Effect of preparation parameters on properties of spray dried ammonium dihydrogen phosphate fire-extinguishing particles

Superfine spherical hollow hydrophobic ammonium dihydrogen phosphate (NH₄H₂PO₄) fire-extinguishing particles were produced by a spray drying method and modified in situ with silicon oil emulsion. The results indicated that the particles prepared at the inlet gas temperature of 180°C, 200°C and 220°C were composed of NH4H2PO4. In the absence of carboxy methyl cellulose sodium (CMC), some nonspherical particles were formed. When 0.5% or 1.0% of CMC was added, the resulting particles had a good spherical shape and hollow particles increased. With an increase in the mass fraction of CMC, the bulk density of particles decreased. 9.0% silicon oil emulsion was the optimal proportion for improving the hydrophobic performance of particles. X-ray Photoelectron Spectroscopy (XPS) analysis suggested that the hydrophobicity of particles was attributed to the migration of silicon oil emulsion to the surface of particles during the spray drying process. Fire-extinguishing test showed the extinguishing capability of superfine spherical hollow NH₄H₂PO₄fire-extinguishing particles prepared by spray drying was improved.