| Engineers are always seeking new techniques to improve plant efficiency and reduce emissions for fossil fueled power plants. The Energy Research Center had previously designed and tested condensing heat exchangers that reduce the temperature of a flue gas below the acid and water vapor dewpoints. Latent and sensible energy were recovered from the flue gas, and, depending on the fuel, acid emissions were reduced.;It is known that condensed acids from flue gas are very corrosive. Therefore, a new type of heat exchanger was designed specifically to resist corrosion. This neutralizing heat exchanger was then fabricated and tested. To specifically combat corrosion, a thin liquid film was evenly distributed on the walls of the heat exchanger to dilute and neutralize the acids when they condense.;Compared to previously tested heat exchangers, this acid neutralizing heat exchanger had much less surface area, yet recovered comparable amounts of energy. Comparisons were made between the neutralizing heat exchanger (3.9 ft2 surface area) and two previously tested heat exchangers: one with fins (30 ft2) and one with no fins (17.5 ft 2). In conditions with the coolest cooling water temperature, the heat flux in the neutralizing heat exchanger was 6.75 times the finned heat exchanger and 3.75 times the heat exchanger without fins. Tests also showed that there was no measurable heat transfer resistance due in part to the presence of the thin liquid film on the heat transfer surface area. The combination of good heat transfer performance and resistance to corrosion make this a promising heat transfer concept for recovering water vapor from flue gas. |
