A description is given of a method as well as a plant for manufacturing
cement clinker by which method cement raw meal is preheated in a preheater
(1), calcined in a calciner (3) comprising an upper end (3a) and a lower
end (3b), burned into clinker in a kiln (5) and cooled in a subsequent
clinker cooler (7). The invention is peculiar in that exhaust gases from
the kiln (5) are introduced into the upper end (3a) of the calciner, in
that fuel is likewise introduced into the upper end (3a) of the calciner,
in that the exhaust gas/fuel suspension is directed down through the
calciner (3), in that preheated air from the clinker cooler (7) and
preheated raw meal from the preheater (1) in combination or separately are
fed into the calciner (3) at a location under the zone where exhaust gases
from the kiln and fuel are introduced, in that the preheated air is
directed down through the calciner (3), being gradually mixed with the
exhaust gas/fuel suspension, in that the raw meal under the action of
gravity is directed down through the calciner (3) along its wall, being
suspended in the exhaust gases at the lower end (3b) of the calciner, and
in that the exhaust gas/raw meal suspension is extracted from the lower
end (3b) of the calciner and conveyed to a separating means (4) for
separating the raw meal which is subsequently directed to the kiln (5).
Hereby is obtained a significant reduction of the NOx which is led to the
calciner together with the kiln exhaust gases, a high degree of fuel burn
out even when using fuels with a low content of volatile constituents, and
a low degree of conversion into NOx of the nitrogen which is led to the
calciner together with the fuel.
