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Hydrogen Safety System Summary. Elwyn Baynham, Tom Bradshaw , Yury Ivanyushenkov Applied Science Division, Engineering and Instrumentation Department RAL. MICE Collaboration Meeting, Osaka, August 1-3, 2004. Scope. Status of hydrogen absorber and system safety Hydrogen system:

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Hydrogen Safety System Summary

Elwyn Baynham, Tom Bradshaw , Yury Ivanyushenkov

Applied Science Division,

Engineering and Instrumentation Department

RAL

MICE Collaboration Meeting, Osaka, August 1-3, 2004


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Scope

  • Status of hydrogen absorber and system safety

  • Hydrogen system:

  • - changes in the system according to the Safety Review Panel recommendations;

  • - ongoing work on safety issues;

  • Hydrogen absorber/system operation:

  • - instrumentation and control.

  • Hydrogen R&D


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Status of hydrogen absorber and system safety

Safety = Safe Design + Safe Operation

  • Operation:

  • Operation analysis - started

  • Safety system analysis - started

  • R&D stage - to be done

  • Operation manual - to be written

  • Design:

  • Internal safety review - passed

  • ( many useful comments, response is ready)

  • Preliminary HAZOP - done

  • Instrumentation - to be

  • implemented

Final safety review – to be passed


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Changes in MICE hydrogen system

  • AFC Safety Review Panel recommendations are implemented:

  • Buffer vessel is removed from venting path.

  • Vent manifold is added. The manifold is filled with nitrogen.

  • Venting lines are separated.

  • Other changes:

  • Buffer vessel is added in between absorber vessel and hydride bed:

  • - together with liquid hydrogen vessel and hydrogen condensation pot forms

  • a quasi-closed system;

  • - improves time response of safety devices in case of catastrophic failure.

  • Ventilation system is removed. Most of the equipment is now sits

  • under hydrogen extraction hood.


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H2 Detector

H2Detector

MICE hydrogen system

High level vent

High level vent

Vent outside

flame arrester

Non return

valve

Vent manifold

Vent manifold

0.1 bar

Hydrogen zone 2

Extract hood

VP2

PV8

P1

P

Metal Hydride storage unit

(20m3 capacity)

P

PV7

P

PV2

PV1

Chiller/Heater Unit

1 bar

Tbed

Buffer

vessel

Hydrogen supply

PV3

1 m3

PV4

P

Fill valve

P

HV1

Pre-cooling

Out In

P2

P

0.5 bar

Liquid level gauge

0.9 bar

P3

HV2

Internal Window

P

P

Purge valve

P

P

P

LH2 absorber

Safety windows

Vacuum

Purge valve

HV3

Vacuum vessel

0.9 bar

Nitrogen supply

PV6

Helium supply

0.5 bar

VP1

Pressure

gauge

Pressure

relief valve

Non-return

valve

Pressure

regulator

Bursting disk

Valve

P

P

Vacuum pump

VP


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Safety issues: Ongoing work

  • Pressure rise rate calculations

  • Valves

  • Hydrogen sensors

  • Control


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Operation issues: Ongoing work

  • Operation from cryocoolers

  • Instrumentation and control


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Hydrogen absorber instrumentation

  • Instrumentation to be implemented into absorber design:

  • Hydrogen level sensor/s:

  • - their functions (what do we need them for)?

  • - continuous/ discrete?

  • - how many and where?

  • Temperature sensors:

  • - their functions ?

  • - how many and where?


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Hydrogen level sensors

Continuous level sensor

Point level sensors


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Cryogenic liquid level sensors from AMI

The capacitance-based liquid level sensor, used in conjunction with

the Model 185 and 186, is manufactured of stainless steel tubing.

Upon request, special assembly techniques can be applied for

sensors required for liquid oxygen or hydrogen measurement _

including minimization of oils during construction and no use of

epoxies. Sensors can be supplied in single-section overall lengths

of up to 30 feet. Multi-section lengths in excess of 50 feet are

available upon request.

Three standard sensor mounting configurations are available. The

typical configuration includes a hermetically sealed BNC connector

with an adjustable 3/8" male NPT nylon feed-through. For higher

pressure or vacuum applications, a welded stainless steel 3/8"

male NPT fitting or conflat flange fitting is available. Twelve feet

of connecting coaxial cable and in-line oscillator/transmitter are

included with the sensor. With additional cable the sensor can

be remotely mounted over 500 feet from the instrument without

effecting performance.

Sensor options include:

1. Rugged service construction 1/2" or 3/4" OD

2. Miniature sensors of 3/16" and 1/4" OD

3. Radius bends up to 90°

4. Capacitance or RTD point sensing elements

Custom sensors are available from AMI to meet your individual


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Level sensor implementation

Continuous level sensor

Connector required

(Swagelok VCR Metal gasket

face seal fittings ?)

Can a sensor be manufactured to this shape ?


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What is known about metal hydride tank

Table 1 The specification of the MH tank for RAL

Hydrogen Storage Capacity20 Nm3

Tank number/system1

Tank Description:

Heat Transfer MediumWater

MH Weight 155kg

Tank StructureShell & Tube type

Dimensions φ216.3×L1600(mm) ( not include attachments )

Tank Total Weight220 Kg

Operating Condition:

Charging Gas ComponentHydrogen of 99.99% purity

Charging Gas Pressure1.2 barA

Hydrogen Charging Rate70NL/min

(up to 90% of Storage Capacity)

Discharging Gas Pressure1.2 barA

Hydrogen Discharging Rate70NL/min

(up to 90% of Storage Capacity)

Utility Requirements:

Cooling MediumWater

Below -10℃ (At 20L/min)

Heating MediumAbove 20℃ (At 20L/min)

Design Code(AD Merkblaetter )

Certification(Declaration of Conformity to Pressure Equipment Directive 97/23/EC

Certified by a Notified Body)

REFERENCE


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What is known about metal hydride tank (2)

Fig.1 Schematics and dimensions of the MH tank


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What is known about metal hydride tank (3)

Fig.2 P-C-T curves of metal hydride for RAL


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What is known about metal hydride tank (4)

Annotation by JSW:

Attached please find the temporary specification of a 20Nm3 metal hydride

(MH) tank, its sketch and the pressure-composition-temperature diagram of

the candidate MH alloy.

It would be better to explain the temperatures and pressures on charging and

discharging hydrogen, referring to the PCT diagram.

As you can see in the diagram (Fig. 2), it is possible for the alloy to

absorb hydrogen gas almost to its maximum capacity at 0 degC if the pressure

of hydrogen gas is maintained at 0.12 MPa. However, we are not yet sure of

the influence of pressure loss inside the tank under such a negative

pressure region. So, at the moment the charging temperature is specified to

be below -10 degC with 0.12 MPa of charging pressure (See Table 1.).

Then, you can see in the diagram (Fig. 2) that the MH alloy can discharge

almost all the hydrogen at +20 degC if the pressure is maintained at 0.17

MPa. To be on the safer side, the discharging temperature is specified to be

"above" +20 degC (See Table 1.). This means that the maximum internal

pressure of the MH tank is likely to be reached during the hydrogen gas

holding period if the water is stopped and the surrounding temperature

increases. However, even at +30 degC, the expected internal pressure is not

so high, approximately 1 MPa.

As a matter of fact, there will be an unknown factor, i.e., how accurately

we could control the materials properties when we newly manufacture an MH

alloy. Due to slight variations in the chemical composition and other

manufacturing parameters, the equilibrium temperature could vary by up to 5

degC for the same pressure. This could cause further changes in the

charging/discharging temperatures and consequently the internal pressure.

Since the relative plateau positions do not change, please assume that a

difference of more than 30 degC is needed between the charging and

discharging temperatures for the given charging and discharging pressures.


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Hydrogen R&D

  • Conceptual question: a small-scale rig vs. a full-scale prototype ?

  • Decision: go for a full-scale system which later will be used in MICE.

  • R&D goals:

  • Establish the working parameters of a hydride bed in the regimes of storage, absorption and desorption of hydrogen.

  • Absorption and desorption rates and their dependence on various parameters such as pressure, temperature etc.

  • Purity of hydrogen and effects of impurities.

  • Hydride bed heating/cooling power requirements.

  • What set of instrumentation is required for the operation of the system?

  • Safety aspects including what is the necessary set of safety relief valves, sensors and interlocks.


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Hydride system test rig

High level vent

High level vent

Vent outside

flame arrester

Non return

valve

Vent manifold

Vent manifold

0.1 bar

Hydrogen zone 2

Extract hood

VP2

PV8

P1

P

Metal Hydride storage unit

(20m3 capacity)

P

PV7

P

Mass spectrometer

M. F.M.

PV2

PV1

Chiller/Heater Unit

1 bar

Mass flow meter

Tbed

Buffer

vessel

Hydrogen supply

PV3

1 m3

PV4

P

Fill valve

P

HV1

Coolant

Out In

P2

P

0.5 bar

0.9 bar

P3

HV2

P

P

Purge valve

P

P

P

H2 Detector

H2Detector

Test absorber assembly

Purge valve

HV3

0.9 bar

Nitrogen supply

PV6

Helium supply

0.5 bar

VP1

Non-return

valve

Pressure

gauge

Pressure

relief valve

Pressure

regulator

Bursting disk

Valve

P

P

Vacuum pump

VP

Tchill


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Next steps

  • Finish pressure rise rates calculations

  • Select safety devices

  • Control system diagram

  • Instrumentation defined and implemented into design

  • Hydrogen R&D:

  • - find suitable place for hydrogen test area (MICE hall ?);

  • - timetable depends on funding

  • but would like to setup test rig in 2005.


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