REMOVAL OF UREA AND AMMONIA FROM EXHAUST GASES

• US 20170137330A1
• Filed: 01/31/2017
• Published: 05/18/2017
• Est. Priority Date: 09/16/2009
• Status: Active Grant

• Current Assignee: Stamicarbon B.V. (MAIRE)
• Original Assignee: Stamicarbon B.V. (MAIRE)
• Inventors: MEESSEN, Jozef Hubert, ORFANIDIS, Pantelis
• Granted Patent: US 10,640,428 B2
• Time in Patent Office: Days
• CPC Class Codes: B01D 2251/506 Sulfuric acid
• CPC Class Codes: B01D 2257/406 Ammonia
• CPC Class Codes: B01D 2257/70 Organic compounds not provided for in groups B01D2257/00 - B01D2257/602
• CPC Class Codes: B01D 53/54 Nitrogen compounds
• CPC Class Codes: B01D 53/58 Ammonia
• CPC Class Codes: B01D 53/80 Semi-solid phase processes, i.e. by using slurries
• CPC Class Codes: C01C 1/12 Separation of ammonia from gases and vapours as part of the ammonia synthesis process C01C1/04
• CPC Class Codes: C01C 1/22 Sulfites of ammonium
• CPC Class Codes: C05C 3/00 Fertilisers containing other salts of ammonia or ammonia itself, e.g. gas liquor
• CPC Class Codes: C05C 3/005 Post-treatment
• CPC Class Codes: C05C 9/00 Fertilisers containing urea or urea compounds
• CPC Class Codes: C07C 273/16 Separation; Purification

Abstract

The invention relates to a method for recovery of urea dust and ammonia from a gas stream by contacting said gas stream with an aqueous sulphuric acid solution, thus forming an acid solution of ammonium sulphate and urea, characterized in that the acid solution is concentrated to a melt comprising less than 5 wt % of water, which melt is subsequently transferred into solid particles comprising urea and ammonium sulphate.

Claims

1. Method for recovery of urea dust and ammonia from a gas stream by contacting said gas stream with an aqueous sulphuric acid solution, thus forming an acid solution of ammonium sulphate and urea, characterized in that the acid solution is concentrated to a melt comprising less than 5 wt % of water, which melt is subsequently transferred into solid particles comprising urea and ammonium sulphate.

2. Method according to claim 1, wherein ammonia is added to the acid solution before the acid solution is concentrated, thus forming a neutralized solution of urea and ammonium sulphate in water.

3. Method according to claim 2, wherein the neutralized solution is concentrated by vaporization of at least part of the water phase, thus forming water vapor and a melt comprising less than 5 wt % of water.

4. Method according to claim 3, wherein vaporization of claim 3 is carried out in more than one step until the amount of water in the melt is less than 5 wt %.

5. Method according to any of the preceding claims, wherein the melt is mixed with an additional amount of ammonium sulphate.

6. Method according to any of the claims 1-4, where the solution before concentrating is mixed with an additional amount of ammonium sulphate.

7. Method according to any of the preceding claims, wherein the melt is transferred into solid particles comprising urea in a pelletizer, comprising a feeding device, a belt and a device to remove the formed pellets from the belt, by feeding a urea-comprising liquid to the feeding device from which droplets of the urea-comprising liquid are dosed to the belt, whereon the urea- comprising droplets solidify, where after the formed urea-comprising particles are removed from the belt.