플라즈마 개질에 의한 고농도 수소생산

Abstract

Renewable energy and environmental pollutions are becoming increasingly more importance due to the rising use of fossil fuels and global warming. With the consequent strengthening focus on developing alternative and clean energy sources, research attention is increasing on the efficient use syngas or hydrogen as an environment-friendly, alternative source of biomass. Ordinary, fuel reforming methods for syngas production are steam reforming, CO2 reforming and Partial oxidation reforming in the view of reaction aspect, and others. However, above methods are technological limitations and economical factors to be use alone for reforming. Plasma reforming technology is considered to be a way with the potential to overcome such weak points. Because plasma is high in energy and can transmit energy to other materials easily, it has suitable characteristics to react easily with low-reactant mixtures. Therefore, it is more effective to combine between plasma reforming and above other existing technologies. Plasma is classified as thermal or non-thermal according to the electricity density and temperature. High temperature plasma, which is equilibrium thermodynamically, has the characteristic of high ionization by higher energy. This has the merit of good reaction control and conversion rate, but has the demerit of high power consumption. Low temperature plasma, which is non-equilibrium, has the characteristic of low ionization and is therefore applied widely in various fields, because it is obtained easily by discharging gas in the low or even atmospheric pressure state. Although the non-thermal plasma reforming process is still in its development stage, many results proving the economic feasibility of the process have been reported, demonstrating the possible commercialization of the process. The gliding arc technology is not complex and presents a high flexibility allowing to work in a high range of flow rates and to treat a large amount of chemical species. The main advantage of the gliding arc is that we can easily vary the power in the discharge, by acting on the device of the electrode, and on the voltage level. This study has developed the several plasma reformers, and compared for the each reformers about the hydrogen yield and energy efficiency. As the results, the AC 3-phase Gliding arc plasma reformer by 53.5% of high hydrogen yield and 98.5% of high energy efficiency results. Pyrolysis technique is the energy conversion technique which produces the industrially useful syngas from various biomass resources. But the energy conversion technique is not easy to use the directly as the fuel. because the condensed tar in process occurs the corrosion and operation problems. Currently plasma technology has been applying to a variety and a division a new method. As to the gliding arc plasma, the control is easy. The conversion ratio and energy efficiency is high. In this study, Experiments should be made to study on optimum design of plasma reformer and reduction of tar. The steam flow rate, power input, and input tar concentration change were used as variables for the test. In the optimum conditions, light tar, such as benzene, naphthalene, anthracene and pyrene concentration was decreased. The mainly generated reformed gas is the hydrogen, carbon monoxide, and carbon dioxide. The tar generated in the continuous pyrolyzer by using the AC 3-phase gliding arc plasma was removed. Tar concentration was showed benzene 6.02 g/m3, naphthalene 1.15 g/m3, anthracene 0.013 g/m3, pyrene 0.017 g/m3 respectively. The gas concentrations of the reformed gas were hydrogen 16.1%, carbon monoxide 8.8%, methane 2.6%, ethylene 0.4%, and ethane 0.21% respectively. The generation of high-purity hydrogen from biogas is essential for efficient operation of fuel cell. In general, most feasible strategies to generate hydrogen from hydrocarbon fuels consist of a reforming step to generate a mixture of hydrogen, carbon monoxide, carbon dioxide and steam followed by water gas shift(WGS) and preferential oxidation reaction(PrOx) steps. The WGS reaction that shifts CO to CO2 and simultaneously produces another mole of H2 was carried out in a two-stage catalytic conversion process involving a high temperature shift (HTS) and a low temperature shift(LTS). In the WGS operation, gas emerges from the reformer is taken through a high temperature shift catalyst to reduce the CO concentration to about 3~4% followed to about 5000ppm via a low temperature shift catalyst. The WGS reactor was designed and tested in this study to produce hydrogen-rich gas with CO to less than 5000 ppm. Also, optimum conditions of PROX I were input air flow rate of 300 mL/min and at the 190 ℃. PROX II were input air flow rate of 200 mL/min and at the 190 ℃ respectively. The results of having passed through each reactor were as follows: 55% of hydrogen yield, 0% of carbon monoxide selectivity, 99% of methane conversion rate, 27% of carbon dioxide conversion rate, respectively. The concentration of biogas that passed through each reactor shows 57.5% of H2,7ppm of CO,9.2% of CO2, and 3.4% of CH4 are at the end of the reforming process and overall system efficiency reaches up to 48.2%. Therefore, less than 10 ppm of CO achieved and it is applicable on PEM fuel cell.