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Circulating fluidized bed combustion (CFBC) power generation technology is known to efficiently reduce the emission of air pollutants, such as SO2 and NO2, from coal combustion. however, CFBC coal ash contains high contents of free CaO, making it difficult to recycle. This research has been conducted to find ways to use the self-hardening property of CFBC coal ash, one of its inherent characteristics. As part of these efforts, the present study intended to investigate the properties and desulfurization efficiency of Ca-based desulfurization sorbents using CFBC fly-ash as a binder. Limestone powder was mixed with CFBC fly-ash and Ca(OH)2 to fabricate desulfurization sorbents, and it generated hydrate of cement, including portlandite, ettringite, and calcium silicate, etc. The compressive strength of the desulfurization absorbent prepared by CFBC fly ash and Ca(OH)2 was 72&ndash, 92% that of the desulfurized absorbent prepared by using general cement as a binder. These absorbents were then compared in terms of desulfurization efficiency using a high-temperature fluidized bed reactor. It was confirmed that the desulfurization absorbents fabricated using CFBC fly-ash as a binder achieved the best performance in terms of absorption time, which reflects the time taken for them to remove over 90% of high-concentration SO2 gas, and the conversion ratio, which refers to the ratio of CaO turning into CaSO4.

Natural hydraulic lime (NHL) is produced by burning a form of low-grade limestone containing silica and alumina which, above certain temperatures, combine with calcium oxide. The resulting silicates and aluminates impart hydraulic properties to the product. This study aims to determine the calcined characteristics of NHL using domestic low-grade limestone with maximized hydraulic properties. Six types of low-grade limestone containing SiO2 were selected and experiments were carried out with different burning temperatures and holding times. The burning temperature and holding time as the most suitable burning conditions were 1,200oC to 1,300oC and 3 to 7 h, respectively, for the manufacturing of NHL from domestic low-grade limestone. These results demonstrate the feasibility of NHL using domestic low-grade limestone to produce NHL.

This study investigated a utilization technology of light burned dolomite. light burned dolomite () generated in furnace (steel manufacturer) is an alternative to quick lime. Using light burned dolomite has an effect on reducing the consumption of fluorite slag MgO concentration in supersaturated solution by prolonging the life of softening effect. Armophous MgO, not containing periclase is formed by firing dolomite under . It has larger surface area and higher reactivity than periclase, and also shows better expansion effect than quicklime. Due to those effects, therefore, armophous MgO produced from light burned dolomite is used as an alternative expansion agent in mortar. In the experiment, characteristics of light burned dolomite were compared to those of existing expansion agents such as anhydrite and quicklime. Then, each expansion and shrinkage rates were measured over a period of about 3 months in both of 1m Jis mold at labscale and apartment mortar flooring at field scale. In the result, it was observed that light burned dolomite in mortar flooring more compensates for the expansion and shrinkage rates than the existing expansion agents, showing low expansion rate of below 0.05% and also decreases the crack.

The effect of alkali activator and fineness of slag on the physical properties of blast furnace slag cement was investigated. Na2SO4 was used as an alkali activator in this study. Blast furnace slag cement was prepared from mixture of blast furnace slag, ordinary Portland cement, and anhydride gypsum. The fluidity and the compressive strength according to each mixture ratio of them were analyzed by using statistical analysis in order to discover the parameters influencing the fluidity and compressive strength. The results showed that the hydration of blast furnace slag took place by addition of Na2SO4, and ettringite with column-crystalline was created as main hydration product of blast furnace slag. And it is found that the compressive strength of blast furnace slag cement tends to increase as ordinary Portland cement content is higher until 3 days. However, it is also known that the compressive strength tends to increase with the increase of higher blast furnace slag content, along with increase in the OPC on 28 days. As a result of this analysis, it is considered that the ordinary Portland cement content influences the initial compressive strength of blast furnace slag cement, and that in later days is greatly influenced by slag content.

This study has been carried out to use the waste sludges generated at Pohang Iron & Steel Co. Ltd. (POSCO) as the raw materials of Ordinary Portland Cement (OPC). The burnability index of the raw mixture and the hydration characteristics and compressive strength of clinker have been examined. The waste sludges were mainly composed of CaO, SiO 2 , Al 2 O 3 , and Fe 2 O 3 , the main component of OPC. The Burnability index of mixture was improved, according to the replacement content of POSCO sludge increase. POSCO sludge can be used as a raw material for cement because the state of mineral development and property of clinker produced from POSCO sludge are similar to the plain. Therefore, POSCO sludges can be used as the source materials of iron and calcium oxide.