• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.6 no.1
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• pp.125-137
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• 1996

This study was designed to investigate effects of relative humidity on the breakthrough of charcoal tubes at a fixed vapor concentration and sampling time during mixed organic vapor sampling. A vapor generator was used to generate three different concentrations of mixed organic vapor and a stainless steel chamber was fabricated and utilized to maintain three different percentages of relative humidity while maintaining a constant temperature. The results were as follows; 1. At high relative humidity, breakthrough of mixed organic vapor occurred quickly at low vapor concentration than at high vapor concentration because of the reduced adsorption volume of charcoal tube due to humidity. 2. Breakthrough by competitive adsorption of vapors onto charcoal tube was observed at first from n-hexane having the lowest boiling point and highest vapor pressure among the three organic vapors investigated, followed by TCE. No breakthrough was observed from toluene under all experimental conditions. 3. For n-hexane, breakthrough was observed after 2 hours of sampling and breakthrough rates were increased as relative humidity increased. For TCE, breakthrough was found after 3 hours of sampling and breakthrough rates by sampling time were increased as vapor concentration increased. 4. The adsorbed amount of mixed organic vapor at breakthrough was shown to have statistically significant correlations with sampling time, relative humidity, and vapor concentration in descending order of correlation. Relative humidity and sampling time for n-hexane and sampling time and concentration for TCE were both statistically significantly correlated. 5. Relative humidity was found to affect the amount of breakthrough of mixed organic vapor and n-hexane. Among three percentages of relative humidity investigated, the amount of breakthrough at 85 % relative humidity was significantly larger than those of at lower percentages of relative humidity. No statistically significant difference was found between 25 % and 55 % relative humidity. 6. The results of multiple regression analysis between breakthrough and relative humidity, vapor concentrations showed that the coefficient of determination of mixed organic vapor was 0.263 and those of n-hexane and TCE were 0.275 and 0.189, respectively. 7. Flow rates of sampling pumps used were found to be affected by relative humidity present. At 25 %, 55 %, and 85 % relative humidity, the relative errors of sampling pump were 1.4 %, 13.4 %, and 18.6 %, respectively. In conclusion, the results of this study showed that high relative humidity could reduce the adsorption volume of charcoal tubes and subsequently increase breakthrough rates. Therefore, to prevent breakthrough when sampling mixed organic vapors, it is suggested that either sampling volume be reduced on the flow rate be lowered so as to minimize breakthrough of the most volatile organic vapor in the mixture. In addition, since the flow rates of a sampling pump can be adversely affected by high relative humidity, it is recommended to use a constant flow mode pump when sampling in the highly humid environment.

• ETRI Journal
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• v.27 no.5
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• pp.585-594
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• 2005

A small electronic nose (E-Nose) system has been developed using an 8-channel vapor detection array and personal digital assistant (PDA). The sensor array chip, integrated on a single microheater-embedded polyimide substrate, was made of carbon black-polymer composites with different kinds of polymers and plasticizers. We have successfully classified various volatile organic compounds such as methanol, ethanol, i-propanol, benzene, toluene, n-hexane, n-heptane, and c-hexane with the aid of the sensor array chip, and have evaluated the resolution factors among them, quantitatively. To achieve a PDA-based E-Nose system, we have also elaborated small sensor-interrogating circuits, simple vapor delivery components, and data acquisition and processing programs. As preliminary results show, the miniaturized E-Nose system has demonstrated the identification of essential oils extracted from mint, lavender, and eucalyptus plants.

• Proceedings of the Membrane Society of Korea Conference
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• 2003.07a
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• pp.69-72
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• 2003

Volatile organic compounds (VOC) cause air pollution problem and deterioration of atmosphere of petrochemical and fine chemical plants. Hybrid process of membrane and cold-condensation were developed and it effectively removed and recycled the VOC. Operation parameters of the process were optimized to attain hish removal and recycle of VOC. Composite membranes for organic vapor separation were developed in this work by PDMS coating and plasma polymerization on polypropylene and polysulfone support membranes. PDMS and various silicone monomers were tested for several organic vapors such as benzene, toluene, TCE, and HCFC, which are produced in petrochemical and fine chemical industry and causes air pollution problems if are released to atmosphere. Composite membranes prepared in this work showed appreciable performance in terms of organic vapor removal and reuse. Performance variation of the membranes was correlated with their surface characteristics.

• Journal of the Korean Society of Safety
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• v.11 no.4
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• pp.79-83
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• 1996

In this study, in attempt to develop a new application technique of discharge plasma, we employed a kind of discharging method called SPCP ( short for Surface discharge induced Plasma Chemical Process). Applications of SPCP have been widely used for years. Compact ozonizers to deodorize household equipments like refrigerators we a part of such applications. We took advantages of the compactness and durability of the SPCP electrode to set up an experimental apparatus for decompositing vapor of aromatic hydrocarbons such as toluene, benzene and xylenes, which are major substances given off In painting or washing processes and aggravate working conditions. Results obtained from this study are summarized as follows. 1) Aromatic hydrocarbon vapors of up to 2,000ppm were almost thoroughly decomposed at the flow rate of 4ℓ/min or lower under the discharge with electric power of 400 Watts. 2) In dry air, as the decomposition progresses, tar-like substance deposits on the discharging areas, which deteriorated the decomposition rate in the end. This substance, however, was almost thoroughly removed by keeping discharge in dry air containing no solvent vapor.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.24 no.2
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• pp.238-245
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• 2014

Objectives: It was known that workers in synthetic leather company are mainly co-exposed to dimethylformamide(DMF) with methyl ethyl ketone(MEK) or toluene(TOL) instead of a single dimethylformamide. This study was examined to the physico-chemical properties in single DMF and binary mixture DMF with MEK or TOL. Materials: Physico-chemical properties were measured by Korean and American Standard Test Methods. Results: Boiling point, specific gravity and flash point in single DMF were significantly higher than binary mixture DMF with MEK or TOL and such difference was dependent on the mixing ratio of MEK and TOL, and low explosion limit in binary mixture DMF with TOL was only significantly lower than single DMF. However, Reid vapor pressure had significantly higher in binary mixture DMF with MEK or TOL compared with single DMF. Conclusions: Our results demonstrate that the binary mixture DMF with MEK or TOL synergistically increases volatilization of DMF. It was concluded that the interaction between DMF and MEK and/or TOL might play a key role in the volatilization process of DMF under environmental conditions of workplace.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.3
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• pp.299-305
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• 2015

In this paper, we propose a simple and low-cost fabrication method of polymer microlens using solvent-vapor-assisted reflow (SVAR). Metal molds for replication of polymer were fabricated using micro milling and the cylindrical shape of polymer was imprinted using hot-embossing process. The cylindrical shape of polymer was changed to hemispherical lens shape by SVAR. The characteristics of fabricated microlens were evaluated according to the condition of SVAR such as temperature and time. The focal length of polymer microlens could be controlled more easily in low-temperature and long-time condition than in high-temperature and short-time condition. That is, the level of concentrated light to focal point could be improved through the control of temperature and time. Also, we confirmed that toluene was more appropriate solvent than acetone in fabrication of PMMA polymer microlens using SVAR.

• Journal of Environmental Health Sciences
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• v.35 no.6
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• pp.500-509
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• 2009

Passive samplers have been used for many years for the sampling of organic vapors in work environment atmospheres. Currently, all passive samplers used in domestic occupational monitoring are foreign products. This study was performed to evaluate variable parameters for the development of passive organic samplers, which include the geometry of the device and diffusive length for the sampler design. Four prototype diffusive lengths; A-1(4.5 mm), A-2(7.0 mm), A-3(9.5 mm), A-4(12.0 mm) were tested for adsorption performances to a chemical mixture (benzene, toluene, trichloroethylene, and n-hexane) according to the US-OSHA's evaluation protocol. A dynamic vapor exposure chamber developed and verified by related research was used for this study. The results of study are as follows. The results in terms of sampling rate and recommended sampling time test indicate that the most suitable model was A-3 (9.5 mm diffusive lengths on both sides) for passive sampler design in time weighted average (TWA) assessment. Sampling rates of this A-3 model were 45.8, 41.5, 41.4, and 40.3 ml/min for benzene, toluene, trichloroethylene, and n-hexane, respectively. The A-3 models were tested on reverse diffusion and conditions of low humidity air (35% RH) and low concentrations (0.2 times of TLV). These conditions had no affect on the diffusion capacity of samplers. In conclusion, the most suitable design parameters of passive sampler are: 1) Geometry and structure - 25 mm diameter and 490 $mm^2$ cross sectional area of diffusion face with cylindrical form of two-sided opposite diffusion direction; 2) Diffusive length - 9.5 mm in both faces; 3) Amount of adsorbent - 300 mg of coconut shell charcoal; 4) Wind screen - using nylon net filters (11 ${\mu}m$ pore size).

• Journal of Environmental Science International
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• v.17 no.12
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• pp.1381-1390
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• 2008

Emission characteristics of volatile organic compounds (VOCs) were investigated in the flue gas emitted from wood drying process for plywood manufacturing. The moisture content of raw timber was average 48%, and its density was $831.55kg/m^3$. But the moisture content of dried wood is needed less than around 10%, thus the moisture contents of flue gas should be remarkably high(about 18.2 V/V%). Therefore, the vapor in flue gas is equivalent to 320 ton-vapor/day when 1100 ton-wood/day is treated in the wood drying process. The temperature of flue gas ranges from $140^{\circ}C\;to\;150^{\circ}C$ in each dryer stack with exception of the input site of wood(about $110^{\circ}C$). The velocity of flue gas in each stack ranges from 1.7 to 9.7m/sec. In order to assess the concentrations and attribution rate of odorous compounds, it was analyzed about 40 VOCs in the flue gases. It was found that the major odorous compounds were 8 compounds, and the concentrations of major VOCs(ppm) were as follows; benzene: $0.054{\sim}0.052$, toluene: $1.011{\sim}2.547$, ethylbenzene: $0.472{\sim}2.023$, m,p-xylene: $0.504{\sim}3.245$, styrene: $0.015{\sim}0.148$, o-xylene : $0.271{\sim}1.097$, ethanol: $11.2{\sim}32.5$, ${\alpha}$-pinene: $0.908{\sim}10.578$, ${\beta}$-pinene: $0.982{\sim}14.278$. The attribution rate of terpenes (${\alpha}$-pinene, ${\beta}$-pinene) was about 60.56%, and that of aromatics and alcohols was about 22.77%, and 16.67%, respectively. It is suggested that the adequate control device should be used to control both the water soluble and non-soluble compounds because both compounds were mixed in flue gas.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.3
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• pp.249-256
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• 2006

Catalytic combustion of toluene was investigated on the Cu-Mn oxide catalysts prepared by the impregnation(Imp) and the deposition-precipitation(DP) methods. The mixing of copper and manganese has been found to enhance the activity of catalysts. It is then found that catalytic efficiency of the Cu-Mn oxide catalyst prepared by the DP method on combustion of toluene is much higher than that of the Cu-Mn oxide catalyst prepared by Imp method with the same chemical composition. The catalyst prepared by the deposition-precipitation method observed no change of toluene conversion at time on stream during 10 days and at the addition of water vapor. On the basis of catalyst characterization data, it has been suggested that the catalysts prepared by the DP method showed uniform distribution and smaller particle size on the surface of catalyst and then enhanced reduction capability of catalysts. Therefore, we think that the DP method leads on progressive capacity of catalyst and promotes stability of catalyst. It was also presumed that catalytic conversion of toluene on the Cu-Mn oxide catalyst depends on redox reaction and $Cu_{1.5}Mn_{1.5}O_4$ spinel phase acts as the major active sites of catalyst.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.11
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• pp.1043-1048
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• 1998

The decomposition performance of the Surface induced Plasma Chemical Processing(SPCP) for benzene, toluene, xylene and $NO_2$ were experimentally examined. Discharge exciting frequency range was 5kHz and 10kHz, and low frequency discharge requires high voltage to inject high electric power in gas and to decompose contaminants. The decomposition rate of dioxide nitrogen for 5kHz power in gas and to decompose contaminants. The decomposition rate of dioxide nitrogen for 5kHz power supply is only 85%, but it’s rate for 10kHz power supply is very high, more than 96% when peak voltage is 12kv. Aromatic hydrocarbon vapor of up to 1000ppm is almost throughly decomposed at the flow rate of 1000$\ell$/min or lower rate under the discharge with electric power of several hundred watts. High decomposition rate is shown in every case, that is, for SPCP reactor is necessary to obtain the decomposition rate of more than 80~98%. The decomposition rate of benzene, toluene and xylene were 90~98% and dioxide nitrogen was 45~96%.