A novel Solar-Driven Molten-Salt methane pyrolysis system with direct Particle-to-Reactor-Wall heat Transfer: Design and Techno-Economic assessment

This study proposes a solar-driven methane pyrolysis system in which a particle-based concentrating solar power (CSP) plant supplies heat directly to an array of molten-salt (MnCl 2 –KCl) bubble-column reactors through the reactor wall, without an intermediate heat-transfer fluid or electric heating step. An hourly-resolved CSP model over a full year, comprising a heliostat field, a free-falling particle receiver, and two-bin thermal energy storage, is coupled to a reactor model that includes reaction kinetics, bubble hydrodynamics, particle-to-salt heat transfer, and equipment sizing. The integrated plant is assessed through a techno-economic analysis for a site in Daggett, California. At the baseline design (hot and cold particle temperatures of 1100 and 950 °C, 14 h of storage), the bulk salt temperature is 936 °C, the plant reaches a capacity factor of 69% and a single-pass methane conversion of 45%, and it produces about 6700 t/yr of hydrogen at a levelized cost of hydrogen (LCOH 2 ) of $3.87/kg without carbon credit and $3.52/kg with credit for the co-produced carbon. Raising the reactor temperature increases the cost of solar heat but lowers LCOH 2 through faster kinetics and fewer reactor modules, so the CSP and reactor subsystems must be designed jointly. Natural gas accounts for about 54% of LCOH 2 , and the particle-to-wall heat transfer coefficient is the most influential design parameter. At an assumed hydrogen price of $4/kg, the project has a positive 30-year net present value of $53 M with the carbon credit and without Section 45 V or LCFS policy support. At a gas price of $6/GJ and a hot-particle temperature of 1200 °C (bulk salt temperature of 1021 °C), approaching the conditions of earlier studies, LCOH 2 falls to $1.9–2.3/kg depending on the carbon credit. The configuration is a conceptual design: experimental validation of the particle-to-wall heat transfer, corrosion, creep, thermal cycling, abrasion, and liner compatibility in molten chloride is required.