Iodine-sulfur cycle for nuclear hydrogen production with improved thermo-chemical efficiency

Abstract

Disclosed herein is an iodine-sulfur cycle for nuclear hydrogen production, which can improve thermochemical efficiency. The iodine-sulfur cycle is advantageous in that the amount of excess water and iodine supplied to a Bunsen reaction process is minimized, thus minimizing the amount of thermal energy consumed in the recovery and recirculation process thereof, in that sulfuric acid having stronger hydrophilicity than hydrogen iodide absorbs excess water in large quantities in a spontaneous liquid-liquid phase separation process, so that, after the spontaneous liquid-liquid phase separation process, the concentration of hydrogen iodide in a hydrogen iodide solution exceeds a concentration at an azeotropic point without conducting an additional concentration process, with the result that highly-concentrated hydrogen iodide gas can be obtained only through a flashing process, thereby decreasing energy consumption and simplifying the process and thus improving economical efficiency, and in that process temperature and pressure can be decreased, thus greatly deceasing the corrosivity in an operational environment. Therefore, the iodine-sulfur cycle according to the present invention can be usefully used for high-efficient and environmentally-friendly nuclear hydrogen production.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001]This patent application claims the benefit of priority under 35 U.S.C. §119 of Korean Patent Application No. 10-2008-0081299 filed on Aug. 20, 2008, the contents of which are incorporated herein by reference.BACKGROUND OF THE INVENTION [0002]1. Field of the Invention[0003]The present invention relates to an iodine-sulfur cycle for nuclear hydrogen production, which can decrease the corrosivity in operational environments and improve thermochemical efficiency by optimizing process conditions.[0004]2. Description of the Related Art[0005]Recently, Kyoto Protocol for preventing global warming has come into effect and oil prices are unpredictably changing as the fossil fuels are getting exhausted, and thus hydrogen energy has been considered as an alternative energy source in order to decrease the emission of carbon dioxide and secure an economical energy source. Accordingly, many attempts to develop processes of economical hydrogen production...

AI Technical Summary

Benefits of technology

The present invention provides an iodine-sulfur cycle for nuclear hydrogen production, which can decrease corrosivity and improve thermo-chemical efficiency by optimizing process conditions. Specifically, the invention includes a process for liquid-liquid phase separation, hydrogen iodide decomposition, and sulfuric acid decomposition. This cycle can reduce the risk of corrosion and improve the efficiency of hydrogen production, making it useful in various industrial applications.

Problems solved by technology

The sulfuric acid solution used in the sulfuric acid concentration and decomposition processes causes apparatuses used in these processes to be aged because it has high corrosive properties in high-temperature environment.

In the hydrogen iodide decomposition process, there are problems in that the decomposition ratio of hydrogen iodide can be greatly decreased by an extremely small amount of iodine included in the hydrogen iodide solution, and the energy efficiency in the hydrogen iodide decomposition process can be decreased by a large amount of excess water included in the hydrogen iodide solution.

The hydrogen iodide decomposition process is problematic in that the amount of energy consumed in the iodine separation process and the excess water circulation process is larger than the amount of energy consumed in the decomposition of hydrogen iodide molecules, and in that although the hydrogen iodide solution has very high corrosivity, its detailed thermo-chemical properties are not well known yet.

The corrosivity of sulfuric acid and hydrogen iodide increases with the increase of process temperature and pressure.

Therefore, in order to overcome this corrosivity of sulfuric acid and hydrogen iodide, there is a method of fabricating apparatuses using materials having excellent corrosion resistance, but this method is also problematic in that economical efficiency is decreased because the apparatuses made of these corrosion resistance materials are expensive.

Second, a large amount of excess water and iodine supplied in the Bunsen reaction process must be recovered and recirculated in subsequent processes.

However, even in this case, there is a problem in that a large amount of thermal energy is consumed during the recovery and recirculation of excess water and iodine, thus decreasing the energy efficiency of the entire iodine-sulfur cycle.

However, this method is also disadvantageous in that a process of recovering phosphoric acid is additionally required, and thus energy consumption is increased and the entire process is complicated.

However, this reactive distillation technology is also problematic in that high temperature is required in order to decompose hydrogen iodide, and vapor-liquid equilibrium must be maintained throughout the reactive distillation column in order to distill the hydrogen iodide solution for the purpose of concentrating the hydrogen iodide solution, so that high-temperature / high-pressure operation conditions are inevitably required, with the result that the basic problem that the operational environment in the reactive distillation column is not suitable to prevent the corrosion of the reactive distillation column cannot be solved.

However, this electro-electrodialysis (EED) technology is also problematic in that the basic limitation that a large amount of expensive electrical energy is required must be overcome, and in that the technical difficulty that the size of the membrane, which is structurally weak, must be increased from that of a small laboratory scale to that of a large hydrogen production plant scale must also be solved, thereby commercially using this electro-electrodialysis (EED) technology.

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