Increase C2 Splitter Capacity with ECMD Traysand HIGH FLUX Tubing

Mohamed S. M. ShakurRaymond E. TuckerKevin J. RichardsonMichael R. Sobczyk

UOP LLCTonawanda, New York, U.S.A.

Richard D. Prickett, TechnologyCharles Polito, Technology

Steve E. Harper, Plant OperationsChevron Chemical Company, Port Arthur, Texas, U.S.A.

Presented at theEthylene Producers Conference Session

American Institute of Chemical Engineers “Ethylene Revamps & Retrofit Technology”

George R. Brown Convention Center, Houston, Texas, U.S.A.March 18th, 1999

Copyright © 1999 by UOP LLC and Chevron Chemical Company All rights reserved.Unpublished

AIChE shall not be responsible for statementsor opinions contained in papers or printed in its publications

Increase C2 Splitter Capacity with ECMD Traysand HIGH FLUX Tubing

Mohamed S. M. Shakur UOP LLC, Tonawanda, New York, U.S.A.Raymond E. Tucker UOP LLC, Tonawanda, New York, U.S.A.Kevin J. Richardson UOP LLC, Tonawanda, New York, U.S.A.Michael R. Sobczyk UOP LLC, Tonawanda, New York, U.S.A.Richard D. Prickett Chevron Chemical Company, Texas, U.S.A.Charles Polito Chevron Chemical Company, Texas, U.S.A.Steve E. Harper Chevron Chemical Company, Texas, U.S.A.

ABSTRACT

The Enhanced Capacity Multiple Downcomer (ECMD) tray is a significant improvementover an MDϑ tray, which has been the mainstay in difficult separations and columnrevamps for the last 40 years. With the use of improved hardware to redirect vapor, anECMD tray can achieve as much as 20 % more capacity than an MD tray.

Doubly enhanced HIGH FLUXϑ tubes utilize boiling and condensing/sensibleenhancements to increase the overall heat transfer coefficients of exchangers by 3 to 5times that of conventional bare tubes. The existing bare tube reboilers and condensers ofthe Chevron C2 splitter were revamped with doubly enhanced HIGH FLUX tubes, resultingin increased heat duties and reduced temperature differences across the exchangers.

By using ECMD trays, doubly enhanced HIGH FLUX tubes and ethylene unitexpansion, the ethylene production of the Chevron Chemical C2 Splitter located at PortArthur, Texas, U.S.A. was increased by 70%.

EXPANSION BACKGROUND

Ethylene production at the Chevron, Port Arthur ethylene plant was increased by 70% in1997 1. The revamp required significant modifications to the C2 splitter system. Theeconomics of the expansion required the use of the existing column and exchanger shells.The refrigeration compressors were replaced with higher capacity machines on the samefootprint. Due to the large capacity increase, and with the new machines in place, theenergy consumption of the C2 splitter column had to be minimized because of refrigerationlimitations. A revamp of the C2 splitter system with ECMD trays and HIGH FLUX tubesmet the capacity and energy requirements for this large expansion project.

Figure 1 shows the simplified process flow diagram for the C2 splitter system. Arevamp of the column with ECMD trays maximized the number of theoretical trays andminimized the energy required for the separation and throughput. Revamping the overheadcondensers and bottoms reboilers with doubly enhanced HIGH FLUX tubing reduced thetemperature difference across the exchangers, thereby unloading the propylene refrigerantcompressor.

Prior to the revamp, the column was operating at an ethylene production rate of54.4 mt/h. After the revamp, an ethylene production of 90.5 mt/h was achieved. Theaddition of the second feed accounted for approximately a 20% increase in ethyleneproduction.

The design for the column and exchanger revamps was carried out in two steps.First, an ECMD revamp scheme that maximized column capacity and minimized energyrequirements was established. The energy required for the column revamp was then used asthe design basis for HIGH FLUX tubes in the reboilers and condensers.

Figure 1. Simplified Process Flow Diagram After the Revamp

C2H6Recycle

C2H4Product

1

164

Feed 2

Vent

EA-410A EA-410CEA-410B

EA-411A/B/C/D

EA-44489

Feed 1

ECMD TRAYS

BACKGROUND

The ECMD Tray was developed in 1989. The first commercial application into an Austriandeethanizer 2 occurred the same year. At the end of 1998, the ECMD tray has been installedand successfully operated in 110 columns.

The ECMD tray was developed to achieve higher capacity than an MD tray. Aphotograph of an ECMD tray is shown in Figure 2. An ECMD tray has a significantlyhigher capacity than other types of trays. The ECMD tray utilizes features that are commonto an MD tray, that result in high capacity. These features include a large number ofdowncomers, a large weir length, and no receiving pans. In addition the ECMD tray hasenhanced sieve decks and downcomer features that allow a 20% capacity increase over anMD tray. An early commercial application proved the higher capacity of the ECMD traywhen a 20 % capacity increase was achieved by replacing flooded MD trays in adeethanizer 3 with ECMD trays.

Figure 2. ECMD Tray Showing Enhanced Deck and Downcomers

High-pressure columns with high liquid to vapor ratios, such as demethanizers,deethanizers, C2 splitters, and C3 splitters are ideal for ECMD trays. The ECMD trayprovides significant benefits in a new column where the diameter and shell length can bereduced, and in the revamp of a column where the internal loads can be increased. Totalinstalled costs for a new column can be reduced by as much as 40%. Difficult separationsthat require a large number of trays, such as ethylene-ethane, propylene-propane and para-orthoxylene, can be done in a single tower shell. Production can be increased by as much as40% on a revamp.

ECMD trays are used in column revamps to increase both capacity and theoreticaltray count. For maximum capacity, the trays can replace original trays on a tray for traybasis. On many revamps, reducing the tray spacing increases the number of trays.Customers often perceive an increased number of ECMD trays as necessary because of thelower efficiency of the ECMD tray when compared to a conventional tray. However, themain reason for increasing the number of trays in a column is to improve the purity of aproduct, and reduce energy requirements. In a Gulf Coast C3 splitter 4, the tray count wasincreased by installing twice the number of existing trays at spacings of 254 mm. Thepropylene product purity improved from 95% (chemical grade), which has low commercialvalue, to 99.6% (polymer grade), which has significantly higher value. In a Gulf Coast C2

splitter 5, the tray count was increased by 25%. Ethylene production rate increased by 25%and the contaminants in the ethylene decreased from 1,000 ppm to less than 400 ppm.

In 1991, Chevron’s C3 splitter column located at Port Arthur, Texas, U.S.A., wasrevamped with 325 ECMD trays with a diameter of 5486 mm. Operating data obtainedfrom the column showed that a 40% increase in capacity was achieved 6. Based on thisexperience, ECMD trays met Chevron’s requirements for a debottleneck of the C2 splitter(see Figure 3).

Figure 3. Chevron C2 Splitter Column

REVAMP OPTIONS FOR THE COLUMN

The main goal of the revamp was to maximize the ethylene production and minimize theenergy requirements. The UOP analysis started with a determination of the separationcharacteristics. The relationship between the number of theoretical trays below the productside draw to the condenser duty required to make the desired separation was determined(see Figure 4). This curve was used to establish the required theoretical tray count for therevamp.

The energy required for a tray-for-tray revamp was too high for the availablerefrigerant load. From Figure 4, it can be seen that energy savings can be realized byincreasing the number of theoretical trays (NTT) in the column. UOP used a design pointof 101 theoretical trays. At this theoretical tray count, the capacity could be achievedwithin the system’s energy limitation. A full performance warranty for the column revampwas issued by UOP based on this design point. UOP expected the ECMD trays to generate112 theoretical trays. A revamp of the column with conventional high capacity trays couldnot achieve this.

Figure 4. Minimizing Energy Required for the C2 Splitter

50

60

70

80

90

100

110

120

130

140

150

160

130 140 150 160 170 180 190 200 210

Main Condenser Duty,GJ/h

Num

ber

of T

heor

etic

al T

rays

Bel

ow S

ide

Dra

wE C M D Guarantee Point

ECMD Expec ted Operation

REVAMP STRATEGY AND INSTALLATION TIME

The ECMD trays were installed in the C2 Splitter in 1997. UOP estimated a revamp timeof 22 days (17,500 man-hours) based on similar experiences 7. The column was worked onsporadically since it was not the critical path item. A multi-tray revamp of the C2 splittercolumn in an ethylene plant should not extend the shutdown schedule, or delay the plannedstartup. The new rings were seal-welded to the column wall and new feed and productnozzles were cut into the column shell.

The original column contained 126 conventional 2-pass valve trays at typical trayspacings of 508 and 610 mm. The 13 trays in the pasteurization section at the top of thecolumn were at 610 mm tray spacings. The side draw location was moved higher in thecolumn to maximize the number of trays used for the ethylene-ethane separation. Thenumber of trays in the pasteurization section was reduced. After the revamp, the ethyleneproduct was drawn below tray 8 with tray 1 being the top tray.

The ECMD trays replaced the original trays on a 1 for 1 basis in the pasteurizationsection. The trays above the bottom feed point were replaced on a 4 for 3 basis. A 3 for 2revamp strategy was used below the bottom feed point. Table 1 summarizes the trayspacings before and after revamp. Figure 5 shows a typical ECMD tray installation.

Table 1. Revamp Strategy

Section Revamp type Tray spacing, mmbefore

Tray spacing, mmafter

Pasteurization 1-for-1 609.6 609.6Above feed 4-for-3 508 381Below feed 3-for-2 508 338.7

Figure 5. Typical ECMD Tray Installation

COLUMN TESTING

UOP personnel assisted Chevron in identifying an optimized control scheme that allowedthe column to reach stable operation at very high rates in order to maximize ethylene

production. Operating data were taken at the same time. Samples for the feed, ethylene,and bottoms product streams were obtained and analyzed. For the product streams, theresults of the lab analysis were almost identical to those from the on-line analyzers.Therefore, the on-line analyzers were believed to be accurate. The feed compositions weretaken from lab analysis and were assumed to be constant throughout the data collectionperiod.

Operating data was collected for evaluation.

SIMULATION OF THE OPERATING CONDITIONS

A discrepancy was observed in the material balance that may be attributable to aninaccuracy in the calibration of the flow meters. UOP assumed that the ethylene productrate is correct. UOP theorized that the lower feed (Feed 2) rate was higher than the dataindicated because more ethane was measured coming out than was going into the column.

The operating data were simulated using UOP’s proprietary C2 splitter model. Tomatch the product rates at the observed compositions, the Feed 2 rate was increased by4.5% (see Table 2). Despite this increase, the bottom rate obtained from the simulation is4.2% lower than the measured value.

In the design phase, a conservative efficiency value of 65% was used. UOP’ssimulations required 118 theoretical trays to match the measured reflux rate and theproduct compositions for an efficiency of 73.1%. This observed efficiency is consistentwith the efficiency observed for MD trays in a Gulf Coast C2 splitter column 6.

An evaluation of the simulated conditions shows that the trays were operated at thehydraulic requirements of the design. The analysis also showed that the column is limitedby the trays located between the ethylene product draw and Feed 1.

Table 2. ECMD Tray Performance After Revamp

Data of Dec. 8th, 1997 Design Data SimulationFeed 1 rate, kg/hr 37,021 33,820 33,820Feed 2 rate, kg/hr 112,220 110,055 115,007Side draw rate, kg/hrSide draw ehane, mol ppm

96,044261

90,709150

90,485150

Bottoms rate, kg/hrBottoms ethylene, mol%

52,9321.00

60,4140.25

58,0060.25

External reflux rate, kg/hrReflux temperature, °CReflux pressure, bara

434,597-35.018.7

445,233-31.0

445,596-30.719.36

Bottom temperature, °C -7.1 -6.5 -7.2Top pressure, baraBottom pressure, bara

19.620.4

19.620.3

19.620.3

Main condenser duty, GJ/hrReboiler duty, GJ/hr

146.494.3

143.492.5

COMPARISON OF ECMD TRAYS AND CONVENTIONAL TRAYS

Prior to the ECMD tray revamp, the C2 splitter column had only one feed point. A secondfeed stream, richer in ethylene, was added increasing the total feed rate by 50% (ReferenceSWEC & Chevron Paper, “Chevron Revamp Achieves 70% Ethylene Expansion”). Byadding a new split feed scheme, increasing the number of trays in the column andrevamping to ECMD trays resulted in over a 65% increase in the ethylene production atonly a 40% increase in the required reflux rate. Table 3 compares the typical operatingconditions before and after the revamp.

Table 3. Chevron’s Operation After Revamp

Before AfterTotal Feed rate, t/h 95.94 143.87Ethylene product rate, t/h 54.4 90.5Reflux rate, t/h 308.0 445.2

HIGH FLUX TUBES

BACKGROUND

When Chevron’s Port Arthur, Texas ethylene plant started up in the late 1960’s, the energyrequirements of the C2 splitter were met using conventional shell and tube heat exchangers.Three horizontal kettles were used for condensing the column overheads, and four verticalthermosyphons were used for partially vaporizing the column bottoms. In 1988, one of thethree bare tube C2 splitter condensers was revamped with an equal number of UOP’s ODcoated / bare ID HIGH FLUX tubing. Because of the higher overall heat transfercoefficient of the HIGH FLUX tubing, the required heat duty was achieved at a lowerLMTD. Operational savings from this lower LMTD were realized by maximizing thepressure and temperature of the propylene refrigerant boiling on the shellside of theexchanger. This increased the suction pressure and unloaded the propylene refrigerantcompressor, up to its hydraulic limit.

For the 1997 expansion project, the C2 splitter reboilers and condensers needed tobe modified for increased duties and reduced temperature approaches.

REVAMP OF THE HEAT EXCHANGERS

Chevron’s objectives for the revamp of the C2 splitter condensers and reboilers were tominimize the total installed cost, achieve an increase in capacity at minimum energy, andutilize the capacity and level of refrigeration available from a modified propylenerefrigeration compressor. UOP’s doubly enhanced HIGH FLUX tubes met all theseobjectives.

C2 Splitter Condenser

A revamp of the overhead condensers was necessary to meet the increased refluxrequirement of the C2 Splitter and alleviate the load on the propylene refrigerantcompressor. A 1 for 1 revamp of the conventional bare exchangers with doubly enhancedOD coated / ID finned HIGH FLUX tubes made it possible for Chevron to minimize costs,by re-using the one HIGH FLUX exchanger and revamping the two bare tube exchangers.Further savings were realized by re-using all of the associated piping, along with the inletand outlet heads of the bare tube exchanger. The existing exchanger containing OD coated/ bare ID HIGH FLUX tubes would now operate in parallel with the two revamped

exchangers containing OD coated / ID finned HIGH FLUX tubes. A comparison betweenthe original bare tube exchangers and the proposed HIGH FLUX design is presented inTable 4.

The heat transfer performance obtainable with OD coated / ID finned HIGH FLUXtubing made it possible to meet the increased capacity of the C2 splitter, with a reducedtemperature difference across the exchangers. Therefore, propylene refrigerant at a highertemperature and pressure could be utilized. Because the compressor suction pressure isnow higher, the compression ratio, and therefore the compressor horsepower can be furtherreduced to its hydraulic limit, resulting in additional energy savings.

Table 4. HIGH FLUX Revamp of the C2 Splitter Condenser

Original design Proposed revampEA-410 A,B,C EA-410 A, C EA-410 B

Type tubing BareOD coated /ID finned

OD coated /bare ID

Total duty, GJ/hr 101.9 108.2 43.4Cond. temp. (in), °C -28.9 -30.8Cond. temp. (out), °C -34.4 -33.6Boiling temp, °C -37.2 -37.2(1)

LMTD (design), °C 6.9 5.6LMTD (minimum), °C 6.9 4.3(1)

U-value (design), W/m²-°C 610 1,563 1,246TEMA type CKNExchanger size, mm 1,450 / 2,440 x 12,192Number of shells 3 2 1Total area 6,720 4,480 2,240(1) At minimum LMTD, maximum boiling temperature expected is -36.0°C.

C2 Splitter Reboiler

Before the 1997 revamp, four vertical shell and tube reboilers provided heat input to the C2

splitter. These reboilers could not supply the required duty for the expansion loads.Modifications had to be accomplished at a minimum cost, by maximizing the use ofexisting equipment.

Because of piping complications, the shell diameters could not be changed. WithHIGH FLUX tubes, the four existing shells along with their inlet and outlet heads could bere-used. In addition, the piping transporting the tubeside and shellside fluids wasmaintained with the exception of the column return piping. The size of the column returnpiping was increased to permit adequate circulation within the thermosyphon loop.

The revamp proposed by UOP involved the use of 31.75 mm ID coated / OD flutedtubes to replace the original 19.05 mm conventional bare tubes. Optimizing the tubecountallowed a total of 764 ID coated / OD fluted HIGH FLUX tubes to fit into the existing1,245 mm shell diameters. Because of the significant improvement in heat transferperformance, the HIGH FLUX exchangers could achieve a capacity increase over 50%,even though the heat transfer area was reduced by 40%. UOP’s evaluations showed thatthree of the four exchangers needed to be revamped to meet the new reboiler dutyrequirement. Chevron decided to retrofit all the four reboilers in order to minimizeconcerns about flow distribution and control. Additional energy savings were achievablebecause propylene refrigerant at a lower temperature and pressure could be used to drivethe reboilers. Again, this results in compressor horsepower savings, up to the hydrauliclimit of the propylene refrigeration system.

Table 5. HIGH FLUX Revamp of the C2 Splitter Reboilers

Original design Proposed revamp Conventional

bare tubesID coated / OD fluted

HIGH FLUX tubes

Total duty, GJ/hr 66.1 101.8Cond. temp., °C 3.3 2.9Boiling temp, °C -6.1 -7.4LMTD (design), °C 9.4 10.2LMTD (minimum), °C 9.4 7.8(1)

U-value (design), W/m²-°C 619 2,056(1)

TEMA type CENNo. & size, mm 4 Shells of 1,245 x 6,096Tube OD, mm. 19.05 31.75Total area, m² 3,160 1,765

(1) Design U-value of proposed revamp can be achieved at minimum LMTD

PRODUCT DESCRIPTION AND EXPERIENCE

UOP HIGH FLUX tubes have been used in the reboilers and main condensers of C2

splitters for over 25 years. Over 300 HIGH FLUX exchangers are in operation in variousethylene plants throughout the world.

HIGH FLUX tubing utilizes a porous metal matrix that is metallurgically bonded toeither the inside or outside surface of a bare tube. The manufacturing process ensures amechanically strong surface that is highly resistant to abrasion and erosion. The HIGHFLUX surface works by providing a large number of cavities or pores that function as idealnucleation sites for the generation of vapor bubbles 8. With a highly extended mircosurfacearea and good matrix thermal conductivity, this surface produces boiling coefficients thatare 10-30 times greater than bare tubes, while extending the nucleate boiling range to verylow temperature differences. High performance is maintained because of the high internalcirculation rates that occur as liquid continually replaces the escaping vapor within theporous structure. The high boiling coefficients achieved with the porous surface usuallyshift the controlling heat transfer resistance to the condensing/sensible side, and createsubstantial incentive to enhance those sides for full exploitation of the boiling technology.

In grassroots applications, one HIGH FLUX exchanger could be used in place ofthree bare tube exchangers. Total installed costs are reduced because of the reduction innumber of shells, lower installation costs, smaller foundations, less piping &instrumentation, and smaller plot space. Lower capital cost was achieved when HIGHFLUX tubing was used in the reboiler and condenser of a C2 Splitter, for a 500,000 MTPYethylene plant in Scotland in 1986 9.

Using HIGH FLUX tubing in revamps can result in a significant increase in duty,while re-using the shell, heads and piping from the existing exchangers. Operationalsavings are realized when HIGH FLUX tubing make it possible for exchangers to operateat reduced temperature differences.

Two types of doubly enhanced HIGH FLUX tubes were used in the Chevronethylene expansion project to meet the increased capacity requirements:

1. OD coated / ID finned2. ID coated / OD fluted

OD Coated / ID Finned HIGH FLUX Tubing

OD coated / ID finned HIGH FLUX tubes utilize a condensing/sensible enhancement onthe inside of the tube to improve the film coefficient. On the inside of the tube, a spiral fingeometry is used to create an extended surface area that promotes turbulence. The overallheat transfer coefficient can be increased by 2.5 to 5.0 times that of bare tubes. There is a20% to 40% improvement over the standard OD coated / bare ID HIGH FLUX tube.

Figure 6. Doubly Enhanced OD Coated / ID Finned HIGH FLUX Tube

The doubly enhanced OD coated / ID finned HIGH FLUX tube was developed in1990 and has been used in eight horizontal shell and tube heat exchangers since its firstapplication in an MEK/toluene chiller in 1994. Seven additional units are expected to startup in 1999. Chevron was the second company to use this product.

In addition to the C2 overhead condenser, other potential applications include the C2

refrigerant condensers, deethanizer condensers and feed chillers, heat pumped propyleneand isobutane fractionators, quench water or oil driven reboilers, and natural gas chillers.

ID Coated / OD Fluted HIGH FLUX Tubing

The second doubly enhanced HIGH FLUX product used in the Chevron ethyleneexpansion project is the ID coated / OD fluted tube as shown in Figure 7. This tube hasbeen used in over 200 vertical thermosyphon reboilers found in olefin plants, refineries,glycol, methanol, and aromatics plants throughout the world.

Figure 7. Doubly Enhanced ID Coated / OD Fluted HIGH FLUX Tubes

This HIGH FLUX tube has the porous boiling surface applied to the inside of thetube and a condensing enhancement on the outside. The exterior surface of the tube haslongitudinal flutes that provide an extended surface area that reduces the condensate filmthickness. The reduction in condensate film thickness occurs as surface tension forcesexert a pressure at the crest of the flutes causing liquid to drain into the valley between theflutes. Because of this condensing enhancement, the condensing coefficient is 5 to 6 timesgreater than bare tubes. The overall heat transfer coefficients are 3 to 5 times higher thanbare tubes.

HIGH FLUX OPERATING DATA

UOP’s evaluation of the operating data indicates that the condenser and reboiler have mettheir design requirements, and have the ability to either handle higher capacities, or operateat lower temperature differences. The OD coated / ID finned condensers were designedwith an overall heat transfer coefficient (U-value) of 1,563 W/m²-°C. Operating dataindicates these exchangers are performing at a U-value of 1,606 W/m²-°C. The ID coated /OD fluted reboilers were designed with a U-value of 2,056 W/m²-°C at an LMTD of10.2°C, while performance has been measured to be 2,109 W/m²-°C at an LMTD of 7.2°C.Further testing and data collection is on-going to confirm how well the predicted exchangerperformance is matching plant data.

C2 Splitter Condenser

Vapor leaving the top of the column is directed to the condenser train where three HIGHFLUX shell and tube heat exchangers operating in parallel condense the vapor and providethe reflux for the column. Two of the exchangers contain OD coated / ID finned HIGHFLUX tubing, while a third exchanger contains OD coated / bare ID HIGH FLUX tubing.The geometry of all three exchangers is identical.

Liquid propylene refrigerant is vaporized on the shellside of the exchangers, as thecolumn overheads are condensed inside the tubes. Varying the refrigerant liquid levels inthe shells regulates the amount of reflux subcooling, and allows the column pressure to becontrolled. A photograph of the three condensers is shown in Figure 8.

Figure 8. Chevron C2 Splitter Overhead Condensers

Doubly enhanced HIGH FLUX tubes produce higher heat transfer coefficients thanthe standard OD coated HIGH FLUX tubes, and are therefore capable of handling highercapacities. Because the hydraulics within the condenser train differ between the two typesof exchangers, flow balancing is required.

Operating data indicate that the revamp of the bare tube exchangers with doublyenhanced HIGH FLUX tubing has allowed the reflux requirement of the column to be met.

In addition, the propylene refrigerant boiling on the shellside of the exchangers is above thedesign temperature of -37.2°C for each of the three exchangers.

C2 Splitter Reboiler

Liquid from the bottom of the C2 splitter is fed to four vertical thermosyphon reboilersoperating in parallel. Propylene refrigerant vapor used as the heating medium is directeddownward through the shellside of the reboilers, where it is desuperheated, condensed, andthen partially subcooled. Liquid from the bottom of the column enters the exchangers andis partially vaporized inside the tubes. A photograph of the HIGH FLUX reboilers isshown in Figure 9.

Figure 9. Chevron C2 Splitter Reboilers.

A comparison between the design conditions and the operating data presented inTable 6 shows the exchangers have exceeded their performance requirement whileoperating at an LMTD 30% below design. This reduction in temperature difference acrossthe exchangers was accomplished by reducing the pressure of the 3rd stage propylenerefrigerant. This in turn reduced the load on the compressor, allowing for additional energysavings up to the hydraulic limit.

Table 6. HIGH FLUX Operating Data for the C2 Splitter Reboiler

Data of Nov. 19, 1998 Design DataTotal duty, GJ/hr 101.8 96.5Condensing temp. (BPT), °C 2.9 0.8Outlet temp. (subcooled), °C 2.9 -6.4Condensing pressure, barg 5.4 4.9Boiling temp. (avg), °C -7.4 -6.7Bottoms press., barg 19.4 19.2LMTD, °C 10.2 7.2LMTD (minimum), °C 7.8 ---Total area, m² 1,765U-value, W/m²-°C 2,056 2,109(1) Design U-value is achieved at minimum LMTD

ACKNOWLEDGMENTS

The authors wish to acknowledge the outstanding efforts of Martin D. Johnson, Gregory J.Wisniewski, and Robert S. Lubelski of UOP, who provided invaluable insight into thedesign and installation phase of the project. The authors also wish to acknowledge theoutstanding efforts of the UOP, Chevron and Stone & Webster engineers, tray installers,and drafters who provided invaluable assistance as the Chevron C2 Splitter column wassimulated, revamped, recommissioned, and performance tested.

REFERENCES

1. R. D. Prickett, K. E. Bush, G. Cruey, “Retrofit your Ethylene Unit: The ChevronExperience,” Hydrocarbon Processing, March 1998.

2. M. R. Resetarits, R. J. Miller, J. L. Navarre, M. Linskeseder and P. Reich-Rohrwig,“New Enhanced Capacity MD Tray Debottlenecks Deethanizer,” I. Chem. E.Distillation and Absorption Conference, Birmingham, U.K., Sept. 7, 1992.

3. P. J. McGuire, M. S. M. Shakur and J. Valverde, “Deethanizer Revamp with ECMDTrays” AIChE 1997 Spring Meeting, Houston, TX, Mar. 22, 1997.

4. M. S. M. Shakur, P. J. McGuire and L. G. Bayer, “Converting UTP’s Chem-grade C3

Splitter to Poly-grade using 10-inch Tray Spacings” AIChE 1997 Spring Meeting,Houston, TX, Mar. 22, 1997.

5. D. R. Summers, S. T. Coleman, and R. M. Venner, “Splitter Revamp Results inSignificant Capacity Increase,” AIChE 1992 Spring Meeting, New Orleans, LA, Apr. 1,1992.

6. D. R. Summers, P. J. McGuire, M. R. Resetarits, E. G. Graves, S. E. Harper and S. J.Angelino, “Enhanced Capacity Multiple Downcomer ECMD Trays Debottleneck C3

Splitter,” AIChE 1995 Spring Meeting, Houston, TX, Mar. 22, 1995.

7. J. R. Ulmer and M. D. Manifould, “Comparing the Turnaround Time Required andCost of Installing Various Types of Distillation Trays,” AIChE 1998 Fall Meeting,Miami Beach, FA, Nov. 15, 1998.

8. J. R. Thome, Enhanced Boiling Heat Transfer, Hemisphere Publishing Corp., NewYork, 1990.

9. P.S. O’Neill, “HIGH FLUX Tubing Application Case History at the Exxon ChemicalOlefins Inc. Fife Ethylene Plant (Mossmorran, Scotland), January 1987.