(An) experimental study on the low temperature explosion characteristic

박정언 Graduate School, Korea University 2019 국내석사

Explosion-proof equipment which are internationally accepted shall meet the IEC 60079-1 standard of the International Electrotechnical Commission (IEC). Explosion-proof equipment is a product that is designed not to affect the flammable environment outside the equipment even if an explosion occurs due to flammable gas or steam inside the equipment. In the specification, two test methods are applied to confirm the explosion proof performance. The first is the overpressure test using the maximum explosion pressure and applied safety factor to verify that the device can withstand the explosion pressure inside. The second test is to confirm that the flame does not propagate through the gap of the equipment. This is a test for non-transmission of an internal ignition. However, there is a lack of theoretical and experimental reference data on the basis of the experimental data mentioned in the specification, and it has been confirmed that further verification is required in relation to explosion characteristics at low temperatures. Therefore, this paper shows the results of the experimental analysis on characteristics and test methods in low temperature explosion, and it is necessary to provide the data to be used for testing and designing the explosion proof equipment used at low temperature.

노외 증기폭발에 대한 원자로 공동의 건전성 분석 방법론 제시 : Methodology development of integrity analysis on reactor cavity from ex-vessel steam explosion

송유성 포항공과대학교 대학원 2014 국내석사

An Ex-vessel steam explosion might occur when hypothetical severe reactor accident causes reactor vessel fails and the molten core pours into the water in the reactor cavity. A steam explosion is a fuel coolant interaction process where the heat transfer from the melt to water is so intense and rapid that the time scale for heat transfer is shorter than the time scale for pressure relief. A steam explosion is a complex, highly nonlinear, coupled multi-component, multi-phase phenomenon. For the last several decades several computational models have been developed to evaluate the steam explosion energetics. The models have been verified with a number of experiment data and recently successfully analyzed in-vessel and ex-vessel steam explosions in new and advanced reactor designs. The TEXAS-V code is one of the models that have a unique feature employing the jet breakup model for the mixing phase and explosion models for the explosion triggering and propagation in one-dimensional fashion. The one-dimensional approach to analyze the steam explosion in this model, however, has a limitation to simulate the reactor case that has multi-dimension in nature. Therefore, in this work, the limitation of the TEXA-V code is supplemented by employing a commercial CFD code, like CFX, that evaluates the dynamic steam explosion pressure propagation from the FCI mixing zone to the reactor cavity wall. Furthermore, to assess the integrity of nuclear reactor cavity by the dynamic loadings from ex-vessel steam explosion, the ANSYS FE code is used for its analysis, and finally, in this study, the new methodology for the analysis on reactor cavity structure from ex-vessel steam explosion using TEXAS-V, CFX, and ANSYS FE is suggested. The developed model for the simulation of underwater shock propagation using CFX is validated by comparing its result with the correlation for underwater TNT explosion, and the result matches with the correlation with an error range of 5%. The structure analysis is performed considering the inertial effect of dynamic loading by shock wave propagation. An Ex-vessel steam explosion might occur when hypothetical severe reactor accident causes reactor vessel fails and the molten core pours into the water in the reactor cavity. A steam explosion is a fuel coolant interaction process where the heat transfer from the melt to water is so intense and rapid that the time scale for heat transfer is shorter than the time scale for pressure relief. A steam explosion is a complex, highly nonlinear, coupled multi-component, multi-phase phenomenon. For the last several decades several computational models have been developed to evaluate the steam explosion energetics. The models have been verified with a number of experiment data and recently successfully analyzed in-vessel and ex-vessel steam explosions in new and advanced reactor designs. The TEXAS-V code is one of the models that have a unique feature employing the jet breakup model for the mixing phase and explosion models for the explosion triggering and propagation in one-dimensional fashion. The one-dimensional approach to analyze the steam explosion in this model, however, has a limitation to simulate the reactor case that has multi-dimension in nature. Therefore, in this work, the limitation of the TEXA-V code is supplemented by employing a commercial CFD code, like CFX, that evaluates the dynamic steam explosion pressure propagation from the FCI mixing zone to the reactor cavity wall. Furthermore, to assess the integrity of nuclear reactor cavity by the dynamic loadings from ex-vessel steam explosion, the ANSYS FE code is used for its analysis, and finally, in this study, the new methodology for the analysis on reactor cavity structure from ex-vessel steam explosion using TEXAS-V, CFX, and ANSYS FE is suggested. The developed model for the simulation of underwater shock propagation using CFX is validated by comparing its result with the correlation for underwater TNT explosion, and the result matches with the correlation with an error range of 5%. The structure analysis is performed considering the inertial effect of dynamic loading by shock wave propagation.

산소소모열량계를 이용한 가연성 목재분진의 폭발효율 및 위험성 평가에 관한 연구

김윤석 인천대학교 일반대학원 2013 국내석사

Abstract A Study on the Explosion Efficiency And Risk Assessment of Combustible Wood Dust by Using the Cone Calorimeter Department of safety engineering Graduate school, University of Incheon Incheon, Korea Yun Seok Kim Fire and explosion accidents often occur from dust explosion in the PB (particle board) manufacturing process in the manufacturing business for recycled wood. Accordingly, the risk assessment on dust explosion was carried out for two type of wooden dust (silo dust and hammer mill dust) and a type of log dust (radiata pine dust) in the process as materials to cause explosions in an effort to quantify the risk of dust explosion in the process to handle flammable wooden powder and establish safety measures for them in order to make contributions to the prevention of accidents caused by dust explosion. Studies were carried out on the basis of four standards for the cone calorimeter combustion test to analyze the physical properties of sample dust, chemical properties of sample dust, fire explosion properties of sample dust, and dust explosion efficiency of dust sample in a bid to analyze the quantitative risk properties of dust explosion. The first study was carried out for the physical properties of sample dust including silo dust, hammer mill dust and radiata pine dust. Tests for measuring specific gravity were carried out in accordance with KS L 5110:2001 and their specific gravity appeared to be 1.56 [g/㎤], 1.46 [g/㎤] and 1.43 [g/㎤], respectively. The measurements for moisture content were 2.81%, 3.90% and 3.91%, respectively. As a result of grain size analysis for each sample dust, the distribution of grains could be identified as the median of each dust appeared to be 48.44㎛, 19.74㎛ and 74.58㎛, respectively. Thermal analysis tests were analyzed using the Differential Scanning Calorimeter (DSC) and Thermo Gravimetric Analysis (TGA). As a result of DSC tests, each sample showed the primary and secondary caloric peak due to the thermal oxidation in the air atmosphere. Each peak was interpreted for the decomposing peak of cellulose and lignin which consist of wood. The caloric peak of lignin for pine log dust appeared to be greater than that of dust sample in the process, which was extracted from the recycled wood. As s result of TGA tests, each sample showed three steps in the weight reduction section in the air atmosphere. The step 1 refers to the weight reduction section due to the moisture evaporation. Most of the weight was decomposed in the second and third weight reduction section depending on samples, which can be interpreted by correlations with the caloric response peak in DSC. This is considered the reduction of mass in the process where macromolecules including cellulose and lignin among others as one of the ingredients consisting of wooden sample dust are decomposed by heat and converted into various gases with caloric decomposition. The second study was carried out for the analysis on the chemical properties of sample dust. As a result of analysis on the element of each sample dust in terms of analysis on elements, the content of carbon (C), hydrogen (H), nitrogen (N), sulfur (S) and Oxygen (O) in the sample dust was analyzed. In an effort to verify the aspects of gases with thermal decomposition in rapid decomposition and combustion during dust explosion, qualitative tests for volatile substances and mass analysis for the qualitative tests for substance with thermal decomposition were carried out applying GC/MS to sample dust. As a result, the aspects of various gases with the combustible thermal decomposition could be confirmed from alkane, aldehyde, hydrazine derivative, phenol, furan and organic acids among others from C3. The third study was carried out for analysis on the risk characteristics of fire explosion in the sample dust, where risk at the autoignition of sedimental dust and the thermal storage were analyzed. tests for measuring maximum explosion pressure (Pmax), maximum rate of explosion pressure rise [(dP/dt)max] and lower explosion limit (LEL) in accordance with EN 14034-1~3, and minimum ignition energy (MIE) were carried out for the explosive characteristics and minimum ignition energy of suspended dust. As a result of measuring autoignition temperature at the sedimental conditions of each sample dust including silo dust, hammer mill dust and pine log dust, it was measures at 234.8℃, 225.5℃ and 253℃, respectively. In the thermal storage test, the self-decomposition risk appeared to be low due to the thermal storage at 150℃. However, as the heating process such as the drying process and thermal pressure exists in the real process, it is necessary to review the self-decomposition risk again in consideration of the operating temperature for them. As a result of maximum explosion pressure (Pmax) tests for silo dust, hammer mill dust and pine log dust, it appeared to be 8.27 [bar], 8.71 [bar] and 8.27 [bar], respectively. The maximum rate of explosion pressure rise [(dP/dt)max] was 340.76 [bar/s], 515.19 [bar/s] and 470.56 [bar/s], respectively. Lower explosion limit (LEL) was 60 [g/㎥], 60 [g/㎥] and 50 [g/㎥], respectively. The explosion grade was St1 [0<Kst<200] depending on the Kst for the dust explosion index. The dust explosion index Kst of each to which the cube root law is applied as dust with the weak explosiveness was calculated as 92.50 [m·bar/s], 139.87[m·bar/s] and 110.63[m·bar/s], respectively. As a result of measuring minimum ignition energy, it was 10mJ < MIE <30mJ and Es (energy for the estimated probability) was 14mJ for silo dust and hammer mill dust. It was measured in 30mJ < MIE <100mJ and Es (energy for the estimated probability) was 45mJ for pine log dust. Although they fall under normal ignition sensitivity, proper actions are necessary depending on the operating conditions in the process because they can be rapidly lowered depending on the operating temperature in the proces 국문요약 재생 목재 제조업종의 PB(Particle Board)제조공정에서 분진폭발로 인한 화재, 폭발사고가 빈발함에 따라 폭발 원인물질인 공정 내 목재분진2종(사일로분진, 함마밀분진)과 원목분진 1종(Radiata Pine분진)에 대한 분진폭발의 위험성평가를 수행하여 가연성 목재 분체의 취급공정에서의 분진폭발의 위험성에 대하여 정량화하고 이에 대한 안전대책을 수립하여 분진폭발로 인한 사고예방에 기여하고자 하였다. 분진폭발의 정량적 위험특성 분석을 위하여 시료분진의 물리적 특성, 시료분진의 화학적 특성, 시료분진의 화재폭발특성, 시료분진의 분진폭발효율 분석을 위한 콘 칼로리미터 연소시험의 4가지 기준으로 연구를 수행하였다. 첫 번째 연구는 사일로분진, 함마밀분진 그리고 Radiata Pine 분진 등 시료분진의 물리적 특성에 대한 연구로 KS L 5110:2001에 따라 비중측정시험을 실시하여 비중이 각각 1.56 [g/㎤], 1.46 [g/㎤], 1.43 [g/㎤]로 나타났다. 함수율 측정결과는 각각 2.81%, 3.90%, 3.91% 였다. 각 시료분진의 입도분석 결과 각 분진의 중앙 분포값이 48.44[㎛], 19.74[㎛], 74.58[㎛]로 나타났고, 그 입도분포를 알 수 있었다. 열분석시험은 시차주사열량계(DSC)와 열중량분석계(TGA)를 사용하여 분석하였으며, DSC 시험결과 각 시료는 공기분위기에서 열적산화에 기인한 1차, 2차의 발열피크가 나타났다. 각각의 피크는 목재 구성성분인 셀룰로오스와 리그닌의 분해피크로 해석되었으며 재생 목재에서 추출된 공정분진 시료에 비해 원목 소나무분진의 리그닌 발열피크가 큰 것으로 나타났다. TGA 시험결과 각 시료는 공기분위기에서 3단계 중량감소 구간을 나타냈다. 첫번째 구간은 수분증발에 의한 중량감소 구간이며, 두 번째와 세 번째의 중량 감소구간에서 시료에 따라 중량의 대부분이 분해됨을 알 수 있었고 이는 DSC의 발열반응 피크와도 상관해석이 가능하다. 이는 목재 시료분진의 구성성분인 셀룰로오스, 리그닌 등 고분자물질이 열에 의해 분해되면서 각종 열분해 가스로 전환되는 과정에서의 질량감소로 판단되어진다. 두 번째 연구는 시료분진의 화학적 특성에 대한 분석으로 각 시료분진의 원소분석을 실시하여, 시료분진의 탄소(C), 수소(H), 질소(N), 황(S), 산소(O)의 함유량과 무기원소 함유량을 조사하였다. 그리고 분진폭발 시 급격히 분해 연소하는 열분해 가스의 양상을 검증하기 위하여 시료분진을 GC/MS를 사용하여 휘발성물질의 정성시험과 열분해물질의 정성시험에 대한 질량분석을 수행한 결과 C3부터의 알칸과 알데히드, 히드라진유도체, 페놀, 퓨란, 유기산 등 다양한 가연성 열분해 가스의 양상을 확인하였다. 세 번째 연구는 시료분진의 화재폭발 위험특성 분석으로 퇴적분진의 자연발화와 축열저장 시의 위험에 대하여 분석하였고, 부유분진의 폭발특성과 최소점화에너지에 대하여 EN 14034-1~3에 따른 최대폭발압력(Pmax), 최대폭발압력상승율((dP/dt)max), 최소폭발농도(LEL)와 EN 13821에 따른 최소점화에너지(MIE) 측정 실험을 실시하였다. 사일로분진, 함마밀분진, 원목 소나무분진 등 각 시료분진의 퇴적상태에서 자연발화점 측정결과 각각 234.8℃, 225.5℃, 253℃로 측정되었으며, 축열저장 시험에서는 150℃에서의 축열에 의한 자기분해위험성이 낮은 것으로 나타났다. 그러나 실제 공정에서는 건조공정과 열압공정 등 가열공정이 존재하므로 이의 운전온도를 고려하여 자기분해위험을 재검토하여야 한다. 부유상태에서의 사일로분진, 함마밀분진, 원목 소나무분진은 최대폭발압력(Pmax) 시험 결과 각각 8.27 [bar], 8.71 [bar], 8.27 [bar]로 나타났으며, 최대폭발압력상승률((dP/dt)max)은 각각 340.76 [bar/s], 515.19 [bar/s], 470.56 [bar/s]로 나타났다. 폭발하한농도(LEL)는 각각 60 [g/㎥], 60 [g/㎥], 50 [g/㎥]으로 나타났다. 분진폭발지수 Kst값에 따른 폭발등급은 St1 [0<Kst<200] 으로 폭발성이 약한 분진으로 Cube root law를 적용한 각각의 분진폭발지수 Kst는 92.50[m·bar/s], 139.87[m·bar/s], 110.63[m·bar/s]로 계산되었다. 최소점화에너지(MIE)측정결과 사일로분진과 함마밀분진이 10mJ < MIE <30mJ, Es (확률적 추정 Energy) 값은 14mJ이고, 원목 소나무 분진에서는 30mJ < MIE <100mJ로 측정되었으며, Es (확률적 추정 Energy) 값은 45mJ로 Normal Ignition Sensitivity의 범주에 속하나 공정운전온도가 증가함에 따라 급격히 낮아질 수 있으므로 공정운전조건에 대한 적절한 대응이 필요하다. 네 번째 연구에서는 KS F ISO 5660-1에 제시된 화재모델 중 콘 칼로리미터 법을 선택하여 분진폭발 전후의 시료분진의 연소에너지를 정량화하기 위하여 연소실험을 실시하였다. 사일로분진, 함마밀분진, 원목 소나무 분진의 폭발 전 연소에너지는 14.9561 [MJ/kg], 15.9292 [MJ/kg], 16.1764 [MJ/kg]이며 폭발 후 연소에너지는 12.2349 [MJ/kg], 12.4083 [MJ/kg], 15.5099 [MJ/kg]로 나타났다. 이 결과를 바탕으로 폭발전후의 질량감소율을 고려한 순연소열과의 분율을 통하여 폭발범위 내에서 가연성 목재분진의 폭발효율이 사일로분진 약 65%, 함마밀분진 약 73%, 소나무 원목분진 약 72%로, 연소범위내의 폭발효율은 불활성물질이 적은 부유분진의 폭발의 경우 η=72~73%로 나타났고, 사일로분진에서와 같이 부

Comparative Analysis of Empirical Gas Explosion Models and Blast Resistant Design of PC Panels

이수현 서울대학교 대학원 2016 국내석사

Equipment in onshore plants is installed densely and therefore highly exposed to gas explosion. For protection of life and property, blast resistant design is applied to main buildings, but there are no guidelines for design. Major petroleum companies like BECHTEL or BP plc. make their specifications for blast resistant designs based on TNT equivalent mass. Recently, because gas explosions have various results depending on various external conditions, the TNO multi-energy method or Baker-Strehlow-Tang (BST) methods are mainly used. The conditions are considered in the form of the class or Mach number in the TNO multi-energy or BST method, respectively. The class or Mach number is rarely chosen except by some well-established overseas consultancy companies. This thesis studies which class or Mach number of the TNO multi-energy or the BST method corresponds to the overpressure by existing guidelines, which are based on the TNT equivalency method. The different overpressure, duration, and impulse of three methods are analyzed. The various design results by these methods are also researched. Based on the studies, overpressure of the most conservative guideline – the explosion by 1 ton of TNT at a distance of 100 ft. (30.5 m) – has the class number between 6 and 7 or the Mach number between 0.7 and 1.0. When the three methods predict the similar overpressure, the TNT equivalency method provides the shortest duration and smallest impulse. The overpressure by the TNT equivalency method decreases with increasing distance. The higher class or Mach number has shorter duration and larger impulse. When these methods are applied in blast resistant designs based on this scenario, the TNT equivalency and the TNO multi-energy methods predict the largest and smallest overpressure, respectively. Two response parameters, ductility ratio and support rotation, are used to check design. When blast resistant PC panels are checked, the TNT equivalency, TNO multi-energy and BST methods predict ductility ratio as 10.5, 0.82 and 25.2. Predicted support rotation is 5.1°, 0.4° and 11.5°. Based on these criteria, this wall design only can be passed as evaluated by the TNO multi-energy method. When blast resistant PC panel connections are designed, the ratio of required connection is 3:1:2; TNT equivalency, TNO multi-energy, BST method. These studies show different results when different gas explosion methods are applied on blast resistant designs. Many domestic engineering companies still use TNT equivalent mass for blast resistant designs. As plant design orders of other countries increase, it may be anticipated that research about the TNO multi-energy and BST methods is needed. Because this thesis suggests the relation the TNT equivalency method and the TNO multi-energy or BST methods and shows the different results generated by each, it can help engineers who do blast resistant design with these methods.

인화성물질 누출원의 특성 변화에 따른 위험범위 설정 방안

김영곤 경일대학교 대학원 2017 국내박사

Classification of Explosion Hazardous Area According to Release Sources Characteristics of Flammable Substance Kim Young-Gon Department of Fire Safety Graduate School, Kyungil University Supervised by Professor Kim Myung-Chul (Abstract) In recent years, there has been a fire and explosion accident caused by flammable liquids and gases, which have been attracting social attention As a result of analyzing the cause, many accidents occurred due to electric ignition sources such as static electricity and spark in the state where explosive atmosphere was formed due to the leakage of flammable liquid and gas. Therefore, electrical appliances and equipment installed in the area should be explosion-proof type in the area where explosive hazard is stored in the places where flammable liquids and gases are stored and handled. On the other hand, the standards of KS C IEC 60079-10-1 ~ 2, which are applied to the explosion prevention-related laws and standards such as the explosion dangerous area setting in Korea, are generally comprehensive and declarative standards. Therefore, It can be cited as the country or the industrial nose. Therefore, the explosion prevention-related technical standards are not clear, so other standards or standards such as the country code, API, EI-15 must be applied. Therefore, it requires extensive knowledge of breadth and experience, However, in Korea, there are not many technical personnel with extensive knowledge and extensive experience in the field of electric explosion prevention Therefore, in order to minimize the confusion caused by the lack of laws and regulations on the establishment of explosion hazard areas, and to provide information for setting the range of explosion hazard areas more accurately, five scenarios that are likely to occur in the chemical process are set up, The risk-based approach and procedures are presented. In addition, the risk range according to the leakage source size according to domestic and foreign codes and standards is set, and compared and evaluated, and the appropriate leakage source size can be selected, In addition, the effect of the ventilation class and effectiveness on the risk range as the wind speed of the workplace increased was evaluated In addition, the explosion risk range design method was proposed by analyzing the effect of increasing the vapor pressure on the danger range when the temperature of the workplace increases depending on the process characteristics and seasons. On the other hand, in order to calculate the appropriate amount of steam evaporation from the liquid pool of the flammable liquid which is not specified in the regulations, standards, etc., various evaporation model equations are applied to calculate leakage amount, 〔Keyword〕 Explosion hazard area, Explosion prevention, release source, ventilation rate, flammable liquid, vapor pressure, volatility.

LNG 연료추진선의 기관실 안전성 확보를 위한 연구

HAMIDETEMAD 한국해양대학교 대학원 2018 국내박사

본 논문은 LNG 연료추진선박의 설계에 대한 안전성을 분석하고 내연기관을 탑재한 LNG연료 추진 시스템의 안전성을 시뮬레이션을 통해 검증 하였다. 주제 1 LNG 연료추진선박의 시스템 설계에 대한 안전성 분석 LNG 연료추진선박에 대한 안정성 및 위험성 분석을 위해 전체 LNG 연료 시스템 중 발생가능한 위험요인 및 결과에 대해 시나리오를 만들고 이를 기존 디젤 연료를 사용하는 선박과 비교하여 위험도를 평가하고 문서화 하였다. 본 논문에서는 대부분의 위험요소에 대해서 검증하였으며 모든 위험요소는 인명피해가능성 (PLL, Potential Loss of Life)과 유해사고율(FAR, Fatal Accident Rate)을 기반으로 정량화 하였다. 결과적으로 LNG 연료추진선으로 인한 인명피해에 대한 위험도는 FAR 4.30이며 이는 디젤연료를 사용하는 선박에 대한 위험도인 FAR 4.16보다 0.14, 즉 약 3.4% 증가한 수치이다. 위험성 분석을 위해 LNG 연료 시스템에서 기인하는 화재 및 폭발 가능성과 충격, 충돌, 좌초, 침몰 등 간접적인 요인으로 인한 화재 및 폭발 가능성을 검토하였다. 본 연구는 선박 건조 혹은 운항 중에 선원 및 선박관리자, 신조 작업자 등 관련 작업자에게 발생가능한 위험요인을 식별하고 각각의 위험요인에 대한 권고사항을 제시한다. LNG 연료탱크 자체는 충돌로 인한 화재 및 폭발 위험성을 증가시키는 주된 요인이지만 종합적인 안전성 및 위험성 평가 결과 LNG 연료추진선박을 신조하거나 개조 시 HSE 분야의 장애요인이 되지 않는다. 본 연구는 가장 위험도가 높은 탱크 배치인 LNG 탱크가 거주구역 아래에 설치 될 경우에 대해서 운영 유지 시 발생 가능한 문제점을 위험성평가를 통해 도출하였다. 또한 관련 국제 법, 규정, 권고 사항들 사이에 존재하는 주요 차이점 및 모순에 대해서도 기술하였다. 주제 2 기관실 내 LNG 연료 시스템에 대한 안전성 분석 LNG 연료추진선은 LNG를 연료로 사용하는 내연기관의 발달과 더불어 개발되었다. 본 연구에서는 엔진에 연결된 연료공급 파이프에서 발생가능한 가스 누설을 분석하였으며, 누설된 가스의 양과 점화 시간에 따라 각각 다른 사고가 발생함을 확인하였다. 누설된 가스가 초기에 점화 될 경우에는 제트파이어(Jet Fire)가 생기나 폭발이 발생하지는 않는다. 하지만 대량의 가스가 누설된 후에 점화가 일어날 경우에는 폭발이 일어날 수 있다. 폭발 가능성은 가스의 농도와 양에 영향을 받는다. 본 연구에서는 기관실 내 고압 이중관이 파열 될 경우 발생할 수 있는 화재 및 폭발 하중을 시뮬레이션을 통해 분석하였으며, 다음과 같은 사항을 고려하였다.  기하학 모델링. 가스 누설이 발생할 공간은 FLACS V10을 통해 실제와 유사하게 모델링 하였으며, 통풍, 기체 확산, 화재 및 폭발에 대한 시뮬레이션을 실시하였다.  통풍 및 기체 확산에 대한 시뮬레이션.(일시 적인 가스 누설의 경우) 설계 공간 및 통풍 용량 등에 대한 기본 조건을 바탕으로 하여 발생가능한 최악의 가스 누설양을 분석하고 두개의 다른 시나리오를 적용하여 시뮬레이션을 시행하였다. 설계 공간 내의 통풍양은 누설 발생 시작 조건을 기반으로 시뮬레이션 하였다.  폭발 시뮬레이션. FLACS를 사용하여 폭발에 대한 시물레이션을 하였으며 기관실 내벽에 작용하는 폭발 압력을 도출하였다. 이를 위해 가스의 누설양과 위치, 점화원의 위치를 바꾸어 총 6번의 시뮬레이션을 시행하였다.  화재 시뮬레이션. 화재 시뮬레이션은 가스 누설 초기에 점화가 되었을 경우를 가정하고 제트파이어를 FLACS에서 설계한 모델을 기반으로 KAMELEON FIREEX(KFX)로 전환하여 시뮬레이션 하였다. 화재 시 구조물의 복사유량을 감안하였으며, 누설양에 따라 세가지의 시뮬레이션을 진행하였다. 화재는 정적 상태에서 화재가 발생할 경우를 가정하였으며, 최악의 경우에 대해서는 제트파이어의 방향을 달리하여 시뮬레이션 하였다.  분석 시뮬레이션을 통해 도출한 폭발 및 화재 하중은 유사한 구조의 기존 디젤을 연료를 사용하는 선박과 비교 하여 제시하였다. 본 분석은 정성적인 평가이며 구조강도에 대한 계산은 포함하지 않았다. 만약 하중이 일반적으로 허용가능한 하중을 초과하는 경우, 추가적인 구조 강도에 대한 시뮬레이션이 필요할 것이며 이를 대응하기 위한 권고사항이 제시되어야 한다. 전형적인 대응책은 검증된 가스 누설 감지 시스템 설치, 가스 누설 부위에 살수, 혹은 중요 구조물 및 배관에 PFP(Passive Fire Protection)적용, 가스 감지 시 연료관 자동 블로우오프(Blow-Off), 통풍 시스템 용량 조절, 발생가능한 점화원 최소화 등이 있다. 본 연구는 또한 누설에 대한 발생 빈도 평가 및 이중관의 전체 파열에 대한 계산을 포함하고 있으며 엔진과 ESD밸브(Emergency Shut-down Valve) 사이의 거리와 밸브가 닫히는 시간의 영향 또한 고려하였다. The abstract has been divided in two parts (1 and 2) as follows: Part 1. Safety analysis and design concept of LNG fueled ship The safety and Risk analyses of LNG fueled ship and system carried out, focusing in particular an analysis of the causes and consequences of hazards scenarios for entire LNG fuel system and with objective to evaluate and document the risk level of the design of the vessel compared to a diesel fueled container vessel of equal type. All major hazards have been considered and the risk is quantified in terms of Potential Loss of Lives (PLL) and Fatal Accident Rate (FAR). In total, the personnel risk for the vessel has been estimated to a FAR of 4.30. A similar new conventional diesel fueled vessel will have an estimated personnel risk level of a FAR of 4.16. The net increase of FAR 0.14 corresponds to an increase in risk by 3.4 % compared to the diesel fueled container vessel. The main categories of hazard scenarios are: Fire and explosion initiated from the LNG system, fire and explosion not LNG initiated, dropped objects, collisions, grounding, foundering and occupational accidents. The purpose of the analysis is to identify safety hazards that may represent risks to crew and third parties such as maintenance personnel, yard workers and other ships during operation. The risks and hazards identified following proposed recommendations with comprehensive summary in term of design and operation. The main result from the safety analysis and HAZID showed that the estimated HAZID increase is mainly due to the presence of the LNG tank and its effect on the risk from fire/explosions due to ship collision. The HAZID results confirm that there is no major HSE showstoppers to carry out construction and conversion on vessel using dual fueled. The main selection criterion was the potential design, worst case scenario for location of LNG tank below accommodation, technical and operational capabilities in conducting such HAZID study and investigations. Several important gaps in mandatory regulations, standards, guidelines or of relevant organizations beyond mandatory regulations have been identified and addressed. Part 2. Safety analysis of LNG fuel for machinery space A LNG gas fuel ship is being developed where LNG gas is used as fuel in internal combustion engines (modified diesels). In this concept to investigate possible consequences of a gas leak in the feeding pipe to the engines. Depending on the size of the leak and the time of ignition, different developments of the accident can occur. Two main developments are foreseen; early ignition and late ignition. If the gas is ignited early, there will be a jet fire and no explosion. If the gas is ignited after most of the gas is released, there may be an explosion. The possibility for a strong explosion is dependent of the gas concentration and size of the gas cloud. The main objective is to find the fire and explosion loads caused by a "rupture of high pressure double wall pipe in machinery space". My safety simulations, modelling and analysis includes the following activities: • Geometry modelling. the entire room is modelled with most details in the area where the leak will start. The geometry is modelled in FLACS v10 so that the geometry model can be applied for ventilation, dispersion, fire and explosion simulations. • Ventilation and dispersion simulations. The leak is modelled as a transient leak. The worst case leak size is estimated based on knowledge of the size of the room, ventilation conditions, etc. Two different leak rates in two different leak scenarios are performed. The ventilation in the room is simulated and used as start conditions when the leak starts. • Explosion simulations. Explosions are simulated in FLACS and explosion pressures on engine room walls are obtained. Total of six simulations are performed with different cloud size, locations and two ignition locations. • Fire simulations. The leak is modelled as a jet fire assuming it is ignited from the start of the leak. The jet fire is simulated in KAMELEON FIREEX (KFX). Radiation flux on the structure is obtained during the fire. three simulations with different constant leak rates are performed. The extent of the fire when a steady state situation is established is presented. One worst case jet direction is performed based on other fire simulations. Note that the geometry model from FLACS will be converted to KFX. • Analysis. The obtained explosion and fire loads are compared with typical collapse loads for similar structures. This evaluation is qualitative, and does not include rigorous calculation of structure strength. If the loads are above typical acceptable loads, simulations of the structure strength will be suggested. Possible mitigating measures will also be recommended. Typical mitigating measures are a good gas detection system, start of deluge on gas detection (this may reduce possible explosion pressures), Passive fire Protection (PFP) on critical structure and piping, automatic blow down of fuel pipe system on gas detection, improved air ventilation, reduced ignition sources, etc. The scope is extended to consider frequency assessment, and full bore rupture calculation. The effect of a smaller ESD segment and shorter ESD closure time are also considered

증기 폭발에 의한 원자로 하부 헤드의 건정성에 관한 연구

석상군(Xi Shangjun) 한국해양대학교 대학원 2011 국내석사

The objective of this paper is to assess the lower head of nuclear reactor under the in-vessel vapor explosion load. Firstly, the calculated explosion pressure loads are applied on the lower head inner wall for 2-D model and 3-D model, respectively, to calculate the equivalent strain and membrane stress intensity; secondly, both calculated explosion pressure loads and thermal loads are imposed on the 2-D model of the lower head to calculate the equivalent stain, membrane stress intensity, and total mechanical and thermal strain. Then, the calculated strain and stress results are compared with the reference standard values of failure criteria to determine the failure probability of the lower head. All the stain and stress calculations are performed by ANSYS 11.0 Program. The structure analysis results show that the lower head failure does not exist under the pressure value up to 118.5 MPa in vessel explosion. The thermo-mechanical results show that the lower head failure under the pressure value up to 118.5 MPa and temperature value up to 700℃ in-vessel explosion also does not exist. During this analysis process, the nucleate boiling crisis will not occur when the outside wall of lower head is cooled by the saturation water at 100℃ and 0.1 MPa.

연료용 에탄올 생산을 위한 보릿짚의 ethanosolv 전처리 공정

김영란 전북대학교 대학원 2011 국내박사

Lignocellulose represents a key sustainable source of biomass for transformation into biofuels and bio-based products. Unfortunately, lignocellulosic biomass is highly recalcitrant to biotransformation, both microbial and enzymatic, which limits and prevents its use. As a result, effective pretreatment strategies are necessary, which invariably involves high energy processing or results in the degradation of key component of lignocelluloses. In this study, barley straw was used as a feedstock and ethanol organosolv (ethanosolv) pretreatment was introduced to enhance the enzymatic hydrolysis to produce bioethanol. First, in order to apply the ethanosolv pretreatment to barley straw, the effects of four process variables (temperature, time, catalyst dose, and ethanol concentration) on the barley straw pretreatment were chosen and analyzed over a broad range using a small composite design and a response surface methodology. The yield of the residual solid and composition of the solid fraction differed as ethanosolv conditions varied within the experimental range. Recovery of glucan and xylan and degree of delignification were 85%, 14% and 69%, respectively under center point conditions (170oC, 60 min, 1.0% (w/w) H2SO4, and 50% (w/w) ethanol). Ethanosolv pretreatment was an effective way to remove lignin without significant degradation of cellulose. Additionally, the highest enzymatic digestibility of 85.3% was obtained after 72 h under center point conditions. Through the severity analysis, ethanosolv pretreatment induced a specific effect on the enzymatic digestibility. Second, ethanosolv pretreatment was catalyzed with inorganic salts because conventional acid catalyst like H2SO4 generally leads to undesirable byproducts inhibiting the following saccharification and fermentation. The addition of several inorganic salts significantly accelerated the enzymatic digestibility of the ethanosolv at 170oC for 60 min. The addition of 0.1M FeCl3, in particular, had a significant effect on the enzymatic digestibility, reaching its value as high as 89%, and the cellulose recovery was up to 90% after the ethanosolv pretreatment. These values were higher than those in case of H2SO4 used as a catalyst. The enzymatic digestibility was 89% and 55% after the addition of 0.1M FeCl3 and H2SO4 (adjusted to the same pH at 1.43), respectively. The enzymatic hydrolysis rate was significantly accelerated as the ethanosolv temperature increased, reaching the highest enzymatic digestibility of 89% after 72 h at 170oC. The 5-hydroxy-2- methyl furfural (HMF) and furfural formations were 0.23 and 2.50 g/100g raw material during the FeCl3-ethanosolv treatment was used. These were lower than those when the H2SO4-ethanosolv treatment. After the pretreatment, 88.5% of the added FeCl3 was removed through a washing/filtration process which indicates that FeCl3 had no effect on the subsequent process. Through sorting by pH of the ethanosolv liquor, hemicellulose removal and enzymatic digestibility lacked consistency but delignification and enzymatic digestibility exhibited a close correlation. It should be noted that lignin did not have to be fully removed in order to obtain a high enzymatic digestibility. Third, a combined process of steam explosion and ethanosolv pretreatment was developed in order to complete hydrolysis of the cellulosic component of barley straw, thereby avoiding the problem associated with the harsh condition of pretreatment and the use of acid catalyst of steam explosion. Therefore the steam explosion and ethanosolv were carried out at lower temperature, 150 and 150oC, respectively than optimum temperature, >180 and >170oC, respectively. The influence of time on steam explosion pretreatment of barley straw was evaluated, showing that the steam explosion time is crucial factor determining the extent of hemicelluloses hydrolysis and that hemicellulose is more sensitive to steam explosion than cellulose. Additional delignification of 33-42% was obtained by further ethanosolv pretreatment, which indicates that ethanosolv improved the delignification significantly. The production of HMF and furfural due to an excessive degradation of sugars after combined process of steam explosion and ethanosolv pretreatment was lower than that in case of single ethanosolv pretreatment. Combined process of steam explosion and ethanosolv had a synergetic effect on enzymatic digestibility compared to single pretreatment conducted separately. The maximum enzymatic digestibility of 89.37% and the maximum value of sugar of 46.55 g from 100 g raw material (equivalent to 66.4% of sugars in raw material) were obtained after combined process of steam explosion (for 10 min) and ethanosolv pretreatment. This study firstly applied the ethanol organosolv pretreatment to agricultural residue and identified the effect of ethanosolv process variables on pretreatment yield. In addition, it was found that FeCl3 could be successfully used as an alternative catalyst for H2SO4 without side effect. Combined process of steam explosion and ethanosolv pretreatment developed in this study showed less formation of inhibitors and enhanced enzymatic digestibility and sugar yields. Threrfore, FeCl3-catalyzed ethanosolv pretreatment and combined process of steam explosion and ethanosolv pretreatment could be suggested as more useful pretreatment tools for bioethanol production from lignocellulosic biomass.

장애물이 있는 부분밀폐계 공간에서의 화염거동에 대한 폭발실험 연구

박남영 서울産業大學校 産業大學院 2004 국내석사

오늘날 가스 사용량의 증가로 인한 잠재 위험요인의 증가로 사고의 부담 또한 커지고 있다. 가스 폭발 사고의 경우 그 피해가 다른 재해에 비해 수십배 이상으로 커지는 경우가 많다. 특히나 가스설비가 위치한 부분 밀폐공간에서의 가스폭발은 큰 과압을 생성하고, 이로 인한 피해는 아주 치명적일 수 있다. 가스폭발의 영향은 발생 설비나 공정에만 국한되지 않고 인근지역의 설비나 인명에까지 영향을 미칠 수 있기 때문에 항상 적절한 안전관리가 필요하다. 그러므로 가스 시설은 설치 및 이용 전에 폭발 사고와 같은 중대 재해 발생 원리 및 그 영향에 대한 연구가 이루어지고, 이를 토대로 적극적인 폭발 예방 대책 및 피해 최소화 대책을 수립하여야 한다. 즉, 폭발은 어떻게 하여 발생되고, 폭발이 일어날 때는 얼마나 큰 과압이 발생되며 그 거동은 어떠한지를 정확히 예측하고, 이를 근거로 한 대책이 수립되어야 한다. 이를 위해서는 먼저 폭발에 의한 피해를 예측할 수 있는 폭발 피해 추정 도구가 개발되어야 한다. 이런 피해 예측도구를 개발하여 사용하기 위해서는 이론적 접근도 중요하지만, 사용 가스시설을 모델화하여 폭발거동 관련 실험을 실시하여 이를 통한 검증 또한 중요하다. 본 연구의 목표는 현재 운용하고 있는 가스 정압실의 구조를 축소하여 폭발장치를 만들고 이 장치를 이용하여 가스폭발 실험을 실시함으로서 폭발장치 주변에 미치는 폭발압력 분포와 이들 압력의 영향과 관련된 자료를 수집하고 이를 토대로 가스시설의 안전한 설계 및 정확한 피해예측 평가도구를 개발하는데 도움을 줄 수 있는 자료를 제시하는데 있다. 연구결과 얻을 수 있는 실험 자료를 요약하면 다음과 같다. 1) 대체 폭발모델 개발의 신뢰성 검증을 위한 실험 데이터 2) 정압실 폭발 방출구의 이탈 압력 및 설계압력 3) 폭발 방출구 주변 시설에 대한 안전 기술 기준 본 실험에서는 모델 내 장애물의 형상 및 크기를 달리하여 실험하였는데, 이는 장애물의 영향에 따른 폭발특성을 알아보는데 중점을 맞췄기 때문이다. 실험 실시 후 얻어진 결과를 정리하면 다음과 같다. 장애물 형상 및 크기에 따른 폭발 실험을 한 결과, 선행 연구 결과에 어긋나는 결과를 가져왔다. 이는 장애물에 대한 기존 실험 이 L/D비가 큰 실험장치로 실험을 실시한데 반해, 본 실험모델은 L/D비가 작은 장치로 실험하였기 때문인 것으로 보인다. 그 결과 선행 연구논문에서 제시한 형상별 실험 결과는 사각형>삼각형>원형 순서로 폭발압력이 줄어든 반면 이 실험의 결과는 그 반대의 현상이 나타났다. 이는 폭발이 모델의 특성에 따라 아주 다른 결과를 가져옴을 알 수 있었다. Past accidents have demonstrated that the most severe threat to gas facilities, chemical and petrochemical industries is the hazard of gas explosions, which have been the predominant causes in view of high damage potential. In particular, the gas explosions occurring in confined and partially confined regions have been concentrated as real concern due to a domino effect and more serious consequences. The consequences due to the explosions have a wide range of the accidental process and equipment as well as the surrounding facility and life, so it is necessary to consider an appropriate safety management. Thus, explosion hazard assessment is an important element in the safe design of the existing installation or new one, and must be considered in the development of an installation safety case. In addition, it is crucial to be able to quantify the magnitude of explosion hazard on existing installations. So that, if necessary, remedial measures can be evaluated and implemented. For such assessments, predictive tools that accurately predict gas explosions are needed. The tools should be tested against sufficient experimental data before it can become a useful tool. A rapidly growing number of CFD explosion codes such as EXSIM, FLACS, AutoReaGas, COBRA, CFX and etc., are being used in explosion assessments. These codes give the better potential of providing high accuracy and more detailed information that are useful for designing gas explosion. However, the tools currently available have only been tested against very limited appropriate experimental data. Exerimental studies are also required to make further understanding of the explosion phenomena, and the data gathered is invaluable to the validation of physical sub-model which may be used to enhance appropriate predictive tools. The main objectives of the present investigation are : (1) to provide new experimental set-up scaled down for real structure (for example, gas governor room) (2) to provide experimental data gathered using various factors influencing on explosion strength, (3) to give more safe design of equipment and process, safety cases and emergency planning from the results of the experiments, (4) to suggest a validation in order to develop reliable predictive tools mentioned above. The main results that are able to achieve from this project can be summarized as follows. 1) Validation data of for a development of an alternative explosion model 2) Design pressure for an explosion vent used in governor room 3) Safety standards on the surrounding facilities of the explosion vent

철원 지진-음파 관측망 자료를 이용한 자연지진과 인공지진 식별연구

제일영 연세대학교 대학원 2003 국내박사

본 논문에서는 한반도 지역의 순수한 자연지진목록 구축과 지진활동 등 자연지진연구의 오염원인 인공지진을 자연지진으로부터 식별하기 위한 연구를 수행하였다. 원거리에서 발생하는 자연지진과 인공지진의 식별을 위하여 저주파수 음파 관측을 이용한 방법과 지진파 스펙트럼 특성을 이용한 식별기술을 연구하였다. 저주파수 음파 관측을 통한 인공지진 식별을 위해 지진파-음파 분석을 정의하였다. 인공지진의 대부분을 차지하는 대규모 지표발파는 수 km 이하에서 발생하는 자연지진과 달리 저주파수의 음파를 발생시킨다. 저주파수 음파는 에너지 감쇠가 작아 장거리 전파가 가능하므로, 이를 관측하고 분석함으로써 자연지진으로부터 인공지진을 식별할 수 있다. 지진파-음파 분석을 철원 지진-음파 관측망 자료에 적용하여 전체 지진기록의 9%에 해당하는 총 663개의 인공지진을 식별하였으며, 한반도에서 발생하는 인공지진 관측과 시간적, 공간적 감시역할을 가능케 하였다. 저주파수 음파의 근거리 전파특성을 규명하기 위하여 하부대기층에서의 전파모델링을 수행하였다. 전파모델링을 위해 기상청의 고층기상자료를 이용하여 유효음파속도구조를 구하였다. 고층기상자료를 이용한 전파모델링으로 하부대기층에서 음파의 근거리 전파 가능성을 설명하였으며, 실측된 음파의 전파시간과 같은 모델링 결과를 보였다. 음파의 근거리 전파특성은 하부대기층에서 형성되는 바람성분에 의해 좌우된다는 것이 밝혀졌다. 또한 근거리를 전파하는 음파는 계절에 따른 음파속도구조에 의해 전파시간과 편향 등의 전파특성이 변화하며, 전파모델링으로부터 이를 확인하였다. 지진파-음파 분석은 대규모 발파로부터 형성되는 미세한 대기 음압 변화를 관측함으로써 인공지진에 대한 명확한 식별을 가능케 하였으나, 지속적으로 변화하는 대기특성 등에 의해 음파 신호를 수반하지 못하는 인공지진은 식별할 수 없었다. 본 연구에서는 이를 해결하기 위하여 지진파에 대한 직접적인 식별연구를 수행하였다. 자연지진과 인공지진에서 발생하는 지진파의 고유한 스펙트럼 특성을 이용한 다변량 판별분석을 적용하였다. 지진원 이론에 기초한 Pg/Lg, Lg1/Lg2, Pg1/Pg2, Rg/Lg 4개 단일 식별기술을 자연지진과 인공지진으로 구성된 표본집단에 적용하여 식별능력을 평가하였다. 단일 식별기술 중 Pg/Lg 식별기술이 가장 효과적인 것으로 연구되었다. 그러나 단일 식별기술로는 표본집단을 완벽히 식별할 수 없었다. 본 연구에서는 식별능력의 향상을 위해 단일 식별기술에 대한 자연지진과 인공지진 모집단의 공통적인 특성을 이용한 복합 판별분석을 정의하였다. 복합 판별분석은 단일 식별기술을 변수로 사용하는 방법으로, 전체 표본에 대해 정확한 식별이 가능하였다. 또한 새로운 지진 관측치에 대한 오분류 확률은 0.7% 이하로 식별능력이 향상되었다. 본 연구에서는 상이한 매질을 통해 전파하는 지진파와 저주파수 음파에 대한 독립적 식별연구에 의해 지진원 식별이 가능하였다. 철원 지진-음파 관측망 자료에 대한 지진파-음파 분석으로 음파 신호를 수반하는 인공지진을 명확하게 식별할 수 있으며, 음파를 수반하지 못하는 지진파에 대해서는 복합 판별분석을 적용하여 지진원을 식별할 수 있다. 향후 한반도에서 발생하는 미소지진 자료에 두 식별연구를 독립적으로 적용함으로써 지진원 식별이 가능하며, 두 기술의 통합적 적용으로 식별능력의 신뢰성을 향상시킬 수 있으리라 판단된다. This discrimination study was performed to develop the discriminant methods for artificial explosion, which is a major potential cause of error when estimating the seismicity of a specific region. In order to discriminate between earthquake and explosion, two discriminant methods were proposed ; one is the use of infrasound observation, and the other is the use of seismic spectral characteristics. A "seismo-acoustic analysis" was defined as one method to identify surface explosion. Surface explosion produces seismic and infrasonic signals simultaneously. As the attenuation of infrasound is extremely small, it can travel over long distance by refraction in the atmosphere. Therefore it is possible to discriminate surface explosion from earthquake by observing and analyzing infrasonic signals. The seismo-acoustic analysis was applied to Cheorwon seismo-acoustic data, and 663 seismo-acoustic events corresponding to 9% of total seismic events were identified as surface explosion. As a result, the seismo-acoustic analysis could be used to monitor surface explosion in and near the Korean Peninsula. In order to understand short-distance propagation characteristics of infrasonic signals, a ray-tracing method was applied to the atmosphere. The atmosphere was simply modeled by effective sound velocity structure by using local meteorological observation. Short-distance propagation of infrasound in lower atmosphere could be explained by ray-tracing, and infrasonic travel time fit well with the observed travel time when a local meteorological model was used. Local wind made it possible to construct infrasonic wave channels in the lower atmosphere and to allow infrasonic wave to arrive at short-distance. Infrasound in lower atmosphere was also influenced by seasonal variation of the sound velocity structures, and it was confirmed by the ray-tracing. In this study the seismo-acoustic analysis was recognized as a definite discriminant method by associating with two different signals which are generated from surface explosion. Surface explosion, however, could not be discriminated by the seismo-acoustic analysis when seismic signals were not accompanied with infrasonic signals in atmospheric condition. Another discriminant method using seismic signal was studied for discrimination of surface explosion. By means of the seismic spectral characteristics, multi-variate discriminant analysis was performed. Four single discriminant techniques - Pg/Lg, Lg1/Lg2, Pg1/Pg2, and Rg/Lg - based on seismic source theory were applied to explosion and earthquake training data sets. The Pg/Lg discriminant technique was most effective among the four techniques. Nevertheless, it could not perfectly discriminate the samples of the training data sets. In this study, a compound linear discriminant analysis was defined by using common characteristics of the training data sets for the single discriminants. The compound linear discriminant analysis was used for the single discriminant as an independent variable. From this analysis, all the samples of the training data sets were correctly discriminated, and the probability of misclassification was lowered to 0.7%. From this study, it was able to discriminate seismic sources from the two discriminant methods by using seismic and infrasonic signals propagating through different mediums from single surface explosion. These two methods can be applied separately or jointly to the seismic events occurring in the Korean Peninsula. The seismo-acoustic analysis will be used to discriminate surface explosion with infrasonic signals, and the compound linear discriminant analysis will be used to discriminate surface explosion which does not accompany infrasonic signals. Simultaneous application of the two methods will improve the ability of discrimination between earthquake and explosion in the future works.