Stable ammonium Polyphosphate liquid fertilizer from merchant grade phosphoric acid

摘要

he invention relates to a stable ammonium polyphosphate liquid fertilizer prepared by reaction of ammonia with concentrated wet-process phosphoric acid having a P205 concentration of 54 to 62 weight percent, said wet-process phosphoric acid prior to concentration having been contacted with a cation exchange resin to remove magnesium and calcium without appreciable reduction of iron and aluminum, said concentrated acid still containing on a weight percent basis referenced to 60% P205: (i) 1.0% or greater iron and aluminum calculated as Fe203 and A1203, (ii) less than 0.3% magnesium calculated as MgO, and (iii) less than 0.15% total of sodium, potassium and calcium calculated as Na20, K20, and CaO, said liquid fertilizer being further characterized by remaining substantially sludge-free when stored at 25°C for 6 months without addition of any sequestering or suspending agent.