Mirosław Dors

Measurements of the velocity field of the flue gas flow in an electrostatic precipitator model using PIV method

Abstract In this paper, results of use of the PIV method to measure the flow field in a wire-plate type ESP model are presented. The results show that the PIV method is well suited to investigate the flow field in ESP models, in particular the characteristics of secondary and reversal flows, which increase the flow turbulence. The PIV investigation of the near-collecting electrode region shows the importance of the secondary flows, the velocity of which is several tens of cm/s. This means that the secondary flows can have a great impact on the motion and precipitation of small particles, mainly those in the submicron range.

Effect of reaction temperature on NO/sub x/ removal and formation of ammonium nitrate in nonthermal plasma Process combined with selective catalytic reduction

This study investigated nonthermal plasma process combined with monolithic V/sub 2/O/sub 5//TiO/sub 2/ catalyst for the removal of nitrogen oxides. The combination process was made in either one-stage (generation of plasma inside catalyst) or two-stage process (plasma reactor, followed by catalyst) in order to understand the role of nonthermal plasma. It was shown that nonthermal plasma does not activate catalyst, but merely changes the gas composition, especially NO and NO/sub 2/ concentrations. The effect of reaction temperature on the removal of NO/sub x/ and the formation of ammonium nitrate was examined to find out an appropriate operating condition. The formation of ammonium nitrate on catalyst surface that is the main cause of catalyst deactivation was identified by scanning electron microscope images. As a result of the change in the gas composition by the nonthermal plasma, the combination process allowed high NO/sub x/ removal efficiency at relatively low temperatures below 200/spl deg/C. For the present process, the NO/sub x/ removal efficiency obtained in the range of 75/spl deg/C-200/spl deg/C was around 80%, which corresponds to an energy yield of 48 eV/NO/sub x/-molecule removed. It was found that the combination process should be operated above 170/spl deg/C to prevent ammonium nitrate from forming.

Production of hydrogen via conversion of hydrocarbons using a microwave plasma

In this paper, results of hydrogen production from hydrocarbons in the atmospheric pressure microwave plasma are presented. As sources of hydrogen, both methane CH 4 and tetrafluoroethane C 2 H 2 F 4 were tested. A new waveguide-based nozzleless cylindertype microwave plasma source was used to convert hydrocarbons into hydrogen. The processed gaseous hydrocarbons were introduced to the plasma by four gas ducts which 2 formed a swirl flow in the plasma reactor. The absorbed microwave power was up to 5 kW. The gas flow rate was up to 212 l min -1. The hydrogen mass yield rate and the corresponding energetic hydrogen mass yield were up to 866 g[H 2 ] h -1 and 577 g [ H 2 ] per kWh of microwave energy absorbed by the plasma, respectively. These parameters are better than our previous results when nitrogen was used as a swirl gas and much better than those typical for other plasma methods of hydrogen production (electron beam, gliding arc, plasmatron).

Hydrogen production from ethanol in nitrogen microwave plasma at atmospheric pressure

Abstract Hydrogen seems to be one of the most promising alternative energy sources. It is a renewable fuel as it could be produced from e.g. waste or bio-ethanol. Furthermore hydrogen is compatible with fuel cells and is environmentally clean. In contrast to conventional methods of hydrogen production such as water electrolysis or coal gasification we propose a method based on atmospheric pressure microwave plasma. In this paper we present results of the experimental investigations of hydrogen production from ethanol in the atmospheric pressure plasma generated in waveguide-supplied cylindrical type nozzleless microwave (2.45 GHz) plasma source (MPS). Nitrogen was used as a working gas. All experimental tests were performed with the nitrogen flow rate Q ranged from 1500 to 3900 NL h-1 and absorbed microwave power PA up to 5 kW. Ethanol was introduced into the plasma using the induction heating vaporizer. The process resulted in an ethanol conversion rate greater than 99%. The hydrogen production rate was up to 728 NL[H2] h-1 and the energy efficiency was 178 NL[H2] per kWh of absorbed microwave energy. Graphical Abstract

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.

River Water Remediation Using Electrohydraulic Discharges or Ozonation

River water cleaning from microorganisms using electrohydraulic discharges and ozonation was investigated. The processed water was highly polluted with the total number of microorganisms (70 400 cfu/mL) and total Escherichia coli bacteria (280 cfu/mL). The processing was conducted in a tube reactor with a hollow needle-rod electrode configuration. A 400-mL sample of river water was treated at different flow rates. Ozonation was performed in a washing bottle with an ozone concentration of 20 g/m3. The corona discharge treatment showed a steady decrease of bacteria and microorganisms but did not kill them completely. Spark discharge killed the bacteria and microorganisms completely; however, its energy efficiency was much lower than that of ozonation. The ozone treatment decreased the concentration of microorganisms and coli bacteria down to 785 and 10 cfu/mL, respectively, in 45 s which resulted in higher energy efficiency than processing using corona and spark discharges. The NPOC analysis of the treated samples showed its concentration of 5 ± 0, 4 ppm in all samples.

Decomposition of fluorohydrocarbons in atmospheric-pressure flowing air using coaxial-line-based microwave torch plasma

Results of the investigation of decomposition of fluorohydrocarbons C2H2F4 (HFC-134a) and CHClF2 (CFC-22) in atmospheric-pressure flowing air using a coaxial-line-based microwave torch plasma are presented. Concentrations of the fluorohydrocarbons in the flowing air were up to 10 %. The decomposition efficiency of both C2H2F4 and CHClF2 was almost 100 %. This suggests the coaxial-line-based microwave torch plasma can be a useful tool for decomposition of highly-concentrated fluorohydrocarbons in air at atmospheric pressure.

Electrohydrodynamic flow and its effect on ozone transport in corona radical shower reactor

New arguments supporting the supposition that the ozone is transported along a corona discharge radical shower (CDRS) reactor by the electrohydrodynamic (EHD) flow are presented. The arguments are based on the analysis of the corona discharge, which is a precursor of the EHD flow in the CDRS reactor, and on the measurements of velocity field of the EHD flow in the CDRS reactor by the particle image velocimetry (PIV). The obtained velocity flow structures and the possible causes of the ozone transport in the CDRS, i.e., diffusion, additional gas flow, EHD flow, and convection by the main flow, were discussed basing on the conservation equations for the EHD flow. The discussion showed that the EHD flow plays a dominant role in the ozone transport. This is also supported by the results of a simple phenomenological model for one-dimensional description of EHD-induced ozone transport in the CDRS reactor. The results of the computer simulation based on this model explained the main features of the measured ozone distribution in the CDRS reactor, establishing the EHD flow as the main cause of the ozone transport from the discharge region upstream, i.e., against the main flow.

Plasma-Based Depollution of Exhausts: Principles, State of the Art and Future Prospects

Nowadays non-thermal plasma technologies are state of the art for the generation of ozone as an important oxidant for water cleaning or bleaching, the incineration of waste gases or for the removal of dust from flue gases in electrostatic precipitators. Furthermore their possibilities of gas depollution are well known. Plasmas contain reactive species, in particular ions, radicals or other oxidizing compounds, which can decompose pollutant molecules, organic particulate matter or soot. Electron beam flue gas treatment is another plasma-based technology which has been successfully demonstrated on industrial scale coal fired power plants. This chapter aims a comprehensive description of plasma-based air remediation technologies. The possibilities of exhaust air pollution control by means of non-thermal plasmas generated by gas discharges and electron beams will be summarized. Therefore plasma as the 4th state of matter, its role in technology and the principle of plasma-based depollution of gases the will be described. After an overview on plasma-based depollution technologies the main important techniques, namely electron beam flue gas treatment, gas discharge generated plasmas including plasma-enhanced catalysis and injection methods will be described in separate sections. In these sections selected examples of commercially available or nearly commercialised processes for flue gas treatment or the removal of volatile organic compounds and deodorization will be described, too. Current trends and concepts will be discussed.

Microwave Plasma Sources for Gas Processing

In this paper atmospheric pressure microwave discharge methods and devices used for producing the non- thermal plasmas for processing of gases are presented. The main part of the paper concerns the microwave plasma sources (MPSs) for environmental protection applications. A few types of the MPSs, i.e. waveguide-based surface wa ve sustained MPS, coaxial-line-based and waveguide-based no zzle-type MPSs, waveguide-based nozzleless cylinder-typ e MPS and MPS for microdischarges are presented. Also, results of the laboratory experiments on the plasma processing of several highly-concentrated (up to several tens percent) vorganie compounds (VOCs), including Freon-type refrigerants, in the moderate (200-400 W) waveguide-bas ed nozzle-type MPS (2.45 GHz) are presented. The results showed that the microwave discharge plasma fully decomposed the VOCs at relatively Iow energy cost. The energy efficiency of VOCs decomposition reached 1000 g/kWh. This suggests that the microwave discharge plasma can be a useful tool for environmerital protection applications. In this paper also results of the use of the waveguide-ba sed nozzleless cylinder-type MPS to methane reforming into hy drogen are presented.