1. Luikov Heat & Mass Transfer Institute
ACTIVATED CARBON FOR GAS ADSORPTION L. L. Vasiliev, A.G. Kulakov, D. A. Mishkinis International Conference on SOLID STATE HYDROGEN STORAGE -Materials and Applications January 31 – February 1,2005 HYDERABAD, iNDIA

2. An alternative to compressed gas is Adsorbed Gas Storage and Transportation. New systems for adsorbed NG and Hydrogen storage have many advantages:
environment - friendly devices
low capital and operating cost of compression and refueling
equipment (single - stage compression)
low - pressure operation equal to ( MPa)
a good design flexibility in tank configuration, placement
the high gas capacity
(The theoretical maximum of this parameter for ANG is v/v for microporous solid sorbent. To be commercially profitable the adsorption storage is required to have at last 150 efficiency value)

3. OBJECTIVES
This work is devoted to thermal controlled ANG and Hydrogen system development. An activated carbon is the main sorbent host material. Metal hydrides disposed in macro pores are additional components to increase sorption capacity.
Two new designs for storage ANG:
experimental sectional cylinder with heat pipes,
gas storage system for the Russian lorry GAZ – 53
Numerical and experimental verification of ANG application to obtain:
low operating pressure (2-3.5 MPa),
effective application of vehicle in winter and summer .

4. The goal of this research program
To increase the efficiency and sorption capacity of sorbent compounds for ammonia, methane and hydrogen storage and transportation we consider such combinations as:
Ammonia - active carbon + metal chlorides
Natural gas (methane) – active carbon + metal hydrates
Hydrogen – active carbon + metal hydrides

5. ANG and H2 systems potential applications
Vessels for vehicles (CNG and CH2 tanks alternative)
Gas fired solid sorption heat pumps and refrigerators, air - conditioning devices
ANG and AH2 storage systems used as gas holders for peak shaving operations
Gas fired drying chambers
ANG and AH2 big tanks transportation
LPG (propane) replace systems
Emergency fuel, etc.

6. The storage of NG and Hydrogen by adsorption presents two new major problems
desorption reaction is endothermic (the heat of adsorption is about 18 KJ/mol), any finite discharge rate will result in a temperature drop of sorbent bed;
the residual amount of NG and Hydrogen remaining at the atmospheric pressure can reach % of initial gas capacity

7. 1.Active carbon fibers and particles as the main sorbent host materials

8. Experimental set - up for H2 sorbent parameters determination
Fast sorbent structure analysis
Т=77 К, P= МPа, mass of the sample g
Surface value of the sample
Pores volume and mean pore diameter
Surface determination , BET
Sorption isotherms analysis
Pore size distribution
NOVA
H2 sorption capacity analysis
(Experimental rig, Luikov Institute)
T= К, P=0-5 МPа
Mass of sorbent g
Combined mass/volume method of analysis
Hydrogen storage tank modeling
Hydrogen sorption isotherms analysis
Exp.rig

9. Activated carbons structural parameters
Micro pores volume
Specific surface

10. Hydrogen volumetric capacity , P = 0.1 MPa, T = 77 K
– experimental data, Luikov Institute
 – experimental data for 21 different carbon materials, Inorganic Chemistry and Catalysis, Debye Institute, Utrecht University .

11. Dubinin- Radushkevich equation
Sorbent
a0, cm3/g
E, J/mol
Busofit - М2
369
3566
Busofit - М4
376
3845
Busofit - М8
482
3420
Sutclife
453
3399
ДАУ 3-00
270
7564
207 С
343
3939

12. Hydrogen volumetric sorption capacity, P = 6 МPa
Hydrogen volumetric sorption capacity, ml/g , P = 6 МPа, following Dubinin – Radushkevich equation
Anomaly high data for ДАУ
1 - Busofit - М8; 2 – Sutcliff; 3 – Busofit - М4;
4 – Busofit - М2; 5 – 207 C; 6 – ДАУ

13. Hydrogen sorption capacity (P = 3,5 МPа,T = 293 К)
1 – 207С, 2 – «Busofit-4М», 3 – ДАУ 3-00
asys %=0.004SBET, H
H2 adsorption/desorption isotherms (T = 77,4 K)
Reversible sorption cycles of Н2

14. “Busofit” advantages:
high rate of adsorption and desorption;
the total porosity ,
uniform surface pore distribution ( nm);
small number of macropores ( nm), with its specific surface m2/g;
small number of mesopores with its specific surface 50 m2/g
the specific volume of micro - pores cm3/g,
the sorbent bed density kg/m3,
the effective heat conductivity ,3 W/m K
high methane storage capacity – 170 v/v.

15. Modes of the NG sorption capacity increasing

16. Heat and mass transfer theoretical model assumptions:
Uniform pressure is within a porous structure during the gas charge/discharge inside the ANG vessel;
Instantaneous phase equilibrium is between adsorbed and gaseous methane, or hydrogen;
The gas inside macropores is ideal;
The energy conversion during the gas expansion, or compression is negligibly small;
There is only radial gas flow through the bed;
Resistance of mass diffusion is small.

17. New elements of multisectional tank design
The sorbent bed in adsorber - is
the core component of ANGS
1 - adsorber envelope; 2 - fin;
3- sorbent; 4 – heater (HP).
New elements of multisectional tank design
Finned HE (HP) is applied to
diminish the negative influence of
latent heat of adsorption
Radial motion of desorbed gas
inside the sorbent bed
Microporous sorbent (carbon
fiber Busofit) is used to increase
the storage capacity and to reduce
operating pressure (3.5 MPa)

18. The dynamic model has five components:
●the energy equation :
●the equation of continuity: ●The equation of kinetic of sorption:
●Dubinin and Radushkevich equation of the state of gas
The solution was found for the fixed gas flow from the ANG vessel
To solve the set of equations the finite element method was chosen.

19. The carbon fiber “Busofit - AYTM"
A new type of microporous material “Busofit” is an active carbon fiber disks. “Busofit” as a product of pyrolized cellulose is an advanced adsorbent, capable of delivering near 170 volumes of methane per volume of the ANG vessel at pressure 3.5 MPa
– the structure of “Busofit” (increased
by 50 times),
– the structure of fiber with pores (scaled by times)

20. Numerical and experimental verification of the ANGS effective operation
multi-sectional tank
with thermal control -
the ANG vessel 7 cylinders
utilizing the carbon
fiber “Busofit-AYTM”
Gas storage system
for the Russian lorry
GAZ – 53 -
the ANG vessel 12 cylinders utilizing an active carbon
207C disks
ANG vessels are environmentally safer than gasoline vehicles producing 99% less CO, 30% less NOx, 96% less HCs

21. Thermally Regulated Seven-Cylinders gas storage tank
1 the flat casing, 2 valve, 3 manometer, 4 safety valve, 5 valve for connection to the automobile fuel system, 6 section steel wall,
7 sorbent; 8 HE (thermosyphon), 9 perforated tube (gas channel).

22. Adsorption gas storage system installed on the Lorry GAS-53
Full-scale ANGS tests were carried out with application of the standard scheme for the NG pneumatic connection to the automobile fuel system, which operates on compressed gas.

23. An advanced 14 cylinder ANG vessel with a heat pipe thermal control inside for methane storage and transportation
1 – Al vessel envelope; 2 – heating elements (heat pipes); 3 – sorbent bed; 4 – gas channels; 5 – metal fins to heat/cool a sorbent bed

24. Test results of the ANGS system for the Lorry GAZ - 53
Variation of pressure (а) and temperature (b) in
the ANG vessels with time
(during of the automobile movement )
1 central cylinder in the cartridge
2 right cylinder from the central one
3_ left cylinder from the central one
t, min

25. The driving distance for GAZ-53 (1) and of the gas volume (2-4) versus the gas pressure
2- in the adsorbed and
compressed states
3 - the adsorbed state only
4 - in the compressed state
for the same volume
without the sorbent
The ANG storage tank has the volume of gas three times more then a tank with the natural gas compressed at P = 3.5 MPa.
1 - the driving range

26. 2. Complex compounds – active carbon + chemicals for ammonia, natural gas and hydrogen storage

27. SORBENT BED – COMPLEX COMPAUND
“Busofit”
“Busofit” + CaCl2

28. CaCl2 + nNH3  CaCl2 (NH3)n + n H
NH3 SORBENT BED – COMPLEX COMPAUND
Diagrams of the thermodynamic equilibrium
Active carbon “Busofit” + CaCl2 -Adsorption isotherms
CaCl2 + nNH3  CaCl2 (NH3)n + n H

29. Hydrogen –”Busofit”+ metal hydride storage system
Sorbent material – Active carbon + LaNi4.65Al0.2 .Sorbent mass – 8.36 kg. Vessel mass – 20 kg. Hydrogen sorption capacity – m3

30. ANG, or AH2 vessels for sorption refrigerators
Infrared porous gas heater supplied with methane, or H2 from adsorbed gas vessel
GAS FIRED refrigerator (2 kW) FOR BYELORUSSIAN
CUSTOMER'S NEEDS 1 - adsorber, 2 - thermosyphon; 3 - evaporator; 4 - thermoelectrical valve,
5 - condenser; 6–expansion valve; 7- storage tank for ammonia, 8 - valve;
9-pressure gauge; 10-vapor pipelines, 11-liquid pipelines,12- fan;
13-device for heating the sorbent bed,14- gas burner; 15 – ANG,or AH2
vessel; 16 - control unit;

31. CONCLUSIONS
A new type of activated carbon fiber “Busofit” and timber based carbon particles ДАУ were suggested as an efficient (ammonia, methane, hydrogen) sorption material to design a gas storage system at low pressure.
To increase gas sorption capacity and decrease the time of sorption cycle a complex compound (activated carbon + chemicals) sorbent bed was applied.
Heat pipes ANG and AH2 thermal control ensure an optimal operational regime in winter and summer times.
A simple theoretical model of cylindrical ANG vessel with radial gas distribution during desorption and internal finned heater for thermal control was suggested.