• Korean Chemical Engineering Research
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• 제59권1호
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• pp.127-137
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• 2021

미세먼지 전구체인 질소산화물(NOx)에 대한 대기배출부과금 제도가 2020년부터 국내에 도입 및 시행됨에 따라 이를 저감하기 위한 경제적인 연소기술 개발은 매우 시급한 실정이다. 본 연구에서는 해외 우드펠릿 대체재로서 REC(Renewable Energy Certificates) 확보가 가능한 국내 미이용 산림 바이오매스를 연료로 하여 0.1 MWth급 순환유동층 연소 설비에서 NOx 저감을 위한 air-staging 효과를 고찰하였다. 운전 변수로는 air-staging 적용 유무, 3차 공기 공급 높이(6.4 m, 8.1 m, 9.4 m) 그리고 air-staging 비율(1차 공기:2차 공기:3차 공기=91%:9%:0%, 82%:9%:9%, 73%:9%:18%) 변화이며 운전 변수에 대한 배기가스 내 NO와 CO 농도, 연소로 높이별 온도와 압력 프로파일, 포집된 비산재(fly ash) 내 미연탄소 함량과 연소효율을 분석하였다. 3차 공기를 가장 높은 9.4 m에서 공급한 air-staging 운전 시 NO 농도는 100.7 ppm으로 air-staging을 적용하지 않은 운전 조건(148.8 ppm)보다 32.3% 감소하지만 CO 농도는 오히려 52.2 ppm에서 99.8 ppm으로 91% 증가하였다. 더불어, NO 농도의 저감을 위한 환원영역과 CO 농도의 저감을 위한 산화영역 확보를 위해 3차 공기 공급 높이를 6.4 m로 유지하며 3차 공기 공급량을 늘리고 1차 공기 공급량을 낮춘 air-staging 운전 조건(73%:9%:18%)에서는 NO와 CO 농도가 각각 90.8 ppm과 66.1 ppm으로 air-staging 적용 조건 중 가장 감소되는 것을 확인하였다. 이러한 최적 운전 조건에서 연소효율 역시, air-staging을 적용하지 않은 운전 조건의 연소효율(98.3%) 보다 높은 99.3%임을 확인하였다.

• Journal of Mechanical Science and Technology
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• 제16권9호
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• pp.1112-1120
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• 2002

Numerical investigations on air staging and fuel staging were carried out with a newly designed coaxial cyclone combustor, which uses the method of two stage coal combustion composed of pre-combustor and main combustor. The pre-combustor with a high air/fuel ratio is designed to supply gas at high temperature to the main combustor. To avoid local high temperature region in this process, secondary air is injected in the downstream. Together with the burned gas supplied from the pre-combustor and the preheated air directly injected into main combustor, coals supplied through the main burner react rapidly at a low air/fuel ratio. Strong swirling motion of cyclone combustor keeps the wall temperature high, which makes slagging combustion possible. Alaska, US coal is used for calculations. Predictions were made for various coal flow rates in the main combustor for fuel staging and for the various flow rate of secondary air in the pre-combustor for air staging. In-scattering angles are also chosen as a variable to increase residence times of coal particles. Temperature fields and particle trajectories for various conditions are described. Predicted temperature variations at the wall of the combustor are compared with corresponding experimental data and show a similar trend. The in-scattering angle of 20° is recommended to increase the combustion efficiency in the main chamber.

• 한국연소학회:학술대회논문집
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• 한국연소학회 1999년도 제19회 KOSCO SYMPOSIUM 논문집
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• pp.149-154
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• 1999

The influences of air staging on NOx emission and burnout of coal flames were investigated using 1MWth combustion test facility. The experiments showed that variation of overall excess air ratio led to a relatively higher NOx emission level for ${\lambda}=1.2.$ When air staging was applied to the combustion air, it was confirmed that a fuel rich primary combustion zone was established and unburned char was burened completely by mixing with the staged air supplied radially around the flame. The NOx emissions were redued by increasing the staged air flow rate, and staging air was suggested to be more than 40% of the total combustion air for the substantial NOx reduction.

• 대한기계학회논문집B
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• 제27권1호
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• pp.32-38
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• 2003

Staged combustion, such as air- and fuel-staging, is a relatively well-known technique fur reduction of NOx emission and used in combination with other techniques nowadays. However, the design variables are still selected depending upon operating conditions. There are many variables tested to investigate the NOx emission characteristics fur changing of fuel or air velocity, swirl intensity, and staging ratio of air and fuel in multi-staged burner. In air-staging case, the fuel-rich condition of the primary combustion zone is very helpful to reduce NOx emission and its range is known to be restricted by the increase of carbon monoxide. However, in many cases carbon monoxide level is not too high to be restricted operating condition. So we tried to expand the equivalence ratio range to the richer condition in the primary combustion zone and certificate the function of each burner component and its contribution to the overall NOx production.

• 대한기계학회논문집B
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• 제34권3호
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• pp.283-290
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• 2010

이 연구의 목적은 NOx 저감을 위한 연료희박 재연소 기법과 산화제 다단 연소 기법의 혼합 기법의 실험적 연구를 목표로 한다. 실험용 연소로에서 재연소 연료 분율, 재연소 노즐 직경, 산소부하도 및 재연소 연료 분사 위치등을 고려한 실험을 수행 하였다. 또한, 산화제 다단 연소를 통하여 생성된 유동장이 NOx 저감에 미치는 영향을 연료희박 기법의 NOx 저감율과 비교하는 실험을 수행하였다. 실험을 통하여 연료희박 재연소와 산화제다단연소 기법의 혼합 기법이 NOx 저감에 미치는 긍정적인 효과를 관찰 하였다.

• 한국연소학회지
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• 제13권2호
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• pp.7-13
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• 2008

The aim of this work is to identify application of ultra low NOx and CO combustor. To achieve this, we developed the premixed oxidizer-staging combustor using a cyclone flow. Various factors such as equivalence ratio for the combustion condition and swirl type for secondary air injection have been tested experimentally for flame stability and NOx, CO emission characteristics. Before to do this, we had been tested cyclone premixed combustor in advance. it is similar to first combustor of premixed oxidizer-staging combustor. As a result, cyclone premixed flame shows the very high flame stability and low NOx emission. however, it can be identified that there were some problems such as a little high CO emission and thermal resistance of combustor wall. Cyclone premixed oxidizer-staging combustor can resolve those of problems. In our combustor, we can found out optimal condition that the secondary air injection method is swirl type, swirl direction is co-swirl and equivalence ratio of first combustor is 1.3. Quantitatively, we can achieve 10.8 ppm for NOx and 30.2 ppm for CO emissions respectively. Form this result, we can identified that cyclone premixed oxidizer-staging combustor can apply to ultra low NOx and CO combustor.

• 대한기계학회논문집B
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• 제40권10호
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• pp.637-644
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• 2016

본 연구의 목적은 석탄 입자 연소 시 공기 다단 연소 적용에 따른 UBC(Unburned Carbon) 및 질소 산화물(NOx) 배출 특성을 분석하는 것이다. 이를 위해 공기 다단 연소가 가능한 2단 하향 분류층 반응기(Two Staged Drop Tube Furnace, Two Staged DTF)를 설계 및 제작하였다. 아역청탄(Tanito)의 단일 및 다단 연소 실험을 진행하여 UBC 및 NOx 배출 특성을 분석하였다. 그 결과, 단일 연소 조건에서 온도 및 공기비가 증가함에 따라서 UBC 함량이 감소했지만 NOx의 농도는 증가했다. 특히 과농 연료 연소 영역에서 NOx 저감 반응이 일어났으며, 이때 반응 온도가 증가할수록 NOx 저감 반응이 활성화 될 뿐아니라 UBC는 감소되었다. 공기 다단 연소 실험의 경우 석탄 입자의 UBC 증가량에 비해 높은 NOx 저감 효과를 얻을 수 있었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.167-171
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• 2001

Air-staging combustion is a relatively well-known technique to reduce NOx emission and used in combination with other techniques nowadays. However, the design variables are still selected depending upon operating circumstances. Though the fuel-rich condition of the primary combustion zone is very helpful to NOx reduction, its range is known to be restricted by the increase of carbon monoxide. However, in many cases carbon monoxide level is so low not to be the restriction at all. So we tried to expand the equivalence ratio range to the richer condition in the primary combustion zone and make the function of each burner component and its contribution to the overall NOx production clear.

• 설비공학논문집
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• 제28권4호
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• pp.137-144
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• 2016

Commercial buildings account for a significant proportion of the total building energy use in Korea, and cooling energy, in turn, accounts for the largest proportion of total energy consumption in commercial buildings. Under this circumstance, chiller staging is considered to be a reasonable and practical solution for cooling energy saving. In this study, the part-load ratio and the operating characteristics of a vapor compression chiller were analysed within an office building. In addition, energy consumption among different chiller staging schemes was comparatively analysed. As a result, significant proportions of total operating hours, cooling load and energy consumption turned out to be in the part load ratio range from 0% through 50%, and thus energy consumption was significantly affected by the chiller COP at low part-load conditions, indicating that the chiller operation at the part-load is an important factor in commercial buildings. In addition, utilizing a sequential chiller staging scheme can reduce the annual cooling energy usage by more than 10.3% compared to operating a single chiller.

• 대한기계학회논문집
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• 제19권2호
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• pp.591-596
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• 1995

In order to investigate the reduction of NO emissions, natural gas was fueled for two-stage combustion apparatus. NO and CO emissions were described by five variables: total air ratio, primary air ratio, secondary air injection position, secondary air injection velocity, and swirl ratio. It was mainly observed that, as the primary air ratios of 0 and 0.4 NO emission decreased with increasing the secondary air injection position and secondary air injection velocity. The effect of weak swirl on NO emission was found to be insignificant.