Study of HI Decomposition Catalyst and Whole Process System Design in Sulfur-iodine Cycle for Hydrogen Production
Author:Fu Guang Shi
Supervisor:zuo ke fa wang zhi hua zhang yan wei
Today’s human society is facing multiple difficulties such as fossil energy shortages,global warming,and environmental pollution."Hydrogen economy",due to its many advantages,is expected to provide solutions to these problems.The efficient and low-cost hydrogen production is the basis of the "hydrogen economy".Compared with other hydrogen production methods,thermochemical water splitting sulfur-iodide cycle process(SI cycle)for hydrogen production has many advantages,such as high thermal efficiency,rich source of raw materials(water),free carbon dioxide emissions,easy to be coupled with solar energy and nuclear energy,easy to be large-scaled,and is considered to be one of the most promising hydrogen production methods.The SI cycle consists of the following three-step thermochemical reactions:Bunsen reaction:2H2O +I2+ SO2 →H2SO4+2HIHI catalytic decompostion reaction:2HI→H2+I2H2SO4 catalytic decompostion reaction:H2SO4 →H2O+SO2+1/2O2Although the principle of hydrogen production from the sulfur-iodide cycle is simple,many problems still need to be solved to achieve the large-scale hydrogen production system.This thesis is devoted to the research on the design and synthesis of HI decomposition catalysts,corrosion-resistant materials and whole process systems design.Under high-temperature HI-I2-H2O corrosive environments,the active components in the HI decomposition catalyst agglomerate on the surface of the support which leads to the deactivation of the catalyst.For this reason,the thesis have proposed the use of[Ni(en3)](NO2)2 as a nickel precursor to prepare a high-stable supported Ni catalyst.Because of the high thermal stability of[Ni(en3)](NO2)2 and viscosity of the impregnating solution,the distribution of Ni in the process of[Ni(en3)](NO2)2 impregnation is inhibited,which hinders the growth of Ni particles in the preparation process and improves the stability of the Ni catalyst.It also reveals that the dispersion of the metal component on the support surface is a major factor affecting the activity of the Ni catalyst.Based on China’s rich coal resources,we have innovatively proposed Zhaotong lignite coal to synthesis semi-coke,explored and established a set of activated modified semi-coke method,synthesized low cost,high activity and stability semi-coke catalyst,and established mechanism of hydroiodic acid decomposition on semi-coke.This thesis also proposed turnover rate(TOR)of the HI decomposition reaction to characterize the intrinsic activity of the catalyst.The intrinsic catalytic activities and activation energies of important transition metal catalysts such as Pt,Pd,Ru,Ni,Co,and Cu were measured,and Ru/AC was proposed and synthesized as a high-efficiency and high-stability catalyst.Aspen Plus,a large-scale chemical process simulation software,was used to simulate the entire chemical process of sulfur iodide cycle hydrogen production system.The process flow of the sulfur iodide cycle system with hydrogen production capacity of 50 L/h was designed.After comprehensive consideration of cost,mechanical properties and processing performance,TC4 titanium alloy was tested and screened as the material of the HIx phase module,and the main equipment in the sulfur iodide cycle hydrogen production system were designed to ultimately complete the 50 L/h sulfur iodine cycle system for hydrogen production.