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WO1997019151A1 - Melanges pour le transport de gaz par pipelines - Google Patents

Melanges pour le transport de gaz par pipelines Download PDF

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Publication number
WO1997019151A1
WO1997019151A1 PCT/CA1996/000749 CA9600749W WO9719151A1 WO 1997019151 A1 WO1997019151 A1 WO 1997019151A1 CA 9600749 W CA9600749 W CA 9600749W WO 9719151 A1 WO9719151 A1 WO 9719151A1
Authority
WO
WIPO (PCT)
Prior art keywords
pressure
psia
ethane
temperature
gas
Prior art date
Application number
PCT/CA1996/000749
Other languages
English (en)
Inventor
Ian Morris
Glen Perry
Original Assignee
665976 Alberta Ltd.
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 665976 Alberta Ltd. filed Critical 665976 Alberta Ltd.
Priority to AU74884/96A priority Critical patent/AU7488496A/en
Priority to CA002205670A priority patent/CA2205670C/fr
Publication of WO1997019151A1 publication Critical patent/WO1997019151A1/fr
Priority to US08/895,583 priority patent/US6201163B1/en
Priority to US09/733,919 priority patent/US20010007915A1/en

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
    • C10L3/00—Gaseous fuels; Natural gas; Synthetic natural gas obtained by processes not covered by subclass C10G, C10K; Liquefied petroleum gas
    • C10L3/06—Natural gas; Synthetic natural gas obtained by processes not covered by C10G, C10K3/02 or C10K3/04

Definitions

  • This invention relates to the transfer by pipeline of mixtures which contain methane or natural gas
  • methane is the largest component of natural gas, and usually accounts for at least 95% by volume ot what is known as "transmission specification" natural gas
  • transmission specification natural gas Other usual components are ethane (usually about 2%), propane (usually about 0 5%), butanes, pentanes and possibly hexanes (altogether amounting to less than about 0 3%), with the balance being nitrogen and carbon dioxide
  • transmission specification natural gas will be hereinafter called "natural gas”
  • the natural gas as transmitted through the pipelines of TransCanada Pipeline Limited from Alberta, Canada to Ontario, Canada has typically the following percentage composition by volume
  • T temperature of the gas
  • the Ideal Gas Equation does not give exactly correct results in actual practice, because gases are compressible. Gas molecules, when compressed, pack more tightly together than would be predicted by the Ideal Gas Equation, because of intermolecular forces and molecular shape. To correct for this, an added term, the compressibility factor z, can be added to the Ideal Gas Equation. This is a dimensionless factor which reflects the compressibility of the particular gas being measured, at the particular temperature and pressure conditions.
  • the compressibility factor is sufficiently close to 1.0 so that it can be ignored for most gases, and so that the Ideal Gas Law can be used without the added term z
  • the z term can be different enough from 1.0 so that it must be included in order for the Ideal Gas Equation to give correct results.
  • the deviation of a natural gas from the Ideal Gas Law depends on how far the gas is from its critical temperature and critical pressure.
  • T R and P R known as reduced temperature and reduced pressure respectively
  • T the temperature of the gas in degrees
  • T c the critical temperature of the gas in degrees
  • P the pressure of the gas in psia
  • P c the critical pressure of the gas in psia
  • Critical pressures and critical temperatures for pure gases have been calculated, and are available in most handbooks. Where a mixture of gases of known composition is available, a pseudo critical temperature and pseudo critical pressure which apply to the mixture can be obtained by using the averages of the critical temperatures and critical pressures of the pure gases in the mixture, weighted according the percentage of each pure gas present.
  • the compressibility factor z can be found by use of standard charts.
  • One of these is "Compressibility Factors for Natural Gases" by M.D. Standing and D.L. Katz, published in the Engineering Data Book, Gas Processors Suppliers Association, 10th edition (Tulsa, Oklahoma, U.S.A.) 1987.
  • Natural gas like methane, shows z factor changes with pressure. However, the z factor does not decrease as much with pressure for natural gas as it does for pure methane. Thus, natural gas containing 2% ethane and 0.5% propane cannot be packed as tightly as methane alone at a given pressure, and needs more energy to compress or pump than methane alone. If the amount of ethane in the natural gas is increased to 4%, the z factor drops still less with pressure, so that the gas is still more difficult to compress or pump and cannot be packed as tightly at a given pressure as could pure methane. (All percentages in this document are percentages by volume).
  • ethane is the additive, enough ethane must be added to methane or natural gas to give a gas composition having a minimum of about 26% ethane for operation at 1 ,000 psia and normal temperatures (-40°F to +110°F) Ethane can be added until just before the mixture separates into separate gas and liquid (which occurs at about 40% ethane for a pressure 1 ,000 psia and a temperature of about 35°F) To reduce the danger of liquefaction if there is inadvertent pressure drop, and to reduce temperature extremes, generally operation at 26-35% ethane and 35°F to +40°F is preferred.
  • an amount is added to give a gas which has at least 26% ethane (but preferably 35% ethane) at 1 ,000 psia, and at least 6% ethane (but preferably 15% ethane) at 2,200 psia, with the minimum percentage of ethane decreasing smoothly with rise in pressure.
  • Ethylene may be substituted for all or part of the ethane on a 1 :1 volume basis.
  • pressure indicated is the maximum pressure to which the gas is compressed. In such a compression-rarefaction arrangement, it is preferred that the ratio between the most compressed and the most rarefied pressures of the gas not exceed 1.25:1.
  • C 3 hydrocarbons alone can also be used as the additive.
  • Minimum useable percentage of the total gas mixture vary from a minimum of 5% at 1 ,000 psia to about 3% at 2,200 psia. Maximum amounts are those which will not cause separation of a Iiquid phase at the temperature used
  • the C 3 hydrocarbons may be any of propane, isopropane or propylene, separately or in admixture.
  • One or more C 3 hydrocarbons may also be substituted, preferably on a 1 :3.5 volume basis, for C 2 hydrocarbons, but not to a point where they cause separation of a Iiquid phase at the pressure and temperature of operation.
  • a 1.3.5 basis means that each standard volume of C 3 hydrocarbon replaces three and a half standard volumes of C 2 hydrocarbon.
  • the limitation that a Iiquid phase should not be formed means that not more than about 12% of C 3 hydrocarbons should be present at 1000 psia and 60°F, and lesser amounts should be used as the pressure or temperature increases.
  • C 2 or C 3 additives Two or more of the C 2 or C 3 additives can also be used.
  • the use of two or more additives has a synergistic effect in many cases, so that less than the minimum amount of each is needed than would be needed if only one were present, in order to produce the z factor over that of an equivalent standard volume of natural gas at the pressure and temperature involved.
  • C 4 hydrocarbons do not contribute much to the improvement of the z factor, because an amount which would be large enough to cause a reduction of the z factor is also large enough to liquify, which is undesirable.
  • C 4 hydrocarbons are not additives contemplated by this invention, however C 4 hydrocarbons which are already present in the natural gas need not be removed if they are present in insufficient quantity to liquify.
  • the presence of more than 1 % C 4 hydrocarbon in the mixture is not preferred, however, as C 4 hydrocarbons tend to liquify easiiy at pressures between 1 ,000 psia and 2,200 psia, and more than 1 % C 4 hydrocarbons give rise to increased danger that a Iiquid phase will separate out.
  • C 4 hydrocarbons also have an unfavourable effect on the mixture's z factor at pressures just under 900 psia, so care should be taken that, during transport through a pipeline, that mixtures according to the invention which contain C 4 hydrocarbons are not allowed to decompress to less than 900 psia, and preferably not to less than 1 ,000 psia.
  • the z factor becomes Iower than that of methane.
  • the z factor continues to get smaller with increased percentages of ethane, to the point where further increase of ethane causes separation of a Iiquid phase (at about 40% ethane at 1 ,000 psia and 35°F).
  • adding ethane to natural gas so that there is a mixture containing more than 26% ethane at 1 ,000 psia and 35°F leads to increased packing of molecules and hence decreased pumping costs and more ability to store within a given volume.
  • liquid phase in this disclosure is meant the avoidance of enough liquid to provide a coherent liquid phase in the pipeline at the temperatures and pressures used Such a phase can create pipeline problems through pooling in low portions of the pipeline or forming liquid slugs which affect pumping efficiency A few iiquid droplets in the line however, can Ue tolerated
  • Figures 1A to 1E are plots of capacity gain in percent against the content of C 2 hydrocarbons in a mixture of methane and ethane Each of the plots shows the results at a different pressure
  • Figures 2A and 2B are plots of capacity gain versus temperature (in degrees Fahrenheit) for pipelines at 800 psia and 1 ,675 psia respectively
  • Figure 3 is a summary of pipeline horsepower requirements for various gas mixes, using a 36" pipeline operating at a maximum operation pressure of 1 ,740 psia, an inlet temperature of 80°F and a ground temperature of 32°F
  • Figure 4 is a plot of the horsepower requirements per thousand cubic feet of gas showing different mixtures of ethane and methane, at different pressures
  • FIG. 1A it is seen that, for an 800 psia pipeline, the best packing occurs when trie line is filled with pure methane. As ethane is added, the packing steadily falls (and the capacity gain percent decreases) until there is about 25% ethane in the line. After this, the capacity gain begins to increase again, but it does not reach the levels obtained for pure methane.
  • Figure 1B shows the effect of addition to methane of ethane for a pipeline at 1 , 150 psia.
  • the capacity gain steadily decreases from 0% ethane to about 12% ethane, and then increases again. After approximately 25% ethane, the capacity gain is greater than occurred with no ethane at all.
  • Figure 1 C shows that this effect is even more pronounced when the pipeline pressure is increased to 1 ,350 psia.
  • Figure 1 D shows that at 1 ,760 psia, the lowest capacity occurs at about 5%, and anything over 12% ethane gives a better capacity gain than is attainable with natural gas or methane alone. For best results, however, at least 15% ethane should be present.
  • Figure 1 E the addition of about 4% ethane gives a benefit, and the benefit steadily increases all the way up to the point at which the ethane begins to separate out in a Iiquid phase. For best results, however, at least 12% ethane, and preferably 15% ethane, should be present.
  • Figure 2 snows how the effect changes with temperature Even at 600 psia ( Figure 2A) there is a capacity increase (i e better packing) as temperature drops, and the capacity gain is greater the more C 2 that is present However, the effect is not nearly as significant as at higher pressures With higher pressure ( Figure 2B) the capacity gain is much greater with temperature, and the improvement in capacity gain becomes still greater as increased amounts of ethane are added Generally, therefore, it is preferred to operate at a relatively low temperature, such as 70° to -20°F Higher temperatures (e g up to about 120°F) can be tolerated, but detract from the benefits of the invention
  • Figure 3 shows horsepower required for different gas mixes of ethane and methane, through a pipeline at a maximum pressure of 1 ,740 psia and a minimum pressure of 1 ,350 psia
  • Figures are for a pipeline of 36" in diameter and a length of 1 ,785 miles, with pumping stations located every 56 miles
  • a throughput of 2 0 million, standard cubic feet per day a mixture of 98% methane and 2% ethane (which corresponds to ordinary natural gas) would require 812,579 horsepower
  • the same standard volume of gas, but containing 35% C 2 can be moved with only 661 ,860 horsepower, for a saving of over 150,000 horsepower
  • the throughput is raised to 2 5 million standard cubic feet, natural gas containing 2% ethane cannot practically be transmitted, because the velocities and temperatures involved are too great
  • gas with 6% ethane can be transmitted, and gas with 35% ethane shows a saving of over 500,000 horsepower over that which is
  • Figure 4 also shows the negative effect of adding ethane to a typical pipeline running at about 800 psia pressure and 35°F Required power for pumping increases until the mix contains 26% ethane and then decreases for higher concentrations approaching the liquid phase limits
  • the decrease is not sufficient so that, by the concentration where iiquefactio ⁇ occurs aoout 40%; there is any saving of horsepower over pumping ordinary natural gas
  • This energy hill however peaks at decreasing concentrations of ethane as operational pressure increases, e g , 14% at 1 , 150 psia, 8% at 1 ,350 psia, 6% at 1 ,475 psia This is due to the rate of decrease in the value of the z factor overcoming the rate of increase in density
  • the preferred composition of the resulting gas is as follows.

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  • Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Pipeline Systems (AREA)
  • Filling Or Discharging Of Gas Storage Vessels (AREA)

Abstract

A des pressions supérieures à 1000 psia, il est avantageux d'ajouter au gaz naturel un additif qui est un composé d'hydrocarbures C2 ou C3 ou un mélange de ce type de composés. Au-dessus d'une limite inférieure (qui varie en fonction de l'additif ajouté et de la pression), ceci permet d'obtenir un facteur z moindre, ce qui représente un compactage accru des molécules, et permet donc de réduire le niveau de puissance nécessaire pour pomper le mélange ou le comprimer.
PCT/CA1996/000749 1995-11-17 1996-11-18 Melanges pour le transport de gaz par pipelines WO1997019151A1 (fr)

Priority Applications (4)

Application Number Priority Date Filing Date Title
AU74884/96A AU7488496A (en) 1995-11-17 1996-11-18 Mixtures for pipeline transport of gases
CA002205670A CA2205670C (fr) 1996-11-18 1997-05-16 Methode de transport par pipeline
US08/895,583 US6201163B1 (en) 1995-11-17 1997-07-16 Pipeline transmission method
US09/733,919 US20010007915A1 (en) 1995-11-17 2000-12-12 Pipeline transmission method

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US56040295A 1995-11-17 1995-11-17
US08/560,402 1995-11-17

Related Parent Applications (1)

Application Number Title Priority Date Filing Date
US56040295A Continuation-In-Part 1995-11-17 1995-11-17

Related Child Applications (1)

Application Number Title Priority Date Filing Date
US08/895,583 Continuation-In-Part US6201163B1 (en) 1995-11-17 1997-07-16 Pipeline transmission method

Publications (1)

Publication Number Publication Date
WO1997019151A1 true WO1997019151A1 (fr) 1997-05-29

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PCT/CA1996/000749 WO1997019151A1 (fr) 1995-11-17 1996-11-18 Melanges pour le transport de gaz par pipelines
PCT/CA1996/000750 WO1997019152A1 (fr) 1995-11-17 1996-11-18 Melanges conçus pour le stockage et le transport par pipeline de gaz

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PCT/CA1996/000750 WO1997019152A1 (fr) 1995-11-17 1996-11-18 Melanges conçus pour le stockage et le transport par pipeline de gaz

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AU (2) AU7488596A (fr)
CA (1) CA2235140A1 (fr)
WO (2) WO1997019151A1 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998053032A1 (fr) * 1997-05-16 1998-11-26 Jl Energy Transportation Inc. Procede et produit de stockage du gaz
WO1998053031A1 (fr) * 1997-05-16 1998-11-26 Jl Energy Transportation Inc. Procede de transport par pipeline
US6201163B1 (en) 1995-11-17 2001-03-13 Jl Energy Transportation Inc. Pipeline transmission method
CN103335682A (zh) * 2013-07-15 2013-10-02 成都千嘉科技有限公司 一种天然气的气体流量计量方法

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA2339859A1 (fr) * 2001-02-05 2002-08-05 Glen F. Perry Systeme et produit de transport de gaz naturel

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1415729A (en) * 1973-10-09 1975-11-26 Black Sivalls & Bryson Inc Method of and system for vaporizing and combining a stream of liquefied cryogenic fluid with a gas stream
US5315054A (en) * 1990-10-05 1994-05-24 Burnett Oil Co., Inc. Liquid fuel solutions of methane and liquid hydrocarbons

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1415729A (en) * 1973-10-09 1975-11-26 Black Sivalls & Bryson Inc Method of and system for vaporizing and combining a stream of liquefied cryogenic fluid with a gas stream
US5315054A (en) * 1990-10-05 1994-05-24 Burnett Oil Co., Inc. Liquid fuel solutions of methane and liquid hydrocarbons

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6201163B1 (en) 1995-11-17 2001-03-13 Jl Energy Transportation Inc. Pipeline transmission method
WO1998053032A1 (fr) * 1997-05-16 1998-11-26 Jl Energy Transportation Inc. Procede et produit de stockage du gaz
WO1998053031A1 (fr) * 1997-05-16 1998-11-26 Jl Energy Transportation Inc. Procede de transport par pipeline
AU747206B2 (en) * 1997-05-16 2002-05-09 Jl Energy Transportation Inc. Pipeline transmission method
CN103335682A (zh) * 2013-07-15 2013-10-02 成都千嘉科技有限公司 一种天然气的气体流量计量方法
CN103335682B (zh) * 2013-07-15 2015-07-15 成都千嘉科技有限公司 一种天然气的气体流量计量方法

Also Published As

Publication number Publication date
AU7488596A (en) 1997-06-11
AU7488496A (en) 1997-06-11
CA2235140A1 (fr) 1997-05-29
WO1997019152A1 (fr) 1997-05-29

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