Method for Producing a Fertilizer Containing Urea and Ammonium Sulphate

• US 20080092614A1
• Filed: 06/30/2005
• Published: 04/24/2008
• Est. Priority Date: 07/01/2004
• Status: Active Grant

• Current Assignee: YARA International ASA
• Original Assignee: YARA International ASA
• Inventors: Ledoux, Francois, Rondeau, Xavier, Ingels, Rune
• Granted Patent: US 7,837,758 B2
• Time in Patent Office: Days
• US Class Current: 71/30
• CPC Class Codes: B01J 19/242 in series
• CPC Class Codes: B01J 2219/00006 Large-scale industrial plants
• CPC Class Codes: C01C 1/242 Preparation from ammonia and sulfuric acid or sulfur trioxide
• CPC Class Codes: C05C 3/00 Fertilisers containing other salts of ammonia or ammonia itself, e.g. gas liquor
• CPC Class Codes: C05C 9/00 Fertilisers containing urea or urea compounds

Abstract

Method for the production of solid urea ammonium sulphate (UAS) fertilizers from sulphuric acid, ammonia and urea, wherein free ammonia and/or as carbamate to be decomposed from urea production, is reacted with sulphuric acid without substantially decomposing urea in the process stream, where after urea and ammonium sulphate (AS) is mixed and particulated. The point of integration of the ammonium sulphate production in the urea production process is chosen according to the desired product composition. The reaction is carried out in a pipe reactor where the head of the reactor enhanced the chemical reaction between sulphuric acid and ammonia and the urea solution surrounds the ammonium sulphate formation.

Claims

1. Method for the production of solid urea ammonium sulphate (UAS) fertilizers, where

urea is formed by reacting CO₂ and NH₃ in a urea reactor and subsequebt carbamate stripper, and

ammonium sulphate (AS) is formed by reacting H₂SO₄ and NH₃ (free or as carbamate) in a reactor downstream of the carbamate stripper, characterised in that

the effluent from the carbamate stripper is sent to the reactor for forming AS which is supplied with H₂SO₄ and eventual additional NH₃ such that the reaction heat from the AS-formation is fully exploited for concentrating the urea and AS-solution, and then

the urea and ammonium sulphate (AS) is mixed and particulated to form solid UAS-particles.

2. Method according to claim 1,

wherein the point of integration of ammonium sulphate production in the urea production process is chosen according to the desired product composition.

3. Method according to claim 1, wherein the reaction is carried out in a pipe reactor where the head of the reactor enhances the chemical reaction between sulphuric acid and ammonia and the urea solution surrounds the ammonium sulphate formation.

4. Method according to claim 3, wherein the pressure drop through the reactor is between 0 and 10 bars and the temperature of the reactor is kept between 120 and 200°

C.

5. Method according to claim 1, wherein additional ammonia can be fed either through the urea reactor or directly to a pipe reactor (2, 5, 21, 36) to achieve higher content of AS in the UAS.

6. Method according to claim 1, wherein elemental sulphur divided into fine droplets is added to the UAS.

7. Method according to claim 6, wherein the droplets are <

50 μ

m, preferably 10-25 μ

m.

8. Method according to claim 6, wherein elemental sulphur is divided into fine droplets before granulation by mixing in the line and coalescence avoided by addition of adequate additive, or directly co-sprayed with UAS in the granulator.

9. Method according to claim 1, wherein the process is carried out utilizing an increased throughput of ammonia to increase the formation of urea in the reactor, by increasing the N/C ratio and extracting the surplus ammonia from the water containing carbamate recycle stream for ammonium sulphate formation.

10. Method according to claim 1, wherein the process is carried out utilizing an increased throughput of ammonia to increase the formation of urea in the reactor, by using the surplus ammonia rich carbamate for the formation of ammonium sulphate, without recycling carbon dioxide to the synthesis.

11. Method according to claim 1, wherein the process is carried out utilizing an increased throughput of ammonia to increase the formation of urea in the reactor by using the surplus ammonia rich carbamate for the formation of ammonium sulphate, recycling the surplus carbon dioxide to the synthesis through an expansion in the carbon dioxide compressor capacity.

12. Method according to claim 1, wherein urea solution is flashed in a first separator tank, before liquid urea/carbamate solution is reacted with sulphuric acid in a first pipe reactor (2), the liquid stream (14) from the separator of the pipe reactor enters a second pipe reactor (5), where vapour phase (8) from a first separator (1) and sulphuric acid is injected, to produce more UAS, before concentration and particulation.

13. Method according to claim 12,

wherein 1-35 weight % AS is produced in the second pipe reactor.

14. Method according to claim 12,

wherein the heat of reaction for AS is utilized for concentration of the UAS-solution.

15. Method according to claim 1,

wherein a part of the urea/carbamate/water stream from the urea reactor is reacted with sulphuric acid to make UAS-slurry, while carbamate from the other part of the stream is decomposed, the resulting urea solution concentrated and mixed with the other stream before particulation of UAS.

16. Method according to claim 15,

wherein the stream is divided ⅓

-⅔

to ⅔

-⅓

or in any suitable proportions between these values.

17. Method according to claim 15,

wherein the vapour phase from the carbamate decomposition is supplied to the pipe reactor.

18. Method according to claim 15,

wherein the heat of reaction for AS and vapour pressure control in the pipe reactor separator allows concentration of the UAS solution.