A desiccant cartridge for a container, which contains moisture-sensitive
product, wherein said desiccant cartridge contains at least one
outside-connection opening via which the desiccant cartridge is
joined to the surrounding air, a desiccant being contained in a
cartridge casing. A surrounding-air duct extends between the outside-connection
opening and the desiccant. This surrounding-air duct forms a long
diffusion path in relation to the breathing cross-sectional area
of the desiccant cartridge.
What is claimed is:
1. A desiccant cartridge for connection to a container which contains
moisture-sensitive products wherein said desiccant cartridge is
comprised of a cartridge casing having a dessicant, means for retaining
the desiccant and having at least two openings for the passage of
air, one opening (a) being connected to the container, the other
opening (b) being connected to the cartridge casing and communicating
with the outside air by means of an outer casing which forms an
air duct which completely surrounds the cartridge casing wherein
said air-duct forms a diffusion path the length of which is at least
eight-times greater than the square root of the breathing cross-sectional
area of the desiccant cartridge.
2. The desiccant cartridge of claim 1 wherein the length of the
diffusion path is at least 10 times greater than the square root
of the breathing cross-sectional area of the desiccant cartridge.
3. The desiccant cartridge of claim 1 wherein the surrounding-air
duct has at least one deflection up to 180.degree. in the opposite
4. The desiccant cartridge of claim 1 wherein the effective cross-section
of the outside-connection openings is designed to correspond to
the maximum flow rate which occurs during the filling or emptying
of the container or, when the container is not being filled, is
designed to correspond to the flow rate caused by heating up or
cooling down the gas situated in the container.
5. The desiccant cartridge of claim 1 wherein the cartridge casing,
along with the desiccant situated therein, is formed as a conventional
cartridge with a cylindrical basic form, either as a refillable
cartridge or as a disposable cartridge with a sealed cartridge casing.
6. The desiccant cartridge of claim 1 wherein the cartridge casing
has a diameter which is great in relation to its length.
7. The desiccant cartridge of claim 1 wherein the surrounding-air
duct has a ventilation tube which extends above the desiccant and
whose diameter is at least eight times less than the length of the
8. The desiccant cartridge of claim 7 wherein the diameter is eight
to eleven times less than the length of the diffusion path.
9. The desiccant cartridge of claim 1 wherein the surrounding-air
duct has a cross-section which increase from the outside-connection
opening towards the desiccant.
10. The desiccant cartridge of claim 9 wherein the increase is
in a stepwise manner.
11. The desiccant cartridge of claim 1 wherein the cartridge opening
is surrounded by the outer casing and the surrounding-air duct extends
partially between the outer casing and the cartridge casing.
12. The desiccant cartridge of claim 11 wherein the outer casing
and the cartridge casing are arranged essentially coaxially and
13. The desiccant cartridge of claim 11 wherein several outside-connection
openings are provided whose total cross-sectional area corresponds
to or is less than the area of the ventilation tube or the breathing
14. The desiccant cartridge of claim 13 wherein the outside-connection
openings are annular in shape and distributed about the outer casing,
are arranged adjacent to the container-side end of the desiccant
cartridge and extend either radially or axially, in each case relative
to the cartridge casing.
15. The desiccant cartridge as claimed in claim 11 wherein the
outer casing has a protective tube sealed with a cover.
16. The desiccant cartridge as claimed in claim 15 wherein the
protective tube is produced from transparent material or has a viewing
window for checking the loading or saturation of the desiccant by
the coloration of the impregnated fields of a moisture indicator
card or of a desiccant with an indicator.
BACKGROUND OF THE INVENTION
The field of art to which this invention pertains is desiccant
Desiccant cartridges are used on containers, casings, reactors
and the like which contain moisture sensitive products.
Desiccants cartridges can usually be exchanged from the outside
of the container which is filled with the product to be protected
from moisture. The cartridges are generally connected to the container
by means of a sleeve or flange joint. The object of the desiccant
in the desiccant cartridge is to protect the contents of the container
from enclosed and penetrating atmospheric moisture.
Desiccant cartridges which are connected to containers, casings,
reactors, and the like which contain moisture-sensitive products
are generally divided into closed, open, or combined systems. The
closed systems are not joined to the air which surrounds the container,
whereas the open systems are joined to the ambient atmosphere. The
combined systems are joined to the ambient atmosphere through pressure
compensation valves which open when there is an under-or-over pressure
in the container.
With the closed systems, there is often the problem that pressure
compensation between the interior of the container and the surroundings
is impossible, so that in some cases desiccant cartridges are provided
with pressure compensation valves. The desiccant cartridges with
the pressure compensation valves should be classed with the combined
systems. The pressure compensation valves respond only when there
is a desired under- or over-pressure in the interior of the container,
joining to the surrounding air then being effected. In this case,
however, air flows comparatively quickly-corresponding to the decrease
in pressure--through the desiccant into the container or to the
Open systems must be used for containers with moisture-sensitive
products which are not designed for large pressure differences.
However, these generally have the disadvantage that the desiccant
is consumed comparatively quickly since an exchange of air with
the surrounding air also takes place at all times.
These systems may nevertheless be necessary in various cases, namely,
for example, when there is the additional object of neutralizing
hydrogen sulfide or other acid/air mixtures and preventing their
unfiltered admission into the atmosphere, by selecting a specific
desiccant, such as aluminum gel or a molecular sieve.
It is precisely in cases of this type, however, that sufficient
safety reserves of desiccant must at all times be kept ready in
the cartridge so that, when there is an ejection of hydrogen sulfide
as a result of inadequate adsorption capacity, no corresponding
contamination of the environment results.
SUMMARY OF THE INVENTION
The present invention is based on the object of providing a desiccant
cartridge which is mainly suited for open systems but is nevertheless
designed for cost-favorable long-term operation so that no appreciable
loading of the desiccant takes place, even when the container is
standing for a relatively long period of time.
The desiccant cartridge of this invention is used with a container,
casing, reactor and the like which contain moisture-sensitive products
wherein said container has at least one outside-connection opening
through which the desiccant cartridge is joined to the surrounding
air and with desiccant which is contained in a cartridge casing.
Between the outside-connection and the desiccant, a surrounding-air
duct forms a diffusion path whose length is at least eight times
greater than the square root of the breathing cross-sectional area
of the desiccant cartridge.
As a result of the especially long surrounding air-duct, provided
according to this invention as a diffusion path, stabilization of
the air joined freely to the surrounding air is achieved before
its contact with the desiccant. There is also created in the region
of the outer air duct a standing column of air which has already
been pre-dehumidified to an extent and, as a result of the poor
circulation of air here, does not give rise to any large losses
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 of the drawings shows a longitudinal cross-sectional view
of the desiccant cartridge of this invention.
FIG. 2 shows a view of the desiccant cartridge from below.
FIG. 3 shows a longitudinal cross-sectional view of a further embodiment
of the desiccant cartridge.
DESCRIPTION OF THE INVENTION
The desiccant cartridge of this invention contains between the
outside connection and the desiccant a surrounding-air duct which
forms a diffusion path whose length is at least eight times, preferably
ten times, greater than the breathing cross-sectional area of the
As a result of the especially long diffusion path, which for reasons
of space or as a condition of the construction may also be deflected,
the movement of air and convection caused by desiccation air is
prevented when possible. The desiccation capacity is maintained
for an optimum length of time as a result of this measure. It is,
furthermore, especially favorable in this connection that an actual
exchange of air takes place only where there is a pressure difference
which generates a continuous flow of air, as occurs when the container
is being emptied or filled or with large differences in temperature,
whereas with small fluctuations in pressure, the air situated in
the surrounding-air duct acts as a buffer and losses of desiccant
capacity are prevented.
The desiccant cartridge according to the invention can nevertheless
be designed such that large pressure gradients are not generated
even when the container is loaded or unloaded quickly. In addition,
the flow resistance is correspondingly measured in both the region
of the desiccant cartridge and the region of outside-connection
openings. The cross-sectional area of the outside connection openings
is selected such that as little moisture as possible enters through
rain, etc. and that any gusts of wind do not cause the air in the
surrounding-air duct to swirl. The cross-sectional area of the outside-connection
openings must, however, ensure that the flow resistance remains
within acceptable limits, where it must also be taken into consideration
that the time required for the air to drift through the desiccant
cartridge should be adapted to the desiccation capacity of the latter.
A vertical arrangement of the desiccation cartridge with the surrounding-air
duct extending between an outer casing and the cartridge casing
is especially favorable since the exchange of air between the upper
and lower layers in the surrounding-air duct is then at its lowest.
The air can advantageously be deflected once by 180.degree. in
the manner of a labyrinth before it can get anywhere near the region
of the desiccant, a further stabilization of the air taking place
in the region of the ventilation tube adjacent to the deflection.
The outer casing can be produced as transparent or be provided
with a viewing window. A change in color of a moisture indicator
card inserted in the region of the desiccant is thus visible from
outside without the need to carry out disassembly. With certain
desiccants, such as blue gel, loading or saturation is visible by
Apart from aluminum gel and molecular sieves, any of the well known
desiccants, such as a granulate of silica gel, blue gel, calcium
sulfate, calcium chloride and the like, also can be used as desiccants.
In spite of the comparatively large length of the surrounding-air
duct, the flow resistance is selected such that a sudden change
in pressure in the container, as is triggered, for example, by filling
or emptying, can rapidly be compensated. It is especially favorable
if the flow resistance and the dimensions of the cartridge casing
are selected such that they correspond to the strength values of
the container to be ventilated, it being necessary for a certain
safety reserve to be included.
The desiccant cartridge can be constructed so that the cartridge
casing is surrounded by an outer casing and the surrounding-air
duct extends partially between the outer casing and the cartridge
casing. The surrounding-air duct can have at least one deflection
up to 180.degree. in the opposite direction. The surrounding-air
duct can have a ventilation tube which extends above the desiccant
and whose diameter is at least eight, preferably eight to eleven
times, less than the length of the diffusion path.
In a modification of the desiccant cartridge, the cross-sectional
area of the surrounding-air duct increases from the outside-connection
opening toward the desiccant, particularly in a stepwise manner.
The outer casing and the cartridge casing are preferably arranged
coaxially and extend vertically.
The desiccant cartridge can have more than one outside-connection
opening wherein the total cross-sectional area corresponds to or
is less than the area of the ventilation tube or the breathing cross-sectional
area. The outside-connection openings are preferably annular in
shape and are distributed about the outer casing, are arranged adjacent
to the container-side end of the desiccant cartridge and extend
radially or axially relative to the desiccant cartridge casing.
The effective cross-section of the outside connection openings
is designed to correspond to the maximum flow rate which occurs
during the filling or emptying of the container or, when the container
is not being filled, is designed to correspond to the flow rate
caused by heating up or cooling down of the gas in the container.
The desiccant cartridge casing along with the desiccant can have
a conventional cartridge shape, i.e., a cylindrical basic form with
a refillable cartridge or a disposable cartridge with a sealed cartridge
The desiccant cartridge in one aspect can have a diameter which
is large in relation to its length.
The outer casing of the desiccant cartridge can have a protective
tube sealed with a cover. The protective tube can be made from transparent
material or can have a viewing window for checking the loading or
saturation of the desiccant. The saturation can be detected by the
coloration of a moisture indicator card or by an indicator in the
Further features, details and advantages are found in two exemplary
embodiments of the invention with reference to the drawings.
The desiccant cartridge according to the invention shown in FIG.
1 exhibits an outer casing 1 which is at the same time designed
as a protective tube. The outer casing 1 completely surrounds a
cartridge casing 2. Coaxial to the cartridge casing 2 and adjoining
the latter from below, a connecting element 3 is provided which
can be produced as a pipe socket, a sleeve or a flange and, in the
case of the example, is designed as a pipe socket with an external
screwthread. The connecting element 3 serves to join the desiccant
cartridge according to the invention to a correspondingly designed
part of a wall etc. (not shown) of a container, a casing etc. in
which the moisture-sensitive product is contained. In the exemplary
embodiment shown, the connecting element 3 in the form of a pipe
socket with an external screwthread is screwed into the corresponding
internal screwthread of the sleeve welded into the container wall,
additional sealing means being provided for the seal between the
sleeve and the pipe socket.
In the exemplary embodiment shown, a ventilation tube 4 is designed
adjoining the cartridge casing from above. The length of the diffusion
path is in this case advantageously eight to ten times greater than
the diameter of the ventilation tube. The ventilation tube 4 is
open at the top.
The cartridge casing 2 is connected to the connecting element 3
by an external screwthread. A ventilation cap 5 is screwed onto
the connecting element 3 by its internal screwthread and, with its
internal screwthread, produces a solid joint to the outer casing
1 as shown in FIG. 2.
As its other end, the outer casing 1 exhibits another external
screwthread onto which a cover 6 is screwed. A sealing device 7
which prevents the inadvertent admission of air or rain at this
point, is provided between the outer casing 1 and the cover 6.
The cartridge casing 2 is closed, at each of its two ends by mesh
inset 9 on each of which rests a web disk 10. A desiccant 11 which
in the case of the example is designed as a 0.4 nm molecular sieve,
is located in the space between the web disks 10. On the outer side
of the cartridge casing 2 a moisture indicator card 12 is attached
which at the same time serves as a load indicator for the desiccant
11. When the outer casing 1 is formed from transparent material
or at least has a corresponding window, it is possible to see the
moisture indicator card 12 without the desiccant cartridge having
to be disassembled.
A surrounding-air duct 13 is provided according to the invention
which extends in the region between the cartridge casing 2 and the
outer casing 1 undergoes a deflection by approximately 180.degree.
in an upper region 14 and then runs further through the ventilation
tube 4 to the upper mesh inset 9.
The surrounding-air duct 13 is joined to the surrounding air via
outside-connection openings 15 which, in the case of the example,
extend in the ventilation cap 5 directly next to the connecting
element 3. Care should be taken here that the outside-connection
openings 15 do not become covered up by screwing the connecting
element 3 too deeply into the sleeve of the container (not shown).
On the other hand, the arrangement of the outside-connection openings
15 shown in FIG. 1 which are arranged annually at the bottom and
facing the container wall in the ventilation cap 5 offers the greatest
safety from contamination.
As can be seen in FIG. 1 the dimensions of the surrounding-air
duct 13 are selected such that the length of the surrounding-air
duct 13 is comparatively large in relation to both the internal
diameter of the ventilation tube 4 and in relation to the cross-sectional
area of the outside-connection openings 15. In the case of the example,
the diffusion path from the outside-connection openings 15 to the
upper mesh inset 9 is 301 mm long, while the internal diameter of
the ventilation tube 4 is 36 mm. The ratio V resulting therefrom
As can be seen from FIG. 2 16 bores with, in each case, diameters
of 4 mm, are provided as outside-connection openings 15 in the exemplary
embodiment shown so that the effective cross-sectional area F is
It is favorable for the cross-sectional area of the surrounding-air
duct 13 to increase moving away from each of the outside-connection
openings 15. This can be achieved in the exemplary embodiments according
to the invention in accordance with FIG. 1 by keeping the annular
gap between the cartridge casing 2 and the outer casing 1 relatively
narrow, a somewhat wider region between the ventilation tube 4 and
the outer casing 1 closing this region. In addition, the ventilation
tube 4 may be tapered in the manner shown in FIG. 1 so that an even
higher degree of homogenization takes place here. This design is
especially favorable since an optimally high degree of flow stabilization
and flow homogenization to the mesh inset 9 and hence to the desiccant
11 takes place as a result.
As shown in FIG. 2 the ventilation cap 5 may advantageously be
provided with an outer octagonal shape or outer hexagonal shape
to enable the outer casing 1 to be screwed on and unscrewed, and
hence the desiccant 11 to be changed with ease.
In the illustration according to FIG. 3 identical or similar parts
correspond to identical or similar parts of the embodiment according
to FIG. 1 and 2 and are designated with corresponding reference
numerals so that an additional description is unnecessary. An adaptor
8 is visible in FIG. 3 via which the cartridge casing 2 is a screwed
together with the outer casing 1. As can be seen in FIG. 3 the
adaptor 8 carries in addition a socket base for the ventilation
tube 4 which can thus be attached simply during assembly.
As distinct from the exemplary embodiment according to FIGS. 1
and 2 the outside-connection openings 15 extend radially and the
ventilation tube 4 is longer than the exemplary embodiment previously
described so that the receptacle for the desiccant 11 is relocated
in a region below the height of the outside-connection openings
15. The desiccant is correspondingly provided between two mesh insets
9 whose diameter corresponds approximately to the diameter of the
outer casing 1 a fairly wide flow homogenization area 16 to which
the ventilation tube 4 is adjacent, being provided above the upper
mesh inset 9. As a result of this design, the ventilation tube 4
correspondingly extends over almost the entire height of the desiccant
cartridge according to the invention.
As a further deviation from the exemplary embodiment illustrated
previously, the cover 6 is designed as a viewing window lid which
makes it possible to look through the ventilation tube 4.
In the exemplary embodiment illustrated according to FIG. 3 twelve
bores are distributed around the circumference as outside-connection
openings 15. The diameter of the outside-connection opening 15 in
the exemplary embodiment shown in FIG. 3 is 15 mm, which gives a
total area of approximately 2120 mm.sup.2. The internal diameter
of the ventilation tube 4 in this exemplary embodiment is 47 mm,
while the length of the diffusion path from the outside-connection
opening 15 to the upper mesh inset 9 is 515 mm. This gives the ratio
V of 1:10.96.