E XPERIMENTAL F ACILITY AND I NSTRUMENTS

In this section, the introduction of using PAC system to reform hydrogen is proposed.

There are two parts, one is experimental facility including power supply, fuel feeding system, plasma reactor, catalyst preparation, and heating system. The other part is experimental instrument including OES, GC, etc.

2.1.1 Plasma Reactor

In this study, all experiments are conducted at air flow rate ranges from 0.5-2 SLM and to meet for this purpose a small gliding arc reactor was designed. The following figure 2.1 describes the gliding arc reactor dimensions. GA reactor mainly consists of two 30 mm long, 7 mm wide and 2 mm thick knife-shaped electrodes fixed on a Peak bed plate, which can sustain at heat deflection temperature at 315℃ and long term property evaluations at 250℃.

For latter on using high-speed camera observation of the arc column motion, a quartz tube with inner diameter 22 mm and 55 mm long is well designed in sealing with Peak bed plate.

2.1.2 AC Power Supply

Gliding arc reactor is supplied with a power supply (PVM500 plasma driver). It has independent voltage control ranges from zero to maximum 20 kV peak-to-peak. And frequency ranges from 20-70 kHz. Though, this power supply is relatively unstable compare to others, its price was low ($449.95). In the next chapter, the influence of different output

16

power magnitude on electrical character and reforming efficiency was studied in detail.

2.1.3 Fuel Feeding System

In this study, the fuel feeding system controls several experimental parameters: C/O (mole) ratio, air flow rate, and ethanol/water mole ratio. C/O (mole) ratio represents the proportion of input C atoms in the ethanol and O atoms in the air and the ethanol. Ethanol and water mole percentage also is an important parameter that would effects the experiment results dramatically. To control accurate parameters, MFC (Multi-gas MFC,MC-100SCCM-D, Alicat Scientific, 100sccm for max) and gradient pump (930d-1428, Young Lin Instrument, 0.0005 to 1 slm) were used to control the flow rate of dry air pumped from compressor though a dehydration process and ethanol-mixed-water solution. Moreover, high purity (99%) ethanol that contains few impurity and DI water were used as fuel, and they were mixed together using ultrasonic wave producer.

As for the fuel feeding system, a controllable nozzle was connected to a stainless steel tube which inside has special design to step up the gasification effect and also has a thermocouple to measure the fuel temperature. The automatic valve was controlled by an adjustable frequency signal at 12 volt voltage and the duty cycle of the frequency was set at a constant cycle: 10/500 to control the valve on and off.

2.1.4 Heating System

In the ethanol steaming reforming, the reactant consisted of water and ethanol needs to

17

be heated in everywhere along the reaction pipeline, started at fuel injection tube to GC analysis ended. Especially, there are two parts of pipeline need to be heated for specific temperature control, gasification and catalyst reaction. The heating system consisted of two heating furnace, each of it is 30 cm long and can control temperature through a thermal controller. The gasification furnace supplies the heat to heat up the reactant, and the experiment results indicate the reactant temperature has an optimum setup for reforming efficiency.

2.1.5 Catalyst Preparation

In this study, 5% Rh/CeO2 was used as reforming catalyst, especially thanks to Department of Applied Chemistry, NCTU for sharing the chemicals and skills. In the catalyst preparation, at first, 1 g porous Al₂O₃ balls used as carrier were pound to small pieces, 1.00-1.41 mm³, mixed with ethanol solution which dissolved 0.125 g Ce(NO₃)₃ and then heated to 50℃ to evaporate ethanol. Thereafter, the Al₂O₃ carrier loaded with Ce(NO₃)₃ were sintering in 300℃ for 5 hours, meanwhile 0.01g RhCl₃ ethanol solution was prepared to mix with 10 % Ce-Al₂O₃ after sintering. Follow the same procedure to evaporate ethanol, the 10

% Ce-Al₂O₃ loaded with 5% RhCl₃ were put into the 600℃ furnace and access 200 sccm hydrogen gas to proceed reduction reaction within 6 hours to produce 1 g porous Al₂O₃ loaded with 5% Rh/CeO₂.

18

2.1.6 Experimental Instrumentations

In this section, the experimental facility and instrumentation for the study are listed below in detail.

The experimental instrumentation includes voltage and current probe for electrical measurements, thermocouple for temperature measurements, optical emission spectral for radical concentration measurements and gas chromatograph for gas composition analyses.

The most common electrical diagnostic consists of the measurement of the voltage applied to the electrodes and the resultant discharge current. It is also common to use a capacitor connected in series to ground; the voltage across the series capacitor is then proportional to the charge stored on the electrodes. All the above-mentioned parameters were recorded with a Rogowski coil (IPC CM-100-MG, Ion Physics Corporation Inc.) and a high-voltage probe (Tektronix P6015A), respectively, through a digital oscilloscope (Tektronix TDS1012B).

The thermocouple (K type) connected to a thermometer will be used to measure the gas temperature distribution in the afterglow region. The optical emission spectral intensity of the GA is measured using a monochromator (PI Acton SP 2500) with a Photomultiplier tube (Hamamatsu R928). It was used to measure the concentration distribution in the post-discharge region to characterize the capability of generating radicals by the system. In addition, hydrogen, carbon monoxide, carbon dioxide and other hydrocarbon were quantified by GC (YL 6100GC with a pulsed discharge helium ionization mode detector (PDHID) and

19

packed column of Molecular Sieve 5A (80/100 mesh) and Porapak N (50/80 mesh) ) by using the calibration curves separately prepared. The standard gases for calibration were prepared in bulbs. Moreover, the gas would access through the gas purifier to condense moisture and remove impurity before analyzing and calibrating.𚰀