• Environmental Engineering Research
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• 제23권2호
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• pp.181-188
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• 2018

Photocatalytic oxidation in the presence of Fe-doped, Zn-doped or Fe-Zn co-doped $TiO_2$ was used to effectively decompose humic acids (HAs) in water. The highest HAs removal efficiency (65.7%) was achieved in the presence of $500^{\circ}C$ calcined 0.0010% Fe-Zn co-doped $TiO_2$ with the Fe:Zn ratio of 3:2. The initial solution pH value, inorganic cations and anions also affected the catalyst photocatalytic ability. The HAs removal for the initial pH of 2 was the highest, and for the pH of 6 was the lowest. The photocatalytic oxidation of HAs was enhanced with the increase of the $Ca^{2+}$ or $Mg^{2+}$ concentration, and reduced when concentrations of some anions increased. The inhibition order of the anions on $TiO_2$ photocatalytic activities was $CO{_3}^{2-}$ > $HCO_3{^-}$ > $Cl^-$, but a slightly promotion was achieved when $SO{_4}^{2-}$ was added. Total organic carbon (TOC) removal was used to evaluate the actual HAs mineralization degree caused by the $500^{\circ}C$ calcined 0.0010% Fe-Zn (3:2) co-doped $TiO_2$. For tap water added with HAs, the $UV_{254}$ and TOC removal rates were 57.2% and 49.9%, respectively. The $UV_{254}$ removal efficiency was higher than that of TOC because of the generation of intermediates that could significantly reduce the $UV_{254}$, but not the TOC.

• Korean Chemical Engineering Research
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• 제45권3호
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• pp.258-263
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• 2007

배가스 이산화탄소 처리를 위한 화학적 흡수공정의 새로운 흡수제로서 암모니아수의 적용 가능성을 고찰하였다. 이산화탄소 흡수용량과 침전 발생의 관점에서 적합한 암모니아수 흡수제 농도와 $CO_2$ 부하(loading, $molCO_2/molNH_3$)를 결정하였다. 이를 위하여 전해액에 대한 Pitzer 모델을 이용하여 암모니아 흡수제 농도에 따른 흡수용량과 침전 발생여부를 계산하였다. $5\;molNH_3/kgH_2O$ 이상의 암모니아수 흡수제를 사용하여 기존 아민류 흡수제 이상의 흡수용량은 얻을 수 있었다. 각 암모니아 흡수제 농도에서 $NH_4HCO_3$ 침전의 발생으로 인하여 조업이 제약되는 $CO_2$ 부하를 구하였다. $5{\sim}14\;molNH_3/kgH_2O$의 암모니아 흡수제는 293, 313 K에서 $CO_2$ 부하 0.5 이상에서 침전이 발행하였다. 침전 생성 $CO_2$ 부하값 이하로 흡수탑을 조업함으로써 고농도 암모니아 흡수제가 배가스 $CO_2$ 처리 공정에 사용될 수 있음을 알 수 있었다. 흡수용량과 침전발생을 고려하여 배가스 이산화탄소 처리를 위한 흡수제 최적온도는 암모니아수 농도에 따라 297~312 K이었다.

• 한국물환경학회지
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• 제25권6호
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• pp.916-921
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• 2009

This study was aimed to both enhance the fluoride removal and to reduce the phosphorus removal in treating semiconductor wastewater using $Ca(OH)_2$ at low pH so as to facilitate struvite crystallization reaction. The struvite crystallization could be introduced after fluoride removal by retaining the phosphorus source. As the results, the method applied in this study achieved high fluoride removal efficiency (about 91%) with retardation of phosphorus removal at pH 4, compared to conventional methods where the removal of fluoride and phosphorus were done at pH 11. Therefore, the fluoride removal at low pH would contribute to the enhancement of nitrogen and phosphorus removals in a consecutive struvite crystallization reactor. Treatment of semiconductor wastewater at low pH using $Ca(OH)_2$ also had lower (about 20%) water content of precipitated sludge compared to conventional method. As the molar ratio of Ca to F increased the removal efficiencies of fluoride and phosphorus increased. Although the amount of seed dosage didn't affect the removal of fluoride and phosphorus, its increase reduced the water content of precipitated matter. Finally, considering consecutive struvite reaction, the optimum condition for the removal of fluoride and phosphorus was as follow: pH: 4, the molar ratio of Ca:F: 1:1.

• 대한기계학회논문집B
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• 제34권1호
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• pp.27-34
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• 2010

본 연구에서는 순환방식의 1000 CMH급 전기집진장치 성능평가 시스템 구축하여, 대용량 순산소 연소 장치 없이 순산소 연소가스 모사 조건(고농도 $CO_2$ 조건)에서 엣지-평판형 전기집진장치를 방전극 형상, 집진판 간격, 유입속도, 가스조성 및 분진 입경에 따라 성능을 평가하였다. $CO_2$ 70% 조건에서 3 종 방전극에 대해 성능 비교를 한 결과, 방전극 편 면적이 넓은 방전극이 상대적으로 높은 포집효율을 나타내었다. 또한 유입속도가 감소할수록, 분진 입경이 증가할수록, 집진판 간격이 좁을수록 분진 집진 효율이 증가하였으나, $CO_2$ 농도가 증가할수록 효율이 감소하였다. 그러므로 $CO_2$ 농도가 높을 것으로 예상되는 순산소 연소 등 배기가스 조건에 적용되는 전기집진장치를 설계할 경우, 기존과 동일한 단위 가스 체적 당 코로나 전력 조건에서 집진장치 내부 유속을 줄이거나 집진판 간격을 좁히는 설계변화가 요구되며, 방전극의 경우 방전편 면적이 넓으면서 코로나 전류가 높은 방전극이 적용되야 할 것으로 판단된다.

• 한국정밀공학회지
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• 제25권9호
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• pp.109-115
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• 2008

The cleaning process of contaminant particles adhering to the microchips, integrated circuits (ICs) or the like is essential in modern microelectronics industry. In the cleaning process particularly working with the application of inert gases, the removal of contaminant particles of submicron scale is very difficult because the particles are prone to reside inside the boundary layer of the working fluid, The use of cryogenic $CO_2$ cleaning method is increasing rapidly as an alternative to solve this problem. In contrast to the merits of high efficiency of this process in the removal of minute particles compared to the others, even fundamental parametric studies for the optimal process design in this cleaning process are hardly done up to date, In this study, we attempted to measure the cleaning efficiency with the variations of some principal parameters such as mass flow rate, injection distance and angle, and tried to draw out optimal cleaning conditions by measuring and evaluating an effective cleaning width called $d_{50}$.

• 에너지공학
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• 제26권2호
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• pp.73-79
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• 2017

In nucleation assisted crystallization process formed $CO_2$ leaves as colloid gas and is used as the template by the rapidly growing crystals in the nucleation site. This emulsion of $CaCO_3$ micro-crystals & $CO_2$ micro-bubbles forms hollow particles. Formed hollow particles are double walled, both internal and external faces belonging to the cleavage aragonites which separate the surrounding water from the enclosed gas cavity. Hence, the reverse reaction of $CO_2$ with water forming Carbonic Acid is not possible and the pH stability is maintained. In fact every excess $CaCO_3$ crystals are buffering any carbonic acid left over. This $CO_2$ based nucleation technology prevents scale formation in water channels, but it also helps to reduce the previously formed scales. This process takes out water dissolved $CO_2$ in almost-visible micro-bubbles forms that helps reducing previously formed scale over a period of time (depends on the usage period). The aragonite crystals can't form scale because of its stable molecular structure and neutral surface electro potentiality.

• 펄프종이기술
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• 제31권2호
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• pp.15-24
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• 1999

A new technique for recycling of white water was developed in order to reduce the calcium hardness in a closed OCC recycling system. Calcium ions present in the white water were precipitated as calcium carbonate by reacting with sodium carbonate, and the precipitated $CaCO_3$ was removed from the system using a flotation fractionation method, which has been commonly used in deinking process. In the flotation stage, a mixed gas of $CO_2$-air was purged into the flotation cell because the pH of $Na_2CO_3$-treated white water was reduced to neutral by $CO_2$ gas. Since $CaCO_3$ precipitate tends to stick onto fine fiber surface and then selectively removed from the white water, a proper amount of suspended solid in white water acts as an important factor for deciding the removal efficiency. By the application of $Na_2CO_3$ addition-$CO_2$ flotation to the short circulated white water, the calcium hardness was significantly reduced by 87% and more. Removal of calcium ions with fine fibers led to a drainage improvement, reduction of fresh water consumption, and enhanced efficiency of wet-end chemicals.

• KEPCO Journal on Electric Power and Energy
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• 제4권1호
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• pp.33-38
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• 2018

This study applied upgrades to the processes of a 10 MW wet amine $CO_2$ capture pilot plant and conducted performance evaluation. The 10 MW $CO_2$ Capture Pilot Plant is a facility that applies 1/50 of the combustion flue gas produced from a 500 MW coal-fired power plant, and is capable of capturing up to 200 tons of $CO_2$. This study aimed to quantitatively measure efficiency improvements of post-combustion $CO_2$ capture facilities resulting from process upgrades to propose reliable data for the first time in Korea. The key components of the process upgrades involve absorber intercooling, lean/rich amine exchanger efficiency improvements, reboiler steam TVR (Thermal Vapor Recompression), and lean amine MVR (Mechanical Vapor Recompression). The components were sequentially applied to test the energy reduction effect of each component. In addition, the performance evaluation was conducted with the absorber $CO_2$ removal efficiency maintained at the performance evaluation standard value proposed by the IEA-GHG ($CO_2$ removal rate: 90%). The absorbent used in the study was the highly efficient KoSol-5 that was developed by KEPCO (Korea Electric Power Corporation). From the performance evaluation results, it was found that the steam consumption (regeneration energy) for the regeneration of the absorbent decreased by $0.38GJ/tonCO_2$ after applying the process upgrades: from $2.93GJ/ton\;CO_2$ to $2.55GJ/tonCO_2$. This study confirmed the excellent performance of the post-combustion wet $CO_2$ capture process developed by KEPCO Research Institute (KEPRI) within KEPCO, and the process upgrades validated in this study are expected to substantially reduce $CO_2$ capture costs when applied in demonstration $CO_2$ capture plants.

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 1999년도 Proceedings of Pre-symposium of the 10th ISWPC
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• pp.164-171
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• 1999

A new technique for recycling process water was developed in order to reduce the calcium hardness of the closed OCC recycling system. Calcium ions present in the white water were precipitated as calcium carbonate by a reaction with sodium carbonate and the CaCO$_3$precipitates were easily removed from the system by a dissolved air flotation(DAF) method. After the DAF stage, CO$_2$-gas was purged into the water because the pH of Na$_2$CO$_3$-treated white water was reduced to neutral by CO$_2$gas. Since CaCO$_3$precipitate tends to stick onto the fine fiber surface and then is selectively removed from the water, a proper amount of suspended solid in the process water acts as an important factor in deciding the removal efficiency. By the application of Na$_2$CO$_3$addition - DAF - CO$_2$purging to the short circulated white water the calcium hardness was significantly reduced by 92% and more. The removal of calcium ions with fine fibers led to drainage improvement, reduction of fresh water consumption, and enhanced efficiency of wet-end chemicals.

• 자원리싸이클링
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• 제30권2호
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• pp.68-74
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• 2021

본 연구에서는 촉매 Co-ZSM5 및 Cu-ZSM5 코팅이 적용된 저품위 실리카를 사용하여 다공성 지지체를 제조하여 포름 알데히드(HCHO) 제거를 수행하였다. 먼저, 지지체 원료는 실리카가 90 % 함유되어 있어 저급 실리카로 확인되었다. EDS 및 FT-IR 분석에 따르면 Co-ZSM5 및 Cu-ZSM5 촉매는 다공성 실리카 지지체의 표면에 성공적으로 코팅되었다. 제조 된 Co-ZSM5 및 Cu-ZSM5 코팅 된 비드를 사용하여 HCHO의 제거 테스트 결과, 반응 온도에 따라 Co-ZSM5 코팅 된 비드는 Cu-ZSM5 비드보다 높은 제거 효율 (> 97 %)을 나타났다. 200 ℃. 전자의 더 높은 효율은 우수한 표면 활성 특성 (BET 표면적 및 기공 부피)에서 기인 할 수 있으며, 아마도 유리한 HCHO 분해로 이어질 수 있다. 따라서 Co-ZSM5 비드는 국산 저급 실리카를 사용하여 제작 된 다공성 지지체를 사용하여 HCHO 제거 용 촉매에 적합한 것으로 판단된다.