1. Performance of the Prototype Gas Recirculation System with built-in RGA for INO RPC system M.Bhuyana, V.M.Datarb, Avinash Joshic, S.D.Kalmania*, N.K.Mondala, B.Satyanarayanaa and P.Vermaa
Department of High Energy Physics, Tata Institute of Fundamental Research, Mumbai , INDIA
Nuclear Physics Division, Bhabha Atomic Research Centre,
Mumbai , INDIA
c) Alpha Pneumatics, 11-Krishna Kutir, Madanlal Dhingra Road,
Thane , INDIA

2. Plan of talk Gas Recovery System : Tool for analysing gas
Open Loop System (Fractional Condensation Method)
Preliminary results
Tool for analysing gas
RGA (Residual Gas Analyser):
Some results
Closed Loop system :
Conclusion

4. Properties of Gases PARAMETER UNIT R134a (C2H2F4) ISOBUTANE (C4H10)
ARGON
(Ar)
SULPHUR HEXA FLUORIDE(SF6)
MOL. WT
gm/mole
102.3
58.12
39.948
146.05
STRUCTURE
RING
------
GAS DENSITY
Kg/M3
4.25
2.82
1.78
6.27
LIQUID DENSITY
1206
593
1400
1880
VISCOSITY cP
0.012
0.006
0.02
0.015
BOILING Pt. °C
-26.3
-11.7
-185.8
TRIPLE PT: -49.4, 2.2BAR
SUB. PT: -63.9
HEAT OF VAPOURIZATION
KJ/MOL
22.021
23.300
6.43
23.681
CRITICAL TEMP.
101.1
134.9
45.5
CRITICAL PRESSURE
BAR A
40.6
36.84
48.98
37.59
GLOBAL WARMING POTENTIAL
CO2=1
4200
-----
22400
PURITY LEVEL USED %
99.8
99.9
99.999
IMPURITIES
O2,H2O
N3,CF4
CH4,H2, H2O,N2
N2,O2,H2O,HC
H2O,O2,CF4

5. STAGES OF RECOVERY PROCESS BY OPEN LOOP PROCESS
Cleaning and purification of gas mixture returning from RPCs.
Separation of condensable gases by selective adsorption on catalyst surface (activated palladium)
Successive Recovery of gases by fractional condensation at decreasing temperatures.

6. CATALYSTS AND ADSORBENTS
MOLECULAR SIEVES : [ TRAP GAS MOLECULES OF PARTICULAR SIZE]
[ Soduim + Potasuim + Calcium + Aluminum Silicate are used in different proportion to formulate the following sieves ]
TYPE 3A TO TRAP MOISTURE [ 23% w/w -Maximum]
TYPE 4A TO TRAP ARGON [Absence of moisture]
TYPE 5A TO TRAP n BUTANE
TYPE 13X TO TRAP OIL VAPOURS
Activated Aluminum( to remove radicals F-,HF etc.)
CATALYST ACTIVATED ALUMINA + PALLADIUM TO PROMOTE
CONDENSATION OF ISOBUTANE (Adsorption surface~200 Sq.mtr /gm)
ACTIVATED CARBON TO ADSORB ISOBUTANE
ZIRCONIA BASED ZEOLITES (ZSM) TO PROMOTE
ISOBUTANE – n BUTANE CONVERSIONS
SILICA GEL: Wide Range of pore size, good for water adsorption (Chemically bonds Water)

7. PARTIAL PRESSURE – TEMPERATURE RELATIONSHIP OF VAPOUR-LIQUID SYSTEM
CLAUSIUS –CLAPEYRON EQUATION FOR BOILING POINT
WHERE:
TB : BOILING POINT, °K
R : IDEAL GAS CONSTANT, J/°K-mol
P0 : VAPOUR PRESSURE OF GAS AT GIVEN
TEMPERATURE, KPa ABS.
ΔHVvap: HEAT OF VAPOURIZATION, J/mol
T0 : GAS TEMPERATURE

8. Liquid phase
Gas Phase
Liquid Phase
Gas Phase
Note :While Conversion of Gas to Liquid :Heat is released by which other gas molecules temperature goes up and efficiency of condensation goes down so cu-plates, cu-collecting jars are used in the condensation unit.

11. RGA :Vacuum Analysis Mass Spectrometer
Stanford Research Systems
Dual Thoriated-Iridium Filament
RS-232c Interface

13. RGA Operation

14. Turbo-Drag Pumping Station
PEFIER VACUUM
Benchtop Station with high pumping speed
Ultimate pressure < 10-8 mbar
DCU allows control and diagnostics
of pumping station
Pumping Speed N2=60L/s
Dry and Oil-Free!
TMH/U 071
MVP 015-2
DCU 001
Turbo-Drag Pumping Station

15. Fine Tune Needle Valve Fine tune Out flow
Controls the fine flow of Gas in the RGA operating range [1.2 X10-5 to 8.2 X10-5 ]mbar
Input flow
Out flow
Fine tune

16. RGA Experimental Set-up

17. Example :RGA Library

19. Comparison of R134a (Domestic and Imported (Praxair))

20. R134a 33
100 69
37.84 83
21.22 31
12.48 51
9.17 30
4.86 68
4.58 63 32
3.44
i-C4H10 43
100 41
50.68 42
49.77 27
31.32 39
17.70 40
12.66 26
11.15 29
6.64 15
5.19
SF6
127
100 89 27
108 9 51 8 54 7 70 5 32 35

22. m
Fragment % 33
CH2F
100 69
CF3 32 83
C2H2F3 15 51
CHF2 9

25. 83 = C2H2F3 51 = CHF2 32 = CHF 69 = CF3 43 = C2F 20 = HF etc
C2H2F4CF3 +CH2F (one of peak in Isobutane)

30. Conclusion
During recovery process the gas mixture is cooled down to -18o C . If moisture content of the gases is more than 50 ppm ( Dew point higher than -18o C), a thin layer of ice will form on Palladium catalyst surface. As a result catalyst is temporarily deactivated and separation stops . recovery process gradually comes to a halt resulting in strong cross contamination between Isobutene and R134a .
Molecular sieve column has been put to take care of small quantity of moisture , but ingress of air adds large amounts of moisture that can not be handled by Desiccation column.
The first sign of this problem appears as rise of condensation pressure. The machine has to be defrosted and dried complete for few hours during which the recovery is not effective.

31. Conclusion
We have also developed a Residual Gas Analyser (RGA) based system to monitor the purity of input gases and their mixing ratio as well to identify the contaminants in the return gas.
The gas going to the RPC and that coming out of RPC which has contaminated radicals ??
Major problem of Air leak entering into Recovery system /Closed need to be addresed , before doing further tests.

32. THANK YOU
INO-TEAM