Condenser Air Extraction — Holding Ejectors

The surface condenser in a steam power plant operates at vacuum (typically 50–70 mbar / 38–53 Torr abs) to maximise the enthalpy drop across the turbine and improve thermal efficiency. Air and non-condensable gases inevitably in-leak through the condenser shell, flanges and expansion joints. If not continuously removed, these gases blanket the condenser tubes and raise the condenser pressure, reducing plant output and efficiency. Two-stage steam ejector air extraction systems (holding ejectors) continuously remove these in-leaked gases, maintaining the design condenser vacuum throughout plant operation.

For every 1 mbar rise in condenser back-pressure, the turbine output reduces by approximately 0.3–0.5 MW. Maintaining tight condenser vacuum with reliable holding ejectors delivers a continuous and measurable power output benefit, making the ejector one of the highest-ROI components in the auxiliary system.

Hogging Ejectors — Plant Start-up

When a power plant starts up from cold, the condenser must be pulled down from atmospheric pressure to operating vacuum (≈50 Torr) as rapidly as possible before turbine rolling. A hogging ejector — typically a large single-stage unit — handles the massive gas load at atmospheric pressure and reduces the condenser pressure to a point where the holding ejectors can take over, typically in 15–30 minutes. Primetech designs hogging ejectors to meet the start-up time required by the plant dispatch specification, switching automatically to holding ejectors once operating vacuum is established.