Hybrid thermochemical processes

Bilgen E (1988) Solar hydrogen production by hybrid thermochemical processes, Solar Energy 41 199-206... 

The scaling factor for current natural-gas-fueled Hj plants is estimated to be 0.66. This implies that if the plant size is increased by 4, the capital cost increases by only a factor of 2.5 that is, the larger facility capital cost is oidy 62% of that for the smaller facihty per unit of capacity. The scaling factor for the hybrid thermochemical process was estimated at 0.54 that is, the larger facility capital cost is only 53% of the smaller facility per unit of capacity. Market and technics factors indicate that the thermochemical process facilities will be very large and couple well to large high-temperature reactors. 

Summers WA, Buckner MR (2005) Hybrid sulfur thermochemical process development, DOE Hydrogen Program Progress Report... 

The copper-chloride hybrid thermochemical cycle is one of the best potential low temperature thermochemical cycles for the massive production of hydrogen. It could be used with nuclear reactors such as the sodium fast reactor or the supercritical water reactor. Nevertheless, this thermochemical cycle is composed of an electrochemical reaction and two thermal reactions. Its efficiency has to be compared with other hydrogen production processes like alkaline electrolysis for example. 

In this paper, we have studied the solar methanol production by a solar-assisted coal gasification system, which will be able to start-up GCRED-system, from a point of fossil/solar energy hybridization using solar thermochemical process (STC). 

Apart from the ANL s current effort on Hybrid Cu-Cl Cycle, there have been only a limited number of other processes proposed for moderate temperature thermochemical hydrogen production. Dokiya and Kotera [3] proposed a cycle with a significant variant of the Hybrid Cu-Cl Cycle involving a direct electrochemical hydrogen generation reaction. More recently, Simpson et al. [4] have proposed a hybrid thermochemical electrolytic process for hydrogen production based on modified Reverse Deacon Reaction (generation of HCl gas) and gas phase electrolysis of HCl. 

Hybrid Thermochemical Electrolytic Process for Hydrogen Production Based on Modified Reverse Deacon Reaction... 

From preliminary efficiency estimates and proof of principle experiments, Simpson et al. [4] have recently proposed a hybrid process based on the reverse Deacon cycle as a promising moderate temperature thermochemical process to produce hydrogen. The basic reactions involved are shown in the three steps in Table 3. As can be seen from the equations given in Table 3, the two-step sequence involving magnesium chloride hydrolysis (Step 1) followed by magnesium oxide chlorination (Step 3) reduces to the Reverse Deacon Reaction. The moderate temperatures involved in these reactions would... 

M.F. Simpson, S.D. Herrmann and B.D. Boyle, A hybrid thermochemical electrolytic process for hydrogen production based on the reverse Deacon reaction, International Journal of Hydrogen Energy, in press December 2005. 

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 ... 

Tire current work by SRNL included the creation of high-efficiency process design for the HyS Process. A block flow schematic for the process is shown in Figure 1. Since HyS is a hybrid thermochemical cycle, energy input in the form of both electricity and thermal energy is required. For a commercial nuclear hydrogen plant, approximately 38% of the nuclear reactor thermal output would be directed to electricity production and 62% to provide process heat. 

The thermochemical hybrid process is a combined cycle process with both thermochemical and electrolytic reactions of water splitting. The hybrid process offers the possibility of running low-temperature reactions on electricity. The expectations for realization of hybrid processes are similar to those for purely thermochemical processes [13]. Various hybrid processes are energetically possible, but not always feasible. Important criteria are the minimum voltage for the electrolysis step, realizability, efficiency. 

Research work has been done on the application of thermochemical (hybrid) cycle processes for the production of hydrogen by proposing an HTGR for the cogeneration of high-temperature energy for process heat and low-temperature energy for electricity production. 

Brown, R.C. (2005), Biomass refineries based on hybrid thermochemical/biological processing - An overview, in Bioreflneries, Biobased Industrial Processes and Products, B. Kamm, RR. Gruber, andM. Kamm, Editors, Weinheim, Germany, Wiley-VCH Verlag 1-24. 

Many types of thermochemical processes for H2 production exist. All of the competitive processes require heat input at temperatures above 750°C. The sulfuric acid processes (sulfur-iodine and Westinghouse hybrid) are the leading candidates. In each of these processes, the high-temperature, low-pressure endothermic (heat-absorbing) reaction is the catalytic thermal decomposition of sulfuric acid to produce oxygen ... 

Several studies of H2 production by thermochemical processes have been presented recently, including reports of several cycle statues such as sulfur—iodine (S—I) cycle, ISPRA Mark 9 cycle, hybrid sulfur cycle, Ca—Br cycle, Cu—Cl cycle, and adiabatic UT-3 cycle (Rosen, 2010). Many of these cycles are driven by nuclear or solar energy sources. H2O thermal decomposition generally holds three distinct steps production of H2, production of O2, and material regeneration. In recent decades, thermochemical cycles have been used for H2O decomposition, because they allow appreciable amounts of H2 and O2 to be attained at lower temperatures (usually less than 1000 °C) than are needed for one-step fliermochemical H2O decomposition (Rosen, 2008, Rosen, 2010). 

Brown RC. Biomass refineries based on hybrid thermochemical-biological processing - an overview. In Kamm B, Gruber PR, Kamm M, editors. Biorefineries - industrial processes and products, status quo and future directions, vol. 1. Weinheim (Germany) WUey-VCH 2006. p. 227-52. 

The University ofWaterloo continued the development in greater detail and showed from an economic evaluation that the process is an interesting alternative for the conventional production of ethanol. " In 1999, they compared the cost of producing ethanol from ceUulosic biomass via the hybrid thermochemical biorefinery approach, to acid hydrolysis and enzymatic hydrolysis technologies. The results indicate that the production cost of ethanol via the fast pyrolysis-based concept is competitive with the production cost via the conventional approaches. 

---