Bobby3
Mechanical
- Sep 14, 2012
- 1
Our plant is considering removing the low pressure (LP) economizer recirculation pump in our heat recovery steam generator (HRSG boiler) to reduce station auxiliaries service. Without the Economizer Recirculation Pump, we have two concerns: (1) Steaming in the LP economizer tubes, and (2) chemical attack from sulfur condensation, dependent on the skin temperature of the boiler tubing and the sulfur dew point. We have a horizontal HRSG (Gas flows horizontally and water flows vertically).
A. I have read that the tube skin temperature will be closer to the side with the larger heat transfer coefficient. I believe that water has a HX Coef approx 20 times larger than the flue gas, therefore, the tube skin temp will be closer to the water temp, but how close?
Please describe any concerns or issues.
B. Have you ever considered removing the LP economizer pump from service?
C. What methods (e.g., thermal models/equations, thermocouple tests, etc.) were used to estimate the tube skin temperature?
D. Did you install thermocouples (T/Cs) on the tubes to monitor skin temperature?
E. If a similar change in equipment or operation was performed, what effects did that have on tube life?
I am not looking to create a model of the HRSG, but just get a general, conservative, answer. If you are curious, the water going in is at 130 deg F. After traveling through several rows, with gas passing over the tubes, it comes out at at approx 280 deg F. The gas comes in at approx 400 to 405 deg F. It then goes out the stack at about 200-205 deg F.
Thanks for your time.
A. I have read that the tube skin temperature will be closer to the side with the larger heat transfer coefficient. I believe that water has a HX Coef approx 20 times larger than the flue gas, therefore, the tube skin temp will be closer to the water temp, but how close?
Please describe any concerns or issues.
B. Have you ever considered removing the LP economizer pump from service?
C. What methods (e.g., thermal models/equations, thermocouple tests, etc.) were used to estimate the tube skin temperature?
D. Did you install thermocouples (T/Cs) on the tubes to monitor skin temperature?
E. If a similar change in equipment or operation was performed, what effects did that have on tube life?
I am not looking to create a model of the HRSG, but just get a general, conservative, answer. If you are curious, the water going in is at 130 deg F. After traveling through several rows, with gas passing over the tubes, it comes out at at approx 280 deg F. The gas comes in at approx 400 to 405 deg F. It then goes out the stack at about 200-205 deg F.
Thanks for your time.