Closed-loop cooling fluid circuit for magnetic bearings of an expander-compressor system

An expander-compressor system for circulating a process gas, comprising:

• an expander configured to expand the process gas;
• a compressor configured to compress the process gas;
• a shaft mechanically coupling the expander and the compressor;
• a casing housing the shaft;
• a dry gas seal arranged at the casing around a first end of the shaft or a second end of the shaft;
• at least one magnetic bearing acting on the shaft;
• a cooling fluid circuit for cooling the at least one magnetic bearing through circulation of a cooling fluid, the cooling fluid circuit comprising a heat exchanger configured to remove heat from the cooling fluid;
• wherein the dry gas seal is configured to avoid leakage of the process gas to the cooling fluid circuit at the shaft,
• wherein the dry gas seal comprises a stationary ring and a rotating ring,
• wherein the stationary ring is mechanically coupled to the casing,
• wherein the rotating ring is mechanically coupled to the shaft,
• wherein the at least one magnetic bearing is positioned inside the casing,
• wherein the heat exchanger, the compressor, and the expander are positioned outside the casing,
• wherein the compressor and the expander are disposed on opposite ends to the casing, and
• wherein the cooling fluid circuit is spaced apart from each of the compressor and the expander and arranged in a closed-loop configuration that cools the at least one magnetic bearing, exits from a first side of the casing, is cooled by the heat exchanger, and then re-enters the first side of the casing.