Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B21/00—Arrangements or duct systems, e.g. in combination with pallet boxes, for supplying and controlling air or gases for drying solid materials or objects
  • F26B21/02—Circulating air or gases in closed cycles, e.g. wholly within the drying enclosure
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B11/00—Machines or apparatus for drying solid materials or objects with movement which is non-progressive
  • F26B11/02—Machines or apparatus for drying solid materials or objects with movement which is non-progressive in moving drums or other mainly-closed receptacles
  • F26B11/04—Machines or apparatus for drying solid materials or objects with movement which is non-progressive in moving drums or other mainly-closed receptacles rotating about a horizontal or slightly-inclined axis
  • F26B11/0404—Machines or apparatus for drying solid materials or objects with movement which is non-progressive in moving drums or other mainly-closed receptacles rotating about a horizontal or slightly-inclined axis with internal subdivision of the drum, e.g. for subdividing or recycling the material to be dried
  • F26B11/0413—Machines or apparatus for drying solid materials or objects with movement which is non-progressive in moving drums or other mainly-closed receptacles rotating about a horizontal or slightly-inclined axis with internal subdivision of the drum, e.g. for subdividing or recycling the material to be dried the subdivision consisting of concentric walls, e.g. multi-pass or recirculation systems; the subdivision consisting of spiral-shaped walls
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B25/00—Details of general application not covered by group F26B21/00 or F26B23/00
  • F26B25/001—Handling, e.g. loading or unloading arrangements
  • F26B25/002—Handling, e.g. loading or unloading arrangements for bulk goods
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B7/00—Drying solid materials or objects by processes using a combination of processes not covered by a single one of groups F26B3/00 and F26B5/00

Definitions

• the present invention relates to a dryer for divided products and, more particularly, to such a dryer operating using a stream of superheated steam, under pressure.
• Many products come in divided forms and must be able to be dried industrially.
• French patent No. 2,524,129 is known in the name of the applicant, a process which calls for direct convective exchange between the product and a stream of superheated steam. According to this process, a constant flow of water vapor is used, circulating in a closed circuit, serving both as a carrier and heat transfer fluid, at a temperature situated beyond the saturation stage, a small fraction of the vapor current is extracted, equivalent to the amount of water extracted from the dried product, this fraction is subjected to mechanical compression allowing its evacuation in liquid form, after recovery and recycling of its latent heat of condensation.
• the aforementioned patent also describes an installation for implementing this process, as well as French patents No. 2,563,327 and No. 2,607,230 also in the name of the applicant, relating to particular configurations of such an installation .
• the present invention therefore aims to achieve a dryer for divided products which does not have these drawbacks of space and therefore heavy investment, drying facilities described above.
• a dryer for divided products of the type which comprises an enclosure, means for establishing in this enclosure a circulation in a closed circuit 'a stream of superheated steam, means for transporting the product to be dried through the enclosure so that it passes into the stream of superheated steam and a steam outlet to allow evacuation from the enclosure of the steam extracted from the dried product.
• the dryer comprises, arranged in this order along the horizontal axis of an enclosure with a cylindrical body maintained under pressure of a few bars, a member for maintaining the circulation in closed circuit of water vapor, an exchanger / superheater for superheating the water vapor to a determined temperature, a circulating bed conveyor comprising at least one rotary drum and vanes to ensure the rainfall of the product in the conveyor and, by action combined with that of the steam flow, the progress of the product, and a member for separating, at the outlet of the drum conveyor, the dried product from the steam, recycled between the conveyor and the body of the enclosure.
• the on-line arrangement on the same axis of the main organs of the dryer proves advantageous by the convenience of their installation and their maintenance in an enclosure of smaller volume and easily accessible.
• this arrangement makes it possible to increase the exchange surface at the level of the exchanger / superheater, to reduce the pressure losses, as well as the fouling and mechanical forces exerted by the pressure of the fluid on the drum conveyor, especially.
• the dryer comprises introduction means divided product to be dried in one enclosure and means for discharging the products treated in this enclosure, these means for introducing and removing being designed to simultaneously seal the enclosure under pressure.
• these take the form of an extrusion screw compressing the extruded product itself so that it constitutes a seal, a function thus hurt combined with the basic function of these screws, which consists in ensuring the introduction or the extraction of the product into or out of the enclosure, respectively.
• FIG. 1 is a diagram in axial section of the dryer according to the invention
• FIG. 2 is a cross section of the dryer according to the invention, taken along the section line II-II of FIG. 1,
• FIG. 3 is a section through the separation device used in the dryer according to the invention, taken along the section line III-III in FIG. 1,
• FIG. 4 is a diagram in axial section of a member for introducing or removing the product divided into or out of the dryer according to the invention.
• FIG. 5 is a diagram in axial section of another embodiment of such a member.
• the dryer according to the invention comprises an enclosure 1 with a cylindrical body with a horizontal axis designed to be vapor-tight under pressure.
• this dryer for drying the beet pulp, given only by way of example, water vapor is used in this enclosure at a pressure of approximately 4 bars. This pressure level is fixed on the one hand by the desired quality of the product and on the other part by the use that one intends to make of the steam extracted from the dryer.
• a divided product to be treated is introduced into this enclosure through a chute 2 and leaves the enclosure through a conduit 3.
• These means for introducing and removing the product are respectively arranged first at the top and upstream, the second at bottom and downstream of a drum conveyor 4 interposed between them.
• a drum conveyor is well known per se in the art under the name of "drum dryer”. It consists of several coaxial cylindrical ferrules 5, 6, 7 of increasing diameters, these ferrules being integral and nested one inside the other so as to form baffles from the axis towards the periphery of the conveyor following the direction of circulation of steam and therefore product in this tumble dryer.
• part 5 opens at its right end (from the point of view of the figure) into the bottom of part 6 which in turn opens into the bottom of part 7 as indicated in FIG. 1 by the arrows f and F respectively.
• the ferrules 5, 6 and 7 are internally lined with vanes 8, constituted, for example, by simple straight or helical gutters.
• the rotary drum conveyor 4 thus conventionally establishes a "circulating" bed of product to be dried which progresses from the inlet 9 towards the outlet 10 of the conveyor, carried at the same time by a stream of superheated steam introduced with the product to be dried by the inlet 9, and by the effect of driving the blades 8 of the cylindrical ferrules 5, 6, 7 of the conveyor of which they are integral.
• These vanes 8 pick up the product at the bottom of each ferrule of the conveyor to raise it up to its upper part from where this product falls back in "oblique rain” in the vapor current.
• This establishes a maximum contact surface between the stream of superheated steam and the product to be dried, which for example takes the form of chips.
• the water which permeates the product is then vaporized by the heat provided by the steam current and a drier product leaves the conveyor to enter the separation device 11.
• the dryer according to the invention further comprises a fan 15 and an exchanger / superheater 16 placed upstream of the conveyor 4, on the axis thereof.
• the fan 15, the exchanger 16, the conveyor 4 and the separation device 11 are they arranged in line and coaxially inside the enclosure, according to a particularly compact arrangement, of easy assembly and maintenance, capable of reducing the dimensions of the installation while allowing recycling of the superheated steam used to dry the product.
• the water vapor which leaves an upper opening 24 of the separation device 11 according to the arrow g is it brought to the left of the dryer (from the point of view of FIG. 1) by the suction developed at this end by the fan 15 (arrows g ′, g ′′).
• the dryer according to the invention described above then operates as follows.
• the wet product divided to dry being placed in the chute 2 and introduced into the enclosure 1 by a member 19 which will be described in the following of this description, falls on a plate 20 which guides it towards the inlet 9 of the drum 4.
• This inlet 9 is itself connected through the seal 12 to the outlet of the conduit 18 so that the steam thus introduced into the conveyor 4 propels the product to be dried, the steam being superheated in the exchanger 16 at a determined temperature higher than the saturation temperature corresponding to the operating pressure of the dryer.
• the drive means (not shown) rotate the conveyor 4 which is carried by the rollers 21 (see FIG. 2) and connected to the duct 18 and to the device 11 by the revolving joints 12, 12 ′, as has been seen above.
• Water extracted from the product then vaporizes and is added to the stream of water vapor which leaves the apparatus 11 for separation.
• a take steam 23 is placed for this purpose upstream of the fan 15, at the end of the path followed by the recycled water vapor between drum and enclosure.
• the energy of the superheated water vapor thus extracted by the outlet 23 can be reused in a factory where the dryer according to the invention is installed, the sources of pressurized water vapor finding numerous applications in the industry, especially in sweets. It is necessary to regenerate at the inlet 9 of the conveyor 4 a stream of superheated steam having a determined total energy.
• the fan 15 restores the initial kinetic energy of the vapor by compensating for the losses suffered in passing through the conveyor, the separation device 11 and in its return to the inlet of the fan 15.
• the thermal energy initial steam is likewise restored in the exchanger / superheater 16 supplied by a high pressure HP steam source, with a condensation temperature higher than the temperature at which the enclosure vapor must be superheated.
• the separation device 11 may conventionally consist of a cyclone separator (see FIG. 3) tangentially connected to the outlet 10 of the conveyor 4. It is necessary for the inlet chute 2 and the outlet conduit 3 provided respectively for 1 introduction of the product into the enclosure and the evacuation of the treated product out of this enclosure, do not introduce steam leaks which would decrease the thermal performance of the dryer and would disturb the vapor pressure adjusted in this enclosure, which can be by example of the order of 4 bars for a temperature of approximately 143 °, in the application envisaged above for drying the beet pulp.
• a debtor member 19 shown schematically in Figure 4 of the accompanying drawing, it takes the form of a cylindrical screw with variable pitch, well known in particular for the extrusion of plastics. As shown in hatching in FIG. 4, a volume of the product entrained by such a screw undergoes compression in its progression along the oriented axis of the screw.
• This compression of the product transported is used in the present invention to ensure effective clogging of the inlet 2 and the outlet 3, using the product to be transported itself which, in its compressed form, constitutes a tight seal which is opposed to any steam leak.
• the invention thus combines two functions, transport and sealing, in the same organ. According to a second embodiment of the invention, it is possible, to limit the steam leaks, to use an air back pressure as is conventionally practiced on steam turbines.
• the invention is not limited to the use of the extrusion screw shown in FIG. 4.
• Other types of sealed debtor organs could also be used, such as capsulometric debtors.
• the dryer according to the invention thus has various advantages which are brought in particular by the horizontal in-line arrangement of its essential organs in an enclosure with a cylindrical body, favorable from the point of view of the bulk, the pressure resistance and the fluid mechanics.
• An installation of equivalent productivity produced in accordance with the invention would have an enclosure volume of approximately 800 m 3 for a diameter of 7 m, this dimension being essentially determined by the outside diameter of the circulating bed conveyor.
• a conveyor that can be used in the present invention consists of the rotary drum dryer 5 m in diameter currently manufactured by the French company PROMILL.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Sustainable Development (AREA)
• Drying Of Solid Materials (AREA)

Applications Claiming Priority (2)

Publications (2)

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ID=9394064

Family Applications (1)

Country Status (4)

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Family Cites Families (3)

• 1990
  • 1990-02-23 FR FR9002253A patent/FR2658904B1/fr not_active Expired - Lifetime
• 1991
  • 1991-02-22 EP EP19910905408 patent/EP0515560B1/de not_active Expired - Lifetime
  • 1991-02-22 DE DE69100808T patent/DE69100808T2/de not_active Expired - Fee Related
  • 1991-02-22 WO PCT/FR1991/000147 patent/WO1991013303A1/fr active IP Right Grant

Non-Patent Citations (1)

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