Solar—Thermal Reforming

Solar—thermal reforming of natural gas is an interesting future prospect, but has yet to be fully demonstrated. Consequently, the practicalities and... 

Epstein, M., et al. (1996), Solar Experiments with a Tubular Reformer , Proc. 8th Int. Symp. on Solar Thermal Concentrating Technologies, M. Becker and M. Bohmer, (Eds.), Cologne, Germany, 6-11 October. 

This is the final year of a three-year project and no future research is plaimed. However, DOE is currently considering a process extension proposal to support a solar-thermal process to rapidly dry reform waste landfill gas to hydrogen and carbon black. Independent of the outcome of that proposal, the following issues need to be addressed ... 

For the process scenario discussed, the solar-thermal process avoids 277 MJ fossil fuel and 13.9 kg-equivalent C02/kg H2 produced as compared to conventional steam-methane reforming and furnace black processing. 

The solar-thermal process is enviromnentally friendly. The most environmentally friendly option is when selling carbon black into the tire carbon black market as the energy and pollution associated with normal carbon black production are avoided. If carbon is fed to a carbon conversion fuel cell, the total green house gas emissions are still 60% of those of a steam reformer and the bulk of the released CO2 is in a pure form so it can be easily sequestered. 

With particular focus on the development of high-temperature reactors and solar thermal power plants, an establishment of these processes has been discussed. With regards to steam reforming and electrolysis, the 50 % efficiency of these cycles is comparatively low. However, the direct use of heat leads to a high utilization rate for the entire system. 

Fig. 10.5 Greenhouse gas intensity of different hydrogen productirai methods CGH compressed gaseous hydrogen, EL electrolysis, SOT solar thermal energy, HVDC high voltage direct current, AER absorption enhanced reforming. Source LBST/FhG-IWES/Hessen Agentur [10]...

The CSP plant consists of a solar collector field, a receiver, a heat transfer fluid loop and a heat storage system. The mirrors of the solar field concentrate the direct solar radiation on the solar receiver set at the focal line. The heat transfer fluid (e.g., molten salts) removes the high temperature solar heat from the receiver that is afterwards collected into an insulated heat storage tank to be pumped, on demand, to the heat users (steam generators, endothermic reactors, etc.), where its sensible heat is released. Finally, the heat carrier fluid is stored in a lower temperature tank ready to restart the solar heat collection loop. The idea to match the CSP plant with natural gas steam-reforming Pd-based MR derives from the thermal level reached by molten salt stream (550°C), which meets the thermal requirements of MR (preferred operating at around 500°C). 

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