Page 40 - Uninterruptible Power Supplies

Standby Power Generating Sets
38 Chapter One

The uncorrected height so obtained has to be corrected for the effect of
nearby buildings. The method is clearly set out in the Memorandum with
illustrations and examples. The heights determined by these procedures
should be rounded to the nearest meter, and should be regarded as a
guide rather than a mathematically precise statement. The conclusions
may need to be modified in the light of particular local circumstances
such as topographical features.

Pollutants Included in Exhaust Discharge
Exhaust gases discharged from the engine include, in addition to carbon
dioxide (CO 2 ) and water vapor (H 2 O), carbon monoxide (CO), various
nitrous oxides (NO X ), aldehydes (HCO), unburnt hydrocarbon fuel (HC),
and particulate matter. There will also be a small quantity of sulphur
dioxide, depending on the sulphur content of the fuel. Carbon dioxide,
water vapor, and any sulphur dioxide are the natural result of burning
hydrocarbon fuel and cannot be reduced. Carbon monoxide and aldehy-
des are the result of incomplete combustion, nitrous oxides are formed by
hot spots within the combustion spaces, unburnt fuel is fuel which has
escaped the burning process, and particulate matter is finely divided mat-
ter, mainly carbon, resulting from incomplete combustion of the atomized
fuel injected into the combustion spaces. All these pollutants are being
reduced as the technology of injectors and combustion spaces advances.
These pollutants are now controlled by European legislation, on a gram
per kWh basis, for road vehicle engines. As the efficiencies of engines are
increased the pollutants are reduced but legislation may appear which
relates to standby installations and installers should be aware of any new
legislation. Engine and generating set makers will of course be aware of
the latest requirements.

Catalytic Converters
Catalytic converters are installed in line with a run of diesel engine
exhaust pipe in the same way as silencers; they include a ceramic hon-
eycomb providing an enormous surface area for a catalytic metallic film
over which the exhaust gases pass. They increase the backpressure of
the exhaust system and therefore reduce, by a few percent, the effi-
ciency of the engine; it follows that their use is not without an environ-
mental “disbenefit.” With the increasing attention being given to health
and safety it may not be long before catalytic converters are required on
some standby sets.
There are two types of catalytic converter: first, the two-way or oxida-
tion converter, and second, the three-way or oxidation-reduction con-
verter. The former uses a platinum and palladium catalyst which oxidizes
carbon monoxide and hydrocarbons to form carbon dioxide and water,

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