• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.9
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• pp.759-769
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• 2021

For aerospace propulsion systems, Titanium Hydride Potassium Perchlorate (THPP) is a material commonly used as a pyrotechnic initiator that generates gas when energy is supplied or as a supplement charge for NASA standard initiator (NSI). However, when the energetic materials are stored for a long time, it faces the problem of 'aging'. In this study, changes in thermodynamic properties of THPP aged under various humidity environments were identified through thermal analysis and surface analysis. First, a considerable amount of cracks on the surface of the oxidant was found in the aged THPPs. Particularly, when the humidity level increased, the number and length of the cracks rapidly increased. Also, the deterioration of Viton was found only in the thermally aged sample whereas the oxidation of the fuel was more pronounced in the hygrothermally aged samples. The extracted kinetic parameters of THPP on the reaction progress vary greatly by the humidity level, indicating that moisture significantly changes the performance and combustion reaction of THPP, which may eventually result in a reduced lifespan.

• Resources Recycling
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• v.31 no.2
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• pp.33-39
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• 2022

In this study, analytical thermochemical modeling factors that contribute to maintaining a specific temperature range during vanadium roasting as a pretreatment using a rotary kiln are investigated. The model-related mechanisms include thermochemical reaction rates, heat balance, and heat transfer, through which the resultant temperature can be estimated intuitively. Ultimately, by optimizing these parameters, the ideal roasting temperature in the kiln is ≈1000 ℃ (or ≈1273 K) for long-term operation. Therefore, the heat generated from hydrocarbon (natural gas) fuel combustion and ore oxidation reactions, as well as the radiant heat transferred to ores, are assessed. In addition, thermochemical methods for relieving the temperature gradient in order to maintain the optimum temperature range of the rotary kiln are suggested.

• Journal of ILASS-Korea
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• v.27 no.3
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• pp.117-125
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• 2022

This study examines whether engine fuel efficiency is improved by optimization of the exhaust valve timing in a state where the intake valve timing has been optimized in a small turbo gasoline engine that has intake cams and exhaust cams with fixed valve opening periods. When the exhaust valve is opened late, the expansion stroke is longer, and the efficiency can be improved. A 2-cylinder turbo gasoline engine with 0.8 liters of displacement and an MPI (Multi Point Injection) fuel system was used. The engine was operated at 1,500 and 3,000 rpm, and the load conditions included a partial load of 50 N·m and a high load of 70 N·m. Data was recorded as the exhaust valve timing was controlled, and this was used to calculate the efficiency of combustion using a heat release, the fuel conversion efficiency, and the pumping loss. Results and the hydrocarbon concentrations in the exhaust gas were compared for each condition. Experiment results confirmed that additional fuel efficiency improvements are possible through exhaust valve timing control at 1,500 rpm and 50 N·m. However, in other operating conditions, fuel efficiency improvements could not be obtained through exhaust valve timing control because cases where the pumping loss and fuel/air mixture slip increased when the exhaust valve timing changed and the fuel efficiency declined.

• Journal of the Korean Society of Propulsion Engineers
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• v.27 no.1
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• pp.37-48
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• 2023

In this study, performance analysis modeling of two spool mixed flow type turbofan engine according to steady-state and transient is performed. The target engine is selected as F100-PW-229 from Pratt & Whitney, and main engine components including fan, high pressure compressors, combustion, high pressure turbines, low pressure turbines, mixer, convergent-divergent nozzle are modeled. The cooling effect of turbine through secondary flow path are considered in engine simulation model. We develop in-house Matlab/Simulink-based engine performance analysis program capable of analyzing internal engine state and compare it with GASTURB which is generally used as a commercial engine analysis program.

• Economic and Environmental Geology
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• v.56 no.1
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• pp.75-85
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• 2023

The potential sources and spatial distribution of heavy metals and polycyclic aromatic hydrocarbons (PAHs) were investigated in the leaf plants of Al-Zubair city. A total of 14 samples of conocarpus lancifolius plant leaf were collected and analyzed for their heavy metals and PAHs content using inductively coupled plasma mass spectrometry (ICP-MS) and a 7890 Agilent capillary gas chromatograph (GC) respectively. Bioaccumulation factor calculation revealed the highest pollution of heavy metals , due to the activity of a petrochemical in the area. The diagnostic ratio of Ant/(Phe+Ant), BaA/BaA+Chr), In/(In+BghiP), Flu/Pyr, FlA/FlA+Pyr), FlA/FlA+Pyr), ∑LMW/∑HMW are commonly used for determining the origin and source of PAHs in various environmental media. The diagnostic ratio indicated the anthropogenic origin. PAHs with five-to-six membered rings were dominant in the plant leaf, which likely results from anthropogenic activities. The leaves of C. lancifolius have a preponderance of high molecular weight PAHs compared to low molecular weight PAHs, indicating a combustion origin (car exhaust, petroleum emissions, and fossil fuel). C. lancifolius leaves are a reliable indication of atmospheric PAHs absorption. The background level of heavy metals in the city (or the near environment) is in the order of Fe > Cu > Ni > Cr. On the other hand, the bioaccumulation in plant leaves showed greater tendencies as follows: Co>Cd>Zn=As>Cu>Mn>Ni>Pb>Cr>Fe. Cobalt showed high bioaccumulation, indicating strong uptake of Co by plant leaves. These findings point to human activity and car emissions as the primary sources of roadside vegetation pollution in Al-Zubair city.

• Safety and Health at Work
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• v.14 no.2
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• pp.215-221
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• 2023

Background: There is little information about the airborne hazardous agents released during the heat treatment when manufacturing a welding material. This study aimed to evaluate the airborne hazardous agents generated at welding material manufacturing sites through area sampling. Methods: concentration of airborne particles was measured using a scanning mobility particle sizer and optical particle sizer. Total suspended particles (TSP) and respirable dust samples were collected on polyvinyl chloride filters and weighed to measure the mass concentrations. Volatile organic compounds and heavy metals were analyzed using a gas chromatography mass spectrometer and inductively coupled plasma mass spectrometer, respectively. Results: The average mass concentration of TSP was 683.1±677.4 ㎍/m³, with respirable dust accounting for 38.6% of the TSP. The average concentration of the airborne particles less than 10 ㎛ in diameter was 11.2-22.8×10⁴ particles/cm³, and the average number of the particles with a diameter of 10-100 nm was approximately 78-86% of the total measured particles (<10 ㎛). In the case of volatile organic compounds, the heat treatment process concentration was significantly higher (p < 0.05) during combustion than during cooling. The airborne heavy metal concentrations differed depending on the materials used for heat treatment. The content of heavy metals in the airborne particles was approximately 32.6%. Conclusions: Nanoparticle exposure increased as the number of particles in the air around the heat treatment process increases, and the ratio of heavy metals in dust generated after the heat treatment process is high, which may adversely affect workers' health.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2019.10a
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• pp.134-134
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• 2019

Utilization of organic waste as a renewable energy source is promising for sustainability and mitigation of climate change. Pyrolysis converts organic waste to gas, oil, and biochar by incomplete biomass combustion. Biochar is widely used as a soil conditioner and adsorbent. Biochar adsorbs/desorbs metals and ions depending on the soil environment and condition to act as a nutrient buffer in soils. Biochar is also regarded as a carbon storage by fixation of organic carbon. Phosphorus (P) and nitrogen (N) are strictly controlled in many wastewater treatment plants because it causes eutrophication in water bodies. P and N is removed by biological and chemical methods in wastewater treatment plants and transferred to sludge for disposal. On the other hand, P is an irreplaceable essential element for all living organisms and its resource (phosphate rock) is estimated about 100 years of economical mining. Therefore, P and N recovery from waste and wastewater is a critical issue for sustainable human society. For the purpose, intensive researches have been carried out to remove and recover P and N from waste and wastewater. Previous studies have shown that biochars can adsorb and desorbed phosphates implying that biochars could be a complementary fertilizer. However, most of the conventional biochar have limited capacity to adsorb phosphates and nitrate. Recent studies have focused on biochar impregnated with metal salts to improve phosphates and nitrate adsorption by synthesizing biochars with novel structures and surface properties. Metal salts and metal oxides have been used for the surface modification of biochars. If P removal is the only concern, P adsorption kinetics and capacity are the only important factors. If both of P and N removal and the application of recovery are concerned, however, P and N desorption characteristics and bioavailability are also critical factors to be considered. Most of the researches on impregnated biochars have focused on P removal efficiency and kinetics. In this study, coffee waste is thermally treated to produce biochar and it was impregnated with Mg/Al to enhance phosphates and nitrate adsorption/desorption and P bioavailability to increase its value as a fertilizer. Kinetics of phosphates and nitrate adsorption/desorption and bioavailability analysis were carried out to estimate its potential as a P and N removal adsorbent in wasewater and a fertilizer in soil.

• The Journal of the Convergence on Culture Technology
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• v.8 no.3
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• pp.493-499
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• 2022

This paper reports the results of the eruption of a volcano on Jeju Island at a certain rate, and the tumulus formed after the eruption and the basalt that erupted from the middle of Mt. Halla washed up to the sea. We analyzed the speed when basalt underground magma breaks through the neutral zone on the ground with an absolute temperature of about 1000K and explodes at an absolute temperature of 1200K at an altitude of 1950m. The density of combustion gas becomes smaller than the surrounding air due to the plume volcanic eruption, which is the heat flow of the flame column due to buoyancy, and buoyancy is generated and an updraft is formed. Flame pillars are classified as continuous, intermittent, and buoyant flame zones. As the speed of the flame pillar of Mt. Halla (1950m) falls from the highest point it has risen, potential energy is converted into kinetic energy and is caused by the flow of fluid, solving these two equations equal, the volcanic eruption velocity is 87.5 m/s. At this time, the density of magma is inversely proportional to the temperature. Geomunoreum (456m) had an explosion speed of 42.6m/s.

• Journal of the Society of Disaster Information
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• v.20 no.2
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• pp.419-429
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• 2024

Purpose: To enhance the non-combustibility of fire protection piping insulation and improve the heat resistance of smoke extraction duct insulation, I plan to verify the suitability of AES insulation materials for these applications through performance testing. Method: The non-combustibility, heat resistance, and thermal insulation performance of AES insulation materials will be verified through various tests. Result: According to the 'Standards for Flame Retardancy and Fire Spread Prevention of Building Finishing Materials,' the results of non-combustibility and gas toxicity tests confirmed the non-combustible properties. The standard fire resistance tests verified the fire resistance performance. Additionally, the thermal insulation performance was confirmed through building insulation tests. Conclusion: As the performance tests on AES inorganic insulation materials have proven their noncombustibility, fire resistance, and thermal insulation performance, these materials are considered a viable alternative for improving fire spread prevention in buildings.

• Applied Chemistry for Engineering
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• v.8 no.5
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• pp.790-795
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• 1997

Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofuransfurans are the archetype of toxic chemicals. So it has absorbed public attention. The majors primary sources of PCDDS and PCDFs are chemical, thermal and photochemical reactions. Municipal solid waste incinerator facilities has been reported as the major contributors of dioxins to the environment. In this paper, Dioxins and furans were examined emission gas and fly ash produced during combustion in municipal solid waste incinerator. More effective method for sampling, extraction was described. The sample was extracted using a soxhlet method and purified using silicagel, alumina and carbon fibre HPLC to remove interfering compound. The extract was then analyzed by HRGC/HRMS. The result of this study showed recovery standard was good and the data resembled those of thermal processes. Total dioxins and furans were $1076.20pg/Nm^3$ and $1452.34pg/Nm^3$ respectively. The amount of highly chlorinated compound was more than that of lowly chlorinated compound. The 2,3,7,8-substituted TCDD was Just 0.34% of the total dioxins/furans amount.