Note: Descriptions are shown in the official language in which they were submitted.
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liETHOD AND ARRANGEMENT FOR THE DISPOSAL OF GAS SPACE CONTENTS
OF LARGE-VOLUME CONTAINERS IN THE CASE OF COMPONENTS WHICH
LOAD THE ENVIRONMENT
The invention is directed to a method and an arrangement
for disposing of gas space contents of large-volume containers
such as tanks or the like when emptying one tank and filling
another tank with materials whose gas phase loads and is
harmful to the environment or is to be reclaimed as valuable
material, wherein the gas space of the tank being emptied is
filled with a substitute material and the gas contents of the
tank being filled are guided via a cooling trap.
Chemicals are often not only stored in tanks but also
transported by means of tank cars, i.e. from the producer to
the consumer, from the producer to intermediate storage and
from there to the consumer or in another manner, wherein the
operators of such tank vehicles are instructed to transport
very different products with their vehicles. When such a tank
is emptied, volatile materials form in its gas space, often
the gas phase of the corresponding products, wherein this gas
phase escapes, at the latest, when refilling the tank. It
works out in practice that the tanks are opened frequently
while being transported in the empty state, so that the
surrounding air blows out the harmful gas phase of the
components which are then given off into the environment. If
the emptying is not complete, it can happen during the
refilling of the tank that the product with which the tank is
subsequently filled combines in a dangerous way with the gas
phase of the previously transported product; this can be not
only toxic but also e.g. highly explosive.
On the other hand, the material flowing into the tank
being filled drives out the corresponding gas volume from this
tank, which gas volume must then escape if the filling is not
effected against a developing counterpressure; the so-called
gas displacement method is used for this purpose, e.g. when
filling gasoline tanks, i.e. the expelled gas volume is
redirected into the gas space of the tank vehicle being
emptied in order to ensure uniformity of pressure. This gas
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displacement method makes sense so long as a single material
is being transported by the tank vehicle.
However, if the product is changed, and this is most
frequently the case, since transport containers are rarely
always used for the same medium, the gas displacement method
no longer works. The gaseous material would contaminate the
new material to be transported in the transport container. In
the worst case, chemical reactions (explosions) occur. For
this reason, the transport containers are rinsed or
neutralized when dealing with water-soluble components. This
is usually not possible with organic solvents, since the
latter are frequently not mixable with water. Moreover, this
results in contaminated water which must be disposed of in
turn in a costly manner.
This creates the opportunity for criminal action. The
transporter will employ the gas displacement method during the
emptying process at the location of the client, but leaves
open the dome cover in transit so that the head wind removes
the gas from the tank. This is strictly prohibited for
reasons of environmental protection. However, there is no
usable solution, since rinsing with water is usually
unsuccessful. Thus, in the case of combustible liquids, an
explosive mixture of air and gas can occur which can lead to
catastrophe in the event of a spark.
It is the object of the invention to provide a solution
with which the gas space contents can be disposed of in a
simple manner, wherein the solution is to be effected in such
a way that the devices which are used have the smallest
possible volume and are simple to manage and can also be used
with conventional tank vehicles regardless of whether the
latter are road vehicles or rail-bound vehicles.
This object is met, according to the invention, in that
the cooling trap is operated with a liquid inert gas, wherein
the inert gas operating the cooling trap is used as substitute
material for filling the tank being emptied.
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The proposed filling of the gas space of the tank being
emptied with a substitute material on the one hand and the
disposal of the gas volume of the tank to be filled via a
cooling trap on the other hand has the special advantage that
it makes no difference for the tank vehicle being emptied
whether or not the product is changed when next used. The
substitute material makes the operation of the tank vehicle
independent of the transported material. On the other hand,
by means of providing a cooling trap, the product which is
guided via the cooling trap and then condenses can be supplied
directly to the consumer again, so that there is no
discrepancy in volume for the consumer with respect to the
quantities agreed upon. As in the gas displacement method,
emptying and filling can be effected without the occurrence of
pressure differences in this case as well.
Moreover, the directing of gases via a cooling trap has
the advantage that these materials are condensed out in the
cooling trap and can possibly be placed at the disposal of the
consumer again, since he shares in the cost of these materials
in practice. It is also possible to receive the materials
exiting via the cooling trap in containers having a very small
volume and to use them for other purposes. A number of
materials can be utilized as substitute materials, including
in some cases surrounding air entering the tanks.
A method is known from DE-A-12 51 233 by means of which
industrial scale vapors can be reclaimed, wherein the vapors
are guided via cooling stages. This text does not describe
the type of filling or the volumes involved when reclamation
is effected, rather the overall disclosure concerns the
surrounding air. The reclamation of a gasoline-vapor mixture
is shown also in DE-A-23 37 055, in which a gasoline-air
mixture is likewise cooled in such a way that the hydrocarbons
contained therein are condensed and frozen out.
The special advantage of the present invention consists
in that the inert gas with which the gas space is filled is
made available as coolant or, conversely, in that the coolant
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is utilized, after the gas volume has cooled, as an inert gas
which fills up the gas space according to corresponding
evaporation. In so doing, the invention makes use of the
understanding that an environmentally friendly inert gas
coolant increases extremely in volume when evaporated.
It is advantageous to use nitrogen as the inert gas
operating the cooling trap and filling the gas space in the
gas phase.
The use of nitrogen is particularly advantageous, since
this is often available in liquid form and the gaseous phase
effects an increase in volume from approximately 1 to 800
compared to the liquid phase. Moreover, nitrogen prevents
explosions and is also completely harmless to the environment.
Since nitrogen atmospheres do not enter into chemical
reactions with air under normal conditions, peroxide formation
and the like can no longer come about e.g. with solvents which
react with air.
The invention also provides that the cooling trap for the
precipitation and condensation of the expelled gases is
operated in a temperature range of -10 to 50C. The utilized
devices can be constructed so as to be comparatively small
with respect to volume in this temperature range, wherein the
selected temperatures ensure that e.g. at least 80~ of the
solvent cools out below its dew point and can accordingly be
reclaimed as condensate.
The highly volatile portion which is not included can
then be guided e.g. via an activated charcoal system which can
likewise be constructed so as to have a small volume, as is
likewise provided according to the invention.
If nitrogen is available in the area of the tanks being
processed, the invention likewise provides that the cooling
trap is used as a partial evaporator for the substitute gas,
particularly for the liquid nitrogen, i.e. the operating
medium of the cooling trap is simultaneously the substitute
gas.
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The invention also provides an arrangement for carrying
out the method which is distinguished by a cooling trap with
condensate collector and residual gas cleaner.
An activated charcoal filter, for example, can be used as
residual gas cleaner according to the invention.
As already stated in the beginning, different materials
are often transported successively in a tank vehicle, so that
different residual gas compositions also come about. In this
respect, the invention provides that the arrangement comprises
a plurality of separately connectable filters for different
residual gases.
The invention is explained in more detail in the
following by way of example with the aid of a drawing. The
single drawing shows a basic diagram of the arrangement
according to the invention.
The arrangement, designated in general by 1,
substantially shows the connection between a first tank 2 of a
tank vehicle 3 and a second tank 4, wherein the outlet
connection piece 5 of the tank 2 is connected with the filling
connection piece 6 of the tank 4 via a filling line 7.
A eooling trap, designated in general by 8, is provided
in addition; liquid nitrogen (N2) flows through its cooling
eoils, shown in a sehematie manner, whieh is indieated by
arrow 9. The liquid nitrogen whieh heats up in the cooling
trap 8 is gasified and enters in the head area 10 into the gas
spaee of the tank 2 when the latter is emptied, the gas spaee
being designated in general by 11.
The gas eseaping in the gas space 12 of the tank 4 to be
filled is directed via a line 13 into the cooling space of the
cooling trap 8 and condensed in the latter, and the condensate
thus obtained is guided again via a condensate line 14 to the
product line 7 and accordingly flows back into the tank 4.
Uncondensed residual gas is given off into the environment via
a line 15, wherein an activated charcoal filter 16 can be
provided.
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The control and regulating of the entire arrangement is
effected in such a way that no pressure difference prevails
between the gas spaces 11 and 12 of the two tanks 2 and 4,
i.e. the evaporating nitrogen can be supplied either in
excess, when greater volumes are needed than would be
necessary per se by the operation of the cooling trap, or in
deficit, i.e. gasified N2 not required in the gas space 11 is
then given off into the environment.
Also indicated is the possibility, designated in general
by 16', to provide a plurality of cartridges with different
filter fillings according to the material to be processed; the
uncondensed residual gas then enters via the line 15 into the
respective cartridge 16 needed at the time.
Naturally, the described embodiment example of the
invention can be modified in many respects without departing
from the basic idea. Thus, the invention is not limited to
the spatial arrangement of the cooling trap 8, which is only
shown schematically here; this cooling trap 8 can be provided
at the face as a securely installed structural component part
in the area of the tank 4 and as an integrated component part
of the tank vehicle 3 and the like.
