Gas seal

This Application claims priority to German Patent Application DE 20 2005 011 689.0, filed Jul. 21, 2005.

FIELD OF THE INVENTION

The present invention relates to a gas seal for the gas-tight sealing of large-volume containers by means of a gas holder foil.

BACKGROUND OF THE INVENTION

Biogas plants produce methane through a microbial degradation process of organic substances. Here, the biogas is created in a multistage process of fermentation or digestion through the activity of anaerobic microorganisms, i.e. under exclusion of air. The type of organism strain is determined substantially by the specific process parameters, such as temperature, substrate, pH value, etc. In this way, an adaptation of the microorganisms to the appropriate substrate is achieved, which makes it possible to degrade a number of organic materials through fermentation.

The biogas thus created can, in principle, be applied to a number of utilization options. In the techniques common today, the biogas is usually stored temporarily between creation and utilization, at slightly elevated pressure in a large-volume container. For practical reasons, storage of the biogas above a fermentation container or liquid manure storage facility has taken hold. The containers, which usually consist of concrete, but in some cases are also made of other materials, are commonly spanned with so-called gas holder foils. These foils are robust, weather resistant and distensible to a certain extent. Gas holder foils usually consist of ethylene propylene diene monomer rubber (EPDM) materials.

Containers spanned with foils in this way are used not only for temporary storage of biogas, but also for covering liquid manure repositories and for preventing outgassing of undesired substances from large-volume containers into the environment.

Currently, two fundamentally different technologies are used for fastening the gas holder foil to the container crown.

In the one fastening type, wooden slats having a trapezoidal cross section are pressed into the wet concrete of the container crown in container manufacture. The gas holder foil is squeezed into the trapezoidal groove encircling the entire container, created when the concrete sets, by means of said wooden slats of trapezoidal cross section. Disadvantages of this method lie in the limited weather resistance of the wood, in the high outlay in manufacturing/mounting the gas seal, and the limited precision in design due to the circumstances in producing a tall, large-volume container.

The other fastening type uses a fully circumferential metal channel attached to the container crown for fixing the gas holder foil. Here, the foil is squeezed into the channel by means of a tube filled with compressed air. In addition to the high production outlay, above all the poor holding power of the metal channel argues against this type of foil fastening. High wind forces are capable of pulling the entire foil out of its anchoring. Moreover, even minimal damage to the tube causes the outage of the entire fastening. Likewise, in principle, a localized replacement of defective sections of the tube is associated with an outage of the entire fastening.

There is thus a need for a gas seal for large-volume containers having a gas holder foil that is easy to mount and, simultaneously, ensures a permanent gas-tight seal of the large-volume container.

SUMMARY

This is where the present invention begins. The object of the present invention, as characterized in the claims, is to provide, for large-volume containers, a gas seal having a gas holder foil that is easy and safe to mount, unproblematic to open and multiply resealable, and that simultaneously ensures a gas-tight seal of the large-volume container.

According to the present invention, this object is solved by the gas seal for large-volume containers according to independent claim 1. Further advantageous details, aspects and embodiments of the present invention are evident from the dependent claims, the description and the drawings.

The present invention provides a gas seal for sealing the upper opening of a large-volume container, the container exhibiting a wall encircling the opening. The gas seal comprises a gas holder foil resting in its peripheral area in the area of the wall, at least four pinch plates mounted circumferentially on the upper edge of the wall, and a sealing cord. The peripheral area of the gas holder foil is overturned and the sealing cord inserted circumferentially in the overturned gas holder foil. The pinch plates squeeze the gas holder foil, in its overturned area, to the upper edge of the wall.

In the context of the present invention, the term “large-volume container” is understood to be a container having an internal volume of at least 10 m³. In particular, the term “large-volume container” includes any type of stationary, immovable container.

According to a preferred embodiment of the present invention, at least one pinch plate is provided per meter perimeter of the wall of the large-volume container. If one pinch plate is mounted per meter of wall perimeter, then a sufficiently tight seal of the large-volume container is possible.

Particularly preferably, at least two pinch plates are provided per meter perimeter of the wall of the large-volume container. In this embodiment, the distance between the individual pinch plates is so small that a largely complete gas-tight seal of the large-volume container is achieved.

The gas seal according to the present invention can be used for sealing the gas holder of biogas plants, but it likewise ensures the odor-tight coverage of liquid manure stores and other large containers outgassing undesirably into the environment. Since, in biogas plants, the fermenter is frequently used as a gas holder, the gas seal according to the present invention especially serves to gas-tightly seal fermenters.

For mounting the gas seal according to the present invention, a gas holder foil is laid over the entire container cross section and placed on the upper edge of the wall of the container to be sealed. A sealing cord is laid on the gas holder foil circumferentially on the upper edge of the wall of the container. The gas holder foil is turned over the sealing cord toward the container interior. Then, in its overturned area, the gas holder foil is squeezed inside the sealing cord onto the container crown by means of pinch plates. If the gas holder foil comes under tension, the sealing cord slips inward until it comes to rest on the outer edge of the pinch plate and, in this way, safely seals the container.

According to a preferred embodiment of the present invention, the pinch plates are pressed toward the container crown by means of set screws.

According to a further preferred embodiment, each pinch plate is supported on the container crown by one counter bearing per pinch plate, preferably a hinge. If a counter bearing is provided, then high pressure can be exerted on the gas holder foil also when the pinch plates have a lower weight.

Each pinch plate forms, together with a set screw and a counter bearing, a pinch unit.

According to a further preferred embodiment, a squish band is additionally provided, the pinch plates applying pressure to the squish band and in this way squeezing the gas holder foil in its overturned area to the upper edge of the wall of the large-volume container. By attaching a squish band, a defined smooth surface is created via which the pressure exerted by the pinch plates can be transferred to the gas holder foil. In this case, the pinch plates can also exert pressure on the gas holder foil when the bearing area of the pinch plates is small. This pressure is distributed to a larger area by the squish band, avoiding damage to the foil. A particularly good seal of the container is achieved with simplified mounting.

According to a further preferred embodiment, additionally, a mounting rail attached circumferentially to the upper edge of the wall of the large-volume container is provided, the gas holder foil resting at least in its overturned area on the mounting rail. By attaching a mounting rail, a defined smooth surface is created on which the gas holder foil rests. If pressure is exerted on the gas holder foil, then, due to the smooth bearing surface, on one hand, damage to the foil is avoided, and on the other hand, a particularly good seal of the container is achieved.

According to a preferred embodiment of the present invention, the mounting rail exhibits a rectangular cross section. Thus, it is especially a metal band that facilitates the mounting of the gas seal on pre-existing containers. In this way, older containers can be retrofitted with a gas seal. Likewise, pre-existing gas seal systems can be replaced by a gas seal according to the present invention.

According to a further preferred embodiment of the present invention, the mounting rail exhibits an L-shaped cross section. This embodiment is provided especially for mounting on containers to be newly erected. Here, one leg of the mounting rail is recessed into the wall of the large-volume container.

According to a particularly preferred embodiment, the wall of the large-volume container consists of concrete. In this case, after the concrete is poured into the formwork of the container wall, one leg of the mounting rail is pressed into the still wet concrete. After the concrete has cured, the mounting rail is firmly anchored in the wall of the container. For easier mounting, the mounting rail can be furnished with additional bearing rails that serve as support on the formwork of the container wall.

According to a further particularly preferred embodiment, two pinch units are provided on each mounting rail. If two pinch units are attached per mounting rail, then, on one hand, the circular cross section of the container to be sealed can be sufficiently reproduced, and on the other hand, the number of individual units to be mounted is kept as low as possible.

Regardless of the type of foil fastening on the container crown, the gas holder foils currently used cause problems due to the pronounced temperature dependence of their distensibility. Under sun exposure in summer, the foil holders expand extremely even when moderately filled. Highly inflated foil containers offer the wind large working surfaces and thus constitute a threat to the entire gas holder. However, the use of tougher EPDM materials is not possible due to the rigidity associated therewith at low temperatures.

To solve this problem, according to a further particularly preferred embodiment of the present invention, a net is attached over the gas holder foil. In this way, the distension of the gas holder foil is limited, also under intensive sun exposure, since, when the net is completely tautened, no further volume increase of the gas holder foil and thus of the gas holder is possible.

According to a further particularly preferred embodiment of the present invention, the net is fastened to the ends of the pinch plates facing away from the large-volume container. As the gas holder increasingly fills, via the net, a tension is exerted on the end of the pinch plates facing away from the container. Via the counter bearings of the pinch plates, this tension is translated into a pressure on the gas holder foil. In this way, an ever better seal of the container is achieved as the gas holder becomes increasingly full.

A particularly simple fastening of the net to the ends of the pinch plates facing away from the large-volume container is possible if the pinch plates exhibit eyelets through which the net can be tied to the pinch plates.

The gas seals described in the context of the present invention are preferably industrially prefabricated. The preferred material for the gas seal components consisting of metal is a corrosion resistant, high-alloy steel. Taken together, the components of the gas seal mounted on the upper edge of the wall of the container to be sealed are typically between 400 mm and 2500 mm long and between 100 mm and 500 mm wide.

BRIEF DESCRIPTION OF THE DRAWINGS

To illustrate the present invention and to clarify its advantages, exemplary embodiments are specified in the following. These embodiments will be explained in greater detail in association with the drawings. It goes without saying that these details are not intended to limit the present invention. Shown are:

FIG. 1 a preferred embodiment of an inventive gas seal in the mounting state; pictured is a section through the container wall, the section plane lying perpendicular to the floor surface of the container;

FIG. 2 a preferred embodiment of an inventive gas seal in the mounting state, looking down on the upper edge of the wall of the container;

FIG. 3 a preferred embodiment of a gas seal according to the present invention; pictured is the section through the container wall according to FIG. 1.

MANNER OF EXECUTING THE INVENTION

FIG. 1 shows a gas seal in the mounting state. Pictured is a section through the container wall, the section plane lying perpendicular to the floor surface of the container.

The present invention is designed to gas-tightly seal large-volume containers by means of foils. It consists substantially of a gas holder foil 1 and, to be mounted circumferentially on the container crown, units into which the gas holder foil 1 is squeezed. When mounting, the gas holder foil 1 is overturned upwards outside the squish band 3, provided in the resulting crease with a circumferential 15 mm thick EPDM sealing cord and guided back inward under the squish band 3. The squish band 3 is pressed onto the mounting rail 2 by tightening the set screws 5 by means of the pinch plates 6. The pinch plate 6 is movably mounted to the hinge 7. In this way, the gas holder foil 1 is squeezed into the units between the mounting rail 2 and the squish band 3 by means of the pinch plates 6.

The exemplary embodiment describes a gas seal on a circular concrete secondary fermenter having a 9 m radius. The gas holder foil and the sealing cord consist of EPDM. To seal a secondary fermenter having a 9 m radius, a total of 56 individual pinch plates are provided that are mounted circumferentially on the upper edge of the wall of the secondary fermenter.

In manufacturing the concrete container, the standing formwork 12 is first filled with concrete. The individual pinch units are set in the wet concrete. The insertion of the pinch units is facilitated by the support rails 10. The support rails are supported on the container interior by the formwork 12. On the container exterior, the pinch units on the mounting rails 2 or the termination brackets 9 mounted thereunder lie on the formwork (see FIG. 2). The mounting rails 2 are designed to be L-shaped and are provided on the concrete side with attached grasps for a better metal/concrete connection. Alternatively to the grasps, other details offering form closure can be provided, such as holes in the rails.

During container construction, the pinch units can be mounted easily, safely and above all precisely on the container crown. After the setting of the concrete and the removal of the formwork, the container can be provided externally with insulation 14 and trapezoidal sheet metal 15 as shown in FIG. 3. The termination bracket 9 of the units is designed so that it keeps rainwater off the insulation 14 and can serve to fasten further elements, such as notice boards.

On the outside of the pinch plate is located an eyelet for fastening the net 13. The net 13 lies over the gas holder foil and prevents the gas holder foil from expanding too much when heated or filled too full. If, due to high fullness, the gas holder foil presses against the net, then the net, for its part, will pull on the eyelets 8. The tension on the eyelets is diverted by the hinge 7 and causes a stronger squeezing of the gas holder foil between the squish band 3 and the mounting rail 2.

If not indicated otherwise, the individual parts of the device according to the present invention consist of stainless steel. The mounting rail 2 is preferably designed as a bracket in the format 100 mm×10 mm with a length of 990 mm with a steel anchor. The squish band 3 is a flat bar whose cross section measures 35 mm×8 mm and whose length measures 990 mm. The set screws 5 are preferably M16 screws having a length of 40 mm. Finally, the pinch plate 6 is likewise preferably a flat bar whose cross section measures 100 mm×10 mm and whose length measures 150 mm and that is furnished with fixing pins and an eyelet 8.