Dunamenti Power Station
Pennguard® protects steel chimney flues in a heavy oil fired power station
6 x 220 MW heavy oil fired Dunamenti Power Station had a problem in its chimneys. The station had two 200 m / 656 ft high chimneys, each with three internal steel flues. Even though the gas temperature was 150 – 160 °C / 302 - 320 °F, the steel flues were under strong acid attack, especially around ‘cold spots’. In order to solve the problem, the steel flues were repaired and partially relined with the Pennguard® Block Lining System.
The problem of heavy oil firing
Most fossil fuels, including coal and lignite contain sulfur, which will be converted into SO2 and SO3 in the combustion process. In the presence of water SO3 will readily convert to sulfuric acid H2SO4 and this is the main cause of corrosion in ducts and chimneys.
In comparison with other fossil fuels, heavy oil creates one of the most acidic and corrosive flue gases. In many cases, the acid dew point of flue gas from heavy oil firing will be higher than 150 °C / 302 °F , due to the high amount of SO3 present in the flue gas. Any steel surface with a lower temperature will quickly be covered with a strongly acidic condensate.
At 125 °C / 257 °F, the sulphuric acid concentration of such a condensate will be around 75-80 % and this combination of temperature and acidity presents an impossible challenge to most materials.
A Pennguard® lining is based on borosilicate glass and therefore has unlimited resistance to sulfuric acid.
Cold spots: a fundamental problem solved by Pennguard® linings
The corrosion problem in the Dunamenti Power Station chimneys centered around ‘cold spots’. Cold spots can be caused by faulty or wet external insulation but also by the presence of external steel reinforcements. Cold spots constantly drain heat from the gas stream, causing the formation of acidic condensate on the inside of a flue.
A Pennguard® lining forms a temperature insulation on the inside of a duct or chimney and therefore prevents cold spots from occurring in the first place.
New structures that will receive a Pennguard® lining can be designed without fear for cold spots. Furthermore, external insulation of the flues becomes unnecessary and can be omitted altogether.
Page 4 of the report provides information on the lining application process.