AD.15.03.02 Extreme Sampling: Flare Gas€¦ · Analytical Solutions by the Sea The 61st Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas,

Analytical Solutions by the Sea The 61st Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas, USA; 24th – 28th April 2016

AD.15.03.02 Extreme Sampling: Flare Gas

Hans-Peter Visser

Analytical Solutions and Products BV (ASaP)

Analytical Solutions by the Sea The 61st Annual Symposium of the Analysis Division

Galveston Island Convention Center, Galveston, Texas, USA; 24th – 28th April 2016

Slide 2

Content

Problems with current installation, effects and root

cause.

Design criteria.

Design considerations.

Tests and field results.



Slide 3

Problems with new flare gas installation

• Problems direct after start-up;

– Plugging of narrow bore sample paths.

– Severe fouling of wetted parts in analyzer installation.



Slide 4

Effects

• Probe

– Green crystals found.

• Sample Conditioning System

– Green/gray deposits on filters.

• Analyzer

– Particles in GC valves.



Slide 5

Root cause

• Undersized process seal drums

QT



Slide 6

“Forgotten” first step

• Cycle time existing GC: 4 minutes.

1. REASON AND PURPOSE OF MEASUREMENT

Reason of measurement Yes/No Purpose of measurement Yes/No Criticality analyser Yes/No

client (external/internal) / Trending / Safety /

legalisation / monitoring / /

product quality / control / Environment /

energy efficiency / alarm / /

environmental / trip / Not critical /

safety /

management / Safety Integrety Level N/A

process reliability /

REMARKS:

Process

Quality



Slide 7

Analytical requirements and existing installation



Slide 8

Requirements in a nutshell

• Eliminate fouling and plugging.

– Increase total system reliability.

– Reduce maintenance.

• Proper sampling.

– Even at upset conditions with process velocity up to 100 m/s.

– Lower water content/ water dewpoint without condensing hydrocarbons.



Slide 9

Conceptual thoughts

• A combination of applied fluid dynamics and

existing sampling techniques



Slide 10

Process conditions (worst case)

• Extreme fluid velocity and Reynolds Number

ID Item Description Symbol Value Unit Reference

20 Pressue Pp 0.076 BarG

21 Temperature Tp 60 °C

22 Reference Pressure Pref 1.01325 BarG

23 Reference Temperature Tref 15 °C

24 Mol Weight Mw 25.85 kg/kmol

25 Density @ Process P & T rPp&Tp 1.009 kg/m3

26 Density @ Reference P & T rPref&Tref 1.098 kg/m3

27 Dynamic viscosity h 0.0000137 Pa.s @ Tprocess

28 Flow fvol 61.51 m3/hour

29 Velocity Vprocess 97 m/s

30 Reynolds Number Reprocess 6,418,316

31 Composition xi]

32 Given/required Fast Loop Flow fv, Fast Loop 4.59 l/min 0.076 60 @ BarG / C

Remarks

Pro

cess D

ata

See Tap "Input "



Slide 11

Flow separation



Slide 12

Fluid dynamics

• Supercritical Reynolds number (6.7 x 105)

• Project case Re 6.4 x 106

Probe entrance



Slide 13

Stokes Law

VF

VP

DH = 18 ∗ h ∗ VfrP − rF ∗ g

Hence: DH : µm ; Liquid droplet or particle larger than DH will fall out.

h : Pa.s ; Dynamic viscosity. Vf : m/s ; Fluid velocity. rP : kg/m3 ; Density particle and/or droplet. rF : kg/m3 ; Density fluid.

g : m/s2 ; Gravitational constant



Slide 14

Inclined orientation

VF

VP

Vv

Vh

VV = VF ∗ SINα

DH = 18 ∗ h ∗ Vf ∗ SINrP − rF ∗ g

Hence:

Vf : m/s ; Fluid velocity. Vv : m/s ; Fluid velocity vertically. Vh : m/s ; Fluid velocity horizontally. : ; Angle probe



Slide 15

Gravity separation

72 Density entrained liquid rel 1800 kg/m3

73 Particle seperation DH 37 µm

Sulphur particles

Particles smaller than DH will pass



Salt particles



60 Fall-back tube OD ODFBT 1.05 Inch

61 Tube wall thickness TWTFBT 0.083 Inch

62 Fall-back tube factor 20 2

63 Total length fall-back tube LFBT 449.07 mm

64 Probe angle FBTangle 60

65 Volume wetted parts VolFBT 0.1778 L

66 Velocity VFBT 0.19 m/s

67 Reynolds Number ReFBT 320 1: page 81, (Table II.2)

68 Flow type Laminar

69 Pressure drop dPFBT 0.08 Pa Darcy equation

70 Lag time @ process conditions LTFBT 2.32 s

71 Lag time @ reference conditions LTFBT,ref 2.13 s



Remarks

Sto

kes L

aw

Falli

ng S

ection

Sch 10

Min.16xID or 400 mm

Water "particles"


3/4" Nominal Bore

Falling from top downwards



Slide 16

Self draining



Slide 17

Pressure drop and lag time


40 Insertion depth in process line Insprobe 100 mm 10.94% of ID main line

41 Probe diameter ODprobe 1.05 Inch

42 Schedule TKNprobe 0.219 Inch

43 Total length Lprobe 276.60 mm

44 Probe angle Prangle 60

45 Volume wetted parts Vw p,pr 0.052 L

46 Velocity Vprobe 0.40 m/s

47 Reynolds Number Reprobe 462 1: page 81, (Table II.2)

48 Flow type Laminar

49 Pressure drop dPprobe 0.20 Pa Darcy equation

50 Lag time @ process conditions LTprobe 0.69 s 0.076 60 @ BarG / C

51 Lag time @ reference conditions LTprobe,ref 0.63 s 1.01325 15 @ BarG / C

Remarks

3/4" NB

Sch 160

Falling from top downwards

Pro

be



Slide 18

Design flare gas probe



Slide 19

CFD Analysis by VSL Dutch Metrology Institute

Reduced pressure; suction effect

Probe entrance P= 108,000 Pa



Slide 20

Sample extraction



Slide 21

Proof of principle 1



Slide 22

Proof of principle 2



Slide 23

Mission accomplished

Quote: “I forgot to specify. Obviously I meant filters

clean in presence of several upsets. We had 3 upsets

and several small discharges since the installation.” unquote.

Documents

AD.15.03.02 Extreme Sampling: Flare Gas€¦ · Analytical Solutions by the Sea The 61st Annual Symposium of the Analysis Division Galveston Island Convention Center, Galveston, Texas,