Influence of Metal Surfaces on Coking in a Reforming/Methanation Thermochemical Transport Distributed Receiver Solar Energy System

摘要

A number of thermochemical cycles have been proposed for energy transport. The one under investigation at Sandia National Laboratories Albuquerque involves converting a carbon dioxide/methane mixture to carbon monoxide and hydrogen during the endothermic reforming reaction, and then back again to carbon dioxide and methane during the exothermic methanation reaction. Carbon formation and deposition in either the reformer or the methanator is a serious concern. We performed simultaneous thermogravimetric and gas spectrometric analyses to measure carbon deposition rate and changing gas composition in the presence of material candidates for use in the reforming/methanation loop. We found that nickel-base superalloys such as Inconel 625 are good candidates for the high temperature endothermic reforming reactor, and stainless steels such as 316L will suffice for the low temperature exothermic methanation reactor. We also found that adding carbon dioxide to the carbon monoxide/hydrogen gas mix in an attempt to reduce carbon formation was not effective, particularly at lower temperatures for iron-base alloys. More important to the propensity to form carbon is the ratio of carbon monoxide to hydrogen. 9 figs., 1 tab. (ERA citation 12:013396)