ABB SCC-K, Руководство оператора

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42/23-52 EN Rev. 2 SCC-K NO
2
/ NO Converter Operator’s Manual 19
Conversion Principle
Reaction Equation The conversion of nitrogen dioxide NO
2
into nitrogen monoxide NO occurs
according to the following gross reaction equation:
2 NO
2
<–> 2 NO + O
2
Reaction Equilibrium The reaction equilibrium is shifted entirely onto the side of the original material
NO
2
. A shift of the equilibrium towards the products and the resultant high product
yield can only be achieved subject to a high expenditure of energy, i.e. temperature
(100% conversion at temperatures over 600 °C).
Using a Catalyst By using a catalyst the activation energy of the above reaction is reduced
considerably so that conversion rates of 99% are possible at temperatures below
400 °C.
Catalyst A carbon-molybdenum mixture is used as catalyst. The carbon supporting
material guarantees optimal contact between the gas to be converted and the
surface of the catalyst combined with a simultaneously low flow resistance.
Catalyst
Temperatures The catalyst temperature can be adjusted continuously using the temperature
controller on the front of the converter.
The recommended settings for catalyst temperatures depending on the gas flow-
rate for a conversion rate above 95% are:
30 l/h: 320 °C – 60 l/h: 320 °C – 90 l/h: 340 °C – 150 l/h: 360 °C
Gas Conditioning For reasons associated with the filter effect of the catalyst filling an appropriate
gas conditioning system is to be mounted upstream of the converter in order to
separate out suspended particles and to dry the sample gas!
Cross-Sensitivities Ammonia NH
3
in the sample gas converts a part of the NO
2
into dinitrogen oxide
N
2
O and elementary N
2
. Depending on the ammonia concentration, this can cause
a substantial reduction in the conversion rate.