EP0815943A1

EP0815943A1 - An apparatus for carrying out a flotation process

Info

Publication number: EP0815943A1
Application number: EP96110202A
Authority: EP
Inventors: Siro Viero; Ambrogio Bonacina; Barbara Bortot
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-06-25
Filing date: 1996-06-25
Publication date: 1998-01-07

Abstract

The apparatus is constituted by a basin (3) containing the liquid to be handled, the basin having an opening (1) for the introduction of the liquid and another opening (15) for removing said liquid. The apparatus also comprises a conduit for removing the flotating product (14) and another conduit for placing the decanted product (13) and also an opening (10) in the middle of the basin for the exit of the clarified liquid, the level of the liquid being controlled. The basin (3) has a circular cross section and has in the interior a screw feeder (4) coaxial with the basin and the speed of rotation of the screw feeder may be regulated in such a manner that the apparent displacement of the propeller helix is equal to the speed of advance of the liquid material being handled.

Description

FIELD OF THE INVENTION

The present invention relates to an apparatus for carrying out the process of flotation of solid substances in suspension according to the general part of claim 1.

DESCRIPTION OF THE PRIOR ART

The flotation process is used in several industrial fields such as treatment of minerals, for instance enrichment of mineral sulfides, purification operations of liquids being refluxed, in particular in the clarification phase.

The flotation process is based on the differences in properties of the free surfaces of several substances, some of which are hydrophilic and therefore are wetted completely by water and other substances which are more or less hydrophobic and therefore are not wetted. In order to carry out a separation by flotation, the mixture of the substances must be in an aqueous suspension; then there are added some chemical substances which increase the degree of wettability in such a manner that the particles which have a tendency to be hydrophobic become completely hydrophobic while the hydrophilic substances remain the same.

Therefore there is introduced a mixture of water and air composed by many small bubbles to which the particles which are not wetted adhere. These particles then go to place themselves in a flotation situation even if the specific weight is substantially greater with respect to the pulp which contains the particles.

On the other hand, the particles which are wetted are not brought to the surface and due to the force of gravity form a sediment at the bottom.

The concentrate which is obtained by flotation is periodically removed while the precipitate or sterile product is removed only at the end of the operation or periodically.

Several apparatuses have been used to carry out the flotation process; in particular apparatuses having a foam by agitation are known and also apparatuses which provide for the injection of free air and other apparatuses which function with dissolved air are also known.

These apparatuses, although they ensure a flotation process which permits to achieve a satisfactory separation of the materials of the pulp which contains these materials, are affected at the present state of the art by significant drawbacks, both structurally as well as functionally which interfere with the productivity. In particular, the methods described hereinabove require the use of basins of substantial dimensions which have in the interior panels for limiting the several conduits which permit the mixing of air with the pulp and the separation of the concentrate from the sterile gangue, all of this being a drawback because of the complexity of the apparatus, of the operation upkeep and the space of the installation.

In addition, in order to ensure a complete separation of the substances from the pulp, it is necessary to carry out the flotation process in a substantially long period of time, a fact which results in a low value of the capacity per square meter of the total surface of the apparatus.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an apparatus to carry out a flotation process with features novel with respect to the known apparatuses and in particular an apparatus which is characterized by minimum space and substantial capacity.

The crux of the present invention resides in an apparatus constituted substantially by two parts, a basin of circular cross section arranged with its axis horizontal and a screw feeder which is placed internally in the basin coaxially and contained within the basin. Further the screw feeder is placed in rotation by means of a gear motor which is located externally to the basin.

The basin is provided at one end with an opening for the introduction of the liquid to be treated and at the opposite end with a device for the removal of the material which has been flotated, and a reservoir for the decanted substances. The basin is also provided with an exit of the clarified liquid as well as a device for the regulation of the level of the liquid being handled. These and other features of the present invention will become more evident by reference to a description of a particular embodiment provided by way of illustration and which is not intended to be limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 -: illustrates a front vertical view in cross section of the apparatus of this invention;
Fig. 2 -: shows a side view of the apparatus in cross section along the line II-II of Fig. 1.

As shown in the figures, the apparatus according to the invention comprises a basin (3) having a cylindrical shape and provided on top with opening (15). A screw feeder (4) is placed in the interior of the basin. The screw feeder is coaxial with the basin and is placed in rotation by means of a geared motor (9) which is integrally connected with the screw feeder and which is placed externally with respect to the basin.

Structurally the basin has at one extremity and in the lower part opening (1) for the introduction of the liquid to be treated, the liquid having been partially enriched with a mixture of water and air and with suitable chemical substances. The liquid then is deposited in the flocculation chamber (2) from which it is uniformly diffused in the basin (3), filling the basin completely. At the end opposite to opening (1) for the liquid, the basin has in the upper part a recovery system (7) for the material (14) which has been flotated, which is formed on the surface of the liquid being treated, and which is discharged in the adjacent collection cell (8). In the lower part there is formed a collection reservoir (12) for the materials (13) which are sterile or decanted. The reservoir is provided with a discharge device (11) which allows the discharge to the exterior in a discontinuous manner of the materials (13) by means of a pneumatic valve.

On the part of the basin opposite to the part which has opening (1) for the introduction of the liquid, there is formed in the middle of the basin, opening (10) which permits the exit of the clarified liquid. This liquid, upstream of the final discharge to the exterior by means of connection (6), for eventual recovery or utilization, is intercepted by control device (5), the latter controlling the level of the liquid, which determines the concentration of the flotated material (14) to be removed.

With respect to the manner of carrying out the flotation process, this process is favored and accelerated by the presence of the screw feeder which rotates and carries the flotated material (14) towards the collection cell (8) and simultaneously carries the decanted material (13) towards the collection reservoir (12). In operation the flotation process is favored and accelerated by the presence of the screw feeder because the speed of rotation of the screw feeder may be varied with respect to the speed of introduction of the liquid. The optimum functional condition is achieved when the speed of rotation of the screw feeder is such that the apparent displacement of the propeller helix is perfectly equal to the speed of advance of the liquid being handled in the interior of the basin. In this situation the screw feeder (4) accompanies the liquid without, however, pushing the liquid being handled towards the terminal part of the basin so as to achieve in this manner a series of inclined cells according to the direction of the spirals of the propeller helix with the result that an increase in the speed of flotation of the solids which are in suspension and which are contained in the same liquid is achieved. Further the cylindrical shape of the basin (3) permits in the upper part to achieve a significant speed of ascent of the flotating material (14) and a contemporaneous increase in the concentration of the same material.

On the basis of what has been explained hereinabove, the advantages according to the present invention are clear because with an apparatus which is relatively simple comprising a basin (3) having a circular section which serves as a channel and with a screw feeder (4) which rotates in the interior, it is possible to achieve a flotation process of the liquids which is very rapid such that the capacity in liters per minute per square meter of the total surface of the apparatus results substantially greater, at least 60% greater with respect to the devices which are presently used.

Claims

An apparatus for carrying out a flotation process which comprises a basin (3) containing the liquid to be handled, said basin having an opening (1) at a first end for the introduction of said liquid and another opening (15) at a second end opposite to said first end for the discharge of said flotated liquid, said liquid advancing from said first end to said second end of said basin, means for separating the flotating product and the product which is decanted; means for regulating the level of the liquid in said basin, characterized by the fact that said basin (3) has a circular cross section, said basin being provided with an upper opening (15) at said second end of said basin, said basin being arranged with its axis horizontal, a screw feeder (4) located in the interior of said basin, said screw feeder being coaxial with said basin (3) end being contained in said basin, a geared motor (9) for placing in rotation said screw feeder, said screw feeder having a propeller helix, said gear motor being integral with said basin and being located externally thereto, the speed of rotation of said screw feeder (3) being regulated in such a manner that the amount of the apparent displacement of said propeller helix is equal to the speed of advance of said liquid.
The apparatus according to claim 1, characterized by the fact that said basin (3) has an interior and has in the lower part thereof at said first end said opening (1) for the introduction of said liquid and a flocculation chamber (2), said liquid having been previously enriched with a mixture of air and water and with suitable chemical substances, said opening (1) being in communication with said flocculation chamber (2) whereby said liquid which is introduced into said basin is uniformally diffused in said interior of the said basin.
The apparatus according to claim 2, characterized by the fact that said flotated liquid is discharged through said opening (15), and it comprises in said second end of said basin opposite with respect to said opening (1) and in the upper position of said basin a recovery system (7) of the material (14) which has been flotated, and a collection cell (8), said material being formed on the surface of said liquid and corresponding to said opening (15), said material being carried to said collection cell (8), said apparatus comprising in the lower part thereof and at said second end of said basin a collection reservoir (12) for the decanted material (13), said reservoir (12) being provided with discharge means (11), said apparatus further comprising in the middle of said basin an opening (10), said opening providing for the exit of the clarified liquid, the apparatus comprising a device (5) for controlling the level of the liquid being handled, said liquid determining the concentration of said flotated material (14), means for the exit of said clarified liquid through conduit (6), said control device being placed upstream with respect to said exit means.