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Adsorption techniques for gas purification
Hardy Simgen Max-Planck-Institute for Nuclear Physics Heidelberg / GERMANY
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H. Simgen, MPI for Nuclear Physics / Heidelberg
Outline Principles of adsorption Column purification Adsorption on activated carbon Single component adsorption Multi component adsorption Individual systems N2/Rn, Ar/Rn, He/Ar The N2/Kr-system Summary 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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Radioactive noble gases in the atmosphere
Source Activity concentration (STP) 42Ar cosmogenic 0.5 µBq/m3 air 50 µBq/m3 Ar 39Ar 17 mBq/m3 air 1.8 Bq/m3 Ar 85Kr 235U fission (nuclear fuel reprocessing plants) 1.4 Bq/m3 air 1.2 MBq/m3 Kr 222Rn Primordial 238U 10 to >100 Bq/m3 air 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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H. Simgen, MPI for Nuclear Physics / Heidelberg
Adsorption in pores 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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n = H • p Henrys Law valid for low partial pressures
n = number of moles adsorbed [mol/kg] p = partial pressure of adsorptive [Pa] H = Henry coefficient [mol/(kg·Pa)] 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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H. Simgen, MPI for Nuclear Physics / Heidelberg
Column purification 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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H. Simgen, MPI for Nuclear Physics / Heidelberg
Column purification 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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H. Simgen, MPI for Nuclear Physics / Heidelberg
Column purification 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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H. Simgen, MPI for Nuclear Physics / Heidelberg
Column purification 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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H. Simgen, MPI for Nuclear Physics / Heidelberg
Column purification 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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H. Simgen, MPI for Nuclear Physics / Heidelberg
Column purification 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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H. Simgen, MPI for Nuclear Physics / Heidelberg
quantitatively … for large N (many stages): VRet = HRTmAds 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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Pore size distribution
Activated Carbon pore size [Å] Pore size distribution 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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H. Simgen, MPI for Nuclear Physics / Heidelberg
Single component adsorption model S. Maurer, Ph.D. thesis, TU Munich (2000) Prediction of Henrys constant for adsorption on activated carbon Only one gas parameter: TC•pC-0.5 allows to compare adsorption of different components 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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for single component adsorption in gas phase !
Maurer formula for H for single component adsorption in gas phase ! Gas TC PC TC·PC-0.5 H [mol/(kg·Pa)] [K] [bar] [K·bar-0.5] T=-100°C T=-196°C He 5.2 2.3 3.4 1E-7 8E-7 Ar 151 49 21.6 2E-4 6E+1 N2 126 34 CH4 191 46 28.0 3E-3 4E+4 Kr 209 55 28.2 Xe 290 59 37.8 2E-1 7E+8 Rn 377 63 47.6 1E+1 1E+13 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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Realization in low-level physics
behaviour at ultralow concentrations? problem of re-contamination practical limitations: column density (troughput) temperature stability … at least 2 components multi-component adsorption 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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H. Simgen, MPI for Nuclear Physics / Heidelberg
N2 / Rn - system 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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H. Simgen, MPI for Nuclear Physics / Heidelberg
N2 / Rn - system 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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MoREx (Mobile Radon Extraction Unit)
-100 -196 -100 -196 -196 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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MoREx (Mobile Radon Extraction Unit)
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HD II propor-tional counter
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Noble gas purification line
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H. Simgen, MPI for Nuclear Physics / Heidelberg
N2 purification plant 222Rn <0.3 μBq/m3 N2 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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H. Simgen, MPI for Nuclear Physics / Heidelberg
222Rn in argon Ar -100 -186 -100 -186 222Rn <0.3 μBq/m3 Ar -186 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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H. Simgen, MPI for Nuclear Physics / Heidelberg
He / Ar - system 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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H. Simgen, MPI for Nuclear Physics / Heidelberg
He / Ar - system 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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H. Simgen, MPI for Nuclear Physics / Heidelberg
Homestake experiment Raymond Davis jr. Nobel prize 2002 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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H. Simgen, MPI for Nuclear Physics / Heidelberg
N2 / Kr - system 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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H. Simgen, MPI for Nuclear Physics / Heidelberg
N2 / Kr - system 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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Noble gas mass spectrometer
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H. Simgen, MPI for Nuclear Physics / Heidelberg
Experimental setup 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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Kr breakthrough (LN2 cooling)
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H. Simgen, MPI for Nuclear Physics / Heidelberg
Gas phase adsorption Problem of N2 condensation at 77 K If pure gas phase, there is higher mobility of gases surface diffusion → Particles reach appropriate pores faster But low temperature is required Liquid argon cooling! alternatively: pressurized liquid nitrogen 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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Kr breakthrough (LAr cooling)
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H. Simgen, MPI for Nuclear Physics / Heidelberg
Adsorption potential 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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Potential for Kr adsorption on activated carbon
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H. Simgen, MPI for Nuclear Physics / Heidelberg
H and pore sizes 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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Pore size distribution
? Carbon molecular sieve Activated Carbon pore size [Å] 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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Kr breakthrough (LAr cooling)
Carbon molecular sieve 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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H. Simgen, MPI for Nuclear Physics / Heidelberg
Three other systems N2 / Ar Impossible Very challenging ! Ar / Kr Rn Xe Should work Xmass 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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H. Simgen, MPI for Nuclear Physics / Heidelberg
Summary Adsorption is powerful tool to produce ultrapure gases. simple operation / cheap Activated carbon is well suited for many applications. Rn purification is very efficient, but problem of re-contamination. Kr removal from N2/Ar can be done with optimized adsorbers and gas phase adsorption 16/11/2018 H. Simgen, MPI for Nuclear Physics / Heidelberg
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