JPH0125960B2 - - Google Patents
Info
- Publication number
- JPH0125960B2 JPH0125960B2 JP55164031A JP16403180A JPH0125960B2 JP H0125960 B2 JPH0125960 B2 JP H0125960B2 JP 55164031 A JP55164031 A JP 55164031A JP 16403180 A JP16403180 A JP 16403180A JP H0125960 B2 JPH0125960 B2 JP H0125960B2
- Authority
- JP
- Japan
- Prior art keywords
- lpg
- supply pipe
- underground
- temperature
- underground cavity
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000003915 liquefied petroleum gas Substances 0.000 description 59
- 239000011435 rock Substances 0.000 description 13
- 239000007788 liquid Substances 0.000 description 9
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- 238000000034 method Methods 0.000 description 4
- 239000001294 propane Substances 0.000 description 4
- 238000010276 construction Methods 0.000 description 2
- 230000000717 retained effect Effects 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 239000006200 vaporizer Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000007710 freezing Methods 0.000 description 1
- 230000008014 freezing Effects 0.000 description 1
- 239000003673 groundwater Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 239000013535 sea water Substances 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
Landscapes
- Filling Or Discharging Of Gas Storage Vessels (AREA)
Description
【発明の詳細な説明】
〔発明上の利用分野〕
本発明は、地下岩盤空洞を利用したLPGの地
下貯蔵用設備のLPG供給管の構造に関する。DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to the structure of an LPG supply pipe for an LPG underground storage facility that utilizes an underground rock cavity.
従来より、石油備蓄用として地下岩盤空洞を利
用した大型の地下備蓄設備の構築が提案され、実
現化しつつある。しかしLPG（液化石油ガス）の
ように揮発性の高い物質を対象として、これを地
下岩盤空洞に貯蔵することは、常温常圧で液相を
維持する石油の貯蔵とは異なつた各種の問題が伴
うことから、世界でも施工例がないし、提案も少
ない。しかし、石油備蓄の場合と同様にLPGの
地下貯蔵ができれば、大量貯蔵性、立地性、経済
性等において、地上施設ではなし得ない有利な面
がある。
BACKGROUND ART The construction of large-scale underground oil storage facilities using underground rock cavities has been proposed and is becoming a reality. However, storing highly volatile substances such as LPG (liquefied petroleum gas) in underground rock cavities poses various problems that are different from storing petroleum, which maintains a liquid phase at room temperature and pressure. As a result, there are no examples of its construction anywhere in the world, and there are few proposals. However, similar to the case of oil stockpiling, if LPG could be stored underground, there would be advantages in terms of mass storage, location, economy, etc. that cannot be achieved with above-ground facilities.
これまで、LPGの地下貯蔵を意図してなされ
た発明提案には、例えば特開昭52−132402号公
報、特開昭52−132856号公報および特開昭53−
89017号公報に記載のものがある。前２者の公報
では、気密が維持された地下空洞内のポンプ類や
計装機器類を故障や点検のために交換するさい
に、不活性ガス雰囲気を維持したケーシングパイ
プ内に機器類を収めて安全に交換する方法を開示
している。また後者の特開昭53−89017号公報は、
火災などの非常時においてパイプ類内に水プラグ
を内圧を利用して形成させてパイプ類を遮断する
方法を開示している。 Until now, invention proposals made with the intention of underground storage of LPG include, for example, JP-A-52-132402, JP-A-52-132856, and JP-A-53-
There is one described in Publication No. 89017. The first two publications state that when replacing pumps and instrumentation equipment in an airtight underground cavity due to failure or inspection, the equipment must be placed inside a casing pipe that maintains an inert gas atmosphere. It discloses how to safely replace the The latter Japanese Patent Application Laid-Open No. 53-89017 is
This disclosure discloses a method of blocking pipes by forming a water plug within the pipes using internal pressure in the event of an emergency such as a fire.
地下の岩盤空洞内にLPGを常温で水封貯蔵す
る場合は、空洞内圧力の変動を許容範囲に抑えな
ければならない。所定の水封圧力以上よりかなり
高い圧力となると岩盤構造物から漏油および漏気
が発生するし、所定の水封圧力以下よりかなり低
圧となると流入地下水量が増加すると共に、排水
設備の負担が大きくなるからである。特にこの圧
力の変動は、搬送容器内の低温（零下数10℃）に
維持されたLPGを常温の地下空洞に受け入れる
さいに大きく現れることになる。前記の公報類に
はこの種のLPG特有の問題の解決については何
らの教示もない。空洞内圧力の変動を防ぐ処法と
しては、LPGのベーパーの排出と供給を制御す
るといつた直接的な処法も考えられるが、この場
合はそのための設備を別途に設ける必要があり、
そのコストアツプの問題と、排出ベーパーの燃焼
処理によるベーパーの浪費という省資源上の問題
がある。また、低温のLPGを直接的に常温の岩
盤地下空洞に供給すると、水の凍結によるトラブ
ルの発生も予想される。
When storing LPG in an underground rock cavity under a water seal at room temperature, fluctuations in the pressure inside the cavity must be kept within an acceptable range. If the pressure is significantly higher than the predetermined water seal pressure, oil and air leakage will occur from the rock structure, and if the pressure is significantly lower than the predetermined water seal pressure, the amount of inflowing groundwater will increase and the burden on drainage equipment will be increased. This is because it gets bigger. In particular, this pressure fluctuation becomes significant when LPG maintained at a low temperature (several 10 degrees Celsius below zero) in a transport container is received into an underground cavity at room temperature. The above-mentioned publications do not teach anything about solving problems specific to this type of LPG. Direct methods such as controlling the discharge and supply of LPG vapor may be considered as a method to prevent fluctuations in the pressure inside the cavity, but in this case, it is necessary to separately install equipment for this purpose.
There is a problem of increased costs and a resource saving problem of wasted vapor due to combustion treatment of the discharged vapor. Furthermore, if low-temperature LPG is directly supplied to room-temperature rock underground cavities, problems may occur due to water freezing.
他方、地上に存在するLPG供給管は太陽熱や
周囲温度によつて地下岩盤の温度以上に昇温する
おそれもある。このような高温の供給管に搬送容
器内の低温のLPGを直接的に接触させることは
急激な膨張による危険を伴うし、この高温が地下
空洞内に伝熱すれば内圧変化の原因ともなる。 On the other hand, there is a risk that the temperature of LPG supply pipes that exist above ground will rise above the temperature of the underground rock due to solar heat and ambient temperature. Directly contacting such a high-temperature supply pipe with the low-temperature LPG in the transport container carries the risk of rapid expansion, and if this high temperature transfers heat into the underground cavity, it may cause a change in internal pressure.
本発明はこのような問題の解決を目的としたも
のである。 The present invention aims to solve such problems.
前記の問題を解決せんとする本発明の要旨とす
るところは、地下の岩盤内に岩盤を壁面として形
成した実質上密閉状態のLPG貯蔵用地下空洞と
この地下空洞にLPGを供給するためのLPG搬送
容器とを継ぐ供給管を、LPG搬送容器側から地
下空洞側に向けて上り勾配となるように配管し、
入荷停止時においてこのLPG供給管の搬送容器
側端部を閉成し地下空洞側端部を地下空洞に連通
させておく構成とすると共に、入荷時に搬送容器
内の低温LPGを常温付近に昇温するための熱交
換器を該供給管に介装したことを特徴とする。
The gist of the present invention, which aims to solve the above-mentioned problems, is to provide an underground cavity for LPG storage in a substantially sealed state formed in an underground bedrock using rock as a wall surface, and an LPG for supplying LPG to the underground cavity. The supply pipe that connects to the transport container is installed so that it slopes upward from the LPG transport container side to the underground cavity side.
When the LPG supply pipe is stopped, the end of the LPG supply pipe on the transport container side is closed, and the end of the pipe on the underground cavity side is communicated with the underground cavity.At the same time, the low-temperature LPG in the transport container is heated to around room temperature when the supply is stopped. It is characterized in that a heat exchanger for this purpose is interposed in the supply pipe.
本発明は、搬送容器からの低温LPGを常温の
地下岩盤空洞に供給するさいの既述のような問題
をLPG供給管の配管構造に工夫することによつ
て簡便に解決したものである。すなわち、地下岩
盤内に形成した地下空洞にLPGを岩盤周囲温度
で貯蔵する場合、タンカー等で搬送されてくる
LPGは例えば−43℃の低温（プロパン主成分の
場合）であるので、この受入LPGと貯蔵LPGと
の間で温度および圧力が異なる状態となりタンカ
ーから地下空洞にLPGを給送する過程でこの状
態変化を危険のないように行わねばならない。ま
た、給送停止時においてこのLPG供給管内に外
気その他の物質の混入も避けねばならないし、密
閉管としておけば太陽熱や外気温によつて管内圧
及び温度が上昇するのでこの圧及び温度調整に特
別の装置を必要とする。本発明はこのような
LPG地下貯蔵に伴うLPG受入の諸問題を特別な
装置を用いることなく解決した点に特徴がある。
The present invention conveniently solves the above-mentioned problems in supplying low-temperature LPG from a transport container to a room-temperature underground rock cavity by devising the piping structure of the LPG supply pipe. In other words, when storing LPG in an underground cavity formed in underground bedrock at room temperature, it is transported by tanker etc.
Since LPG has a low temperature of, for example, -43℃ (in the case of propane as its main component), the temperature and pressure will be different between the received LPG and the stored LPG, and this state will occur during the process of feeding LPG from the tanker to the underground cavity. Changes must be made without risk. In addition, it is necessary to prevent outside air and other substances from entering the LPG supply pipe when the supply is stopped, and if the pipe is sealed, the pressure and temperature inside the pipe will rise due to solar heat and outside temperature, so it is necessary to adjust this pressure and temperature. Requires special equipment. The present invention
A distinctive feature of this project is that it solves the various LPG receiving problems associated with underground LPG storage without using any special equipment.
以下に図面に従つて本発明の内容を具体的に説
明する。 The contents of the present invention will be specifically explained below with reference to the drawings.
第１図に示したように、本発明においては、地
下岩盤内に形成した実質上密閉状態のLPG貯蔵
用地下空洞１とこの地下空洞１にLPGを供給す
るためのLPG搬送容器２とを継ぐLPG供給管３
を、LPG搬送容器２の側から地下空洞１の側に
向けて上り勾配となるように配管し、入荷停止時
においてこのLPG供給管３の搬送容器側端部を
閉成すると共に地下空洞側端部４を地下空洞１に
開口しておくように構成する。なお第１図におい
て、５は供給管３の搬送容器側端部に設けた開閉
弁を示し、６は地下空洞１からの出荷用配管を示
している。 As shown in FIG. 1, in the present invention, a substantially airtight LPG storage underground cavity 1 formed in underground rock and an LPG transport container 2 for supplying LPG to this underground cavity 1 are connected. LPG supply pipe 3
is piped so that it slopes upward from the side of the LPG transport container 2 toward the side of the underground cavity 1, and when the arrival of goods is stopped, the end of the LPG supply pipe 3 on the transport container side is closed, and the end on the underground cavity side is closed. The section 4 is configured to open into the underground cavity 1. In FIG. 1, reference numeral 5 indicates an on-off valve provided at the end of the supply pipe 3 on the side of the transport container, and reference numeral 6 indicates a shipping pipe from the underground cavity 1.
地下空洞１内に貯蔵されるLPGは、周辺岩盤
温度の影響を受けてその温度に近い温度で貯蔵さ
れる。例えば岩盤温度約15℃であれば、その付近
の温度のLPGとして貯蔵され、約８Kg／cm2abs.
（プロパン主成分の場合）内圧を示す。タンカー
２においては例えば−43℃のLPG（プロパン主成
分の場合）が入荷される。このときのタンカー内
圧は例えば１Kg／cm2abs.である。このタンカー２
内の低温LPGを常温地下空洞に給送する場合、
これをLPG供給管３に介装した熱交換器８を通
して常温付近まで昇温する。この熱交換器８は例
えば海水を加熱媒体とする多管式熱交換器であり
この熱交換器８を通過することにより、例えば−
43℃のLPGは約＋５℃まで昇温する。そのさい
−43℃で約１Kg／cm2abs.の圧力（プロパン主成分
の場合）を有する低温LPGはこの昇温によつて
圧が上昇する。この昇圧に抗して地下空洞に
LPGを送り込むためには、LPG供給管内はあら
かじめ出来るだけ低温の液体で充填しておくのが
望ましい。本発明はこのLPG供給管３に勾配を
もたせ、入荷を停止している場合においてはこの
LPG供給管３にLPGの液を滞留させ、このLPG
供給管３内の液面が地下空洞１の側に面するよう
にしたものである。 The LPG stored in the underground cavity 1 is influenced by the temperature of the surrounding rock and is stored at a temperature close to that temperature. For example, if the bedrock temperature is approximately 15℃, it will be stored as LPG at a temperature around that temperature, and will be approximately 8Kg/cm 2 abs.
(In case of propane main component) Indicates internal pressure. Tanker 2 receives, for example, -43°C LPG (in the case of propane as the main component). The tanker internal pressure at this time is, for example, 1 Kg/cm 2 abs. This tanker 2
When feeding low-temperature LPG inside to room-temperature underground cavities,
This is heated to around room temperature through a heat exchanger 8 installed in the LPG supply pipe 3. This heat exchanger 8 is, for example, a shell-and-tube heat exchanger that uses seawater as a heating medium, and by passing through this heat exchanger 8, for example, -
LPG at 43°C heats up to approximately +5°C. At this time, the pressure of low-temperature LPG, which has a pressure of about 1 kg/cm 2 abs. (in the case of propane as a main component) at -43°C, increases due to this temperature increase. Against this pressure increase, the underground cavity
In order to feed LPG, it is desirable to fill the LPG supply pipe with liquid as low as possible in advance. The present invention provides this LPG supply pipe 3 with a slope, so that when the LPG supply pipe 3 is stopped, this
LPG liquid is retained in the LPG supply pipe 3, and this LPG
The liquid level in the supply pipe 3 faces the underground cavity 1 side.
すなわち、入荷停止時には開閉弁５を閉成して
この供給管の上流側を閉じ、この開閉弁５から地
下空洞１の立上り管７に向けて上り勾配をもたせ
た供給管３内に液を滞留させることによつて、こ
の供給管３内の液の表面がこの立上り管７を介し
て地下空洞１の側に面するようにすると共に、こ
の液の表面と地下空洞１とは圧の連動が行えるよ
うに地下空洞１内にこの供給管の端部４を開口し
ておく。 That is, when the arrival of goods is stopped, the on-off valve 5 is closed to close the upstream side of this supply pipe, and the liquid is retained in the supply pipe 3 that has an upward slope from this on-off valve 5 toward the riser pipe 7 of the underground cavity 1. By doing so, the surface of the liquid in the supply pipe 3 faces the underground cavity 1 through the riser pipe 7, and the pressure between the surface of the liquid and the underground cavity 1 is maintained. The end 4 of this supply pipe is opened into the underground cavity 1 so that it can be carried out.
これにより、供給管３に太陽熱または外気温に
よつて入熱があつても、供給管３内の液が蒸発し
てこの入熱を吸収し、このベーパーは地下空洞１
に入つて地下空洞１の平衡温度および圧力として
吸収される。したがつて、この供給管３内の液は
地下空洞１に近い方の側から地下空洞の温度およ
び圧力とほぼ等しい状態に保持されることにな
る。地下空洞１は大面積の岩盤からなり、この岩
盤が保有するエンタルピーは供給管３内のエンタ
ルピー変化を吸収するに十分な無限大の大きさを
有するから、供給管３に特別な圧力または温度調
整装置を設けなくとも、本発明の構造によればこ
の供給管３内の圧力および温度調整が自動的にな
されることになり、非常に有益である。 As a result, even if there is heat input into the supply pipe 3 due to solar heat or outside temperature, the liquid inside the supply pipe 3 evaporates and absorbs this heat input, and this vapor is transferred to the underground cavity 1.
and is absorbed as the equilibrium temperature and pressure of the underground cavity 1. Therefore, the liquid in this supply pipe 3 is maintained at a temperature and pressure substantially equal to the temperature and pressure of the underground cavity from the side closer to the underground cavity 1. The underground cavity 1 is made up of a large area of rock, and the enthalpy held by this rock is infinitely large enough to absorb the enthalpy change in the supply pipe 3. Therefore, a special pressure or temperature adjustment is applied to the supply pipe 3. According to the structure of the present invention, the pressure and temperature inside the supply pipe 3 can be automatically adjusted without providing any equipment, which is very beneficial.
また、開閉弁５から地下空洞１に到るLPG供
給管３が短く、供給管３内のLPGが全て気化す
る様な場合は、冷却用供給管１５を通し出荷
LPGの１部をLPG供給管３にLPG液を充填する
ことも有効である。なお、図において９は脱水装
置、１０は出荷容器、１１は脱気装置、１２は排
水用配管、１３は気化器を示している。 In addition, if the LPG supply pipe 3 from the on-off valve 5 to the underground cavity 1 is short and all the LPG in the supply pipe 3 is vaporized, it may be shipped through the cooling supply pipe 15.
It is also effective to fill part of the LPG into the LPG supply pipe 3 with LPG liquid. In the figure, 9 indicates a dehydrator, 10 a shipping container, 11 a deaerator, 12 a drainage pipe, and 13 a vaporizer.
このようにして本発明によれば、極めて簡単な
構成でありながら、常温の地下空洞に低温LPG
に安定して供給することができ、地上タンクへの
供給管構造で採用されているような特別の配管構
造を不要化した点において、省設備および防災の
面で多大の貢献をなし得るものである。 In this way, according to the present invention, although the configuration is extremely simple, low-temperature LPG is placed in an underground cavity at room temperature.
It can provide a stable supply of water to above-ground tanks, and eliminates the need for special piping structures such as those used for supply pipes to above-ground tanks, making it possible to make a significant contribution in terms of equipment savings and disaster prevention. be.
第１図は本発明に従うLPG地下貯蔵設備の配
管構造図である。
１……地下空洞、２……LPG搬送容器、３…
…LPG供給管、５……開閉弁、６……出荷用配
管、７……立上り管、８……熱交換器、９……脱
水装置、１０……出荷容器、１１……脱気装置、
１２……排水用配管、１３……気化器。
FIG. 1 is a piping structural diagram of an LPG underground storage facility according to the present invention. 1... Underground cavity, 2... LPG transport container, 3...
... LPG supply pipe, 5 ... Opening/closing valve, 6 ... Shipping pipe, 7 ... Rise pipe, 8 ... Heat exchanger, 9 ... Dehydration device, 10 ... Shipping container, 11 ... Deaerator,
12... Drainage piping, 13... Vaporizer.
Claims (1)
質上密閉状態のLPG貯蔵用地下空洞とこの地下
空洞にLPGを供給するためのLPG搬送容器とを
継ぐ供給管を、LPG搬送容器側から地下空洞側
に向けて上り勾配となるように配管し、入荷停止
時においてこのLPG供給管の搬送容器側端部を
閉成し地下空洞側端部を地下空洞に連通させてお
く構成とし、且つ入荷時に搬送容器内の低温
LPGを常温付近に昇温するための熱交換器を該
供給管に介装してなるLPG地下貯蔵用供給管。1. A supply pipe that connects a substantially airtight LPG storage underground cavity formed in the underground bedrock with the bedrock as a wall and an LPG transport container for supplying LPG to this underground cavity is connected from the LPG transport container side to the underground cavity. The pipe is installed so that it has an upward slope toward the side, and when the LPG supply pipe is stopped, the end of the LPG supply pipe on the transport container side is closed, and the end of the LPG supply pipe on the underground cavity side is connected to the underground cavity. Low temperature inside the transport container
A supply pipe for underground storage of LPG, which is equipped with a heat exchanger for raising the temperature of LPG to around room temperature.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP55164031A JPS5790483A (en) | 1980-11-22 | 1980-11-22 | Feeding pipe for storing lpg underground |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP55164031A JPS5790483A (en) | 1980-11-22 | 1980-11-22 | Feeding pipe for storing lpg underground |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5790483A JPS5790483A (en) | 1982-06-05 |
| JPH0125960B2 true JPH0125960B2 (en) | 1989-05-19 |
Family
ID=15785488
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP55164031A Granted JPS5790483A (en) | 1980-11-22 | 1980-11-22 | Feeding pipe for storing lpg underground |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5790483A (en) |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5530519A (en) * | 1978-08-22 | 1980-03-04 | Ishikawajima Harima Heavy Ind Co Ltd | Liquid extracting device for stored liquid convey pipe of low temperature tank |
-
1980
- 1980-11-22 JP JP55164031A patent/JPS5790483A/en active Granted
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5530519A (en) * | 1978-08-22 | 1980-03-04 | Ishikawajima Harima Heavy Ind Co Ltd | Liquid extracting device for stored liquid convey pipe of low temperature tank |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5790483A (en) | 1982-06-05 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US2513749A (en) | Insulated container and method of insulating the same | |
| EP0754904B1 (en) | Cryogenic pump system | |
| KR100696079B1 (en) | A method and apparatus for keeping cold tanks for storing or transporting a liquefied gas | |
| US2670605A (en) | System and method for charging carbon dioxide containers | |
| US2522026A (en) | Apparatus for vaporizing liquefied gas | |
| US2155340A (en) | Fuel supply system | |
| JPH0125960B2 (en) | ||
| Wordu et al. | Estimation of boil-off-gas BOG from refrigerated vessels in liquefied natural gas plant | |
| US3364689A (en) | Sub-cooled pipe line for removal of liquid from refrigerated storage tank | |
| US3276213A (en) | Reservoir for the underground storage of liquefied gases | |
| US2406540A (en) | Method of reducing evaporation losses | |
| US2561506A (en) | Liquefied gas evaporator | |
| US2983409A (en) | Means for the storage and transportation of a liquefied gas | |
| US2788637A (en) | Underground storage systems and improved method of operating | |
| US3251191A (en) | Frozen earth storage for liquefied gas | |
| US3041841A (en) | Storage means for a liquefied gas | |
| US2190367A (en) | Gas generator | |
| JPH0125957B2 (en) | ||
| JPH0125958B2 (en) | ||
| JP4378124B2 (en) | Natural gas hydrate storage method and apparatus | |
| US2971345A (en) | Apparatus and method for vaporizing butane | |
| US2405846A (en) | Gas dispensing apparatus | |
| JPH0125959B2 (en) | ||
| US3163013A (en) | Storage of low pressure gases | |
| US2537815A (en) | Gas distribution method and apparatus |