Removal of urea and ammonia from exhaust gases

• US 9,464,009 B2
• Filed: 08/10/2010
• Issued: 10/11/2016
• 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): Johnson, Jonathan
• Assistant Examiner(s): NASSIRI MOTLAGH, ANITA
• Application Number:
  US13/496,192
• Publication Number:
  US 20120240649A1
• Time in Patent Office: 2,254 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 preparing a urea/ammonium sulfate (UAS) fertilizer from urea dust and ammonia in a gas stream which comprises contacting said gas stream with an aqueous sulphuric acid solution, thus forming an acid solution of ammonium sulphate and urea;

followed by

adding ammonia to the acid solution, thus forming a neutralized solution of urea and ammonium sulphate (AS) in water, followed by

concentrating said neutralized solution to a melt comprising less than 5 wt % of water, and mixing the melt with an additional amount of ammonium sulphate, followed by

transforming said melt into solid particles comprising urea and ammonium sulphate as a UAS fertilizer,

wherein said gas stream is an exhaust waste gas from a urea plant, a urea-granulation tower, a urea-prilling tower or chemical fertilizer plant, and

which exhaust waste gas stream is the sole source of the urea in the UAS fertilizer.

2. The method of claim 1, 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.

3. The method of claim 2, wherein said vaporizing is carried out in more than one step until the amount of water in the melt is less than 5 wt %.

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

5. 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 said pelletizer by feeding the UAS-comprising liquid to the feeding device from which droplets of the UAS-comprising liquid are dosed to the belt, whereon the UAS-comprising droplets solidify followed by

removing the formed UAS-comprising particles from the belt.

6. A method for preparing a UAS fertilizer from urea dust and ammonia in a gas stream which comprises contacting said gas stream with an aqueous sulphuric acid solution, thus forming an acid solution of ammonium sulphate and urea;

followed by

adding ammonia to the acid solution, thus forming a neutralized solution of urea and ammonium sulphate in water, followed by

concentrating said neutralized solution to a melt comprising less than 5 wt % of water, followed by

transforming said melt into solid particles comprising urea and ammonium sulphate 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 said pelletizer by feeding the UAS-comprising liquid to the feeding device from which droplets of the UAS-comprising liquid are dosed to the belt, whereon the UAS-comprising droplets solidify to obtain a UAS fertilizer followed by

removing the formed UAS-comprising particles from the belt to recover said UAS fertilizer,

wherein said gas stream is an exhaust waste gas from a urea plant, a urea-granulation tower, a urea-prilling tower or chemical fertilizer plant, and

which exhaust waste gas stream is the sole source of the urea in the UAS fertilizer.

7. The method of claim 6, 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.

8. The method of claim 7, wherein said vaporizing is carried out in more than one step until the amount of water in the melt is less than 5 wt %.

9. The method of claim 6, which further comprises mixing the melt with an additional amount of ammonium sulphate.

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

11. A method for preparing a UAS fertilizer from urea dust and ammonia of a gas stream which comprises contacting said gas stream with an aqueous sulphuric acid solution, thus forming an acid solution of ammonium sulphate and urea;

followed by

adding ammonia to the acid solution, thus forming a neutralized solution of urea and ammonium sulphate in water and mixing the solution with an additional amount of solid ammonium sulphate, followed by

concentrating said neutralized solution to a melt comprising less than 5 wt % of water, followed by

transforming said melt into solid particles comprising urea and ammonium sulphate, thus obtaining UAS fertilizer

wherein said gas stream is an exhaust waste gas from a urea plant, a urea-granulation tower, a urea-prilling tower or chemical fertilizer plant, and

which exhaust waste gas stream is the sole source of the urea in the UAS fertilizer.

12. The method of claim 11, 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.

13. The method of claim 12, wherein said vaporizing is carried out in more than one step until the amount of water in the melt is less than 5 wt %.

14. The method of claim 11, which further comprises mixing the melt with an additional amount of ammonium sulphate.

15. The method of claim 11, 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 said pelletizer by feeding the UAS-comprising liquid to the feeding device from which droplets of the UAS-comprising liquid are dosed to the belt, whereon the UAS-comprising droplets solidify followed by

removing the formed UAS-comprising particles from the belt.