Compressor train of chemical plants and method of operating compressor train of chemical plants

A compressor train of a chemical plant comprising:

• a compression unit which is driven to compress a process gas of the chemical plant;
• a steam turbine which is rotated by steam generated in accordance with processing of the process gas of the chemical plant to drive the compression unit;
• a motor which is able to assist a rotation of the steam turbine;
• a frequency conversion unit which is connected to an electric power system and controls a rotation of the motor;
• a shaft seal device which seals a gap between a stator of the steam turbine and a rotor of the steam turbine;
• a vacuum pump which is driven to be able to reduce pressure inside the steam turbine;
• and
• a control device which controls an operating status of the steam turbine, wherein
• the control device includes a vacuum pump driving unit which reduces the pressure inside the steam turbine by driving the vacuum pump while an inflow of the steam generated in accordance with the processing of the process gas into the steam turbine is stopped, a motor starting section which starts to drive the steam turbine by starting to drive the motor while the pressure inside the steam turbine is reduced and the inflow of the steam into the steam turbine is stopped, a motor driving section which continues to drive the motor, and a steam switching unit which starts the inflow of the steam into the steam turbine when an amount of the steam generated in accordance with a driving of the motor becomes a specified amount or more while the motor continues to drive.