US3471138A - Integral gas quencher for tilting furnaces - Google Patents

Description

Oct 7, 1969 1.. A. LOHNER ETAL INTEGRAL GAS QUENCHER FOR TILTING FURNACES Filed llay 1'7. 196? LOUIS A. LOHNER WILLIAM B, MIDDLETON HARRY L. RICHARDSON INVENTORS.

' AGENT United States Patent U.S. Cl. 26616 2 Claims ABSTRACT OF THE DISCLOSURE Apparatus is provided for continuous removal of hot off-gas from furnaces which are tilted during the operating cycle. The apparatus features a first conduit which is permanently attached to the furnace and receives the hot off-gas. The first conduit terminates at an outlet which is juxtaposed opposite to and spaced away from a gas inlet opening of a second conduit. The second conduit has a vertical gas quench section and a horizontal extension at its lower end. The horizontal extension terminates in a swivel joint which connects with an inlet section of a third conduit. The second conduit is permanently attached to the furnace by a beam. The third conduit is connected to a fourth conduit by mean of a fluid-impervious wiper seal. The fourth conduit terminates in a means for disposal of the quenched off-gas. Thus in summary, the apparatus attains continuous ventilation of a tilting furnace and removal of hot off-gas with integral gas cooling or quenching, regardless of the degree or angle to which the furnace is tilted.

BACKGROUND OF THE INVENTION Field of the invention The invention relates to the continuous removal and quenching of the hot off-gas generated by furnaces which tilt to various positions about a horizontal axis during the normal operating cycles, which may include a charge period, a processing period and a product removal period. The various types of furnaces to which the invention is applicable include metallurgical furnaces such as electric furnaces and oxygen steel converters.

Description of the prior art Numerous types of apparatus arrangements have been proposed for the removal of hot off-gas from furnaces. In many instances a movable hood is proposed, which is placed in position during periods of off-gas discharge, and is displaced from the furnace mouth or outlet during periods when the furnace is tilted, such as during the. discharge of a molten product stream. Some of the prior art shows off-takes which are secured permanently to the furnace roof, whil other apparatus includes flexible olftakes. The prior art disclosures include U.S. Patents Nos. 3,220,826; 3,173,980; 3,138,649; 2,908,737; 2,781,251; 2,684,392; 2,426,643 and 2,334,275. The quenching of hot off-gas from furnaces has been suggested in such prior art disclosures as U.S. Patents Nos. 3,262,685 and 3,212,761.

The basic concept of the present invention is for a discharge flue system from a furnace, such as an electric furnace producing either mild steel or stainless. For mild steel production by single slag, there is no objection to the furnace being under a negative pressure which would infiltrate air for an oxidizing atmosphere. Were this the only consideration, a direct exhaust could be used on the furnace roof. In operation, this furnace produces gases to create a positive pressure in the furnace. These gases are high in carbon monoxide and carry an objectionable 3,471,138 Patented Oct. 7, 1969 amount of fume, principally iron oxide. This leaks into the shop through the doors, which are not sealed, and around the three electrodes through the roof of the furnace. These electrodes must be retracted, consequently the openings cannot be designed for a. close clearance. Th gas and fume is discharged to a large extent from these openings.

The predominant design in the industry is top charge. This means that the electrodes are retracted, the roof removed, the charge placed in the furnace by cranes, roof returned to location and the electrodes lowered. This precludes a fixed exhaust mounted on the roof and solidly connected to an exhaust system. In addition, the explosion hazards in exhausting carbon monoxide from a cyclic operation with inherent explosive mixtures plus the fact that this gas in the intermittent amount cannot be used makes this a very questionable design.

For stainless or alloy steel production the two slag, or carbide slag and white slag heats are made. After the usual first slag the alloying materials are added and all operators demand that this second working be under a reducing atmosphere requiring positive pressure in the furnace. There is about 0.02 inch of positive pressure under the roof and a fourth hole built into the roof will allow the furnace to exhaust itself. The method approved by industry is the immediate combustion of these gases. In prior art facilities, large areas of the operating levels of the shop are blocked with the exhaust system.

SUMMARY OF THE INVENTION The present invention provide apparatus for continuously removing and quenching a hot oif-gas stream discharged from a vertically oriented furnace which tilts about a horizontal axis during a portion of the furnace operating cycle, such as during discharge of a molten product stream. The apparatus of the present invention permits continuous ventilation of the furnace and removal of off-gas, regardless of the angle to which the furnace is tilted. The apparatus includes a first conduit which extends from upper means for ventilation of the furnace and hot off-gas removal. The off-gas flows into the first conduit, and then flows downward through a vertical gas quench section of a second conduit, in which liquid water is sprayed or otherwise dispersed into the hot off-gas to provide quench-cooling by water'evaporation. The second conduit terminates with a lower horizontal extension, which terminates at a swivel joint which connects the first conduit to the horizontal inlet section of a third conduit. The third conduit terminates with a vertically downward extending terminal portion which is connected with a lower coaxial fourth conduit by a closure or connection which permits vertical movement of the third conduit relative to the stationary fourth conduit. The closure consists of a frusto-conical baflle with an inwardly extending flexible wiper seal and an inverted frusto-conical portion. The frusto-conical baffle extends downwards and outwards from the third conduit and a flexible wiper seal is mounted on the lower end of the baflle. The third conduit has an inverted frusto-conical portion on its terminal end. The fourth conduit is spaced vertically below the third conduit, and extends coaxially downwards below the lower end of the third conduit to means for disposal of quenched off-gas.

The principal advantage of the present invention is that continuous removal of hot off-gas from a tilting furnace is attained, regardless of the angle to which the furnace is tilted from -a vertical orientation about a horizontal axis. Another advantage is that, in a preferred embodiment, the furnace off-gas is effectively and completely quenched to a lower temperature by the provision of apparatus which attains total and uniform quenching of the off-gas in the vertical section of the second conduit. A

further advantage is that the apparatus is relatively simply and readily fabricated, and may be readily provided in existing facilities as well as new installations. Still another advantage is that a tilting furnace is effectively ventilated and quenched off-gas is passed from the furnace to a permanently fixed means for disposal of quenched off-gas, regardless of the motion or tilting of the furnace.

It is an object of the present invention to provide an improved apparatus for the removal of off-gas from a tilting furnace.

Another object is to provide an apparatus which continuously removes off-gas from a tilting furnace, regardless of the angle to which the furnace is tilted.

A further object is to provide an apparatus for effectively quenching hot off-gas from a tilting furnace, while the off-gas is being continuously removed from the furnace.

An additional object is to provide a readily fabricated and easily assembled apparatus for removing and quenching off-gas from a tilting furnace.

Still another object is to provide an apparatus for continuously quenching and transferring hot off-gas from a tilting furnace to a stationary means for disposal of quenched off-gas.

Still a further object is to provide an apparatus for the combined ventilation of a tilting furnace, and removal and quenching of hot off-gas from the furnace, which continuously operates regardless of the angle to which the furnace is vertically tilted about a horizontal axis.

These and other objects and advantages of the present invention will become evident from the description which follows.

DESCRIPTION OF THE DRAWING The figure is a sectional elevation view of the apparatus of the present invention.

Referring now to the figure wherein the invention is illustrated, in which an auxiliary conduit is provided which is permanently attached to the furnace roof. The outlet of the auxiliary conduit is juxtaposed opposite to the inlet of the gas quenching conduit, and spaced away from the quench conduit inlet to allow for combustion air entry and movement of the furnace roof from the top of the furnace during periods when the furnace is being charged. In addition, a preferred type of dry seal connection between conduits downstream of the swivel joint is shown, which permits vertical movement and a tolerable amount of air leakage into the quenched gas stream.

The furnace 19 in the figure is typically an electric furnace provided with retractable electrodes such as element 20, however furnace 19 may alternatively consist of other types of tilting furnaces such as an oxygen steel converter. A movable roof 21 is provided over the top opening in furnace 19, and during charge periods the electrodes such as 20 are retracted, and the roof 21 is disengaged and displaced to allow entry of feed materials into the furnace. Off-gas removal conduit 22 is permanently attached to roof 21 and extends from an upper opening in the roof 21. Conduit 22 serves to remove hot off-gas from the furnace during the operating cycle. In most instances, three electrodes such as 20 will be provided in the roof 21, with the electrodes extending through individual holes in the roof. In this case, the conduit 22 will extend from :a fourth hole in the roof 21. Conduit 22 is provided with an external cooling water jacket 23, and cooling water stream 24 is passed via nozzle 25 into the annular space between conduit 22 and jacket 23. stream 24 circulates external to conduit 22 to provide a cooling effect and protect conduit 22 from excessive temperature effects due to internal contact with the hot olfgas. Warmed cooling water is removed from jacket 23 via nozzle 26 as stream 27. An inner refractory lining may be provided within conduit 22, instead of or in addition to jacket 23.

The outlet of conduit 22 is juxtaposed opposite to the inlet of the gas quenching conduit 28, and spaced away from the quench conduit inlet to allow for combustion air entry via streams 29, which react with the hot off-gas in the inlet section of conduit 28 and serve to burn combustible components such as carbon monoxide. The inlet section of conduit 28 is provided with external cooling water jacket 30, which is similar in arrangement and function to jacket 23 described supna. Cooling water stream 31 is passed via nozzle 32 into the annular space between conduit 28 and jacket 30, and nozzle 33 serves to remove warmed cooling water stream 34. The cooling water streams 24 and 31 may be derived from a cooling ring, not shown, disposed about the furnace 19.

The off-gas stream next flows vertically downwards through the vertically oriented gas quenching section of conduit 28. A primary quench water stream 35 is passed through horizontal duct 36, which extends into the vertical section of conduit 28 and terminates at a central liquid water outlet nozzle 37, which sprays liquid quench water centrally downwards into the hot gas stream. An inverted frusto-conical baffle 38 is disposed in conduit 28 below nozzle 37, and extends inwards and downwards from the vertical wall of conduit 28 and terminates at a central opening, through which the off-gas flows at an accelerated velocity. The liquid water stream 35 sprayed through nozzle descends into the central opening in baffle 38. In addition, liquid water stream 39 is passed through the plurality of pipes 40 which extend tangentially into conduit 28 immediately above baffie 38 and below duct 36. The pipes 40 are spaced apart and extend substantially horizontally into conduit 28, and discharge liquid water onto the upper surface of bafiie 38 in the form of a liquid film which flows downwards across the upper surface of baffle 38 in a spiral flow pattern. The downfiowing water is projected into the accelerated gas stream at the central opening in baffle 38, to attain complete gas quenching in the vertical section of conduit 28.

The quenched and cooled gas stream, which may also contain entrained liquid droplets, passes from the vertical quench section of conduit 28 into a lower terminal horizontal extension at the lower end of conduit 28. The conduit 28 terminates at a swivel joint 41 which is provided with a gasket 42 or other suitable fluid closure means. The swivel joint 41 connects the horizontal terminal portion of conduit 28 to the horizontal inlet section of conduit 43, which extends to a vertically downward extending terminal portion. The terminal portion of conduit 43 is preferably provided with a lower inverted frusto-conical portion 44, and the terminal portion of conduit 43 including section 44 extends into the upper end of lower coaxial conduit 45. A frusto-conical baffle 46 is preferably provided at the lower end of conduit 43. The bafi le 46 extends downwards and outwards from conduit 43 external to the slip joint between conduits 43 and 45, and the baffle 46 is provided with a lower flexible wiper seal or gasket 47 to allow for greater tolerances in the slip joint and also to wipe accumulated liquid from the upper external surface of conduit 45. The wiper 47 also minimizes excess amounts of infiltrated air flow through the slip joint in instances where excessive air inflow through the slip joint is undesirable. The slip joint between conduits 43 and 45 is essentially a dry joint, except for water droplets carried through the system. Since conduit 43 extends into conduit 45, any water in the system will flow downwards through conduit 45, instead of out of the slip joint clearance between conduits 43 and 45.

The quenched gas flows downwards through conduit 45 and enters exhaust blower 48, which discharges the quenched gas via conduit 49 as stream 50. In some instances, conduit 49 may serve to pass stream 50 to a discharge stack. In other cases, such as when the original hot off-gas discharged from furnace 19 contains a substantial proportion of entrained solid particles, the conduit 45 may extend to suitable means for scrubbing or cleaning of the gas stream, such as a venturi scrubber or dry filter, followed by an exhaust blower such as unit 48.

An attachment beam 51 extends between the conduit 28 and furance 19, to provide a permanent attachment between these apparatus elements. A plurality of spaced apart attachment means such as beam 51 may be provided in practice. In operation of the apparatus of the figure, the electrodes such as element 20 are retracted, the assemblage of roof 21 and conduit 22 and their appurtenances are displaces from the top of the furnace, and a charge of feed material is passed into the furnace. The roof 21 with attached conduit 22 is then positioned back on the top of furnace 19, with the outlet of conduit 22 juxtaposed opposite to the inlet of conduit 28, and the electrodes such as 20 are positioned for the processing period. The blower 48 is started up, and furnace operation is initiated, with resultant generation of hot off-gas, which passes through conduits 22, 28, 43, 45 and 49 as described supra. During portions of the operating cycle, such as a pour period, the furnace 19 is tilted, and due to the permanent attachment such as beam 51, the conduit 28 also tilts, so that the juxtaposed relationship between the opposed ends of conduit 22 and 28 remains constant during the various portions of the operating cycles when the furnace is tilted to various angles as required. The tilting of conduit 28 about a horizontal axis causes the lower terminal portion of conduit 28 to pivot about swivel joint 41. In addition, the lower terminal portion of conduit 28 moves vertically. This motion in turn causes vertical movement of conduit 43 relative to the fixed conduit 45, however the lower end of conduit 43 remains coaxial with and continuously extends into the upper end of conduit 45 during all portions of the operating cycle.

What is claimed is:

1. An apparatus for continuously removing and quenching a hot off-gas stream discharged from a vertically oriented furnace which tilts about a horizontal axis during a portion of the furnace operating cycle, which comprises a first conduit, said first conduit extending from an off-gas outlet opening in the roof of a vertically oriented furnace for ventilation of said furnace and hot offgas removal, a second conduit, said first conduit terminating at an outlet which is juxtaposed opposite to and spaced away from the gas inlet opening of said second conduit, whereby atmospheric air fiows into the inlet opening of said second conduit together with hot off-gas from said first conduit and combustion of combustible components in said oif-gas takes place in said second conduit, said second conduit being provided with a vertical gas quench section through which said hot off-gas flows vertically downwards, means in the vertical section of said second conduit to quench said hot gas stream with liquid water, a terminal horizontal extension at the lower end of the vertical section of said second conduit, said horizontal extension terminating at a swivel joint, said second conduit being permanently attached to said furnace by one beam, said beam extending from an attachment to said second conduit at a point between the quench section of said second conduit and said swivel joint to an attachment to said furnace, said swivel joint connecting to the horizontal inlet section of a third conduit, said third conduit having a vertically downward extending terminal portion, a fourth conduit, said fourth conduit extending vertically downward from adjacent to the lower end of said third conduit to means for disposal of quenched off-gas and being rigidly attached to said disposal means, with the adjacent ends of said third conduit and said fourth conduit being juxtaposed whereby off-gas flows downwards from said third conduit into said fourth conduit, and means vertically movable and connecting the juxtaposed ends of said third conduit and said fourth conduit by a fluid-impervious seal, whereby said third conduit moves vertically relative to said rigidly fixed fourth conduit when said vertically oriented furnace is tilted while gas transfer from said third conduit to said fourth conduit is continuously maintained, said means vertically movable and connecting the lower end of said third conduit with the upper end of said fourth conduit including a frusto-conical bafile, said baflle extending downwards and outwards from said third conduit and external to said fourth conduit, the lower end of said baffie being provided with inwardly extending flexible sealing means for wiping the outer surface of the upper end of said fourth conduit, said third conduit having an inverted frusto-conical portion at its lower end extending into the upper end of said fourth conduit.

2. The apparatus of claim 1, in which said second conduit is provided with an'external jacket, said jacket extending over the outer surface of said second conduit from said inlet opening of said second conduit to said means in the vertical section of said second conduit for quenching said hot gas stream with liquid water, together with means to circulate cooling water in the space between said second oonduit and said external jacket.

References Cited UNITED STATES PATENTS 2,268,918 1/ 1942 Allan et al.

2,684,392 7/ 195 4 Moore.

2,908,737 10/1959 Dominicis 13-10 2,925,289 2/1960 Brown et al. 287-58 X 3,075,753 1/1963 Akin 261-119 3,169,160 2/ 1965 Johansson 266-36 3,215,523 11/1965 Richardson 266-35 X 3,262,685 7/1966 Pike et al.

3,331,591 7/1967 DellAgnese et al. 261-115 X 3,353,803 11/1967 Wechselblatt et al.

RONALD A. WEAVER, Primary Examiner US. Cl. X.R.

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