Patent GB-921844-A (GB)
Title: Means for sealing a ground reservoir for the storage of liquefied gases
Inventor: SCHLUMBERGER ETIENNE MAURICE
IPC: E04H7/02
Filed: 1961-02-07
Abstract: 921,844. Storing liquefied gases. CONCH INTERNATIONAL METHANE Ltd. Oct. 16, 1961 [Feb. 7, 1961], No. 4513/61. Class 8(2). A reservoir for the storage of liquefied gases, e.g. natural gas, methane, ethane, propane or butane, comprises a hole 4 excavated in the earth and a thermally insulated roof 7 completely covering the hole, the reservoir being sealed by a continuous, vapour-impervious membrane 14 which extends from the roof into a slot 5 in the earth, the slot being filled by a material which is liquid at ambient temperature but is solid when the reservoir is in use. The hole is preferably circular in cross-section and is excavated from ground which has been frozen by the passage of a refrigerant, e.g. liquid propane through pipes 1, the latter being connected to ring mains 2 and 3. The hole may be lined with a coarse cotton cover, wood shavings embedded in wax or frozen mineral oil, or glass fibre mats; the lining need not be liquid-tight. The circular roof 7 may be made of wood but is preferably made of aluminium or carbon steel and comprises radial I-beam stiffeners; it is preferably insulated on its under surface with polyurethane or polystyrene foams. The insulation may be suspended a short distance from the roof. The latter is supported on plates disposed on top of the pipes 1, Figs. 3 and 4 (not shown), the plates carrying wooden blocks 11 which are covered by metal liners on which the I-beams rest and, when necessary, slide, the roof being held down by tie rods. The membrane 14 is preferably made of aluminium or stainless steel and is provided with horizontal corrugations above the ground and vertical corrugations in ground; at least part of the membrane may be formed from dimpled sheet. When the liquefied gas being stored is natural gas, the material used for filling the slot 5 preferably has a melting point about, but not below -90‹C.,e.g. n-heptane, n-octane, n-butyl alcohol, the monoethyl ether of ethylene glycol, ethyl acetate, isopropyl alcohol and appropriate mineral oil fractions. When the liquefied gas being stored is n-propane the material used for filling the slot 5 preferably has a melting point about, but not below, -10‹C., e.g. suitable mixtures of water with ethylene glycol or isopropyl alcohol. Alternatively, water alone may be used or waxy mineral oils. The reservoir is provided with a second continuous, vapourimpervious membrane 15, e.g. of metal or wood or a rubber or canvas sheet, which extends from the roof into a hole 6 in which it is sealed, e.g. by water or a bitumen composition. The annular space between the membranes 14 and 15, the roof and the earth is continually purged by an inert gas, e.g. nitrogen or carbon dioxide. The reservoir is provided with a gas vent and conduit and pumping means (not shown) for filling and discharging the reservoir. In a modification, Fig. 5 (not shown), the radial I-beam stiffeners are replaced by a circular girder. The conduit means for filling and discharging the reservoir extend through the membrane 14 which is provided locally with bellows to allow for relative movement between the conduit means and the membrane. Specification 894,762 is referred to.