Sulfur—iodine cycle

The sulfur—iodine cycle has been studied extensively by the nuclear industry since the mid-1970s. It employs iodine (I2) to promote the oxidation of S(IV) to S(VI), as follows  

Two immiscible phases are first formed. The upper phase contains almost all of the sulfuric acid and the lower, dense phase holds most of the hydrogen iodide (HI) and iodine. These are separated and the upper phase is then 

Pilot-plant operation in Japan identified the following difficulties  

Clearly, further studies have to be conducted on the chemistry and chemical engineering aspects of each of the process steps. In particular, a method must be found to reduce the excesses of water and iodine that are presently required over and above the reaction stoichiometry and thereby minimize material flows and attendant energy losses. 

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Knoche, K.F. et al, Second law and cost analysis of the oxygen generation step of the general atomic sulfur-iodine cycle, in Proc. 5th World Hydrogen Energy Conf, Toronto, 2, 487, July, 1984. 

Ozturk, I.T. et al, An improved process for H2S04 decomposition of the sulfur-iodine cycle, Energ. Corners. Manag., 36,11,1995. 

Fig. 2.8 Process flow schematics of a sulfur-iodine cycle.

Figure 4.83 Sulfur-iodine cycle and simulated phase behavior of the ternary system H20/Hl/I2 [132].

S 2] With the steady-state process simulator Aspen Plus , thermodynamic models for the sulfur-iodine cycle given in [132] are combined with chemistry models which describe the dissociation and precipitation reactions. 

Mathias, P. M., Brown, L. C., Thermodynamics of the sulfur-iodine cycle for thermochemical hydrogen production, in Proceedings of the 68th Annual Meeting Of the Society of Chemical Engineers (23 March 2003), Japan, 2003. 

Hadj-Kali, M.K., et al. (2009a), HIX System Thermodynamic Model for Hydrogen Production by the Sulfur-iodine Cycle , Int. J. Hydrogen Energy, 34,1696-1709. 

Buckingham, R., et al. (Buckingham, 2008), Modeling the Sulfur-Iodine Cycle A Comparison of Techniques , World Hydrogen Energy Conference, Brisbane, Australia, June. 

Mathias, Paul M., Lloyd C. Brown, et al. (2003), Thermodynamics of the Sulfur-Iodine Cycle for Thermochemical Hydrogen Production , 68th Annual Meeting of the Society of Chemical Engineers, Japan, 23 March. 

At General Atomic (GA), attention has been devoted during the last five years to the sulfur-iodine cycle and a program under the joint sponsorship of the U.S. Department of Energy, the Gas Research Institute (previously the American Gas Association) and General Atomic is presently under way. The sulfur-iodine cycle is characterized by the following chemical equations ... 

The Bench Scale Investigations of the sulfur-iodine cycle include a system which was planned to study the cycle under continuous operation conditions and a smaller unit, the Closed Loop Cycle Demonstrator, aimed at a simple demonstration of the feasibility of the cycle in a closed loop using recycled materials. 

Sulfur-Iodine Cycle and Other Sulfur Cycles The SI cycle has been proposed in several forms. (The SI cycle and other... 

Iodine-Sulfur cycle (or Sulfur-Iodine cycle, or ISPRA Mark 16 cycle) combines following... 

The Hybrid Sulfur (HyS) Process is one of the two baseline thermochemical cycles identified for development in the NHI program. (The sulfur-iodine cycle is the other). HyS is an all-fluids, two-step hybrid thermochemical cycle, involving a single thermochemical reaction and a single electrochemical reaction. The chemical reactions are shown below ... 

The information exchange meeting participants strongly endorsed further international cooperation on issues related to nuclear hydrogen production. Extensive collaboration already exists in some research areas, including the sulfur-iodine cycle. Additional areas of cooperation could include ... 

Chemical Cycle Example Sulfur-Iodine Cycle... 

However, until the study for CSP is complete and performance and cost estimates for commercial plants developed, the best available information about thermochemical hydrogen production comes from the nuclear studies. Consequently, the basis for the CSP inputs used in this model is the same as for the nuclear thermochemical case - based on the sulfur-iodine cycle cost and performance information from Schultz (2003). 

Thermochemical cycles are a solution to this problem as they split water using special catalysts and heat As an example, the sulfur-iodine-cycle will briefly be discussed. When heat is added, the sulfuric acid is split into sulfur dioxide, water and oxygen. In a second step, heat is added again to produce hydrogen iodide and... 

Liberatore et al. [11] detail the state of the art for a thermochemical cycle producing hydrogen on the basis of the sulfur-iodine cycle using a planning calculation for a plant with a productirai rate of 100 t/day. As a source of heat and power, a combination of parabolic thermal collectors and heliostats with a central receiver is used. An economic viability analysis resulted in hydrogen costs of 8.30 /kg. 

The sulfur-iodine cycle is a series of thermo-chemical processes used to obtain hydrogen. It consists of three chemical reactions whose net reactant is water and whose net products are hydrogen and oxygen. 

The sulfur-iodine cycle has been proposed as a way to supply hydrogen for a hydrogen-based economy. It does not require hydrocarbons like current methods of steam reforming. 

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