• Korean Journal of Chemical Engineering
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• 제35권11호
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• pp.2321-2326
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• 2018

We evaluated the optimal conditions for fluidization of nickel oxide (NiO) and its reduction into high-purity Ni during hydrogen reduction in a laboratory-scale fluidized bed reactor. A comparative study was performed through structural shape analysis using scanning electron microscopy (SEM); variance in pressure drop, minimum fluidization velocity, terminal velocity, reduction rate, and mass loss were assessed at temperatures ranging from 400 to $600^{\circ}C$ and at 20, 40, and 60 min in reaction time. We estimated the sample weight with most active fluidization to be 200 g based on the bed diameter of the fluidized bed reactor and height of the stocked material. The optimal conditions for NiO hydrogen reduction were found to be height of sample H to the internal fluidized bed reactor diameter D was H/D=1, reaction temperature of $550^{\circ}C$, reaction time of 60 min, superficial gas velocity of 0.011 m/s, and pressure drop of 77 Pa during fluidization. We determined the best operating conditions for the NiO hydrogen reduction process based on these findings.

• 기본간호학회지
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• 제4권1호
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• pp.43-60
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• 1997

This study was to identify the nursing intervention method in finding out the incidence, risk factor, prevention and treatment of bed sore cilents who received regional home care nursing services. The eleven home care nurse practitioners took the survey on 97 patients who received home care nursing service from Seoul City Nurses Association for one month from September 26 to October 26 1996. A modified version of Braden's bed sore assessment tool for bed sore risks and a tool for assessment of bed sore stage and measurement bed sore sizes by Bergstrom, Braden, Laguzza and Holman(1987) were as research tools for this study and a questionnare with 40 questions and 12 items on nursing activities was used to find out the prevention and treatment of bed sores. Also, two open ended questions were used on current approaches and efforts of the treatment being applied to clients. The finding of the study were summarized as following : 1. The rate of bed sore occurrence was 47.4% 2. The areas of bed sore occurrence were hip(28.9%), sacrum(18.6%), great trochanter(14.4%) and the average number of sore spots were 2.26 3. Two groups-one with bed sores and the other without-were studied to determine prediction factors for bed sore risks. Sensory function, humidity, level of activity, mobility, nutrition, skin friction and chapping and body temperature turned out to be statistically significant factors for bed sores. Also the age of clients turned out to be a individual characteristic variable significantly affecting the rate of bed sore occurrences. 4. The education for clients and family on systematic skin assessment and bed sores and practice of active/passive R.O.M. are mainly used as nursing activities for bed sore care. 5. The treatment method varied by stages of bed sores. Sometimes folk remedies like applying the powders of dried elm tree roots to sores were used. Good nutrition, frequent position change and skin care turned to be the most effective means to fast recovery of sores.

• 청정기술
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• 제7권2호
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• pp.141-149
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• 2001

본 연구는 활성탄이 충진된 고정 흡착층에서 흡착특성에 영향을 줄 수 있는 다양한 변수들, 흡착온도, 흐름속도, 흡착질의 종류와 농도, 형상비(L/D)에 따른 영향이 조사되었다. 고정층내의 파과시간은 흡착온도, 흐름속도와 흡착질의 농도가 증가함에 따라 감소하였다. 또한 고정 흡착층의 파과곡선으로부터 얻어지는 물질전달영역(mass transfer zone)과 미사용길이(length of unused bed)는 흡착가스 유속, 흡착가스의 농도 및 흡착온도에 영향을 많이 받는 반면 고정 흡착층의 형상비에 대한 영향은 상대적으로 작았으며, 이 중에서 흡착가스의 농도에 대한 영향이 가장 큰 것으로 나타났다. 단일성분에 대한 흡착평형실험 데이터를 가장 잘 예측할 수 있는 모델식을 구하기 위해 Langmuir, Freundlich 및 Langmuir-Freundlich 모델식을 적용하여 실험결과와 비교해 보았을 때 세가지 이론식 모두 benzene과 toluene의 흡착평형을 잘 표현하는 것을 알 수 있었다.

• 한국재료학회지
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• 제27권2호
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• pp.63-68
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• 2017

A black nickel oxide powder, one of the commercial nickel oxide ores, was reduced by hydrogen gas in a batch-type fluidized-bed reactor in a temperature range of 350 to $500^{\circ}C$ and in a residence time range of 5 to 120 min. The hydrogen reduction behavior of the black nickel oxide was found to be somewhat different from that of green nickel oxide ore. For the black nickel oxide, the maximum temperature (below which nickel oxide particles can be reduced without any agglomeration) was significantly lower than that observed for the green nickel oxide. In addition, the best curve fittings of the Avrami model were obtained at higher values of the overall rate constant "k" and at lower values of the exponent "m", compared to those values for the green nickel oxide. It may be inferred from these results that the hydrogen reduction rate of the black nickel oxide is faster than that of the green nickel oxide in the early stages, but the situation reverses in the later stages. For the black nickel oxide ore, in spite of the low temperature sintering, it was possible to achieve a high degree fluidized-bed reduction at lower temperatures and at lower gas consumption rates than was possible for the green nickel oxide. In this regard, the use of black nickel oxide is expected to yield a benefit if its ore price is sufficiently lower than that of the green nickel oxide.

• 공업화학
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• 제7권6호
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• pp.1181-1191
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• 1996

본 연구는 고온용 열구동형 화학열펌프에 있어서 폐열 및 태양에너지를 유용하게 이용하기위한 목적으로 $Ca(OH)_2$ 탈수반응시 원주형 반응기 충진층내 핀을 주입 전열촉진한 경우의 전열 및 반응촉진효과에 대해 이론적 평가를 행하였다. 그 결과 탈수흡열 반응시 반응층내 온도분포변화, 반응완결시간, 방열량에 대한 수치해석 결과 구리판 전열핀을 설치한 경우 입자 충전층의 탈수반응 소요시간을 크게 단축시킬 수 있었으며, 본 실험조건 하에서는 전열핀을 주입하지 않았을 때보다 탈수반응 소요시간이 1/2정도 단축됨을 알 수 있었다. 또한 해석결과 열화학반응은 온도 및 농도에 주로 의존하였고, 경계조건과 입자충전층의 열전도도에 의해 크게 좌우되었음을 알 수 있었다.

• 한국수소및신에너지학회논문집
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• 제22권6호
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• pp.884-894
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• 2011

Effects of temperature, volatile content, particle diameter and solid input weight were investigated in the batch fluidized bed reactor using OCN703-1100 particle as oxygen carrier and Roto coal and char as fuels. Two solid fuels represented the best reactivity at different temperature, $900^{\circ}C$ for Roto coal and $950^{\circ}C$ for char, respectively. However, we selected $900^{\circ}C$ as the best operating temperature because the improvement of reactivity of char at $950^{\circ}C$ was negligible. Char represented better reactivity than Roto coal because char contains low volatile than Roto coal. For both solid fuels, reactivities were improved with increasing of the particle diameter. These results were explained by solid mixing tests in a transparent fluidized bed using two char particles having different particle size ranges and OCN703-1100 particle. The bigger particle showed better solid mixing with OCN703-1100 particle, and therefore, represented better reactivity. For both solid fuels, reactivities were improved with increasing of the solid input weight within the experimental conditions of this study because the weight of coarse particles increased with the solid input weight increased, and therefore, these coarse particles can mix well with the oxygen carrier.

• Journal of the Korean Wood Science and Technology
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• 제34권2호
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• pp.30-36
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• 2006

Wood fuel must be dried before combustion to minimize the energy loss. Sawdust of Japanese red pine was dried in a batch type fluidized-bed to investigate the drying characteristics of sawdust as a raw material for bio-fuel. The minimum fluidization air velocity was increased as particle size was increased. It took about 21 minutes and 8 minutes to dry 0.08 m-deep bed of particles with average particle size of 1.3 mm from 100% to 10% moisture content at air temperature of $20^{\circ}C$ and $50^{\circ}C$, respectively.

• 대한기계학회논문집
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• 제19권1호
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• pp.202-211
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• 1995

Heat and hydrogen transfer characteristics have been experimentally investigated for a hydride reaction bed, in which hydride material LaN $i_{4,7}$A $l_{0.3}$ is contained for hydrogen storage. This problem is of particular interest in the design of metal hydride devices such as metal-hydride refrigerators, heat pumps, or metal-hydride storage units. Transient behavior of hydrogen transfer through the hydride materials as well as heat transfer is studied during absorption and desorption processes in detail. The experimental results obtained indicate that the mass flow of the hydrogen is strongly affected by the governing parameters, such as the initial pressure of the reaction bed, absorption or desorption period, and cooling or heating temperature. These mass transfer results are along with the heat transfer rate between hydride materials and heat transfer medium in the reaction bed.d.d.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2000년도 제21회 KOSCO SYMPOSIUM 논문집
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• pp.236-245
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• 2000

A laboratory scale fluidized bed reactor was developed to treat the combustion characteristics of some fuels (wood, paper sludge, refuse derived fuel). The aims were to introduce the means of experiment and interpretation of the results and finally determine the particle characteristics on the pyrolysis and combustion process of the fuel. A single particle combustion process in the fluidized bed was closely observed. Understanding experimental facility characteristics and determining parameters were also carried out. The fuel combustion processes were observed by carbon conversion rate, recovery and mean carbon conversion time. They were estimated with the CO, $CO_2$ gas concentration monitored at the exit of the combustor. Fuel drying and pyrolysis process were governed by temperature distribution in the fuel particle. There was a significant overlap of the drying and devolatilization. However, transition process from devolatilization to char combustion seemed to be determined by mechanical solidity of the fuel particle after devolatilization process.

• 한국연소학회지
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• 제16권1호
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• pp.1-7
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• 2011

340 MWe circulating fluidized bed (CFB) boiler in Yeosu power station is under construction. The circulating fluidized bed boiler in the Yeosu power plant has a number of differences from other domestic boilers in terms of scale and design. Evaluation of design parameters of the Yeosu CFB boiler should be required because the direct application of existing technology is limited. In this study, design characteristics of the Yeosu CFB boiler was summarized. And thermogravimetric analysis was conducted with comparing other rank coals. Watersteam side heat absorption, flue gas temperature and heat transfer coefficient were calculated by heat and mass balance. Design parameters for the Yeosu CFB boiler were discussed along with typical value in the CFB design range.