EP0244400A1 - Refrigeration d'un gaz provenant d'un pipeline - Google Patents

Refrigeration d'un gaz provenant d'un pipeline

Info

Publication number
EP0244400A1
EP0244400A1 EP85905474A EP85905474A EP0244400A1 EP 0244400 A1 EP0244400 A1 EP 0244400A1 EP 85905474 A EP85905474 A EP 85905474A EP 85905474 A EP85905474 A EP 85905474A EP 0244400 A1 EP0244400 A1 EP 0244400A1
Authority
EP
European Patent Office
Prior art keywords
gas
refrigeration
pressure
transmission pipeline
methanol
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.)
Withdrawn
Application number
EP85905474A
Other languages
German (de)
English (en)
Other versions
EP0244400A4 (fr
Inventor
Irving Weiss
Hans P. Schorr
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Kryos Energy Inc
Brooklyn Union Gas Co
Original Assignee
Kryos Energy Inc
Brooklyn Union Gas Co
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Kryos Energy Inc, Brooklyn Union Gas Co filed Critical Kryos Energy Inc
Publication of EP0244400A1 publication Critical patent/EP0244400A1/fr
Publication of EP0244400A4 publication Critical patent/EP0244400A4/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17D—PIPE-LINE SYSTEMS; PIPE-LINES
    • F17D1/00—Pipe-line systems
    • F17D1/02—Pipe-line systems for gases or vapours
    • F17D1/065—Arrangements for producing propulsion of gases or vapours
    • F17D1/07—Arrangements for producing propulsion of gases or vapours by compression
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17D—PIPE-LINE SYSTEMS; PIPE-LINES
    • F17D1/00—Pipe-line systems
    • F17D1/02—Pipe-line systems for gases or vapours
    • F17D1/04—Pipe-line systems for gases or vapours for distribution of gas
    • F17D1/05—Preventing freezing
    • 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
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
    • F25B9/06—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point using expanders

Definitions

  • This invention relates to the production of refrigeration during the reduction of pressure of gas withdrawn from a transmission pipeline. More specifically, the invention produces refrigeration with energy recovered when gas at elevated pressure in a transmission pipeline is supplied to a branch or regional pipeline maintained at a lower high pressure.
  • the gas pressure of transmission or trunk pipelines is reduced at many letdown stations or city gates simply by isenthalpic expansion, i.e., by passage through a reducing valve. Such pressure reduction is a waste of valuable energy.
  • a principal object of this invention is to convert energy derived from reducing the pressure of transmission pipeline gas to low-cost refrigeration. Another important object is to maximize the generation of refrigeration by isentropic expansion of the transmission pipeline gas, i.e., expansion with the performance of work.
  • transmission pipeline gas reaching a letdown station generally at a pressure in the range of about 400 to 1000 psia.more frequently in the range of about 500 to 800 psia(pounds per square inch absolute), is expanded in a turbo-expander to a reduced pressure which is in most cases at least 50 psi below the desired delivery pressure but is not reduced enough to drop the temperature of the expanded gas below ahout -100°F, recovering refrigeration from the expanded gas, and thereafter compressing the expanded gas to the deLivery pressure in a centrifugal compressor driven by the turbo-expander.
  • the gas pressure is often reduced by the expander at least 250 psi to a reduced pressure which is below the ultimate delivery pressure but which does not drop the temperature of the expanded gas below about -100°F. Limiting the reduction of pressure so that the temperature does not fall below about -100°F avoids excessive condensation of hydrocarbons usually present in natural gas. Furthermore, there is no significant commercial market for the very low temperature refrigeration that is recoverable from expanded gas having a temperature below -100°F. Low level refrigeration is generally recovered from the expanded gas at a temperature below about -40°F, and if desired, additional high level refrigeration is recoverable at a temperature below about 20°F.
  • the transmission pipeline gas Prior to entering the turbo-expander, the transmission pipeline gas is desirably cooled, usually to a temperature below about 45°F, by heat exchange with the expanded gas after refrigeration has been recovered therefrom so that the recovered refrigeration is at a lower temperature than it would be without such prior cooling.
  • the warmed expanded gas is passed through the centrifugal compressor which increases the pressure so that the gas can be delivered at the desired pressure in the range of about 200 to 450 psia, frequently in the range of about 250 to 350 psia.
  • Transmission pipeline gas is herein used to mean natural gas or synthetic natural gas having a very high methane content and a heating value of at least about 950
  • Transmission pipeline gas reaching letdown stations invariably contains moisture which would freeze during the expansion of the gas and cause plugging of the equipment with possible damage thereto.
  • a simple and inexpensive method of removing moisture from the pipeline gas involves the injection of a small, quantity of methanol into the gas so that the moisture merely condenses during expansion of the gas and is separated from the expanded gas as a water-methanol solution.
  • This method has been integrated with the novel generation of refrigeration according to this invention so that some of the energy derived from reducing the pressure of the pipeline gas is utilized to separate methanol from the water-methanol solution.
  • regenerated methanol can be recycled for injection into transmission pipeline gas to be work expanded according to this invention.
  • Fig. 1 is a flow diagram of a preferred embodiment of the invention in which the dehydration of the pipeline gas is integrated with the production of low level refrigeration;
  • Fig. 2 is a partial flow diagram showing a modification of the portion of Fig. 1 indicated thereon within an encircling dotted line.
  • Fig. 1 as modified by Fig. 2 is the flow diagram of another preferred embodiment of the invention yielding both low level and high level refrigeration. DESCRIPTION OF PREFERRED EMBODIMENTS
  • Fig. 1 is a flow diagram of the basic process of the invention incorporating the method of eliminating the moisture usually present in pipeline gas through the use of methanol.
  • the description of Fig. 1 will include a specific example of a transmission pipeline feeding a branch pipeline with gas which is substantially pure methane containing small amounts of moisture, carbon dioxide and higher hydrocarbons.
  • Methanol is injected into tower 21 at the rate of about 200 pounds per million standard cubic feet of gas passing through tower 21.
  • the gas expanded with very little liquefaction of hydrocarbons such as propane and butane leaves expander 29 at 230 psia and -60°F, discharging from line 30 into separator 31 wherein an aqueous methanol condensate is removed from the expanded cold gas which flows through line 32 to refrigeration recovery exchanger 33.
  • Antifreeze or other suitable fluid is passed through refrigeration exchanger 33 to convey the recovered refrigeration to one or more operations requiring refrigeration, such as the commercial feezing of fish and meat.
  • the gas issues from exchanger 26 at 224 psia and
  • Control valve 44 in line 42 is used to divert about 30% of the gas in line 42 through branch line 45 and reboiler 64 whence at 313 psia and 215°F it returns to line 42.
  • the recombined stream of compressed gas flows from air cooler 43 at 310 psia and 195°F through line 46 and exchanger 36 from which it discharges into branch pipeline 47 at its normal operating conditions of 305 psia and 70°F.
  • the condensate passing through valve 50 discharges into separator 51 at about 23 psia. Traces of gases released from the condensate are vented from separator 51 through valved line 52.
  • the condensate flows from separator 51 through line 53 into mixing tank 54.
  • Warm water at 205°F drawn from the bottom of distillation column 55 through line 56 is passed by line 57 and pump 58 for admixture with the aqueous methanol of line 53 discharged into tank 54.
  • the warm mixture causes the small quantity of hydrocarbons that may have been carried in solution by the aqueous methanol into tank 54 to separate out as a supernatant layer on the aqueous methanol.
  • the separated hydrocarbon layer is removed from tank 54. by line 59 and pump 60 and in moat cases is injected into the compressed gas before it is delivered to branch pipeline 47.
  • the bottom layer of aqueous methanol passes from tank 54 through line 61 and control valve 62 into an intermediate section of column 55.
  • the distillation separates the aqueous methanol into methanol vapor which rises to the top of column 55 and into water bottoms.
  • Water in the bottom of column 55 circulates through line 56, line 63 and reboiler 64, discharging back into column 55 to supply the heat required for the distillation.
  • Valved line 74 is used to drain water from column 55 as required.
  • Methanol vapor passes from the top of column 55 via line 65 to reflux condenser 39, discharging therefrom as liquid methanol into line 66.
  • pump 67 returns part of the liquid methanol through line 68 as reflux into the top of column 55 while part is returned via line 69 to storage tank 22.
  • the division of the liquid flow from pump 67 into lines 68 and 69 is controlled by valve 70.
  • the methanol recovered by distillation in column 55 and returned by line 69 to tank 22 together with condensed methanol discharged from separator 27 through line 71 and reducing valve 72 into tank 22 for recycling through line 23 and pump 24 to tower 21 amounts to almost 99.5% of the methanol injected into tower 21.
  • the invention generates refrigeration at a lower temperature level than would otherwise be reached and the amount of refrigeration is increased about 30 to 50%
  • Another feature of the invention is the use of exchanger 36 to transfer heat from the recompressed gas of
  • FIG. 2 shows a modification of the flow diagram of Fig. 1 which permits the recovery of refrigeration at two temperature levels. Reference numerals appearing in Fig. 1 are applied to corresponding elements of Fig. 2. The only new element in Fig. 2 is a high level refrigeration recovery exchanger with reference numeral 75 which is placed in line 34 between refrigeration recovery exchanger 33 and exchanger 26.
  • Fig. 2 yields 70% more refrigeration than Fig. 1 but the additional refrigeration made available by exchanger 75 is at a temperature level of about -5°F whereas the low level refrigeration is available at a temperature of about -55°F.
  • Fig. 2 is justified when there are customers who require refrigeration at different temperature levels for their respective operations, for example, a customer utilizing low level refrigeration to freeze fish and a customer utilizing high level refrigeration in a cold storage warehouse.
  • low level refrigera- tion is recovered at a temperature below about -40°F and high level refrigeration is recovered at a temperature below about 20°F.
  • pump 60 may discharge into line 42 just before it enters air cooler 43.
  • a water-cooled exchanger could be used in place of air cooler 43.
  • the cold gas in line 32 may flow through a single exchanger, replacing exchangers 33 and 75, in countercurrent relation to a heat transfer fluid entering the warm end of the exchanger and exiting at an intermediate portion of the exchanger where another heat transfer fluid would enter for flow to, and withdrawal from, the cold end of the exchanger.
  • the first mentioned heat transfer fluid would convey refrigeration to the customer requiring high level refrigeration and the other heat transfer fluid would convey refrigeration to the customer requiring low level refrigeration.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Separation By Low-Temperature Treatments (AREA)

Abstract

Selon la figure 1 la réfrigération est réalisée lors de la livraison d'un gaz (20) d'un pipeline de transmission à pression élevée à un pipeline de dérivation à pression inférieure grâce à l'expansion du gaz dans un turbo-détendeur (29) pour atteindre une pression inférieure à celle du pipeline de dérivation (47) et en obtenant la réfrigération au moyen du gaz détendu, qui est ensuite comprimé par un compresseur centrifuge (41) entraîné directement par le turbo-détendeur (29) pour atteindre la pression requise en vue de son introduction dans le pipeline de dérivation (47). Le gaz (20) est déshydraté par l'adjonction de méthanol par une pompe (24), et par la séparation dans le séparateur (31) du condensat de méthanol aqueux du gaz détendu, le condensat étant distillé dans la colonne (55) à l'aide de chaleur de compression dans le rebouilleur (64) afin de récupérer le méthanol pour une utilisation ultérieure.
EP19850905474 1985-10-22 1985-10-22 Refrigeration d'un gaz provenant d'un pipeline. Withdrawn EP0244400A4 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US1985/002079 WO1987002758A1 (fr) 1985-10-22 1985-10-22 Refrigeration d'un gaz provenant d'un pipeline

Publications (2)

Publication Number Publication Date
EP0244400A1 true EP0244400A1 (fr) 1987-11-11
EP0244400A4 EP0244400A4 (fr) 1988-10-20

Family

ID=22188897

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19850905474 Withdrawn EP0244400A4 (fr) 1985-10-22 1985-10-22 Refrigeration d'un gaz provenant d'un pipeline.

Country Status (2)

Country Link
EP (1) EP0244400A4 (fr)
WO (1) WO1987002758A1 (fr)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2103354A (en) * 1981-08-03 1983-02-16 Olajipari Foevallal Tervezoe Gas transfer station
US4522636A (en) * 1984-02-08 1985-06-11 Kryos Energy Inc. Pipeline gas pressure reduction with refrigeration generation

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4251249A (en) * 1977-01-19 1981-02-17 The Randall Corporation Low temperature process for separating propane and heavier hydrocarbons from a natural gas stream
US4419114A (en) * 1982-04-19 1983-12-06 Sappsucker, Inc. System and method for converting wellhead gas to liquefied petroleum gases (LPG)

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2103354A (en) * 1981-08-03 1983-02-16 Olajipari Foevallal Tervezoe Gas transfer station
US4522636A (en) * 1984-02-08 1985-06-11 Kryos Energy Inc. Pipeline gas pressure reduction with refrigeration generation

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of WO8702758A1 *

Also Published As

Publication number Publication date
WO1987002758A1 (fr) 1987-05-07
EP0244400A4 (fr) 1988-10-20

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Inventor name: WEISS, IRVING

Inventor name: SCHORR, HANS, P.