• Nuclear Engineering and Technology
• /
• v.55 no.1
• /
• pp.169-179
• /
• 2023

Filtered containment system is a passive safety system that controls the over-pressurization of containment in case of a design-based accidents by venting high pressure gaseous mixture, consisting of air, steam and radioactive particulate and gases like iodine, via a scrubbing system. An indigenous lab scale facility was developed for research on iodine removal by venturi scrubber by simulating the accidental scenario. A mixture of 0.2 % sodium thiosulphate and 0.5 % sodium hydroxide, was used in scrubbing column. A modified mathematical model was presented for iodine removal in venturi scrubber. Improvement in model was made by addition of important parameters like jet penetration length, bubble rise velocity and gas holdup which were not considered previously. Experiments were performed by varying hydrodynamic parameters like liquid level height and gas flow rates to see their effect on removal efficiency of iodine. Gas holdup was also measured for various liquid level heights and gas flowrates. Removal efficiency increased with increase in liquid level height and gas flowrate up to an optimum point beyond that efficiency was decreased. Experimental results of removal efficiency were compared with the predicted results, and they were found to be in good agreement. Maximum removal efficiency of 99.8% was obtained.

• Journal of Soil and Groundwater Environment
• /
• v.16 no.5
• /
• pp.42-52
• /
• 2011

In this laboratory study, the changes in gas-exposed perchloroethene (PCE) saturation in sand during a PCE removal process were measured using gaseous tracers. The flux of fresh air through a glass column packed with PCEcontaminated, partially water-saturated sand drove the removal of PCE from the column. During the removal of PCE, methane, n-pentane, difluoromethane and chloroform were used as the non-reactive, PCE-partitioning, water-partitioning, and PCE and water-partitioning tracers, respectively. N-pentane was used to detect the PCE fraction exposed to the mobile gas. At water saturation of 0.11, only 65% of the PCE was found to be exposed to the mobile gas prior to the removal of PCE, as calculated from the n-pentane retardation factor. More PCE than that detected by n-pentane was depleted from the column due to volatilization through the aqueous phase. However, the ratio of gas-exposed to total PCE decreased on the removal of PCE, implying gas-exposed PCE was preferentially removed by vaporization. These results suggest that the water-insoluble, PCE-partitioning tracer (n-pentane in this study), along with other tracers, can be used to investigate the changes in fluid (including nonaqueous phase liquid) saturation and the removal mechanism during the remediation process.

• Journal of the Korean Wood Science and Technology
• /
• v.36 no.6
• /
• pp.69-76
• /
• 2008

To estimate removal ability of harmful gas by charcoal, we carbonized Red oak (Quercus mongolica Fischer) wood and Larch (Larix leptoepis) bark at $300^{\circ}C$, $600^{\circ}C$ and $900^{\circ}C$ for 1 hour. Gas removal ratios was increased with carbonization temperature but there is no difference between wood and bark charcoal. In the case of bad smell and VOC gas, woody charcoal including bark charcoal carbonized at $300^{\circ}C$ showed low removal ratio, less than 50%, whereas woody charcoals which was carbonized at more than $600^{\circ}C$ reached almost 100% removal ratio to bad smell gas such as trimethylamine, methymercaptan, hydrogen sulfide, and to VOC such as benzene, toluene, xylene in $5{\ell}$ tedler bag with each gas of 100 ppm. It was thought that because charcoals carbonized at high temperature, for example, $600^{\circ}C$ or $900^{\circ}C$ have enough specific surface area to adsorb gas of 100 ppm. Moreover these charcoals rapidly removed almost gas in 10 minutes. However, acetylene, $SO_2$ and $NO_2$, charcoals which was carbonized more than $600^{\circ}C$ and which showed high removal ratio had low gas removal ratio of 40% at even 4 hours adsorption. It was concluded that adsorptive ability of woody charcoal was mainly influenced with carbonizing temperature, so that different charcoals carbonized at different temperature brings different gas removal ratio because these charcoals have not only different physical factor such as specific surface area but different chemical characteristic such as functional group, expected.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.19 no.7
• /
• pp.32-38
• /
• 2005

A hybrid discharge type ozonizer, which is superposed silent and surface discharges, has been designed and manufactured to apply for Nitrogen Oxides(NO) gas removal. The ozonizer consists of three electrodes, and is classified three types of ozonizer by changing applied voltage. Investigation was carried out variance with the flow rate of supplied oxygen gas, discharge power and the sorts of superposed discharge type ozonizer. Moreover, NO(1200[ppm])/$N_2$ gas removal investigation was also conducted to apply for environment improvement field. Two kinds of NO gas removal investigations were conducted. It distinguishes the investigations into NO gas reaction method. According to these studies, maximum removal rate of 100[%] in NO gas was obtained, and 8334[ppm] and 3249[mg/h] of maximum ozone concentration and generation were also obtained respectively.

• Journal of environmental and Sanitary engineering
• /
• v.13 no.2
• /
• pp.88-94
• /
• 1998

This study was investigated the application of biofiltration using cometabolic process to remediate gaseous toluene that are highly recalcitrant to adsorption, absorption and biodegradation. The investigation was conducted using specially built steel columns packed with granular activated carbon for removal of toluene and G.A.C was also coated with Pseudomonas putida microorganisms by addition of KH$_{2}$PO$_{4}$. The biofilter unit was operated in the condition of dry and 27.5% moisture content at gas loading rate of 12.5 l/min. Gaseous toluene taken from tedlar bag was analyzed by the use of G.C. equipped with F.I.D. detector. The removal efficiency of gaseous toluene was 85% at average inlet concentration of 970 ppm during dry operating condition. For gaseous toluene, 91% removal efficient was obtained at the filter material with moisture content and 97% removal efficiency was obtained with Pseudomonas putida microorganisms at gas loading rate of 12.5 l/min.

• Journal of Korean Society for Atmospheric Environment
• /
• v.18 no.3
• /
• pp.173-182
• /
• 2002

We investigated the effects of operating variables, such as electrical. reactor and gas parameters on toluene removal and discharge property in the dielectric barrier discharge (DBD) process. The toluene removal was initiated with the energy transfer to the reactor by loading of voltages higher than the discharge onset value. The energy transfer and toluene removal increased with the applied voltage. Higher removal rate was observed with smooth surface electrode despite of lower energy transfer compared with the coarse electrode, because more uniform discharge can be obtained on smooth surface state. The decrease of dielectric material thickness enhanced the removal efficiency by increasing the discharge potential. The toluene removal efficiency decreased with the increase of the inlet concentration. The increase of gas retention time enhanced the removal efficiency by the increase of energy density. The oxygen and humidity contents seem to exert significant influences on the toluene removal by dominating the generation of electrons, ions, and radicals which are key factors in the removal mechanism.

• KSBB Journal
• /
• v.19 no.3
• /
• pp.231-235
• /
• 2004

This paper was investigated to clarify the possibility of ammonia gas removal by essential oil. First of all, the chemical analysis was peformed to analyze the composition of an essential oil by GC-MS. The monoterpenes in an essential oil react with ammonia by neutralization and their reaction mechanism was elucidated. Based on their chemical neutralized reaction, the removal efficiencies of ammonia gas were studied to derive the optimal conditions in the scrubber tower such as optimal temperature and pH. The experimental result shows that the removal efficiency of ammonia gas was achieved over 98 % by the misty aerosol dispersion of scrubber tower.

• Particle and aerosol research
• /
• v.7 no.3
• /
• pp.87-97
• /
• 2011

In this study, we organized the test results obtained from the performance tests for the CA certificated air cleaners which had been commercially available in Korea since 2003, and analyzed the correlation among the test parameters such as flow rate, particle collection efficiency, clean air delivery rate (CADR), ozone emission, odor removal efficiency and noise level etc. The noise level of 267 air cleaners were increased as concentrated at the 45, 50, 55 dB, which are the required noise level for CA certification according to flow rate, and ozone emissions from the CA air cleaners were significantly lower than the requirement limit, 50 ppb for 24 hour operation. The average particle collection efficiency and odor removal efficiency were 89.3 and 80.8%, approximately 20% higher than the requirement of CA certification, regardless of flow rates. The particle removal performance of an air cleaner was clearly discriminated by its CADR, and the CADR was obtained with a simple calculation: 0.79 x flow rate. The low differentiation of gas removal performance of air cleaners by the current CA gas test method was improved by 3.2, 751.3, 13.4 times for ammonia, acetic acid, respectively, by adopting the CADR concept and the real time measurement method, FTIR, for gas removal performance test.

• Nuclear Engineering and Technology
• /
• v.45 no.2
• /
• pp.203-210
• /
• 2013

The objective of this conducted research is to study the iodine removal efficiency in a self-priming venturi scrubber for submerged and non-submerged operating conditions experimentally and theoretically. The alkaline solution is used as an absorbent, which is prepared by dissolving sodium hydroxide (NaOH) and sodium thiosulphate ($Na2S_2O_3$) in water to remove the gaseous iodine ($I_2$) from the gas. Iodine removal efficiency is examined at various gas flow rates and inlet concentrations of iodine for submerged and non-submerged operating conditions. In the non-submerged venturi scrubber, only the droplets take part in iodine removal efficiency. However, in a submerged venturi scrubber condition, the iodine gas is absorbed from gas to droplets inside the venturi scrubber and from bubbles to surrounding liquid at the outlet of a venturi scrubber. Experimentally, it is observed that the iodine removal efficiency is greater in the submerged venturi scrubber as compare to a non-submerged venturi scrubber condition. The highest iodine removal efficiency of $0.99{\pm}0.001$ has been achieved in a submerged self-priming venturi scrubber condition. A mathematical correlation is used to predict the theoretical iodine removal efficiency in submerged and non-submerged conditions, and it is compared against the experimental results. The Wilkinson et al. correlation is used to predict the bubble diameter theoretically whereas the Nukiyama and Tanasawa correlation is used for droplet diameter. The mass transfer coefficient for the gas phase is calculated from the Steinberger and Treybal correlation. The calculated results for a submerged venturi scrubber agree well with experimental results but underpredicts in the case of the non-submerged venturi scrubber.

• International Journal of Precision Engineering and Manufacturing
• /
• v.9 no.2
• /
• pp.39-43
• /
• 2008

Atmospheric pressure plasma polishing (APPP) is a noncontact precision machining technology that uses low temperature plasma chemical reactions to perform atom-scale material removal. APPP is a complicated process, which is affected by many factors. Through a preliminary theoretical analysis and simulation, we confirmed that some of the key factors are the radio frequency (RF) power, the working distance, and the gas ratio. We studied the influence of the RF power and gas ratio on the removal rate using atomic emission spectroscopy, and determined the removal profiles in actual operation using a commercial form talysurf. The experimental results agreed closely with the theoretical simulations and confirmed the effect of the working distance. Finally, we determined the element compositions of the machined surfaces under different gas ratios using X-ray photoelectron spectroscopy to study the influence of the gas ratio in more detail. We achieved a surface roughness of Ra 0.6 nm on silicon wafers with a peak removal rate of approximately 32 $mm^{3}$/min.