1. Industrial Prospective for Hydrogen Utilization - Safety Aspect -
10 September 2005
K.Takeno
Mitsubishi Heavy Industries, Ltd.
添付-2

2. MHI’s Activities for Hydrogen
MHI, general machinery and power plant maker, focuses on two aspects concerning hydrogen.
1. When hydrogen is used as the alternative energy resources from fossil energy, we should provide the high-quality and high-efficiency devices for hydrogen production, storage, and utilization.
2. Utilization as the media of energy chain among natural reproducible energy (wind, solar, geothermal, water, biomass, etc.), and nuclear energy.

3. Energy Chain through Hydrogen
On-site hydrogen station
As the final conversion device from hydrogen, PEFC has highest efficiency

4. Role of Hydrogen in Natural Energy System
Electricity
DC/AC
DC/AC H2
Wind Power O2
Solid Polymer Water
Electrolysis
Polymer Electrolyte
Fuel Cell
Solar Cell
Rechargeable battery
Methanol
(Storage)
Solid Oxide Fuel Cell
Engine
Biomass Gasification
to produce H2 and CO
Power Source
If biomass gasification is combined, performance becomes higher (oxygen from electrolysis can be utilized and carbon from biomass can be fixed to liquid fuel).

5. Introduction of Future Plan (RERE System)
＊RERE(Renewable Energy based Rural Electrification)

6. Research on Safety EXPLOSION or Diffusion Flame Wind Buoyancy
Mixing of air with H2
Buoyancy
Flow & Diffusion
LH2 : Evaporation Diffusion
GH2 : Diffusion
Flammable H2/Air Mixture
EXPLOSION or
Diffusion Flame H2
Tank
Pressure Wave
Radiation
Leak of LH2 (Liquid) or
GH2 (High-PressurizedGas)

7. Research on Safety (continued)
Hypothesis Accidents
Probability study
# Evaporation of LH2
# Diffusion of GH2
# Immediate Ignition ⇒　Diffusion Flame
# Delayed Ignition ⇒　Explosion
Experiments
Computer Simulation
# Spread of Flammable Mixture
# Scale of Diffusion Flame
# Propagation of Pressure Wave
# Radiation from High Temp. Steam
Evaluation of Safety
(Risk Analysis)
Safety Regulation

8. Research on Safety (continued)
High-pressure H2 flame（d=10mm，P=28MPa）
(Visualized by Na addition)
Correlation of flame scale
Lf: flame length
rfmax: maximum flame diameter
d: nozzle (opening) diameter
This formula is used for the Japanese regulation of hydrogen safety.
Schuliren photo image（d=1mm，P=20MPa）
(Flame is stabilized behind shock wave)

9. Research on Safety (continued)
Large scale (300m3) explosion experiment, conducted by IAE / SRI
(H2 (30%) / Air mixture)
Typical result on the atmospheric diffusion of leaked H2 at an assumed hydrogen supply station.
(40MPa-400m3, d=10mm opening, t=3s)
75～90m/s
[Pa]
Velocity of flame propagation
Pressure distribution at t=100ms

11. Principal Conclusion and Perspectives
# Problem seems to be the energy efficiency. It is difficult to overcome the direct use of natural gas to gas engine or turbine.
# At the standpoint of industrial researcher, it is the urgent demand to raise the conversion efficiency from NG or nuclear energy to hydrogen. Specially, MHI expects membrane reformer, which can be operated at low temperature (～550℃) and conversion efficiency is high (～75%).
# From CO2 problem, the use of natural renewable energy is expanding globally. If hydrogen is the core of energy flow, many kinds of natural energy can be combined.

12. Membrane Reformer CH4＋H2O+heat→CO+3H2
This can be operated at low temperature (～550℃) and conversion efficiency is high (～75%)