Nitrophosphate process 767350 223657148 2008-07-05T03:11:23Z Rifleman 82 1255637 +ref The '''nitrophosphate process''' (also known as the '''Odda process''') was a method for the industrial production of [[nitrogen]] [[fertilizer]]s invented by Erling Johnson in the city of [[Odda, Norway]] around [[1927]]. The process involves acidifying [[calcium phosphate|phosphate rock]] with [[nitric acid]] to produce a mixture of [[phosphoric acid]] and [[calcium nitrate]]. :Ca<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub> + 6 HNO<sub>3</sub> + 12 H<sub>2</sub>O &rarr; 2 H<sub>3</sub>PO<sub>4</sub> + 3 Ca(NO<sub>3</sub>)<sub>2</sub> + 12 H<sub>2</sub>O The mixture is cooled to below 0 degrees Celsius, where the calcium nitrate crystallizes and can be separated from the phosphoric acid. :2 H<sub>3</sub>PO<sub>4</sub> + 3 Ca(NO<sub>3</sub>)<sub>2</sub> + 12 H<sub>2</sub>O &rarr; 2 H<sub>3</sub>PO<sub>4</sub> + 3 Ca(NO<sub>3</sub>)<sub>2</sub>.4H<sub>2</sub>O The resulting calcium nitrate produces nitrogen fertilizer. The filtrate is composed mainly of phosphoric acid with some nitric acid and traces of calcium nitrate, and this is neutralized with [[ammonia]] to produce a compound fertilizer. :Ca(NO<sub>3</sub>)<sub>2</sub> + 4 H<sub>3</sub>PO<sub>4</sub> + 8 NH<sub>3</sub> &rarr; CaHPO<sub>4</sub> + 2 NH<sub>4</sub>NO<sub>3</sub> + 3(NH<sub>4</sub>)<sub>2</sub>HPO<sub>4</sub> If [[potassium chloride]] or [[potassium sulfate]] is added, the result will be NPK fertilizer. The process was an innovation for requiring neither the expensive [[sulfuric acid]] nor producing [[gypsum]] waste. The calcium nitrate mentioned before, can as said be worked up as calcium nitrate fertilizer but often it is converted into [[ammonium nitrate]] and [[calcium carbonate]] using [[carbon dioxide]] and ammonia. :Ca(NO<sub>3</sub>)<sub>2</sub> + 2 NH<sub>3</sub> + CO<sub>2</sub> + H<sub>2</sub>O &rarr; 2 NH<sub>4</sub>NO<sub>3</sub> + CaCO<sub>3</sub> Both products can be worked up together as straight nitrogen fertilizer. Although Johnson created the process while working for the Odda Smelteverk, his company never employed it. Instead, it licensed the process to [[Norsk Hydro]], [[BASF]], [[Hoechst]], and DSM. Each of these companies used the process, introduced variations, and licensed it to other companies. Today, only [[Yara International|Yara]] (Norsk Hydro), BASF, AgroLinz, and GNFC still use the Odda process. Due to the alterations of the process by the various companies who employed it, the process is now generally referred to as the nitrophosphate process. ==References== <references/> * {{cite book |editor = Nielsson, F.T. |title=Manual of fertilizer processing |publisher=[[CRC Press]] |year=1986 |pages= |isbn=0-8247-7522-8 |chapter = 15. The Norks Hydro Nitrophosphate Process | pages = 393-420 | author = J. Steen; H. Aasum; T. Heggeboe}} [[Category:Chemical processes]] [[Category:Industrial processes]] [[fr:Nitrophosphate]] [[nl:Oddaprocedé]] [[no:Oddaprosessen]] [[nn:Oddaprosessen]]