An artificial underground coal gasification (UCG) gas is generated by heating crushed coal, the artificial UCG gas is reformed by a packed-bed dielectric barrier discharge (PB-DBD), and then the reforming characteristics of the UCG gas are investigated. H2S, H2, CH4, CO, CO2, N2 and O2, which have been known as typical UCG gas components, are found to be contained in the gas, and alkanes (CnH2n+2), alkenes (CnH2n), etc. are also detected. When the UCG gas containing H2S of 400 ppm is reformed at an input power of 40W and a flow rate of 0.1 L/min, it is found that the decomposition rate and the decomposition efficiency of H2S are approximately 80% and 1.94 mmol/kWh, respectively, and that the production amount of H2 increases by approximately 14-40% and the production efficiency of H2 is 81.4 mmol/kWh. It is also found that the concentration of alkenes decreases obviously, while the concentration of alkanes is not affected significantly by discharge plasma reforming. This indicates that H2 may be produced from alkenes contained in the UCG gas by discharge plasma reforming. This leads that desulfurization and H2 production can be done simultaneously in a single reactor.
In this study, we carried out a simultaneous measurement of the negative ion mobility and the H2O concentration in different purities O2 using a high pressure ion drift tube for an investigation on effects of impurities. We used four different purities O2 as ultrahigh-purity (99.99995% with a gas purifier), high-purity 1 (99.99995%), high-purity 2 (99.9999%) and low-purity (99.9%). The H2O concentration in ultrahigh-purity O2 through the chamber equipped the ion drift tube was monitored between 15 to 100 ppb although the gas purifier could be removed the H2O concentration less than 100 ppt because of an outgassing from the inner surfaces of the chamber, ion drift tube and so on. In contrast, the ion mobility was observed as a constant value of 2.39 cm2/V·s as O4-. Then, a mobility 2.31 cm2/V·s was observed in high-purity 1 and 2 of which the H2O concentrations were 500 and 550 ppb, respectively. An interest result was found in low-purity O2 that is two mobilities 2.41 and 2.50 cm2/V·s corresponding to CO4- and N2O2- were measured in the H2O concentration between 400 to 580 ppb. One of the reasons considered as the effects of CO2 and N2 contained in O2.
The characteristics of acetic acid decomposition were investigated by a negative DC corona discharge over water. The corona discharge is 4 mm away from the water surface. Hence, this method does not directly treat water using discharge plasma. During corona processing, oxygen or ozone was supplied to the reactor. The concentration of gaseous ozone over water in the reactor was measured by infrared spectroscopy. The optimal discharge treatment conditions were investigated by varying the gas flow rate. It was found that the decomposition rate of acetic acid increased when the gas flow rate was high at the same gaseous ozone concentration. Furthermore, as the gas flow rate increased, the concentration of the water vapor measured by infrared spectroscopy decreased. Our results indicate that the concentration of water vapor and ozone are important for water treatment using a DC corona discharge.
On-line Partial discharge (PD) measurement is very important for insulation monitoring of high-voltage equipment. One of the biggest challenges performing on-line monitoring is discrimination between PD detect signals and external noises. Experimental results using high frequency CT sensor show that the current waveforms associated with various PD signals are all damped cosine waveforms, and have unique frequency and decay times of damped oscillation. Therefore we focused attention on the damped oscillation waveform of the PD current, especially damped cosine waveform having a different number of oscillations. In addition to this, the noise discrimination method using wavelet transform or short-time Fourier transform is effective. Those noise discriminating process are applicable to on-line PD current measurement system.