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High-Efficiency Gasification of Low-Grade Coal by Microwave Steam Plasma
Uhm, Han Sup,Na, Young Ho,Hong, Yong Cheol,Shin, Dong Hun,Cho, Chang Hyun,Park, Young Ki American Chemical Society 2014 ENERGY AND FUELS Vol.28 No.7
<P>High-power steam plasma for heating the coal powders were developed, where the magnetron power at 915 MHz was available up to 75 kW. The steam plasma itself is an impedance load, which depends on physical conditions, including the microwave power. By monitoring the minimum reflected power, the optimum injection rate of the steam and the corresponding reflected power ratio in terms of the microwave power was found, showing that most of the microwave power is absorbed by the torch plasma with a minimal reflected wave-power of less than a few percent, once the plasma torch was ignited. Indonesian brown coal with high ash content is gasified by two microwave steam plasmas heating up the gas temperature in a reaction chamber of 1145 L in a swirl-type gasifier. With additional heating of synthetic gas from a partial oxidation, the inner temperature of the gasifier can reach to 1700 °C. The carbon conversion rate at the average chamber temperature of 1640 °C is almost 100%, ensuring a complete gasification of carbon in a low-grade coal. The cold gas efficiency is 84%, very high in a relatively small gasifier like the experiment here. The total calorific power of the synthetic gas is 500 kW. Therefore, this gasification system may serve as a moderately sized power plant due to its compactness and lightweight nature. A power plant utilizing low-grade coal would be useful in rural or sparsely populated areas without access to a national power grid.</P>
Plasma Burner Enlarged by Coal Injection Into Microwave Plasma
Yong Cheol Hong,Sang Ju Lee,Dong Hun Shin,Ye Jin Kim,Yong Uck Shin,Bong Ju Lee,Han Sup Uhm IEEE 2011 IEEE transactions on plasma science Vol.39 No.9
<P>An apparatus for generating a flame and, more particularly, a microwave plasma burner for obtaining a large-volume high-temperature plasma flame are designed using a coal injection into the microwave plasma. The plasma burner was mainly composed of a coal feeder and a stainless steel tube, as the exit for the plasma flame, in series with a 2.45-GHz microwave plasma torch, in which a mixture of air and oxygen could immediately burn the powdered coal, with the help of a high atomic-oxygen density and the high-temperature plasma. In order to examine the possibility of implementing microwave plasma burners at power plants, a feasibility test was conducted using the coal plasma burner, with information obtained on the optical emission lines of the plasma torch, the coal plasma flames, the temperature profile along the axis of the flame, gas compositions at different coal-injection rates, etc.</P>
Band gap narrowing of TiO<sub>2</sub> by nitrogen doping in atmospheric microwave plasma
Hong, Yong Cheol,Bang, Chan Uk,Shin, Dong Hun,Uhm, Han Sup Elsevier 2005 Chemical physics letters Vol.413 No.4
<P><B>Abstract</B></P><P>Nitrogen (N)-doped titanium dioxide (TiO<SUB>2</SUB>) particles of nanometric size are directly synthesized in an atmospheric microwave plasma-torch using gas-phase titanium tetrachloride (TiCl<SUB>4</SUB>). The absorption edge of the TiO<SUB>2−<I>x</I></SUB>N<SUB><I>x</I></SUB> powders shifts from 365 to 500nm in UV–visible spectrum, as the content <I>x</I> of nitrogen in titanium dioxide powders increases from <I>x</I>=zero. From the results of the XRD, XPS, and UV–visible data, incorporation of N into the O site of TiO<SUB>2</SUB> was enhanced in a mixture of N<SUB>2</SUB> and O<SUB>2</SUB> by an atmospheric microwave plasma torch, contributing to the band gap narrowing.</P>
Electrodelss Plasma Torch Powered by Microwave and Its Applications
홍용철(Hong, Yong-Cheol),전형원(Jun, Hyung-Won),노태협(Lho, Tai-Hyeop),이봉주(Lee, Bong-Ju),엄환섭(Uhm, Han-Sup) 한국신재생에너지학회 2009 한국신재생에너지학회 학술대회논문집 Vol.2009 No.06
A microwave plasma torch at the atmospheric pressure by making use of magnetrons operated at the 2.45 GHz and used in a home microwave oven has been developed. This electrodeless torch can be used to various areas, including industrial, environmental and military applications. Although the microwave plasma torch has many applications, we in the present work focused on the microwave plasma torch operated in pure steam and several applications, which may be used in future and right now. For example, a high-temperature steam microwave plasma torch may have a potential application of the hydrocarbon fuel reforming at one atmospheric pressure. Moreover, the radicals including hydrogen, oxygen and hydroxide molecules are abundantly available in the steam torch, dramatically enhancing the reaction speed. Also, the microwave plasma torch can be used as a high-temperature, large-volume plasma burner by injecting hydrocarbon fuels in gas, liquid, and solid into the plasma flame. Lastly, we briefly report an underway research, which is remediation of soils contaminated with oils, volatile organic compounds, heavy metals, etc.