Investigation of the SO2 capture and iodine-sulfur cycle for H2-H2SO4-electricity-heat polygeneration system based on spectral splitting

Solar energy is a renewable resource that has the potential to reduce industrial pollution and facilitate large-scale hydrogen production. This study proposes a novel polygeneration system for producing H2, H2SO4, electricity, and heat. The system converts the full-spectrum solar energy into high-temperature heat and electricity by spectral beam splitting. The high-temperature heat is utilized for solvent regeneration during SO2 capture, which is subsequently integrated into the open-loop iodine-sulfur (I-S) cycle for H2SO4 production. Simultaneously, the generated electricity is employed to drive HI electrolysis for H2 generation, while the surplus electricity and heat are exported to the power and heat grids. The system is simulated using Aspen Plus, which comprehensively evaluates its energy, exergy, and economic performance. A heat integration strategy is initially applied to recover internal waste heat and minimize thermal energy demand. Subsequently, a comparative analysis of the HI electrolysis and pyrolysis cases is conducted to assess improvements in the system. Results show that the system processes 5000 kmol/h of industrial flue gas, producing 153.92 tons of H2 and 7542.08 tons of H2SO4 annually. The HI electrolysis case achieves higher solar energy utilization efficiency and lower HI decomposition energy consumption, with energy and exergy efficiencies of 55.27 % and 31.52 %, improving by 39.08 and 12.29 %-points over the HI pyrolysis case. Economic analysis indicates a dynamic payback period (DPP) of 4.06 years and a net present value (NPV) of 28327.07 k$, reducing the DPP by 0.87 years and increasing the NPV by 9204.63 k$ compared to the HI pyrolysis case.