Flare Radiation Analysis

FLARE RADIATION Analysis y

Flare System Design

Flare Radiation depends on fraction of heat radiated from the flame • Gas composition • Flame type • State St t off air-fuel i f l mixing i i • Soot/smoke formation • Quantity of fuel being burned • Flame temperature • Flare burner design Flare System Design

Flare Radiation basic calculation Radiant Epicentre

D H

Q F D K

Heat release KW fraction of heat radiated distance to point radiant heat flux kw/m2

Receptor point perpendicular to D K= FQ/4πD2 Vary H to meet radiation limit

Flare System Design

Fraction of heat radiated

f factor

Many different methods for predicting Year

Author

1964 1967 1969 1973 1979 1980 1981 1984 1987 1987

Kent Tan API single point Brzustowski and Sommer Leahey et al. Oenbring and Sifferman B k and Becker d LLaing i Leahey and Davies Cook et al. Chamberlain Flare System Design

Flare Radiation basic calculation Computer software now allows d t il d calculations detailed l l ti ; • multipoint analysis • Τ transmissivity (humidity)

D

• Ø angle of incidence for inclined receptor p points p • ε receptor emissivity • shielding

H

• view angle • temperature calculations Ø Flare System Design

Flare Radiation view angle

Partial view

Partial view stack store

Flare System Design

Flare Radiation view angle

Roof sees entire flame

stack store

Flare System Design

Radiation – Recommended Limits Radiation Level w/m2

Radiation Level btu/ft2

Temp Above ambient C

Duration

1270 0

400 00

12

Helicopter e copte dec decks s no rotors

1900

600

19

acceptable

3100

1000

31

Uncomfortable U f bl ffor long periods

4730

1500

46

Several minutes

6300

2000

61

30-60 seconds

9460

3000

89

Few seconds only mustt retreat t t

Flare System Design

Radiation Isopleths - sizing the stack

Flare System Design

Radiation Isopleths - Flaresim

Can also calculate similar plots for temperatures and noise levels Flare System Design

Meeting Flare Radiation Limits „

Increase length of flare boom

„

Increase height of flarestack

„

Provide radiation shielding

„

Provide water sprays p y

„

Reduce flaring rate

„

Use high velocity tips

Flare System Design

Flare Shielding

Plan View with shielding

Flare System Design

Water Curtains

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

Flare System Design

Water Curtains

Too much water ?

M require May i a relight…… li ht … Flare System Design

Radiation

Sonic vs Pipeflare Up to 5 times as much radiation from a pipeflare

Radiation level

Sonic

PIPEFLARE

Distance along boom Flare System Design

Radiation

Red cing Flare Rate Reducing

Scenario

Flow

Power failure

258000

Cooling Water failure

220000

85% design flow

Fire Zone 1

125000

48%

Fire Zone 2

45000

17%

Fire Zone 3

98000

38%

Depressuring Zone 1

245000

95%

Depressuring p g Zone 2

6500

3%

Probably very little reduction possible.

Flare System Design

=> flare design flow

Radiation

Red cing Flare Rate Reducing

Scenario

Flow

Depressuring Zone 1

445000

=> flare design flow

Power failure

258000

58% of design

Cooling Water failure

220000

49%

Fire Zone 1

125000

28%

Fire Zone 2

45000

10%

Fire Zone 3

98000

22%

6500

1.5%

Depressuring p g Zone 2

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

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 Use high h velocity l it titips if possible. ibl

Flare System Design