successive charges, to thereby provide uniform distribution into the furnace together with decreased drop heights.

Description

United States Patent 1 Tokarz BLAST FURNACE HIGH TOP PRESSURE Inventor:

U.S. Cl. 214/37, 266/27 Int. Cl. F27b 11/12 Field of Search 214/35 R, 35 A, 36,

[56] References Cited UNITED STATES PATENTS 9/1972 Mahr et al. 214/35 R 6/1964 Renkes et a1. 266/27 X Oct. 9, 1973 [57] ABSTRACT A blast furnace high top pressure charging system, and a method of operating such a system, in which burden materials are charged into a receiving hopper which is pressure isolated from the balance of the charging system, and thence into a small bell hopper from whence it is charged into the furnace. A conical revolving hopper is located within the furnace in lieu of the conven' tional bell system. The revolving hopper can be operated either during passage of burden materials into the furnace, or between successive charges, to thereby provide uniform distribution into the furnace together with decreased drop heights.

4 Claims, 5 Drawing Figures Patented ()ct BLAST FURNACE HIGH TOP PRESSURE CHARGING SYSTEM BACKGROUND This invention relates to blast furnace high top pressure charging systems and specifically to a method and apparatus which is economical and efficient in operation.

Furnace top charging equipment has two main functions which are, firstly, to receive the burden materials such as coke, ore, sinter, pellets, etc., and charge into the furnace, and, secondly, to prevent the escape of furnace gases.

With respect to its function of receiving burden materials, it is of paramount importance in the successful operation of the furnace that the materials flow into the furnace at a uniform rate and that the materials are uniformly distributed within the furnace.

In uncontrolled charging, the larger lumps of different materials have the tendency of collecting at one side or the other of the furnace. This results in segregation which is the formation of more or less open and continuous channels through the materials extending from the top towards the bottom of the furnace stack. A lesser resistance is offered to the passage of gases in the furance through these channels than through the remainder of the materials in the furnace. The channeling or segregation results in the passage of a disproportionately large quantity of gas through the channels. This condition also results in excessive temperatures along the passages.

The irregular distribution of materials will cause the furnace to work hot and wear lining excessively on one side and cold on the other side, thus preventing the furnace from obtaining its optimum performance.

To overcome this deficiency, various plans and devices have been employed to introduce the materials into the furnace in such a way that this segregation of coarse and fine materials will not occur, or, if it happens, it can be corrected. By and large these plans and devices have not been efficient, economical, and widely applicable to furnaces currently in operation.

With respect to the second function of preventing the escape of furnace gases it has now been well established that gases resulting from the melting operation must be captured for subsequent use to ensure economical operation of the furnace. Thus, any leakages or losses of blast furnace gas is undesirable from the operating and economical standpoints.

It has also been well established that the functioning of a blast furnace can be materially improved by increasing the gas pressure in the furnace, as for example even higher. However, operation at higher pressures with conventional equipment in present use causes excessive gas losses and malfunction of some parts of the system.

For example, conventional systems for distribution of materials and gas sealing in large furnaces of high top pressure with oversized bell are not satisfactory for sustained furnace performance. The oversized bell is expensive to fabricate, difficult to operate, and laborious to replace. Such a bell is easily worn and is subject to too frequent failure, all of which cause limitations in the production of iron.

The escaping gases are of high temperature and have a high content of extremely abrasive dust which in turn causes additional difficulties in the charging system and in the satisfactory performance of the furnace.

In view of the above described difficulties it has been impossible to date to operate a blast furnace with super high top pressures for periods of time longer than the conventional periods of time experienced by non-high top pressure installations.

SUMMARY OF THE INVENTION The present invention provides a blast furnace high top pressure charging system capable of operating for relatively longperiods of time with none of the serious difficulties which have heretofor been experienced.

Accordingly, a primary object of the invention is to provide a new and improved blast furnace, and a method of operating it, in which flow of materials into the furnace at a uniform rate is provided, and the materials are uniformly distributed within the furnace.

A further object is to provide :a new and improved blast furnace high top pressure charging system, and a method of operating it, which enables materials to flow into the furnace at a uniform rate, and the materials to be uniformly distributed within the furnace.

Another object is to provide a new and improved blast furnace, and a method of operating it, which minimizes the escape of furnace gases.

Another object is to provide a blast furnace high top pressure charging system, and a method of operating it, which minimizes escape of furnace gases.

Yet a further object is to provide a new and improved blast furnace, and a method of operating it,which does not require the use of a conventional charging bell located within the furnace.

Yet a further object is to provide a blast furnace high top pressure charging system, and a method of operating it, capable of functioning uninterruptedly for long periods of time.

Yet a further object is to provide a blast furnace high top pressure charging system in which charged materials may be handled easier than in conventional systems, and which includes a reduced drop height.

Another object is to provide a blast furnace high top pressure charging system having independently controlled means for placement of burden materials at any desired location in thefurnace.

A further object is to provide a blast furnace high top pressure charging system having positively sealed hoppers and receiving chambers which may be equipped with either small bells or flap gate type valves, but in which, whatever form of sealing is provided, protection of the burden material containers from the furnace interior is provided.

Yet a further object is to provide a charging system for a blast furnace high top pressure charging system, and a method of charging, in which gas losses resulting from charging and leakage are minimal.

Yet a further object is to provide: a blast furnace high top pressure charging system, and a method of operating it, in which the only charge supporting apparatus located within the furnace is a revolving distributing hopper, and in which only the valve member of an offset discharge hopper is directly exposed to the furnace atmosphere.

Another object is to provide a blast furnace high top pressure charging system, and method of operating it, which does not require extra power to actuate the rotating elements and associated charging gear.

Yet a further object is to provide a blast furnace high top pressure charging system, and method of operating it, in which the dome charging mechanism is isolated from the furnace by a hinged flap gate, and further characterized in that the hinged flap gate is operated outside the pressurized chamber.

Yet another object is to provide a blast furnace high top pressure charging system, and a method of operating it, which includes two independent charging systems having two primary feeding sources, each of which discharges into an independent run of receiving hopper, bell hopper, and discharge hopper, the two independent systems having a common discharge mechanism feeding into a single revolving distributing mechanism within the furnace, each receiving hopper being isolatable for repair or other reasons from the balance of the system whereby said furnace can be maintained in operation during repair and maintenance periods.

Another object is to provide a blast furnace high top pressure charging system so constructed and arranged that lesser amounts of dust are carried out the uptakes with the gas.

Other objects and advantages of the invention will become apparent from a reading of the following description thereof.

DESCRIPTION OF VIEWS The invention is illustrated more or less diagrammatically in the following drawing wherein FIG. 1 is an elevation with parts in section of the blast furnace high top pressure charging system of the invention;

FIG. 2 is a section in elevation of another embodi- -ment of the hopper portion of the charging system;

FIG. 3 is a detail view to an enlarged scale with parts in section of a sealing arrangement for bell valves in the system;

FIG. 4 is a time-pressure diagram of the furnace top pressure and associated charging chamber pressures; and

FIG. 5 is atime-differential pressure diagram for the furnace top and charging vvalves.

DETAILED DESCRIPTION Like reference numerals will be used to refer to like parts throughout the following description of the Figures.

The upper portion of a blast furnace is indicated generally at 11, the furnace top dome at 12 and offtake and uptake discharge fiues for the hot dirty gases at 13.

A conical revolving hopper is indicated generally at 14, the hopper having a single chute indicated at 15. In operation the chute may rotate continuously or intermittently and deposit material circumferentially around the furnace at the stockline zone, or it may be stationary during charging.

Charge materials are received in the revolving hopper 14 from a charging system which includes a suitable long distance conveying mechanism 16 for transporting the burden material from a primary location, such as a stock bin, to the furnace.

The conveyor 16 discharges into a receiving hopper indicated generally at 17. The discharge outlet 18 of the receiving hopper is closed by top small bell 19 which is operable, by any suitable conventional mechanism, such as hollow shaft 26, to open and close communication with the balance of the system located below. Top small bell 19 and the discharge outlet portion of the receiving hopper is constructed and arranged in such fashion that a seal is formed between the bell and the discharge outlet portion as at 20.

The receiving hopper discharges into a small bell hopper indicated generally at 21. The small bell hopper includes a discharge outlet portion indicated at 22. Communication between the small bell hopper 21 and the charging equipment therebelow is controlled by bottom small bell 23 which is constructed and arranged to form a seal with the discharge outlet portion 22 of the small bell hopper as at 24.

The bottom small bell is movable from the illustrated solid line position to the dotted line position to close and open discharging communication between small bell hopper 21 and the charging apparatus therebeneath. Any suitable actuating mechanism may be employed, such as the suspension shaft 25 which slides within hollow supporting shaft 26 in receiving hopper 17.

An offset discharge hopper is indicated generally at 27. The discharge hopper is located off-center from the center line of the furnace and, as best illustrated in FIG. 1, its discharge outlet terminates at substantially the level of the cover dome 28. The outlet portion 29 of the offset discharge hopper is alternately closed and opened by a flap gate 30 which is movable from the illustrated solid line position to the dotted line position to permit discharge of burden from the discharge hopper into the conical revolving hopper 14.

Flap gate 30 interrupts the material flow from small bell hopper 21 and provides a closure which protects the charging equipment above the furnace top from pressure surges often encountered in the furnace. Some gas leakage between the seating surfaces of flap gate 30 and the bottom rim of offset discharge hopper 27 may occur. This leakage, however, will not be deterimental to furnace operation. The contact surfaces of flap gate 30 and the bottom rim of offset discharge hopper 27 are preferably covered with a wear resistant hard facing, such as a special alloy deposit, not shown.

The conical revolving hopper or revolving chute 14 is supported and actuated by an external drive which consists of a bit spur gear 32, and associated top, bottom and side guide rollers, the placement and operation of which will be apparent to those skilled in the art.

The spur gear 32 is fast with a spider neck 33 which terminates, at its lower end, in arms 34, 35 which support the skewed, funnel shaped conical revolving hopper. Driving power is furnished by motor 36 driving through the reducer 37. It will be understood that suitable seal means is provided between the spider neck 33 and the furnace cover dome 28. A probe is indicated at 39.

An alternative embodiment of the invention is illustrated in FIG. 2.

In this Figure burden material from primary raw material sources, such as stock piles, is delivered by two conveyors or other transporting means 40,41 (such as skips), each conveyor discharging into an associated receiving hopper, 42,43, respectively. The receiving hoppers in turn discharge into a generally U-shaped small bell hopper 44. The discharge outlet of each receiving hopper 42,43 is closed by a flap gate type valve 46,47 respectively, each of which is actuated by a piston and cylinder assembly 48,49 respectively. The use of either bell 19 or a flap gate valve 46 and 47 is a design option.

Discharge from the U-shaped small bell hopper is controlled by a small bell 45 similarto small bell 23, bell 45 forming a seal with the lower end of the small bell hopper as at 50.

A useful sealing system capable of application to all bell valve seals in the system is indicated in FIG. 3. In this instance bell 19 has been chosen for purpose of description.

Outlet portion 20 includes a seat ring 52 having upper and lower flanges which are bolted to flanges carried by the receiving hopper 17 and small bell hopper 21 respectively, said seat ring having a hard surfacing material 53. A resilient gasket is indicated at 54, the gasket being held in place against the undersurface of seat ring 52 by a clamp ring 55 and bolt 56. A plenum chamber 57 is formed between a partition 58 and the .seat formed in seat ring 52 by the flanges. The resilient gasket is purged, preferably continuously, by blowing a jet of air or nitrogen or equivalent fluid past the gasket from inlet pipe 59 and passage 60 which terminates at gasket 54.

The operation of the single source charging system of FIG. 1 is substantially the same as the operation of the dual charging system of FIG. 2, and accordingly, only the system of FIG. 1 will be described in detail.

Conveyor 16 transports burden material from any suitable source, such as a stock pile, to receiving hopper 17.

Top small bell 19 is maintained in sealing engagement with the discharge outlet of the receiving hopper as the charge is loaded into the receiving hopper from the conveyor.

After build-up of a desired quantity of material in receiving hopper 17, the top small bell 19 is lowered to the dotted line position and the material discharged from the receiving hopper 17 into the small bell hopper 21.

Bottom small bell 23 is maintained in sealing engagement with the discharge portion 22 of the small bellhopper while the charge material is admitted to it.

Upon completion of the charging of small bell hopper g 21 the top small bell 19 is returned to the solid line position of FIG. 1 and a seal reestablished between the top small bell 19 and the receiving hopper.

After a charge is collected in the small bell hopper 21, the small bell 23 is moved from the solid line position to the dotted line position to transfer the materials in the small bell hopper 21 into the offsetdischarge hopper 27.

Prior to actuation of small bell 23, the flap gate 30 may be moved from the illustrated solid line position to the dotted line position so that the material passes through the offset discharge hopper and directly into the conical revolving hopper 14.

It should be understood however that flap gate valve 30 may be maintained in the illustrated closed position during transfer of charge material from the small bell hopper 21 into the discharge hopper 27, and, after collection in discharge hopper 27, thereafter opened to discharge the material into the conical revolving chute 14.

The internal revolving chute 14 can either be rotated in a spinning action as material from discharge hopper 27 is admitted to it, or the chute can be turned to a desired position prior to charging. If the chute is rotated as material is discharged into it, the burden will be distributed along an arcuate, generally circumferential path within the furnace at the stockline zone. If the chute is stationary when flap gate 30 is opened, material will be deposited in a more concentrated area within the furnace.

One advantage of rotating the chute 14 while emptying is that lesser driving power is required. If the chute is stationary during charging, it may be pre-positional in a manner well known in the art as by. indexing to any one of six positions, 0, 30, etc. in either direction, or rotating :1 fixed number of degrees.

In any event, indexing or start or stop of rotation at the desired angle may be initiated by a rotary stepping switch which is adapted and interlocked with the proper sequential opening of bottom small bell 23 or top small bell 19, or flap gate valves 46,47. The programming is incorporated and coordinated with the furnace charging program control and indicating system. Since the provision of suitable electronic, pneumatic or hydraulic control circuits for performing these functions are well known in the art they are not here illustrated or further described.

The bells and the gate valves, if employed, are made gas leak tight by inclusion of a suitable replaceable seal which is subjected to jets which continuously blow gas,

air or nitrogen across the seat, as shown best in FIG. 3.

A typical operating cycle is illustrated in FIGS. 4 and 5. In these Figures, 0 indicates the appropriate valve or small bell is open, and C indicates the closed condition.

Referring first to FIG. 4, it will be noted that the highest gage pressure exists in the furnace top, this pressure varying from time to time as represented by the saw tooth configured pressure line.

Since one or the other, or both of bells l9 and 23 are always seated at any given time, small bell 23 is always pressurized as indicated by the straight line. It will be understood that even though flap gate valve 30 may permit fme gas leakage, it will moderate the effect of the pressure surges in the furnace top on bell 23, and accordingly the pressure line is flatter than the pressure line for the furnace top.

When top bell 19 is open, the interior of small bell hopper 21 is exposed to atmospheric pressure as well as receiving hopper 17, which is always open to atmosphere. Accordingly, the pressure line for bell 23 reflects a maximum pressure differential.

Referring next to FIG. 5, it will be noted that when top bell 19 or flap valves 46,47 are closed, a pressure differential will exist across the valve, irrespective of the position of bottombell 23.

With respect to bottom bell 23,. no pressure differential across it will exist in either an open or closed condition so long as top bell 19 is closed. However, when top bell 19 is open, bottom bell 23 must be closed and accordingly a pressure differential will exist.

Since leakage can occur around flap valve 30, no pressure differential will be present at any time, except for pressure surges in the furnace top.

It will also be noted the system is so constructed that all rotating machinery is outside of pressurized chambers. This is extremely advantageous in that gas sealing difficulties associated with the rotating machinery is eliminated, and easy access to the machinery is provided for maintenance.

In super high top pressure operation of the furnace, the chamber assembly between bells l9 and 23 may be pressurized with washed blast furnace gas or nitrogen or indeed any suitable inert gas. This is a procedure well known in the art, the pressurizing gas being delivered through an arrangement of pipes, valves, pressure regulators, etc.

The exact sequence of pressurizing depends on the charging mode. For example, the chamber 21 may be kept over pressurized except for the period of bell 19 opening, or, possibly, opening of the flap gate valves 30 during chamber charging. The chamber is depressurized and the furnace gas within it released to atmosphere to enable opening of the small bell 19. Although there is a loss of furnace gas, the vented gas volume is comparatively small as contrasted to venting the conventional chamber with distributor.

From the above described charging sequence, and assuming minimal or zero gas leakage losses due to the sealing system, the only gas lost will be that volume represented by chamber assembly 21, which chamber is pressurized before small bell 23 is actuated to transfer a charge into the discharge hopper 27. Subsequently, when top bell 19 is actuated, some of the gases in the chamber will escape through the receiving hopper.

It will be noted that the system is relatively compact with each material drop being relatively small, and the total drop being relatively small as compared to many charging systems in current operation. The lower total drop, as well as the shorter individual drops, is beneficial in preventing excessive degradation of the charge material and excessive wear on furnace parts.

Further, in the illustrated construction the amount of dust particles carried out by the blast furnace gas will be less than in conventional constructions.

In a conventional furnace top having a large bell and hopper, the passage area that the gases must pass through to reach uptakes 13 is restricted. This restriction causes higher gas velocities which in turn carries more dust particles. The revolving hopper l4 and chute 15 occupy less space in the furnace top thereby increasing the passage area for the gases. This increase in passage area will result in lower gas velocities which in turn reduces the amount of dust that will be carried out the uptakes with the gas.

In addition, the position of a conventional large furnace bell and hopper is such that when the bell is dropped, or opened, the falling material is washed by the ascending gases which increases the amount of dust particles carried out by the gases.

With respect to FIG. 2 it will be noted that small bell hopper 44 can be charged from either one of receiving hoppers 42,43 or both. This makes possible speedier operation since the small bell hopper can be filled nearly twice as fast as can the single entry hopper 21.

By the same token, should a malfunction occur in one or the other of receiving hoppers 42 or 43, the malfunctioning hopper can be sealed off and operation continued from the functioning assembly.

Although a preferred and alternative embodiment of the invention has been illustrated and described, it will at once be apparent to those skilled in the art that the invention is not limited to the exact construction and operation illustrated and descibed. Rather, the scope of the invention should be limited and defined only by the scope of the hereinafter amended claims as interpreted in light of the pertient prior art.

I claim:

1. In a blast furnace high top pressure charging system the combination of a revolving burden distributing chute within the furnace,

power shaft means located axially of the furnace,

said distributing chute being suspended from said power shaft means,

power means located outside the furnace, said power shaft means having means for connecting said power shaft means to said power means,

a receiving hopper for burden material,

a pressure isolatable hopper, said receiving hopper being positioned to discharge into said pressure isolatable hopper,

first valve means and associated sealing means between an outlet end portion of the receiving hopper and an inlet end portion of the pressure isolatable hopper,

a discharge hopper, said pressure isolatable hopper being arranged to discharge into said discharge hopper,

second valve means and associated sealing means between an outlet end portion of the pressure isolatable hopper and an inlet end portion of the discharge hopper, and

flow control means at an outlet end portion of the discharge hopper,

said flow control means having contact surfaces seated sufficiently tightly to moderate pressure changes occurring in the furnace,

said discharge hopper being located in a position radially offset of the central vertical axis of the furnace,

said discharge hopper being positioned to discharge burden held therein into said suspended revolving distributing chute,

said power means rotating said revolving chute prio to or during discharge of burden from the discharge hopper.

2. The combination of claim 1 further characterized in that one of said first or second valve means is a flap gate valve.

3. The combination of claim 1 further characterized in that one of said valve means is a bell valve, and its associated sealing means comprises a seat ring which makes peripheral contact with the bell valve,

a resilient sealing member in engagement with joint surfaces formed by the junction of the bell with the seat ring, and

a gas purging system capable of continually blowing gas past the sealing member.

4. The combination of claim 1 further characterized in that the gas purging system includes a plenum chamber surrounding the sealing member and gas passage means for blowing a purging gas past the sealing member.

Claims (4)

1. In a blast furnace high top pressure charging system the combination of a revolving burden distributing chute within the furnace, power shaft means located axially of the furnace, said distributing chute being suspended from said power shaft means, power means located outside the furnace, said power shaft means having means for connecting said power shaft means to said power means, a receiving hopper for burden material, a pressure isolatable hopper, said receiving hopper being positioned to discharge into said pressure isolatable hopper, first valve means and associated sealing means between an outlet end portion of the receiving hopper and an inlet end portion of the pressure isolatable hopper, a discharge hopper, said pressure isolatable hopper being arranged to discharge into said discharge hopper, second valve means and associated sealing means between an outlet end portion of the pressure isolatable hopper and an inlet end portion of the discharge hopper, and flow control means at an outlet end portion of the discharge hopper, said flow control means having contact surfaces seated sufficiently tightly to moderate pressure changes occurring in the furnace, said discharge hopper being located in a position radially offset of the central vertical axis of the furnace, said discharge hopper being positioned to discharge burden held therein into said suspended revolving distributing chute, said power means rotating said revolving chute prior to or during discharge of burden from the discharge hopper.

2. The combination of claim 1 further characterized in that one of said first or second valve means is a flap gate valve.

3. The combination of claim 1 further characterized in that one of said valve means is a bell valve, and its associated sealing means comprises a seat ring which makes peripheral contact with the bell valve, a resilient sealing member in engagement with joint surfaces formed by the junction of the bell with the seat ring, and a gas purging system capable of continually blowing gas past the sealing member.

4. The combination of claim 1 further characterized in that the gas purging system includes a plenum chamber surrounding the sealing member and gas passage means for blowing a purging gas past the sealing member.

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