동력학-전달 모델을 활용한 식품 폐기물 감량 해석

조선주,김태욱,권성현,조대철,Cho, Sun-joo,Kim, Tae-wook,Kwon, Sung-hyun,Cho, Daechul 한국환경과학회 2021 한국환경과학회지 Vol.30 No.6

Food waste is both an industrial and residential source of pollution, and there has been a great need for food waste reduction. As a preliminary step in this study, waste reduction is quantitatively modeled. This study presents two models based on kinetics: a simple kinetic model and a mass transport-shrinking model. In the simple kinetic model, the smaller is the reaction rate constant ratio k₁, the lower the rate of conversion from the raw material to intermediate products. Accordingly, the total elapsed reaction time becomes shorter. In the mass transport-shrinking model, the smaller is the microbial decomposition resistance versus the liquid mass transfer resistance, the greater is the reduction rate of the radius of spherical waste particles. Results showed that the computed reduction of waste mass in the second model agreed reasonably with that obtained from a few experimantal trials of biodegradation, in which the microbial effect appeared to dominate. All calculations were performed using MATLAB 2020 on PC.

굴패각 모르타르에의 휘발성 유기화합물 흡착에 대한 연구

권성현(Sung-Hyun Kwon),조대철(Daechul Cho) 한국청정기술학회 2013 청정기술 Vol.19 No.2

굴패각과 석고를 대상으로 고형화시킨 후 포름알데히드 및 벤젠으로 대표되는 휘발성 유기화합물(volatile organic compounds, VOCs)를 흡착챔버 내에서 노출시켜 흡착특성을 관찰하였다. VOC를 챔버에 노출 후 굴패각과 같은 친환경재료를 혼입한 모르타르를 각각 개별적으로 주입한 후 180분간 흡착특성을 고찰하였다. 굴 패각분말을 0, 10, 30, 50%로 혼입한 시험체를 대상으로 포름알데히드와 VOC(벤젠, 톨루엔, 자일렌)를 27.7~28.5 mg/㎥의 고농도 조건과 175~150 μg/㎥의 저농도 조건에서 각각 노출시켜 흡착성 실험을 수행한 결과, 전반적으로 노출된 조건과 무관하게 굴패각의 혼입 함량이 많을수록 흡착성이 증가함을 관찰할 수 있었다. 또한 대류-확산-흡착이 고려된 모델을 사용하여 실험과 비교하였다. 확산계수 및 확산 길이(diffusion length)로 대변되는 흡착재의 친화력(affinity)을 고려한 모델을 시험한 결과, 피흡착제의 종류와 흡착재의 친화성에 따른 차이를 잘 표현하였으며 전반적으로 실험데이터와 일치하는 경향을 보였다. VOCs such as formaldehyde and benzene in a control chamber were adsorbed onto gypsum incorporating oyster shell powder, which was solidified and dried. VOC was first exposed in air and then gypsum mortar was placed in the chamber for 180 min for adsorption. The mortar was prepared with 0, 10, 30, and 50% of oyster shell powder. Two initial concentrations of VOCs including formaldehyde were 27.7~28.5 mg/㎥ or 175~150 μg/㎥. We found out that the initial concentrations did not seem to make any difference in adsorption performance but higher oyster content strongly led to higher adsorption. We used a convectiondiffusion-adsorption model to compare the experiment. The model which considers diffusion coefficients of adsorbates and affinity of the adsorbents well represented the experimental data with a fair agreement.

해양생물 Botryococcus braunii에서 유래한 바이오연료의 고급생산기술: 전처리 용매추출법

권성현 ( Sung-hyun Kwon ),조대철 ( Daechul Cho ) 한국환경과학회 2019 한국환경과학회지 Vol.28 No.11

A lipid-enriched strain of Botryococcus braunii (UTEX 572) was cultivated in a semi-batch aeration tank to enhance biomass as well as to develop intracellular lipids and fatty acids. A 30 day period of incubation produced 1.39 g/L of biomass and 0.31 g/L of total lipids in the biomass. The grown biomass was pre-treated using several methods to extract the total lipid content efficiently: ultrasonication was found to yield the highest percentage of lipids-namely 19.8% per biomass. Direct heating of biomass in an autoclave also showed better performance than when using only conventional solvent extraction. To enhance the biomass harvest and lipid extraction efficiency, coagulation and flocculation steps were added to the extraction process. It is noteworthy that not only the solvent type but also the solvent/biomass ratio greatly affected efficiency. In addition, the moisture content of the harvested(wet) biomass affected the efficiency significantly. This study elucidated the need for future research on optimizing this extraction process.

굴패각 배합 석고재료의 열전도 특성 연구

권성현(Sung-Hyun Kwon),조대철(Daechul Cho) 한국청정기술학회 2013 청정기술 Vol.19 No.2

굴 패각분말을 함유한 석고시험체를 통하여 1차원 열전달 특성을 조사하였다. 굴패각 성분의 함유량이 늘어날수록 기공을 포함한 시험체의 구조적 변형에 근거하여 흡착과 같은 물리화학적 특성이 증가함에 따라 시험체 전체의 열전달 특성도 달라질 것으로 예측되었다. 푸리에(Fourier) 열전도 방정식을 기초로 하여 1차원 슬랩의 열전도 현상을 수치모사한 결과 패각 분말의 배합도 및 각 성분재료의 열전달관련 물리적 계수에 따라 상당한 열전도 분포의 변화를 관측할 수 있었으며 이는 모형실험 결과와도 잘 부합하였다. We investigated one-dimensional thermal conduction for gypsum objects incorporating oyster shell powder. We presumed that according to the portion of oyster shell in the hybrid structure conductive characteristics of that would also change as some physicochemical properties such as volatile organic compound (VOC) adsorption were found to be changed considerably. Based on Fourier"s 2nd law of heat conduction an analytical analysis in a flat slab (one axis perpendicular to an infinite plane) was performed. We found that composition of oyster shell and conduction-related coefficients and parameters could greatly influence on the thermal profile of that conduction, and some model experiments also served for it in the affirmative.

바이오필터 담체 모델링 및 운전자료 비교에 대한 연구

허남수(Huh Nam-Soo),조대철(Cho Daechul),권성현(Kwon Sung-Hyun) 한국산학기술학회 2004 한국산학기술학회 학술대회 Vol.- No.-

Filter media are one of themost important choices when bilfiltration is applied. Filter media provide adsorbing microbes with available sites for residence and the residential cells grow to degrade or decompose target waste gases. Up to date, filter media were only qualitatively analyzed. As a quantitative approach to filter material for biofiltration, a simple model based on reaction kinetics and mass action law (Ottengraf’s Model in1983) was presented. Cork, zeolite, and granulated activated carbon were tested in terms of effective surface area, cell covered fraction of adsorbing sites, surface roughness, and pore size distribution. The cell covered fraction, surface roughness and hydrophilicity was found to be closely related to the efficiency of gas degradation in biofiltration. The cork was the best candidate for cell residence and growth in this work.

토양 미생물에 의한 PAH 분해 특성

장태식(Jang Tae sik),조대철(Cho Daechul),허남수(Huh Nam-Soo) 한국산학기술학회 2005 한국산학기술학회 학술대회 Vol.- No.-

PAHs의 분해를 위해 Bacillus subtilis 와 Phanerochaete chrysosporium의 두 미생물을 사용하였고, 이들을 부착시킬 담체로 코르크와 톱밥를 선정하여 미생물을 접종시켰다. Phenanthrene 분해의 경우, 반응 초기에는 분해 속도가 매우 빠르지만 반응 12일째 분해 속도가 떨어졌다. 분해 속도는 1)톱밥에 담지한 Bacillus subtilis, 2)코르크에 담지한 Bacillus subtilis, 3)톱밥에 담지한 Phanerochaete chrysosporium, 4)코르크에 담지한 Phanerochaete chrysosporium의 순으로 나타났다.

발포 Polyurethane에 점착하는 미생물 Biomass측정

송인상(Song In Sang),조대철(Cho Daechul),허남수(Huh Nam-Soo) 한국산학기술학회 2005 한국산학기술학회 학술대회 Vol.- No.-

미생물 고정화를 위하여 PU 폼을 세 가지 처리 방법으로 처리하였다. 플라즈마 처리, 플라즈마 유도 그라프팅, 플라즈마 유도 그라프팅 후 플라즈마로 재처리 방법을 사용하였다. 플라즈마 처리는 bacteria adhesion에 큰 효과를 주지 못하였고, 아크릴산의 플라즈마 유도 그라프팅은 adhesion을 세 배 이상 증가시켰다. Bacteria의 adhesion 성능 향상은 표면의 친수성을 증가시키고 새로운 groove나 cavity들을 형성시킴으로 가능하였다. 반면, 그라프팅 후 plasma re-treatment는 미생물 고정화를 크게 향상시키지 못하였다. SEM 관찰을 통하여 대부분의 E.coli.는 groove나 cavities라는 shear-free area에 서식함을 알 수 있었다. PU폼의 bacteria adhesion은 미생물과 고분자 표면 사이의 정전기적 인력이나 van der Waals 인력에 의해 주로 영향을 받는다고 사료된다.

STOAT 시뮬레이터를 이용한 MLE공정 질산화 개선에 대한 연구

김태욱(Taewook Kim),조선주(Sunjoo Cho),권성현(Sung-Hyun Kwon),조대철(Daechul Cho) 대한환경공학회 2021 대한환경공학회지 Vol.43 No.6

재활용 패각의 산-염기치환 반응을 통한 과산화칼슘의 제조와 산소발생 특성

권성현 ( Sung Hyun Kwon ),유길선 ( Gilsun Yoo ),조대철 ( Daechul Cho ) 한국폐기물자원순환학회(구 한국폐기물학회) 2019 한국폐기물자원순환학회지 Vol.36 No.2

The Korean coastal sediment area is apt to be contaminated by prevailing aquafarming and inland eutrophic sources. Furthermore, oyster shells are being overproduced every year with little recycling. Oxygen-releasing compounds (ORCs) are paramount in bioremediation or bioaugmentation. Calcium peroxide, one of the primary ORCs, was prepared using recyclable oyster shells via acid?base reactions based on double replacement, and this was followed by oxidation with hydrogen peroxide. Hydrogen peroxide, which is known to be effective as oxidizing agent, required an optimum dose for higher content of oxygen in the final product, because the literature shows that the oxidative reaction is reversible. A variety of concentrations of HCl and NaOH were examined in stoichiometry for the breakdown of calcium carbonates (or CO₂ production) and formation of calcium hydroxide in the initiation reaction. Acid and base overdoses helped the oxygenation reaction to be extended further, thus leading to calcium peroxide with the highest content of oxygen at a combination of 6 N-12 N acid-base treatment. With an elevated temperature, more oxygenated calcium peroxide was likely to be formed. Carbon dioxide and free oxygen during the experiments were determined with DO probing and gas capture in a water bath.

패각 분말기반 과산화칼슘 제조와 산소 유리 특성

유길선 ( Gilsun Yoo ),안지은 ( Jieun An ),조대철 ( Daechul Cho ),권성현 ( Sung Hyun Kwon ) 한국환경과학회 2018 한국환경과학회지 Vol.27 No.9

Bioremediation in situ is heavily dependent on the oxygenic environment which would privide the dwelling microorganism with sufficient oxygen. The situation could be easily resolved with supply of an Oxygen Releasing Compound (ORC). In this paper we prepared that sort of material out of oyster shell powder (mostly calcium carbonate) that prevails every shore areas of the country. We used two different oxidizing methods in the first step of the whole manufacturing process-conventional heating in a furnace and an ultrasound generator to obtain calcium oxide. Then that calcium oxide was further oxidized into calcium peroxide which may release oxygen under a moisturized condition. The oxygen releasing experiments were run to test the performance of our products, and to determine the gas kinetics during the experiments. Interestingly, calcium peroxide derived from ultrasound treatment was much more energy-effective as ORC than that from furnace heating although the heat derived process was better than that of ultrasound in terms of oxygen content and its releasing rate. We also found that most of the data collected from the gas releasing experiments fairly supported an ordinary 1^st order kinetics to oxygen concentration, which shaped a sharp discharge of oxygen at the very early moment of each test.