MAY 1982
`
`ISSN 0018-8190
`
` fi
`Hydrocarhom
`fatOCesSsingE ,
`
`i PILOT EXHIBIT 2008, PAGE1
`
`PILOT EXHIBIT 2008, PAGE 1
`
`

`

`f'}o -r
`1tit0
`Hydrocarbon Processing®
`
`Vol. 61
`
`No. 5
`
`May 1982
`
`Y Chauvin, J. Gaillard, J. Leonard, P. B onnif ay & J. W. Andrews 110
`
`105
`
`Optimize energy usage in phthalic anhydride units
`
`,yd,oc,..,, '""""''
`
`
`Registered U.S. Patent Office
`"
`
`by Gulf Publishing Company
`
`Copyright © 1982 by Gulf Publishing Co. All
`
`
`
`
`rights reserved.
`
`SPECIAL REPORT: NP RA/GPA/ API MEETINGS
`& j. D. Elliott 99 Delayed coking: latest trends R. DeBiase
`
`
`
`
`
`Building to handle more resid
`
`
`D. P. Teichman, A.G. Bridge & E. M. Reed
`
`Another use for Dimersol
`Departments
`
`
`
`
`
`
`Advertisers ............. 359
`TBA aids methanol/fuel mix
`
`
`Classified ads ........... 353
`
`
`E.G. Guetens,jr.,J. M. Dejovine & G.J. Yogis
`113
`Editorial
`
`Upgrade resld or shut
`
`Improve construction safety R. L. Bru.nner
`118
`
`
`down your refinery ...... 93
`D. J. Willette 120
`
`Profile: safety system in action
`
`
`Free llterature capsules .. 350
`for high CO2 removal C. S. Goddin 125
`Pick treatment
`
`HP Impact ............... 11
`Letters to the editor ...... 95
`
`
`Process improves acid gas separation
`New developments In
`
`A. S. Holmes,]. M. Ryan, B. C. Price & R. E. Styring 131
`products, services
`C. j. Wormald 137
`Thermo data for steam/hydrocarbons
`am:J free technical
`
`literature ............. 331
`
`
`Extraction upgrades resid
`
`Reader services ......... 329
`
`R. T. Penning, A. G. Vickers
`& B. R. Shah
`Who's building In HPI ..... 39
`
`
`Shutdown systems for better managed process
`T. Rhodes
`operations
`
`Engine trends: Impact on refining
`155
`
`
`J.D. Dickson, F. P. Frederick & R. W. Hurn
`
`
`Using computers as robots for refining operations
`160
`J. P. Kennedy
`Cover: Chalmette, La. re­
`
`in the 1980s T. S. Govindan 165
`Energy management
`
`finery by B.J. Nixon. Photo
`courtesy Tenneco, Inc.,
`Houston.
`
`
`
`
`A. de Virgiliis & A. Gerund.a
`Ethanol versus naphtha under Brazil's economy
`
`
`N. R. Luchi & S. C. Trindade
`
`
`natural with varying Control NH3 process
`
`gas LHV F. Yazhari
`gas drying costs E. L. Ezell & j. F. Gelo
`Cut cracked
`
`
`
`Finite element analysis aids nonclrcular
`M. S. Kalsi & D. C. Guerrero
`valve specification
`
`
`
`Evaluation of percent critical damping of
`Hydrocarbon Processing is published
`
`
`
`
`J110nthly. Second class postage paid at Hous­
`
`process towers
`ton, Texas.
`K.C. Karamchandani, N. K. Gupta & J. Pattabiraman
`
`
`
`Effective pressure relief of offsite piping T. Uchiyama
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`.to libraries and others registered with the
`to find hot spots A. G. lmgram & j. B. McCandless
`219
`Use infrared
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`Copyright Clearance Center (CCC) to photo·
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`copy any articles herein for the base fee of $1
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`A better way to revise piping and instrument diagrams
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`per copy of the article plus 35 cents per page.
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`J. Williams
`
`21 Congress St.. Salem, Mass. 01970. Copy­
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`ence use without express permission is pro­
`MANAGEMENT GUIDELINES
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`Aids to effective negotiation
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`SAFETY GUIDELINES
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`Beware of the hazards in new technologies
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`297
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`
`Hydrocarbon Processing, May 19823
`
`PILOT EXHIBIT 2008, PAGE 2
`
`

`

`Best Papers From
`
`NPRA, GPA and API
`
`Process improves acid
`
`
`gas separation
`
`
`
`
`
`Ryan/Holmes cryogenic processes
`
`1,300
`
`1,200
`
`
`
`overcome roadblocks to distillation of
`1,100
`C1-C02, C2-C02 and C02-H2S systems
`
`1,000
`
`900 "'
`'lg_ 800
`
`,
`
`Mixture convergenc,-.--,
`
`
`
`(critical) locus /
`/
`// (V+ L)
`I
`I
`
`CO2 critical
`point
`
`700
`A. S. Holmes and J. M. Ryan, Koch Process Systems,
`
`
`
`Inc, Westboro, Mass., and B. C. Price and R. E. Styring,
`600
`
`
`ARCO Oil and Gas Company, Dallas, Texas.
`500
`400
`e
`
`
`CARBON DIOXIDE SEPARATES CLEANLY from trouble­
`if (S(COJ+
`
`
`
`some systems when distillation additives are strategi­
`V)
`300
`
`
`cally used. This technique is used in patented Ryan/
`200
`
`
`Holmes Processes for three otherwise now impossible
`100
`distillations:
`
`I
`
`Q.
`
`point (V + L + SJ
`2 triple
`
`0
`-150 -100 -50 0 50
`100 150
`-200
`
`Temperature, °F
`
`Fig. 1 -Phase diagram, CH,-CO2 binary.
`
`•Processing gases from EOR fields.
`
`•Methane from carbon dioxide
`
`•Carbon dioxide from ethane and heavier liquids
`
`
`
`
`
`•Carbon dioxide from hydrogen sulfide mixtures.
`
`A number of additives can be used in these processes,
`
`
`
`but NGL's normally found at plantsite are preferred.
`Atlantic Richfield has concluded a license agreement
`
`
`
`
`
`
`
`Process performance is technically outstanding since
`
`
`to assure that these processes will be used full scale in
`from a C/CO/H2S stream
`
`methane is produced directly
`
`
`their EOR operation at the Willard unit, Wasson Field.
`
`
`
`to meet either pipeline specifications or LNG feed re­
`
`
`
`quirements, and carbon dioxide suitable for pipelining
`
`
`can be produced with good ethane recovery from a CO/
`C/H2S stream.
`
`
`
`Process economics and operability show
`Increasing need to separate methane from carbon
`
`
`
`
`
`
`dioxide while removing hydrogen sulfide occurs in sev­
`
`
`advantages over physical absorption.
`
`
`
`
`eral situations, including gas treatment at fields using
`
`
`Three industrial opportunities now exist:
`
`
`
`
`enhanced oil recovery by carbon dioxide miscible flood­
`
`
`
`•Upgrading natural gas containing large amounts
`
`
`
`ing. In other operations, it is necessary to separate eth­
`of CO2 and H2S
`
`
`ane from carbon dioxide. These separations have in­
`
`
`•Achieving high NGL recovery m treating
`
`
`
`
`herently difficult characteristics that make simple distil­
`
`hydrocarbon-rich sour gases
`
`lation unacceptable.
`
`THE PROBLEMS
`
`
`
`
`
`Hydrocarbon Processing, May 1982 131
`
`PILOT EXHIBIT 2008, PAGE 3
`
`

`

`100
`
`Q)
`1/)
`Ol
`.s::
`
`. !2"
`
`10
`a. -0 ·5
`C ·,.0
`Q) �
`Q) 0 ::E
`
`()
`
`C:
`
`Q)
`a.
`
`
`ubility limit of CO2
`• Left of and above this line, solid CO2
`
`
`
`is formed. Conversely, below and to the right, vapor­
`
`
`
`
`liquid equilibrium exists and no solid formation is ob­
`pressure
`
`
`served. The curved lines show calculated tray-to-tray,
`500psia
`600psia
`
`
`
`point-to-point conditions for the liquid phase ranging
`-715psia
`
`with low CO2 content at the
`from cold temperatures
`
`
`upper end of a column to warmer temperatures and
`
`
`
`The of a column. high CO2 content at the lower end
`
`
`
`dashed portions are liquid compositions which ignore
`
`
`the possibility of solid formation. Their conditions ex­
`
`ceed solubility limit. The column will freeze here .
`
`
`Unless operation is above 705 psia (the tip of the solid
`CO2 boundary,
`
`Fig. 1), distillation will always pass
`
`
`through the solids formation to go from a high CO2
`
`
`
`mixture to pure methane. Operation at 715 psia could
`avoid solid CO2 formation,
`
`however, the limit on meth­
`
`
`ane purity is set by how close to the mixture critical one
`• The
`
`
`
`wishes to operate. The mixture critical is 2% CO2
`be 5 to 15% CO2•
`
`practical limit would probably
`of CO2 from C2 + hydrocarbons. Distillation
`Separation
`of ethane from CO2 is limited
`
`by formation of an azeo­
`of 67% CO2 and
`
`trope at an approximate composition
`33% ethane.
`
` This azeotrope does not significantly
`
`
`
`change in composition with different operating pres­
`
`
`
`sures (Fig. 3), therefore, distillations from either side of
`
`
`
`the azeotrope is limited by the azeotrope composition.
`
`A . Solubility limit
`
`B . Limit of
`distillation
`conditions No solid CO2
`zone
`
`·9
`
`8
`
`- � - -�- �
`����-�
`0.1 �-�--�-
`-200 -180 -160 -140 -120 -100 -80
`-60
`
`Temperature, °F
`CH.-C02 binary.
`Fig. 2-Distillation profile,
`
`
`15Q,---;.----.- -,--- ""'T - -- --,- - - - ,-- - - --,
`of methane and CO2• Based on relative vol­
`
`Separation
`1 1
`Column solution
`
`
`atility, separation of methane from CO2 by distillation
`I
`Feed: Btms. of C1 -CO2 column
`
`
`
`should be easy. At typical demethanizer conditions rela­
`125
`CO2 60.2%
`I
`V
`
`
`
`tive volatility is approximately 5 to 1; however, at deme­
`C2 17.5%
`I
`
`
`thanizer conditions, CO2 co-exists
`as vapor and solid
`\
`C3 22.1%
`\
`
`phases in some section of the column if CO2 is suffi­
`
`Additive: Multicomponent ct
`\ \
`Column 400 psia
`
`ciently concentrated.
`100
`i
`
`The problem of CO2 solid formation
`in a distillation
`\ \
`
`
`
`column becomes evident by examination of a phase dia­
`\ \
`gram for the methane-CO
`2 binary1
` (Fig. 1). Single
`\ \
`
`component lines for methane and CO2 vapor-liquid
`
`equilibrium are shown as the left-and right-hand
`75
` �
`\ �
`
`
`boundaries of the phase diagram ending at the critical
`\ \
`:, �
`
`
`
`points for these components. The unshaded area in be­
`
`
`tween these two boundaries is the area of coexistence of
`a. E
`'',
`
`
`
`
`equilibrium vapor and liquid phases of the binary mix­
`Q) .....
`','
`
`
`
`tures. The shaded area in the lower left-hand portion of
`50
`
`
`this figure represents the particular problem area
`',"
`' ' """e ••• "::·��' .
`
`
`where phases in equilibrium consist of a binary vapor
`and solid CO
`present.
`
`Operation here has solid CO
`
`
`
`Because the tip of this area extends to a higher pres­
`25
`
`
`
`sure (approximately 705 psia) than the critical pressure
`
`
`of methane, there is no way to go from a composition of
`
`
`pressure without high CO2 to pure methane at constant
`
`
`
`passing through this solid region. A number of combi­
` operat­
`
`
`nations of single and double column systems
`0
`
`
`ing at different pressures have been proposed.
`
`
`
`
`However, these schemes involve operation close to the
`
`
`2 mixtures critical or to
`
`
`methane critical, or methane-CO
`CO2 - C2 bi nary
`335psia
`
`
`
`CO2 freezing conditions. They also require high energy
`--�-- -�
`-25 �--�---�---�
`
`
`
`use and capital. Therefore, they are uneconomic com­
`0
`0.2 0.4 0.6 0.8
`1.0
`pared to other CO
`
`removal systems.
`CO2 mole fraction COz
`Figure 2 shows the solid barrier as solubility limits of
`
`
`
`C02+C2
`solid CO2 in CO2-methane
`
`
`liquid mixtures. The line ex­
`C02-C2•
`
`Fig. 3 - Vapor-liquid equilibria,
`
`
`
`tending diagonally across the figure represents the sol-
`132 Hydrocarbon
`
`May 1982
`Processing,
`
`Azeotrope
`
`•7
`5•6
`
`2
`
`u.. 0
`
`Q)
`
`•4
`•3
`•2
`
`2.
`
`2
`
`PILOT EXHIBIT 2008, PAGE 4
`
`

`

`Solubility (freeze) data
`
`
`
`• C1-CO2
`■ C2-CO2
`• C3-C02
`o C1-CO2-C2
`V C1-C02-C3
`o C1-CO2-C2-C3
`
`100r-- -.- - -.---- �--�----
`
`
`Solubility (freeze) data
`• C1-CO2
`■ C2-CO2
`• C3-CO2
`o C1-CO2-C3
`v C1-CO2-C3
`o C1 - CO2-C2-C3
`
`-::::::•• 2
`
`C,1,2
`theo. tray
`
`/·· t•· nC4 additive
`__ ..
`
`mole/100 mole
`
`feed
`
`0
`
`VO
`
`C
`
`0
`(.)
`
`c Q)
`e Q)
`
`a.
`Q)
`0
`:iE
`
`Feed 50% C1, 50% CO2
`Column 600 psia
`nC4 added to condenser
`
`Freeze line for
`C1-CO2-C4
`
`I
`I
`/0.98% COPHD
`I
`C
`
`Feed: N2 4.8%
`C1 25.7%
`CO2 50.0%
`c; 19.5%
`Column 600 psia
`nC4 added to condenser
`
`8 moles/100 moles feed
`
`_ __Jc_ _ __,__
`0.1 --�--�
`- '------'----'- - --'
`0.1 �---'----'---�-
`__
`_._ __
`,__ _ __,
`-200 -180 -160 -140 -120 -100 -80 -60
`-200 -180 -160 -140 -120 -100 -80 -60
`
`Temperature, °F
`
`Temperature, °F
`
`
`Fig. 4 - Distillation profile, binary feed with nC, additive.
`
`Fig. 5 - Distillation profile, multicomponent feed with nC, additive.
`
`In cases where feed contains substantial quantities of
`
`
`
`bottoms product containing less than I% methane. Op­
`
`
`
`
`
`erating conditions of this column pass through a signifi­
`
`
`
`ethane, it is often desirable to recover ethane with the
`
`cant portion of the solid CO2 formation region. This
`
`
`
`other NGL components as a salable product. A plot of
`
`
`
`indicates that distillation is not possible and that solid
`
`
`
`
`the vapor-liquid equilibria of a typical bottoms composi­
`CO2 forms.
`
`
`tion from the demethanizer column (dotted line, Fig. 3)
`
`
`shows that a pure CO2 bottoms product could be made
`The next curve to the right shows a significant im­
`
`
`from the distillation column but that the overhead
`
`
`provement in column operation with only a small
`
`
`amount of n-butane added to the condenser. (4 moles
`
`
`
`product would be limited to the azeotrope composition
`
`
`per 100 moles of feed.) The tray profile barely enters
`
`
`which would contain essentially all the ethane.
`
`
`into the freeze zone. Subsequent distillation curves
`of CO2 and H2S. In the separation of CO2
`
`Separation
`
`
`
`show further shifting away from freezing as additional
`
`
`
`
`vol­from H2S, distillation is difficult because the relative
`
`
`
`amounts of n-butane are added to the column. There­
`
`
`
`
`atility between the substances is quite small. While an
`
`
`
`fore, the designer or the operator can specify a close­
`
`CO2 and H2S does not exist, vapor­
`
`azeotrope between
`
`
`ness of approach to freezing which sets a corresponding
`
`
`
`
`
`liquid equilibrium approaches azeotrope character at
`
`amount of additive to be fed to the top of the column.
`high CO2 concentrations.
`
`
`Figure 5 goes a step further in illustrating the role of
`
`
`
`
`additive for avoiding freezing. The actual freeze line is
`
`drawn to the left and above the most conservative freeze
`
`
`line that we had before. This actual freeze line is based
`
`
`
`
`on data for certain applicable ternary systems of meth­
`The Ryan/Holmes approach to these distillations is to
`
`
`
`
`12 This illustrates the beneficial
`ane, CO2 and n-butane.
`
`
`
`add a suitable agent to the distillation in order to signifi­
`+ hy­
`
`
`
`shift for multicomponent systems which include C
`
`
`
`cantly alter the system. These additives are normally
`
`
`
`drocarbons in addition to methane and CO2•
`
`of C3 + hydrocarbons, which are ob­
`simple mixtures
`Other NGL hydrocarbons demonstrate similar be­
`
`
`
`
`
`
`tained by distillation and separation from the feed mix­
`
`
`havior. Tray profiles (Fig. 5) are based on a multicom­
`ture itself.
`
`ponent feed. As shown, 8 moles of additive per 100
`moles of feed are about the right amount to keep the
`
`
`demetha­2• An example is a Ryan/Holmes
`Methane-CO
`0.98% CO2 overhead
`
`
`operation out of the conservative
`
`
`nizer column with a pure n-butane additive, (Fig. 4).
`freeze zone. The 2.4% CO2 overhead
`profile is just in­
`
`The solid diagonal line (Fig. 4) is the most conservative
`
`
`
`side the conservative freeze zone, but nonfreezing rela­
`
`boundary that can be drawn from all of the available
`
`
`tive to the freeze limit for butane-containing mixtures.
`
`ty.11,12 The solid tray profile line
`data on CO2 solubili
`
`
`The 2.4% profile shows that the closest approach to
`
`shows a binary C1-CO2 distillation
`
`
`without additive pro­
`
`
`
`
`
`freezing occurs in the condenser (point "C") whereas, in
`2% CO2 and a
`
`
`ducing a methane top product containing
`
`10
`
`
`
`RYAN/HOLMES APPROACH
`
`2
`
`May 1982 133
`
`Hydrocarbon Processing,
`
`PILOT EXHIBIT 2008, PAGE 5
`
`

`

`NGL product
`C02,Hi8
`CO2 product
`Sales gas product
`
`Sales gas- -- - -- --,
`product
`
`CO2 product
`
`Dry
`feed gas
`
`Dry feed gas
`
`
`
`Additive recycle
`
`Additive recycle
`
`Make-i;p additive
`
`(ii required)
`
`�-----
`
`Surplus additive
`
`(if any)
`
`
`
`
`
`Fig. 6 - Ryan/Holmes process, EOR plant.
`
`
`
`
`
`Fig. 7 - Ryan/Holmes process, low Btu gas (no H2S).
`
`A number of agents are suitable as addi­
`
`
`contrast, the 0.98% profile shows the closest approach
`
`
`CO2-ethane.
`
`
`
`tives to a distillation column to eliminate formation of
`
`on theoretical tray 1.
`ethane-CO
`
`
`azeotrope. One class particularly suitable
`
` is extremely high
`
`
`
`Volatility of methane relative to H
`
`
`
`for gas processing operations is a mixture of light hy­
`
`
`
`in the demethanizer. In separating methane from CO
`
`
`
`drocarbons such as butanes and heavier hydrocarbons.
`
`to normal pipeline quality (<2% Co
`, pipeline quality
`
`
`
`The upper dashed phase envelope (Fig. 3) indicates the
`for H
`
`
` is easily achieved. Therefore, the Ryan/Holmes
`
`
`
`demethanizer operation achieves both acid gas removal
`
`
`
`behavior of a multicomponent feed distilled with a mul­
`ethane
`
`
`
`on a COticomponent plotted c. + additive
`
`specifications simultaneously.
`
`
`
`Other advantages of NGL-based additive for the de­
`
`
`
`
`pseudo-binary basis. All ranges of composition from 0
`
`
`methanizer have also been observed:
`to 100% CO
`
`can be achieved in this mode of distillation.
`
`Volatility of CO2 to ethane remains
`above 1.0, and the
`
`
`
`•Additives significantly raise operating tempera­
`
`azeotrope is circumvented.
`
`
`tures which lowers refrigeration requirements.
`
`The top portion of the column above the additive
`
`
`
`introduction tray represents a knockback zone to re­
`
`
`•Additives increase the methane/CO
`
`relative volatil­
`
`
`duce the concentration of additive in the CO
`product.
`
`
`ity above that for the binary system.
`
`
`
`Immediately above the additive introduction point the
`
`
`
`
`•Additives permit higher pressure operation.
`
`
`
`
`
`relative volatility reverses (i.e., CO/C2 volatility< 1).
`
`
`
`The same additive compositions that are effective for
`NGL product
`can be used for CO2-ethane.
`
`demethanizer operation
`Treat Hp as
`required
`
`H2S. When H2S is present
`it must be thoroughly re­
`
`
`
`
`moved from all product streams. Typical sales gas speci­
`
`
`
`fications require < 1/4 grain of H2S per 100 cu ft and
`
`
`
`
`typical carbon dioxide specifications require< 100 ppm
`H2S in CO2 product.
`
`Finally, H2S is normally converted
`
`
`
`to elemental sulfur by the Claus process where feeds
`to a molar ratio of CO2 to H2S of
`
`are practically limited
`
`
`no more than 3 to 1. These required separations can be
`
`
`accomplished by the Ryan/Holmes processes.
`
`
`
`
`Improved separation is obtained by the addition of n­
`
`
`butane ( or other suitable additives) to the system.
`
`
`In the presence of additive, the column separating
`
`
`CO2 and ethane also benefits from a significant en­
` This
`
`
`hancement in the separation of H2S from CO
`
`
`
`
`allows carbon dioxide to be produced at substantially
`
`
`
`less cost than would be otherwise possible without addi­
`
`
`tive present. In fact, the carbon dioxide column can be
`
`
`operated to meet three separate criteria:
`
`2•
`
`.
`
`
`with respect to ethane and H
`
`•Purity of CO
`
`
`•Recovery of ethane and higher hydrocarbons
`
`2S
`
`2
`
`Dry feed gas
`
`2
`
`Additive recycle
`
`---,---�t-..
`
`
`Fig. 8
`
`
`
`- Ryan/Holmes process, combined CHJCO2 product.
`
`
`
`134 Hydrocarbon Processing,
`May 1982
`
`2-
`
`2
`
`2
`
`2
`
`2
`
`2S
`
`2)
`
`2
`
`2S
`
`CHJC02------�
`product
`
`PILOT EXHIBIT 2008, PAGE 6
`
`

`

`NGL---,
`
`•CO
` ratio control in the bottoms product.
`
`
`to H
`is the ratio of CO2 to H2S that will be
`(This ultimately
`
`removed and fed to the Claus plant.)
`
`2S
`
`2
`
`TYPICAL FLOW SCHEMES
`
`CO2
`to injectio
`n
`
`� - --
`
`Amine
`unit
`
`Fig. 6 describes a flow scheme which that can be used
`
`
`
`
`
`
`for an enhanced oil recovery project (i.e., varying CO2
`
`
`
`content in the feed and high N GL content which is to be
`
`
`recovered to the maximum economic level). This sys­
`
`
`tem consists of three columns: demethanizer, CO2 prod­
`
`
`uct column, and NGL product column.
`
`
`Dry feed is cooled by both appropriate cold products
`
`
`and refrigeration before entering the demethanizer
`Inlet Dehy- Feed
`
`
`
`column. An optimum NGL mixture for this service is
`com- dration
`chilling
`
`
`
`added in the demethanizer condenser. Product gas is
`pression
`
`
`
`
`produced overhead at essentially column pressure (nor­
`
`
`
`mally 450-650 psi) and sent to the battery limits after
`
`
`
`
`heat exchange. For LNG projects, this overhead could
`
`
`
`be fed directly to the LNG plant, resulting in significant
`TABLE 1 -EOR gas production
`
`
`
`energy and capital savings because of its low tempera­
`Mole%
`ture and high pressure.
`Early Mlddle
`is fed to the CO2 recovery column after
`
`The bottoms
`Component
`Year
`Year
`
`
`
`heat exchange. The additive NGL mixture is intro­
`.24
`.09
`
`duced to the column several trays down from the top.
`N2
`57.58 81.83
`CO2
`The CO2 product
`
`which meets required hydrocarbon
`.39
`.15
`H2S
`and H
`
`
` specifications, is produced at essentially
`16.67 6.56
`c,
`
`
`column pressure (normally 350 to 550 psig).
`8.64
`3.41
`C2
`7.38
`2.96
`
`
`Bottoms product is fed to NGL recovery. CO2 has
`C3
`1.22
`.51
`
`
`been stripped to the required ratio of CO2 to H2S. A
`iC4
`3.39
`1.47
`nC4
`
`
`
`light hydrocarbon is produced overhead which contains
`1.01
`.57
`iCs
`all the H2S and CO2 fed to the column.
`A bottom stream
`1.18
`.64
`nCs
`.84
`.61
`
`
`
`is suitable for use as an additive. A slip stream, taken
`Ce
`1.46
`1.20
`
`
`from the bottom to remove the net C4 + contained in
`c,+
`MMSCFD 12
`59
`
`feed, is mixed with net overhead for NGL product.
`
`
`
`
`The NGL product can be treated either as a liquid or
`vapor by an amine system to remove the acid gas con­
`associated gas containing small amounts of CO2• With
`
`
`
`
`
`tent. This sweetening step is significantly less expensive
`
`
`
`CO2 injection, the CO2 content of the produced gas will
`
`
`than original feed treatment would have been. Sepa­
`
`increase as CO2 breaks through
`
`in the reservoir. Even­
`
`rated acid gases can be fed directly to a Claus plant.
`tual CO
`
`content may reach the 85 to 90% range. The
`
`
`
`Many other combinations of Ryan/Holmes distilla­
`
`
`
`will be recycled to reduce the purchased COvol­
`CO
`
`
`
`tions can be envisioned. Each must be evaluated as to
`
`ume. It is desirable to remove NGLs for sales and meth­
`
`
`optimum configuration. Some variations are:
`
`
`
`ane removal may be required. Additionally, any H2S in
`the CO2 must be removed
`
`to an acceptable level (usually
`
`
`
`lean•A scheme for processing a naturally occurring
`less than 100 ppm).
`gas when H2S is not present
`(Fig. 7). Only two columns
`A processing facility for such a project must be able to
`
`
`
`
`are required, the second being an additive recovery
`
`
`handle a wide range of operating conditions. Table 1
`
`
`column which operates as a conventional distillation.
`
`
`shows an example of what might be encountered on a
`
`
`This is the least expensive configuration for the process.
`CO2 project.
`typical
`
`•A process where methane-CO
`
`2 separation is not re­
`A flow sheet for such an applicaton is shown in Fig. 9.
`
`
`quired (Fig. 8). This applies where combined methane­
`
`
`Produced gas after compression, dehydration and chill­
`
`
`
`CO2 overhead can either be reinjected, burned directly
`
`
`
`ing is fed at 500 psia. A process sequence similar to Fig.
`
`
`
`as low Btu fuel, further distilled conventionally to pro­
`6 can be used.
`
`
`duce a 7-800 Btu methane fraction, or by Ryan/Holmes
`C1 and CO2 producing a sales gas
`
`Column 1 separates
`
`
`
`
`distillation to produce a higher purity methane. Ethane
`
`or fuel with 2% CO2• Column 1 condenser operates at
`
`
`
`and heavier hydrocarbons are recovered in the bottoms
`
`
`about -120 °F. The bottoms is fed to the COcolumn,
`
`
`
`and processed in the additive recovery column.
`
`
`which is operated at 350 psia with an overhead tempera­
`ture of about 5 °F. CO2 is produced
`with 50 ppm or less
`H2S. The CO2 column bottoms
`
`contain NGLs and addi­
`Application of the processes to EOR gas processing
`
`
`
`
`tives to be recycled which are separated in the third
`
`
`and high CO2 natural gases are two examples that illus­
`
`
`
`column. The additive column can usually be designed
`
`trate the potential for full scale installation.
`
`
`to use cooling water for its condenser. The NGL prod­
`
`
`uct contains practically all the H
`
` and the residual CO
`Enhanced oil recovery projects.
`
`
`CO2 injection
`for en­
`
`unit. H2S can
`
`these are removed in an amine sweetening
`
`
`
`hanced oil recovery (EOR) is an ideal application. Can­
`didate fields for CO2 flooding
`
`
`be converted to sulfur in a Claus unit.
`
`
`typically produce rich
`
`2
`
`2
`
`2
`
`APPLICATIONS
`
`2
`
`2;
`
`2S
`
`
`
`Hydrocarbon Processing, May 1982 135
`
`
`
`Sour
`CO2
`NGL
`com-
`lique-
`pression
`faction
`
`Claus
`unit
`
`Inlet gas
`
`Fuel
`
`Sulfur
`
`3colum n:
`
`separation, fuel,
`C02,NGL(sour),
`
`recycle additive
`
`
`
`Fig. 9 -Ryan/Holmes process, EOR application.
`
`Peak
`Year
`.07
`85.97
`.12
`4.95
`2.58
`2.25
`.39
`1.14
`.40
`.51
`.53
`1.09
`73
`
`2S
`
`PILOT EXHIBIT 2008, PAGE 7
`
`

`

`C:i
`
`C:i
`
`92.8
`99.6
`99.4
`
`59.3
`95.5
`99.5
`
`TABLE 3 -High CO2 gas separation
`
`Basis: Pipeline sales gas, 1000 psig, 2% CO2
`Product CO2 2000 psig
`Feed 2000 psig
`Feed: C1, MMSCFD
`CO2, MMSCFD
`Total
`Fuel, MMSCFD
`CO2, MMSCFD
`Sales gas, MMSCFD
`Power, H.P.
`
`24,000
`
`high CO2 gas field.
`Naturally occurring
`
`
`f
`
`
`
`
`
`TABLE 2 -EOR gas separation material balances
`
`Early Year (Moles/hr.)
`Feed
`Fuel CO2 NGL
`% recovery
`gas product product product
`3.1
`3.1
`N2
`739.3 4.2 72.51 10.0
`CO2
`5.0
`5.0
`HiS
`5 ppm
`c, 214.2 199.2 15.0
`8.0 102.9
`110.9
`C2
`.3 94.4
`94.8 .1
`.7
`116.1
`116.8
`C4+
`Total 1284.1 207.3 748.4 328.4
`MMSCFD 11.7 1.89 6.73
`93,200
`GaVda}'.
`Peak Year (Moles/hr.)
`Feed
`Fuel CO2 NGL
`% recovery
`gas product product product
`5.6
`5.6
`N2
`6880.5 7.3 6855.5 17.7
`CO2
`8.8
`9.2
`HiS
`50 ppm
`c, 396.9 352.2 44.7
`84.0 122.5
`206.5
`C2
`7.9 171.9
`.2
`180.0
`.4 323.2
`324.9 1.3
`C4+
`Total 8003.6 366.6 6992.9 644.1
`MMSCFD 72.9 3.34 63.7
`196,800
`GaVday
`
`methane t_o
`cascade refrigeration. In the early years,
`
`
`
`
`Required recycle volume 1s
`CO2 ratio is much higher.
`
`much greater than in the -120 °F case. But, in the early
`
`
`years, the facility has excess capacity in the Column 3
`
`
`
`
`system. Thus, the recycle volume per Mcf of feed can 1:>e
`
`
`increased to make -35 °F operation attractive even 1n
`
`the early years.
`
`For some CO2 projects, removal of methane is not
`
`required or economically attractive. In these cases,
`
`
`
`Columns 2 and 3 are used for NGL recovery and H2S
`
`
`
`removal similar to Fig. 8. The NGL's are handled as in
`
`
`the previous case and the methane is reinjected along
`
`with the CO2•
`Methane is
`
`
`
`desired as a purified product stream where CO2 occurs
`
`
`naturally in high concentrations in a gas field. In these
`
`
`cases either a pipe line quality gas (2% CO2
`
`) or an LNG
`
`
`quality gas (less than 100 ppm CO2
`) can be produced.
`
`
`
`Some applications have very remote locations and do
`
`
`
`product. In not require production of CO2, as a salable
`
`
`these cases, CO2 can be vented to the atmosphere
`after
`
`
`
`expansion and heat exchange. Often no external refrig­
`
`
`eration is required. In cases where CO2 is a valuable
`
`
`byproduct, production at 300 to 500 psig is a substantial
`
`
`
`economic advantage over solvent processes. This per­
`
`
`
`
`mits direct compression for pipeline or injection pur­
`
`
`poses or alternatively condensation and sale.
`
`
`When field pressure is higher than required for the
`
`
`
`process, the feed stream can be expanded to the
`
`
`
`demethanizer pressure level to produce cold tempera­
`
`
`
`tures and to recover some of inherent energy. The
`
`
`
`process requires two columns along the lines of Fig. 7.
`27.
`
`In applications where CO2 is more than half of the feed
`73.
`
`
`
`stream it is often possible to recompress product meth­
`100.
`ane stream to feed pressure using recovered energy
`4.1
`
`from feed expansion. Table 3 sets forth some typical
`73.4
`
`performance data for a 70% CO2 feed stream.
`22.5
`
`
`
`
`Integration of the Ryan/Holmes process for LNG has
`15,800
`
`
`
`
`significant potential economic benefit because cold high
`
`
`
`
`pressure methane from the demethanizer is suitable for
`
`
`
`
`direct feeding to the liquefaction cycle. Table 4 com­
`LNG/CO2 removal
`TABLE 4 -Integrated
`Basis: LNG Production
`
`
`pares a typical sweetening and LNG system and the
`Product CO2 2000 psig
`Feed 2000 psig
`
`
`
`
`combined integrated Ryan/Holmes LNG system. This
`Feed
`Ryan/Holmes Physlcal solvent
`
`
`
`
`assumes that a cascade refrigeration process is used for
`
`
`the LNG production, however, alternative LNG ap­
`C, MMSCFD
`27.
`27.
`CCi MMSCFD
`73.
`73.
`
`
`proaches, such as mixed refrigerant loops, could easily
`Total
`100.
`100.
`be incorporated.
`Fuel MMSCFD
`7.8
`6.1
`CCiMMSCFD
`73.4
`73.4
`ACKNOWLEDGMENT
`LNG MMSCFD
`20.5
`18.8
`
`
`
`
`Adapted from a P3:pcr presented at the 61st Annual Gas Processors Association Conven­
`Power HP, net
`30,300
`
`tion, March 15--17, 1g82, Dallas, Texas.
`LITERATURE CITED
`
`
`Material balances (Table 2) show both an early year
`
`
`
`
`
`1 Davis, J. A.; Rodewald, N.; Kurata, F., "Solid-Liquid-Vapor Phase Behavior or the
`
`
`and a peak volume year. In the early years, there is extra
`
`
`
`Methane-Carbon Dioxide System," A.I.Cb.E.J. Vol. 8, No.�. p. 537, 1962.
`
`
`
`
`2 Donnelly, H. G.; Kau, D. L, "Pha,e Equilibria in the Carbon Dioxide-Methane System,"
`
`
`capacity compared to the peak volume year. Recovery
`Ind. Eng. Chem., Vol 46, p. 511, 1954.
`
`
`
`• Mraw, S. C.; Hwang, S. C.; Kobayashi, R., "Vapor-Liquid Equilibrium or the CH4-C02
`
`of H2S can, therefore, be more
`of C2 and elimination
`
`System at Low Temperatures," J. Chcnt-Eng. Data, Vol. 23, No. 2,_p. 135, 1978.
`
`
`
`4 Sterner, C. J., "Pha,e Equilibria in CO,-Metha.ne Systems," Adv. Cryo. Eng., Vol. 6, p.
`
`
`thorough. Equipment is sized for peak year require­
`467, 1961.
`
`
`
`
`Air, Carbon Gases Containing or Low-Btu S Jones, J. K., "The C'togenic Upgrading
`
`
`
`ments but project evaluation needs recoveries and utili­
`
`
`bioxide and Niuogen, 'Proc. Gu Proc. A11n., 1974.
`
`
`
`6 Pagani, G.; Guerreri, G.; Peri, B., "Method for the Purification of Natural Gas Having a
`
`
`ties to be evaluated for each year of reservoir use.
`
`
`
`
`High Content of Acidic Gases," U.S. PaL 4,097,250, June 27. 1978.
`
`
`
`
`7 Sdiianni,G. C., .. Cryogenic Removal of Carbon Diox.1dc from Natural Gas," lnsL Chem.
`
`Due to the low methane content in years of peak CO2
`Eng. Symp. Soc., No. �4. p. 50, 1976.
`
`production, the C/CO2 column can be designed
`and
`
`
`Hydro­Va�-1..iquid Equilibria or Carbon Dioxide-Light
`8 Naiiahitmi,, K., ti al, "Binary
`
`caroonsat Low Temperature," . Cbent-Eng. 'baca, Vol. 7, No. 5, p. 323, 1974.
`
`
`
`
`operated in a different manner. By increasing volume
`
`
`
`
`9 Davalos,]., ti al, "liquid-Vapor uilibria at 250.00 K for Systems Containing Methane,
`
`
`Ethane and Carbon l>ioxide," J. cnt-Eng. Data, Vol. 21, No. I, p. 81, 1976.
`
`
`
`
`of recycle additive to the column, the overhead temper­
`
`
`
`
`
`10 Sobocinski, D. P.; Kurata, F., "Fleterogeneous Phase Equilibria or the Hydrogen Sulfide­
`
`
`
`Carbon Dioxide System," A.],Cl,_E.J., Vol, 5, No. 4, p. 545, 1959.
`
`
`ature can be raised to -35 °F. This allows the column to
`
`
`
`
`II Cheung, H.; Zander, E. H., "Solubility or Carbon Dioxide and Hyd�en Sulfide in
`
`
`
`
`
`Liquid Hydrocarbons at Cryogenic Temperatures," Chem. Eng. Progr. Symp., Ser. No.
`
`
`be fabricated of carbon steel and eliminates need for
`88, vol. 64, e, 34, 1968.
`
`
`
`12 Kura ta, F., 'Solubility or Solid Carbon Dioxide in Pure Light Hydrocarbons and Mix•
`
`tures of Light Hydrocarbons," GPA Res. Rep., RR-10, Feb. 1974.
`■
`
`136 Hydrocarbon Processing, May 1982
`
`PILOT EXHIBIT 2008, PAGE 8
`
`