NOx-separation
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Washer programme |
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NOx separation from waste air
Method of recovery of raw
materials from waste gas without any origin of waste |
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|
| 1. Process
description : |
| Waste gases containing
NOx have its origin in inorganic industry, in the course of galvanic processes,
in pickling baths and during other processes. Waste gases containing NOx
consist of the most important components NO, NO2, N2O4 and N2O3. These
components are interconnected by means of the following chemical equilibrium: |
|
| (1) |
2 NO + O2 |
« 2 NO2 |
D HR = +
26.920 cal |
| (2) |
2 NO2 |
«
N2O4 |
D HR = +
13.600 cal |
| (3) |
NO + NO2 |
«
N2O3 |
D HR = +
9.600 cal |
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|
The other chemical
equilibria play a secondary role.
Reaction step of this scheme which is determining for velocity is given
by equation (1). Starting from temperatures of approximately of 50 °C
the equilibrium of equation (2) in direction to NO2 is shifted completely.
The BUNSEN´s absorption coefficient a
and Henry´s coefficient for gaseous compounds N will be as follows
/1/ : |
|
|
a |
H (298 K) |
|
|
kPa |
| NO |
0,000025 |
2,15 - 2,92 x106 |
| NO2 |
0,0005 |
1,01 - 1,37 x105 |
| N2O3 |
|
1,66 x102 |
| N2O4 |
1,6 |
2,5 - 5,91 x103 |
| HNO2 |
37 |
|
| HNO3 |
1140 |
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|
|
| This comparison
shows, that it is possible to eliminate the direct contribution of NO
and NO2 to acidity of aqueous phase. In spite of this, the solubility
of N2O4 is well and it is approximately in correspondence with SO solubility. |
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|
NOx-separation
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