Environmental Engineering Reference
In-Depth Information
Solid
Fuel/ Waste
Synga s
High Temp .
Syngas
Slagging
Gasifier
Gas
Cleanup
Engine
or Boiler
Power
Output
Steam
High Temperature Air
and Steam Generator
Water
Air
grated boiler/engine using syngas produced from solid waste using high
temperature air and steam.
FIGURE 6.7
Inte
2.
Large volume reduction of almost all types of wastes.
3.
Permanent disposal method for solid wastes, including low grade coals.
4.
Minimum amount of dioxin generation due to the reactor operation at
high temperatures under reducing conditions.
5.
Negligible amount of dioxin generation with the refined gas since almost
all of the chlorine has been removed in the preprocessing stage. Any dioxin
present will be decomposed in the high temperature air combustion pro-
cess.
6.
Rapid reduction of the exhaust gas temperature as the gases pass through
a very large surface area honeycomb regenerator used to preheat the air.
The regenerator acts as an efficient heat recovery system and prevents the
formation of dioxins via rapid cooling of the exhaust gases to a temper-
ature below the region where the dioxins are formed (see the discussion
below on the formation of dioxins and furans). This is in contrast to the
conventional system in which exhaust gases are cooled with a water spray
so that the heat is lost to the exhaust and high levels of dioxins are formed.
Possible measures to reduce emissions of dioxins and related compounds from
waste combustion furnaces are: (1) reducing the volume of such materials as they
may generate dioxins and furans in the furnace, (2) preventing reproduction of
dioxins and furans at low temperatures, (3) decomposition or elimination of dioxins
and furans by catalysts or adsorption. Effective measures for the thermal destruc-
tion of wastes are to implement the three Ts (high Temperature, high Turbulence
and long residence Time). This is consistent with the basic characteristics of high
temperature air combustion. Fluidized-bed combustion can be suitable for burning
refuse derived fuel (RDF). However, because of the low temperature operation of
fluidized beds, proper measures must be taken to reduce the formation of dioxins
and furans. A study conducted by IHI on simulated waste consisting of RDF and
PVC laminated paper, using a fluidized-bed furnace and high temperature air,
showed reduction of dioxin and related compounds by rapid cooling of the exhaust
gases. This reduction is consistent with the following general information on the
formation of dioxins.
 
 
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