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

Capítulo 2
In obtaining high energy efficiency with the trichloroethylene destruction
method, used in this work, entails removing a large amount of contaminant per unit time
by using as little energy as possible. Such efficiency can be increased simply by
increasing the flow-rate of input gas and the inner diameter of the nozzle, while keeping
the velocity within the optimum range.
Figure 2.5 shows the energy efficiency of the helium plasma as a function of the
inner diameter of the coupler tip at five different C2HCl3 concentrations. As can be seen,
the larger the inner diameter of the tip, the higher the energy efficiency at a constant
output velocity of gas. This testifies to the high flexibility of the system, which allows
the energy efficiency to be increased by altering the dimensions of the coupler tip,
simply replacing with a new one.
The data shown in figure 2.5 maintain a constant velocity of the gas at its
optimum value, which for an internal diameter of 1.4 mm corresponds to approximately
3 L/min, but greater energy efficiency can be achieved by increasing the gas flow,
though this causes a reduction in the destruction efficiency.
2.3.1.4. Influence of the contaminant concentration
Figure 2.6a shows the variation of the output concentration of C2HCl3 as a
function of that introduced in the helium plasma at six different applied microwave
power values from 100 to 1000 W. For values of power less than 300 W it is not possible
to use a high concentrations of C2HCl3 in the inlet gas because the plasma is unstable. As
can be seen, below 300 W the output concentration increases with an increased input
concentration; no such effect is observed above 300 W because the output concentration
is already very low.
In any case, the increase in concentration at the reactor outlet is not an accurate
measure of the destructive ability of the plasma since this is receiving an increased
amount of product per unit time. It is therefore preferable to use an alternative
parameter: the destruction and removal efficiency, %DRE [21].
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