Question 6 QMED01 - Junior Engineer

The Correct Answer is C ### Explanation of Why Option C ("condensate and feed system") is Correct The air ejector (AE) system uses steam to create a vacuum in the main condenser. This steam, along with non-condensable gases drawn from the condenser, passes through a series of intercondensers and aftercondensers. These condensers are cooled by passing a flow of **main condensate** through them. The purpose of using main condensate as the cooling medium is twofold: 1. **Heat Recovery:** The heat recovered from the condensing steam in the AE condensers preheats the main condensate (which is the feedwater source). This heat is not wasted and improves overall cycle efficiency. 2. **Water Conservation:** The steam condensed in the AE condensers (known as AE drains) is high-quality pure water. This pure water is mixed directly with the cooling water (the main condensate). Since the cooling water is the main condensate, the combined stream (main condensate + recovered AE drains/condensate) is discharged directly back into the **condensate and feed system** (specifically, usually downstream of the low-pressure heater stage or directly to the deaerator/boiler feed pump suction line, depending on the plant design, but fundamentally it remains part of the main closed loop system). ### Explanation of Why the Other Options Are Incorrect **A) main condenser hotwell:** The main condensate has already been pumped out of the main condenser hotwell by the condensate pump before it is routed to the air ejector condensers for cooling. Discharging back to the hotwell would short-circuit the flow path and prevent the condensate from moving forward in the feed system. **B) atmospheric drain tank:** The water leaving the air ejector condensers is high-quality main condensate (used for cooling) combined with high-quality AE drains (condensed steam). This water is crucial for the boiler cycle. The atmospheric drain tank is typically used for lower quality drains or vented steam that may need treatment before returning to the cycle, or for collecting small, intermittent overflows, making it unsuitable for the continuous, high-volume flow of main condensate. **D) auxiliary condenser hotwell:** An auxiliary condenser handles steam from auxiliary turbines or systems (like gland sealing steam or turbo generator exhaust) and has its own associated hotwell. The main condensate flow from the main cycle would not be discharged into the hotwell of a separate auxiliary system, as this would mix it with auxiliary drains and disrupt the main condensate flow path required for boiler feeding.