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Modular design of smaller-scale GTLplants

Modularisation is a construc-tion method that involvesdesigning and buildingre nery and gas processing facili -ties as series of unitised (ormodularised) process and utility

systems. The units are designedand fabricated in a controlled shopenvironment, then shipped to theproject site, where they are installedon foundations and connectedtogether. Compared to traditional

eld construction methods, whereall materials are delivered to theproject site and then built on loca -tion, modularisation is proving to be an effective solution for achiev -ing fast-track project schedules, and

for building re ning and gasprocessing facilities in remotelocations. For example, VentechEngineers International LLC(Ventech), based in Pasadena,Texas, is an engineering, procure -ment and construction companythat specialises in the design andfabrication of modularised facilities.

A project in Siberia illustratesthe capabilities of modularisationwhen dealing with remote andchallenging environments. Ventechdesigned, fabricated and shipped a2000 b/d crude processing plant tothe remote Siberian town of Urai in just six months after contract sign -ing. Urais temperatures drop aslow as -45C (-50F), so the moduleswere designed and fabricated toaccommodate these conditions. Inparticular, the crude processmodule was completely enclosedand heated. Ventech personnel,assisted by local labour, installed

the modules at the project site andstarted re nery operations fourweeks after the modules delivery.

Modularisation is opening up opportunities for GTL plants to monetise small-scalenatural gas deposits both on- and offshore

KENNETH ROBERTSVelocys

Ventech has applied modulardesign and construction mostrecently in the Kurdistan region ofnorthern Iraq. A large-scale expan -sion to a re nery in Kurdistanstarted during 2010, with Ventechproviding a 20 000 b/d modular -ised crude processing plant thatwas added to the existing 20 000 b/d re nery. Made up of26 modules, the new crude unitwas designed and fabricated atVentechs Pasadena fabrication site.The modules were shipped to theport of Mersin, Turkey, then trans -ported by truck to the project sitein Kurdistan, where the re nerywas erected in 16 weeks.

The re nery has continued toexpand in a modular fashion; once

completed in 2013, total capacitywill be over 185 000 b/d and itwill remain the sole producer of

unleaded gasoline in Iraq. In all,Ventech has provided modularisedcrude distillation units, naphthahydrotreaters, catalytic reformers,isomerisation units, demercaptani -sation systems, gas plants andsupporting utilities to this three-phase project. Modularisation hasmade the difference in thisgeographically and politically chal -lenging location, enabling expansionwork to be accomplished quickly.

Design concepts for modularisationIn modular plant design, the differ -ent process units are contained inseparate modules. For ease of ship -ment to any location, Ventechfabricates its modules to a standardsize of 13.5ft wide x 12ft high x 40ft

long. Each of the modules andits associated equipment has areference code, which helps

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Figure 1 Fischer-Tropsch module process unit Courtesy of Ventech

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communicate where the modulewill be installed on the plot plan.Connections between the modulesare designed to be similar in con g -uration so that construction isrelatively straightforward. Ventechestimates that, with modularisation,approximately 70% of a project isalready complete even before themodules are shipped from theirfacility. This greatly decreases eldconstruction time to deliver anoperational facility (see Figure 1).

These methods also facilitate easydisassembly and relocation, ifnecessary, at some point in thefuture. For example, a remotelylocated gas processing facility could be easily taken apart and moved toa new natural gas source if an exist -ing supply was depleted in its

current location.Applying modularisation to re n -

ery construction has advantageswith regard to productivity, prod -uct quality and ensuring the safetyof construction personnel. Since themodules are built in a well-lit,climate-controlled environment,work can continue around the clockregardless of weather conditions,for greater productivity and easierquality control. Since module height

is restricted, safety is enhanced, asworkers build at limited heightswithin the fabrication facility.

Modularising GTLThe same advantages of modular

construction of re neries are beingapplied to the construction ofdistributed GTL plants. The GTLprocess involves two operations: theconversion of natural gas to amixture of carbon monoxide (CO)and hydrogen (H 2), known assyngas, followed by a Fischer-Tropsch (FT) process to convert thesyngas into paraf nic hydrocarbonsthat can be further re ned toproduce a wide range ofhydrocarbon-based products, includ -ing clean-burning, sulphur-freediesel and jet fuel. Speciality prod -ucts including food-grade waxes,solvents and lubricants can also beproduced from the paraf nichydrocarbons.

Large, commercial-scale GTLplants, including the Sasol Oryx and

the Shell Pearl plants (both locatedin Qatar), have been built at enor-mous capital cost. The Oryx plant,designed for production levels of34 000 b/d, cost around $1.5 billionto build. The Shell Pearl plant, withan ultimate design capacity of 140000 b/d of GTL products and 120 b/d of natural gas liquids, costaround $18-19 billion. ConventionalGTL plant designs rely on econo -mies of scale to drive positive

nancial returns and are viable onlywhere there are large supplies oflow-priced natural gas.

However, another option beingdeveloped smaller-sized anddistributed GTL plants shows

promise for deriving value fromsmaller accumulations of unconven -tional gas that would otherwise beleft underground, such as shale gas,tight gas, coal bed methane andstranded gas (gas elds located toofar from existing pipeline infra -structure). A small, modularisedGTL plant has the exibility to beinstalled close to the trappedresource and then used to processthat resource locally. Associated gas(gas produced along with oil) isanother area of opportunity formodularised GTL plants. This gasis typically disposed of either by re-injection, at considerable expense, back into the reservoir or by thewasteful and environmentallydamaging practice of aring, whichis subject to increasing regulation.

Modularised GTL plants enable thisotherwise wasted gas to beconverted into additional revenue.

In the larger economic picture, amodular GTL capability can be thekey factor that enables the construc -tion of upstream projects thatwould otherwise be cancelled because of poor results derivedfrom economic models. For exam -ple, some shale gas discoveries are being hampered by high develop -

ment costs, which result in marginaleconomics due to gas prices thatare often low. These projects can beenhanced by converting the gas tohigher-value clean fuels producedin the GTL process.

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Distributed GTL plants, usingsmaller Fisher-Tropsch (FT) reactorsand located near the natural gassource, can be designed for use in both offshore and remote on-shorelocations. The FT reactors devel -oped by Velocys, the US-basedmember of the Oxford CatalystsGroup, employ microchannel tech -nology. This is a developing eld ofchemical processing that intensi eschemical reactions and reduces thedimensions of the reactor systems by increasing the heat removalcapability to enable reactions tooccur at rates 10-1000 times fasterthan in conventional systems. Thismakes it possible to use more activeFT catalysts.

Velocys reactors are the only FTreactors to use a highly active FT

catalyst developed by OxfordCatalysts to accelerate FT reactions by a factor of 10-15 times comparedto conventional reactors. Individualreactors are designed to produce125 b/d of FT product, and desiredplant capacity is reached by linkingtogether, or numbering up, multiplereactors to meet the availability ofgas feed. For example, by linkingup 40 individual 125 b/d reactors,a capacity of 5000 b/d can be

achieved with a natural gas feedrate of approximately 50 million cuft/day. As a result, the distributedGTL plant technology developed byVelocys has the exibility to scaleproduction to match the availableresource. Plants of this type canalso be used as a exible andeconomical way to expand thecapacity at existing petroleum re n -eries when an economic gas supplyis available.

Velocys is currently working withHaldor Topse and Ventech todesign a modular GTL plant usingits microchannel FT reactor (seeFigure 2). The modular GTL plantwill be comprised of standard-sized13.5 x 12 x 40ft (4.1 x 3.65 x 12m)modules that will be built inVentechs fabrication facility. Inthese GTL plant designs, autother -mal reforming (ATR) reactors fromHaldor Topse will be used toproduce the syngas feedstock for

the Velocys FT reactors. HaldorTopse is also providing the hydro -processing unit that takes raw

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products from the FT reactor and

produces nished fuels.

First commercial plantThe rst company to select themodular GTL plant design isCalumet Specialty Products PartnersL.P., an independent producer ofspeciality hydrocarbon products inNorth America. Calumet plans touse the modular GTL plant, whichhas a nominal capacity of 1000 bpd,in the expansion of its Specialty

Products facility at Karns City,Pennsylvania. The very pure,paraf nic hydrocarbons produced by the GTL plant will be used asfeedstock for some of Calumets1500 products, including food-gradewaxes, solvents and lubricants.Calumet was attracted to the ideaof modular GTL technology becauseit offers the ability to use readilyavailable, low-cost natural gas toreduce overall costs, increase thesecurity of feedstock supply andimprove product quality.

The GTL plants modules will befabricated in Ventechs Texas fabri -cation facility, then transported bytruck to the Karns City site forinstallation and integration withCalumets existing re nery. Velocysengineers are working with Ventechand Haldor Topse on the plantdesign, which is due be completed by late 2012. Fabrication is expectedto begin during the rst half of 2013

and the modular GTL plant wouldcome on-stream during the secondhalf of 2014.

More projects

Meanwhile, both Velocys andVentech expect that the Calumetproject will be just the rst of manysmall-scale modular GTL plantsannounced, several of which arealready undergoing preliminarydesign. Velocys continues to receivenumerous inquiries about themicrochannel technology, not onlyfor distributed GTL but also for biomass-to-liquids (BTL) applica -tions. For example, Solena has

recently chosen the Velocys FTprocess for its GreenSky LondonProject, which will produce renew -able jet fuel in the UK.

Given the low natural gas pricesin the US, and the small and oftenremote nature of many gas depositsaround the world, interest in modu -lar distributed GTL plantsincorporating microchannel FT reac -tors is expected to grow. Once theCalumet GTL plant comes onstream, Velocys, Ventech and HaldorTopse are con dent that suchplants will prove to be the best wayforward for monetising strandedand undervalued natural gas.

Kenneth Roberts is Senior BusinessDevelopment Director with Velocys, Houston,Texas. With over 35 years experience in theenergy industry, he supports engineeringand business development activities incollaboration with Ventech and Haldor Topsefor the modular GTL design. He holds a BS in

mechanical engineering and a MBA in strategicplanning from the University of Texas atAustin.

High heat flux10 times higher than

conventional reactors

Syngas

FT products

0.25 to 10mm

0.25 to 10mm

Figure 2 Microchannel FT reactor internals Courtesy of Oxford Catalysts Group