Sulphur-containing fertilizers and process for the preparation thereof

1. A process for the manufacture of sulphur-containing fertilizer compositions, said process comprising the steps of:

a) providing a slurry of at least one phosphate-based fertilizer material selected from the group consisting of ammonium phosphates, ammonium phosphate based nitrogen-phosphorus-potassium (NPK) compounds, super phosphates and partially acidulated phosphate rocks;

b) bringing said slurry into contact with at least one cationic or amphoteric surfactant and a liquid phase of elemental sulphur; and

c) introducing the mixture obtained in step b) into a granulator unit in order to obtain granules of the fertilizer composition,

wherein the elemental sulphur is present in an amount in the range of from 1 to 25 wt. % and the at least one cationic or amphoteric surfactant is present in an amount in the range of from 0.001 to 3 wt. %, based on the total weight of the fertilizer composition.

2. A process as claimed in claim 1 , wherein the liquid phase of elemental sulphur comprises molten sulphur.

3. A process as claimed in claim 1 , wherein the at least one cationic or amphoteric surfactant comprises an ethylene or propylene oxide adduct of an aliphatic amine, said aliphatic amine containing 12 to 20 carbon atoms.

4. A process as claimed in claim 1 , wherein the at least one cationic or amphoteric surfactant is present in an amount in the range of from 0.001 wt. % to 0.05 wt. % with respect to the weight of the overall fertilizer composition.

5. A process as claimed in claim 1 , wherein the at least one cationic or amphoteric surfactant is a nitrogen-containing cationic surfactant or a nitrogen-containing amphoteric surfactant.

6. A fertilizer composition comprising:

a) elemental sulphur in an amount in the range of from 1 to 25 wt. %, based on the total weight of the fertilizer composition;

b) at least one phosphate-based fertilizer material selected from the group consisting of ammonium phosphates, ammonium phosphate based nitrogen-phosphorus-potassium (NPK) compounds, super phosphates and partially acidulated phosphate rocks; and

c) at least one cationic or amphoteric surfactant in an amount in the range of from 0.001 to 3 wt. %, based on the total weight of the fertilizer composition, wherein the cationic or amphoteric surfactant is dispersed throughout the fertilizer composition.

7. A fertilizer composition as claimed in claim 6 , wherein the at least one cationic or amphoteric surfactant comprises a nitrogen-containing cationic surfactant.

8. A fertilizer composition as claimed in claim 7 , wherein the at least one cationic or amphoteric surfactant comprises an ethylene or propylene oxide adduct of an aliphatic amine, said aliphatic amine containing 12 to 20 carbon atoms.

9. A fertilizer composition as claimed in claim 6 , wherein the at least one cationic or amphoteric surfactant is present in an amount in the range of from 0.001 wt. % to 0.05 wt. % with respect to the weight of the overall fertilizer composition.

10. A fertilizer composition as claimed in claim 6 , wherein the elemental sulphur is present in the form of particles having a size in the range of from 1 to 200 microns.

11. A fertilizer composition as claimed in claim 10 , wherein the elemental sulphur is present in the form of particles having a size in the range of from 5 to 150 microns.

12. A fertilizer composition as claimed in claim 11 , wherein the elemental sulphur is present in the form of particles having a size in the range of from 30 to 100 microns.