Granulation by spray coating aqueous solution of ammonium sulfate to produce large spherical granules in a fluidized bed--颗粒学报PARTICUOLOGY

Wang, G., Yang, L., Lan, R., Wang, T., & Jin, Y. (2013). Granulation by spray coating aqueous solution of ammonium sulfate to produce large spherical granules in a fluidized bed. Particuology, 11(5), 483–489. https://doi.org/10.1016/j.partic.2012.10.005

Granulation by spray coating aqueous solution of ammonium sulfate to produce large spherical granules in a fluidized bed

Guanda Wang, Ling Yang, Rui Lan, Tingjie Wang^*, Yong Jin

Department of Chemical Engineering, Tsinghua University, Beijing 100084, China

10.1016/j.partic.2012.10.005

Volume 11, Issue 5, October 2013, Pages 483-489

Received 9 July 2012, Revised 5 October 2012, Accepted 14 October 2012, Available online 13 March 2013.

E-mail: wangtj@tsinghua.edu.cn

Highlights

► High efficiency of (NH₄)₂SO₄ aqueous solution coating granulation was achieved.

► Sand-like structure in the granules of pure (NH₄)₂SO₄ was found.

► Compact structure of granules was achieved by adding CaCO₃ or SiO₂ additives.

► Granules with higher strength were produced from heterogeneous crystallization.

Abstract

Spherical 2–4 mm granules of ammonium sulfate (NH₄)₂SO₄ are promising fertilizer for practical use, though only much smaller grains are being produced in industry. This work used coating granulation to produce large spherical granules of (NH₄)₂SO₄ in a fluidized bed by spraying its aqueous solution onto 0.9–1.6 mm (NH₄)₂SO₄ core particles. However, the overall coating efficiency was only 58% due to loss as dust by attrition of (NH₄)₂SO₄ in the vent gas. By adding CaCO₃ or SiO₂ particles into the feed solution, the coating efficiency was increased to over 90%. This increase in coating efficiency was due to a change in the crystallization mechanism of (NH₄)₂SO₄. The added CaCO₃ or SiO₂ particles provided a heterogeneous surface that induced (NH₄)₂SO₄ to crystallize uniformly to form a more compact structure less susceptible to attrition.

Graphical abstract

Keywords

Ammonium sulfate; Spray coating; Granulation; Fluidized bed; Heterogeneous crystallization

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