Integrated solar-driven hydrogen generation by pyrolysis and electrolysis coupled with carbon capture and Rankine cycle

Abstract

Reduction of carbon emissions from conventional gray Hydrogen (H2) production is a promising option in moving towards much greener H2 generation. To minimise carbon emissions and improve plants’ efficiencies of conventional gray H2 production, this study focused on process simulation of hybrid CSP, catalytic Methane (CH4) and biomass pyrolysis and Water (H2O) electrolysis plants with 1000 °C HTF output temperature. This integrated system differs from current pyrolysis and electrolysis technologies for H2 production because of the involvement of CSP as a thermal energy source; the use of part of recovered heat from the reactor to power downstream units including thermolysis of Sulphuric Acid (H2SO4) and steam generation for both H2O electrolysis and Rankine cycle; the use of H2O as a reaction media and carbon looping to promote biomass decomposition; anodic oxidation of SO2 in AEC to promote hydrogen evolution reaction. In that regard, CSP systems were modelled and simulated in SAM and MATLAB software. The output result of the simulated CSP system got exported to the Simulink to feed simulated CH4 and biomass pyrolysis coupled with TES and Rankine cycle from Aspen plus. In addition, simulated thermal disassociation of H2SO4, electrolysis of H2O with SOEC and AEC from Aspen plus was also exported to the Simulink to feed the CSP system. Both integrated systems were fed with CH4 as the working fluid of the solar furnace. About $1.7/kg is estimated to be a H2 selling price for simulated pyrolysis of CH4 and biomass plant which is cheaper than SMR with a CCS system. While between 4.6 and 10.48 is also estimated to be a H2 selling price for another simulated CH4 pyrolysis and H2O electrolysis. Just like existing CSP systems for electricity generation, both simulated hybrid systems generate electricity for up to 200 min in the absence of the Sun. Similar to SMR with a CCS system, CO2 by-product from biomass pyrolysis was captured. Due to coking issues related to catalytic pyrolysis, noncatalytic pyrolysis of CH4 was investigated. Results of the research work show that a return on investment within a period of 6 years is possible with the adoption of these new innovative technologies while reducing carbon footprints in H2 generation plants.