Solar steam reforming for enriched methane production: Reactor configurations modeling and comparison

A solar low-temperature steam reforming process for the production of an Enriched Methane (EM) mixture composed by CH4 and H-2 (20%vol) exploiting the solar energy stored in a Molten Salt stream heated up by a Concentrating Solar Plant (MS-CSP) is presented and simulated through a two-dimensional steam reforming reactor model. Two configurations are considered and compared: the Integrated Heat Exchanging (IHE) configuration, where the steam reformers are tubes-and-shell reactors continuously heated up by the hot MS stream, and the External Heat Exchanging (EHE) configuration composed by a series of heat exchangers and insulated reformers where the reactions are adiabatically driven. The effect of the main operating conditions as Gas Hourly Space Velocity (GHSV), inlet reactor temperature and reactant mixture composition is assessed for both the configurations, demonstrating the process feasibility. Furthermore, in order to increase the process performance, an electrical power generation unit is also included, exploiting the sensible heat of the residual MS stream after the EM production unit: in this case, with a feed of 2000 Nm(3)/h of natural gas, about 6130 Nm(3)/h of enriched methane and 475 kW(el) are produced with the EHE configuration, while 3720 Nm(3)/h and 585 kW(el) are obtained with IHE configuration.