Urea finishing method

Patent metadata

Field	Value
Publication number	US-9890115-B2
Application number	US-201214127962-A
Country	US
Kind code	B2
Filing date	Oct 12, 2012
Priority date	Oct 14, 2011
Publication date	Feb 13, 2018
Grant date	Feb 13, 2018

Abstract

Disclosed is a method for urea finishing. A urea solution is subjected to crystallization and, other than in conventional processes, the urea crystals are shaped by exerting mechanical force onto them. Thus, the conventional prilling or granulation finishing steps can be avoided, and so are the corresponding emissions of ammonia and/or dust. The crystallization comprises a flash crystallization. The invention also pertains to the urea particles obtainable by the process, to a urea plant, and to a method of modifying an existing urea plant.

First claim

The invention claimed is:

1. A process for the production of urea pellets or flakes from an aqueous urea solution comprising subjecting said aqueous urea solution to dry flashing so as to result in a product that contains substantially no liquids and which product consists essentially of solid urea particles and an ammonia and water containing vapor, followed by
exerting mechanical force on the urea particles, thus producing said urea pellets or flakes;
wherein the urea pellets or flakes are of a size in the range of from 1 mm to 20 mm, and wherein
the urea particles obtained by dry flashing are of a size between 10 and 500 μm;
the dry flashing is carried out at 2 to 10 kPa;
the dry flashing is adiabatic; and
the aqueous urea solution has a urea concentration of 85 to 95% by weight.

2. The process of claim 1 , wherein the mechanical force is exerted onto the urea particles by means of compression forces.

3. The process of claim 1 , wherein said aqueous urea solution comprises formaldehyde or urea formaldehyde as an additive.

4. The process of claim 1 , wherein the dry flashing comprises distributing the aqueous urea solution using a liquid distributor.

5. The process of claim 1 wherein said process further comprises extracting the urea particles from the dry flashing using a extractor for extracting solid products from vacuum systems, directly conveying said extracted urea particles to a urea shaping device, and subjecting the urea particles into a mold and pressing the urea particles into pellets or flakes.

6. The process of claim 1 which further comprises capturing any dust with a cyclone or wet washer from said exerting of mechanical force; wherein the mechanical force is exerted onto the urea particles by means of compression forces.

Assignees

• Stamicarbon

Inventors

• Mennen Johannes Henricus

Classifications

• C07C273/14 Primary

  Separation; Purification; Stabilisation; Use of additives · CPC title

• B29C43/006

  Pressing and sintering powders, granules or fibres · CPC title

• C05C9/005

  Post-treatment · CPC title

• C05C9/02

  containing urea-formaldehyde condensates · CPC title

• B29K2075/02

  Polyureas · CPC title