• 한국연소학회:학술대회논문집
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• 한국연소학회 2015년도 제51회 KOSCO SYMPOSIUM 초록집
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• pp.69-72
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• 2015

Computational fluid dynamics (CFD) modeling of large-scale coal-fired boilers requires a complicated set of flow, heat transfer and combustion process models based on different degrees of simplification. This study investigates the influence of coal devolatilization, char conversion and turbulent gas reaction models in CFD for a tangential-firing boiler at 500MWe capacity. Devolatilization model is found out not significant on the overall results, when the kinetic rates and the composition of volatiles were varied. In contrast, the turbulence mixing rate influenced significantly on the gas reaction rates, temperature, and heat transfer rate on the wall. The influence of char conversion by the unreacted core shrinking model (UCSM) and the 1st-order global rate model was not significant, but the unburned carbon concentration was predicted in details by the UCSM. Overall, the effects of the selected models were found similar with previous study for a wall-firing boiler.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.967-972
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• 2001

The emission of $NO_{x}$ during coal combustion is a major reason of environment impact. $NO_{x}$ is an acid rain precursor and participates in the generation of smog through ozone production. $NO_{x}$ can be divided into thermal $NO_{x}$, fuel $NO_{x}$ and prompt $NO_{x}$. Thermal $NO_{x}$ is formed in a highly temperature condition dependent. Fuel $NO_{x}$ is dependent on the local combustion characteristics and initial concentration of nitrogen bound compound, while prompt $NO_{x}$ is formed in a significant quantity in some combustion environments, such as low temperature and short residence times. This paper presents numerical simulation of the flow and combustion characteristics in the furnace of a tangential firing boiler of 500MW with burners installed at the every comer of the furnace. The purpose of this paper is to investigate the reduction of $NO_{x}$ emission in a 500MW pulverized coal tangential firing boiler with different OFA's and burner angles. Calculations with different air flow rates of over fired air(OFA) and burner angles are performed.

• 에너지공학
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• 제23권4호
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• pp.49-55
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• 2014

석탄화력 발전소 보일러의 부식 메카니즘에 대한 실증적 고찰을 위하여 500MW 표준화력 발전소 보일러에 대한 보일러 튜브의 두께측정 및 수치해석을 병행하여 분석을 시행하였다. 그 결과 접선연소방식의 보일러 수냉벽 튜브의 부식에 가장 핵심적인 영향을 미치는 메카니즘은 퇴적된 미연탄소분에 포함된 유황분에 의한 부식이었으며, 두 번째 요소는 보일러 내부에서 국부적인 환원성 분위기가 생성되는 위치에서의 $H_2S$ 가스에 의한 부식으로 나타났다. 이와 같은 수냉벽튜브 부식을 완화시키기 위해서는 보일러의 다단연소 운전을 감소시키는 것이 필요하며, 미연분 감소를 위한 엄격한 미분도 관리 및 부식 취약부위에 대한 내부식 코팅보강 작업이 필요하다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2015년도 제51회 KOSCO SYMPOSIUM 초록집
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• pp.103-106
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• 2015

• Korean Chemical Engineering Research
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• 제55권4호
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• pp.548-555
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• 2017

본 연구는 560 MWe급 접선연소식 미분탄 보일러에서 공기단계연소에 의한 연소 및 NOx 배출 특성과 슬래깅성에 대하여 분석한 것이다. 이를 위해 고급 석탄 연소 모델이 적용된 전산유체역학(CFD) 시뮬레이션을 이용하여 전체 연소공기의 당량비(SR)는 1.2로 고정하고, 버너 영역의 SR을 0.94에서 0.995까지 변화시켰다. 공기 배분의 변화에 따라 버너 영역 및 열교환기의 온도 및 전열량 분포가 변하지만 보일러의 전체 효율은 거의 동일하게 나타났다. 버너 영역의 SR이 0.94로 낮아지면 Fuel NO의 생성이 억제되어 절탄기 출구 NOx 배출량은 20% 감소하나, 미연분과 슬래깅성에는 큰 영향이 나타나지 않았다. 따라서, 이 보일러에서 NOx 배출 저감을 위해 공기배분을 조절하여 버너 영역의 SR를 낮추고 상부연소공기(OFA)의 값을 높여 운전하는 것이 타당함을 확인하였다.

• 한국연소학회지
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• 제11권2호
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• pp.1-6
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• 2006

This report presents a study of the development of an advanced coal nozzle used in burners to reduce unburned carbon (UBC) in a tangential coal-fired boiler. To understand the mechanism of UBC reduction, experiments using conventional burners were carried out to evaluate the effects of air injection velocity, coal fineness and over fired air (OFA) on combustion efficiency. It was confirmed that ignition of pulverized coal particles close to the burner is helpful toward the complete burn of residual carbon in fly ash. These efforts indicated the additional results that UBC was strongly dependent on the primary air velocity and coal fineness; especially that UBC dramatically decreased when the weight fraction of pulverized coal under $75{\mu}m$ was over 85 %. New coal nozzles, modified from conventional nozzles, were prepared and tested to improve the combustion efficiency. Some of these nozzles offered relatively lower unburned carbon than those of conventional burners and are referred to as HPFS (High Performance Flame Stability) coal nozzles.

• 한국분무공학회지
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• 제19권2호
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• pp.69-74
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• 2014

The comparison of the flow characteristics between circular and swirl jets which were controlled by the spinner attachment inside the airtube were conducted in this study. Swirl jet means a flow in whirls by mixing the flow of axial and tangential direction. Swirl flow has been used for the improvement of the combustion efficiency in the combustor. This flow is controlled by the spinner which has several vanes inclined by certain angles to the axial direction. In this study, angle of vane $30^{\circ}$ and diameter ratio of outlet to inlet of the airtube 0.73 were made. These spec. should find on the general gun type burner built in the domestic small size boiler. As the flow characteristics, axial and tangential velocities were measured by using the 2-D hot-wire velocimeter system and analyzed statistically. And also this research conducted a practical experiment considering to the attached belongings likes as ignitor, nozzle etc. on the airtube of the gun type burner. As a result, swirl occurred at the occasion of beingness and flow region extended considerably toward the radial direction. But effect of swirl did not transmit to the downstream. And the complicated flow was appeared regardless of the existence of spinner because of the effect of belongings.

• 한국연소학회지
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• 제20권1호
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• pp.15-23
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• 2015

This paper presents the results of field demonstration for fuel switching to bio-fuel oil in 4 commercial heavy oil fired power plants. The 100% fuel switching field demonstration was successfully carried out in two tangential-firing boilers at a capacity of 75 and 100 MWe respectively without major equipment retrofit, and also 25% bio-fuel oil blending for two opposite firing boilers at a capacity of 350 and 400 MWe respectively. Despite the low density and heating value, the bio fuel was successfully replaced heavy fuel oil at the full load by only adjusting operational parameters. Incase of bio fuel oil combustion, heat absorption of radiative heat transfer section was reduced while convection section has opposite trend. In pollutants emission, a major reductionin SOx as well as 10-20% reduction in NOx were achieved by the fuels witching. On the other hand, boiler efficiency was slightly underestimated.