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Performance of the Prototype Gas Recirculation System with built-in RGA for INO RPC system M.Bhuyan a , V.M.Datar b , Avinash Joshi c , S.D.Kalmani a *, N.K.Mondal a , B.Satyanarayana a and P.Verma a. Department of High Energy Physics, Tata Institute of Fundamental Research, Mumbai 400005, INDIA
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Performance of the Prototype Gas Recirculation System with built-in RGA for INO RPC systemM.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 400005, INDIA Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, INDIA c) Alpha Pneumatics, 11-Krishna Kutir, Madanlal Dhingra Road, Thane 400602, INDIA
Plan of talk Gas Recovery System : Open Loop System (Fractional Condensation Method) Preliminary results Tool for analysing gas RGA (Residual Gas Analyser): Some results Closed Loop system : Some results Conclusion
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.
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.) • CATALYSTACTIVATED 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)
PARTIAL PRESSURE – TEMPERATURE RELATIONSHIP OF VAPOUR-LIQUID SYSTEM CLAUSIUS –CLAPEYRON EQUATION FOR BOILING POINT WHERE: TB : BOILING POINT, °K R : IDEAL GAS CONSTANT, 8.314 J/°K-mol P0 : VAPOUR PRESSURE OF GAS AT GIVEN TEMPERATURE, KPa ABS. ΔHVvap: HEAT OF VAPOURIZATION, J/mol T0 : GAS TEMPERATURE
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.
Stanford Research Systems Dual Thoriated-Iridium Filament RS-232c Interface RGA :Vacuum Analysis Mass Spectrometer
TMH/U 071 MVP 015-2 DCU 001 Turbo-Drag Pumping Station
Input flow 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 Fine Tune Needle Valve
83 = C2H2F3 51 = CHF2 32 = CHF 69 = CF3 43 = C2F 20 = HF etc C2H2F4CF3 +CH2F (one of peak in Isobutane)
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.
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.
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