techincal journal

8/12/2019 techincal journal

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MAY 2011 VOLUME 1, ISSUE 6

Happiness is something that you are, and it comes from the way you think

Contents

HYDROCOM

TECHNOLOGY 3

FLOW ASSURANCE

CAPABILITY

DEVELOPMENT5

IMPORTANCE OF

PIPING STRESS

ANALYSIS &

SUPPORTING

7

SUPER-CRITICAL

TECHNOLOGY - PRE-

SENT & FUTURE10

SIMULATE GAS

SWEETENING UNITS

FOR OIL & GAS IN-

DUSTRY USING MASS

TRANSFER RATEBASED MODELS

13

DESIGN OF DISTRIBU-

TOR PLATE FOR

AVOIDING FLOW MAL-

DISTRIBUTION

IN X-SHELL

17

Engineering Talk is BACK andBETTER than ever. We welcomeall our readers once again to thisdynamic issue of EngineeringTalk.As we began editing this issue ofengineering talk, we were thumb-ing through the back issues of ourjournal. Surprisingly we realizedof how dramatically our journalhas changed (read improved)since its inception. Our articleshave turned more focused on thesubject, covered in-depth, ex-tremely varied, more crisp andvisually exciting. All thanks to ourcontributors for providing us theirvaluable articles to be producedon this dynamic platform.The series of events that havetaken place in Japan shows thathow vulnerable we human beingsare to Mother Natures fury. How-ever, good engineering practiceswill always help to face and pumpout of such situations with cour-age. So lets pledge to make Indiaan engineering superpower.Now we wont hold you back formunching through all the excitingengineering extravaganza we

have here for you. And dont missout on the bizarre facts and therisible cartoons that lie strewnover the following pages. Hopeyou have as much fun reading it,as we had writing it!!!Happy Reading:))

- Editorial Team


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valve and diverts the excess flowback to the compressor suction.This system of capacity control ishighly inefficient. Consider that we

are taking gas at an elevated dis-charge pressure after having in-vested considerable energy in com-pressing it to that discharge pres-sure. Now we are going to expand itback down to the suction pressuresimply so that we can invest moreenergy by compressing it again.

Suction ThrottlingTechnique is to reduce the suctionpressure to the compressor by limit-

ing or throttling the flow into thecylinder.Limitations: It takes fairly dramaticreduction in suction pressure togive any sizeable reduction in ca-pacity. Also, as the suction pressureis reduced and discharge pressureheld constant, the compression ra-tio is increased causes higher dis-charge temperature and higher rodloads.

Clearance PocketsBefore going into the detail letsknow what is clearance volume??

Clearance volume is nothing but thespace or volume kept at the headend side of reciprocating compres-sor or engine for the ease of move-ment of the suction as well as dis-charge valves.Now as this clearance increasesvolumetric efficiency decreases,thus reducing the amount of flow tothe process.

Clearance pocket is essentially anempty volume, typically on the outerend of the cylinder, with a valvedpassage to the cylinder bore. Duringnormal operation, the valve isclosed and cylinder operates at fullcapacity. For reduced capacity op-erations the valve is opened, andthe cylinder capacity is reduced by

the effect of this added clearanceon the volumetric efficiency.

Suction Valve UnloadingTechnique here is to keep the cylin-ders away from compressing gas bymaintaining an open flow path be-tween the cylinder bore and the cyl-inder suction chamber. The cylindertakes gas normally, instead of com-pleting the normal cycle of compres-sion and discharge; the cylinder willsimply pump the gas still at suctionpressure back into the suctionchamber via this open pathway.There is absolutely no gas dischargeto process. Additionally there is nocompression occurring, there is vir-tually no energy consumed otherthan passage way losses.Since suction valve unloaders keepcompression from occurring, theycontrol capacity in discrete steps.For example, a double acting cylin-der can be operated 100% loaded,

50% unloaded by unloading oneend of the cylinder, or fullyunloaded by unloading both ends ofthe cylinder.An interesting alternative to thesediscrete steps of unloading is thestepless capacity control systemoffered by Hoerbiger compressorcontrols.

HYDROCOM TECHNOLOGYCAPACITY CONTROL FOR RECIPROCATING COMPRESSORS

By Divyesh Jivaraj Aghera, LTC, Vadodara

Reciprocating process compres-sors are an efficient and reliablemethod to compress almost any gas

mixture from vacuum to over 3000atm. Reciprocating compressorshave numerous applications in re-finery as well as in petrochemicalplants. Being a positive displace-ment machine it can compress awide range of gas densities fromhydrogen having molecular weightof 2 to the gases like chlorine with amolecular weight of 70.

Why capacity control in recipro-

cating compressors?As this machine being a positivedisplacement type, unlike the cen-trifugal machines it cannot selfregulate its capacity against a givendischarge pressure; it will simplykeep displacing gas until told not to.This would not be a problem if wehad an unlimited supply of gas todraw from and an infinite capacitydownstream to discharge into; how-ever practically this situation neverhappens. So it is essential to controlthe capacity of reciprocating com-pressor.Also, during start up of positive dis-placement machine at first it is nec-essary to unload it, as start up ofthe machine in fully loaded condi-tion may lead to the over loading ofthe driver.

Methods of capacity controlSome of the methods for capacitycontrol of reciprocating compres-

sors are briefly motioned below

Recycle / BypassThis is one of the simplest methodsto control the capacity. Take a pip-ing from the compressor dischargeline trough some control valve andconnect it back to the suction line.To reduce the flow to the processline one can easily open the bypass

Clearance Volume

Clearance Pocket



Common sense is instinct, and enough of it is genius


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in steps (i.e 100%, 75%,50%,25% ).While with the HydroCOM capacitycontrol system stepless capacitycontrol is possible. System senses

the flow requirement in the down-stream and according to that signal

is sent to the actuator. Actuator setsthe timing of unloading of suctionvalve based on downstream proc-ess requirement. In this waystepless capacity control is possiblefrom 10% to 100% capacity range.

Energy Saving By Using Hydro-COM Technology

As shown in the diagram the indi-cated power for approximately 50%load is only about half of the powerrequired for full load. This showsthat HydroCOM Technology is themost efficient technology for capac-ity control of reciprocating compres-sors.

Recently, for MRPL-DHDT projectHydroCOM capacity control methodis used for 4.46MW ReciprocatingCompressor. Service for this com-

pressor is make-up Hydrogen(99.5% Hydrogen) and compressoris supplied by GE-Nuovo Pignone Italy.

HYDROCOM TECHNOLOGYCAPACITY CONTROL FOR RECIPROCATING COMPRESSORS

By Divyesh Jivaraj Aghera, L&T-Chiyoda Limited, Vadodara

How HydroCOM Works??

Principle: Normally gas is beingcompressed during the compres-sion stroke. With HydroCOM the

suction valve is kept open by theunloader so that a certain amountof gas is pushed back into the suc-tion chamber. Then, at preciselydefined point of time, the unloaderis released and the suction valvecloses. Therefore only the gas re-maining in the cylinder is beingcompressed.By allowing compression to occurduring only part of the stroke, oneobtains partial flow instead of full

flow or no flow for a fully unloadedcylinder. Actuation of these unload-ers is by a specially designed con-trol panel that monitors processflow requirements and unloads thecompressor flow as necessary.

As informed earlier, with the fixedvolume clearance pocket and suc-tion valve unloaders, it is not possi-ble to have a stepless capacity con-trol. They all do the capacity control

Circuit forHydroCOM

Actuator

Unloader


Follow your instincts. That's where true wisdom manifests itself

Ways to GoWays to GoWays to GoWays to Go

GreenGreenGreenGreen

Turn off the lights / Fanswhen you leave the

place/conference rooms Mail or telephone instead

of documents as far as

possible.

Reuse paper bags. Use

Recycled Products

Purchase Energy saving

appliances

Turn Computers off whennot in use. They Con-sume as much electricity

as three 60 watts bulbs,so avoid standby mode.

Walk, don't drive. If youhave to buy a packet ofchips, dont drive to thestore next door. Instead

Walk.

Print and photocopy on

both sides of the paper

Check your vehicle tires.Maintaining the right de-

gree of pressure in carsand motor bike tires im-proves on mileage con-siderably and saves fuel

with money

Make the running waterwalk.


5/20

Flow Assurance CapabilityDevelopment InitiativeThe various simulation softwarecommercially available or in devel-

opment stage for multiphase tran-sient pipe flow simulation are OLGA,TACITE, SimSuite Pipeline, ProFESTransient and Aspen Traflow.1These software finds their use atvarious stages of projects i.e. con-ceptual stage, feasibility, FEED anddetailed design, operation & con-trol. L&T has recently acquiredOLGAFlow Assurance software forcarrying out such studies.The key application areas identified

by L&T for providing the flow assur-ance services are -

Slug TrackingSlug TrackingSlug TrackingSlug Tracking- Quantification of terrain slugging(sluggingdue to the geometry & ele-vation changes of pipelines) andHydrodynamic slugging (sluggingdue to different flow regimes).- Slugging during production start-up and rate changes.- Tracking slug generation from pig-ging operation.

Operability AnalysisOperability AnalysisOperability AnalysisOperability Analysis- Determining the adequacy of insu-lation type and thickness to keep

the fluid temperature well abovethe hydrate formation temperatureduring a shutdown period.

- Pipeline start up and shutdown

scenario.- Real time depressurization simula-tions to asses hydrate formationpotential and selection of suitablematerial of construction for pipe-lines.

Gas Condensate or Crude TransportGas Condensate or Crude TransportGas Condensate or Crude TransportGas Condensate or Crude TransportPipeline AnalysisPipeline AnalysisPipeline AnalysisPipeline Analysis

- Pigging Simulation for schedulingpig launching and receipt operationand determining surge volume for

accurate sizing of downstream fa-cility.- Surge volume analysis for check-ing design adequacy of separationfacility during turndown and ramp-up scenario.

Water / ThreeWater / ThreeWater / ThreeWater / Three----Phase Flow Simula-Phase Flow Simula-Phase Flow Simula-Phase Flow Simula-tionstionstionstions

- Identifying areas of the pipelinesusceptible to corrosion.

- Estimating volume of slugs of oil orwater at the pipeline exit duringrate changes.

- Prediction of changes in liquid vis-cosities with water cut for oil-watermixtures.

FLOW ASSURANCE CAPABILITY DEVELOPMENT

By Dr. Rohit P. Kulkarni & Vipender Singh, L&T Engineering, Vadodara

Introduction

The subsea production and distri-bution systems are now expanding

into more challenging areas withlonger tiebacks, deep and ultra-deep water and more complex flu-ids. The evaluation of productionscenarios such as start-up, shut-down, blowdown, rate changes andpigging can well be addressed usinga transient multiphase flow simula-tor. Today, Flow Assurance has be-come a critical part of the overallsubsea design to ensure an optimaldevelopment solution for both new

and expanding fields. Flow Assur-ance is - guaranteeing the safe andeconomical supply, transport andprocessing of multiphase mixturesof gas, oil and water. It includeanalysis of various aspects of pro-duction from the reservoir throughpipeline to the plant inlet such as-

Hydraulic analysis - pressureloss

Thermal analysis - heat loss

Operability cooldown, slugging

Blockages - hydrates, wax,scale, sand

Phase behaviour & viscosity Mechanical integrity - corrosion,

erosion Mechanical integrity - corrosion,

erosion

A typical optimized operating enve-lope for subsea oil production pipe-line is indicated in Figure 1.It appears that a stable oil produc-

tion envelope is constrained andcovers relatively small area of oper-ating scenario. Thus, achieving flowstability in an oil production pipelineis a critical activity from design andoperation perspective.

Figure-1:Optimized Operating Envelope for Oil Production Pipeline


Never be prisoner of your past, Be an architect of your future


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knowledge acquired for flow assur-ance can now be extended for up-stream oil & gas development pro-ject where flow assurance applica-tion is required.

References:Bratland, O. Update on Commer-cially Available Flow AssuranceWhat they can and cannot do?2009, Petromin PIPELINER, pp 33-40.

FLOW ASSURANCE CAPABILITY DEVELOPMENT

By Dr. Rohit P. Kulkarni & Vipender Singh, L&T Engineering, Vadodara

CASE STUDY:Cairn Energy India Limited(CEIL) - Bhagyam Field Devel-opment Project

L&T Engineering Vadodara (LTEV)has successfully carried out FlowAssurance studies for BhagyamField Development Project. The ob-jective of the study was to ensurethe operation of crude gatheringpipelines above wax appearancetemperature and accordingly opti-mize the injection water quantity atrespective production manifolds. Asthe water cut in the crude oil wassubstantially high (more than 0.4)

the system behaved as an oil- wateremulsion. As a result, WATEROP-TIONS module was used to correctlypredict three phase behaviour andemulsion viscosity. A typical tem-perature and pressure profileacross the wellpad to cluster pipe-line is shown in the Figure 2 andFigure 3, respectively.Further, the results were well ac-cepted by the client.

Conclusions:The flow assurance capability devel-oped is successfully implementedfor oil field development project.The in-house expertise, skills and

Figure-2:Pressure Profile across Wellpad to Cluster Production Pipelines (Design Flow Case)

Figure 3: Temperature Profile across Wellpad to Cluster Production Pipelines


Self Confidence is the first requisite to great undertakings

The Editorial Team

1. Jitesh Sheth from LTC,

Baroda

2. Darshan Shah from LTC,

Baroda

3. Shaunak Bhatt from L&T-

S&L, Baroda

4. Anirban Pandit from L&T

Engineering, Baroda

5. C. Manoj from LTC, Mum-

bai

6. Devendra Parab, L&T En-

gineering, Mumbai

7. Sanjay S. Shenoy from

Mid and Downstream In-

ternational

8. Pradeep Thakur from L&T

Engineering, Faridabad

9. Pradumna from L&T-Gulf

10. Ravi Prakash from L&T-

Valdel


7/20

stand by pump for not affectingprocess but within a week periodsecond pump also failed, Image 1.3shows clear failure of the centrifu-gal pump Leading to Cost of 2 lakhfor each pump. Now all processstops, which is depending on thesepumps & also all site engineers eye

on this system. After all why thissystem failed, even though engi-neers done Stress analysis for thissystem by using latest piping stresssoftware CAESAR II 5.0 & accordingto that they provide required loop tothe discharge system. Then what isthe reason behind failure of cen-trifugal pump? Where went wrong?

IMPORTANCE OF PIPING STRESS ANALYSIS & SUPPORTING

By Harshvardhan B. Khatkole, L&T-Chiyoda Limited, Mumbai

Introduction

We are all know that stressanalysis plays a critical role in Pip-

ing Engineering, & however it ismost important to pass the stresssystem in Piping stress analysis forsmooth running of the plant in fu-ture. But in many cases eventhrough by taking greatest carethere are occurrence of piping orequipment failure, below mentionedone such kind of case where due toimproper supporting leads to failureof centrifugal pump.

Problem DefinitionImage 1.1 shows Hot water pumpsuction & discharge system whosoperating & design temperaturesare 95 & 110 Degree Celsius.Whereas pump suction & dischargesizes are 6 inch & 4 inch respec-tively.So stress Analysis had done for thissystem & Isometric along with re-quired support drawings are issued.Figure 1.1 & 1.2 shows IssuedDrawing for required support.But after commissioning of theplant one pump failed, because ofthis plant operator starts second

Image 1.1

Figure 1.2 Pipe Shoe (C.S/ S.S./ A.S. Pipe)

Figure 1.1 Adjustable Base support for Elbow (Carbon steel pipe)


Simplicity is the ultimate sophistication


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looking at the site in this supportboth Nut & Bolt ( Which is used foradjusting the support height) are

welded to the Base plate that be-comes rigid support See Image 1.3(a)2) Also remaining Shoe type pro-vided along the line has welded tobottom supporting steel instead ofwelding to pipe See Image 1.3(b)Above these two errors occurs dueto contractor's negligence.3) Discharge line doesn't havingsupport after vertical drop from Noz-zle.

Solution Provided1) Revised Drawing For the Adjustedtype Support are issued to siteclearly stating that Bolt should notbe weld to the Base plate & insert 2mm thk S.S. mirror finish plate ( forreducing friction) between con-tacted surface of Adjustable sup-port.2) Change all shoe support , Weld-ing to be done R.F. Pad & pipe & notat shoe & supporting structure.

3) Adding one more support at dis-charge line as shown in Image 1.4.4) Support need to be checked aftererection at site by Piping Stress En-gineer for all Stress critical lines.



Failure Analysis

After analyzing suction & dischargepiping for the pump finally got thereason why the pump fails & hear itis1) First support form the pumpshould be Adjustable type, But while

Image 1.2

Image 1.3


It's good to be slow and steady; but it's better to be fast and reliable in today's life


9/20



Conclusion:Stress Analysis is important activityin Piping Engineering & need tocarry out for High Temperature linesaccording to that we have to providesupporting to the stress lines. Andafter erection Piping Stress engi-

neer need to check all supports forall stress critical lines

Image 1.4


Our greatest glory is not in never failing, but in rising up every time we fail

Pappu called FM radio &said

"I've found a purse withRs.15000/- a creditcard & an ID card of Mr.Mani, No.13,Halls road,kannur.

Radio jockey : How hon-est .so you want toreturn his purse?Pappu : no...i justwanted to dedicate asad song for him...

Pappu Rox

has huge medical bills thatare far beyond her ability topay?'

Embarrassed, the Charity Or-ganization representativemumbles, 'Uh... no, I didn'tknow that.'

'Secondly,' says the lawyer, 'did it show that my brother, a

disabled veteran, is blind andconfined to a wheelchair and

is unable to support his wifeand six children?

The stricken Charity Organi-zation representative beginsto stammer an apology, but

is cut off again.

'Thirdly, did your researchalso show you that my sis-

ter's husband died in dread-ful car accident, leaving herpenniless with a mortgageand three children, one ofwhom is disabled and an-other that has learning dis-abilities requiring an array ofprivate tutors?'The humiliated Charity Or-ganization representative,

completely beaten, says, 'I'mso sorry, I had no idea.'

And the lawyer says, 'So...if Ididn't give any money tothem, what makes you thinkI'd give any to you?

A Millionaire LawyerA Millionaire LawyerA Millionaire LawyerA Millionaire LawyerA Charity Organization real-ized that it had never re-ceived a donation from the

city's most successful lawyer.So a Charity Organization vol-

unteer paid the lawyer a visitin his lavish office.

The volunteer opened themeeting by saying, 'Our re-search shows that eventhough your annual incomeis over two million dollars,you don't give a penny tocharity. Wouldn't you like to

give something back to yourcommunity through our Char-ity Organization?'

The lawyer thinks for a min-ute and says, 'First, did yourresearch also show you thatmy mother is dying after along, painful illness and she


10/20

tion requirements will be tightenedup in the future. The need for highfuel utilization at reasonable powergeneration costs and acceptable

emissions extends application op-portunities for wide implementationof supercritical (SC) and ultra-supercritical (USC) steam cycles.

Thermodynamical Expressionof Heat EngineThe Carnot Cycle is the thermody-namical expression of a heat en-gine. It is the most efficient existingcycle capable of converting a givenamount of thermal energy into work

or vice versa. Carnot Efficiency isthe highest for any heat engine op-

erating between specified tempera-ture limits, source (T1) and sink (T2)(Fig. 1). Though it is the most effi-cient cycle, but it cannot be realized

practically.

The Rankine Cycle and its evo-lutionThe Rankine Cycle is generally the

practical approximation of CarnotCycle. The Rankine Cycle is a va-pour power cycle that forms thethermodynamic basis for moststeam power plants. Rankine cyclecombines constant-pressure heataddition and rejection processeswith adiabatic reversible compres-sion and expansion processes. Itutilizes a working fluid that changesphase during the heat-transferprocesses to provide essentially

isothermal heat addition and rejec-tion.Quest to improve the efficiency ofpower plants led to several modifi-cations of Rankine Cycle.Following modifications of theRankine Cycle led to efficiency im-provement of power plants

- Increasing live steam parameters- Lowering condenser pressure- Using single/double reheat

- Using multi stage regenerativefeed water heating- Going beyond Critical Point

The above changes in Rankine Cy-cle are manifested in the T-s dia-grams below:-

Introduction

Coal has played a major role inelectricity production worldwide

since 1880's. In 1884, the moreefficient high speed steam turbinewas developed by British engineerCharles A. Parsons which replacedthe use of steam engines to gener-ate electricity. In the 1920s, thepulverized coal firing was devel-oped. This process brought advan-tages that included a higher com-bustion temperature, improved ther-mal efficiency and a lower require-ment for excess air for combustion.

The steam cycle in a power plant ischaracterized by the maximum op-erating pressure with associatedtemperature of the cycle. The typicalsteam turbine power plant operateson the Rankine cycle, the workhorse of the coal-fired utility indus-try. This has been using water va-pour to generate useful power sincelate 19thcentury.With improvement in higher steamconditions and the advent of mod-ern super alloys, the Rankine steamcycle has marched into the Super-Critical (SC) region of the coolantand is generating thermal efficien-cies into 40% plus range at GrossCalorific Value (GCV) of coal.Growing concern about climatechange worked in favour of naturalgas. Gas contains 25 percent lesscarbon than oil and half as muchcarbon in coal. Since 1990, the newcapacity added consisted of largely,efficient gas-fired power plants.

However, due to increase in price ofcrude oil & gas and growing powerdemand, coal continues to enjoy itstop importance in power generation.It is obvious that most efficient andenvironmentally friendly, coal-based, power generation units haveto be widely commercialized andimplemented to enable affordableand reliable electricity productioneven though environment protec-

SUPER-CRITICAL TECHNOLOGY - PRESENT & FUTURE

From an Architects PerspectiveBy B.K. Basu, Chief Executive, L&T- Sargent & Lundy Limited, Vadodara


Rudeness is the weak man's imitation of strength

Fig 1:Basic Rankine Cycle

An Impactful presentationAn Impactful presentationAn Impactful presentationAn Impactful presentation

on this Paper was madeon this Paper was madeon this Paper was madeon this Paper was madeby Mr. B.K. Basu, CE, L&Tby Mr. B.K. Basu, CE, L&Tby Mr. B.K. Basu, CE, L&Tby Mr. B.K. Basu, CE, L&T----

S&L, at Power India 2010S&L, at Power India 2010S&L, at Power India 2010S&L, at Power India 2010


11/20

Genesis of Super-Critical UnitsWorlds first SC power plant125MW (31 MPa/621oC/565oC/538oC) US Philo Power Plant at

Ohio commenced commercial op-eration in 1957, followed by 325MW Eddy Stone 1 Power Plant in1960 in Philadelphia. The EddyStone plant was designed to oper-ate with steam conditions of 34.5Mpa and 650/565/565C. How-ever, due to mechanical and metal-lurgical problems the plant was de-rated to 32.2 Mpa and 610C. In2003, this plant was honoured byASME as Historic Mechanical Engi-

neering Landmark. Making an earlyentry, SC Plants took some time toresurface, mostly due to metallurgi-cal and economic reasons.India also have ventured into super-critical technology, to meet the in-creasing demand for power in thecountry. Following are the develop-ments which have taken in this di-rection.- NTPC first opted for SC technologyfor Sipat (2001) and Barh (2004)

Super Thermal Power Stations- UMPPs opted for SC units in 2006- 12th& 13th Five Year Plans envis-age 60% and 90% capacity addi-tion, respectively through SC Units.

Below graph shows the number ofsupercritical units and power out-put of these plants world-wide.


Management works in the System; Leadership works on the System



Fig 2Fig 3

Fig 4: Basic Rankine Cycle with Superheat & Reheat

Fig 5: Rankine Cycle with Single Reheat and 2 Stages of Feed Water Heating-Sub-Critical

Fig 6: Rankine Cycle with Single Reheat and 2 Stages of Feed Water Heating-Super-Critical

Basic Rankine Cycle with Superheat

0

20

40

60

80

100

120

140

160

180

USA Japan Russia Germany Korea China Other

Countries

No.OfUn

its

0

20

40

60

80

100

120

140

160

180

GW

No. Of Units Power Output

Source: Latest Development In SC SteamTechnology-Powergen Asia-2008


12/20

pacities of the BOP equipments arecomparatively smaller than thoseused in sub-critical plants. SC boil-ers can be designed to accept wide

range of coal quality variations.

Ultra Super-Critical (USC) Tech-nology - The New FrontierThe new frontier in power plant isthe ultra supercritical technologythat operates at pressure (25.0

MPa or higher) and Main Steam andReheat temperatures at 1100 F(593C )/1150 F (621C) or

higher as defined by EPRI. The tur-bine cycle becomes more efficientin USC Plants.Research and Developmental workis presently underway to enable Ad-vanced USC plants to reach pres-sure of 35 MPa and temp of700/720C with net efficiency of50-55% and beyond on LHV basis,over the next decade....

Challenges of SC/USC PlantsThe major challenge for the SC/USCshall be the material of constructionin order to address the following :

- High Temperature Oxidation ofboiler tubes

- Fire Side Corrosion of tubes- High resistance to thermal fatigueand creep

- Resistance against embrittlement- Requirement of high tensilestrength in high temperature zone

- Use of Ni or Fe-Ni-base alloys- Thermal Expansion in Main Steamand Hot Reheat pipes

- Structural reliability of Valves un-

der high temp applicationAnother major challenge will bemanufacturing technology, since itwould need special focus on- Acquisition of knowledge of themicrostructure, joint strength andtoughness

- Development of bendingtechnology

- Development of welding materials- Development of heat treatmentprocesses.

R&D Activities in AdvancedUSC TechnologyIn the 21stcentury, the world facesthe challenge of providing cheapand adequate amount of electricityto meet the ever increasing demanddue to growing economies andpopulation. At the same time it willalso be a challenge meet the envi-ronmental norms. Towards this end,many R&D activities have beentaken up as below:-

- USA Vision 21 Program (Target:60% efficiency, near zero emissionby year 2020)- Europe AD 700 (Advanced SCPF Power Plant operating at 700oC,Efficiency~50% )- Japanese A-USC (Steam Parame-ters at 35 Mpa, 700oC, Efficiency~50%)

Supercritical TechnologyThe advent of the supercritical tech-nology gave a boost to the powerplant industry. Its implementation

not only led to higher unit size but

also better plant performance, avail-ability and comparable reliability.Following table indicates the com-parison of typical performance ofsub-critical vis--vissuper-critical technology

Advantages of Super-CriticalTechnology

SC Technology aided in higher cycleefficiency of power plant which inturn led to fuel saving, lesser emis-sions, less auxiliary power con-sumption and water consumption.The adoption of SC also led to op-erational flexibility which helped inbetter temperature control and loadchange and shorter start-up time.SC/USC plants are suitable for vari-able pressure operation. The ca-


If you ask a question, you are a fool for 5 minutes. If you dont ask you are a fool forever



Definition;

Misumi P/S

1998-2000(1,000MW)

Haramachi P/S

1997-2000(1,000MW)

Shinchi P/S

1995-2000(1,000MW)

Matsuura P/S

1991-2000(700MW)

0

20

40

60

80

100

Availability(%)

Availability=(Calendar date hours(h)-Forced outage hours (h))

(Calendar date hours(h))

Source: MHI

Source: MHI

Table 1

Fig 9


13/20

Susta, IMTE AG, Power ConsultingEngineers, Switzerland, PowerGenAsia 2008, Kaula Lumpur-Malaysia

2. PF-Fired Supercritical Boilers-Operational Issues and Coal QualityImpacts-March 2002 (TechnicalNote 20):-B.J.P. Buhre, R. Gupta, S.Richardson, A. Sharma, C. Spero, T.Wall-CRC for Coal in SustainableDevelopment

3. Mateirals for Ultra SupercriticalFossil Power Plants-Final Report-TR114750, March 2000-EPRI- R.Viswanathan, W.T. Bakker

4. www.powermag.com :- Evaluat-ing Materials Technology for Ad-

vanced Ultrasupercritical Coal-FiredPlants- R.Vishwanathan and JohnShingledecker, EPRI and RobertPurgert, Energy Industries of Ohio,August 2010

5. CoalFleet Guideline for AdvancedPulverized Coal Power Plants:-EPRI

6. www.wikipedia.org

About the PaperPower India 2010 was organized byIndia Tech Foundation in Mumbaifrom 27thto 30th Oct 2010.

Technology and Innovations arevital to our economic and socialprogress. In an increasingly global-ised world, it is recognized that highlevel of investment in research andinnovation are essential, both foreconomic competitiveness and forbetter yields in areas which maketangible improvements in our qual-ity of life. In Power & related sec-tors, it has been successfully intro-duced in many fields, but there still

exists quiet some gap, which needsto be filled-up rapidly. Keeping thisneed in perspective, the theme out-lined for the event was 'Power withTech-Innovation' to emphasize on'Emerging Technologies for Power &related sectors'.

L&T-Power was one of the majorsponsor in the event. Mr. SunilPande, EVP-L&T Power and our CE,Mr. B.K.Basu were the key speak-

ers in the Power Producers Meeton 27th Oct.

Mr. Pande shared his views on thetopic Impact of Foreign Supplierson Indian Power Generation Equip-ment Market - Equipment Manufac-turers View Point. While Mr. Basumade an impactful presentation onSuper-Critical Technology-Presentand Future

Mr. R. V. Shahi- Former Secretary

Power, was the session chairman.Other key speakers in the sessionwere Mr. Shoeb Ahmed- DirectorCommercial, SAIL and Mr. SunilChaturvedi, COO, Bharat Forge Ltd.

Presented over here is the techni-cal write up of Mr. B. K. Basuspresentation.

Summary

SC and USC technologies providenot only stable and high qualityelectric power but also contribute toapproximately 15 to 20% reductionof CO2 emissions, ash generationand adverse impact to the environ-

ment. SC/USC power plants havevery high availability and allow use

of wide range of fuels.

Major R&D efforts are in progress inUS, Japan & Europe for next genera-tion USC 700 oC class plants toachieve a plant efficiency of 50%plus and 30% reduction in CO2compared to existing subcriticalplants. Advanced material andmanufacturing technology are un-der development to face the mate-rial challenges in 21st century nec-essary for the next generation ultrasupercritical plants. These plantsshall operate at 37.5 Mpa at700/720/720 deg C, with efficiencyin excess of 50% on LHV.

References1. Latest Development in Supercriti-cal Steam Technology- Miro R.


Failure is only the opportunity to more intelligently begin again



Material for Advance SC Plants (EPRI)


14/20

length to achieve better distributionmaintaining piping symmetry. (Refer

Figure b)- Different distribution devices likeAnnular distributor, Distributor plateetc. can be employed to ensureproper flow distribution along thetube length. (Refer Fig c)

- Combination of distributor withmultiple nozzles (Refer Fig d).

Sometimes, in typical gas serviceapplication, mal-distribution mayalso lead to acoustic vibration.Proper distribution of flow using dis-tributor plate also helps to negatesuch issues.This article includes step-wise pro-cedure for designing distributorplate. Sample calculations with acase study of Air pre-heater of Sul-

phur Recovery Plant where imple-mentation of such distributor platein X-shell was considered to over-come flow mal-distribution problem.The sample study was performedusing commercially available HTRIsoftware and same is used for illus-tration purpose.

Case Study:Sulphur Recovery Plant typically in-volves Air pre-heater associatedwith Claus air blowers. Because of

constraint of very low allowablepressure drop across Air Pre-heater,X-shell design is typically adopted.Air is passing through shell side andit gets heated from approx. 80 C to225C by means of High Pressuresteam flowing on the tube side.Initial design of Air Pre-heater washaving serious mal-distribution andacoustic vibration problems. Toovercome these, it was consideredto provide two or more no. of noz-

zles at the shell inlet with full sup-port plates. In spite of provision ofmultiple inlets and strengthen sup-ports, issue of mal-distribution andacoustic vibration remained unre-solved. Hence, to resolve these is-sues, it was ultimately consideredto provide distributor plate to en-sure uniform gas distribution acrossthe tube length.Details of step wise procedure ofdesigning the distributor plate isspecified as further:

Design Guidelines for Distribu-tor plateHTRI (Xist module) envisages X-shell side mal-distribution mes-sages for the following reasons:- The nozzle pressure drop is morethan 50% of the total pressure drop- The tube length greater than 4times the shell diameter.- The tube length divided by thenumber of inlet nozzles is greater

than 4 times the bundle diameter.For handling above concerns aboutshell side flow distribution, it is rec-ommended to consider an inlet per-forated distributor plate or annulardistributor on shell side. HTRI doesnot have provision to design thedistributor plate.

DESIGN OF DISTRIBUTOR PLATE FOR AVOIDING FLOW MAL-DISTRIBUTION

IN X-SHELL

By Mr. Ragin Shah & Mr. Rahul Dole, L&T-Chiyoda Limited, Vadodara

Introduction:

Several Shell configurations des-ignated as E, F, G, H, J, K, X, by Tu-

bular Exchangers ManufacturersAssociation Inc, (TEMA), are avail-able for Shell and Tube Heat Ex-changers. Out of these TEMA X shellis pure cross-flow shell where theshell side fluid enters at the top (orbottom) of the shell flows across thetubes and exits from the oppositeside of the shell. There are no baf-fles and only full support plates areemployed to negate the vibrationissues.

Due to the un-baffled shell configu-ration, the pressure drop offered isextremely low and in many casesnegligibly small. Hence X shell isquite often employed in applica-tions where pressure drops are ex-tremely critical and must be main-tained within a small allowablerange. Typical such examples in-

clude column overhead condensersin vacuum columns, air pre-heatersin blower circuits etc. Refer Figure(a) for typical X shell with top entryand bottom exit.

Flow Distribution:Un-baffled shell design, leads to atypical problem of fluid mal-distribution with the usage of X-shellleaving quite a substantial fractionof heat transfer area ineffective.This poses serious performanceissue if not properly dealt with. Dif-ferent techniques are applied tominimize the mal-distribution to anacceptable level.- Flow can be distributed throughmultiple nozzles along the tube

Figure a: Typ. X-Shell

Figure b

Figure c

Figure d


Failure is as precious as success, but only if we learn from it


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Considering the length (L) & Width(W) and above specified hole dia (D)& Hole Pitch (P), total no. of holescan be accommodated in this plate= 9168 holes.Hence, the total open area (Slotarea) = Area of one hole x total no.

of holes = 0.000314 x 9168= 2.88 m2.

From above,Open area fraction = Open area /Total perforated plate area

= 2.88 /5.64=0.51(Which is more than

50% as specified in guideline (1)

2. With Open Area fraction, esti-2. With Open Area fraction, esti-2. With Open Area fraction, esti-2. With Open Area fraction, esti-mate the value of Resistance comate the value of Resistance comate the value of Resistance comate the value of Resistance co----efficient (K) from the followingefficient (K) from the followingefficient (K) from the followingefficient (K) from the followinggraph or using the equation speci-graph or using the equation speci-graph or using the equation speci-graph or using the equation speci-fied in below plot.fied in below plot.fied in below plot.fied in below plot.

It is recommended that value of Kshould be greater than or equal to 2to ensure sufficient resistance andthus the proper flow distribution.Based on the graph (1), Resistanceco-efficient K is arrived at ~ 4 (K=4)by plotting against the open areafraction value. (Value of K is morethan 2 satisfying the guideline (2).

3. Ensure the first tube row is far3. Ensure the first tube row is far3. Ensure the first tube row is far3. Ensure the first tube row is farenough away from the distributorenough away from the distributorenough away from the distributorenough away from the distributorplate so that it is fully wetted by theplate so that it is fully wetted by theplate so that it is fully wetted by theplate so that it is fully wetted by theexpanding jets from the orifices.expanding jets from the orifices.expanding jets from the orifices.expanding jets from the orifices.

Now, based on the guideline (3),Distributor plate Clearance frombundle is considered as approxi-mately 0.2 m (Refer below mechani-cal sketch)

Further, pressure drop across thedistributor plate can be calculatedas,

= 4 x x 1.567 (kg/m3) x*8.2^2 (m/s)2

= 0.0022 kg/cm2 (by unit con-version

Design Steps1. Keep open area (slot area) moreKeep open area (slot area) moreKeep open area (slot area) moreKeep open area (slot area) more

than 50% of total distributor plate area.than 50% of total distributor plate area.than 50% of total distributor plate area.than 50% of total distributor plate area.

Open area plays important role in

ensuring proper distribution. Lessopen area will tend to create dis-crete jets and in turn may result intopoor distribution coupled withhigher pressure drop. Conversely,higher open area will lead to poorflow distribution due to lower resis-tance for flow. Open area fractionin the range of 50% to 60% is idealrange of 50% to 60% is idealrange of 50% to 60% is idealrange of 50% to 60% is idealto ensure proper distribution alongwith optimal pressure drop.Supposing, Shell ID and Tube length

is finalized based on preliminarydesign of HTRI run and arrived asShell ID: 1600 mmTube length: 5000 mmEffective Tube Length (excludingtubesheet thickness & other weld-ing margin), L= 4700 mm.Based on the effective tube length,effective distributor plate length isconsidered as 4700 mm to ensurethe flow distribution though out theeffective tube length. Now, consid-ering the guideline given below (1),

width of the distributor is assumedas 1200 mm.W = 1200 mm.Total perforated plate Area = L x W

= 4700 mm x 1200 mm=5640000 mm2

= 5.64 m2 (by unit conversion)

As a rough thumb rule, Hole diame-ter can be selected same as tubeoutside diameter and hole pitch as1.25 times hole diameter. Preferred

Hole layout angle is normally 30(triangle) as more no. of holes canbe accommodated within the totaldistributor plate area.

Considering,Hole diameter, D = 20 mmHole pitch, P = 25 mmArea of one hole = 0.000314 m2


IN X-SHELL



Go confidently in the direction of your Dreams. Live the Life you have Imagined

Graph-1


16/20

space between shell and bundle iskept to accommodate the distribu-tor plate and top entry is consideredfor condensing service. In this case,

distributor plate directlywelded withbaffles and minimum space of 25mm is kept between first tube rowand distributor plate. A typical

sketch indicating the details aredepicted for ready reference (Fig.2).In hindsight, requirement of suchdistributor plates are inevitable foravoiding flow mal-distribution andthus to ensure better performanceof X shell heat exchangers.

Bibliography:Kevin J. Farrell, Design Guidance forDistributor Plates (Tech Tips 5,www. htri.net, 2008)

Acknowledgement:The authors are grateful to the man-agement of L&T-Chiyoda Ltd., forpermission to publish this article

and acknowledge the use of HeatTransfer Research, Inc.s softwarefor worked out examples and theirdesign methodology.

Ensure that screen Pressure Drop +Exchanger Pressure Drop is withinthe allowable pressure drop. If not,increase the open area fraction

within the suggested range above in(1).Based on above results, distributorplate design is performed and im-

plemented for aforementioned typi-cal application.

Another Typical ApplicationAn alternate application of distribu-tor plate involving condensation oftwo phase fluid is also implementedwith multiple nozzles. Unlike theprevious case study, no separate


IN X-SHELL


Mechanical Sketch:Fig 2

Mechanical Sketch:Fig 1


Chance favors the prepared mind

Fun Zone


17/20

brings out the superiority of thesemodels over the equilibrium stagemodels using the actual simulationcase studies with Hydrocarbon-H2S-

CO2-MDEA system.

IntroductionAlkanolamines such as monoetha-nolamine (MEA), diethanolamine(DEA), methyldiethanolamine(MDEA), triethanolamine (TEA) ordiisopropanolamine (DIPA) arewidely used in the oil and gas indus-tries to remove acid gases i.e.H2Sand CO2 from natural gas, LPG orsour water striper (SWS) offgas

streams (Kohl and Neilsen,1997).The process of removal of H2S andCO2 using aqueous alkanolaminesinvolves various chemical reactionsincluding formation of zwitterionsfollowed by its deprotonation(Danckwerts, 1979).The principalreactions occurring between aque-ous solution of amine and H2S/CO2can be represented as below equa-tions:

Aqueous methyldiethanolamine(MDEA) is the most commonly usedalkanolamine for selective removalof H2S in tail gas treating units(TGTU). Being a tertiary amine

MDEA doesnt contain proton (H+)and hence do not form carbamatecomplex (reaction 2) with CO2. Therole of MDEA is only to provide asink for the hydrogen ions that areproduced when CO2is hydrolysed inwater. The chemical absorption ofacid gas in MDEA is frequently ac-companied with considerable heatof reaction, which reduces theamine contactor efficiencies

Aqueous methyldiethanolamine(MDEA) is the most commonly usedalkanolamine for selective removalof H2S in tail gas treating units

(TGTU). Being a tertiary amineMDEA doesnt contain proton (H+)and hence do not form carbamatecomplex (reaction 2) with CO2. Therole of MDEA is only to provide asink for the hydrogen ions that areproduced when CO2is hydrolysed inwater. The chemical absorption ofacid gas in MDEA is frequently ac-companied with considerable heatof reaction, which reduces theamine contactor efficiencies

(Seagraves and Weiland, 2009).Apart from generic alkanolamines,proprietary formulations comprisingmixtures of amines with variousadditives are also finding wide use.These are usually based on MDEA,but contain other amines as well ascorrosion inhibitors, foam depres-sants, buffers, and promotersblended for specific applications.They are tailored to provide selec-tive H2S removal, partial or com-plete CO

2 removal, high acid gas

loading, COS removal, and otherspecial features. MDEA added withPiperazine (PZ) is one such formu-lated amine solution, which is pre-dominantly used for bulk removal ofCO2 from acid gas streams. The keyadvantages of PZ is its strong reac-tivity towards CO2 and being a dia-mine, it contains two reactiveamine groups per molecule both ofwhich can attach to CO2, so it hasexceedingly high CO2 carrying ca-

pacity (Refer Table1) PZ acts as a

Abstract

The removal of hydrogen sulfide(H2S) and carbon dioxide (CO2) from

natural gas, LPG or sour gas treat-ment units using alkanolamines ispracticed extensively in the oil andgas industries. The design of acidgasamine contactors are oftenbased on equilibrium stage models.These models assume that vaporand liquid phases attain thermody-namic equilibrium and then designengineers resort to correction fac-tors such as tray efficiency or HETPto account for any departure from

equilibrium. A further advancementin this direction includes empiricalmodeling of reaction kinetics usingan adjustable parameter (H2S andCO2 tray efficiencies and/or liquidresidence times), that forces thesimulation to reproduce a treatedgas composition. However, themodel prediction viz. CO2 slip maydeviate when the amine-sweeteningunit is put in actual operation and

the treated gas may not meet thedesired product specifications. Thiscould be avoided at the design de-velopment stage only using the ro-bust non-equilibrium stage masstransfer rate based models. Thesemodels include additional transportequations i.e. i) solute equilibriumacross interfaces, ii) the effect ofchemical kinetics on mass transferrates, particularly in the liquidphase, and iii) mass and heat trans-fer rate models for transport acrossinterfaces. Thus, it is possible tocapture the actual performance ofthe columns. The present work

SIMULATE GAS SWEETENING UNITS FOR OIL & GAS INDUSTRY USING MASS

TRANSFER RATE BASED MODELS

By Anirban Pandit,Rohit P. Kulkarni,,,,Larsen & Toubro Limited, Vadodara

Table 1: Reaction Rate Constants with CO2of Com-mon Gas Treating Amines (Weiland, 2008)



This paper from L&Twas conferred with theBest Paper Awards inDownstream Categoryin PETROTECH 10


18/20

and mass transfer rate based simu-lation is presented. The synergisticeffect of PZ for bulk removal of CO2is compared with operational plant

data.

MethodologyTwo systems i.e.Hydrocarbon-H2S-CO2-MDEA and Hydrocarbon-CO2-MDEA-PZ are modeled and simu-lated for studying the amine contac-tor behaviour .The simulations areperformed using ProMax Ver. 3.1and ASPEN Plus Ver. 7.1 software.Following steps are involved in themodel development:

1. The components are specifiedfrom the simulation software li-brary.

2.In order to simulate amine unitaccurately, an Electrolytic thermo-dynamic model is selected. TheElectrolytic model accounts foracid gas and amines dissociationto form ions in aqueous solutions.The recommended property pack-age for acid-amine system in As-pen Plus and ProMax is electro-lyte-NRTL and Amine Sweeteningpackage, respectively.

3.To enable electrolytic calculationsfor PZ and CO2in Aspen Plus soft-ware the binary and ternary VLEdata for PZ-H2O and PZ-H2O-CO2are provided as an additional in-put.

4.The composition, mass flow rate,temperature and pressure for theinput feed streams are specified.

5.The kinetic expression and rate

constants for each reaction arespecified separately in AspenPlus. Whereas, in ProMax soft-ware TSWEET kinetics model isselected. This model estimatesthe kinetic effects based on theresidence time, which is calcu-lated from tray/packing geometri-cal details.

6.The model is simulated initially asan equilibrium stage.

7.Further, the non-equilibriumstage mass transfer rate basedmodel is simulated using AspenPlus RateSep. The input to Rate-

Sep included vapour phase filmresistance and reaction in liquidfilm.

Results and DiscussionsThe aim of this study is to demon-strate suitability of rate based masstransfer modeling for acid gas treat-ment. For this purpose, a Hydrocar-bon-H2S-CO2-MDEA system hasbeen taken as a test case. The re-sults for two models are presented.

Further, an operating case of Hydro-carbon-CO2-MDEA-PZ system ismodeled using the first principleapproach. The results were verifiedwith actual plant data. A detaileddiscussion of on these case studiesis presented below.

Hydrocarbon-H2S-CO2-MDEASystemA test case of treating natural gas(feed rate: 456 gmol/s, methane

content: 96 mol%) containing CO2(3.47 mol%) and H2S (0.006 mol%)as the acidic component is consid-ered for comparison of absorberperformance using various masstransfer models. The evaluation hasbeen made among an equilibriumstage model built on Aspen Plus,TSWEET kinetics model built on Pro-Max and rate based non-equilibrium stage model built onAspen RateSep. The feed gas at32.4 C temperature is treated us-

ing generic MDEA solution (6.9mol%). The diameter of absorbercolumn is 1.28 m and it contains21 single pass valve trays (trayspacing= 609 mm, weir height=46.8 mm). The column was initiallysimulated according to reactionmodified, equilibrium stage model.The results of Aspen Plus equilib-rium model indicated that H2S andCO2 concentration in treated gas

promoter and reacts instantane-ously with CO2 at the gas-liquid in-terface. It then shuttles CO2(as car-bamate) into the bulk of the liquid

where it is dissociated back into thefree amine and transfers CO2 toMDEA (Refer Figure 1). The pro-moter diffuses back to the interfacefor more CO2capture.

The accurate engineering design ofH2S-CO2-MDEA-PZ absorber systemrequires capturing underlying reac-tion and mass transfer mechanismas discussed above. Apart from this,thermodynamic property packagealso play an important role for de-sign of such system. Two designmethods viz. equilibrium stage andnon-equilibrium stage mass transferrate based approach area popularamongst design engineers foramine contactors. A detailed analy-sis of various mass transfer andsolubility model is discussed by theauthors elsewhere (Kulkarni andPandit, 2009). In equilibrium stageapproach, interfacial mass flux andthe reaction rates are not consid-

ered. Often a suitable tray efficiencybased on operational experience isassumed. In the rate based ap-proach, mass and heat transferphenomena, occurring on an actualtray rather than on a theoretical trayis used.In this work, Hydrocarbon-H2S-CO2-MDEA-PZ system is simulated usingcommercial software. The resultcomparison between equilibrium




Figure 1: Piperazine Shuttle Mechanism (Weiland,2008)


Invention requires an excited mind; execution, a calm one


19/20

inside the column.

Hydrocarbon-CO2-MDEA-PZSystem

In this case complete amine unitincluding absorber and regeneratorare simulated. The feed gas(20,700 kg/h) containing 4.62mol% of CO2 is entering the ab-sorber column at 30.8 C. The gasis counter-currently contacted withPZ promoted MDEA solution enter-ing at 60.6 C. The absorber col-umn is packed column (columni.d.=1.18 m, packing type=IMTP

25mm metallic, total packed sec-tion height=16.5 m). Similarly, theregenerator column details are:(column i.d.=1.22 m, packingtype=IMTP 35mm metallic, totalpacked section height=8 m). Thesimulations are carried out usingnon-equilibrium stage mass transferrate based model in Aspen RateSepsoftware to validate the column per-formance. Since reaction with PZ isinstantaneous and occurring pri-marily in liquid phase, liquid filmreaction is given as an inputwhereas film resistance is providedon gas side. For estimating masstransfer coefficient and interfacialarea method proposed by Onda et

al. (1968) is used. The comparisonof simulation results and operatingdata is shown in the Table 2. Theresults are found in close agree-ment with the operating plant data.The simulated column temperatureprofile is indicated in Figure 3. Thetemperature bulge observed at 3 m(i.e. 2ndstage) from column bottomline indicates maximum CO2 re-moval occurring in the lower portion

of the column. This also justifiesthat the column can handle higherCO2 concentration, which presentlythe operating plant is handling.

ConclusionIn the case of Hydrocarbon-H2S-CO2-MDEA system, it was foundthat the rate-based model predictsthe column temperature profilequite adequately compared to anequilibrium model. Further, bulkremoval CO2 from acid gases withusing PZ promoted MDEA is suc-cessfully modeled with the ratebased approach. The simulated

results are found in confirmationwith the operating plant data. Forthe case studied, most of CO2 re-moval took place in the lower por-tion of absorber column.

ReferencesDanckwerts, P.V. The Reaction ofCO2 with Ethanolamines.1979,Chem. Eng. Sci.34, 443.Kohl, A. L.; Neilsen, R. Gas Purifica-tion 5th Edition: Gulf PublishingCompany: Houston, 1997.

Kulkarni, R.; Pandit, A. Modelingand Simulation of Amine Sweeten-ing Units for Acid Gas Removal AReview. 2009, 5th SOGAT Interna-tional Conference: Abu Dhabi.Onda, K.; Takeuchi, H.; Okumoto, Y.Mass Transfer Coefficients betweenGas and Liquid Phases in PackedColumns. 1968, J. Chem. Eng. Ja-pan,1, 56.Seagraves, J.; Weiland, R. Treating

could be reduced to level of 1 ppmand 0.9 mol%, respectively. How-ever, the rate based model in AspenPlus RateSep indicated a consider-

able CO2slip in the treated gas withthe outlet concentration reaching ashigh as 1.4 mol%. Further, simula-tions using TSWEET Kinetics modelshowed 1.83 mol% CO2 concentra-tion in the treated gas. Though,TSWEET kinetics is equilibriumstage model, the higher CO2 slipcaptured can be attributed to itsapparent reaction kinetics which isbased on tray liquid residence time.Figure 2 indicate the simulated col-

umn temperature profile for equilib-rium and rate based model. In thisfigure, the temperature bulge seenacross the column is a result of coldinlet gas absorbing heat from richsolution at the bottom of column,then later losing this heat to thecooler solution near the upper partof the column. The size, shape andlocation of temperature bulge de-pend upon where in the column thebulk of the acid gas is absorbed, theheat of reaction and relativeamounts of gas liquid loads. Sinceheat is transferred from hot liquid tothe cooler gas at the bottom of thecolumn and in the opposite direc-

tion near the column, the liquid andvapor temperature profiles crosseseach other near the temperaturebulge. For equilibrium model, as thevapor and liquid temperature pre-dicted is same, the column tem-perature profile does not representthe actual heat transfer occurring




Table 2: Result Comparison for Hydrocarbon-CO2-

MDEA-PZ System

1

3

5

7

9

11

13

15

17

19

21

40 45 50 55 60 65 70 75 80 85

StageNumber

Temperature, oC

Bottom

Top

Figure 3: Column Axial Temperature Profile forHydrocarbon-CO2-MDEA-PZ System


Best is not the end point, but a starting point for innovation


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High CO2 gases with MDEA. 2009,PTQ, 103.Weiland, R. Piperazine Why it'sUsed and How it Works. 2008, The

CONTACTOR, 2(4).

About the PaperPETROTECH-2010, 9th InternationalOil & Gas Conference and Exhibitionwas held at New Delhi from 31stOctober to 3rd November 2010.From L&T Engineering Vadodara,Dr. Rohit P. Kulkarni and Mr. Anir-ban Pandit jointly presented paperon Simulate Gas Sweetening UnitSimulate Gas Sweetening UnitSimulate Gas Sweetening UnitSimulate Gas Sweetening Unitfor Oil & Gas Industry using Massfor Oil & Gas Industry using Massfor Oil & Gas Industry using Massfor Oil & Gas Industry using Mass

Transfer Rate based ModelTransfer Rate based ModelTransfer Rate based ModelTransfer Rate based Model in thein the conference.This paper captured the superiorityof robust non-equilibrium stagemass transfer rate based model fordesign of Gas Sweetening Units.This model included additionaltransport equations i.e. i) soluteequilibrium across interfaces, ii) theeffect of chemical kinetics on masstransfer rates, particularly in theliquid phase and iii) mass and heattransfer rate models for transportacross interfaces. Through such adetailed study, it was possible tocapture the actual performance ofthe column. The studies performedon Hydrocarbon-H2S-CO2-MDEA sys-tem concluded that the rate-basedmodel could exactly capture theAmine Contactor Column tempera-ture profile. Also, bulk removal CO2from acid gases using piperazinepromoted MDEA was successfullymodeled using similar approach.

The simulated results closelymatched with the operating plantdata.

This paper from L&T was conferredThis paper from L&T was conferredThis paper from L&T was conferredThis paper from L&T was conferredthe Best Paper Awards in Down-the Best Paper Awards in Down-the Best Paper Awards in Down-the Best Paper Awards in Down-stream Category in PETROTECHstream Category in PETROTECHstream Category in PETROTECHstream Category in PETROTECH2010.2010.2010.2010.





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