estudio y caracterización de un plasma de microondas a presión ...

Distribución de temperaturas y especies
8.1. Manuscript
176
Volatile organic compounds (VOCs) such as carbon tetrachloride (CCl4) are
widely used as industrial solvents on account of their high evaporation rate, and low
inflammability and reactivity, and also of their ability to dissolve in a rapid, efficient
manner, a wide range of organic substances; hence their utility in degreasing, and metal
and dry cleaning processes [1]. The toxicity of VOCs has promoted the development of a
variety of methods for their destruction, but in last years non-thermal plasmas have been
constituted as an effective alternative to the previous classical methods and afford the
production of highly reactive species.
In addition to their high residue destruction ability, studied in previous works [2],
non-thermal plasmas provide valuable advantages that make them highly competitive
with other decomposition techniques including low installation and maintenance costs,
and the need for no high power levels in order to obtain high residue removal efficiency.
The plasma torch used in this work is described in detail in a paper by Moisan et
al. [3]. Microwave energy propagates to the end of a coaxial line, a conical nozzle at the
tip of which the helium flows and creates the discharge. The helium plasma thus
produced acts as a load at the end of the coaxial-like transmission line. This area is
coupled to the reactor patented by our group [4]. The antenna tip is extended into the
reaction chamber of the plasma reactor, which constitutes the lower section and is fitted
with two windows intended to facilitate spectroscopic analyses. The recombination
chamber, which constitutes the upper section, is furnished with a central hole for
evacuating output gases and two additional holes for collection of gas samples from the
reactor.
In order to characterize these plasmas and the excited species formed inside by
measuring the values of their main parameters, spectroscopical methods are widely used.
In these kind of measurements the light collected from the plasma and an Abel inversion
is necessary to obtain the emissivity at each radial position. The Abel inversion
procedure used in this work, viz. the Hankel-Fourier method, is described in detail in a
previous paper of our group [5]. As a result of the carbon tetrachloride decomposition
and of air entrainment, the plasma contains a large number of species apart from helium.
In this work the radial distribution of the most intense emission lines and molecular