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Use of the Confined Impinging Jet Reactor for production of nanoscale Iron Oxide particles
- Author / Creator
- Siddiqui, Shad Waheed
The confined impinging jet reactor gives efficient mixing performance as required for fast reactions. In this work the mixing performance of CIJR is characterized through three measures: estimates of the energy dissipation, micromixing efficiency based on the yield of a homogeneous (iodide-iodate) reaction and particle size resulting from a heterogeneous (iron oxide) precipitation reaction. Whereas product yield and energy dissipation are used to test operational robustness of CIJR, iron oxide model system is used to study the effect of feed flow rate (mixing) and reactant concentration on precipitate agglomerate size. Mixing and concentration effects on nucleation, particle growth and particle agglomeration are tracked to understand the agglomeration process. Various types of stabilizers and additive concentrations to limit particle agglomeration are also tested. Effects of in situ and post-reaction sonication on agglomerate size are also investigated. Efforts are made to determine variations in mixing efficiency the operational robustness of the scale-up (2X and 4X) geometries. Also efforts are made to identify scaling parameters and the limit on geometric scale-up for good mixing performance.
Energy dissipation is found to vary between 20 W/kg and 6800 W/kg in CIJR and decreases on scale-up at constant Reynolds number. The operation of the CIJR and the scale-up geometries is robust to changes in flow rate, exhibiting stable performance up to 30% difference in inlet flow rates. Reliable mixing performance is obtained until 2X scale-up, while at low flow rates, the jets fail to impinge in 4X scale-up, and sometimes failing to fill the reactor volume.
Iron oxide primary and agglomerate particles are seen to vary with flow rate and reactant concentrations. Largest primary particles (and smallest agglomerates) are obtained at high flow rates and high reactant concentrations, which indicate to size dependent agglomerative tendency of the primary particles. Stabilizers added in situ see limited success. Post-reaction sonication is helpful in dispersing soft agglomerates, but in situ sonication shows no significant reduction in agglomerate size with or without stabilizer. Primary particles are understood to agglomerate due to collisions induced by Brownian motion, simple shear and velocity fluctuations in turbulent flows. These collision mechanisms operate at different length scales in the fluid mass.
- Graduation date
- Fall 2009
- Type of Item
- Doctor of Philosophy
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