Machine train for producing nitric acid

A machine train (102) for producing nitric acid, comprising:

• a steam turbine (10) having a steam turbine rotor (11) configured to rotate at a first rotational speed (n10);
• a first compressor (20) having a first compressor rotor (21) configured to rotate at a second rotational speed (n20);
• a second compressor (30) having a second compressor rotor (31) configured to rotate at a third rotational speed (n30);
• and
• an expander (40) having an expander rotor (41) configured to rotate at a fourth rotational speed (n40),
• wherein the steam turbine (10) is configured to drive the first compressor (20), and the rotor (11) of the steam turbine (10) is operationally connected to the rotor (21) of the first compressor (20) via a first coupling (K1),
• wherein the rotor (21) of the first compressor (20) is operationally connected to the rotor (31) of the second compressor (30) via a second coupling (K2) and drives the second compressor (30).
• Therein the expander (40) is configured to drive the second compressor (30) and the rotor (41) of the expander (40) is operationally connected to the rotor (30) of the second compressor via a third coupling (K3), and
• wherein the second compressor (30) is configured and efficiency optimized with respect to its third rotational speed (n30) such that during operation of the machine train (102) the first rotational speed (n10) of the steam turbine (10), the second rotational speed (n20) of the first compressor (20), the third rotational speed (n30) of the second compressor (30) and the fourth rotational speed (n40) of the expander (40) are equal.