• 한국수소및신에너지학회논문집
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• 제28권4호
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• pp.426-432
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• 2017

Hydrothermal carbonization (HTC) is an effective and environment friendly technique; it possesses extensive potential towards producing high-energy density solid fuels. it is a carbonization method of thermochemical process at a relatively low temperature ($180-250^{\circ}C$). It is reacted by water containing raw material. However, the production and quality of solid fuels from HTC depends upon several parameters; temperature, residence time, and pressure. This study investigates the influence of operating parameters on solid fuel production during HTC. Especially, when food waste was reacted for 2 hours, 4 hours, and 8 hours at $200^{\circ}C$ and 2.0-2.5 MPa, Data including heating value, proximate analysis and water content was consequently collected and analyzed. It was found that reaction temperature, residence time are the primary factors that influence the HTC process.

• 신재생에너지
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• 제10권2호
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• pp.12-18
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• 2014

The objective of this work is to produce solid biofuel from sawdust using the HTC (Hydrothermal carbonization) process. The HTC process of feedstock involves the raw material coming into contact with high temperature and pressurized water. The HTC process could produce gaseous, liquefied and solid products, but this study focused on solid product only as an alternative to coal. In this study, sawdust used for a feedstock and its moisture content was under 5%. Water was added with the feedstock to raise moisture content to 80% and also used catalysts. The HTC process was performed at temperature range from 200 to $270^{\circ}C$ and reaction time was 15 to 120 min. Rising temperature resulted in increasing the higher heating value (HHV) of HTC product. In case of adding catalyst, HHV of solid biofuel was higher and reaction occurred at lower temperature and pressure. Also, HTC solid product had been characterized and found to be hydrophobic, increased HHV (over 40%), and pelletized easily compared to raw material.

• 한국지하수토양환경학회지:지하수토양환경
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• 제19권5호
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• pp.45-52
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• 2014

Torrefaction and hydrothermal carbonization (HTC) are productive methods to reclaim energy from lignocellulosic biomass. The hydrophobic, homogenized, energy dense and carbon rich solid fuel can be obtain from torrefaction and hydrothermal carbonization. Dead leaves were carbonized in a stainless steel reactor of volume 200 ml with torrefaction ($250-270^{\circ}C$) for 120 minutes and hydrothermal carbonization ($200-250^{\circ}C$) for 30 minutes, with mass yield solid fuel ranging from 57-70% and energy content from 16.81MJ/kg to 22.01 MJ/kg compare to the biomass. The char produced from torrefaction process possess high energy content than hydrothermal carbonization. The highest energy yield of 89.96% was obtained by torrefaction at $250^{\circ}C$. The energy densification ratio fluctuated in between 1.15 to 1.30. On the basis of pore size distribution of the chars, the definition of the International Union of Pure and Applied Chemistry (IUPAC) was used as a classification standard. The pore diameter was ranging within 11.09-19 nm which play important role in water holding capacity in soil. Larger pores can hold water and provide passage for small pores. Therefore, it can be concluded that high pore size char can be obtained my HTC process and high energy content char of 22.01 MJ/Kg with 34.04% increase in energy can be obtain by torrefaction process.

• 열처리공학회지
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• 제28권6호
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• pp.300-309
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• 2015

The aim of the present study was to predict the variations in microstructure and deformation occurring during gas carburizing and quenching processes of a SCM420H planetary gear in a real production environment using the finite element method (FEM). The motivation for the present study came from the fact that previous FEM simulations have a limitation of the application to the real heat treatment process because they were performed with material properties provided by commercial programs and heat transfer coefficients (HTC) measured from laboratory conditions. Therefore, for the present simulation, many experimentally measured material properties were employed; phase transformation kinetics, thermal expansion coefficients, heat capacity, heat conductivity and HTC. Particularly, the HTCs were obtained by converting the cooling curves measured with a STS304 gear without phase transformations using an oil bath with an agitator in a real heat treatment factory. The FEM simulation was successfully conducted using the aforementioned material properties and HTC, and then the predicted results were well verified with experimental data, such as the cooling rate, microstructure, hardness profile and distortion.

• 공업화학
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• 제33권1호
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• pp.28-37
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• 2022

석탄화력발전소들은 여전히 저급 석탄인 lignite와 bituminous coal을 이용한 발전이 이루어지고 있지만, 이는 CO₂와 같은 GHG를 배출하는 문제를 유발하고 고갈의 위험성이 있어 이를 대체할 에너지원이 필요하다. 이를 해결하기 위해 바이오매스를 이용한 hydrochar 생산이 주목받고 있다. 본 연구에서는 고품질 hydrochar의 생산을 위해 용매열법을 열수탄화에 적용하여 에탄올 수용액을 기반으로 진행되었다. 본 실험은 다양한 조건에 따른 영향을 파악하기 위해 케나프를 이용해 고액비(1:4, 1:8, 1:2), 반응온도(150~300 ℃)와 체류시간(15~120분)을 다양하게 변화하며 진행되었다. 또한 생산된 hydrochar의 특성을 파악하기 위해 EA, FT-IR. TGA와 SEM을 이용해 분석을 진행하였다. Hydrochar의 탄소 함량은 kenaf에 비해 48.11% 증가하였고, 휘발성 물질은 39.34%가 감소하였다. 추가적으로 반응온도에 따라 연료적 특성이 강화되는 것 또한 확인하였다. 본 연구에서 나타난 결과는 kenaf가 열수탄화와 용매열법을 통해 연료 대체재로써 변화하는 것을 확인하였으며, 이는 석탄의 새로운 대체재가 될 수 있는 가능성을 보였다.

• Carbon letters
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• 제25권
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• pp.103-112
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• 2018

Hierarchically porous, chemically activated carbon materials are readily derived from biomass using hydrothermal carbonization (HTC) and chemical activation processes. In this study, empty fruit bunches (EFB) were chosen as the carbon source due to their sustainability, high lignin-content, abundance, and low cost. The lignin content in the EFB was condensed and carbonized into a bulk non-porous solid via the HTC process, and then transformed into a hierarchical porous structure consisting of macro- and micropores by chemical activation. As confirmed by various characterization results, the optimum activation temperature for supercapacitor applications was determined to be $700^{\circ}C$. The enhanced capacitive performance is attributed to the textural property of the extremely high specific surface area of $2861.4m^2\;g^{-1}$. The prepared material exhibited hierarchical porosity and surface features with oxygen functionalities, such as carboxyl and hydroxyl groups, suitable for pseudocapacitance. Finally, the as-optimized nanoporous carbons exhibited remarkable capacitive performance, with a specific capacitance of $402.3F\;g^{-1}$ at $0.5A\;g^{-1}$, a good rate capability of 79.8% at current densities from $0.5A\;g^{-1}$ to $10A\;g^{-1}$, and excellent life cycle behavior of 10,000 cycles with 96.5% capacitance retention at $20A\;g^{-1}$.

• 한국지하수토양환경학회지:지하수토양환경
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• 제21권1호
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• pp.22-27
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• 2016

Hydrothermal carbonization (HTC) is a carbonization method of thermochemical process at a relatively low temperature (180-250℃). It is reacted by water containing raw material. In this study, it was selected for effective disposal method of food waste because food waste in Korea has large amount water. 5 kg, 10 kg, 15 kg of food waste were reacted for 6 hours at 200℃ for selecting the optimum amount of raw material. Since the derived optimum amount, food waste was reacted for 2 hours, 4 hours and 6 hours at 200℃ and 1.5 MPa. After carbonization, it was analyzed to evaluated the properties by ultimate analysis, iodine adsorption, BET surface area and SEM. After analyzing the characteristics, it can be utilized as a basic data for applied.

• 적정기술학회지
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• 제7권1호
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• pp.59-71
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• 2021

하이브리드수열탄화 (Hybrid HTC) 기술은 2가지 이상의 유기성폐기물을 혼합한 특허 받은 열역학 공정으로 공정온도 180~250℃, 압력 20~40 bar에서 반응시간이 2시간 이내이며 에너지 소비가 적고, 폐기물의 부피감소 및 악취 저감효과가 크다. 폐기물 중 대부분의 탄소가 최종 생성물에 축적되므로 유기성 폐기물 고형연료화에 가장 적합한 기술로 평가받고 있다. 본 연구에서는 하이브리드 수열탄화기술을 활용하여 캄보디아 망고 폐기물을 대상으로 온도 및 반응시간의 변화에 따라 발열량 및 수율 등에 미치는 영향에 대하여 평가하였다. 본 연구를 통해 공정변수를 최적화하고, 전공정플랜트의 에너지 효율성을 향상시킬 수 있으며, 수연탄화기술에서 분해되어 가스가 생성되는데 이때 수소(H₂) 및 메탄(CH₄) 등 제조 및 생산기술개발을 할 수 있다. 본 연구 결과를 토대로 망고폐기물(2t/day)실증 물질수지 및 에너지 수지 도출과 함께 경제성도 평가하였다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제19권1호
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• pp.1-7
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• 2014

When processing the biomass by Hydrothermal carbonization (HTC), a slow pyrolysis process, it produces bio-gas, biooil, and biochar. Among these end products, biochar is known for isolating or storing carbon and being used as a soil amendment. In this study, the characteristics of biochar generated by HTC at $250^{\circ}C$ for 1 hour, 2 hours, 3 hours, and 20 hours with synthetic food wastes and wood wastes were analyzed for potential uses in soil contaminated with heavy metals. The yield of biochar (weight %) increased when the ratio of wood wastes increased and showed a decreasing tendency as reaction time increased. Elemental analysis of biochar based on various conditions showed a maximum of 70% carbon (C) content. The carbon content showed an increasing tendency with the increase of wood wastes. Iodine adsorption test was peformed to determine the optimum reaction condition, which was 15% wood waste for mixing ratio and 2 hours for reaction time. Using biochar generated at the optimum condition, its capability of adsorbing heavy metals (Cd, Cu, Pb, Zn, Ni) was evaluated. It was concluded that lead (Pb) was removed efficiently while zinc (Zn) and nickel (Ni) were hardly adsorbed by biochar.

• International Journal of Air-Conditioning and Refrigeration
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• 제14권1호
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• pp.19-27
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• 2006

The characteristics of heat transfer and pressure drop have been investigated experimentally during gas-cooling process of carbon dioxide. The results of this study are useful information in the design of a heat exchanger of $CO_2$ refrigerator. The test section consists of 6 series of copper tube, 4.15 and 2.18mm ID, respectively. The inlet temperature, the operating pressure, and the mass flux are varied in the range of $80{\sim}120^{\circ}C,\;{7\sim}10MPa,\;and\;400{\sim}1,900kg/m^2s$, respectively. The heat transfer coefficient of $CO_2$ is affected by temperature, inlet pressure, and mass flux of $CO_2$. At the maximum HTC, the temperature of $CO_2$ nearly accords with the psuedocritical temperature. It is found that the pressure drop is substantially affected by mass flux and inlet pressure of $CO_2$ . The results have been compared with those of previous work. The heat transfer correlation at the gas-cooling process has been also suggested which predicts within the error of 20%.