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The possibilities of achieving a substantial reduction in NO(x) and SO(2) emissions with two-stage combustion in a fluidized bed are investigated. This process divides the combustion air so that the primary air flow is fed to the bed and the secondary air flow is introduced into the freeboard. Emissions below 200 mg/nm3 (7% O(2)) and an excellent combustion efficiency are easily realised. Initially the work was carried out in a 60 x 60cm AFBC unit at Twente University. In the second phase the larger 4MWth TNO AFBB unit was engineered for two-stage combustion. The third phase comprised verification and optimisation of the TU findings at TNO. Although the trends could be up-graded the absolute emission levels were lower in the larger unit. Bed temperature reduction and the use of fine limestone lowered the SO(2) emission levels, as did higher primary air to coal ratios. CO emission is affected by bed and freeboard temperatures and the fly ash recycle rate. The secondary air injection procedure is crucial to the optimum design.

Additional information

Authors: TOSSAINT H H J, Stork Boilers (NL);LUTTIKHOLT J J M, Stork Boilers (NL);VALK M, Twente University (NL);BRAMER E A, Twente University (NL);WORMGOOR J W, TNO (NL);BIJVOET U H C, TNO (NL)
Bibliographic Reference: EUR 12546 EN (1990) 31 pp., MF, ECU 4
Availability: (2)
Record Number: 199010175 / Last updated on: 1994-12-01
Original language: en
Available languages: en
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