Modeling of hydrogen explosion on a pressure swing adsorption facility*B. Angers1, A. Hourri1, P. Benard1

E. Demaël2, S. Ruban2, S. Jallais2

1 Institut de recherche sur l’hydrogène, Université du Québec à Trois-Rivières, Québec, Canada2 Air Liquide, Centre de Recherche Claude-Delorme, 78350 Jouy en Josas, France

Project scopeNumerical study of the consequences of

an hydrogen release from a Pressure Swing Adsorption installation operating at 30 barg

Tool: FLACS-Hydrogen from GexConWe investigated :

◦The impact of different leak orientation and wind profile on the explosive cloud formation (size and explosive mass) and on explosion consequences

◦Overpressures resulting from ignition as a function of the time to ignition

Pressure Swing Adsorption installation

Three of the 43.3 m3 reservoirs contain hydrogen◦ P = 30.4 barg ◦ T = 45°C

ScenariosDispersion

◦The jet was directed either horizontally or 45 ° toward the ground

◦Some scenarios were done with wind 3 m/s Pasquill class F 5 m/s Pasquill class D

Combustion◦The ignition point was positioned on the

ground inside the 30% concentration envelop along the centreline of the jet

◦ Ignition occurred at 2 seconds and 20 seconds after the leak onset

◦ In one case (35NW45°), the time to ignition was varied between 0.5 second and 60 seconds

Leak (1) The leak was assumed to originate from a

broken branch connection at one end of the system 0.5 m above the ground

Two leak diameters were considered: ◦ 20 mm (3/4")◦ 35 mm (1"1/2)

Leak (2)Initial mass flow rates :

◦0.50 kg/s for d = 20 mm◦1.54 kg/s for d = 35 mm

Grid

Dispersion Combustion

Dispersion and combustion simulations are done on two different grids

The size of the cells encompassing the PSA was set at 0.5 m on both grids

Grid sensitivity studies were also conducted

Hydrogen 4% molar concentration envelop profile d = 35 mm, no wind

2 seconds after the onset of the leak

20 seconds after the onset of the leak

45° horizontal

45° horizontal

2 seconds after the onset of the leak

20 seconds after the onset of the leak

45° horizontal

45° horizontal

Hydrogen 4% molar concentration envelop profile d = 35 mm, Wind 5 m/s Pasquill D

2 seconds after the onset of the leak

20 seconds after the onset of the leak

45° horizontal

45° horizontal

Hydrogen 4% molar concentration envelop profile d = 20 mm, no wind

Maximum Overpressure, d = 35 mm(ignition time = 2 sec and 20 sec)

0 5 10 15 20 250

0.5

1

1.5

2

2.5

Monitor points

Ignition delay (sec)

OverP

ressure

(barg

)

0 5 10 15 20 250

0.5

1

1.5

2

2.5

Domain

45 degree, no windhor, no wind45 degree, Wind 3Fhor, Wind 3F45 degree, Wind 5Dhor, Wind 5D

Ignition delay (sec)

OverP

ressure

(barg

)

Maximum Overpressure, d = 20 mm(ignition time = 2 sec and 20 sec)

0 5 10 15 20 250

0.05

0.1

0.15

0.2

0.25

Monitor points

Ignition delay (sec)

OverP

ressure

(barg

)

0 5 10 15 20 250

0.05

0.1

0.15

0.2

0.25

Domain

45 degree, no windhor, no wind45 degree, Wind 3Fhor, Wind 3F45 degree, Wind 5Dhor, Wind 5D

Ignition delay (sec)

OverP

ressure

(barg

)

Maximum travel distance of 50 mbar, 140 mbar and 200 mbar overpressure fronts measured from the origin of the leak

0 50 100 150 2000

5

10

15

20

25

30

35

40

45

Time to ignition = 2 sec

Overpressure (mbar)

Maxim

um

Dis

tance f

rom

Rele

ase P

oin

t (m

)

0 50 100 150 2000

2

4

6

8

10

12

Time to ignition = 20 sec

35NW45°35NWHor35W3F45°35W3FHor35W5D45°35W5DHor20NW45°20NWHor20W3F45°20W3FHor20W5D45°20W5DHor

Overpressure (mbar)

Maxim

um

Dis

tance f

rom

Rele

ase P

oin

t (m

)

Maximum overpressure and hydrogen mass at stoichiometric concentration (28-32%) as a function of time to ignitiond = 35 mm, no wind, 45°

0 10 20 30 40 50 600.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

Maximum OP on Monitor points Maximum OP in DomainHydrogen mass

Ignition delay (sec)

Maxim

um

overp

ressure

(barg

)

Hydro

gen m

ass a

t sto

ichio

metr

ic c

oncentr

ati

on (

kg)

0 10 20 30 40 50 600

2

4

6

8

10

12

14

16

0

20

40

60

80

100

120

140

160

Flammable mass between 4-75% (vol.) Flammable mass between 11-75% (vol.)Equivalent stoichiometric cloud (Q9)

Ignition delay (sec)

Fla

mm

able

mass o

f hydro

gen (

kg)

Equiv

ale

nt

sto

ichio

metr

ic c

loud v

olu

me (

m3)

Flammable mass of hydrogen between mole fraction intervals of 4-75% (vol.) and 11-75% (vol.) as a function of time to ignitiond = 35 mm, no wind, 45°

Future perspectiveComparing results with

traditional non-CFD methods

Questions ?

Thank you!

Grid sensitivity

Max overpressure in domain(barg)

Max overpressure on monitor points

(barg)

Tign = 2 sec Tign = 20 sec Tign = 2 sec Tign = 20 sec

Coarser grid (0.50 m) 0.332 0.280 0.230 0.191

Refined grid (0.20 m) 0.318 0.349 0.227 0.190

difference -4% 25% -1% -1%

Grid sensitivity (overpressure)

0 10 20 30 40 50 600.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

Max OP on MP (GridSize:0.5m)Max OP in Dom (GridSize:0.5m)Hydrogen massMax OP on MP (GridSize:0.2m)Max OP in Dom (GridSize:0.2m)Max OP on MP (GridSize:0.2m, Same IgnPos as 0.5m)Max OP in Dom (GridSize:0.2 m, Same IgnPos as 0.5m)

Time to ignition (sec)

Maxim

um

overp

ressure

(barg

)

Hydro

gen m

ass a

t sto

ichio

metr

ic c

oncentr

ati

on (

kg)

Grid sensitivity (what was done)Dispersion

◦PSA zone cell size: 0.5m compared to 0.25m

◦Without any geometry: no PSACombustion

◦Various boundaries, with and without WIND (Plane_Wave, Euler, Nozzle)

◦More precise domain (0.25, 0.2 m, 0.1 m)◦Without any geometry: no PSA◦Varied ignition position based on

concentration contours (15%, 45%, 60%)

Grid sensitivity (fuel mass)

Mass histogram prior to ignition d = 35 mm, no wind, 45°

[4; 8

[[8

; 12[

[12;

16[

[16;

20[

[20;

24[

[24;

28[

[28;

32[

[32;

36[

[36;

40[

[40;

44[

[44;

48[

[48;

52[

[52;

56[

[56;

60[

[60;

64[

[64;

68[

[68;

72[

[72;

76]

02468

101214161820

9.34

13.1

5 15.6

912

.95

17.5

415

.30

7.24

3.68

1.60

1.62

0.64

0.18

0.19

0.21

0.21

0.21

0.00 0.26

Hydrogen mole fraction interval (% (vol))

% o

f tot

al m

ass

[4; 8

[[8

; 12[

[12;

16[

[16;

20[

[20;

24[

[24;

28[

[28;

32[

[32;

36[

[36;

40[

[40;

44[

[44;

48[

[48;

52[

[52;

56[

[56;

60[

[60;

64[

[64;

68[

[68;

72[

[72;

76]

0

10

20

30

40

50

60

54.8

516

.96

11.0

07.

934.

452.

381.

040.

450.

380.

280.

030.

040.

040.

090.

000.

040.

050.

00

Hydrogen mole fraction interval (% (vol))

% o

f tot

al m

ass

Simulation time: 2 seconds

Simulation time: 20 seconds