Mid-Sem Presentation of Modeling of Ethane Hydrate in micro-DSC

1. BITSPilani
K K Birla Goa Campus
Modeling of Gas Hydrate
Formation Dissociation
Kinetics
Supervisor
Prof. S. Krishnaswamy
Presentation By
Kishlay Bhaskar

2. Overview
1. Introduction
2. Conditions for Formation of Gas Hydrate
3. Types of Gas Hydrates
4. Comparison of Hydrate Crystal Structure
5. Properties
6. Ice, sI and sII Comparison
7. Potential Application of Gas Hydrates
8. Literature Survey for DSC
9. µDSC Equipment Setup and Diagram
10. µDSC Operating Conditions for Ice
11. µDSC Operating Conditions for Ethane Hydrate
12. Future Work
13. References

3. Introduction
Gas Hydrate are a class of solid ice-like non-
stoichiometric compounds.
These are not salt hydrates which are
stochiometric compounds(e.g.:-MgCl2.6H2O, etc.).
First discovered in 1810 by Sir Humphrey Davy.
Former + n-water Gas
(guest) (host) Hydrate
High pressure
Low temp

4. Conditions for Formation
High Pressure Low Temperature
Presence of free
Water
Gas should be at
or below the dew
point of water
Under agitation, mixing of water and gas
favours hydrate

6. Types of Gas Hydrates
There are 3 forms of gas hydrates
Structure I
Structure II
Structure H

7. Comparison of Hydrate
Crystal Structure
Structure I Structure II Structure H
Cavity
Cavities/ Unit Cell 2
Avg. Cavities
Radius,nm
Coordination
Number
Water Molecules
per Unit Cell
46 136 34
Lattice Type Cubic Face-Centered
Cubic
Hexagonal
Density, Kg/m^3 912 940 1952
Small Large Small Large Small Medium Large
2 6 16 8 3 2 1
0.395 0.433 0.391 0.473 0.391 0.406 0.571
20 24 20 28 20 20 36

8. Properties
Heat of Dissociation
∆Hd is a function of the number of crystal hydrogen
bonds (loosely taken as hydration number).
∆Hd is relatively constant for molecules which
occupy the same cavity.
Size and Volume
Size Ratio = 0.9
Size of Guest Molecule = 0.35 – 0.75 nm
1 m^3 Hydrate = 180 m^3 Gas
Thermal Conductivity
5 times lower than that of Ice near it’s melting point
More than 20 times lower than Ice at much lower
temperature

9. Ice, sI and sII Comparision
Properties Ice sI sII
Refractive index,
638 nm, -3°C
1.3082 1.3460 1.350
Density, kg m-3 916 912 940
Heat Capacity, J kg-
1 K-1
3800 3300 3600
Thermal conductivity
(263 K), W m-1 K-1
2.23 0.49±0.02 0.51±0.02
Dielectric constant
at 273 K
94 ~58 58
Linear thermal
expn., at 200 K, K-1
56 10-6 77 10-6 52 10-6
Bulk Modulus
(272K)
8.8 5.6 NA

10. Potential Applications of
Gas Hydrates
NATURAL
GAS
STORAGE
&
TRANSPOR
T
CO2
SEQUESTRAT
ION
HYDOGEN
STORAGE
GAS
SEPERATIO
N
WATER
TREATMENT
AND
DESALINATIO
N

11. Literature Survey For DSC
Literature Reported
Results
Limitations
Measurement of Methane
Hydrate Heat of Dissociation
using High Pressure DSC.
Arvind, Jason(2008)
Clapeyron equation should be
used for hydrate heat of
dissociation estimations at high
pressures instead of Clausius-
Clapeyron equation.
1. Used for Methane.
2. Extremely high pressure
3. Ex-situ methane hydrate
was used, which may result
in change of mass.
Prediction of Gas Hydrate
Formation with DSC
Technique. Dalmonzze(03)
Carried out experiments for
water-methane-salt and same-
glycol validated the results
Both the mixtures taken were of
methane
Modulated DSC for Gas
Hydrate Analysis.
Giavarini(2006)
Methane and ethane
hydrates (sI) decompose after
the melting of the
ice while propane hydrates
melt and decompose slightly
lower than the ice
Different mixture of gases were
used at very high pressure to
compare normal DSC and TM-
DSC
Machanism of Gas Hydrate
Formation and Inhibition. Koh,
QAB exhibit better hydrate
growth than PVP and VC-713
Doesn’t conduct on ethane gas

12. µDSC Equipment Diagram

13. µDSC Equipment and Pump

14. µDSC Calibration for
Naphthalene

15. µDSC Operating Conditions
For Ice
Sample Weight 20-50 mg
Temperature Profile 25°C to -10°C @ 1°C/min
-10°C to -25°C @ 0.1°C/min
-25°C for 1/2 Hours
-25°C to 25°C @ 0.1°C/min
Water Double Distilled
Deionized

17. µDSC Operating Conditions
For Ethane Hydrate
Sample Weight 20-50 mg
Ethane Pure Water (Double
Distilled Deionized)
Ethane Pressure 10, 15 and 20 bar
Temperature
Profile
25°C to -10°C @ 1°C/min
-10°C to -25°C @ 0.1°C/min
-25°C for 8 Hours
-25°C to 25°C @ 0.1°C/min

19. Future Work
• 6-7 experiments to be carried out
• Validation of DataExperiments
• Experiments to be carried out
with Surfactants
Experiments with
Surfactants
• Comparison of enthalpy change
• Thermodynamic stability &
behaviour
Heat of
Dissociation
• Modeling of kinetics to be done
from data generated and whether
it is mass or heat dominated
reaction
Modeling

20. References
Application of High Pressure DSC to the Kinetics of Formation of Methane
Hydrate in Water-in-Oil Emulsion. Dalmazzone, Hameed (2006).
Measurements of Methane Hydrate Heat of Dissociation using High Pressure
Differential Scanning Calorimetry. Arvind Gupta, Jason Lachance (2008).
Mechanisms of Gas Hydrate Formation and Inhibition. Koh, Westacott (2002)
Differential Scanning Calorimetry Studies of Clathrate Hydrate Formation.
Zhang, Pablo(2004).
A Review of Gas Hydrate Growth Kinetic Models. Zhenyuan Yin, Maninder
Khurana (2018).
Review of Gas Hydrate Dissociation Kinetic Models for Energy Recovery.
Zhenyuan Yin, Zheng Rong Chong (2016)

21. Thank you