A. Ahlstrom Corporation

Foster Wheeler Energia Oy

Juha Sarkki

Matti A Hiltunen

Pertti Kinnunen

Ragnar Lundqvist

A method of combusting oil shale in a circulating fluidized bed boiler. Fuel, including oil shale, is introduced into a furnace of the circulating fluidized bed boiler, primary oxygenous gas is introduced through a bottom grid of the furnace, and secondary oxygenous gas is introduced to the furnace at a first level above the level of the bottom grid. The primary oxygenous gas is introduced to the furnace at a rate providing below the first level a fluidizing velocity of less than 2.5 m/s, and the primary and secondary oxygenous gases are introduced to the furnace in such a way that a circulating fluidized bed is formed, and the fluidizing velocity at the first level is less than 70% of the fluidizing velocity in the upper portion of the furnace.

Method of combusting oil shale in a circulating fluidized bed boiler

In a fast fluidized bed reactor having, in a lower region, downwardly and inwardly inclined walls, a change in the direction of the wall surface or a ledge or protrusion is provided to change the direction of the particles flowing downwardly adjacent the wall for directing the particles inwardly away from the wall and into the region acted on by the nozzles providing the fluidizing gas. The change of direction, abutment or projection is preferably provided along the refractory wall surface at an elevation 200-1100 mm above the grid plate. In this manner, clogging of the nozzles is prevented and more efficient and effective fluidization and combustion processes occur.

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Kirkkonummi, Finland

Juha Sarkki