Environmental Engineering Reference
In-Depth Information
(generating almost the same low concentration of NO
2
and NO
3
) in the liquid,
resulting in a sharp increase in the NO
2
concentration
and a particularly low NO
3
concentration.
Fig. 4.7
Product of the absorption solution in different concentrations of SO
3
2
4.4.2 Effect of pH with the Existence of Tetravalent-S
Components
Definitely, the SO
2
removal performance will be better under an alkaline
environment within a desulfurizer, but unfortunately, such a removal process is
capable of blockage happening. Therefore, the solution pH value in a desulfurizer
is often set at a weak acidity (e.g., pH 5 - 7) to ensure the dissolution rate of
limestone particles
[22,23]
. Accordingly, evaluating the NO
2
removal performance
under different pH values with the existence tetravalent-S components is necessary.
The pH value was regulated but the total concentration of tetravalent-S
components was kept at 0.01 mol/L to conduct the NO
2
removal experiments. The
acquired results are shown in Fig. 4.8. The NO
2
removal efficiency significantly
increases with the pH value. For example, the low removal efficiency of 52% at a
pH value of 4 increases sharply to a high level of 83% at a pH value of 8.
Evidently, here the pH-value effect on the NO
2
removal is different from that in
subsection 4.3 (results in Fig. 4.3, without the existence of tetravalent-S
components). A detailed explanation of these observations is as follows. Under the
Search WWH ::
Custom Search