Air Preheater Enhancement – Kingsnorth Power Station, UK
By replacing adjustable sealing with fixed sealing on the air heaters of Units 1 & 2 of Kingnorth PS, the leakage was reduced from 14 to 7%
Kingsnorth is a 4x500MW dual fired station. At certain times, for example when operating with high turbine backpressure, the capacity of the induced draught fan was limiting station MW
output. The root cause was determined to be high air leakage in the air preheater, caused by gradual deterioration of the sealing system. Howden proposed that the sealing system should be modified to the Howden VN design. At the same time it was decided to take the opportunity to increase the depth and to change the profile of the elements in the rotor.
The adjustable radial and axial sector plates were replaced by a fixed sector plate design. In addition, doubling the number of radial seals and improving their design completed the change to the advanced VN system. By carefully optimising the container supports it was possible to release space to permit an increase in the depth of elements from 1930 to 2130mm.
The original 2.5DU elements were replaced by a configuration of 9.5/3CU and 11/3CHB.
This resulted in the air leakage being reduced from 14 to 7% and the gas exit temperature had dropped by the anticipated 6°C. The overall effect was an increase in boiler efficiency of 0.3%. When performance verification was carried out three years later, the sealing system was operating satisfactorily and there had only been a marginal increase in leakage. A further benefit was obtained in the reduction in maintenance required due to the elimination of adjustable sector plates.