Abstract: A ring-gap nozzle for distributing a fluid medium over a plate, for instance over a bottom plate in a fluidized bed dryer, having two dish-shaped pressed parts suiting to each other complementarily being assembled in facing relationship and nested into each other and forming a ring gap through which the medium, deflected by 90.degree. or more, flows to the bottom plate, preventing both the settling of the product to be treated in the fluidized bed dryer on the plate as well as the reflux of the product backwardly into the nozzle when the flow of medium is cut off. This type of nozzle is simple to manufacture and does close the passage without any complicated manipulation automatically.

Abstract: The air dispersion plate at a lower part of a fluidized bed combustion furnace is provided with a large number of air injection nozzles uniformly distributed therethroughout and made of a porous refractory material having good air permeability and high heat and wear resistances. All of the fluidizing air supplied into the wind box below the dispersion plate is injected through these nozzles into the combustion chamber to fluidize the fluidizable material, which, after combustion is stopped, cannot flow through the nozzles into the wind box to cause heat damage and contamination therein and in the air supply pipe.

Abstract: For processing matter in a turbulent mass of particulate material, a substantially annular processing region (14; 104; 206) is provided and is preferably in the form of a substantially annular processing chamber having a radially inner wall which includes a waist (38; 122). A flow of fluid and matter to be processed are admitted to the processing region through one or more inlets (28, 46; 108, 124; 214, 220) with the flow of fluid being directed generally circumferentially into the processing region. In the processing region, matter to be processed is embedded in a compact turbulent band of particulate material for processing. Once processing is complete, the processed matter is withdrawn from the processing region, preferably by entrainment in an exhaust flow of the fluid.

Abstract: To prevent the tube to a pressure measuring means from being blocked by solid material mobile in a pressure container, a small part of the clean pressure medium from a source of such medium is injected into the tube so that the tube is continuously purged with clean pressure medium. By locating the pressure medium input at a suitable position along the tube relative to the pressure measuring means, the desired purging of the tube is obtained without appreciably increasing the pressure in the tube, and thus minimizing possible errors in measurement of the pressure. If, for example, pressure medium is passed into a pressurized combustion chamber through a surrounding pressurized container, and the tube to the pressure-measuring means passes through said surrounding pressurized container, the clean pressure medium can be bled into the tube through a hole bored in the side of the tube within the pressurized container.

Abstract: A pot-type oil burner is disclosed which is capable of effectively preventing the generation of bad odor and soot during the igniting operation by turning on an electric heater positioned above a heat-resistant fabric spread on the bottom surface of a pot to previously heat the pot and fabric to a temperature sufficient to vaporize fuel oil prior to introducing fuel oil to the pot by means of a nozzle pipe.

Abstract: A chamber for the treatment of particulate matter in a fluidized bed, e.g. at elevated temperatures, comprises an apertured bottom for the admission of carrier gas into the overlying space. The latter is divided by upstanding partitions into at least one medial compartment and at least two additional compartments adjoining the at least one medial compartment at the opposite sides of the latter. The apparatus further comprises a duct of substantially triangular cross-section with a horizontal base and an upwardly sloping side walls located in the at least one medial compartment, with the side walls of the duct extending in directions parallel to the partitions, and the base of the duct being imperforate and resting on the wall of the chamber and preventing the entry of the carrier gas into the at least one medial compartment from below; and a nozzle arrangement in each of the upwardly sloping side walls of the duct.

Abstract: A pot-type oil burner is disclosed which is capable of stabilizing the vaporization rate of fuel oil in a pot to accomplish the stable complete combustion with a good efficiency. The oil burner is constructed to arrange a heat-resistant fabric on the bottom surface of the pot to vaporize fuel oil with a constant rate. The oil burner is also capable of significantly reducing retention of tar in the pot and facilitates removing tar from the pot as desired.

Abstract: A support structure for a distribution grid to be mounted in a reaction vessel wherein the reaction vessel is formed with an inwardly-extending annular shoulder portion to which is mounted, such as by welding, a ring-member whereby the distribution grid is mounted on such support structure.

Abstract: A fluidized bed combustor is adapted to deprive a combustion gas issuing therefrom of dust by bringing the combustion gas into contact with a filter medium which is a fluidizing solid discharged in conjunction with slagging ash out of the combustor.

Abstract: In all refractory gas distributor is used to distribute fluidization gas to a fluidized bed reactor. The distributor slabs contain cast-in gas passages which distribute the gas to uniformly distributed grid holes to the surface. The slabs are continuously supported by a bed of refractory filling the bottom head of said reactor vessel and pressure equalization passages are provided to place the lower surface of the grid plate in fluid communication with the upper surface of the grid plate.

Abstract: In a tube boiler, fuel is burned in a fluidized bed which has a shallower part and a deeper part. The tubes extend only through the shallower part which can be fluidized independently of the deeper part so that the rate of heat transfer from the bed to the tubes can be varied according to demand. Water flows through specially configurated, upwardly oriented tubes by natural convection. There is also a general circulation of particles within the bed.

Abstract: A gas particulate solid system has a chamber capable of containing a bed of particulate solid and a supply of an oxygen containing gas. A line or lines having their outlet or outlets above the slumped bed directs the oxygen containing gas downwardly to impinge on the surface of the bed material so as to form a crater surrounded by circulating bed material. Fuel is supplied to the crater either in the gas stream or from an external source and after ignition combustion occurs in or near the crater.

Abstract: Diverse ceramic briquettes, for example clay tiles, are fired in holders which are stacked on top of one another on a firing conveyor. Firing takes place in a tunnel kiln which is primarily heated with gas or oil. Firing with solid fuel has the disadvantage that the firing conveyor is heavily dirtied. With the new holder according to the invention, the holder floor is filled with solid fuel and thereafter the briquettes are put in. This holder and the method used for firing permit a clean firing without dirtying the kiln and without high dust emission.

Abstract: A fluid bed reactor system for olefin polymerization composed of a cylindrical reaction vessel equipped with a distribution plate and an agitator, characterized in that the distribution plate satisfies the following conditions,(i) each of many passage holes provided in the distribution plate for passage of the fluidizing gas medium is covered with a cap having an opening,(ii) the opening in said cap is provided only on one side of the cap, and the direction (A) of the opening is not opposite to the direction (B) of the rotational flow,(iii) the direction (A) of the opening varies with the distance (d) from the center (X) of the plate to the center (Y) of the hole,(iv) the opening direction (A) of a cap or caps at a hole or holes whose distance (d) is minimum is directed nearer to the center (X) than is the tangential direction of a circle having the center (X) as a center and the distance (d.sub.min.

Abstract: The burner system is adapted for retrofit into the combustion chambers of firetube boilers. The burner is comprised of a hollow shell molded from a porous ceramic fiber matrix. Fuel and air reactants flow outwardly through the fiber matrix shell and are combusted along a shallow reaction zone on the outer surface. Heat is transferred primarily by radiation to the walls of the combustion chamber at temperatures which result in relatively low NO.sub.x emissions and high combustion efficiencies as compared to boiler systems with conventional burners.

Abstract: In a reactor for gasification of solid carbonaceous materials in a fluidized bed under elevated pressure and at high temperatures using a hot gasification agent, a feed device for the gasification agent is installed in the lower part of the reactor chamber and traverses this chamber in the form of a bridge, which has an arch joined to the walls of the reactor chamber, said arch consisting of refractory brick and supporting a section of metal pipe. The latter is shielded from the outside by the arch and by a top-mounted structure of refractory material. On the inside, the metal pipe is also provided with a tubular lining of refractory material. Metal pipe, lining, and arch have openings for passage of the gasification agent. The size and shape of the openings are selected to assure passage of the gasification agent even if the parts undergo changes in length as a result of the effects of temperature.

Abstract: The apparatus comprises a process vessel, containing a process bed of fluidized particles, having a first submerged port at a first end and a second submerged port at a second end. Both ports are inclined in the same sense so that particles leave the second end of the bed at a higher level than they enter the first end. Fluidized bed material entering the second port becomes defluidized and slides down the port, optionally with the assistance of a fluid injected into the port. The first port conducts particles into the process bed from a second fluidized bed and the second port conducts particles out of the process bed (e.g. into the second bed). The process bed rests on a fluid distributor having a horizontal first part adjoining, and no higher than the level of, the lower end of the first port and a horizontal second part adjoining, and at the level of, the second port, there being a vertical step connecting the first and second distributor parts at a location between the first and second ports.

Abstract: An apparatus and method for the environmentally safe disposal of material by combustion using a hot body having a plurality of open pores.

Abstract: A method and system for injecting coal and process fluids into a fluidized bed gasification reactor. Three concentric tubes extend vertically upward into the fluidized bed. Coal particulates in a transport gas are injected through an inner tube, and an oxygen rich mixture of oxygen and steam are injected through an inner annulus about the inner tube. A gaseous medium relatively lean in oxygen content, such as steam, is injected through an annulus surrounding the inner annulus.

Abstract: A fluidized bed gasifier (10) for gasifying a first fuel (50) receives heat indirectly from a combusting fluidized bed (24) disposed at least partially within the gasifier fluidized bed (12). Fuel for the combusting bed (24) may be provided by removing a portion of the fluidized first fuel from the gasifier bed (12) and transporting (30,34) this removed portion into the combusting bed (12). Heat is transferred across the conductive walls of the combustor vessel (26). Product gas heating value is increased by separately removing (28) the products of combustion from the gasifier (10) and by recycling a portion of the product fuel gas (74) as the fluidizing gas (54) for the gasifier fluidized bed (12). A radiation shield (18) is also provided to reduce heat loss from the gasifier bed (12) and to remove elutriated material from the product fuel gas.

Abstract: A reactor in which a plurality of vertical panels are disposed in a vessel and are constructed and arranged so as to form three combustion cells. Three of the panels each form a common wall between adjacent cells, and each cell is heated by a fluidized bed.

Abstract: For processing matter in a turbulent mass of particulate material, a substantially annular processing region (14; 104; 206) is provided and is preferably in the form of a substantially annular processing chamber having a radially inner wall which includes a waist (38; 122). A flow of fluid and matter to be processed are admitted to the processing region through one or more inlets (28, 46; 108, 124; 214, 220) with the flow of fluid being directed generally circumferentially into the processing region. In the processing region, matter to be processed is embedded in a compact turbulent band of particulate material for processing. Once processing is complete, the processed matter is withdrawn from the processing region, preferably by entrainment in an exhaust flow of the fluid.

Abstract: The present invention is directed to a fluidized-bed combustion apparatus provided with a U-shaped combustion zone. A cyclone is disposed in the combustion zone for recycling solid particulate material. The combustion zone configuration and the recycling feature provide relatively long residence times and low freeboard heights to maximize combustion of combustible material, reduce nitrogen oxides, and enhance sulfur oxide reduction.

Abstract: An injection head introduces H.sub.2 and O.sub.2 into one end of an elongate combustion chamber. At the same time, water is injected into the chamber through peripheral ducts to form a water curtain, or through inlets in the injection head, or through apertures facing away from the injection head in water-cooled tubing extending in a plane perpendicular to the chamber axis.

Abstract: The invention comprises a steam generator having a circulating fluidized bed combustion system whereby there is provision to admit air flow incrementally along the gas path to control combustion rate and firing temperature in a manner to maintain differential temperatures along the gas path. The initial portion of the gas path where combustion is initiated can be held in one temperature range as 1550.degree. F. which is optimum for sulphur retention and the final portion of the combustion zone can be elevated in temperature as to 1800.degree. F. to produce a greater degree of heat transfer through the gas to fluid heat exchange surface downstream of the combustion zone.

Abstract: A fluidized-bed combustion system for a boiler, a heating furnace for heating steels or the like, in which a plurality of gas distribution pipes are disposed at the bottom of the combustion chamber. The lower end of each gas distribution pipe is communicated with an air supply line with an air flow rate control valve and a fuel supply line with a fuel flow rate control valve and the air and fuel admitted into the gas distribution pipe are mixed within the same and the air and fuel mixture is injected or sprayed into the fluidized bed through injection ports of the gas distribution pipe which are positioned adjacent to the bottom of the fluidized bed, whereby the complete combustion within the fluidized bed can be ensured and the combustion can be controlled over a wide range and optimized depending upon a load.

Abstract: A process and system of operation for combusting nitrogen-containing fuels with resulting low NO.sub.x emissions. A fuel-rich mixture of the fuel is combusted in a catalytic bed which is carried by a support structure. Active or passive means are provided for limiting transfer of heat from the bed into the support structure for minimizing formation of NO.sub.x during combustion. The active means for limiting the heat transfer includes, in different embodiments, electrical resistance back heating, induction back heating, exhaust gas back heating, and combustion fired back heating. The passive means for limiting the heat transfer includes, in different embodiments, a body of heat insulating material between the bed and support structure, or the insulating effect of the outer cells of the bed within a recess in the support structure.

Abstract: The invention comprises a dense pack heat exchanger for a steam generator having a circulating fluidized bed combustion system whereby a bed of solid particles comprising fuel and inert material is entrained in the furnace gas stream. Means are provided for collecting high temperature bed solid particles downstream of the furnace. The dense pack heat exchanger directs the hot collected particles down over heat transfer surface, such surface being a portion of the steam generator fluid circuits. Flow is induced by gravity means. The dense compaction of the solid particles around the fluid heat exchange circuits results in high heat transfer rates as the fluid cools the compacted solid material. The heat exchange surface is arranged to facilitate flow of the solid particles through the heat exchanger.

Abstract: The invention comprises a drying and sorting apparatus which is integrated with a conventional steam generator for separating organically derived solid fuel from solid inert materials and for removal of moisture from the solid fuel prior to feeding such fuel to a combustor. Low level heat in the steam generator combustion gases, after heat exchange with the steam generator fluid circuits, provides the means for removing moisture from the solid fuel when hot air/gas (unsaturated with respect to moisture) is passed through a bed containing a mixture of solid fuel and waste inert material particles, fluidizing them. When in a fluidized state the lighter organically derived solid fuel particles separate from the heavier inert material particles.

Abstract: A system comprising a method and apparatus by which a double cone dispenser causes discharge of granular or particulate materials from a vessel at a uniform rate across the entire cross section of the vessel. In one form, the invention comprises a fluidized bed vessel which was a tramp removal and bed recirculation system associated therewith, which system comprises a novel dual cone apparatus at the bottom of the vessel.

Abstract: A fluidized bed furnace is provided in which liquid fuel can be burned. Injectors extend up through an imperforate bed plate which properly mix the oil or other liquid fuel with the fluidizing air causing evaporation of the oil. This mixture is passed through restricted openings as it enters the fluidized bed, thus resulting in high velocity flow and fairly even fuel and combustion distribution throughout the cross-section of the fluidized bed.

Abstract: The invention comprises a steam generator having a migrating fluidized bed combustor system. The bottom, head end of the bed incorporates a support floor system through which air is admitted tangential to the floor in a manner which causes the bed to migrate in a retraceable track. Tangential admission of air cools the floor and inhibits reverse flow down through the floor when the bed is slumped. Particle entrainment velocities are developed at mid-point in the bed. Tangential entrainment gas flow assures uniform distribution of combustibles and inert material throughout the lower bubbling bed and furnace area above the mid-point. Platens in the furnace zone straighten gas flow for gravity separation of particulate at the outlet of heat transfer surface above the furnace.

Abstract: The invention comprises a steam generator having a circulating fluidized bed firing system. Particles of fuel and solid inert material are recirculated in a furnace wherein gas velocities are maintained at levels sufficient to entrain the fuel and inert material particles in the gas stream. A plenum is provided at the furnace outlet wherein gas velocity drops below entrainment level and the particles are directed to a collection hopper for recycle. The gas is withdrawn from the plenum through ducting in a manner to assure uniform gas distribution through the plenum. High gas velocity through the ducting improves heat transfer in the fluid cooled enclosure surface where such surface is incorporated into the ducting. The ducting connect to the downstream gas path.

Abstract: The invention comprises a steam generator fluidized bed which recirculates through a major portion of the normal gas to fluid heat transfer circuits. Solid bed material is separated, collected and recirculated. Bed temperatures are limited by regulation of density of bed inert material to inhibit the radiant aspects of combustion. Gas recirculation is used to supplement air flow to achieve higher than entrainment bed gas velocity in the fuel ignition and reaction zone. Fuel ignition and reaction are controlled by limiting the amount of atmospheric air flow to the circulating fuel rich bed mixture to regulate extent of propagation of the ignition and reaction zone into the initial portion of the circulating bed loop, starting from the point of highest gas pressure.

Abstract: A fluidized bed reactor in which a grate is disposed in a housing for receiving a single bed of particulate material. The interior of the housing below the grate is divided into a plurality of zones and air is selectively passed through portions of the grate to fluidize corresponding portions of the bed above the zones. A plurality of air distributors are provided in the bed for reducing the height of the particulate material accumulating in various portions of the bed.

Abstract: A heating flue for a coke oven includes a flow plate to replace the base in the heating flue. The thickness of the flow plate is greater than the thickness of the flue base and disposed above a chamber which is divided into two halves in a gas-tight manner by a central web of refractory material. Each chamber communicates with ducts that feed preheated air from regenerators during rich-gas firing and feed preheated air and lean gas during firing with lean gas. The height of the chamber to the thickness of the flow plate is a ratio within 0.3 to 0.7, preferably 0.5. The flow plate has a plurality of bores each with a cross-sectional area which, when compared with the cross-sectional area of the plate, forms a ratio of between 20 and 200, preferably 30 to 60. The diameter of a cylindrical bore is between 10 and 60 millimeters, preferably 20 and 50 millimeters.

Abstract: A fluidized bed shell boiler for producing steam or hot water or a fluidized bed hot gas generator or incinerator in which the position at which bed material is deposited downstream of the bed is controlled. A baffle of firebrick with gas-flow passages extending through the baffle is positioned in the tube downstream of the bed.Gas velocities are distributed across the tube so that bed material is preferentially deposited in the combustion chamber downstream of the furnace tube.Deposition in the furnace tube is reduced to zero or to a negligible amount and deposition downstream of the combustion chamber is reduced.

Abstract: A low pollution method of burning a fuel comprises gasifying the fuel in a gasifier bed containing particles which are fluidized by a fluidizing gas containing substantially no inert components. The resulting combustible gas is burned with air diluted with nitrogen to reduce NO.sub.x formation. In addition, NO.sub.x production from the nitrogen content of the fuel is reduced as a result of the gasification of the fuel to combustible gas before combustion with air. Preferably the gasifier bed contains CaO to fix sulfur from the fuel as CaS. In one embodiment, the gasifier bed (51) contains CaSO.sub.4 and the fluidizing gas contains H.sub.2, inter alia, which mediates the transfer to the fuel of chemically-bound oxygen from the CaSO.sub.4 (which is thereby reduced to CaS). Particles containing CaS are passed to an oxidizer bed (72) wherein they are fluidized by air. The CaS is exothermically oxidized to CaSO.sub.4 by extracting oxygen from the air which is thereby heated and substantially exhausted of oxygen.

Abstract: A fluidizable bed combustion chamber comprises an intermediate partition (2,7) which divides the chamber into an upper combustion space (1a) and a lower plenum (1b) and which is provided with means (4,4a,8) for injecting fuel into the upper combustion space in which, during use of the combustion chamber, a bed of fluidized material (6) is created. The intermediate partition is composed of a plurality of nested modules (7), each of polygonal shape and having a substantially centrally positioned fuel supply member (8). Each corner surface (9) of each module is upwardly inclined in the direction away from the center of the module, and these corner surfaces are provided with openings (10) enabling air to be injected into the upper combustion space from the plenum chamber. Preferably, the modules are of regular polygonal shape, for example triangular, quadratic or hexagonal.

Abstract: In a calcining furnace usable particularly for regenerating sands used in casting boxes and cores, a bed of refractory particles is fluidized by means of a combustible gas which is fed into the bed together with air, so as to enable the combustible gas to burn. The base wall on which the bed of refractory particles is supported has a plurality of holes for the air supply. Each hole for the air supply has associated therewith a nozzle for supplying the combustible gas, disposed coaxially with the respective hole and having at least one discharge aperture for the combustible gas disposed adjacent the plane of the base plate.

Abstract: A method of treating a particulate material in a fluidized bed reactor includes supplying a particulate material into a working space above at least one zone which is characterized by reduced passage of a fluidizing gas. A fluidizing bed reactor is designed so that its means for supplying a particulate material is arranged above at least one zone of the reduced passage of the fluidizing gas. The passage of the fluidizing gas in this zone can be completely prevented. Jalousie-shaped inserts are arranged above edges of the zone and have inclined surfaces.

Abstract: The invention provides a means for more effectively adapting fluidized bed combustors for retrofit of existing boilers for burning of low grade inexpensive solid fuels. The operating discharge gas from a fluidized bed combustor is substantially lower in temperature from what exists at the furnace gas outlet of a conventional steam generator. Thus, outlet gas from fluidized bed combustors needs to be placed in the downstream gas path differently from conventional practice. The external combustors of the present invention permit placement of hot gas in the steam generator gas path where it can be effectively utilized. The invention also teaches how new steam generators can be configured advantageously to accommodate multiple fluidized bed combustors particularly as pertains to larger capacity steam generators in the 200 MW electrical and larger range.

Abstract: A system for the fluidized reinjection of fine particles (carryover) into a fluidized bed combustor. The carryover recirculation system includes a fluidized reinjection bed which is fluidized using clean gas from the induced draft fan outlet boosted by a small auxiliary fan. The fluidized fine particles can be reinjected into the fluidized combustor bed by either dense phase transport or by dilute phase transport.

Abstract: A drain and sampling valve assembly for a fluidized bed reactor in which a pipe extends from the fluidized bed supporting structure to a location externally of said reactor. A valve seat is supported by said supporting structure and a valve stem is disposed in the pipe and extends for the length of the pipe and has a valve head mounted at one end of the stem for cooperating with the valve seat. A mechanical actuator assembly is provided externally of said reactor for selectively moving the stem relative to the pipe and the movement of the valve head relative to the valve seat to control the flow of material from the fluidized bed into the pipe. A discharge pipe and a sampling valve cooperate with the other end of the first mentioned pipe for selectively controlling the discharge of material from said latter pipe for permitting samples to be taken.

Abstract: A combustor grid for use in an incinerator having air bars for distribution of fluidizing air. Air is distributed from a source of pressurized air to a configuration of air bars in fluid communication with each other. Each air bar in the grid has an upper surface with air injection ports and side walls which converge toward the bottom surface. The air injectors may be refractory covered metal tubes on a conduit or individual air nozzles.

Abstract: A fluidized bed combustor having a distributor plate assembly including an inverted frustopyramidal surface with slots and offset shields thereover to form laterally oriented air flow openings into the combustion chamber from a first plenum for debris particle classification along said surface. At the bottom of each frustopyramidal surface is an outlet for classified debris. Air flow riser tubes project up from a second plenum to a position above said surface. Forced air is supplied to the slots and the risers, with means to regulate relative flow to them.Projecting down from the debris outlets are drop tubes having cooling fins, such tubes connecting to inlets of an auger conveyor. The auger conveyor has a coolant-cooled housing and a coolant-cooled auger.

Abstract: A method and apparatus for controlling steam production by controlling the flow rate of particulate solids from a fluidized bed combustion chamber through a vertical heat exchanger. The pressure drop across a section of the vertical heat exchanger is monitored and compared with a set point pressure drop. When the pressure drop being monitored falls below the set point pressure drop, a signal is provided to a particulate solids feed control means which then allows more particulate solids to be circulated through the vertical heat exchanger. The vertical heat exchanger receives heat from the particulate solids. The additional amount of particulate solids fed to the vertical heat exchanger are recirculated along with the previous amount of particulate solids through the heat exchanger into the fluidized bed combustion chamber. Because of the additional cooled particulate solids in the fluidized bed combustion chamber the temperature of the fluidized bed combustion chamber drops.

Abstract: A catalytic combustor for generating a mixture of steam and combustion gas is located downhole in an oil well, so that the gas mixture can be injected directly into the oil reservoir to displace heavy oils from the reservoir. There can be a single stage of catalytic combustion, or there can be a stage of thermal combustion followed by a catalytic stage. In either case the purpose of the catalyst is to drive the combustion to completion so that the gas mixture contains no soot that would plug the face of the reservoir.

Abstract: An apparatus for the fluidized catalytic cracking of a hydrocarbon feedstock comprises a riser reactor and a collar positioned along the same axis as the downstream end of the riser reactor. The collar is further positioned in close proximity to, but not in contact with, the riser reactor such that an annular space is defined between the riser reactor and the collar. The collar has a diameter greater than the diameter of the riser reactor at its downstream end and communicates directly and laterally with the inlets of the cyclone separation system. The riser reactor may or may not include a flow reversal cap to redirect the flow of the hydrocarbons and the catalyst.

Abstract: This invention relates to a fluidized bed for use in heat treating articles, the bed having a container for containing a mass of refractory particles. The container has a porous base and a supply pipe for supplying a fluidizing gas to the underside of the porous base from which the gas will flow through the porous base and into the mass of refractory particles. The fluidizing gas flows through an adjustable control valve arranged in the supply pipe. There are also provided at vertically spaced positions above the upper surface of the porous base a pair of temperature transducers which are connected together to provide a signal which is dependent upon the difference in the temperatures at the vertically spaced positions, there being also provided power actuated means in the form of an electric motor which in use is arranged to receive the signal from the temperature transducers and then actuate the adjustable valve in accordance with the signal received.