Removal of urea and ammonia from exhaust gases

摘要

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.

主权项

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.