US2159286A - Reduction furnace - Google Patents

Description

5 Sheets-Sheet l W. E. MQORE REDU'JTIofl FURNACE Filed Sept. 25, 1935 May 23, 1939.

3mm wz'llzizm E Moore May 23, 1939. w. E. MOORE REDUCTION FURNACE Filed Sept. 25, 1935 3 Sheets-Sheet 2 wlzzm' E. Mo

W. E. MQOFQE May 23, 1939 REDUCTION FURNAC E Filed Sept. 25, 1935 3 Sheets-Sheet 3 Patented May 23, 1939 UNITED STATES PATENT OFFICE REDUCTION romance William E. Moore, Pittsburgh, Pa., assignor to Pittsburgh Research Corporation, Pittsburgh, Pa.

Application September 25, 1935, Serial No. 42,121

8 Claims. (Cl. 13-1) This invention relates to furnaces for reducing Figure 9 is a detail section of a portion of the ores or oxides, and more particularly to furnaces explosion door and frame, for reducing phosphate rock, ores and oxides and Figure 10 is a detail elevation of one of the other phosphorus containing materials, although electrode glands and cooling pipes therefor, shownot limited to this use. ing its relation to the furnace roof and roof cover,

An important object of this invention is to Figure 11 is a top plan view of a furnace emprovide a furnace of the above mentioned charbodying this invention, showing the workmans acter with means to prevent the leakage or escape platform on top thereof,

of poisonous or noxious fumes. Figure 12 is a vertical sectional view of one Another object of this invention is the proof the poke hole castings, m vision of a furnace of this character with im- Figure 13 is a detail view showing the poke hole proved means for feeding ores or other materials casting applied to the roof of a furnace in which thereto and to distribute said material within a roof cover is not used,

the furnace in a manner to promote rapid and Figure 14 is a similar view showing its location 5 efficient reduction thereof, without damaging the when used with a roof and roof cover, 15 furnace walls. Figure 15 is a side elevation of a furnace shell A further object of this invention is to prevent in which the sides of the shell are inclined, the accumulation of excessive gas pressures with--. Figure 16 is an elevation, parts being broken in the furnace, and thereby prevent damage away, of a charge spout for use with this imcaused by such pressures. proved furnace, 20

Still another object of this invention is to facili- Figure 17 is an elevation at right angles to tate the removal of slag from the furnace; to Figure 16 showing the hanger fo e Charge p u permit control of the disposition of the ore or n the upp portion f the p other material within the furnace; to prevent the Figure 18 is a top p View e f, adhesion of material to the side walls of the fur- Figure 19 is a detail of the lower Portion of the 26 mace; and to provide a platform on the roof of central charge Sp the furnace for workmen, Figure 20 is a detail sectional view of a modi- Other objects and advantages of this invention fled form of Slag p will be apparent during the course of the follow- In 'P drawings, wherein for the Purpose Of ing description, illustration is shown a preferred embodiment of In the accompanying drawings hi h form a this invention, the numeral 2| designates the furpart of this specification and wherein like char- Dace embodlfing this invention and {lavmg f acters of reference denote like or corresponding trodes 22 slldably mounted for Vertlcal parts throughout the Same, ment on columns 23. The electrodes are shown Figure 1 is a side elevation of a. furnace emas 81x m number m Figures 1 and 2 and as three bodying. this invention, showing one arrangement in number in Figures 4, 5 and 11. Their number depends upon the size and requirements of the of buildings for housmg the furnace conveyors particular furnace. When six electrodes are proetc., and the transformers,

vided they are supplied with power from two v Figure 2 1s plan Vlew thereof the bulldmgs transformers 24 preferably located in transformer being shown in Sectlon, rooms 25 arranged at each side of the furnace u e 3 is a eleva at right angles room. The ore or other material tobereduced Figures 1 and 2 and showing the relation of the is crushed and mixed with suitable fluxes and filmace and Precipitation owe carbon for reduction in the usual manner and Figure 4 is an elevation of the furnace of this carried by conveyor 21 to' hopper 28, and passes 5 invention. through screw conveyor 28 to vertical feed pipe Figure 5 is a vertical sectional view thereof, 30 which enters the furnace roof. While the screw Figure 6 is an elevation of the furnace showing conveyor 29 is not necessary for feeding the maits connection to the gas producing apparatus, teriaI it is desirable because it forms a gas seal Figure 'l is a detail sectional view of a portion and prevents escape of gases from the furnace of the roof cover of the furnace showing the through hopper 28. packing glands for the electrodes and charge A pipe 3| connects the interior of the furnace spout, with a precipitating tower or Cottrell 32. A suit- Figure 8 is a detail elevation of the gas offtake able, blower or draft producing device may be and explosion door, prov ded as at 33 to produce a balanced draft.

The material to 'be treated may be phosphates or other phosphorus containing ores or compounds mixed with a flux such as silica and carbon which may be in the form of coke. The phosphorus containing material is reduced by heat from the electrodes in the presence of carbon, and the phosphorus is vaporized, combining with oxygen to produce phosphoric acid. The phosphorus vapor is condensed in tower 32, being drawn from the furnace through pipe 3i by the exhaust fan 33, and the non-condensible gases are drawn out through conduit 33' by fan 33. The gases exhausting from the blower 33 may be discharged into the atmosphere, or otherwise disposed of. If desired, all or a portion of these gases may be used in the furnace plenum chamber hereinafter described.

In the reduction of phosphorus compounds there is a large production of slag which must be tapped from time to time or continuously during the operation of the furnace. Due to the distance between the slag tap hole and the electrodes in the usual furnace, a large thickness of frozen slag will close up the slag hole and it is difficult to loosen this frozen slag without damaging the furnace walls. This difliculty is obviated in the present invention by cropping off the lower portion of the furnace shell at the slag tap hole 34, as shown at 35 thereby placing the inner portion of the tap hole nearer to the electrodes. As a consequence, due to the fact that the slag ad- .iacent the electrode will not freeze, there will be a much smaller thickness of frozen slag at the inner end of the tap hole which can easily beknocked out or dislodged to permit tapping of the slag into suitable cars 36 arranged on rails 31 adjacent the furnace.

ures 4 and 5 illustrate the construction of a furnace embodying this invention. The metallic furnace shell 38 is preferably circular in horizontal cross section and is made in any suitable size. A layer 39 of suitable heat insulation lines the shell and insulates it from the furnace refractories. Where desired, as in large furnaces, an additional layer 39' of heat insulation having high strength characteristics may be used, as indicated in Figure 20, and maybe used in any type of furnace. The furnace hearth and the lower portions of the furnace walls are lined with carbon blocks 40 as indicated in Figure 5, and the upper portions of the furnace walls are lined with suitable refractory material such as firebrick indicated at 4|. The furnace lining terminates short of the top of the shell 38 and a roof ring 42 is adapted to fit within the top of the shell and rests upon the top of the lining. 'A

refractory arched roof 43 is supported by the ring 42 and the electrodes 22 extend through this roof into the furnace.

In the reduction of phosphorus compounds, or

other materials which give off poisonous or noxious fumes, it is important that escape of these fumes from the furnace be prevented. The provision of the blower 33 in pipe 33 assists in the prevention of escape of fumes from the furnace but in order to prevent the escape of fumes through the electrode openings and other apertures in the furnace roof it is necessary to seal the roof of the furnace. This object is accomplished in the present invention by the provision of an additional roof spaced above the roof 43 to provide a plenum chamber 44 for the reception of a non-poisonous gas such as producer gas. The

plenum roof comprises a metal cover plate 45 areacee horizontal flanges at top and bottom. The lower flange is removably bolted to the top of the furnace shell while the upper flange is removably bolted to a cover disk or slab 46 of any suitable insulating and heat resisting material such as soapstone or the like which is spaced a substantial distance above the roof 43 to form the plenum chamber Electrode glands 47 are arranged about the electrodes and rest upon the refractory roof 43. These glands may be loosely fitted around the electrodes, and are cooled by a cooling fluid from pipes 48 extending through suitable packing glands 49 in cover disk 46, as indicated in Figure 10. Suitable packing glands 5i) in the disk :36 slidably receive the electrodes.

Producer gas, or suitable non-poisonous gas enters the plenum chamber 44 through a pipe 5| from a gas producer 52 which enters the top of the furnace shell as seen in Figures 5 and 6. Gas may be produced by burning coke from feeder 53' on grate 54' within the gas producer 52, and a blower 55 is preferably provided to assist in the burning of the coke. Other sources of gas may obviously be used.

Plenum gas in plenum chamber 44 is maintained at a pressure greater than the pressure of the noxious fumes in the furnace and consequently prevents their escape through the roof of the furnace.

The firebrick walls of the furnace converge inwardly as they approach the top of the furnace to produce the inclined surfaces seen in Figure 5. With this construction the material treated in the furnace will pass down the furnace walls without adhering thereto.

While the material to be treated may be fed through the center of the furnace only, it is preferred also to distribute the material around the electrodes by feeding it through selected portions of the furnace roof, as indicated in Figures 5 and 11. In Figure 11, in addition to the center feed pipe 30, there is a feed pipe 5| between each electrode and the adjacent portions of the furnace walls. As a consequence, when material is fed through pipes 30 and 5! it will form mounds or high places in the center of the furnace between the electrodes and between each electrode and the adjacent portion of the furnace wall with low spots between the mounds of material. Poke holes 52 are located in the furnace roof between the feed pipes 5| and permit a rod or the like 53 to be inserted through the roof of the furnace to poke the loose material in the furnace into the desired position.

The pipes 5| are preferably fed from branch pipes 54 so that the pipes 5.! may also be used as poke holes. Pipes 54 have enlarged ends arranged under hoppers 28 and suitable clam shell valves 55 are pivoted to extensions of hopper 28 to control the discharge of material therefrom. Pipes 54 have a removable telescoping sleeve connection with branches 54' of pipes 5|, and their upper ends are pivoted to pins 56 on the hopper extensions. When the pipes are disengaged from branches 54 they may be swung out of the way about pivots 56. The upper ends of pipes 5| are each preferably open and provided with an inverted frusto-conical sleeve 51 which is closed by a ball 58 through which a poke rod may be extended. The center feed pipe 30 instead of the arrangement shown in Figures 1 and 3 may be suspended in the same manner as pipes 54, and may terminate in an enlarged hopper 59 which enters the furnace roof. A pivoted closure or cover 60 may be provided to be opened to permit a rod to be inserted into the furnace for arranging the material therein as seen in Figure 19.

The poke holes 52 are each provided with a metal casing iii of hour glass shape, shown in Figure 12, and open at both ends. Where a single roof is used the casing 6| extends through the thickness of the roof as seen in Figure 13. Where a double roof is used the casing BI is of sufllcient height to extend through both, as seen in Figure 14. The ball 58 rests in the restricted portion of the casing and has an opening through which rod 53 may be inserted. When the poke hole is not in use, rod 53 is removed, and ball 58 is rotated until its opening is out of communication with the lower portion of the casing.

While the furnace is shown in Figure as having vertical casing walls, the casing may have walls parallel to the converging inner walls of the furnace, as indicated at 62 in Figure 15. Packing glands 63' are provided in disk 46 to receive the feed pipes 30 and 5|.

In order to prevent damage from excessive pressures built up inside the furnace, an explosion door is provided to open when a predetermined excessive pressure is reached within the furnace. One or more of these doors may be used, and they may be used alone or in combination with a gas offtake flue. A refractory lined pip 63 opens into the interior of the furnace in the upper portion thereof, and has its open end provided with a door frame 64 to which an explosion door 65 is pivotally secured. An annular groove 66 in the face of the door frame receives an annular flange 61 on the door in the closed position of the door and forms a seal to prevent escape of gas or fumes from within the pipe 53. .A coil spring 68 is mounted on a rod 69 pivotally connected to an extension of the door frame and engages an extension of the door 65 to maintain it in closed position and resist opening of the door. Tension of spring I may be adjusted by nut 10, to determine the pressure at which door will open. Where pipe 63 is also to be used as a gas ofl'take or flue, it is provided with a vertical branch II for this pur-' pose. A boss I! is provided to engage a suitable support for assisting in supporting a fine or the like attached to branch II.

In large furnaces it is often necessary for workmen to ascend to the furnace roof for adjustment and repairs, and in Figure 11 a walkway 13 is provided to support workmen on the roof. The walkway is generally triangular in shape and surrounds the electrodes and feed pipes. The walkway is secured at 14 to the roof cover or other suitable part of the roof and has supports 15 which are attached to center feed pipe 59.

The cropped of! shell slag outlet 34 may be operated intermittently by using a suitable plug, or it may be left open to permit slag to trickle out continuously. Slag freezes about the open- .ing and reduces the effective size of' the slag opening. In order to increase and hasten this freezing action, a cooling coll-I8 may be coiled around slag opening 11, as indicated in Figure 20 to reduce thesize of the opening and allow continuous trickling of the slag from the furnace. This cooling coil may obviously be used with the cropped off shellif desired.

The furnace of this invention may be continuously operated without the escape of poisonous or noxious fumes, and the material to be treated is fed in such. manner as to pile up the material around each electrode leaving low spots between the electrodes. This condition may be accentuated or maintained by manipulation of the material through the poke holes, and as a consequence the material is reduced more rapidly and efficiently than heretofore, and without damage to the furnace walls caused by direct exposure to the electric arc. The carbon blocks 40 extend up the walls to a point above the, liquid level in the furnace while adhesion of material to the walls is effectively prevented by the inclination of the furnace walls.

While the preferred form of this invention has been shown and described, it is to be understood that various changes in the size. shape and arrangement of parts may be resorted to without departing from the spirit of this invention or the scope of the subjoined claims.

Having thus described my invention what I claim and desire to protect by Letters Patent is:

1. In an electric furnace having a roof and electrodes extending through said roof, a supplementary roof spaced above said furnace rod and forming a plenum chamber out of communication with said furnace, and means to fill said chamber with a plenum gas.

2. In an electric furnace having a roof and electrodes extending through said roof, a cover arranged above said roof and forming a plenum chamber surrounding the roof and out of communication with said furnace, means to force gas into said plenum chamber, and means to feed material through said plenum chamber and roof into the furnace.

3. In an electric furnace having a roof and electrodes extending through the roof, a conduit communicating with the interior of the furnace, means to draw fumes from said furnace through said conduit, 9. cover arranged over said roof and forming a plenum chamber surrounding the roof out of communication with said furnace, and means to fill said plenum chamber with gaseous material.

4. In an electric furnace having a roof and electrodes extending through the roof, a conduit communicating with the interior of the furnace, means to draw fumes from said furnace through said conduit, a'cover arranged over said roof and forming a plenum chamber out of communication with the interior of the furnace, means to fill said plenum chamber with gaseous material, and means to feed material through said plenum chamber and roof into the furnace.

5. In an electric reduction furnace, a furnace shell having a roof thereon. electrodes extending through said roof, means to feed charge materials through said roof, and means to adjust at will and in a plurality of directions the position of the charge materials inside of said shell while the roof is in place thereon while preventing communication between the interior of the furnace and the. outside atmosphere.

6. In an electric furnace, a furnace crucible; a roof therefor, a plurality of electrodes extending through said roof and into the crucible, a feed tube extending through the-centra1 portion of the roof between the electrodes, a feed tube extending through the roof between each electrode and the side wall of the furnace crucible, whereby charge materials fed through said feed tubes into said crucible will pile up into mounds around the electrodes, and means to adjust at will and in a plurality of directions the position of the charge materials inside of said crucible while the roof artaaen is in place thereon while preventing communication between the interior of the furnace and the outside atmosphere.

7. In an electric reduction furnace, a furnace shell, a roof thereon, a metallic cover secured to said shell I and extending upwardly above said roof, said cover having a central opening of substantial size, a slab of insulating and heat resisting material secured to said metallic cover and closing the opening therein, said slab being spaced above said furnace roof to form a plenum chamher out of communication with the interior of said furnace, electrodes extending through said slab and furnace roof, and means to pass a gaseous material into the space between the slab and furnace roof.

8. In an electric reduction furnace, a furnace shell, a roof thereon, a metallic cover secured to said shell and extending upwardly above said roof, said cover having a central openingof substantial size, a slab of insulating and heat resisting material secured to saidrmetallic cover and closing the opening therein, said slab being spaced above said furnace roof to form a plenum chamber out of communication with the interior of said furnace, an electrode extending through said slab and furnace roof, means to pass a gaseous material into the space between the slab and furnace roof, and a charge material feed tube extending through said slab and furnace roof and communicating with the interior of said furnace shell.

WILLIAM E. MOORE.

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