Abstract: A fluidized bed combustion chamber (3) is provided with a perforated bottom plate (4) into which air nozzles (18, 19) are pressed in a manner similar to that used for tubes in a tube sheet of a heat exchanger. About one-third of the nozzles (18) are connected to a startup or auxiliary combustion chamber (14) for blowing in hot gas for heating the bed to the flash-point or ignition temperature of the fuel. Further, the bottom plate is insulated (20) between the nozzles. (FIGS. 1, 4.) A method of operating such a combustion chamber also is disclosed.

Abstract: There is provided a ceramic heat exchange module 10 having fluid inlet and outlet conduits (12,20) extending from one side of horizontal manifolds (14,18). Serpentine tubes 16 extend from the opposed sides and connect the manifolds. In use, in a fluidized bed combustor 22, the manifolds are positioned between the base 30 and air inlets 32. Serpentine tubes extend into the fluidized bed 36, the fluid inlet and outlet conduits extend through the base for coupling to a working fluid supply.

Abstract: A method of at least partially burning a hydrocarbon and/or carbonaceous fuel in order to yield hot gaseous products of relatively low pollutant content, in which the fuel is partially burned in a first stage flame under such conditions that the partially combusted fuel has a temperature in the range 800.degree. to 1600.degree. C., (e.g., about 1150.degree. C.) and is substantially free of smoke and/or carbon, bringing the partially combusted fuel at 800.degree. to 1600.degree. C. into contact with a substantially non-volatile catalyst (19) which is active for reducing the amount of NO.sub.x in the partially combusted fuel, and then at least partially burning the partially combusted fuel, after contact with the catalyst (19) in a second stage flame to yield the desired low pollutant hot gaseous products. Preferably one or both of the said flames burns in contact with a substantially non-volatile catalyst (25, 23) to reduce still further the NO.sub.x content of the final gaseous products.

Abstract: A bed support, and a fluidized bed reactor incorporating the bed support, the bed support including a conical-shaped support with downwardly converging surfaces terminating in a conduit for removing tramp material and/or agglomerated material from the reactor. The downwardly converging surfaces have main air source nozzles for directing pressurized air parallel to and downwardly along the downwardly converging surfaces toward the conduit. In a first embodiment, the conduit has downwardly diverging walls. In a second embodiment, the conical-shaped support further includes an inverted cone positioned over the conduit, the inverted cone having central air source nozzles and slots in the lower portion of the cone. In a third embodiment, the conical-shaped support further includes a bar grate having central air source nozzles positioned within the conduit.

Abstract: A fluidized bed reactor e.g. for the burning of fuels of different calorific values. The bottom part of the combustion chamber is divided into an outer and an inner fluidization zone by a partition wall adjacent to the distributor plate. Heat transfer surfaces are disposed in the outer fluidization zone. Heat can be withdrawn from the outer fluidization zone which is activated when burning fuel having a high calorific value. When burning fuel of lower calorific value the outer fluidization zone is not operated. The inner fluidization zone will be in operation in both cases. The supply of fluidizing gas to the second fluidization zone is controlled in order to maintain predetermined conditions in this zone.

Abstract: A fluidized bed call (10) having a static ignition bed (18) of inert heat storage particles (50) disposed immediately beneath and adjacent to a fluidizing region (44) wherein fuel particles are combusted, characterized in that the heat storage particles (50) are generally spherical in shape, each particle having a plurality of protuberances (52) extending outwardly from the surface of the particle a preselected length thereby maintaining a minimum spacing, equal to the preselected length of the protuberances, between neighboring spherical particles within the static ignition bed thereby ensuring that sufficient void space (54) exists within the static ignition bed for the fluidizing air to flow upward through the static ignition bed into the fluidizing region without an excessive pressure drop and for the fuel particles to laterally penetrate the static ignition bed.

Abstract: A hot blast stove for use with high capacity blast furnaces incorporates a gas flow baffle particularly configured for improving mixture of combustion air and gas within the combustion chamber to enhance fuel burning characteristics with a concomitant reduction in pressure-pulsation experienced within the system and without an appreciable reduction in fuel firing rate.

Abstract: A fluidized bed combustor having in its distributor plate assembly at the bottom of the combustion chamber, air outlets in the distributor plate surface, air flow riser tubes projecting above said surface, light liquid fuel nozzles located adjacent certain of the riser tubes for injection of liquid fuel into the air forcefully flowing up these riser tubes, and the share of air flowing through the riser tubes relative to the share of air flowing through the outlets being controlled by regulating means.

Abstract: A fluidizable bed apparatus comprises a container containing a bed of fluidizable particulate material which becomes hot in use. The apparatus is characterized in that it includes at least one passage for the flow of cooling medium therethrough arranged beneath a bottom wall of the container. The or each passage has communicating therewith at least one inlet, preferably arranged beneath the bottom wall, and at least one outlet, preferably arranged adjacent side walls of the container. Nozzles for supplying fluidizing medium to the container for fluidizing the bed are arranged to pass through the bottom wall of the container.

Abstract: A fluidized bed furnace having a vessel with cooled or insulated walls and an inflow plate. A fluidized bed of inert material is maintained by air nozzles in the inflow plate and heated to the ignition temperature of coal. Pressure pipes deliver the coal and, if appropriate, additives such as lime, into the vessel below the upper boundary of the fluidized bed for combustion.

Abstract: A fluid bed heater or vaporizer unit has a generally cylindrical configuration with its major axis horizontally disposed. A mixture of coal and limestone is fed into the elongated fluidized bed within the unit for combustion; the limestone being present to minimize sulfur emissions due to the sulfur present in the coal. The wall of the unit in the region of the freeboard is lined with horizontally disposed heat exchange tubing. The delivery of air to the fluidized bed is regulated so as to establish a combustion zone of high turbulence and one or more heat transfer zones of lower turbulence. A plurality of heat exchange tubes are located in the heat transfer zone or zones and within the expanded bed level of the fluidized bed but above the region occupied by the slumped bed. Economizer heat exchange coils may be located in the passageway for exhaust gases.

Abstract: A fluidized bed combustor wherein a combustion chamber and a regeneration chamber are both contained in a single hollow body is provided. These two chambers are formed by vertically partitioning the body by a partition wall, which has an upper opening and a lower one, and also each have a perforated plate at the bottom part thereof on which a heat transfer medium containing a desulfurizing agent is placed and fluidized. The desulfurizing agent is transferred from the combustion chamber through the lower opening to the regeneration chamber and circulated by overflow through the upper opening again to the combustion chamber. Various modifications of the above-mentioned fundamental embodiment are proposed. Combustion and desulfurization are automatically and effectively carried out in a single apparatus to give a high percentage desulfurization, make an apparatus compact, and reduce an initial cost and a running cost thereof.

Abstract: A fluidized bed boiler, and a method of operating same in which air is passed through a grate to fluidize a bed of particulate material containing fossil fuel disposed on the grate. A raw acceptor for the sulfur produced as a result of the combustion of the fuel is introduced into the housing and confined within an area of the housing isolated from the bed of particulate material. The area containing the acceptor is maintained at conditions optimal for calcining the acceptor, after which the latter is introduced into the fluidized bed.

Abstract: A system for supporting a fluidized bed in a boiler in which a plurality of support frames are supported in an abutting relationship spanning the interior of the boiler. One or more of the support frames are connected or attached relative to each other and to their supports in a manner to permit limited relative movement between the frames and between each frame and its support. A grid is supported by each frame and is connected or attached thereto in a maner to permit limited movement of the grid relative to the frame.

Abstract: A fluidized bed reactor which is capable of burning material containing incombustible matter which during operation accumulates in the form of large particles in the lower part of the reactor, is provided. A discharge system which causes coarse particles to be discharged in a continuous manner without discharging fine particles or combustible matter is provided. The discharge means comprises a discharge compartment connected to an outlet of the distributor plate of the reactor. An upward flow pipe is centrally disposed in the discharge compartment. Air is supplied to the lower part of the discharge compartment. Coarse particles are withdrawn from the discharge compartment through a discharge pipe. Fine particles are blown back to the reactor through the upward flow pipe.

Abstract: A combustion furnace or reactor with a multi-stage fluidized bed system wherein upper and lower fluidized bed formation zones in which the fluidized beds of bed particles containing particles of lime stone are separated through a partition device. The partition device is provided with a plurality of exhaust gas distribution holes for distributing the exhaust gases produced in the lower fluidized bed into the upper fluidized bed and a plurality of nozzles through which issue the combustion air and/or recirculated exhaust gases into the upper fluidized bed. Combustion products such as NO.sub.x and SO.sub.x are desulfurized and denitrified respectively within the reactor by calcium compounds which absorb SO.sub.2 and act as catalysts for reducing NO.sub.x.

Abstract: There is disclosed a furnace which is particularly suitable for domestic use, having means to generate infra-red radiation in a sealed combustion chamber to thereby rapidly heat the same and in turn impart that heat to air ciculated therearound, and ultimately directed to the area to be heated, the combustion arrangement including a fibrous pervious burner member to and through which an air/gas mixture under pressure is directed and caused to burn over the surface thereof to effect the infra-red heat generation, the same effecting greatly improved heating efficiency, reduction in air pollution and a decreased demand for fuel to provide for heating of given area.

Abstract: A ceramic burner includes a fuel gas supply conduit having a gas delivery region opening into a mouth portion and a mixing and aspiration region communicating with the gas delivery region, and an air supply conduit having nozzles opening into the mixing and aspiration region of the fuel gas supply conduit. The mixing and aspiration region has an angular configuration including a first segment inclined with respect to the axis of a combustion chamber of an air heater within which the burner is positioned and a second segment inclined with respect to the first segment and in communication therewith at a position of directional change. The gas delivery region extends coaxially with respect to the combustion chamber.

Abstract: A vertically-fired blast furnace stove includes a mixing bed comprised of a multitude of spheres, cylinders or berl saddles supported by a carrier having openings therein located in the bottom portion of a vertically-extending combustion chamber. The bed extends within the walls of the combustion chamber above the floor to form a chamber coupled to pipes for delivering fuel and air to pass in the inner space openings in the bed where mixing and heating of the fuel and air supplies occurs for combustion above the bed. The hot products of combustion are directed by a dome into a heat-storage chamber having a filling of checkerbrick and then into a flue pipe.

Abstract: The vertical fuel pipe of a fluidized bed extends up through the perforated support structure of the bed to discharge granulated solid fuel into the expanded bed. A cap, as a deflecting structure, is supported above the discharge of the fuel pipe and is shaped and arranged to divert the carrier fluid and granulated fuel into the combusting bed. The diverter structure is spaced above the end of the fuel pipe and provided with a configuration on its underside to form a venturi section which generates a low pressure in the stream into which the granules of solid fuel are drawn to lengthen their residence time in the combustion zone of the bed adjacent the fuel pipe.

Abstract: A fluid-bed furnace has at least one combustion chamber, preferably two side-by-side, housing a bed of incombustible particulate material to be fluidized when burning fuel fed thereto. Bed fluidization is by forced release in the incombustible material of combustion promoting gas, normally air, from a plenum chamber arrangement externally of the bed proper at a side or end thereof to save overall height.

Abstract: Fluidized bed combustors and provision for the operation of such combustors so that the fluidizing medium supplied to one part is at a velocity different from that at which air is supplied to an adjacent part.

Abstract: A burner apparatus for burning liquid fuels is equipped with a swirl atomizer nozzle (4), a flame holder (22) that is connected behind the nozzle mouth, and a combustion air delivery duct (8), in which the nozzle (4) is arranged coaxially. A thermally decoupled duct-like heat conductor (10) functions as a fuel vaporizer in the operation of the apparatus. In its main portion, which starts a small distance downstream from the nozzle, the heat conductor has an inside diameter such that droplets in the spray cone from the nozzle tend to impact evenly over the whole area of its inner surface. The heat conductor (10) is of silica nitride. It comprises at least partially a capillary inner layer.

Abstract: This invention relates to an improved method and apparatus for continuous autogenic incineration of high-moisture easily friable combustible agglomerates in a fluidized bed. The improvement comprises introducing the waste materials into the bed in a "tube" of air provided by supplemental air means which surrounds the in-bed feed means.

Abstract: A pressurized, fluidized bed combustor including a housing having a combustor chamber therein with a distributor plate closing the lower portion of the housing and arranged above a fluidizer windbox, which, in turn, is arranged above a heat exchanger inlet plenum which is mounted above a bottom of the combustor. A coal gun is provided for discharging coal into the fluidized bed, and it comprises an outer guide tube which extends from a spaced location above the distributor plate downwardly through the bottom of the combustor chamber and it includes a portion which extends exteriorly of the combustor chamber. This exterior portion carries a ball valve which has a passage therethrough which makes it possible to insert a coal supply pipe upwardly in the interior of the outer guide pipe and through the passage of the ball valve up to substantially the top of the outer pipe at a location above the distributor plate within the reaction bed.

Abstract: A fluidized bed combustor comprises a housing having a chamber therein with a top having a discharge for the gases which are generated in the chamber and a bottom with a discharge for heated fluid. An assembly is arranged in the lower portion of the chamber and the assembly includes a lower plate which is mounted on a support flange of the housing so that it is spaced from the bottom of the chamber and defines a fluid plenum between it and the bottom of the chamber for the discharge of heated fluid. The assembly includes a heat exchanger inlet plenum having tubes therethrough for the passage of fluidizer air and a windbox above the heat exchanger plenum which has a distributor plate top wall. A portion of the chamber above the top wall defines a fluidized bed.

Abstract: This invention relates to Rankine cycle engines and to improved methods of operation whereby catalytic oxidation of a major proportion of the fuel takes place in the boiler section of the engine.In order to improve the operation of a Rankine engine, the engine is modified to include a combustor having a thermally stable and oxidation resistant monolith containing a multiplicity of flow paths or channels, the monolith being made from a catalyst material or supporting a catalyst material for the catalytic combustion of the combustible gases and injected fuel.

Abstract: An improved fluidized bed reactor of the type having dual shells spaced apart to define a gaseous fluid inlet passageway which is in communication with a source of gaseous fluid and a gaseous fluid distribution partition to form within the inner shell a reaction zone and having a heat exchange unit in the reaction zone for temperature control. The improvement comprises two manifolds which are disposed adjacent the gaseous fluid distribution partition and each in communication with the inlet passageway to receive gaseous fluid from the latter. One manifold communicates with the distribution partition passages while the other manifold communicates with the heat exchange unit.

Abstract: The invention provides a fluidized bed combuster for fuel or waste material, preferably having a fluidized bed which is arranged to circulate about a horizontal axis, in which one or more baffles are provided to define respective quiet zones adjacent the fluidized bed; material flowing in operation of the bed over the top of the baffle from the fluidized bed to the quiet zone and under the baffle from the quiet zone to the fluidized bed; and means is provided for feeding material to be burnt into the quiet zones to be carried therefrom beneath the baffles into the fluidized bed for combustion therein.

Abstract: PCT No. PCT/US 79/00843 Sec. 371 Date Oct. 15, 1979 Sec. 102(e) Date Oct. 15, 1979 PCT Filed Oct. 15, 1979 A combination rotating fluidized bed combustor and rotating fluidized bed heat exchanger particularly adaptable as the combustor and heat exchange unit, respectively, of conventional gas turbine engines is preferably arranged with the combustor nested within the heat exchanger for maximum compactness. The heat exchanger comprises an annular fluidized bed, defined by inner and outer spaced apart coaxial cylindrical, perforated walls, which rotates about the longitudinal axis of the cylinders. The bed is comprised of pulverulent inert particulate material and includes fluid-containing heat exchange tubes passing substantially longitudinally therethrough. Hot gases, such as turbine exhaust gases, enter the bed through the outer perforated wall, heat and fluidize the bed particles, heat the gas, usually compressed air, in the tubes, and exit the bed through the inner perforated wall.

Abstract: A fluid-bed furnace has one or more combustion chambers containing a fluidizable bed 10 of particulate material. At least adjacent pairs of combustion chambers are shown to share a common exhaust gas outlet system 30. For the or each combustion chamber there is an in-bed removable chamber 35 for housing a bed preheating burner 36 and supplying fluidizing combustion promoting gas via transverse feed pipes 38, usually equipped with upstanding outlet heads. Bed material support is by a V- or U-section trough 32 also at least partially accommodating the chamber 35 and a material extraction feed 34.

Abstract: A boiler wherein the combustion unit includes a fluidized bed which may be fluidized in a non-uniform manner to effect circulation of bed material by means of dual air distributors located within the bed.

Abstract: This invention relates to fluidized bed combustors and provides for the operation of such combustors so that the bed forms an upper fluidized layer and a lower, more static, layer into which larger particles may fall to be drained away.

Abstract: A ceramic burner for the combustion chamber of air heaters and the like has a mixing body composed of layers of shaped ceramic bricks, the shaped bricks adjoin each other with radial flanks and engage and mutually interlock with one another by knobs or protuberances and corresponding recesses. The layers of shaped bricks are held together vertically by a ceramic bolding bar. In assembly, the mixing body has a mushroom shape wherein the upper layer shaped bricks have a larger radius than the lower layers.

Abstract: A distributor for distributing a fluid into the volume of a fluidized bed contained in a vessel comprises a base member in which are mounted upstanding nozzles having outlets for directing the fluid horizontally away from the nozzles into the volume of the bed, the outlets of some nozzles being arranged at a lower level than the outlets from other nozzles so that fluidizable bed material will be fluidized above a contour substantially defined between the outlets of the nozzles. Thus, there will be a "well" or depression in the countour around each nozzle, and the countour will extend to just below the outlet of each nozzle. The contour may be formed by the upper surface of unfluidized fluidizable material (e.g., from the bed) or by the upper surface of non-fluidizable material (e.g. blocks of refractory cement or metal sheeting) which may constitute at least part of the base member.

Abstract: An incinerator including a first combustion chamber having a rotatable hearth for initially drying and partially burning waste materials and a second combustion chamber comprising a fluidized bed furnace for receiving the partially burnt materials from the first chamber and completing the burning thereof.

Abstract: A fuel supply system for use in a fluid bed furnace or the like of the type which includes a bed comprising a quantity of particles, which bed fluidizes in response to the flow of heated gases upwardly therethrough and a burner for burning a supplied fuel and providing the fluid bed with a sufficient gas mixture flow at an elevated temperature for heating and fluidizing the fluid bed.

Abstract: A method and associated apparatus for carrying out fluidized bed combustion and transferring heat produced thereby to a boiler includes providing a fluidized bed of particulate matter and introducing fuel particles thereinto, causing a portion of the fluidized bed constituents to flow upwardly through a heat exchanger which is essentially free of any obstructions to said flow, and reintroducing the portion of fluidized bed constituents which flow through the heat exchanger, back into the fluidized bed. As preferably embodied, the portion of fluidized bed constituents flows into an inlet at the bottom of the heat exchanger from a quiescent zone adjacent the combustion bed and a gas having a combustible component is introduced into the heat exchanger. Advantageously, additional fuel particles are also introduced into the heat exchanger to flow upwardly therethrough.

Abstract: An improved fluid bed furnace which includes a new and improved pilot light assembly and which is of the type having a fluid bed comprising material which fluidizes upon being subjected to a flow of gas mixture therethrough and a burner for burning a fuel mixture for providing the flow of gas mixture at an elevated temperature through the fluid bed material for fluidizing and agitating the fluid bed material. The pilot light assembly includes an ignition means for providing a pilot flame, pilot flame confining means for directing the pilot flame into the furnace fluid bed above the fluidizable material for causing the pilot flame to ignite the burner fuel mixture, and pilot flame detecting means for sensing the presence of the pilot flame and enabling the supply of the fuel mixture to the burner.

Abstract: The invention relates to fluidized bed combustors that might tilt in use so that the depth of the bed progressively changes across its width. Air is supplied from two or more sources and means are provided to vary the flow from the sources as the bed tilts so that the air supplied to the portion of the bed of increased depth is increased relatively to the air supplied to the portion of the bed of lesser depth.

Abstract: This invention relates to a process and a reactor for conducting exothermal reactions, for instance combustion, between relatively heavy and relatively light phases in a circulating fluidized bed having vertical cooling surfaces for absorption of the reaction heat resulting from the reaction. The light phase is divided into a primary flow for maintaining a dense conventional part bed and a secondary flow for maintaining a less dense rapid part bed above the dense bed. Said rapid part bed is recycled outside the part beds to the dense part bed for producing the circulating bed. Solid phase is continuously supplied to and withdrawn from the circulating bed, and the secondary flow is supplied to the circulating bed mainly below the cooling surfaces.

Abstract: A fluidized bed combustion or gasification unit in which a grate is disposed in a housing to divide the housing into an upper chamber and a lower chamber. A bed of particulate material including burning fuel is supported by the grate and extends in the upper chamber. The lower chamber has an inlet for receiving pressurized air for passing through the lower chamber, the grate, and the bed of particulate material to fluidize the particulate material. A cooling device is provided for receiving the particulate material from the bed and cooling same prior to the material being discharged to external equipment.

Abstract: The invention provides a fluidized bed combustion apparatus comprising in a common structure a plurality of modules, each module comprising: a diffuser bed support arranged to support and fluidize a bed of granular material by means of air diffusion into the bed, feed means for supplying material to be burnt to a bed supported on the bed support, and control means for controlling the operation of the bed independently of the operation of the other modules.

Abstract: An underfeed fuel feeder for introducing granular material into a fluidized bed. One embodiment introduces material into the bed through a perforated cavity-shaped feed nozzle disposed beneath an air distribution plate. A second embodiment introduces material through a T-shaped nozzle disposed above the plate. A housing protects the nozzle. A third embodiment depicts the nozzle-housing combination in a fluidized bed boiler employing water cooled floors.

Abstract: A fluid bed combustion method and apparatus are disclosed utilizing an induced draft fan downstream of the exhaust port of the combustion chamber. Fluidizing air is given a velocity vector toward one side of the chamber for moving foreign objects to that side where the objects are removed and separated by air classification from bed particles which are returned to the fluid bed. Air classification is accomplished using a blower which is valved off during preheat operation to draw hot air from above the fluid bed down through the particle bed.

Abstract: A coal feed system for use in a fluidized bed in which a grate is supported in a housing and is adapted to receive, on its upper surface, a bed of particulate material including a combustible fuel. Air is passed through the grate and into the bed to fluidize the particulate material. The particulate fuel material is separated externally of the bed into a relatively coarse material which is distributed over the upper surface of the bed and a relatively fine material which is distributed into the bed below the upper surface.

Abstract: A process for treatment of antimony-containing materials in a fluidized bed by way of calcination of the materials at a temperature within the range of from 800.degree. to 1,100.degree. C. obtained by combusting a mixture of a fuel gas and an oxygen-containing gas in said fluidized bed. Said mixture of the gases is formed directly in said fluidized bed by supplying, thereinto, the fuel gas and oxygen-containing gas in separated streams uniformly distributed over the bottom cross-section of said fluidized bed so that the fuel gas stream is surrounded over the entire perimeter by the oxygen-containing gas streams.The process according to the present invention makes it possible to treat antimony-containing materials with a content of antimony ranging from 0.3 to 15% by weight and to obtain antimony-rich sublimates with a content of antimony as high as 40 to 75% by weight.

Abstract: A fluidized bed furnace for consuming a liquid fuel in which there is a fluidization zone of increasing cross-sectional area adjacent to and downstream of the liquid fuel injection nozzles. This arrangement allows better dispersion of the oil and bed material giving more efficient combustion.

Abstract: A flameless catalytic combustion apparatus includes a combustion chamber with a hydrogenous fuel inlet and a mass of catalyst in the chamber between the inlet and an outlet. Preferably the catalyst mass comprises porous pellet bodies supporting varying high and low concentrations of platinum family metals dispersed therein. For spontaneous starting of combustion the fuel is one of the lower alcohols and the high catalyst concentration is at the fuel inlet. The fuel may be in a container pressurized by air, or a lower ether or lower hydrocarbon which is also a fuel. Preferably separate, valved conduits from the fuel container first supply either atomized fuel droplets or air and fuel vapor to the high catalyst concentration for spontaneous ignition of combustion and vaporized fuel for continued combustion throughout the catalyst mass. The catalytic combustion apparatus may include a heat exchanger for fluids such as air, water or personal care foams and creams, or may be used in heating and cooking apparatus.

Abstract: An improved air injector for use in feed preparation in the primary reformer of a HABER processor for ammonia synthesis. In the HABER process, process gas is introduced at relatively high velocity downwardly in a process reactor through a vertical conduit. Along the axis of the conduit is an air supply pipe with a fixture which produces a plurality of downwardly and radially outwardly directed pipes attached to a plenum on the bottom of the air pipe. In this invention the number of circumferentially spaced pipes is doubled over the prior art and they are spaced circumferentially into rows directed outwardly at about a 45.degree. angle so as to present, more or less, a continuous plurality of streams of air which block the annular space and force the downflowing process gas to be turbulently mixed with the air and to form a pressurized mass of process gas and air, which is then forced, by the gas pressure, to flow downwardly in, more or less, a uniform manner through a volume of catalyst.