• 상하수도학회지
• /
• 제33권4호
• /
• pp.243-250
• /
• 2019

This objective of this study was to investigate the degradation characteristics of phenol, a refractory substance, by using a submerged dielectric barrier discharge (DBD) plasma reactor. To indirectly determine the concentration of active species produced in the DBD plasma, the dissolved ozone was measured. To investigate the phenol degradation characteristics, the phenol and chemical oxygen demand (COD) concentrations were evaluated based on pH and the discharge power. The dissolved ozone was measured based on the air flow rate and power discharged. The highest dissolved ozone concentration was recorded when the injected air flow rate was 5 L/min. At a discharge power of 40W as compared to 70W, the dissolved ozone was approximately 2.7 - 6.5 times higher. In regards to phenol degradation, the final degradation rate was highest at about 74.06%, when the initial pH was 10. At a discharged power of 40W, the rate of phenol decomposition was observed to be approximately 1.25 times higher compared to when the discharged power was 70W. It was established that the phenol degradation reaction was a primary reaction, and when the discharge power was 40W as opposed to 70W, the reaction rate constant(k) was approximately 1.72 times higher.

• 상하수도학회지
• /
• 제32권6호
• /
• pp.535-550
• /
• 2018

Total organic carbon (TOC) will replace chemical oxygen demand ($COD_{Mn}$) as an effluent water quality standard in public sewage treatment works (PSTWs) from 2021 in Korea. To ensure effective control of TOC in the effluent, investigation was carried out into TOC levels and sewage treatment operation factors in five target PSTWs using anaerobic-anoxic-aerobic ($A_2O$) processes, media, membrane, and sequencing batch reactor (SBR) technologies. TOC removal efficiencies appeared to be 93-96% on average. As a fraction of TOC, biodegradable dissolved organic carbon (BDOC) was reduced from 64% in the influent to 9% in the effluent in these PSTWs. During the investigation, biological treatment processes were applied flexibly for operation factors such as HRT, SRT, MLSS, F/M ratios and BOD volume loads, based on the influent characteristics and design conditions. As a result, we suggest efficient operating conditions in PSTWs by evaluating relationships between TOC removal and operation factors.

• Journal of the Korean Wood Science and Technology
• /
• 제47권2호
• /
• pp.189-199
• /
• 2019

This study addresses the biorefinery feedstock from Pinus densiflora. This raw material is a major tree species in the Republic of Korea; it is renewable, has cost-effective, and is readily available. In this study, steam explosion of P. densiflora was performed in a reactor at $225^{\circ}C$ and with 1 to 13 min reaction times with or without previous water impregnation. The combined severity factor (Ro), which is an expression relating the reaction temperature and reaction time used in the steam explosion treatment, ranged from 3.68 to 4.79. The influence of both impregnation and steam explosion conditions were investigated by examining color variations, chemical composition, and mass balance on the pretreated solids. The results showed that steam-exploded P. densiflora that was not impregnated with water exhibited significantly darker color (chroma 28.8-41.4) than water-impregnated and steam-exploded P. densiflora (chroma 18.8-37.3). The increased ${\alpha}$-cellulose and lignin contents were detected as the severity factor increased. Furthermore, the ${\alpha}$-cellulose and lignin contents in the non-impregnated/steam-exploded P. densiflora were higher than those in the water-impregnated/steam-exploded P. densiflora. However, the decreased holocellulose content was detected as the severity factor increased. In mass balance, the holocellulose yield from water-impregnated/steam-exploded P. densiflora was higher than that from the non-impregnated P. densiflora.

• 공업화학
• /
• 제22권4호
• /
• pp.433-438
• /
• 2011

본 연구에서는 SNCR 공정에서 온도, NSR, 산소 농도가 질소산화물 제거 효율에 미치는 영향을 실험과 CHEMKIN-II 프로그램을 사용하여 수치적으로 조사하였다. 산소가 없는 조건에서 NO 제거 효율은 반응기 온도에 따라 증가하였다. 반면 산소농도가 4%일 때, NO 제거 효율은 $900{\sim}950^{\circ}C$에서 최대를 나타내었다. 산소의 존재는 저온에서 NO 제거를 증가시키는 것으로 나타났다. 산소농도와 무관하게 NO 제거 효율은 NSR에 따라 증가하였다. CHEMKIN-II에 의해 예측된 NO 제거 효율의 온도와 NSR-의존성은 실험결과와 유사하였다.

• 공업화학
• /
• 제22권6호
• /
• pp.711-717
• /
• 2011

전자충격반응을 고려한 three moment 플라즈마 모델과 전기적 중성성분의 반응을 고려한 유체 유동 모델을 결합하여 용량결합형 산소플라즈마에 대한 2차원적 전산모사 연구를 수행하였다. 전자의 에너지에 의하여 좌우되는 전자충격반응에 대한 반응속도는 전자와 $O_2$ 및 O 사이의 전자충돌단면적으로부터 계산되었다. 플라즈마 모델과 유체 유동 모델을 결합하고 상세한 반응메커니즘을 포함시킴으로써 전하를 띠는 전자와 이온($O_2{^+}$, $O^+$, $O_2{^-}$, and $O^-$) 그리고 기저상태의 산소($O_2$ and O)뿐만 아니라 $O_2(a^1{\Delta}_g)$, $O_2(b^1{{\Sigma}_g}^+)$, $O(^1D)$, $O(^1S)$ 등과 같이 산소플라즈마 특성에 중요한 역할을 하는 준안정상태 성분들의 시공간적 분포를 예측할 수 있었다. 또한 산소플라즈마의 전산모사로부터 sheath 경계에 이중층이 존재함을 확인할 수 있었다.

• Advances in environmental research
• /
• 제9권4호
• /
• pp.233-249
• /
• 2020

To date, there is no central wastewater (WW) treatment plant in Erbil city, Kurdistan region, Iraq. Therefore, raw WW disposes to the environment and sometimes it used directly for irrigation in some areas of Erbil city. Disposal of the untreated WW to the natural environment and using for irrigation it causes problems for the people and the environment. The aims of the current work were to study the characteristics, design of primary and different secondary treatment units and reusing of produced WW. Raw WW samples from Ashty city-Erbil city were collected and analyzed for twenty three quality parameters such as Total Suspended Solids (TSS), total dissolved solids, total volatile and non-volatile solids, total acidity, total alkalinity, total hardness, five-day Biochemical Oxygen Demand (BOD5), Chemical Oxygen Demand (COD), biodegradability ratio (BOD5/COD), turbidity, etc. Results revealed that some parameters such as BOD5 and TSS were exceeded the standards for disposal of WW. Design and calculations for primary and secondary treatment (biological treatment) processes were presented. Primary treatment units such as screening, grit chamber, and flow equalization tank were designed and detailed calculation were illustrated. While, Conventional Activated Sludge (CAS), Sequencing Batch Reactor (SBR) and Moving Bed Biofilm Reactors (MBBR) were applied for the biological treatment of WW. Results revealed that MBBR was the best and economic technique for the biological treatment of WW. Treated WW is suitable for reusing and there is no restriction on use for irrigation of green areas inside Ashty city campus.

• Composites Research
• /
• 제35권3호
• /
• pp.161-174
• /
• 2022

SiC 섬유강화 복합체는 경수형 원자로의 안전성을 획기적으로 향상시킬 수 있는 사고저항성 핵연료 피복관 소재이다. 지르코늄 합금 피복관 및 금속기반 사고저항성 핵연료 피복관에 비해, 중대 사고 환경에서도 우수한 구조적 안정성을 가지고 부식 속도가 매우 낮아, 사고 시 원자로의 온도를 낮추고 사고 진행을 늦출 수 있다. 본 논문에서는 현재 개발되고 있는 사고저항성 SiC 복합체 핵연료 피복관의 개념 및 가동/사고환경에서의 다양한 특성, 상용화를 위해 해결해야 할 다양한 이슈에 대해서 소개하고자 한다.

• 한국수소및신에너지학회논문집
• /
• 제33권5호
• /
• pp.515-524
• /
• 2022

In this study, the on-site hydrogen production process for refueling stations that were not energy-optimized was improved through exergy analysis and heat exchange network synthesis. Furthermore, the process was scaled up from 30 Nm3/h to 150 Nm3/h to improve hydrogen production capacity. Exergy analysis results show that exergy destruction in the SMR reactor and the heat exchanger accounts for 58.1 and 19.8%, respectively. Thus, the process is improved by modifying the heat exchange network to reduce the exergy loss in these units. As a result of the process simulation analysis, thermal and exergy efficiency is improved from 75.7 to 78.6% and 68.1 to 70.4%, respectively. In conclusion, it is expected to improve the process efficiency when installing on-site hydrogen refueling stations.

• 한국가스학회지
• /
• 제27권1호
• /
• pp.1-12
• /
• 2023

석탄가스화는 석탄을 불완전 연소하여 수소와 일산화탄소로 이루어진 합성가스를 생성하는 공정이다. 기 존 석탄 연소와 달리 질소 산화물이나 황 산화물이 배출되지 않고 미세먼지 발생량이 적어 석탄을 청정하게 이용할 수 있으며 합성가스를 통해 부가적인 화학물질을 생산할 수 있다. 석탄가스화는 합성가스 생산방식에 따라 석탄가스화복합화력발전(Integrated Gasification Combined Cycle, IGCC), 플라즈마 석탄가스화, 지하석탄 가스화(Underground Coal Gasification, UCG)로 분류된다. 최근에는 합성가스의 수소를 활용하기 위하여 일산화탄소를 수소로 전환하는 수성가스전환(Water Gas Shift, WGS) 반응기와 이산화탄소를 포집하는 설비를 결합하는 사례가 늘고 있다. 본 연구에서는 석탄가스화와 합성가스를 이용한 수소 생산 방법에 대하여 정리하였으며 현재 진행되고 있는 석탄가스화를 이용한 수소 생산 프로젝트를 조사하였다.

• Korean Chemical Engineering Research
• /
• 제54권4호
• /
• pp.533-542
• /
• 2016

Lab-scale 기포유동층 반응기(D=0.1 m, H=1.5 m)에서 왕겨와 모래를 혼합하여 가스화를 통해 합성가스를 얻고 남은 왕겨 회재는 고부가가치 물질로 사용하기 위한 연구의 선행연구로서 왕겨/유동사/왕겨 회재(실리카)의 혼합 및 유동 특성을 규명하였다. 왕겨/유동사를 5:95, 10:90, 20:80, 30:70의 부피비로 유속 범위(0~0.63 m/s)조건으로 수행하였으며, 또한 왕겨 회재는 왕겨를 기준으로 부피비 6%로 결정하였다. 왕겨/유동사, 왕겨/유동사/왕겨 회재의 혼합실험을 통해 왕겨 부피비 0%, 5%, 10%에서는 최소유동화속도가 0.19~0.21m/s임을 확인하였고, 20%일때는 0.3m/s로 증가하였으며, 30%일때는 분리현상이 나타나 최소유동화속도가 측정 되지 않았다. 또한, 실험데이터에 따라 Brereton과 Grace의 mixing index를 이용하여 각 조건 별로 mixing index값을 도출한 결과 왕겨/유동사의 혼합은 0.8~1, 왕겨/유동사/왕겨 회재의 혼합은 0.88~1 사이임을 확인하였다. 이를 통하여 왕겨/유동사의 혼합과 왕겨/유동사/왕겨 회재 혼합의 최적 조업조건을 도출할 수 있었으며, 운전조건을 결정할 수 있었다.