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(11) | EP 2 574 841 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Method for reducing nitrogen oxide emissions and corrosion in a bubbling fluidized bed boiler and a bubbling fluidized bed boiler |
| (57) To reduce nitrogen oxide emissions and corrosion in a bubbling fluidized bed boiler
that burns biofuel or waste, air is supplied into the boiler furnace (1) in stages
so that two sub-stoichiometric combustion zones (I), (II) and a superstoichiometric
zone (III) are brought about. The first combustion zone (I) begins from the height
level of primary air supply nozzles (3) and it extends above the fluidized bed (2),
ending under the height level (hS) of secondary air nozzles (6). The second combustion
zone (II) begins from the height level (hS) of the secondary air nozzles (6) and ends
under the height level (hT) of tertiary air nozzles (7). The third combustion zone
(III) begins from the height level (hT) of the tertiary air nozzles. The length of
the first combustion zone (I) is optimized by placing the secondary air nozzles (6)
at a height (hS) from the top surface of the fluidized bed (2), which height (hS)
is chosen according to a given calculation formula and calculated according to furnace-specific
variables, reference values and design point-specific variables. The design point-specific
variables are different in a boiler with a high furnace load and in a boiler with
a low furnace load.
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