APPARATUS FOR SOLIDIFYING LIQUID SULPHUR INTO ORTHORHOMBIC CRYSTALS AND RELATED METHOD

Abstract

An apparatus for solidifying liquid sulphur into orthorhombic crystals includes a liquid sulphur feeding tank, connected to a sulphur cooling screw feeder, and at least one electromagnetic field source external to the screw feeder, for example a solenoid with current flowing through it, acting on the sulphur, in such a way as to prevent it from crystallising in the monoclinic form above 100° C.

Claims

1. An apparatus for solidifying liquid sulphur into orthorhombic crystals, that it comprises at least one liquid sulphur feeding tank, connected to a sulphur cooling screw feeder, and at least one electromagnetic field source external to the screw feeder, acting on the sulphur, in such a way as to prevent it from crystallising in the monoclinic form above 100° C.

2. The apparatus according to claim 1, wherein it comprises a sulphur packaging station downstream of the screw feeder.

3. The apparatus according to claim 1, wherein it comprises at least one ultrasonic generator applied to the screw feeder, suitable for preventing the formation of deposits in the screw feeder.

4. The apparatus according to claim 2, wherein it comprises a packaged sulphur transporting and solidifying station.

5. The apparatus according to claim 1, wherein it comprises a temperature sensor, suitable for detecting the temperature of the sulphur coming out of the feeding tank, and a solenoid valve, controlled by the sensor, suitable for preventing the sulphur from entering the screw feeder if the temperature detected by the sensor is higher than a predetermined value.

6. The apparatus according to claim 1, wherein the electromagnetic field source comprises a solenoid surrounding the screw feeder, said solenoid being passed through by an electric current flow.

7. The apparatus according to claim 1, wherein the electromagnetic field source comprises a plurality of permanent magnets distributed along the surface of the screw feeder.

8. The apparatus according to claim 1, wherein it comprises a variable speed drive, suitable for determining the sulphur transit time in the screw feeder.

9. The apparatus according to claim 2, wherein the packaging station comprises an access solenoid valve, suitable for preventing the passage of the sulphur if the temperature is higher than a predetermined value, a feeding device for feeding empty containers, a doser for dosing the sulphur to be transferred into the containers, closing means for closing the filled containers.

10. The apparatus according to claim 4, wherein the transporting and solidifying station comprises at least one sliding belt, suitable for transferring the packaged sulphur during its cooling.

11. The apparatus according to claim 10, wherein the transporting and solidifying station comprises an upper belt and a lower belt which move forward in opposite directions so as to favour overturning of the packaged sulphur.

12. The apparatus according to claim 4, wherein the transporting and solidifying station comprises cooling means, suitable for speeding up the cooling of the sulphur.

13. The apparatus according to claim 12, wherein the cooling means comprise a nebulising device.

14. The apparatus according to claim 12, wherein the cooling means comprise a ventilating device.

15. A method for solidifying liquid sulphur into orthorhombic crystals, wherein it comprises at least the following steps: storing the liquid sulphur in a feeding tank; feeding the liquid sulphur into a cooling screw feeder subjected to the field generated by an electromagnetic field source, so as to prevent crystallisation of the sulphur in the monoclinic form above 100° C.; packaging of the pasty sulphur coming out of the screw feeder into empty containers; solidifying of the sulphur inside the containers on at least one sliding belt.

16. The method according to claim 15, wherein it comprises a step of overturning the containers so as to speed up the cooling of the sulphur.

17. The method according to claim 15, wherein it comprises a step of wrapping the containers with black plastic film, so as to reduce their light sensitivity.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Further advantages and features of the invention will be more apparent in the detailed description which follows, with reference to the accompanying drawings, which illustrate a non-limiting example embodiment, in which:

[0019] FIG. 1 is an overview of the invention;

[0020] FIG. 2 shows a detail of the invention, with some parts cut away to better illustrate others;

[0021] FIG. 3 is a schematic illustration of a part of the method;

[0022] la FIG. 4 shows a detail of the part of the method of FIG. 3;

[0023] FIG. 5 shows a further detail of the invention;

[0024] FIG. 6 shows the simplified phase diagram for the sulphur, in which the cooling line at atmospheric pressure has been highlighted.

PREFERRED EMBODIMENT OF THE INVENTION

[0025] As can be seen from the figures, this invention relates to an apparatus for solidifying liquid sulphur into orthorhombic crystals and the related method.

[0026] The apparatus (10) comprises a liquid sulphur feeding tank (1), connected to a sulphur cooling screw feeder (2), at least one electromagnetic field source (3), for example a solenoid (31), passed through by electric current, which externally surrounds the screw feeder (2), acting on the sulphur in such a way as to prevent it from crystallising in the monoclinic form above around 100° C. Indeed, as shown in FIG. 6, at atmospheric pressure the sulphur would start to crystallise in the monoclinic form at just below 120° C.: however, during the course of the cooling process, and in particular around about 100° C., the monoclinic form would become unstable and would tend to transform unevenly into a non-compact disaggregated mass made up mostly of ortho-rombic crystals, producing potentially dangerous dusts and gases in contact with air and water.

[0027] Although sulfur is not a metal, but a diamagnetic substance, the action of the electromagnetic field surprisingly modifies the spin axis of the sulfur electrons and prevents the sulfur from starting its crystallization above about 100° C.

[0028] Immediately below this temperature, the sulfur begins to crystallize in an orthorhombic form, giving rise to a compact and homogeneous mass.

[0029] As an alternative to the solenoid (31), the source (3) of the electromagnetic field could be constituted by a plurality of permanent magnets (32) distributed along the surface of the screw feeder (2), even if not showned in the figures.

[0030] It may also be advantageous for the apparatus to comprise a plurality of ultrasonic generators (5) applied to the screw feeder (2), which are suitable for preventing the formation of sulphur deposits in the screw feeder.

[0031] Located downstream of the screw feeder (2), from which the sulphur comes out in a pasty form, formed by twinned crystals and liquid sulphur, there are, in order, a sulphur packaging station (4) and a packaged sulphur transporting and solidifying station (6).

[0032] A temperature sensor (11) allows detection of the temperature of the sulphur coming out of the tank (1), and a solenoid valve (12), controlled by the sensor (11), prevents the sulphur from entering the screw feeder (2) if the temperature detected by the sensor (11) is higher than a predetermined value. A variable speed drive (13) which drives the rotation of the screw feeder (2) allows definition of the sulphur transit time in the screw feeder (2), depending on the infeed temperature and the desired thermal gradient.

[0033] The packaging station (4) comprises an access solenoid valve (45), suitable for preventing the passage of the sulphur if the temperature is higher than a predetermined value, a feeding device (41) for feeding empty containers (42), for example multi-layer paper bags or barrels, a doser (43) for dosing the sulphur to be transferred into the containers (42), closing means (44) for closing the filled containers (42).

[0034] The subsequent transporting and solidifying station (6), shown in FIG. 4, comprises at least one sliding belt (61), suitable for transferring the packaged sulphur during its further cooling. It is also preferable for the transporting and solidifying station (6) to comprise an upper belt (61a) and a lower belt (61b) which move forward in opposite directions, so that the falling of the containers (42) from the upper belt (61a) onto the lower belt (61b) favours container overturning, causing faster cooling of the sulphur.

[0035] The transporting and solidifying station (6) may also be provided with cooling means (62), such as a nebulising device (62a) and a ventilating device (62b), which are suitable for speeding up the cooling of the sulphur.

[0036] In these last stations, the solidification in orthorhombic form becomes complete, stable and irreversible, giving rise to compact and homogeneous blocks, unassailable by acid solutions, free from releases of gaseous and non-reactive emissions in water.

[0037] The method for solidifying liquid sulphur into orthorhombic crystals therefore comprises at least the following steps:

[0038] storing the liquid sulphur in a feeding tank (1);

[0039] feeding the liquid sulphur into a cooling screw feeder (2) subjected to the field generated by an electromagnetic field source (3), so as to prevent crystallisation of the sulphur in the monoclinic form above 100° C.;

[0040] packaging of the pasty sulphur coming out of the screw feeder (2) into empty containers (42);

[0041] solidifying of the sulphur inside the containers (42) on at least one sliding belt (61).

[0042] It is appropriate for there to also be a step of overturning the containers (42) so as to speed up the cooling of the sulphur.

[0043] Finally, the method comprises a step of wrapping the containers (42) with plastic film, preferably black, so as to reduce the light sensitivity of the package.