• Journal of the Korean Institute of Gas
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• v.23 no.6
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• pp.1-7
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• 2019

Most oil refineries and chemical plants have flare systems designed to mitigate pressure rises in process facilities in case of emergencies that require the release of large amounts of gas due to sudden process shutdowns such as power outages. However, the rise of the flame of the flare system causes civil complaints from residents around the factory due to visible pollution, and economic loss occurs in the company, which requires constant management. In this study, two items were diagnosed and analyzed in order to derive the optimal operation method of flare system. First, to detect the cause of the rise in flame height, the acoustic leak detector was used to check gas leaks in safety valves and pressure control valves. Second, to identify the cause of flame instability, the pulsation phenomenon was diagnosed through the CFD simulation and modeling experiments of the sealing drum. By confirming the leak at 4.3% of the safety valve and 10% of the pressure control valve, the cause of abnormal sparking was derived. The information presented in this study can be easily applied to any company that has a flare system, and is expected to prevent complaints and product loss.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.135-139
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• 2017

The main reason for heat accidents occurring at the after stern tube bearing (STB) is excessive local pressure caused by the deflection of the propulsion shaft due to propeller loads. The probability of a heat accident is increased by the low flexibility of the shaft system in very large crude oil carriers (VLCCs) as the engine power and shaft diameter increase and the distance decreases between the forward and after STBs. This study proposed shaft system with only an after STB and no forward STB for a flexibility acquisition method for a VLCC shaft system under hull deformation. A Hertzian contact condition was applied, which assumes a half-elliptical pressure distribution along the contact width for the calculation of the local squeeze pressure. The propeller loads, heat effect, and hull deflection under engine operating conditions are also considered. The results show that the required design criteria were satisfied by building a partial slope at the white metal, which is the material at the axial contact side in the after STB. This system could reduce building cost by simplification of the shaft system.

• International Journal of Fluid Machinery and Systems
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• v.10 no.1
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• pp.40-46
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• 2017

Small valves including ball valves, gate valves and butterfly valves have been adopted in the fields of steam power generation, petrochemical industry, carriers, and oil tankers. Butterfly valves have normally been applied to fields where in narrow places installing the existing valves such as gate valves and ball valves have proven difficult due to the surrounding area and the heavier of these valves. Butterfly valves are used to control the mass flow of the piping system under low pressure by rotating the circular disk installed inside. The butterfly valve is benefitted by having simpler structure in which the flow is controlled by rotating the disc circular plate along the center axis, whereas the weight of the valve is light compared to the gate valve and ball valve above-mentioned, as there is no additional bracket supporting the valve body. The manufacturing company needs to acquire the performance and life test equipment, in the case of adopting the improving factors to detect leakage and damage on the seat of the valve disc. However, small companies, which are manufacturing the industrial valves, normally sell their products without the life test, which is the reliability test and environment test, because of financial and manpower problems. Furthermore, the failure mode analysis of the products failed in the field is likewise problematic as there is no system collecting the failure data on sites for analyzing the failures of valves. The analyzing and researching process is not arranged systematically because of the financial problem. Therefore this study firstly tried to obtain information about the failure data from the sites, analyzed the failure mode based on the field data collected from the customers, and then obtained field data using measuring equipment. Secondly, we designed and manufactured the performance and life test equipment which also have the real time monitoring system with the naked eye for the butterfly valves. The concept of this equipment can also be adopted by other valves, such as the ball valve, gate valve, and various others. It can be applied to variously sized valves, ranging from 25 mm to large sized valves exceeding 3000 mm. Finally, this study carries out the life test with square wave pressure, using performance and life test equipment. The performance found out that the failures from the real time monitoring system were good. The results of this study can be expanded to the other valves like ball valves, gate valves, and control valves to find out the failure mode using the real time monitoring system for durability and performance tests.

• Korean Journal of Mineralogy and Petrology
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• v.35 no.4
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• pp.423-430
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• 2022

Pressure-dependent elastic behavior and chemical reaction of natural sepiolite (Mg₈Si₁₂O₃₀(OH)₄·12H₂O) was studied under two different pressure-transmitting medium (PTM) conditions using synchrotron X-ray powder diffraction. Under non pore-penetrating silicone oil PTM, we observed that the b-axis length increases up to ca. 3.6 GPa, marking an anisotropic compression region with negative linear compressibility of β^b= -0.0012 GPa^-1, which then decreases at 7.7 GPa. Under pore-penetrating water PTM, the anisotropic compression behavior is enhanced with doubled negative linear compressibility of β^b= -0.0025 GPa^-1 up to 3.2 GPa, where transformation into stevensite is observed upon ex-situ temperature treatment at 280 ℃ as confirmed via XRD and SEM. Derived bulk moduli (K₀) and linear compressibilities (β) were compared to other structurally and chemically related minerals.

• The Journal of Engineering Geology
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• v.32 no.4
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• pp.643-659
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• 2022

Geologic sequestration technologies such as CCS (carbon capture and storage), EGS (enhanced geothermal systems), and EOR (enhanced oil recovery) have been widely implemented in recent years, prompting evaluation of the mechanical stability of storage sites. As fluid injection can stimulate mechanical instability in storage layers by perturbing the stress state and pore pressure, poroelastic models considering various injection scenarios are required. In this study, we calculate the pore pressure, stress distribution, and vertical displacement along a surface using commercial finite element software (COMSOL); fault slips are subsequently simulated using PyLith, an open-source finite element software. The displacement fields, are obtained from PyLith is transferred back to COMSOL to determine changes in coseismic stresses and surface displacements. Our sequential use of COMSOL-PyLith-COMSOL for poroelastic modeling of fluid-injection and induced-earthquakes reveals large variations of pore pressure, vertical displacement, and Coulomb failure stress change during injection periods. On the other hand, the residual stress diffuses into the remote field after injection stops. This flow pattern suggests the necessity of numerical modeling and long-term monitoring, even after injection has stopped. We found that the time at which the Coulomb failure stress reaches the critical point greatly varies with the hydraulic and poroelastic properties (e.g., permeability and Biot-Willis coefficient) of the fault and injection layer. We suggest that an understanding of the detailed physical properties of the surrounding layer is important in selecting the injection site. Our numerical results showing the surface displacement and deviatoric stress distribution with different amounts of fault slip highlight the need to test more variable fault slip scenarios.

• Economic and Environmental Geology
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• v.56 no.3
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• pp.311-330
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• 2023

Development of Carbon Capture and Storage (CCS) technique is becoming increasingly important as a method to mitigate the strengthening effects of global warming, generated from the unprecedented increase in released anthropogenic CO₂. In the recent years, the characteristics of basaltic rocks (i.e., large volume, high reactivity and surplus of cation components) have been recognized to be potentially favorable in facilitation of CCS; based on this, research on utilization of basaltic formations for underground CO₂ storage is currently ongoing in various fields. This study investigated the feasibility of underground storage of CO₂ in basalt, based on the examination of the CO₂ storage mechanisms in subsurface, assessment of basalt characteristics, and review of the global research on basaltic CO₂ storage. The global research examined were classified into experimental/modeling/field demonstration, based on the methods utilized. Experimental conditions used in research demonstrated temperatures ranging from 20 to 250 ℃, pressure ranging from 0.1 to 30 MPa, and the rock-fluid reaction time ranging from several hours to four years. Modeling research on basalt involved construction of models similar to the potential storage sites, with examination of changes in fluid dynamics and geochemical factors before and after CO₂-fluid injection. The investigation demonstrated that basalt has large potential for CO₂ storage, along with capacity for rapid mineralization reactions; these factors lessens the environmental constraints (i.e., temperature, pressure, and geological structures) generally required for CO₂ storage. The success of major field demonstration projects, the CarbFix project and the Wallula project, indicate that basalt is promising geological formation to facilitate CCS. However, usage of basalt as storage formation requires additional conditions which must be carefully considered - mineralization mechanism can vary significantly depending on factors such as the basalt composition and injection zone properties: for instance, precipitation of carbonate and silicate minerals can reduce the injectivity into the formation. In addition, there is a risk of polluting the subsurface environment due to the combination of pressure increase and induced rock-CO₂-fluid reactions upon injection. As dissolution of CO₂ into fluids is required prior to injection, monitoring techniques different from conventional methods are needed. Hence, in order to facilitate efficient and stable underground storage of CO₂ in basalt, it is necessary to select a suitable storage formation, accumulate various database of the field, and conduct systematic research utilizing experiments/modeling/field studies to develop comprehensive understanding of the potential storage site.

• The Korean Journal of Physiology
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• v.15 no.1
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• pp.61-66
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• 1981

In 1944 Cavallito and Bailey first extracted an essential oil, a powerful antibacterial principle, from the garlic and named it allicin. Later Stoll and Seeback elucidated that allicin was produced from alliin by the enzymatic action of arinase. Damaru observed the depressor responses following intraperitoneal administration of garlic juice in cats. And Thiersch presented evidence that garlic had a protective action against experimental arterosclerosis in cholesterol-fed animals. On the other hand it was also reported that anemias were caused by long-term ingestion of garlic as a result of reduction in hemoglobin and RBC. From the experiment in which the effect of garlic on the blood sugar level was studied, Lee insisted garlic elevated blood sugar level. However, August and Jain claimed that hypoglycemia was induced by garlic administration. Recently Bordia and Bansal suggested that essential oils extracted from onion and garlic have a strong preventive effect on hyperlipemia and prolonged coagulation time resulted from fat-feeding. Furthermore Bordia et al indicated that garlic exerted a strong fibrinolytic activity. In early 1920 s Sugihara reported that essential oil of garlic not only decreased arterial blood pressure but also had a paralytic effect on the isolated heart and intestinal strip of animals. The present study was proposed to investigate the effect of garlic juice and the mechanism of its action on the motility of the isolated rabbit duodenum. The motility of the isolated duodenum was recorded on polygraph by means of force transducer connected with Magnus apparatus. And the isolated duodenum was separtely pretreated with $acetylcholine(5{\times}10^{-7}\;gm/ml)$, $pilocarpine(2.5{\times}10^{-6}\;gm/ml)$, $histamine(5{\times}10^{-6}\;gm/ml)$ and barium $chloride(2.5{\times}10^{-5}\;gm/ml)$ in order to find out interations of these drugs with ASJ. The results obtained were as follows; At concentrations of 0.25%, 0.5% and 1.0% ASJ markedly inhibited contractions of isolated duodenum while tonus as well as contractility of the isolated intestine were decreased also with 0.5% and 1.0% ASJ. Since ASJ markedly abolished augmented motility of isolated intestine by histamine and partly reduced that by $BaCl_2$, it is strongly suggested that inhibitory action of ASJ on the intestinal motility is caused mainly by its antihistamine effect and partly by its direct action on the intestinal smooth muscle.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.6
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• pp.655-662
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• 2012

Gas leakage in an oil refinery causes damage to the environment and unsafe conditions. Therefore, it is necessary to develop a technique that is able to detect the location of the leakage and to filter abnormal gas-leakage signals from normal background noise. In this study, the adaptation filter of the finite impulse response (FIR) least mean squares (LMS) algorithm and a cross-correlation function were used to develop a leakage-predicting program based on LABVIEW. Nitrogen gas at a high pressure of 120 kg/$cm^2$ and the assembled equipment were used to perform experiments in a reverberant chamber. Analysis of the data from the experiments performed with various hole sizes, pressures, distances, and frequencies indicated that the background noise occurred primarily at less than 1 kHz and that the leakage signal appeared in a high-frequency region of around 16 kHz. Measurement of the noise sources in an actual oil refinery revealed that the noise frequencies of pumps and compressors, which are two typical background noise sources in a petrochemical plant, were 2 kHz and 4.5 kHz, respectively. The fact that these two signals were separated clearly made it possible to distinguish leakage signals from background noises and, in addition, to detect the location of the leakage.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.9
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• pp.909-916
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• 2015

In this study, to investigate the effect of spray behavior characteristics, we induce the mixing ratio of emulsified fuel using impinging spray. We formulate the emulsified fuel by mixing diesel and hydrogen peroxide($H_2O_2$). We set the temperature of the heating plate to $150^{\circ}C$, $200^{\circ}C$, and $250^{\circ}C$, and set the injection pressures to 400, 600, 800, and 1000bar. The surfactants for the emulsified fuel mixture, which were mixed span80 and tween80 was mixed as 9:1, were fixed to 3% of the total volume of the emulsified fuel. We set the mixing ratio of $H_2O_2$ in the emulsified fuel as emulsified fuel(EF)0, EF2, EF12, and EF22. Further, we visualize the evaporation impinging spray using the Schlieren method. Based on the results of this study, we found that a higher temperature and injection pressure of the heating plate impingement led to the active diffusion of the fuel vapor, which promoted emulsified fuel evaporation. When the emulsified fuel is utilized in an actual engine, because of the temperature-drop effect of the combustion chamber, which is due to the evaporation of $H_2O_2$ in fuel and faster mixture formation is expected to decrease the engine emissions.

• Journal of the Korean Applied Science and Technology
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• v.35 no.3
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• pp.731-743
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• 2018

In bio-jet fuel production, selecting operating conditions of hydro-upgrading is of great importance to make iso-Paraffin rich hydrocarbons with carbon distribution including jet fuel range. Herein, iso-Paraffin rich biofuel including jet fuel range hydrocarbons ($C_8-C_{16}$) is produced from simultaneous cracking and isomerization using n-Paraffin rich hydrocarbon derived from hydrotreated vegetable oil over 0.5 wt..% Pt/Zeolite catalyst. We report and analyze the yields and compositions in the produced hydrocarbons affected by various operating conditions, such as reaction temperature, reaction pressure, molar ratio of reactants, and weight hourly space velocity. Aforementioned operating conditions not only can help interpret the reaction dynamics of hydro-upgrading, but also further produce bio jet-fuel after distillation.