• Journal of the Korean Ceramic Society
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• v.54 no.5
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• pp.380-387
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• 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.

• Analytical Science and Technology
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• v.13 no.1
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• pp.5-11
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• 2000

During the commissioning period in Tonghae thermal power plant which is the largest circulating fluidized bed boiler in the nation, a considerable amount of clinker was formed at FBAC and seal pot. Various attempts, for example, concentration analysis, surface phenomena, thermal characterization, and crystal structure of ash, bed sand, limestone, clinker, and mixture of each gradients have been studied to identify the causes of clinker formed in circulating fluidized bed boiler. As the results, the characterization of black particles in which separated from the clinker is more similar to that of bed sand, on the other hand, white particles are more similar to ash. In addition, the sintering temperature of sand is over $1,200^{\circ}C$ and this temperature was decreased as limestone is added to bed material. The cause of clinker was proved that ash was sticked to molten or sintered sand or limestone in the area of high temperature in the circulating system.

• Journal of the Korean Ceramic Society
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• v.54 no.2
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• pp.128-136
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• 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.

• Applied Chemistry for Engineering
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• v.28 no.1
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• pp.29-34
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• 2017

This study provides the identification of corrosion cause substances in super heater tube from a commercial scale circulating fluidized bed boiler. Electricity is produced by the combustion of biomass mainly wood waste. The biomass, super heater tube, super heater tube ash, and boiler ash were collected and components associated with corrosion were analyzed. A large amount of oxygen-containing material was found due to oxidation. The chlorine content was analyzed as 6.1% and 4.3% in super heater tube ash and boiler ash respectively which were approximately 20 and 14 times higher than those of designed values. Also, alkaline metal contents (K, Na, Ca) were very high in ash samples collected from super heater tube and boiler. The tendency of slagging and fouling was predicted based on X-Ray Fluorescence (XRF) results. Basicity that can lead to slagging was estimated as 3.62 and 2.72 in super heater tube and boiler ash, respectively. Slagging would occur with ash content when considering the designed value as 0.35.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.2
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• pp.319-325
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• 2018

Pot-holes are steadily increasing due to abnormal climate such as heavy rainfall and frequent snowfall. Pot-hole related to traffic accidents cause injuries, car damage and distress of road facilities. To reduce pot-holes, the use of an anti-stripping agent is mandatorily recommended to asphalt concrete mixture. Hydrated lime is commonly used as anti-stripping agent due to the convenience and economics. Byproduct ash from circulating fluidized bed boiler was reviewed as an anti stripping agent. According to the test results, the byproduct ash is satisfied with TSR specification using 1% to 3% by weight of the asphalt mixture. The byproduct ash was examined under various condition changes of aggregate and asphalt concrete mixture considering quality movement. According to the results, using the byproduct ash was measured average 0.87 of TSR and coverage rates of 60% after rolling bottle test. Test results also revealed that the byproduct ash showed stable performance. Using the byproduct ash to decrease pot-hole in asphalt concrete pavement is suitable for demonstrating stable performance as anti-stripping agent.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.5
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• pp.119-126
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• 2018

Recently, the production of circulating fluidized bed combustion ash has been increased in thermal power plants. The addition of limestone for the desulfurizing effect of circulating fluidized bed boiler ash increases the content of CaO and $SO_3$ contained in ash, which is higher than the free fly ash in general fly ash. Unlike conventional fly ash, the circulating fluidized bed combustion ash has a high reactivity when it comes into contact with water due to its hydraulic properties and high free-CaO content. The aim of this study is to investigate the possibility of non-sintered binder by using self-cementing properties of circulating fluidized bed combustion ash. The mechanical and hydration characteristics were investigated according to the content of CFBC ash. In addition, the effects of gymsum type and content on the compressive strength and micro-structure of non-sintered binder pastes.

• Plant Journal
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• v.6 no.2
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• pp.70-77
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• 2010

This study investigated the characteristics of co-combustion of mixed anthracite (domestic and Vietnam) and bituminous coal (Sonoma, Australia) at circulating fluidized bed boiler in Donghae thermal power plant when mixing ratio of bituminous coal is variable. Co-combustion of bituminous coal contributes to improvement in general combustion characteristics such as moderately retaining temperature of furnace and recycle loop, reducing unburned carbon powder, and reducing discharge concentration of NOx and limestone supply owing to improvement in anthracite combustibility as the mixing ratio was increased. However, bed materials were needed to be added externally when the mixing ratio exceeded 40% because of reduction in generating bed materials based on reduction in ash production. When co-combustion was conducted in the section of 40 to 60% in the mixing ratio while the supplied particles of bituminous coal was increased from 6 mm to 10 mm, continuous operation was shown to be possible with upper differential pressure of 100 mmH2O (0.98 kPa) and more without addition of bed materials for the co-combustion of mixed anthracite and bituminous coal (to 50% or less of the ratio) and that of domestic coal and bituminous coal (to 60% of the ratio).

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.11a
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• pp.225-226
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• 2017

Recently, there has been a growing interest in the development of non-sintered binder to reduce CO2 emissions from the cement clinker manufacturing process and a number of studies have been conducted on fly ashes as an industrial by-product. However, in order to utilize fly ashes as a non-sintered binder, it is necessary to solve problems such as safety issues and economical efficiency due to use of an alkali activator. This study evaluates the material properties and compressive strength characteristics of three types of circulating fluidized bed boiler ashes. As a result, it was confirmed that the characteristics of each binder vary depending on the location of the power plant and the types of raw materials. In addition, it has been confirmed that the fluidized bed boiler ash shows a high compressive strength and can be used sufficiently as an non-sintered binder.

• Journal of the Korean Society of Combustion
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• v.8 no.2
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• pp.34-40
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• 2003

Analyses for concentration, surface phenomena, and crystal structure were performed to identify the causes of clinker formation in three type of pulverized coal fired boilers. Some clinkers had partially molten surface and more CaO and $Fe_2O_3$ as compared with fly ash, and the major crystalline phases identified in the clinker were mullite and quartz. Clinkers were formed in high temperature zone of the boiler according to the identification of mullite by XRD. Free $SiO_2$ in sand combined with K, Na and Ca in limestone served as a fluxing agent to form clinkers in a circulating bed boiler.

• Journal of Environmental Science International
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• v.15 no.6
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• pp.587-592
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• 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.