Operation and Kinetic Modeling of Membrane-assisted Crystallization

• Main Authors: Po-Chen Su, 蘇柏丞
• Other Authors: 吳哲夫
• Format: Others
• Language: en_US
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/789h5b

碩士 === 國立臺灣大學 === 化學工程學研究所 === 106 === Membrane-assisted crystallization processes have the potential to reduce energy consumption and equipment size (footprint) compared to evaporative crystallization. In this thesis, reverse osmosis membranes and porous hydrophobic membranes are considered for the removal of water from solution to facilitate crystallization. Experiments using both types of membranes are performed and mathematical models of membrane-assisted crystallization processes are also constructed. Simulation of the process is also conducted to identify conditions that minimize the nucleated crystal volumetric ratio (μ_(3,n)⁄(μ_3)). Adipic acid and potassium chloride are used in the experimental work for the reverse osmosis membrane and the porous hydrophobic membrane respectively. Preliminary experimental work has been done including solubility measurements, data collection and regression for relation of temperature and conductivity measurements for online measurement of concentration, and salt rejection tests to measure membrane selectivity. Five substances are chosen for the membrane-assisted crystallization simulation: potassium nitrate, potassium sulfate, pentaerythritol, succinic acid, and potassium alum; the kinetic parameters from literature are used. Two limiting cases of crystallizer design are considered: one in which only clear solution is circulated from the crystallizer to the buffer tank, and one in which a crystal slurry is circulated. In the simulation, the effect of seed loading and seed size on the objective function is discussed. Furthermore, in order to understand the influence of membrane water removal rate on the product nucleation volumetric ratio, different water removal trajectories as function of time were considered.