Jae Ou Chae

Decomposition of volatile organic compounds in plasma-catalytic system

A plasma-catalytic combined reactor system was used to decompose volatile organic compounds. Metal oxide catalysts, as well as Pt-based catalyst, were employed in the studies. The plasma treatment alone leads to the formation of high concentration of byproducts. A Pt-based catalyst, combined with plasma reactor, was helpful in minimizing the byproduct formation. The plasma reactor significantly enhances the catalytic performance. Plasma reactor, combined with Pt-based catalyst, removed more than 90% of toluene. The Pt-based catalyst completely removed the CO produced by plasma reactor. In order to determine the mechanism of the plasma treatment, the plasma reactor was replaced by ozone reactor and the results were compared with plasma-catalytic reactor. It was found that ozone plays a significant role in enhancing the catalytic activity.

Experimental study for indoor air control by plasma-catalyst hybrid system

This paper describes the experimental study of indoor air control by the plasma catalytic hybrid system. The basic characteristics of the ammonia and toluene decomposition were investigated as a model of the deodorizing process. It was found that the application of plasma discharge without catalyst can be dangerous for humans due to the ozone and carbon monoxide (CO) formation. The catalyst, which was applied to the plasma unit, decreases the ozone concentration more than ten times and the CO amount up to five times. Catalyst decreases a little bit the ions generated by the discharge but the catalyst application in the plasma treatment was recognized as necessary. The plasma catalytic hybrid system can be a promising method of the indoor air ionization and deodorization.

Removal of NOx and SO2 from Air Excited by Streamer Corona: Experimental Results and Modeling

The effect of pulse corona discharge on NOx and SO2 concentrations in air has been studied. The initial concentrations and ammonia addition have been shown to influence the removal efficiency. An SO2 removal efficiency of 96% and an NO removal efficiency of 70% in pulse corona have been achieved with ammonia addition, for initial SO2 and NO concentrations of 480 ppm and 230 ppm, respectively. A numerical model for NO and SO2 conversion in homogeneous gas flow has been developed. The spatial nonuniformity of gas parameters associated with the existence of many streamer channels in a discharge chamber is taken into account. A comparison between experiments and modeling shows that SO2 removal is mainly determined by OH and O3-. NO conversion is achieved the reactions of O3, OH and N.

A Study of Volatile Organic Compounds Decomposition with the Use of Non-Thermal Plasma

Non-thermal plasma processing is an effective method to decompose diluted VOC contaminants in manufacturing rooms for the electronic industry. In this paper, two different discharge-type laboratory scale reactors (Double Dielectric Barrier Discharge and Packed-Bed Discharge) that generate non-thermal plasma have been developed and the decomposition tests were conducted. The tested VOC was Benzene, Toluene, Xylene, P-cumene, Diethylether and Dichlormethane. It was found from the experimental results for the present reactors that Benzene oxidization required higher energy than the other aromatic hydrocarbons with side branches. The decomposition efficiency was high for Cumene and Xylene (two methyl-side groups) and low for Toluene (one methyl group) and Diethylether. One of the frequently used solvents in semiconductor industry, Dichlormethane which can destroy atmospheric ozone layer, could be decomposed in the Double Dielectric Barrier Discharge with minimum power consumption and the DDBD reactor had a little higher decomposition efficiency than the Packed-Bed reactor.

EFFECT OF TWO-STAGE COMBUSTION ON NOX EMISSIONS IN PULVERIZED COAL COMBUSTION

Abstract The effects of NO reduction by two-stage combustion in a pilot scale combustor have been investigated using propane gas flames loaded by pulverized coal particles with a nitrogen content of 1.3%. The secondary air is radially injected into the combustion chamber through four injection points. The combustion air is divided into primary and secondary stages. In the primary stage partial combustion is carried out with a much lower air ratio than that of normal combustion. Afterwards secondary air is supplied to complete the combustion. Experiments have been carried out using the primary to secondary air ratio, the total air ratio, the secondary air injection points and the coal size (and size distribution). The reduction of NO emission is barely influenced by the total air ratio. When the secondary air is injected where there is a reducing atmosphere, NO emission is reduced effectively. The results of NO reduction in fine coal combustion using a staged combustion are better than those from coarse coal combustion.

Oyster Shell Recycling and Bone Waste Treatment Using Plasma Pyrolysis

Investigations on the recycling of oyster shells and bone waste treatment using the plasma pyrolysis technique are presented in this paper. A arc based plasma torch operated at 25 kW was employed for the experiments. Fresh oyster shells were recycled using the plasma torch to convert them to a useful product such as CaO. Bone waste was treated to remove the infectious organic part and to vitrify the inorganic part. The time required for treatment in both cases was significantly short. Significant reduction in the weight of the samples was observed in both cases.

A Study on Combustion Characteristics of Superadiabatic Combustor in Porous Media

Because of the energy resource exhaustion, the aggravating environmental air pollution, the smoke phenomena and so on, the recent trends and targets in designing combustor are reduction of pollutant emissions and improvement of combustor efficiency. Therefore many combustion methods and emission control technologies have been proposed by many researchers through numerical and experimental analyses, One of the most available and effective combustion methods is the excess enthalpy combustion, so called, the superadiabatic combustion. In this study, the superadiabatic combustion with the reciprocating flow in a porous media has been investigated with the variation of equivalence ratio, flow velocity and reciprocating cycle time. In this system, the flow direction is reversed regularly by the solenoid valves. The results of this study show that the maximum gas temperature is remarkably higher than the theoretical adiabatic flame temperature and the emission characteristic is very excellent. The analyses reveal several attractive characteristics of the flame and the proposed idea is promising to burn mixtures of low heat content in a reciprocating type combustor. This combustor can be applied to the elimination of unburned compound, with more intensive and continuous study.

SynGas Production from Organic Waste Using Non-Thermal-Pulsed Discharge

Abstract The purpose of this study was to develop a technology that can convert biogas to synthesis gas (SynGas), a low-emission substituted energy, using a non-thermal-pulsed plasma method. To investigate the characteristics of Syn-Gas production from simulated biogas, the reforming characteristics in relation to variations in pulse frequency, biogas component ratio (C3H8/CO2), vapor flow ratio (H2O/total flow rate [TFR]), biogas velocity, and pulse power were studied. A maximum conversion rate of 49.1% was achieved for the biogas when the above parameters were 500 Hz, 1.5, 0.52, 0.32 m/sec, and 657 W, respectively. Under the above conditions, the dry basis mole fractions of the SynGas were as follows: H2 = 0.645,CH4 = 0.081, C2H2 = 0.067, C3H6 = 0.049, CO = 0.008 and C2H4 = 0.004. The ratio of hydrogen to the other intermediates in the SynGas (H2/ITMs) was 3.1.

A Study on the Design and Application of Optimized Solenoid for Diesel Unit Injector

With the Environmental Protection Agency (EPA) regulating the amount of NOx, Particulate, HC and CO at all driving conditions, emission standards for diesel engines are becoming more stringent than ever. To meet future emission regulations, researchers have proposed two solutions based on injection control, the common-rail type injection system, and the unit injection system. Most researchers agree that the electronically controlled unit injector, which realizes high injection pressure and precise control of SOI (Start Of Injection) and injection quantity, has an advantage in meeting future emission regulations. In order to control the start and end of injection, each unit injector contains a time-controlled high speed solenoid valve. Thus, the fuel injection quantity is determined by the time interval between closing and opening of the solenoid valve. This study introduces a method for the design of the solenoid which is installed in the unit injector. It is shown that there are certain significant parameters to be optimized to improve solenoid performance: inductance, stroke, input voltage, coil resistance, load and switching time.

Comparisons of predicted and measured results on performance and emission of engine effected by intake air dilution and supercharging

An experimental study was conducted on a single cylinder direct injection diesel engine to investigate the effects of diluting intake air, with different gases and increasing intake pressure on combustion process and exhaust emissions. The intake O2 concentration is changed from 15% to 21% by diluting intake air with different gases (CO2, Ar, N2), and the intake pressure is changed from one to two bar by a screw compressor. A modified program for calculating heat release rate, is used to study the characteristics of combustion and exhaust emissions in detail. The main results show that the addition of either CO2 or Ar to the intake air increases the ignition delay. The variations of ignition delay with CO2 are much larger than those of ignition delay with Ar for the same O2 concentration. The emission of NOx decreases with the decrease of O2 concentration and the smoke level is lower with the addition of the CO2 than with that of Ar. As the intake pressure is increased, the ignition delay is shortened. Furthermore the high intake air pressure enhances the air-fuel mixing and diffusion combustion, and reduces the premixed combustion, so that NOx emission is decreased without increasing smoke emissions. The addition of CO2 at high intake pressure, drastically reduces NOx emissions and smoke emission simultaneously at a high load condition, and the addition of CO2 reduces NOx emissions without affecting the smoke emissions substantially at a low load condition. A zero-dimensional combustion simulation program incorporated with the present heat release correlation and ignition delay correlation is used to predict ignition delay, cylinder pressure and engine power. The results show that the correlations are likely to be adequate for the engine operating under diluted intake air and various intake pressure.