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The effect of Type-III AntifreezeProteins (AFPs) on CO2 hydrate

formationHongxia Zhou

Carlos Infante Ferreira

Process & Energy Department, TU Delft, Netherland

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Content

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What is hydrate?

Clathrate hydrates are ice-likecompounds and have crystallinestructures that are formed withproper combination of small guestmolecules, such as methane,ethane, propane, carbon dioxide,and hydrogensulfides, which aretrapped in cavities of a hydrogen-bonded water framework.

Structure of hydrate

Background

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1. Hydrate was firstly found by Sir HumphreyDavy in 1810

2. Hammerschmidt defined hydrate as anannoyance for the natural gas industry in 1934

3. Hydrates were found to plug large offshore pipelines in the 1970s.

4. ...

Hydrate history

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CO2 hydrate=CO2 + H2O

Latent heat: 507 kJ/kg

Phase change temperature:4~8°C

Advantages

Why CO2 hydrate?

Compared with other gases, formation condition is easier toreach

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Slow down the reaction

Problem specification

Additives:

• Thermodynamic inhibitors• Kinetic inhibitors• Anti-agglomerant

Non-posionous

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Working principle of AFPs on ice(Kelland, 2006)

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Set‐up for CO2 hydrate formation.

Notice:1) Cold bath vs Warm bath2) Flow rate control

Experimental Method

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Phase Equilibrium of CO2 hydrate.

Formation condition of CO2 hydrateYang et al. (2000).

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wallsolution bath

. . .

expln

Pm i m QlosssU

A T

ln1 1 1

2

oo

i o

pred o w i i

ddd d

U h k d h

ln ln1 1 1

2 2

o io i

i h o

pred o w h h i

d dd dd d d

U h k k d h

No hydrate

With hydrate

1/4

9/16 4/9

0.518*0.36 0.559(1 ( ) )Pr

oRaNu

Churchill and Chu 1975

2/3

0.065 Re Pr3.66

1 0.04 Re Pr

i

cs

i

c

dLNudL

Edwards et al., 1979

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0 1000 2000 3000 4000 5000 6000 7000 8000 9000100

120

140

160

180

200experimentalpredicted

over

all h

eat t

rans

fer c

oeffi

cien

t, W

m-2 K

-1

Time, s0 1000 2000 3000 4000 5000 6000 7000 8000 9000

100

120

140

160

180

200 experimental predicted

over

all h

eat t

rans

fer c

oeffi

cien

t, W

m-2 K

-1

Time, s

1/4

9/16 4/9

0.518*0.36 0.559(1 ( ) )Pr

oRaNu

0.20.36 0.58*oNu Ra

2/3

0.065 Re Pr3.66

1 0.04 Re Pr

i

cs

i

c

dLNudL

2/3

0.065 Re Pr3.66

1 0.04 Re Pr

i

cs

i

c

dLNudL

Comparison of overall heat transfer coefficient of CO2 water solution

pResults—set-up validation

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0 5000 10000 15000 20000 25000 30000-50

0

50

100

150

200

250

experimental predicted

over

all h

eat t

rans

fer c

oeffi

cien

t, W

m-2 K

-1

Time, s0 5000 10000 15000 20000 25000 30000

-50

0

50

100

150

200

250 experimental predicted

over

all h

eat t

rans

fer c

oeffi

cien

t, W

m-2 K

-1

Time, s

0.20.36 0.58*oNu Ra

2/3

0.065 Re Pr3.66

1 0.04 Re Pr

i

cs

i

c

dLNudL

0.20.36 0.58*oNu Ra

2/3

0.065 Re Pr2.6

1 0.04 Re Pr

i

cs

i

c

dLNudL

AFPs 5 ppm

Comparison of overall heat transfer coefficient of CO2 water solution with 5 ppm AFPs

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0 10000 20000 30000 40000 50000 60000 70000 80000 900001000000

20

40

60

80

100

120

experimental predicted

over

all h

eat t

rans

fer c

oeffi

cien

t, W

m-2 K

-1

Time, s

0.20.36 0.58*oNu Ra

2/3

0.065 Re Pr2.6

1 0.04 Re Pr

i

cs

i

c

dLNudL

AFPs 10 ppm

Comparison of overall heat transfer coefficient ofCO2 water solution with10 ppm AFPs

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0 5000 10000 150002

3

4

5

6

7

8

9

10x 10

-3 hydrate diameter

Time, s

inte

rnal

dia

met

er d

urin

g hy

drat

e fo

rmat

ion,

m No AFPs

0 0.5 1 1.5 2 2.5 3

x 104

0

0.001

0.002

0.003

0.004

0.005

0.006

0.007

0.008

0.009

0.01hydrate diameter

Time, s

inte

rnal

dia

met

er d

urin

g hy

drat

e fo

rmat

ion,

m

5 ppm AFPs

2 21 ( )/ ( )

4h i h c

h

d d LG kg ht

Figure 1:Hydrate diameter change without AFPs

Figure 2:Hydrate diameter change with 5 ppm AFPs

Results—Growth rate

0.5e-3 mm/sTube internal diameter

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0 1 2 3 4 5 6 7 8 9 10

x 104

0

0.002

0.004

0.006

0.008

0.01

0.012hydrate diameter

Time, s

inte

rnal

dia

met

er d

urin

g hy

drat

e fo

rmat

ion,

m 10 ppm AFPs

Hydrate diameter change with 10 ppm AFPs

0.033e-3 mm/s

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AFPs /ppm

Supercooling /K

Formation rate / (mm/s)

(this study)

Formation rate / (mm/s)(Uchida et al. 2002)

0 1.00

5 0.72 0.3 0.5e-3 0.519

10 0.72 2.1 0.033e-3 3.63

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The addition of AFPs changes significantly (0~2.1K) thesupercooling degree of the CO2 water solution needed to initiate theformation of hydrates.

The hydrates production rate can be determined with the additionof AFPs; however, the growth rate of hydrates without the additionof AFPs is too large to measure from the present experiments.

Conclusions

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The authors would like to thank KoudeGroepDelft/Wageningen for their financial support.