Teknologi Pemrosesan Gas (TKK 564) Instructor: Dr. Istadi idi …tekim.undip.ac.id/staf/istadi/files/2009/08/gasprocessing14.pdf · yObviously, gas processed for LNG must have much

Teknologi Pemrosesan Gas (TKK 564)

Instructor: Dr. Istadi(http://tekim.undip.ac.id/staf/istadi )

il  i di di idEmail: [email protected]

I t t ’ B k dInstructor’s Background

BEng. (1995): Universitas DiponegoroMeng. (2000): Institut Teknologi BandungPhD. (2006): Universiti Teknologi Malaysia

Specialization: Catalyst Design for Energy ConversionP  D i  f  E  C iProcess Design for Energy ConversionCombustion EngineeringComputational Fluid Dynamic (CFD)Computational Fluid Dynamic (CFD)

Course Syllabus: (Part 2)Course Syllabus: (Part 2)y ( )y ( )1. Hydrocarbons Recovery (Pengambilan Kembali Hidrokarbon)2. Nitrogen Rejection/Removal (Penghilangan Nitrogen)g j ( g g g )3. Trace Component Removal (Penghilangan Komponen

lainnya)4 Natural Gas Liquid Processing and Sulfur Recovery4. Natural Gas Liquid Processing and Sulfur Recovery

(Pemrosesan Cairan Gas Alam dan Penghilangan Sulfur)5. Gas Transportation and Storage (Transportasi dan

Penyimpanan Gas)Penyimpanan Gas)6. Liquified Natural Gas #1 (Gas Alam Cair)7. Liquified Natural Gas #2 (Gas Alam Cair)8. Second Assignment9. Ujian Akhir Semester

Natural gasNatural gas processing

Natural gas processingg p g

Natural GasesRaw natural gas typically consists primarily of methane (CH4), the shortest and lightest hydrocarbon molecule, containing of:

Heavier gaseous hydrocarbons: ethane (C2H6), propane (C3H8), normal butane (n-C4H10), isobutane (i-C4H10), pentanes and even higher molecular weight hydrocarbons. When processed and purified into finished by-products, all of these are collectively referred to as NGL (Natural Gas y p , y (Liquids).Acid gases: carbon dioxide (CO2), hydrogen sulfide (H2S) and mercaptanssuch as methanethiol (CH3SH) and ethanethiol (C2H5SH).O h i (N2) d h li (H )Other gases: nitrogen (N2) and helium (He).Water: water vapor and liquid water.Liquid hydrocarbons: perhaps some natural gas condensate (also referred to as casinghead gasoline or natural gasoline) and/or crude oilto as casinghead gasoline or natural gasoline) and/or crude oil.Mercury: very small amounts of mercury primarily in elemental form, but chlorides and other species are possibly present.

Natural Gas SupplyPipeline CapacityStorageStorageGas Drilling RatesNatural Phenomena, i.e. hurricane, etc.atu a e o e a, e u ca e, etcTechnical IssuesImportsp

Why Liquified?The rationale for liquefying natural gas is simple:

t t h i th li id d it t that atmospheric pressure, the liquid density at the normal boiling point of methane is approximately 610 times greater than that of the gas at ambient g gtemperature and pressure. consequently, a given volume of liquid contains over 600 times the heating value as the same volume of600 times the heating value as the same volume of ambient gasLiquefaction and transport becomes economically q p yfeasible when the size of the reserves justify the capital investment of a liquefied natural gas (LNG) plantplant.

Natural Gas Liquefaction Processes

Currently there are 4 Liquefaction processes available:APCI: designed by Air Products and Chemicals, Incorporation.Cascade: designed by ConocoPhillips.g y pShell DMRLinde

The majority of the liquefaction processes use either APCI orThe majority of the liquefaction processes use either APCI or Cascade technology.The other processes, used in a small minority of some liquefaction plants include Shell's DMR technology and the Linde technologyplants include Shell s DMR technology and the Linde technology.APCI technology is the most used liquefaction process in LNG plants

PEAK SHAVING/DEMAND PLANTS AND SATELLITE FACILITIESAND SATELLITE FACILITIES

When underground storage is unavailable,When underground storage is unavailable, aboveground storage of natural gas as LNG becomes attractive, and utilities use relatively small li f ti t d ifi ti l t tliquefaction, storage, and regasification plants to meet the demand. Plants that combine all three of these tasks arePlants that combine all three of these tasks are referred to as peak shaving plants.Any LNG facilities like these, which contain onlyAny LNG facilities like these, which contain only storage and regasification units, are called “satellite facilities.”

Schematic of peak‐shaving facilitySchematic of peak shaving facility

Another Technology?gyWhen compressed gas pipelines are impractical or impossible, a limited number of conventional poptions are open :

compression and transport of the gas in specially b ilt hibuilt ships conversion of the natural gas into a liquid through gas to- liquid (GTL) technology,gas to liquid (GTL) technology, and liquefaction and shipment of the gas in specially built LNG vessels.

Presently, LNG is the most viable option in almost all situations involving stranded reserves, if the gas can be pipelined to a seaportcan be pipelined to a seaport

Schematic of a baseload plant combined with transporting, receiving, and regasification

facilities

Gas DistributionGas st but obringing the gas from the field to the customer involves f tfour steps:

1. Gas production, gathering, and processing2 LNG production including gas treating liquefaction NGL2. LNG production, including gas treating, liquefaction, NGL condensate removal, and LNG storage and loading3. LNG shipping4. LNG receiving facilities, which include unloading, storage, regasification, and distribution

D di th ifi it ti t ll l t illDepending on the specific situation, not all plants will have all the processes shown, and some plants may have additional processes.have additional processes.

Worldwide LNG exports in 2002

Worldwide LNG Import in 2002Worldwide LNG Import in 2002

Price of imported LNG compared ith H H b iwith Henry Hub price

GAS TREATING BEFORE LIQUEFACTIONLIQUEFACTION

Production of LNG requires temperatures as low asProduction of LNG requires temperatures as low as −258°F (−161°C), the normal boiling point of methane, Consequently, the allowable impurity levels in a gas to be liquefied are much lower than that of a

i li litpipeline-quality gasObviously, gas processed for LNG must have much more aggressive removal of water nitrogen andmore aggressive removal of water, nitrogen, and carbon dioxide than does gas destined for pipelines

LIQUEFACTION CYCLESThe two most common methods that have been used in engineering practice to produce lowused in engineering practice to produce low temperatures are:

Joule-Thomson expansion and expansion in an engine doing external work

JOULE‐THOMSON CYCLESJOU O SO C C SThe Joule-Thomson coefficient is the change in t t th t lt h i d dtemperature that results when a gas is expanded adiabatically from one constant pressure to another in such a way that no external work is done and no ynet conversion of internal energy to kinetic energy of mass motion occurs. Thermodynamically, it is an irreversible process that wastes the potential for doing useful work with the pressure dropthe pressure drop. However, it is as simple as a valve or orifice and finds wide use in refrigeration cycleg y

The thermodynamic definition of the Joule-Thomson coefficient:

Combination of the above relation with the ideal gas law (PV = RT) gives µ= 0 andgives µ= 0, and thus no temperature change occurs when an ideal gas undergoes a Joule-Thomson expansion. F l th J l Th ffi i t b iti (thFor a real gas, the Joule-Thomson coefficient may be positive (the gas cools upon expansion), negative (the gas warms upon expansion), or zero.Th t t i i t t b th J lThe temperature increase remains constant because the Joule-Thomson coefficient remains nearly constant over the temperature range considered

The behavior of several gases upon expansion from 101 bar (1,470 psia) to 1 bar (14.5 psia)101 bar (1,470 psia) to 1 bar (14.5 psia)

Simple Joule‐pThomson 

liquefactionliquefaction cycle

Joule‐ThomsonThomson 

liquefactionliquefaction plant

EXPANDER CYCLESEXPANDER CYCLESJoule-Thomson expansion that it was a th d i ll i iblthermodynamically irreversible processExpansion of high-pressure gas to the lower pressure in a reversible or nearly reversiblepressure in a reversible or nearly reversible manner provides two distinct improvements over the Joule-Thomson expansion:

First, in the reversible expansion, a large fraction of the work required to compress the gas can be recovered and used elsewhere in the cycle Thisrecovered and used elsewhere in the cycle. This property provides an increase in cycle efficiency. Second, the reversible process will result in a much larger cooling

Simple closed cycle liquefaction processprocess

Open cycle expander 

l tplant

Peak‐shaving l i hplant with open cyclopen cycl

Schematic of commercial closed‐cycle PRICO® systemcycle PRICO® system

STORAGE OF LNG

Discussions of LNG storage facilities are normally g ydivided into two major categories:

aboveground and in ground

CRYOGENIC ABOVEGROUND STORAGESTORAGE

Three basic types of aboveground storage vessels are in use:

SteelPrestressed concretePrestressed concreteHybrid (combinations of steel and concrete)

Single‐containment tankg

Double‐containment tank

Full‐containment tank

CRYOGENIC IN GROUND STORAGE

Three basic types of in ground storage have been used:

• Conventional concrete or steel tanks in an underground configurationunderground configuration• Tanks formed around a frozen-earth cavity• Mined caverns

Conventional TankageCo e t o a a ageWith aboveground tank storage discussed in the previous section the walls must supply all of theprevious section, the walls must supply all of the mechanical strength. In ground tanks may use either the surrounding g y gearth to provide mechanical support or an in-pit construction in which the tank is built as a separate

it d th it id t i t i funit and the pit provides containment in case of leakage or rupture.The tanks are unique not only because of their sizeThe tanks are unique not only because of their size but also because of the fact that the entire tank, including the domed roof, is buried.

Frozen‐Earth CavitiesThe cavity is initially cooled by spraying LNGcooled by spraying LNG into the vapor space. The roof reaches its t d t t t tsteadystate temperature

rapidly. Because of the lowBecause of the low thermal conductivity of the frozen earth, the surrounding soil maysurrounding soil may take several years to reach its steady-state t ttemperature.

Mined CavernsIn this storage concept, a subterranean cavity is created to hold the LNG, with the cavity walls either in direct contact with the liquid or separated by anin direct contact with the liquid or separated by an insulating wall.Presently neither of the above techniques has beenPresently, neither of the above techniques has been applied commercially

TRANSPORTATIONlarge gas reserves often the only alternative to pipelines is shipping by LNGpipelines is shipping by LNG. Three options are possible for transporting LNG:

• Truck transport Truck transport• LNG pipelines• Marine carriers

TRUCK TRANSPORTTRUCK TRANSPORT

Cryogenic liquids including liquid helium liquidCryogenic liquids, including liquid helium, liquid hydrogen, liquid nitrogen, and liquid oxygen, are routinely moved by truck transport. Thus, over-the-road movement of LNG is a relatively simple, straight-forward process that requires no

t h lnew technology. The major consumers of trucked LNG are vehicle fueling stations and “stranded local utilities ” thosefueling stations and stranded local utilities, those who are not connected to the national network of natural gas pipelines

PIPELINESlong-distance LNG pipelinesP i li id i t d f i kPumping liquid instead of compressing gas makes the concept seem attractive

Marine Transportthe evolution of LNG ship designseveral basic design criteria:

1. The low density of LNG and the requirement for separate water ballast containment require a large hull, with low draft and high freeboard*.2. The low temperature of LNG requires the use of special and expensive alloys in tank construction For free standing tanks only aluminum or 9%alloys in tank construction. For free-standing tanks, only aluminum or 9% nickel steel are suitable, whereas for membrane tanks, stainless steel or Invar is used.3. The large thermal cycling possible in the storage tanks demands special supporting arrangements for free standing tanks and membrane flexibility in membrane designs.4. The hull of the vessel is carbon steel, so good thermal insulation is required between the tanks and the hull In addition for membrane tanks therequired between the tanks and the hull. In addition, for membrane tanks, the insulation must be capable of supporting the full weight of the cargo.5. The cargo handling equipment must be carefully designed to account for thermal expansion and contraction.

Application of these principles in the design of LNG carriers resulted in a number of different LNG containment concepts, but today only three systems are in general use, and they may be grouped into two designs:

Independent tanks membrane tanks, which use different membrane configurations

Presently, all LNG carriers are double-hulled. With two exceptions, they use steam-powered turbines fueled by boil-off natural gas. Movement has begun toward use of duel-fuel diesel gengines, with efficiencies of 38 to 40%, compared with steam-powered turbines, with efficiencies of 28%. Diesel engines also have lower NOX emissions

Spherical LNG storage tank before installation on carrier hullinstallation on carrier hull

Ship with three of four storage tanks installedtanks installed