Page 23 - Plastics News September 2017

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Incineration - The Heating Power of Refuse equivalent of one ton of fuel oil. Two types of energy are

Incineration is not only a way to get rid of waste, it’s also produced in an incineration plant: heat and power. Each
a way of generating energy. Many different types of waste, type has its own production process and level of energy
whether from households, industry or agriculture, can be effi ciency.
converted into heat or power. Heat production:
This involves simply heating water through waste
Excluding all types of recycling, about 70% of our
combustion. This process is energy effi cient, with 70 to
waste is combustible. That includes paper, cardboard,
80% of the combustion heat recovered after incineration,
biodegradable waste, textiles, plastics and more. In
or about 1,500 kWh of thermal energy per ton of refuse. Of
addition to households, many industries produce waste
course, the heat produced then has to be used somewhere
whose value can be captured through incineration. There
near the incineration plant
are many kinds of industrial waste, including hydrocarbon Power. production:
residue, tar and used solvents.
The heat exchanger has to contain steam at the highest
There are also various kinds of agricultural waste, such as
possible pressure. This steam is sent to a turbine that
straw from wheat, corn and rice, as well as agro-industrial
drives an electric generator. The power produced can be
waste, which mostly comes from sugar and oil mills.
supplied to the grid all year round. The energy effi ciency
Papermaking creates waste, too. After extracting cellulose
of this process is about 20 to 25% (300 to 400 kWh). A
from wood to make pulp, pulp mills burn the by-product
better solution to producing just heat or just power
known as “black liquor.”
through incineration is producing both simultaneously
Incineration is fi rst and foremost a way of eliminating a through cogeneration, also known as combined heat and
sizable amount of our waste. Some 90% of its initial volume power (CHP). This involves using the residual heat in the
goes up in smoke. This represents a healthier solution exhaust steam from the power-generating turbine. With
than the huge landfi lls of the past. An incineration plant this process, energy effi ciency improves to 50 to 60%.
includes a furnace and a post-combustion chamber. The It is estimated that by recovering 50% of all municipal waste
waste is burned in the furnace in a process called pyrolysis, in France, about 1% of the country’s energy consumption
which produces combustible gases. These are burned in needs could be met. This solution is therefore very far
the post-combustion chamber at temperatures of 800 to from adequate.
900°C. A heat exchanger — in which very hot water or Moreover, the fl ue gas from incinerating waste is highly
superheated steam circulates — is used to recover energy toxic. The resulting gas must therefore be scrubbed and
from the fl ue gas emitted. neutralized (because of its acidity) before being released.
About 5 to 7 tons of waste is needed to produce the Air pollution around incineration plants is particularly high.

Inventor converts waste plastics to fertilizer, fuel calls it POET

An Australian inventor has developed a technology he says can convert waste plastic into energy
and fertilizer using anaerobic digestion.

avid Thompson, based in Adelaide, said his plastic-to-
Denergy technology, which he calls "poet," an acronym
for polymer organic energy treatment, has been used
successfully for polyethylene, polypropylene, polystyrene
and expanded polystyrene.
He said, the poet system "prepares waste plastic in a way
that microbial digestion can take place quickly and I think
that's really the key to making it a commercial opportunity."
POET Systems expects to have its fi rst two machines –
each capable of processing 20 tonnes of plastic a week.

23 September 2017 | Plastics News