| 摘要 |
Purified diammonium phosphate is produced by neutralizing relatively pure melamine orthophosphate, prepared from wet-process phosphoric acid, with ammonia in a hot solution of diammonium phosphate to give a slurry of melamine in concentrated diammonium phosphate solution. The liberated melamine is virtually insoluble in concentrated diammonium phosphate solutions; it is filtered from the hot mixture, washed, and recycled to produce more melamine phosphate by reaction with wet-process phosphoric acid. The hot, concentrated diammonium phosphate filtrate is cooled to precipitate purified diammonium phosphate crystals. The product is separated from its mother liquor by filtration, and the resulting filtrate is recycled to the reactor. The small amount of impurities introduced with the melamine phosphate are removed partly with the liberated melamine and partly by centrifugation of the diammonium phosphate solution. The only starting materials for the process are phosphoric acid and ammonia.
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