심태석 Tae-suk Sim , 김윤지 Yun-ji Kim , 황선진 Sun-jin Hwang

DOI:10.9786/kswm.2020.37.8.513

Abstract

This study investigates the correlation between soluble extracellular polymeric substances (sEPS) and fouling evoked according to mixotrophic metabolism in microalgae membrane bioreactor (MMBR) . The Somogyi-Nelson (SN) method is used to the sEPS because, it can be applied also for low concentration levels (<200 mg/L) in the case of glucose solutions unlike the dinitrosalicylic acid method. The concentrations of sucrose, a nonreducing polysaccharide that can replace sEPS, and reducing sugar, which can serve as a substrate, are normally estimated via the total organic carbon (TOC) analysis. The sEPS content could be quantified by excluding the reducing sugar concentration through the SN method, which includes the residual reducing sugar injected as a substrate in the MMBR. The SN method could accurately measure the widest range at the 500-nm wavelength. To confirm the applicability of the proposed method for various types of reducing sugars, sucrose was then analyzed in mixtures with three reducing sugars, that is, glucose, fructose, and galactose. The resulting coefficient of the slope variation of the regression analysis, excluding the reducing sugar content via the SN method in the TOC of the mixed solution, was ≤15% and the determination coefficient was ≥0.99, indicating high accuracy and linearity. This confirmed that the SN method can be used to quantify sEPS in MMBR experiments by excluding the reducing sugars content, especially at low concentrations (<200 mg/L for glucose).

Key Words

Microalgae, Microalgal-MBR, MMBR, Reducing Sugar, Soluble Extracellular Polymeric Substances, sEPS, Somogyi-Nelson method, SN method

김지은 Jee-eun Kim , 전경원 Kyung-won Jeon , 윤조희 Cho-hee Yoon , 장원준 Won-jun Jang

DOI:10.9786/kswm.2020.37.8.521

Abstract

This study explores the optimal reaction condition for combined steam reforming of biogas produced from organic waste by conducting thermodynamic equilibrium analysis (Gibbs free energy minimization). The ratio of methane to carbon dioxide conventionally produced in biogas plants is fixed at 60 : 40. CH₄ conversion, CO₂ conversion, H₂ yield, CO yield, carbon yield, and H₂/CO ratio are estimated at various H₂O/(CO₂ + CH₄) ratios (0 ~ 3.0) and temperatures (500 ~ 1000℃). The optimal reaction condition was explored with consideration of the amount of generated steam, the conversion, the yield, and the carbon yield . When the H₂O/(CO₂ + CH₄) ratio is above 1.5, carbon formation can be avoided for all temperature ranges. However, the H₂ yield at the same ratio is lower than that at thermodynamic equilibrium. This is due to the reverse water-gas shift reaction. By contrast, when the H₂O/(CO₂ + CH₄) ratio is 2.0, the conversion and yield in the experimental results are consistent with those at thermodynamic equilibrium. Thus, it can be confirmed that the optimal reaction for hydrogen production from the combined steam reforming of biogas occurs at an H₂O/(CO₂ + CH₄) ratio of 2.0 and a temperature of at least 650℃.

Key Words

Biogas, Thermodynamic equilibrium analysis, Combined steam reforming, Hydrogen, Coke formation

이용희 Yong-hee Lee , 정창훈 Chang-hoon Jeong , 진홍덕 Hong-deok Jin , 구윤정 Yun-jeong Gu , 변희주 Hui-ju Byeon , 김학민 Hak-min Kim , 정대운 Dae-woon Jeong

DOI:10.9786/kswm.2020.37.8.531

Abstract

In this study, a fast pyrolysis system is optimized to produce bio-oil with high yield and high heating value (HHV) from agricultural by-products. The agricultural by-products is screened by elemental analysis and HHV analysis. Among the various agricultural by-products, the fruit tree waste is selected as a feedstock to generate bio-oil because it shows the highest HHV. The pyrolysis reaction system is to produce bio-oil optimized by controlling gas velocity and reaction temperature. Consequently, the highest bio-oil yield is obtained when the gas velocity is 3.0 and the reaction temperature is 500℃. This is because the heat transfer rate increases as the gas velocity increases, and the pyrolysis of organic matter accelerates as the temperature increases. In addition, deoxygenation reaction is performed to increase the HHV of the produced bio-oil. The CoMo catalyst have been used for the deoxygenation reaction. The HHV of the bio-oil increases to 7,400 kcal/kg by deoxygenation reaction. This result is due to that the oxygen content is decreased by deoxygenation reaction.

Key Words

Bio-oil, Fast pyrolysis, Deoxygenation, Agricultural by-products

우기정 Gi Jeong Woo , 김영민 Young-min Kim

DOI:10.9786/kswm.2020.37.8.542

Abstract

In this study, the effect of biomass torrefaction on the production of aromatic hydrocarbons via the catalytic pyrolysis of Miscanthus over HZSM-5 and HY was investigated using a pyrolyzer-gas chromatography/mass spectrometry. During the torrefaction of Miscanthus, acetic acid, furfural, vinyl phenol, and vinyl guaiacol were emitted mainly by the partial decomposition of hemicellulose and lignin. Compared to the untorrified Miscanthus, torrified Miscanthus produced the larger amount of aromatic hydrocarbons during the catalytic pyrolysis over HZSM-5 and HY, suggesting the effect of biomass torrefaction. Between two catalysts, HZSM-5 produced the larger amount of aromatic hydrocarbons during the catalytic pyrolysis of Miscanthus than HY due to its high acidity and proper pore size.

Key Words

Pyrolysis, Miscanthus, Torrefaction, Aromatic hydrocarbons

장하나 Ha-Na Jang , 박문식 Mun-Sik Park , 연승재 Seung-Jae Yeon , 채도원 Do-Won Chae , 정승환 Seung-Hwan Jeong , 정은정 Eun Jeong Jeong , 손광표 Kwang-Pyo Son , 강승모 Seung-Mo Kang , 안선용 Seon-Yong Ahn , 양승현 Seung-Hyun Yang , 최동혁 Dong-Hyuk Choi , 현혜림 Hye-Lim Hyun , 류은선 Eun-Sun Ryu , 김범석 Bum-Seok Kim , 홍성완 Seong-Wan Hong , 홍승현 Seung-Hyun Hong , 임상봉 Sang-Bong Lim , 최수은 Su-Eun Choi

DOI:10.9786/kswm.2020.37.8.549

Abstract

Recently, MBT (Mechanical Biological Treatment) facilities were built up and operated to separate and recycle MSW (Municipal Solid Wastes)in South Korea. However, the size distribution of MSW is very rough, and it is causing operation problem because MSW would be crushed in undersize diameter by mechanical equipment before feeding each separation process. Also, the organic material should be pre-separated to reuse recycle material in MSW. In this research, the reactor of 1ton/batch using hydro-thermal reaction was tested to present the separation efficiency and the size distribution of MSW by experimental factors.

Key Words

Hydro-thermal, MBT, MSW, Organic fraction, Size distribution

김장영 Jang Yeong Kim , 조우리 Woori Cho , 이진주 Jin Ju Lee , 최정우 Jeong Woo Choi , 이재섭 Jae Seop Lee , 이재영 Jai-young Lee

DOI:10.9786/kswm.2020.37.8.557

Abstract

Coffee drinks are one of the most popular beverages around the world, and coffee beans are grown in about 80 countries. In addition, the consumption of coffee beans in Korea is about 150,000 tons as of 2018, the world's sixth largest, and the annual consumption of coffee per capita by people over 20 years old is about 353 cups, up 21 percent from 291 cups in 2015, which is about three times the consumption per capita of 132 cups by the world's population. However, despite the continued increase in coffee bean consumption, 99.8% of the coffee beans used remain as dregs, with the cost of handling them reaching 764.2 billion won a year, and environmental problems caused by CO₂ from the process cannot be ignored. Common coffee wastes have the advantage of high moisture content and high absorbency due to porous surface. Here, hydrothermal carbonization (HTC) is one of the thermal treatment methods and is a method of carbonation using temperatures of 180 ~ 300℃ and high pressure in a closed environment with limited oxygen. Unlike other pyrolysis methods, thermo-degradation methods have the advantage of cost-benefit that does not require pre-treatment of dryness because they conduct at a relatively low temperature and use water vapor pressure caused by evaporating moisture in the raw material itself. Therefore, it is suitable to recycle coffee wastes effectively using thermal water pressure carbonation reaction. We also want to evaluate the performance of adsorption by generating Activated Biochar through chemical activation as a method of utilizing Biochar produced after HTC reaction. Therefore, in this study, the optimum generation conditions of Biochar are derived by applying HTC method, which is suitable for utilizing the high moisture content and porous properties for recycling coffee wastes, and after deriving the optimal generation conditions for chemical activation of the Biochar produced, PAC(Powdered Activated Carbon) is compared with the characteristics analysis of coffee wastes and Biochar and Activated Biochar to check and evaluate the absorption performance of heavy metals.

Key Words

Hydrothermal carbonization, HTC, Coffee waste, Biochar, Activated carbon

김종범 Jong Bum Kim , 류재용 Jae Yong Ryu

DOI:10.9786/kswm.2020.37.8.564

Abstract

SF₆ was decomposed using the high-temperature heat generated during cement production and plasma pyrolysis, followed by the immobilization of the CaO and SF₆ byproducts in the kiln combustion reactor and the resource recovery; based on the results, some ways to prevent the SF₆ recombination, analyze the byproduct characteristics, and identify their generation path are suggested. In this study, the plasma power range from 5.9 to 10.1 kW; with increasing its value, the SF₆ destruction and removal efficiency also increased. When the water vapor was not added or added equivalently, the SF₆ byproducts were HF, F₂, SO₂, and SO₂F₂; when the water vapor was added in excess, they were only HF and SO₂. Therefore, adding excessive water vapor would be appropriate to produce gypsum by immobilizing the byproducts from CaO and SF₆ decomposition in the cement kiln combustion reactor.

Key Words

Sulfur hexafluoride, Plasma, Pyrolysis, Immobilization

최상규 Sang-kyu Choi , 최연석 Yeon-seok Choi , 정연우 Yeon-woo Jeong , 한소영 So-young Han , 응웬반꾸잉 Quynh Van Nguyen

DOI:10.9786/kswm.2020.37.8.574

Abstract

The combustion characteristics of mixed fuels, consisting of bio-crude oil from coffee grounds and pyrolysis oil from polystyrene foam waste, were studied in a pilot-scale burner, along with blends of pyrolysis oil from polystyrene foam waste and kerosene. The used burner system was previously developed for bio-crude oil combustion; thus, it was equipped with an air-blast atomizing nozzle and adopted downward injection. The mixture of bio-crude oil from coffee grounds and kerosene exhibited a distinct phase separation and could not be placed into the burner directly. The bio-crude oil was heated before being supplied to the fuel nozzle due to its high viscosity, while the blends of pyrolysis oil from polystyrene foam waste did not require preheating because they were less viscous. Under atmospheric conditions, the pyrolysis oil from polystyrene foam waste was blended at least 50% to prevent incomplete combustion. The blends of bio-crude oil from coffee grounds and pyrolysis oil from polystyrene foam waste emitted relatively more NO due to the fuel-bound nitrogen in bio-crude oil. When kerosene was mixed with the pyrolysis oil from polystyrene foam waste, the flame temperature generally increased while the CO emission initially increased drastically and then decreased. The NO emission decreased with the kerosene mixing ratio, which might be attributed to the combined effect of fuel-bound nitrogen and other NO formation mechanisms.

Key Words

Pyrolysis oil, Coffee ground, Waste polystyrene foam, Burner, Combustion characteristics