Complex sentence: It passes through five Curtis wheels and numerous reaction stages before exiting at low pressure, almost certainly to a condenser to provide a vacuum that maximizes the energy extracted from the steam, and condenses the steam into feedwater to be returned to the boilers.
Split into simpler sentences: It passes through five Curtis wheels and numerous reaction stages before exiting at low pressure, almost certainly to a condenser. The condenser provides a vacuum that maximizes the energy extracted from the steam, and condenses the steam into feedwater to be returned to the boilers.