WO2007057896A1 - Dispositif et procede de deshydratation - Google Patents

Dispositif et procede de deshydratation Download PDF

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Publication number
WO2007057896A1
WO2007057896A1 PCT/IL2006/001323 IL2006001323W WO2007057896A1 WO 2007057896 A1 WO2007057896 A1 WO 2007057896A1 IL 2006001323 W IL2006001323 W IL 2006001323W WO 2007057896 A1 WO2007057896 A1 WO 2007057896A1
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WO
WIPO (PCT)
Prior art keywords
plate
cell
product
apertures
dehydration
Prior art date
Application number
PCT/IL2006/001323
Other languages
English (en)
Inventor
Roman Maryakhin
Original Assignee
Particle Treatment Technologies Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Particle Treatment Technologies Ltd filed Critical Particle Treatment Technologies Ltd
Publication of WO2007057896A1 publication Critical patent/WO2007057896A1/fr

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B3/00—Drying solid materials or objects by processes involving the application of heat
    • F26B3/02—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air
    • F26B3/06—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air the gas or vapour flowing through the materials or objects to be dried
    • F26B3/08—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air the gas or vapour flowing through the materials or objects to be dried so as to loosen them, e.g. to form a fluidised bed
    • F26B3/092—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air the gas or vapour flowing through the materials or objects to be dried so as to loosen them, e.g. to form a fluidised bed agitating the fluidised bed, e.g. by vibrating or pulsating
    • F26B3/0926—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air the gas or vapour flowing through the materials or objects to be dried so as to loosen them, e.g. to form a fluidised bed agitating the fluidised bed, e.g. by vibrating or pulsating by pneumatic means, e.g. spouted beds
    • 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
    • F26B17/107—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 pneumatically inducing within the drying enclosure a curved flow path, e.g. circular, spiral, helical; Cyclone or Vortex dryers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B3/00—Drying solid materials or objects by processes involving the application of heat
    • F26B3/02—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air
    • F26B3/06—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air the gas or vapour flowing through the materials or objects to be dried
    • F26B3/08—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air the gas or vapour flowing through the materials or objects to be dried so as to loosen them, e.g. to form a fluidised bed
    • F26B3/082—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air the gas or vapour flowing through the materials or objects to be dried so as to loosen them, e.g. to form a fluidised bed arrangements of devices for distributing fluidising gas, e.g. grids, nozzles

Definitions

  • the present invention is generally in the field of drying techniques, and relates to a dehydration apparatus and method.
  • U.S. patent No. 4,479,310 discloses a dehydration apparatus typically used for the dehydration of leaves. Apparatuses similar to said that of U.S. 4,479,310 are known in the market and are used e.g. for the dehydration of parsley.
  • the capacity of one known in the art apparatus is 2,000 kg parsley per hour, wherein fresh product is fed to the apparatus to be blown by hot air while conveyed via a complex of several floors of stainless steel conveyor grids through which the hot air is blown from the bottom to the top of the apparatus.
  • Fresh product fed to the inlet of the apparatus reaches its outlet about an hour later, with about 5% remaining wet.
  • the parsley product loses its fresh-green color. Since the process lasts about an hour, the temperature of hot air should be kept sufficiently low in order to avoid burn damages to the product resulting from its long exposure to heat.
  • the temperature of hot air is thus normally kept in the range of about between 50 and 80 Celsius degrees, a temperature which is too low to cause burn damage, but is also insufficient to destroy undesired microorganisms normally present in the pre-treated product.
  • the product typically has to be prepared for dehydration by a preceding disinfection step in order to destroy bacteria and spores which otherwise will damage product quality and will shorten its shelf life term.
  • the raw material is to be exposed (in a separate device) for a short period to a temperature of about 150 Celsius degrees or more, believed to be sufficient for destroying any parasite microorganisms accompanying it.
  • the dimensions of the concerned known device are about 50 meters length, 5 meters width and 4 meters height.
  • Stainless steel conveyor grids are not low priced, so four or five floors of conveyors plus their motors and motion transmission mechanism make the apparatus too expensive.
  • the present invention relates to a dehydration device especially useful for reducing the wetness of leaf vegetables such as parsley.
  • the dehydration device of the present invention comprises a dehydration cell having a product inlet, a product outlet, and a bottom plate with a plurality of apertures forming gas permeable open areas, wherein said apertures are arranged such that the open areas gradually decrease in a direction between first and second ends of the plate along the plate's width such that, when gas is forced into the cell through the plurality of apertures, a plurality of respective separate gas jets eject upwardly from the plate with a gas flow rate decreasing in said direction along the plate thus creating a global directional circulation of the gas throughout the cell and a plurality of local circulations of said gas inside the cell.
  • the local circulations are formed due to the pressure differentiations created either between individual air jets and the space surrounding them above the respective plate region, or between neighboring jet regions of different flow rate.
  • the gradual decrease in floor plate's open area results from a decrease in the average diameter of the apertures in the respective bottom portions.
  • the diameter of apertures near the first end of the plate may be between about 4 and 5 millimeters and gradually decrease to about 2-3 millimeters for the apertures near the second end of the plate.
  • the average distance between the centers of adjacent apertures is preferably about 30 millimeters, and the apertures are preferably arranged in hexagonal arrays, with a 30 mm distance maintained between each aperture and all the adjacent ones surrounding it.
  • the plate width (a distance between the first and second ends) is about 1.7 meters.
  • the width of the device influences the cell quality of sorting between product amounts of different dehydration stages.
  • the length of the device that is its dimension along an axis perpendicular to the width and along which the flow rate of air flow across the plate remains substantially invariable, is not restricted, and is to be determined according to the required work capacity.
  • a device of 1.7 meters width and having a length of about 5 meters has a dehydration capacity of about 1,000 kg raw product parsley per 1 hour of operation through which the product is dehydrated from about 90% wetness to about 5%.
  • the average stay of product inside the dehydration cell is approximately only 2-3 minutes, which permits exposing the product to temperatures around 200 Celsius degrees, without damaging the product. Accordingly, it can be appreciated that the average weight of product present inside the cell at any given moment is about 35 - 50 kg.
  • the gradual decrease in the plate's open area results from a decrease in the average number of apertures per unit area in respective regions of the bottom plate.
  • the gradual decrease in the plate's open area results from a decrease in the average diameter of the apertures and/or reduction in the average number of apertures per unit area.
  • the cell is delimited at its top by a grid.
  • This may be a net having apertures of about 1-2 millimeters in size.
  • the device in order to prevent blockage of the net by the accumulation of ground-up product particles trapped in the apertures, which may influence the dynamic properties of the device, the device preferably comprise a plurality of parallel rods or wires spaced from one another with a gap of between about 1 and 2 millimeters. By having slots instead of apertures, the accumulation rate of product particles is reduced, and the cleaning (if necessary) of the grid becomes faster and easier.
  • the cell height from the plate to a top grid delimiting the cell from above is between 1 and 1.5 meters.
  • the gas is hot air forced through the bottom plate into the cell from a gas supply plenum located underneath the plate (such that the plate serves as a ceiling to the supply plenum).
  • the gas supply plenum accommodates hot air, preferably at an average temperature of about 150-220 Celsius degrees (for parsley, more preferably 200 Celsius degrees), and at an average pressure equivalent to the pressure of about 800 to 1000 millimeters water post.
  • the hot air supply plenum preferably receives the pressurized hot air from a blower and air (or gas) heater connected to an inlet of the supply plenum; said inlet is located underneath the floor plate.
  • the hot air may be formed from room temperature air heated by a burner being a part of the gas supply system in gas communication with the supply plenum (which as described is located underneath the plate).
  • the dehydration cell preferably further comprises a row of horizontally oriented nozzles located near the second end of the plate for injecting pressurized air (or other gas) having flow direction substantially parallel to the plate.
  • pressurized air or other gas
  • This is useful for enhancing the flow of material through the device, by eliminating product accumulation at the corner of the device near the second end of the plate. For two main reasons, the product may tend (in some scenarios) to accumulate on said corner.
  • the upwardly oriented air jets erupting from smaller diameter apertures near the second end of the floor plate are of smaller flow rate thus having smaller swept capacity compared to the air jets erupting from the other plate portions.
  • the product inlet opening preferably extends above the plate lengthwise of its first end. Furthermore, the product outlet opening preferably extends lengthwise a second end of the top grid, delimiting the cell from above, and remotely from a first end of the top grid which is substantially straight above the first end of the plate.
  • the product outlet opening communicates with an inverted U-shaped tunnel delivering the dehydrated product out of the device.
  • Such arrangement of the inlet and outlet of the product cooperates with the unique air circulation properties of the cell to generate a fully automated flow of the product from the inlet to the outlet of the cell, wherein a fresh wet product enters the cell through the inlet while dehydrated prepared product exits the cell through the outlet in continuous endless flow without requiring any moving parts or additional conveying mechanism.
  • the fresh product is continuously fed to the product inlet at a predetermined rate.
  • the product inlet opening has an inlet slope leading the supply of the fresh product from outside of the cell to the inlet opening, simply by a gravity force.
  • the fresh product enters the cell, it is immediately swept upwardly by means of the highest flow rate air jets erupting from the plate near its first end and where the inlet opening is located, to join the global air circulation in the cell. The swept amount of product clears place for additional fresh product reaching at the opening.
  • the swept product circulates through the global air circulation, while portions of the product diverge from the global circulation to join the local air circulations formed by the air jets injected from the plate in gradually decreasing flow rate from the first end of the plate to its second end.
  • wet fresh product weighs more than the dehydrated one (and furthermore since partially dehydrated product containing predetermined wet percentage weighs more than partially dehydrated product containing less wet) it is statistically approved that more wet product will sooner diverge by gravity from the global air flow, falling down from its path near the top of the cell to join the local air circulations formed by the upwardly erupting air jet, while less wet product will continue its motion with the global air flow to greater extents along the cell, before falling down to join local circulations.
  • the product amounts of a whole spectrum of wet percentage simultaneously being treated in the cell are dynamically and automatically sorted according to wetness, such that on average most wet product becomes circulated and most intensively dehydrated by the most flow rate flows of air in the cell, while less wet (or partially dehydrated) product becomes circulated and further dehydrated by least flow rate flows of air.
  • the outlet opening is adjustable, such that the amount of prepared product escaping the cell is controllable.
  • the adjustment can be made by a pivoting flap determining what thickness extent of the global flow measured from the top of the cell will be allowed to reach the outlet. By this way, only product pieces swept by the uppermost extent of the global flow can escape the cell. By periodically examining the properties (e.g., wetness, color, etc.) of the product pieces thus released from the cell, it is possible to determine whether or not the product stays optimal time inside the cell.
  • the flap (and according to other embodiments, other types of adjustable covers) can be readjusted to increase the product releasing rate, thus shortening the average stay of product pieces inside the cell.
  • the flap can be readjusted to decrease the product releasing rate, thus lengthening the average stay period of product pieces inside the cell.
  • the product inlet opening is arranged lengthwise the entirety of a rear wall of the cell and the product outlet opening is arranged lengthwise along the entirety of a front wall of the cell (the front and rear walls of the cell corresponding to the second and first ends of the plate).
  • the plate extends between the rear wall and the front wall with the plate's open area decreasing gradually from the plate's end near the rear wall to its opposite end near the front wall.
  • the cell further comprises two side walls extending respectively from both sides of the cell between the front wall and the rear wall.
  • the cross section of the cell is substantially the same at any vertical plane parallel to the side walls, the flow of product across the cell between the front and the rear wall or vice versa is in paths substantially perpendicular to these walls and substantially parallel to the side walls.
  • This arrangement is especially useful for relatively short cells having the side walls distant from one another a length smaller than a distance between the front and rear walls.
  • the product inlet opening and the product outlet opening do not have to extend along the entirety of the rear and of the front walls. Instead, the product inlet opening may be located in the rear wall near one of the side walls, while the product outlet opening may be located in the front wall near the opposite side wall, both openings extending along only short portions of the rear and front walls respectively.
  • the cross section of the cell varies along a vertical plane parallel to the side walls. Actually, three different types of vertical cross section geometry are distinguishable in this cell embodiment.
  • the section crosses via the product inlet opening, but not via the product outlet opening (which is located near the opposite cell's side wall, remotely from the product inlet).
  • the section crosses via the product outlet opening, but not via the product inlet opening (which is located near the first cell's side wall, remotely from the product outlet).
  • the section crosses neither the inlet opening nor the outlet opening (which both are located remotely from the center portion, near the side walls).
  • the above-described asymmetric design of the cell adds to the global air flow circulation in the cell a diagonal flow component resulting from the air swept from the outside of the cell with the product entering through the product inlet and from the air leaving the cell through the outlet opening. Accordingly, the product flow through the cell will also have a diagonal motion component, and the global flow path of product through the cell from the inlet to the outlet will be spiral.
  • the cell may be provided with flow deflectors located near its ceiling.
  • the deflectors e.g. partitions made of sheet metal plates, can be positioned parallel to one another yet diagonally to the cell walls, with a predetermined gap between each pair of adjacent deflectors.
  • the deflectors partition the cell into a plurality of sub-cells communicating with one another beneath the deflectors where global air circulation is weak while local air circulation is more dominant.
  • the deflectors have a diagonal orientation respective to the cell's walls such that, for each deflector, the end of the deflector at the front wall side is closer to the respective side wall which is near the product inlet than the opposite end of the same deflector. Due to this diagonal orientation, the global flow in each sub-cell is deflected away from the outlet opening, such that the product quantities which were expected to advance with the spiral global flow from the product inlet towards the product outlet in some hypothetic flow rate (i.e. in case there were no deflectors) will now be delayed due to the deflection so that their actual flow rate will be smaller.
  • the device may be further provided with a heat exchanging mechanism allowing for gaining heat from hot and wet waste air escaping from above the cell through an air permeable top of the cell (e.g. the aforementioned net or grid) and using it for preliminary heating fresh air to be further heated e.g. by a burner, and then forced through the apertures in the plate into the cell.
  • a heat exchanging mechanism allowing for gaining heat from hot and wet waste air escaping from above the cell through an air permeable top of the cell (e.g. the aforementioned net or grid) and using it for preliminary heating fresh air to be further heated e.g. by a burner, and then forced through the apertures in the plate into the cell.
  • a novel dehydration method especially useful for reducing wetness of leaf vegetables such as parsley product is also within the scope of the present invention.
  • the method comprises exposing the product to a plurality of intensive local air circulations formed inside a predetermined dehydration space and having gradually decreasing flow rate from a first end of the space towards a second end of the space remote from said first end, and to a global intensive air circulation formed throughout said space as a result of the gradually decreasing flow rate of the local circulations.
  • Fig. 1 is a vertical cross section view of an example of a dehydration device according to the present invention.
  • Fig. 2 illustrates an example of dynamic equilibrium in the device of Fig. 1, during a dehydration process.
  • Fig. 3 illustrates a general top view of the device of Fig. 1.
  • Fig. 4 illustrates a general top view of some portions of the bottom plate of the device of Fig. 1. DETAILED DESCRIPTION OF THE INVENTION
  • Fig. 1 illustrates a vertical cross section view of a dehydration device according to an example of the present invention.
  • the cross section is taken at two remote vertical planes indicated by arrows A-B of Fig. 3.
  • the device 1 includes a dehydration cell 4 having a product inlet 60, a product outlet 62, and a bottom plate 5.
  • the latter is formed with a plurality of apertures - apertures 6, 7, 8, 9 and 10 being seen in the figure.
  • the apertures form gas permeable open areas, and are arranged such that the open areas gradually decrease in a direction between first and second ends 25 and 26 of the plate along the plate's width.
  • This arrangement of apertures results in that, when gas is forced into the cell through the plurality of apertures, a plurality of respective separate gas jets 16, 17, 18, 19 and 20 eject upwardly from the plate 5 with a gas flow rate decreasing in said direction along the plate, thus creating a global directional circulation (shown by arrows 30-39) of the gas throughout the cell and a plurality of local circulations of said gas inside the cell.
  • the cell 4 is defined by the bottom plate 5, a top grid 40, front and rear walls 14 and 13, and side walls (90 and 91 in Fig. 3).
  • the device 1 further includes an air supply plenum 2 communicating through a duct 3 with an air blower (not illustrated) for receiving pressurized hot air.
  • the air from the blower is heated on its way to the plenum 2 by means of a burner (not illustrated).
  • the plenum 2 communicates with the dehydration cell 4, through the plurality of apertures forming gas permeable open areas in a top barrier of the plenum being the bottom plate 5 of the cell 4.
  • the open areas of respective portions of the plate decrease gradually from a region near the first end 25 of the plate towards a region near the second end 26 of the plate remote from said first end 25.
  • the gradual decrease in the plate's open area results from a decrease in the average diameter of the apertures 10, 9, 8, 7, 6, in the respective portions of the plate.
  • a plurality of apertures represented symbolically by the aperture 10, each having a diameter of about 4 millimeters are arranged in an array (one- or two-dimensional) near the first end 25 of the plate 5.
  • Another plurality of apertures, represented symbolically by the apertures 9, each having a 3.5 mm diameter are arranged in an array near the first array of the aperture 10.
  • Another array of apertures represented by apertures 8 and having a 3 mm diameter is located between the apertures' array 9 and another array of apertures represented by the apertures 7 having a 2.5 mm diameter.
  • the apertures become smaller as they approach the second end 26 of the floor plate.
  • the last array of apertures (closest to the second end 26) represented by apertures 6 comprises apertures of a diameter of 2 mm each. Said gradual decrease in the diameter of the apertures from the first end 25 of the plate 5 towards the second and 26, results in respective gradual decrease in the flow rate of air through the different open area regions in the plate.
  • the air jets injected from the different arrays (or groups) of cross apertures are represented by inverted truncated conic shapes 20, 19, 18, 17, and 16 delimited by respective pairs of inclined dotted lines.
  • the circulation path may further include flow components in directions angled to the plane of drawing. In certain cases, this will result in spiral-like global air flow throughout the cell.
  • the cell is delimited from above by a grid 40, through which air is constantly released from the cell during operation as to maintain a dynamic equilibrium in the cell while fresh hot air is constantly streamed into it through the bottom plate.
  • Arrows 41 to 52 represent the release of air through the grid.
  • a heat exchanger 56 which may be of any known suitable type, may be useful for saving energy, and is mounted above the cell's top grid 40.
  • the heat exchanger 56 is comprised of an array of air pipes 54 opened at their left end to receive fresh air represented by array of arrows 53. At their right end, the pipes 54 open to a duct 55 in air communication with a blower (not illustrated).
  • the fresh air 53 may be sucked into and through pipes 54 to the blower by the suction power of the blower itself, and alternatively or in order to boost the blower suction, by means of an additional suction device.
  • the hot air released through the top opening 57 of the heat exchanger 56 as indicated by arrows 49 to 52, is of a lower temperature than that of the air in the cell since a part of the heat is transferred to the fresh air in pipes 54.
  • the top opening 57 of the heat exchanger 56 preferably communicates with a flue, for delivering the exhausted air out of the plant building.
  • the cell 4 further comprises a product inlet opening 60 made along the rear wall 13 of the cell 4, through which a fresh product is to be fed into the device for dehydration.
  • the product inlet opening 60 is located at the bottom end of the rear wall 13 of the cell, right above the first end 25 of the plate 5.
  • a diagonally oriented feeding tray 61 is provided with lower end thereof attached to the lower end of the product inlet opening 60, such that the fresh product may be poured as indicated by arrow 68 from a feeding conveyor to be guided by the inlet slope tray 61 into the cell 4 through the opening 60.
  • the device of the present invention sorts the product automatically for exposing it to heat and mass exchange in correlation with its different wetness degrees during the dehydration process.
  • the width of the device influences the sorting quality of the cell between product amounts of different wetness stages.
  • a width of substantially not less than 1.7 meters was found to be substantially appropriate for good sorting quality.
  • the intensive circulations of the product through both the global and the local hot air flows result in an intensive heat and mass exchange and in a fast dehydration process.
  • the actual duration of the dehydration process depends on the specific product and on the parameters and adjustments of the specific device being used. Therefore, optimization of the process, its duration, and the resulting qualities of the prepared product may be achieved based on preliminary experiments to be made by a designer when adapting a specific device to a specific dehydration application.
  • two or three minutes process duration i.e. the average lasting time of individual product item inside the cell
  • this time may be shortened or lengthened (even significantly, e.g. to about 15 minutes) if so required.
  • the change may be carried out by changing the parameters of the device, e.g. its dimensions, the air pressure in the plenum, the temperature of the hot air/gas, the open area of the plate, the dimensions of the product outlet opening or any other device parameters.
  • an elevated member 69 lengthwise the second end 26 of the plate 5, with a row of horizontally oriented apertures 66, which inject substantially horizontal air jets 15. Furthermore, one or two rows of apertures are missing at the second end of the plate (i.e. the plate has no apertures near its second end 26), such that there is no interference of upwardly oriented air jets with the effect of the horizontally oriented air jets at this region.
  • the front wall 14 of the cell 4 has an inclined orientation for guiding the product to reach a region of less pressure created by the high velocity air jets 15 injected horizontally from the horizontally oriented apertures 66.
  • the horizontally oriented apertures 66 are of a diameter of between 3.5 and 4.5 millimeters, and preferably of about 4 millimeters diameter.
  • a gap formed between the bottom end of the diagonally oriented front wall 14 and the elevated member 69 near the second end 26 of the floor plate 5 is utilized to allow access into the cell through a service door 67 formed lengthwise said gap. When the need arises, the service door 67 may be opened allowing the device operator to reach the cell's inside and perform the required treatment (e.g. cleaning the plate or removing stacked product).
  • the inner surfaces of the cell are preferably smooth, and the corners of the cell are preferably round, in order to avoid product sticking and accumulation.
  • the walls of the device are preferably provided with heat isolation in order to reduce energy loss and also in order to protect surroundings and factory workers from heat damage.
  • the side walls of the device are preferably provided with transparent windows enabling inspection of the dehydration process.
  • hot air of temperatures of between about 130 to 220 Celsius degrees (and more preferably between 170 and 200 Celsius degrees) may be used without burning or damaging the product.
  • the exposure of the product to such temperatures is sufficient to neutralize any microorganisms, bacteria or spores, suspected to be present in the product, thus improving product quality and extending its shelf life term while eliminating the need for a separate disinfection process.
  • the relatively short process duration reduces the pulverization of the product thus improving the uniformity of the prepared product particles and reducing product loss.
  • the product outlet opening 62 is adjustable by means of a pivoting flap 63 whose orientation can be determined by a butterfly screw 64 (or alternatively by any other acceptable mechanism).
  • the orientation of the flap determines the dimensions of the gap 75 through which the prepared product may escape the cell.
  • the rate of release of product is slow, thus on average more product stays in the cell and is exposed to the dehydration process.
  • the gap is adjusted to be wider, and thus the rate of release of product becomes greater, the product stays on average less in the cell and is less exposed to the dehydration process. Accordingly, by sampling and checking the prepared product it is possible to determine whether or not the flap is adjusted properly, and to optimize the process and in turn the quality of the prepared product by adjusting the flap more accurately, if so required.
  • the flap 63 may be adjusted by the butterfly screw 64 to totally close the product outlet, in order to allow build-up of the required dynamic equilibrium inside the cell. After such an initial period, the flap 63 may be opened and adjusted such that there will be substantially equal amounts of prepared product evacuated through the outlet and of fresh product fed through the inlet.
  • the feeding slope tray 61 and between the plate 5, ending with opening 83 there is a gap between the feeding slope tray 61 and between the plate 5, ending with opening 83.
  • Said gap may be provided with a door, if so desired, and alternatively the height of the feeding slope tray 61 from above the plate 5 may be adjustable such that if so desired the lower end of the tray 61 may be brought to a contact with the end of the plate, thus canceling the opening 83.
  • the opening 83 is useful for automatic removal of parsley stems from the cell. The inventor has found that during the dehydration process the parsley stems, which become separated from the leaves, tend to accumulate on the plate, and thus by providing said gap and said opening 83, the stems may automatically be removed from the cell propelled by a breeze of hot air being part of the global air circulation in the cell. This way, the prepared product evacuated through the product outlet 62 requires no further sorting for separating stems.
  • Fig. 2 illustrates an example of dynamic equilibrium in the device of Fig. 1, during the dehydration process.
  • Fig. 3 illustrates a transverse cross section view of the device of Fig. 1, taken at the horizontal plane marked by arrows C-C of Fig. 1.
  • the device 1 includes an air supply plenum (not seen in this Fig.) located beneath the plate 5 and communicating through the duct 3 with air blower (not illustrated) for receiving pressurized hot air.
  • the air from the blower is heated on its way to the plenum by means of a burner (not illustrated).
  • the plenum communicates with the dehydration cell 4 located above the plate 5, through the plurality of apertures forming gas permeable open areas in the plate 5.
  • the open areas of respective portions of the plate decrease gradually in a direction along the plate, from near the first end 25 of the plate towards near the second end 26 of the plate remote from said first end 25.
  • Said gradual decrease in the diameter of the plate's apertures results in a respective gradual decrease in the flow rate of air flowing through the different open area regions in the plate.
  • Due to this unique air flow design global air circulation throughout the cell is generated.
  • the direction of this global circulation in the cell is from near the product inlet above the first end 25 of the plate and upwards towards the top of the cell, then turning left adjacent to the cell ceiling, and downwards from above the second end 26 of the plate towards the plate 5, thereafter to the right adjacent to the plate 5, and again upwards from above the first end 25, repeating said path recurrently.
  • the cell includes a product inlet opening made along a portion of the rear wall 13 against the product inlet tray 61 through which a fresh product is to be fed into the device for dehydration.
  • a large cell design is used, having side walls 90 and 91 which are significantly distant from one another.
  • the product inlet opening and the product outlet opening do not need to extend along the entirety of the quite long rear and front walls 13 and 14.
  • the product inlet opening 60 is located in the rear wall 13 against the inlet tray 61 near the side wall 90
  • the product outlet opening (62, not seen in this Fig.) is located in the front wall 14 right above the adjustable flap 63, near the opposite side wall 91.
  • the lengths of the inlet opening and of the outlet opening are substantially similar to the lengths of the inlet tray 61 and of the adjustable outlet flap 62, respectively. It can thus be appreciated according to this figure that both openings extend along only short portions of the rear and front walls respectively.
  • the cross sections of the cell in this embodiment are not the same along any chosen vertical plane parallel to the side walls 90 and 91. Actually, three different types of such vertical cross sections are distinguishable. In the first type, taken between the lines E-E near the side wall 90 the section crosses via the product inlet, but not via the product outlet opening (which is located near the cell's opposite side wall 91, remotely from the product inlet). In the second type, taken between the lines F-F near the side wall 91 the section crosses via the product outlet, but not via the product inlet (which is located near the first cell's side wall 90, remotely from the product outlet). In the third type, taken between the lines G-G at cell's center portion the section crosses neither through the inlet nor through the outlet (which are both located remotely from the center portion, near the side walls 90 and 91).
  • the asymmetric design of the cell in this embodiment adds to the global air flow circulation in the cell a diagonal flow component resulting from aix swept from the outside of the cell with the product entering through the product inlet and from air leaving the cell through the outlet opening. Accordingly, the product flow through the cell will also have a diagonal motion component, and the global flow path of the product through the cell from the inlet to outlet will be spiral.
  • the cell also includes a plurality of flow deflectors 101 to 105.
  • the flow deflectors are located near the cell's ceiling, leaving a free space between their bottom and the plate, e.g., in case the cell's ceiling is located 150 cm above the plate and the deflectors are of about 25-30 cm height, there will remain a free space of about 120-125 cm between the bottom of each deflector and the plate.
  • the deflectors which in the illustrated embodiment are partitions made of sheet metal plates, are positioned parallel to one another yet diagonally to the cell walls, with a predetermined gap between the adjacent deflectors.
  • the deflectors may extend about only 20% of the cell's height, from the point of view of the product flow they can be thought as partitioning the cell into a plurality of sub-cells. This is because the global flow of product through the cell is divided into a respective plurality of sub flows. Each such sub cell is defined between a pair of neighboring deflectors or between a side wall of the cell and a neighboring deflector. The sub cells communicate with one another beneath the deflectors where the global air circulation is weak while the local air circulations are more dominant.
  • the deflectors have a diagonal orientation respective to the cell's walls such that the near front wall's end 101a-105a of each deflector is closer to the side wall 90 (which is near the product inlet) than the near rear wall's end 101b-105b of the same deflector. Due to this diagonal orientation, the global flow in each sub-cell is deflected away from the outlet opening, such that the product quantities which were expected to advance with the spiral global flow from the product inlet towards the product outlet in some hypothetic flow rate (i.e. in case there were no deflectors) will now be delayed due to the deflection so that their actual flow rate will be smaller.
  • the flow of the product throughout the cell is spiral like.
  • fresh product is fed from a feeding conveyor onto the inlet slope of tray 61, it enters the cell through the inlet opening located in the rear wall 13 against the tray 61.
  • it is sucked into the cell due to under-pressure near the opening resulting from high velocity air jets injected uprightly from the floor plate 5 near the inlet opening.
  • the fresh product is then swept upwardly by the air jets adjacent to the inlet (and may be also by some further adjacent less great flow rate air jets) to join the upper part of the global circulation in the cell indicated by arrows 32 to 35 and then join the lower part of the global circulation indicated by arrows 37 to 39 and 30.
  • the upper part of the global circulation narrows as it comes closer to the front wall 14, due to the diagonal orientation of the deflectors 101 -105. This causes the product swept by the upper part of the global circulation to deflect and converge toward the side wall 90. The product at the upper part of the global circulation thus becomes denser when approaching the front wall 14. Since the lower part of the cell is not partitioned by the deflectors, the product diverges when reaching the lower part of the global circulation, and thus flows somewhat diagonally as indicated by arrows 106-110. A similar converging and diverging process of the product flow is repeated with respect to each of the deflectors, until the product reaches the cell's end near the side wall 91, and thereafter it is released through the outlet.
  • the device of the present invention sorts the product automatically, thus exposing it to heat and mass exchange in correlation with the product's different wetness degrees during the dehydration process.
  • an elevated member 69 lengthwise the second end 26 of the floor plate 5, with a row of horizontally oriented apertures 66, which inject substantially horizontal air jets 15. Furthermore, one or two rows of the apertures are missing at the second end of the plate such that there will be no interference of the upwardly oriented air jets with the effect of the horizontally oriented air jets at this region. Also, the front wall 14 of the cell 4, has a diagonal orientation for guiding the product to reach the low-pressure region created by the high velocity air jets 15 injected horizontally from the horizontally oriented apertures 66.
  • the horizontally oriented apertures 66 are of a diameter of between 3.5 and 4.5 millimeters, and preferably of about 4 millimeters diameter.
  • the side walls 90, 91 of the device are preferably provided with transparent windows 92 and 93 respectively, making the dehydration process visible.
  • Fig. 4 illustrates a general top view of some portions of the plate 5 of the device of Fig. 1.
  • a plurality of through apertures 10, 9, 8, 7, 6 is formed in the plate.
  • the apertures are arranged such that the open areas gradually decrease in a direction (as for example indicated by arrow R) along the plate. This decrease can be made by reducing the number of apertures per unit area in a direction along the plate, by reducing the area of each aperture or of groups of apertures in direction along the plate (i.e. without changing the number of apertures per unit area), or a combination thereof (i.e. reducing the number of apertures and their diameters).
  • the number of apertures per unit area remains unchanged, and the open areas of the respective plate portions decrease since the apertures are arranged in arrays, each of which contains apertures of greater diameter compared to a neighboring one in a specific direction along the plate.

Abstract

La présente invention concerne un dispositif (1) et un procédé de déshydratation d'un produit, particulièrement utiles pour réduire la teneur en eau des légumes à feuilles tels que le persil, le dispositif (1) comprenant une cellule de déshydratation (4) possédant une admission de produit (60), une sortie de produit (62) et une plaque de fond (5) pourvue d’une pluralité d’ouvertures (6 à 10) formant des zones ouvertes perméables aux gaz. Les ouvertures (6 à 10) sont disposées de telle sorte que les zones ouvertes diminuent progressivement dans une direction entre les première et seconde extrémités (25, 26) de la plaque (5) sur la largeur de la plaque de telle sorte que, lorsque le gaz est introduit dans la cellule (4) à travers la pluralité d’ouvertures (6 à 10), une pluralité de gicleurs de gaz séparés respectifs (16-20) éjectent vers le haut depuis la plaque (5) avec un débit de gaz diminuant dans ladite direction le long de la plaque créant de ce fait une circulation directionnelle globale (30 à 39) du gaz dans la totalité de la cellule (4) et une pluralité de circulations locales (70 à 72, 76 à 78) dudit gaz à l'intérieur de la cellule (4).
PCT/IL2006/001323 2005-11-17 2006-11-16 Dispositif et procede de deshydratation WO2007057896A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IL172012 2005-11-17
IL172012A IL172012A0 (en) 2005-11-17 2005-11-17 Dehydration apparatus and method

Publications (1)

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WO2007057896A1 true WO2007057896A1 (fr) 2007-05-24

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103673529A (zh) * 2013-12-09 2014-03-26 李仲之 一种晒粮机

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GB2085564A (en) * 1980-10-01 1982-04-28 Mccloy John Frederick Fluidised bed drier
DE3325967A1 (de) * 1983-07-19 1985-02-07 NEOTEC Gesellschaft für Nahrungsmittelverfahrenstechnik mbH & Co KG, 2000 Norderstedt Wirbelschicht-vorrichtung
WO1988004020A1 (fr) * 1986-11-21 1988-06-02 Moszkowski Stefan J Dispositif de sechage pour materiau granulaire
US5020239A (en) * 1990-06-08 1991-06-04 Wenger Manufacturing, Inc. Air suspension enrober
EP0451546A2 (fr) * 1988-05-09 1991-10-16 Bühler Ag Tour de traitement d'un matériau pulvérulent ou granuleux, et procédé pour sa mise en oeuvre
DE4416666C1 (de) * 1994-05-11 1995-08-31 Rieter Automatik Gmbh Vorrichtung zum Entwässern und Trocknen von Feststoffen, insbesondere von unterwassergranulierten Kunststoffen
JPH07265683A (ja) * 1994-04-01 1995-10-17 Freunt Ind Co Ltd 流動層装置および粉粒体の造粒、コーティング、乾燥方法
EP1452224A1 (fr) * 2003-02-28 2004-09-01 Herbert Dr. h.c. Hüttlin Dispositif en forme de tunnel pour traiter une matière particulaire
EP1584371A1 (fr) * 2004-04-07 2005-10-12 Urea Casale S.A. Procede et dispositif de granulation en lit fluidise

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Publication number Priority date Publication date Assignee Title
US2513369A (en) * 1946-07-02 1950-07-04 Terminal Island Sea Foods Ltd Drying by fluidization of the work
GB663121A (en) * 1949-07-19 1951-12-19 Oswald Stott Improvements in machines for drying grass, grain and the like
GB730789A (en) * 1950-12-16 1955-06-01 Ruhrchemie Ag Process and apparatus for the continuous treatment of granular materials with gases
GB843705A (en) * 1957-04-05 1960-08-10 Buettner Werke Ag A drier, more particularly for material of low specific gravity
US3360867A (en) * 1965-11-18 1968-01-02 Komline Sanderson Eng Corp Batch-type fluidizing apparatus and process
FR1499678A (fr) * 1966-11-09 1967-10-27 Molekularzerstaubung Meissen V Appareil de séchage à courant hélicoïdal
US4033555A (en) * 1971-01-11 1977-07-05 The Motch & Merryweather Machinery Company Fluidized bed for treating granular material
DE2165345A1 (de) * 1971-07-23 1973-02-01 Buettner Schilde Haas Ag Trockner fuer schuettgueter
DE3045134A1 (de) * 1980-01-16 1981-08-27 VEB Schwermaschinenbau Kombinat "Ernst Thälmann" Magdeburg, DDR 3011 Magdeburg Vorrichtung zur strahlschichttrocknung von feststoffen mit gasfoermigen medien
GB2085564A (en) * 1980-10-01 1982-04-28 Mccloy John Frederick Fluidised bed drier
DE3325967A1 (de) * 1983-07-19 1985-02-07 NEOTEC Gesellschaft für Nahrungsmittelverfahrenstechnik mbH & Co KG, 2000 Norderstedt Wirbelschicht-vorrichtung
WO1988004020A1 (fr) * 1986-11-21 1988-06-02 Moszkowski Stefan J Dispositif de sechage pour materiau granulaire
EP0451546A2 (fr) * 1988-05-09 1991-10-16 Bühler Ag Tour de traitement d'un matériau pulvérulent ou granuleux, et procédé pour sa mise en oeuvre
US5020239A (en) * 1990-06-08 1991-06-04 Wenger Manufacturing, Inc. Air suspension enrober
JPH07265683A (ja) * 1994-04-01 1995-10-17 Freunt Ind Co Ltd 流動層装置および粉粒体の造粒、コーティング、乾燥方法
DE4416666C1 (de) * 1994-05-11 1995-08-31 Rieter Automatik Gmbh Vorrichtung zum Entwässern und Trocknen von Feststoffen, insbesondere von unterwassergranulierten Kunststoffen
EP1452224A1 (fr) * 2003-02-28 2004-09-01 Herbert Dr. h.c. Hüttlin Dispositif en forme de tunnel pour traiter une matière particulaire
EP1584371A1 (fr) * 2004-04-07 2005-10-12 Urea Casale S.A. Procede et dispositif de granulation en lit fluidise

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103673529A (zh) * 2013-12-09 2014-03-26 李仲之 一种晒粮机
CN103673529B (zh) * 2013-12-09 2015-08-19 李仲之 一种晒粮机

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