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On the Formation of Nitrogen Oxides During the Combustion of ...

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C Design Details <strong>of</strong> Experiment Equipment<br />

Performance <strong>of</strong> Surface Coating<br />

The exhaust gas samples are withdrawn from <strong>the</strong> combustion chamber via<br />

four symmetrically aligned, uncooled fine-orifice probes (see Chaps. 3.1.3 and<br />

3.1.4). Even though critical flow through <strong>the</strong> probe orifices was not achieved<br />

here, <strong>the</strong> cooling rate <strong>of</strong> <strong>the</strong> products was assumed to be sufficient to quench<br />

<strong>the</strong> NO forming reactions, which <strong>the</strong>mselves require a high activation energy.<br />

Chemical transformations <strong>of</strong> NO x in <strong>the</strong> temperature range <strong>of</strong> 300 to 700 K are<br />

<strong>of</strong> special interest here, since moderate temperature probing is encountered<br />

and <strong>the</strong> sample has an extended residence time at lower temperatures while<br />

undergoing transport and storage in <strong>the</strong> EGS system. Figure C.6 shows <strong>the</strong><br />

stability <strong>of</strong> hydrogen sulfide (H 2 S) when Sulfinert ® coating is applied. It <strong>of</strong>fers<br />

inertness for active compounds, including polar and volatile organic compounds<br />

(VOCs). Sample collection and storage <strong>of</strong> sulfur, nitrogen, and mercury<br />

containing species are reliable at ppb levels [351, 406, 407]. In Figure C.6,<br />

<strong>the</strong> concentration stability <strong>of</strong> H 2 S at 11ppb is illustrated for dry and humid<br />

conditions.<br />

120<br />

%<br />

Time t<br />

H2S recovery rate RH2S<br />

80<br />

40<br />

Coated cylinder (dry)<br />

Coated cylinder (wet)<br />

Electropolished cylinder<br />

0<br />

0 2 4 6 d<br />

Figure C.6: Stability <strong>of</strong> Hydrogen Sulfide in Sample Cylinder (reprinted from Refs. [351,<br />

407]).<br />

222

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