• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1389-1394
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• 2003

$CO_2$ is a well-known green house gas, which is the major source of global warming. Many researchers have studied to reduce $CO_2$ emission in combustion processes. Among the method for reducing $CO_2$ emission, oxygen-enriched combustion has been proposed. But the adiabatic flame temperature is too high. So existing facilities must be changed, or the adiabatic flame temperature in the combustion zone should be reduced. The combustion characteristics, composition in the flame zone, temperature profile and emission gases were studied experimentally for the various oxygen-enriched mtios(OER) by addition of $CO_2$ under coustant $O_2$ flowrate. Results showed that the reaction zone was quenched, broadened, as addition of $CO_2$ was increased. Temperature has a large effect on the NOx emission. The emission of NOx in flue gas decreased due to the decreased temperature of reaction zone. It was also shown that the reaction was delayed by the cooling effect. As the addition of $CO_2$ was increased, the composition of CO in the flame zone increased due to the increase of reaction rate by increasing mixing effect of oxidant/fuel at OER=0, but the composition of CO decreased by quenching effect at OER=50 and 100%.

• 열처리공학회지
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• 제25권3호
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• pp.115-120
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• 2012

It has been known that the ferritic stainless steel can be changed to martensitic stainless steel when nitrogen is added. However the high hardness of martensitic stainless steel prevents the plastic deformation. In this study, instead of martensite, the surface microstructure was changed into nitrogen pearlite to increase the plastic deformation easily by isothermal heat treatment after high temperature gas nitriding (HTGN) the AISI 430 ferritic stainless steel. The isothermal treatment was carried out at $780^{\circ}C$ for 4, 6, and 10 hrs, respectively, after HTGN treatment at $1100^{\circ}C$ for 10 hrs. The surface layer of isothermal-treated steel appeared nitrogen pearlite composed with fine chromium nitride and ferrite. Hence, the interior region that was not affected by nitrogen permeation exhibited ferrite phase. When quenching the isothermal treated steel at 1100oC, martensitic phase formed at the surface layer. The hardness of surface layer of isothermal-treated steel and quenched steel measured the value of 150~240 Hv and 630 Hv, respectively.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2192-2197
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• 2008

An experimental study was performed to investigate the effects of configuration of burner and air excess ratio on CO & NOx emission characteristics of the cooktop burners which are used extensively. In this study, the combustion characteristics were investigated with the variation of design factor of cooktop burners. The results showed that as the thermal input increases, flammable region go narrower. With the increase of loading height from the cap to grate, the CO emission decrease owing to the reduction of quenching by flame impingement on the load. Additionally, the CO emission increase with angle of main slot, however the NO emission is almost unaffected.

• 전기학회논문지
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• 제57권4호
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• pp.635-640
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• 2008

New gas mixtures are now finding applications such as interrupting media for high-voltage circuit breakers. These mixtures consist of a high content of carbon tetrafluoride($CF_4$) added to sulfur hexafluoride($SF_6$). Nowdays $SF_6$ has been established for the use in gas insulated substations due to its high insulation withstand level and good arc quenching capability. At this paper Breakdown characteristics were investigated for $SF_6/CF_4$ mixtures when AC voltage and standard lightning impulse voltage(LI) was applied in a needle-plane electrodes. And partial discharge(PD) experiments were carried out in the test chamber which was made in needle-plane electrode. And ${\Phi}$-Q-N distribution of partial discharge signals was analyzed. The total pressure of the $SF_6/CF_4$ mixtures was varied within the range of 0.1-0.5 Mpa in the test chamber. The breakdown voltage in needle-plane electrode displayed N shape characteristics for increasing the content of $SF_6$ at positive impulse voltage and the PD inception voltage was increased slightly when pressure of $SF_6/CF_4$ Mixtures was increased. Maximum PD inception voltage is showed in 80% SF6/20%$CF_4$.

• 한국가스학회:학술대회논문집
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• 한국가스학회 1997년도 추계학술발표회 논문집
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• pp.45-52
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• 1997

The objective of this study is, with concept of fitness-for-purpose, to evaluate the fracture toughness in X-grooved weld HAZ(heat-affected zone) of QLT(quenching, lamellarizing and tempering)-processed $9\%$ Ni steel, qualitatively and quantitatively, and analyze the relation with the change of microstructure. In general, CTOD test is widely used to determine the fracture toughness of steel weldments. But several problem of accuracy has been brought up. Therefore, in this study, modified CTOD test was used for X-grooved weld HAZ for $9\%$ Ni steel. Additionally, microstructure of HAZ is observed and analyzed by OM, SEM and XRD. From the resulty, HAZ toughness of QLT-$9\%$ Ni steel decreased as the evaluated region approaches the fusion line. The decreased toughness was partly caused by reduction of the retained austenite content, resulted from decreased nucleation site of the retained austenite content, resulted from decreased nucleasion site for reverse transformation due to the increasing fraction of coarse grained region. On the other hand, unexpectedly, the increasing fraction of ductile weld did not increase the HAZ toughness. Therefore, in this X-grooved weld HAZ, the primary factor affecting fracture toughness was the fraction of coarse grained region, i.e., the weakest region.

• 한국수소및신에너지학회논문집
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• 제33권6호
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• pp.636-642
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• 2022

The "Hydrogen Economic Activation Road map" was announced in 2019, and hydrogen demand is expected to exceed 470,000 tons per year in 2022 and keep increasing. Under this circumstance, it has become important to understand the greenhouse gas (GHG) emissions associated with various hydrogen production pathways. In this study, the evaluation of life cycle GHG emissions regarding the hydrogen produced as by-product from coke oven gas (COG) in steel mill is conducted. To cover the possible range of operations, three literatures were reviewed and their data of inputs and outputs for the process were adopted for calculation. Life cycle inventories and emission factors were mostly referred to GaBi and Intergovernmental Panel on Climate Change (IPCC) guidelines, respectively. When there are multiple products from a single process, the energy allocation method was applied. Based on these sources and the assumptions, the life cycle emission values of COG-based hydrogen were found to be 3.8 to 4.7 kg/CO₂-eq./kg-H₂.

• 한국주조공학회지
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• 제22권6호
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• pp.281-287
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• 2002

In order to investigate the variation of microstructure and property of the Electro-slag Remelted M2 steel, microstructure observation, hardness, and bending test were performed by using optical microscope. SEM/EDS, rockwell hardness tester, charpy impact tester and bending tester, respectively. It was revealed that the number of inclusions and content of gas elements(S, O, N) in M2 steel fabricated by ESR process decreased markedly compared to those of AIM. It seems to be due to refining effect of ESR process. The volume fraction of carbides in quenched and tempered specimens after austenitizing at 1150$^{\circ}C$ and 1240$^{\circ}C$ was measured. The volume fraction of grain boundary carbides were found to be similar for both specimens. However, The volume fraction of carbides in grain decreased with an increase of austenitizing temperature. When specimen was austenitized at 1150$^{\circ}C$, grain boundary carbides showed needle like morphology. But, the carbides were broken with an increase of austenitizing temperature. The specimen austenitized at 1240$^{\circ}C$ showed higher hardness and lower bending strength compared to that of 1150$^{\circ}C$. As expected, toughness increased with sub-zero quenching treatment.

• 청정기술
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• 제17권3호
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• pp.250-258
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• 2011

Thermal plasma has been presented for the decomposition of perfluorocompounds (PFCs) which are extensively used in the semiconductor manufacturing and display industry. We developed pilot-scale equipment to investigate the large scale treatment of PFCs and called it a "thermal plasma scrubber". PFCs such as $CF_4$, $C_2F_6$, $SF_6$, and $NF_3$ used in experiments were diluted with $N_2$. There were two different types of experiment setup related to the water spray direction inside the thermal plasma scrubber. The first type was that the water was sprayed directly into the gas outlet located at the exit of the reaction section. The second type was that the water was sprayed on the wall of the quenching section. More effective decomposition took place when the water was sprayed on the quenching section wall. For $C_2F_6$, $SF_6$, and $NF_3$ the maximum destruction and removal efficiency was nearly 100%, and for $CF_4$ was up to 93%.

• 대한화학회지
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• 제44권6호
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• pp.573-580
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• 2000

MPT는 최근에 개발된 마이크로파 플라즈마로서 수용매에 강하다. 여러 가지의 변형된 형태의 MPT를 개발하여 구조에 따른 플라즈마의 방전되는 형태를 조사한 결과 이중관 토치는 플라즈마 기체를 적게 소모하며 쉽게 플라즈마가 형성되었으나 토치의 끝이 높은 온도에 견디지 못하고 쉽게 상했다. ICP토치와 같은 형태의 삼중관 토치에 석영관을 중심관으로 사용할 때 가장 안정되고 대칭적인 플라즈마를 형성할 수 있었다. 바탕선을 조사해 본 결과 He MPT는 대기 중으로 돌출되어 대기와 많이 혼합되고 질소에 의해 quenching되는 것으로 보여진다. Membrane desolvator를 탈용매화 장치로 사용하여 헬륨 MPT의 감도를 조사해 본 결과 아르곤 MPT와 비교할 때 대부분의 원소에 대해 검출한계가 10배 이상 높았다. 그러나 여기 에너지가 높은 원소는 비교적 효율적으로 검출할 수 있었다. 헬륨 마이크로파 플라즈마는 적은 양의 플라즈마 기체만 필요하여(약 1.6 L/min) 경제적이며 매우 안정된 형태를 보여주었다. 플라즈마의 분광특성을 조사한 결과 들뜸온도 4950K, 전자밀도 $3.28{\times}10^{14}cm^{-3}$로 측정되었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.335-335
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• 2008

눈에 안정한(1.53um) 인산염 레이저 유리를 제조하기 위한 기본 조성 (mole%)은 $55P_2O_5\cdot24BaO\cdot10K_2O\cdot4Al_2O_3\cdot6Yb_2O_3$로 하고, 활성 이온은 $Er^{+3}$로, sensitizer로는 $Cr^{+3}(Yb^{+3})$을 사용하였다. 혼합된 원료 조성은 대기와 원료로부터 혼입되는 OH group을 제거하기 위하여 open 시스템에서 가스 버블을 공급하였으며, 용융물에 공급된 시간 변화에 따라 분광학적 특성 변화를 조사하였다. OH oscillations linear 에 의해 quenching된 $Er^{+3}$ 형광방출 확률은 $3500cm^{-1}$ 에서 OH stretching vibration band의 흡수계수에 의존하고 있으며, 이때 $Er^{+3}$의 농도는 $1.6\times10^{19}$에서 $21.2\times10^{19}$ ion/$cm^2$ 범위에서 존재하였다.