Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
  • B29B13/00—Conditioning or physical treatment of the material to be shaped
  • B29B13/02—Conditioning or physical treatment of the material to be shaped by heating
• • 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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D9/00—Crystallisation
  • B01D9/0018—Evaporation of components of the mixture to be separated
  • B01D9/0031—Evaporation of components of the mixture to be separated by heating
• • 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
  • B01J2/00—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic
  • B01J2/16—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic by suspending the powder material in a gas, e.g. in fluidised beds or as a falling curtain
• • 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
  • B01J8/1836—Heating and cooling the reactor
• • 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
  • B01J8/24—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles according to "fluidised-bed" technique
• • 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
  • B01J8/24—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles according to "fluidised-bed" technique
  • B01J8/26—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles according to "fluidised-bed" technique with two or more fluidised beds, e.g. reactor and regeneration installations
• • 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
  • B01J8/24—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles according to "fluidised-bed" technique
  • B01J8/34—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles according to "fluidised-bed" technique with stationary packing material in the fluidised bed, e.g. bricks, wire rings, baffles
• • 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
  • B01J8/24—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles according to "fluidised-bed" technique
  • B01J8/36—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles according to "fluidised-bed" technique with fluidised bed through which there is an essentially horizontal flow of particles
• • 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
  • B01J8/24—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles according to "fluidised-bed" technique
  • B01J8/44—Fluidisation grids
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
  • B29B13/00—Conditioning or physical treatment of the material to be shaped
  • B29B13/02—Conditioning or physical treatment of the material to be shaped by heating
  • B29B13/021—Heat treatment of powders
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
  • B29B13/00—Conditioning or physical treatment of the material to be shaped
  • B29B13/06—Conditioning or physical treatment of the material to be shaped by drying
• • 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
  • B01J2208/00—Processes carried out in the presence of solid particles; Reactors therefor
  • B01J2208/00008—Controlling the process
  • B01J2208/00017—Controlling the temperature
  • B01J2208/0053—Controlling multiple zones along the direction of flow, e.g. pre-heating and after-cooling
• • 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
  • B01J2208/00—Processes carried out in the presence of solid particles; Reactors therefor
  • B01J2208/00008—Controlling the process
  • B01J2208/00548—Flow
  • B01J2208/00557—Flow controlling the residence time inside the reactor vessel
• • 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
  • B01J2208/00—Processes carried out in the presence of solid particles; Reactors therefor
  • B01J2208/00008—Controlling the process
  • B01J2208/00619—Controlling the weight
• • 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
  • B01J2208/00—Processes carried out in the presence of solid particles; Reactors therefor
  • B01J2208/00008—Controlling the process
  • B01J2208/00654—Controlling the process by measures relating to the particulate material
  • B01J2208/00672—Particle size selection
• • 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
  • B01J2208/00—Processes carried out in the presence of solid particles; Reactors therefor
  • B01J2208/00008—Controlling the process
  • B01J2208/00654—Controlling the process by measures relating to the particulate material
  • B01J2208/00681—Agglomeration
• • 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
  • B01J2208/00—Processes carried out in the presence of solid particles; Reactors therefor
  • B01J2208/00796—Details of the reactor or of the particulate material
  • B01J2208/00823—Mixing elements
  • B01J2208/00831—Stationary elements
  • B01J2208/0084—Stationary elements inside the bed, e.g. baffles
• • 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
  • B01J2208/00—Processes carried out in the presence of solid particles; Reactors therefor
  • B01J2208/00796—Details of the reactor or of the particulate material
  • B01J2208/00884—Means for supporting the bed of particles, e.g. grids, bars, perforated plates
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2067/00—Use of polyesters or derivatives thereof, as moulding material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2995/00—Properties of moulding materials, reinforcements, fillers, preformed parts or moulds
  • B29K2995/0037—Other properties
  • B29K2995/0041—Crystalline
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
  • C08G63/88—Post-polymerisation treatment

Definitions

• the invention relates to a device for the continuous thermal treatment of granular bulk materials, in particular for crystallizing polymer granules, such as e.g. Polyethylene terephthalate (PET), with a product inlet that opens into a first most upstream chamber and a product outlet that connects to a most downstream chamber.
• the invention also relates to a method for the continuous thermal treatment of a granular bulk material, in particular for crystallizing polymer granules, such as e.g. Polyethylene terephthalate (PET), using the device according to the invention.
• PET Polyethylene terephthalate
• Such a device is e.g. known from EP 0 712 703 A2. It consists of a housing with an input and an output for thermally treated plastic flakes (chips). The interior of the housing is divided by a plurality of partitions into a first large chamber and a number of smaller chambers, the partition between the first chamber and the chambers adjoining it being higher than the partitions between the respective smaller chambers. All chambers can be gassed from below via a sieve tray in order to fluidize the flaky product. In operation, the fluidized product flows from chamber to chamber over the upper edge of the respective partition.
• Unwanted backmixing can occur due to the bubbling movement in the respective fluidization chambers, in that flakes spring back from a chamber or are blown back into the chamber located upstream from it. This then results in different residence time spectra for different flakes, which inevitably leads to flakes with different product quality.
• DE 195 00 383 A1 discloses a device for the continuous crystallization of polyester material in granular form.
• the thermal treatment takes place in a cylindrical treatment room, which is also gassed from below through a sieve tray in order to fluidize the granulate with the treatment gas.
• the Ver- Turning only one treatment room, in which the fluidization takes place, saves costs and makes the use of stirring tools and the like superfluous, but here too a very narrow residence time spectrum of the particles and thus a largely uniform product quality of the granules cannot yet be achieved.
• EP 0 379 684 A2 discloses an apparatus and a method for the continuous crystallization of polyester material in granular form.
• the device consists of two separately arranged fluidization chambers (fluidized bed apparatuses), the first chamber being a bubbling fluidized bed with a mixing characteristic and the second chamber being a fluidized bed with a piston flow characteristic.
• This combination of two different fluidization chambers achieves a surprisingly homogeneous product quality, but each of the two separate fluidized bed apparatuses requires its own circuit with channels, fans, heat exchangers for the gassing and fluidizing gas, and cyclone separators or filters for separating dust that is caused by abrasion from the granulate particles.
• the present invention is therefore based on the object of providing an inexpensive and easy-to-operate device and a method of the type mentioned at the beginning, in which or in which a narrow residence time spectrum of the fluidized and thermally treated granulate particles in the device and thus a homogeneous product quality is achieved ,
• the device has a plurality of adjoining fluidization chambers, each with a sieve bottom, through which a fluidization gas for fluidizing the granules can be blown into the respective chamber, which escape via a gas outlet in the ceiling area of the device can, wherein the first chamber occupies a large part of the total volume of all chambers, and that adjacent chambers each have a fluid connection via product passages in the partition walls arranged between them.
• Product passages between adjacent chambers are preferably arranged on the bottom side between the sieve bottom and a lower end region of the dividing wall between the adjacent chambers.
• the product passages can also be arranged between adjacent chambers on the wall side between a side wall and a lateral end region of the partition between the adjacent chambers.
• Product passages are also expediently arranged in the partition approximately at the height of the upper end of the fluidized bed.
• the product passages extend over the entire width or over the entire height of the device from one side wall to the other side wall or from the sieve bottom to the upper end of the fluidized bed, the product passages preferably being designed as horizontal or vertical slots.
• the slit-like product passages each extend along the entire width or along the entire height of a partition.
• only horizontal slots are used as product passages in order to achieve a narrow residence time spectrum.
• the product passages are arranged alternately on the floor and at the level of the upper end of the fluidized bed on dividing walls which follow one another along the product conveying direction.
• the product passages were on the floor in the case of successive partition walls, a particle could, under certain circumstances, migrate directly from product passage to product passage through this chamber without being in this chamber for longer. This would be counterproductive for the narrow residence time spectrum aimed for in the device.
• the product passages can also be arranged alternately on the left-hand end of the wall and on the right-hand end of the dividing wall on partitions that follow one another along the product conveying direction.
• the particles are forced here on a slalom-like path within the device.
• Both the roller coaster configuration and the slalom configuration have a positive effect on the homogenization of the product residence times and thus additionally contribute to the multi-chambered nature of the device for a narrow residence time spectrum.
• the position of the product passages is adjustable. This allows product-specific optimizations to be carried out, e.g. an adjustment of the average residence time of the granules in the device.
• the cross-sectional extent of the product passages is adjustable. This enables optimization by adapting to the respective grain size of the granulate.
• a minimum dimension, in particular the slot width of the cross-sectional dimension of the product passages is preferably set such that it lies in the range between a minimum granule dimension and approximately 20 cm.
• a particularly preferred minimum dimension, in particular the slot width of the cross-sectional dimension of the product passages is in the range between twice the minimum granule dimension and approximately 10 times the minimum granule dimension. Also this helps to make a direct flow through a chamber for a granulate particle from the entrance into the chamber to the exit from the chamber less likely. Thus, at least short dwell times are made practically impossible. This is particularly advantageous and useful for the crystallization of polyesters such as PET, since a too short dwell time of a polyester pellet leads to inadequate crystallization, which results in pellets that tend to stick.
• Another preferred embodiment is characterized in that the bottom or the product passages arranged approximately at the level of the upper end of the fluidized bed in the partition or the wall-side product passages are each essentially parallel to the bottom or the respective side wall and essentially perpendicular to the partition have arranged sheet metal, which is attached to the edge of the respective product passage and extends through the product passage on both sides of this partition in each case into the two adjacent chambers. In this way, a product passage is created, which is designed as a kind of tunnel between this sheet and the floor or the side wall.
• a particle that gets into this tunnel against the predominant flow of the fluidized product is therefore likely to be reflected back and forth between the tunnel walls and thus has a longer dwell time in the product passage, which greatly increases the likelihood that sooner or later it will be caused by impacts entrained with other particles of the fluidized product stream.
• This version of the tunnel also makes backmixing with the negative consequences mentioned more difficult and ultimately makes it practically impossible.
• the sieve tray in the area of the product passages at the bottom and essentially opposite the sheet metal, there are blow-in areas in the sieve tray which allow fluidizing gas to be blown into the chamber at a speed. which enables both a speed component perpendicular to the blowing area and a speed component parallel to the blowing area in the direction of the fluidized granulate flow.
• so-called Konidur sheet metal is preferably used, in which the openings of the sieve bottom are not formed by completely punching out and removing material, but rather are formed by only partially punching out and then bending over the partially punched-out material part.
• the first chamber via its sieve plate to an associated feed channel for fluidizing gas, which is separated from a common feed channel for the remaining chambers.
• This can e.g. can be achieved by a common air circuit which has a branch in front of the sieve plate of the first chamber and the common sieve plate of the remaining chambers, an adjustable flap being provided in each branch serving as a feed line to the respective sieve plate and as a discharge line from the respective chambers of the device , by means of which the gas distribution and thus also the gas velocity for the fluidization of the respective chambers can be adjusted.
• This enables the first chamber to be gassed and fluidized under different conditions than the remaining chambers.
• the higher gas velocity means greater fluidization and thus more Prevention of agglomerate formation is effected.
• an impact resolver is provided at the product outlet, into which the product outlet opens. This impact resolver finally dissolves agglomerates that have formed despite all the other precautions.
• the sieve trays of all chambers can be arranged on one level.
• the device can consist of chambers lined up along the fluidized granulate stream with mutually offset heights.
• the first chamber is preferably defined in its floor plan by a wall which surrounds it cylindrically, and the remaining chambers are concentrically connected radially outward around the first chamber with cylindrical walls. This design is particularly space and material saving, and the heat losses are also low.
• the first chamber can be defined by a pair of concentric cylindrical walls, the remaining chambers within the inner cylindrical wall of the first chamber adjoining radially inward concentrically with cylindrical walls.
• the plan of the first chamber can also be rectangular and the remaining chambers adjoin the outside of the first chamber.
• the rectangular shape is particularly easy to build.
• the first chamber can also be rectangular in shape here, with the remaining chambers inside the first chamber e.g. connect nested with each other with a rectangular plan concentrically.
• the remaining chambers are each designed in such a way that the ratio between the layer height of the fluidized granules and the smallest floor plan chamber dimension is in the range from 0.5 to 2.
• This preferred benchmark for that This ratio ensures that no excessive blistering can take place inside the fluidized product. If the layer height of the fluidized product is much greater than twice the smallest floor plan chamber dimension, many small bubbles can form a few or even one large bubble during the ascent, which due to the decreasing gravitational pressure in the fluidized Move the product upwards and then create impacts when reaching the fluidized bed surface and / or cause the granulate particles to be thrown around. On the other hand, if the floor is only thinly covered with product, economical fluidization is not possible.
• the most upstream first chamber preferably takes up a large part of the total volume of all chambers, in particular approximately half of the total volume of all chambers.
• the sieve bottom surface of the first chamber expediently also takes up a large part of the total sieve bottom surface of all the chambers, again about half of the total sieve bottom surface of all chambers. This is particularly advantageous in the crystallization of polyester. As a result, extensive crystallization can be achieved in the first chamber in a first crystallization step for the majority of all particles. Since individual particles are still sticky in this first phase, it is particularly important to generate large-volume fluidization with a lower particle density in the first chamber than in the subsequent remaining chambers. Then the likelihood of two sticky particles hitting each other and thus agglomerate formation is much less.
• the product outlet in a wall is expediently designed like a window with a slide, by means of which the lower edge of the window can be adjusted.
• the product outlet can be designed as a kind of pivotable weir, the height of which can be adjusted by pivoting the weir.
• a so-called zigzag separator is arranged in front of the fluidized bed, which allows gas to pass through and holds up granulate particles and directs them back into the fluidized bed.
• the granules are passed through the several fluidizing chambers arranged in a row, each having a sieve plate through which a fluidizing gas (for example pure nitrogen or air) is blown into the respective chamber from below to fluidize the granules and is drawn off in the ceiling area of the device, the absolute filling level of the fluidized granules in the first chamber is at least as high as the absolute filling level of the remaining chambers downstream.
• a fluidizing gas for example pure nitrogen or air
• fluidization gas is blown into all chambers with a uniform first treatment temperature, the fluidization gas preferably also being used as a heat source for heating the fluidized granulate.
• This uniform first treatment temperature is in the case of crystallization of PET about 180 C C.
• the still predominantly amorphous starting material occurs in the form of pellets with a temperature of about 20 ° C and at this low temperature non-adhesive in the first chamber.
• In the first chamber there is still no complete heat transfer to the PET granulate, which in turn is advantageous since the tendency to stick when heated is still very strong in the amorphous or only slightly crystallized state.
• the fluidizing gas can at least partially contain a gas reacting with the fluidized granulate. This can be a disinfectant or flavoring gas, for example when drying food.
• a fluidizing gas with a second treatment temperature is expediently blown into at least one of the remaining chambers and is preferably used as a heat sink for cooling the fluidized granules.
• Fluidizing gas is preferably blown into all chambers with the same excess pressure and the same gas velocity. If necessary, however, fluidizing gas can be blown into the first chamber at a higher pressure and / or higher gas velocity than in the remaining chambers.
• the higher gas velocity leads to greater fluidization, i.e. Expansion of the fluidized bed, while the higher gas pressure enables more heat to be supplied via the fluidizing gas.
• Fig. 1 is a sectional view along a vertical plane of a first
• Embodiment of the invention is;
• Fig. 2 is a sectional view along a vertical plane of a second
• Embodiment of the invention is;
• 3a and 3b are a sectional view along a vertical plane and a
• Fig. 4 is a sectional view along a horizontal plane of a third embodiment of the invention.
• FIG. 4 is a diagram showing the dependence of the residence time spectrum of granulate particles in the device according to the invention as a function of the number of chambers of the device;
• 5a and 5b schematically show a one-stage fluidized bed and a 5-stage fluidized bed, respectively;
• 5c shows the local temperature profile of the product of the fluidized bed from FIG. 5a or the fluidized bed from FIG. 5b;
• 6b shows a second special embodiment of the product passages between the chambers in an enlarged view.
• the device 1 schematically shows a vertical sectional view of a first exemplary embodiment of the device 1 according to the invention.
• the device 1 according to the invention forms a multi-box crystallizer with a housing 13, in the interior of which several chambers 2, 3, 4, 5 and 6 are separated from one another by partition walls 14, 15, 16 and 17 are separated.
• the bottom of the chambers is formed by a sieve bottom 11 through which a fluidizing gas can be blown in from below.
• the chambers are delimited at the top by a zigzag separator 12, which forms the chamber ceiling.
• the front and rear boundaries of the chambers 2, 3, 4, 5 and 6 run parallel above and below the plane of the drawing and are therefore not shown in the sectional view.
• the product to be fluidized and thermally treated which is in particular polyethylene terephthalate (PET)
• PET polyethylene terephthalate
• Fluidizing gas is introduced via a gas inlet 9 blown into the device 1 below the sieve tray 11 and, after it has passed through the zigzag separator 12, is drawn off via a gas outlet 10 in the ceiling area of the device 1.
• the granulate entering the device 1 first reaches the first chamber 2, which takes up a large part of the total chamber volume, and is fluidized by the fluidizing gas entering via the sieve tray 11, whereby a fluidized bed 23 of granules and fluidizing gas is formed.
• the fluidized bed behaves like a fluid, i.e.
• a gravitational pressure forms within the fluidized bed, and the fluidized bed flows through the product passages 18, 19, 20 and 21 between a lower end region of the partition walls 14, 15, 16 and 17 respectively and the sieve plate 11 from the first chamber 2 into the adjoining chambers 3, 4, 5 and 6.
• a window 22 in the end wall at a certain height above the sieve plate 11 and defines this height the height of all fluidized beds 23 in all chambers 2, 3, 4, 5 and 6.
• the fluidized bed 23 is shown schematically in FIG.
• Bubbles can form within the fluidized bed 23, which rise upward within the fluidized bed and can combine to form larger bubbles 24, which burst as soon as they reach the fluidized bed surface 26 and can hurl the granules around within the chamber. This is shown schematically in the area of reference number 25.
• FIG. 2 shows a vertical sectional view of a second exemplary embodiment of the device 1 according to the invention.
• the second exemplary embodiment differs from the first exemplary embodiment in that in the successive partition walls 14, 15, 16 and 17 between the chambers 2, 3, 4, 5 and 6, the product passages 28, 29, 30 and 31 are arranged alternately at a certain height above the sieve plate 11 in the partitions 14 and 15 and directly on the sieve plate 11 in the partitions 15 and 17.
• the granulate particles are transported on their way through the chambers 2, 3, 4, 5 and 6 in an alternating way running up and down, similar to a roller coaster.
• This has the advantage that the upstream product passage and the downstream product passage are as far apart as possible in each chamber.
• all of the granulate particles are forced as long as possible through each of the chambers 3, 4, 5 and 6, which at least ensures that as few granule particles as possible have a short residence time.
• FIG. 3a shows a vertical sectional view of a third exemplary embodiment of the device 1 according to the invention
• FIG. 3b shows a horizontal sectional view of this third exemplary embodiment.
• the device 1 consists of a centrally arranged cylindrical chamber 2, which in turn takes up a large part of the entire chamber volume of the device 1, and of peripheral chambers 3, 4, 5 and 6, which are separate connect radially to the central chamber 2 and surround it along its entire circumference.
• the central chamber 2 is separated by a partition 14 from the radially surrounding chambers 3, 4, 5 and 6, which in turn are limited to the outside by the housing wall 13.
• FIG. 3a At a certain height above the sieve bottom (FIG. 3a) there is a product passage 18 which forms the connection between the first chamber 2 and the second chamber 3.
• the product passages between the chambers 3, 4, 5 and 6 are not shown. However, they correspond to the product passages 18, 19, 20 and 21 of FIG. 1 and the product passages 28, 29, 30 and 31 of FIG. 2.
• the height and / or cross-sectional dimension of the window 22 can be adjustable both in FIG. 1 and in FIG. 2 and in FIG. 3b.
• the height of the fluidized bed 23 is determined by the adjustability of the height, while the throughput through the device 1 can be adjusted by the adjustability of the cross-sectional dimension.
• the product passages can only be arranged on the floor (see product passages 18, 19, 20 and 21 in FIG. 1), or they can alternate at the top and be arranged below, which creates a roller coaster arrangement (see product passages 28, 29, 30 and 31 in Fig.
• FIGS. 1, 2 and 3a and 3b Three different exemplary embodiments of the device 1 according to the invention have been described in FIGS. 1, 2 and 3a and 3b described above. In all three cases, there are different construction variants of a 5-stage fluidized bed 23. They differ in the arrangement of the chambers 2, 3, 4, 5, 6 and the product passages 18, 19, 20, 21; 28, 29, 30, 31 and the product openings 22.
• the 5-stage fluidized bed 23 each consists of a large chamber 2, the (main) crystallization chamber, and four subsequent smaller chambers 3, 4, 5, 6 of the same size, which for are responsible for the homogenization of the product.
• the chambers 3, 4, 5, 6 are either strung together or arranged concentrically around the larger chamber 2.
• the fluidized bed apparatuses 1 are fed by a single gas supply. Due to the pressure drop across the sieve plate 11 and the fluidized bed 23, the gas is distributed over the individual chambers 2, 3, 4, 5, 6.
• the product passages 18, 19, 20, 21; 28, 29, 30, 31 are arranged below, above or alternately below / above. In the exemplary embodiment of FIG.
• a fluidized bed 23 of uniform height is established in the chambers 2, 3, 4, 5, 6 due to the product passages 18, 19, 20, 21 located below. This can be regulated by the height of the product outlet window 22 in the last chamber 6.
• the layer height of the fluidized bed 23 in the chamber 2, the chambers 3 and 4 and the chambers 5 and 6 can be adjusted independently of one another due to the product passages 28, 29, 30, 31 alternating at the top and bottom by the height position of the overhead product passages 28, 30 is set.
• 5a and 5b schematically show a one-stage and a 5-stage fluidized bed.
• 5c shows as a result of a calculation example the local course of the product temperature of both this single-stage and this 5-stage fluidized bed.
• the local product temperature profile (temperature distribution) of the 5-stage fluidized bed was compared with the local product temperature profile (temperature distribution) of the single-stage fluidized bed.
• the product throughput and the operating parameters represent the industrial plants built today. It must be noted at this point that the heat of crystallization released was taken into account in the heat balance of the first chamber (a large part of the exothermic crystallization reaction also takes place here).
• the efficiency of the heat exchange between gas and granules could be significantly improved, while improving the quality and homogeneity of the end product.
• the thermal efficiency (defined and measured as the ratio [product temperature at the product outlet - product temperature at the product inlet] / [treatment gas temperature at the gas inlet - product temperature at the product inlet]) was increased by around 7.5% for this example. Due to the higher product temperature after crystallization, a subsequent process step for solid-phase post-condensation (SSP) can be saved on the apparatus size required there.
• SSP solid-phase post-condensation
• the multi-stage fluidized bed of the present invention is characterized both by an improved, i.e. narrower residence time spectrum of the product in this multi-stage fluidized bed as well as an improved, i.e. increased thermal efficiency of the thermal treatment of the product.
• 6a and 6b show a particularly advantageous first embodiment of the product passages between the chambers of the device according to the invention.
• FIG. 6a corresponds to a detail from FIG. 1, which shows the partition walls 14, 15, 16 and 17 in their lower region in the vicinity of the sieve plate 11.
• the sieve bottom 11 has Holes 11a formed by punching out material and removing material.
• the lower end of the partitions 14, 15, 16 and 17 is provided with a guide plate 33, 34, 35 and 36 in this embodiment, which is on both sides of the respective partition and perpendicular to it into the chambers extends on both sides of the respective partition.
• FIG. 6b shows a second embodiment of the product passages 18, 19, 20, 21 which is improved compared to the first embodiment of FIG. 6a.
• the section of FIG. 6b corresponds to the section of the first embodiment of the product passages circled in FIG. 6a with the difference that here in the area of the tunnel opposite the respective guide plate 33, 34, 35, 36, the sieve plate 11 has holes 11b, which were formed by only partially punching out material and bending this partially punched out material. Through these holes 11b, in addition to their vertical fluidization component perpendicular to the direction of flow of the granulate, a movement component parallel to and in the same direction as the direction of flow of the granulate is impressed on the blown-in air. This makes backmixing even less likely than in the embodiment of FIG. 6a.
• Sieve plate a punched holes with removed material b partially punched holes with bent material

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