298 94 307/02 Untersuchungen zum Stand der Umsetzung des ...

Teil 3 Seite 10-6
combustion chamber; the lower boundary is formed by the air diffuser. Swirling air, which
at the same time serves as incineration air, flows through the fluidisation bed mass in an
upward direction. At a certain air velocity, the individual particles of the layer lift from one
another somewhat. Through the air stream and the resultant turbulence, these are placed
into irregular and undirected motion and bump and rub against one another in rapid suc-
cession. During this process, the layer mass is intensively and evenly mixed and in the
process achieves an exchange of material and heat that is characteristic and practically
ideal in terms of the fluidised bed. The heating of the oven takes place through natural gas
or heating oil that is ignited in the swirl chamber by means of start-up burners or heat the
turbulent air in a pre-incineration chamber. After reaching the ignition temperature, addi-
tional fuel can be introduced directly into the hot fluidised bed through lances. The fuel is
introduced directly into the hot fluidisation bed through helixes, where it is liberated
through sudden heating, dried and then comminuted by the turbulent particles. The com-
bustible components are gasified through the intense heat transfer and already largely
burn up in the fluidisation bed. The expansion of the combustion chamber upwards guar-
antees that only tiny small-grained solid matter particles can be discharged. Above the
fluidisation bed, secondary air is injected through nozzles, which ensures that even the
last remaining combustible components are incinerated at a temperature of at least 850
degrees C.
Using animal meal as an example fuel, it can be shown that at an assumed heating
value fluctuation range of 17 to 21 MJ/kg, a thermal load range of approx. 9-12 MW and a
throughput performance of 1.550 to 2.550 kg/h can be attained.
If, in the same fluidisation bed oven on which the incineration performance diagram was
based, raw material is incinerated, a throughput performance of 2.500 – 7.500 kg/h of raw
material and a thermal output of 4,8 – 9,7 MW is attained in this fluidisation bed oven. At a
fixed thermal output, the throughput performance is determined by the heating value of
the fuel, so that the maximum throughput is attained at the lowest fuel heating value of
4MJ/kg, whereas the highest heating value corresponds to the lowest throughput per-
formance.
Achieved environmental benefits
Cross media effects
Operational data Applicability
Economics
Which plant setting represents the most economical and sensible solution is strongly in-
fluenced by local factors (supply volume, transportation routes etc.) In the following table,
only a few important economic criteria are therefore contrasted. A comprehensive plant is
in each case assumed. Location dependent inflow volumes are not taken into account
here. For the purposes of simplification, a raw material volume of 100.000 t/a and a corre-
sponding volume of animal meal of 20.000 t/a is assumed in the following illustration.
Raw material incineration Animal meal incineration
Basis 100.000 t/a raw material 20.000 t/a animal meal