GB2419659A

GB2419659A - A continuous multistage drying tower heated with microwaves comprises plural fluidised beds

Info

Publication number: GB2419659A
Application number: GB0423911A
Authority: GB
Inventors: Amedeo Pagotto
Original assignee: S M C Srl
Current assignee: S M C Srl
Priority date: 2004-10-28
Filing date: 2004-10-28
Publication date: 2006-05-03
Also published as: GB0423911D0

Abstract

A continuous multistage evaporator-dessicator apparatus A for melted or granular material comprises a container 1 with several vertical stages S and a rotating stirrer 13, 14, 40. Each stage S corresponds to an intercommunicating chamber with at least one adjacent chamber, where on the interior of said chambers a fluidised bed (8, 9, 10, figs. 3-5) to support the material is provided, that is permeable and compatible with microwaves. An upper part of each fluidised bed (8, 9, 10, figs. 3-5) is in communication with the stirrer 13, 14, 40 and a lower part of each fluidised bed (8, 9, 10, figs. 3-5) defines a cavity 11 that communicates with a unit 12 that generates a controlled airflow. There is provided at least one vacuum pump group 16 that controls the atmospheric environment on the interior of the intercommunicating chambers. A logic control unit may be provided that controls the ventilation, temperature and atmospheric pressure in each chamber. The fluidised beds (8, 9, 10, figs. 3-5) may comprise a porous plastic panel of propylene. The fluidised beds (8, 9, 10, figs. 3-5) may comprise modular ceramic elements. The vacuum pump group 16 may be connected to a number of valves linked to the logic controller. There may be provided at least one microwave generator 15 and at least one fan 12 provided per chamber.

Description

CONTINUOUS, MULTISTAGE EVAPORATORDESSICATOR TOWER,

WITH CHAMBERS HEATED BY MICROWAVE DEVICES FOR THE

TREATMENT IN AN ATMOSPHERIC ENVIRONMENT CONTROLLED

BY MELTED OR GRANULAR MATERIALS

The main aim of this invention is an apparatus with a continuous, fluidised evaporator-dessicator function of the microwave and vacuum type, for the treatment of melted or granular material along a vertical tower.

FIELD OF USE OF THE INVENTION

The invention finds particular if not exclusive application in the field of treatments of granular or melted materials, conventionally indicated as materials, intended to reduce or control the percentage of humidity in said materials.

It is certainly known that many materials once collected, whether they are natural, raw or even semi-worked, such as for example the plastic material in granules for plastic product stamping apparatus or for foodstuffs such as cereals, can present more or less high humidity percentages that are completely undesirable for the subsequent processes.

The result it that to allow the use of said materials, conventionally not treated in usual production draw-plates, and all things considered with the purpose of improving the yield and quality of the finished product, the more or less considerable reduction of the humidity percentage found at the origin is often rendered necessary. In the case of cereals such as grain, for example, if said cereals are collected in large containers even if only temporarily, or packaged for long periods without treatment allowing an uncontrolled humidity percentage, the result would be fermentation that causes the production of yeast, mould and the like to the detriment of the quality of the product.

It is therefore a priority to devise processes and apparatus that have the control, if not total elimination, of the percentage of humidity as a main aim. These processes and the relative apparatus, pioréssively being developed over time, substantially intend to use devices capable of achieving the evaporation of the water, a result achieved by means of the use of thermal energy or with the aid of dry gas. In other words, on the interior of a container, previously filled with material, according to certain working cycles, the material itself is spread over by one of the forms of water removal or by both, in order to reduce it progressively. In certain cases, there are containers for treatment where the material is substantially static, in others said material is dynamic, sometimes also fluidised, following a certain process that is divided into more treatment stages.

PRIOR ART

Several different designs are known in the related literature that intended to solve the problem of humidity control in a more or less efficient way.

For example, U53574951 (Oetjen) describes an apparatus composed of two units, respectively a first as a hopper wherein the material is introduced as frozen particles which by falling are accumulated in correspondence to a vibrating surface. A second unit adjacent to said first unit receives the frozen particles from the vibrating surface. Said second unit consists of a vertical cylindrical container, coaxially to which a rotation shaft is provided around a helicoidal bed in correspondence on one side which at the beginning of the helicoid receives the frozen particles from the vibrating table. Inside said second unit, a vacuum as well as heating means are provided.

EP1108967 (Marcheschi) provides a vertical dessicator made up of a chamber in which the vacuum originates, and a series of vibrating trays each one above and parallel to the other in correspondence to which the granular material to be dried is deposited and that when falling follows a downward vertical path.

The chamber is of the type heated by induction, peripherally providing a cavity inside which the heated fluid circulates.

US4015341 (McKinney) in particular, proposes the dehydration of the grain using a cylindrical section vertical container with one opening in correspondence to the upper end and one in correspondence to the lower end. During the process the container is kept with a reduced pressure atmosphere, while eight microwave generators are positioned along one side to heat the environment. At least one condenser is also provided inside the container.

To the aforementioned list, it is possible to add many other less significant patents, among which the following are cited for the completeness of the information.

CH347767 (Norbert) describes a vertical container, along which a fall path of the material in granules is provided. The path is defined by a zigzag channel, which is transversely brushed with hot air. DE10111582 (Volk et al) proposes a vertical dryer that has an opening on the upper part to supply the material to be treated and an opening on the lower part for the discharge of the treated material. In this case, the material to be treated is to be arranged peripherally with respect to a central body, that is contained inside said vertical dryer, which being provided with convenient generator means, is provided in this way to irradiate heat towards the peripheral chamber.

US4347670 (Wear et al.) describes a container made with transparent walls, on the interior of which columns are provided that develop vertically, these also have transparent walls, each of which leads the material to be treated from top to bottom, in particular seeds and granular products to be dried, in an environment where the vacuum is created by means of vacuum pumps. Microwave generators means involve the material to be treated.

US4023279 (Janda) suggests a method for drying the material, particularly resin for plastic material injection processes. For the object of this invention an apparatus is provided of the type with vertical development, in which the concourse is provided in a convenient container, of the microwave energy and of the convective motion airflow.

W00154519 (Persson) describes a method and a device to continuously treat with heat a flow of cereal to reduce the micro-organism content, such as bacteria, yeast and moulds and to deactivate certain micro-organism or enzymes and proteins. In this case a cylindrical tube is provided, with the lower end peripherally insulated in an intermediate part of the microwave generators, placed peripherally with respect to said pipe.

DE3916479 (Grasshoff) suggests a container to dry pharmaceutical products or foodstuffs, deposited in correspondence to a porous bed with a microwave heater (to pasteurize or sterilize) and a condenser in a dischargeable container. After filling at a first pressure with the material at rest, the gas is pumped, maintaining a low pressure, to allow the fluidification of the bed by the drying gas.

W08705991 (Agdal) discloses an apparatus, of the type with vertical development, in which the concourse is provided in a convenient vacuumized container with means that generate heat through microwaves, to dry the liquid susceptible to being heated which provides solids in suspension.

US3742614 (Bettermann) is a device for the thermal treatment of pulverized or granular material that includes a container with a plurality of small circular crates mounted one above the other in said container for the sequential transfer of the material from top to bottom, with a selective control system of the crate temperature and a vibration device for vibrating crates to move the material towards the subsequent stages with pre-selected layer depths US3004349 (White) is a circular stage dryer with an oscillating drying airflow. Each circular stage is provided with an arm that is moved by means of a common central shaft.

Finally US3733714 (Connor) also concerns a circular dryer, with vertically superimposed stages, with a central shaft that radially moves the distribution arms of the material in correspondence to each stage. The gas for the drying treatment supplies each stage and exits by the corresponding base that is of the porous type.

There are solutions that for certain parts of their content have been retained by the applicant, being more significant than the previous solutions.

PRIOR ART MOST SIMILAR TO THE INVENTION

It is the case, for example, of US4332092 (Hansotte) that suggests a process and an apparatus to remove and to dry the solvent from humid materials. This concerns an apparatus where the solvent enriched material is to be introduced into an apparatus to remove solvent-roasting tower to obtain material free of solvents, that is then introduced into a drier and heater in the absence of air to form the dried material. To a large extent, the apparatus to remove the solvent consists of a cylindrical container, on the interior of which crates are provided at different levels for the support of the material, in this case seed flax. Coaxial to said container, a rotation shaft is provided along which a corresponding movement arm of the melted material in correspondence to each crate is made mobile. In this way the material is progressively pushed until it corresponds to the openings made in the crates, causing the material to fall on the crate positioned below.

US3063848 (Van Gelder) is also interesting. This concerns an apparatus to treat food such as garlic, onions, potatoes and the like by means of a dehydration process. The apparatus, to a great extent, provides for the use of more vibrating levels that are divided into two opposite groups, with the inclined levels superimposed and alternated in such a way that the lower extremities of each are arranged in correspondence to the top of the inclined surface underneath. A peripheral circuit is provided to supply hot air and a cavity is provided along the vibrating surface in the part under the collection surface of the material to be treated. The air hot can, in one case, be combined with dehydrating gas and be supported by a single ventilating unit that causes in correspondence to the cavity underneath the collection surface of the material to be treated. The air forced into the cavity of the vibrating surface is conducted upwards determining a floating effect on the material to be treated. In this case the support surface consists of a stainless steel wire net with links of 20 X 200.

To summarise, with regard to the information thus acquired it is possible to say the following are known: - Apparatuses for continuous material treatment with a run with more stages developed vertically, commonly called "towers" and apparatuses also with a run with more stages, but developed horizontally, commonly called "tunnel"; - Apparatuses that for material treatment use hot airflow generators with forced convective motion; or apparatuses with dry gas circulation, alternatively a hot air flow combined with dry gas; or apparatuses with microwave devices alternatively combined with a hot air flow; - Apparatuses for material treatment provide the generation of the vacuum in the main container; Apparatuses, such as towers, that in order to subdivide the material to be treated progressively provide intercommunicating chambers, wherein each chamber is provided with a material support bed which is connected by rotating arms with spatula- shaped appendices for moving the material; Apparatuses, such as tunnels, which provide vibrating surfaces, one after another, along which the material to be treated is forced to flow.

DRAWBACKS

According to the applicant, although these proposals appear valuable, they do yet not seem capable of treating the material in a suitable way. More particularly, a problem relates to the fact that the material distributed on the support bed, usually tends to be dried excessively, giving rise to a "toasting" effect rather than to the correct control of the humidity. This produces a substantial loss of the original qualitative characteristics of the treated material, reducing the benefit that each one is expected to gain from such treatment. In other cases, by acting on the control parameters to avoid the "toasting" of the material, there is the risk of obtaining a rather ineffective treatment that does not achieve the desired values.

Nor is it negligible that the material distributed on the support bed usually tends to aggregate. This phenomenon that mainly regards the initial phase of the cycle when the material is still rich in humidity, from a practical point of view does not allow the uniform and progressive treatment of said material.

Some of the previous solutions, which use vibrating surfaces, do not seem effective since it remains difficult to prevent aggregation and in any case it seems that deaggregation is only achieved when each assembly is already superficially the object of treatment, while the core is still in the initial stage. In any case, the vibrating effect produces the constant striking of the material, between granule and adjacent granule as well as against the support bed, causing a persistent intense activity that on one side deteriorates the material, abrading it, and on the other impedes the uniform treatment in correspondence to the surface.

To solve this problem, in US3063848 (Van Gelder) suggests a support surface for the material to be treated which is permeable in air.

Even if this characteristic allowed, during the treatment, the maintenance of the floating effect of the material, to obtain a more uniform treatment and to avoid the abrading of the single granules of material, for the most part the result is rather unsatisfactory. From a practical point of view, the structural characteristic of the mesh in the stainless steel net does not allow the uniform floating of the material, therefore providing as a result a material treated incorrectly of insufficient quality.

The quality of the material once subjected to treatment and also the speed of execution of the cycle, are in any case two negative aspects particularly noted and not yet optimized in the previous solutions.

An essential aim of this invention is also to avoid the aforementioned drawbacks.

BRIEF DESCRIPTION OF THE INVENTION

This and other aims are achieved with this invention according to the characteristics as in the included claims, solving the problems disclosed by means of a continuous, multistage, fluidised evaporator- dessicator apparatus, of the type with chambers heated by microwave devices in a controlled atmospheric environment, for melted or granular material, comprising: - a container like a tower for Continuous material treatment with a multistage run developed vertically, said Container is provided with a rotating vertical shaft that radially supports arms with spatula-shaped appendices for the movement of the material; - every stage of the container, corresponding to an intercommunicating chamber with at least one adjacent chamber, where on the interior of said chamber a bed to support the material is provided that is permeable and compatible with the microwaves, that on the upper part is involved by said arms with spatula-shaped appendixes for the movement of the material while on the lower part a cavity is defined that communicates with a unit that generates a controlled airflow; - means for the treatment in temperature of the material, provided in correspondence to each chamber, which include controlled airflow generators with forced convective motion and microwave devices; at least one vacuum pump group that controls the atmosphere of the environment on the interior of the single intercommunicating chambers; - a logic control unit of the apparatus, which individually controls and makes the single functions interact, respectively ventilation, temperature and atmospheric pressure provided in correspondence to each chamber of the container.

AIMS

In this way, by means of the considerable creative contribution the effect of which constitutes immediate technical progress, certain aims are achieved including the optimization of the conditioning cycle of the material that includes the drying-evaporation stage of the humidity present.

A first aim is to allow rapid treatment, deeper and with greater uniformity with respect to the material introduced into the container. The result derives, for instance, unlike DE3916479 (Grasshoff) and US3733714 (Connor), from the original combination for each atmosphere controlled chamber involved by the microwave device, of the specific base fluidised with the unit that generates the airflow. In other words, in the previous solutions the concourse at least of the fluidised base with the microwave device was not provided, nor was it obvious. This is because on one hand it is judged that the microwave device should have other applications, while on the other hand it is not a question of bases of the type compatible with the relative microwave generator device. However, it is true that the originality also resides in having provided the concourse of the vacuum pump, which allows the qualitative characteristics originating from the material to be treated to be maintained unaltered.

In conclusion, this concerns a rather original solution with good technological content not present in any of the mentioned prior arts.

A second aim intends to reduce significantly the abrading of the single granules of the material to be treated, this is because, unlike US3063848 (Van Gelder) the concourse of the vibrating table with the fluidised base is avoided, allowing said material to float without the turbulence and shaking of the particles.

A third significant aim was that of controlling individually, by means of one convenient logical unit, the atmosphere of each chamber. In fact, it was possible to intervene individually and independently with the control parameters of each function, making said parameters react with the predetermined values relative to the adjacent chambers. Obviously, the conditioning cycle, in addition to being optimized, can be adjusted different to a level of each stage in an extremely flexible way making possible the obtainment of multiple results and adapting it in the best possible way to the characteristics of the material to be treated and to the needs of the user.

These and other advantages or objectives appear in the subsequent detailed description of a preferred embodiment with the aid of the enclosed schematic drawings, the details of which should be considered as non-limitative examples.

CONTENT OF THE DRAWINGS

Figure 1 is a side view of a continuous, multistage evaporator-drier apparatus of the type with chambers whose fluidised bed is involved by microwave devices for the treatment, in a controlled atmospheric environment, of a melted or granular material.

Figure 2 is a plan view of a permeable bed to support the material, involved by the corresponding rotating movement arm.

Figure 3 is a partial sectional view of a first example of a fluidised bed of the material.

Figure 4, is a partial sectional view of a second variant of a fluidised bed of the material.

Finally, Figure 5 is a partial sectional view of a third variant of fluidised bed of the material.

PRACTICAL DESCRIPTION OF REALIZATION OF THE

INVENTION

Also with respect to the Figures, in the first place it is possible to observe that a continuous evaporator-dessicator apparatus A for conditioning a granular or melted material in a vertical tower M, consists of a container 1, (Figure 1) essentially partly cylindrical and metallic, closed at both ends. On the interior of the cylindrical container 1, following a certain path with stages characterised by temporary rests alternated by transfers to the following stage for gravitational fall, the material is to be treated M, said material is introduced into the container 1, through an upper filling entrance 100 intercepted by a relative gate valve 2.

Said load entrance 100 is obtained laterally, in correspondence to the closing flange 101 that occludes the top of the container 1 and is conventionally in-line with other possible adducing means. The lower part of the container 1, also being closed, presents a deep drawn collection end 102, with the base, a discharge opening 103 obtained for the material M, intercepted by a corresponding gate valve 3.

Along the cylindrical section of the container 1 circular dividing partitions are obtained 7, which separate said cylindrical section, in many chambers S constituting the working stages, one above the other each intercommunicating with the adjacent chamber S by means of an opening obtained in correspondence to the dividing partition 7. Above each dividing partition 7 and separated from the latter a fluidised bed is provided 8, 9, 10, this is also circular and almost parallel to the base. In this way, a cavity 11 is obtained on the interior of the which is to be introduced, through an entrance 110 an airflow controlled by the logic control unit of the apparatus A. The airflow controlled in this way introduced into the cavity 11, is therefore invited to pass across the fluidised bed 8, 9, 10 that consists of a layer of air permeable material, in such a way that the material M distributed on the upper side floats.

The controlled airflow, for each S chamber, is generated by a fan 12, in this case outside the container 1, said fan 12 which is controlled by the logic control unit of the apparatus A, is provided with means 120 to generate air at a controlled temperature, for example hot air.

Coaxially to the container 1 a vertical shaft 4 is hinged that with its upper end 40, supported in an annulated way by convenient bearing means exits from the closing flange 101 to be aligned to the movement members 6 of a geared motor 60. Said movement members 6 impart a rotatory motion to the vertical shaft 4, controlled by the logic control unit of the apparatus A, in such a way that by rotating the vertical shaft 4, the radial arms 13 rotate with it, aligned orthogonally to said shaft 4 and being at least equal in number to the chambers S provided along the cylindrical container 1. In this way, each arm 13 is arranged almost parallel but separated from the fluidised bed 8, 9, 10 of each corresponding chamber S. above which the material M to be treated is arranged to fall. Spatulas 14 that brush the fluidised bed 8, 9, 10 with the lower profile are supported by the corresponding arm 13 by means of orthogonal connecting joints 140 and are aligned to each other, arranged at equal distances in such a way as to involve the whole fluidised bed 8, 9, 10 in their circular movement. In completing the circular movement of the arm assembly 13 and spatulas 14, the material M is finally invited to pass by falling through at least one opening 71 made in correspondence to the fluidised bed 8, 9, 10 and therefore through the corresponding opening 70 obtained in correspondence to the dividing partition 7.

Devices that generate microwaves 15, individually controlled by the logic control unit of the apparatus A, are also provided along the side of the exterior of the cylindrical container 1. The microwave devices 15, are numerically equal to the chambers S and are active in correspondence to the upper part of each chamber S in such a way as to orient the action radius itself towards the part underneath and that corresponds to the fluidised bed 8, 9, 10. In Figure 1 the microwave devices 15 like the fans 12 are represented as conventionally aligned and grouped together along two diametrically opposed sides of the container 1, however the arrangement of the said devices can be optimized along the perimeter and combined in different ways.

Also on the exterior of the container 1, said part of the apparatus A, a vacuum pump group 16 is provided which, by means of single connection 160 is in communication with each chamber S. Every connection 160 is intercepted by a valve 17, controlled by the logic control unit of the apparatus A, thus making possible the control of the atmosphere present in each chamber S and the interaction of the function itself with the other functions provided by the apparatus A, in particular the ventilation and thermal treatment of the material M. To coordinate and control the single functions, provided on the interior of each chamber S, they are furthermore provided with convenient sensors, such as at least a humidity sensor and/or a temperature sensor.

In conclusion, the logic control unit of the apparatus A reacts, for each chamber S, to the control of the single functions provided on the interior of said unit and respectively powered by the microwave device 15, by the fan 12 with relative means which generate a hot airflow, as well as by the vacuum pump group 16, 160 and 17.

In terms of the fluidised bed 8, 9, 10 it is possible to observe that it must substantially present two necessary characteristics, i.e. in the first place should be air permeable and secondly should not be an obstacle to the crossing of the microwaves generated by the devices 15 placed on the upper part.

In a first case, (Figure 3) such as for example the situation in which the material M of value to be treated takes place, it has been observed that the more suitable fluidised bed 8 consists of at least one panel, compatible with the microwaves, made of porous plastic material, for example an open cell polymer such as propylene.

In a second case, (Figure 4) where the working requirements of products of lesser value can be more convenient, a fluidised bed 9 of the lamellar type is provided. This concerns a compound surface, obtained by joining several coplanar elements 90, compatible with the microwaves with one slightly separated from the other in such a way as to leave a crossing interstice of the surface. Each element 90 is a shaped module that includes two staggered horizontal levels joined by an inclined intermediate surface in such a way that the first surface of the two staggered levels is superimposed on the opposite surface of the adjacent element 90. In this way, a cavity is created between the two superimposed levels, said cavity is crossed by the airflow originating from the area underneath, to be redistributed in correspondence to the upper side of the fluidised bed 9 by shaking and making the material M to be treated float.

In a third case, (Figure 5) the fluidised bed 10, also for the manufacture of the lowest value products, consists of a surface made up of modular elements in ceramic, compatible with the microwaves, positioned side-by-side at the same level at a short distance from each other, between said elements an air discharge channel is to be found, discharging said air that originates from the are underneath. More particularly, the discharge channel is determined by the shape of each head of the modular element, that in this case, presents a geometric form essentially with symmetric surface, inclined in correspondence to the head in such a way as to orient the airflow in a non-perpendicular way with respect to the fluidised bed 10.

Claims

1. Continuous, multistage evaporator-dessicator apparatus, for melted or granular material, including a container like a tower for the continuous treatment of material with a run with several stages developed vertically, said container is provided with a rotating vertical shaft that radially supports movement arms of the material with spatula-shaped appendices, characterjsed in that: every stage of the container corresponds to an intercommunicating chamber with at least one adjacent chamber, where on the interior of said chamber a fluidised bed to support the material is provided, that is permeable and compatible with microwaves, which on the upper part is involved by said arms with appendixes for the movement of the material while on the lower part a cavity is defined that communicates with a unit that generates a controlled airflow; and that provides means for the treatment at a temperature of the material, provided in correspondence to each chamber, said means include generators of a controlled airflow with forced convective motion and of microwave devices; and provides at least one vacuum pump group that controls the atmospheric environment on the interior of the single intercommunicating chambers.

2. Continuous multistage, evaporator-dessicator apparatus for melted or granular material, according to claim 1, characterised in that the logic control unit of the apparatus, also controls individually and makes the single functions interact together, respectively ventilation, temperature and atmospheric pressure provided in correspondence to each chamber.

3. Continuous multistage evaporator-dessicator apparatus for melted or granular material, according to claims 1 and 2, characterjsed in that the fluidised bed consists of at least one panel, compatible with the microwaves, made of porous plastic material such as propylene.

4. Continuous multistage evaporator-dessicator apparatus for melted or granular material, according to the claims 1 and 2, characterjsed in that the fluidised bed consists of a surface obtained as a result of joining several coplanar elements, compatible with the microwaves, where each element, slightly separated from the next in such a way as to leave a crossing interstice of the surface, is a shaped module including two staggered horizontal levels joined by an inclined intermediate surface and in which said first surface of the two staggered levels is superimposed on the opposite surface of the adjacent element thus obtaining a cavity between the two superimposed levels

5. Continuous multistage evaporator-dessjcator apparatus for melted or granular material, according to claims 1 and 2, characterjsed in that the fluidised bed consists of a surface made up of modular elements compatible with the microwaves, made of ceramic positioned side by side on the same level at a short distance from each other, between which is found an air discharge channel that discharges the air originating from the area underneath and in such a way that the airflow is directed non- perpendicularly with respect to the fluidised bed.

6. Continuous multistage evaporator-dessicator apparatus for melted or granular material, according to the previous claims, characterised in that the vacuum pump group outside the container, by means of single connection, is in communication with each chamber, and in which each connection is intercepted by a valve controlled by the logic control unit of the apparatus.

7. Continuous multistage evaporator-dessicator apparatus for melted or granular material, according to the previous claims, characterised in that on the exterior of the container devices are provided that generate microwaves that are individually controlled by the logic control unit of the apparatus, which are at least numerically equal to the number of chambers and each is active in correspondence to the upper part of each chamber in such a way as to orient the radius of action towards the part underneath and corresponding to the fluidised bed.

8. Continuous multistage evaporator-dessicator apparatus for melted or granular material, according to the previous claims, characterjsed in that the controlled airflow introduced into the corresponding cavity positioned underneath the fluidised bed, for each chamber, is generated by a corresponding fan, on the exterior of the container, said fan being controlled by the logic control unit of the apparatus and is provided with means to generate air at a controlled temperature, such as hot air.

9. Continuous multistage evaporator dessicator apparatus for melted or granular material as herein before described with reference to Figures 1 to 5.