|Institution:||Washington University in St. Louis|
|Keywords:||Engineering, Environmental; Corona charger, Magnetic filter, Particles, Photocharing|
|Full text PDF:||http://openscholarship.wustl.edu/etd/210
Particle separation technologies have been utilized in many industrial fields, such as pigment and filler production, mineral processing, environmental protection, the food and beverage industry, and the chemical industry, as well as in biomedical application, such as cell biology, molecular genetics, biotechnological production, clinical diagnostics, and therapeutics. A lot of particle separation technologies using various mechanics in terms of the differences in the physical or physico-chemical properties of the particles have been developed. Among these categories, electrical and magnetic separations are of great interest in recent researches. The overall objective of this dissertation is to advance our current knowledge on these two particle separation technologies. Accordingly, it has two major parts:: 1) Charge Conditioning for Particle Separation, and: 2) Magnetic Filtering for Particle Separation. In the first part, a new DC-corona-based charge conditioner for critical control of electrical charges on particles and a UV aerosol charger for fundamental investigation particle photocharging process were developed. The chargers' performances including charging efficiencies and charge distributions were evaluated upon different operational conditions such as aerosol flow rates, corona operations, and ion-driving voltages for the charge conditioner, particle material and irradiation intensity for the UV charger. The birth-and-death charging model with the Fuchs limiting sphere theory for calculating the ion-particle combination coefficient was applied to obtain the charging ion concentration inside the charge conditioner. The UV charging model with the photoemission rely on the Fowler-Nordheim law was applied to predict the charging performance of the UV charger. In the second part, a magnetic filter system has been constructed, and its performance has been investigated. To retrieve the magnetic property of characterized particles from the measured penetration data, a numerical model was further developed using the finite element package COMSOL Multiphysics 3.5. The numerical model was first validated by comparing the experimental penetration with the simulation results for the cases of 100, 150, and 250 nm r-Fe2O3 particles having the magnetic susceptibility characterized by Vibrating Sample Magnetometer: VSM). The magnetic susceptibilities of other sizes from 100 to 300 nm were then derived from this model according to the measured penetration data. To control or remove the lunar dust through a magnetic approach, eight samples: three JSC-1A series lunar dust simulants, two NU-LHT series lunar dust simulants, and three minerals) in the size range from 150 to 450 nm were characterized. Magnetic susceptibilities were obtained from the difference in particle penetration through magnetic mesh filters with and without an applied external magnetic field.