specifying separators

7/23/2019 Specifying Separators

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Specifying Separators

Basic parameters: temperature, pressure, flow rates, physicalproperties of the fluids as well as degree of separation

Define time frame of separation occurrence

For known fluids, specify type and amount, also state ie. mist, freeliquid or sludge

Select worst case scenario and apply safety factors: safer to ewrong on the right side!

A compressor suction scrubber designed for 70-150 MMscfd gas at 400-600 psig

and 65-105 oF would require the separator manufacturer to offer a unit sied for the

worst conditions! ie" 150 MMscfd at 600 psig and 105 oF


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ecifying Separators

Basic design equations for

separators with mist

e"tractors #$ertical%:

critical #elocit$ %ma&'

correlation

b$ (ounders and )rown

*m+ ma&imum allowable gas mass-#elocit$

necessar$ for particles of sie ,pto drop or

settle out of gas

sec)/()(ftKV

g

gl

t

=

)./()( 2fthrlbCG glgm =

Separator TypeK factor

(ft/sec)

C factor

(ft/hr)

Horizontal (w/verticalpad)

0.4 50 0.5 1440 to1800

Spherical 0.2 to 0.35 720 to

1260

ertical or Horizontal(w/horiz. !ad)

"at# pre$$%re

"300 p$i&

"600 p$i&

"'00 p$i&

"1500 p$i&

0.18 to0.36

0.36

0.33

0.30

0.27

0.21

648 to1260

1260

1188

1080

'72

756

et Stea# 0.25 '00

o$t apor %nder vac%%# 0.20 720

Salt and *a%$tic+vaporator$

0.15 540

,ote-

(1) 0.35 "100 p$i& $%tract 0.01 or ever100 p$i aove 100 p$i&

(2) or &lcol and a#ine $ol%tion$ #%ltipl 0.6 0.8

(3) picall %$e one hal o the aove or *val%e$ or approi#ate $izin& o vertical$eparator$ witho%t woven de#i$ter$

(4) or co#pre$$or $%ction $cr%er$ andepander inlet $eparator$ #%ltipl 0.70.8


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Specifying Separators

1ass flow rates:

0n most instances it is con$enient to use mass flow rate for

si'ing purposes. 2hen handling gas flows, the flow is gi$en in

$olume flow rate #11S+FD%

3he fraction of the total area a$ailale for gas flow

can e found using the following tale

gtVM 3600=

FMdm 2785.0=

h/D F

0 1

0.0

5

0.'8

1

0.1 0.'48

0.15

0.'06

0.2 0.858

0.25

0.804

h/D F

0.30

0.748

0.35

0.688

0.40

0.626

0.45

0.564

0.5

0

0.5

0.5 0.43

:

h


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8"ample

A horiontal gra#it$ separator % without mist e&tractor' is required to

handle 60 MMscfd %"2 .b3s' of 0"75 specific gra#it$ gas %M

1"7' at a pressure of 500 psig and a temperature of 100 F"

compressibilit$ is 0"! #iscosit$ is 0"01 cp and liquid specific

gra#it$ is 0"50" .t is desired to remo#e all entrainment greater than

150 microns in diameter" o liquid surge is required"

ote8

1 micron 0"00007 in

MMscfd 1000000 ft3da$


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8"ample

(olution

Assume a diameter! ,# "5 ft

?essel


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Separators with 2ire 1esh 1ist 8"tractors


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8"ample 9

2hat si'e of $ertical separator equipped with a wire mesh mist

e"tractor is required for conditions used in the pre$ious e"amples

From tale for $alues: ; 5.9 ft


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= ; >.4 ft-

7essel 0D ; >5 in

ftDv 59.4=


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Separators with 7ane 3ype 1ist 8"tractors

?o draining ack through rising gas stream

= downcomer is used to routes

liquid out to drain

0nertia forces liquid droplets

against the $ane walls

@ffer similar separation performance to wire mesh with the addedad$antage of higher resistance to plugging and cane e easily

installed in smaller $essels

3he dependence on inertial forces can e a disad$antage at

reduced production rates


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Aetention 3ime in Separators

Liquid retention time

6 ;etention ti#e i$ avera&e ti#e a li


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Aetention 3ime in Separators

Oi/!ater retention time

6 ,eed certain a#o%nt o oil $tora&e $o that oil reache$e


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)iquid)iquid Separators

Di$ided into - road separation categories: gra$ity and coalescing

&ori'ontal and $ertical separators share the same principles of

separationG hori'ontal separators ha$e the ad$antage of a larger

surface area

- factors affecting gra$ity separation in the liquid phase:

6 e"tra fine particles with random mo$ement

6 electric charge from dissol$ed ions #repelling instead of

coalescing%

Separator si'ing is ased on StokesH )aw


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)iquid)iquid Separators

7alues of +I

"musion

Charactersitics

Dropet

diameter(microns)

C#

ree li


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Separators with +entrifugal 8lements

8"ample 4

Determine the si'e of a $ertical separator to handle >55 pd of 44 o=0 condensate

and 45 pd of produced water. =ssume the water particle si'e is -55 microns.

@ther operating conditions are as follows:

@perating temperature ; 5 F@perating pressure ; 555 psig

2ater specific gra$ity ; .5

+ondensate $iscosity ; 5.44 cp J 5 F

+ondensate specific gra$ity for 44o=0 ; 5.K>

For -55 microns, +I ; 55

2*

)785.0(

)(v

llhl

cl D

SS

CW

=


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Separators with +entrifugal 8lements

8"ample 4

Csing manufacturerHs std si'e $essels might result in specifying a -5! @D

separator

2)785.0(55.0

)76.001.1(1100/600 vDdaybbl

=

ftDv 24.1=


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Separators: +onstruction =spects

Farication specifications:

go$erned y specific codes and standards

=S18 pressure $essel code # the most widely used: Di$ and -%

BS


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7essel Shell 3hickness

as specified y =S18 7000, Di$ #sect C3-K%

PSE

PR

t

6.0=

t thicEne$$;i internal radi%$ o $hell (ec. *orro$ion allowance)

;o eternal radi%$ o $hell

! worEin& pre$$%reS #ai#%# allowale $tre$$+ Foint eGcienc

:o%le elded D%tt oint%ll radio&raphed 1.0Spot radio&raphed 0.85

,o radio&raphed 0.70

Sin&le elded D%tt oint%ll radio&raphed 0.'Spot radio&raphed 0.80,o radio&raphed 0.65

PSE

PRt

!

4.0+=

PSE

PRt

2.0=

Sphere$-


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2eight and Deck =rea calculations

3he weight of the internals #2i% may e estimated from the following tale:

dtWb 15= #a$$ per %nit len&th (C#/t)d internal dia#eter int wall thicEne$$ (inc. corro$ion allowance) in

For skidded equipment the following factors ha$e een

found satisfactory for preliminary estimates:

iping, 2p6 /5M of 2$8lectrical and 0nstumentation, 2e6 M of 2$

Skid Steel, 2s6 5M of 2$2skid ; 2$( 2p( 2e( 2s


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3he total weight of the $essel can now e estimated using:

2$; 2) ( 20( 2?


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Separators: 0nstrumentation and +ontrols

)iquid residence time and control

specifying separators

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