🔍 Key Concepts

• Function of downcomers in a water-tube boiler circulation system • Difference between combustion process and water/steam circulation • Meaning of end point of combustion vs end point of circulation in boiler operation

💭 Think About

• Ask yourself: Do downcomers carry water/steam mixture or combustion gases, and between which parts of the boiler? • Which process do downcomers directly affect: how fuel burns, or how water moves through the boiler tubes? • If a component is outside the furnace gas path, is it likely to change the end point of combustion?

✅ Before You Answer

• Be clear on the primary purpose of downcomers in a water-tube boiler (what they carry and why). • Verify which term—end point of combustion or end point of circulation—relates to gas-side versus water-side processes. • Confirm whether any boiler casing connection would directly influence combustion completion, or only the circulation loop.