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Content archived on 2022-12-27

INDUSTRIAL PILOT PROJECT FOR UNDERGROUND CRYOGENIC STORAGE OF LIQUEFIED GASES

Objective

The objective of the proposed project is to build a pilot facility and operate it under industrial working conditions and over a sufficiently long length of time in order to prove in practice the reliability of all the innovative facilities ie:
- Design of the storage cavity and its equipment to resist the constraints due to cryogenic conditions and depth (specially in the case of clay)
- Operating equipment - and its maintenance - working under such conditions
- Operating process. The pilot should demonstrate the technical feasibility and the advantages of the technology in terms especially of safety and lower capital and operating costs.
Thanks to the LABORATORY TESTS, we determined the characteristics of the Yper clay at first for the geotechnical properties at ambient temperature (elastoplastic behaviour, Cu, E, nu), secondly for the geotechnical properties at low temperature, between + 13 deg. C and - 160 deg. C (dilatometry, E, nu, Lemaitre's rheological law, tensile strength), and finally the properties of thermal conductivity. One important result is an anisotropy between vertical and horizontal directions as regards the dilatometry.
EXCAVATION ASPECT
Although excavation is difficult in clay for the considered diameter (7.2 m internal diameter), it is feasible, provided that it is performed at a depth of 180 m.
CRYOGENIC ASPECT
The main results indicate that :
- the radial stress remains compressive at every point which necessitates a lining of great thickness;
- the axial and shear stresses result in tensile stresses on the wall.
The axial stress is the most preoccupying, since it reaches the tensile strength of the ice.
Although the thickness of the zone subject to the traction remains less than a metre, the disturbance caused by a possible fracturing can lead to the propagation of thermomechanical tractions deeper down in the body.
TIMETABLE-COSTS
We consider for this chapter the execution of the pilot, his operation, and the execution of the industrial extension (100.000 m3).
The total of the works will be spread over nine to ten years.
Cost of pilot : 1,500 MBEF
Cost of industrial extension : 2,500 MBEF
GENERAL CONCLUSIONS
The excavation and process feasibility are confirmed. There is an uncertainty about the cryogenic aspect.
In the light of the above mentioned costs and periods for this underground solution compared to the classic overground equivalent, the costs and timetable of which are reduced by 40% and 50% respectively, and on the type of clay found in Zeebrugge, we can recommend neither a possible additional study designed to lift the technical uncertainty, nor the pursuit of this underground LNG project in the clay of Zeebrugge.
However it is important to note that while a technical uncertainty exists concerning feasibility at vey low temperature (as in the case of LNG), THE CONCLUSIONS REMAIN POSITIVE FOR LESS LOW TEMPERATURE (AS IN THE CASE OF LPG).
This industrial pilot facility will have a capacity of the order of 6000 m3 and exhibit all the specific features of a full-scale industrial unit and the equipment needed for its operation.
The Distrigaz LNG Terminal at Zeebrugge has been chosen as the project site. It provides the LNG needed for the initial cooling down phase and all the facilities for the subsequent testing and operating phase.
Moreover there exists in the terminal underground a clay layer which seems adequate for the projected gallery.
The programme will break down into three phases :
1. Feasibility study :
Its content will of course depend on information available but must
necessarily include :
1.1. Drilling to achieve a full geological survey of the clay layer
and take fresh samples;
2.2. Laboratory testing - to determine the clay properties at ambient
and cryogenic temperatures;
2.3. The feasibility study in itself;
2.4. General design, including for example tunneling methods and the
main items of operating equipment, as well as capital cost
estimates.
2. Construction :
Will involve driving a single tunnel of 8 m diameter with a length of approximately 2400 m at a depth of roughly 180 m below ground level in a clay formation. The access shaft will have a diameter of +/- 5 m and will be afterwards converted to an operating shaft. The tunnel will be supported with concrete segments for mechanical integrity during the excavation.
This equipment will include :
- LNG pump at ground level;
- Spraying line along the tunnel roof;
- Submersible pump for lifting LNG to surface;
- Boil-off treatment unit;
- Operating instrumentation and boil-off return lines;
- Monitoring and control equipment and safety systems.
3. Cooling-down and operation :
The timing of the cooling down phase will last 5 - 6 months at least. Once cooled down, the unit will be operated for at least one year to provide an opportunity for simulating various operating phases, observing cavity response, checking the performance of equipment and control systems and optimising operating performances.

Call for proposal

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Coordinator

DISTRIGAZ SA
EU contribution
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Address
AVENUE DES ARTS 31
1040 Bruxelles
Belgium

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Total cost
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