• 한국세라믹학회지
• /
• 제54권2호
• /
• pp.128-136
• /
• 2017

Fly ash from a circulating fluidized bed combustion boiler (CFBC fly ash) is very different in mineralogical composition, chemical composition, and morphology from coal ash from traditional pulverized fuel firing because of many differences in their combustion processes. The main minerals of CFBC fly ash are lime and anhydrous gypsum; however, due to the fuel type, the strength development of CFBC fly ash is affected by minor components of active $SiO_2$ and $Al_2O_3$. The initial hydration product of the circulating fluidized bed combustion fly ash (B CFBC ash) using petro coke as a fuel is Portlandite which becomes gypsum after 7 days. Due to the structural features of the portlandite and gypsum, the self-cementitious strength of B CFBC ash was low. While the hydration products of the circulating fluidized bed combustion fly ash (A CFBC ash) using bituminous coal as a fuel were initially portlandite and ettringite, after 7 days the hydration products were gypsum and C-S-H. Due to the structural features of ettringite and C-S-H, A CFBC ash showed a certain degree of self-cementitious strength.

• KEPCO Journal on Electric Power and Energy
• /
• 제8권2호
• /
• pp.97-101
• /
• 2022

In this study we investigated the gas to solid heat transfer of bubbling fluidized bed bottom ash cooler installed at the Donghae power plant in South Korea. Several different analyses are done through 1-D calculations and 3-D CFD simulation to predict the bottom ash exit temperatures when it exits the ash cooler. Three different cases are set up to have consideration of unburnt carbon in the bottom ash. Sensible heat comparison and heat transfer calculation between the fluidization air and the bottom ash are conducted and 3-D CFD analysis is done on three cases. We have obtained the results that the bottom ash with unburnt carbon is exiting the ash cooler, exceeding the targeted temperature from both 1-D calculation and 3-D CFD simulation.

• 한국건축시공학회지
• /
• 제21권2호
• /
• pp.141-148
• /
• 2021

본 연구에서는 산업부산물 중 순환유동층 연소방식과 미분탄 연소과정에서 발생되는 플라이애시와 고로슬래그 미분말을 치환한 시멘트 모르타르의 특성을 파악하였다. 연구 결과, 순환유동층 플라이애시 및 미분탄 플라이애시 혼합 사용 시 강도발현 뿐만 아니라 내구성 측면에서도 유리하게 나타난다. 순환유동층 플라이애시는 초기 반응성 향상에 기여하며, 미분탄 플라이애시는 포졸란 반응으로 장기 강도 발현에 관여하게 된다. 따라서 순환유동층 플라이애시와 미분탄 플라이애시의 혼합사용은 고로슬래그 미분말을 치환한 시멘트 모르타르의 상호 보완적인 요소로 작용함을 알 수 있다.

• 한국토양비료학회지
• /
• 제47권1호
• /
• pp.66-70
• /
• 2014

Bed-soils can be used to help plants to overcome unfavorable conditions of soils, especially hydraulic properties of soils. This study was conducted to evaluate the effect of organic and inorganic raw materials on saturated hydraulic conductivity ($K_s$) of bed-soils. Perlite and bottom ash, which are inorganic materials, increased more $K_s$ of bed-soils than coco peat, an organic material. However, vermiculite, an inorganic material, increased less than coco peat. Saturated hydraulic conductivity of bed-soil mixed with fine vermiculite ($0.14{\pm}0.02mh^{-1}$) was much lower than one containing coarse vermiculite ($0.85{\pm}0.21mh^{-1}$). Such effect was more apparent when pressure was added on bed-soils containing fine vermiculite ($0.07{\pm}0.01mh^{-1}$), probably reflecting the decrease in pore size with the expansion of vermiculite wetted. Compacting decreased more $K_s$ in the bed-soils containing coco peat or vermiculite than other mixtures. Those results suggest that perlite and bottom ash in bed-soils play an important role in improving saturated hydraulic conductivity but vermiculite in bed-soils may suppress the improvement of saturated hydraulic conductivity with the decrease of its size and with the increase of compacting pressure.

• 한국연소학회:학술대회논문집
• /
• 한국연소학회 2005년도 제31회 KOSCO SYMPOSIUM 논문집
• /
• pp.231-237
• /
• 2005

Interruption of good fluidization in a fluidized bed ash cooler(FBAC) for discharging bed materials such as sand or coal ash particles from the CFB combustor is frequently happened because of agglomeration of the particles in the bed. This unstable operation may, in the worst case, result in an unscheduled boiler shut down. In this study, we examined the operation problems of the FBAC of Tonghae CFB boiler and studied and introduced the simple detection and solution techniques with analyzing the mixing property and the occurrence of defluidization in a simulated fluidized bed ash cooler system (0.5m-H x 0.5m-W x 1.0m-L). The bridge of the large particles at the bed surface could be observed, and this caused to form the defluidization area at the entrance of the FBAC. The defluidization was affected not only by airflow rates but also by the particles discharging rates as well as particle size distribution in the FBAC. The local defluidization could be detected by analysis of the accumulated standard deviation error at a given period of time. Also, the regulation of the overall or local airflow rate made clearing up the local defluidization possible.

• 한국구조물진단유지관리공학회 논문집
• /
• 제22권5호
• /
• pp.119-126
• /
• 2018

최근 화력발전소에서는 순환유동층 연소방식의 발전소가 증가하는 추세이다. 순환유동층 보일러애시는 탈황 효과를 위해 석회석을 첨가함에 따라 애시 중에 포함되는 CaO, $SO_3$성분이 증가하여 일반적인 플라이애시 보다 free-CaO 함량이 높다. 또한 순환유동층 보일러애시는 기존의 플라이애시와 다르게 자기수경성 특성과, 높은 free-CaO함량에 의해 물과 만나면 높은 반응성을 갖는다. 본 연구는 순환유동층 보일러애시의 자기수경성 특성을 이용하여, 시멘트를 대체할 수 있는 비소성 결합재로써 활용 가능성에 대해 분석하였다. 순환유동층 보일러 애시의 함량에 따른 역학적 및 수화특성에 대해 검토하였다. 또한 석고의 종류 및 함유량에 따른 순환유동층 보일러애시 활용 비소성 결합재에 대한 압축강도 및 미세구조에 미치는 영향을 분석하였다.

• 한국환경과학회지
• /
• 제15권6호
• /
• pp.587-592
• /
• 2006

The advantage of CFBC(Circulating fluidized bed combustor) is that it can apply to various fuel sources including the lower rank fuel and remove SOx by means of direct supply of limestone to the combustor without additional desulfation facility. In this paper, we denote characteristics of fly and bed ash to reuse finer limestone usually abandoned(used spec[Coarse LS] 0.1mm under 25%, new spec[Fine LS] 0.1mm under 50%). According to the results, the chemical composition of fly ash was as follows; $SiO_2\;40.8%,\;Al_2O_3\;31.9%,\;CaO\;10.7%,\;K_2O\;4.46%$ in the case of coarse limestone and $SiO_2\;41.1%,\;Al_2O_3\;31.3%,\;CaO\;10.9%,\;K_2O\;4.66%$ in the case of fine limestone. The chemical composition of bed ash was as follows; $SiO_2\;54.2%,\;Al_2O_3\;33.1%,\;CaO\;1.56%,\;K_2O\;4.34%$ in the case of coarse limestone and $SiO_2\;53.8%,\;Al_2O_3\;32.6%,\;CaO\;2.21%,\;K_2O\;4.45%$ in the case of fine limestone. It showed that there was no significant change in chemical composition. And it is conformed that there was no significant change in particle size and shapes.

• Environmental Engineering Research
• /
• 제25권1호
• /
• pp.104-113
• /
• 2020

Adsorptive breakthrough modelling is essential for design of a sorption packed bed. In this work, breakthrough modelling of the furfural uptake in bagasse fly ash (BFA) packed bed has been performed. Effect of various parameters like bed height (Z = 15-60 cm), flow rate (Q = 0.02-0.04 L/min) and initial furfural concentration (C_o = 50-200 mg/L) on the breakthrough curve of furfural sorption in a BFA packed bed have been studied. Enhanced breakthrough performance was observed for the higher value of Z, and lower values of C_o and Q. For C_o = 100 mg/L, packed bed operated at Q = 0.03 L/min and Z = 60 cm was found to have lowest adsorbent utilization rate of 5.61 g/L with highest breakthrough volume of 14.67 L. Bed depth service time and Thomas models well represented the experimental data points under all experimental conditions. It can be concluded that BFA can be utilized efficiently in continuous system for the removal of furfural. Overall, more than 99% of furfural was adsorbed in BFA packed bed at experimental conditions.

• 한국세라믹학회지
• /
• 제54권5호
• /
• pp.380-387
• /
• 2017

In this study, unstable CaO was converted into a stable Ca compound by using carbonation in a circulating fluidized bed boiler of fly ash to confirm material usability as cement admixture; also undertaken was carbonation test and mortar to examine chemical and physical change by measuring absorption rate and compressive strength. To investigate the chemical properties of circulating fluidized bed boiler fly ash, XRD and TG-DTA were used to determine how the properties of the reaction product change quantitatively during carbonation. In order to stabilize CaO, carbonation of CaO is considered to be the most desirable process. This is because $CaCO_3$, which is a Ca compound, was produced by carbonate reaction of unstable CaO, and decrease of the absorption rate and improvement of the compressive strength were observed when the carbonated fly ash was replaced with cement.

• 분석과학
• /
• 제13권1호
• /
• pp.5-11
• /
• 2000

시운전중인 국내 최대 규모의 유동층 보일러에서 발생한 크링커의 생성원인을 규명하기 위해 현장에서 크링커 및 사용중인 무연탄의 회, 모래, 석회석을 채취하였다. 발전소에서 시행중인 운전조건을 고려하여 이들에 대한 비율별 및 온도 조건 변화에 따른 각 시료의 성분 분석, 표면형상 관찰, 열특성 분석 및 결정구조 분석을 실시하였다. 크링커는 횐 색과 검은 색 및 갈색 부분으로 되어 있었으며 이를 색깔별로 크게 흰 색 및 검은 색으로 구분하여 실험을 하였다. 그 결과 검은 색은 모래, 흰 색은 무연탄 회에 보다 유사한 특성을 지녔고, 온도에 따른 실험 결과, 모래의 소결온도는 $1,200^{\circ}C$ 이상의 고온인 반면에 모래에 석회석을 혼합할 경우, 소결온도가 낮아짐을 알 수 있었다. 따라서 크링커의 생성원인은 유동층 보일러 내에 고온부가 형성되어 모래와 석회석이 용융 또는 소결된 상태에 무연탄회가 부착되어 형성된 것으로 판단되었다.