Exam Question

### (a) Exhaust Gas Economizer: Definition and Components
An Exhaust Gas Economizer (EGE), also known as a waste heat recovery boiler, is a critical component for improving the overall thermal efficiency of a marine propulsion plant. It is a forced circulation, water-tube heat exchanger that utilizes the high-temperature thermal energy from the main or auxiliary engine exhaust gas, which would otherwise be lost to the atmosphere.
**Primary Function:**
To absorb waste heat from the exhaust gases (typically at 250°C - 400°C) and use it to generate low-pressure saturated steam (typically 7-9 bar). This steam is then used for various shipboard services, significantly reducing the operational load on the oil-fired auxiliary boiler, thereby saving fuel and reducing emissions.