Valmet Technologies Oy

Mikko Varonen

Matti Nieminen

Pekka Lehtonen

Tero Luomaharju

Juha Hiljanen

Pertti Tapiainen

A method for heating a heat exchange medium in a fluidized bed boiler (), the method comprising burning first fuel () in a first furnace () of the fluidized bed boiler () to produce first flue gas (); recovering heat from the first flue gas () to a heat exchange medium using a first heat exchanger (); conveying the heat exchange medium from the first heat exchanger () to a second heat exchanger (), of which at least a part is arranged in contact with a fluidized bed of the fluidized bed boiler (); burning second fuel () in a second furnace () of the fluidized bed boiler () to produce second flue gas (); conveying the heat exchange medium from the second heat exchanger () to a third heat exchanger (); and recovering heat from the second flue gas () to the heat exchange medium using the third heat exchanger (). A fluidized bed boiler () for performing the method. A loopseal heat exchanger () that is, when installed in a loopseal of a circulating fluidized bed boiler, configured to burn second fuel () in a second furnace () of the loopseal heat exchanger () to produce second flue gas (); convey the heat exchange medium from the second heat exchanger () to a third heat exchanger (); and recover heat from the second flue gas () to the heat exchange medium using the third heat exchanger ().

Method for heating a heat exchange medium in a fluidized bed boiler, a fluidized bed boiler, and a loopseal heat exchanger

The solution comprises a method of and a system for maintaining steam temperature and therefore electricity production efficiency with decreased loads of a steam turbine power plant comprising a fluidized bed boiler () and a fluidized bed superheater () adapted to superheat steam supplied to a steam turbine (). According to the solution, the steam temperature may be maintained by providing, outside a furnace (), additional heating to the fluidized bed material in its outer circulation, thereby increasing the amount of thermal energy available in the fluidized bed material to be transferred in the fluidized bed superheater () to the steam supplied to the steam turbine (). Such additional heating may be performed by selectably supplying combustible gas with nozzles () into and/or burned with a burner in or in the vicinity of the fluidized bed material outside the furnace (). As an additional aspect of the disclosed solution, the combustible gas may be produced with a gasifier ().

Method and a system for maintaining steam temperature with decreased loads of a steam turbine power plant comprising a fluidized bed boiler

A method and an arrangement for optimizing combustion conditions in a fluidized-bed boiler, in which combustion gas is fed at two or more height levels, the first of which is a primary level (P) which is located at the height of a furnace bottom and the second is a secondary level (S) which is located above fuel feed height (F), above which secondary level (S) there can be still other combustion gas feed levels (T, . . . ). At least one combustion gas feed level (P, S, T, . . . ) is fed at different points of the furnace () in its horizontal direction with combustion gases having different oxygen contents such that zones of different oxygen content can be formed in the horizontal direction of the furnace ().

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Tampere, Finland

Mikko Varonen