Robert Miotk

Liquid fuel reforming using microwave plasma at atmospheric pressure

Hydrogen is expected to be one of the most promising energy carriers. Due to the growing interest in hydrogen production technologies, in this paper we present the results of experimental investigations of thermal decomposition and dry reforming of two alcohols (ethanol and isopropanol) in the waveguide-supplied metal-cylinder-based nozzleless microwave (915 MHz) plasma source (MPS). The hydrogen production experiments were preceded by electrodynamics properties investigations of the used MPS and plasma spectroscopic diagnostics. All experimental tests were performed with the working gas (nitrogen or carbon dioxide) flow rate ranging from 1200 to 3900 normal litres per hour and an absorbed microwave power up to 5 kW. The alcohols were introduced into the plasma using an induction heating vaporizer. The ethanol thermal decomposition resulted in hydrogen selectivity up to 100%. The hydrogen production rate was up to 1150 NL(H2) h−1 and the energy yield was 267 NL(H2) kWh−1 of absorbed microwave energy. Due to intense soot production, the thermal decomposition process was not appropriate for isopropanol conversion. Considering the dry reforming process, using isopropanol was more efficient in hydrogen production than ethanol. The rate and energy yield of hydrogen production were up to 1116 NL(H2) h−1 and 223 NL(H2) kWh−1 of microwave energy used, respectively. However, the hydrogen selectivity was no greater than 37%. Selected results given by the experiment were compared with the results of numerical modeling.

High-performance method of carbon nanotubes modification by microwave plasma for thin composite films preparation

In this work we present a simple and efficient method of nitrogen plasma modification of carbon nanotubes (CNTs). The process allows for treatment of the nanotubes in the form of powder with quite a high yield (65 mg of CNTs per hour). The modified carbon nanotubes contain approx. 3.8% nitrogen, mostly in the pyridinic form. Plasma treated CNTs exhibit better dispersibility in water and higher electric capacitance than pristine CNTs. Modified CNTs are a proper component of novel nanocomposites based on the conducting polymer poly(3,4-ethyleneidoxythiophene). Electrodeposited thin layers of the nanocomposite exhibit improved electrochemical properties (higher capacitance, better stability, lower resistance, faster diffusion) compared to the pure polymer layers.

Spectroscopic study of atmospheric pressure 915 MHz microwave plasma at high argon flow rate

In this paper results of optical emission spectroscopic (OES) study of atmospheric pressure microwave 915 MHz argon plasma are presented. The plasma was generated in microwave plasma source (MPS) cavity-resonant type. The aim of research was determination of electron excitation temperature Texc gas temperature Tg and electron number density ne. All experimental tests were performed with a gas flow rate of 100 and 200 l/min and absorbed microwave power PA from 0.25 to 0.9 kW. The emission spectra at the range of 300 – 600 nm were recorded. Boltzmann plot method for argon 5p – 4s and 5d – 4p transition lines allowed to determine Texc at level of 7000 K. Gas temperature was determined by comparing the measured and simulated spectra using LIFBASE program and by analyzing intensities of two groups of unresolved rotational lines of the OH band. Gas temperature ranged 600 – 800 K. The electron number density was determined using the method based on the Stark broadening of hydrogen Hβ line. The measured ne rang ed 2 × 1015 − 3.5×1015 cm−3, depending on the absorbed microwave power. The described MPS works very stable with various working gases at high flow rates, that makes it an attractive tool for different gas processing.

Microwave plasma for hydrogen production from liquids

Abstract The hydrogen production by conversion of liquid compounds containing hydrogen was investigated experimentally. The waveguide-supplied metal cylinder-based microwave plasma source (MPS) operated at frequency of 915 MHz at atmospheric pressure was used. The decomposition of ethanol, isopropanol and kerosene was performed employing plasma dry reforming process. The liquid was introduced into the plasma in the form of vapour. The amount of vapour ranged from 0.4 to 2.4 kg/h. Carbon dioxide with the flow rate ranged from 1200 to 2700 NL/h was used as a working gas. The absorbed microwave power was up to 6 kW. The effect of absorbed microwave power, liquid composition, liquid flow rate and working gas fl ow rate was analysed. All these parameters have a clear influence on the hydrogen production efficiency, which was described with such parameters as the hydrogen production rate [NL(H2)/h] and the energy yield of hydrogen production [NL(H2)/kWh]. The best achieved experimental results showed that the hydrogen production rate was up to 1116 NL(H2)/h and the energy yield was 223 NL(H2) per kWh of absorbed microwave energy. The results were obtained in the case of isopropanol dry reforming. The presented catalyst-free microwave plasma method can be adapted for hydrogen production not only from ethanol, isopropanol and kerosene, but also from different other liquid compounds containing hydrogen, like gasoline, heavy oils and biofuels.

Hydrogen production by dry reforming of kerosene using microwave plasma

This paper presents results of study of dry reforming of kerosene using a microwave plasma. The plasma was generated in waveguide supplied metal-cylinder-based nozzleless microwave plasma source (MPS) operated at 915 MHz. The rotational temperature of heavy species (assumed to be close to gas temperature) was up to 5500 K (for plasma without kerosene). The hydrogen production rate was up to 470 NL[H2]/h and the energy efficiency was 89.5 NL[H2] per kWh of absorbed microwave. Streszczenie. Artykuł przedstawia wyniki badań suchego reformingu nafty w plazmie mikrofalowej (915 MHz). Temperatura rotacyjna cząstek ciężkich (przyjmowana jako zbliżona do temperatury gazu) wynosiła do 5500 K (dla plazmy bez dodatku nafty). Uzyskana wydajność produkcji wodoru wynosiła do 470 NL [H2]/h, natomiast efektywność energetyczna do 89,5 NL [H2] na kWh zaabsorbowanej energii mikrofal. (Produkcja wodoru na drodze suchego reformingu nafty w plazmie mikrofalowej).

Optical emission spectroscopy of plasma generated by a waveguide-supplied microwave plasma source operated at 915 MHz

In this paper we present the results of an optical emission spectroscopic study of an atmospheric pressure microwave (915 MHz) nitrogen and nitrogen with carbon dioxide (1%) plasma at high working gas flow rate. This study was aimed at determining rotational Trot and vibrational Tvib temperatures of N2+ ions and N2, CN molecules. The plasma was generated in a waveguide-supplied cavity-resonant type microwave plasma source. All experimental tests were performed with working gas flow rates QN2 between 80 and 320 l min−1 and a power PA absorbed by the plasma microwave varied from 1.5 to 3 kW. The Trot and Tvib temperatures of selected heavy species were determined by comparing the measured and simulated spectra. The measured temperatures of N2+ ions and N2, CN molecules were 6800 to 7500 K (± 250 K), 5000 to 5200 K (± 150 K) and 6100 to 6600 K (± 100 K), respectively, depending on the PA.

Electrodynamic characterization of a cavity-type microwave plasma source

In this work the electrodynamic characterization of a cavity-type microwave plasma source (MPS) operated at 915 MHz was presented. The work was aimed at finding a better design of the MPS for ensuring a higher microwave power energy transfer from the microwave feeding line to the sustained plasma. In this analysis a standard model of microwave plasma and two-port method, developed by Nowakowska et al., supported with one-time simulation of the electric field distribution inside the MPS with plasma, was used.

Optimization of microwave power transfer from electric field to the plasma inside an microwave 915 MHz plasma source

This paper presents an optimization of the waveguide-supplied coaxial-line-based nozzleless microwave plasma source. This field applicator operated at a frequency f equal to 915 MHz at an atmospheric pressure. The optimization objective was to maximize an efficiency of power transfer from electric field to plasma inside this device. In the optimization we used a model of plasma which was determined in this work.

Equivalent circuit of a coaxial-line-based nozzleless microwave 915 MHz plasma source

This paper presents a new concept of an equivalent circuit of a microwave plasma source (MPS) used for gas treatment. The novelty of presented investigations is the use of the Weissfloch circuit as equivalent of an area of waveguide discontinuity in the MPS which is a result of entering a coaxial-line structure. Furthermore, in this area the microwave discharge is generated. Verification of the proposed method was carried out. The proposed equivalent circuit enabled calculating the MPS tuning characteristics and comparing them with those measured experimentally. This process allowed us to determine the impedance ZP ofplasma in the MPS.