Liquefaction of Helium ‐
Past and Present Scenario
Prof. Subhash Jacob
Indian Institute of Science, Bangalore
Scheme of the talk
• Brief look at helium resources and its history
• Small scale helium liquefaction and recondensation
using GM and low frequency pulse tube cryocoolers
• Novel concept of helium recondensation using high
f
frequency
pulse
l tube
t b cooler
l with
ith JT expansion
i
–
work being carried out at IISc
Discovery of helium
• 1868 – Pierre Janssen, a French astronomer , studying solar
spectrum during a solar eclipse in Guntur, A. P., discovers an
spectral line unknown of the earth elements
• Norman Lockyer , an astronomer and Edward Frankland, a
chemist concur with the existence of the new element
named helium
h li
helium
Æ helios
h li : Greek
G k – means Sun
S
• 1895 ‐ Sir William Ramsay at Royal Institute,
London, identifies helium on Earth after
examining the gases released on treating
cleveite a uranium containing mineral,
cleveite,
mineral with
acid.
Milestones in the history of helium
•
1903: Helium discovered in the gas fields in Kansas, USA
•
1908: Heike Kamerlingh Onnes of Leiden laboratories,
Holland becomes the first to liquefy helium
¾ Using helium, given by Ramsay and helium extracted from the
Monazite sand from Kerala coast sent by his brother Onno, an
officer in the Dutch East India company
First helium liquefier
•orange is helium
•Blue
Bl iis air
i
•green is hydrogen
•Pink is (warm) alcohol
•The lighter colors are gas
•The darker colors high
pressure gas or liquid
Milestones in the history of helium
• 1972 : First L‐He production facility outside Unites States, set up in
P l d
Poland
• 1993 : L‐He production expanded in Russia to supply to Western
markets
• 1994: Algeria becomes a major source
• 2005: First helium extraction facility in Qatar, Phase I – 20 million nm3
per annum
• 2013: Qatar, Phase II – 38 million nm3 per annum
Supply of helium
World wide reserves:
40 billion nm3
( 2007, US Geological Survey)
Natural gas fields containing
helium
Production of helium (2007)
Reserves by country
Usage of helium
• Current annual demand is around 190 million nm3
Demand by region
Demand by application
Helium Liquefiers/Recondensors using
Cryocoolers
• Need for conserving helium
– World’s helium supply is finite and non renewable
– Helium shortage and high prices due to growing demand
and limited production
• Growing number of applications: to maintain zero boil off in
cryostats for MRI, NMR, SQUIDS, FTMS etc.
• Commonly used technology
– GM cycle coolers with JT expansion ( Sumitomo Heavy
Industries)
d
i )
– Low frequency pulse tube coolers ( Cryo Mech)
Critical factors in liquefying helium using cryocoolers
• Effective pre‐cooling is vital
– Gas enthalpy change from 300 – 4.2
4 2 K : 1534 J/g
– Latent heat of condensation at 1 atm : 20.7 J/g
•
Liquefaction rate governed by the refrigeration capacity of lower
temperature stages of the cryocooler
Cryocooler
Available refrigeration at 4.2 K
Latent heat at 4.2 K
Liquefaction rate
Cryo Mech, PT 415
1.5 W
20.7 J/g
0 075 g/s
0.075
2.2 l/hr
• To
T achieve
hi
th
the above
b
liliquefaction
f ti rate
t 117 W off sensible
ibl h
heatt
is to be removed ( 300‐4.2 K).
Early use of GM cooler for helium liquefaction
•
High heat capacity of helium at lower
temperatures constrained the lowest
temperature obtained
using GM
cooler
•
With the
th use off lead
l d spheres
h
i
in
second stage a lower temperature of
10 ‐12 K was achieved
•
This is below the inversion tempe‐
rature at the operating pressure and
liquefaction could be achieved by JT
expansion
•
Reliability of the JT compressor &
clogging due to impurities were issues
Helium liquefaction using GM cooler alone
• Advent of rare earth magnetic regenerator materials
• Development of two stage coolers (GM & Pulse tube) with rare earth
regenerator
g
materials
• 1996: First GM cooler with rare earth regenerator material
• A second stage temperature of 2.5 K was achieved.
Helium liquefaction using GM cooler alone
Precooling is done on the first stage heat exchanger
Pulse tube coolers for helium liquefaction
• First report:
p
– Published in 1997 by G. Thummes, C. Wang, C. Heiden –
University of Giessen
– Title “Small scale He liquefaction using a two stage 4 K pulse
tube cooler”
• After Dr. Wang moved to CryoMech, USA the company has
become a leader of low frequency pulse tube based helium
liquefiers
Why pulse tube coolers are more efficient than GM
q
coolers for helium liquefaction?
• In GM coolers the second stage regenerator materials are
packed inside the displacer.
• The annular gap and the high thermal resistance of the wall
materiall impedes
d the
h pre‐cooling
l off the
h incoming h
helium
l
gas.
Why pulse tube coolers are more efficient than GM
q
coolers for helium liquefaction?
• In pulse tube cooler the second stage regenerator materials are filled
into thin walled stainless steel tubes
• Heat exchange over the length is feasible giving effective pre
pre‐cooling
cooling
Advances in the use of pulse tube coolers for helium liquefaction
1.
2.
3.
4.
Advances in the use of pulse tube coolers for helium liquefaction
5.
6.
Current level of the Technologies
• At Sumitomo:
– 2 X 1.5 W at 4.5 K GM cooler has a liquefaction rate of 6 l/day
– Input electric power of 15 kW
– Only first stage pre‐cooling up to 35‐45 K
• At Cryomech
– PT 410 cryocooler provides 39 W at 45 K and 1W at 4.1 K
– Input electric power of 7.5 kW
– Liquefaction rate of 14.2 l/day of room temperature helium gas, 29
l/day for liquid helium boil off
• Vibration level of pulse tube cooler less than that of GM cooler by a
factor of 2 making it suitable for sensitive applications
Work at Center for Cryogenic
Technology, IISc
Recondensation system for a
Zero helium loss cryostat
• Liquefaction rate 17.86 l/day
• Main Components
–
–
–
–
–
Valved linear motor compressor
Pulse tube cryocoolers
Recuperative heat exchangers
JT valves
Cryostat
• Active cooling mechanisms
– Pulse tube cooler
– JT expansion
Simplified Helium
y
Recondensation System
• System for initial phase of studies
• LN2 precooling
li is
i used
d instead
i t d off the
th
first stage pulse tube cooler.
• Pulse tube cooler second stage
temperature specification determined
by inversion temperature of helium.
Valved linear motor compressor
Dimensions
Length
Height
Width
Helium Gas Pressure
Operating (Supply Side)
Operating (Return Side)
64.8 cm
40.0 cm
43.4 cm
20‐24 bar(g) ‐‐‐ approx.
1 bar(g) ‐‐‐ approx.
Ambient Operating Temperature
Weight
0°‐ 30°C
93 kg ‐‐‐ approx.
Power
2 3 kW
2.3
•
Two stage compression using flexure bearing
linear motors
•
Flexure bearings provide oil free operation ‐
crucial for trouble free operation of JT valves :
No clogging
•
Best operating condition: Pressure 21.5 – 22.5
bar(g), volume flow: 55 slm
Active cooling – Two stage pulse tube cooler
• Sage software was used to design the
pulse tube cooler with a design goal of
2 W at 20 K
•A commercially available pressure
wave ggenerator capable
p
of deliveringg
900 W PV power is used, input power
is 1.4 kW
• The first stage is anchored at 80 K
using a LN2 thermal link
•SS mesh is used as the regenerator
material for first stage and warmer
portion of II stage
• In the lower temperature (60‐20K)
portion of II stage regenerator, Erbium
Proscenium is used
Active cooling : JT expansion
•Selection of JT expansion pressures
22 bar
22
11
12bar
12.56
56 K bar
b
11 bar
1 bar
11.7 K
71K
7.1
1 bar
b
9.3 K, x = 0
4.2 K, x = 0.19
•A
A single stage expansion requires a lower pre‐cooling
pre cooling temperature
•Two stage expansion: first stage helps in pre‐cooling, second stage results in liquefaction
Heat exchangers for the Recondensation system
• Operation at cryogenic temperatures
requires that the heat exchangers
are compact and highly effective
effective,
effectiveness > 90 %
• Specification for heat exchanger
design : pressure drop in the low
pressure < 5 – 10 kPa
• A tube in tube configuration
g
was
chosen for the heat exchangers
Heat exchanger design methodology
•
Effectiveness – Number of Transfer Units method is used
•
Correlations available in literature were used
•
Fortran program was written to perform the numerical calculations
Example: Design of HX1 (300 – 100 K)
Fabrication and testing of heat exchangers
•
Coiling of the tubes done by cryo‐bending procedure to prevent kinking.
•
Each heat exchanger is tested individually before final integration
Currently the Heat Exchanger ‐1 pressure drop tests are completed
Components of the liquefier
•Final
Fi l assembly
bl off th
the system
t
expected
t d tto b
be completed
l t d iin M
May 2013
2013,
followed by test operation
Summary
• World helium resources are limited and getting fast depleted
• Th
There is
i a need
d for
f helium
h li
conservation
i and
d GM & Pulse
P l tube
b cooler
l
based helium liquefiers/ recondensors are getting popular
• Large
g improvements
p
have been made in the last ten yyears in the
technology of helium liquefaction using cryocoolers
• A novel concept of a small scale helium recondenser was introduced
by our research group at IISc to liquefy helium at 18 l/day using
linear motor compressor based JT and high frequency pulse tube
cooler down to 20 K
• DST Sponsored
S
d R&D workk on this
thi conceptt is
i in
i the
th final
fi l phase
h
off
testing and integration of components
• High compactness, lower power consumption, high reliability and no
maintenance schedules are the salient features of this helium
recondenser
Thank You