Abstract: There is provided an apparatus for use in drying a sample of geological material having a substantial moisture content. In one aspect, the apparatus comprises a means for providing a flow of heated fluid, and a means for managing the thermal state of the flow of heated fluid. The means for managing the thermal state of the flow of heated fluid is arranged operable with the means for providing a flow of heated fluid so that exposure of the sample to the flow of heated fluid facilitates a reduction of the moisture content of a portion of the sample while substantially preserving one or more chemical and/or physical properties of the portion.

Abstract: An apparatus for refining molten glass that includes a housing having a vertically oriented longitudinal axis and a transverse axis perpendicular to the longitudinal axis. Molten glass is received at an upper end of the housing and is discharged from a lower end of the housing. A guide extends at least partway across the housing and directs molten glass in a generally downward direction through the housing and in a parallel or oblique direction relative to the transverse axis of the housing.

Abstract: A combustion gas supply system and method includes: a cyclonic air filter (or separator), a blower having an inlet and an outlet, and a combustible gas inlet, wherein the cyclonic air filter, the blower, and the combustible gas inlet are in fluid communication.

Abstract: The present invention relates to a cotton opening and dust collecting device for refined cotton, which comprises a first cyclone separator, a second cyclone separator, a first draught fan, a second draught fan and a spiral conveyer, and further comprises a suction pipe, a dust collecting cabin, a screen plate, a motor, a dust extraction pipe, a first bearing, a second bearing, a first pipeline, a second pipeline, a third pipeline and a forth pipeline. The device is able to complete collection to the cotton dust in the air in the cotton opening workshop, which not only can effectively prevent the screen plate from being blocked by the cotton dust, but also has good dust collection effect and complete collection of cotton dust.

Abstract: The invention relates to a method for producing an anhydrous powder having a calcium nitrate content of between 92 and 99.9 weight %, a water content of between 0.1 and 8 weight %; and a particle size of between 0.05 and 1.5 mm, wherein the method comprises the step of subjecting a calcium nitrate solution having a water content of between 70 and 15 weight % and a calcium nitrate content of between 30 and 85 weight % to a drying step in an industrial turbo-dryer, resulting in the anhydrous calcium nitrate powder. The invention furthermore relates to such an anhydrous calcium nitrate powder and the use of an industrial turbo-dryer to produce such anhydrous calcium nitrate powder.

Abstract: Providing a cement production apparatus in which raw material is supplied into a duct with being dispersed uniformly so that heat-exchanging efficiency is improved by even preheating and clogging and the like are prevented, so that stable operation can be carried out.

Abstract: The present invention relates to a process for producing free-flowing, agglomeration resistant amorphous poly-alpha-olefin based adhesive pellets. The process includes (a) extruding the adhesive through an orifice of a die plate immersed in a cooling fluid; (b) cutting the adhesive into a plurality of pellets in the cooling fluid; (c) solidifying the pellets at a temperature range of about 25° C. to about 40° C. for at least 30 minutes; and (d) separating the pellets from the recrystallization fluid and drying the pellets. The pellets harden at least three folds faster than conventionally formed pellets.

Abstract: A rotary drying cylinder (1) for plants for the production of bituminous macadams, extending along a main axis (2). The drying cylinder (1) comprises a burner (7), connected to the cylinder, which generates a flame (9) that extends inside the cylinder (1). The drying cylinder (1) internally comprises a tube-shaped shielding structure (10) having an axis of extension which is substantially parallel with the main axis (2) and extending from the burner (7) so that, in practice, the flame (9) is at least mainly confined within the shielding structure (10), there thus being a separating ring (12) between the shielding structure (10) and the inner surface (13) of the drying cylinder (1). The shielding structure (10) comprises a plurality of hollows (17) facing towards the inner surface (13) of the drying cylinder (1) for containing, in practice, the material being dried. The shielding structure (10) is at least mainly made of heat conducting materials.

Abstract: Solid silanol salts are produced by drying an alkali siliconate solution in a fixed bed dryer containing solids.

Abstract: A method of treating untreated low calorific coal containing moisture and organic volatiles includes feeding untreated coal to a dryer, and drying the coal. The dried coal is subjected to a pyrolyzing step where oxygen-deficient gases are brought into contact with the coal, thereby lowering the volatile content of the coal and producing a stream of pyrolysis effluent gases. The pyrolysis effluent gases are subjected to a separation process to separate lean fuel gases from liquids and tars, wherein the separation process removes less than about 20 percent of the pyrolysis effluent gases as the liquids and tars, with the remainder being the lean fuel gases. The lean fuel gases are returned to the dryer combustor, the pyrolyzer combustor, or the pyrolyzer.

Abstract: The invention relates to a method for the simultaneous storage and drying of sewage sludge, comprising the following steps: a) mechanically dewatering the sewage sludge down to a dry substance concentration of 10 to 35 percent; b) applying the dewatered sewage sludge to a floor of a greenhouse-type drying hall in which a transparent building envelope forms the roof over the floor; c) drying the sewage sludge using solar radiation that radiates into the drying hall; d) mechanically dewatering additional sewage sludge down to a dry substance concentration of 10 to 35 percent; e) introducing the dewatered additional sewage sludge into the drying hall and mixing the additional sewage sludge with the sewage sludge already in the drying hall; f) drying said mixture using solar radiation that radiates into the drying hall; and g) evacuating the mixture from the drying hall or repeating steps d) to f), wherein in step e), the additional sewage sludge is mixed with the mixture in the drying hall rather than with the s

Abstract: A process for producing metal oxide from a metal salt includes supplying a first part of the metal salt to a hydrate drier so as to indirectly heat the first part of the metal salt in the hydrate drier using a heat transfer medium from a first stage of a multi-stage indirect cooler so as to dry the first part of the metal salt in the hydrate drier and so as to control a waste gas temperature of the process. A second part of the metal salt is guided as a partial stream past the hydrate drier. The metal salt is preheated in a first preheating stage and precalcined in a second preheating stage. The metal salt and a fluidizing gas having a temperature of 150° C. or less are supplied to a fluidized bed reactor so as to calcine the metal salt to form a metal oxide product. The metal oxide product is cooled in at least one suspension heat exchanger and then in the multi-stage indirect cooler.

Abstract: The present invention harvests and utilizes fluidized bed drying technology and waste heat streams augmented by other available heat sources to dry feedstock or fuel. This method is useful in many industries, including coal-fired power plants. Coal is dried using the present invention before it goes to coal pulverizers and on to the furnace/boiler arrangement to improve boiler efficiency and reduce emissions. This is all completed in a low-temperature, open-air system. Also included is an apparatus for segregating particulate by density and/or size including a fluidizing bed having a particulate receiving inlet for receiving particulate to be fluidized. This is useful for segregating contaminants like sulfur and mercury from the product stream.

Abstract: This invention discloses systems and methods for conversion of high moisture waste materials to dry or low moisture products for recycle or reuse. The equipment systems comprise a gas turbine generator unit (preferred heat source), a dryer vessel and a processing unit, wherein the connection between the gas turbine and the dryer vessel directs substantially all the gas turbine exhaust into the dryer vessel and substantially precludes the introduction of air into the dryer vessel and wherein the processing unit forms the dried material from the dryer vessel into granules, pellets or other desired form for the final product. Optionally, the systems and methods further provide for processing ventilation air from manufacturing facilities to reduce emissions therefrom.

Abstract: A process for energy recovery and transfer including: warming fresh air in a heat recovery and pressure control unit; feeding waste feed and the warm fresh air into a processor; reducing a moisture content of the waste feed by breaking the waste feed into a fuel powder in the warm fresh air in the processor; filtering contaminated air through an initial filter to remove the fuel powder from the contaminated air; pre-heating the contaminated air in the heat recovery and pressure control unit; raising the temperature of the pre-heated contaminated air in a chamber; passing the chamber discharge air through the heat recovery and pressure control unit to pre-heat contaminated air passing on to the chamber and to warm fresh air passing on to the processor; and filtering terminal air through a terminal filter to remove particles from the terminal air.

Abstract: The present invention relates to a process for preparing a granular hydrohalide salt of a particular metal complex compound which is composed of a divalent metal cation as central ion and of an amino dicarboxylic acid ion and, where appropriate, water as ligand, where the hydrohalide salt is obtained with a specific particle size distribution.

Abstract: A drier apparatus for removing water from various materials includes a heating portion, a drying chamber, a first fluid recirculation system, a regenerator and a makeup heater. Also, a method for use of the apparatus. The material to be dried is heated with the first fluid and transferred to the drying chamber. The material is passed counterflow through the drying chamber relative to a second fluid. The second fluid upon exiting the drying chamber is used to preheat the first fluid.

Abstract: A lithographic mask is placed in a chamber which is then sealed. The gas pressure in the chamber is reduced to dislodge contaminant particles on the mask surface.

Abstract: This invention discloses systems and methods for conversion of manure to novel fertilizer and/or soil builder products useful as input for organic farming operations. The equipment systems comprise a gas turbine generator unit (preferred heat source), a dryer vessel and a processing unit, wherein the connection between the gas turbine and the dryer vessel directs substantially all the gas turbine exhaust into the dryer vessel and substantially precludes the introduction of air into the dryer vessel. The dryer vessel receives the manure for contact with the turbine exhaust gases to convert the manure to a dry material, which is passed to the processing unit where it is formed into granules, pellets or other desired form for the final dry fertilizer product. The method comprises drying, heating and converting the manure to form novel self binding fertilizer and soil builder type products for organic farming and other uses.

Abstract: The invention relates to a method for conditioning fibrous substances, especially wood fibers that are dried in a dryer. In a substantially closed drying circuit (1) a vapor-gas mixture is guided in said dryer as a circulating gas (referred to as vapors) that is separated from the dried fibers (6) in a separator (5) once it has passed the drier, and is then returned to a first heat exchanger (7) connected to the drying circuit (1). Gas is heated in a furnace (11) and is supplied to the heat exchanger to heat the vapors. A partial flow (8) of the vapors is coupled out upstream of the first heat exchanger (7) when seen in the direction of the drying circuit (1), heated in a second heat exchanger (10) and is then supplied to the furnace (11) and combusted. In order to reduce emissions and save energy, the partial flow (8) of vapors coupled out, before being heated in the second heat exchanger (10), is cooled in a vapor condenser (9) and depleted, and the resulting condensation product (14) is fed out.

Abstract: Method of drying a medium for producing a porous matrix from a solution, a paste, an extract, a granulated material or such, where a liquid inert agent is fed into a vessel (5) at controlled pressure and amount through a valve (7), transferring the pressurized liquid inert agent to a mixing vessel (4), said mixing vessel (4) also receiving the solution, such as paste, extract or granulated material, through an inlet valve (10), adjusting the pressure and temperature inside the mixing vessel (4) to desired levels by a release valve (6), upon complete mixing of the inert agent with the solution, the mixture is expanded into a porous matrix and injected into a drying circuit through a drying chamber (3), the matrix thereby being kept suspended in the drying chamber by the flowing drying medium, supplied by the blower (2), the matrix moisture being removed from the mixture through a heat exchanger coil comprising a first heat exchanger (11) where the water vapour is condensed and removed from the circuit and fina

Abstract: A drying device for drying bulk material has one or more storage containers for the bulk material and a heating device for heating the drying air for drying the bulk material. A drying air conduit is connected to the heating device and the storage containers and guides the drying air to the storage containers. One or more first mixing valves are arranged in the drying air conduit upstream of the storage containers, wherein the first mixing valves are used to adjust the temperature of the drying air before the drying air enters the storage containers. The heating device has also the function of regenerating the drying units provided for removing the moisture from the drying air.

Abstract: Method and apparatus for reducing contamination of a substrate in a substrate processing system. The apparatus has a substrate support, a gas directing shield circumscribing the substrate support and a shadow ring disposed vertically above the substrate support and gas directing shield for retaining the substrate. The gas directing shield and substrate support define an annular channel that is provided with an edge purge gas. The edge purge gas imparts a force at the edge of a substrate resting on the substrate support the lifts it off the substrate supports and against the shadow ring. The shadow ring further has a plurality of conduits extending from its upper surface to its sidewall to provide a path for the edge purge gas to vent and to impede the flow of process gases under the backside and around the edge of the substrate.

Abstract: Apparatus for agglomerating and drying particulate material, including an agglomerator (4) for forming and discharging wet granules of a predetermined size or smaller, and a dryer (12). The agglomerator utilizes a rotary blade assembly (100) that repeatedly impacts and cuts the wet mixture of material to be agglomerated, which is forced radially outward through the blade assembly under centrifugal and air pressure force. Wet granules pass through an annular screen (104) where they reach a predetermined maximum size. The dryer has an inlet (50) for wet granules from the agglomerator, an outlet (78) for granules having passed through the dryer, and one or more baffles (64) within the dryer defining a spiral path through which the granules pass from the dryer inlet towards the dryer outlet. The baffles are configured such that their pitch increases with distance from the dryer inlet, whereby the cross-sectional area of the spiral path increases toward the dryer outlet.

Abstract: A method and apparatus of heating or cooling a charge of a solid material are disclosed. The method includes the steps of supplying a charge of the material to form a packed bed of solids in a process vessel having one or more passageways through which a heat transfer fluid can flow, passing a heat transfer fluid through the one or more passageways and supplying a working fluid to said vessel. The method is characterized by circulating the working fluid through the bed, the circulation step including removing at least part of the working fluid from one or more sections of the vessel and then returning the working fluid to other sections of the vessel.

Abstract: A spray dryer apparatus and method suitable for the production of detergents, cleaners and components thereof wherein the inner wall of the drying chamber is provided with an air-permeable textile material lining at a distance from the inner wall, and at least one outlet for compressed gas is provided between the inner wall and the textile material lining whereby adherence of sticky deposits on the inner wall of the drying chamber is avoided or reduced.

Abstract: A method and apparatus for heating or cooling a solid material (93) in a process vessel (80) is disclosed. The Method includes supplying a working fluid to a vessel which holds a packed bed (93) of the solid material. The method is characterised by reversing the flow of the working fluid to enhance heat transfer between a heat exchange fluid and the solid material.

Abstract: Method and apparatus for the removal of liquid from particulate material by evaporation through the supply of heat, said heat being transferred substantially by superheated vapours or steam of the liquids existing in the particulate material, and where said method is executed in a substantially closed system. The particulate material is supplied continuously to a process chamber which is configured as an annual or partly annular chamber (1) which lies in a substantially horizontal manner, where the superheated vapours are introduced from below and up through openings (11) in a bottom (10) in the annular chamber, so that the particulate material is brought into movement by the superheated vapours, and such that a transport of the particulate material takes place through the annular chamber (1).

Abstract: Apparatus for agglomerating and drying particulate material, including an agglomerator (4) for forming and discharging wet granules of a predetermined size or smaller, and a dryer (12). The agglomerator utilizes a rotary blade assembly (100) that repeatedly impacts and cuts the wet mixture of material to be agglomerated, which is forced radially outward through the blade assembly under centrifugal and air pressure force. Wet granules pass through an annular screen (104) where they reach a predetermined maximum size. The dryer has an inlet (50) for wet granules from the agglomerator, an outlet (78) for granules having passed through the dryer, and one or more baffles (64) within the dryer defining a spiral path through which the granules pass from the dryer inlet towards the dryer outlet. The baffles are configured such that their pitch increases with distance from the dryer inlet, whereby the cross-sectional area of the spiral path increases toward the dryer outlet.

Abstract: A process and an apparatus for drying of a material in the form of a paste or a filter cake in a spin flash dryer. Particles are separated by a classifier (6) in the chamber (1) in such a way that oversize fraction is withheld in the chamber (1) and the desired fraction is removed (3, 9). A possible undesired undersize fraction is strained off and recycled (4, 10, 11) externally back to the dryer chamber (1). The spent drying gas is recycled to the dryer chamber (1). In either, the energy in the spent drying gas may be made use of in a heat exchanger and there is no or only little emission to the environment. Products preferably dried according to the invention are fruit and beet pulps, destillers residues, pesticides, pigments, dyes, ceramics, active coal, sludge and zeolites.

Abstract: The present invention provides a method and apparatus for agitation-free, low temperature drying of fragile, temperature sensitive, granular materials at atmospheric pressure using Radio Frequency (RF) energy to provide the heat of evaporation. A relatively low velocity flow of purge air through either a continuously moving or stationary product bed provides means for removing moisture from the product at atmospheric pressure. The purge air is maintained at a controlled humidity, temperature and velocity, and the intensity of the RF field is controlled in response to temperature sensing means to control the temperature of the product. For the case of a continuously moving product bed the RF applicator is preferably divided into multiple zones, which may be independently controlled, to effect control of the moisture and temperature profile of the product as it passes through the apparatus.

Abstract: A method and apparatus for drying of a material containing a volatile component, in which the material is disposed in a bed in a drying zone which is in communication with a closed circuit in which a gaseous drying medium is circulated. Associated with the drying gone is a closed heat pump system including a compressor, at least one condenser in the drying zone, a super heat exchanger and a working medium. The drying zone is supplied with super heat from the super heat exchanger, and the condenser is supplied with working medium from a super heat exchanger, thereby increasing the temperature in the drying zone.

Abstract: A method and apparatus for drying solid foodstuffs is disclosed. The apparatus comprises a housing in which a gas permeable conveyor carrying the foodstuffs is arranged. The housing is divided into at least one drying section and at least one cooling section near the discharge end of the conveyor. Each section comprises means for generating a flow of drying or cooling gas along the foodstuffs, perpendicular to the conveyor. After passing along the foodstuffs, the gas is recirculated to drying or cooling means arranged in each section. The foodstuffs are thus first heated and then cooled down, so that the temperature thereof at the discharge end is substantially equal to the temperature at which the foodstuffs are supplied. The drying and cooling means are arranged such, that the temperature of the foodstuffs does not exceed 40.degree. C., and that the foodstuffs leave the apparatus at a temperature of less than 5.degree. C.

Abstract: A fluidized bed heat treatment apparatus is provided to be heated by combusting fuel gas in a manner to minimize or prevent the exhaust of carbon monoxide, the apparatus including a retort containing refractory particles to be fluidized, a first inlet in a lower region of the retort for introducing fuel/air mixture into the retort, a second inlet in a lower region of the retort for introducing secondary air into the retort, a temperature sensor located above the first and second inlets, a flame initiator located above the refractory particles, an externally located mixer to mix fuel and air in desired proportions and to supply same to the first inlet, and a control device arranged to control said externally located mixer in response to temperatures sensed by said temperature sensor whereby when the temperature sensor is below a predetermined temperature indicative of the bed being substantially not fluidized, a stoichiometric fuel/air mixture is supplied to the first inlet and when the temperature sensor sens

Abstract: A process and apparatus for the drying or kilning of malt in a substantially continuous operation. The malt is transported through one or more separate drying zones by means of fluid bed dryer units at which time tempered or conditioned air at a predetermined temperature and moisture content is passed through the malt to effect a drying of the malt. The rate of malt movement through the drying zones is varied according to the moisture content of the malt at predetermined points in its travel whereby to acheive a desired drying rate and moisture content in the malt as it travels through the various drying zones. Sulfur dioxide gas is selectively infused with the air in the drying zones to minimize carcinogens within the malt. Optional treatments are provided for the malt as it passes through the drying zones, including subjecting the malt to a vacuum to facilitate moisture removal and to effect a sanitizing of the malt.

Abstract: A flowable solid material, such as wet-milled corn germ, is continuously fed into the upper portion of a large vessel having a cylindrical shell with a vertical axis and a series of vertically spaced horizontal decks. Each deck has concentrically spaced annular zones of holes or perforations, and heated air from a set of blowers and a gas-fired or steam heat exchanger is forced countercurrently or upwardly through the perforations to produce a recirculating bed of material above each deck with an upward spouting flow of the material above the zones of perforations and a downward flow of material between the zones of perforations. The recirculating material forming the lower beds is also heated by cylindrical steam heat exchangers which extend vertically between the zones of perforations, and the material is fed progressively downwardly through the vessel to form the beds and for discharge from the lowermost bed.

Abstract: A cone-shaped bubbler for use with solid metal organic source material used in metal organic chemical vapor phase deposition systems, and a method of producing carrying gas saturated with source material that is injected into such systems. The bubbler comprises a sealed container having a slanted wall with an inverted cone-shaped cross section. Solid metal organic source material is disposed in the container. A heat bath surrounds the sealed container. A carrying gas inlet is disposed adjacent the top of the container. Carrying gas is injected in a tangential direction relative to the source material, and a whirlpool effect is generated by the tangential gas flow that imparts a centrifugal force to gas molecules, pushing the source material against the wall to promote heat flow from the heat bath to sustain high rate sublimation. A gas outlet is disposed adjacent the bottom of the container.

Abstract: A method and apparatus are provided for operating a pressurized reactor system in order to precisely control the temperature within a pressure vessel in order to minimize condensation of corrosive materials from gases on the surfaces of the pressure vessel or contained circulating fluidized bed reactor, and to prevent the temperature of the components from reaching a detrimentally high level, while at the same time allowing quick heating of the pressure vessel interior volume during start-up. Superatmospheric pressure gas is introduced from the first conduit into the fluidized bed reactor and heat derived reactions such as combustion and gassification are maintained in the reactor. Gas is exhausted from the reactor and pressure vessel through a second conduit.

Abstract: A process and device for operating a drier for at least one of powdered, granulated and pourable materials. During operation of the drier, a drying air current is introduced into a drier and rises through the material to be dried, thus removing moisture therefrom. To reduce the costs of generating a drying air current, the drying air current is drawn from the outlet of a blow molding, stretch-blow forming or other plastic molding process.

Abstract: A flowable solid material, such as wet-milled corn germ, is continuously fed into the upper portion of a large vessel having a cylindrical shell with a vertical axis and a series of vertically spaced horizontal decks. Each deck has concentrically spaced annular zones of holes or perforations, and heated air from a set of blowers and a gas-fired or steam heat exchanger is forced countercurrently or upwardly through the perforations to produce a recirculating bed of material above each deck with an upward spouting flow of the material above the zones of perforations and a downward flow of material between the zones of perforations. The recirculating material forming the lower beds is also heated by cylindrical steam heat exchangers which extend vertically between the zones of perforations, and the material is fed progressively downwardly through the vessel to form the beds and for discharge from the lowermost bed.

Abstract: A process and apparatus are disclosed for drying solid materials, which allows the thermal energy used for drying to be recovered and the emissions produced during degassing and gasification to be reduced. A solid material which contains an evaporable material, particularly water, is fed to a fluidized bed drier. The solid material is fluidized by fluidizing medium, the fluidizing medium being the evaporable material. The dried solid material is removed from the drier and is fed to further processing, use or disposal. The non-condensable components of the solid material which are insoluble in the condensate of the evaporable material are separated by cooling and condensation of the vapor and released for subsequent use or disposal.

Abstract: The subject invention is an integrated process for economically drying and briquetting coal to produce strong briquettes. The subject invention utilizes a conditioner to output dried coal having a selected moisture content and temperature and mean particle size and size distribution for briquetting. The conditioner reduces the moisture content of coal particles by contacting them with steam. The preferred conditioner fluidizes a bed of coal particles with steam generated during the coal drying process. The moisture content of the dried coal is in the form of steam which fills the pores and inter-particle void spaces of the coal particles. The moisture content of the dried coal is controlled by supplying heat to heat exchange tubes in the coal bed in response to coal bed temperature. The bed temperature is related to the moisture content of the dried coal.

Abstract: Water-containing solids are dried in a fluidized bed, which is indirectly heated by at least one heat exchanger. Water vapors having a high water vapor content are withdrawn from the fluidized bed and a part of the vapors is passed as a fluidizing fluid through the fluidized bed. The remaining vapors are cooled to form an aqueous condensate. At least part of the aqueous condensate is contacted in a purification zone with a gaseous or vaporous stripping fluid. Purified condensate and contaminated stripping fluid are separately withdrawn from the purification zone. Water vapor is preferably used as a stripping fluid in the purification zone.

Abstract: An arrangement of apparatus and process thereof for cooling hot fluid solid particles, especially hot regenerated catalytic particles are disclosed. The apparatus comprises a substantially vertical, cylindrical and close ended heat removal vessel through the shell sid passage of which is passed the fluid solid particles that flow downwardly in the form of dense phase fluidized bed, and one or more seperate heat exchange tube units through the tube side passage of which the coolant is passed and evaporized, each of said heat exchange tube units comprising a supply coolant inlet tube, a supply coolant collecting chamber, one or more heat exchange tubes, a vapour collecting chamber and a resulting vapour discharge tube, all of which constitute a close type coolant-to-vapour circulation.

Abstract: An apparatus known per se for the thermal treatment of a mixture of solids and gases, comprising a vessel having an axially symmetrical interior, which vessel has in the lower part and in the upper part in each case at least one tangentially arranged opening, in the interior of the vessel at least one annular baffle tightly sealing to the vessel wall being arranged between the two openings, and the lower part of the vessel having a smaller diameter, is operated or is designed so that in the lower part a high radial velocity and short residence time prevail and in the upper part a low radial velocity and long residence time prevail.