Use of supercritical CO2 as solvent for organic polymers in a method for coating urea-containing granules

Patent metadata

Field	Value
Publication number	US-12172144-B2
Application number	US-201917254117-A
Country	US
Kind code	B2
Filing date	Jun 14, 2019
Priority date	Jun 20, 2018
Publication date	Dec 24, 2024
Grant date	Dec 24, 2024

Abstract

A process may be utilized to coat urea-containing granules with organic polymers. The process may involve compressing gaseous carbon dioxide and condensing the carbon dioxide to obtain liquid carbon dioxide, increasing the pressure and/or the temperature above the critical point of carbon dioxide and obtaining supercritical carbon dioxide, dissolving an organic polymer in the supercritical carbon dioxide to obtain a polymer-containing solution, and mixing the polymer-containing solution with urea-containing granules and lowering the temperature and/or the pressure below the critical point of carbon dioxide and obtaining coated urea-containing granules and gaseous carbon dioxide. In some cases the organic polymer may include biodegradable polymers, and the polymer-containing solution may contain between 20 to 70% by weight biodegradable polymers.

First claim

What is claimed is:

1. A process for coating urea-containing granules with organic polymers, the process comprising:
compressing and condensing gaseous carbon dioxide to obtain liquid carbon dioxide, wherein the compressing of the gaseous carbon dioxide occurs in a first step in a low-pressure compression step and in a second step in a high-pressure compression step, wherein the low-pressure includes from 5 bar to 10 bar and the high-pressure includes from 20 bar to 35 bar;
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.

2. The process of claim 1 wherein the organic polymer includes biodegradable polymers.

3. The process of claim 2 wherein the biodegradable polymer includes polylactides (PLA), polyglycols, polycaprolactones, poly(hydroxybutyric acid), poly(hydroxyvaleric acid), polyalkyl terephthalates, polyanhydrides, poly(1,4-dioxane-2,5-dione), polyamino acids, polysaccharides, cellulose esters, cellulose hydrate, cellulose acetate, carboxymethyl cellulose, lignin, polyhydroxy fatty acids, starch, biodegradable polyesters, biodegradable polyamides, biodegradable polyimides, polyhydroxyalkanoates and polybutylene succinates (PBS), amylose, amylopectin, and/or mixtures, oligomers, derivatives, and copolymers thereof.

4. The process of claim 1 wherein the polymer-containing solution contains between 20 to 70% by weight biodegradable polymers.

5. The process of claim 1 comprising returning the gaseous carbon dioxide to the compressing and condensing step and converting the gaseous carbon dioxide to supercritical carbon dioxide.

6. The process of claim 1 comprising providing the gaseous carbon dioxide and the supercritical carbon dioxide in a connected industrial plant complex.

7. The process of claim 1 wherein the condensation occurs with the aid of ammonia from a connected ammonia refrigerating system.

8. The process of claim 1 comprising subjecting the liquid carbon dioxide, after the compressing and condensing, to a flash process for at least one of removal or outgassing of inert, non-condensable gases.

9. The process of claim 1 wherein a cold/heat recovery and/or cooler are provided at least one of before the first step, between the first and second steps, or after the second step.

10. The process of claim 1 wherein the urea-containing granules and/or the coated urea-containing granules contain at least one of, nitrates, phosphates, potassium, calcium, or sulfur.

11. The process of claim 1 wherein the urea-containing granules have a mean particle size of 0.5 to 8 mm.

12. The process of claim 1 comprising mixing the polymer-containing solution with the urea-containing granules in one or more coaters with tangential spraying.

13. The process of claim 1 wherein the first and second compression steps occur within a first housing.

Assignees

• Thyssenkrupp Ind Solutions Ag
• Thyssenkrupp Ag
• Thyssenkrupp Uhde Gmbh

Inventors

• Makhynya Yevgeny
• El Hawary Tarek

Classifications

• F25J2220/80

  Separating impurities from carbon dioxide, e.g. H2O or water-soluble contaminants · CPC title

• F25J2210/80

  Carbon dioxide · CPC title

• F25J1/0027

  Oxides of carbon, e.g. CO2 · CPC title

• C07C273/10

  combined with the synthesis of ammonia · CPC title

• B05D1/025

  using gas close to its critical state · CPC title