• 한국컴퓨터정보학회:학술대회논문집
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• 한국컴퓨터정보학회 2018년도 제58차 하계학술대회논문집 26권2호
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• pp.55-56
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• 2018

화력발전소의 중요 구성품인 보일러 튜브의 예기치 못한 누설 사고로 인해 수억원에 해당하는 손실이 발생하고 있다. 본 논문에서는 보일러 튜브의 누설 감지를 위해 유전 알고리즘을 이용하여 추출 가능한 특징들 중 누수 감지에 유용한 특징들을 선택하고, 선택된 특징으로 서포트 벡터 머신을 이용하여 보일러 튜브의 누설 감지하는 방법을 제안한다. 이는 뛰어난 성능을 보였으며, 향후 본 기술을 이용하면 발전소의 손실 예방에 크게 도움이 될 것으로 기대된다.

• 플랜트 저널
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• 제6권3호
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• pp.53-61
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• 2010

This paper presents failure analysis on weld-joint of the waterwall tubes in USC boilers. Visual inspections were performed to find out the characteristics of the fracture. Additionally both microscopic characteristics and hardness test were carried out on failed tube samples. Failures seem to happen mainly because the welding process such as preheating and PWHT(post-weld heat treatment) was not conducted strictly. Thus, this paper has the purpose to describe the main cause of the poor welding process and to explain how to prevent similar failures in those weld-joints.

• Corrosion Science and Technology
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• 제18권2호
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• pp.55-60
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• 2019

Corrosion failure in the convection part of peak load boiler (PLB) of the district heating system led to water leakage. Herein, Internal Rotary Inspection System (IRIS) inspection was employed to examine wall thinning and the cause of leakage in the flue tube. The corrosive products of the turbulator and tube were investigated using scanning electron microscope combined with energy dispersive spectroscopy, X-ray diffraction, and inductively coupled plasma (ICP). Majority of the serious corrosion damage was observed near the turbulator located in the upper flue tube. ICP analysis of the boiler water revealed oxide formation of sodium chloride in the lower end part of the flue tube. A cross-sectional view of the turbulator revealed the presence of double-layers of the oxide film, indicating environmental change during operation associated with water leakage. The outer surface of the turbulator consisted of the acid oxides such as $NO_x$ and $SO_x$ along with sodium and chloride ions. Dew-point corrosion is hypothesized as the main cause for the formation of acid oxides in the region of contact of the flue tube and the turbulator.

• 한국지능시스템학회논문지
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• 제26권3호
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• pp.246-252
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• 2016

화력발전소의 설비들은 매우 높은 온도와 압력의 환경에서 운전되므로, 설비고장은 상당한 인적 물적 손실로 이어진다. 그러므로 발전설비의 비정상정인 동작 상태를 사전에 확인할 수 있는 고장탐지 시스템이 필수적이다. 본 연구에서는, 화력발전소 증기보일러의 고장탐지를 위해서 마할라노비스 거리(Mahalanobis distance, MD)를 이용하였다. MD 기반의 고장탐지방법에서는, 비정상샘플은 정상샘플들로부터 멀리 떨어져 있다고 가정한다. 정상상태로 동작중인 대상시스템으로부터 수집된 다변량 샘플을 이용하여 평균벡터와 공분산행렬을 계산하고, MD값의 문턱값을 설정한다. 검증단계에서는, 평균벡터와 검증샘플들 간의 MD를 구한 후, 계산된 MD 값이 미리 설정된 문턱값보다 높으면 알람신호가 발생하게 된다. MD 기반의 고장탐지방법의 성능을 검증하기 위해서, 200MW 유연탄 화력발전소의 증기보일러 튜브누설로 인해서 발전정지 된 사례를 사용하였다. 실험결과는 MD 기반의 고장탐지기법이 발전정지가 발생하기 이전의 이상징후를 성공적으로 탐지할 수 있음을 보여준다.

• KEPCO Journal on Electric Power and Energy
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• 제5권1호
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• pp.33-38
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• 2019

화력발전은 국내 발전량 중 가장 높은 비율을 차지하고 있으며, 그 중 석탄보일러 발전이 가장 높은 비율을 차지하고 있다. 석탄보일러는 석탄 연소 중 유해 물질 및 미세먼지가 발생하여 대기오염에 심각한 영향을 미친다. 이에 친 환경 석탄보일러로 유동층보일러가 도입 되었으며, 이는 유동매체를 활용하여 기존의 석탄보일러보다 약 1/10정도 적은 오염물질을 배출한다. 수냉벽튜브는 이 유동층보일러에서 중요한 역할을 하는 구조물로, 유동층보일러의 특성상 기존의 보일러보다 외벽손상이 심하다. 하지만 아직까지 이에 대한 정량적인 유지보수 기법이 없다. 원격장 와전류 탐상은 튜브형태의 내, 외벽 검사에 많이 사용되는 비파괴평가 기법으로, 비접촉이며 빠른 검사가 장점이다. 하지만 원격장 와전류 탐상은 본래 배관 내부에서 진행하는 검사이며, 수냉벽튜브는 특성상 내부 진입이 불가능하다. 이에 본 연구에서는 시뮬레이션을 활용해 유동층보일러 수냉벽튜브에 적합한 외부 원격장 와전류 탐상 센서에 대한 설계를 진행하고, 시뮬레이션을 수행하였으며, 기존 원격장 와전류 탐상과 유사한 신호를 얻음으로써 추후 실제 제작 될 원격장 와전류 탐상 센서에 대한 기준을 제시하였다.

• 설비공학논문집
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• 제24권3호
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• pp.281-287
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• 2012

The internal oxide scale of twelve superheater and reheater tubes were tested which were serviced for 30,000~120,000 hours in thermal power plants. The oxide scale was formed in three layers. The Cr-rich area was observed beneath the original metal surface. The hematite ($Fe_2O_3$) phase was formed on the outer surface. The intermediate layer was magnetite ($Fe_3O_4$). The thickness of Cr-rich layer was about half of the total scale. All layers grew during the operation hour of the plant. The thickness of thickest scale was 0.2mm in superheater tubes. This can increase the tube metal temperature about $7^{\circ}C$ more than initial state. $7^{\circ}C$ tube metal temperature can reduce tube life about 30%, but the boiler tube's design margin is big enough therefore it has been analyzed that it would not effect on the life span.

• 한국수소및신에너지학회논문집
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• 제21권5호
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• pp.452-459
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• 2010

This study is aimed to investigate changes of combustion characteristics and heat efficiency when syngas from gasification process using low-rank fuel such as waste and/or biomass is applied partially to an industrial boiler. An experimental study on syngas co-combustion was performed in a 0.7 MW (1 ton steam/hr) water tube boiler using heavy oil as a main fuel. Three kinds of syngas were used as an alternative fuel: mixture gas of pure carbon monoxide and hydrogen, syngas of low calorific value generated from an air-blown gasification process, and syngas of high calorific value produced from an oxygen-blown gasification process. Effects of co-combustion ratio (0~20%) for each syngas on flue gas composition were investigated through syngas injection through the nozzles installed in the side wall of the boiler and measuring $O_2$, $CO_2$, CO and NOx concentrations in the flue gas. When syngas co-combustion was applied, injected syngas was observed to be burned completely and NOx concentration was decreased because nitrogen-containing-heavy oil was partially replaced by the syngas. However, heat efficiency of the boiler was observed to be decreased due to inert compounds in the syngas and the more significant decrease was found when syngas of lower calorific value was used. However, the decrease of the efficiency was under 10% of the heat replacement by syngas.

• 한국안전학회지
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• 제24권2호
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• pp.17-22
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• 2009

Thermal stress and elastic creeping stress analysis was conducted by finite element method to simulate start-up process of a boiler header of 500MW standard fossil power plant. Start-up temperature and operating pressure history were simplified from the real field data and they were used for the thermal stress analysis. Two kinds of thermal stress analysis were considered. In the first case only temperature increase was considered and in the second case both of temperature and operating pressure histories were considered. In the first analysis peak stress was occurred during the temperature increase from the room temperature. Hence cracking or fracture may occur at the temperature far below the operating maximum temperature. In the results of the second analysis von Mises stress appeared to be higher after the second temperature increase. This is due to internal pressure increase not due to the thermal stress. When the stress components of radial(r), hoop($\theta$) and longitudinal(z) stress were investigated, compression hoop stress was occurred at inner surface of the stub tube when the temperature increased from room temperature to elevated temperature. Then it was changed to tension hoop stress and increased because of the operating pressure. It was expected that frequent start-up and shut-down operations could cause thermal fatigue damage and cracking at the stub tube hole in the header. Elastic-creeping analysis was also carried out to investigate the stress relaxation due to creep and stabilized stress after considerable elapsed time. The results could be used for assessing the creep damage and the residual life of the boiler header during the long-tenn service.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2009년도 추계학술대회 논문집
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• pp.533-534
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• 2009

• 동력기계공학회지
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• 제5권2호
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• pp.5-12
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• 2001