🔎 What is Steaming in HRSG Economizers? And How Do We Prevent It?

In gas turbine Heat Recovery Steam Generators (HRSGs), economizer steaming is a common challenge—especially during low or part-load operation.

When exhaust gas temperature drops (e.g., 385°C vs. 500°C), steam generation in the evaporator and superheater decreases. The economizer, however, still absorbs significant enthalpy due to unchanged gas-side flow. As a result, the feedwater reaches saturation temperature, forming steam bubbles inside economizer tubes.

⚠️ Why is this a problem?

• Tube vibration
• Salt deposition and fouling
• Flow blockage
• Reduced efficiency and reliability

✅ How to Prevent Steaming in HRSG Economizers

Engineers and operators can apply several strategies:

1. Increase blowdown rate → Boosts mass flow through tubes, reducing steaming during short-duration events.
2. Supplementary firing → Raises exhaust gas temperature, increasing steam generation and stabilizing economizer operation.
3. Relocate feedwater control valve → Positioning it between economizer and evaporator raises operating pressure, increasing saturation temperature above exhaust gas temperature.
4. Optimize tube flow direction → Ensure steaming surfaces have upward water flow so bubbles can escape smoothly.
5. Gas-side bypass → Reduces economizer duty (though at the cost of efficiency).
6. Partial water-side bypass → Diverts a fraction of feedwater to control outlet temperature and avoid steaming.

References: Heat Recovery Steam Generator Technology, V Eriksen.

Photo: Research Gate