The treatment of plastic waste
Since
the 1950's, over 150 million tonnes of plastics have accumulated
in the oceans, almost forming a continent and spilling out
onto beaches. Even if this famous 7th continent would ultimately
be not very noticeable to the naked eye, it is nevertheless
a massive pollution which, if drastic solutions are not
found quickly, could lead to having more plastic than fish
in the oceans (source Ellen McArthur Foundation).
The collection of plastics which will then be transformed
can create jobs thanks to the establishment of dedicated
recycling centers in a region. Products resulting from this
transformation could also be developed (for example, carbon
residues remain from which to create new products).
One of the scientifically proven possibilities is to turn
plastic into fuel..
The
pyrolysis of plastic waste is an oxygen-free heating that
recycles this waste into fuel and gas.
We
must differentiate between the terms "Pyrolysis" and
"Incineration":
-
Pyrolysis
is carried out without flame and in the absence
of oxygen. Example your household oven in pyrolysis
mode
-
Incineration
is carried out with flame in the presence of oxygen.
Example your fireplace or living room insert
It
is important to specify that pyrolysis does not produce
Dioxin unlike incineration which involves this risk.
For
this, pyrolysis is based on the thermal cracking process
which will decompose the plastic to recover diesel
and gasoline to supply, among other things, the pyrolyzer
itself, electric generators or boat engines.
The pyrolysis machine also generates light non-condensable
gases which are purified by the PTC System process
before supplying the pyrolyzer to provide heat or
before simple discharge to the atmosphere.
The
gas composition resulting from the pyrolysis of plastic
waste varies according to its nature:
Source INRS
Diagram
of heat treatment of plastic waste
The
Biogreen and GasWash modules are both patented.
Pyrolysis Biogreen module - Heat treatment of plastics
This
Biogreen pyrolysis module allows a treatment of 1.8 ton/day
(75 kg/h) of crushed plastic waste.
Plastic
pyrolysis is a distillation process that transforms plastic
waste into fuel.
The waste is heated to over 400 ° C in the pyrolyzer and
is transformed into vapors recovered by condensation.
Depending on the condensation (cooling) temperatures of
this gas, different types of fuel are obtained:
-
between
390 and 170 ° C, the condensed gas produces diesel fuel
(diesel).
-
between
210 and 20 ° C, the condensed gas produces gasoline.
-
below
20 ° C, non-condensable residual gas remains
This
process, which does not include combustion, is self-sufficient
in energy and produces approximately 0.9 liters of fuel
per kilogram of plastic (For the record 1 kg of plastic
represents 50 bottles of water) treated, of which 2/3 of
diesel for 1/3 of gasoline under certain distillation conditions.
The
gas portion is composed of:
-
Chemically neutral fuels such as non-condensable light
hydrocarbons
-
Substances
of a functional nature such as acids (hydrochloric, hydrocyanic,
hydrofluoric, ...), ammonia, nitrogen oxides, sulfur dioxide,
hydrogen sulphide, etc...
The
Biochar carbonaceous residue will be inerted in concrete
for the production of submersible plots, elements of dikes,
docks or other ...
Washing GasWash module - Gas purification
treatment
The
P.T.C. system is a newly patented for the purification of gaseous,
liquid or vesicular aerosol compositions containing pollutants
harmful to health and the environment or simply malodorous.
- Pollutants
are Volatile Inorganic Compounds (VICs)
-
CO2, COS, NOx, hydrohalic acids, H2S, SO2, SOCl2, SO2Cl2,
etc ...
-
Pollutants are functional Volatile Organic Compounds (VOCs)
- amine,
amide, nitrile, aldehyde, ketone, ester, carboxylic acid,
alcohol, thiol, disulfide, thioester, halogenated organic
compounds, phosgene and hydrocyanic acid, etc...
This
innovative "one-pot" process therefore consists in capturing gaseous
pollutants in a physicochemical treatment, the liquid effluents
of which are subsequently digested by the aerobic bio-purification
process.
The
originality of the process lies on the one hand in the choice
of the reagent which combines with the pollutants to be treated
and on the other hand in the final natural biological destruction
or in a wastewater treatment plant that does not generate new
gaseous pollution.
Installation
diagram:
Horizontal tower model Waterleau/Socrematic
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The
process is characterized by a physico-chemical washing of
the stale gas flow against the current using aqueous alkaline
solutions, inside the washing tower.
The basic neutralizing agent is added to the water in order
to accelerate the gas-liquid transfer, and thus increase
the efficiency of the treatment.
The
complementary addition of a specific reagent contributes
in turn, not only to intensify this transfer process, but
also to regenerate the washing water by chemically modifying
the molecules absorbed, which have the property of being
odorless and biodegradable.
The
tower is equipped with a recycling pump and lined with inert
material which promotes gas-liquid contact.
The
base of the tower serves as a retention volume and as a
suction cover for the bath recirculation pump.
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The
GasWash module can be supplied with filtered seawater because
the minerals formed are of the same nature as those present in
seawater. The only important point is to monitor the limit saturation
concentrations.
The
treatment of the gas flow by PTC System makes it possible to separate:
- Chemically
neutral fuels such as non-condensable light hydrocarbons
-
Substances of a functional nature such as acids (hydrochloric,
hydrocyanic, hydrofluoric, ...), ammonia, nitrogen oxides, sulfur
dioxide, hydrogen sulphide, etc...
In this process the chemically neutral fuels are injected into
the boiler while the functional compounds are removed with the
aqueous phase of the washing column.
PowerPlast
on the operational field
This
gas washing unit is complementary to the pyrolysis unit to provide
it with environmental security for the emission of gases into
the atmosphere. All of the two modules are housed in a container
that can be installed either:
-
On the field
On an area set up near a plastic waste storage location.
- On
a flatbed truck
Each
module in a container will therefore be mobile to access
the various waste storage locations. It can provide local
electrical or thermal energy.
- On
a boat
The whole will be mobile at sea in cabotage mode.
The "PLASTIZOL" fuel resulting from the treatment of plastics
will be used in part for the engine of this boat, thus
ensuring good autonomy.
It is possible to recover the calories on the exhaust
of the marine engine. The gas outlet temperature 450 to
500 ° C on average for an indirect injection diesel, 550
to 580 ° C for a direct injection.
The exhaust gases will thus be directed and joined to
the pyrolyzer gases for treatment by the GASWASH module,
the assembly being able to participate in the production
of electricity by the electric turbine.
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The
advantage of recycling marine engine exhaust gases lies in the
combustion of its unburnt materials and a bi-combustion of the
fumes to limit the pollution of the boat with CO2 emissions.
The
storage of an electrical production is envisaged in batteries.
It is also possible to envisage using this electrical energy for
the production of hydrogen by electrolysis of water.
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