Purification of nitrogen (argon)
description
Transcript of Purification of nitrogen (argon)
IDEA Meeting, LAL-Orsay, 14-15 April 2005IDEA Meeting, LAL-Orsay, 14-15 April 2005
Purification of nitrogen (argon)Purification of nitrogen (argon)
Grzegorz ZuzelGrzegorz ZuzelMPI-K HeidelbergMPI-K Heidelberg
Grzegorz ZuzelGrzegorz Zuzel IDEA Meeting, LAL-OrsayIDEA Meeting, LAL-Orsay 14-15 April 200514-15 April 2005
Motivation of this researchMotivation of this research Radioactive noble gases in the atmosphereRadioactive noble gases in the atmosphere Methods of analysisMethods of analysis Purification of NPurification of N22/Ar/Ar
Measurements of Measurements of 222222Rn content in argon gasRn content in argon gas Conclusions and planned activityConclusions and planned activity
OutlineOutline
Grzegorz ZuzelGrzegorz Zuzel IDEA Meeting, LAL-OrsayIDEA Meeting, LAL-Orsay 14-15 April 200514-15 April 2005
Ultra-pure LNUltra-pure LN22/LAr will be used in the /LAr will be used in the
GERDA experimentGERDA experiment
- Cooling medium for Ge-crystals- Cooling medium for Ge-crystals
- Passive shield against external radiation- Passive shield against external radiation
- Active shield (LAr)- Active shield (LAr)
Developed techniques could be applied in Developed techniques could be applied in other low-level projectsother low-level projects
MotivationMotivation
Grzegorz ZuzelGrzegorz Zuzel IDEA Meeting, LAL-OrsayIDEA Meeting, LAL-Orsay 14-15 April 200514-15 April 2005
OutlineOutline
Motivation of the researchMotivation of the research Radioactive noble gases in the atmosphereRadioactive noble gases in the atmosphere Methods of analysisMethods of analysis Purification of NPurification of N22/Ar/Ar
Measurements of Measurements of 222222Rn content in nitrogen Rn content in nitrogen and argon gasand argon gas
Conclusions and planned activityConclusions and planned activity
Grzegorz ZuzelGrzegorz Zuzel IDEA Meeting, LAL-OrsayIDEA Meeting, LAL-Orsay 14-15 April 200514-15 April 2005
Radioactive noble gases in the Radioactive noble gases in the atmosphereatmosphere
SourceSource Concentration (STP)Concentration (STP)
222222RnRn Primordial Primordial 238238UU 10 - ?00 Bq/m10 - ?00 Bq/m33 air air
8585KrKr235235U fission (nuclear fuel U fission (nuclear fuel
reprocessing plants)reprocessing plants)1.4 Bq/m1.4 Bq/m33 air air
1.2 MBq/m1.2 MBq/m33 Kr Kr
3939ArAr CosmogenicCosmogenic 17 mBq/m17 mBq/m33 air air1.8 Bq/m1.8 Bq/m33 Ar Ar
4242ArAr CosmogenicCosmogenic0.50.5 µµBq/mBq/m33 air air50 50 µµBq/mBq/m33 Ar Ar
Grzegorz ZuzelGrzegorz Zuzel IDEA Meeting, LAL-OrsayIDEA Meeting, LAL-Orsay 14-15 April 200514-15 April 2005
OutlineOutline
Motivation of the researchMotivation of the research Radioactive noble gases in the atmosphereRadioactive noble gases in the atmosphere Methods of analysisMethods of analysis Purification of NPurification of N22/Ar/Ar
Measurements of Measurements of 222222Rn content in nitrogen Rn content in nitrogen and argon gasand argon gas
Conclusions and planned activityConclusions and planned activity
Grzegorz ZuzelGrzegorz Zuzel IDEA Meeting, LAL-OrsayIDEA Meeting, LAL-Orsay 14-15 April 200514-15 April 2005
Low-level proportional countersLow-level proportional counters
Grzegorz ZuzelGrzegorz Zuzel IDEA Meeting, LAL-OrsayIDEA Meeting, LAL-Orsay 14-15 April 200514-15 April 2005
Counter filling lineCounter filling line
Töpler pump
PusherHg diff.pump
P10Ar
Charcoal trap for He purification
with flowmeter
He
Getter pump
Molecular sieve trap
Si-Getrap
Chromo-sorb trap
Radon transport
trap
NaOHtrap
To the pump
To the bubbler
Counter flange
Mai
n li
ne
Pressure gauge
• Sample Sample purificationpurification
• Mixing with Mixing with counting counting gas (P10)gas (P10)
• Counter fillingCounter filling
Grzegorz ZuzelGrzegorz Zuzel IDEA Meeting, LAL-OrsayIDEA Meeting, LAL-Orsay 14-15 April 200514-15 April 2005
222222Rn: Rn: -- only only α-α-decays detected decays detected
- 50 keV - 50 keV threshold (bkg: 0.2 – 2 cpd)threshold (bkg: 0.2 – 2 cpd) - total detection - total detection efficiency ~1.5efficiency ~1.5 abs. detection limit ~30 abs. detection limit ~30 µBq µBq (15 atoms)(15 atoms)
3939Ar and Ar and 8585KrKr: : - - ββ-decays detected -decays detected - 0.6 keV threshold (bkg: 1 – 5 cpd) - 0.6 keV threshold (bkg: 1 – 5 cpd)
- total det. efficiency ~0.5 - total det. efficiency ~0.5 abs. det. limit ~100 µBq abs. det. limit ~100 µBq
(5x10(5x1044 8585Kr atoms)Kr atoms)
SensitivitiesSensitivities
Grzegorz ZuzelGrzegorz Zuzel IDEA Meeting, LAL-OrsayIDEA Meeting, LAL-Orsay 14-15 April 200514-15 April 2005
Measurements of Measurements of 222222Rn in gases – Rn in gases – MoRExMoREx ( (MoMobile bile RRadon adon ExExtraction Unit)traction Unit)
222Rn detection limit: ~0.3 μBq/m3
Grzegorz ZuzelGrzegorz Zuzel IDEA Meeting, LAL-OrsayIDEA Meeting, LAL-Orsay 14-15 April 200514-15 April 2005
Ar and Kr: mass spectrometryAr and Kr: mass spectrometry
Ar: 10Ar: 10-9-9 cm cm33 (1 ppb; ~1.4 nBq/m (1 ppb; ~1.4 nBq/m33 for for 3939Ar in NAr in N22) )
Kr: 10Kr: 10-13-13 cm cm33 (0.1 ppt; ~0.1 µBq/m (0.1 ppt; ~0.1 µBq/m33 for for 8585Kr in NKr in N22))
Grzegorz ZuzelGrzegorz Zuzel IDEA Meeting, LAL-OrsayIDEA Meeting, LAL-Orsay 14-15 April 200514-15 April 2005
OutlineOutline
Motivation of the researchMotivation of the research Radioactive noble gases in the atmosphereRadioactive noble gases in the atmosphere Methods of analysisMethods of analysis Purification of NPurification of N22/Ar/Ar
Measurements of Measurements of 222222Rn content in nitrogen Rn content in nitrogen and argon gasand argon gas
Conclusions and planned activityConclusions and planned activity
Grzegorz ZuzelGrzegorz Zuzel IDEA Meeting, LAL-OrsayIDEA Meeting, LAL-Orsay 14-15 April 200514-15 April 2005
Distillation Distillation - high costs and energy consumption- high costs and energy consumption
Sparging (e.g. with He) Sparging (e.g. with He) - boiling point for contaminants must be - boiling point for contaminants must be
lower than lower than for the gas to be purified for the gas to be purified - high purity carier gas needed- high purity carier gas needed
AdsorptionAdsorption - successfully used for - successfully used for 222222Rn removal from Rn removal from nitrogen nitrogen - a lot of experience at - a lot of experience at MPI-KMPI-K
Different possibilitiesDifferent possibilities
Grzegorz ZuzelGrzegorz Zuzel IDEA Meeting, LAL-OrsayIDEA Meeting, LAL-Orsay 14-15 April 200514-15 April 2005
Henrys lawHenrys law
n = number of moles adsorbed [mol/kg]n = number of moles adsorbed [mol/kg] p = partial pressure of adsorptive [Pa]p = partial pressure of adsorptive [Pa] H = Henry constant [mol/(kgH = Henry constant [mol/(kg··Pa)]Pa)]
H determines the retention volume:H determines the retention volume:
n = H p
VRet = HRTmAds
Grzegorz ZuzelGrzegorz Zuzel IDEA Meeting, LAL-OrsayIDEA Meeting, LAL-Orsay 14-15 April 200514-15 April 2005
Purification in the columnPurification in the column
C0
CN
VPVRet H ()
CN
= ½
C0
ads
t
RTm
VH Re
n = Hp
Grzegorz ZuzelGrzegorz Zuzel IDEA Meeting, LAL-OrsayIDEA Meeting, LAL-Orsay 14-15 April 200514-15 April 2005
Adsorption modelsAdsorption models
GasGas TTC C [K][K] PPC C [bar][bar]TTCC··PPCC
-0.5-0.5
[K[K··barbar-0.5-0.5]]
H [mol/(kgH [mol/(kg··Pa)]Pa)]
@ 77 K@ 77 KPore size [Pore size [ÅÅ]]
ArAr 151151 4949 21.621.6 22××101022 6.8 6.8
NN22 126126 3434 21.621.6 22××101022 77
KrKr 209209 5555 28.228.2 22××101055 77
RnRn 377377 6363 47.647.6 10101414 ~8~8
Grzegorz ZuzelGrzegorz Zuzel IDEA Meeting, LAL-OrsayIDEA Meeting, LAL-Orsay 14-15 April 200514-15 April 2005
Strong binding to almost all adsorbersStrong binding to almost all adsorbers Easy trapping with activated carbon @ 77 KEasy trapping with activated carbon @ 77 K Problem: Problem: 222222Rn emanation due to Rn emanation due to 226226RaRa
- Requires careful material selection- Requires careful material selection
- Activated carbon „CarboAct“:- Activated carbon „CarboAct“: 222222Rn emanation rate (0.3 Rn emanation rate (0.3 0.1) mBq/kg, 0.1) mBq/kg,
~100 times lower than other carbons~100 times lower than other carbons
Purification of NPurification of N22/LN/LN22 from from 222222RnRn
Grzegorz ZuzelGrzegorz Zuzel IDEA Meeting, LAL-OrsayIDEA Meeting, LAL-Orsay 14-15 April 200514-15 April 2005
Advanced models needed to describe adsorption of Advanced models needed to describe adsorption of multi-component system Nmulti-component system N22/Kr – e.g. pore size of the /Kr – e.g. pore size of the adsorber and its internal polarity has to be taken into adsorber and its internal polarity has to be taken into accountaccount
Henry coefficient is expected to be higher for pure Henry coefficient is expected to be higher for pure gas phase adsorption (@ T > 77 (87) K for Ngas phase adsorption (@ T > 77 (87) K for N22 (Ar)) (Ar))
- Cooling: LAr (for N- Cooling: LAr (for N22), pressurized liquid gases ), pressurized liquid gases
(for LAr) or gas phase cooling (for LAr) or gas phase cooling
Pores, low polarity and adsorption from gas phase should Pores, low polarity and adsorption from gas phase should lead to H ~1 mol/kg/Palead to H ~1 mol/kg/Pa
Purification of NPurification of N22/LN/LN22 from Kr from Kr
Grzegorz ZuzelGrzegorz Zuzel IDEA Meeting, LAL-OrsayIDEA Meeting, LAL-Orsay 14-15 April 200514-15 April 2005
Henry constant and pore sizeHenry constant and pore size
0 .01
0.1
1
10
100
1000
10000
100000
1e+06
1e+07
1e+08
1e+09
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Hen
ry c
oeffi
zien
t H
[ m
ol/(
kg*P
a)
]
Pore size b [ Angstroem ]
N itrogen
Krypton
Grzegorz ZuzelGrzegorz Zuzel IDEA Meeting, LAL-OrsayIDEA Meeting, LAL-Orsay 14-15 April 200514-15 April 2005
Molecular sieves, polar (Si/Al ~ 1) 5/10 Molecular sieves, polar (Si/Al ~ 1) 5/10 ÅÅ Hydrophobic zeolite MFI-type: low internal polarity Hydrophobic zeolite MFI-type: low internal polarity
(Si/Al ~ 75), pores ~6.6 (Si/Al ~ 75), pores ~6.6 ÅÅ Hydrophobic zeolite BEA-type: Si/Al ~ 200, pores Hydrophobic zeolite BEA-type: Si/Al ~ 200, pores
~5.3 ~5.3 ÅÅ ““Carbo Act” F3/F4: low Carbo Act” F3/F4: low 222222Rn emanation rate, wide Rn emanation rate, wide
pore size distributionpore size distribution Charcoal Cloth FM 1-250, fabricCharcoal Cloth FM 1-250, fabric Activated Carbon C38/2, optimized for solvent Activated Carbon C38/2, optimized for solvent
recoveryrecovery
Considered adsorbersConsidered adsorbers
Grzegorz ZuzelGrzegorz Zuzel IDEA Meeting, LAL-OrsayIDEA Meeting, LAL-Orsay 14-15 April 200514-15 April 2005
Experimental setupExperimental setup
gas
liquid
600-L dewar with Kr-enriched (100 - 400 ppt)
liquid nitrogen
Mass spectr.
N2
6.0
Samplepurif ication
LN2, LAr
100/300-cm3 column filled w ith adsorber
bubbler
VRet H ()VP
C0
CN
Grzegorz ZuzelGrzegorz Zuzel IDEA Meeting, LAL-OrsayIDEA Meeting, LAL-Orsay 14-15 April 200514-15 April 2005
ResultsResults
0 2 4 6 8 10Vmadsm3kg0
0.2
0.4
0.6
0.8
1
nCoC
0 10 20 30 40Vmadsm3kg0
0.2
0.4
0.6
0.8C NC 0ZEOCAT, 5.3Å, Si/Al ZEOCAT, 5.3Å, Si/Al 200 200
Synthetic carbon, CarboActSynthetic carbon, CarboAct
Grzegorz ZuzelGrzegorz Zuzel IDEA Meeting, LAL-OrsayIDEA Meeting, LAL-Orsay 14-15 April 200514-15 April 2005
ResultsResults
Adsorber descriptionAdsorber description NN
HH
[mol/Pa/kg][mol/Pa/kg]
Molecular sieve 5Molecular sieve 5Å, Si/Al Å, Si/Al 1 1
(Carl Roth GmbH)(Carl Roth GmbH)
no purification observedno purification observed
Molecular sieve 10Molecular sieve 10Å, Si/Al Å, Si/Al 1 1
(Carl Roth GmbH)(Carl Roth GmbH)
≥ ≥ 11 >> 2 2 10 10-4-4
Zeolite, ZEOCAT, 5.3Å, Si/Al Zeolite, ZEOCAT, 5.3Å, Si/Al 200 200
(Südchemie(Südchemie))
4 4 ± 1± 1 (6 (6 ± 1± 1) ) 10 10-3-3
Zeolite, MFI-Type (powder), 6.6Å, Si/Al Zeolite, MFI-Type (powder), 6.6Å, Si/Al 75 (Zeochem)75 (Zeochem)
1 1 ± 1± 1 (6 (6 ± 2± 2) ) 10 10-3-3
Synthetic carbon, CarboActSynthetic carbon, CarboAct
(CarboAct)(CarboAct)
1 1 ± 1± 1 (6 (6 ± 2± 2) ) 10 10-2-2
Grzegorz ZuzelGrzegorz Zuzel IDEA Meeting, LAL-OrsayIDEA Meeting, LAL-Orsay 14-15 April 200514-15 April 2005
222222Rn removal rather easy, even from LNRn removal rather easy, even from LN22
– Low Low 222222Rn emanation rate of the adsorber requiredRn emanation rate of the adsorber required
Ar removal impossible (no Ar reduction observed)Ar removal impossible (no Ar reduction observed)
Kr removal requires:Kr removal requires:– Low temperature gas phase adsorptionLow temperature gas phase adsorption– Activated carbons seem to be more suitable than zeolitsActivated carbons seem to be more suitable than zeolits– Pore size-tuning required Pore size-tuning required
Purification of NPurification of N22 – Summary – Summary
Grzegorz ZuzelGrzegorz Zuzel IDEA Meeting, LAL-OrsayIDEA Meeting, LAL-Orsay 14-15 April 200514-15 April 2005
Purification of ArPurification of Ar
(Almost) no difference between Ar and N(Almost) no difference between Ar and N22 for for adsorption on activated carbonadsorption on activated carbon
However higher temperatures have to be However higher temperatures have to be considered (~100 K for pure gas phase considered (~100 K for pure gas phase adsorption)adsorption)
222222Rn removal is not a problemRn removal is not a problem
Grzegorz ZuzelGrzegorz Zuzel IDEA Meeting, LAL-OrsayIDEA Meeting, LAL-Orsay 14-15 April 200514-15 April 2005
OutlineOutline
Motivation of the researchMotivation of the research Production of NProduction of N22 and Ar and Ar
Radioactive noble gases in the atmosphereRadioactive noble gases in the atmosphere Methods of analysisMethods of analysis Purification of NPurification of N22/Ar/Ar
Measurements of Measurements of 222222Rn content in nitrogen Rn content in nitrogen and argon gasand argon gas
Conclusions and planned activityConclusions and planned activity
Grzegorz ZuzelGrzegorz Zuzel IDEA Meeting, LAL-OrsayIDEA Meeting, LAL-Orsay 14-15 April 200514-15 April 2005
222222Rn in nitrogen and argonRn in nitrogen and argon
LN2 class 4.0, usually ~ 50 m3 (STP) of gas taken
CRn ~ 50 µBq/m3
Two measurements performed for Ar, class 4.6
Sample Sample No.No.
DescriptionDescription CCRnRn in trap 1 in trap 1
[mBq/m[mBq/m33]]CCRnRn in trap 2 in trap 2
[mBq/m[mBq/m33]]
11 117 m117 m33 of gas taken of gas taken 2.9 2.9 ± 0.2± 0.2 ––
22 141 m141 m33 of gas taken of gas taken 0.20 0.20 ± 0.02± 0.02 < 0.0005 (90% CL)< 0.0005 (90% CL)
Grzegorz ZuzelGrzegorz Zuzel IDEA Meeting, LAL-OrsayIDEA Meeting, LAL-Orsay 14-15 April 200514-15 April 2005
OutlineOutline
Motivation of the researchMotivation of the research Production of NProduction of N22 and Ar and Ar
Radioactive noble gases in the atmosphereRadioactive noble gases in the atmosphere Methods of analysisMethods of analysis Purification of NPurification of N22/Ar/Ar
Measurements of Measurements of 222222Rn content in nitrogen Rn content in nitrogen and argon gasand argon gas
Conclusions and planned activityConclusions and planned activity
Grzegorz ZuzelGrzegorz Zuzel IDEA Meeting, LAL-OrsayIDEA Meeting, LAL-Orsay 14-15 April 200514-15 April 2005
Nitrogen purification intensively studiedNitrogen purification intensively studied - Adsorbers selection based on the adsorption theory- Adsorbers selection based on the adsorption theory - Experimental tests are ongoing (zeolites already tested)- Experimental tests are ongoing (zeolites already tested) - For Kr removal from nitrogen better suitable seem to be - For Kr removal from nitrogen better suitable seem to be activated carbonsactivated carbons - Adsorption from the pure gas phase has to be studied- Adsorption from the pure gas phase has to be studied
First results of purity and purification tests for Ar available First results of purity and purification tests for Ar available - - 222222Rn removal from Ar possibleRn removal from Ar possible - - 222222Rn concentration in argon seems to be significantly higher than in Rn concentration in argon seems to be significantly higher than in nitrogen of similar qualitynitrogen of similar quality
Purity tests for different supply chains are planned (NPurity tests for different supply chains are planned (N22/Ar)/Ar) Although the program was slightly extended it is Although the program was slightly extended it is
progressing as scheduled progressing as scheduled
Conclusions and planned activityConclusions and planned activity