Volume 10 Issue 4
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Zhang, X., Shen, Z., Cai, C., Yu, X., Du, J., Xing, Y., & Ma, S. (2012). Modification of ADP extinguishing powder by siliconization in spray drying. Particuology, 10(4), 480–486. https://doi.org/10.1016/j.partic.2011.11.001
Modification of ADP extinguishing powder by siliconization in spray drying
Xiaojing Zhang a *, Zhigang Shen a, Chujiang Cai a, Xiaozheng Yu a b, Jun Du c, Yushan Xing a, Shulin Ma a
a Beijing Key Laboratory for Powder Technology Research and Development, Beijing University of Aeronautics and Astronautics, Beijing 100191, China
b Science School, Beijing University of Civil Engineering and Architecture, Beijing 100044, China
c Beijing Institute of Structure and Environment Engineering, Beijing 100076, China
10.1016/j.partic.2011.11.001
Volume 10, Issue 4, August 2012, Pages 480-486
Received 13 December 2010, Revised 14 October 2011, Accepted 8 November 2011, Available online 20 January 2012.
E-mail: zhangxiaojing@buaa.edu.cn

Highlights

► An activation index was introduced as a measure of particle surface hydrophobicity. 

► According to activation index measurements and characterization of modified ADP powder, optimum modification conditions were determined as MHSO-to-ADP mass ratio 3%, exit air temperature below 100 °C and low humidity of inlet air for spray drying.


Abstract

Superfine spherical fire-extinguishing powder, ammonium dihydrogen phosphate (ADP, NH4H2PO4), was prepared by spray drying and modified in situ with methyl hydrogen silicone oil (MHSO) emulsion and the fluorinated surfactant FK-510. The influences of the MHSO mass ratio on the hydrophobicity, surface composition, surface morphology, dispersion and particle-size distribution of the NH4H2PO4 were studied, and the influence of the drying air temperature on the decomposition of the NH4H2PO4 was also researched. The results indicate that the MHSO and FK-510 congregate on the particle surfaces and then form a hydrophobic shell. This shell improves the particle hydrophobicity and leads to a fine dispersion of the particles. During the process of preparing the precursor solution, 3 wt% (based on the weight of NH4H2PO4) was chosen as the optimum value of the MHSO mass ratio. During the spray drying, a low absolute humidity of the air should be maintained, and it is very important to keep the exit-air temperature below 100 °C to avoid decomposition.

Graphical abstract
Keywords
Methyl hydrogen silicone oil (MHSO); Ammonium dihydrogen phosphate (ADP); Fire-extinguishing powder; Spray drying; Drying air temperature; Agglomeration