US2306069A - Reversing valve for regenerative furnaces or the like - Google Patents

Description

Patented Dec. 22, 1942 REVERSING VALVE FOR REGENERATIVE FURNACES OR THE LIKE Henry R. Loxterman, Oakmont, Pa., assignor to Blaw-Knox Company, Pittsburgh, Pa., a corporation of New Jersey Application January 16, 1942, Serial No. 427,006

Claims.

This invention relates to a valve for controlling the flow of waste combustion gases and air from and to the checker chambers of a regenerative furnace such as a blast furnace, open-hearth furnace, or the like.

Reversing valves for regenerative furnaces operating under blast have heretofore generally included separate waste-gas and air-inlet valves, viz., a sliding-closure valve in the waste-gas flue from each regenerative checker chamber to the stack, and a mushroom-type air-inlet valve in a branch from each waste-gas flue between the checker chamber and the sliding-closure valve. A typical example of this arrangement is disclosed in Knox Patent 1,397,380. In operating an installation of this kind, the waste-gas valves are opened alternately to a variable degree to regulate the draft from the checker chamber through the stack and control the gas pressure in the furnace, the air-inlet valve of each checker chamber being open when the waste-gas valve of the same chamber is closed.

Mushroom-type valves are subject to numerous serious objections, particularly when made relatively large in size. It is very difiicult to make them fit perfectly in the first place, and continue to seat properly after they have been opened and closed, even if a good fit is obtained initially. Mushroom-type valves, furthermore, cannot be placed as close to the main waste-gas flue as would be desirable, because of the danger of warpage when subjected to high temperature. This is the reason for installing the air-inlet valves in branches from the waste-gas flue instead of in the flue itself. Waste gases accumulate in the branches while the air-inlet valves are closed and they are, of course, full of air at the moment of reversal, which is a further objection. The use of mushroom-type valves has continued, however, despite the aforementioned objections because of the lack of anything better and the necessity of separate air-inlet and wastegas valves to permit adjustable opening of the latter for the purpose of draft control. While combined air-inlet and waste-gas valves have been known heretofore, they have not been of such construction as to permit the control of the How of waste-gases in the manner of a damper.

I have invented a novel reversing valve which entirely eliminates the mushroom-type inlet valve, thereby obviating the aforementioned objections; incorporates in, a single valve, provisions for controlling both the waste gases flowing out from the checker chamber to the stack and, upon reversal, the air flowing into the checker chamber; and is capable of damper action to control the flow of waste gases. In a preferred embodiment, I provide a valve seat adapted to be installed in the lines between the checker chambers and the stack. A closure member is slidable along the seat. The seat is provided with openings spaced therealong, forming a waste-gas outlet and an inlet for the normal air supply. The closure member is adapted to cover the outlet when properly positioned. The outlet and inlet openings are so dimensioned and spaced that the air inlet will be entirely closed when the closure has been moved to partially open the waste-gas outlet, and maintained closed when the closure is moved to open the outlet further. This permits operation of the closure member as a damper to regulate the size of the opening for outflowing waste gases, thereby to control the furnace draft. The spacing and dimensions of the openings, furthermore, are such that when the waste-gas outlet is covered by the closure member, the air inlet is uncovered or opened.

The air inlet is dimensioned for normal air supply, 1. e., from a suitable fan, blower, or any convenient source of air under appropriate pressure. I also provide means for enlarging the air inlet, should it become necessary under emergency conditions to operate the furnace under natural draft, i. e., without means for supplying air under pressure through the inlet opening of the valve. Such means includes an auxiliary or emergency inlet which is normally closed by an openable or removable cover. The emergency inlet is so positioned relative to the normal inlet that both are covered by the valve closure when it is positioned to open fully the waste-gas outlet. My invention thus permits continued operation of the furnace after failure of the normal source of air under pressure, by merely opening or removing the cover of the emergency air inlet and raising the valve sufficiently to cover the emergency air inlet each time it is necessary to stop the air flow. Further lift of the valve may be provided, to allow it still to be used as a damper in the flue leading to the stack. It is much more important that the furnace should not be shut down during the running of a heat, than that all the refinements of control employed under normal conditions be maintained continuously.

Further details, novel features and advantages of the invention will become apparent during the following complete description and explanation which refer to the accompanying drawing illustrating the preferred embodiment briefly outlined above. In the drawing,

Figure 1 is a partial longitudinal section through the waste-gas flue of a regenerative furnace showing the reversing valve of my invention; and

Figure 2 is a sectional View taken along the plane of line IIII of Figure 1 showing parts in elevation.

Referring now in detail to the drawing, a flue I0 extends to a stack port II from the end of a checker chamber (not shown) opposite that which is connected directly to the furnace. The flue ID, of course, alternately conducts waste combustion gases from the checker chamber and entering air to the checker chamber. It will be understood that a complete installation includes two flues such as that shown in ID, the general arrangement being shown in the Knox patent above mentioned.

The flue I0 has an offset I2 near the port H. A valve seat I3 installed in the flue adjacent the offset has an upwardly extending portion I3a overlying the latter and a lower portion I31) overlying generally the section of the flue proper. The seat I3 may conveniently be a suitable casting and is provided with water-cooling passages I 4 and supply and discharge connections l5 for the cooling water. A hood or cap I6 closes the space between the edge of the offset I2 and the seat I3.

The lower portion I3b of the valve seat I3 is provided with an opening I! conforming generally to the interior of a section through the flue I0 and affording an outlet for waste combustion gases passing through the flue from the end of the checker chamber to the stack port II. The valve seat also is provided with an opening I8 providing an inlet for the normal air supply. A housing I9 fabricated from plate i ously, constitutes a continuation of the duct 23.

As shown, the housing is open at the top and is provided with a removable cover.

The valve seat I 3 also has an opening 2 above the opening I8 which is adapted to serve as a supplemental inlet for air under emergency conditions. The opening 24 is normally closed by an openable or removable cover 25. As clearly shown in Figure 1, the cover 25 is somewhat L-shaped in section, the lower portion overlying the open top of the housing IS. The cover 25 is secured to the valve seat I3 by screws 26 so that it may readily be removed when desired. When the cover is removed, outside air may freely enter through both the openings I8 and 24.

A valve closure 21 is slidable along the valve seat. The seat may have a plane face but as shown has a rib 28 around the several openings therethrough to reduce the friction between the closure and the seat and to facilitate the making of a tight joint therebetween. The seat %3, as illustrated, is inclined from the vertical so that the weight of the closure 27 tends to hold it against the seat. The closure may be entirely of metal, preferably hollow and water-cooled, with a plane face; or it may have a plane face on only those portions which engage the seat, or the closure may be similar to those shown on the Knox patent aforementioned, comprising a panel of refractory material assembled on a suitable frame and within an enclosure fabricated from plate and structural sections. A pull rod 29 extends downwardly through the hood I6 and is connected to the top of the closure member. An operating cable 30 is secured to the pull rod by a suitable terminal fitting 3I adapted to cooperate with a cushioning spring 32 coiled about the rod and adapted to be compressed between the fitting and the hood I6.

It will be clearly apparent from the drawing that the valve closure 21 is so dimensioned as to completely cover the opening I! in the valve seat l3, when in its lowermost position, i. e., when the fitting 3| bears against the spring 32. When the closure is in such position, as illustrated in solid lines, air from the fan or blower is delivered through the duct 23, the housing I9 and the opening or inlet I8 into the flue ID, as illustrated by arrows 33. When the closure 21 of the valve illustrated is in its lowermost position, the closure of the other valve (not shown) is in position to permit the outflow of waste-combustion gases to the stack port II as indicated by the arrow 34.

When it is desired to reverse the flow of air and combustion gases through the checker chamber, the valve closure 21 is shifted to the position shown in chain lies thereby permitting outflow of the gases as indicated by arrow 35. At the same time, the closure of the other valve is lowered to shut off the flow of combustion gases therethrough and permit the entrance of air. It will be observed from the drawing that the air inlet I8 is closed when the closure 21 is only partly raised and is maintained closed as the closure is raised farther. This result is obtained by reason of the vertical dimension of the inlet l8 and its spacing from the waste-gas outlet I1. The degree to which the opening I! is uncovered may be varied within Wide limits without uncovering the inlet l8. Thus, when the valve closure 21 is in position to permit outflow of waste combustion gases, it may be adjusted to regulate the furnace draft and is effective at all times to maintain the air inlet I8 fully closed.

If the normal supply of air should fail for any reason, it is imperative to continue the furnace in operation nevertheless. In such an emergency, the removal of the cover 25 permits air to flow into the flue I0 through the openings I8 and 24 when the valve closure 21 is in its lowermost position. Under these circumstances, reversal of the flow of air and waste gases necessitates raising the closure 21 high enough to fully close the opening 24, and. the lowering of the other valve closure to its lowermost position.

In this way, the flow of air through both the openings I8 and 24 is cut off while the opening I! is uncovered to permit outflow of combustion gases. Under these circumstances, the valve closure can serve as a damper to regulate the furnace draft only after it has been raised high enough to fully close the opening 26. The lack of this refinement of control, however, is negligible compared to the advantage of making possible continued operation of the furnace after failure of the normal air supply.

It will be apparent from the foregoing descrip tion and explanation that the invention is characterized by numerous advantages. The elimination of mushroom-type valves avoids all the objectionable features incident thereto, The use of a single valve for controlling both the incoming air and the outgoing combustion gases reduces the cost of regenerative furnace installations and simplifies the control thereof. The principal advantages of the invention, of course, are the ability to operate the valve as a damper to control the outflowing combustion gases while maintaining the air inlet closed and the provision for admitting air under natural draft through the auxiliary inlet as well as the normal inlet, after failure of the normal air-supply means.

Although I have illustrated and described but a preferred embodiment of the invention, it will be recognized that changes in the construction and arrangement of parts disclosed may be made without departing from the spirit of the invention or the scope of the appended claims.

I claim:

1. In a reversing valve, a valve seat, a closure slidable along said seat, said seat having an outlet therethrough for waste gases and an inlet spaced from said outlet for admitting normal air supply, said closure being dimensioned to leave said inlet open when positioned to close the outlet and to close the inlet when positioned to open the outlet partially, and a supplemental air inlet in said seat so positioned as to be closed by said closure when the outlet is substantially fully open, and means normally closing said supplemental inlet.

2. In a reversing valve, a valve seat, a closure slidable along said seat, said seat having an outlet therethrough for Waste gases, an inlet for normal air supply and an emergency air inlet, said closure being eiiective to open fully the normal air inlet when closing said outlet, to close said normal air inlet when partially opening said outlet, and to close the emergency inlet when substantially fully opening said outlet, and a closure for said emergency inlet removably secured to said seat.

3. In a reversing valve, a valve seat, a closure slidable along said seat, said seat having an outlet therethrough for Waste gases and an inlet spaced from said outlet for admitting normal air supply, said outlet having a dimension in the direction of closure travel much greater than that of said inlet and the outlet and inlet being so positioned relative to each other that when the outlet is closed the inlet is fully open and when the outlet is partially open the inlet is closed, and a supplemental air inlet normally closed by a removable closure but positioned so as to be closed by said first mentioned closure when said outlet is substantially fully open.

4. In a reversing valve, a valve seat, a closure slidable therealong, said seat having spaced openings including a waste-gas outlet, a normal air inlet and an emergency air inlet, said closure being dimension d to fully close said outlet while leaving said normal inlet open, to close said normal inlet when only partly opening said outlet, and to close said emergency inlet when substantially fully opening said outlet and an openable cover for said emergency inlet.

5. In a reversing valve, a valve seat, a closure slidable therealong, said seat having spaced openings including a waste-gas outlet, a normal air inlet and an emergency air inlet, said closure being dimensioned to fully close said outlet While leaving said normal inlet open, to close said normal inlet when only partly opening said outlet, and to close said emergency inlet when said outlet is substantially fully open, an air duct leading to said normal air inlet, an opening in said duct adjacent said inlet for admitting air directly thereto under natural draft, and means normally closing said last-mentioned opening.

HENRY R. LOXTERMAN.

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