Powder Incorporation into Liquids using Ytron ZC1 - poster
James C. Bacon, Chris D. Rielly, N. Gül Özcan-Taskin
Loughborough University, Dept. of Chemical Engineering, Loughborough, LE11 3TU, UK
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The introduction of nanoparticles in new formulations has resulted in enhanced product performance or entirely new product properties that cannot be achieved otherwise. Adhesives, coatings, packaging, catalysts, paints and inks, sunscreens are a few examples. The first step in the production of final or intermediate products in the form of nanoparticulate dispersions is the incorporation of a dry powder into a liquid, which is often performed using a stirred tank [1]. Previous work on powder incorporation has therefore focused on stirred tanks, with only one study which made use of a batch rotor-stator[2]. Incorporation is then followed by a deagglomeration stage with power-intensive devices, such as inline rotor-stators, which are commonly used for large scale manufacture of such products.
In this project, the powder dispersion performance of an in-line rotor-stator, Ytron ZC1, has been studied. The specific design of Ytron ZC1 allows the introduction of the powder directly into the rotor-stator head; subsequently the dispersion can be recirculated to achieve deagglomeration. The part of the study presented here is concerned with powder incorporation with the objective of establishing the performance of the device. Concentrations up to 10% w:w were studied by making incremental additions of 1% w:w silica powder into water, over a range of flow rates. Air velocity values at the powder inlet were also measured.
For a given rotor-stator head and speed, there exists a range of liquid flow rates over which the incorporation rate is highest. Initially, increasing the flow rate increases the incorporation rate and above an optimum range, incorporation slows down and eventually ceases. This is due to the liquid starting to flow up the powder inlet which can have severe consequences if the partly wetted powder forms a soft solid, blocking the powder inlet as this would require stopping the operation to dismantle and clean.
It was shown that using the Ytron ZC1, the incorporation rate can be maintained constant over a wide range of powder concentrations compared to surface additions (Figure 1). This is in agreement with previous findings reported with Ytron Y-Jet, a batch rotor-stator and holds as long as the increased concentration does not result in non-Newtonian rheology.
It could be shown that the air suction velocity at the powder inlet is indicative of powder incorporation performance. This would be of significant benefit for industrial practice as trials can be run with just liquids to identify optimum operating conditions, saving time and costs associated with materials and waste.
- 1. Özcan-Taskin, N.G. (2015) Dispersion of fine powders in liquids- particle incorporation and size reduction in Pharmaceutical Blending and Mixing, Wiley DOI:10.1002/9781118682692
- 2. Özcan-Taskin, N.G. (2013) Incorporation of nanoparticle clusters into a liquid using a proprietary design mixer, Ytron Y Jet, Chemical Engineering Research and Design, 1-7 (DOI: 10.1016/j.cherd.2013.03.019)