Systematic simulation strategy of plasma methane pyrolysis for CO2-free H2

Recently, the direct conversion of methane into hydrogen using cold plasma reactors has attracted increasing attention, since hydrogen has considerable potential as a future feedstock in the steel and chemical industries. However, the simulation of plasma pyrolysis reactors is extremely complex due to the vast temporal and spatial ranges of the variables involved and steep gradients. Previously, methane pyrolysis has been meticulously modeled by 0D simulations, and 3D plasma modeling has been largely confined to Argon systems. In this paper, a systematic methodology is presented, which provides an expedient and efficient hierarchy of 0D to 3D simulations, in order to approximate the methane pyrolysis simulation of a plasma reactor in its entirety. Various simulation tools are applied in a coordinated and pragmatic manner. The results show that the proposed synergy allows simplification of the reaction set and arc characteristics, significantly reducing the runtime required for the simulations

New and versatile minature microwave plasma source

Miniature Microwave Inductively Coupled Plasma (MMWICP) source is characterized by means of Optical Emission Spectroscopy (OES) in nitrogen gas flow, which gives the information on basic plasma properties. Depending on the incident power the discharge runs in E-mode or in more efficient H-mode. The high resolution radial images of the source reveal different morphologies of different discharge modes. The measurements show an unexpected limitation in dissipated power, accompanied by spontaneous transition from H- to E-mode. The efficiency of the source is high: about 67% of incident power (P0) is deposited in the discharge, which is estimated from OES

Theoretical investigation of a novel microwave driven ICP plasma jet

Theoretical investigation of a novel microwave driven ICP plasma jet 26 Jun 2019, 16:15 15m Gold Coast III/IV (Double Tree at the Entrance to Universal Orlando) Oral 2.7 Microwave Plasma Interaction 2.7 Microwave Plasma Interaction III Speaker Mr Michael Klute (Ruhr University) Description Microwave and radio frequency driven plasmas-jets play an important role in many technical applications. They are usually operated in a capacitive mode known as E-mode. This mode, however, couples considerable power to ions which limits the plasma density and the efficiency and gives rise to negative side effects such as erosion. The inductive coupling, known as H-mode, eliminates these disadvantages and is attractive for large scale plasmas. A novel small scale, microwave driven plasma-jet has been proposed by \textit{Porteanu et al.}[1]. It is operated as an inductive discharge and that has been recently characterized using optical emission spectroscopy (OES) by \textit{Stefanovic et al.}[2]. In this work the proposed plasma-jet is examined theoretically. A global model of the new device is presented based on the volume-integrated balances of particle number and electron density, and a series representation of the electromagnetic field in the resonator. An infinite number of modes can be found ordered by the azimuthal wave number m. The mode m=0 can be identified with the inductive mode and will be called H-mode, the mode m=1 is the capacitive mode and will be called E-mode. By equating the electromagnetic power that is absorbed by the plasma with the loss power, stable operating points and hysteresis effects can be investigated. In a second step the spatially resolved electromagnetic field strength will be considered. All results will be compared to the results of the OES measurements and imagines obtained from CCD-imaging. [1]Porteanu et al.\textit{Plasma Sources Sci.Technol.}\textbf{22}, 035016 (2013) [2] Stefanovic et al.\textit{Plasma Sources Sci.Technol.}\textbf{27}, 12LT01 (2018) [3] Porteanu et al.\textit{Plasma Sources Sci.Technol.} accepted (2019

Inductively Coupled Plasma at Atmospheric Pressure, a Challenge for Miniature Devices

Inductively coupled plasma (ICP) sources are preferred to the capacitive (CCP) sources because of their higher electron density and plasma purity. The use of microwaves for the plasma excitation allows not only to obtain a dense plasma with a low gas temperature but also to generate such a plasma at higher pressures. We present a miniaturized device capable of working up to atmospheric pressure. The plasma is generated in a quartz tube with an outer diameter of 7 – 12 mm. The microwave plasma interaction has been studied using an original method, the “Hot-S-Parameter” spectroscopy, presented in detail in [1]. The variation of the resonance frequency and generally of the reflected power as a function of frequency provides information about the type of coupling and about the plasma conductivity, i.e., electron density and scattering frequency. The microwave data are correlated with photographs of the plasma shape and with results of the optical emission spectroscopy (OES) of nitrogen [2]. At 1000 Pa, and 80 W at 2.45 GHz, a nitrogen plasma reaches an electron density of 3 1019 m−3 and a gas temperature of 1600 K [2]. The miniaturized source includes an impedance matching circuit. Based on microwave and optical measurements we estimate the power absorbed by the plasma at 1000 Pa to be about 60 % of the incident power. This efficiency is much higher than in standard reactors driven at 13.56 MHz. The source has been successfully tested with argon at atmospheric pressure. This fact opens new perspectives for the use as an array of remote plasma sources for thin-film depositions

Power Consumption in a Miniature Microwave Inductively Coupled Plasma Source

Miniature Microwave Inductively Coupled Plasma (MMWICP) source is a novel and versatile non-thermal plasma source, which profit of high electron density and high power efficiency. In its compact version a single MMWICP source comprises a quartz tube of 5 mm inner diameter enclosed by a copper resonator of 8 mm thickness. This basic unit can be combined in an array of two (double), four (Quadriga) or more sources. Here, the single source is characterized by Optical Emission Spectroscopy (OES). A continuous stream of nitrogen gas is running through the glass cylinder at a pressure of 2000 Pa. This specific pressure is chosen to satisfy the Local Field Approximation (LFA), which is used in the latter data analysis. For the OES measurements nitrogen as a test gas is selected for its well-known population kinetics. In particularly, the second positive system of neutral nitrogen (380 nm line) and first positive system of nitrogen molecular ion (391 nm) are monitored, for which the population kinetics can be described by a simple collision radiative model. The OES measuring unit consists of a macro objective, CCD camera and two narrow band-pass filters, which isolate the corresponding emission lines. With previously absolutely calibrated OES unit, the radially resolved absolute line intensities are collected with a 28 micrometer resolution. Simultaneously, an absolutely calibrated high resolution Echelle spectrometer monitors the rotational lines distribution form respective emissions. Using the rate equations of collision-radiative model and BOLSIG+ for solving a Boltzmann equation under the assumption of LFA, it is possible to measure the spatially resolved electron density and electric field. Moreover, the spatially resolved deposited power density is calculated. In the presentation we will discussed the power dissipation in CCP, ICP and hybrid mode of operation. In respect to power efficiency MMWICP will be compared to other microwave plasma sources

Amorphous carbon film deposition on inner surface of tubes using atmospheric pressure pulsed filamentary plasma source

Uniform amorphous carbon film is deposited on the inner surface of quartz tube having the inner diameter of 6 mm and the outer diameter of 8 mm. A pulsed filamentary plasma source is used for the deposition. Long plasma filaments (~ 140 mm) as a positive discharge are generated inside the tube in argon with methane admixture. FTIR-ATR, XRD, SEM, LSM and XPS analyses give the conclusion that deposited film is amorphous composed of non-hydrogenated sp2 carbon and hydrogenated sp3 carbon. Plasma is characterized using optical emission spectroscopy, voltage-current measurement, microphotography and numerical simulation. On the basis of observed plasma parameters, the kinetics of the film deposition process is discussed