Turbomachinery for Nitric Acid Plants - MAN Diesel & Turbo

This procedure ensures optimum,
gentle cleaning of the flow channel and
has little influence on the process mass
flow rate as only small quantities of
water are injected.
The poisonous effect of nitrous gas
makes it necessary to prevent any escape
of gas from the compressor. This
requirement is met as folIows:
Double sealing chambers are provided
at the main shaft in the casing.
The inboard chambers are fed with
sealing air (from the discharge of
the air compressor), while the outboard
chambers are provided with a
connection to atmosphere. This is led
outside the machine house in case
any leakage does arise. The ingress
of NO-gas into the lube-oil circuit is
prevented by an additional sealing
chamber in each bearing housing
of the machine train.
A special sealing agent is applied
at the horizontal joint flanges of the
casing. In addition, the casing joint
bolts are tightened at an exactly
defined force by means of a hydraulic
tightening device.
All parts in contact with the gas are
made of acid resistant CrNi steel to
counteract the corrosive effect of the
nitrous gases. The chemical reactions
that occur during compression have to
be taken into account when designing
such a compressor. These reactions
are the dissociation of N2O4 to NO2 and
to a much lesser degree and the
oxidation of NO to NO2. The latter
reaction causes heat to be released,
whereas for dissociation considerable
amounts of heat are needed. In
designing the compressor, these heat
quantities/temperature changes are
determined stage by stage and considered
when sizing the flow channel
sections.
Nitrous-gas compressor
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