|
|
 |
Combustion Plant
Within the framework of a programme for the requalification
of its gas emission treatment plants run since
2002 in collaboration with DIIAR (Department
of Hydraulic Engineering, Environmental, various
Infrastructures and Surveys) Environmental
Section of the Polytechnic of Milan, LATI
had found, at the E 6 emission point of its site
at Gornate Olona (VA), the locality of Torba,
a possible source of olfactory disturbance
for the people living in the houses closest to
the production site, as demonstrated by a specific
study (see M. Gadda, S. Cernuschi, G. Lonati,
2003 - "Valutazione delle molestie olfattive
associate alle emissioni del nuovo impianto di
trattamento del flusso gassoso proveniente dalle
vasche di decantazione delle acque di degasaggio
dello stabilimento di Gornate Olona") at
the time handed in to the Mayor and the competent
A.R.P.A. agency.
In particular it was found that, together with
special production regimes characterised by the
working of thermoplastic material containing phosphorous,
the emission coming from the stocking tanks and
the re-circulation of the degassing waters (E
6), despite the passage through two sequential
washing oxidation towers, could contain traces
of phosphine, a fairly critical substance for
the environment as it is characterised by a very
low olfactory perception threshold (0,02 ppm)
still lower than the value of the TLV (Threshold
Limit Value = 0,3 ppm - TWA; 1 ppm -STEL) or that
is to say the value over which sanitary evaluation
is necessary.
Following to a somewhat extensive series of tests
conducted in 2003 using a thermal conversion plant,
the thermo-oxidation technology was found to be
the most suitable system of treatment for the
gas flow in question. Consequently, during the
last year, LATI has adopted this technical solution
installing a treatment unit composed of a wet-way
dust pre-laving column (scrubber), followed by
a regenerative-type thermo-combustion plant.
In particular, the gas to be purified which comes
from production enters into the scrubber where
they are chilled and saturated and where the water
flow necessary to obtain the removal of the dust
is re-circulated against the current; a part of
the volume of water is discarded in order to maintain
a constant level in the scrubber and avoid an
excessive decline in the quality of the water
which is constantly reintegrated by the column
head.
The regenerative-type thermo-combustion plant
has three chambers
Each regenerative chamber contains a bed with
ceramic filling bodies, which work as heat accumulators,
as they are heated or chilled according to the
direction of the gas flow which crosses them.
The air which must be purified reaches the first
chamber and crosses the bed with the ceramic filling
bodies, heated during the previous phase, vertically
from the bottom to the top.
During this passage the polluted air is heated
until it reaches the closest possible temperature
to that of oxidation (about 850° C), consequently
lowering the temperature of this ceramic bed gradually.
If the above mentioned oxidation temperature isn't
reached thanks to the auto-ignition of the organic
substances present in the exhaust air, an auxiliary
burner supplied by fuel (methane) and installed
in the combustion chamber is used.
The medium duration of the gas at the combustion
temperature is higher than one second. After having
left the combustion chamber, the purified gas
passes vertically, from the top to the bottom,
into the second chamber transferring the heat
and they are therefore directed to the emission
stack. That way the second bed is heated and is
ready for the next sequence, which is to heat
the gas on arrival at the plant.
The special type of ceramic filler used allows
the optimisation of both fuel consumption, thanks
to the elevated specific surface, and energy consumption,
thanks to the reduced pressure drop.
The solution with three chambers avoids the possibility
of a certain volume of untreated gas being directed
to the chimney during the flow inversion, thereby
guaranteeing maximum efficiency of the system
which can reach values even higher than 99 %.
Thanks to the third chamber it is also possible
to degass the towers at every inversion.
Although regenerative-type thermo-combustion plants
with two chambers, which are less costly and less
technically complicated than the one adopted,
and in the event of installation would in any
case have respected the restraints imposed by
the Region for the emission in question, are commercially
available, LATI opted for a technology
with three chambers for all of the above mentioned
reasons, in line with its environmental policy
which has enabled it to be one of the very first
completely Italian companies to have obtained,
in 1995, the environmental certification according
to the UNI EN ISO14001 normative.
The information obtained from the first internal
campaign of analysis conducted on the new plant
(see the analysis report given to the Mayors in
question and the competent A.R.P.A. on
20.12.2004) have confirmed that the objectives
set have been completely satisfied, having evidenced
characteristic values of the combustor outlet
gas flow which are comparable with those of the
atmosphere, but no doubt very soon the competent
regional body will carry out their own control
of the results obtained.
 
Combustion Plant
These documents are presented
as Portable Document Format (PDF) files.
You'll need the Acrobat Reader software
on your computer to view or print these
files. This software can be downloaded at
no charge from Adobe web site by selecting
"Get
Adobe Reader". |
| Contact: |
email:
marketing@it.lati.com
LATI Industria Termoplastici S.p.A.
Via F. Baracca, 7 21040
Vedano Olona (VA) - Italia
Tel. : +390332409111 - Fax: +390332409307
|
|
|