A Fuel-Cell Electric Vehicle with Cracking and Electrolysis of Ammonia

Hydrogen has difficulties in handling in a fuel cell vehicle, and has a fault with taking a big space there. The authors have proposed a hydrogen generation system using ammonia as a liquid fuel for fuel-cell electric vehicles. Ammonia has an advantage not to emit greenhouse effect gases because it does not contain a carbon atom. Hydrogen content of ammonia is 17.6 wt% and hydrogen quantity per unit mass is large. Ammonia can be easily dissociated to hydrogen and nitrogen by heating. Therefore, ammonia is an attractive hydrogen supply source for fuel cell vehicles. The ammonia hydrogen generation system of this study consists of a vaporizer, a heat exchanger and a cracking reactor with a separator. Ammonia is heated with the heat exchanger and sent to the cracking reactor, after it is evaporated through the vaporizer from the liquid ammonia. The ammonia is cracked to hydrogen and nitrogen with an appropriate catalyst. The residual ammonia is collected with the separator by using the property of solubility easily into water. But it cannot be gradually dissolved in water, as the ammonia concentration in water increases. The authors also propose electrolysis of the ammonia water to remove the residual ammonia. The concentration of ammonia decreased in the separator by the electrolysis, and nitrogen and hydrogen was generated by electrolysis. The hydrogen was supplied to a fuel cell through the system. The system will be useful as a fuel supply system for fuel cell vehicles in the near future, when energy efficiency and safety are improved.