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( Sujeeta Karki ),( Ja Hyung Choi ),( Jeeban Poudel ),( Sea Cheon Oh ) 한국폐기물자원순환학회(구 한국폐기물학회) 2017 한국폐기물자원순환학회 심포지움 Vol.2017 No.1
The falling fuel resources along with the insistence to diminish greenhouse gas emissions has been a dominant objective for the development of alternative fossil fuels. The efficient evolution of the use of solid biomass in the past few years over prevalent solid fuel supply chains including but not limited to easy and cost-effective incorporation, high efficiency, high volume manufacturing and transportation system have now become the grounds of world’s economy. Notwithstanding several advantages it holds some limitations encompasses its high moisture content, lack of bulk density, its tendency to degrade and low calorific value strengthening its increment in cost for energy input. Interest in research on torrefaction of biomass and waste materials is thriving due to its potential of energy valorization. This study has provided an insight on the co-torrefaction of two freely available resources, sewage sludge (SS) and waste wood (WW). Effect of torrefaction temperature on mass and energy yield, HHV, elemental composition and gas yield were studied at a torrefaction temperature range of 200 to 450 ℃. The decomposition rate of hemicellulose and organic component in lignocellulosic and non-lignocellulosic component had crucial role in determining the characteristics of the torrefied products. In addition, the gaseous products from torrefaction were also analyzed. Comparatively low emission of carbon dioxide and thermal hydrocarbon is one of the primary benefits of using the blends. The blends exhibited higher HHV compared to SS whereas an upsurge in the torrefaction temperature resulted in declined CO<sub>2</sub> in the product gas. In addition, blending increased the detection temperature of THC to around 290 ℃ featuring the benefits of blending. As aforementioned, blending can not only cutback transportation and storage cost but can also have productive clout on pyrolysis, gasification and co-firing units operation by cutting down power usage and biomass grinding tariff.
( Karki Sujeeta ),( Ja Hyung Choi ),( Jeeban Poudel ),( Sea Cheon Oh ) 한국폐기물자원순환학회(구 한국폐기물학회) 2018 한국폐기물자원순환학회 심포지움 Vol.2018 No.1
Comparative analysis of the performance of fluidized bed and downdraft fixed bed reactor in torrefaction is the primary objective of the research. Many researches have focused on the performance of fixed bed reactors with a few published works in fluidized bed. However, no research has focused on the comparison of fluidized bed and downdraft fixed bed reactors in spite of their immense potential as torrefaction reactors. Sewage sludge was taken as the raw material to study the torrefaction characteristics. The effects of the main torrefaction variables, temperature and residence time, on the performance parameters such as fixed carbon, calorific value; molar ratios, ultimate and proximate analysis, chemical exergy etc. were investigated for torrefied sewage sludge. Although continuous research with multiple replicated data is required before developing a concrete conclusion, the study showed that the fixed bed reactor is more favorable compared to fluidized bed despite the leverage that fluidized bed offers.
( Karki Sujeeta ),( Ja Hyung Choi ),( Jeeban Poudel ),( Sea Cheon Oh ) 한국폐기물자원순환학회(구 한국폐기물학회) 2018 한국폐기물자원순환학회 춘계학술발표논문집 Vol.2018 No.-
The aim of this project was to explore the potential of the torrefaction treatment for upgrading sewage sludge into valuable product. An ancillary investigation on the cold fluidization and the behavior of sewage sludge was analyzed. The effects of the main torrefaction variables, temperature and residence time, on the performance parameters such as fixed carbon, calorific value; molar ratios, ultimate and proximate analysis, chemical exergy etc. were investigated for torrefied sewage sludge. Results for both the reactors showed that the thermochemical transformations that sewage sludge underwent, as a results of the release of volatile matter due to thermal decomposition of its organic constituents, resulted in significant improvement of their chemical and physical properties. Results obtained from this study showed that despite the leverage that fluidized bed offers (heat and mass transfer) fixed bed configuration was more pronounced for torrefaction of sewage sludge. However, a decisive conclusion cannot be made at this stage as more detail study would be required to draw a definitive conclusion over the preference of reactor for torrefaction.
Karki Sujeeta,Ja hyung Choi,Jeeban Poudel,Sea Cheon Oh 한국폐기물자원순환학회 2018 한국폐기물자원순환학회 학술대회 Vol.2018 No.05
The aim of this project was to explore the potential of the torrefaction treatment for upgrading sewage sludge into valuable product. An ancillary investigation on the cold fluidization and the behavior of sewage sludge was analyzed. The effects of the main torrefaction variables, temperature and residence time, on the performance parameters such as fixed carbon, calorific value; molar ratios, ultimate and proximate analysis, chemical exergy etc. were investigated for torrefied sewage sludge. Results for both the reactors showed that the thermochemical transformations that sewage sludge underwent, as a results of the release of volatile matter due to thermal decomposition of its organic constituents, resulted in significant improvement of their chemical and physical properties. Results obtained from this study showed that despite the leverage that fluidized bed offers (heat and mass transfer) fixed bed configuration was more pronounced for torrefaction of sewage sludge. However, a decisive conclusion cannot be made at this stage as more detail study would be required to draw a definitive conclusion over the preference of reactor for torrefaction.
A Study on Torrefaction of Sewage Sludge
( Karki Sujeeta ),( Poudel Jeeban ),오세천 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.1
Torrefaction of biomass can produce an energy dense and consistent quality solid biomass fuel for combustion and co-firing applications. This study presents the effects of torrefaction on the basic characteristics of sewage sludge. Sewage sludge was torrefied in a horizontal tubular reactor at temperatures ranging from 200 °C to 550 °C, for heating rates 5, 10 and 15 °C/min. The torrefied sewage sludge was characterized in terms of their elemental composition, energy yield, ash content, and volatile fraction. The gaseous products were also analyzed.
( Karki Sujeeta ),( Poudel Jeeban ),오세천 한국공업화학회 2017 한국공업화학회 연구논문 초록집 Vol.2017 No.1
In the present work, fluidization of sewage sludge, a non-lignocellulosic biomass, was studied using a bench scale fluidized bed. The influence of torrefaction temperature ranging from 200 - 350°C and residence time of 0 - 50 minutes on the physical and chemical properties of sewage sludge was investigated. The properties of torrefied product were analyzed on the basis of degree of torrefaction, ultimate and proximate analysis, gas analysis and chemical exergy. The degree of torrefaction and chemical exergy showed positive influence on increasing the torrefaction temperature. The effect of torrefaction temperature and residence time was studied on elemental variation of sewage sludge which exhibited a decrease of H/C and O/C ratios. The product gas emitted during torrefaction was analyzed to study the pathway of hydrocarbons and oxygen containing compounds. Torrefaction using fluidized bed improved the overall physiochemical properties of sewage sludge.
50ton/day 이상 Stoker Boiler 연소장애 극복을 위한 CFD 해석연구
최자형,Jeeban Poudel,Karki Sujeeta,오세천 한국폐기물자원순환학회 2018 한국폐기물자원순환학회 학술대회 Vol.2018 No.05
현재 국내 도시 생활쓰레기 및 산업쓰레기의 처리 시, 매립지 부족과 침출수 등으로 인한 2차 오염문제로 매립처리 방법은 우리나라에서는 적절치 않다. 하지만 쓰레기의 소각처리의 경우, 소각으로 인한 열작감량이 매우 크고 폐에너지 회수의 장점도 있기에 국내 쓰레기의 처리는 소각에 많이 의존하고 있다. 또한 국내 대체에너지의 목표치가 높아지는 상황에서 폐기물의 대체 에너지가 큰 역할을 해 주어야 한다. 폐기물 고형연료를 연소하는 과정 중에는 여러 문제점이 있는데, 설비의 고온 부식의 영향 및 연소로 내 국부적인 가열로 인한 설비의 파손, 연소로 내 불규칙적 유동현상으로 인한 연소 장애 등이 있다. 따라서 앞에서 말한 문제점들을 보안하며 보일러의 안정적인 운전 및 열효율 향상을 위해서는 기본적으로 연소로 내 유동현상을 정확히 예측할 수 있어야 한다. 이를 위해 우리는 상용화 되고 있는 50ton/day 이상 Stoker 보일러 현장 운전조건을 대입, Ansys CFD Fluent.18을 사용하여 시뮬레이션을 진행하였다. 연소로 내 열의 유동해석, 배출가스의 흐름 등을 예측하여 연소장애의 원인을 찾아보고 이에 맞는 대안을 찾기 위한 연구를 하였다.