Removal of urea and ammonia from exhaust gases
First Claim
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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 byadding ammonia to the acid solution, thus forming a neutralized solution of urea and ammonium sulphate (AS) in water, followed byconcentrating 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 bytransforming 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, andwhich exhaust waste gas stream is the sole source of the urea in the UAS fertilizer.
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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.
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Citations
15 Claims
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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. - View Dependent Claims (2, 3, 4, 5)
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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. - View Dependent Claims (7, 8, 9, 10)
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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. - View Dependent Claims (12, 13, 14, 15)
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Specification