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Busan, South Korea

Lee C.,Pusan National University | Lee B.,Pusan National University | Kim G.,Pusan Clean Coal Center | Jeon C.,Pusan National University | And 2 more authors.
Thermochimica Acta | Year: 2011

A one-dimensional model that describes diffusion and advection process has been developed. The approximate solution to the nonlinear equations has been obtained analytically with an iterative method. A two-dimensional numerical solution with computational fluid dynamics (CFD) software is also derived for a two-dimensional crucible around which the convective and diffusive flows are more precisely presented. The results showed that as long as both heat and oxygen diffusion processes are considered at a time, the one-dimensional solution could provide as accurate a result as that obtained by using the two-dimensional solution evaluated in terms of temperature, but not in terms of the oxygen content. The weight and the geometry of the soot bed significantly affect the distribution of temperature and oxygen content that warrants the use of two-dimensional model because a two-dimensional character such as a buoyant upward flow from the relatively hot bed is predominant. © 2010 Elsevier B.V. All rights reserved. Source


An K.-J.,Pusan National University | Lee B.-H.,Pusan National University | Kim S.-I.,Pusan National University | Kim M.-C.,Pusan Clean Coal Center | And 2 more authors.
Transactions of the Korean Society of Mechanical Engineers, B | Year: 2013

The char oxidation characteristics of high ash coal were experimentally investigated at several temperatures (from 900 to 1300°C) for 4 types of coals (Gunvor, Glencore, Noble, and ECM) under atmospheric pressure in a drop tube furnace (DTF). The char reaction rate was calculated from the exhaust gas concentrations (CO and CO2) using FTIR, and the particle temperature was measured using the two-color method. In addition, the activation energy and preexponential factor for high ash coal char were calculated based on the Arrhenius equation. The results show that as the ash content increases, the particle temperature and area reactivity decreases. This is because in high ash coal, the large heat capacity of the ash, ash vaporization, and relatively low fixed carbon content of ash suppress combustibility during char oxidation. As a result, the higher ash content of coal leads to high activation energy. © 2013 The Korean Society of Mechanical Engineers. Source


Hwang M.Y.,Pusan National University | Jeon C.H.,Pusan National University | Song J.H.,Pusan National University | Kim G.-B.,Pusan Clean Coal Center | Kim S.M.,Pusan Clean Coal Center
Transactions of the Korean Society of Mechanical Engineers, B | Year: 2011

In thermal power generation companies, the recycling of refined ash (LOI < 6%) obtained from a PC-firing furnace is beneficial for the companies, e.g., it can be used for making lightweight aggregates. However, ash having a high LOI, which cannot be reused, is still buried in the ground. To obtain refined ash, the re-burning of high-LOI ash (LOI > 6%) in a PC-firing furnace can be an alternative. In this study, a numerical analysis was performed to demonstrate the effects of ash re-burning. An experimental constant value was decided by TGA (thermo-gravimetric analysis), and a DTF (drop-tube furnace) was used in the experiment for calculating the combustion of ash. On the basis of the trajectory of the moving particles of coal and ash, it was concluded that supplying ash near the burner, which is located high above the ground, is appropriate. On the basis of numerical results, it was concluded that an ash supply rate of 6 ton/h is suitable for combustion, without affecting the PC-firing boiler. © 2011 The Korean Society of Mechanical Engineers. Source


Kim S.-I.,Pusan National University | Lee B.-H.,Pusan Clean Coal Center | An K.-J.,Pusan National University | Kim M.-C.,Southern Company | And 2 more authors.
Transactions of the Korean Society of Mechanical Engineers, B | Year: 2014

Four coal sources that had different ash contents were evaluated in a drop tube furnace (DTF). Combustion experiments were conducted by using several sources with different particle sizes and excess air ratios under air-staging conditions to determine the optimized combustion conditions of high-ash coal, with an emphasis on the combustion efficiency and NOx emissions. The results show that the higher ash content results in a large amount of carbon remaining unburned, and that this effect is dominant when the largest particle size is used. Furthermore, the ash content of coal does affect the Char-NOx concentration, which decreases with the particle size. The results of this study suggest that an air-staged system can be useful to reduce the NOx emissions of high-ash coal and that control of the air stoichiometric ratio of the primary combustion zone (SR1) is effective for reducing NOx emissions, especially by considering unburned carbon contents. © 2014 The Korean Society of Mechanical Engineers. Source

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