METHOD FOR PRODUCING SOLID UREA BY GRANULATION

Abstract

Method for producing solid urea by granulation, wherein the granulation is fed with liquid urea having a purity greater than 98% by weight and not containing formaldehyde.

Claims

1) Method for producing solid urea by granulation, characterized in that the granulation is fed with urea melt having a concentration of more than 98% by weight and in that no formaldehyde is added to said urea melt.

2) Method according to claim 1, characterized in that said urea melt has a concentration of at least 99.5% by weight and preferably at least 99.7% by weight.

3) Plant for producing solid urea in granule form, operating using a method according to claim 1 or 2.

4) Solid urea in granule form, free from formaldehyde, obtained with a method according to claim 1 or 2.

5) Method for revamping a plant for producing solid urea, wherein the plant comprised a prilling section for production of solid urea by means of prilling of a high-concentration urea melt, the method comprising the steps of: installing a granulation section and feeding at least part of said urea melt originally intended for the prilling section, and without the addition of formaldehyde, to said new granulation section.

6) Method according to claim 5, wherein a portion of said urea melt is used in the prilling section to produce seeds for said new granulation section.

Description

DESCRIPTION OF THE FIGURES

[0025] FIG. 1 is a scheme of a first embodiment of the invention.

[0026] FIG. 2 is a scheme of a second embodiment.

[0027] FIG. 3 is a scheme of a third embodiment.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0028] FIG. 1 shows a schematic urea plant comprising a synthesis section US and a recycling section UR. The recycling section UR provides an aqueous solution of urea SOL containing about 70% by weight of urea.

[0029] Said solution passes through evaporation section EV inside which the water is removed, obtaining a urea melt UM containing more than 98%, for example 99.7%, by weight of urea. Said urea melt UM, without the addition of formaldehyde, is fed to a granulation section GS, obtaining granules of urea U.

[0030] FIG. 2 shows an example of revamping of a plant in which the urea melt UM is originally fed to a prilling section PS which produces urea prills P. At least a part UM′ of said urea melt UM is fed to a granulation section GS which is arranged parallel to the prilling section PS, also in this case without the addition of formaldehyde.

[0031] In some embodiments, the UM stream is directed entirely towards the new granulation section GS, i.e. the production of prills P is discontinued.

[0032] FIG. 3 illustrates an embodiment which is a variant of FIG. 2, wherein a portion UM″ of the urea melt is used in the existing prilling section PS to produce solid seeds S for the granulation section GS.