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Effects of operating factors in the coal gasification reaction
Hai-Kyung Seo,Seik Park,Joogwon Lee,Miyung Kim,Seok-Woo Chung,Jae-Hwa Chung,Kitae Kim 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.9
The effects of operating factors on a gasification system were reviewed by comparing a computational simulation and real operation results. Notable operation conditions include a conveying gas/coal ratio of 0.44, an oxygen/coal ratio of 0.715, a reaction temperature of 1,000 ℃, and reaction pressure of 5bar in the case of Adaro coal; based on this, the cold gas efficiency was estimated as 82.19%. At the point of the reaction temperature effect, because the cold gas efficiencies are more than 80% when the reaction temperatures are higher than 900 ℃, the gasifier inner temperature must remain over 900℃. At high reaction temperature such as 1,400 ℃, the reaction pressure shows little effect on the cold gas efficiency. The addition of steam into the gasifier causes an endothermic reaction, and then lowers the gasifier outlet temperature. This is regarded as a positive effect that can reduce the capacity of the syngas cooler located immediately after the gasifier. The most significant factor influencing the cold gas efficiency and the gasifier outlet temperature is the O_2/coal ratio. As the O_2/coal ratio is lower, the cold gas efficiency is improved, as long as the gasifier inner temperature remains over 1,000 ℃. With respect to the calorific value (based on the lower heating value,LHV) of produced gas per unit volume, as the N_2/coal ratio is increased, the calorific value per syngas unit volume is lowered. Decreasing the amount of nitrogen for transporting coal is thus a useful route to obtain higher calorific syngas. This phenomenon was also confirmed by the operation results.
Evaluation of a Prototype SF<sub>6</sub> Purification System for Commercialization
Seo, Hai-Kyung,Lee, Jeong Eun,Kim, Kwang Sin,Kim, Kyeongsook Korea Electric Power Corporation 2020 KEPCO Journal on electric power and energy Vol.6 No.1
Korea Electric Power Corporation (KEPCO) uses large amount of SF<sub>6</sub>, one of the potent greenhouse gases, in electric equipment for electrical insulation. KEPCO is developing SF<sub>6</sub> recovery and purification technology to minimize the release of SF<sub>6</sub> into the environment, to secure certified emission reduction, and to save purchase cost of new SF<sub>6</sub> by reusing the refined SF<sub>6</sub>. A prototype SF<sub>6</sub> purification system using cryogenic solidification technology has been built in demonstration scale. To evaluate the feasibility of the commercialization, the system has been operated to purify large amount of used SF<sub>6</sub> in a long-term operation and the performance has been economically evaluated. The system was stable enough for commercial operation such that it was able to purify 5.4 tons of used SF<sub>6</sub> from power transmission equipment in 2-month operation. Over 99% of the SF<sub>6</sub> was recovered from the used gas and the purity of the purified gas was over 99.7 vol%. The operation cost, which is the cost of refrigerant (liquid nitrogen), electricity and labor, per kilogram of purified SF<sub>6</sub> was 6,526 KRW. Considering the price of new SF<sub>6</sub> in Korea is about 15,000 KRW per kilogram this year, about 56% of the purchase cost can be saved.
Hai-Kyung Seo,신동훈,Jae Hwa Chung,Beomjoo Kim,Soo Man Park,Hee Chun Lim 한국화학공학회 2009 Korean Journal of Chemical Engineering Vol.26 No.1
The asymmetric inner structure of a catalytic combustor causes wall cracking because of regional overheating. Thus, a symmetric shape is proposed in the present work and analyses of the computational fluid dynamics of the existing combustor and the proposed type have been performed. A simulation of the revised combustor without a swirl device revealed that the flow of gases is concentrated on the center of the combustor and only catalysts around the center are used. In the revised combustor with a swirl device, the overall temperatures were estimated to be uniform. However, near the swirl device, high temperature exceeding 1,700 K was measured. Therefore, a heatproof surface coating on the swirl device is necessary for protection of the material. At the initial start-up of the catalytic combustor, hydrogen and natural gas are used. When only natural gas is used, the simulation indicated that the gas does not burn in the revised combustor without a swirl device. However, in the combustor with the swirl device, methane of 34.8% volume burns in the simulation. On the other hand, when hydrogen and natural gas are burned together, methane of 91.7% volume burns in the simulation.
서경 ( Kyung Seo ),오진경 ( Jin-kyoung Oh ),신해림 ( Hai-rim Shin ) 한국모자보건학회 2008 한국모자보건학회지 Vol.12 No.1
Objectives: Aim of study is to review efficacies of two human papillomavirus vaccines in different study populations and examine importance of HPV vaccine as a routine vaccine. Methods: Four phase-3 efficacy studies of two HPV vaccines were reviewed. Magnitude of efficacies were compared among different study populations. Results: Recently, two kinds of papillomavirus (HPV) vaccines were developed. "Cervarix" is a bivalent vaccine which contained L1 protein of HPV 16 and HPV 18, and "Gardasil" is a quadrivalent vaccine which contained L1 protein of HPV 6 and HPV 11 in addition. Efficacy study showed that both vaccine are highly effective to prevent cervical, vaginal and vulvar precancerous lesion in the population who are naive to HPV infection. Quadrivalent vaccine also showed high efficacy to prevent genital warts. Efficacy of the vaccine decreased in the general population who included both HPV-naive and HPV-infected peoples. Both vaccines showed high immune responses for 5 years after vaccination. Conclusions: From the point of public health, HPV vaccine is an important vaccine for young adolescents who have not begun sexual activity. However, development of guidelines for HPV vaccination for each country will be dependent on cost effectiveness of HPV vaccines of each population.
Kim, Moon-Sun,Seo, Yoo-Kyung,Park, Hye-Jin,Lee, Kye-Hyang,Lee, Kyung-Hoon,Choi, Eun-Jin,Kim, Jin-Kyung,Chung, Hai-Lee,Kim, Woo-Taek The Korean Pediatric Society 2010 Clinical and Experimental Pediatrics (CEP) Vol.53 No.10
Purpose: The neuroprotective effects of erythropoietin (EPO) have been recently shown in many animal models of brain injury, including hypoxic-ischemic (HI) encephalopathy, trauma, and excitotoxicity; however, limited data are available for such effects during the neonatal periods. Therefore, we investigated whether recombinant human EPO (rHuEPO) can protect against perinatal HI brain injury via an antiapoptotic mechanism. Methods: The left carotid artery was ligated in 7-day-old Sprague-Dawley (SD) rat pups ($in$ $vivo$ model). The animals were divided into 6 groups: normoxia control (NC), normoxia sham-operated (NS), hypoxia only (H), hypoxia+vehicle (HV), hypoxia+rHuEPO before a hypoxic insult (HE-B), and hypoxia+rHuEPO after a hypoxic insult (HE-A). Embryonic cortical neuronal cell culture of SD rats at 18 days gestation ($in$ $vitro$ model) was performed. The cultured cells were divided into 5 groups: normoxia (N), hypoxia (H), and 1, 10, and 100 IU/mL rHuEPO-treated groups. Results: In the $in$ $vivo$ model, Bcl-2 expressions in the H and HV groups were lower than those in the NC and NS groups, whereas those in the HE-A and HE-B groups were greater than those of the H and HV groups. The expressions of Bax and caspase-3 and the ratio of Bax/Bcl-2 were in contrast to those of Bcl-2. In the $in$ $vitro$ model, the patterns of Bcl-2, Bax, and caspase-3 expression and Bax/Bcl-2 ratio were similar to the results obtained in the in vivo model. Conclusion: rHuEPO exerts neuroprotective effect against perinatal HI brain injury via an antiapoptotic mechanism.
VRFB-ESS용 전해질의 이온가수 분석방법 및 SOC 분석
서혜경,박원식,김강산,Seo, Hai-Kyung,Park, Wonshik,Kim, Kangsan 한국전력공사 2021 KEPCO Journal on electric power and energy Vol.7 No.2
For the detection of the state of charge in VRFB-ESS, the analyses of UV-Visible spectrometry and the measurements of potential between the anolyte and catholyte were used in parallel. This paper includes the production of 4-valant ion from VOSO4 powder, 3- and 5-valant ions from electrochemical charge of 4-valant ion and 2-valant ion from 3-valant ion. It also includes the analyses of these valance ions and unknown electrolyte at any time using UV-Visible spectrometry. Through the analyses of the valance ions in samples, the SOCs of the samples at any charge-discharge times were verified.