Question 36 QMED01 - Junior Engineer

The Correct Answer is A. **Explanation for why Option A is correct:** In a two-stage air ejector assembly, the primary purpose is to remove non-condensable gases (primarily air) and water vapor from the main condenser to maintain the required vacuum. The operation proceeds sequentially: 1. **First Stage Ejector (Hogging or High-Vacuum Stage):** This ejector takes suction directly from the main condenser's hotwell area (or vacuum space). It uses high-velocity motive steam to entrain the steam/air mixture and compresses it to a slightly higher pressure. 2. **Discharge:** The discharge from the first stage ejector is routed directly into the **intercondenser**. The intercondenser cools this mixture, condensing most of the motive steam used by the first stage before the mixture (now concentrated air and remaining vapor) proceeds to the second stage. Therefore, the statement that the steam/air mixture from the main condenser is discharged by the first stage air ejector to the intercondenser is true. **Explanation for why the other options are incorrect:** * **B) Air is removed from the condensate as it passes through the tubes.** This is incorrect. Air is removed from the *main condenser vacuum space*. In both the intercondenser and the aftercondenser, cooling water (usually condensate) passes through the tubes to condense the motive steam. Air and non-condensable gases remain on the shell side to be drawn off by the next stage ejector. Air is removed from the system, not necessarily from the condensate passing through the tubes (though the condensate is the cooling medium). * **C) The first stage air ejector takes suction on the second stage to increase vacuum.** This is incorrect. The operational flow is sequential, where the first stage takes suction from the main condenser, and the **second stage** (the low-vacuum stage) takes suction on the discharge (shell side) of the intercondenser. The first stage does not take suction on the second stage; it operates independently to achieve the initial high vacuum. * **D) Steam to the aftercondenser is condensed and returned to the main condenser via the loop seal.** This is incorrect. While the condensed steam from the aftercondenser is returned, it is typically returned to the **hotwell** of the main condenser (which collects condensate). The loop seal is designed to drain the condensed steam (drains) from both the intercondenser and the aftercondenser while preventing air from leaking back into the vacuum space of the condenser/ejector assembly. The loop seal facilitates the return of condensed motive steam, but it does not return "steam to the aftercondenser"; it returns the condensed *drains* from the aftercondenser.