This invention was made in the course of, or under, a contract with the Energy Research and Development Administration. It relates generally to the art of thermochemical hydrogen production.
Hydrogen is presently considered to be an attractive energy source for future application. Hydrogen has many attributes which make it a logical replacement for fossil fuels which are being rapidly consumed. The combustion of hydrogen produces no obnoxious products and thus no insult to the environment. Existing energy transport means and consuming equipment can be adapted with present technology for a hydrogen-based energy system. Natural gas pipelines, for example, can be converted to hydrogen carrying pipelines with minor modifications. Experimental automobiles are presently operating with modified conventional internal combustion engines using hydrogen as fuel.
With prospects for hydrogen utilization becoming evident, means for producing hydrogen need to be upgraded and increased. Conventionally, hydrogen has been produced by the electrolysis of water. Electrolysis, however, is highly inefficient when considering the inefficiencies present in electricity production coupled with an efficiency of about 80 percent for electrolysis. Inherent in the use of electrolysis to produce hydrogen is the general futility of using one energy source, typically fossil fuels at present, at the point of electricity production to ultimately produce hydrogen at the point of electrolysis. The disadvantages and excess consumption of fossil fuels are obviously not overcome by such a process. Chemical processes for the direct conversion of fossil fuels and water into a hydrogen product are presently at the point of technical feasibilty. This overcomes many of the inefficiencies and disadvantages of electrolysis. However, prudence indicates that fossil fuels should be preserved to the extent possible for long term pharmaceutical, chemical and metalurgical uses.
Thermochemical processes present the most attractive means for producing hydrogen. Via this technique water is broken down into hydrogen and oxygen through a series of chemical reactions not involving the use of fossil fuels. This series of reactions is desirably carried out in a closed cyclic manner such that all products except hydrogen, and oxygen are reused as reactants in the other reactions. One such process is disclosed in U.S. Pat. No. 3,490,871, which utilizes the reaction of cesium with water to release hydrogen. Another such process is disclosed in commonly assigned copending application Ser. No. 487,323 of July 10, 1974, which involves the reaction of copper and magnesium chlorides with water to produce hydrogen in a closed cyclic manner. Another such process is disclosed in commonly assigned copending application Ser. No. 545,042. Such process as is therein disclosed comprises reacting chromium oxide with an alkali metal hydroxide to produce hydrogen, water, and alkali metal chromate as reaction products. Commonly assigned application Ser. No. 504,790 discloses another closed cyclic process for splitting water wherein magnetite is reacted with an alkali metal hydroxide to produce hydrogen, alkali metal ferrate and water as products.
One of the subjects of the thermochemical process is the direct utilization of heat from an energy producing facility such as a nuclear reactor or solor sources. The upper temperature limit of such source is presently about 1300.degree. K for a high-temperature, gas-cooled reactor and 3500.degree. K for a solar furnace.