초기 pH 조건이 C. ljungdahlii를 이용한 합성가스 발효공정에 미치는 영향

왕용 ( Long Wang ),홍성구 ( Seonggu Hong ) 한국농공학회 2010 한국농공학회 학술대회초록집 Vol.2010 No.-

Clostridium ljungdahlii, a microorganism which has an ability to ferment hydrogen and carbon monoxide to ethanol and acetic acid, was cultured in a nutrient medium under anaerobic conditions and synthesis gas. The optimal pH for synthesis gas fermenting is known to be between 5.8 and 6.0. The initial pH of growth medium was about 6.0. In this study phosphate buffer solution was used to adjust pH value of growth medium, but production of ethanol was slow. It is found that C. ljungdahlii can grow fast in this medium and the production of ethanol concentration reached to 0.117g/L and acetic acid concentration 0.753g/L at 117 hours. The most ethanol concentrations reached to 0.22g/L and acetic acid concentration reached to 2.67g/L at 120 days. Groups of experiment of medium change showed C. ljungdahlii can grow well either in medium with or without phosphate buffer solution. The experiments showed the ethanol production needed longer time in the medium with phosphate buffer solution. C. ljungdahlii can grow well in another medium which removed NaHCO₃ and added NaOH to adjust pH value and initial pH was 7.40. The production of ethanol concentration reached to 0.51g/L and acetic acid reached to 0.43g/L just for 4 days. The second growth medium promoted the ethanol production and restrained acetic acid production.

원료조건에 따른 하향식 가스화 효과 분석

왕용 ( Long Wang ),홍성구 ( Seong Gu Hong ) 한국농공학회 2013 한국농공학회 학술대회초록집 Vol.2013 No.-

Biomass is a promising renewable energy resource. It can be converted into fuels, heat or power through thermo chemical processes. Gasification is a popular technology convert biomass into synthesis gas which composited of carbon monoxide, hydrogen and methane. Syngas can directly used as fuel or materials to produce chemicals or power generation to meet the need of ever-increasing energy in the world and reduce CO2 emission. The composition of syngas usually depend on feedstock conditions. In this study RDF, woodchip and charcoal was used as feedstock in downdraft gasification process. RDF and charcoal mixed with woodchip as some certain proportions. woodchip used as two different sizes- 0.7~0.9 cm size and 2~3 cm size. The results presented that methane composition was as high as 10% and LHV as high as 1600kacl/Nm³ when use RDF mixed with woodchip as feedstock. LHV was low as 683kcal/Nm³ use charcoal. The H₂ composition usually more than 10% and LHV usually keep in 1100~1200kacl/Nm³ when use woodchip as feedstock. The cold gas efficiency reach to 65% when use 0.7~0.9 cm size woodchip. It is presented that small size woodchip is a good feedstock for downdraft gasification as lower reaction temperature, higher cold gas efficiency and carbon conversion.

The Impacts of Operational Conditions on Charcoal Syngas Generation using a Modeling Approach

왕용,홍성구,Wang, Long,Hong, Seong Gug The Korean Society of Agricultural Engineers 2013 한국농공학회논문집 Vol.55 No.4

바이오매스 가스화는 세계적인 증가 추세에 있는 에너지 수요를 충족할 수 있는 기술 중의 하나이다. 바이오매스 가스화를 통해서 농업 폐기물 등 다양한 바이오매스 자원을 에너지로 전환할 수 있고 $CO_2$ 배출량 또한 줄일 수 있다. 본 연구에서는 COMSOL$^{(R)}$ 3.4 소프트웨어를 이용하여 바이오매스 원료와 운전 조건에 따른 가스화 효율 및 합성가스 조성의 변화를 분석하였다. 원료와 구동조건을 최적화하기 위해 가스화 모델을 세우고 원료와 구동조건을 달리하여 합성가스의 성분을 분석 및 예측하였다. 이 모델은 물리적인 실험을 통해 알고 있는 조건을 통해서 합성가스 성분을 시간에 따라 예측할 수 있다. 모델을 이용하여 함수비 5~30 %, 공기중 산소함량 5~50 %, 공기공급 유량 5~45 L/min, 온도 973~1273 K의 조건에서 합성가스의 성분을 예측한 결과 실제 실험 결과와 일치하는 것을 알 수 있다. 모델링 결과 양질의 합성가스를 생산하려면 원료의 회분함량이 적어야 하고 수소 함량이 높은 합성가스를 생산하려면 반응 온도가 높게 유지되고 원료의 함수비가 높아야 한다. 가스화장치의 온도를 높이면 합성가스의 성분 중 CO의 함량이 많아지고, CO의 함량이 많아지면 가스의 발열량이 높아지는 것을 알 수 있다. 또한 CO의 농도가 높고 발열량이 높은 합성가스를 생산하기 위해서는 ER값은 작아야 한다.

소규모 하향식 바이어매스 가스화 발전 시스템 개발

왕용 ( Long Wang ),김덕형 ( Dukhyeong Kim ),조태성 ( Taesung Cho ),홍성구 ( Seonggu Hong ) 한국농공학회 2011 한국농공학회 학술대회초록집 Vol.2011 No.-

Biomass is a promising renewable energy resource which can be converted into fuels, heat or power through thermo chemical processes. Gasification is a popular technology convert solid biomass into synthesis gas which composited of carbon monoxide, hydrogen and methane. It is a technology which can meet the need of ever-increasing energy in the world and reduce CO₂ emission. Syngas can directly used as fuel or materials to produce chemicals or power generation. In this study a small-scale biomass gasification power generation system was developed to obtain the optimum biomass condition and operational conditions of gasification for power generation. The system including a downdraft gasifier, a cyclone, a convector cooler, a woodchip-filled filter, a water cooling type vacuum pump and a 6KW syngas power generator. A series of experiments were conducted with woodchip as feedstock. It was presented that good gasification occurred in temperature more than 800℃ and moisture of woodchip less than 20%. For producer gas-syngas composition, CO range from10 to 20%, H₂ range from 10% to 20%, CH₄ range from 1% to 3%, CO₂ less than 15%. The power generator generated electricity successful using syngas from the system. Gas drying and tar formation reducing is the future direction of the research in the gasification process.

Influences of pH Conditions on Syngas Fermentation using Clostridium ljungdahlii

왕용,홍성구,Wang, Long,Hong, Seong Gu The Korean Society of Agricultural Engineers 2012 한국농공학회논문집 Vol.54 No.6

바이오에탄올 생산공정은 당 (Sugar)을 기반으로 하는 공정과 합성가스를 이용하는 공정으로 분류할 수 있다. 이 가운데 합성가스를 이용하는 공정은 촉매를 이용한 화학적 공정과 혐기성 발효에 의한 생물학적 공정의 두 가지로 나뉜다. Clostridium ljungdahlii는 일산화탄소와 수소가 주요 성분으로 구성되는 합성가스를 이용하여 에탄올과 아세트산을 생산할 수 있는 균주 중의 하나로 알려져 있다. 합성가스 발효공정에서 pH는 미생물의 증식과 에탄올 등의 생산에 아주 중요한 요인 중의 하나이다. 본 연구에서는 pH 조건이 미생물의 생장과 에탄올 생산성에 미치는 영향을 조사하였다. C. ljungdahlii 배양은 엄격한 혐기성 조건에서 100 ml의 serum bottle과 pH 제어가 가능한 반응기를 이용한 실험결과, 회분식 배양 조건에서는 미생물의 생장과 에탄올 생산을 위한 최적 초기 pH는 7.0로 나타났다. 미생물 농도는 0.57 g/L, 에탄올 농도 0.91 g/L로 나타났다. pH 4.5 이하에서는 미생물의 생장이 멈추는 것으로 나타났다. pH 제어가 가능한 생물반응기에서는 pH 6.0 일때 에탄올 생산량이 pH 7.0 일때 보다 높게 나타났다. 일정 수준의 미생물 농도를 유지한 조건에서 합성가스를 기포식으로 주입하고 pH 5.9에서 5.4까지 제어하였을 때 미생물량과 에탄올 농도가 증가하였다. 60 시간이 지난 후에 미생물의 농도는 0.498 g/L, 에탄올은 1.056 g/L까지 이르렀다.

pH 제어식 미생물 반응조를 이용한 합성가스 발효에 의한 바이오에탄올 생산성 검토

왕용 ( Long Wang ),조태성 ( Taesung Cho ),김덕형 ( Dukhyeong Kim ),홍성구 ( Seonggu Hong ) 한국농공학회 2011 한국농공학회 학술대회초록집 Vol.2011 No.-

Clostridium ljungdahlii is a bacterium can transform synthesis gas or mixture of carbon monoxide and hydrogen to ethanol and acetate acid according anaerobic processes. Many researches have been conducted about medium optimum conditions, genes researches and effects of syngas composition and pressure on cell population and ethanol production. Especially it was found that pH is very important for cell growth and ethanol production. This study was to research effect of pH range on cell growth and ethanol production. A series of experiments were conducted under strictly anaerobic conditions with pH at 7.0, 6.0 and 5.4 to 5.9 in a pH-controlling bioreactor. It was observed that ethanol production started from pH reducing and acetate acid appearance. Cell concentration increased fast when pH between 5.6 and 5.9. It was presented that the maximum cell concentration was reached to 0.498g/L in 60 hours when pH to 5.6. The ethanol production was 1.056g/L at the same time. In a typically cell growing process, cell growing occurred in optimum growth pH 5.0 to 7.0, carbon source such as syngas and fructose was transferred to cell, ethanol and acetic acid or other organic acid in this process.

COMSOL을 이용한 바이오매스 가스화장치의 운전조건 분석

왕용 ( Long Wang ),심재훈 ( Jaehoon Shim ),홍성구 ( Seonggu Hong ) 한국농공학회 2009 한국농공학회 학술대회초록집 Vol.2009 No.-

바이오매스 가스화는 세계적으로 점점 증가하는 에너지 수요를 만족시킬 수 있는 유용한 기술 중의 하나이다. 바이오매스 가스화를 통해 농업폐기물을 에너지로 전환할 수 있고 이산화탄소의 배출도 저감할 수 있다. 양질의 합성가스를 생성하는 가스화장치의 구동 조건을 확인하고 제어하기 위해 가스화장치에서 이루어지는 화학반응과 가스화 과정을 이해한다. 본 연구는 가스화 이론과 실제 물리적인 실험에 의거하고 COMSOL 3.4를 이용하여 가스화 장치 모델을 구성하고 이 모델을 실제 물리적인 데이터를 통해 검증하여 최적 원료 조건과 반응조건(원료 함수비, 송기량, 온도, 당량비 등)을 추정하였다. 1. 원료인 숯의 함수비는 6.98%, 송기량은 1000L/min, 원료 공급 속도는 21.42kg/hr, ER값은 0.32의 조건으로 가스화장치 모델을 시뮬레이션 한 결과 CO 33.8%, CO₂ 1.07%, H₂ 2.15%, CH₄ 0.21%, O₂ 0.05%, N₂ 62.7%로 나타났다. 실제 물리적 실험결과 치 CO 30%, CO₂ 1.1%와 비교할 때 적정한 수준으로 가스화반응을 나타내고 있음을 알 수 있다. 2. 원료 회분을 10~50%로 시뮬레이션 한 결과 회분의 함량이 많아지면 CO와 H₂의 발생량은 감소하고 CO₂의 발생량은 증가하였고, 함수비를 10~30%로 시뮬레이션 한 결과 함수비가 증가하면 CO의 발생량이 감소하고 H₂와 CO₂의 발생량이 증가하였다. 또, 산소함량을 20~50%로 시뮬레이션 한 결과 산소함량이 증가하면 CO와 H₂의 발생량이 감소하고 CO₂의 발생량이 증가하였다. Biomass gasification is one of promising technology to meet the ever-increasing energy demand in the world. The agricultural wastes can be converted to energy and the carbon dioxide emission can be reduced. Studying on the chemical reactions in a gasify can help understanding gasification process in order to determine and control the gasification operational conditions to produce higher quality and increase conversion efficiency. In this paper a gasification model which depend on gasification theory and experiments was using COMSOL 3.4 software. The model consists of kinetic model part and Computational Fluid Dynamics (CFD) model part. The concentrations of the synthesis gas were predicted under the experimental conditions in the kinetic model part. The CFD model based on the structure and geometry of the gasifier, residence time can be calculated and temperature distribution can also be simulated. A simulation of charcoal gasification was did under the experimental condition that moisture was 6.98%, air flow rate was 1000L/min, feedstock rate was 21.24kg/hr and Equivalence Ratio was 0.32. The results showed syngas composition was CO 33.8%, CO₂ 1.07%, H₂ 2.15% O₂ 0.05%, N₂ 62.7%. The model well agree with the experimental results through compared with syngas composition from experiment which was CO 30% and CO₂ 1.1%.

합성가스 발효에 의한 바이오에탄올 및 아세트산의 생산성 검토

왕용 ( Long Wang ),홍성구 ( Seonggu Hong ) 한국농공학회 2010 한국농공학회 학술대회초록집 Vol.2010 No.-

Clostridium ljungdahlii, a microorganism was grown on synthesis gas to produce ethanol and acetic acid. The series of experiments were conducted in two different reactors: gas bubbling reactor and pressurized rotating disk reactor. A growth medium which is based on and improved from ATCC® PETC medium was feed in reactors and initial pH was 7.35. The gas bubbling reactor used micro gas pump circulated and bubbled synthesis gas to increase contact between synthesis gas and liquid growth medium aimed to promote ethanol production. The pressurized rotating disk reactor installed and rotated thin disks to increase the mass transfer of synthesis gas to medium and the initial pressure of synthesis gas was 1.0 bar. The cell concentration reached to 0.035g/L and pH was dropped to 4.44 and 4.63 in babbling reactor and pressurized rotating disk reactor at 24hours, respectively. The ethanol and acetic acid concentration in pressurized rotating disk reactor reached to 0.039g/L and 0.444g/L in 24 hours. No ethanol and acetic acid produced in bubbling reactor at the same time. The maximum ethanol production in bubbling reactor was 0.7g/L in 4 days and in 0.9g/L in 5 days. The pressurized rotating disk reactor has achieved higher and faster ethanol production than gas bubbling reactor.

숯과 미건조 우드칩 혼합에 따른 가스화특성 분석

왕용 ( Wang Long ),홍성구 ( Hong Seong Gu ) 한국농공학회 2014 한국농공학회 학술대회초록집 Vol.2014 No.-

Biomass is a promising renewable energy resource. It can be converted into fuels, heat or power through thermo chemical processes. Gasification is a popular technology convert biomass into syngas which composited of carbon monoxide, carbon dioxide, hydrogen and methane. Syngas can directly use as fuel or materials to produce chemicals or power generation to meet the need of ever-increasing energy in the world and reduce CO₂ emission. Nowadays, woods are a main resource for biomass gasification feedstock of downdraft gasifier. Most of the biomass such as woodchip usually need to dry before gasification because of high moisture leads to low temperature of combustion zone and “bridging” in the gasification process. But the drying of biomass needs amount of heating energy. The solution to wet biomass gasification is supplying Oxygen to gasifier or mix high calorific materials with feedstock. However, supply Oxygen is not economic than air gasification. In this study charcoal was mixted with wet woodchip in different ratios to downdraft gasification. It was found that the CO composition and the calorific value of syngas was increased with charcoal ratio. The CO₂ and CH₄ composition was decreased in the same time. Wet woodchip was gasificated with charcoal addition. Mix high calorific materials with biomass is an economic and simple way to achieve the gasification of the wet biomass directly and it can save the energy that spend in biomass drying process.

환경관리를 위한 환경사무 지방이양 탐색 연구: 공무원 인식조사를 바탕으로

왕재선,홍성만 한국공공관리학회 2023 한국공공관리학보 Vol.37 No.4

The purpose of this study was to explore the appropriateness of transferring the central government’s environmental affairs to local governments and an analysis was attempted based on perceptions of officers. As a result of the analysis, the Ministry of Environment, a central government agency, showed the highest agreement rate as the most appropriate entity for environmental affairs. There were high percentage of agreement that metropolitan governments were the most suitable candidates for carrying out some of national environmental tasks, next to the Ministry of Environment. As a result of analyzing the degree of agreement on transfer of 10 functions performed by Local Environmental Management Office, central and local public officials showed a relatively high rate of agreement on transferring ‘waste management’ and ‘environmental monitoring’ functions. Through this study, the transfer of the central government’s environmental affairs for environmental management to local governments not only requires understanding the characteristics of the affairs, but also the agreement between the opinions of the entities transferring and receiving the affairs, and their overall perception of the transition. It was suggested as an implication. 본 연구목적은 환경관리를 위한 중앙정부 환경사무의 지방정부이양 적절성을 탐색하는 것이었으며, 환경부와 지방자치단체 환경담당 공무원을 대상으로 한 설문조사를 토대로 분석을 시도하였다. 분석결과, 환경사무의 가장 적합한 수행주체로 중앙부처인 환경부가 가장 높은 동의비율을 나타내었다. 또한 환경관련 국정과제 중 일부 과제의 수행주체에 환경부 다음으로 광역자치단체가 적합하다는데 동의비율이 높았다. 지방유역환경청이 수행하는 10가지 기능의 이양 동의 정도를 분석한 결과 중앙과 지방공무원공통적으로 ‘폐기물관리’, ‘환경감시’ 기능의 이양에 상대적으로 높은 동의비율을 보여주었다. 즉, 이러한 기능의 지방이양은 상대적으로 중앙과 지방공무원이 수용할 가능성이 상대적으로 높은 사무라고 할 수 있다. 반면, ‘국가측정망운영’ 기능은 중앙과 지방공무원 모두 이양동의비율이 가장 낮았다. 본 연구를 통해서 환경관리를 위한 중앙정부환경사무의 지방이양은 사무의 특성을 파악해야 하는 것은 물론이고, 사무를 이양하고, 이양받는 주체 간 의견의 합치 여부, 이들의 이양에 대한 전반적인 인식도 파악할 필요가 있다는 점을 시사점으로 제시하였다.