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

Destrucción de VOCs con plasma de Aire
5.1. Introduction
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Air pollution by chlorinated volatile organic compounds (VOC) negatively
affects human health and the environment. Volatile organic compounds such as
trichloroethylene (C2HCl3) and carbon tetrachloride (CCl4) are widely used as industrial
solvents due to their low flammability, high evaporation rate and low reactivity.
Moreover, VOCs can efficiently dissolve a wide range of organic substances; thus, they
are often used as degreasers and in the dry-cleaning process [1]. The toxicity of these
compounds has promoted the development of a variety of technologies for the
destruction of VOCs [2]. Besides thermal incineration, catalytic technologies such as
catalytic and photocatalytic destruction [3], catalytic hydrodechlorination [4], catalytic
steam reformation [5] and catalytic combustion have been employed [6, 7].
Methods based on non-equilibrium (non-thermal) plasmas are attractive
procedures for the removal of VOCs because the plasmas can be operated at atmospheric
pressure and a wide range of temperatures, including room temperature. These plasmas
are highly efficient in producing radicals and oxidising agents, which can react with
VOCs, resulting in decomposition [8-13]. Pulsed corona discharge (PCD), glyding arc
(GA) and dielectric barrier discharges (DBD) are examples of non-equilibrium plasmas
[14-17].
The device used in this study is based on the axial injection torch (AIT)
developed by Moisan et al. in 1994 [18]. This non-equilibrium, non-thermal plasma is an
effective energy medium for the removal of waste and is highly stable to impedance
changes that result from the introduction of molecular gases and organic compounds.
The plasma can operate over a wide range of flow rates and concentrations. In addition,
due to its small size and high species diffusion, thermodynamic equilibrium between
neutral species, ions and electrons is not achieved inside the plasma [19, 20].
In this work, the aforementioned plasma torch was operated with an air plasma at
atmospheric pressure, and the efficiency of the system in the destruction of
trichloroethylene and carbon tetrachloride was evaluated. With an argon or helium
plasma at atmospheric pressure, this system was proven to be effective at destroying
carbon tetrachloride and trichloroethylene [21-23], and destruction rates greater than