Teruel Power Station
Pennguard® linings protect the FGD outlet ducts of a lignite fired power station
In 1992, Spanish utility Endesa decided to retrofit wet flue gas desulfurization plants to all 3 units of its Teruel Power Station, located roughly between Madrid and Barcelona, about 100 km southeast of the city Zaragoza.
Endesa also decided that the desulfurized flue gas should be reheated to at least 75 °C / 167 °F. The method chosen for reheating is the injection of hot air from the air preheaters into the desulfurized gas stream, at a point directly downstream of the Flue Gas Desulfurization (FGD) absorbers.
The Flue Gas Desulfurization (FGD) outlet ducts are exposed to highly corrosive operating conditions and sometimes to a total or partial FGD bypass of the unscrubbed gas stream. The Pennguard® Block Lining System was chosen for the internal protection of the three large FGD outlet ducts, which have a combined internal area of 7,035 m2 / 75,720 sqft.
Highly corrosive flue gas
Even after a highly efficient desulfurization process, the flue gas is still extremely corrosive to mild steel. The reason is that SO3, which causes the formation of acidic condensate in the ductwork, is only partially removed from the gas stream by the wet FGD process. The average SO3 content of the unscrubbed flue gas in Teruel power station is 140 mg/Nm3 / 50 ppm and much of this will ‘slip’ through the absorbers into the outlet ducts.
The reheating of the scrubbed flue gas by 15–25°C / 59-77°F will raise the temperature above its water dewpoint, but it can never raise the temperature above the acid dewpoint.
Operating experience shows that even under highly acidic conditions, Pennguard® linings offer an estimated service life of 20 years and require very little maintenance.
Due to the insulating properties of the Pennguard® lining system, the FGD outlet ductwork did not require expensive external insulation.
Pennguard® lining application details
After mounting the three large outlet ducts onto their support construction, they were first grit blasted and cleaned. Then, Pennguard® Block Primer was spray applied to the steel surface. Construction details such as flanges of expansion joints and manholes were protected by 2 mm thick strips of a special corrosion resistant alloy.
The Pennguard® lining system itself was installed by a group of 6 – 8 Spanish brick layers and the average production rate was ca. 1.5 m2 / 16 sqft per installer per hour.
Two Hadek QA inspectors and one site manager were present on site to support the applicators and to monitor the quality of the installed linings.
The complete application details are described on page 4 of the Project Report.