Removal of urea and ammonia from exhaust gases

• US 9,556,077 B2
• Filed: 12/05/2013
• Issued: 01/31/2017
• Est. Priority Date: 09/16/2009
• Status: Active Grant

• Current Assignee: Stamicarbon B.V. (Maire Tecnimont SpA)
• Original Assignee: Stamicarbon B.V. (Maire Tecnimont SpA)
• Inventors: Meessen, Jozef Hubert, Orfanidis, Pantelis
• Primary Examiner(s): Smith, Jennifer A
• Assistant Examiner(s): Nassiri Motlagh, Anita
• Application Number:
  US14/098,496
• Publication Number:
  US 20140090433A1
• Time in Patent Office: 1,153 Days
• Field of Search: None
• US Class Current: 1/1
• 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. A method for recovery of urea dust and ammonia from a gas stream to obtain urea/ammonium sulphate (UAS) fertilizer particles which method comprises contacting said gas stream with an aqueous sulphuric acid solution, thus forming an acid solution of ammonium sulphate and urea, and

concentrating said acid solution to a melt comprising said ammonium sulphate and urea and less than 5 wt % of water, followed by transforming said melt into solid particles comprising urea and ammonium sulphate, and recovering said UAS fertilizer particles from said transformed melt;

wherein all of the urea in said solid particles is derived from said gas stream.

2. The method of claim 1, which further comprises adding ammonia to the acid solution before the acid solution is concentrated, thus forming a neutralized solution of urea and ammonium sulphate in water.

3. The method of claim 2, which further comprises vaporizing at least part of the water phase of the neutralized solution, thus forming water vapor and a melt comprising less than 5 wt % of water.

4. The method of claim 3, wherein said vaporizing is carried out in more than one step until the amount of water in the melt is less than 5 wt %.

5. The method of claim 1, which further comprises mixing the melt with an additional amount of ammonium sulphate.

6. The method of claim 1, which further comprises mixing the solution with an additional amount of ammonium sulphate before concentrating.

7. The method of claim 1, wherein said transforming is conducted in a pelletizer, said pelletizer comprising a feeding device, a belt and a device to remove the formed pellets from the belt, wherein said melt is transferred to the pelletizer by said melt to the feeding device from which droplets of the melt are dosed to the belt, whereon the droplets solidify followed by

removing the formed solid particles from the belt.