Multiphase flow modelling for hazard

assessment of dense phase CO2

pipelines containing impurities

Dr Solomon Brown, Dr Sergey Martynov, Prof Haroun Mahgerefteh

Department of Chemical Engineering,

University College London, London, UK

UKCCSRC Biannual Meeting

21-22 April 2015, Cranfield

2

CO2 pipeline transportation – hazards

At concentrations higher than 10%, CO2 gas can cause severe injury or death due to asphyxiation.

In case the of accidental leakage/ release of CO2 from a pipeline:

• the CO2 gas can accumulate to potentially dangerous concentrations in low-lying areas,

• the released cloud could cover an area of several square kilometres.

Courtesy of Laurence Cusco, HSL

3

CO2 pipeline transportation – hazards cont.

4

P T3 P T3 P T3 P T3

12m 6m 12m 6m50

High speed camera HD camera

T 2F+T T T

CO2Quest experimental facilities

5

Full bore rupture

Puncture release

Video recording during release

6

Pressurised CO2

Rupture

plane: 1 atm

• At the rupture plane the fluid is exposed to ambient air

• Following the rupture, the rarefaction wave starts propagating along the

pipe

• The vapour phase emerges in the expansion wave

• Due to rapid cooling of the fluid in the decompression wave, the solid

phase may also be released from the pipe

Physics of decompression

Mathematical model -Pipeline discharge

where ρ, u, P, H, z and E are the density, velocity, pressure, total enthalpy, vapour quality and total energy of a two-phase fluid mixture as function of time t and space x.

Homogeneous Relaxation Model

Mixture

𝜕𝜌𝑚𝑖𝑥𝑧

𝜕𝑡+𝜕𝜌𝑚𝑖𝑥𝑢𝑚𝑖𝑥𝑧

𝜕𝑥= 𝑆𝑧

𝜕𝜌𝑚𝑖𝑥𝑢𝑚𝑖𝑥

𝜕𝑡+𝜕𝜌𝑚𝑖𝑥𝑢𝑚𝑖𝑥

2 + 𝑃

𝜕𝑥= 𝑆𝑢

𝜕𝜌𝑚𝑖𝑥𝐸𝑚𝑖𝑥

𝜕𝑡+𝜕𝜌𝑚𝑖𝑥𝐻𝑚𝑖𝑥

𝜕𝑥= 𝑆𝑒

𝜕𝜌𝑚𝑖𝑥

𝜕𝑡+𝜕𝜌𝑚𝑖𝑥𝑢𝑚𝑖𝑥

𝜕𝑥= 𝑆𝜌

Balance equations:

8

This works reasonably well…

Mathematical model -Pipeline discharge

where α is the volume fraction as function of time t and space x.

Characterisation of these terms is difficult

Two-Fluid Model

Vapour

Liquid 𝜕𝛼𝑖𝜌𝑖𝜕𝑡

+𝜕𝛼𝑖𝜌𝑖𝑢𝑖𝜕𝑥

= 𝑆𝜌

𝜕𝛼𝑖𝜌𝑖𝑢𝑖𝜕𝑡

+𝜕𝛼𝑖𝜌𝑖𝑢𝑖

2 + 𝛼𝑖𝑃𝑖𝜕𝑥

= 𝑃𝑖𝜕𝛼𝑖𝜕𝑥

+ 𝑆𝑢

𝜕𝛼𝑖𝜌𝑖𝐸𝑖𝜕𝑡

+𝜕𝛼𝑖𝜌𝑖𝐻𝑖

𝜕𝑥= −𝑃𝑖𝑢𝑖𝑛𝑡

𝜕𝛼𝑖𝜕𝑥

+ 𝑆𝑒

𝜕𝛼𝑣𝜕𝑡

+ 𝑢𝑖𝑛𝑡𝜕𝛼𝑣𝜕𝑥

= 𝑆𝑖

Balance equations:

Inter-phase heat transfer model:

Inter-phase mass transfer model:

Inter-phase heat and mass transfer

𝑞𝑣𝑖 =

1

𝜏𝐴𝑖𝑛𝑡 𝑇𝑠𝑎𝑡 − 𝑇𝑣

𝑞𝑙𝑖 =

1

𝜏𝐴𝑖𝑛𝑡 𝑇𝑠𝑎𝑡 − 𝑇𝑙

Γ𝑣 = −Γ𝑙 =𝑞𝑙𝑖 + 𝑞𝑣

𝑖

ℎ𝑠𝑎𝑡,𝑣 − ℎ𝑠𝑎𝑡,𝑙

These are both governed by the relaxation time scale 𝜏

Simple models for the heat and mass transfer are applied.

11

Pressurised CO2

Rupture

plane: 1 atm

HRM Two-Fluid mode

Switching between the models

Coupled model results

0

2

4

6

8

10

12

14

0 5 10 15 20

Pre

ssu

re (

MP

a)

Time (s)

Experimental

5x10⁻³

1x10⁻³

5x10⁻⁴

Liquid

0

0.5

1

1.5

2

2.5

3

3.5

4

0 5 10 15 20

Pre

ssu

re (

MP

a)

Time (s)

Experimental5x10⁻³ 1x10⁻³ 5x10⁻⁴

Liquid

13 CO2QUEST

Contact details

Solomon Brown

University College London

Gower Street, London,

United Kingdom

Tel: +44-2076793809

Thank you

Questions