JP2637611B2 - Method for recovering NGL or LPG - Google Patents

Method for recovering NGL or LPG

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Publication number
JP2637611B2
JP2637611B2 JP2175373A JP17537390A JP2637611B2 JP 2637611 B2 JP2637611 B2 JP 2637611B2 JP 2175373 A JP2175373 A JP 2175373A JP 17537390 A JP17537390 A JP 17537390A JP 2637611 B2 JP2637611 B2 JP 2637611B2
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JP
Japan
Prior art keywords
gas
liquid
demethanizer
separated
cooled
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 - Lifetime
Application number
JP2175373A
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Japanese (ja)
Other versions
JPH0465487A (en
Inventor
一登 小林
厚雄 右近
隆俊 渋田
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Mitsubishi Heavy Industries Ltd
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Mitsubishi Heavy Industries Ltd
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Priority to JP2175373A priority Critical patent/JP2637611B2/en
Publication of JPH0465487A publication Critical patent/JPH0465487A/en
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Publication of JP2637611B2 publication Critical patent/JP2637611B2/en
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/0204—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the feed stream
    • F25J3/0209—Natural gas or substitute natural gas
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/0228—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream
    • F25J3/0233—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream separation of CnHm with 1 carbon atom or more
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/0228—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream
    • F25J3/0238—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream separation of CnHm with 2 carbon atoms or more
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/0228—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream
    • F25J3/0242—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream separation of CnHm with 3 carbon atoms or more
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/04—Processes or apparatus using separation by rectification in a dual pressure main column system
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/50—Processes or apparatus using separation by rectification using multiple (re-)boiler-condensers at different heights of the column
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/74—Refluxing the column with at least a part of the partially condensed overhead gas
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/78—Refluxing the column with a liquid stream originating from an upstream or downstream fractionator column
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2205/00—Processes or apparatus using other separation and/or other processing means
    • F25J2205/02—Processes or apparatus using other separation and/or other processing means using simple phase separation in a vessel or drum
    • F25J2205/04—Processes or apparatus using other separation and/or other processing means using simple phase separation in a vessel or drum in the feed line, i.e. upstream of the fractionation step
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2210/00—Processes characterised by the type or other details of the feed stream
    • F25J2210/06—Splitting of the feed stream, e.g. for treating or cooling in different ways
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2215/00—Processes characterised by the type or other details of the product stream
    • F25J2215/02—Mixing or blending of fluids to yield a certain product
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2215/00—Processes characterised by the type or other details of the product stream
    • F25J2215/62—Ethane or ethylene
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2230/00—Processes or apparatus involving steps for increasing the pressure of gaseous process streams
    • F25J2230/08—Cold compressor, i.e. suction of the gas at cryogenic temperature and generally without afterstage-cooler
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2235/00—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams
    • F25J2235/60—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams the fluid being (a mixture of) hydrocarbons
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2240/00—Processes or apparatus involving steps for expanding of process streams
    • F25J2240/02—Expansion of a process fluid in a work-extracting turbine (i.e. isentropic expansion), e.g. of the feed stream
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2245/00—Processes or apparatus involving steps for recycling of process streams
    • F25J2245/02—Recycle of a stream in general, e.g. a by-pass stream
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2270/00—Refrigeration techniques used
    • F25J2270/12—External refrigeration with liquid vaporising loop
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2270/00—Refrigeration techniques used
    • F25J2270/60—Closed external refrigeration cycle with single component refrigerant [SCR], e.g. C1-, C2- or C3-hydrocarbons

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)

Description

【発明の詳細な説明】 〔産業上の利用分野〕 本発明は、天然ガスや石油随伴ガスからLPGやNGLを回
収する方法に関する。Description: TECHNICAL FIELD The present invention relates to a method for recovering LPG and NGL from natural gas and gas accompanying petroleum.

〔従来の技術〕[Conventional technology]

天然ガスや石油随伴ガスからNGLやLPGを回収する方法
としては、一般に深冷分離法が広く用いられている。こ
の方法では、天然ガスあるいは石油随伴ガスから成る原
料ガスに、脱水、脱硫等の前処理を施した後、これを高
圧に圧縮、冷却して、NGLやLPGの成分となるエタン，プ
ロパン，ブタンおよび天然ガソリンを、液化し分離回収
する。回収した液は精製して製品とし、分離後のガス
（これはほとんどがメタンから成る）は、系外に放出す
るか、またはセールスガスとする。As a method of recovering NGL or LPG from natural gas or petroleum-associated gas, a cryogenic separation method is generally widely used. In this method, a raw gas consisting of natural gas or petroleum accompanying gas is subjected to pretreatment such as dehydration and desulfurization, and then compressed and cooled to a high pressure to produce ethane, propane, and butane as components of NGL and LPG. And natural gasoline are liquefied and separated and recovered. The recovered liquid is purified to produce a product, and the separated gas (which is mostly composed of methane) is released outside the system or used as a sales gas.

原料ガスを冷却するには、膨張タービン（エキスパン
ダ）を使用する方法が広く実施されている。この方法で
は、圧縮した原料ガスをエキスパンダによってほぼ等エ
ントロピー膨張させ、ガスを自己冷却させてその一部を
液化させるとともに、得られた冷熱を原料ガスの冷却に
利用している。また、原料ガスの冷却用熱量が不足する
場合には、プロパン冷凍機などの外部冷凍システムを利
用して、不足冷却量を補っている。In order to cool the raw material gas, a method using an expansion turbine (expander) is widely practiced. In this method, the compressed raw material gas is substantially isentropically expanded by an expander, the gas is self-cooled to partially liquefy, and the obtained cold heat is used for cooling the raw material gas. If the amount of heat for cooling the raw material gas is insufficient, an external refrigeration system such as a propane refrigerator is used to compensate for the insufficient amount of cooling.

このような回収方法の従来例を第４図、第５図を用い
て詳細に説明する。これらはいずれもLPG回収の例であ
る。天然ガスや石油随伴ガスなどの原料ガスには、メタ
ンが約70〜90％、エタンが約５〜10％、プロパン以上の
重質成分が約３〜10％含まれている。このガスは、脱
水，脱硫，脱炭酸等の前処理を経て、約20〜40気圧に昇
圧される。但しこの部分は図示されていない。A conventional example of such a recovery method will be described in detail with reference to FIGS. These are all examples of LPG recovery. Source gases such as natural gas and petroleum accompanying gas contain about 70 to 90% of methane, about 5 to 10% of ethane, and about 3 to 10% of heavy components such as propane. This gas is subjected to pretreatment such as dehydration, desulfurization, and decarboxylation, and is pressurized to about 20 to 40 atm. However, this part is not shown.

まず第４図において、（１）は前処理、圧縮後の原料
ガスである。この原料ガス（１）は、ストリッパ（脱メ
タン塔）（13）で分離された低温の分離ガス（23）と脱
エタン塔（24）で分離された分離ガス（30）とによっ
て、熱交換器（２）内で冷却される。この熱交換器
（２）としては、プレートフィン熱交換器が好適であ
る。熱交換器（２）の次には、例えばプロパン冷凍機の
ような外部冷凍機（３）により冷却される。引き続き、
原料ガス（１）は熱交換器（４）、（６）および外部冷
凍機（５）によって冷却される。原料ガスは、このよう
に熱交換器（２），（４），（６）および外部冷凍機
（３），（５）によって約20〜50℃から約−30〜−50℃
にまで冷却され、原料ガス（１）中の主としてプロパン
以上の重質成分が凝縮液化する。そこで、高圧セパレー
タ（高圧気液分離器）（７）により凝縮液（９）と分離
ガス（８）とに分離する。本プロセスでは、分離ガス
（23），（30）の他に脱メタン塔（13）で回収された回
収液（14）も、原料ガス（１）の冷却用流体として利用
される。First, in FIG. 4, (1) is a raw material gas after pretreatment and compression. This raw material gas (1) is separated into a heat exchanger by a low-temperature separation gas (23) separated by a stripper (demethanizer) (13) and a separation gas (30) separated by a deethanizer (24). Cooled in (2). As the heat exchanger (2), a plate fin heat exchanger is suitable. After the heat exchanger (2), it is cooled by an external refrigerator (3) such as a propane refrigerator. Continued
The raw material gas (1) is cooled by the heat exchangers (4) and (6) and the external refrigerator (5). The raw material gas is thus heated by the heat exchangers (2), (4), (6) and the external refrigerators (3), (5) to about -20 to -50 ° C.
, And the heavy components mainly of propane or more in the raw material gas (1) are condensed and liquefied. Then, the condensate (9) and the separation gas (8) are separated by a high-pressure separator (high-pressure gas-liquid separator) (7). In the present process, in addition to the separation gases (23) and (30), the recovered liquid (14) recovered in the demethanizer (13) is also used as a cooling fluid for the raw material gas (1).

分離ガス（８）は、エキスパンダ（膨張タービン）
（11）においてほぼ等エントロピー的に約10〜20気圧ま
で膨張し、原料ガス（１）の圧力降下に伴う自己冷却に
よって温度が約−70〜−90℃まで低下して一部は凝縮す
る。この時、原料ガス（１）の圧力エネルギーが膨張タ
ービン（11）の軸動力として回収される。膨張後の気液
混合流体はストリッパ（脱メタン塔）（13）に供給され
る。The separation gas (8) is an expander (expansion turbine)
In (11), it expands almost isentropically to about 10 to 20 atmospheres, and the temperature drops to about -70 to -90 ° C due to self-cooling accompanying the pressure drop of the raw material gas (1), and a part of it condenses. At this time, the pressure energy of the raw material gas (1) is recovered as shaft power of the expansion turbine (11). The gas-liquid mixed fluid after expansion is supplied to a stripper (demethanizer) (13).

次に、高圧セパレータ（７）で分離された凝縮液
（９）は、主としてプロパン以上の重質成分から成る
が、断熱膨張弁（10）において断熱膨張し、一部気化し
てストリッパ（13）に供給される。Next, the condensate (9) separated by the high-pressure separator (7) is mainly composed of a heavy component such as propane, but is adiabatically expanded in the adiabatic expansion valve (10), partially vaporized and stripped (13). Supplied to

ストリッパ（脱メタン塔）（13）では、前記エキスパ
ンダ（11）からの気液混合流体と、断熱膨張弁（10）か
らの気液二相流体とを接触させ、前記エキスパンダ（1
1）からの流体中に含まれる凝縮液によって、前記断熱
膨張弁（10）からの流体中、主として蒸気中に含まれる
プロパン以上の重質成分を凝縮させる。回収液（14）
は、ストリッパ（脱メタン塔）（13）の底部から抜出さ
れ、ポンプ（15）で脱エタン塔（24）へ送られる。この
際、前記熱交換器（４），（６）で冷熱回収され、脱エ
タン塔（24）における分離に適切な温度まで加熱され
る。In the stripper (demethanizer) (13), the gas-liquid mixed fluid from the expander (11) is brought into contact with the gas-liquid two-phase fluid from the adiabatic expansion valve (10), and the expander (1
The condensed liquid contained in the fluid from 1) condenses heavy components, such as propane, contained in the fluid from the adiabatic expansion valve (10), mainly in the steam. Recovery liquid (14)
Is withdrawn from the bottom of the stripper (demethanizer) (13) and sent to the deethanizer (24) by the pump (15). At this time, the heat is recovered by the heat exchangers (4) and (6) and heated to a temperature suitable for separation in the deethanizer (24).

一方、ストリッパ（脱メタン塔）（13）で分離された
ガス（23）は、熱交換器（２），（４），（６）で冷熱
回収され、更にコンプレッサ（33）で所定の圧力まで再
圧縮された後、エア・フィン・クーラ（34）でほぼ常温
まで冷却され、セールスガスとして貯蔵される。上記コ
ンプレッサ（33）は、前記膨張タービン（11）における
回収動力で駆動される。On the other hand, the gas (23) separated by the stripper (demethanizer) (13) is cooled and recovered by the heat exchangers (2), (4) and (6), and further cooled to a predetermined pressure by the compressor (33). After being recompressed, it is cooled to almost room temperature by the air fin cooler (34) and stored as sales gas. The compressor (33) is driven by recovery power of the expansion turbine (11).

脱エタン塔（24）では、リボイラ（25）における加熱
によって駆出された、主にメタン、エタンから成るガス
（30）が分離される。リフラックス（27）は、外部冷凍
機（26）によって脱エタン塔（24）塔頂から取出された
ガスを冷却し、一部を凝縮させることによって形成され
る。この凝縮液は、セパレータ（29）によって分離さ
れ、ポンプ（28）によってリフラックス（27）として脱
エタン塔（24）に戻される。In the deethanizer (24), a gas (30) mainly composed of methane and ethane, which is ejected by heating in the reboiler (25), is separated. The reflux (27) is formed by cooling the gas extracted from the top of the deethanizer (24) by the external refrigerator (26) and condensing a part of the gas. This condensate is separated by the separator (29) and returned to the deethanizer (24) as reflux (27) by the pump (28).

脱エタン塔（24）で分離された分離ガス（30）は、圧
力調整弁（31）を経て前記熱交換器（４），（２）で冷
却回収され、セールスガスとされる。また、脱エタン塔
（24）における回収液（32）は、実質的にプロパン以上
の重質成分から成り、そのままLPG製品として貯蔵され
るか、または、更に精製工程へ送られて精製された後、
製品とされる。The separation gas (30) separated in the deethanizer (24) is cooled and recovered in the heat exchangers (4) and (2) via a pressure regulating valve (31), and is used as a sales gas. The recovered liquid (32) in the deethanizer (24) is composed of heavier components than propane, and is stored as an LPG product as it is, or is sent to a purification step and purified. ,
Products.

LPG回収ブラントでは、プラント内の動力をできる限
り低減し、プラントコストのほとんどを占めるコンプレ
ッサコストを下げることによって、プラントコストと同
時に所要動力を低減して経費も削減することが特に望ま
れるため、上記のプロセスフローのように、低温流体の
冷熱エネルギーを回収利用している。In the LPG recovery brand, it is particularly desirable to reduce the power in the plant as much as possible and reduce the compressor cost, which accounts for most of the plant cost, to reduce the required power as well as the plant cost. As shown in the process flow, the cold energy of the low-temperature fluid is recovered and used.

次に第５図は、この冷熱回収を更に強化したプロセス
フローの従来例を示す。この例では、原料ガス（１）を
一旦約５〜−20℃まで冷却した後、第１セパレータ（7
a）で原料ガス（１）中の凝縮液（41）を分離回収す
る。そしてこの回収液（41）を断熱膨張弁（43）を経て
熱交換器（２），（４）で冷熱回収した後、脱エタン塔
（24）へ供給する。第１セパレータ（7a）で分離された
分離ガス（42）は、熱交換器（40），（６）および外部
冷凍機（５）によって更に冷却され、主にプロパン以上
の重質分が凝縮し、第２セパレータ（7b）へ供給され
る。第２セパレータ（7b）以後のプロセスの流れは、第
４図のプロセスフローの高圧セパレータ（７）以後の流
れと同様なので、説明を省略する。Next, FIG. 5 shows a conventional example of a process flow in which the cold heat recovery is further enhanced. In this example, after the raw material gas (1) is once cooled to about 5 to -20 ° C, the first separator (7)
In a), the condensate (41) in the raw material gas (1) is separated and recovered. Then, the recovered liquid (41) is cooled and recovered by the heat exchangers (2) and (4) through the adiabatic expansion valve (43) and then supplied to the deethanizer (24). The separation gas (42) separated by the first separator (7a) is further cooled by the heat exchangers (40), (6) and the external refrigerator (5), and the heavy components, mainly propane or more, are condensed. Is supplied to the second separator (7b). The flow of the process after the second separator (7b) is the same as the flow after the high-pressure separator (7) in the process flow of FIG.

上記のようなプロセスフローにおいては、原料ガス
（１）の冷却系を構成する熱交換器の数は多いものの、
原料ガス（１）の冷却温度変化に沿った冷却ができるた
め、冷却必要熱量は少なくてすみ、外部冷凍機の所要動
力と図示されていない原料ガスコンプレッサの動力とが
低減される。In the above process flow, although the number of heat exchangers constituting the cooling system for the raw material gas (1) is large,
Since the raw material gas (1) can be cooled in accordance with a change in the cooling temperature, the amount of heat required for cooling can be reduced, and the required power of the external refrigerator and the power of the raw gas compressor (not shown) can be reduced.

なお、ここで対象にしている所要動力は、次の式で与
えられるものを示す。In addition, the required power shown here is given by the following equation.

（所要動力）＝（原料ガスコンプレッサ動力）＋（外部
冷凍機のコンプレッサ動力） 例えば第５図に示すプロセスフローにおいて、原料ガ
スの全流量および組成が表１のような場合、98％のプロ
パン回収率を得るためには表２に示すような所要動力が
必要であった。(Required power) = (source gas compressor power) + (compressor power of external refrigerator) For example, in the process flow shown in FIG. 5, when the total flow rate and composition of the source gas are as shown in Table 1, 98% propane recovery is performed. To obtain the rate, the required power as shown in Table 2 was required.

表 １ 成 分 組 成（mol％） 窒素 0.48 二酸化炭素 0.77 メタン 70.95 エタン 11.71 プロパン 8.91 イソブタン 2.07 ノルマルブタン 2.91 イソペンタン 0.96 ノルマルペンタン 0.78 ヘキサン以上の炭化水素 0.46 全 流 量 1992 kg mol/h 表 ２ 原料ガスコンプレッサ 1,998kW外部冷凍機コンプレッサ 1,512kW 計 3,510kW またこの場合、主要プロセス条件は表３、回収LPG組
成は表４に示すとおりであった。Table 1 Composition (mol%) Nitrogen 0.48 Carbon dioxide 0.77 Methane 70.95 Ethane 11.71 Propane 8.91 Isobutane 2.07 Normal butane 2.91 Isopentane 0.96 Normal pentane 0.78 Hydrocarbons with hexane or higher 0.46 Total flow 1992 kg mol / h Table 2 Raw material gas compressor 1,998 kW external refrigerator compressor 1,512 kW total 3,510 kW In this case, the main process conditions were as shown in Table 3 and the recovered LPG composition was as shown in Table 4.

表 ３ 項 目 圧力（kg/cm2） 温度（℃） 原料カ゛スコンフ゜レッサ出口 42.0 − 第１セパレータ 40.0 −15.6 第２セパレータ 39.5 −53.0 脱メタン塔塔頂 17.4 −82.5 脱エタン塔塔頂 23.5 −32.9 セールスガス 20.0 50.0 表 ４ 成 分 組 成（mol％） エタン 0.85 プロパン 54.39 イソブタン 12.89 ノルマルブタン 18.16 イソペンタン 5.95 ノルマルペンタン 4.88 ヘキサン以上の炭化水素 2.88 全 流 量 319.6 （Kgmol/h） ここに示したデータは、原料ガスコンプレッサの出口
圧力について最適化して得られた結果であり、このプロ
セスフローでは、プロパン回収率を98％に保って更に原
料ガスコンプレッサの出口圧力を下げることはできなか
った。Table 3 Item Pressure (kg / cm 2 ) Temperature (° C) Raw material gas compressor outlet 42.0 − First separator 40.0 −15.6 Second separator 39.5 −53.0 Demethanizer tower top 17.4 −82.5 Deethanizer tower top 23.5 −32.9 Sales Gas 20.0 50.0 Table 4 Composition Composition (mol%) Ethane 0.85 Propane 54.39 Isobutane 12.89 Normal butane 18.16 Isopentane 5.95 Normal pentane 4.88 Hydrocarbons of hexane or higher 2.88 Total flow 319.6 (Kgmol / h) The data shown here are raw materials This is a result obtained by optimizing the outlet pressure of the gas compressor. In this process flow, it was impossible to further reduce the outlet pressure of the raw material gas compressor while maintaining the propane recovery rate at 98%.

〔発明が解決しようとする課題〕[Problems to be solved by the invention]

本発明の目的は、天然ガスや石油随伴ガスからLPGま
たはNGLを回収する方法において、高回収率を保ちなが
らプラント所要動力を更に低減することのできる方法を
提供することにある。An object of the present invention is to provide a method for recovering LPG or NGL from natural gas or petroleum accompanying gas, in which the power required for the plant can be further reduced while maintaining a high recovery rate.

〔課題を解決するための手段〕[Means for solving the problem]

本発明は、前記従来の課題を解決するために、天然ガ
スまたは石油随伴ガスからNGLまたはLPGを深冷分離する
方法において、次の工程（ａ）ないし（ｈ）を含むこと
を特徴とするNGLまたはLPGの回収方法を提案するもので
ある。According to the present invention, there is provided a method for cryogenically separating NGL or LPG from natural gas or petroleum accompanying gas, which comprises the following steps (a) to (h). Alternatively, it proposes a method for collecting LPG.

（ａ） 原料ガスを冷却して一部を凝縮させ、気液二相
流体とする。(A) The raw material gas is cooled and partially condensed to form a gas-liquid two-phase fluid.

（ｂ） 上記気液二相流体を高圧気液分離器で気体と液
体に分離する。(B) The gas-liquid two-phase fluid is separated into gas and liquid by a high-pressure gas-liquid separator.

（ｃ） 上記高圧気液分離器で分離された気体を膨張さ
せて一部を凝縮させ、その気液混合流体を脱メタン塔の
上部領域に供給する。(C) The gas separated by the high-pressure gas-liquid separator is expanded and partially condensed, and the gas-liquid mixed fluid is supplied to an upper region of the demethanizer.

（ｄ） 上記高圧気液分離器で分離された液体を断熱膨
張・減圧して一部を気化させ、その気液二相流体を加熱
した後、上記脱メタン塔の上記気液混合流体供給位置よ
りも低い位置に供給する。(D) The liquid separated by the high-pressure gas-liquid separator is adiabatically expanded and decompressed to partially vaporize the liquid, and the gas-liquid two-phase fluid is heated. To a lower position.

（ｅ） 上記脱メタン塔の塔頂から冷ガスを取出し、加
熱・昇温した後、圧縮して他工程へ送給する。(E) A cold gas is taken out from the top of the demethanizer, heated and heated, compressed, and sent to another process.

（ｆ） 上記脱メタン塔の上記気液二相流体供給位置よ
りも低くない位置から、同脱メタン塔内を上昇する冷ガ
スの一部を抜出して加圧した後、沸点以下まで冷却して
液化する。(F) From a position not lower than the gas-liquid two-phase fluid supply position of the demethanizer, a part of the cold gas rising in the demethanizer is extracted and pressurized, and then cooled to a boiling point or lower. Liquefy.

（ｇ） 上記液化物を膨張させて減圧し、リフラックス
として上記脱メタン塔の塔頂に供給する。(G) The liquefied product is expanded and reduced in pressure, and supplied as reflux to the top of the demethanizer.

（ｈ） 上記脱メタン塔の塔底から、脱メタン化液体を
取出す。(H) Take out the demethanized liquid from the bottom of the demethanizer.

〔作 用〕(Operation)

本発明においては、脱メタン塔の塔内を上昇するガス
の一部を抜出し、圧縮冷却して液化し、主にメタン，エ
タンから成るリフラックスを形成してこれを上記脱メタ
ン塔の頂部に供給する。これによって脱メタン塔塔頂付
近のガス中に分離されずに含まれる注目成分（エタンま
たはプロパン以上の重質成分）を凝縮液化し、分離回収
する。そうすると注目成分の回収率が向上するので、原
料ガスの圧縮条件および冷却条件を緩和することがで
き、したがってプラント所要動力を低減することができ
る。In the present invention, a part of the gas rising in the demethanizer tower is extracted, compressed, cooled and liquefied to form a reflux mainly composed of methane and ethane, and this is formed at the top of the demethanizer tower. Supply. As a result, the target component (heavy component of ethane or propane or more) contained in the gas near the top of the demethanizer without being separated is condensed and liquefied, and separated and recovered. As a result, the recovery rate of the component of interest is improved, so that the conditions for compressing and cooling the raw material gas can be relaxed, and the required power for the plant can be reduced.

〔実施例〕〔Example〕

第１図は本発明方法をLPG回収に適用した第１の実施
例を示す系統図である。FIG. 1 is a system diagram showing a first embodiment in which the method of the present invention is applied to LPG recovery.

原料ガスは、脱水、脱硫、脱炭酸等の前処理後、図中
には示されていないコンプレッサで昇圧され、更に再度
モレキュラー・シーブで脱水された後、図示のプロセス
内へ供給される。この原料ガス（１）は熱交換器
（２），（４），（６）と外部冷凍機（３），（５）に
よって冷却され、主としてプロパン以上の重質成分が凝
縮液化する。冷却のためには、ストリッパ（脱メタン
塔）（13）から導かれた分離ガス（23）、回収液（14）
および高圧セパレータ（高圧気液分離器）（７）で分離
された凝縮液（９）が利用される。The raw material gas is subjected to pretreatment such as dehydration, desulfurization, and decarboxylation, then pressurized by a compressor (not shown), dehydrated again by a molecular sieve, and supplied to the illustrated process. This raw material gas (1) is cooled by the heat exchangers (2), (4) and (6) and the external refrigerators (3) and (5), and a heavy component such as propane is mainly condensed and liquefied. For cooling, the separation gas (23) led from the stripper (demethanizer) (13) and the recovered liquid (14)
And a condensate (9) separated by a high-pressure separator (high-pressure gas-liquid separator) (7).

冷却後の原料ガスは、高圧セパレータ（７）で分離ガ
ス（８）と凝縮液（９）とに分離される。その分離ガス
（８）をエキスパンダ（膨張タービン）（11）において
ほぼ等エントロピー膨張させ、ガスの圧力エネルギーを
軸動力に変換するとともに、分離ガス（８）の自己冷却
により冷熱を得てガス中の凝縮成分を液化させ、脱メタ
ン塔（13）へ供給する。また得られた軸動力は、ストリ
ッパ（13）で分離したガス（23）を再加圧するコンプレ
ッサ（33）を駆動する動力とする。The cooled raw material gas is separated into a separation gas (8) and a condensate (9) by a high-pressure separator (7). The separated gas (8) is substantially isentropically expanded in an expander (expansion turbine) (11) to convert the pressure energy of the gas into shaft power, and to obtain cold heat by self-cooling of the separated gas (8) to produce gas. Is condensed and supplied to the demethanizer (13). The obtained shaft power is used to drive a compressor (33) for repressurizing the gas (23) separated by the stripper (13).

一方、高圧セパレータ（７）で分離された凝縮液
（９）は、断熱膨張バルブ（10）で膨張させて液の一部
を蒸発させ、自己冷却させる。この流体（12）を熱交換
器（６）に供給して原料ガス（１）で加熱し、更に蒸気
を発生させて脱メタン塔（13）に供給する。On the other hand, the condensed liquid (9) separated by the high-pressure separator (7) is expanded by the adiabatic expansion valve (10) to partially evaporate the liquid and self-cool. The fluid (12) is supplied to the heat exchanger (6), heated by the raw material gas (1), and further generates steam to be supplied to the demethanizer (13).

この供給位置とほぼ同一の理論段位置であり、その供
給段よりも実質的に高い位置から、塔内を上昇するガス
の一部を抜出しガス流体（17）を作る。その流体（17）
を小型コンプレッサ（18）を用いて昇圧する。昇圧後の
流体を外部冷凍機（17）と熱交換器（20）により冷却し
て液化させる。この流体は主としてメタンとエタンから
成るので、液化後の流体を断熱膨張弁（21）を用いて膨
張させれば、低温の流体（22）が得られる。この流体
（22）をリフラックスとして脱メタン塔（13）の塔頂に
供給すれば、前記分離ガス（８）がエキスパンダ（11）
で膨張して生じた気液二相流体（16）中の蒸気に含まれ
ていたプロパン以上の重質成分が、主に凝縮液化して回
収されるので、プロパンの回収率を向上させることがで
きる。A part of the gas rising in the column is withdrawn from a position substantially the same as the theoretical position of the supply position and substantially higher than the supply position to produce a gas fluid (17). The fluid (17)
Is boosted using a small compressor (18). The pressurized fluid is cooled and liquefied by an external refrigerator (17) and a heat exchanger (20). Since this fluid is mainly composed of methane and ethane, a low-temperature fluid (22) can be obtained by expanding the liquefied fluid using the adiabatic expansion valve (21). If this fluid (22) is supplied as reflux to the top of the demethanizer (13), the separation gas (8) is converted to an expander (11).
In the gas-liquid two-phase fluid (16) generated by the expansion, the heavy components above the propane contained in the vapor are mainly condensed and liquefied and recovered, so that the recovery rate of propane can be improved. it can.

脱メタン塔（13）で回収された液（14）は、ポンプ
（15）で熱交換器（４）へ送られて原料ガス（１）を冷
却した後、脱エタン塔（24）へ供給される。The liquid (14) recovered in the demethanizer (13) is sent to the heat exchanger (4) by the pump (15) to cool the raw material gas (1), and then supplied to the deethanizer (24). You.

脱エタン塔（24）では、塔底に設けられたリボイラ
（25）で加熱されて駆出されたメタン，エタンが、塔内
を上昇し、塔頂のコンデンサ（26）によって一部が液化
する。その液をセパレータ（29）で分離し、リフラック
ス（27）としてポンプ（28）で再度脱エタン塔（24）に
供給する。In the deethanizer (24), the methane and ethane heated and ejected by the reboiler (25) provided at the bottom of the tower rise in the tower and are partially liquefied by the condenser (26) at the top . The liquid is separated by a separator (29) and supplied again as a reflux (27) to a deethanizer (24) by a pump (28).

セパレータ（29）で、分離したガス（30）の方は、圧
力調整弁（31）を介して熱交換器（４），（２）に供給
し冷熱を回収した後、セールスガス（35）とする。脱エ
タン塔（24）の塔底からは、プロパン以上の重質成分を
回収液（32）として抜出し、LPGとする。The gas (30) separated by the separator (29) is supplied to the heat exchangers (4) and (2) through the pressure regulating valve (31) to recover the cold heat, and then the sales gas (35) I do. From the bottom of the deethanizer (24), heavy components equal to or greater than propane are withdrawn as a recovered liquid (32) to obtain LPG.

第２図は本発明の第２の実施例を示す系統図である。
この実施例では、昇圧、脱水後の原料ガス（１）を２つ
に分け、一方の流体は熱交換器（２）で冷却し、他方を
脱メタン塔（13）のリボイラ（37）、サイドリボイラ
（36）、外部冷凍機（３）によって冷却している。他の
プロセス構成は、前記第１図で説明した第１の実施例と
同じである。FIG. 2 is a system diagram showing a second embodiment of the present invention.
In this embodiment, the raw material gas (1) after pressurization and dehydration is divided into two, one fluid is cooled by a heat exchanger (2), and the other is cooled by a reboiler (37) and a side of a demethanizer (13). It is cooled by a reboiler (36) and an external refrigerator (3). Other process configurations are the same as those of the first embodiment described with reference to FIG.

第３図は本発明の第３の実施例を示す系統図である。
この実施例は、前記第５図により説明した従来の方法に
対して本発明を適用した例である。前記第２の実施例と
同様に、約30〜50気圧に昇圧後、脱水した原料ガスを２
つに分け、一方を熱交換器（２）によって、また他方を
脱メタン塔（13）のリボイラ（37）とサイドボイラ（3
6）、および熱交換器（44）、外部冷凍機（３）によっ
て、約５〜15℃までそれぞれ冷却し、再合流後、第１セ
パレータ（7a）へ供給する。この冷却によって、原料ガ
ス中の主としてプロパン以上の重質成分が凝縮し、第１
セパレータ（7a）で凝縮液（41）と分離ガス（42）とに
分離される。FIG. 3 is a system diagram showing a third embodiment of the present invention.
This embodiment is an example in which the present invention is applied to the conventional method described with reference to FIG. As in the second embodiment, after the pressure is increased to about 30 to 50 atm, the dehydrated raw material gas is
And the other one with a heat exchanger (2) and the other with a reboiler (37) and a side boiler (3) of a demethanizer (13).
6), and cooled to about 5 to 15 ° C. by the heat exchanger (44) and the external refrigerator (3). By this cooling, a heavy component mainly of propane or more in the raw material gas is condensed,
The condensate (41) and the separation gas (42) are separated by the separator (7a).

凝縮液（41）は、断熱膨張弁（43）によって断熱膨張
し、液の一部が蒸発して温度が下がる。この低温を利用
して熱交換器（44）で原料ガスを冷却した後、脱メタン
塔（13）へ供給される。The condensed liquid (41) is adiabatically expanded by the adiabatic expansion valve (43), and a part of the liquid evaporates to lower the temperature. The raw material gas is cooled by the heat exchanger (44) using the low temperature, and then supplied to the demethanizer (13).

第１セパレータ（7a）で分離されたガス（42）は、熱
交換器（４），（６）および外部冷凍機（５）によって
更に約−30〜−50℃まで冷却され、第２セパレータ（7
b）で主としてメタンから成るガス（８）と凝縮液
（９）とに分けられる。分離後のガス（８）は、エキス
パンダ（膨張タービン）（11）でほぼ等エントロピー膨
張し約−70〜−90℃まで冷却した後、脱メタン塔（13）
へ供給される。脱メタン塔（13）にはリボイラ（37）と
サイドリボイラ（36）が設けられ、主にメタンの駆出の
ための熱を供給する。The gas (42) separated by the first separator (7a) is further cooled to about −30 to −50 ° C. by the heat exchangers (4) and (6) and the external refrigerator (5). 7
In b), it is divided into a gas (8) mainly composed of methane and a condensate (9). The separated gas (8) is almost isentropically expanded by an expander (expansion turbine) (11), cooled to about -70 to -90 ° C, and then demethanized (13).
Supplied to The demethanizer (13) is provided with a reboiler (37) and a side reboiler (36) to supply heat mainly for methane ejection.

第２セパレータ（7b）で分離された凝縮液（９）は、
断熱膨張弁（10）、熱交換器（６）を介して、脱メタン
塔（13）へ供給される。この供給位置に対応する脱メタ
ン塔（13）の理論段にほぼ等しい段であって、その供給
位置よりも実質的に高い位置から、脱メタン塔（13）を
上昇するガスの一部を抜出す。このガス（17）を小型コ
ンプレッサ（18）で約20〜40気圧に圧縮し、外部冷凍機
（19）、熱交換器（20）によって約−60〜−80℃まで冷
却、液化させた後、断熱膨張バルブ（21）を介して脱メ
タン塔（13）の頂部にリフラックス（22）として供給す
る。抜出しの際、ガス硫れ（17）を乾燥させてコンプレ
ッサ（18）内での液発生を防ぐため、加熱器（45）を設
けて若干加熱してもよい。The condensate (9) separated by the second separator (7b) is
It is supplied to the demethanizer (13) via the adiabatic expansion valve (10) and the heat exchanger (6). From a position substantially equal to the theoretical stage of the demethanizer tower (13) corresponding to this supply position, and from a position substantially higher than the supply position, a part of the gas rising through the demethanizer (13) is extracted. put out. This gas (17) is compressed to about 20 to 40 atm by a small compressor (18), cooled to about -60 to -80 ° C by an external refrigerator (19) and a heat exchanger (20), and liquefied. It is supplied as reflux (22) to the top of the demethanizer (13) via the adiabatic expansion valve (21). At the time of extraction, a heater (45) may be provided to slightly heat the gas sulfur (17) in order to dry it and prevent liquid generation in the compressor (18).

その他のプロセスの構成は、前記第１および第２の実
施例と同様なので、詳しい説明を省く。The configuration of the other processes is the same as that of the first and second embodiments, and a detailed description thereof will be omitted.

前記表１に示した組成の原料ガスから、この第３実施
例の方法によってLPGを98％回収する場合につき、プラ
ント内の主要所要動力を求めた結果は、表５のとおりで
ある。Table 5 shows the results of determining the main required power in the plant when 98% of LPG was recovered from the raw material gas having the composition shown in Table 1 by the method of the third embodiment.

表 ５ 原料ガスコンプレッサ 1,730kW 外部冷凍機（３）（５）（19）（26） 1,160kWリフラックスコンプレッサ（18） 90kW 計 2,980kW 表２と表５を比較すれば、本発明を適用したことによ
って従来よりも動力が約15％低減されることが分かる。
なお、この場合プロセスの主要条件は表６のとおりであ
る。Table 5 Source gas compressor 1,730 kW External refrigerator (3) (5) (19) (26) 1,160 kW reflux compressor (18) 90 kW total 2,980 kW By comparing Table 2 and Table 5, it can be seen that the present invention was applied. It can be seen that the power is reduced by about 15% as compared with the conventional case.
In this case, the main conditions of the process are as shown in Table 6.

表 ６項 目 圧力（kg/cm2） 温度（℃） 原料カ゛スコンフ゜レッサ出口 37.6 − 第１セパレータ 36.5 5.0 第２セパレータ 36.0 −45.0 脱メタン塔塔頂 17.6 −78.8 脱エタン塔塔頂 28.5 5.7 セールスガス 20.0 50.0 〔発明の効果〕 本発明のLPGまたはNGLの回収方法によれば、従来の方
法に比べて、所要動力を格段に引下げることができる。Table 6 Item Pressure (kg / cm 2 ) Temperature (° C) Raw material gas compressor outlet 37.6 − First separator 36.5 5.0 Second separator 36.0 −45.0 Demethanizer tower top 17.6 −78.8 Deethanizer tower top 28.5 5.7 Sales gas 20.0 50.0 [Effect of the Invention] According to the method for recovering LPG or NGL of the present invention, the required power can be significantly reduced as compared with the conventional method.

【図面の簡単な説明】 第１図は本発明の第１の実施例を示す系統図、第２図は
本発明の第２の実施例を示す系統図、第３図は本発明の
第３の実施例を示す系統図である。第４図および第５図
はいずれも従来のNGLまたはLPG回収方法の例を示す系統
図である。 （１）……原料ガス；（２），（４），（６）……熱交
換器； （３），（５）……外部冷凍機； （７）……高圧セパレータ（高圧気液分離器）； （7a）……第１セパレータ； （7b）……第２セパレータ；（８）……分離ガス； （９）……凝縮液；（10）……断熱膨張弁； （11）……エキスパンダ（膨張タービン）； （12）……膨張後の流体； （13）……ストリッパ（脱メタン塔）； （14）……回収液；（15）……ポンプ； （16）……エキスパンダ出口流体； （17）……塔内ガス抜出し流体； （18）……小型コンプレッサ； （19）……外部冷凍機；（20）……熱交換器； （21）……断熱膨張弁；（22）……リフラックス流体； （23）……分離ガス；（24）……脱エタン塔； （25）……リボイラ；（26）……外部冷凍機； （27）……リフラックス；（28）……ポンプ； （29）……セパレータ；（30）……分離ガス； （31）……圧力調整弁；（32）……回収LPG; （33）……コンプレッサ； （34）……エア・フィン・クーラ； （35）……セールスガス；（36）……サイドリボイラ； （37）……リボイラ； （38）……サイドリボイラ用流体； （39）……リボイラ用流体；（40）……熱交換器； （41）……凝縮液；（42）……分離ガス； （43）……断熱膨張弁；（44）……熱交換器； （45）……加熱器。BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a system diagram showing a first embodiment of the present invention, FIG. 2 is a system diagram showing a second embodiment of the present invention, and FIG. It is a system diagram which shows Example of a. 4 and 5 are system diagrams showing examples of a conventional NGL or LPG recovery method. (1) ... source gas; (2), (4), (6) ... heat exchanger; (3), (5) ... external refrigerator; (7) ... high-pressure separator (high-pressure gas-liquid separation) (7a) ... first separator; (7b) ... second separator; (8) ... separation gas; (9) ... condensate; (10) ... adiabatic expansion valve; (11) ... ... Expander (expansion turbine); (12) ... Expanded fluid; (13) ... Stripper (demethanizer); (14) ... Recovered liquid; (15) ... Pump; (16) ... Expander outlet fluid; (17)… Fluid for removing gas from the tower; (18)… Small compressor; (19)… External refrigerator; (20)… Heat exchanger; (21)… Adiabatic expansion valve (22) ... reflux fluid; (23) ... separation gas; (24) ... deethanizer; (25) ... reboiler; (26) ... external refrigerator; (27) ... reflux ; 28) Pumps (29) Separators (30) Separation gas; (31) Pressure regulating valves (32) Recovered LPG; (33) Compressors; (34) Air fin cooler; (35) Sales gas; (36) Side reboiler; (37) Reboiler; (38) Fluid for side reboiler; (39) Fluid for reboiler; ) Heat exchanger; (41) condensate; (42) separation gas; (43) adiabatic expansion valve; (44) heat exchanger; (45) heater.

フロントページの続き (56)参考文献 特開 昭58−17191（ＪＰ，Ａ) 特開 昭58−17192（ＪＰ，Ａ) 特開 昭60−96686（ＪＰ，Ａ)Continuation of front page (56) References JP-A-58-17191 (JP, A) JP-A-58-17192 (JP, A) JP-A-60-96686 (JP, A)

Claims (1)

(57)【特許請求の範囲】(57) [Claims] 【請求項１】天然ガスまたは石油随伴ガスからNGLまた
はLPGを深冷分離する方法において、次の工程（ａ）な
いし（ｈ）を含むことを特徴とするNGLまたはLPGの回収
方法。 （ａ） 原料ガスを冷却して一部を凝縮させ、気液二相
流体とする。 （ｂ） 上記気液二相流体を高圧気液分離器で気体と液
体に分離する。 （ｃ） 上記高圧気液分離器で分離された気体を膨張さ
せて一部を凝縮させ、その気液混合流体を脱メタン塔の
上部領域に供給する。 （ｄ） 上記高圧気液分離器で分離された液体を断熱膨
張・減圧して一部を気化させ、その気液二相流体を加熱
した後、上記脱メタン塔の上記気液混合流体供給位置よ
りも低い位置に供給する。 （ｅ） 上記脱メタン塔の塔頂から冷ガスを取出し、加
熱・昇温した後、圧縮して他工程へ送給する。 （ｆ） 上記脱メタン塔の上記気液二相流体供給位置よ
りも低くない位置から、同脱メタン塔内を上昇する冷ガ
スの一部を抜出して加圧した後、沸点以下まで冷却して
液化する。 （ｇ） 上記液化物を膨張させて減圧し、リフラックス
として上記脱メタン塔の塔頂に供給する。 （ｈ） 上記脱メタン塔の塔底から、脱メタン化液体を
取出す。1. A method for cryogenically separating NGL or LPG from natural gas or petroleum accompanying gas, comprising the following steps (a) to (h): (A) The raw material gas is cooled and partially condensed to form a gas-liquid two-phase fluid. (B) The gas-liquid two-phase fluid is separated into gas and liquid by a high-pressure gas-liquid separator. (C) The gas separated by the high-pressure gas-liquid separator is expanded and partially condensed, and the gas-liquid mixed fluid is supplied to an upper region of the demethanizer. (D) The liquid separated by the high-pressure gas-liquid separator is adiabatically expanded and decompressed to partially vaporize the liquid, and the gas-liquid two-phase fluid is heated. To a lower position. (E) A cold gas is taken out from the top of the demethanizer, heated and heated, compressed, and sent to another process. (F) From a position not lower than the gas-liquid two-phase fluid supply position of the demethanizer, a part of the cold gas rising in the demethanizer is extracted and pressurized, and then cooled to a boiling point or lower. Liquefy. (G) The liquefied product is expanded and reduced in pressure, and supplied as reflux to the top of the demethanizer. (H) Take out the demethanized liquid from the bottom of the demethanizer.
JP2175373A 1990-07-04 1990-07-04 Method for recovering NGL or LPG Expired - Lifetime JP2637611B2 (en)

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