Obtaining ammophosphate and sulfoammophosphate fertilizers on base of the washed dry concentrate containing 26% P₂O₅

Abstract

The process of obtaining ammophosphate by means of phosphoric acid decomposition of washed dried concentrate (WDC with 26% P2O5 and 10% CO2) - raw material for the production of thermally fired concentrate, has been studied. The wet process phosphoric acid (WPA) contains (wt.%): 16.46 P2O5, 0.06 CaO, 1.11 MgO, 0.27 Fe2O3, 0.41 Al2O3, 2.98 SO3 and 0.99 F. The weight ratio of WPA:WDC ranged from 100: 10 to 100: 30. Then acidic phosphate pulps (at 65 °C) after 45 minutes were ammoniated to pH = 3.8, granulated and dried at 85-90 °C. It has been shown that the nitrogen content in the finished product ranges from 4.92-7.11%, total phosphorus (P2O5t.) 41.48-46.44%, phosphorus acceptable by citric acid (P2O5ac.c.a.) 34.79-45.11%, phosphorus form of water soluble (P2O5w.s.) 23.49-37.73%. Weight fractions of H2SO4 - 5 and 7.5 were optimal and the product contains 37.6 and 34.47% of P2O5t.; 24.11 and 22.06% CaOt., 88.75 and 92.40% P2O5ac.c.a.by citric acid: P2O5t., 84.21 and 89.7% P2O5ac.tr.b. by trilon B: P2O5t., 77.39 and 79.54% P2O5w.s.:P2O5t., 6.03 and 7.08% nitrogen, respectively. The strength of granules of fertilizers averages 3.50 MPa and are quite suitable for bulk storage and transportation.