• Journal of the Korean Geotechnical Society
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• v.34 no.6
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• pp.17-24
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• 2018

In this study, static load test and dynamic load test were performed to evaluate pile-filling material (ZA-Soil) of soil-cement injected precast pile method which was developed by using the ash of circulating fluidized boiler as a stimulant for alkali activation reaction of blast furnace slag. As a result of the static load test, the allowable bearing capacity of pile was 1,350 kN, which was the same as the result of using ordinary portland cement. And total settlement was 6.97 mm, and net settlement was 1.48 mm. These are similar to the total settlement, 7.825 mm, and net settlement, 2.005 mm of ordinary portland cement. As a result of the dynamic load test and CAPWAP analysis, the skin friction was 375.0 kN, the end bearing capacity was 3,045.9 kN, and the allowable bearing capacity was 1,368.36 kN. These results are similar to the results of using ordinary portland cement as pile-filling material.

• Korean journal of applied entomology
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• v.49 no.1
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• pp.49-55
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• 2010

Bumblebees are widely used to pollinate crops in greenhouses and fields. Here we firstly developed an apparatus for the oviposition induction of the bumblebee Bombus ignitus using electricity. The apparatus consists of boxes for colony initiation, part of temperature control, part of heat transfer, and moving shelf. The result shows that the rates of oviposition and colony foundation in the newly developed apparatus are respectively 3.9% and 5.2% higher than in the existing apparatus using hot water. More importantly, the newly developed apparatus is 75% cheaper in costs and can more save energy than existing apparatus. These results indicate that the newly developed apparatus could serve as an effective apparatus for the oviposition induction of B. ignitus.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.11
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• pp.727-736
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• 2016

In this study, a high-pressure multistage pump used in the combined cycle power plants is analyzed. The pump performance characteristics (differential head and efficiency) are numerically analyzed for different shapes of the radial diffuser. The design variables selected for the radial diffuser are, number of vanes, diameter ratio ($D_4/D_3$), return channel outlet angle(${\alpha}_6$), and pressure recovery factor ($C_p$). The numerical analysis results showed that the differential head and efficiency are the highest when the diameter ratio is the highest. Further, it was observed that the differential head was lower when the return channel outlet angle was $60^{\circ}$ than when it was $90^{\circ}$, because of pre-swirl at the diffuser outlet.

• Journal of the Korean Geosynthetics Society
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• v.16 no.4
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• pp.13-20
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• 2017

In this study, laboratory tests were performed to evaluate for new filling materials (ZA-Soil) for bored pile that were developed using by high calcium ash. As a result of laboratory test, the uniaxial compression strength of 2 types of ZA-Soil are shown 68.0% and 64.6% compared to ordinary portland cement. And it have a suitable flowability and environmental stability. Also, after 28days, uniaxial compression strength of material mixed with soil and high strength filling material (ZA-Soil) for bored pile is 1.10-1.23 times bigger than material mixed with ordinary portland cement.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.3
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• pp.1488-1494
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• 2011

In this paper, we propose an algorithm using linear regression model that forecasts the demand of heated water in winter. To supply heated water to apartments, stores and office buildings, Korea District Heating Corp.(KDHC) operates boilers including electric power generators. In order to operate facilities generating heated water economically, it is essential to forecast daily demand of heated water with accuracy. Analysis of history data of Kangnam Branch of KDHC in 2006 and 2007 reveals that heated water supply on previous day as well as temperature are the most important factors to forecast the daily demand of heated water. When calculated by the proposed regression model, mean absolute percentage error for the demand of heated water in winter of the year 2006 through 2009 does not exceed 3.87%.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.185.2-185.2
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• 2011

1900년대 이후 산업발전에 따른 인구의 도시 집중화로 인한 하수량 증가에 따라 하수슬러지 발생량이 점차 증가하게 되면서 하수슬러지 처리에 관한 문제 등이 제기되기 시작하였다. 국내의 경우 2003년 하수슬러지의 매립이 금지된 후, 발생슬러지 대부분을 해양투기 등을 통해 처리하여왔다. 2009년 기준으로 국내에서 발생되는 하수슬러지량과 처리 분포를 살펴보면 전국 433개소 하수처리장에서 1일 평균 8,295톤(3,028천톤/년)이 발생되고 있으며, 이 중 47%가 해양투기 되고 있는 실정이다. 그러나 해양투기마저도 런던협약'96의정서 가입으로 2012년부터 금지됨에 따라 국내에서는 슬러지처리 및 재활용 방안과 관련한 연구개발이 활발히 진행되고 있는 중이다. 하수슬러지 처리 및 재활용기술의 경우 다양한 공법 등이 개발 중에 있으나 설비의 불안정 및 높은 투자비 등으로 인해 아직까지 상용화 된 설비 등은 많지 않은 실정이다. 이에 따라 본 연구에서는 POSCO 건설에서 개발한 슬러지 연료화 기술을 통해 생산된 슬러지 탄을 석탄 화력발전소 등에 석탄 보조연료로 활용할 수 있는 방안을 강구하여 상용화 가능한 혼소 기술을 개발하고자 하였다. 슬러지탄(발열량 3.000kcal 이상)을 석탄 화력발전소 보일러에 일정 비율로 혼소하여 슬러지탄의 품질평가, 중금속 용출시험 및 함량분석, 잔재물의 중금속 용출시험 등을 실시하였으며, 그 결과 모든 시험항목에서 연료화 관련 법적기준을 만족하는 것으로 나타났다. 슬러지탄을 화력발전소에 혼소하여 사용할 경우, 2012년부터 시행예정인 RPS(Renewable Portfolio Standard)법 대응 및 석탄사용량 저감 등을 통한 $CO_2$ 저감으로 저탄소 녹색성장의 자원순환사회를 구축하는 데 이바지 할 것으로 판단된다.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.4
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• pp.272-277
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• 2009

Three dimensional numerical analysis for the coal fired boiler has been performed to investigate the effect of yaw angle variation of the secondary air nozzles on the combustion characteristics and NOx emission. It was found that the prediction gives a good agreement with plant data. The increase in yaw angle up to $20^{\circ}$ have results in the decrease in NOx emission at furnace exit and recirculation flow intensity, together with the increase of unburned carbon in ash. It also has been recognized the remarkably change in configuration of fire ball with increase in yaw angle. The results from this study would be valuable in the case of the combustion modification of the corner firing coal-fired utility boiler.

• Proceedings of the KAIS Fall Conference
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• 2012.05a
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• pp.356-359
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• 2012

SNCR 기술은 SCR에 비해 탈질 효율은 떨어지지만 촉매없이 고온 배출가스에 NH3 또는 요소수를 직접 분사하여 질소와 물로 환원시키는 방법이므로 초기 투자비 및 운영비가 적어 최근 국내 대다수의 소각장, 산업용 보일러 등에 널리 적용되고 있다. 단, SNCR 기술은 급격한 온도 강하나 접근의 불용이성, 불균일한 혼합, 액적의 증발시간 지연, 불균일한 운전 조건 등의 영향을 크게 받으며, 특히 반응 온도가 가장 중요한 변수로서 최적 반응 온도 영역대가 약 800~$1,000^{\circ}C$라는 점에서 이상적인 반응 온도 조건을 찾아서 환원제를 분무하는 것이 매우 중요하다. 이에 본 연구에서는 열유동 전산해석을 통해 스토커식 소각로의 폐기물 성상별 화염 온도 분포를 예측하고 적정 반응 온도 영역을 확인하여 요소수 주입 고도를 선정, 폐기물 성상별 분무 조건을 확립하고자 수치 해석적 연구를 수행하였다. 폐기물 성상(고질/중질/저질 폐기물)별로 화염 온도를 예측한 결과, 최적 반응 온도 영역대가 약 800~$1,000^{\circ}C$, 폐기물 성상의 심한 변화 때문에 소각로의 효율적인 연소 조건 제어에 어려움 등을 고려하여 약 700~$1,000^{\circ}C$ 온도 영역대를 환원제 분무 온도로 선정하였다. 폐기물별로 발열량에 따른 화염 온도가 모두 다르기 때문에 환원제 분무 위치를 3지점으로 선정하여 각 지점별로 분무 운전 조건을 확립하였다.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.1
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• pp.17-22
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• 2010

The aim of this study is to research applicable possibility of DSI (Dry Sorbent Injection) technique in $SO_2$ removal process using lab-scale facility based on 500MW in capacity coal-fired thermal power plant operated by South Korea N. Power Co., Ltd. To increase the $SO_2$ removal efficiency, it is considered the mixing enhancement as different shapes called lobed-plate and stepplate tested ultimately for optimum shape. Also it tested to analysis $SO_2$ removal efficiency by numbers of injection holes. At experimental it showed the $SO_2$ removal efficiency is higher using mixing enhancement than not installed mixing enhancement and case on the step-plate was shown the most $SO_2$ removal efficiency. Also, $SO_2$ removal efficiency was higher recording which will increase the injection holes case on not installed mixing enhancement. But, the $SO_2$ removal efficiency was higher 4 injection holes case on installed mixing enhancement.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.4
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• pp.264-269
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• 2016

This paper reports a fundamental study of temperature characteristics of a solar pond with an insulation layer. Further, these characteristics were compared with those of a solar pond without the insulation layer. The governing equation was discretized via finite difference method. The governing equations are two-dimensional unsteady-state second-order partial differential equations. The conclusions of the study are as follows: 1) If the depth of the solar pond was increased, the desired effect of increase in temperature was not produced because the amount of solar insolation received by the bottom of the solar pond decreased. 2) As the temperature of the soil during winter is higher than the temperature of the water in a solar pond, heat was transferred from the soil to the solar pond. 3) For the case of the solar pond with insulation layer, it was estimated that the dependence rate of solar energy was 83.3% and that of the boiler was 16.7%.