DE102004052854B4 - Method for the long-term storage of caverns and cavern systems - Google Patents

Abstract

Method for the safe long-term storage of saturated brine caverns and cavern systems in the salt marshes using the saline solution in the cavern and a solid made from waste materials, which are introduced into the cavern after treatment as a suspension, characterized in that as a building material for the production of a the cavern space-filling solid under constant maintenance of cavern filling with brine and optionally an additional stabilizing head pressure gradually saturated brine taken from the cavern and mixed with a fine-grained waste and a binder to a flowable and settable solid suspension, the so prepared solid suspension then in the caverns is initiated, where it sinks without segregation to the cavern floor and hardens without excess water to a solid.

Description

The The invention relates to a method for safe long-term storage from with saturated Brine filled Caverns and cavern systems after final abandonment of their intended use, For example, as an underground storage for flowable media.

caverns in the Salzgebirge are in the Solverfahren by targeted dissolution of the Salt rock by means of fresh water produced. The resulting solution is largely saturated Brine, the volume of which far exceeds the volume of the cavern, is either supplied for economic use or disposed of. To ensure the stability of the cavern remains a part of the brine in the caverns or must be against other suitable medium should be exchanged so that the geostatic Mountain pressure is compensated and it in connection with the creep the salt rock does not come to a large volume reduction or even a collapse (break) of the cavern occurs.

in the Storage mode will use the brine against the medium to be stored (gas or liquid) exchanged and temporarily stored for the storage of the stored material, being the for Cavity internal pressure required for the stability of the cavern also over the storage medium completely or partially stored in the cavern be maintained by its own weight or an additional head pressure got to.

By the not completely suppressed creep deformation of the upcoming salt rock or other defects at the cavern or at the cavern bore the useful life of the cavern is limited. Caverns in general about a huge one Volume of several hundred thousand cubic meters, the entering Instability to an impairment the earth's surface and the earth structure and / or by the continued convergence of the rock salt to the exit highly mineralized NaCl solution or from other media, the one hazard or at least a significant impairment of the biosphere after to pull oneself.

from that arise in abandonment of their intended use requirements after a stable long-term safekeeping of the caverns, in the long run a squeezing out of usually harmful media and / or one Preventing the caverns from breaking. To reach this goal must they Convergence of cavern prevented and found ways and means be the constant Effectively compensate for effective geostatic pressure over time or the mountain tensions of the upcoming salt rock in the long run to record safely.

to safe long-term safekeeping of caverns were therefore already different Procedures examined. In a research project (BMBF project 02 WA 8937: Gerardi u. a .: Experimental studies on deposition of waste in Solkavernen; NGS m. b. H; 1989) was a solid filling the Caverns with a dry free-flowing solid examined and theoretically for possible.

Of the Replacement of the to their stability in the cavern located However, medium through a solid must be done so that the cavern too no time filled with air is and constantly under an additional, locking internal pressure is available. Otherwise, the rock pressure in huge Teufen of about> 500 m to <2,000 m, in which the cavern is located, pending, trigger an accelerated convergence, the to considerable damage at the cavern, at the cavern bore leading to the earth's surface, and at the earth's surface leads yourself.

For the application However, in the above-described method, the cavern was previously to empty. With the emptying of the cavern can also be to their Stability required internal pressure can no longer be applied. This means that with the elimination of the captive internal pressure associated disadvantages were to be accepted. The thick matter technology and the backfilling with free-flowing dry solid was therefore discarded as unworkable.

In another study (D.-A. Becker: Development and Application a short-range model for analyzing the long-term safety of salt caverns with chemically toxic waste; GRS mbH and GFS GmbH; GRS 128, 08/1996; FKZ: 02 C 0153 and 02 C 04551), the thick matter method was found to be less applicable and a dry bed proposed. To carry out this Procedure is again a complete removal of the NaCl solution the cavern required what for reasons of mountain safety, as above described, extremely questionable is and therefore had to be discarded. In addition, the production is of the thick substance using water as mixing liquids due to water solubility the salt mountain disadvantageous and dissolves after introduction of thick matter unwanted in the cavern Solprozesse in the contact zones between the salt rock and the Thick matter out.

Also known methods - for example DE 27 54 269 A1 and DE 38 17 549 C2 - after which suitable cavities used in the salt rock for the disposal of radioactive and other environmentally hazardous waste and this wastes as solid containers in a safe enclosure, which prevents the contact and the ingestion of water by the waste, are stored in the cavity via a tube or probe. A safe long-term storage of caverns is also not possible with these solutions, since the stored substances form only loose backfills that are not or only after a very long time in a position to counteract the convergence of the cavern, safely absorb the mountain stresses and on the upcoming rocks transferred to.

DE 197 17971 C1 and DE 102 07 969 A1 describe methods for the production of thick materials for use as Bergversatz, which is introduced into stable safety and unstable mined cavities and processing spaces. These cavities and processing spaces are empty before introducing the processed thick matter, ie not filled and usually walkable. The thick materials are mixed in compliance with specified conditions with water and achieve a high intrinsic strength on site after introduction. Thus, the thick fabrics are subject to the requirements for a "building material replacement". For the safe long-term storage of caverns, the technical teaching is out DE 197 17971 C1 and DE 102 07 969 A1 not fully applicable because the conditions of use are very different due to the cavities filled with saturated brine and under an internal pressure of the back-up.

A method for storage or disposal of solid, small-scale waste in salt caverns is also out DE 34 11 998 C2 known. According to this process solid, finely divided waste material is treated with the extracted from the cavern rock salt solution to a pumpable mixture and then introduced into the caverns, where the solid waste sediment after switching on a rest period at the bottom of the cavern and gradually fill the cavern cavity. If the technical and technological requirements exist, the stored solid can be removed again at any time and recycled if necessary. The brine extracted by this method from the cavern invariably serves as a transport liquid for the introduction of the solids, whereby the surplus of brine resulting from the backfilling of the cavern cavity is otherwise disposed of, for example by pressing or sinking into suitable porous rock formations. The procedure according to DE 34 11 998 C2 suffers from the same disadvantages as described above and is inapplicable for safe long-term storage of brine-filled caverns, since the solids sedimented in the cavern cavity, which essentially form a loose bed, are unable to recover from the convergence of the salt rock absorb and transmit resulting geomechanical forces.

Another method for the disposal of pumpable waste in caverns that have been built in salt rock and are to be closed, is out DE 31 41 884 A1 known. According to this proposal, the hydrous, liquid and pumpable waste materials to be introduced into the cavern, which may also contain suspended solids, soluble or dissolved salts which crystallize with binding of water of crystallization, or organic substances which solidify in the liquid phase of the cavern content or increase the density of the cavern content, or otherwise fed solids. For the safe long-term storage of brine-filled caverns this solution proposal is also not applicable.

If the added to the waste soluble or dissolved Salts actually among those changed in the cavern Temperature conditions wholly or partially with binding of water of crystallization crystallize out directly or after chemical conversion form yourself in the solution individual salt crystals or salt crystal groups in a total pasty consistency within the liquid cavern content. It However, no total solids is formed from the cavern content has its own shear strength or developed over time and thus immediately or after a certain setting time the rock tensions can record permanently. This also applies to the addition of solid, crushed Waste. These sediment at the bottom of the cavern, without a solid body Shear strength and do not set the mountain convergence sufficient Deformation resistance, the mountain voltages permanently can keep in balance. The formation of a substance mixture with higher Density as the original one Cavern content can increase the speed of mountain convergence However, it can not reduce a certain amount - as it does for long-term security required - permanently prevention.

It is still not guaranteed that in the remodeling or crystallization of the admixed soluble or dissolved Salts the formation of free water of crystallization, which is the dissolving process continue in the slightly soluble salt rock surrounding the cavern can, for sure is.

Subject of the DD 272 972 A3 are silicate aggregates with which the strength and other properties of self-hardening, organic and inorganic binders are to be improved. Such improved binders are used, for example, to produce cemented intervals in or on cavern bores. An indication of safe long-term safekeeping caverns does not contain this publication.

Of the The invention is therefore based on the object to develop a method with which the saturated Brine in the cavern is solidified so that the resulting block the cavern volume completely fills developed its own shear strength and thus is able to to block the convergence and to safely absorb the mountain tensions and transfer.

According to the invention this Task by a method according to the features of claim solved. Advantageous developments of the method according to the invention arise from the dependent claims 2 to 13

Around one with saturated NaCl solution filled Caverns or an equivalent Cavern system without impairment their stability in an effective and cost effective way permanently and safe to keep, the brine contained in the cavern is over a solid suspension prepared therefrom into the brine filled with brine is introduced near the ground, to a packing with solid state properties solidified, which is capable of the geostatic rock pressure permanently record and transmit and by preventing convergence, the ultimate, lasting stabilization to lead the cavern.

To the proposed solution will be first a low initial fraction of otherwise available saturated brine overground with the addition of a solid and, if necessary, a binder for Production of a flowable and used pumpable solid suspension. The thus prepared solid suspension After the principle of Dickstoffversatzes then over a Production tubing tour near the ground into the cavern, where they meet at the Karvernenboden settles and excess water free to a solid solid cures.

For the initiation the overground Spread solids suspension into the cavern should the pipe shoe the conveyor tube tour first preferably be positioned close to the area of the cavern floor to access this relatively easy way to contribute supportively, that no segregation of the solid suspension takes place, the disadvantageous Consequences for the deposition and curing process and for the reusability of surplus brine displaced and removed by the solid would have.

For the production the flowable solid suspension are preferably particulate Residues from the waste incineration or mud (eg contaminated harbor sediments), the particulate Solid preferably a particle size distribution of 0 to 500 microns and a maximum particle sizes of 0.5 to 0.8 mm, which is a rapid sedimentation of Allow solid fractions and prevent segregation of the suspension.

Favorable The way is the flowable solid suspension another solids fraction immediately before discharge into the cavern fed directly at the entrance to the backfilling at the cavern whose Grain size far above the Grain size of in the suspension contained solids, but well below the passage cross section of the conveyor tube lies. The proportion of this coarse-grained phase may only be so great that the fine-grained Phase is able to completely fill the resulting pore spaces. This way you can a better solidification effect can be achieved in the cavern. The pore spaces have to from the fine-grained Shares of the suspension are completely filled out, so that no free residual quantities of cavern liquid remain in the cavern.

The In any case, suspension is adjusted so that it relaxes Discharges into the cavern at the bottom and solidifies into a solid, wherein the solidification primarily by the properties of the used particulate Solid in conjunction with the NaCl solution occurs or optionally is achieved by adding a binder in small amounts

When Binders can For example, cement, stone or lignite filter bags or other suitable substances with setting properties are used, to add in the preparation of the suspension to the mixing process are, wherein the binder components in the solid suspension in should be about 5% to 10%.

Of the Addition of binder is especially in the backfilling of Cavern and the solidification of the brine in the upper cavern area made to higher Strengths of the solidifying suspension in particular in upper cavern area to achieve and thus the squeezing possibly. not completely solidified suspension components to prevent safe.

Before introducing the flowable solids suspension into the caverns, the gases possibly formed during mixing of the particulate solid with the saturated brine and any residues of the medium stored in the cavern, which are carried in the brine taken from the cavern, by shearing the treated suspension in a Agitator released and discharged controlled. By shearing in a stirrer and any existing tixotrophe properties of the prepared, flowable suspension are changed by mechanical treatment until a Solid suspension has formed with constant rheological flow properties.

By online measurements, preferably in a stirrer, the mixing plant is downstream, the flow properties of the suspension continuously recorded and over an electronic feedback the mixing plant becomes the scattering in the properties of the components the particulate Solids so regulated that always a suspension with largely constant rheological properties is introduced into the cavern.

to permanent and safe long-term custody becomes the entire cavern cavity filled according to the proposed method as long as throughout the cavern a solid filler emerged is about 50% of the formerly contained NaCl solution (cavernous brine) and to further parts of the particulate solid used exists and is able to absorb the mountain pressure in the long term and to prevent convergence. The excess of saturated Sole, about 50% of the former cavern volume, which is used for brine hardening and for backfilling the cavern is not needed is outsourced and disposed of in a known per se or stored.

There the caverns from the beginning in mighty Rock salt formations were created, the structures of the Rock salt formations in the vicinity of the caverns even after their backfilling according to the proposed Process and the formation of a solid packing obtained. deformations in the geological structures are thus permanently prevented and the cavern remains permanently sealed.

For the implementation of the inventive method must be under pressure and saturated Brine filled Cavern at any time be emptied or depressurized. Your stability is thus always guaranteed and never endangered.

One further, not insignificant advantage of the method according to the invention is that in the settling phase and during curing of the in the cavern initiated solid suspension releases no solutions be the other sol processes in the contact zones between the could trigger upcoming salt rock and the forming solid packing.

The cavern solidified by the process meets the legal requirements the long-term security. For this reason, as particulate solids also dangerous Waste materials are used in the sense of recycling according to KrWAbfG, such as residues the waste incineration and others, for the preparation of the solid suspension suitable waste. Thus, the process is both economical and beneficial to the environment.

The Invention will be explained in more detail below by way of examples. The accompanying drawing shows a schematic representation of a possible plant for processing the flowable solid suspension and to carry of the procedure.

example 1

The in a storage tavern that was built in salt rock, stored storage medium is completely outsourced by the introduction of driving brine - saturated NaCl solution and the liquid content the cavern is replaced in this way. The Treibsole remains in the cavern and takes over the function of a support fluid for the Cavern cavity. To compensate for the upcoming geostatic Mountain pressure becomes the brine-filled cavern with a required pressure is charged and stands constantly under this internal pressure.

For a safe and permanent long-term storage of the cavern is according to the inventive method saturated Brine taken from the cavern and surface for making a flowable and used pumpable solid suspension. The suspension is with particulate Residues the waste incineration and NaCl solution the cavern is made to be a suspension stable mixture for the Line transport and for the entry into the cavern arises. About the installed for the memory operation Production tubing tour will the over Days with the NaCl solution mixed suspension with simultaneous displacement of the placed in the cavern NaCl solution near the ground. When entering the cavern, the suspension sinks without mixing with the brine in the cavern to the bottom of the cavern and in the suspension starts the solidification process, wherein the Hardening or setting process for forming a solid packing in the Inside the cavern leads. Is the cavern in this way with solidifying suspension filled, The cavern convergence decreases after a short period to zero. The mountain tensions are absorbed by the resulting solid. The cavern stays stable, saturated NaCl solution or a contaminated by the registered solid solution can not be squeezed out more. The solid suspension can also be as in Example 2 can be produced.

The for the production of Feststoffsuspensi Unnecessary, excess NaCl solution is disposed of in a conventional manner. Since the hardening of the introduced solid suspension according to the formulation of the mixture according to the method is excess water-free, only during the process of introducing the solidifying suspension can an uncontaminated NaCl solution be discharged from the cavern volume above the suspension solidified on the ground. After complete filling of the cavern with the solidified suspension no brine is discharged.

Example 2

Of the Solid suspension may, in the absence of the required Eigenabbindvermögenmögens of a suitable binder is added to the solid used, depending on the type of solid, a suspension of about 50% NaCl solution and 50% solid is used. The solids content is too about 90 to 95% of a particulate solid, for example from residues the waste incineration, and about 5 to 10% of a binder. The components are depending on the chemical composition of the solids used and to set the binder in advance by experiments. As a binder can Cement, filter ash from brown and hard coal combustion, or bypass dust used in the cement industry.

A possible Plant for implementation the method according to the invention and for the preparation of the solid suspension is in the attached drawing and shown schematically.

With 1 is called filled with saturated NaCl solution and under an internal pressure storage tavern, which had been built in a suitable salt marshes and the storage cavity must be kept permanently and safely after completion of the storage operation to ensure the necessary mountain safety. For producing a suitable solid suspension, for solidifying the brine contained in the cavern and for forming a permanently solid packing in the interior of the cavern 1 serves, is via a riser 2 saturated NaCl solution from the cavern 1 taken and in a mixing plant 3 directed. With computer-controlled dosage is via the feeder 9 a solid component and via the feed 10 optionally an additional binder in the mixing plant 3 introduced and processed with the saturated NaCl solution to a flowable and pumpable solid suspension. The thus prepared solid suspension is then placed in a shear vessel / agitator 4 passed to release the gases possibly formed during the mixing of the particulate solid with the saturated brine and controlled by the discharge 11 derive and mechanically treat any existing or resulting tixotrophe properties of the treated suspension by shearing and adjust the rheological flow properties of the solid suspension. The prepared and treated solids suspension is continuously monitored by measurement and the data processed in a measuring station in which the relevant data such as suspension pressure at various points of the transport line, temperature of the suspension, material composition, rheological properties, etc. are recorded and registered. The results will be feedbacked 13 for changing and adjusting the dosage to the mixing station 3 given. With the help of the suspension pump 6 the solid suspension is via the conveyor tube 7 into the cavern 1 introduced where sediment the solid fractions of the suspension on the bottom of the cavern and harden to a solid filler with solidification of the brine.

Of the Pipe shoe of the conveyor tube is as close to the beginning of the custody process as possible the cavern floor is positioned and will become in the course of the procedure until the complete backfilling of the cavern interior constantly changing Mirror tracked the introduced solid suspension.

The excess NaCl solution, which is not required for carrying out the process, is passed over the line 8th derived and fed to a temporary storage or disposal.

Claims (13)

Method for the safe long-term storage of saturated brine caverns and cavern systems in the salt marshes using the saline solution in the cavern and a solid made from waste materials, which are introduced into the cavern after treatment as a suspension, characterized in that as a building material for the production of a the cavern space-filling solid under constant maintenance of cavern filling with brine and optionally an additional stabilizing head pressure gradually saturated brine taken from the cavern and mixed with a fine-grained waste and a binder to a flowable and settable solid suspension, the so prepared solid suspension then in the caverns is initiated, where it sinks without segregation to the cavern floor and hardens without excess water to a solid. A method according to claim 1, characterized in that for the preparation of the flowable solid suspension particulate residues the waste incineration are used. Method according to claim 1, characterized that for the preparation of the flowable solid suspension suitable sludges, For example, contaminated harbor sediments can be used Method according to Claims 1, 2 and 3, characterized that the particulate Solid preferably a particle size distribution of 0 to 500 microns and a maximum particle sizes of 0.5 to 0.8 mm, which is a rapid and unmixed Allow the suspension to fall. Process according to Claims 1 to 4, characterized that of the flowable solid suspension another solids fraction immediately before discharge into the cavern supplied whose grain size is far above the Grain size of in the suspension contained solids. Method according to claims 1 to 4, characterized that of the flowable solid suspension an additional Binder is mixed. Method according to Claim 6, characterized that as binder cement, or filter ash from the brown and Hard coal combustion, or bypass dusts from the cement industry or similar fine-grained Substances with setting properties are used and the binder content in the flowable solid suspension about 5% to 10%. Method according to one of claims 1 to 7, characterized that the binder of the flowable solid suspension preferably for filling the cavern in the upper borehole near area is mixed. Method according to one of claims 1 to 8, characterized that before the introduction of the flowable suspension into the cavern when mixing the particulate solid with the saturated Brine possibly resulting gases by shearing the treated Suspension in a stirrer be released and controlled discharged. Process according to claims 1 to 3 and 9, characterized characterized in that any existing tixotrophic properties the prepared, flowable suspension while mechanically treated by shearing in a stirrer be until constant rheological flow properties have arisen. Method according to one of claims 1 to 10, characterized that the flow properties the suspension by online measurement in a stirrer, the mixing plant is downstream, captured and over an electrical feedback to Mixing plant dispersions in the properties of the components of particulate Solids are adjusted so that a suspension with largely constant rheological properties introduced into the cavern becomes. Method according to one of claims 1 to 11, characterized that the pipe shoe of the conveyor tube tour, over the the flowable suspension is introduced into the cavern, positioned directly above the cavernous sump is and with the degree of backfilling changing mirror level of the introduced Tracking tracked becomes. Method according to one of claims 1 to 12, characterized that excess saturated Sole, which is not needed for its consolidation and for the filling of the cavern, derives and intercalated or disposed of in a known manner becomes.