The region of Narva in Estonia is one of the largest ranges of oil shale in the world. That is why the area is a concentration of a considerable number of power plants fuelled by oil shale. During 2002-2004, Foster Wheeler Energia Oy has provided Balti Elektrijaam and Eesti Elektrijaam, the two largest power plants in the area, with two new 215 MW CFB boilers each.
Pneumatic NI250 acoustic cleaners were chosen as cleaners for the economisers of the boilers. Each boiler was provided with 24 cleaners, for a total of 96 in all.
The special feature of oil shale is its great percentage of incombustible matter: about 50 % of its constituents turn into cinder and 10 % of them are incombustible. This causes particular problems in regard to keeping the heat transfer surfaces clean. The cinder of oil shale is strongly contaminating and forms an insulating layer on the heat transfer surfaces, quickly reducing the operating efficiency of the plant. As for the old plants in Narva, the problem is dealt with by shutting down the boilers at about two weeks’ intervals and spraying them with water and cleaning them mechanically.
Several years after the introduction of the new plants Nirafon acoustic cleaning system has proved to be a most practicable solution even in intractable conditions of this extent. The cleaning systems integrated with the operating systems of the plants have fully met the objectives set.
The sound pressure shocks programmed into continuous cleaning cycles keep the economisers free from cinder and there has been no need for expensive shut-downs, nor for manual cleaning. The acoustic cleaners have not damaged the structures of the plants. 96 NI250 pneumatic acoustic cleaners Cleaning objects: ECOTemperature: 460 – 300 C°.