Low polyphosphate suspension fertilizers from wet-process acid

摘要

An energy efficient process and apparatus is described that allows production of concentrated polyphosphate containing ammonium phosphate suspension fertilizers that can be stored and handled at temperatures well below 0° F. Ammoniation of the merchant-grade wet- process phosphoric acid provides all of the heat required by the process. Use of a unique enlarged dual pipe-type reactor system allows operation for extended periods without clogging. To obtain the high concentration and excellent low temperature storage and handling properties, the ammonium phosphate must be produced within closely specified and previously undisclosed N:P.sub.2 O.sub.5 and solution concentration ranges. Operation outside the specified composition range will reduce the maximum plant food concentration and may cause some of the ammonium phosphate salts to crystallize and foul the heat-transfer surfaces.