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Hwang D.J.,Korea Institute of Limestone and Advanced Materials | Ryu J.Y.,Ulimeng Co. | Yu Y.H.,Korea Institute of Limestone and Advanced Materials | Cho K.H.,Korea Institute of Limestone and Advanced Materials | And 3 more authors.
Journal of Industrial and Engineering Chemistry | Year: 2014

In the conventional kiln, mega-crystalline calcite (m-CC) breaks apart easily during calcinations, and cannot be easily converted to CaO due to that it requiring a lot of heat. In this study, m-CC was calcined to CaO of around 1mm using the rotary microwave kiln. Furthermore, CaCO3 was produced by the carbonation process and hydrothermal process, and the form of CaCO3 was characterized. Calcination of m-CC using the rotary microwave kiln resulted in CaO (97. wt%) of relatively fine size. CaCO3 of colloidal-shaped and 6μm in size could be prepared by applying the carbonation process to Ca(OH)2 using a bubble reactor at 25°C. As the carbonation temperature increased from 25 to 80°C, the shape of prepared CaCO3 changed from a colloidal-type to spindle-type of 1μm due to self-assembly. Also, hexagonal-shaped aragonite could be prepared by the hydrothermal process with the supersaturated Ca(HCO3)2 solutions. © 2013 The Korean Society of Industrial and Engineering Chemistry. Source


Hwang D.J.,Korea Institute of Limestone and Advanced Materials | Hwang D.J.,Chungbuk National University | Ryu J.Y.,Ulimeng Co. | Park J.H.,Ulimeng Co. | And 5 more authors.
Journal of Industrial and Engineering Chemistry | Year: 2012

Mega-crystalline calcite (m-CC) breaks apart easily during calcination, and is converted to CaO with difficulty due to its thermal decomposing characteristics that necessitate large heat consumption. To overcome this problem, m-CC was calcined using either a microwave furnace or an electric furnace for 15. min and 30. min at 950. °C.Following 15 and 30min calcinations of m-CC, almost all (96.6wt%) and all (100%) of the calcite was calcined to CaO in the microwave furnace, compared to only 11.3wt% and 11.0wt% in the electric furnace, respectively. The excellent conversion rate in the microwave furnace was attributed to its internal heating method. Therefore, calcination of m-CC to CaO was optimized in the microwave furnace at 950°C for 30min. The results demonstrated the potential for the microwave furnace calcination of m-CC, previously known as a non-calcinable material, as a material source for CaO, Ca(OH) 2 and CaCO 3. © 2012 The Korean Society of Industrial and Engineering Chemistry. Source


Hwang D.J.,Korea Institute of Limestone and Advanced Materials | Hwang D.J.,Chungbuk National University | Ryu J.Y.,Ulimeng Co. | Park J.H.,Ulimeng Co. | And 6 more authors.
Journal of Industrial and Engineering Chemistry | Year: 2013

Mega-crystalline calcite (m-CC) breaks apart easily during calcination, and cannot be easily converted to CaO due to its characteristic that requires massive heat consumption. To solve this problem, the calcination characteristics were compared using electrical furnace (EF) and batch type microwave kiln (BM). After hydrating the manufactured CaO, Ca(OH)2 was produced, and through the carbonation process, CaCO3 was synthesized. The results of the XRD pattern of CaO that was formed through calcinations indicated that decarbonation reaction occurred as 98.2wt.% by EF for 240min, and 97.8wt.% by BM for 30min at the same temperature of 950°C. Hydration results revealed that CaO by EF was high-reactive whereas CaO by BM was medium-reactive. CaCO3 was synthesized through the carbonation process. At 25°C, in both cases, colloidal-shaped CaCO3 was found, and the more spindle-shaped CaCO3 by cubic-shaped self assembly was synthesized at higher temperatures. However, in case of EF, Ca(OH)2 existed in products. © 2013 The Korean Society of Industrial and Engineering Chemistry. Source

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