Preliminary Study Of Hydrogen Production With Partial Decomposition Of Water

Hydrogen is the cleanest fuel for transportation because the product of burning hydrogen is only water. Especially, PEMFC technology makes it available. We put forward a novel method of hydrogen production via partially decomposition of water. This method is hydrogen production cycle, including three processes with iron as contact mass: in the first phase, steam reacts with iron to produce hydrogen and iron is oxidized; in the second phase, the contact mass is reduced by lower energy fuel gas; in the third phase, lower energy fuel gas generated. The reaction temperature is lower and hydrogen comes from water without any impurity. The hydrogen production is suitable for application in any kind of fuel cells. At normal pressure, the theory hydrogen storage rate is 4.76 %( mass ratios).In this thesis, a novel process was designed and developed which can enlarge the source of fuel, not only hydrocarbon and alcohol but also coal or regeneration fuel such as biologic mass. The bulk of this thesis is concerned with the thermodynamic analyzing and reaction mechanisms for the whole reaction system. A supported iron medium which has high specific surface area was prepared. The hydrogen production , rate, hydrogen quality and cycle stability of reaction which used the supported iron as cycle contact mass, hydrogen or carbon monoxide as reducing gas at temperature range from 500 to 800oC were investigated. When carbon monoxide is used as reducing gas, a large of carbon depositions occurs on the iron contact mass during the reducing process. The product of carbon deposits on the surface of the contact mass and initiates the reaction of carbon between water during latter oxidation process, and leads to higher hydrogen production than theory value. The hydrogen production quality decreases because of larger carbon monoxide being.The experimental results show that carbon deposition can be controlled and the hydrogen production quality will be advanced by elevating reducing temperature or decreasing carbon monoxide concentration. At the same time the results also show that the reducing process occurs easily at elevated temperature in this cycle process. Taking into account that the reaction of steam oxidation at elevated temperature is controlled by thermodynamic and the hydrogen production rate will decrease with increasing temperature, thus hydrogen production efficiency improves by operating at variation temperature in theory. The cycle stability is poor during all experiments with the supported iron as cycle contact mass. The total hydrogen production and rate decrease with increasing cycle index, especially at the higher temperature the effect is larger, for example, there is almost not hydrogen production after three cycles at 800oC.