The turbodevelopenatural gachieves heavier cdistillatio The turboresults inexpanderthe reducThomson Turbo-exexchangeplant to areached bmost of tthe feed g Fig. 5.21arrangemrecoveryhydrocar

                

F

o-expander ped in the earlas, as ethanevery low tem

compounds ion.

o expander rn a drop in prr to recover ection in gas tn) expansion

xpander procers. The gas a very low wby the gas bethe water, fogas. Gas pre

1 is an illustrments possibl

. Whether thrbons from n

Fig. 5.21—Sc

Tu

process for tly 1960s. Its e is an impormperatures ain natural ga

removes eneressure and tenergy fromtemperature n across a va

cess configurentering the

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chematic dr

urbo Exp

treating natumain applic

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an also inclu

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pander

ural gas streacation was toock for the pre, liquefies us fractions

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essure gas, thhan can be ob

vary greatly.nder processhydrates formually requiresieve unit to ude CO2 and

mple turbo-exs compositionely the best ciderable ana

urbo-expand

Process

ams for high o improve thpetrochemicaa substantiaof the liquid

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They all incs must be dehm when the ls a glycol deremove virtuH2S remova

xpander faciln and the de

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s

liquids recohe recovery oal industry. Tl portion of t

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corporate vahydrated upslow temperaehydration uually all of thal.

lity. There aresired level ocovering eth

ent.

overy was of ethane froThe process the ethane anrecovered b

stream, whicergy. By usins enhanced, ahalpic (Joule-

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atures are unit for remohe water fro

re many otheof liquids hane and hea

 

om

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avier

Gas Preconditioning

Expander processes for NGL recovery can chill the gas as low as –160°F. To dry the gas to this low a water dewpoint temperature requires the use of molecular sieves in drying towers as illustrated in Fig. 5.15. A common class of molecular sieve used for deep drying has a pore opening of 4 Å. Instead of drying the gas with molecular sieves, it is also possible to prevent potential freezing problems with the addition of minor amounts of methanol into the gas stream upstream of the chilling section.

Turbo-Expander Design

The design of a turbo-expander unit involves detailed heat and material balances and many flash calculations. Such design calculations are performed by computer.