Air Preheater Enhancement – Shajiao A Power Station, China

Replacing the stationary matrix design of air preheaters at Shajiao Power Station, with Howden VN preheaters resulted an increase in unit output of 20MW and a payback period of less than 2 years. Shajiao A consists of 3x200MW coal fired boilers and the regenerative air preheaters, which were of the stationary matrix type, were permitting an excessive amount of air to leak into the flue gas stream towards the end of each yearly operating cycle. This resulted in a shortfall of around 20MW in electrical output. It was decided that the best solution was to remove the heaters and replace them with the Howden VN design, which operates on the more common rotating matrix principle. A second objective of the project was to improve the heat recovery and increase the temperature of the air entering the boiler. As the duct layout for the two types of air preheaters is significantly different, Howden accepted responsibility for the design of a revised layout, which in addition to matching the terminal points would result in a lower pressure drop

Tests have confirmed that the leakage has been reduced to less than 6%. At the same time, the air temperature to the boiler has increased by 20ºC, which equates to an increase in boiler efficiency of around 1%.

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