Patent Description:
Reference is made, in particular, to an apparatus and/or a method in which a process fluid (generally hot air) is introduced into a hopper to pass through incoherent material and is then extracted from the hopper.

Specifically, but not exclusively, the invention can be advantageously applied in the context of a plant for treating incoherent plastics, like, for example, a plant for dehumidifying and/or drying and/or crystallizing and/or packaging and/or conveying in a vacuum and/or under pressure the incoherent plastics. This plant may be intended, in particular, to supply a user machine, such as, for example, a machine for processing and transforming plastics, in particular an extruder that supplies extruded plastics to an injection moulding and/or blow moulding and/or compression moulding apparatus.

It is known that in the process of drying and/or dehumidifying polymer granules the latter are heated by creating a thermal gradient between the external surface and the central part of the granule. The drying and/or dehumidifying process has to be maintained in as stable condition as possible, such that all the dried and/or dehumidified polymer granules reach with constancy the same temperature and humidity conditions. This need is all the more evident the greater the mass of polymeric granular material to be heated.

Patent publication <CIT> shows an apparatus according to the preamble of claim <NUM>.

Patent publication <CIT> shows a solution intended to obtain a better distribution of thermal energy in the mass of the polymer granules and to reduce energy consumption. This solution diffuses the process fluid (hot air) inside a drying and/or dehumidifying hopper not only vertically (in general from bottom to top), but also horizontally. This combined mode involves the use of a great flowrate of the process fluid to ensure the transmission of the thermal energy to the granule. It has been established that this flowrate is about double the flowrate in a traditional process that uses a distributing cone that distributes in a vertical manner. Document <CIT> discloses an apparatus having a similar structure as the apparatus claimed. However, instead of an outlet chamber, an inlet chamber is disclosed, the inlet chamber being connected to inlet nozzles extending into the internal volume.

This great flowrate nevertheless generates the drawback of clogging the filtering means of the process fluid, both during the step of loading the incoherent material into the hopper, and during the treatment step proper. This could be caused by the granules falling that are introduced from above into the hopper through a feeding port and/or by the high speed of the process fluid. An undesired granule conveying phenomenon has been detected of granules that "fly" to the outlet of the process fluid, thus creating in fact clogging of the filters. This conveying phenomenon is particularly intense in the initial step of filling the "empty" hopper when the fall distance of the granules is greater.

Another drawback, found in the solution known from <CIT>, is a certain imbalance in the transfer of the thermal energy into the volume of the hopper that contains the material. This heat imbalance could be caused by the formation of preferential routes in the process fluid inside the hopper. These preferential routes seem to be at least partially due to the aforesaid phenomenon of granules conveyed "in flight" by the process fluid, a phenomenon that causes localized decreases in load losses inside the hopper, generating in fact preferential routes with a high flow rate and a consequent increase in the phenomenon of conveying and clogging of the filters.

In one test, it was observed that during a stable process with <NUM>/h production and an airflow near <NUM><NUM>/h, the quantity of material conveyed inside the containers of the filters was about <NUM> in <NUM>.

One object of the invention is to provide an apparatus and/or a method that is able to overcome the aforesaid limits and drawbacks of the prior art.

One object is to provide a solution, which is alternative to the prior art solutions, for processing incoherent plastics.

One advantage is to reduce the phenomenon of conveying the granule to a hopper and/or optimizing the distribution of the air inside the hopper.

One advantage is to limit the material conveyed "in flight" by the process fluid and reduce clogging of the filters of the fluid.

One advantage is to transmit thermal energy to the granule so as to homogenize the temperature of the granule and reduce the thermal gradient between the heart of the granule and the external surface thereof.

One advantage is to reduce or eliminate the powder deposit (coming from the granule) along the conduits evacuating the process fluid.

One advantage is to obtain high process efficiency, in particular of a process that involves heating material.

One advantage is to make available a constructionally simple and cheap apparatus for processing incoherent plastics.

These objects and advantages and still others are achieved by an apparatus and/or a method according to one or more of the claims set out below.

In one embodiment, a method for processing incoherent plastics with a process fluid comprises the step of generating a flow of the process fluid through the incoherent plastics contained in an internal volume of a container and the step of extracting the process fluid through at least one tubular portion, which is permeable to the process fluid, of at least one tubular body that is provided above with an opening that leads into an outlet chamber of the process fluid that is arranged above the internal volume and is separated from the internal volume by a diaphragm that is impermeable to the process fluid. The method may comprise the step of introducing the incoherent plastics into the internal volume through at least one inlet port separated from the outlet chamber by separating means that is impermeable to the process fluid.

In one embodiment, a method for processing incoherent plastics with a process fluid comprises the step of generating a flow of the process fluid through the incoherent plastics contained in an internal volume of a container and the step of extracting the process fluid through at least one tubular portion, which is permeable to the process fluid, of at least one tubular body that is provided above with an opening connected to an outlet of the process fluid, in which the aforesaid at least one tubular body may be, in particular, arranged eccentrically with respect to a vertical central longitudinal axis of the aforesaid container. It is possible to provide two or more tubular bodies, each comprising at least one tubular portion which is permeable to the process fluid and at least one upper opening connected to the outlet, arranged angularly spaced apart with respect to a vertical central longitudinal axis of the aforesaid container.

In this description, "permeable to the process fluid" means a means (for example a perforated wall) that lets the process fluid pass through and retains the incoherent material or at least the less fine particles.

In practice, the only escape route for the incoherent plastics to the outlet chamber consists of each of the aforesaid tubular portions that are permeable to the fluid that advantageously represent a significantly effective barrier against the undesired aspiration of incoherent plastics.

The possibility of providing a plurality of tubular bodies that are suitable for the transit of the exiting process fluid (tubular bodies immersed in the internal volume of the container of the incoherent plastics) enables the transit surface of the process fluid to be increased. It is further observed that the tubular bodies can be completely surrounded by the incoherent plastics, when the internal volume is sufficiently filled, so that flowing of the material contributes to keeping the surfaces of the tubular bodies clean by eliminating the depositing of powder. The eccentric arrangement with respect to a central axis of the container of one, two or more tubular bodies enables the material to be limited that is conveyed "in flight" by the process fluid and also obtains the advantage of reducing clogging of the filters by the material conveyed.

The invention can be better understood and implemented with reference to the enclosed drawings that illustrate embodiments thereof by way of non-limiting example, in which:.

For the sake of simplicity, in the appended figures similar elements of different embodiments are indicated by the same numbering.

With reference to the aforesaid figures, overall with <NUM> an apparatus has been indicated for processing incoherent plastics with a process fluid (for example heated air). The apparatus <NUM> comprises a container <NUM> extending vertically with an internal volume configured to contain the incoherent plastics. The container <NUM> may comprise, in particular, a drying and/or dehumidifying hopper for drying and/or dehumidifying incoherent plastics (polymer granules). The container <NUM> may comprise, in particular, a vertical central longitudinal axis.

The apparatus <NUM> may comprise, in particular, an outlet chamber <NUM> of the process fluid arranged above the internal volume containing the material. The outlet chamber <NUM> is provided with at least one outlet <NUM> of the process fluid. The outlet chamber <NUM> may be, in particular, separated from the internal volume, where the plastics are situated, by a diaphragm <NUM> (for example made of sheet metal) that is permeable to the process fluid. The diaphragm <NUM> is provided with one or more openings <NUM> to enable the process fluid to exit the internal volume.

The apparatus <NUM> comprises, for each of the aforesaid openings <NUM>, a tubular body <NUM> extending below the diaphragm <NUM> and arranged inside the internal volume. Each tubular body <NUM> is open above at the respective opening <NUM> in the diaphragm <NUM>. Each tubular body <NUM> may comprise, in particular, at least one segment 7a that is permeable to the process fluid. This segment 7a that is permeable to the fluid may comprise, in particular, a tubular segment, for example a perforated tubular wall. This segment 7a that is permeable enables the process fluid to exit the internal volume through the respective opening. This segment 7a that is permeable may be, in particular, arranged in the internal volume so as to be completely immersed and surrounded (at <NUM>° degrees) by the incoherent plastics that are processed once the internal volume has been sufficiently filled with the material.

The apparatus <NUM> comprises means for generating a flow of the process fluid inside the internal volume to the outlet chamber <NUM>. The means for generating a flow may comprise, in particular, at least one fan <NUM> to send the flow to an inlet <NUM> of the container <NUM>. The means for generating a flow may comprise, in particular, at least one filter <NUM> for filtering the process fluid coming from the outlet <NUM> of the container. It is possible, as in the embodiment of <FIG>, for the apparatus <NUM> to comprise a closed circuit for the circulation of the process fluid. The fan <NUM> may operate in a closed circuit by removing the fluid from the outlet <NUM> and sending the fluid to the inlet <NUM>. The apparatus <NUM> may comprise, in particular, regenerating means, for example of known type (not illustrated), to regenerate the fluid exiting the container <NUM>. The regenerated fluid may be sent in a closed circuit to the inlet <NUM> by the fan <NUM>.

The outlet chamber <NUM> may be, in particular, of annular shape. The outlet chamber <NUM> may be, in particular, internally bounded by a tubular wall <NUM> that is permeable to the process fluid. The tubular wall <NUM> may define, in particular, a passage for the entry of the incoherent plastics into the internal volume.

The apparatus <NUM> may comprise, in particular, a loader <NUM> for feeding the incoherent plastics to the internal volume through the tubular wall <NUM>. It is possible, as in the embodiments in <FIG> and <FIG>, for the material supplied by the loader <NUM> to pass inside the tubular wall <NUM> remaining isolated from the flow of the process fluid that exits through the outlet chamber <NUM>.

The apparatus <NUM> may comprise, in particular, a discharge <NUM> for the processed material to exit. The discharge <NUM> may comprise, in particular, an outlet port arranged at the lower end of the internal volume.

The diaphragm <NUM> may be, in particular, arranged radially around the tubular wall <NUM> starting from the tubular wall <NUM>, so as to ensure substantial impermeability to the process fluid. The diaphragm <NUM> may comprise, in particular, a wall of annular shape with an edge inside a closed loop (for example, of circular shape) directly connected (substantially coincident with) to a lower end edge of the tubular wall <NUM>.

The aforesaid passage for the entry of the material and the aforesaid outlet chamber <NUM> of the fluid may be, in particular, separated from one another by the tubular wall <NUM>, so that the outlet chamber <NUM> is substantially isolated, almost hermetically, from the course of the incoherent plastics, apart from the fluid communication represented by the permeable segment/s 7a. This fluid communication is anyway conformed and arranged so as to constitute an effective barrier to reduce or eliminate the undesired transit of incoherent material.

Each tubular body <NUM> (for example of cylindrical shape) may, in particular, extend along a longitudinal (for example, vertical) axis not coinciding with a longitudinal axis (for example, vertical) along which the tubular wall <NUM> (for example of cylindrical shape) extends. The longitudinal axis of each tubular body <NUM> may be spaced apart from the longitudinal axis of the tubular wall <NUM>. In particular, the tubular wall <NUM> may be arranged centrally with respect to a vertical central longitudinal axis of the container <NUM>, or with respect to a center of gravity of the diaphragm <NUM>, whereas each tubular body <NUM> may be arranged eccentrically with respect to the vertical central longitudinal axis of the container <NUM>, or with respect to the center of gravity of the diaphragm <NUM>.

The apparatus <NUM> may comprise, in particular, an inlet conduit <NUM> of the process fluid that is connected to the inlet <NUM> and is arranged in the internal volume and is permeable to the process fluid. The inlet conduit <NUM> may, in particular, terminate below with a permeable portion <NUM> (for example, perforated) that is arranged to enable the process fluid to enter the internal volume. The permeable portion <NUM> may be, in particular, arranged below each of the tubular bodies <NUM>, in particular below the segments 7a that are permeable of the tubular bodies <NUM>. The permeable portion <NUM> may comprise, in particular, a distributing cone.

The permeable portion <NUM> may be, in particular, arranged in a manner that is central or coaxial with respect to the vertical central longitudinal axis of the container <NUM>. Each tubular body <NUM> may be, in particular, arranged in a manner that is eccentric or offset with respect to the permeable portion <NUM> and/or with respect to the vertical central longitudinal axis of the container <NUM>. This eccentric or offset arrangement, together with the fact that the segment 7a that is permeable can be completely immersed and surrounded by the incoherent material, promotes the regularity and efficiency of the extraction of the process fluid from the internal volume of the container to the outlet <NUM>.

The diaphragm <NUM> may be, in particular, provided with two, or three, or four, or five, or more than five openings <NUM>, with each of which a respective tubular body <NUM> is associated. The openings <NUM> may be arranged, in particular, spaced angularly apart from one another around a vertical axis of the container <NUM>.

As said, the tubular body <NUM> may comprise a segment 7a (lower and/or tubular) that is permeable to the process fluid to enable the transit thereof from the outside inside the tubular body <NUM>. The tubular body <NUM> may comprise, in particular, an (upper or lower) segment 7b that is impermeable to the process fluid. The segment 7b that is impermeable may be arranged (for example coaxially) above the segment 7a that is permeable. The segment 7a that is permeable (perforated) may be of cylindrical shape. The segment 7b that is impermeable (unperforated) may be of cylindrical shape. The (upper) segment 7b that is impermeable may extend, in particular, between the respective (lower) segment 7a that is permeable and the respective opening <NUM> on the diaphragm <NUM>. A vertical length of the (upper) segment 7b that is impermeable may be, in particular, greater than a vertical length of the respective (lower) segment 7a that is permeable.

The apparatus <NUM> may comprise, in particular, at least one perforated wall <NUM> which is permeable to the process fluid and arranged to bound laterally the internal volume and define an annular circulating zone of the process fluid. The apparatus <NUM> may comprise, in particular, at least one external wall <NUM> that is permeable to the process fluid to bound laterally and externally the aforesaid annular zone. The apparatus <NUM> may comprise, in particular, one or more septa <NUM> that are impermeable to the process fluid to divide the aforesaid annular zone into two or more compartments arranged one on top of the other. The aforesaid annular circulating zone of the process fluid promotes circulation with at least one component of the flow in a horizontal direction. The division into two or more compartments arranged one on top of the other promotes complex circulation in which the flow can enter and exit each compartment so as to be able to enter or exit each compartment so as to generate flow components in a horizontal direction radially outwards and several components of the flow in a horizontal direction radially inwards.

The operation of the apparatus may actuate, in particular, a method for processing incoherent plastics with a process fluid, in particular to dry and/or dehumidify incoherent plastics.

The method may comprise, in particular, the step of generating a flow of a process fluid through incoherent plastics contained in an internal volume of a container <NUM>. The method may comprise, in particular, the step of extracting the process fluid from the internal volume through a tubular body <NUM> which is at least partially permeable (for example perforated) to the fluid and provided above with an opening <NUM> that leads into an outlet chamber <NUM> of the process fluid arranged above the internal volume and separated from the internal volume by a diaphragm <NUM> which is permeable to the process fluid.

The method may comprise, in particular, the step of extracting the process fluid through two or more tubular bodies <NUM> (each of which is at least partially permeable to the fluid) that are arranged angularly spaced apart from one another around a central vertical axis of the container <NUM>. The process fluid may then be extracted, in particular, through two or more removal zones (in particular, tubular removal zones), i.e. through N removal zones, with N = <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or more. The number N of removal zones may be chosen in function of the maximum flowrate of the process fluid and/or of the diameter/height ratio of the container <NUM> (hopper). The embodiments of <FIG> and <FIG> differ from one another substantially through the number of removal or extraction zones for removing or extracting the process fluid, i.e. tubular bodies <NUM>.

Claim 1:
Apparatus for processing incoherent plastics with a process fluid, said apparatus (<NUM>) comprising:
- a container (<NUM>) extended vertically with an internal volume configured to contain the incoherent plastics;
- a process fluid outlet chamber (<NUM>) arranged above said internal volume and separated from said internal volume by a diaphragm (<NUM>) impermeable to the process fluid and provided with one or more openings (<NUM>) for the outlet of the process fluid from said internal volume;
- for each of said one or more openings (<NUM>), a tubular body (<NUM>) open at the top at the respective opening (<NUM>) and at least partially permeable to the process fluid so as to allow the process fluid to exit from said internal volume through the respective opening (<NUM>);
- a tubular wall (<NUM>) which is impermeable to the process fluid, and which defines a passage for the inlet of the incoherent plastics in said internal volume, said outlet chamber (<NUM>) being internally delimited by said tubular wall (<NUM>);
- means for generating a flow of the process fluid inside said internal volume towards said outlet chamber (<NUM>);
characterized in that said tubular body (<NUM>) extends below said diaphragm (<NUM>) inside said internal volume.