Abstract: A pressure probe for an arc furnace having a roof provided with an access opening. The probe is located above the opening and includes side and end walls defining a bottom periphery for sealing the opening and an upper periphery which is sealed by a removable cover. The open cover and side walls are releasably secured in surrounding relation to the furnace roof by cross bars and threaded tie rods. A plurality of holes are formed in each of the side walls and each hole is adapted to be coupled to a conduit for communicating a pressure measuring device to the openings. A baffle is fixed to each side wall and is disposed between the opening and the holes to shield the holes from any direct line of sight from within the furnace but does not prevent pressure communication between the furnace interior and the holes.

Abstract: Into an opening (11) in the bottom part or wall part (2) of a smelting furnace (1) or of a casting ladle, a hollow cylindrical carrier element (7) is inserted which, for example, is releasably connected by means of screws with this bottom or wall part (2). This carrier element (7) surrounds an outlet casing (6) made of refractory material in which a channel of passage (5) for the melt is provided. At places facing each other with regard to the channel of passage (5), recesses (13, 14) are formed in the carrier element (7) in the manner of annular grooves. In each of these recesses (13, 14), there is a coil (17, 19) which is protected from a direct contact with the outlet casing (6) by sections of wall (15, 16) forming the bottom of the recesses (13, 14). One of the coils (17) may be connected with an AC current source for the production of a magnetic field, while the second, opposite coil (19) is connected to an evaluation circuit in which the signals induced in this second coil (19) are evaluated.

Abstract: A method of measuring the water content of charge materials in a shaft furnace, such as a blast furnace, wherein a known quantity of material is introduced into the shaft furnace, the gases emerging from the throat of the shaft furnace are analyzed; and the results of this analysis are used to calculate the value of the water content of the charged material.

Abstract: The invention provides a new method and apparatus for the detection of non-conductive particulates in molten metals, such as aluminum, gallium, zinc and lead, that can be liquified and drawn into a suitable refractory container. The passage into the container is of very small diameter (about 300 micrometers for aluminum) and it forms part of a current path between two electrodes carrying a current of about 1 to 500 amperes. The path is surrounded by liquid metal which forms an effective Faraday cage screening the path, enabling the passage of a particulate of about 15 micrometers or larger to produce a voltage pulse between the electrodes of greater than 5 microvolts, which is detectable above the inevitable background noise, which is of about that value.

Abstract: A thermocouple probe assembly for a billet furnace is provided with replaceable contact tips joined to the shanks of the probe rods within a surrounding insulator to inhibit oxidation of the junctions. Two pairs of probes are used, each pair being associated with an independent control circuit as a safety backup system. The assembly is preferably mounted on a bracket that is extendable on an angle forty-five degrees to the horizontal to provide correct probe positioning for various sizes of billets, and has a heat shield correspondingly adjustable along the probe assembly to accommodate various degrees of penetration of the probe assembly into the furnace.

Abstract: The invention provides a new method and apparatus for the detection of non-conductive particulates in molten metals, such as aluminum, gallium, zinc and lead, that can be liquified and drawn into a suitable refractory container. The passage into the container is of very small diameter (about 300 micrometers for aluminum) and it forms part of a current path between two electrodes carrying a current of about 1 to 500 amperes. The path is surrounded by liquid metal which forms an effective Faraday cage screening the path, enabling the passage of a particulate of about 15 micrometers or larger to produce a voltage pulse between the electrodes of greater than 5 microvolts, which is detectable above the inevitable background noise, which is of about that value.

Abstract: The device is to include a cylindrical carrier member for insertion into a tubular lance, also having an overhanging flange on the opposite side thereof being disposed a tapered electrode carrier either a cone with rounded apex or a symmetrical wedge with rounded apex and steep rounded sides.

Abstract: There is disclosed an arrangement for exchanging measuring and/or sampling probes capable of being slipped on to a holding means arranged on the lower end of a vertically movable lance with friction-tight contact. It includes a grab clamping the probe and movable from an operation position below the lance into a position laterally therebeside. In order to be able to slip on a probe to a holding means assuming a position that deviates from the ideal position, without damage to the holding means and the probes, the grab is mounted on the arrangement by universal joint means.

Abstract: An apparatus and process for rapidly injecting or blowing solid combustible material into a metal pool is presented. In a preferred embodiment, the apparatus essentially comprises at least one nonoxidizing compressed gas source, a circuit which supplies granulated carbonaceous material suspended in a carrier gas, at least one circuit which supplies flushing gas, various means for metering different flow rates of the gas and solid particulate streams and means for separately or jointly connecting the above described circuits to appropriate conduits which terminate in a blowing lance.

Abstract: A simultaneous multiple points sounding apparatus, comprising a plurality of weights to be suspended on burden charged in a furnace, a plurality of wire ropes attached to the weights with their one ends and extending at their other ends outside of the furnace, and a plurality of wire drums installed outside of the furnace on which the wire ropes are coiled, and a single driving device on which a plurality of wire drums are communicated, wherein the plurality of wire ropes are disposed on pulleys which travel downward when the respective weights reach the burden, thereby lessening the tension on the respective wire rope, and detectors are disposed for detecting the downward movement of the respective pulleys.

Abstract: A method for diagnosing the interior of a rotary kiln, which method permits one to make a correct determination as to the state of deposit of ash on the inner wall of the rotary kiln. According to the method, a detector is inserted into a gas stream from the rotary kiln and kept there for a certain period of time so as to allow ash to deposit thereon. Then, the weight, density and composition of the thus-formed deposit of ash are determined. The weight is corrected in view of the ash present in pulverized coal which was used as a fuel for burners, thereby obtaining corrected ash deposit weight (Wa). The weight is also corrected in accordance with the percentage of fine iron ores present in prefired pellets and the percentage of fine iron ores present in the deposit of ash and determined by the composition of the deposit and that of the fine iron ores, thereby obtaining corrected weight (Wd) of the deposited fine iron ores.

Abstract: A blast furnace off-gas sampling apparatus comprising a valved sample line for continuously withdrawing a sample off-gas from an off-gas line, pressure and temperature sensing means for determining the pressure and temperature within the sample line and pressure filter means attached to the sample line for removing particulate matter from the off-gas going through the sample line, and:A method for determining gas scrubber efficiency in steel mill furnace off-gas systems which comprises the steps of:(a) Withdrawing a side stream sample from untreated gas flowing through an off-gas line,(b) passing said sample through a pressure filter for a fixed period of time whereby the particulate matter in the sample is collected,(c) withdrawing a side stream sample from the same off-gas line after chemical treatment has been added to the off-gas and passing the treated sample through a pressure filter for the same fixed period of time used in step (b), whereby the particulate matter in the treated matter is collected.

Abstract: A molten metal filter effectiveness indicator comprising means for detecting the molten metal level on at least one side of a molten metal filter, and method.

Abstract: A method and apparatus are disclosed for monitoring the condition of the stirring block and solid plug therein as incorporated in the normal refractory brick lining of a molten metal ladle to provide a structure through which gas can be introduced into the molten metal, the method utilizes heat sensors and/or Hall Effect transducers embedded in the stirring block and/or solid plug therein in connection with apparatus providing a warning of critical wear and/or erosion in the gas stirring devices by the molten metal in the ladle. An appropriately shaped stirring block provides for the positioning of some of the normal refractory brick lining of the ladle partially thereover so as to eliminate loosening or cracking of the stirring block and the undesirable escaping of molten metal from the ladle.

Abstract: A melting furnace of a rigid structure includes a hollow body for receiving a material to be melted, the body comprising bricks joined together. A shell of iron surrounds the brick body so as to restrain a thermal expansion of the brick body during an operation of the furnace. A heating device is mounted around the iron shell for heating it to control the degree of thermal expansion of the iron shell, thereby controlling compressive forces exerted by the iron shell on the brick body when the brick body is thermally expanded during the operation of the furnace.

Abstract: A refractory protection tube for immersion molten metal parameter determining devices having a thin perforated metal tube with a coating of refractory fibers and a binder to provide thermal insulation, freedom from out-gassing and mechanical strength.

Abstract: The invention comprises a charging apparatus for melting furnaces, especially for plasma melting furnaces, for the continuous melting of preferably prepared aluminum scrap material.With the help of the proposed solution a controlled and regulated supply of the scrap material along with the prevention of a direct application of the plasma arc or other energy sources directly to the material to be melted, can be accomplished with the simultaneous pre-warming and cleaning of the material to be melted, wherein the metal loss resulting from burning is minimized, the contents of the contaminants within the metallic smelt is reduced and, in addition, an effective environmental protection can be accomplished. This is attained by the provision of an axially movable shaft 4 arranged vertically or tilted in the opening 1 of the furnace and having on the charging side a charging funnel 6 with an exhaust ring nozzle 7.

Abstract: A probe for detecting wear of a refractory wall, including plural sheathed probe elements of different lengths each consisting of a pair of high melting point wires disposed in parallel and insulated from each other except at least the fore end portions of the wires which form a normally closed or normally open sensing point, a sheath enclosure accommodating the probe elements such that the sensing points of the respective probe elements are located at different positions along the length of the sheath enclosure and holding the probe elements in parallel relation and out of contact with each other, and a number of dummy elements formed of a material similar to the probe elements and connected to the fore ends thereof in a manner to complement the lengths of the shorter of the probe elements. There is also disclosed a detection circuit for monitoring wear of a refractory wall in a molten metal processing apparatus in a simple and accurate manner by the use of the probe.

Abstract: This invention presents a rotary support for continuous casting ladles, which comprises a vertical column, a drive mechanism for pivoting this column about its vertical axis, a cross arm structure carried by this column and having at least one of its ends in the form of a horizontal fork, each of the two branches of which comprises means for carrying between them a casting ladle, means for raising and lowering the ladle independently of the cross arm, means for weighing the ladle, and means for stabilizing the ladle without influencing the measurement of the weight, the means for carrying the ladle and the means for raising and lowering it being composed, in each of the branches of the fork, of a ladle carrier carriage sliding vertically between a pair of rails under the action of at least one hydraulic jack.

Abstract: A signal processing system for use with a radar ranging system which transmits a radio frequency beam of finite angle to a sloping target of not greater than some known slope and creates from the return signal a beat frequency signal comprising various frequencies corresponding to the various distances from the ranging system to the target. The processing system includes a first tracking bandpass filter which is caused to seek and lock onto the lowest frequency F.sub.L in the beat frequency signal. Given frequency F.sub.L, the angle of the beam and the maximum slope of the target, a theoretical maximum frequency F.sub.X is computed. A second tracking bandpass filter tracks down from frequency F.sub.X to and locks onto frequency F.sub.H, the frequency component in the beat frequency signal associated with the maximum range to the target. From frequencies F.sub.L and F.sub.H and the beam angle, the average range to and/or slope of the target can be computed.

Abstract: A refractory clad metallurgical lance comprises a temperature sensing thermocouple means in combination with an internal gas conduit encased within exterior refractory cladding material wherein the conduit provides a passage way for transmitting inert gas under pressure. The thermocouple means is disposed within the refractory cladding and directed radially outward toward the outer peripherary of the refractory cladding whereby the temperature sensing portion is located near the peripheral surface of the cladding. The thermocouple is disposed within a ceramic protective tube which in turn is embedded within the refractory material secured around the internal gas conduit. In use, the metallurgical lance is operative to process molten metal by submerging the lower portion of the lance below the molten metal surface and bubbling inert gas through the metal while simultaneously directly measuring the temperature of the molten metal.

Abstract: Materials, methods and articles for the electrochemical determination of sulfur and carbon in fluids are provided. In accordance with a preferred embodiment, an electrolyte is furnished comprising a solid solution of an oxide of either zirconium, thorium or hafnium together with an oxide of an element of groups IIA or IIIB of the periodic table of the elements together with a sulfide or carbide of an element of groups IIA or IIIB of the periodic table. Processes employing such electrolytes together with articles incorporating them are also contemplated.

Abstract: A two electrode probe is lowered into a vessel and the electrodes are electrically interconnected by liquid steel; the resistance condition then existing is ascertained as reference value against which subsequent resistance measurements are referenced as the probe is lifted from the vessel. The traversal of the slag-liquid metal interface causes a relative resistance change permitting selection of a threshold level that is independent from other measuring and operating parameters. The threshold device operates a counter in that for example forward and reverse counting tracks the lowering and lifting of the probe, but counting is halted when the interface level is reached, the count state then indicating the spacing of a zero level of the probe position from the level in which the threshold was exceeded in a particular direction.

Abstract: A poking system for use in checking the condition of and agitating the contents of a coal gasifier utilizes a carriage (22) for transporting a poker (50) around the gasifier from one poke hole (12) to another. The carriage (22) mounts a poker assembly (24) comprising a tiltable arm (30) controlled by hydraulic ram (36) and the poker is incrementally inserted into and with withdrawn from each pokehole (12) by means of a reciprocable slide (38) provide with poker engaging clamps (60) which are operated during the advance or return stroke of the slide (38) depending on whether the poker is to be inserted or withdrawn. A pyrometer (72) is provided on the arm (30) for detecting, during withdrawal, the location of that portion of the poker (50) which has been resident within the oxidation zone of the gasifier.

Abstract: An improved method for hot working materials previously considered to be difficult or impossible to hot work is described. The method consists of varying the deformation conditions in order to achieve an essentially constant energy input, to the material being worked, on a time basis.

Abstract: A steel refining system has a crucible having an upwardly open mouth and containing a steel melt covered by slag, an oxygen lance directed downwardly into the mouth at the melt, a hood fitting downwardly over the mouth and having a hood wall formed by a multiplicity of coolant tubes, and an arrangement for circulating a coolant through these tubes. The tubes form a tubular hood-wall extension that has an outer end and is centered on an axis trained on the melt on the crucible. A holder is mounted on the outer end of this extension and contains a sound transducer carried by the holder and directed along the axis at the melt. A circuit is connected to this transducer for determining slag thickness by means of the sound detected by the transducer. The holder itself comprises a circularly annular hollow cell fixed by means of a collar to the extension and a transducer housing that is fixed to this cell and therethrough to the extension.

Abstract: A furnace to contain molten zinc, molten aluminum, or other molten metal has an outer vessel, an inner vessel, and particulate matter packed therebetween so as to enable the inner vessel to be lifted readily from the outer vessel. Electrical conductors are imbedded in said matter and arranged to close an electrical circuit including a signalling means if bridged by any molten metal leaking from the inner vessel. The furnace is provided with a removable bonnet, a beam mounted across the inner vessel, and a partition mounted to and beneath the beam so as to extend into the molten metal deeply. The inner and outer vessels, the removable bonnet, and the beam are insulative. The partition is a good conductor of heat.

Abstract: Hot briquetting apparatus for ferrous or non-ferrous particles has a furnace having upper and lower chambers. The particles are supplied to the lower chamber and leave the lower chamber through a discharge tube to enter a briquetting press. A passage is performed between the lower and upper chambers and sensing means sense the constituents of the gases in that passage. Control means control the air-to-fuel ratio of a zone of the lower chamber. The control means are connected to the output of the sensing means so as to maintain the atmosphere within the zone as a reducing atmosphere, the whole of the lower chamber being a reducing atmosphere.

Abstract: Sonde apparatus for a blast furnace whose wall is provided with a lance ingress and egress port through which a lance is able to enter into the furnace and withdraw therefrom wherein a gas check valve, lance cutting means, lance cooling means, lance straightening means, and gas seal means are provided in succession and in communication with one another, and drive means for inserting and withdrawing the lance is further provided in succession therewith, all said elements being arranged along a line which is an extension of the axis of the lance ingress and egress port.

Abstract: A method of and an apparatus for determining the level of slag above a metallurgical melt, especially a steel melt, and for determining a physical characteristic or property of the slag, such as its viscosity or consistency, utilizes a plurality of nozzles opening into the bath-containing vessel at different levels above the melt and supplied with inert gas. The difference in hydrostatic pressures at the nozzles can be ascertained by measurement of the pressures upstream thereof and the measured values are converted into indications of slag level and consistency.

Abstract: Method and apparatus for determining when the cast of a blast furnace is substantially completed in a blast furnace cast system wherein direct viewing of the taphole is obstructed during the cast. In a system wherein viewing of the taphole is obstructed by hood means covering the iron trough, substantial completion of the cast may be determined by sensing changes in ambient conditions, e.g., a change in temperature within the hood means, vibration of the hood, and/or a change in the color of the flame generated at the discharge end of a slag runner.

Abstract: A shielded pressure probe for measuring the pressure within a metallurgical vessel includes a tubular housing extending through and spaced from an opening in the vessel's refractory lining. The housing has an opening at its external end for receiving a probe therein and its interior end is closed. A plurality of perforations are formed in the housing and open toward the refractory defining the vessel opening to expose the probe to the vessel's interior while eliminating any straight line paths therebetween.

Abstract: Apparatus for measuring the contour of a surface without establishing contact therewith includes an energy transmitter movable in at least two directions. When employed in a shaft furnace the transmitter is movable along a longitudinal axis, so as to be either retracted to a protected location where it may be isolated from the furnace environment or extended so as to enable measurements, and is rotatable about the longitudinal axis so that the transmitted energy may be scanned across the surface.

Abstract: An apparatus and method is provided for heat treating a tubular type heat exchanger. A heat fluid is passed through the tube bundle in order to heat the exchanger from within.

Abstract: A process to continuously determine by an optical arrangement the profile of a charge fed into a blast furnace in which the surface of the charge is swept by a beam of light moving in a plane intersecting the surface so as to produce at the intersection of the plane with the surface a luminous trace, observing the luminous trace from a point outside the sweeping plane, and determining on the basis of the data defining the sweeping plane, the observation point and the direction of observation with respect to the plane the true position of the points constituting the luminous trace; and an apparatus for carrying out the process and including an illuminating system for illuminating the surface of the charge with a beam of light sweeping in a plane intersecting the surface to produce on the surface a luminous trace and a reception system cooperating with the illumination system for producing a picture of the actual profile of the luminous trace.

Abstract: The invention relates to a mounting for a casting ladle for use in a steel strand casting plant where one or more ladles are cantilevered from a revolving turret atop a central support column. Each cantilevered ladle is set in the mounting of the invention which permits the monitoring of the ladle weight before and during casting.

Abstract: A method for measuring the thickness of a refractory laid-up against the interior surface of the steel shell of a metallurgical apparatus includes placing at least one monitoring device in a critical wear area of the apparatus in a manner such that the free end of the device is at a known distance from the hot face of the refractory and the confined end extends beyond the outer surface of the steel shell. The device is connected to an electronic time-domain reflectometer by electrical connecting means. Timed pulses are generated and impressed in the device by the instrument and reflections of the pulses are received by and are visually displayed on the reflectometer. The length of the device appears on the display as a straight line bounded by two inflections. The straight line is indicative of the thickness of the refractory.The device includes a metallic conductor coaxial with an outer metallic sheath and separated therefrom by a refractory having a desired dielectric constant.

Abstract: A tuyere for the injection of both a refining gas such as oxygen into a melting or refining vessel, and a fluid protective medium such as a hydrocarbon gas or a liquid surrounding the injected refining gas, in which there is a solid center in the pipe through which the refining gas is suplied so that the refining gas enters the refining vessel as an annulus around which the protective fluid is disposed.The tuyere is installd in the refractory lining of the refining vessel and the fluids passing into the vessel through the tuyere are proportioned so that burning back of the tuyere and erosion or wear of the lining take place at the same rate.The protective medium cools the tuyere and avoids reactions between the refining gas and the tuyere material.

Abstract: A method of operating a blast furnace comprising the steps of selecting sight factors mathematically and statistically as effective in determining the operating condition of a blast furnace, sensing the eight factors as sample data, converting the sample data into variable factors, comparing the sample data and the variable factors with predetermined limiting factors, generating numerical non-dimension values corresponding to the level of satisfaction between the sample date or variable factors and the corresponding limiting values, multiplying the numerical non-dimensional values by predetermined corresponding weight allocation indices, summing separately the results of the multiplication for the sample data and the variable factors to form a numerical factor grand addition output and a variable factors grand addition output, summing the numerical factors grand addition output and the variable factors grand addition output to form an overall grand addition output and taking appropriate action to control the

Abstract: One form of the invention discloses an apparatus and a method for positioning the snorkel of a vacuum degassing apparatus beneath the interface of the molten metal and slag in a ladle utilizing means for determining the interface, which means comprises an electrode adapted for positioning within the ladle in electrical contact with the material, indicating means for indicating a first range of voltages produced at said electrode by an electrochemical reaction between the molten metal and the electrode as well as a second range of voltages produced at the electrode by an electrochemical rection between the slag and the electrode, with means for supporting the electrode independently of the ladle and adapted to enable the electrode to be raised or lowered within, and relative to, the ladle, wherein the electrode is moved to a position within the ladle and relative movement is subsequently produced between the electrode and the ladle whereby the position of the interface will be determined by noting a change in

Abstract: An apparatus for the control of the carburizing of parts under vacuum in a acuum furnace, with which as a carbon carrier a hydrocarbon gas is introduced controlled in the furnace. A detector detects the occurrence of a soot mist formation. Upon the occurrence of the soot mist a feeder for the hydrocarbon addition is completely or partially interrupted. The detector cooperates with the feeder such that the hydrocarbon addition is again received when the soot mist formation has decayed.

Abstract: A radar, such as a ranging radar, includes a non-scanning antenna which directs a beam of microwave energy toward and receives a return beam from a microwave reflector. A microwave reflector is mounted to a movable platform. As the platform moves, the microwave beam is scanned along a desired object. In one application, the heighth of a non-flowing material in different parts of a container is measured.

Abstract: Apparatus for manufacturing steel includes a hood adapted to be connected to the mouth of a converter. The hood has at least one conduit opening into it for introducing secondary materials into the hood. In order to arrange monitoring points of the pressure within the hood cheaply and conveniently, the pressure-measuring points are incorporated into the upper sides of the conduits. Each conduit may also have a connection which enables it to be flushed out with an inert gas, thus preventing a dangerous build up of inflammable gases within the conduit.

Abstract: In a scum removing apparatus including a suction source, a suction pipe having one end communicating with the suction source and the other free end positioned above the surface of scum to suck the scum and apply water to the sucked scum in the vicinity of the free end, and a scum separator provided at an intermediate portion of the suction pipe, a device for detecting the level of the scum surface relative to the free end of the suction pipe. The detecting device comprises a pair of electrode rods provided on the outer periphery of the free end of the suction pipe and projecting from the pipe end by a suitable length, and means for detecting variations in the electric resistance between the electrode rods. The electrode rod comprises a tube having accommodated therein a slider slidingly projectable from the front end of the tube and slidingly retractable into the tube.

Abstract: Process for indurating dried pellets in a rotary kiln, characterized by charging the dried pellets and coke in the range of from about 2% by weight to about 20% by weight on the weight of the pellets into the rotary kiln, the coke having a size of from about 5 millimeters to about 30 millimeters, drum index (DI.sub.5.sup.80) of more than 70, reactivity index (AG) of less than 50 and tumbler index (TI.sub.50.sup.400) of more than 50 measured on the basis of Japanese Industrial Standard K2151, and heating the pellets in the kiln is disclosed.

Abstract: A method and apparatus for reducing particulate iron oxide to metallic iron utilizing solid carbonaceous fuel as reductant in a shaft type reducing furnace, in which a furnace burden is formed of a mixture of iron oxide lumps or pellets and particulate solid fuel. Reacted top gas is upgraded and recirculated through the burden in counter-flow relationship thereby heating and partially reducing the burden. The heat for final reduction is generated by passing electric current through the burden.

Abstract: An automated poking system includes a plurality of pokerod assemblies positioned around the periphery of a two-stage, fixed-bed coal gasifier at two separate elevations. Each pokerod assembly includes an elongated pokerod selectively actuatable to extend into the coal bed within the gasifier, and appropriate sensors to provide data relating to the temperature of the coal bed, the resistance encountered by the pokerod, and the position of the pokerod. Alternatively, the temperature sensing function is separate from the pokerod activation, and the coal bed temperature is continuously moinitored. The mechanism for controlling activation of the pokerod may be a hydraulic cylinder-piston device or an electric motor driving the pokerod via mechanical means, such as a rack and pinion apparatus. Poking of the lower zone coal bed agitates the bed, detects and breaks up clinkers, and monitors the coal bed temperature.

Abstract: The invention is directed to a combination of a lance and nozzle assembly for supplying gas to a basic oxygen furnace. The lance and nozzle include an arrangement to accommodate a sensing device or unit which is adapted to transmit signals providing information in connection with the refractory or contents of the bath contained within the vessel. The arrangement is such that it accommodates the normal expansion and contraction of the lance resulting from the atmosphere within which the lance is utilized.

Abstract: The weight of the slag floating on a steel bath is determined by multiplying the surface area of the slag by the pressure head at the slag-steel interface. The pressure head is determined by a method including passing a gas through a tubular member that is lowered through the slag and into the steel.

Abstract: A pressure vessel base closure means including a pair of flat disc-like members spaced apart by a peripheral outer cylindrical member and an inner perforated cylindrical member, and there being provided between the two flat disc-like members a plurality of radially directed ribs to provide rigidity to the base closure means. The base closure means is particularly useful for a reactor in which a bed of fluidized solid is maintained by the passage of a gas into the reactor through the base via the chamber between the two flat disc-like members.