CPH inlet design temperature is 60 degrees and we keep flue gas outlet temperature above 85 degrees to avoid corrosion due to sulfuric acid dew point. For efficiency point of view we wanted to reduce CPH inlet temperature and it will ultimately reduce CPH outlet flue gas temperature.

So what should be minimum CPH inlet temperature and minimum flue gas temperature at outlet of CPH in case of HRSG running on Natural Gas?

Please advice.

 

The answer lies inside you question itself.

Check the dew point of the flue gas. Maintain the stack temperature at least 5 degree above the dew point and ensure zero condensation. CPH inlet temperature is not the control variable here rather it is a dependent variable of stack temperature.