Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B17/00—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement
  • F26B17/10—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement with movement performed by fluid currents, e.g. issuing from a nozzle, e.g. pneumatic, flash, vortex or entrainment dryers
  • F26B17/101—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement with movement performed by fluid currents, e.g. issuing from a nozzle, e.g. pneumatic, flash, vortex or entrainment dryers the drying enclosure having the shape of one or a plurality of shafts or ducts, e.g. with substantially straight and vertical axis
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
  • B01J8/18—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles

Definitions

• the present invention relates to a process and apparatus for the treatment of solid particles using a fluid serving both to transport them and to carry out a transfer of material and / or heat between the various phases. . in the presence.
• the invention relates in particular to design and construction improvements made to pneumatic transport drying devices and to chemical engineering reactors based on a similar principle.
• the invention consists in treating more or less moist and more or less consistent solid particles in a tubular column, most often vertical, using one or more fluids which serve both to transport them, and to transfer material and / or heat between the various phases involved.
• Devices of this type find numerous applications in the chemical, parachemical, biological and agro-food industries, for example. This is why the devices of the present invention will be designated several times in the description under the generic term of reactors, although they may also only be used for thermal treatment operations such as drying or more or less total pyrolysis.
• Devices comprising a single vertical tube or several vertical tubes mounted in successive pins and used both for drying powders, fibers or any particular substances, as well as for carrying out chemical or biological reactions in heterogeneous phase by fluidization of particles -of materials such as a catalyst in one or more liquid or gaseous phases.
• Another way of improving the contact between the phases involved consists in modifying the shape of the tube, so that one no longer has recourse to a straight cylindrical tube, but to a tube of section for example parallelipipedic formed of successive seghi ' ents assembled one on the other according to a broken line of elements of equal length forming between them obtuse equal and opposite angles.
• a practice known in the pneumatic handling of pulverulent solids to lead to the construction of "zig-zag separators", is not suitable for conveying and placing in the presence of gas and pulverulent solid phases when the particle size distribution of the particles constituting the latter is too widely dispersed.
• French patent n ° 76 34 846 of November 17, 1976 proposed to return to the design usual smooth tube when filling however the interior of the latter with corners or tabs suitably sized with respect to the section of the duct, the rate of ascent of the circulation fluid, the minimum rate of fluidization of the particles transported, and their slope angle, when they are heaped at rest.
• These obstacles or baffles distributed at appreciably regular intervals inside the column forming the reactor constitute a plurality of fluidization stages in which the mixing is intense, the particles in circulation between two successive baffles traveling several times in alternately ascending and descending direction the distance between the two baffles before being transferred to the stage immediately above that in which they were previously.
• French patent n ° 1,192,565 has recommended using a convergent / divergent injector device mounted in a drying chamber and thereby causing automatic recycling of the air and the material to be dried inside the drying chamber.
• O tf. V V ⁇ . ' II the ent on the outer surface of the drying chamber in its upper part in order to increase the drying potential by increasing the dry temperature and decreasing the relative humidity of the drying air, while increasing the swirling of transported particles in proportion to their individual masses.
• Such a dryer has various notable advantages, such as in particular that of allowing the transport of particles of small diameter.
• the object of the invention is therefore to eliminate the various drawbacks of the state of the art by improving the known methods and apparatuses used for drying by pneumatic transport as well as for the execution of continuous chemical reactions in heterogeneous phase between solid and / or liquid and gaseous products.
• the process for treating solid particles with the aid of a fluid both serving to transport them transfer of material and / or heat between the various phases present uses a fluidized mixture of solid particles suspended and in natural circulation in the fluid inside an enclosure.
• the fluidized mixture is subjected inside said enclosure on its path to vortex movements in a plurality of cells.
• the fluidized mixture undergoes in each cell or portion of the enclosure a vortex movement effecting a partial recir ⁇ culation of the fluidized mixture so as to increase its residence time in the treatment enclosure.
• a supplementary flow of fluid is additionally introduced into at least one of the cells in order to provide a quantity of movement creating or increasing the vortex movement of the mixture in the cell considered.
• internal recirculation means are provided in at least some of the cells of the enclosure and thus contribute to reducing the passage section for the fluidized mixture in certain portions. In this way, the vortex movement is further increased inside the cell.
• the temperature, hygrometry or other physical characteristics of the additional fluid can be controlled so as to act on the conditions for the treatment of solid particles.
• the additional fluid thus introduced can come from an external supply.
• the additional fluid comes from the recovery of the fluid from another portion of the enclosure.
• This recovery can be done in the same cell downstream of the introduction of the fluid. It can be done from another cell located downstream of the introduction of the fluid, which can be either the immediately adjacent cell or a cell further away in the direction of flow of the fluidized mixture.
• the processing device of the invention allowing the implementation of the method comprises an enclosure constituted by the assembly of individualized elements that are easily superposable - sable or juxtaposable and defining a plurality of cells.
• the enclosure is provided at its base with a fluid supply means capable of causing the sus ⁇ pension and circulation of solid particles in the form of a fluidized mixture.
• the solid particles can be introduced into the enclosure so as to define operation in co-currents or, in a variant, operation against the current.
• At least one of the cells of the enclosure has a return or introduction orifice connected to an introduction conduit for the additional fluid.
• This conduit is connected to a circulating means ⁇ external fluid which may be a pump or the like and the duct may further comprise means for varying the additional fluid temperature.
• Means for separating the fluids and the solids mixed in the cell are preferably provided in said conduit.
• At least some cells include internal re ⁇ circulation means in the form of a hollow body disposed at least partially inside the cell in order to vary the passage section for the fluidized mixture passing through the cell.
• the hollow body is provided with at least one portion of perforated surface and is connected to the conduit for introducing additional fluid.
• the return orifice is advantageously provided on the wall of the cell and preferably includes a paddle grid or a filter element.
• a continuous filter driven in translation or in rotation, either continuously, or as a function of the value of the pressure drop across the filter element.
• Means for closing the return orifice can also be provided in the case where the implementation of the
• the hollow body is open and has a first perforated suction surface disposed downstream of the general circulation of the fluidized mixture in the cell.
• This first surface is mounted at the end of the largest section of a frustoconical convergent element fixed to a frustoconical diverging element, the largest section of which is surrounded by a second perforated delivery surface.
• a closure plate closes the hollow body at its upstream end.
• the additional fluid introduction conduit passes through the outside wall of the cell and opens into the interior of the hollow body substantially at the junction of these two frustoconical elements.
• the hollow body is closed and made up of two substantially frustoconical elements which are identical, assembled by their large or small base of the same section with a substantially cylindrical central element.
• the hollow body is provided with vents allowing the tangential escape of the additional fluid coming from the fluid introduction conduit which crosses the exterior wall of the cell and opens into the interior of the hollow body.
• the hollow bodies of the different cells can be connected to each other by cylindrical connecting elements in order to improve the mechanical strength of the assembly and to promote the flow of the fluidized mixture between the wall of the enclosure and the hollow bodies thus connected. each other.
• the above hollow body is in the form of a tab or a corner forming a baffle attached to the wall of the cell and comprising a first solid surface substantially perpendicular to the flow of the fluidized mixture causing a decrease of the passage section.
• the hollow body has a second perforated surface inclined relative to the direction of flow.
• the hollow body is directly connected to the conduit for introducing additional fluid.
• the different baffles of the various cells can be fixed along the same generator or on the same side of the device. They can also be mounted in opposition on two opposite sides or on two diametrically opposite generators. Finally, the baffles can also be mounted in quadra ⁇ ture.
• FIG. 1 shows from curves illustrating the variation of the residual humidity as a function of the length of a duct in a reactor according to the invention applied to a drying process
• fig. 2 schematically shows the internal structure of an individual cell of an apparatus according to the present invention
• FIGS. 9, 10 and 11 show embodiments using an assembly of cells similar to those shown ⁇ in Fig. 8; fig. 12, 13, 14, 15, 16 and 17 each time illustrate an assembly of cells similar to that which is illustrated in FIG. 8 and a cross-sectional view showing the internal arrangement of the baffles; and fig. 18 illustrates a variant of a cell that can be used in an apparatus according to the invention showing a particular baffle structure.
• Curve A in fig. 1 shows the variation in the residual humidity of the drying air as a function of the length of the vertical tube used in the case of a dryer formed from a simple smooth tube. It can be seen that the transport and drying air quickly reaches a limit relative humidity L equal to the ratio between the solvent vapor pressure at the surface of the particles and the saturation vapor pressure of the same solvents in the transport fluid to the temperature at which the drying process is carried out. At this stage, the drying does not continue any more and the course of the two phases in the tube is no longer useful.
• the present invention recommends for such a drying application, the use of a vertical enclosure constituted by the assembly of a plurality of cells each constituting a stage inside which the solid particles to be dried are subjected to a vortex movement which results in partial internal recirculation.
• Curve B in fig. 1 shows, in the case of four stages referenced 1, 2, 3 and 4, the variation in the residual humidity of the transport air which it is possible to obtain.
• an additional flow of desiccated and heated air comes from the outside of the apparatus or, possibly after recovery from another stage, into the different cells each constituting a stage. This results in the appearance discontinuities that can be seen in fig. B and obtaining a more rapid reduction in residual humidity over the entire length of the apparatus, which very significantly improves the drying process.
• the cell 5 is constituted by a segment of cylindrical tube provided at each of its open ends with a flange 6 allowing a tight assembly using bolts not shown in the figure.
• a hollow body 7 Inside the cell 5 is mounted a hollow body 7 provided with a first perforated suction surface 8 disposed downstream of the general circulation of the fluid mixture in the cell 5, circulation materialized by the arrows 9.
• the apparatus constituted by the assembly of the different cells 5 being here arranged vertically, the fluidized mixture flows from the bottom upwards, the first perforated surface 8 therefore being at the top of the hollow body 7.
• This first perforated surface 8 constituted for example by a suction grid is mounted at the extremity of larger section of a conical convergence element 10 fixed itself on a frustoconical divergent element 11 placed in the lower part of the hollow body 7..
• the largest section of the divergent element 11 is surrounded by a second perforated delivery surface 12 which is fixed around the open end of the element 11.
• a closure plate 13 in the form of a curved disc with directed concavity upwards is fixed to the periphery of the perforated surface 12 thus closing the hollow body 7 at its upstream end.
• a conduit 14 allowing the introduction of an additional fluid - crosses the external wall of the cell 5 as well as the wall of the hollow body 7 and opens by means of a nozzle 15 inside said hollow body substantially at right of the junction of the two frustoconical elements 10 and 11.
• the assembly of several identical cells 5 by the flanges 6 allows the production of a drying or heterogeneous phase reaction apparatus.
• the solid phase can be introduced by any known means, either in the lower part of the vertical tubular enclosure in which case the process takes place in co-currents, -or in the vicinity of its upper part which results in counter-current operation. In the latter case, it may be advantageous to turn the cell over so that the cup 13 is then in the upper part of the element.
• the fluids are extracted through an orifice located at the top of the treatment enclosure.
• each cell 5 is supplied by the conduit 14, at the venturi formed by the two associated truncated cones 10 and 11, a flow of air dried and heated outside the apparatus. This air brought from the outside induces in the converging 10 a downward circulation illustrated by the arrows 16 which entrains part of the air used to convey the granules.
• This air already humidified and cooled due to the isenthalpic decrease in temperature resulting from the partial absorption of the water contained in the granules, heats up and therefore expands and dries out by mixing with the air injected into the hollow body 7 by the nozzle. 15.
• This mixture is returned through the perforated discharge surface 12 thanks to the existence of the closure plate 13, inside the cell 5 at a speed sufficient to considerably increase the turbulence of the flow. of the vein thus making more effective the contacting of air and granules inside the cell considered.
• This swirling movement is illustrated in particular by the arrows 17.
• the addition of an additional amount of movement by the outside air thus injected also leads to increasing the upward speed of the fluidized mixture, which facilitates the separation of the granules and the air at the first perforated return surface 8 acting as a separation grid.
• Figs. 3 and 4 illustrate a variant of an individual cell which can be used to produce, by assembling several identical cells, a treatment device according to the invention.
• the cell 18 also consists of a segment of cylindrical tube open at its two ends provided with flanges 19 allowing the fixing of the different cells 18 to each other by bolts.
• the hollow body mounted inside the cell 18 is closed and is consti ⁇ killed according to FIG. 3 by two identical frustoconical elements 20 and 21 assembled by their large open base and of the same section to a cylindrical central element 22 which is provided with vents 23 shaped so as to cause a tangential exhaust illustrated by the arrows 24.
• a conduit introduction of additional fluid 25 passes through the exterior wall of the cell 18 and opens into the hollow body slightly downstream of the central element 22, that is to say into the upper frustoconical element 20.
• the fluid thus fed escapes tangentially through the vents 23 of the central element 22 thus increasing the vortex movement of the fluidized mixture passing from bottom to top of the cell 18.
• the existence of the closed hollow body formed by the elements 20, 21 and 22 arranged inside the cell 18 practically over its entire height drives, as can be seen in FIG. 3, a variation of the passage section for the fluidized mixture inside the cell 18, this passage having a minimum section in line with the central element 22.
• O temperature, hygrometry or any other physical characteristic. can be modified allows to act effectively on the conditions of the treatment process.
• the hollow body is similar to that of FIG. 3 except that the identical frustoconical elements 26 and 27 are assembled to the cylindrical central element 28 by their small open base, their large base being closed.
• the additional fluid supply conduit 29 opens, as for the variant of FIG. 3, slightly downstream of the central element 28 provided, with vents 23.
• the stage of treatment is therefore defined inside each cell 18.
• FIGs. 5 and 6 illustrate two possible modes of implementation using the assembly of several cells similar to those illustrated in FIG. 3 and comprising partial recycling means.
• the various hollow bodies of the cells 18 are assembled together by cylindrical connecting elements 30 so as to improve the mechanical strength of the assembly and to facilitate the flow of the fluidized mixture - to The outside of the hollow bodies between the latter and the internal wall of the enclosure.
• a return orifice 31 which can be provided with a filter element not shown and is connected to a return duct 32 provided with a suction fan 33 and a reheating 34.
• the duct 32 may comprise an injector or a vapor recompression member.
• the fluid thus taken up and put into circulation is introduced through the duct 25 after reheating by the element 34, into the hollow body located in the cell 18 immediately adjacent upstream of the circulation of the fluidized mixture. This fluid leaves tangentially through the vents 23.
• EXAMPLE 2 In this example, an apparatus partially illustrated in FIG. 7 to constitute a pneumatic transport reactor comprising three superimposed elements 36, 37 and 38, the lower and upper parts of the apparatus not being shown in the figure.
• the lower element 36 and the upper element 38 are identical and constitute cells similar to those illustrated in FIG. 4 except that the hollow bodies 39, instead of having the shape of two truncated cones joined by their small base as illustrated in FIG. 4, have a hyperboloid shape of revolution, the vents 23 being in the region of smallest section and the additional fluid supply conduits 29 opening slightly above this region in said closed hollow bodies.
• the intermediate element 37 is
• the hollow body 40 serves as a connecting element between the hollow bodies 39 of the lower 36 and upper 38 cells. It defines between its outer surface grooved and the inner wall of the element 37 a passage of reduced section increasing the turbulence of the mixture and allowing for example to ensure an acceleration for a particular chemical kinetics.
• an internal diameter of the reactor 600 mm, the maximum diameter of the central connecting hollow body 40 being approximately 300 mm. It has been shown that this suitably supplied device could be perfectly suitable for partial pyrolysis of wood waste by operating continuously.
• the cell 42 is constituted by a segment of parallelipipedic tube with interlocking capable of being secured to two adjacent cells by latches produced in the form of two frustoconical end portions 43 and 44 of inverted conicity.
• a baffle-shaped hollow body 45 is attached to one of the walls 46 of the cell 42 in the vicinity of its lower end or upstream end.
• the baffle 45 has a first solid surface 47 perpendicular to the flow of the fluidized mixture and defining a throttled passage section inside the cell 42.
• the baffle 45 also has a second perforated surface 48 inclined towards the downstream direction of the flow, that is to say here upwards.
• the inclination of the surface 48 is preferably chosen around 45 °. In general, it is advisable that the solid particles cannot remain on this inclined surface, which controls the choice of the inclination.
• the baffle-shaped hollow body 45 is directly connected to the additional fluid introduction conduit 49 which here comprises, by way of example, a heating means 50.
• the fluid comes from a return orifice 51 located in the end high of the same wall 46 of the cell 42 and comprising a rotary filter element 51a driven continuously by the motor 51b.
• the return duct 52 makes it possible to direct the fluid from the orifice 51 to a centrifugal suction fan 53.
• the fan 53 which plays the role of a fluid circulation member could be rem ⁇ placed by an injector or a pump depending on the applications.
• the heating element 50 can be produced in the form of a heat exchanger controlled by a regulator not shown in the figure.
• Figs. 9 and 10 show alternative embodiments of devices according to the invention constituted by the assembly of
• each cell 42 also includes a perforated baffle 45 in its lower part and a return orifice 51 provided with a vane grate 51c in its upper part.
• the conduit conveying the additional fluid coming from the return orifice 51 of a cell ends this time in the perforated baffle 45 of the immediately lower cell, that is to say upstream of the circulation of the mixture.
• EXAMPLE 3 Using cells 42 as shown in fig. 8 a reactor illustrated in FIG. 11.
• the reactor comprises six superimposed cells 42.
• Hot drying air is introduced into the lower part of the reactor by the supply pipe 55 connected by a conical element 56 to the lower end of the first cell 42.
• the air thus introduced makes it possible to fluidize and transport solid particles to be dried and in particular fine powdery materials such as wheat flour or semolina.
• At the upper part of the device are arranged means for taking up the fluidized mixture.
• the return air taken from the fifth stage 42e passes through a cyclone 57, then through a heat exchanger 58 before being reinjected into the reactor partially through the pipe 59 in the third stage 42 ⁇ and in the first stage 42a by line 60 * .
• air taken from the sixth stage 42f is re-injected partly into the fourth stage 42b and partly into the second stage 42b after passing through a cyclone 57 and a heat exchanger 58.
• the reactor constituted by all of the above six floors have a height of 2.5 m and a diameter of 0.6 m.
• the dryness rate of the materials collected is comparable, due to the increase in the drying efficiency caused by the intensive recycling of the partially dehydrated carrier gas and undergoing in each cell a strong vortex movement due in part to the existence of 19 baffles arranged alternately on the opposite walls of the reactor.
• such a device could be used in the same way to treat, for example, poor products of dry matter such as sugar pulps or drafts or brewery residues by recycling them several times in the column in the presence of steam. superheated water which dries them by saturating them almost instantaneously.
• the same device could be used for the implementation of processes involving the treatment of two phases in the presence of a third, one of these phases being for example a liquid which is vaporized in the reactor and from which the vapors to reinject them after having recompressed them with or without intermediate desuperheating. It is then advisable to provide in recir ⁇ culation pipes suitable means for vapor recompression.
• cells 61. 61a and 61b making it possible to assemble an apparatus according to the invention, are formed from segments of tube of circular section and comprise at their upper end a tab or corner 62 provided with a perforated surface inclined downward substantially at 45 ° and a solid surface 62a perpendicular to the flow of the mixture. At their - lower end, the cells have another tab or corner 63 provided with an inclined perforated surface oriented upwards and with a solid surface 63a perpendicular to the flow of the mixture.
• two corners 62 and 63 therefore form a baffle com ⁇ carrying two isolated compartments. Each of these compartments is also connected to a pipe 64 which can be plugged in so as to ensure either recovery or the introduction of fluid into the different cells. The connection can be made in any way according to the requirements of the process to be implemented.
• FIGS. 12 to 17 could be replaced by a square, rectangular or other section.
• the branching and external circuits to the various cells 61 are connected as desired, the compartments of the adjoining corners 62, 63 can then be connected together on the same conduit or separately on two separate conduits.
• Fig. 18 illustrates another variant of a cell 65 in which the corners 62 and 63 are replaced by circular crowns 66 ′ and 67 of triangular section with perforated surface forming a solid of revolution around the axis of the cell and arranged respectively in the upper part and in the lower part of the cell 65.
• the ring 66 therefore has a surface 66a of conical perforated shape oriented downwards, and a solid annular surface 66b oriented perpenicularly to the main flow.
• the crown 67 has a surface 67a of conical perforated shape facing upwards and a solid annular surface 67b oriented perpendicular to the main flow.
• the assembly of several cells 65 makes it possible to produce an apparatus according to the invention, the external recirculation of the fluid being carried out according to the requirements of the treatment process by the pipes 68 and 69.
• One or the other of the rings 66, 67 can therefore be used either for resumption of the fluid phase or for blowing.
• Certain pipes 68, 69 can also be closed off for external recir ⁇ ulation between certain cells only.
• the invention makes it possible to significantly improve the operation and the operating economy of reactors and dryers based on the principle of pneumatic transport.
• the invention Thanks to the production of an apparatus by assembling identical individual cells, it also makes it possible to simplify the manufacture and modifications of the various processes carried out in the apparatus.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Combustion & Propulsion (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Devices And Processes Conducted In The Presence Of Fluids And Solid Particles (AREA)

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• 1981
  • 1981-12-03 FR FR8122685A patent/FR2517565B1/fr not_active Expired
• 1982
  • 1982-11-29 EP EP19820903461 patent/EP0096047A1/de not_active Withdrawn
  • 1982-11-29 WO PCT/FR1982/000202 patent/WO1983001995A1/fr not_active Ceased

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