Abstract: The invention relates to apparatus for the introduction of reagents in powder form into a melting pan, in which the lance is arranged eccentrically with respect to the pan axis and the outlet nozzles are directed into the larger region of the pan enclosing the pan axis. Such apparatus is distinguished by optimum mixing in of the added reagents.

Abstract: An apparatus for mounting a gas washing sink in a centered manner within an opening through a perforated brick in a wall of a metallurgical vessel and for removing the sink from the perforated brick includes a support assembly to be fixedly mounted on the exterior of the wall of the metallurgical vessel adjacent the opening in the perforated brick. A fastening assembly supports the sink and is mounted with respect to the support assembly for movement relative thereto between an operating position, whereat the sink is pressed into the opening throgh the perforated brick in a centered manner, and a maintenance position, whereat the sink is withdrawn from the opening through the perforated brick. Structure moves the fastening assembly relative to the support assembly to the operating position. A withdrawal apparatus moves the fastening assembly relative to the support assembly from the operating position to the maintenance position.

Abstract: Tundish for continous casting of steel, of the type comprising a permanent refractory, cast on a frame of sheet metal defining the outer wall of the tundish and on which a refractory wear has been laid. In the body of the permanent refractory, there is provided a gas duct which penetrates into the permanent refractory at the level of the upper edge of the tundish and extends to the bottom of the tundish into a gas distribution chamber, which is covered with a surface distributed gas permeable plate. Application to the continuous casting of steels for tundish between casting ladle and ingot molds.

Abstract: A process and device for the removal of arsenic, tin and antimony from crude lead by industrial oxygen is disclosed in which the oxygen is introduced into a turbulent fluid stream of lead restricted in a limited volume. The oxygen containing fluid stream passes into a larger volume in which the compounds which are to be separated float on the surface in the form of oxides and run off from the surface. The device includes two cylinders of different volume and one within the other. The cylinders are immersed at different depths in molten lead in the smelting crucible, a steam of fluid lead is introduced in the smaller cylinder by a lead pump and oxygen is introduced into this fluid lead stream.

Abstract: An apparatus for gas treatment for a bath of liquid aluminum at rest in a furnace having a roof and in which the bath has a surface area of at least 10 m.sup.2. The apparatus comprises a movable gantry placed over the furnace and from which are suspended at least three gas injector assemblies which are more than 2 m long each. The injector assemblies are partially immersed in the bath through openings in the roof of the furnace and the immersed parts are separated from each other solely by the bath. The assemblies each comprise a rotary shaft having a rotor at its lower end joined to a plurality of blades. Through the axis of the shaft there is a cavity which opens above the furnace and which communicates at its lower end with passages in the blades. Means are provided above the furnace for rotating the shafts and for connecting the cavities to a source of treating gas.

Abstract: An improved apparatus and method of the inline degassing of the molten metal employing a fluxing gas.

Abstract: An apparatus repairs a perforated brick employed in a wall of a metallurgical vessel and having an opening into which is to be fit a gas washing sink for introducing gas into molten metal within the metallurgical vessel, during which gas introduction the inner end of the gas washing sink and the perforated brick around such area become worn. The apparatus includes a casing having an outer contour corresponding to the outer contour of the gas washing sink and to be inserted into the worn opening of the perforated brick upon removal therefrom of the worn gas washing sink. The casing thus forms a template defining the contour of the opening to be repaired in the worn portion of the perforated brick. A repair material feed pipe extends through and is guided by the casing for supplying therethrough repair material for repairing the worn portion of the perforated brick. A spray head is attached to the inner end of the feed pipe for directing the repair material toward the worn portion of the perforated brick.

Abstract: A gas injection lance for use in metal refining is disclosed. The lance includes a tube having an inner diameter profile and a throttle member slidably received with the tube. The tube and throttle member define an annular gas flowpath. The throttle body may be moved axially within the tube to modify the characteristics of the flowpath.

Abstract: An injection device for introducing gases into metallurgical vessels includes a gas sink with a plurality of gas-carrying ducts and formed as a refractory frustum, a metal layer enclosing an outer generated surface of the gas sink and its base area, a gas supply pipe exposed at a center of the metal-coated base area of the gas sink ad supplying gas to the gas-carrying ducts, and a perforate block enclosing the metal-coated generated surface of the gas sink. The upper end of the gas sink is not enclosed by the perforate block, extends beyond the lining of the ladle bottom into the inside of the ladle, and is surrounded by refractory material.

Abstract: A metal continuously melting and retaining furnace including a retaining chamber which retains therein a molten metal fed from a melting chamber, a ladling chamber from which the molten metal is ladled out, and a treating chamber between the retaining and ladling chambers and having means of producing bubbles of a molten metal-refining gas and means of stirring the molten metal. A molten metal inlet port between the retaining chamber and the treating chamber and a molten metal outlet port between the treating chamber and the ladling chamber are disposed so as not to face directly to each other. In addition, a bubble baffle plate stands on the bottom surface of the treating chamber near the molten metal outlet port so as to oppose thereto. This makes it possible to provide a molten metal with a good yield, which is refined to a higher degree and is most suitable for producing a high quality thin cast product by casting.

Abstract: A continuous melting furnace in which a metal is melted, so that the melted metal is held to maintain the temperature of the melted metal and is ladled to a mold, comprising a melting tower chamber for receiving metal to be melted and for melting such metal, an inclined floor chamber connected to the melting tower chamber, a holding chamber connected to the inclined floor chamber, a gas treatment chamber connected to the holding chamber and having a bubbling device for ejecting an inert gas into the melted metal and a ladling chamber connected to the gas treatment chamber and which is bounded to the holding chamber through a thermally insulative separation wall from which the melted metal is ladled into a mold.

Abstract: A one-piece refractory stopper rod has an axial bore formed therein for the introduction of inert gas into molten steel within a tundish. A metal bushing insert is compressed into the refractory stopper rod and has a threaded bore which is positioned coaxially with the bore of the stopper rod body. A metal attachment rod having an axial bore therethrough and a threaded lower shank portion is secured within the threaded bore of the metal bushing insert. The metal attachment rod has an upper threaded shank which is adapted to be secured to a stopper rod lifting mechanism associated with the tundish. The metal rod further includes a flanged portion intermediate the upper and lower shank portions which carries an annular chamfered surface. The annular chamfered surface faces a like annular chamfered surface formed in the bore of the stopper rod to define a gas-tight seal at a sealing interface therebetween.

Abstract: The invention encompasses a pneumatic steelmaking vessle and a method for the production of steel from hot carbon-bearing metallized raw materials such as direct reduced iron. The vessle is a refractory-lined ladle, having an eccentric ladle cover with an opening on one side. Opposite the opening in the ladle cover is at least one downwardly directed oxygen lance or tuyere. The vessel is mounted on trunnions for rotation about its central axis to a generally horizontal position. The bottom of the vessel has a porous plug, and a hot metal outlet controlled by a sliding gate closure member or other convenient type closure. The vessel is used in connection with a method of steelmaking by serving as the means for transporting molten metal to melting, refining, ladle metallurgy, and teeming operations.

Abstract: The invention comprises a metallurgical vessel, more particularly an electric arc furnace, having means for introducing inert stirring (purging) gases into a metal melt. The vessel has an outer sheet metal jacket, a refractory lining, and means for introducing stirring gases into the melt being disposed in the furnace hearth, which comprises a permanent lining of refractory bricks and a wear lining of a refractory ramming mass. The means for introducing the stirring gases are disposed in the permanent lining.

Abstract: An apparatus for coupling a metallurgical ladle to a gas supply is presented wherein gas is used for the treatment of molten metal contained in the ladle. The gas is injected through the bottom of the ladle into the liquid metal. The ladle rests on a support located at a treatment station. The apparatus comprises a base mounted on the bottom of the ladle support in a manner as to be slidable in two directions at right angles to one another against the action of springs. The apparatus is provided with a male connection head which has an axial through passage that communicates with the gas supply. This apparatus also includes a foot fixed on the ladle which is provided with a female connection member for engagement on the connection head when the ladle is placed in its support.

Abstract: A descending stream of molten metal is directed from a ladle into a bath of molten metal in a tundish. Molten alloying ingredient is added to the molten metal, either directly to the descending stream within a shroud, or it is injected into the bath, through a sidewall of the tundish, at a region of turbulence. The molten alloying ingredient is protected from the atmosphere outside the tundish.

Abstract: Basic oxygen furnaces such as used in the production of steel comprise a vessel having a tap hole in an upper side wall section, the vessel being mounted for tilting motion with respect to its normal vertical position. Molten metal and slag thereon are separated in the area of the tap hole when the metal is being tapped by the introduction of gas such as argon or nitrogen through several slag controlling devices comprising refractory bodies defining a plurality of controlled passageways positioned around and about the tap hole.

Abstract: A method of constructing a refractory brick lining on a bottom tuyere plate for a vessel for refining or otherwise treating a metal melt comprises the improvement of constructing the lining in an imperforate manner on the bottom tuyere plate and then drilling tuyere ducts in the lining. The brick lining is preferably constructed with the bottom tuyere plate in an upright position and the ducts are then drilled while the plate and the lining are still upright. The bottom tuyere plate is preferably mounted in an assembly frame which is itself pivotally mounted to enable the frame together with the bottom tuyere plate to be swung from a horizontal position to the upright position.

Abstract: An aluminum refining vessel has two refining stages positioned side-by-side, with flow of molten aluminum into and out of the vessel being from the same side thereof. The vessel is readily adaptable for the reversal of flow therethrough, and for ease of installation, operation and maintenance.

Abstract: An apparatus for separating a gas from a liquid but truly suited for use in a zero gravity environment. The apparatus includes first and second closed vessels each of which are separated into a gas and liquid zone. The first vessel is separated by gas de-entrainment means and the second vessel by a plurality of elongated passageways for capillary containment of a body of liquid. The passageways provide the sole source of fluid communication between the gas and liquid zones. The gas zones of the first and second vessels are in fluid communication with one another as are the liquid zones of the first and second vessels.

Abstract: A nozzle for the refining of metals by oxygen blasting from above the melt is presented. The nozzle includes a nozzle head having a blast pipe therethrough upstream of the mouth of the nozzle. The blast pipe directs a jet of gas comprised, at least in part, of oxygen, having a supersonic speed onto the melt. The blast pipe includes an inner tube. The lower portion of the inner tube has a throat positioned between a convergent and divergent sections, this lower portion defining a laval nozzle. The blast pipe also includes an outer tube coaxial with the inner tube and having a greater cross section than the inner tube. The mouth of the inner tube is spaced back (downstream) from the mouth of the blast pipe. The inner and outer tubes are each provided with flow control valves, and are connected to sources of pressurized gas. Devices are provided to vary the cross sectional area of the mouth of the inner tube.

Abstract: The tapping passage of a metallurgical furnace is disposed generally horizontally in a lower region of the furnace wall structure below the upper level of the liquid metal; a closure member is pivotally movable relative to an outer end of the tapping passage to open and close access to the passage; the closure has a gas injection nozzle for injecting air under low pressure into the tapping passage to remove temporary plugging material in said passage in preparation for discharge of the liquid metal.

Abstract: A method and apparatus for reducing molten metals and/or slags thereof which involves top-blowing at least one reduction gas stream wherein fine grained coal or coke particles and injected for covering the surface of the molten metal beyond the blow impression formed by the reduction gas stream. The particles of the stream are at least partially gasified into a carbon monoxide (CO) contained reduction gas stream before they hit the metal surface, so that a mixture of carbon monoxide and coke is blown onto the metal surface together with the reduction gas stream. The coke particles are then radially moved toward the outside of the blow impression at all sides to form a thin veil beyond the perimeter of the blow impressions.

Abstract: A rotary device for dispersing a gas in molten metal, for example argon in molten aluminum, contained in a vessel, comprises a hollow shaft and a hollow rotor fixedly attached to the shaft, the rotor having a plurality of vanes each extending from the shaft, or a location adjacent the shaft, towards the periphery of the rotor whereby the hollow interior of the rotor is divided into a plurality of compartments, at least one aperture in the top or bottom of the rotor adjacent the shaft and at least one aperture in the peripheral surface of the rotor such that when the rotor rotates molten metal can enter each of the compartments through the aperture or apertures in the top or bottom, and flow outwardly through the peripheral aperture or apertures and at least one duct for the passage of the gas extending from the hollow interior of the shaft to each of said compartments.

Abstract: A device comprising a rotary shaft to be disposed in a liquid substantially vertically and rotatable about its own axis, the rotary shaft having a gas channel extending therethrough axially of the shaft, and a rotor fixed to the lower end of the rotary shaft and having at its bottom surface a gas discharge outlet communicating with the gas channel. The rotor is formed in its bottom surface with radial grooves extending from the gas outlet to the peripheral surface of the rotor and each having an open end at the peripheral surface. A recess is formed in the peripheral surface between the open ends of immediately adjacent grooves and has an open lower end at the bottom surface. When the rotary shaft is rotated in a liquid while supplying a gas to the gas channel of the shaft, the gas flows out from the discharge outlet into the radial grooves and is released from the open ends of the grooves at the peripheral surface into the liquid in the form of finely divided bubbles.

Abstract: The present invention relates to a ladle for the chlorination in co-flow mode of aluminium alloys in a molten state.It is divided by a vertical partition (6) which, with the bottom, leaves a space (7) for the flow of the metal, into a feed compartment (8) and a treatment compartment (9) in which a chlorinated gas distributor rotor (10) is immersed. It is characterized in that the treatment compartment is closed at its base by a horizontal wall (13) which extends at the level of the bottom of the partition and which is apertured at its center by an opening whose axis coincides with the axis of rotation of the rotor.It is used in the removal of magnesium from aluminium alloys and, with ladles of a capacity of close to 1 m.sup.3 and which can therefore be easily maneuvered, it makes it possible to attain treatment capacities of the order of 20 T/hour with suitable levels of efficiency in regard to the removal of magnesium.

Abstract: An elongated, vertical conduit has an upper end, communicating with the bottom opening in an upper container or ladle, and an open lower end disposed above the top surface of a bath of molten metal in a lower container or tundish. A descending stream of molten metal is directed from the conduit into the bath. A shroud encloses the conduit and the descending stream. The pressure within the shroud is lower than the outside pressure and is regulated. A mixture of transport gas and solid, particulate alloying ingredient prone to excessive fuming is injected into the descending stream within the shroud.

Abstract: A nitrogen bubbling lance for a hot metal ladle having a refractory lining has a refractory body shaped to facilitate the positioning of the lance in a vertical groove in the side wall of the ladle so as to become part of the refractory lining. A tubular member is positioned longitudinally within the lance and communicates with one or more openings in the lower side wall thereof communicating with the interior of the ladle and the molten hot metal therein. The openings are plugged with porous or nonporous material. Nitrogen introduced through the tubular member is delivered through the openings and/or the porous plugs to bubble upwardly through the molten hot metal in a stirring action.

Abstract: A method of preheating a ladle addition to a melt contained in an enclosed or covered ladle without significant loss of melt temperature. A gas stream is heated in a non-transferred arc electric arc heater to a temperature in excess of that of the melt. The ladle addition is introduced into the heated gas stream in the arc heater downstream of the arc heater wherein its temperature is increased to be about equal to or greater than the melt temperature. The heated gas stream and the entrained ladle addition is then introduced into the ladle. As the gas stream impinges on the melt, the ladle addition separates out and combines with the melt with the resulting off-gas being exhausted from the ladle. The off-gas can be recycled to the arc heater for reuse.

Abstract: The invention provides an apparatus for selectively connecting a gas supply to a vessel employed to contain molten metal. Generally stated, the apparatus includes a sealer plate connected to an external portion of the vessel to receive the gas and direct it into a fluid conduit that is in fluid communication with a selected interior portion of the vessel. A seal holder disposed in approximate alignment with the sealer plate receives the gas from the gas supply and directs it toward the sealer plate. A spacing mechanism interposed between the seal holder and the sealer plate maintains a selected spaced distance therebetween and delimits the side walls of a substantially sealed gas conduit chamber when the sealer plate and the seal holder simultaneously contact opposite end portions of the side walls defined by the spacing means. The conduit chamber is thereby configured to conduct the gas directed from the seal holder toward and into the sealer plate.

Abstract: An apparatus for producing a particulate metal or alloy having a diameter of less than 5 microns by the reaction of a molten metal or alloy with activated hydrogen. The apparatus has (1) a metal melting hearth for melting a starting metal or alloy placed thereon and supporting the molten metal or alloy, (2) a discharge electrode positioned above, and opposite to, the metal or alloy placed on the melting hearth, (3) a closed vessel for containing the melting hearth and the discharge electrode, and (4) a gas inlet port in the wall of the closed vessel for introducing hydrogen or a hydrogen-containing gas into the vessel.

Abstract: The device for removing inclusions and especially oxides of the molten metal which is poured into a casting tundish comprises elements which are placed within the interior of the casting tundish and immersed in the molten metal. The elements are formed of heat-insulating material which is sinterable at the temperature of the molten metal. A duct is formed within the interior of the elements and connected to a supply of gas such as argon which is inert with respect to the molten metal.

Abstract: A nozzle is disclosed for use in the decarburization of molten pig iron by means of a jet of oxygen from a lance provided with such nozzle. The nozzle according to the invention is characterized by a divergent portion which, beyond the neck, has a frustoconical part, with an apex angle of between 60.degree. and 70.degree. and preferably between 62.degree. and 66.degree., and wherein an angle of 65.degree. is preferred. The nozzle according to the invention can be used in particular for the decarburization of chromium containing pig iron and makes it possible to achieve very high chromium and iron yields.

Abstract: A gas blowing nozzle is produced by molding a non-porous substance into a molding frame under pressure and at the same time positioning a plurality of gas passageways forming members at predetermined spaces and distances from each other. The passageway holes have cross sectional shapes as desired, so that the gas blowing may be accurately controlled to perform refining of molten metal.

Abstract: A molten iron containing vessel includes a refractory fireproof inner lining of dolomite bricks and bauxite bricks. The lining includes magnesia bricks positioned between the dolomite and bauxite bricks, thereby avoiding contact reactions between the dolomite and bauxite. A gas permeable brick member extends through an end portion of the vessel for injecting a gas into the molten iron contained therein.

Abstract: The invention relates to a rotary gas dispersion device for the treatment of a bath of liquid metal such as aluminum and its alloys, comprising a cylindrical rotor equipped with blades immersed in the bath, connected to a hollow control shaft for the supply of gas, and is characterized in that the rotor is pierced by oblique ducts coupled to radial ducts in which the metal and the gas circulate respectively before being mixed at the point where these ducts join up, emerging in the bath so as to form a fine dispersion which is then distributed in the said bath by means of blades.

Abstract: A solid non-permeable refractory plug has a spaced stainless steel jacket and is located in a pocket block for incorporation in the normal refractory brick lining of a ladle to provide a structure through which gas can be introduced into the molten metal, primary and secondary covers protect the device from metal and/or slag penetration during the filling of the ladle with molten metal.

Abstract: Aluminum pellets are ejected from the nozzle of an elongated tube into a stream of liquid steel flowing from a tundish into a continuous casting mold. Protective gas is utilized to propel the pellets of aluminum from the elongated tube into the molten stream. A special nozzle structure for the elongated tube insures that the aluminum pellets will properly impinge upon and mix with the molten stream. The elongated tube is retained within a larger cylindrical tube that directs low velocity, protective gas at the molten stream. The protective gas, such as nitrogen or argon, provides essentially nonreactive atmosphere that envelops the molten stream of steel.

Abstract: An improved molten metal pump and gas injection apparatus comprising a submersible pump housing 10 enclosing a rotatable impeller 30, an impeller drive 12 supported above the housing and an elongate drive shaft 16 operatively connected to the impeller. Rotation of the drive shaft effects fluid flow between a pump inlet 35 and a pump outlet 44 both being at least partially defined by the impeller housing. A gas injection conduit 54 extends downwardly from a drive motor support platform 20 and includes an output end 54a that terminates near the pump inlet and which is received by a gas inlet collar 58 that defines a venturi 60, coaxial with the axis of the pump inlet. A passage 62 formed in the collar communicates the end of the gas injection conduit with the throat of the venturi so that the gas is injected into the incoming molten metal in an area of low pressure, thereby reducing the gas pressure needed to effect injection.

Abstract: A vessel, such as a ladle or converter has a wall having extending therethrough a bore. A tube is fixed in a gas tight manner within the bore. The tube has therethrough a cylindrical passage. At least one gas permeable insert is fitted in a gas tight manner within the passage. The insert may be a pre-shaped insert or may be a mass tamped and packed into the passage. The insert may be replaced by drilling the insert from the passage of the tube and fitting a new insert within the passage. A gas connection is connected to the outer end of the tube to supply gas into the tube and through the insert into the interior of the vessel.

Abstract: A melt and hold furnace includes a melt and hold chamber configured for containing a molten metal bath and having a tap for withdrawing molten metal and a preheat hearth disposed above a top surface of the molten metal bath. A sealed combustion chamber is disposed above the melt and hold chamber and is separated therefrom by radiation plates for radiating heat into the molten metal and hearth. Disposed in an operative relationship with the combustion chamber is a recouperative type burner for causing unimpeded circulation of hot combustion exhaust gases over the radiation plates from the burner and return to exhaust ports disposed within the burner. Conduits, passing through the combustion chamber and into the molten metal provides additional heating of the metal by heat conduction and the introduction of hot non-oxidizing gas into the metal.

Abstract: A process and apparatus for making steel in a basic oxygen furnace by the top-blowing of pure oxygen and the bottom-blowing of a gas mainly composed of carbon dioxide are disclosed, in which a waste gas discharged from said basic oxygen furnace is utilized as the only source of the gas to be blown into a molten metal.

Abstract: An improved method and apparatus for degassing molten metal is disclosed in which the molten metal is passed in countercurrent relationship with a fluxing gas which is introduced through a sparger plate provided with a plurality of orifices of controlled size and spacing so as to minimize fluxing gas bubble size while maximizing fluxing gas bubble density thereby optimizing the degassing of the molten metal.

Abstract: The disclosure teaches an improvement in the degassing and filtration of molten metal, especially aluminum, using an apparatus which employs a pair of sequentially placed, removable filter-type plates and at least one fluxing gas inlet positioned therebetween. The first of said filter-type plates is characterized by a plurality of holes which provide a preferential path through which the fluxing gas flows upwardly through the first of said filter plates in counter-current contact with the melt. Said plate serves to break up said fluxing gas into a fine dispersion to assure its intimate and extensive contact with the melt. Dissolved gases and non-metallic inclusions are thereby abstracted and removed from the melt.

Abstract: Apparatus for protecting a molten metal pouring stream between a teeming vessel and a hot metal receiving mold beneath the vessel, including a heat resistant metal shroud tube, carrying at its lower extremity a replaceable, flexible, high temperature, heat resistant cloth tube extending downwardly therefrom.

Abstract: Metallurgical grade silicon is melted and the resulting impure molten metal is continuously flowed downwardly as a thin film through an atmosphere of impurity-reactive gas or gases directly into a crucible, wherein it is subjected to directional solidification. The preferred apparatus for carrying out the process comprises a heated reaction chamber fed peripherally from a superimposed melting chamber, the reaction chamber having horizontally rippled interior wall surfaces of a substantially non-reactive material, such as graphite, silicon carbide, or silicon nitride, so the descending film of molten metal will be agitated and spread laterally. Means are provided for introducing the reactive gas or gases near the bottom of the reaction chamber and for exhausting the spent gas at the top. The reaction chamber is superimposed above and in vertically spaced relationship with an electric furnace, which encircles a columnar crucible.

Abstract: An improved method and apparatus for degassing molten metal is disclosed in which the molten metal is passed in countercurrent relationship with a fluxing gas which is introduced through a sparger plate provided with a plurality of orifices of controlled size and spacing so as to minimize fluxing gas bubble size while maximizing fluxing gas bubble density thereby optimizing the degassing of the molten metal.

Abstract: Air injectors are located in a ladle additive chute to eliminate the chimney effect created by the chute and hot gases present when a furnace is tapped. Air is supplied through openings about the chute below an open upper end, through which ladle additives are charged. The openings direct the air downward and inward of the chute and the air is supplied at a pressure and flow sufficient to prevent smoke, fumes and eruptive flames from rising through the chute when alloys are added to the metal being poured into the ladle.

Abstract: An apparatus for shielding a stream of molten metal during teeming consisting of a pair of cylinders aligned on a common axis by means adapted to position one cylinder against a ladle around the pouring spout and the second cylinder proximate a tundish, ingot mold or pouring trumpet. Also included are means to form a gas barrier between the cylinders to contain a shielding (inert) gas around the molten metal stream to protect the stream from contact by the ambient atmosphere and means to mount the apparatus on a pouring ladle carriage.

Abstract: In an apparatus for refining molten metal comprising, in combination:(a) a vessel;(b) inlet and outlet means for molten metal and gases; and(c) at least one rotating gas distributing means disposed in said vessel, said gas distributing means comprising (i) a rotatable shaft coupled to drive means at its upper end and fixedly attached to a vaned circular rotor at its lower end; (ii) a hollow stationary sleeve surrounding said shaft and fixedly attached at its lower end to a hollow circular stator; (iii) an axially extending passageway for conveying and discharging gas into the clearance between the rotor and stator, said passageway being defined by the inner surface of the sleeve and stator and the outer surface of the shaft; and (iv) means for providing gas to the upper end of the passageway under sufficient pressure to be injected into the vessel,the improvement comprising utilizing, in the combination, a smooth outer surface construction for the stator and a ratio of the diameter of the stator to the root d