• Journal of Energy Engineering
• /
• v.26 no.2
• /
• pp.99-120
• /
• 2017

In SS branch of Korea District Heating Corporation, Combined Heat & Power power plant with 99MW capacity and 98Gcal / h capacity is operated as a district electricity business. In this region, it is difficult to operate the generator due to the problem of surplus heat treatment between June and September due to the economic recession and the decrease in demand, so it is urgent to develop an economical energy new business model. In this study, we will develop an optimized operation model by introducing a renewable energy hybrid system based on actual operation data of this site. In particular, among renewable energy sources, fuel cell (Fuel Cell) power generation which can generate heat and electricity at the same time with limited location constraints, photovoltaic power generation which is representative renewable energy, ESS (Energy Storage System). HOMER (Hybrid Optimization of Multiple Energy Resources) program was used to select the optimal model. As a result of the economic analysis, 99MW CHP combined cycle power generation is the most economical in terms of net present cost (NPC), but 99MW CHP in terms of carbon emission trading and renewable energy certificate And 5MW fuel cells, and 521kW of solar power to supply electricity and heat than the supply of electricity and heat by 99MW CHP cogeneration power, it was shown that it is economically up to 247.5 billion won. we confirmed the results of the improvement of the zone electricity business condition by introducing the fuel cell and the renewable energy hybrid system as the optimization process model.

• The Journal of Engineering Geology
• /
• v.18 no.1
• /
• pp.17-26
• /
• 2008

In this study, the design method of slope reinforced by the earth retention systems were systematically developed, and the flow chart of design procedure fur each system were constructed to design the slope rationally. The proposed design method is composed of 5 steps such as field condition investigation step, slope design step, landslide occurrence prediction step, slope failure scale estimation step and reinforcement countermeasure selection step. The quantitative standard of slope failure scale was established based on the arrangement of various overseas standards which is estimating the slope failure, and the analysis of slope failure scale which is occurred in the country. The slope failure scale is classified into three categories the small scale of slope failure is less than $150m^3$ of slope failure volume, the middle scale of slope failure is from $150m^3$ to $900m^3$ and the large scale of slope failure is more than $900m^3$. The earth retention system could be selected by the proposed slope failure scale based on the slope failure volume. Meanwhile, the design methods of earth retention system such as piles, soil nails and anchors were developed. The optimal countermeasure for slope stability could be proposed using above design methods.

• Ecology and Resilient Infrastructure
• /
• v.4 no.3
• /
• pp.180-185
• /
• 2017

Restoration of min-impacted arable land is often performed through stabilization of trace elements by amendment treatment combined with (clean) soil covering on the surface. Recently, soil loss problem from sloping remediated agricultural lands has risen as an emerging concern. In this study, efficacy of aggregation formation was assessed by single and binary treatments of four potential amendments (bentonite, lime, organic matter, and steel slag) applied on three cover soils having different clay contents (9.4, 14.7, and 21.2% for A, B, and C soils respectively). In results of single treatments, 5% organic matter for A soil and 5% lime for B and C soils were found most effective for the aggregation formation compared to the respective controls (without amendments). Among nine binary treatments, 3% organic matter + 1% lime for A soil and 1% organic matter + 3% lime for both B and C soils led to the highest formation of aggregation (30.4, 25.0, and 36.5% for A, B, and C soils). For a site-application, the soil erodibility difference between the cover soils (0.045, 0.051, and 0.054 for A, B, and C soils, respectively) and the national average of arable land (0.032) was assumed to be compensated by amendment addition, which is equivalent to 29.1% aggregation formation. To achieve the aggregation goal, 5% lime for A and B soils and 3% lime for C soil were best in the consideration of benefit/cost, thereby effectively and economically reducing soil loss from sloping remediation site. Soil alkalinity induced by lime treatment was not considered in this work.

• Journal of Environmental Impact Assessment
• /
• v.26 no.1
• /
• pp.44-56
• /
• 2017

Sustainable development is important because the ultimate objective is efficient development combining the economic, social, and environmental aspects of urban conservation. Despite Korea's rapid urbanization and economic development, the distribution of resources is inefficient, and land-use is not an exception. Land use distribution is difficult, as it requires considering a variety of purposes, whose solutions lie in a multipurpose optimization process. In this study, Yangpyeong-eup, Yangpyeong, Gyeonggi-do, is selected, as the site has ecological balance, is well-preserved, and has the potential to support population increases. Further, we have used the genetic algorithm method, as it helps to evolve solutions for complex spatial problems such as planning and distribution of land use. This study applies change to the way of mutation. With four goals and restrictions of area, spatial objectives, minimizing land use conversion, ecological conservation, maximizing economic profit, restricting area to a specific land use, and setting a fixed area, we developed an optimal planning map. No urban areas at the site needed preservation and the high urban area growth rate coincided with the optimization of purpose and maximization of economic profit. When the minimum point of the fitness score is the convergence point, we found optimization occurred approximately at 1500 generations. The results of this study can support planning at Yangpyeong-eup.ausative relationship between the perception of improving odor regulation and odor acceptance.

• 한국방재학회:학술대회논문집
• /
• 2011.02a
• /
• pp.159-159
• /
• 2011

수자원 공급의 시 공간적 편차가 큰 우리나라에서는 수자원을 이용하기 위해서 다수의 댐을 건설하고 있다. 특히, 생활수준의 향상으로 용수 수요가 급증하였기 때문에 용수가 부족한 곳에는 광역상수도 사업 등을 통하여 용수를 공급하고 있다. 댐에서 용수가 공급되기까지의 과정은 일종의 관수로 흐름으로 생각할 수 있다. 관수로 내를 흐르는 유체가 갑자기 정지하게 되면, 유체 운동 에너지의 변화가 유발되고, 그로 인해 관내에 급격한 압력의 상승이 일어나게 된다. 반대로 정지하고 있던 유체가 빠른 속도로 흐르게 되면 압력 감소가 급격하게 발생한다. 이와 같이 유체 운동 상태의 급변에 의한 압력변화와 그에 따른 압력파가 음속의 속도로 상 하류로 전파되는 현상을 수격작용(waterhammer)이라 한다. 통상적으로 수격작용은 밸브 개폐 정도가 갑자기 바뀔 때, 펌프의 급격한 기동이나 정지 시, 터빈 내 전력소요가 갑자기 바뀔 때, 댐 수위의 갑작스런 변화, 펌프 임펠러의 진동, 물 수요의 급격한 변화 등에 의해 발생하며, 수격작용은 유체의 질량과 운동량 때문에 관 벽에 큰 힘을 가하게 되어 정상적인 동수압 보다 몇 배나 큰 압력을 발생시킴으로 관 자체는 물론 펌프, 밸브, 터빈 등 관 시설물을 파손시키거나 진동, 소음 등을 야기시킴으로 대규모 건물, 공장, 발전소 등을 설계할 경우 그에 대한 적절한 대책을 강구하여야 한다. 특히 댐에 연결된 저수지 또는 조정지로부터의 도수로가 압력수로이며 그 길이가 상당히 크면 수차가 급정지했을 경우 수격작용에 의해서 압력터널 내에 과도한 압력상승이 일어난다. 이 압력상승을 방지함과 함께 발전소 부하의 증감에 따라서 수량을 공급하거나, 흡수할 목적으로 압력도수로와 수압관과의 접합부에 자유수면이 있는 수조를 설치한다. 이것을 조압수조(surge tank)라 한다(최영박, 1979). 조압수조에서 부하의 급속한 차단에 의해서 수차로 유입될 수량이 차단되면 도수로 내로 흘러 들어온 물은 관성 때문에 수조 내의 수위를 상승시키고, 수조 수위가 어느 정도 이상으로 되어 저수지 수위 보다 상승하면 수조로의 유입이 정지하고 반대로 수조에서 저수지로 역류하여 수조수위는 하강한다. 즉, 조압수조는 도수로 내에 발생한 과도한 압력을 수조 내 수면의 승강운동을 이용하여 감소시키고 원래의 안정적인 수위로 회복시킨다. 본 연구에서는 수격작용에 대한 댐 안정성을 확보하는 수단 중의 하나인 조압수조에 대해 살펴보았다. 연구대상으로 용담댐을 선정하였다. 용담댐에 대한 기존의 검토결과 수직 갱의 지름이 5m 이상이면 조압수조의 동적안정조건을 만족 시키는 것으로 조사되었다. 댐의 설계홍수위인 EL. 265.5m를 기준으로 조압수조의 안정성을 감소시키지 않는 범위 내에서 조압수조 내 격벽 설치 유 무에 따른 수조의 최적 크기를 산정하였다. 산정결과를 분석한 결과 동일 조건에서 격벽을 설치한 경우가 격벽을 설치하지 않은 경우에 비해서 조압수조의 면적이 약 21% 감소하는 것으로 나타났다.

• The Korean Journal of Pesticide Science
• /
• v.18 no.4
• /
• pp.321-329
• /
• 2014

This experiment was conducted to establish an analytical method for residues of amisulbrom, as recently developed an oomycete-specific fungicide showing inhibition of fungal respiration, in crops using HPLC-UVD/MS. Amisulbrom residue was extracted with acetonitrile from representative samples of five raw products which comprised apple, green pepper, kimchi cabbage, potato and hulled rice. The extract was diluted with 50 mL of saline water and directly partitioned into dichloromethane to remove polar co-extractives in the aqueous phase. For the hulled rice sample, n-hexane/acetonitrile partition was additionally employed to remove non-polar lipids. The extract was finally purified by optimized Florisil column chromatography. On an octadecylsilyl column in HPLC, amisulbrom was successfully separated from sample co-extractives and sensitively quantitated by ultraviolet absorption at 255 nm with no interference. Accuracy and precision of the proposed method was validated by the recovery test on every crop samples fortified with amisulbrom at 3 concentration levels per crop in each triplication. Mean recoveries ranged from 85.3% to 105.6% in five representative agricultural commodities. The coefficients of variation were all less than 10%, irrespective of sample types and fortification levels. Limit of quantitation (LOQ) of amisulbrom was 0.04 mg/kg as verified by the recovery experiment. A confirmatory method using LC/MS with selected-ion monitoring technique was also provided to clearly identify the suspected residue. The proposed method was sensitive, reproducible and easy-to-operate enough to routinely determine the residue of amisulbrom in agricultural commodities.

• Applied Chemistry for Engineering
• /
• v.9 no.2
• /
• pp.232-237
• /
• 1998

This study was carried out to find the optimal operating conditions for separation of residual uranium from the simulated radwaste solution containing 19 elements, and to evaluate the validity of the process. The selected process was based on the solvent extraction with TBP(tributyl phosphate). As an extractor, two miniature mixer-settlers with a total of 18 stages were used. Extraction yield of U, Np and Tc was about 99.2%. 32.1%, and 99.9%, respectively. The other elements were coextracted in the range of 1~4%. Extraction yield of U exceeded those of the previous work performed with batch system, which resulted in the low extractability of U (about 80%) according to the coexisting element such as Nd and Fe. It was due to the characteristics of multi-stage extractor. On the other hand, low extractability of Np was caused by various oxidation states in the nitric acid medium. In the case of Tc, its high extractability may be attributed to the complex formation with Zr and U, which is not well proved yet. All elements extracted with TBP were stripped into aqueous phase more than 99% by 0.01M $HNO_3$. From the results, this process has no problem with respect to in the same step was required, because Np was distributed in the raffinate and U product, respectively.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.24 no.4
• /
• pp.69-76
• /
• 2016

To produce the primary data for best management of soil nutrient in organically practiced soils, 75 leading organic farms whose paddy fields were certified as organic were selected. Soil samples were collected from the paddy fields before plowing, and then analyzed for the determination of physico-chemical properties. Soil pH, organic matter and available phosphate were analyzed and averaged 6.2, $25.6mg\;kg^{-1}$ and $88.4mg\;kg^{-1}$, respectively. Contrary to the national-scale-surveyed paddy soils including organic and conventional farming, pH was higher, available phosphate was lower in the organically practiced soils, but organic matter was similar. With the increasing cultivation period in organic, soil pH and porosity were also increased, EC, available phosphate, bulk density and soil hardness were lower than those from the national survey. Organic matter, however, was not significantly changed. The bulk density was negatively correlated with the organic matter content for both surface topsoil ($R^2=-0.5424$) and subsoil ($R^2=-0.6429$) (p<0.05). Soil quality is improved in most of soil chemical and physical composition factors excluding organic matter and available phosphate. However, it is necessary to establish the counter measure plan for organic matter management and to develop phosphate-containing materials which can be used as organic agricultural material in the future.

• Journal of Korean Society of Environmental Engineers
• /
• v.30 no.11
• /
• pp.1075-1086
• /
• 2008

In order to investigate the applicability and suitability of the industrial by-products to apply mono-layer cover system for non-sanitary landfill sites, 6 different industrial by-products, such as construction waste, bottom ash, gypsum, blast furnace and steel manufacture slags, and stone powder sludge, were evaluated. Various physicochemical and hydrodynamic properties of the industrial byproducts were investigated. The environmental safety was monitored using batch and long-term leaching tests as well. In addition, the flexibility of plants was observed by cultivating them in the industrial by-products. The results for physicochemical properties indicate that most of the materials considered appeared to be suitable for landfill cover. Particularly, the concentration levels of hazardous elements regulated by the Korean Law for Waste Management did not exceed the regulatory limits in all target materials. In addition, the concentrations of regulated elements for the Korean Soil Conservation Law were examined below the regulatory limits in most of materials considered, except for the stone powder sludge. The results of batch and long-term experiments showed bottom ash and construction waste were the most suitable materials for landfill cover among the industrial by-products considered. The results of plant studies indicate that the bottom ash among industrial by-products considered was most effective in developing vegetation on landfill site, showing fast germination and large growth index. At the final covering system made of mixture of soil and bottom ash, the optimum application rate of farmyard manure was observed to be 40-50 Mg/ha.

• Environmental and Resource Economics Review
• /
• v.15 no.4
• /
• pp.693-712
• /
• 2006

A pre-feasibility test is done for renewable energy hybrid power systems at off~grid islands in which the current power supply is provided only by diesel generation. We apply Homer (Hybrid Optimization Model for Electric Renewables) which was developed by the National Renewable Energy Laboratory (NREL) for the analysis to identify the cost-minimizing combination of power generating facilities for the given load profiles. Chuja-Do, Geomun-Do and Youngsan-Do have been selected for our analysis considering the wind resources data of the Korea Institute of Energy Research (KIER). Information on wind speed, solar radiation and temperature is also used for the analysis. System component cost information from overseas market has been used due to the lack of domestic information. Site specific Load profile for electricity demand for those islands are reconstructed based on the partial survey results obtained form other sources. The LCOE of the least cost hybrid power systems for Chuja-Do, Geomun-Do and Youngsan-Do are $0.278/kWh, $0.234/kWh and $0.353/kWh, respectively Considering the fact that diesel generation is being subsidized at the price of $0.300/kWh by the government, first 2 cases are economically feasible for the introduction of renewable energy hybrid systems to those islands. But the third case of Youngsan-Do does not meet the criteria. The basic differences of these pre-feasibility test results are from the differences of the site specific renewable energy conditions, especially wind resources. In summary, promoting hybrid systems in the off-grid remote island should be based on the economic feasibility test results. Not all the off-grid islands are feasible for introducing this renewable energy hybrid system.