🔍 Key Concepts

• Boiler economizer function – what does the economizer do to the feedwater and how does that affect overall efficiency? • Heat recovery from exhaust gases – what happens to stack (uptake) heat when you bypass the economizer? • Relationship between feedwater temperature, fuel consumption, and tube metal temperature.

💭 Think About

• When feedwater bypasses the economizer, does the boiler receive hotter or colder feedwater? How does that change the fuel needed to make steam at the same pressure and temperature? • If no relatively cool water is flowing through the economizer tubes, what happens to tube metal temperature when hot exhaust gases keep flowing past them? • Does a change in feedwater routing through or around the economizer directly affect the amount of heat going to the superheater, or mainly affect something else? Think about the flow path of gases and water/steam.

✅ Before You Answer

• Be clear on the flow path: furnace → boiler tubes → superheater → economizer → stack. Where exactly is the economizer in that sequence? • Decide whether bypassing the economizer makes stack losses higher or lower, and how that ties to fuel use for the same steam output. • Ask: Is each option (A, B, C) independently correct under normal operating conditions, or is any one of them clearly inconsistent with how boilers and economizers actually work?