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

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

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

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

Research on Safety Wind Buoyancy Flow & Diffusion Mixing of air with H 2 EXPLOSION or Diffusion Flame Leak of LH2 (Liquid) or GH2 (High-PressurizedGas) H2 Tank LH2 : Evaporation Diffusion GH2 : Diffusion Flammable H2/Air Mixture Pressure Wave Radiation

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

Research on Safety (continued) High-pressure H2 flame （ d=10mm ， P=28MPa ） (Visualized by Na addition) Schuliren photo image （ d=1mm ， P=20MPa ） (Flame is stabilized behind shock wave) 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.

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

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.

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