• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.6
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• pp.587-597
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• 2010

Air-staged combustion is known to be one of the techniques of NOx reduction. The objective of this study is to determine the optimal ratio of air flow distributed for CCOFA and SOFA; at this optimal ratio, the combustion and exhaust emission characteristics of a pulverized coal-fired boiler are maintained at a satisfactory level. A numerical investigation was performed at various airflow ratios of 16.7/83.3%, 25/75%, 50/50%, 75/25%, and 83.3/16.7%. An inert gas was considered as a substitute for air to isolate the effects of the cooling process and chemical reaction on NOx reduction; during NOx reduction in air-staged combustion, both the effects typically occur simultaneously. The results of our study show that the optimum condition, under which the maximum NOx reduction and highest boiler efficiency can be obtained, corresponds to the equal splitting of the over-fire air between CCOFA and SOFA.

• Journal of Energy Engineering
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• v.4 no.1
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• pp.115-125
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• 1995

본“천연가스 다단연소기술 연구”는, 공업적으로 널리 쓰이는 선회확산 방식으로 천연가스를 연소시킬 때 그 연소 특성과 발생되는 환경오염물질인 일산화탄소(CO)와 질소산화물(NOX)의 저감에 대한 연구로서, 천연가스의 난류확산화염과 선회확산화염의 유동장, 온도장, 농도장을 실험과 수치해석을 통하여 분석하여 각각 연소방식의 화염구조와 특성을 규명하고 해석하였다. 그리고 그 결과를 토대로하여 다단확산 연소실험 장치를 제작 다단확산연소의 중요한 인자인 1차당량비, 2차공기주입위치, 유속, 선회도 등을 변화시켜 질소산화물 저감과 높은 연소효율을 얻을 수 있는 최적의 연소조건을 찾아 내었다. 본고에서는 실험부분만을 간추려 발표하고 수치해석 부분은 다음 기회로 미루고자 한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.57-64
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• 2017

Today, due to the environmental regulations regarding air pollution in the EU, the use of EPS (Styrofoam) as the cushioning material in the packaging industry is decreasing. In effect, air cushioning based cushioning materials are rapidly expanding into the market and replacing EPS, due to their excellent buffering ability and environmental friendliness. This is a new selective filling type air filling material manufacturing technology that affords improvements in the amount of raw materials required, its processing and its aesthetic appearance compared to the conventional air filling cushioning materials. In this study, a multi-stage air cell filling valve molding technology is developed based on selective filling technology, which allows packages to be selectively filled in various forms by applying valve forming structure technology. This multi-stage air cell filling valve molding technology is a technique in which a plurality of injection ports are formed by laminating three layers of films, viz. a first injection film, a valve film, and a second injection film having valve ends. In the conventional technology, a separate external air injection path for injecting air into a plurality of connected air bags is needed. However, in the proposed system, an external air injection path is formed inside the air bag, Due to the lack of need for an injection furnace, the raw material and process are reduced and air is injected and then discharged, while the air bag is reduced in length to 63 ~ 66% of its normal value. The outer surface of the outer air injection path is integrated inside by maintaining the original length of the cross section, while the unnecessary folded air is injected into the interior of the air bag, This smart air filling type cushioning material manufacturing technology constitutes a big improvement over the existing technologies.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.12
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• pp.963-969
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• 2014

Four coal sources that had different ash contents were evaluated in a drop tube furnace (DTF). Combustion experiments were conducted by using several sources with different particle sizes and excess air ratios under air-staging conditions to determine the optimized combustion conditions of high-ash coal, with an emphasis on the combustion efficiency and NOx emissions. The results show that the higher ash content results in a large amount of carbon remaining unburned, and that this effect is dominant when the largest particle size is used. Furthermore, the ash content of coal does affect the Char-NOx concentration, which decreases with the particle size. The results of this study suggest that an air-staged system can be useful to reduce the NOx emissions of high-ash coal and that control of the air stoichiometric ratio of the primary combustion zone (SR1) is effective for reducing NOx emissions, especially by considering unburned carbon contents.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.3
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• pp.283-290
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• 2010

The main goal of this study is to examine the use of a hybrid -fuel lean reburning system with air staging for $NO_X$ reduction. The experimental variables include the reburn fuel fraction, sizes of reburn- fuel-injection nozzles, oxygen enrichment ratio, and location of reburn- fuel- injection. The effect of the flow field induced by air- staging combustion on $NO_X$ reduction is considered, and then, the $NO_X$ reduction rate is compared with only fuel lean reburning system. On the basis of the effectiveness of each De-$NO_X$ process, the advantage of using the hybrid reburning system with air staging is determined and discussed.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1996.10b
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• pp.85-90
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• 1996

석탄 직접연소의 신기술인 Cyclone 연소기술은 환경오염저감 기술증의 하나로서, 고온 연소로 인해 회분이 연소실 내부에서 용융, 제거된 후 고온의 청정연소가스만 보일러로 유입된다. 또한 연소기의 fuel-rich 연소조건하에서 생성된 고온의 불완전연소가스는 보일러 입구에서 충분한 재연소공기를 공급함으로서 완전연소시킬 수 있으므로 적은 시설투자 비용으로 기존 오일이나 가스용 보일러를 석탄용으로 전환이 용이할 뿐만 아니라 이러한 다단 연소방식을 채택하여 NOx 제어도 가능하다는 이점이 있다. Cyclone 연소기술의 개발은 석탄의 청정연소 뿐만 아니라 그 기술을 토대로 석탄가스화, MHD 발전, 가연성 폐기물 소각등에도 활용할 수 있다. 따라서 국내 기술자립을 위해 실험용 Cyclone 연소기를 설계, 제작 및 연소실험을 수행한 결과, Peco-semi탄을 연료로 공급량 약 30 kg/hr, 공기비 약 1.0 일 때 탄소전환율은 약 95% 이며 회분제거율은 약 70%임을 확인할 수 있었다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.11
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• pp.858-868
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• 2009

A numerical investigation has been carried out about the performance of a 500MW class tangentially coal-fired boiler, focusing on the optimization of separated overfire air (SOFA) position to reduce NOx emission. For this purpose, a comprehensive combination of NOx chemistry models has been employed in the numerical simulation of a particle-laden flow along with solid fuel combustion and heat and mass transfer. A reasonable agreement has been shown in baseline cases for predicted operational parameters compared with experimental data measured in the boiler. A further SOFA calculation has been made to obtain optimum elevation and position of SOFA port. Additionally, clarifying on the effect of SOFA on NOx emission has been carried out in the coal-fired boiler. As a result, this paper is valuable to provide an information about the optimum position of SOFA and the mechanism by which the SOFA would affect NOx emission.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.3
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• pp.335-342
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• 2012

Nowadays, automobile manufacturers are focusing on the reduction of exhaust-gas emissions because of the harmful effects on humans and the environment, such as global warming by greenhouse gases. Gasoline direct injection (GDI) combustion is a promising technology that can improve fuel economy significantly compared to conventional port fuel injection (PFI) gasoline engines. In the present study, ultra-lean combustion with an excess air ratio of over 2.0 is realized with a spray-guided-type GDI combustion system, so that the fuel consumption is improved by about 13%. The level of exhaust-gas emissions and the operation performance with the multiple injection strategy and exhaust-gas recirculation (EGR) are examined in comparison with the emission regulations and from the point of view of commercialization.