Air Preheater Enhancement – Matra Power Station, Hungary
Modifications to the air preheaters on the Unit 3 boiler of Matra Power Station reduced leakage and improved boiler efficiency by 1.9%
Matra Unit 3 is a 200MW lignite fired power station in Hungary. The air preheaters (2 per boiler) were fitted with moving radial and axial sector plates that were intended to reduce gaps between the rotor and the housing in an attempt to cut down air leakage.
The sealing had deteriorated to such an extent that a large amount of air was short circuiting the system through the air preheater and thus bypassing the furnace. In addition, a proportion of the air and gas was found to be flowing through gaps between the element baskets and the rotor walls and was therefore not contributing to the heat exchange process. The net effect was a high flow of high temperature flue gas to the chimney, resulting in a reduction in boiler efficiency.
Modifying the existing sealing system to the Howden VN concept has reduced the air leakage from 24% to 4.7% and the mass flow of flue gas dropped by a corresponding amount. Flue gas leaving the air preheater fell in temperature from 205°C to164°C (undiluted), and the boiler efficiency increased by 1.9%. An additional benefit was that the considerable reduction in flow through the FD and ID fans resulted in a significant saving in auxiliary power. The elimination of moving sector plates means that annual maintenance hours are reduced.
The life of the radial and axial seals is increased because there is no possibility of mal-operation of the sector plates causing seal wear. Operational experience since the modification has been good and no increase in air leakage has been detected by the station