US3575401A - Blast furnace backdraft valve - Google Patents

Abstract

The disclosure pertains to blast furnace installations in which during periods when the furnace is shut down it is connected to a backdrafting stack which produces a reversal of flow of the gaseous products in the furnace which are vented through the stack. The stack is connected to the furnace''s hot air blast system during backdrafting by means of a valve which includes a movable section and a fixed section which when coupled together condition the furnace for backdrafting. Upon resumption of the furnace operation the movable valve section is withdrawn out of contact with the fixed section and the backdraft opening is closed by a valve element thus disconnecting the stack from the hot air blast system during normal furnace operation.

Description

United States Patent [72] inventor William H. Malone Northfield, Ohio [21 Appl. No. 764,857 [22] Filed Oct. 3, 1968 [45] Patented Apr. 20, 1971 [73] Assignee Republic Steel Corporation Cleveland, Ohio [54] BLAST FURNACE BACKDRAFT VALVE 11 Claims, 3 Drawing Figs.

[52] US. Cl 266/30, 263/ 19 [51] Int. Cl .1 F27d 7/00 [50] Field of Search 266/30, 31; 263/19;98/115; 137/560 [56] References Cited UNITED STATESv PATENTS 2,601,979 7/ 1952 Rice et al 263/ 19 2,931,635 4/1960 Braun et a1.

Primary Examiner-James M. Meister Attorneys-Robert P. Wright and Joseph W. Malleck ABSTRACT: The disclosure pertains to blast furnace installations in which during periods when the furnace is shut down it is connected to a backdrafting stack which produces a reversal of flow of the gaseous products in the furnace which are vented through the stack. The stack is connected to the furnaces hot air blast system during backdrafting by means of a valve which includes a movable section and. a fixed section which when coupled together condition the furnace for backdrafting. Upon resumption of the furnace operation the movable valve section is withdrawn out of contact with the fixed section and the backdraft opening is closed by a valve element thus disconnecting the stack from the hot air blast system during normal furnace operation.

Patented April 20, 1971 3,575,401

2 Sheets-Sheet 1 INVENTOR. WILLIAM H. MALONE BY 2 wlm/floflmwmvgTAiwL/a ATTORNEYS.

Patented A iril 20, 1971 2 Sheets-Sheet 2 FIG lNVEI VTOR. WILLIAM H.MALONE BY WafiMHoqmFAhbM-(M ATTORNEYS.

BLAST FURNACE IBACIKDRAIFT VALVE BACKGROUND OF THE INVENTION In conventional blast furnace operation it is common practice to employ three hot blast stoves which provide a continuous hot air blast for the furnace. The hot air blast enters the furnace through blow pipes connected to a header or bustle pipe surrounding the bosh or lower portion of the furnace. The bustle pipeis connected to a hot blast main extending alongside the stoves. Each of the stoves has a hot blast exit connected to the main which may be opened or closed depending on whether the stove is conditioned for reheating or is onblast. While onblast, cold air is forced through the previously heated checker work of the stove where the air picks up heat and then flows into the hot blast main for delivery to the furnace. Usually only one stove at a time is onblast while the other two are going through the reheating cycle. During this cycle, the hot blast exit is closed and the stove burner is ignited heating up the checker work in preparation for the next on blast cycle. Products of combustion are exhausted from the stove to a flue and chimney system.

1. Prior Art When the blast furnace is shut down, each stove is placed in a standby condition in which the cold air blast is interrupted. The stove which is to be used in backdrafting has its hot blast exit open to the hot blast main so as to assure that the backdrafting gases which issue from the furnace will flow into the combustion chamber of the stove where they will be ignited either by the gas burner of the stove or by the heated checker work. These burned gases then are drawn off through the stove flue and chimney system.

Backdrafting gases are highly contaminated with many materials which are detrimental to the stove checkers causing chemical damage to the checker work as well as a buildup of solids which hinder the passage of gases when the stoves are being heated and when on blast.

To avoid using the stoves as dust collectors during the backdrafting operation it has become common practice to employ a separate backdrafting stack the sole purpose of which is to allow the backdraft gases to bypass the stove flue and chimney system. This not only protects the stove checkers from damage, but also minimizes the chance of a stove explosion. At the present time practically all new blast furnace installations are being provided with separate backdrafting stacks.

These stacks may employ a cap valve at the top of the stack which is merely opened during backdrafting and closed during normal furnace operation. With the valve at the top of the stack, the stack itself becomes a part of the hot air blast system and subject to the same pressures and temperatures as the blast furnace lining. Thus, the backdrafting stack requires special refractory materials and structural considerations to compensate for the exigencies of the blast.

In other prior art backdrafting systems, a gate valve is placed adjacent the hot blast main so that the backdrafting stack is not subjected to the hot blast pressures during the normal furnace operation. These are internal water-cooled valves and thus not readily accessible for inspection and maintenance inasmuch as they are completely enclosed within the backdrafting ductwork. Moreover, gate valves tend to be plagued with mechanical difficulties particularly under conditions of high heat and pressure. For example, the unequal expansion of parts may cause the valve element to stick. Thus, in order to avoid the sticking problem, it is necessary to employ expansion joints which are also mechanically troublesome in the blast furnace environment.

2. Need Served by the Invention These and other difficulties are overcome with the present invention in which a backdrafting stack is connected adjacent the hot blast main by means of a backdrafting valve which is mechanically simple, readily accessible from the outside and requires no cooling water or expansion joints to assure continued trouble-free operation.

SUMMARY OF THE INVENTION The invention provides a backdrafting stack and valve adapted to connect the stack to the hot blast system of the furnace during periods when backdrafting is required and disconnect the stack when the furnace is operating. During backdrafting the backdraft valve is open connecting the interior of the furnace directly to the stack. Owing to the draft created by the stack there is a reversal of flow of the gaseous products from within the furnace, through the valve and out the stack.

The backdrafting valve comprises a fixed tubular body section and a movable tubular body section, the latter moving relative to the fixed section between idle and backdrafting positions. In the idle position the movable section is withdrawn and is'spaced from the fixed section to provide a discontinuity in the flue passage between the hot blast main and the stack. In the backdrafting position the movable section is seated on the fixed section to provide a continuous flue passage for the flow of gases into the stack. A valve element is movable between open and closed positions in the open area created by withdrawing the movable section to seat upon the fixed section. In the closed position, the valve element is seated on the fixed section so that the hot blast main is isolated from the backdrafting stack. In the open position of the valve element, the movable section is seated on the fixed section to condition the furnace for backdrafting.

Further in accordance with the invention the lower extremity of the backdrafting stack is located adjacent the backdraft valve and is adapted to receive a portion of the movable tubular body section of the valve when it is withdrawn in the idle position. A pivoted arm is connected at one end to the movable section causing it to swing in an are between its backdrafting and idle position.

The invention also provides that the backdrafting valve includes a valve element pivoted adjacent the fixed tubular body section so as to swing between the open and closed positions in an arc inscribed within the open area created by withdrawing the movable tubular body section. The pivotal arrangement of the movable tubular body section and valve element is such that the two are moved in cooperative fashion so that the furnace goes into a backdrafting condition as rapidly as possible thus minimizing the escape of gases while the valve is opened and before the movable tubular body section can be brought into seating engagement with the fixed tubular body section.

Among the advantages of the invention is the provision of a backdrafting system which bypasses the hot stoves of a blast furnace installation thereby avoiding contamination and chemical damage to the stove checker work.

Another advantage of the invention is in providing a backdrafting valve adjacent the hot blast main so that the backdrafting stack is not subjected to the pressures of the hot blast during normal operation of the furnace.

A unique advantage of the invention is the novel backdrafting valve which enables the use of a simple closure between the hot blast main and backdrafting stack. The valve closure is mechanically simple, readily accessible from the outside and requires no cooling or complicated expansion joints commonly associated with gate valves or the like which have heretofore been used unsuccessfully, for the most part, due to mechanical difficulties encountered in operating such valves over long periods of time in the environment of temperature and pressure of the hot blast.

These and other advantages and objects will become more apparent by referring to the following description and the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view in schematic form of a common blast furnace installation utilizing an arrangement of three stoves connected in parallel between cold air blast and hot air blast mains for delivering heated air under pressure to a blast furnace only a fragmentary portion of the bustle pipe of which is shown;

FIG. 2 is an elevational view showing a preferred embodiment of the invention in which a pair of backdrafting valves are used to connect the hot air blast main to the backdrafting stack only a fragmentary lower portion of which is shown;

FIG. 3 is a partial side elevational view showing another embodiment of the invention utilizing a single backdrafting valve.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, FIG. 1 is a schematic plan view of a conventional hot stove arrangement for a blast furnace. The blast furnace has a bustle pipe 14 encircling it which is connected to the hot blast stoves 10, 11, 12 by a hot blast main 16. A cold blast main 18 supplies air to each of the stoves 10, 11, 12 through a cold blast valve 19,20, 21. Each of the stoves has a pair of chimney valves 22, 23, 24 connected to a flue 26 which delivers the products of combustion from the stoves to the stove chimney (not shown). A gas main 30 supplies blast furnace gas to each stove burner 31, 32, 33 which is supplied by a blower and gas/ air burner valve 42, 44, 46.

As is well understood by those skilled in the art, the hot blast stoves 10, 11, 12 provide a continuous hot blast of air for the blast furnace operation. One of the hot blast stoves is at all times connected, by means of the hot blast main 16, to the bustle pipe 14. The bustle pipe 14 acts as a header and delivers hot blast air under pressure to the blow pipes opening into the furnace s interior. While one or both of the hot blast stoves I0, 11, 12 are being heated by the stove burners, the remaining stove has its hot blast valve open to the hot blast main 16 in the onblast condition.

Before a stove is placed in the onblast condition, the interior checker work 47, 49, 51 must be heated. Assuming stove 10 is to be conditioned for reheating having just come off of blast operation and stove 12 is partially reheated, the latter stove hot blast valve 40 and cold blast valve 21 are closed while the burner valve 46 and the chimney valves 24 are opened. The companion stove, for example stove II, which is onblast has each of these valves closed and only the cold blast valve 20 and the hot blast valve 38 open. Thus, while the stove 11 which is presently supplying the blast furnace with hot air is engaged in heating up the incoming cold air from the cold blast main 18 and delivering it to the hot blast main 16, the other hot blast stove 12 is having its checker work 47 heated up by the burner 33. The products of combustion circulate through the checker work from combustion chamber 48, 50, 52 on the way to the flue 26. When the stove 11 which is onblast no longer contains enough heat in its checker work to raise the incoming cold air to the required blast temperature, the stove 12, which in the meantime has completed the reheating cycle, is connected for on-blast operation while the stove 11 is conditioned for reheating. correspondingly, stove will by this time be in some partial stage of reheating.

Referring now to FIG. 2, furnace backdrafting is accomplished by connecting the furnace to a backdrafting stack 56 through the hot blast main 16. Only the lower extremity of the stack 56 is shown. Between the stack 56 and hot blast main 16 is a pair of backdrafting valves 58, 60. Each of the valves 58, 60 is connected at its lower end to a saddle 61, 62 having a collar 63, 64 through which the hot blast main 16 is exhausted and to which the valves 58, 60 are secured. The valves 58, 60 with their associated operating mechanisms, are duplicates of each other and will normally be operated in unison, although for purposes of illustration, the valve 58 is shown in a closed position while valve 60 is shown in the open position. Both valves will be opened during backdrafting or closed when the blast furnace is being operated. Like numerals will be used to identify the same parts on each valve and it will be understood that the following description applies equally to both valves 58, 60.

With reference to valve 58 and in accordance with the invention, there is a fixed tubular body section 66 and a movable tubular body section 67. The fixed body section 66 is attached at its lower end to the collar 63 and at its upper end provides a seat 69 which is engaged by either the movable body section 67 or a cap 71, depending on whether the valve 58 is conditioned for backdrafting or not as described 5 hereinafter.

The cap 71 is mounted on an arm 72 pivoted at 73 to a bracket 74 secured to the outer shell of the fixed tubular body section 66. A latch 75 is pivotally mounted on each side of the fixed tubular body section 66 to engage a lug 76 on the cap 71. The latches 75 are operated from linkages 77 in conjunction with the opening and closing movement of the cap 71. A motorized valve operator 78 includes a gearbox 79 having an output shaft 80 for driving linkages 77, 81 to move the cap 71 and latches 7S simultaneously between an open position; the cap tilted back as shown in valve 60, or a closed position; the cap engaging seat 69 as shown in valve 58. Alternatively, a chain 82 and chain wheel 83 drive the gearbox 79 for manually raising and lowering the cap 71. Conventional electrical controls at a remote operator station control the motorized gearbox 76 for opening and closing the cap 71 and limit switches (not shown) interrupt the opening and closing movements at the desired position.

As provided in the invention, the tubular body section 67 is attached to one end of a swinging arm or frame 90 having a counterweight 92 at the opposite end. The arm 90 is pivoted approximately intermediate the two ends at 93. A motorized gear unit (not shown) like the valve operator 78 for the cap 11 is provided for each section 67 and will have its output shaft connected at 93 for moving the arm and rotating the section 67 between the backdrafting and idle positions.

The backdrafting stack 56 has its lower end located between each of the valves 58, 60 with the centerline of the stack generally intersecting the centerline of the hot blast main. An intake mouth 94 of the stack 56 widens out into bifurcated passages 96 each of which define a backdraft openings 95 at the lower extremity adjacent each valve 58, 60. The movable sections 67 telescope into the openings 95 in the idle position. In the backdrafting positions, the sections 67 move out of the openings 95 to engage the seat 69 of the fixed tubular body section 66. Shock absorbers 97, 98 cushion the movements of the tubular body sections 67 between the respective positions. The stack 56 usually has a refractory brick lining. The intake mouth 94 will have a cast refractory lining the same as the backdrafting valves 58, 60 capable of standing the pressures and temperatures of the hot blast system.

It is important to note that intake mouth 94 is closely adjacent the hot blast main so that when the movable sections 67 are connected to the swinging arm 90 a maximum arc of about 30 is made between the backdraft and idle positions. This arc is greater than the space required for the cap 71 to move between its open and closed positions. The significance of this is that the pivotal arrangement of the cap 71 and movable section 67 of each valve is such that the sections 67 are moved as quickly as possible to a backdrafting position. This minimizes the escape of gases while the caps 71 are opened and before the sections 67 can be brought into seating engagement with the fixed sections 66. For example, with the arrangement shown, each backdrafting valve requires only about seconds to open or close. There is no mechanical linkage between the caps 71 and the movable sections 67. Both are actuated by separate motorized gear units 78 which are interlocked electrically to prevent operating them in the wrong sequence.

When the signal is given to go "on backdraft" and after the pressure is relieved in the hot blast main by the snort valve, the caps 71 of both valves will first be opened. Thereafter the movable sections 67 are rotated out of the openings 95 until engaging the seat 69 on the fixed tubular section 66. In this position there is a continuation of the bifurcated passages 96 through the valves 58, 60 to the hot blast main 16 establishing dual flue passageways 99. When the furnace is ready to be put back on-blast," the movable sections 67 are withdrawn from the sections 66 and telescoped into the passages 96 completely disconnecting the stack 56 from the hot blast main 16. The caps 70 and 71 are then closed to shut off flow to atmosphere.

Generally the hot combustible gases from the blast furnace will ignite and burn as they mix with the air in the hot blast main 16. As has sometimes occurred in prior art systems backdrafting through the stoves and stove stacks, if insufficient air is available in the hot blast main, it is possible for the main, the hot blast stove being used for backdrafting, and the stove stack to become filled with the combustibles. A sudden addition of cold air during this condition can result in a severe explosion possibly destroying a stove. Thus it is important to note that the present invention positions the backdrafting stack between the hot blast stoves 10, ll, 12 and the blast furnace so as to bypass the stoves entirely. Moreover, the present invention has the unique advantage of providing that the backdrafting valve means is adjacent the hot blast main so that when closed during furnace operation, the backdrafting stack is not subjected to the pressures and temperatures of the hot blast system. Also the valves are closed by a simple cap 71 which is readily accessible from the outside and requires no cooling or complicated expansion joints to insure against mechanical difficulties at the temperatures and pressures encountered in blast furnace operation. These factors contribute considerably to insuring that the refractory lining of the stoves is not subjected to the chemical attack from the gases .carried by the hot blast main during furnace operation.

ANOTHER EMBODIMENT OF THE INVENTION Referring now to FIG. 3, there is shown a modification of the invention in which a single backdrafting valve 101 is used to connect a hot blast main 16 to a backdrafting stack 56. The parts of the valve 101 are similar to those of the valves 58, 60 in FIG. 2, thus the same numerals with a prime mark will be used to identify similar parts. The backdrafting valve 101 includes a fixed tubular body section 66 and a movable tubular body section 67' which may be rotated between an idle position (shown in dot-dash lines) and a backdrafting position in engagement with the fixed tubular section 66. A.

cap 71 is mounted on an arm 72 which pivots at 73' for rotating it between open and closed positions.

As with the arrangement shown in FIG. 2, movable tubular section 67' and the cap 71' are not mechanically connected, each being operated by a motorized gear unit 78' which is electrically interlocked to insure that the movement of one is completed before the movement of the other is commenced.

This arrangement differs from the preferred embodiment of the invention in that backdrafting stack is offset from the axis of the hot blast main 16 rather than being directly over it. It also can be rotated 90 in relation to the hot blast main if there is an advantage in the layout. An intake snout 103 inclines downwardly from the stack 56' toward the valve 101. The valve is secured to the top of the hot blast main [6 at an angle so that the backdraft opening 95' is adjacent the upper end of the fixed tubular section 66. As with the preferred embodiment of the invention, the space between the backdraft opening 95' and the fixed tubular section 66' is traversed by the movable tubular section 67 when rotated from the idle position to the backdrafting position so that a continuous passageway from the hot blast main 16 through the valve 101 and into the stack 56- is established when the furnace goes on backdraft." The reverse sequence takes place when the furnace is ready to be put back onblast."

Modifications and changes may be made to the invention as will be apparent to those skilled in the art to which it pertains which modifications and changes are to be regarded as reasonable equivalents thereof and are intended to be covered by the appended claims except insofar as limited by the prior art I claim:

1. In a blast furnace installation including a blast furnace, a cold air blast main, a hot air blast main, one or more stoves between the cold and hot air blast mains for heating up incoming cold air and discharging a blast of hot air to the furnace, and a backdrafting stack adapted to be connected between the blast furnace and stoves to cause a reversal of flow and removal of gases from within the furnace during backdrafting, the improvement comprising a backdrafting valve including:

a. a fixed tubular body section;

b. a movable tubular body section movable relative to the fixed section between idle and backdrafting positions providing a continuous flue passage from the furnace to the backdrafting stack in the backdrafting position and being spaced from the fixed section to provide a discontinuity in the flue passage in the idle position; and

c. a valve closure movable between open and closed positions with respect to the fixed tubular body section to shut off the flow of gases from the furnace corresponding in the closed position with the idle position of the movable tubular body section and vice versa so that the backdrafting stack is disconnected when the furnace is onblast and connected to the furnace when backdrafting.

2. The improvement according to claim 1 wherein the lower extremity of the backdrafting stack is located adjacent the backdrafting valve and, with the movable tubular body section of the valve, forms an extendable flue passageway movable into engagement with and seating on said fixed tubular body section in the backdrafting position.

3. The improvement according to claim 1 wherein the movable tubular body section is pivotally mounted intermediate the stack and fixed tubular body section so as to swing in an are between said idle and backdraft positions.

4. The improvement according to claim 1 wherein the valve closure is a cap pivotally mounted to swing between said open and closed positions within the space providing the discontinuity in the flue passage when said movable tubular body section is fully withdrawn to the idle position.

5. The improvement according to claim 1 wherein the backdraft stack is positioned over the hot blast main and has an intake mouth at its lower extremity defining bifurcated passages, each associated with a backdraft valve mounted on the hot blast main.

6. The improvement according to claim 5 wherein the movable tubular body sections of each valve telescope into the associated passage of the stack in the backdrafting position.

7. The improvement according to claim 1 wherein the stack is offset from the centerline of the hot blast main.

8. A backdrafting valve for connecting a stack to a blast furnace during backdrafting operations comprising:

a. a fixed tubular body section;

b. a movable tubular body section alignable with the fixed section to establish a continuous backdraft flue passage from the furnace to the stack;

c. means for moving said movable tubular body section relative to the fixed section to provide a discontinuity in the flue passage; and,

d. closure means operable to close off said fixed tubular body section.

9. A backdrafting valve according to claim 8 wherein the movable tubular body section is rotated with respect to the fixed tubular body section to provide said discontinuity in the flue passage.

10. A backdrafting valve according to claim 8 wherein the a movable tubular body section is pivotally mounted to swing in an arc.

11. A backdrafting valve according to claim 10 wherein the lower end of the stack is closely adjacent the fixed tubular body section and receives a substantial portion of the movable tubular body section to minimize the length of arcuate movement necessary by the latter.

Claims (11)

1. In a blast furnace installation including a blast furnace, a cold air blast main, a hot air blast main, one or more stoves between the cold and hot air blast mains for heating up incoming cold air and discharging a blast of hot air to the furnace, and a backdrafting stack adapted to be connected between the blast furnace and stoves to cause a reversal of flow and removal of gases from within the furnace during backdrafting, the improvement comprising a backdrafting valve including: a. a fixed tubular body section; b. a movable tubular body section movable relative to the fixed section between idle and backdrafting positions providing a continuous flue passage from the furnace to the backdrafting stack in the backdrafting position and being spaced from the fixed section to provide a discontinuity in the flue passage in the idle position; and c. a valve closure movable between open and closed positions with respect to the fixed tubular body section to shut off the flow of gases from the furnace corresponding in the closed position with the idle position of the movable tubular body section and vice versa so that the backdrafting stack is disconnected when the furnace is onblast and connected to the furnace when backdrafting.

2. The improvement according to claim 1 wherein the lower extremity of the backdrafting stack is located adjacent the backdrafting valve and, with the movable tubular body section of the valve, forms an extendable flue passageway movable into engagement with and seating on said fixed tubular body section in the backdrafting position.

3. The improvement according to claim 1 wherein the movable tubular body section is pivotally mounted intermediate the stack and fixed tubular body section so as to swing in an arc between said idle and backdraft positions.

4. The improvement according to claim 1 wherein the valve closure is a cap pivotally mounted to swing between said open and closed positions within the space providing the discontinuity in the flue passage when said movable tubuLar body section is fully withdrawn to the idle position.

5. The improvement according to claim 1 wherein the backdraft stack is positioned over the hot blast main and has an intake mouth at its lower extremity defining bifurcated passages, each associated with a backdraft valve mounted on the hot blast main.

6. The improvement according to claim 5 wherein the movable tubular body sections of each valve telescope into the associated passage of the stack in the backdrafting position.

7. The improvement according to claim 1 wherein the stack is offset from the centerline of the hot blast main.

8. A backdrafting valve for connecting a stack to a blast furnace during backdrafting operations comprising: a. a fixed tubular body section; b. a movable tubular body section alignable with the fixed section to establish a continuous backdraft flue passage from the furnace to the stack; c. means for moving said movable tubular body section relative to the fixed section to provide a discontinuity in the flue passage; and, d. closure means operable to close off said fixed tubular body section.

9. A backdrafting valve according to claim 8 wherein the movable tubular body section is rotated with respect to the fixed tubular body section to provide said discontinuity in the flue passage.

10. A backdrafting valve according to claim 8 wherein the movable tubular body section is pivotally mounted to swing in an arc.

11. A backdrafting valve according to claim 10 wherein the lower end of the stack is closely adjacent the fixed tubular body section and receives a substantial portion of the movable tubular body section to minimize the length of arcuate movement necessary by the latter.

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