Dimensionless spray flux in wet granulation: Monte-Carlo simulations and experimental validation

Hapgood, Karen P., Litster, James D., White, Edward T., Mort, Paul R. and Jones, Damien G. (2004) Dimensionless spray flux in wet granulation: Monte-Carlo simulations and experimental validation. Powder Technology, 141 1-2: 20-30. doi:10.1016/j.powtec.2004.02.005

Author Hapgood, Karen P.
Litster, James D.
White, Edward T.
Mort, Paul R.
Jones, Damien G.
Title Dimensionless spray flux in wet granulation: Monte-Carlo simulations and experimental validation
Journal name Powder Technology   Check publisher's open access policy
ISSN 0032-5910
Publication date 2004-03-18
Sub-type Article (original research)
DOI 10.1016/j.powtec.2004.02.005
Volume 141
Issue 1-2
Start page 20
End page 30
Total pages 11
Place of publication Lausanne, Switzerland
Publisher Elsevier
Language eng
Subject 290000 Engineering and Technology
290600 Chemical Engineering
290602 Process Control and Simulation
Abstract Dimensionless spray flux Ψa is a dimensionless group that characterises the three most important variables in liquid dispersion: flowrate, drop size and powder flux through the spray zone. In this paper, the Poisson distribution was used to generate analytical solutions for the proportion of nuclei formed from single drops (fsingle) and the fraction of the powder surface covered by drops (fcovered) as a function of Ψa. Monte-Carlo simulations were performed to simulate the spray zone and investigate how Ψa, fsingle and fcovered are related. The Monte-Carlo data was an excellent match with analytical solutions of fcovered and fsingle as a function of Ψa. At low Ψa, the proportion of the surface covered by drops (fcovered) was equal to Ψa. As Ψa increases, drop overlap becomes more dominant and the powder surface coverage levels off. The proportion of nuclei formed from single drops (fsingle) falls exponentially with increasing Ψa. In the ranges covered, these results were independent of drop size, number of drops, drop size distribution (mono-sized, bimodal and trimodal distributions), and the uniformity of the spray. Experimental data of nuclei size distributions as a function of spray flux were fitted to the analytical solution for fsingle by defining a cutsize for single drop nuclei. The fitted cutsizes followed the spray drop sizes suggesting that the method is robust and that the cutsize does indicate the transition size between single drop and agglomerate nuclei. This demonstrates that the nuclei distribution is determined by the dimensionless spray flux and the fraction of drop controlled nuclei can be calculated analytically in advance.
Keyword Granulation
Dimensionless spray flux
Liquid distribution
Binder addition
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

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