9.

Task ９9.1

Development of Liquid Hydrogen Transportation and Storage Facilities

9.1.1

Development of Hydrogen Transportation and Storage Technology

R&D Goals

Continuing from last year, we conduct insulation performance tests on two
specimens and low-temperature strength tests on one specimen, to develop a design
database on thermal insulation structure for large-scale storage to be used for liquidhydrogen tankers and land-based liquid hydrogen tanks. In the thermal insulation
tests, a thermal flow meter is attached to the specimens to measure the heat flow andcomparison with conventional evaporation method was made.
Small-capacity liquid hydrogen transportation and storage system is studied for the
purpose of supplying hydrogen to hydrogen stations for fuel cell powered vehicle. In
the study applicable laws and standards for liquid hydrogen transportation andstorage tank (container tank) are investigated, and conceptual design of tanks withcapacity of 30m 3 and 15m 3 are produced. Preliminary study is also started onsloshing (splashing) of liquid hydrogen that occurs during transportation.
We study a medium-sized hydrogen supply chain for marine transportation
system, which is about halfway between large-scale and small-scale transportationand storage. A marine transportation system is studied with Tokyo Bay area as amodel case.
9.1.2
9.1.2.1

Results FY2001
FY 2001
Thermal insulation test with thermal insulation structure specimens(1) Design and production of specimens for insulation test
As specimens for thermal insulation test, a perlite vacuum insulation structure
specimen (for land use) and a vacuum panel type insulation structure (for tanker)
were designed and produced.
(1.1) Powder vacuum insulation structure specimen (for tank)
Powder vacuum insulation structure specimen (dimensions: 1,000mm diameter x
250mm thickness, filler material: microsphere (glass microscopic hollow powder,average grain diameter: 50µm), degree of internal vacuum: 0.1Pa or less) was
designed and produced to conduct a liquid hydrogen test. Fig.9.1.2-1 shows SEM
image of micro sphere.

-77-Fig. 9.1.29.1.2 - 2 Panel vacuum typeinsulation structure specimen

Fig.9.1.2 - 1 SEM image of microsphere(1.2) Panel vacuum type insulation structure specimen (for tanker)
A panel vacuum type insulation structure specimen (dimensions: 1,019mm
diameter x 200mm thickness, filler core material: polyurethane foam, outer jacket
material: SUS (thickness: 0.5mm and 0.3mm), degree internal vacuum: 0.1Pa orless) was designed and produced to conduct a liquid hydrogen test . Fig. 9.1.2-2
shows Panel vacuum type insulation structure specimen.
(2) Results of thermal insulation tests
We reviewed the results of last year's tests on solid-vacuum insulation structure
specimen and perlite atmospheric pressure insulation structure specimen andconducted additional studies. We then conducted an outline study on the test resultson this year's vacuum panel type insulation structure and perlite vacuum insulation
structure specimens.
(2.1) Study on solid-vacuum insulation structure specimen (urethane foam withsupport, for tanker)
Side heat input was evaluated from the temperature difference between positionof specimens with 780mm diameter and 1,180mm diameter to correct the heat input
into the liquid hydrogen container for measurement. The results indicated that actual
thermal conductivity improved by 11% over the value of 5.6mW/m-K given in last
year's Study Report. With the above-mentioned side heat input included in theconditions, a detailed temperature distribution analysis was conducted using ageneral-purpose code NASTRAN to study the effects on insulation properties of the
support structure.
(2.2) Study on perlite atmospheric pressure insulation structure specimen (for tank)
For the perlite atmospheric pressure insulation structure specimen (dimensions:-78-

1,100mm diameter x 200mm thickness, filler material: perlite, filler gas: helium gas
at atmospheric pressure), actual measurement data of gap part (20mm average) was
input for recalculations using a general-purpose code PHOENICS. The results
indicated that thermal conductivity of the perlite part was about 3 times larger(100mW/m-K) than for the case using nitrogen filler gas. Natural convection of gas
was confirmed in the gap part, verifying that effect of helium thermal conductivity(70mW/m-K@80K) was large.
(2.3) Study on perlite vacuum insulation structure specimen (for tank)
Test on perlite vacuum insulation structure specimen was started with internal
vacuum set at 10Pa, and thermal conductivity in a quasi-steady state was about
20mW/m-K. The test was aborted as liquid hydrogen supply could not keep up during
the test. We plan to conduct a retest next year in a steady state.
(2.4) Study on panel vacuum type insulation structure(for tanker)

Guard vessel（LH 2 ）For this test a heat flux sensor (thermopiletype) was attached to the high-temperature face ofthe specimen to compare with thermal conductivity
equivalent to amount of evaporation. The measured

Test specimen

thermal conductivity was 5.1mW/m-K. Fig. 9.1.2-3
shows Thermal insulation test apparatus with

Hot platepanel vacuum test insulation structure specimen.
9.1.2.2

LowLow - temperaturetemperat ure strength test

Bottom insulation material for land-based storage
tank

and

the

lightweight

concrete

specimen(100mm diameter x 50mm height) were designed

Fig. 9.1.29.1.2 - 3 Thermal insulation test
apparatuswith panel vacuum typeinsulation structure specimen

and produced, and strength tests at normal temperature and at low temperatures inliquid nitrogen and liquid hydrogen were conducted. Compressive strength in liquidhydrogen was 93.2~130.6N/mm 2 , increasing by 3.1 to 4.4 times the strength at normal
temperature (30N/mm 2 ). Compressive strength at low temperatures tended to vary,
but strength tended to increase as the temperature dropped. Fig.9.1.2-4 shows
Strength test apparatus with the lightweight concrete specimen. Fig.9.1.2-5 shows
Relationship between the temperature and the increase of compressive strength.

-79-

200
Resultsof the lightweight concrete
軽骨コンクリート試験結果

Cover flame

Rod
Swivel joint
Test piece

Increase of 圧縮強度増加量
compressive ∆σc (N/mm2)

Miura,
三浦ら et al150

コンクリート標準示方書
JSCEStandards

100

JGA guide
LNG地上式貯槽指針
for LNG
aboveground tank
(設計基準強度の割増量)

50

0

-200

-100

0

温度 T (℃)
Temperature

Fig.9.1.2Fig.9.1.2 - 5 Relationship between thetemperature and the increase ofcompressive strength

Fig.9.1.2Fig.9.1.2 - 4 Strength test apparatus
with the lightweight concrete specimen
9.1.2.3

Study on small
sm allall - capacity liquid hydrogen transportation and storage system(1) Legal regulations for transporting liquid hydrogen and investigation on standards
on transportation and storage tanks
We

investigated

the

High

Pressure

Gas

SafetyLaw(Container

SafetyRegulations, General High Pressure Gas Safety Regulations), Vehicles Act (Safety
Standards), Nippon Kaiji Kyokai (NK) Regulations (Marine Container Regulations,
Marine Container Inspection Guideline), etc. to reflect on trial design of tank.
(2) Conceptual design of small liquid hydrogen tank for transportation and storage(container tank)
Inner tank support methods were compared for liquid hydrogen tank fortransportation and storage with capacity of 30m 3 and 15m 3 , and trial design (strength
calculation, heat input calculation) was conducted for tank with a target thermal
insulation (BOG) of 0.5%/day. Fig.9.1.2-6 shows Conceptual design of small liquidhydrogen tank.
(3) Preliminary study on thermal flow by sloshing during transportation in liquidhydrogen container
We estimated the splashing energy from sloshing caused by disturbance such as
acceleration during transportation and found that the heat converted from this-80-

energy was small compared to the steady heat input. We also studied the splashingon free surface of liquid hydrogen and other cryogenic liquids and confirmed thatsplashing on free surface of liquid hydrogen tended to be larger than others.
(4) Pressure rise and stratification phenomenon in liquid hydrogen container tank
We created a simplified model in which liquid and gas phases were integrated toestimate the pressure rise with amount of condensation in gas phase as parameter.
Also, preliminary study was conducted on stratification phenomenon, which
occurs in the upper portion of liquids in association with pressure rise in the tank.

Container Flame

Outer Vessel
BaffleControl
Box

Inner Vessel

Fig.9.1.2Fig.9.1.2 - 6

Conceptual design of small liquidhydrogen tankPrincipal specifications
Type

Double-hull horizontal cylindrical container

Capacity

30m 3 /15m 3

Insulation system

Vacuum multilayer insulation

Degree of vacuum

10 -2 Pa

Insulation performance (evaporation rate)
0.5%/day or less [target performance]
Principal dimensions

Inner tank inner diameter:φ2,100 mm
Outer tank inner diameter:φ2,400 mm

Liquid hydrogen container tank (15m 3 ) and principal specifications-81-9.1.2.4

Study of mediummedium - sized liquid hydrogen supply chain

With Tokyo Bay coastal area as the model, we studied a marine transportation
system with tank capacity of transport barge as parameters (90m 3 , 250m 3 , 480m 3 ), for
medium-sized liquid hydrogen supply chain.
9.1.3

Subject in future

We plan to conduct insulation performance tests on two specimens (microsphere,etc.) and low-temperature strength tests on GFRP, and review the results of eachconceptual design for tankers and land-based tanks that was conducted in Phase 1,
based on results of elemental tests conducted so far.
As research and development on small-capacity liquid hydrogen transportationand storage system, we also plan to develop and produce a liquid hydrogentransportation

andstoragetank(container

tank)

and

conductpreliminary

performance tests using liquid nitrogen. In small-capacity systems, we plan to
conduct feasibility studies and equipment review on other modes of hydrogentransportation and storage (hydrogen-absorbing alloy, chemical hydride, pipeline,etc.) to identify technical tasks and evaluate energy efficiency, cost effectiveness, etc.,
to verify that liquid hydrogen is a promising transportation and storage mode.
9.2

Development of Devices for Common Use

9.2.1

R&D Goals

This fiscal year, we select a theme related to small capacity transportation andstorage of hydrogen assuming hydrogen stations. A test equipment was newly madefor testing hydrostatic bearing, which is a non-contact bearing similar to magnetic
bearing and considered for application in small-scale liquid hydrogen pumps, andbearing evaluation by rotation test is conducted.
Then, we examine the required specifications for small-scale liquid hydrogen
pumps to be used in liquid hydrogen stations and carry out the basic plans for pumpspecifications, motor specifications and bearing specifications according to the fixedbasic specifications.
Also, as part of equipment development for liquid hydrogen stations, we conduct
studies on recovery and utilization of boil-off hydrogen that is generated duringstorage of liquid hydrogen. Specifically, the energy balance related to utilization isreviewed, including re-liquefaction of recovered hydrogen, storage of high-pressuregas, fuel cell generation, etc.

-82-

9.2.29.2.2.2

Results FY2001
FY 2001
Evaluation tests for hydrostatic bearing(1) Design of hydrostatic bearing
In order to obtain basic data on hydrostatic bearings to be used in the bearing
system of liquid hydrogen pumps, test equipment for testing hydrostatic bearing were
designed and made. For the radial bearing pad, three types of bearing pad were
designed and made: ① fluid hydrostatic bearing, ②hydrogen gas hydrostatic bearing
and ③ fluid foil hydrostatic bearing. For the thrust bearing pad, ④ hydrogen gashydrostatic bearing was designed and made for use in all three pad types.
Specifications are listed in Table 9.2.2-1
Table 9.2.2
9.2. 2 - 1 Design specifications

φ20

Radial bearing②Hydrogengashydrostatic
bearing
φ20

20

20

20

φ1mm×4
with recess
0.5,1.0,2.0

φ1mm×8×2 rows1.5

Not needed

Thrust bearing④Hydrogengashydrostatic
bearing
Thrust innerdiameter: φ42
Thrust outer
diameter:φ63
φ1mm×180.2

0.3

Liquidhydrogen30

Hydrogen gas

Liquidhydrogen200(Movable
range)

Hydrogen gas

Type
Item

Bearing innerdiameter [mm]Bearing width
[mm]
Inlet
configuration
Inlet pressure[MPa]
Working fluid
Radial gap[µm]①Fluidhydrostatic
bearing20③Fluid foilhydrostatic
bearing
φ20

150(Movable
range)(2) Evaluation test
We used a bearing test equipment which simulates operation of actual pumps to
conduct a rotation performance test with gas and liquid hydrogen externally supplied.
Performance data at a rated speed of 20,000 rpm was acquired.
Cross section of the prototype test equipment is shown in Fig.9.2.2-1. This figure
shows a typical configuration with a fluid hydrostatic bearing built in, and three
types of test can be conducted by changing the bearing pad unit. As a representative
bearing pad, photograph of a foil bearing unit is displayed in Fig.9. 2.2-2.

-83-

Photographs of setup for foil bearing test is shown in Figure9.2.2-3. Test
equipment was fixed on a mount and connected to the piping system on the test
equipment side, and tests were conducted with the entire equipment covered withthermal insulation material.
(3) Performance evaluation test
[Foil bearing test]
Foil bearing unit was filled with LH 2 and rotor shaft rotation was gradually
increased. The rotor shaft lifted up at around 8,000rpm and steady operation up to a
maximum rotation of 58,000rpm was confirmed. The shaft lifted up again after ittouched down due to an error in feed pressure control, and steady operation ataround 20,000rpm was confirmed. It was confirmed that shaft vibration could becontained within 10µmp-p. Vibration during the rotation test is shown in Fig.9.2 2-4.
[Fluid hydrostatic bearing test]
LH 2 was gradually supplied to the radial bearing unit and it was confirmed thatthe rotor shaft lifted up in the center of the radial shaft at around 1.0MPa. Rotor
shaft rotation was gradually increased to monitor rotational vibration and the rotor
shaft started to rotate after about 250 seconds into the test. When rotation rose toaround 50,000rpm, rotor shaft and bearing pad touched, causing rotation to stop
immediately.
(4) Summary of the evaluation tests① In radial bearing design, rotor shaft diameter was set at φ20mm to calculate thebearing performance for fluid hydrostatic bearing, hydrogen gas hydrostatic
bearing and fluid foil hydrostatic bearing. Optimum values for supply pressureof lubricating fluid and bearing radial gap were calculated by parameter survey.
② In thrust bearing design, hydrogen gas hydrostatic bearing system was selected,
which was common to all three types of radial bearing. Although thrust wasapplied from only one direction, thrust bearing with the same specifications
were also placed on the non-load side and thrust reactive force were applied asnecessary, for stability control against disturbance.
③ It was confirmed that thrust bearing could be held at a prescribed position. Its
rigidity was also confirmed by hand pushing to be sufficient against the design
load of 73N.
④ In foil bearing test it was confirmed that rotor shaft lifted up normally between
6,000rpm and 8,000rpm and a stable increase up to a maximum rotation of
58,000rpm was confirmed. In steady operation at 20,000rpm it was confirmedthat rotor shaft vibration was stable, within 10µmp-p at maximum.

-84-

⑤ In overhaul after the foil bearing test, peeling off of coating was found on therotor shaft side, caused by contact between rotor shaft and foil plate. The cause
seems to be the foil plate scratching the coating due to roughness of the foil
plate surface. In general, this should not be a problem in ordinary design ascoating will be applied to the foil side. (In the case of foil bearing, coating wasapplied to the rotor shaft side as a special measure to provide commonality
among three types of bearing pad.)⑥ In hydrogen gas hydrostatic bearing test, it was confirmed that radial bearing
lifted up normally and could be held at the center of bearing pad. As turbine
supply pressure was gradually increased, rotor shaft started to rotate after
about 250 seconds. After passing the primary critical speed of about 14,000rpm,
rotor shaft and bearing pad touched at around 50,000rpm and rotation stopped
immediately. As design primary critical speed is around 30,000rpm andsecondary critical speed is around 40,000rpm, cause of the failure is estimatedto be that rigidity of the bearing was not up to the designed level.
9.2.2.2

Design of compact liquid hydrogen pumps for hydrogen stations

Required specifications for pumps to be used in liquid hydrogen stations were
fixed as listed in Table 9.2.2-2, based on research of specifications for pumps used inexisting liquid hydrogen pump and automobile LNG stations.
Table 9.2.29.2.2 - 2
Parameter
Flow Rate
Pump HeadNs Value
Rotation
Speed

Liquid hydrogen pump specifications
Basic Specification
Unit
3
3.6
m /h
160
m
109
(m 3 /h,m,rpm)
20,000rpm(1) Review of pump impeller specifications
After conducting the basic design based on the above pump specifications, closed
centrifugal pump with a guide vane was selected. It was found that specifications
could be achieved with 5 blades, impeller outer diameter of 60mm and one stage.
(2) Review of motor specifications
After conducting an outline review, an AC motor with two poles, rated power of
0.5kW and source voltage of 200V was selected. Rough dimensions were: For rotator,
inner diameter =φ25mm, outer diameter =φ63.8mm, width = 55mm; For stator, innerdiameter =φ65mm, outer diameter =φ135mm, width = 150mm. When selecting-85-

magnetic material and insulation material, attention should be given to cryogenic
characteristics and brittleness against hydrogen.
(3) Study of bearing specifications
When using an electric motor for driving the pump, problems arise such asincrease in load capacity on bearing and instability in rotating system associatedwith drop in natural frequency of spring-mass system, which are caused by increasein the weight of rotor shaft iron core. Therefore, a method to support the bearing withelastic material should also be considered in bearing design.
9.2.2.3

Review of technology to recover boilboil - off hydrogen gas in liquid hydrogenh ydrogenstationRe-liquefaction was reviewed as a technology to recover boil-off hydrogen gas andit was found to be very inefficient, as a re-liquefaction unit requires three times thetotal power consumption of the entire hydrogen station facility. On the other hand, it
was found that boil-off hydrogen gas, when used as fuel for fuel cells, yielded
sufficient power to cover power consumption for the entire station. It was also foundthat it would be effective to recover the boil-off gas that is generated when liquidhydrogen is fed to automobiles, store it in high-pressure tank using hydrogencompressor, and supply to high pressure hydrogen vehicles or hydrogen-absorbing
alloy vehicles.
9.2.3

Subject in future① We will conduct detail design and production of compact general-purpose liquidhydrogen pump, which is applicable to liquid hydrogen station.
② We will conduct detail design, production and evaluation of a QD that canrecover the boil-off gas that is emitted when liquid hydrogen is supplied.
③ We will modify the hydrogen gas hydrostatic bearing test equipment to conduct
validation tests, using as parameters bearing conditions that reflect basic motor
specifications.

-86-Fig9.
Fig 9.2.
9. 2.2
2. 2 - 1 The cross section of the test equipment

Fig9.
Fig 9.2.
9. 2.2
2. 2 - 2 The photograph of

Fig9.
Fig 9.2.
9. 2.2
2. 2 - 3 The photograph of Foil

Foil Bearing

Bearing in test conditions-87-

Thrust Disk

80

Rotation Speed [rpm]Shaft vibration [μm]Turbine

70000
First Time
MAX:58,000rpm

60

X1 vibration

60000

Second Time
MAX:45,000rpm

40

50000
Maximum amplitude
10μmp-p

Y1vibration

20

40000

0

30000

-20

Y1

X1
Y1
REV

X1
View from

20000
Target rotation of
20,000rpm

-40
-60
0.0

10000

Lift up point
8,000rpm

50.0

Lift up point
6,000rpm

100.0

150.0

200.0

250.0

300.0

350.0

400.0

450.0

0
500.0

Time [sec](1)Shaft vibration (Turbine side)

Thrust Disk

80

70000

60

60000

Y2 vibration
X2 vibtation

40

50000
Maximum amplitude
5μmp-p

20

40000

0

30000

-20

20000

Rotation Speed [rpm]Shaft vibration [μm]Turbine

Y2
X2
Y2
Z
REV

Thrust vibration

-40
-60
0.0

10000

50.0

100.0

150.0

200.0

250.0

300.0

350.0

400.0

450.0

0
500.0

Time [sec](2)Shaft vibration (Thrust disk side) and Thrust vibration
Fig 9.2.
9. 2.2
2. 2 - 4 Shaft vibration in rotation test of Foil Bearing

-88-

X2
View from

9.3

Conceptual Design of Hydrogen Liquefaction Facilities

9.3.1

R&D Goals

In the research and development plan of WE-NET Phase 2, we decided to work on
development items assuming automobile hydrogen stations in coordination with
development of fuel cell powered vehicles, in parallel with development of large-scaleuse of hydrogen, for gradual introduction of hydrogen energy. I n Ta s k 9 - 3 , w e a r eworkingondevelopmentofhydrogenliquefaction

machinewitharelatively small capacity of 30 ton/day or less, in preparation for thevalidation phase for automobile hydrogen stations, which is scheduledt o s t a r t i n P h a s e 3 . This fiscal year, we study hydrogen expansion turbines for
power recovery and power reduction in h y d r o g e n l i q u e f a c t i o n m a c h i n e b yutilizing the cryogenic heat of LNG for the purpose of reducing thecompression

power

in

hydrogencompressors,

which

we

have

been

reviewing.
9.3.2

Results FY2001
FY 20019.3.2.1

Study of power recovery technology using hydrogen expansion turbine

For a relatively small hydrogen liquefaction machine to be used in automobilehydrogen stations, we conducted an outline study on the expansion turbine for power
recovery. The expansion turbine extracts hydrogen gas from the high-pressurehydrogen gas line in the liquefaction cycle and expands it to recover power before
returning it to the low-pressure line. The recovered power is intended to reduce therequired power for the liquefaction compressor.
We decided to use the expansion turbines on the high temperature side and low
temperature side of the hydrogen liquefaction machine shown in Figure 9.3.2-1,
which had also been selected for 300t/d large scale hydrogen liquefaction facility inPhase 1.
Temperature and pressure conditions for the hydrogen expansion turbine were set assame as for the 300t/d facility, and flow rate was reduced in proportion to the amountof hydrogen liquefaction that was used as liquefaction capacity in this case study.
Three cases of liquefaction capacity were studied: 1t/d, 5t/d and 10t/d.

-89-Nitrogen re-liquefaction
machineHydrogen liquefaction
machineFigure 9.3.29.3.2 - 1. Process flow of hydrogen liquefaction machine(1) Study of rough outline of centrifugal turbo-type hydrogen expansion turbine
In this study we selected radial turbine as expansion turbine for power recovery,
which is a centrifugal type expansion turbine as shown in Figures 9.3.2-2 and 9.3.2-3.
With this type, gas is entered through the inlet pipe and passes the scroll, then is
expanded and accelerated through the nozzle to have a circular component in thecircumferential direction, and fed into the rotor blades.
Gas is further expanded in the rotor blades and direction of the flow is changed
from radial to axial, and discharged through the outlet pipe. As gas temperaturedrops due to adiabatic expansion, gas energy can also be recovered through rotor
blades as shaft power.
In this study, three-dimensional rotor blades were reviewed with the aim to
reduce the flow loss in the rotor blades and improve the efficiency of the expansion
turbine. By warping the blades in the height direction as shown in Fig. 9.3.2-3,
three-dimensional rotor blades can reduce the secondary flow loss (loss caused by aflow that occurs perpendicularly to the flow passage).

-90-

Direction of rotation
New three-dimensionalrotor blades

NozzleRotor blades
Direction ofrotation

Reduction ofloss at rotor
blade outlet

OutletGas
inlet

CasingScrollThree-dimensionalrotor blades

Fig.9.3.2Fig.9.3.2 - 2. Rough outline of centrifugal
t urbourbo - type hydrogen expansion
turbineFlow

Fig. 9.3.29.3.2 - 3. Shape of rotor blades incentrifugal turboturbo - typehydrogen expansion turbine

Results of study on primary dimensions, power and efficiency for the rotor
blades of the above-mentioned centrifugal turbo type hydrogen expansion turbine
are listed in Table 9.3.2-- 1, with liquefaction capacity of hydrogen liquefaction
facility as a parameter. Outer diameter of rotor blades becomes smaller asliquefaction quantity decreases.
Under the assumptions for this study, outer diameter of rotor blades was under
40mm for 5t/d turbine on high temperature side as well as for 1t/d turbine on highand low temperature sides, which are smaller than generally used centrifugal turbo
type hydrogen expansion turbines.
There is a possibility here that effects of leakage flow may relatively increasein the clearance between rotor blades and casing. Therefore, there is a possibility
that actual performance may be lower than the estimated performance based on
calculation (Denoted by (*) in Table 9.3.2-- 1.)
As temperature and pressure conditions are constant in this study and flowrate is proportional to the liquefaction quantity, power output of the expansion
turbine will be proportional to the product of efficiency and flow rate. From theabove results, the efficiency of the expansion turbine is estimated to decrease asliquefaction quantity decreases. On high temperature side of 5t/d turbine and onhigh and low temperature sides of 1t/d, actual efficiency can be estimated to belower than the results obtained by the above calculations.
Thus, in this study on power recovery with centrifugal turbo type turbine using
the temperature and pressure conditions for 300t/d, there is a possibility thatliquefaction quantity may decrease and the power to be recovered by may decrease-91-

relative to the power required for liquefaction.
As shown in the results of outline study, coupling/tie-in with the hydrogencompressor, to which recovered power is supplied, is expected to be very difficult toachieve technical viability with gear systems, as turbine speed exceeds 100,000rpm.
Therefore,

power

recoverybyuniaxial

directcoupling

with

the

hydrogencompressor seems to be the realistic solution under the power recovery conditions
for expansion turbine.

5ton/day

1ton/day

3.6

2.5

1.1

Outer diameter of rotor blades D3(mm)

43.5

30.8

13.9

Outer diameter of rotor blade outlet D4T(mm)

31.5

22.3

10.0

Inner diameter of rotor blade outlet D4R(mm)

12.8

9.1

4.1

198128279525621078Output power(KW)

104

51

10

Efficiency(− )0.815

0.802(＊ )0.766(＊ )Width of rotor blade outlet b3(mm)

4.9

3.5

1.6

Outer diameter of rotor blades D3(mm)

60.1

42.6

19.2

Outer diameter of rotor blade outlet D4T(mm)

43.5

30.9

13.9

Inner diameter of rotor blade outlet D4R(mm)

17.7

12.6

5.7

122935173260385091

74

36

7

0.828

0.817

0.785(＊ )Dimensions

10ton/dayWidth of rotor blade outlet b3(mm)Speed of rotation(rpm)Dimensions

Low temperature
expansion turbine LT

High temperature
expansion turbine WT

Table 9.3.29.3.2 - 1 . Results of Study on Rough Outline of the Expansion Turbine

Speed of rotation(rpm)Output power(KW)
Efficiency(− )(2) Study of thrust force of a centrifugal turbo-type hydrogen expansion turbine
The expansion turbine for power recovery has an inlet pressure of 4.05MPa on
high temperature side and 16.8MPa on low temperature side, and therefore thrustforce on turbine is expected to be large. Since thrust force affects the viability of the
shaft, it is necessary to consider reducing it. In this study we conducted a study on
the thrust force working on the turbine and measures to reduce it using balancerings, based on results of the above-mentioned form review and operating conditionsof the turbine. As shown in Figure 9.3.2-- 4, turbine thrust works in the direction ofhydrogen outflow at the turbine outlet. In a hydrogen liquefaction facility of 10t/d,
thrust force is about 60kgf for high temperature expansion turbine and about 50kgf
for low temperature expansion turbine.
Thus, we conducted a study on thrust control with balance rings. Figure 9.3.2-- 5shows results of study on thrust control in expansion turbine on high-temperature-92-

side in a 10t/d liquefaction machine. Results indicated that it was possible to reduce
the above thrust force by optimizing the diameter of balance rings.
Thrust adjustmentof 10t/d high temperature
10ton/day高温側膨脹タービンスラスト調整
expansion turbine
Expansion
turbinePower recovery
compressor

Ｆ
Ｃ

Compressor
thrust force

Ｄ
ＤＳ

Ｃ

Ｆ
Ｄ
Ｔ

Journalbearing
Thrustbearing

Expansion
turbinethrustforce

0

Thrust balance ring

Shaft
軸径
diameterFigure 9.3.29.3.2 - 4. Thrust force working on
the expansion turbine

9.3.2.2

100
90
80
70
60
50
40
30
20
10
0

Thrust スラスト力(kgf)force (kgf)NozzleLabyrinth

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Relative
positionouter
相対的ラビリンス位置(-) Turbine
タービン外径diameterof labyrinth (− )Figure 9.3.29.3.2 - 5. Results of study onthrust force (high temperature
expansion turbine)

Study on reduction of required power for hydrogen liquefaction using LNG
cooling

We assumed a case where hydrogen is produced from natural gas and liquefied
at or near an LNG base, and conducted a study on required power for hydrogenliquefaction using LNG c o o l i n g . It was confirmed that substantial reduction of
power would be possible.
(1) Hydrogen liquefaction power by conventional methods
Results of past studies on required power for liquefaction by conventional
methods for 1t/d, 10t/d and 30t/d liquefaction machines are summarized in Table
9.3.2-- 2. Also, an outline flow of hydrogen liquefaction machine is shown in Figure
9.3.2-- 6.
Table 9.3.2-2.
9.3.2 2. Power required
re quired for hydrogen liquefaction by conventional method
Scale of supply
Number of hydrogen liquefaction machines
Hydrogen expansion turbine
Hydrogen compressor
Nitrogen re-liquefaction cycle
Number of nitrogen re-liquefaction
machines
Expansion turbine
Power recovery
Required power
Raw hydrogen compressor
Low pressure recycle compressor
High pressure recycle compressor-40deg.C-level refrigerating machine
Nitrogen re-liquefaction machine
Total power
Theoretical minimum power
Process efficiency

t/d

MW
MW
MW
MW
MW
MW
MW
%

-93-

1

10

30

1
2
3(Reciprocating
type)

1
3
3(Reciprocating
type)

1
3
3(Reciprocating
type)

1
1
No

1
1
Yes

1
2
Yes

0.08500.01330.24800.00500.13410.4854
0.165
34.0

0.850
0.133
2.217
0.050
1.283
4.533
1.65
36.4

2.550
0.408
6.408
0.144
3.775
13.285
4.95
37.3

Boil-off
ボ イ ル compressor
オ フ 圧 縮 機

Low pressure nitrogen gas

Recycle compressor

リ サ イ ク ル 圧 縮 機

低 圧 窒 素 ガ ス
中 圧 窒 素 ガ スMedium pressure nitrogen gas
Raw hydrogen
原

料

水

素

原
圧

Raw
料 水 素
Hydrogen縮 機
Compressor

Liquid nitrogen
液

化

窒

素

高 温 膨 張タ ー ビ ンHigh temperature
expansion turbine

低 温 膨 張タ ー ビ ン

Low temperature
expansion turbine

Liquid hydrogen
液

化

水

素

Figure 9.3.2-6
9.3.2 6 . Hydrogen liquefaction process flow sheet(2) Conditions for study
We decided to use LNG with the following composition: methane: 90.78mol%,ethane: 5.92mol%, propane: 2.39mol%, butane: 0.88mol%, pentane: 0.02mol% andnitrogen: 0.01mol%. With this composition, boiling point is -160.3℃ at atmosphericpressure and -90℃ at 3.2MPa, and dew point is -30.2℃ . LNG temperature afterpressurization was set at 153℃ at inlet of heat exchanger for cooling recovery. For
production of H 2 from NG, combination of steam reforming, CO conversion and PSA
was assumed. Although typical reforming process pressure is around 1.0-2.8MPa,
3.0MPa was selected to match the booster pressure for raw hydrogen. The followingcase was studied for utilizing the cryogenic heat of LNG.
Case 1: (See Figure 9.3.2-- 7)
After boosting the LNG by pump, its cryogenic heat is used to cool the raw
hydrogen down to -150℃ in the hydrogen liquefaction machine. After that, LN 2 isused as an auxiliary coolant to cool down to 80K level. The following values were set
for pressure: pump inlet: atmospheric (0.101325MPa), pump outlet: 3.3MPa,
LNG/NG inside the heat exchanger: 3.2MPa, raw hydrogen inside the heatexchanger: 3.0MPa. Ortho-to-para conversion was also assumed. Excess cooling nearroom temperature was to be used for cooling the cooling water.
Case 2: (See Figure 9.3.2-- 8)-94-

LNG cooling is also used for re-liquefaction of LN 2 , which is used as an auxiliary
coolant. Nitrogen is used for cycle gas to re-liquefy LN 2 , and a cryogenic compressor
was selected as a circulating compressor.
Case 3: (See Figure 9.3.2-- 9)
Furthermore, cryogenic compressor was also selected for high pressure hydrogen
recycle compressor for hydrogen liquefaction machine. A separate LNG system wasused for this compressor with the following pressures: pump inlet: atmospheric(0.101325MPa), pump outlet: 1.1MPa, LNG/NG inside the heat exchanger: 1.0MPa.
天然ガス
Naturalgas

Hydrogengenerator/
refiner

Natural
天然ガス
gas

水素ガス
Hydrogengas

HydrogenHydrogen gas
水素ガス

水素生成精製装置
generator/

水素生成精製装置

refiner

Mediumpressure
nitrogen gas
中圧窒素ガス

冷却水

高圧窒素ガス

Cooling water

冷却水
Coolingwater

High pressure
nitrogen gas

Low
temperature
低温水素ガス

LNG

低圧窒素ガスLNG

Low pressure
nitrogen gas

Figure 9.3.2-7.
9.3.2 7. Process flow for

Naturalgas
天然ガス

Hydrogengenerator/
水素生成精製装置
refinerLow pressure
低温窒素ガスnitrogengas

Hydrogen
水素ガス gas

Medium pressure
中圧窒素ガス

天然ガス
Naturalgas

nitrogen gas

High pressure
nitrogen gas

高圧窒素ガス

冷却水

Cooling
water

リサイクル水素
Recyclehydrogen

LNG

低圧窒素ガス
Low
pressure
nitrogen gas

LNG

Low temperaturehydrogengas
低温水素ガスFigure 9.3.29.3.2 - 9. Process flow for-95-

Figure 9.3.29.3.2 - 8. Process flow for(3) Summary of study results
The results are shown in Table 9.3.2-- 3. In Case 1, required LNG volume isdetermined by temperature region below the boiling point of LNG, and the results
indicated that 0.4555Nm3/h of LNG per 1Nm3/h of hydrogen gas was required. Since
re-liquefaction of flashed hydrogen (15%) is also required in the raw hydrogensystem of the hydrogen liquefaction machine, required LNG volume was determined
as shown in Table 3.
In case 2, to also use LNG for re-liquefaction of nitrogen to generate auxiliary
cooling, we assumed that cooling at higher than -150℃ can be obtained "free ofcharge" from LNG. First, optimization of power for nitrogen cycle below -150℃ wasstudied and it was found that high pressure of nitrogen should be higher than
2.94MPa but as low as possible.
On the other hand, it was found that required LNG volume was determined by
the amount of heat required to liquefy high pressure flow of nitrogen, due to heatbalance over -150℃ . It was also found that required LNG volume would infinitely
increaseasconditions

approachedtheoptimum

power

conditions

for

the

above-mentioned nitrogen cycle below -150℃ . Based on the above, we conducted astudy to determine the required power, where high pressure of nitrogen was 4.5MPa
and a cryogenic compressor was used as circulating compressor.
In case 3, we studied a case where high pressure hydrogen recycle compressor of
the hydrogen liquefaction machine was used as low temperature compressor,
utilizing LNG cooling. As required volume for cooling increases, high pressure ofnitrogen re-liquefaction was reduced to 3.5MPa. Since the boiling point (BP) of LNG
at 1MPa is -121.5 ℃ , we were able to lower the operating temperature of highpressure hydrogen recycle compressor, contributing to reduction of power.
(4) Comments
Case 1 shows that it is possible to substantially reduce power, as power required
to boost LNG is very small. Increase in construction cost to cool the raw hydrogen
down to -150℃ is negligible. Reduction in power and construction cost can also be
expected.
In case 2, a realistic solution for a small facility of around 1t/d would be to omit thenitrogen re-liquefaction machine and to supply LN 2 externally by a tank lorry. If LNG
cooling is not used for nitrogen re-liquefaction, one or two units of nitrogen expansion
turbine and a nitrogen cold compressor will be used. Because cryogenic compressors
are relatively expensive at present, overall trade-off between equipment cost power-96-

must be considered. As the compressor becomes larger, it is expected to become morecost-effective. In case 3, further power reduction is possible if cryogenic compressor isused for high pressure hydrogen recycle compressor, utilizing LNG cooling. Based on
above results, utilizing LNG cooling is very effective in reducing required power.
9.3.3

Subject in futureThis year, we conducted studies on hydrogen expansion turbine for power recovery
and power reduction in hydrogen liquefaction machine utilizing LNG cooling, for the
purpose of further reducing the power required for compression in hydrogencompressors in a small-capacity hydrogen liquefaction facility, which we had been
studying.
We

now

plan

to

conduct

developmentofelemental

technology

forhydrogen compressor and hydrogen expansion turbine, validation withm o d e l t e s t s , a n d d e t a i l d e s i g n o n t e c h n o l o g y t o u t i l i z e L N G cooling, f o rvalidation of highly efficient, small-capacity liquefaction machine.
As specific items for next year, we plan to conduct performance validation ofh y d r o g e n e x p a n s i o n t u r b i n e for power recovery by model tests, and a moredetailed study on s m a l l - c a p a c i t y cryogenic compressor.

-97-

Table 9.3.2
9.3.2-3.
3. Comparison of power requirements using LNG cooling
1t/d Liquefaction machine
Case
Required power
Raw hydrogen compression
Low pressure hydrogen compression
High pressure hydrogen compression− 40deg.C
Nitrogen re-liquefaction
LNG pump
Total required power
Power unit requirement
Relative power
LNG volume

MW
MW
MW
MW
MW
MW
MW
KWh/Nm3%t/dConventional
methodCase 1Case 2

Case 30.08500.01330.24800.00500.13410.0000
0.485
1.048
100
0

0.00000.01330.24800.00000.06040.0005
0.322
0.696
66.4
4.7

0.00000.01330.24800.00000.01370.0012
0.276
0597
56.9
13.0

0.00000.01330.15790.00000.01150.0012
0.184
0.397
37.9
4.7+24.2

Conventional
methodCase 1Case 2

Case 3

0.850
0.133
2.217
0.050
1.283
0.000
4.53
0.978
100
0

0.000
0.133
2.217
0.000
0.577
0.005
2.93
0.633
64.7
47

0.000
0.133
2.217
0.000
0.137
0.012
2.50
0.540
55.2
130

0.000
0.133
1.291
0.000
0.115
0.012
1.55
0.335
34.2
47+242

Conventional
methodCase 1Case 2

Case 3

2.550
0.408
6.408
0.14
3.775
0.000
13.29
0.955
100
0

0.000
0.408
6.408
0.000
1.690
0.014
8.52
0.613
64.1
140

0.000
0.408
6.408
0.000
0.410
0.037
7.26
0.522
54.7
391

0.000
0.408
3.731
0.000
0.345
0.035
4.52
0.325
34.0
140+725

10t/d Liquefaction machine
Case
Required power
Raw hydrogen compression
Low pressure hydrogen compression
High pressure hydrogen compression− 40deg.C
Nitrogen re-liquefaction
LNG pump
Total required power
Power unit requirement
Relative power
LNG volume

MW
MW
MW
MW
MW
MW
MW
KWh/Nm3%t/d

30t/d Liquefaction machine
Case
Required power
Raw hydrogen compression
Low pressure hydrogen compression
High pressure hydrogen compression− 40deg.C
Nitrogen re-liquefaction
LNG pump
Total required power
Power unit requirement
Relative power
LNG volume

MW
MW
MW
MW
MW
MW
MW
KWh/Nm3%t/d-98-