flare radiation analysis

FLARE RADIATIONAnalysis y

Flare System Design

Flare RadiationFlare Radiation

depends on fraction of heat radiated from the flame

• Gas composition• Flame type

St t f i f l i i• State of air-fuel mixing• Soot/smoke formation• Quantity of fuel being burned• Quantity of fuel being burned• Flame temperature• Flare burner design

Flare System Design

Flare burner design

Flare Radiation basic calculationFlare Radiation basic calculation

Q Heat release KWRadiant Epicentre

Q Heat release KWF fraction of heat radiatedD distance to pointK radiant heat flux kw/m2

DReceptor point perpendicular to D

K radiant heat flux kw/m

D perpendicular to D

K= FQ/4πD2HK= FQ/4πD

Vary H to meet radiation limit

Flare System Design

Fraction of heat radiated f factorFraction of heat radiated f factor

Many different methods for predictingMany different methods for predictingYear Author

1964 Kent1967 Tan1969 API single point1973 Brzustowski and Sommer1973 Brzustowski and Sommer1979 Leahey et al.1980 Oenbring and Sifferman1981 B k d L i1981 Becker and Laing 1984 Leahey and Davies1987 Cook et al.

Flare System Design

1987 Chamberlain

Flare Radiation basic calculationFlare Radiation basic calculation

Computer software now allows d t il d l l tidetailed calculations ;

• multipoint analysis

D

• Τ transmissivity (humidity)

• Ø angle of incidence for inclinedreceptor pointsD p p

• ε receptor emissivity

• shieldingH

• view angle

• temperature calculations

H

Flare System Design

Ø

Flare Radiation view angleFlare Radiation view angle

Partial view

Partial view

stack

store

Flare System Design

Flare Radiation view angleFlare Radiation view angle

Roof sees entire flame

stack

store

Flare System Design

Radiation Recommended LimitsRadiation – Recommended Limits Radiation

LevelRadiation

LevelTemp Above

ambient Duration

w/m2 btu/ft2 C

1270 400 12 Helicopter decks0 00 e copte dec sno rotors

1900 600 19 acceptable

3100 1000 31 U f bl f3100 1000 31 Uncomfortable for long periods

4730 1500 46 Several minutes

6300 2000 61 30-60 seconds

9460 3000 89 Few seconds only t t t

Flare System Design

must retreat

Radiation Isopleths sizing the stackRadiation Isopleths - sizing the stack

Flare System Design

Radiation Isopleths FlaresimRadiation Isopleths - Flaresim

Can also calculate similar plots for temperatures and

Flare System Design

temperatures and noise levels

Meeting Flare Radiation Limits

Increase length of flare boom

Meeting Flare Radiation Limits

Increase length of flare boom

Increase height of flarestack

Provide radiation shielding

Provide water spraysp y

Reduce flaring rate

Use high velocity tips

Flare System Design

Flare ShieldingFlare Shielding

Plan View with shielding

Flare System Design

Water CurtainsWater Curtains

high pressure atomised water is sprayed behind thehigh pressure atomised water is sprayed behind the burners to absorb upto 70% of the incident radiation

Flare System Design

Water CurtainsWater Curtains

Too much water ?

M i li ht

Flare System Design

May require a relight…… …

Radiation Sonic vs PipeflareRadiation Sonic vs Pipeflare

Up to 5 times as muchUp to 5 times as much radiation from a pipeflare

Radiationlevel Sonic PIPEFLARE

Flare System Design

Distance along boom

Radiation Red cing Flare RateRadiation Reducing Flare Rate

Scenario Flow

Power failure 258000 => flare design flowCooling Water failure 220000 85% design flowCooling Water failure 220000 85% design flowFire Zone 1 125000 48%Fire Zone 2 45000 17%Fire Zone 3 98000 38%Depressuring Zone 1 245000 95%Depressuring Zone 2 6500 3%p g

Probably very little reduction possible.

Flare System Design

Radiation Red cing Flare RateRadiation Reducing Flare Rate

Scenario Flow

Depressuring Zone 1 445000 => flare design flowPower failure 258000 58% of designPower failure 258000 58% of designCooling Water failure 220000 49% Fire Zone 1 125000 28%Fire Zone 2 45000 10%Fire Zone 3 98000 22%Depressuring Zone 2 6500 1.5%p g

DP of Zone 1 is by far the highest flow reducing this will result in a smaller flare system, saving $$$$$$

Flare System Design

smaller flare system, saving $$$$$$

Summary on Radiation Limits

Evaluate the radiation levels expected and

Summary on Radiation Limits

Evaluate the radiation levels expected and

reduce stack size by ..

provide radiation shielding where needed

Provide water sprays

Review relief loads and reduce flaring rate

U hi h l it ti if iblUse high velocity tips if possible.

Flare System Design