As is known, there are various processes for treating alloys, in particular noble metals, in order to refine them. Among said processes, the most common ones are those of chemical separation of materials, which however have various drawbacks such as material loss or inefficiency and pollution. An alternative solution which overcomes these drawbacks is the one of the vacuum distillation processes already described in patents U2609581C2 and PCT/EP2016/000121, hereinafter referred to as a whole as PCT'121. The vacuum distillation processes provide for positioning the alloy to be treated in a special crucible, placed in a vacuum chamber, in which the alloy will be subjected to treatments for the heating, the melting, the evaporation, the distillation and finally the condensation of the materials composing it in order to obtain different layers of condensed and separated materials.

In fact, the conditions of high temperatures and vacuum atmosphere allow the metals to evaporate, each of them evaporating at certain levels of such conditions.

Therefore in PCT'121 it was found that, by bringing the alloy, placed in a crucible within a vacuum chamber, to these conditions, it is possible to have some of the metals present therein evaporate.

In particular, according to the process described in PCT'121, the alloy to be separated is melted, for example by electromagnetic induction or other means, within a crucible arranged inside a high vacuum chamber equipped with one or more condensation devices suitable for condensing the gaseous substances deriving from the melting and evaporation of the alloy.

In particular, this procedure initially includes arranging the crucible under a condensation device suitable for condensing and collecting the evaporated metal.

Specifically, the alloy is brought to a temperature value and at the same time a vacuum degree is created in the high vacuum chamber, so as to cause the evaporation of the components of the alloy with the volatility degree corresponding to this vacuum-temperature combination.

If account is taken of the fact that each metal evaporates at a specific volatility degree, and if this operation is repeated by applying the specific conditions to the metals, components of the alloy to be treated, collecting it once it has evaporated, it is thus possible to obtain a substantially distilled metal.

To do this, an apparatus for the separation and recovery of components has been proposed in the patent PCT'121. This apparatus provides for a crucible placed in a vacuum chamber, and a plurality of condensation devices suitable for being placed above said crucibles and for collecting the various metals present in the alloy.

Said condensation devices include, in the specific case, a cold element, advantageously constituted by a hollow body, and a baffle, which is suitable for laterally dispersing the gaseous substances produced by melting and evaporation of the alloy to be separated, redirecting their flow towards the internal lateral walls of the cold element.

Moreover, as already mentioned in the document PCT'121, said baffle component used in the condensers is vertically movable. This feature makes it possible to vary the distance between the baffle and the crucible and to make a greater surface area of said condenser useful.

The efficiency of said method therefore lies in the evaporation of each of the metals, which however can have significant durations.

Furthermore, depending on the type of impurities present in the melting bath, a layer of slag can form on the surface of the melting bath, slowing down or even blocking the evaporation of the metals present below this layer, in the melting bath, thus inhibiting the entire distillation method.

Aim of the present invention consists in realizing a device for increasing metal evaporation efficiency which solves the technical problem described above, obviates the drawbacks and overcomes the limits of the known art, allowing to increase the evaporation efficiency of a metal during a vacuum distillation process, reducing the time necessary and coping with the possible creation of the impurity layer on the surface of the melting bath.

The Applicant has realized that these and other results can be obtained starting from the solution described and claimed in PCT'121, suitably modifying the baffle both in shape, in structure and in its stroke.

Within this scope, it is the object of the present invention to realize a device for increasing metal evaporation efficiency for use in crucibles, in particular in the alloy vacuum distillation processes.

Another object of the invention consists in realizing a device for increasing metal evaporation efficiency.

A further object of the invention consists in realizing a device for increasing metal evaporation efficiency which is capable of giving the greatest guarantees of reliability and safety in use.

Another object of the invention consists in realizing a device for increasing metal evaporation efficiency which is easy to make and economically competitive if compared to the prior art.

The aforementioned aim, as well as the aforesaid objects and others which will become clearer hereinafter, are achieved by means of a device for increasing metal evaporation efficiency as claimed in the attached independent claim 1, and a relative method as claimed in the attached independent claim 12.

Other features are provided for in the dependent claims.

Additional features and advantages will become more apparent from the description of two preferred, but non exclusive, embodiments of a device for increasing metal evaporation efficiency, illustrated by way of non limiting example with the aid of the appended drawings, in which:

Figures la-lf are schematic views of the operation of a first embodiment of a device for increasing metal evaporation efficiency, according to the invention;

Figures 2a-2f are schematic views of the operation of a second embodiment of a device for increasing metal evaporation efficiency, according to the invention;

Figure 3 schematically shows a modified view of a detail of the embodiment illustrated in Figures la-lf;

Figure 4 schematically shows a modified view of a second detail of the device illustrated in Figures la- lf;

Figure 5 schematically shows a second modified view of the second detail of the device illustrated in Figures la-lf; and

Figures 6-9 show further embodiments of the device according to Figures 2a-2f.

With reference to the cited figures, the features common to the two embodiments will be described in relation to a device for increasing metal evaporation efficiency for use in crucibles, globally indicated with the reference number 10, which comprises a perforated surface 1, on which a plurality of through holes 5 is provided, movable vertically with respect to the crucible 3, with a vertical stroke permitting the device 1 according to the invention to be dipped in the melting liquid 2 contained in said crucible 3.

Furthermore, said device 10 includes lateral edges 4, which could also be provided with holes 5, as shown in figure 3, connected to the surface 1 so as to realize a continuous wall, which extend in a direction higher than or substantially opposite to the melting liquid 2, so as to realize, in combination with said at least one perforated surface 1, a hollow/container suitable for collecting and containing an amount of said melting liquid 2, once the device 1 is lifted from the melting bath 2.

During the upward stroke of the device 10, that is to say away from the melting bath 2, it performs the function of a shower head, creating a continuous shower of molten metal droplets passing through the holes 5, said droplets increasing the evaporation surface (Total surface = melting bath surface + droplet surface), increasing the evaporation rate (g/min) and thus improving the efficiency and performance of the entire distillation process.

Advantageously, the dimension of the hollow, in combination with diameter and number of holes must ensure a dripping maintenance time sufficient to permit the surface of the droplets to evaporate (for example for 10 seconds).

Advantageously, by means of the vertical movement and the dipping in the melting liquid 2, said device 10, in its downward stroke, that is towards the melting bath 2, breaks the eventual surface impurity layer 6 formed in the meantime, as illustrated for example in the Figures lb and lc.

In a first embodiment, illustrated in Figures la to If, the device for increasing metal evaporation efficiency 10 is formed by a perforated and flat surface 1, or with another shape, substantially parallel to the melting liquid 2 and connected to the baffle 7, connected in turn to the condenser 8.

Said surface 1 can be of any shape (circular, polygonal, etc.) (see in particular Figures 4 and 5 of the attached drawings), i.e. it will have a shape such as to have a sufficiently large surface for an effective breaking of the impurity layer, but at the same time leaving sufficient space between its edges 4 and the inner wall of the crucible 3 for the passage of the metals in evaporation.

In the second embodiment, illustrated in Figures 2a to 2f, the device 10 is integral with the baffle 7 described in PCT'121, forming a single component having the role of both baffle and efficiency increasing device.

Figures 6, 7, 8 and 9 illustrate various solutions which reflect the characteristics of the solution illustrated in Figures la - If and/or 2a - 2f, in combination with the solutions illustrated in Figures 3, 4, 5, 6, 7, 8.

In the particular case illustrated, the device for increasing metal evaporation efficiency 10 has a conical shape.

Alternatively, the device 10 can also have a quadric shape.

Further, the holes 5 can be fan-shaped (e.g. Figures 2a-2f) or parallel (e.g. Figures la-lf).

The operation of the device 10 is clear and evident from what has been described.

By way of example, the operating steps of the device 10 will be described with reference to Figures la to If or similarly 2a to 2f.

This operation includes the steps of, respectively in Figures la-f or 2a-2f, respectively:

- moving the device 10 and/or the baffle 7, whether integral to each other or not, toward a melting bath contained within said crucible (3);

- eventually breaking the impurity layer 6 formed on the melting bath;

- dipping the device 10 within the melting liquid

2;

- lifting the device 10 from the melting bath 2 collecting an amount of melting liquid 2;

- vertically moving upwards permitting dripping of the melting liquid collected by the plurality of holes 5;

- vertically moving downwards once the device 10 is substantially emptied of melting liquid 2.

In practice it has been found that the device for increasing metal evaporation efficiency, according to the present invention, fulfils the task as well as the predefined aims as it allows to increase the evaporation surface of the metal and at the same time to periodically break any eventual impurity layer 6 formed on the surface of the melting bath.

The present invention has been described by way of a non-limiting illustrative example according to preferred embodiments thereof, however, it is understood that variations and/or modifications may be made by those skilled in the art, without thereby departing from the relative scope of protection, as defined in the attached claims.