(580e) Secondary Nucleation and Growth Kinetics of Aluminum Hydroxide Crystallization from Potassium Aluminate Solution Using FBRM
- Conference: AIChE Annual Meeting
- Year: 2018
- Proceeding: 2018 AIChE Annual Meeting
- Group: Separations Division
- Time: Wednesday, October 31, 2018 - 4:55pm-5:15pm
There are many different experimental techniques that have been used to measure the secondary nucleation and growth kinetics. As a promising apparatus of process analytical technologies(PAT), focused beam reflectance measurement (FBRM) can directly monitor the chord length distribution (CLD) at a very short time interval, such as 2s, so more detailed information can be recorded during crystallization without sampling. A method is developed to calculate the low-order moments from the CLD directly without converting the CLD to PSD. Therefore, secondary nucleation and growth rates were measured by FBRM directly.
In this work, moments of crystal population were estimated from the measured CLD, generated by the FBRM, and the supersaturation was calculated from the measured solution concentration by ICP-AES. The moments were uesed to approximate the secondary nucleation and growth rates. Meanwile, the secondary nucleation and growth rates were also generally represented by a power-law function of the main driving force for crystallization process, supersaturation. Therefore, kinetics parameters for secondary nucleation and crystal growth were calculated based on experimental data at different supersaturations and temperatures. Also, the kinetic model was verified in further experiments by comparison of experimental data and predicted data.
Another method was perfomed to estimated gibbsite secondary nucleation and crystal growth using a semiempirical power-law model by BET and ICP-AES. Instead of measuring total particle surface area by BET, moments of crystal population by FBRM were uesed to calculate total particle surface area in this work. And the kinetics calculated by FBRM showed a same trend in comparision with the results by BET.
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