Electrolysis steam

Three types of electrochemical water-spHtting processes have been employed (/) an aqueous alkaline system (2) a soHd polymer electrolyte (SPE) and (J) high (700—1000°C) temperature steam electrolysis. The first two systems are used commercially the last is under development. 

Eig. 6. Comparison of current density and cell voltage characteristics of the electrolysis systems where lines A and B represent steam electrolysis and the use of SPE, respectively, the conventional KOH water electrolysis, and, 2ero-gap cell geometry employing 40% KOH, at 120—140°C. 

J.E. O Brien, J.S. Herring, P.A. Lessing, and C.M. Stoots, High Temperature Steam Electrolysis from Advanced Nuclear Reactors using Solid Oxide Fuel Cells, presented at the First International Conference on Fuel Cell Science, Engineering, and Technology, Rochester, NY, April 21-23, 2003. 

High temperature short time (HTST) continuous sterilization, in fermentation, 11 35-36, 45 High temperature steam electrolysis, 13 784... 

Solid Oxide Electrolysers (SOE) are in development for steam electrolysis. As electrolysis is an endothermic process, a supply of waste heat can be used beneficially to reduce the electrolyzer voltage, and thus increase its electrical efficiency. Combination with nuclear power generation and geothermal heat sources is often encountered in development programs for SOE. 

The limitation of solvent evaporation could be avoided by working at high temperature with water vapor in the presence of a solid electrolyte (steam electrolysis). Nominally, at about 4000°C, at which AG = 0, electroless thermal water splitting would be realized. In practice, problems of material stability, necessary... 

Figure 7.17 shows a summary of the available conditions of water electrolysis [72]. For each configuration there exists a range of performance. Conventional electrolyzers, which nevertheless are still the most common in the current production of H 2 on the intermediate and small scale, show high overpotential and a relatively small production rate. Membrane (SPE) and advanced alkaline electrolyzers show very similar performance, with somewhat lower overpotential but a much higher production rate. Definite improvements in energy consumption would come from high temperature (steam) electrolysis, which is, however, still far from optimization because of a low production rate and problems of material stability. 

Fig. 2.4 Requirement of electrical and heat energies for steam electrolysis.

Liepa MA, Borhan A (1986) High-temperature steam electrolysis Technical and economic evaluation of alternative process designs. Int J Hydrogen Energy 11 435... 

Arashi H, Naito H, Miura H (1991) Hydrogen production from high-temperature steam electrolysis using solar energy. IntJ Hydrogen Energy 16 603-608... 

High-temperature steam electrolysis uses heat (approximately 1000°C) to provide some of the energy needed to split water, making the process more energy efficient. 

Clean production of hydrogen - thermochemistry and steam electrolysis combined with future high-temperature nuclear reactors and biomass. 

Entergy, which is known to take up challenges and participate in FOAK endeavours, supports HTGR technologies to widen applications of nuclear production with encouraging views on the potential performance of high-temperature steam electrolysis and thermochemical cycles. 

The steam electrolysis at high temperature (600-800°C) features a potential efficiency of -100% LHV with extra heat available. Its technology benefits from current developments made of solid oxide fuel cells. However, many uncertainties and issues remain to achieve a commercial viability. Prominent issues include improving the reliability and the lifetime of electrolytic cells and stack of cells and decreasing the investment and operating costs with a view to decreasing the currently estimated production cost from 4 to about EUR 2/kg H2 [from 5.2 to about USD 2.6/kg H2],... 

The French R D focuses on three baseline processes which require high temperatures high temperature steam electrolysis (HTSE), and the sulphur-iodine (S-I) and hybrid sulphur (HyS) thermochemical cycles. Alternative cycles able to operate at lower temperatures (Cu-Cl in particular) have also been investigated. All these cycles are being assessed from a feasibility point of view and some technical hurdles remain. Laboratory-scale experiments are ongoing and will give important... 

Rivera-Tinoco, R., C. Mansilla, C. Bouallou (2008), Techno-economic Study of the High Temperature Steam Electrolysis Process Coupled with a Sodium Nuclear Reactor , WHEC 2008, Brisbane, June. 

Evaluation studies (Shin, 2007) on the efficiency of the SI thermochemical cycle, the high temperature steam electrolysis, and the hybrid sulphur cycle is ongoing based on the recent achievements over the world (Shin, 2008). 

The preliminary simplified principal flow diagram of the MHR-T module (option with methane reforming) is given in Figure 3. The flow diagram for the option with water steam electrolysis may differ by components of intermediate helium circuit between RP primary circuit and chemical-technological sector. 

In the intermediate term, nuclear-heated steam reforming of natural gas could be utilised, using medium-temperature reactors, in spite of some carbon dioxide emissions, because of its advantages in economic competitiveness and in technical feasibility. Also, high-temperature reactors could be used to carry out high-temperature steam electrolysis, with higher conversion efficiency and fewer materials problems. 

Stoots, C.M., J.E. O Brien, M.G. McKellar, G.L. Hawkes, J.S. Herring (2005), Engineering Process Model for High-temperature Steam Electrolysis System Performance Evaluation , AIChE 2005 Annual Meeting, Cincinnati, OH, USA, 30 October-4 November. 

HIGH-TEMPERATURE STEAM ELECTROLYSIS FOR HYDROGEN PRODUCTION FROM MATERIAL DEVELOPMENT TO STACK OPERATION... 

High-temperature steam electrolysis for hydrogen production From material development to stack operation... 

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