• Journal of ILASS-Korea
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• v.11 no.2
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• pp.98-104
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• 2006

A charged droplet scrubber was introduced to remove visible smokes generated in many industrial facilities. Lab-scale and field tests were conducted in this study. The system consists of a corona discharger to effectively charge the fine particles, fellowed by an electrostatic chamber to promote coagulation between charged fine particles and oppositely charged droplets and a demister to remove resultant particles. Overall collection efficiency, 98.4% was obtained from a lab-scale test, when a high voltage was applied to an ionizer and a charged droplet scrubber. Field tests also show the high collection efficiencies, 93.5% with one stage and 99.4% with two stage system. This system can be used to increase the collection efficiency of the conventional air pollution control devices to satisfy the national emission standard.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2003.05b
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• pp.355-356
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• 2003

Coagulation is a process whereby particles collide with one another due to their relative motion, and adhere to form large particles. Coagulation caused by the random Brownian motion of particles is called Brownian coagulation. Many properties, such as light scattering, electrostatic charges, toxicity, as well as physical processes, including diffusion, condensation and thermophoresis depend strongly on their size distribution. Therefore, Brownian coagulation is substantially important in atmospheric science, combustion technology, inhalation toxicology and nuclear safety analysis. (omitted)

• Particle and aerosol research
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• v.10 no.1
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• pp.27-31
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• 2014

A simple bimodal model has been developed to analyze charged particle coagulation by modifying previously suggested bimdal model for evolution of particle generation and growth. In the present model, two monodisperse modes are used and 40 charge nodes are assigned to each mode to account both change of the particle size and charge distribution. In addition, we also implemented the effect of electrostatic dispersion loss in the present model. Based on the developed model, we analyzed coagulation of asymmetric bipolar charged particles by computing evolutions of particle number concentration, geometric mean diameter of particles, charge asymmetric ratio and geometric standard deviation of particle size distribution for various initial charge asymmetric ratios. The number concentration of asymmetric bipolar charged particles decreases faster than that of neutral particles but that does not give faster growth of particles since the electrostatic dispersion loss overwhelms particle growth by coagulation.

• Journal of the Korean Vacuum Society
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• v.9 no.2
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• pp.172-178
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• 2000

We developed the model equations to investigate the particle movement and growth theoretically in a-Si plasma CVD reactor, where those particles act as the source of contamination. We included the effects of fluid convection, particle diffusion and external forces (ion drag force, electrostatic force and gravitational force) onto the particles to analyze the movements of particles in plasma reactor. Taking into account the particle charge distribution, the particle growth by coagulation between the charged particles was investigated. Most of those particles are located in the region near the sheath boundaries by the balance between the ion drag and electrostatic forces. The particle concentrations in the sheath region and in the bulk plasma region are almost zero. The sizes of the predator particles increase with time by the coagulation with protoparticles and, as a result, the surface area and the average charge of predator particles also increase with time.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.4
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• pp.522-528
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• 2004

Microfiltration with in-line rapid coagulation for drinking water production was examined. The in-line rapid coagulation was conducted using newly developed mixing device instantaneous flash mixer. The flux decline during membrane filtration was monitored with coagulant dosage varied. Flux decline was minimized at 1.1mg/L of coagulant dosage, where streaming potential of coagulated water was near zero. The optimum dosage for the process control was explained by dimensionless distance (${\kappa}{\times}a$) of particle pairs, obtained from electrophoresis parameter describing electrostatic repulsion relative to Van der Waals energy between particle pairs in the pre-coagulated water.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2006.10a
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• pp.239-240
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• 2006

• Journal of Korean Society of Water and Wastewater
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• v.21 no.4
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• pp.477-483
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• 2007

A coagulation process for RO (reverse osmosis) membrane pretreatment system was an effective technology to remove colloidal and particulate matters. However, coagulant residuals from the pretreatment process may negatively affect RO membrane performance. The bench-scale coagulant exposure study was performed to investigate the effect of their residual on adsorbed mass which related to the membrane performance. Coagulant addition in this study ranged from 0 to 5mg/L ferric chloride, alum, and 2mg/L cationic polymer(poly-di-methyldiallyl ammonium chloride) as coagulant aids. This results showed that adsorbed mass is not significantly increased during short-time period, however, accumulated mass of coagulants on the membrane surface is significantly increased during long-time experimental period. The effect of pH on coagulants adsorption characteristics was significantly differed due to the electrostatic repulsive interactions between soluble coagulants and membrane surface charge. This data suggest that the RO membrane performance of drinking water treatment plant could be decreased by adsorption of residual coagulants when applied for the coagulant pretreatment process.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.12
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• pp.1691-1701
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• 1998

Fly ash produced in coal combustion is a fine-grained material consisting mostly of spherical, glassy, and porous particles. A study on the formation mechanism of the fly ash from coal particles in the pulverized coal power plant is investigated with a physical, morphological, and chemical characteristic analysis of fly ash collected from the Samchonpo power plant. This study may contribute to the data base of domestic fly ash, the improvement of combustion efficiency, fouling phenomena and ash collection in the electrostatic precipitator. The physical property of fly ash is determined using a particle counter for the measurement of ash size distribution. Morphological characteristic of fly ash is performed using a scanning electron micrograph. The chemical components of fly ash are determined using an inductively coupled plasma emission spectrometry(ICP). The distribution of fly ash size was bi-modal and ranged from 12 to $19{\mu}m$ in mass median diameter. Exposure conditions of flue gas temperature and duration within the combustion zone of the boiler played an important role on the morphological properties of the fly ash such as shape, particle size and chemical components. The evolution of ash formation during pulverized coal combustion has revealed three major mechanisms by large particle formation due to break-up process, gas to particle conversion and growth by coagulation and agglomeration.

• Particle and aerosol research
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• v.5 no.2
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• pp.83-90
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• 2009

This paper describes a condensation-evaporation method (CEM) to produce size-controlled spherical silver nanoparticles by perturbing coagulation and coalescence processes in the gas phase. Polydisperse silver nanoparticles generated by the CEM were first introduced into a differential mobility analyzer (DMA) to select a group of silver nanoparticles with same electrical mobility, which also enables to make a group of nanoparticles with elongated structures and same projected area. These silver nanoparticles selected by the DMA were then in-situ sintered at ${\sim}600^{\circ}C$, and then they were observed to turn into spherical shaped nanoparticles by the rapid coalescence process. With the assistance of modified converging-typed quartz reactor, we can also produce the 10 times higher number concentration of silver nanoparticles compared with a general quartz reactor with uniform diameter. Finally, the spherical silver nanoparticles with 30 nm were electrostatically deposited on the surface of silicon substrate with the coverage rate of ~4%/hr. This useful preparation method of size-controlled monodisperse silver nanoparticles developed in this work can be applied to the various studies for characterizing the physical, chemical, optical, and biological properties of nanoparticles as a function of their size.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.12
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• pp.2135-2139
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• 2000

The coagulation of anionic colloidal particles by the cyanoguanidine(CG)-formaldehyde resin has been reported to be caused by an electrostatic interaction of the diaminomethylene urea (DU) cation with an anionic surface charge of particles. In this research, 100~500 nm sized cationic cyanoguanidine-formaldehyde resin was synthesized to coagulate anionic dye wastewater, and the results showed that the less pH of aqueous cyanoguanidine-formaldehyde resin solution was, the higher Zeta potential of that was. In case of coagulating 0.4 g/L reactive dye by cyanoguanidine-formaldehyde resin at pH 3, 5, 7, 9, and 11, COD removal and the percent decolorization of synthetic dye wastewater at pH 3 are higher than those of other pH conditions. The COD removal and the percent decolorization of synthetic dye wastewater were 74% and 90% at 400 ppm, pH 3.