The condensation process of acidic vapor in flue gas discharged from the boiler has been tested for its visibility

thereby the acidic dew point of discharged flue gas being determind

and the acidic dew point of flue gas discharged from the boiler being compaired with results calculated by commonly used formulae.The visibility test and practice in operation show that the results from a majority of calculation formulae all have larger deviation with the actual situation

however

the graph-checking method given in 《Design and Operation of heat-recovery boilers》 as well as the empirical formula put forward from Japanese Electric Power Industry Center Institute are conformed better to the actual situation.Furthermore

the visibility test and practice in operation also show that the condensated liquid can't remarkably form on the wall surface

and corrosion on the heat-exchange surface is weak in the case of wall temperature being lower than the acidic dew point and in a range of about 30 ℃ below the acidic dew point

but the flue gas temperature being higher than the acidic dew point.