Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Ka/eh 31.10.88 88/106
Modified Version for
Foreign Applications
(4.8.89)
S TITLE OF THE INVENTION
Process for removing liquid containing
chlorinated organic compounds from liquid-impregnated
components of an appliance and apparatus for carrying out
said process.
BACKGROUND OF THE INVENTION
Field of the Invention
The invention is based on a process as defined
in the preamble of Patent claim 1. The invention relates
also to apparatuses for carrying out the process.
Discussion of Back~round
A process of the type mentioned in the intro-
duction is disclosed, for example, by D~-A-2,756,298 and
US-A-4,6~9,667. The known process is intended to remove
from transfor~ers the residual polychlorinated biphenyls
remaining in very inaccessible components such as, for
instance, organic insulating materials based on wood,
paper, cotton-or plastic, after insulating liquid based
on polychlorinated biphenyls tPCB) has been drained. For
this purpose, the components impregnated with the biph-
enyls are treated with the vapour of a solvent such as
water or methanol in an autoclave at elevated temper-
atures and a gaseous azeotropic mixture of solvent and
biphenyls then produced is discharged from the autoclave
and cooled to for~ a li~uid containing the residual
biphenyls. The biphenyls from this liquid are then
destroyed, preferably by irradiation with W light or by
adding ozone. Depending on the solvent used, the biph-
enyls may, however, also be destroyed by adding metallic
sodium. The dissolution and discharge cycle described
above has to be repeated several times in order to removP
the biphenyls from the biphenyl-impregnated components at
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least in a fairly satisfactory manner. Such a process i5
therefore extremely lengthy. In addition the biphenyls
cannot be completely removed thereby. In particular, as
a result of the desiqn of the components, even vaporous
S solvent can frequently not reach all the points of the
biphenyl-impregnated components.
To remove polychlorinated biphenyls from trans-
formers, it is further suggested to comminute the entire
transformer by shredding and then to treat the shredded
material thereby formed with solvent. Metal parts are
thereupon separated from organic constituents. Such a
process requires, however, numerous technologically
demanding process steps and is therefore relatively
expensive.
A further proposal relates to a pyrolysis process
in which the transformer core, which is impregnated with
insulating oil, is heated in a pyrolysis furnace with air
excluded. Organic components impregnated with chlorinated
biphenyls are thereby pyrolytically decomposed and burnt
in an afterburner. In this process, however, undecomposed
chlorinated biphenyl may reach the afterburner, at least
in the heating-up phase as a result of which the risk of
dioxin formation cannot be eliminated.
SUMM~RY OF THE I~VENTION
Accordingly, one object of this invention as it
is defined in patent claims 1, 8, 9 and 10, is to achieve
the object of providing a process and apparatuses for
carrying out the said process which make it possible to
dispose of components, impregnated with chlorinated
organic compounds, of any appliance in a comparatively
short time and with comparatively simple, and, con-
sequently, operationally reliable technology.
The process and the apparatuses as claimed by the
invention are outstanding for the fact that it is
possible to render harmless, rapidly and without risk,
very inaccessible environmental poisons in process steps
which are technologically simple to carry out, such as
thermal release of the chlorinated organic compounds,
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with at least partial decomposition of the appliance
components to be disposed of and trapping of the chlorine
from the compounds released with a reactant yielding
alkali chlorides and/or alkaline earth chlorides.
BRIEF DESCRIPTION OF THE DRAWINGS
A more complete appreciation of the invention and
many of the attendant advantages thereof will be readily
obtained as the same becomes better understood by
reference to the following detailed description when
considered in connection with the accompanying drawings,
wherein:
Fig. 1 shows an apparatus for carrying out the process
according to the invention in which the com-
ponents to be disposed of are treated in an
aqueous, sodium-containing solution,
Fig. 2 shows an apparatus for carrying out the process
according to the invention in which the com-
ponents to be disposed of are outgassed and the
chlorine-containing process gas then produced is
washed out in an aqueous solution of sodium
hydroxide, and
Fig. 3 shows an apparatus for carrying ou~ the process
according to the invention in which the com-
ponents to be disposed of are outgassed and the
chlorine-containing process gas then produced is
passed through a melt of sodium hydroxide.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings, wherein like
reference numerals designate identical or corresponding
parts throughout the several views, in the apparatus
shown in Figure 1, 1 denotes an au~oclave having a
heating system 2 with a pressure monitoring system P and
a temperature monitoring system T. The interior of the
autoclave contains a core 3 of a transformer filled with
an insulating oil, for instance, based on polychlorinated
biphenyls and~or trichlorobenzine. After the insulating
oil has been drained, the core 3 contains the residual
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insulating oil remaining in the very inaccessible pores
of its organic components. In a 630 kV transformer
containing, for example, 40 kg of organic components
comprising, for example, wood, paper, cotton and/or
plastic, and about 400 kg of insulating oil, the mass of
this residual oil may be approx. 10 kg. An aqueous sol-
ution containing alkali and/or alkaline earth and sub-
jected to a pressure of 5-50, preferably 10-20, bar is
fed to the autoclave 1 via a pump 4. This solution
preferably contains hydroxide~ of the alkali metals of
alkaline earth metals and may be, for instance, a 10%-
strength sodium hydroxide solution. The solution may,
however, also contain salts of the alkali metals and
alkaline earth metals such as, for instance, sodium
sulphate or sodium carbonate.
At temperatures between approx. 200 and 300,
preferably 220 and 280, C, the organic components of the
core 3 dissolve after a few hours and the chlorinated
organic compound~ are released even from very inacces-
sible pores, partly with decomposition and possibly withdetachment of chlorine. The ionised alkali and/or
alkaline earth contained in the solution reacts with the
partially still organically bound chlorine or even
chlorine present in the form of hydrochloric acid to form
alkali chloride and/or alkaline earth chloride. After the
treatment, which lasts only a few hours, a vapour stream
enriched with alkali chlorides and/or alkaline earth
chlorides, hydrocarbons and aqueous alkali starting
solution and/or alkaline earth starting solution may be
drawn off via a reducing valve 5 and fed to a storage
tank 6. The hydrocarbons deposit therein as an easily
removable layer 7 on the surface of the remaining un-
treated water 8. The untreated water 8 may then be
depleted of remaining hydrocarbons and alkali chlorides
and/or alkaline earth chlorides, for instance, by wet
oxidation, ozone/ W treat~ent, distillation, desalination
or biological treatment in a water processor 9. It may
thereupon be removed or transferred again to the process
described in order to process the aqueous alkali solution
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and/or al~aline earth solution.
When all the components of the core 3 Lmpregnated
with insulating oil have been dissolved after several
hours, the autoclave 1, which is free of insulating oil
S but possibly contains residues of the components which
are still undissolved but free of insulating oil, as well
as residues of the solvent, is washed out with pure water
vapour. After cooling, the core 3 may then be removed
from the autoclave and is free of chlorinated organic
compounds.
Instead of a transformer core, components,
impregnated with insulating oil, of other electrical
appliances, for example high-voltage capacitors, or any
other appliances containing components which are impreg-
lS nated with chlorinated organic compounds, can also be
disposed of in a corresponding manner.
In the embodiments of apparatuses for carrying
out the process according to the invention shown in
Figures 2 and 3, reference symbols corresponding to
Figure 1 relate to parts functioning in accordance with
Figure 1. In the apparatus according to Figure 2 the
autoclave 1 is used to outgas the core 3 Lmpregnated with
insulating oil. The organic components of the core 3
impregnated with insulating oil are outgassed by heating
to approx. 300-600C, preferably 350-450C, with an inert
carrier gas such as nitrogen being supplied, with partial
decomposition. The process gas thereby formed containing
chlorinated and chlorine-free organic compounds, water,
hydrogen chloride and nitrogen is fed into a gas scrubber
10 heated to approx. 200-300C. Liquid is forced into the
gas scrubber 10 from a storage container 11 filled with
an aqueous alkali solution and/or alkaline earth solu-
tion, for example, with 10~-strength sodium hydroxide
solution, at a pressure between 0.5 and 10 bar. In this
process, the chlorine contained in the process gas
predominantly in the form of hydrogen chloride gas,
po~sibly, however, also still in the for~ of chlorinated
orsanic hydrocarbons, for instance as PCB, becomes bound
to form alkali chlorides and/or alkaline earth chlorides.
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The vapour emerging from the gas scrubber 10 via an
overflow valve 12 contains, in addition to excess alkali
solution and/or alkaline earth solution, water and alkali
chlorides and/or alkaline earth chlorides, only
unchlorinated organic compounds and some carbon dioxide.
The discharged vapour is condensed in a condenser 13 and
the liquid condensate formed in the condenser is fed into
the storage tank 6 in which, similarly to the apparatus
according to Figure 1, the layer 7 formed from chlorine-
free hydrocarbons is removed from the surface of the
untreated water 8 and the untreated water is fed into the
water processor 9 for further treatment. In this process
it may be advantageous to remove any solid particles
contained in the untreated water and produced in the
process described abo~e by means of a filter 14 fitted
between storage tank 6 and water processor 9. The carrier
gas fed into the storage tank 6 is fed back into the
autoclave 1, optionally via an analytichl apparatus 15
which examines its components and a pump 16.
The process according to Figure 2 has the
additional advantage that fresh alkali or alkaline earth
is always introduced into the gas scrubber 10. This
reliably achieves the result that any chlorinated hydro-
carbons still contained in the process gas and introduced
into the gas scrubber 10 are dechlorinated to form alkali
chloride or alkaline earth chloride. In addition, this
process is outstanding for a high flow rate, accompanied
by high operating reliability.
Similarly to the apparatus according to Figure 2,
process gas containing predominantly chlorine-free
organic compounds, hydrogenchloride, water and nitrogen
is formed in the apparatus according to Figure 3. The
process gas is fed into a heatable reactor 17. This
reactor contains a melt 18 containing alkali and/or
alkaline earth. If a sodium hydroxide melt is used, it is
heated to approx. 400C. The process gas is fed into
regions of the melt 18 near the base. As the process gas
rises, the chlorine contained in the process gas becomes
bound as alkali chloride and/or alkaline earth chloride.
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The remaining parts of the process ~as, such as chlorine-
free organic compounds and also proportions of
carbondioxide and water, are fed into the condenser 13.
The condensate formed during this operation reaches the
storage tank 6. After examination for organic chlorine
compounds in the analytical apparatus 15, incondensable
organic hydrocarbons are fed to a combustion apparatus
l9. After the condensates formed have been demonstrated
to be safe, the liquid portion 20 of the condensate may
also be fed to this combustion apparatus. Instead of a
melt, a porous solid or granular material, for instance
based on calcium oxide/silicon dioxide, containing alkali
and/or alkaline earth may be used.
The reaction products produced can be monitored
in a particularly simple manner for freedom from chlorine
and disposed of both if a reactant of this type is used
and also if a melt is used as reactant. In addition, the
pressure can be set both in the autoclave 1 and also in
the reactor 17 in any desired manner, for instance by
means of a pump 21 fitted downstream of the condenser 13.
If the pump 21 is fitted, the connecting pipe indicated
in Figure 3 between storage tank 6 and analytical
apparatus 15 is omitted. By means of an operating
procedure employing underpressure, it is thus possible,
in a simple manner, to achieve the result that chlorin-
ated hydrocarbons definitely do not escape to the outside
from the apparatus during the process.
Obviously, numerous modifications and variations
of the present invention are possible in the light of the
above teaching. It is therefore to be understood that
within the scope of the appended claims, the invention
may be practiced otherwise than as specifically described
herein.
