• 대한환경공학회지
• /
• 제35권11호
• /
• pp.809-814
• /
• 2013

본 연구는 광안대교 하부의 퇴적토 오염조사를 위해 퇴적토의 기본물성 및 중금속 함량을 측정하였다. 퇴적물 시료의 산화물을 분석한 결과, $SiO_2$와 CaO의 경우 강하구에서 멀어 질수록 $SiO_2$는 증가하고 CaO는 감소하는 경향을 보였다. 강열감량의 경우, 7.2~14.3%의 분포를 보여 비교적 높은 값을 나타내었고 TOC는 0.9~5.5%로 지역에 따라 편차가 큰 것을 알 수 있었다. 이는 USEPA 퇴적물환경기준(비오염, 중간오염, 심한오염)에 따라 심한오염으로 평가되었고, TOC의 경우, 강하구에서 가장 먼 시료채취 지점(GW7)은 영향없음으로 평가되었고 나머지 지역은 최소영향수준으로 평가되었다. 중금속의 경우에는 USEPA와 캐나다 기준으로 평가하였을 때 모두 비오염으로 평가되어 중금속에 대한 오염도는 없는 것으로 평가되었다. 다만, 강열감량의 값이 크기 때문에 USEPA 기준으로 평가할 때 중금속의 오염은 없지만 전체적으로는 심한 오염으로 평가되었다.

• 대한기계학회논문집B
• /
• 제28권6호
• /
• pp.697-704
• /
• 2004

Bifurcation behavior of ignition and extinction of catalytic reaction is theoretically investigated in a stagnation-point flow. Considering that reaction takes place only on the catalytic surface, where conductive heat losses are allowed to occur, activation energy asymptotics with a overall one-step Arrhenius-type catalytic reaction is employed. For the cases with and without the limiting reactant consumption, the analysis provides explicit expressions, which indicate the possibility of multiple steady-state solution branches. The difference between the solutions with and without reactant consumption is in the existence of an upper solution branch, and the neglect of reactant consumption is inappropriate for determining extinction conditions. For larger values of reactant consumption, the solution response is all monotone, suggesting that multiple solutions are not possible. It is shown that bifurcation Damkohler numbers increase (decrease) with increasing of conductive heat loss (gain) on the catalytic surface, which means that smaller (larger) values of the strain rate allow the surface reaction to tolerate larger heat losses (gains). Lewis number of the limiting reactant can also significantly affect bifurcation behavior in a similar way to the effect of heat loss.

• 한국입자에어로졸학회지
• /
• 제10권4호
• /
• pp.131-136
• /
• 2014

The importance of waste treatments is increasing because of the lack of resources and environmental problems resulted from economic growth policy. Especially, the pollutant dust which is one of the wastes should be treated considerately because it could cause secondary damages on the human health as well as environmental systems. Recently, massive amount of coal fly-ash is being produced in thermoelectric power plants. In this study, we compared two general methods used in estimating the amount of unburned carbon in fly-ashes to categorize the coal fly-ashes into several groups following their carbon contents. One is the "loss on ignition(KS L 5405) method" which estimates the change of mass after combustion, and it is generally used. Another one is measuring $CO_2$ gas content by burning solid carbon in the fly-ash, and it is called "$CO_2$ analysis method."

• 환경생물
• /
• 제18권2호
• /
• pp.227-235
• /
• 2000

As a part of basic investigation to Fishery Purge Project for the Special Administrative in Chollanamdo Province, the sedimentary environmental characteristics of Yoja Bay at 15 stations were studied. The analysis was carried out in July, 1998, through studies of Loss On Ignition (LOI) by depth, Total Sulfide (T-5), Chemical Oxygen Demand (COD) concentrations and Grain-size distribution. The LOI value was found to be 6.20-12.20% (mean of 8.89%), with the neighboring Sunhakri and Haksanri areas showing slightly higher values. These values were similar to the LOI values observed in the Hansan-Koje Bay and Jinju Bay areas on the southern coast of Korea. T-S and COD concentrations were found to be, respectively, 0.060-0.104 mg/gㆍd (mean of 0.052 mg/gㆍd) and 5.53-29.71 mg/gㆍd(mean of 13.24 mg/gㆍd), not exceeding eutrophication limits. T-S concentration was especially high at stations close to the central areas of the bay and inland areas, which caused by organic matter input from the nearby agricultural areas. COD concentration was very high at stations nearby the bay entrance and Doonbyungdo, but the mean value was lower than that of Hansan-Koje Bay. This leads us to believe that the level of pollution in Yoja Bay is not significant. The prevailing sediment composition was mud, consisting of 61.38% silt and 34.87% clay. [Sediments in Yoja Bay, Loss On Ignition, Total Sulfide, Chemical Oxygen Demand, Grain-Size Distribution].

• 대한토목학회논문집
• /
• 제8권2호
• /
• pp.117-124
• /
• 1988

국산 플라이애쉬 6종류에 대한 AE제의 흡착특성(吸着特性)을 살펴 본 결과 플라이애쉬 입자의 AE제흡착(吸着)은 30분 정도에서 거의 완료되었으며 강열감량이 클수록 포화흡착량이 크게 나타났다. 플라이애쉬 강열감량의 대부분은 미연소탄소(未燃燒炭素)이며 따라서 미연소탄소량이 AE콘크리트 중의 공기량을 감소시키는 요인임을 알았다. 한편, 유동화제(流動化劑)의 경우 플라이애쉬 입자의 포화흡착량은 시멘트보다 적으며 시멘트의 경우보다 분산성(分散性)도 다소 낮으나 플라이애쉬를 혼합한 콘크리트에 유동화제를 사용할 경우 유동성이 저하되는 현상은 없었다.

• 한국화재소방학회논문지
• /
• 제24권1호
• /
• pp.122-127
• /
• 2010

외부복사 열원(20, 25, 35, 50, $70kW/m^2$)과 산소/질소의 혼합가스의 농도 변화에 따른 페놀폼의 연소 특성을 분석하였다. 산소지수는 KS M ISO 4589-2를 만족하는 산소지수시험기를 사용하였으며, 점화시간, 임계열속, 그리고 질량감소속도는 ISO 5660-1를 만족하는 mass loss calorimeter를 사용하여 측정하였다. 연구결과, 외부 복사열원에서 임계열유속은 $28.99kW/m^2$, 평균질량감소속도는 $0.56{\sim}1.77g/m^2s$로 측정되었으며, 한계산소지수는 45.1%를 나타내었다. 모든 연구결과를 종합한 결과 페놀 폼이 다른 발포 물질에 비해 아주 우수한 화재안정성을 나타낸다는 것을 알 수 있었다.

• Nuclear Engineering and Technology
• /
• 제54권8호
• /
• pp.2960-2973
• /
• 2022

Since Fukushima nuclear power plant (NPP) accident in 2011, the importance of research on various severe accident phenomena has been emphasized. Particularly, detailed analysis of combustion risk is necessary following the containment damage caused by combustion in the Fukushima accident. Many studies have been conducted to evaluate the risk of local hydrogen concentration increases and flame propagation using computational code. In particular, the potential for combustion by local hydrogen concentration in specific areas within the containment has been emphasized. In this study, the process of flame propagation generated inside a reactor core to containment during a loss of coolant accident (LOCA) was analyzed using MELCOR 2.1 code. Later in the LOCA scenario, it was expected that hydrogen combustion occurred inside the reactor core owing to oxygen inflow through the cold leg break area. The main driving force of the oxygen intrusion is the elevated containment pressure due to the molten corium-concrete interaction. The thermal and mechanical loads caused by the flame threaten the integrity of the containment. Additionally, the containment spray system effectiveness in this situation was evaluated because changes in pressure gradient and concentrations of flammable gases greatly affect the overall behavior of ignition and subsequent containment integrity.

• 한국연소학회:학술대회논문집
• /
• 한국연소학회 2002년도 제25회 KOSCI SYMPOSIUM 논문집
• /
• pp.231-235
• /
• 2002

A theoretical and experimental study on the combustion process in a constant volume micro combustor is described. Unlike in a macro scale constant volume combustor, the heat loss to the wall plays a major role in flame propagation in a micro micro combustor. In order to analyze the effect of heat loss on combustion phenomena, pressure transition from ignition was measured. A number of cylindrical micro combustors with different diameter and depth were used for experiment to study the effect of length scales and shape factor. The diameter of combustor ranged from 7.5mm to 22.5 mm and the height of cylinder was from 1mm to 4mm. Initial pressure was also varied for the experiment. The diagnostic methods were severely limited due to the size of the apparatus and uncertainties of certain quantities to be measured in a small-scale environment. An analytical method to derive physical quantities that are essential for performance prediction from the pressure measurements is described.

• 한국분무공학회지
• /
• 제26권2호
• /
• pp.57-66
• /
• 2021

The reactivity controlled compression ignition (RCCI) is the technology that provides two different types of fuel to the combustion chamber with the advantage of significantly reducing particulate matter and nitrogen oxides emissions. However, due to the characteristics of lean combustion, combustion efficiency is worsened. The conventional type of pistons for conventional diesel combustion (CDC) has mostly been used in the researches on RCCI. Because the pistons for CDC are optimized to enhance flow and target spray, the pistons are unsuitable for RCCI. In this study, a piston that is suitable for RCCI is designed to improve combustion efficiency. The new piston was designed by considering the factors such as squish geometry, bowl depth, and surface area. The experiment was carried out by fixing the energy supply to 0.9kJ/cycle and 1.5kJ/cycle respectively. The two pistons were quantitatively compared in terms of thermal efficiency and combustion efficiency.

• 한국연소학회지
• /
• 제5권1호
• /
• pp.1-6
• /
• 2000

Surface reaction occurs at a certain surface temperature when a catalyst is heated up in a reactive mixture. If homogeneous ignition does not occur, a steady state is observed because the heat produced by the surface reaction is balanced with the heat loss caused by convection, conduction and radiation. The present paper treats the effects of pressure on the surface temperature at the steady state. Hydrogen and oxygen are used as reactants and nitrogen as an inert gas. A spherical platinum catalyst of 1.5 mm in diameter is sustained in the chamber with two wires of 0.1 mm in diameter. As results, there exists a maximum steady temperature at a certain relative hydrogen concentration which increases with total pressure. At the steady state, it can be approximated that the heat release is estimated by the mass transfer considering the effect of natural convection. The experimental results are explained qualitatively by the approximation.