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(11) | EP 0 176 293 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Recirculating fluid bed combustor - method and apparatus |
| (57) A fluidized bed combustor (10) for burning solid fuel or dirty liquid fuels comprised
of a bubbling fluid bed (15) with heat exchanger tubes (13) in the bed, a hot recycle
cyclone (21). a convective heat exchanger (26) and a particle filter (27). The bubbling
fluid bed (B) is operated at low superficial velocities of 0.5 to 6 ft/second (0.15
to 1.8 m/s) and is composed of fine particulate 45 to 2000 microns in diameter with
up to 40% less than 200 microns. Fines elutriated from the bed are isothermally recycled
back to the bed resulting in high combustion efficiency and good sulphur oxide suppression
from sorbents contained in the bed. The material recycled in one hour is equivalent
to twice the weight of the bed. Ammonia (24) injected upstream of the recycle cyclone
(21) suppresses nitrogen oxides with high efficiency because of the excellent mixing
in the cyclone (21). The heat transfer coefficient on the tubes in the bed is increased
at least 2 to 4 times because of the fine particulate nature of the bed. Fluidization
occurs over a 10:1 range in superficial velocities. |