(best examples and good practices) on household organic waste ...

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<strong>and</strong> release of volatile substances from the combustible material, Ignition <strong>and</strong>
oxidation of volatile substances <strong>and</strong> finally combustion of solid carbon in the
presence of oxygen finishes the process. (Bontoux.,1999)
3.2.2.. Mass-burn incineration
During combustion (Figure.14), the waste is burnt in the presence of a <strong>good</strong>
supply of air, so that organic carbon is essentially completely oxidized to
CO2.In order for this process to be effective, the waste to be burnt is mixed well
at the drying stage in order to dry properly. Along with water vapor <strong>and</strong> trace
products of combustion, CO2is discharged to the atmosphere. Energy is
recovered in the form of steam, which is used to drive energy production
turbines for electricity generation which is usually used for the incineration
plant energy consumption. Some incinerators may also provide steam or hot
water for process or community heating schemes as well as electricity in
combined heat <strong>and</strong> power (CHP) applications. There are two main approaches
to waste combustion – mass-burn incineration <strong>and</strong> process <strong>and</strong> burn
incineration, in which a refuse derived fuel (RDF) is first prepared.
Mass-burn incineration (Figure 2.18) is currently the most widely deployed
thermal treatment option, with almost 90% of incinerated waste being
processed through such facilities. As the name implies, waste is combusted
with little or no sorting or other pre-treatment. Waste arriving at a mass burn
incinerator is tipped into a loading pit <strong>and</strong> from there after the drying process
takes place usually at 75-80 o C (something that differs between different
facilities), it is transferred by crane <strong>and</strong> grab system into the combustion
chamber loading chute. The waste is then conveyed through the combustion
chamber, usually on a moving grate system (of which there are many designs)
or through the slow rotation of the combustion chamber itself (rotary kilns).
Whatever system is used, its purpose is to ensure thorough mixing, effective
drying <strong>and</strong> even combustion of the waste, so that complete burn-out has
occurred by the time the ash residue is discharged into a water-filled quenching
tank at the end of the combustion chamber. Air is introduced from below <strong>and</strong>
above the grate at flow rates adjusted to suit the rate of combustion.
The hot combustion gases pass through heat exchange sections of the
combustion chamber, where steam is generated for energy recovery. The
cooling combustion gases then pass through various stages of emission control.
These include dry or wet scrubbers for removing acid gases (SO, HCl), injection
of reducing agents such as ammonia or urea for controlling NOx emissions,
activated carbon injection for dioxin control, <strong>and</strong> finally particulate removal by