Separator & Production Facilities: SEPARATOR:Closed vessels to remove liquid from gases

SEPARA SEPARATOR TOR & PRODUCT P RODUCTION ION FACILITIES Introduction: SEPARATOR :Closed vessels to remove liquid from gases An oil/gas separator is a pressure pressure vessel used for separating a well stream into gaseous and liquid components.  Te! are installed installed eiter in an onsore onsore processing station station or on an o"sore platform. #ased on te vessel con$gurations% te oil/gas separators can &e divided into ori'ontal% vertical% or sperical separators. (n teams of )uids to &e separated% te oil/gas separators can &e grouped into gas/liquid two*pase separator or oil/gas/water tree* pase separator. separator. #ased on separation function% te oil/gas separators can also classi$ed into primar! pase separator% test separator% ig*pressure ig*pressu re separator low*pressure separator deliquili'er deliqui li'er degasser etc. To meet process requirements% te oil/gas separators are normall! designed in stages% in wic te $rst stage separator is used for preliminar! pase separation% wile te second and tird stage separator are applied for furter treatment of eac individual pase +gas% oil and water,. -epending on a speci$c application% oil/gas separators are also called deliquili'er or degasser. degasser. Te deliquili'ers are used to remove dispersed droplets from a &ul gas stream wile te degassers are designed to remove contaimined gas &u&&les from te &ul liquid stream

:Conventional oil/ga e!arator na"e •

Oil/gas separator

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0as/liquid separator

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-egasser

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-eliquli'er

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Scru&&er

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 Trap  Trap

:Se!arator container 1

An oil/gas separator generall! consists of following components •

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(nlet device located in pre*separation 'one/section for preliminar! pase separation #a2es downstream te inlet component to improve )ow distri&ution Separation enancement device located in te primar! separation +gravit! settling, section for ma3or pase separation 4ist e5traction device located in gas space to furter reduce liquid content in te &ul gas stream 6arious weirs to control te liquid level or interface level 6orte5 &reaer to prevent gas carr! under at outlet of liquid pase

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7iquid level/interface detection and control% etc.

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0as% oil% water outlet

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Pressure relief devices

(n most oil/gas processing s!stems% te oil/gas separator is te $rst vessel te well stream )ows troug after it leaves te producing well. 8owever% oter equipment suc as eaters ma! &e installed upstream of te separator.

Function of a separator  Te primar! functions of an oil/gas separator% along wit separation metods% are summari'ed in Ta#le $

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Requirements of separators Separators are required to provide oil/gas streams tat meet .salea&le pipeline speci$cation as well as disposal •

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Oil must ave less tan 1 +&! volume, water and less tan ; l&m water/44scf gas. cient margin. Te separator is generall! divided into te following functional 'ones •

(nlet 'one

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?low distri&ution 'one

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0ravit! separation/coalescing 'one

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Outlet 'one

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Inlet zone Appropriate inlet device is needed to o&tain an initial &ul separation of liquid/gas. (n most cases% gas will ave alread! come out of solution in te pipeline% leading to te separator +&ecause of pressure drop across an upstream coe or a control valve,. 8ence% te ma3orit! of te gas is separated from te liquid in te inlet 'one. #ecause of foaming issues and te need for iger capacities% c!clonic inlets are now &ecoming increasingl! popular. ?or applications wit inlet momentum sa!ing less tan  Pa% a vane .inlet can &e used : T!pical inlets include •

?lat impact plates

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-ised*ead plates

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8alf*open pipes

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6ane*t!pe inlet

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C!clone*cluster inlet

 Tese inlets% altoug ine5pensive% ma! ave te sortcoming of negativel! a"ecting separation performance. 8owever% for iger* momentum )uids% tese inlets can cause pro&lems. Te )at or dised*ead plates can result in small drops and foam. Te open* pipe designs can lead to )uid sort*circuiting or canneling. Altoug inlet momentum is a good starting guideline for selection% te process conditions% as well as te demister coice% sould also &e considered. ?or e5ample% if te liquid loading is low enoug tat a demister can andle all te liquid% ten inlet devices can &e .applied &e!ond teir t!pical momentum ranges

Flow distribution Zone Regardless of te si'e of te vessel% sort*circuiting can result in poor separation e>cienc!. (ntegral to an! inlet device is a )ow straigtener suc as a single perforated &a2e plate. A full*diameter plate allows te gas/liquid to )ow more uniforml! after leaving te vane*t!pe inlet% inlet c!clones% or even te impact plates. Te plate also acts as an impingement demister and foam &reaer as well.  T!pical net*free area +B?A, ranges in te 1= to ;= range. As te B?A lowers% te sear of te )uids gets iger% so te B?A sould &e matced to te particular application. One concern of tese plates is 

solids &uildup on te upstream side. 0enerall!% te velocities are ig enoug in te inlet 'one to carr! te solids troug te perforations. (n an! case% a )us no''le sould &e installed in te inlet 'one. Oter designs include )ow straigtening vanes. 8owever% .te open area is generall! too ig to &e e"ective

Gravity/coalescing zone  To assist in separation +and foam &reaing,% mes pad% vane pac% and/or plate/matri5 pacs are sometimes introduced in te gas/liquid separator. Tese internals provide more impingement or searing surfaces to enance coalescing e"ect of te dispersed pase. ?or te gas pase% matri5/plate pacs and vanes ave &een used to aid in liquid drop coalescence or foam &reaing. Te teor! &eind installing te ig surface internals suc as plate pacs for foam &reaing is tat te &u&&les will stretc and &rea as te! are dragged along te surfaces. 8owever% if most of te gas )ows troug te top portion of te pac% te foam! la!er will not &e su>cientl! seared% and te &u&&les will meander troug to te .oter end

Outlet zone 4ist capture can occur &! tree mecanisms it sould &e ept in mind tat tere are no sarpl! de$ned limits &etween mecanisms. As te momentum of a droplet varies directl! wit liquid densit! and te cu&e of te diameter% eavier or larger particles tend to resist following te streamline of a )owing gas and will strie o&3ects placed in teir line of travel. Tis is inertial impaction% te mecanism responsi&le for removing most particles of diameter D 1= m. Smaller particles tat follow te streamlines ma! collide wit te solid o&3ects% if teir distance of approac is less tan teir radius. Tis is direct impaction. (t is often te governing mecanism for droplets in te 1* to 1=*m range. cient. Almost all mist elimination equipment falls :into four categories •

4es

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6anes

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C!clones

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?i&er*&eds

Separator performance Separation performance can &e evaluated &! liquid carr!ing over and gsa carr!ing down rates% wic are a"ected &! man! factors% :suc as •

?low rates

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?luid properties

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6essel con$guration

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(nternals

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Control s!stem

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ETC.

Se!arator Co"!onent:

1, Primar! Separation Section G Removes te &ul of te )uid from te well stream. A tangential inlet wic imparts a circular motion to te )uids.

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9, 7iquid Accumulation Section G To receive te liquids after separation. 4ust &e large enoug to andle surges. @, Secondar! Separation Section G Removing smaller droplets of liquid &! using gravitation. Slows te velocit! of te gas to minimi'e tur&ulent )ow. , 4ist E5traction Section G Removes entrained droplets. (mpingement is used for tis. Te )uid stries o&structions wic act as a collecting surface.

Classifcation by Operating Confguration : Separators are classi$ed &! sape and si'e. 6ertical% ori'ontal% and sperical are te most common

:Advantage o% te di'erent t(!e vertical separator  ) $ A*7iquid level control not as critical #*