• 한국대기환경학회지
• /
• 제6권1호
• /
• pp.85-96
• /
• 1990

Simultaneous removal efficiencies of hydrophilic and hydrophobic gaseous pollutants are experimentally determined, and the macroscopic removal mechanism of pollutants in a dry scrubber is analyzed using the extended model of three phase equilibrium distribution of pollutant at high temperatures that can describe the different morphological conditions of adsorbent and water at varying relative humidities. For the simplicity, the inside of spray dryer is divided into three regions of ; (1) absorption, (2) three-phase equilibrium, and (3) adsorption, and the removal efficiencies of each pollutants at three regions are observed at different experimental conditions to estimate the effects of important parameters of dry scrubber. The laboratory experiments simulate the three regions of spray dryer with the temperature control and thus evaporation rate of water from the slurry particle. $SO_2$ as a hydrophilic gaseous pollutant and vinyl chloride as a hydrophobic toxic gas are selected for the future field application to soid waste incineration, and the two types of slurry are made of the two sorbents ; 10 wt.% $Ca(OH)_2$, and 10 wt.% NaOH. Result of temperature effect shows the height of absorption plus three-phase region is decreased as the operation temperature is increased, which results in the lower removal efficiency of $SO_2$ but higher removal for vinyl chloride in the adsorption region of dry scrubber. The removal efficiency of $SO_2$ is higher by NaOH slurry than by $Ca(OH)_2$ slurry due to the hygroscopic nature of NaOH, while the removal of vinyl chloride is higher in $Ca(OH)_2$ case. From the analysis of redults using three-phase equilibrium distribution model, the effective two-phase partition coefficients can be obtained, and the possible extention in the application of the three-phase equilibrium model in a dry scrubber design has been demonstrated.

• 한국대기환경학회지
• /
• 제11권3호
• /
• pp.263-272
• /
• 1995

Characteristics of anbient at Korean, Cheju Island have been studied during the intensive field study period on March 11 .sim. 17, 1994 in collaboration with other research organizations from Korea and abroad. The particle size distribution was measured using an Electrical Aerosol Analyzer(EAA) and an Optical particle Counter(OPC). Fine particles(PM1 and PM3) have been collected by filter pack samplers and their ionic compositions have been analyzed. sampling errors inherent to the filter pack sampling method are discussed and the method to analyze those errors are presented. The rine mass concentrations of this study show very similar mass concentrations when Seoul is clear. This is somewhat surprising result, because the most of researchers believe that Kosan is one of the cleanest area in Korea. Bimodal volume size distributions with peak values around 0.1 .sim. 0.2.mu.m and 3.mu.m in particle dimeter were observed for most of the measurement period, particle mass loadings and ionic composition data show a large fraction of particles are from non-sea salt origins. Estimation of water content and acidity of particles based on measurement by a gas/particle equilibrium model, SCAPE, reveals that the pH values of particles are comparable to or lower than those estimated based on measurements in Los Angeles, U.S.A. during the SCAQS study. These findings with the meteorological conditions during the study period suggest that the particles collected during the period have originated from outside Cheju Island.

• 천문학회보
• /
• 제43권1호
• /
• pp.56.2-56.2
• /
• 2018

Astrophysical shocks accelerate particles to high velocities, which we observe as cosmic rays. The acceleration process changes the nature of the shock because the particles interact with the local magnetic field, removing energy and potentially triggering instabilities. In order to simulate this process, we need a computational method that can handle large scale structures while, at the same time, following the motion of individual particles. We achieve this by combining the grid magnetohydrodynamics (MHD) method with the particle-in-cell (PIC) approach. MHD can be used to simulate the thermal gas that forms the majority of the gas near the shock, while the PIC method allows us to model the interactions between the magnetic field and those particles that deviate from thermal equilibrium. Using this code, we simulate shocks at various sonic and Alfvenic Mach numbers in order to determine how the behaviour of the shock and the particles depends on local conditions.

• 대한기계학회논문집B
• /
• 제21권2호
• /
• pp.264-274
• /
• 1997

A numerical analysis on condensation and coagulation of the metallic species with fly ash particles pre-existing in an incinerator was performed. Waste was simplified as a mixture of methane, chlorine, and small amounts of Pb and Sn. Vapor-phase amounts of Pb- and Sn -compounds were first calculated assuming a thermodynamic equilibrium state. Then theories on vapor-to-particle conversion, vapor condensation onto the fly ash particles, and particle-particle interaction were examined and incorporated into equations of aerosol dynamics and vapor continuity. It was assumed that the particles followed a log-normal size distribution and thus a moment model was developed in order to predict the particle concentration and the particle size distribution simultaneously. Distributions of metallic vapor concentration (or vapor pressure) were also obtained. Temperature drop rate of combustion gas, fly ash concentration and its size were selected as parameters influencing the discharged amount of metallic species. In general, the coagulation between the newly formed metal particles and the fly ash particles was much greater than that between the metal particles themselves or between the fly ash particles themselves. It was also found that the amount of metallic species discharged into the atmosphere was increased due to coagulation. While most of PbO vapors produced from the combustion were eliminated due to combined effect of condensation and coagulation, the highly volatile species, PbCl$_{2}$ and SnCl$_{4}$ vapors tended to discharge into the atmosphere without experiencing either the condensation or the coagulation. For Sn vapors the tendency was between that of PbO vapors and that of PbCl$_{2}$ or SnCl$_{4}$. To restrain the discharged amount of hazardous metallic species, the coagulation should be restrained, the number concentration and the size of pre-existing fly ash particles should be increased, and the temperature drop rate of combustion gas should be kept low.

• 대한기계학회논문집B
• /
• 제24권10호
• /
• pp.1368-1379
• /
• 2000

A numerical study on swirling pulverized coal combustion in an axisymmetric enclosure is carried out by applying the 2-phase weighted sum of gray gases model (WSGGM) approach with the discrete ordinate method (DOM) to model the radiative heat transfer equation. In the radiative transfer equation, the same polynomial equation and coefficients for weighting factors as those for gas are adopted for the coal/char particles as a function of partial pressure and particle temperature. The Eulerian balance equations for mass, momentum, energy, and species mass fractions are adopted with the standard and RNG k-${\varepsilon}$ turbulence model, whereas the Lagrangian approach is used for the particulate phase. The eddy-dissipation model is employed for the reaction rate for gaseous mixture, and the single-step and two-step first-order reaction model for the devolatilization process for coal. Special attention is given to establish the thermal boundary conditions on radiative transfer equation By comparing the numerical results with experimental ones, the radiation model used here is confirmed and found to provide an alternative for simulating the radiative transfer.

• 대한기계학회논문집
• /
• 제18권9호
• /
• pp.2404-2412
• /
• 1994

A mathematical model has been developed for predicting kinematic, thermal, and solidification histories of atomized droplets during flight. Liquid droplet convective cooling, recalescence, equilibrium-state solidification, and solid-phase cooling were taken into account in the analysis of the solidification process. The spherical shell model was adopted where the heterogeneous nucleation is initiated from the whole surface of a droplet. The growth rate of the solid-liquid interface was determined from the theory of crystal growth kinetics with undercooling caused by the rapid solidification. The solid fraction after recalescence was obtained by using the integral method. The thermal responses of atomized droplets to gas velocity, particle size variation, and degree of undercooling were investigated through the parametric studies. It is possible to evaluate the solid fraction of the droplet according to flight distance and time in terms of a dimensionless parameter derived from the overall energy balance of the system. It is also found that the solid fraction at the end of recalescence is not dependent on the droplet size and nozzle exit velocity but on the degree of subcooling.

• 대한환경공학회지
• /
• 제30권2호
• /
• pp.190-198
• /
• 2008

본 연구에서는 주유소 등의 지하 유류저장탱크나 파이프의 제한된 수명으로 인해 발생할 수 있는 가솔린의 누출에 의해 MTBE로 토양이 오염되었을 경우를 가정하여, 칼럼실험을 수행하고, CXTFIT 기법을 이용하여 토양 내 MTBE의 이동특성을 살펴 보았다. 칼럼실험에서는 토성, 수분함량, 유기물함량, 주입유속을 달리하여, 주입액과 유출액의 MTBE의 농도 측정값을 비교하고, CXTFIT기법을 이용하여 two-site 비평형 흡착모델에 사용된 매개변수(D, R, $\beta$, $\omega$)를 구하였다. 이들 매개변수와 파과곡선을 이용하여 MTBE의 토양 내 이동특성을 살펴보았다. 토양 내 미세입자와 유기물함량이 많을수록 이류에 의한 영향이 감소하는 것으로 나타났으며, 수분함량과 유속의 증가는 이류에 의한 MTBE의 이동을 더욱 가속시키는 것으로 나타났다.

• 한국대기환경학회지
• /
• 제33권1호
• /
• pp.64-74
• /
• 2017

In this study, we have analyzed relationship between the measured Water Soluble Organic Carbon (WSOC) concentrations and the estimated aerosol water content of $PM_{10}$ (particulate matter with an aerodynamic diameter of less than or equal to $10{\mu}m$) for the period between September 2006 and August 2007 at Seoul, Korea. Water content of $PM_{10}$ was estimated by using a gas/particle equilibrium model, Simulating composition of Atmospheric Particles at Equilibrium 2 (SCAPE2). The WSOC concentrations showed low correlation with Elemental Carbon (EC), but Water Insoluble Organic Carbon (WISOC) were highly correlated with EC. It seemed that hydrophilic groups were produced by secondary formation rather than primary formation. As with the previous studies, WSOC showed good correlation with secondary ions ($NO_3{^-}$, $SO_4{^{2-}}$, $NH_4{^+}$), especially WSOC was highly correlated with $NO_3{^-}$ that is a secondary ion formed by photochemical oxidation from more local sources than $SO_4{^{2-}}$. No apparent correlation between the measured WSOC and estimated water content was observed. However, WSOC showed good correlation with estimated water content when it was assumed that relative humidity was higher than the deliquescence relative humidity of the system. In conclusion, WSOC is correlated with water content by hygroscopic ions and it is expected that nitrate play an important role among the water content and WSOC.

• Korean Chemical Engineering Research
• /
• 제54권6호
• /
• pp.838-846
• /
• 2016

산업체에서 많이 사용되는 연소공정은 배가스 성분의 회수나 제거를 필요로 한다. 최근에는 배가스로부터 이산화탄소를 회수하기 위해 제올라이트 13X를 사용하는 MBA(이동상흡착) 공정이 개발되었다. 본 연구에서는 제올라이트 13X에 대한 이산화탄소, 질소, 이산화황 및 수증기의 흡착 실험을 수행하여 흡착평형 및 고체입자 안으로의 흡착속도를 조사하였다. 여러 실험온도에서의 흡착데이터를 Langmuir, Toth, Freundlich 등온흡착식에 적용하여 각 흡착등온식의 파라미터를 구했고, 이론식에 의한 예측값과 실험데이터가 잘 일치함을 확인하였다. 이산화황과 수증기가 불순물로 존재할 경우에 주성분인 이산화탄소의 흡착량을 측정하였다. 이성분 흡착 데이터는 순수 성분에 대해 얻어진 파라미터를 extended Langmuir 등온흡착식에 적용하여 예측한 결과와 잘 일치하였다. 다만, $H_2O$ 불순물이 대략 ${\sim}10^{-5}H_2O\;mol/g$ zeolite 13X 이하 존재할 때에는 $CO_2$ 흡착량이 순수 $CO_2$의 흡착보다 오히려 소량 증가하는 현상이 관찰되었다. 실험으로 측정한 흡착속도를 구형 입자 확산모델에 적용하여 이산화탄소, 이산화황, 질소, 수분의 확산계수와 활성화에너지를 구했다. 미량의 불순물이 흡착되어있을 때는 이산화탄소나 이산화황의 확산계수가 줄어들었다. 본 연구에서 얻어진 파라미터 값들은 실제 흡착공정의 설계에 유용할 것이다.