Method for preparing slow-release phosphate fertilizer from monoammonium phosphate byproduct ammoniation slag

• Main Authors: ZHAO QIANG, LIU SONGLIN, FU YONG, ZHANG QUN, ZHANG JUN, WANG FENGXIA, XIE JUAN, MA PEIGEN, TANG JIANWEI, YANG JUN, TAO SHAOCHENG, LIU XU
• Format: Patent
• Language: Chinese; English
• Published: 06.06.2023
• Subjects: CHEMISTRY; FERTILISERS; FERTILISERS CHARACTERISED BY THEIR FORM; MANUFACTURE THEREOF; METALLURGY; MIXTURES OF FERTILISERS COVERED INDIVIDUALLY BY DIFFERENTSUBCLASSES OF CLASS C05; MIXTURES OF ONE OR MORE FERTILISERS WITH MATERIALS NOT HAVINGA SPECIFIC FERTILISING ACTIVITY, e.g. PESTICIDES,SOIL-CONDITIONERS, WETTING AGENTS; PHOSPHATIC FERTILISERS

The invention discloses a method for preparing a slow-release phosphate fertilizer from monoammonium phosphate byproduct ammoniated residues, which specifically comprises the following steps: step 1, adding phosphoric acid or phosphate into the ammoniated residues, adjusting the ratio of citrate-soluble phosphorus to water-soluble phosphorus in a mixture to be 0.5-1.5: 1, controlling the ratio of the mass of sulfur, magnesium, iron and calcium in the mixture to the mass of P2O5 in the mixture to be 0.1-0.3: 1, controlling the pH value of the mixture to be 1-4, adding urea, and uniformly stirring to obtain a mixture A; adjusting the molar ratio of P2O5 to N to be (2-3): 1, and heating until the urea is dissolved to obtain mixed slurry; according to the method, part of orthophosphate in the ammoniated residues is converted into ammonium polyphosphate by controlling polymerization conditions, meanwhile, it is ensured that the proportion of available phosphorus is as high as 97%-100%, and in the polymerization pr