Jerzy Mizeraczyk

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.

CFC-11 destruction by microwave torch generated atmospheric-pressure nitrogen discharge

A novel plasma method and its application for destruction of Freons using a moderate-power (several hundred watts) microwave torch discharge (MTD) in atmospheric-pressure flowing nitrogen are presented. The capability of the MTD to decompose Freons is demonstrated using a chlorofluorocarbon CCl3F (Freon CFC-11) as an example. The gas flow rate and microwave power (2.45 GHz) delivered to the MTD were 1–3 litre min−1 and 200–400 W, respectively. Concentration of the CFC-11 in the nitrogen was up to 50%. The results show that the decomposition efficiency of CFC-11 is up to 100% with the removal rate of several hundred g h−1 and energy efficiency of about 1 kg kWh−1. This impressive performance, superior to that of other methods, is achieved without generating any significant unwanted by-products. As a result of this investigation, a relatively low-cost prototype system for Freon destruction based on a moderate-power MTD and a scrubber is proposed.

Hazardous gas treatment using atmospheric pressure microwave discharges

Atmospheric pressure microwave discharge methods and devices used for producing non-thermal plasmas for control of gaseous pollutants are described in this paper. The main part of the paper is concerned with microwave torch discharges (MTDs). Results of laboratory experiments on plasma abatement of several volatile organic compounds (VOCs) in their mixtures with either synthetic air or nitrogen in low (∼100 W) and moderate (200–400 W) microwave torch plasmas at atmospheric pressure are presented. Three types of MTD generators, i.e. low-power coaxial-line-based MTDs, moderate-power waveguide-based coaxial-line MTDs and moderate-power waveguide-based MTDs were used. The gas flow rate and microwave (2.45 GHz) power delivered to the discharge were in the range of 1–3 litre min −1 and 100–400 W, respectively. The concentrations of the processed gaseous pollutants were from several to several tens of per cent. The results showed that the MTD plasmas fully decomposed the VOCs at a relatively low energy cost. The energy efficiency of decomposition of several gaseous pollutants reached 1000 g (kW-h) −1 . This suggests that MTD plasmas can be useful tools for decomposition of highly concentrated VOCs. (Some figures in this article are in colour only in the electronic version)

Laser Flow Visualization and Velocity Fields by Particle Image Velocimetry in an Electrostatic Precipitator Model

AbsractAlthough improving electrostatic precipitator (ESP) collection of fine particles (micron and submicron sizes) remains of interest, it is not yet clear whether the turbulent flow patterns caused by the presence of electric field and charge in ESPs advance or deteriorate fine particle precipitation process. In this paper, results of the laser flow visualization and Particle Image Velocimetry (PIV) measurements of the particle flow velocity fields in a wire-to-plate type ESP model with seven wire electrodes are presented. Both experiments were carried out for negative and positive polarity of the wire electrodes. The laser flow visualization and PIV measurements clearly confirmed formation of the secondary flow (velocity of several tens of cm/s) in the ESP model, which interacts with the primary flow. The particle flow pattern changes caused by the strong interaction between the primary and secondary flows are more pronounced for higher operating voltages (higher electrohydrodynamic numbernehd) and lower primary flow velocities (lower Reynolds number Re). The particle flow patterns for the positive voltage polarity of the wire electrodes are more stable and regular than those for the negative voltage polarity due to the nonuniformity of the negative corona along the wire electrodes (tufts).

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).

Numerical Analysis and Optimization of Power Coupling Efficiency in Waveguide-Based Microwave Plasma Source

Three-dimensional electric field distributions in a waveguide-based microwave plasma source (MPS) have been determined numerically. Tuning characteristics of the MPS have been calculated using a direct and newly proposed two-port network method. A method for easy assessment of the quality of a set of the tuning characteristics is presented. Optimization of the plasma source has been performed using these characteristics to ensure good power coupling and stability of the plasma source operation. The calculated tuning characteristics have been compared with experimental ones. Good agreement has been found.

Two-dimensional imaging of NO density profiles by LIF technique in a pipe with nozzles electrode during NO treatment

Two-dimensional NO concentration distribution was studied by a planar laser-induced fluorescence (PLIF) technique in nonthermal plasma during NO treatment. A pipe with a nozzles-to-plate electrode system, having an electrode gap of 50 mm, was used. A stable DC streamer corona discharge was generated in an NO/air mixture at atmospheric pressure. Laser pulses in the form of a sheet were shot between the electrodes during the discharge. LIF signal emitted at 90/spl deg/ to the laser sheet was imaged onto a gated-ICCD camera and two-dimensional distributions of NO concentration in the reactor were measured as a function of time during NO treatment. NO concentration was also monitored at the reactor outlet. The images of NO concentration covering almost the whole length of the reactor show that the density of NO molecule decreased not only in the plasma region formed by corona streamers but also in the upstream region of the reactor. This information is important for modeling and optimizing the plasma processes and designing the nonthermal plasma reactors.

Two-dimensional distribution of ground-state NO density by LIF technique in DC needle-to-plate positive streamer coronas during NO removal processing

Two-dimensional distribution of the ground-state NO molecules density was investigated using a laser-induced fluorescence (LIF) technique in a DC positive streamer corona reactor (needle-to-plate electrode geometry) during NO removal from a flue gas simulator (NO/air). NO density in the corona discharge reactor was monitored under the steady-state DC corona discharge condition. It was found that NO molecules density decreased due to the corona discharge processing not only in the discharging region but also in the upstream vicinity of the discharge.

Electrohydrodynamic secondary flow and particle collection efficiency in spike-plate multi-electrode electrostatic precipitator

In this work the results of electrohydrodynamic (EHD) secondary flow measurements in a spike-plate type electrostatic precipitator (ESP) are presented. In the investigated ESP two-sided and one-sided spike electrodes were used as a discharge electrodes. The results of 2D PIV measurements showed that flow pattern obtained for a different spike tips positions in respect to the primary flow direction significantly changing the flow structures in the ESP duct. The submicron dust particles collection measurements in this ESP were also performed. The obtained results showed that the collection efficiency of submicron dust particles depends on the generated EHD secondary flow.

Comparison of airflow patterns produced by DBD actuators with smooth or saw-like discharge electrode

In this paper we compare the performance of DBD actuators when either a smooth or saw-like electrode is employed. Two electrode arrangements of DBD actuators are investigated. The first is the classic DBD actuator and the second is a DBD actuator with floating electrode. The usefulness of the saw-like electrode in these two types of DBD actuators is studied.