Use of supercritical co2 as solvent for organic polymers in a method for coating urea-containing granules

A process for coating urea-containing granules with organic polymers, the process comprising:

• compressing and condensing gaseous carbon dioxide to obtain liquid carbon dioxide;
• increasing at least one of pressure or temperature above a critical point of carbon dioxide to obtain supercritical carbon dioxide;
• dissolving an organic polymer in the supercritical carbon dioxide to obtain a polymer-containing solution;
• and
• mixing the polymer-containing solution by at least one of spraying the polymer-containing solution onto or bringing the polymer-containing solution into contact with urea-containing granules, in which
• a simultaneous or subsequent lowering of temperature and/or pressure below the critical point of carbon dioxide occurs, and
• coated urea-containing granules and gaseous carbon dioxide are obtained.

A plant complex for coating urea-containing granules with biodegradable polymers including a urea synthesis plant and a plant for coating the urea-containing granules, wherein the plant for coating the urea-containing granules comprises:

• a feed line for supercritical carbon dioxide from the urea synthesis plant;
• a feed line for a biodegradable polymer;
• a mixing device for the supercritical carbon dioxide and the biodegradable polymer, the mixing device being connected to the feed lines;
• a coater connected to the mixing device;
• and
• a feed line for granules, wherein the coater has a first outlet for gaseous carbon dioxide and a second outlet for a coated product.