GB1247365A - Continuous nitrophosphate fertilizer process - Google Patents

Abstract

1,247,365. Nitrophosphate fertilizers. ESSO RESEARCH & ENG. CO. 28 Nov., 1968 [30 Nov., 1967; 23 Aug., 1968], No. 56577/68. Heading C1A. A continuous process for the production of nitrophosphate fertilizers of varying N/P 2 O 5 ratios comprises acidulating a calcium containing phosphorous source in the presence of "NH 4 HS0 4 ", removing the precipitated CaSO 4 , converting the CaSO 4 to CaCO 3 and (NH 4 ) 2 SO 4 and removing the CaCO 3 precipitate, converting the (NH 4 ) 2 SO 4 to "NH 4 HSO 4 " and recycling the latter to the acidulation step. After the removal of CaSO 4 , NH3 and agricultural nutrients such as KCl, KNO 3 , K 2 SO 4 , ammonium polyphosphates or mixtures thereof, and traces of Zn, B, Mn, Cu, Fe and Mo or other known nutrients, may be added to the calcium-free liquor. The CaSO 4 may be removed by filtering. The CaSO 4 may be converted to CaCO 3 and (NH 4 ) 2 SO 4 by reaction with NH 3 and CO 2 , (NH 4 ) 2 CO 3 or ammonium carbamate. The (NH 4 ) 2 SO 4 may be converted to "NH 4 HSO 4 " by heating (the NH 3 produced may be recycled) for example by adding to molten NH 4 HSO 4 or alternatively by the addition of H 2 SO 4 , use of ion exchange resins, or electrolytic convertion. By "NH 4 - HSO 4 " is meant true NH 4 HSO 4 or (NH 4 ) 2 S 2 O 7 or mixtures thereof and (NH 4 ) 2 SO 4 may also be present. The "NH 4 HSO 4 " may be added to the phosphorus source either prior to, during or after the addition of the acid. The phosphorus source may be phosphate rock. The acid used for the acidulation is preferably nitric acid which may also contain H 3 PO 4 and/or H 2 SO 4 . The heat required for the CaSO 4 conversion or the (NH 4 ) 2 SO 4 decomposition may be supplied by heat exchange with molten "NH 4 HSO 4 ". An external source of CaSO 4 may be added to the reaction sequence whereupon a (NH 4 ) 2 SO 4 by-product may be removed. The resultant nitrophosphosphate fertilizer product may be recovered by prilling a concentrated melt, granulating a concentrated melt, or evaporating a solution thereof in a heated granulator. In a comparative example the NH 4 HSO 4 may be replaced by (NH 4 ) 2 SO 4 and the recycling may be dispensed with.