JP5888727B2 - Low temperature liquefied gas underground freezing controlled storage facility - Google Patents

Description

本発明は低温液化ガスの地下凍結制御型貯蔵施設に関し、とくに地盤・岩盤（以下、両者をまとめて地盤ということがある）の凍結を制御しながら低温液化ガスを地下に貯蔵する施設に関する。   The present invention relates to a cryogenic liquefied gas underground freezing controlled storage facility, and more particularly to a facility for storing cryogenic liquefied gas underground while controlling freezing of the ground / rock (hereinafter sometimes referred to as the ground).

火力発電等のエネルギー源として使用される気体燃料（常温・常圧下で気体の天然ガスや石油ガス等）は、そのままでは固体・液体燃料（石炭や石油等）に比べて輸送・貯蔵に不利であるが、加圧・冷却により液化ガス（以下、低温液化ガスという）として輸送・貯蔵することができる。日本では、産出国からＬＮＧやＬＰＧ等の低温液化ガスを輸入して国内の貯蔵施設（受入基地）に一旦貯え、例えば需要に応じて必要量ずつ気化器によりガス化して払い出すことにより利用している。低温液化ガスの貯蔵施設として従来から金属二重殻式の地上タンクが利用されているが、地上タンクは液化ガスの漏出対策が不可欠であり、タンク周囲に漏出時の流出範囲を局限化する防液堤等を構築するため比較的広い敷地面積を必要とする（非特許文献１参照）。これに対し、施設の大部分又は全てを地下に埋設して液化ガスが地上に流出する危険を低減した地下貯蔵施設が開発されている（特許文献１〜３参照）。   Gaseous fuels (such as natural gas and petroleum gas that are gaseous at normal temperature and pressure) that are used as energy sources for thermal power generation, etc., are disadvantageous for transportation and storage compared to solid and liquid fuels (coal, oil, etc.). However, it can be transported and stored as liquefied gas (hereinafter referred to as low temperature liquefied gas) by pressurization and cooling. In Japan, low-temperature liquefied gases such as LNG and LPG are imported from the country of origin and stored in a domestic storage facility (acceptance base). ing. Conventionally, metal double-shell type ground tanks have been used as storage facilities for low-temperature liquefied gas, but liquefied gas leakage countermeasures are indispensable for ground tanks, and the outflow range at the time of leakage is localized around the tank. A relatively large site area is required to construct a liquid bank (see Non-Patent Document 1). In contrast, underground storage facilities have been developed in which most or all of the facilities are buried underground to reduce the risk of liquefied gas flowing out to the ground (see Patent Documents 1 to 3).

例えば特許文献１及び２は、図４（Ａ）に示すように、円筒状に構築した地中連壁２１の内側を最深部まで掘削し、その内側にコンクリート製の側壁２２及び底壁２３を打設して躯体（有底の槽体）を形成し、その躯体の開口部をドーム状の屋根２４で覆った地下貯蔵タンク２０を開示している。躯体（側壁２２及び底壁２３）の内面全体にメンブレンと呼ばれる鋼材層および断熱材層２６（図４（Ｂ）参照）を敷設したうえで、受入ライン４から低温液化ガスＬＧを導入して貯蔵する。貯蔵した液化ガスＬＧは、払出ライン５から気化器５ａを介して適宜払い出すことができる。図示例の地下貯蔵タンク２０は、躯体が地表面下に存在し地上からはドーム状の屋根２４しか見えないので周囲の景観を損なわず、液化ガスＬＧが地上に漏れ出すおそれが小さく防液堤等が不要となるので敷地の利用効率が高い利点がある。また、図示例のタンク２０は屋根２４が破損すると液化ガスＬＧが大気中に漏出するおそれがあることから、特許文献３のようにドーム状の屋根２４を地中に埋設して漏出の危険を更に抑えた地下タンクも提案されている。   For example, in Patent Documents 1 and 2, as shown in FIG. 4 (A), the inside of the underground continuous wall 21 constructed in a cylindrical shape is excavated to the deepest part, and a concrete side wall 22 and a bottom wall 23 are formed inside thereof. An underground storage tank 20 is disclosed in which a housing (bottomed tank body) is formed by casting and the opening of the housing is covered with a dome-shaped roof 24. A steel material layer called a membrane and a heat insulating material layer 26 (see FIG. 4B) are laid on the entire inner surface of the housing (the side wall 22 and the bottom wall 23), and the low temperature liquefied gas LG is introduced from the receiving line 4 and stored. To do. The stored liquefied gas LG can be appropriately discharged from the discharge line 5 via the vaporizer 5a. The underground storage tank 20 in the illustrated example has a skeleton under the ground surface and only the dome-shaped roof 24 can be seen from the ground, so that the surrounding landscape is not impaired and the liquefied gas LG is less likely to leak to the ground. Since there is no need for such a site, there is an advantage that the use efficiency of the site is high. Further, since the tank 20 in the illustrated example may cause the liquefied gas LG to leak into the atmosphere if the roof 24 is damaged, the dome-shaped roof 24 is buried in the ground as in Patent Document 3 to reduce the risk of leakage. A more conserved underground tank has also been proposed.

極低温の液化ガスＬＧ（例えば−１６２℃のＬＮＧ等）を貯蔵する地下貯蔵タンク２０は、冷熱により周囲の地盤（地下水）が凍結するのでタンクの液密性・気密性が向上するものの、凍結の拡大により凍上（氷層の発生により地盤が***・変形する現象）が発生してタンクの躯体に大きな圧力（凍結土圧）が加わるおそれがあるので、安全のために周囲の凍結を人為的に制御する必要がある。例えば図４（Ｂ）に示すように、地下タンク２０の躯体外面に沿って側部ヒータ２７及び底部ヒータ２８（例えば４ｍ程度の間隔で並べた直径約１０ｃｍのパイプ）を敷設して加熱用熱媒（例えばスチーム等を熱源とした温水やブライン）を循環させ、液化ガスＬＧの冷熱とヒータ２７、２８の温熱とを熱的にバランスさせることにより凍結地盤Ｆの進行・拡大を停止させる（非特許文献２参照）。他方、タンク２０内の液化ガスＬＰの気化・蒸散を抑えるためには凍結地盤Ｆを周囲からの自然入熱を防ぐ厚さとすることが有効であり、ヒータ２７、２８によって凍結地盤Ｆを適当な厚さとなるように制御する。なお、図示例ではヒータ２８を地中に配置しているが、底壁２３のコンクリート中に温水パイプ等を埋設する方式、又は底壁２３の下方に敷設した砂利層等に熱媒を供給する方式等とすることもできる。   The underground storage tank 20 for storing the cryogenic liquefied gas LG (for example, LNG at −162 ° C.) is frozen, although the surrounding ground (groundwater) is frozen by cold heat, so that the liquid and air tightness of the tank is improved. Because of the frost heaving (the phenomenon that the ground rises and deforms due to the formation of an ice layer) due to the expansion of the surface, there is a risk of applying large pressure (freezing earth pressure) to the tank housing, so the surrounding freezing is artificially done for safety Need to control. For example, as shown in FIG. 4B, side heaters 27 and bottom heaters 28 (for example, pipes having a diameter of about 10 cm arranged at intervals of about 4 m) are laid along the outer surface of the underground tank 20 to heat for heating. The medium (for example, warm water or brine using steam or the like as a heat source) is circulated, and the progress and expansion of the frozen ground F are stopped by thermally balancing the cold heat of the liquefied gas LG and the heat of the heaters 27 and 28 (non- Patent Document 2). On the other hand, in order to suppress the vaporization and transpiration of the liquefied gas LP in the tank 20, it is effective to make the frozen ground F thick enough to prevent natural heat input from the surroundings. Control to be thick. In the illustrated example, the heater 28 is disposed in the ground. However, a heating medium is supplied to a method in which a hot water pipe or the like is embedded in the concrete of the bottom wall 23 or a gravel layer laid below the bottom wall 23. It can also be a method.

特開２０００−１３０６９８号公報JP 2000-130698 A 特開２００２−００４６２７号公報JP 2002-004627 A 特開平４−３１２２９７号公報Japanese Patent Laid-Open No. 4-312297

社団法人日本エネルギー学界天然ガス部会編「天然ガスのすべて」コロナ社、１０６〜１１３頁（３．４ ＬＮＧの受入基地と貯蔵タンク）、２００８年１０月３日発行Japan Energy Academic Natural Gas Division, “All about Natural Gas” Corona, 106-113 (3.4 LNG receiving terminal and storage tank), issued October 3, 2008 後藤貞夫・田中益弘「土の凍結と地盤工学 １０．ＬＮＧ地下タンク周辺地盤の凍結制御」、土と基礎、地盤工学会、２００３年１２月、第５１巻１２号、ｐｐ．８６−９１Goto Sadao and Tanaka Masuhiro “Soil Freezing and Geotechnical Engineering 10. Soil Freezing Control around LNG Underground Tank”, Soil and Foundation, Geotechnical Society, December 2003, Vol. 86-91

しかし、図４（Ｂ）のように地下タンク２０の周囲に側部ヒータ２７及び底部ヒータ２８を設けて凍結地盤Ｆを制御する方法は、大きな凍結土圧の発生を避けて地下貯蔵施設の設計・施工を容易にするために有効であるが、低温液化ガスＬＧの貯蔵中は各ヒータ２７、２８に熱媒を循環させ続ける維持管理コストを必要とする。例えば最近ではエネルギー需要の季節変動等に対応するため複数の地下タンクを用いて大量の低温液化ガスＬＧを長期間貯蔵することも検討されているが、図４のように地下タンク毎にそれぞれヒータ２７、２８を設けて凍結地盤Ｆを制御する方法では貯蔵施設の維持管理コストが膨大になってしまう。複数の地下タンクを用いる場合は、隣接するタンク相互の配置により熱の出入を工夫することも可能であり、タンクが一基の場合と異なるヒータ２７、２８の配置・運転によって凍結地盤Ｆを制御するための維持管理コストをできるだけ小さく抑えることが望まれている。   However, as shown in FIG. 4B, the method of controlling the frozen ground F by providing the side heater 27 and the bottom heater 28 around the underground tank 20 avoids the generation of a large frozen earth pressure and designs the underground storage facility. Although it is effective for facilitating the construction, it requires maintenance and management costs to keep circulating the heat medium through the heaters 27 and 28 during storage of the low-temperature liquefied gas LG. For example, recently, it has been studied to store a large amount of low-temperature liquefied gas LG for a long time using a plurality of underground tanks in order to cope with seasonal fluctuations in energy demand, etc., but as shown in FIG. In the method of controlling the frozen ground F by providing 27 and 28, the maintenance cost of the storage facility becomes enormous. When multiple underground tanks are used, it is possible to devise heat input and output by arranging adjacent tanks, and the frozen ground F is controlled by arrangement and operation of heaters 27 and 28 different from the case of one tank. Therefore, it is desired to keep the maintenance management cost as small as possible.

そこで本発明の目的は、地下貯蔵タンク周囲の凍結地盤を長期にわたり経済的に維持管理することができる地下凍結制御型貯蔵施設を提供することにある。   Therefore, an object of the present invention is to provide an underground freezing control type storage facility that can economically maintain and maintain the frozen ground around the underground storage tank for a long period of time.

図１及び図２の実施例を参照するに，本発明による低温液化ガスの地下凍結制御型貯蔵施設は，地表Ｅの相互に隔てた複数地点Ｑ１，Ｑ２，Ｑ３，Ｑ４，……（図２参照）の地下にそれぞれ構築した鉛直下方に延びる冷温液化ガスＬＧの貯蔵タンク２，複数地点Ｑ１，Ｑ２，Ｑ３，Ｑ４，……を囲む環状線Ｕ（図２参照）に沿った複数位置の地下にそれぞれ構築した鉛直下方に延びる熱媒管１０Ｕ，複数地点Ｑ１，Ｑ２，Ｑ３，Ｑ４，……のうち隣接する地点Ｑ１，Ｑ２，Ｑ３，Ｑ４，の間の境界線Ｒ（図２参照）に沿った複数位置の地下にそれぞれ構築した鉛直下方に延びる熱媒管１０Ｒ，及び各熱媒管１０Ｕ，１０Ｒに熱媒Ｔを循環させると共に各熱媒管１０Ｕ，１０Ｒに対する熱媒Ｔの循環を独立に制御する熱媒循環装置１５を備え，熱媒Ｔの循環により各貯蔵タンク２の周囲の凍結を制御してなるものである。 1 and 2, the low temperature liquefied gas underground freezing control type storage facility according to the present invention has a plurality of points Q1, Q2, Q3, Q4,. storage tank 2 of the cold liquefied gas LG extending vertically downward constructed respectively in the basement of the reference), a plurality of points Q1, Q2, Q3, Q4, a plurality of positions along the annular line U (see FIG. 2) surrounding the ...... underground To the boundary line R (see FIG. 2) between the adjacent points Q1, Q2, Q3, Q4 among the heating medium pipes 10U extending vertically downward, and the points Q1, Q2, Q3, Q4,. The heating medium pipe 10R extending vertically below and constructed in the basement at a plurality of locations along the heating medium 10C and the heating medium pipes 10U, 10R are circulated and the circulation of the heating medium T to the heating medium pipes 10U, 10R is independent. comprising a heating medium circulation device 15 for controlling the, The circulation of the medium T is made by controlling the freezing around each storage tank 2.

好ましくは，図２（Ａ）に示すように，複数地点Ｑ１，Ｑ２，Ｑ３，Ｑ４，……を地表面Ｅ上の多角形の各頂点位置とする。この場合は，図２（Ｂ）に示すように，複数地点Ｑ１，Ｑ２，Ｑ３，Ｑ４，……に囲まれた内側域Ｎの周縁に沿った複数位置の地下にそれぞれ構築した鉛直下方に延びる内側熱媒管１０Ｎを設け，熱媒循環装置１５から各内側熱媒管１０Ｎへの熱媒Ｔの循環により内側域Ｎの凍結を防止することができる。 Preferably, as shown in FIG. 2A, a plurality of points Q1, Q2, Q3, Q4,. In this case, as shown in FIG. 2 (B), it extends vertically downward constructed respectively at a plurality of positions underground along the periphery of the inner area N surrounded by a plurality of points Q1, Q2, Q3, Q4 ,. The inner heat medium pipe 10N is provided , and freezing of the inner area N can be prevented by circulation of the heat medium T from the heat medium circulation device 15 to each inner heat medium pipe 10N.

更に好ましくは、図３（Ｃ）〜（Ｄ）に示すように、熱媒循環装置１５に加熱用熱媒Ｔと冷却用熱媒Ｔ´とを切り替える熱媒切替手段１９を含め、各貯蔵タンク２への冷温液化ガスＬＧの受入れ前に各熱媒管１０Ｕ、１０Ｒに冷却用熱媒Ｔ´を循環させて貯蔵タンク周囲を凍結し且つ受入れ後に各熱媒管１０Ｕ、１０Ｒに加熱用熱媒Ｔを循環させて貯蔵タンク周囲の凍結を制御する。図３（Ａ）〜（Ｃ）に示すように、各熱媒管１０Ｕ、１０Ｒを各貯蔵タンク２に先行して穿設し、各熱媒管１０Ｕ、１０Ｒに冷却用熱媒を循環させて形成した凍結領域Ｆを鉛直に掘削して各貯蔵タンク２を構築することも可能である。   More preferably, as shown in FIGS. 3 (C) to 3 (D), each storage tank includes a heat medium switching device 19 for switching between a heating heat medium T and a cooling heat medium T ′ in the heat medium circulating device 15. The cooling medium T ′ is circulated through the heating medium pipes 10U and 10R before receiving the cold / liquefied liquefied gas LG to 2 to freeze around the storage tank, and after receiving the heating medium pipes 10U and 10R, the heating medium for heating. Circulate T to control freezing around the storage tank. As shown in FIGS. 3A to 3C, the heating medium pipes 10U and 10R are drilled in advance in the storage tanks 2, and the cooling heating medium is circulated through the heating medium pipes 10U and 10R. It is also possible to construct each storage tank 2 by excavating the formed frozen region F vertically.

望ましくは、図１に示すように、各貯蔵タンク２に、地下所定深さＤから鉛直下方に延びる所定口径Ｗ２の本体部２ａと、その本体部２ａの頂端を縮径された口径Ｗ３で地表Ｅと連結する導坑部２ｂとを含め、各貯蔵タンク２に本体部２ａの容積以上の低温液化ガスＬＧを受入れて液面位を導坑部２ｂ内に保ちつつ貯蔵する。   Desirably, as shown in FIG. 1, each storage tank 2 has a main body portion 2a having a predetermined diameter W2 extending vertically downward from a predetermined depth D underground, and a diameter W3 having a reduced diameter at the top end of the main body portion 2a. The low temperature liquefied gas LG more than the capacity | capacitance of the main-body part 2a is received in each storage tank 2 including the guiding shaft part 2b connected with E, and it stores it, keeping a liquid level in the guiding tunnel part 2b.

本発明による低温液化ガスの地下凍結制御型貯蔵施設は，地表Ｅの複数地点Ｑ１，Ｑ２，Ｑ３，Ｑ４，……の地下を鉛直下方に掘削して冷温液化ガスＬＧの地下貯蔵タンク２を構築し，その複数地点Ｑ１，Ｑ２，Ｑ３，Ｑ４，……を囲む環状線Ｕに沿って複数の熱媒管１０Ｕを鉛直下方に穿設すると共に，複数地点Ｑ１，Ｑ２，Ｑ３，Ｑ４，……のうち隣接する地点Ｑ１，Ｑ２，Ｑ３，Ｑ４，……の間の境界線Ｒに沿って複数の熱媒管１０Ｒを鉛直下方に穿設し，各熱媒管１０Ｕ，１０Ｒにそれぞれ熱媒循環装置１５から熱媒Ｔを循環させると共に各熱媒管１０Ｕ，１０Ｒに対する熱媒Ｔの循環を独立に制御することにより各貯蔵タンク２の周囲の凍結地盤を制御するので，次の有利な効果を奏する。 Underground freeze-controlled storage facility low-temperature liquefied gas according to the present invention, a plurality of points Q1 of surface E, Q2, Q3, Q4, and excavating the underground ...... vertically downward build underground storage tank 2 of the cold liquefied gas LG A plurality of heating medium pipes 10U are drilled vertically downward along an annular line U surrounding the plurality of points Q1, Q2, Q3, Q4,... And a plurality of points Q1, Q2, Q3, Q4,. A plurality of heat medium pipes 10R are drilled vertically downward along a boundary line R between adjacent points Q1, Q2, Q3, Q4,..., And each of the heat medium pipes 10U, 10R circulates the heat medium. The frozen ground around each storage tank 2 is controlled by circulating the heat medium T from the device 15 and independently controlling the circulation of the heat medium T to each of the heat medium pipes 10U, 10R. Play.

（イ）複数の地下タンク２の境界部Ｒにおいて熱媒管１０Ｒを共有させ、その熱媒管１０Ｒの熱媒Ｔの循環によって両側の地下タンク２周囲の凍結地盤Ｆを同時に制御することにより、地下タンク２ごとに熱媒管を設ける従来の方法に比して熱媒管１０の設置数を節約し、凍結地盤Ｆの維持管理コストを抑制できる。
（ロ）また、複数の地下タンク２を囲む外側環状部Ｕに比して境界部Ｒは周囲からの自然入熱が抑制されるので、境界線上の熱媒管１０Ｒに対する熱媒Ｔの循環を環状線上の熱媒管１０Ｕとは独立に制御して効率的に運用することにより、凍結地盤Ｆの維持管理コストを一層低減することが期待できる。
（ハ）さらに、複数の地下タンク２で囲まれた内側域Ｎの周縁に沿って熱媒管１０Ｎを設け、その内側熱媒管１０Ｎへの熱媒Ｔの循環によって内側域Ｎの凍結を防止することにより、凍結の影響を避けるべき構造物や自然植生が存在する地域の地下を低温液化ガスの貯蔵施設として利用することが可能となる。 (A) By sharing the heat medium pipe 10R at the boundary portion R of the plurality of underground tanks 2 and simultaneously controlling the frozen ground F around the underground tanks 2 on both sides by circulation of the heat medium T of the heat medium pipe 10R, Compared to the conventional method of providing a heat medium pipe for each underground tank 2, the number of heat medium pipes 10 can be saved, and the maintenance cost of the frozen ground F can be suppressed.
(B) Further, since the boundary portion R suppresses natural heat input from the surroundings compared to the outer annular portion U surrounding the plurality of underground tanks 2, the circulation of the heat medium T to the heat medium pipe 10R on the boundary line is prevented. It can be expected that the maintenance cost of the frozen ground F can be further reduced by controlling the heating medium pipe 10U on the annular line independently and operating efficiently.
(C) Furthermore, a heating medium pipe 10N is provided along the periphery of the inner area N surrounded by the plurality of underground tanks 2, and the freezing of the inner area N is prevented by circulation of the heating medium T to the inner heating medium pipe 10N. By doing so, it becomes possible to use the underground of the area where there is a structure and natural vegetation where the influence of freezing should be avoided as a storage facility for low-temperature liquefied gas.

以下、添付図面を参照して本発明を実施するための形態及び実施例を説明する。
は、本発明による地下凍結制御型貯蔵施設の一実施例の説明図である。 は、本発明による地下凍結制御型貯蔵施設の水平断面図である。 は、図１の地下凍結制御型貯蔵施設の構築方法及び運転方法の説明図である。 は、従来の低温液化ガスの地下貯蔵施設の説明図である。 DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments and examples for carrying out the present invention will be described with reference to the accompanying drawings.
These are explanatory drawings of one Example of the underground freezing control type | mold storage facility by this invention. These are horizontal sectional views of the underground freezing control type storage facility according to the present invention. These are explanatory drawings of the construction method and operation method of the underground freezing control type | mold storage facility of FIG. These are explanatory drawings of the conventional underground storage facility of low-temperature liquefied gas.

図１は本発明の地下凍結制御型貯蔵施設の一実施例を示し、図２（Ａ）はその貯蔵施設の水平断面図を示す。図示例の貯蔵施設１は、地表面Ｅ上の四角形の各頂点位置Ｑ１、Ｑ２、Ｑ３、Ｑ４をそれぞれ鉛直に掘削して構築した４基の貯蔵タンク２と、その相互に隔てた４基の貯蔵タンク２を囲む地表Ｅの外側環状線Ｕに沿った複数位置にそれぞれ鉛直に穿設した熱媒管１０Ｕ（以下、環状熱媒管１０Ｕということがある）と、隣接する貯蔵タンク２の間の境界線Ｒに沿った複数位置にそれぞれ鉛直に穿設した熱媒管１０Ｒ（以下、境界熱媒管１０Ｒということがある）とを備えている。各熱媒管１０Ｕ、１０Ｒはそれぞれ熱媒循環装置１５に接続されており、循環装置１５から各熱媒管１０Ｕ、１０Ｒに加熱用熱媒Ｔ（例えば温水やブライン等）を送入し且つ戻して循環させることにより、各貯蔵タンク２の周囲に形成される凍結地盤Ｆの厚さを制御する。   FIG. 1 shows an embodiment of the underground freezing control type storage facility of the present invention, and FIG. 2 (A) shows a horizontal sectional view of the storage facility. The storage facility 1 in the illustrated example has four storage tanks 2 constructed by excavating each vertex position Q1, Q2, Q3, Q4 of the quadrangle on the ground surface E vertically, and four sets separated from each other. Between a heat medium pipe 10U (hereinafter, sometimes referred to as an annular heat medium pipe 10U) vertically drilled at a plurality of positions along the outer annular line U of the surface E surrounding the storage tank 2 and the adjacent storage tank 2 Heat medium pipes 10R (hereinafter also referred to as boundary heat medium pipes 10R) that are vertically drilled at a plurality of positions along the boundary line R. Each of the heat medium pipes 10U and 10R is connected to the heat medium circulation device 15, and the heating medium T (for example, hot water or brine) is sent to the heat medium pipes 10U and 10R from the circulation device 15 and returned. The thickness of the frozen ground F formed around each storage tank 2 is controlled by circulating them.

図示例の各貯蔵タンク２はそれぞれ、地下所定深さＤから鉛直下方に延びる所定口径Ｗ２の本体部２ａと、その本体部２ａの頂端を縮径された口径Ｗ３で地表Ｅと連結する導坑部２ｂとで構成されている。また、各貯蔵タンク２には、貯留すべき低温液化ガスＬＧを導坑部２ｂ経由で本体部２ａ内に送り込む受入ライン４と、貯留中の低温液化ガスＬＧを本体部２ａの底部から送り出す払出ライン５と、貯蔵中に液化ガスＬＧの一部分が気化・蒸散したボイルオフガス（以下、ＢＯＧということがある）を導坑部２ｂから排出するＢＯＧライン６とが設けられている。各貯蔵タンク２の内側にメンブレン（鋼材層および断熱材層）２６を敷設したうえで（図４（Ｂ）参照）、受入ライン４から本体部２ａの容積以上の液量の低温液化ガスＬＧを受入れ、本体部２ａ内を液化ガスＬＧで充填すると共に液化ガスＬＧの一部を導坑部２ｂ内に溢出させ、液面位を導坑部２ｂ内に保ちながら各貯蔵タンク２内に液化ガスＬＧを貯蔵する。必要に応じて、各貯蔵タンク２の均衡を図るため、４基の貯蔵タンク２を相互に連絡する横坑を設けることも有効である。   Each of the storage tanks 2 in the illustrated example has a main body 2a having a predetermined diameter W2 extending vertically downward from a predetermined depth D below, and a guide shaft connected to the surface E by a diameter W3 having a reduced diameter at the top end of the main body 2a. Part 2b. Moreover, in each storage tank 2, the receiving line 4 which sends the low temperature liquefied gas LG which should be stored in the main-body part 2a via the guide shaft part 2b, and the discharge which sends out the low-temperature liquefied gas LG currently stored from the bottom part of the main-body part 2a A line 5 and a BOG line 6 for discharging a boil-off gas (hereinafter sometimes referred to as BOG) in which a part of the liquefied gas LG is vaporized and evaporated during storage from the guide shaft portion 2b are provided. After laying a membrane (steel material layer and heat insulation material layer) 26 inside each storage tank 2 (see FIG. 4B), a low-temperature liquefied gas LG having a liquid volume larger than the volume of the main body 2a is received from the receiving line 4. The main body 2a is filled with the liquefied gas LG, and a part of the liquefied gas LG overflows into the guide shaft portion 2b, and the liquefied gas is stored in each storage tank 2 while keeping the liquid level in the guide shaft portion 2b. Store LG. If necessary, it is also effective to provide lateral shafts that interconnect the four storage tanks 2 in order to balance the storage tanks 2.

図示例のように貯蔵タンク２の本体部２ａの口径Ｗ２に比して導坑部２ｂの口径Ｗ３を小さくし、その導坑部２ｂ内に液面位を形成することにより、本体部２ａ内に液面位が形成された場合に比して液化ガスＬＧの蒸発面積及び蒸発速度を小さく抑え、貯蔵タンク２に貯蔵中のＢＯＧ発生量を低減することができる。また、導坑部２ｂを本体部２ａの頂端に接続することにより、液化ガスＬＧの受入れ時に本体部２ａの全体が液化ガスＬＧで充填されて空気溜り等の気相部が残らないようにすることができる。望ましくは、図示例のように本体部２ａの頂面を半球状又は円錐状とし、液化ガスＬＧの受入れ時に本体部２ａ内の液面位の上昇によって残存気体が全て導坑部２ｂへ送り出されるようにする。   By reducing the diameter W3 of the guide shaft portion 2b as compared to the diameter W2 of the main body portion 2a of the storage tank 2 and forming a liquid level in the guide shaft portion 2b as in the illustrated example, the inside of the main body portion 2a As compared with the case where the liquid level is formed, the evaporation area and evaporation rate of the liquefied gas LG can be suppressed to be small, and the amount of BOG generated during storage in the storage tank 2 can be reduced. Further, by connecting the guide shaft portion 2b to the top end of the main body portion 2a, the whole main body portion 2a is filled with the liquefied gas LG when receiving the liquefied gas LG so that no gas phase portion such as an air pocket remains. be able to. Desirably, the top surface of the main body 2a is formed in a hemispherical shape or a conical shape as in the illustrated example, and when the liquefied gas LG is received, all of the residual gas is sent out to the tunnel portion 2b by the rise of the liquid level in the main body 2a. Like that.

図示例の環状熱媒管１０Ｕは、貯蔵タンク２の本体部２ａを間隙ＳＵで取り囲む外側環状線Ｕに沿って所定間隔ＧＵの複数部位に、それぞれ地表面Ｅから鉛直下向きに穿設した小径の立坑、例えば口径１０ｃｍ程度のボーリング孔とすることができる。図２（Ａ）に示すように、熱媒循環装置１５から加熱用熱媒Ｔを循環させて各熱媒管１０Ｕを非凍結温度（０℃以上）に維持し、複数の環状熱媒管１０Ｕが熱的に結合されて４基の貯蔵タンク２を取り囲む非凍結温度の環状壁を形成することにより、外側環状線Ｕを越えて凍結地盤Ｆが拡大することを防止する。図１の符合Ｃは貯蔵タンク２の周囲温度分布曲線を示しており、同曲線Ｃから分かるように、液化ガスＬＧを貯蔵するタンク２の内部は低温（例えばＬＮＧでは−１６２℃）であるが、タンク２の側壁（メンブレンおよび断熱材層）で温度が急激に上昇し、タンク２の外側は非凍結温度の外側環状線Ｕに向けて徐々に上昇する温度勾配を示す。   The annular heat medium pipe 10U of the illustrated example has small diameters drilled vertically downward from the ground surface E at a plurality of portions with a predetermined interval GU along the outer annular line U surrounding the main body 2a of the storage tank 2 with a gap SU. A shaft, for example, a boring hole having a diameter of about 10 cm can be used. As shown in FIG. 2A, the heating medium T is circulated from the heating medium circulating device 15 to maintain each heating medium tube 10U at a non-freezing temperature (0 ° C. or higher), and a plurality of annular heating medium tubes 10U. Are thermally coupled to form an annular wall having a non-freezing temperature surrounding the four storage tanks 2, thereby preventing the frozen ground F from expanding beyond the outer annular line U. 1 indicates an ambient temperature distribution curve of the storage tank 2. As can be seen from the curve C, the inside of the tank 2 for storing the liquefied gas LG is at a low temperature (for example, −162 ° C. for LNG). The temperature rises rapidly at the side wall (membrane and heat insulating material layer) of the tank 2, and the outside of the tank 2 shows a temperature gradient that gradually rises toward the outer annular line U at the non-freezing temperature.

図２（Ａ）において、環状熱媒管１０Ｕの相互間隔ＧＵは、例えば熱媒Ｔの循環時に熱媒管１０Ｕが相互に熱的に結合されて、４基の貯蔵タンク２を取り囲む非凍結温度の環状壁が形成されるように、また地盤強度・初期地圧力等を勘案して地盤の安定性が損なわれないように、掘削解析、熱伝導解析、熱応力解析等の解析手法を用いて設計することができる。貯蔵タンク２と熱媒管１０Ｕとの間の温度分布曲線Ｃの勾配（図１参照）は両者の間隙ＳＵに応じて変化するが、間隙ＳＵに応じて適切な相互間隔ＧＵを選択することにより環状線Ｕに沿った凍結地盤Ｆの厚さを均等に制御することができる。また、熱媒管１０Ｕ毎に循環させる熱媒Ｔの流量、温度等を調節することも可能である。   In FIG. 2A, the mutual interval GU of the annular heat medium pipes 10U is a non-freezing temperature surrounding the four storage tanks 2 when the heat medium pipes 10U are thermally coupled to each other, for example, when the heat medium T is circulated. Using an analysis method such as excavation analysis, heat conduction analysis, thermal stress analysis, etc., so that the annular wall is formed, and the stability of the ground is not impaired in consideration of ground strength, initial ground pressure, etc. Can be designed. The gradient of the temperature distribution curve C between the storage tank 2 and the heat transfer pipe 10U (see FIG. 1) changes according to the gap SU between the two, but by selecting an appropriate mutual interval GU according to the gap SU. The thickness of the frozen ground F along the annular line U can be controlled uniformly. It is also possible to adjust the flow rate, temperature, etc. of the heat medium T to be circulated for each heat medium pipe 10U.

他方、図示例の境界熱媒管１０Ｒは、隣接する貯蔵タンク２から間隙ＳＲだけ隔てた中間境界線Ｒに沿って所定間隔ＧＲの複数部位に、それぞれ地表面Ｅから鉛直下向きに穿設した立坑であり、上述した環状熱媒管１０Ｕと同様のボーリング孔とすることができる。例えば図２（Ａ）に示すように、境界熱媒管１０Ｒを外側環状線Ｕと同じ間隔ＧＲ（＝間隔ＧＵ）で穿設し、熱媒循環装置１５から各熱媒管１０Ｒに加熱用熱媒Ｔを循環させて非凍結温度（例えば０℃）に維持すると共に、隣接する熱媒管１０Ｒを熱的に結合して境界線Ｒに沿って延びる非凍結温度の環状壁を形成することにより、４基の貯蔵タンク２の境界部における凍結地盤Ｆの厚さを外側環状線Ｕと同程度に制御することができる。図示例のように貯蔵タンク２の境界線Ｒに沿って熱媒管１０Ｒを列状に配置し、その熱媒管１０Ｒによって両側の凍結地盤Ｆを同時に制御することにより、貯蔵槽２ごとに熱媒管を配置する従来の方法（図４（Ｂ）参照）に比して熱媒管１０Ｒの設置数を節約し、凍結地盤Ｆの維持管理コストを抑制することができる。   On the other hand, the boundary heat transfer medium pipe 10R in the illustrated example is a vertical shaft drilled vertically downward from the ground surface E at a plurality of portions with a predetermined interval GR along an intermediate boundary line R separated from the adjacent storage tank 2 by a gap SR. It can be set as the boring hole similar to the annular heat medium pipe | tube 10U mentioned above. For example, as shown in FIG. 2 (A), the boundary heat medium pipe 10R is drilled at the same interval GR (= interval GU) as the outer annular line U, and heat for heating is supplied from the heat medium circulation device 15 to each heat medium pipe 10R. By circulating the medium T and maintaining it at a non-freezing temperature (for example, 0 ° C.), the adjacent heat medium pipes 10R are thermally coupled to form a non-freezing temperature annular wall extending along the boundary line R. The thickness of the frozen ground F at the boundary between the four storage tanks 2 can be controlled to the same extent as the outer annular line U. As shown in the illustrated example, the heat medium pipes 10R are arranged in a row along the boundary line R of the storage tank 2, and the frozen ground F on both sides is simultaneously controlled by the heat medium pipes 10R. Compared with the conventional method (refer FIG. 4 (B)) which arrange | positions a medium pipe, the installation number of the heat medium pipe | tube 10R can be saved, and the maintenance management cost of the frozen ground F can be suppressed.

また、図示例のように複数の貯蔵タンク２で囲まれた内側境界線Ｒにおける凍結地盤Ｆの厚さは、必ずしも複数の貯蔵タンク２を取り囲む外側環状線Ｕの凍結地盤Ｆと同じ厚さとしない場合もある。外側環状線Ｕは凍結地盤Ｆの厚さに上限値がなく、厚さの増加に応じてタンク２に作用する凍結土圧が大きくなるのに対し、内側境界線Ｒは隣接する凍結地盤Ｆが干渉するので厚さに限界があり、例えば貯蔵タンク２と境界熱媒管１０Ｒとの間隙ＳＲが狭いときはその全体が凍結地盤Ｆで覆われる場合も想定される。このような場合は、地盤強度・初期地圧力等を勘案して地盤の安定性が損なわれない範囲内において境界熱媒管１０Ｒを外側環状線Ｕより大きい間隔ＧＲ（＞間隔ＧＵ）とし、その熱媒管１０Ｒへの加熱用熱媒Ｔの循環によって凍結地盤Ｆの凍結がむやみに進行して二次凍上等が発生しないように制御することができる。境界熱媒管１０Ｒの間隔ＧＲを大きくすることにより、熱媒管１０Ｒの設置数を節約すると共に、凍結地盤Ｆの維持管理コストを一層抑制することができる。   Moreover, the thickness of the frozen ground F in the inner boundary line R surrounded by the plurality of storage tanks 2 is not necessarily the same as the frozen ground F of the outer annular line U surrounding the plurality of storage tanks 2 as in the illustrated example. In some cases. The outer annular line U has no upper limit on the thickness of the frozen ground F, and the frozen earth pressure acting on the tank 2 increases as the thickness increases. For example, when the gap SR between the storage tank 2 and the boundary heat medium pipe 10R is narrow, the entire case may be covered with the frozen ground F. In such a case, considering the ground strength, initial ground pressure, etc., the boundary heat medium pipe 10R is set to a gap GR (> gap GU) larger than the outer annular line U within a range where the stability of the ground is not impaired. It is possible to control so that the freezing of the frozen ground F proceeds unnecessarily due to the circulation of the heating medium T to the heat medium pipe 10R and secondary freezing is not generated. By increasing the interval GR between the boundary heat medium pipes 10R, the number of installed heat medium pipes 10R can be saved, and the maintenance cost of the frozen ground F can be further suppressed.

必要に応じて、図２（Ｂ）に示すように、複数の貯蔵タンク２で囲まれた内側域Ｎの周縁に沿って所定間隔ＧＮの複数位置に、それぞれ地表面Ｅから鉛直下向きに内側熱媒管１０Ｎを鉛直に穿設し、熱媒循環装置１５から各内側熱媒管１０Ｎに熱媒Ｔの循環により内側域Ｎへの凍結を防止することができる。貯蔵施設１の地表Ｅには様々な施設構造物を構築する必要があり、また保護すべき自然生態系等が存在している場合がある。例えば図示例において、貯蔵タンク２で囲まれた内側域Ｎに施設構造物を設ける場合に、循環装置１５からの熱媒Ｔの循環によって内側Ｕの凍結を防止することにより、施設構造物に対する貯留液化ガスＬＧの影響を避けることができる。また、図示例の内側域Ｎと同様に、保護すべき自然生態系の周囲を囲むように内側熱媒管１０Ｎを穿設して凍結領域の拡大を防止することにより、そのような自然生態系の地下を低温液化ガスＬＧの貯蔵施設１として利用することが可能となる。   If necessary, as shown in FIG. 2 (B), the inner heat is applied vertically downward from the ground surface E to a plurality of positions at predetermined intervals GN along the periphery of the inner area N surrounded by the plurality of storage tanks 2. The medium pipe 10N is vertically drilled, and freezing into the inner region N can be prevented by circulating the heat medium T from the heat medium circulation device 15 to each inner heat medium pipe 10N. It is necessary to construct various facility structures on the surface E of the storage facility 1, and there may be natural ecosystems to be protected. For example, in the illustrated example, when the facility structure is provided in the inner area N surrounded by the storage tank 2, storage of the facility structure is prevented by preventing freezing of the inner side U by circulation of the heat medium T from the circulation device 15. The influence of the liquefied gas LG can be avoided. Further, like the inner area N in the illustrated example, the inner heat transfer pipe 10N is drilled so as to surround the natural ecosystem to be protected, thereby preventing the expansion of the frozen area. Can be used as the storage facility 1 for the low-temperature liquefied gas LG.

さらに、複数の貯蔵タンク２で囲まれた内側境界線Ｒは、外側環状線Ｕに比して周囲からの自然入熱が抑制されるので、境界熱媒管１０Ｒに対する熱媒Ｔの循環を環状熱媒管１０Ｕとは独立に制御して効率的に運用することにより、凍結地盤Ｆの維持管理コストを一層低減することが期待できる。図示例の熱媒循環装置１５は、環状熱媒管１０Ｕに対する熱媒Ｔの循環と境界熱媒管１０Ｒに対する熱媒Ｔの循環とを別々に制御する循環制御手段１６Ｕ、１６Ｒを有している。環状線Ｕには片側の本体部２から冷熱が流入するのに対し、境界線Ｒには両側の本体部２から冷熱が流入するので、各熱媒管１０Ｕ、１０Ｒに対する熱媒Ｔの循環を分けることにより、各貯蔵タンク２の周囲の凍結地盤Ｆを合理的・効率的に制御することができる。例えば、境界熱媒管１０Ｒに循環させる熱媒Ｔの流量又は温度を、環状熱媒管１０Ｕに循環させる熱媒Ｔに比して上昇させる。このように熱媒管１０Ｕ、１０Ｒ毎に熱媒Ｔの循環を独立に制御することにより、凍結地盤Ｆの維持管理コストを一層抑制することが期待できる   Furthermore, since the inner boundary line R surrounded by the plurality of storage tanks 2 suppresses natural heat input from the surroundings compared to the outer annular line U, the circulation of the heat medium T to the boundary heat medium pipe 10R is circular. It can be expected that the maintenance cost of the frozen ground F can be further reduced by controlling the heat medium pipe 10U independently and operating efficiently. The illustrated heat medium circulation device 15 includes circulation control means 16U and 16R that separately control the circulation of the heat medium T to the annular heat medium pipe 10U and the circulation of the heat medium T to the boundary heat medium pipe 10R. . While cold heat flows from the main body 2 on one side into the annular line U, cold heat flows from the main body 2 on both sides into the boundary line R. Therefore, circulation of the heat medium T to the heat medium tubes 10U and 10R is performed. By dividing, the frozen ground F around each storage tank 2 can be controlled rationally and efficiently. For example, the flow rate or temperature of the heat medium T circulated through the boundary heat medium pipe 10R is increased as compared with the heat medium T circulated through the annular heat medium pipe 10U. In this way, by independently controlling the circulation of the heat medium T for each of the heat medium pipes 10U and 10R, it can be expected that the maintenance cost of the frozen ground F is further suppressed.

こうして本発明の目的である「地下貯蔵タンク周囲の凍結地盤を長期にわたり経済的に維持管理することができる地下凍結制御型貯蔵施設」の提供が達成できる。   Thus, the provision of the “underground freezing control type storage facility capable of economically maintaining and managing the frozen ground around the underground storage tank” for a long time, which is the object of the present invention, can be achieved.

なお、図１及び図２では地下貯蔵タンク２の側部に配置した環状熱媒管１０Ｕ、境界熱媒管１０Ｒのみを記載しているが、必要に応じて図４（Ｂ）の場合と同様に貯蔵タンク２の底部にも熱媒管を敷設して凍結地盤Ｆの厚さを制御することができる。例えば内部掘削での過掘り、自在ボーリング（曲がりボーリング）等によって貯蔵タンク２の底部に熱媒管を設置する。また、図示例では複数の貯蔵タンク２を地表面Ｅ上の四角形の各頂点位置Ｑ１、Ｑ２、Ｑ３、Ｑ４に配置しているが、貯蔵タンク２の配置は図示例に限定されるものではなく、例えば三角形又は五角形以上の多角形の各頂点位置にそれぞれ貯蔵タンク２を配置して本発明の貯蔵施設１を構成することができる。また、複数の貯蔵タンク２が一列に並べられている場合であっても、その貯蔵タンク２の境界線Ｒに沿って列状に境界熱媒管１０Ｒを設けて両側の凍結地盤Ｆを同時に制御することにより、凍結地盤Ｆの維持管理コストを抑制する本発明の値貯蔵施設１とすることも可能である。   1 and 2, only the annular heat transfer medium pipe 10U and the boundary heat transfer medium pipe 10R arranged at the side of the underground storage tank 2 are shown, but if necessary, the same as in the case of FIG. 4B. In addition, the thickness of the frozen ground F can be controlled by laying a heat transfer pipe at the bottom of the storage tank 2. For example, the heat transfer medium pipe is installed at the bottom of the storage tank 2 by overdrilling in internal excavation, free boring (curved boring) or the like. Further, in the illustrated example, a plurality of storage tanks 2 are arranged at the respective quadrature vertex positions Q1, Q2, Q3, and Q4 on the ground surface E, but the arrangement of the storage tanks 2 is not limited to the illustrated example. For example, the storage tank 1 of the present invention can be configured by arranging the storage tank 2 at each vertex position of a triangle or a polygon of pentagon or more. Further, even when a plurality of storage tanks 2 are arranged in a line, the boundary heat medium pipes 10R are provided in a row along the boundary line R of the storage tanks 2 to simultaneously control the frozen ground F on both sides. By doing, it is also possible to set it as the value storage facility 1 of this invention which suppresses the maintenance management cost of the frozen ground F.

また、図示例のように縮径された口径の導坑部２ｂを有する貯蔵タンク２を用い、その導坑部２ｂ内に液面位を保ちつつ低温液化ガスＬＧを貯蔵することによりＢＯＧ発生量を小さく抑えることができるが、ＢＯＧの発生を完全に抑えることは困難であり、液化ガスＬＧを長期間保存する間に徐々にＢＯＧが発生して本体部２及び導坑部２ｂ内に蓄積しうる。図示例において、貯蔵タンク２の内圧はＢＯＧライン６の圧力計７ａによって検出され、その検出信号に応じた圧力制御装置７の制御信号で圧力調節弁８の開度を調節することによりＢＯＧライン６から導坑部２ｂ内に蓄積したＢＯＧが適宜排出され、貯蔵タンク２が適正な内圧（例えば１０ｋＰａ程度の正圧）に保持される。必要に応じてＢＯＧライン６にＢＯＧ圧縮機９を設け、排出したＢＯＧを圧縮液化して貯蔵タンク２へ戻すことも可能である。また、貯蔵タンク２内の液化ガスＬＧは、必要に応じて本体部２の底部のポンプＰにより払出ライン５及び気化器５ａを介して払い出すことができる。   Moreover, the amount of BOG generation | occurrence | production is produced by storing the low temperature liquefied gas LG, using the storage tank 2 which has the diameter reduced diameter guide shaft part 2b like the example of illustration, and maintaining a liquid level in the guide hole part 2b. However, it is difficult to completely suppress the generation of BOG, and during the storage of the liquefied gas LG for a long period of time, BOG is gradually generated and accumulated in the main body portion 2 and the guide shaft portion 2b. sell. In the illustrated example, the internal pressure of the storage tank 2 is detected by a pressure gauge 7a of the BOG line 6, and the opening degree of the pressure control valve 8 is adjusted by a control signal of the pressure control device 7 according to the detection signal, thereby causing the BOG line 6 to The BOG accumulated in the guide shaft portion 2b is appropriately discharged, and the storage tank 2 is maintained at an appropriate internal pressure (for example, a positive pressure of about 10 kPa). It is also possible to provide a BOG compressor 9 in the BOG line 6 as necessary, and convert the discharged BOG into a compressed liquid and return it to the storage tank 2. The liquefied gas LG in the storage tank 2 can be discharged through the discharge line 5 and the vaporizer 5a by the pump P at the bottom of the main body 2 as necessary.

図３は、熱媒循環装置１５に加熱用熱媒Ｔと冷却用熱媒Ｔ´とを切り替える熱媒切替手段１９を含めた本発明の地下凍結制御型貯蔵施設の他の実施例を示す。図１及び図２を参照して説明したように、本発明の貯蔵施設１では、貯蔵タンク２の周囲及び境界に沿って列状に設けた環状熱媒管１０Ｕ及び境界熱外管１０Ｒにそれぞれ熱媒循環装置１５から加熱用熱媒Ｔを循環させることにより凍結地盤Ｆの厚さを経済的に制御できるが、循環装置１５から冷却用熱媒Ｔ´を循環させることにより、各熱媒管１０Ｕ、１０Ｒを凍結地盤Ｆの厚さの制御以外の用途に利用することができる。図示例の循環装置１５は、切替弁等の熱媒切替手段１９を介して温熱源１８及び冷熱源１７と接続されており、切替手段１９によって加熱用熱媒Ｔと冷却用熱媒Ｔ´とを切り替えて各熱媒管１０Ｕ、１０Ｒへ供給することができる。   FIG. 3 shows another embodiment of the underground freezing control type storage facility of the present invention including the heat medium circulating device 15 and the heat medium switching means 19 for switching the heating heat medium T and the cooling heat medium T ′. As described with reference to FIGS. 1 and 2, in the storage facility 1 of the present invention, the annular heat medium pipe 10U and the boundary heat outer pipe 10R provided in a row along the periphery and boundary of the storage tank 2 are respectively provided. Although the thickness of the frozen ground F can be economically controlled by circulating the heating medium T from the heating medium circulating device 15, each heating medium tube can be obtained by circulating the cooling heating medium T ′ from the circulating device 15. 10U and 10R can be used for purposes other than controlling the thickness of the frozen ground F. The circulation device 15 in the illustrated example is connected to a heat source 18 and a cold source 17 via a heating medium switching means 19 such as a switching valve, and the switching means 19 causes a heating heat medium T and a cooling heat medium T ′ to be connected. Can be switched and supplied to the heat medium pipes 10U and 10R.

図３（Ａ）〜（Ｃ）は、本発明の貯蔵施設１において貯蔵タンク２の掘削に先行して環状熱媒管１０Ｕ及び境界熱外管１０Ｒを穿設し（同図（Ａ））、各熱媒管１０Ｕ、１０Ｒに冷却用熱媒Ｔ´を循環させて凍結地盤領域Ｆを形成し（同図（Ｂ））、その凍結地盤領域Ｆを鉛直に掘削して各貯蔵タンク２を構築する実施例を示す（同図（Ｃ））。すなわち、例えば図２（Ａ）において外側環状線Ｕに沿った熱媒管１０Ｕ、及び境界線Ｒに沿った熱外管１０Ｒを貯蔵タンク２の構築に先立って穿孔し、循環装置１５から各熱媒管１０Ｕ、１０Ｒに冷却用熱媒Ｔ´を導入して外側環状線Ｕの内側に凍結地盤領域Ｆを形成することにより地盤を固化・安定化させ、その凍結地盤領域Ｆに地表Ｅから鉛直下方に先ず所定深さＤまで口径Ｗ３の導坑部２ｂを掘削し、更に口径Ｗ２に拡径して鉛直下方に本体部２ａを掘削する凍結工法によって貯蔵タンク２を構築する。ただし、凍結工法は本発明に必須のものではなく、安定した硬質地盤等はそのまま鉛直に掘削して貯蔵タンク２及び熱媒管１０Ｕ、１０Ｒを構築することができる。   3 (A) to 3 (C), an annular heat medium pipe 10U and a boundary heat outer pipe 10R are drilled prior to excavation of the storage tank 2 in the storage facility 1 of the present invention (FIG. 3 (A)). The frozen ground region F is formed by circulating the cooling heat medium T ′ through each of the heat medium pipes 10U and 10R (FIG. 5B), and each frozen storage region F is vertically excavated to construct each storage tank 2. (Example (C)). That is, for example, in FIG. 2A, the heat medium pipe 10U along the outer annular line U and the heat outer pipe 10R along the boundary line R are perforated prior to the construction of the storage tank 2, and each heat is supplied from the circulation device 15. The cooling medium T ′ is introduced into the medium pipes 10U and 10R, and the ground is solidified and stabilized by forming the frozen ground region F inside the outer annular line U. The ground is perpendicular to the frozen ground region F from the surface E. The storage tank 2 is constructed by a freezing method in which the guide shaft portion 2b having a diameter W3 is first excavated downward to a predetermined depth D, further expanded to the diameter W2 and the main body portion 2a is excavated vertically downward. However, the freezing method is not essential for the present invention, and the storage tank 2 and the heating medium pipes 10U and 10R can be constructed by directly excavating a stable hard ground or the like as it is.

図３（Ｃ）において複数の貯蔵タンク２を構築したのち、受入ライン４、払出ライン５、ＢＯＧライン６等を敷設したうえで低温液化ガスＬＧを受入れるが、冷却用熱媒Ｔ´の循環により形成される凍結地盤領域Ｆは、低温液化ガスＬＧの受入れ時におけるＢＯＧ発生量を小さく抑えるクールダウンのためにも有効である。すなわち、図３（Ｂ）の場合と同様に、貯蔵タンク２の完成後に冷温液化ガスＬＧを受入れる前に各熱媒管１０Ｕ、１０Ｒに冷却用熱媒Ｔ´を循環させて貯蔵タンク２の周囲を凍結し、クールダウンのための凍結地盤領域Ｆを形成する。また、常温の貯蔵タンク２の内部に極低温の液化ガスＬＧ（例えば−１６２℃のＬＮＧ等）を直接投入すると熱環境が激しく変化し、全体が安定状態に至るまでの間に大きな熱応力が構造各所に発生する可能性があることから、各熱媒管１０Ｕ、１０Ｒへの冷却用熱媒Ｔ´の循環による貯蔵タンク２の周囲の予冷は、この劇的な温度環境変化を緩和する効果も期待できる。各貯蔵タンク２に冷温液化ガスＬＧを受入れた後、循環装置１５の切替手段１９を切替えて各熱媒管１０Ｕ、１０Ｒに加熱用熱媒Ｔを循環させ、図１及び図２を参照して上述したように各貯蔵タンク２の周囲の凍結地盤Ｆの厚さを制御しながら冷温液化ガスＬＧを長期間貯蔵する。   After constructing a plurality of storage tanks 2 in FIG. 3 (C), the low-temperature liquefied gas LG is received after laying the receiving line 4, the dispensing line 5, the BOG line 6 and the like. The formed frozen ground region F is also effective for cool-down that reduces the amount of BOG generated when receiving the low-temperature liquefied gas LG. That is, as in the case of FIG. 3B, the cooling medium T ′ is circulated through the heating medium pipes 10U and 10R before the cold and liquefied gas LG is received after the storage tank 2 is completed. Is frozen to form a frozen ground region F for cool-down. In addition, when a cryogenic liquefied gas LG (for example, LNG at −162 ° C.) is directly put into the room temperature storage tank 2, the thermal environment changes drastically, and a large thermal stress is generated until the whole reaches a stable state. Since there is a possibility of occurrence in various places of the structure, the precooling around the storage tank 2 by circulating the cooling medium T ′ to the heating medium pipes 10U, 10R has the effect of alleviating this dramatic change in temperature environment. Can also be expected. After the cold / hot liquefied gas LG is received in each storage tank 2, the switching means 19 of the circulation device 15 is switched to circulate the heating medium T in the heating medium tubes 10U, 10R, referring to FIG. 1 and FIG. As described above, the cold / hot liquefied gas LG is stored for a long period of time while controlling the thickness of the frozen ground F around each storage tank 2.

１…地下貯蔵施設 ２…貯蔵槽
２ａ…（貯蔵槽の）本体部 ２ｂ…（貯蔵槽の）導坑部
４…受入ライン ５…払出ライン
５ａ…気化器 ６…ＢＯＧライン
７…圧力制御装置 ７ａ…圧力計
８…圧力調節弁 ９…ＢＯＧ圧縮機
１０Ｕ…環状熱媒管 １０Ｒ…境界熱媒管
１０Ｎ…内側熱媒管
１５…循環装置 １６…循環制御手段
１７…冷熱源 １８…温熱源
１９…切替手段
２０…地下貯蔵タンク ２１…地下連壁
２２…底壁 ２３…側壁
２４…屋根 ２５…切欠き部
２６…メンブレン ２７…側部ヒータ
２８…底部ヒータ
Ｄ…貯蔵槽の本体部の頂端深さ Ｅ…地表
Ｆ…凍結地盤 Ｇ…熱媒管の相互間隙（ギャップ）
Ｌ…深さ（鉛直方向長さ） ＬＧ…低温液化ガス
Ｎ…内側域 Ｐ…ポンプ
Ｑ…貯蔵槽の掘削地点 Ｒ…境界線
Ｓ…貯留槽と熱媒管との間隔 Ｔ…熱媒（温熱）
Ｔ´…熱媒（冷熱） Ｕ…環状線
Ｗ２…貯蔵槽の本体部の口径 Ｗ３…貯蔵槽の導坑部の口径 DESCRIPTION OF SYMBOLS 1 ... Underground storage facility 2 ... Storage tank 2a ... Main part 2b (of storage tank) Leading part 4 (of storage tank) 4 Reception line 5 ... Discharge line 5a ... Vaporizer 6 ... BOG line 7 ... Pressure control apparatus 7a DESCRIPTION OF SYMBOLS ... Pressure gauge 8 ... Pressure control valve 9 ... BOG compressor 10U ... Annular heat medium pipe 10R ... Boundary heat medium pipe 10N ... Inner heat medium pipe 15 ... Circulation device 16 ... Circulation control means 17 ... Cooling heat source 18 ... Heat source 19 ... Switching means 20 ... underground storage tank 21 ... underground connecting wall 22 ... bottom wall 23 ... side wall 24 ... roof 25 ... notch 26 ... membrane 27 ... side heater 28 ... bottom heater D ... depth of top end of main body of storage tank E ... Ground surface F ... Frozen ground G ... Mutual gap (gap) between heat transfer tubes
L: Depth (length in the vertical direction) LG ... Low temperature liquefied gas N ... Inner zone P ... Pump Q ... Excavation point of storage tank R ... Boundary line S ... Distance between storage tank and heat transfer pipe T ... Heat transfer medium (heat) )
T '... heat medium (cold heat) U ... annular line W2 ... diameter of main part of storage tank W3 ... diameter of main shaft part of storage tank

Claims (5)

地表の相互に隔てた複数地点の地下にそれぞれ構築した鉛直下方に延びる冷温液化ガスの貯蔵タンク，前記複数地点を囲む環状線に沿った複数位置の地下にそれぞれ構築した鉛直下方に延びる熱媒管，前記複数地点のうち隣接する地点の間の境界線に沿った複数位置の地下にそれぞれ構築した鉛直下方に延びる熱媒管，及び前記各熱媒管に熱媒を循環させると共に前記各熱媒管に対する熱媒の循環を独立に制御する熱媒循環装置を備え，前記熱媒の循環により各貯蔵タンク周囲の凍結を制御してなる低温液化ガスの地下凍結制御型貯蔵施設。 A storage tank of cold / warm liquefied gas extending vertically below each of a plurality of underground locations separated from each other on the ground surface, and a heat transfer tube extending vertically below each of a plurality of locations underground along an annular line surrounding the plurality of locations. , Heat medium pipes extending vertically below each of a plurality of locations along a boundary line between adjacent points among the plurality of points, and circulating each heat medium in the heat medium pipes and each heat medium A low-temperature liquefied gas underground freezing control type storage facility comprising a heat medium circulation device for independently controlling the circulation of the heat medium to the pipe and controlling the freezing around each storage tank by the circulation of the heat medium. 請求項１の貯蔵施設において，前記複数地点を，地表面上の多角形の各頂点位置としてなる低温液化ガスの地下凍結制御型貯蔵施設。 2. The storage facility according to claim 1, wherein the plurality of points are used as the vertex positions of polygons on the ground surface. 請求項２の貯蔵施設において，前記複数地点に囲まれた内側域の周縁に沿った複数位置の地下にそれぞれ構築した鉛直下方に延びる内側熱媒管を設け，前記熱媒循環装置から各内側熱媒管への熱媒の循環により内側域の凍結を防止してなる低温液化ガスの地下凍結制御型貯蔵施設。 3. The storage facility according to claim 2, wherein inner heat medium pipes extending vertically downward are respectively provided in a plurality of positions along the periphery of the inner area surrounded by the plurality of points, and each inner heat pipe is provided from the heat medium circulation device. An underground freezing controlled storage facility for low-temperature liquefied gas that prevents the inner zone from freezing by circulating the heat medium to the medium pipe. 請求項１から３の何れかの貯蔵施設において，前記熱媒循環装置に加熱用熱媒と冷却用熱媒とを切り替える熱媒切替手段を含め，前記各貯蔵タンクへの冷温液化ガスの受入れ前に各熱媒管に冷却用熱媒を循環させて貯蔵タンク周囲を凍結し且つ受入れ後に各熱媒管に加熱用熱媒を循環させて貯蔵タンク周囲の凍結を制御してなる低温液化ガスの地下凍結制御型貯蔵施設。 The storage facility according to any one of claims 1 to 3, wherein the heating medium circulating device includes a heating medium switching means for switching between a heating heating medium and a cooling heating medium, and before receiving the cold and liquefied liquefied gas in each of the storage tanks. A cooling heat medium is circulated in each heat medium pipe to freeze around the storage tank, and after receiving, a heating heat medium is circulated in each heat medium pipe to control freezing around the storage tank. Underground freezing controlled storage facility. 請求項１から４の何れかの貯蔵施設において，前記各貯蔵タンクに地下所定深さから鉛直下方に延びる所定口径の本体部とその本体部の頂端を縮径された口径で地表と連結する導坑部とを含め，前記各貯蔵タンクに本体部の容積以上の低温液化ガスを受入れて液面位を導坑部内に保ちつつ貯蔵してなる低温液化ガスの地下凍結制御型貯蔵施設。 5. The storage facility according to claim 1, wherein a main body portion having a predetermined diameter extending vertically downward from a predetermined depth underground and a top end of the main body portion are connected to the ground surface with a reduced diameter in each storage tank. A cryogenic liquefied gas underground freezing control type storage facility that receives low-temperature liquefied gas more than the volume of the main body in each storage tank, including a pit, and stores the liquefied gas while maintaining the liquid level in the guide pit.

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