Study On The CO₂ Sorbents In The Single-Step Hydrogen Production From Carbonaceous Energy

The conventional utilization of fossil fuels bring severe harm to the environment of human being living and working, and the global problems, such as'greenhouse effect', already brought widely attention from the governments in the world. But, fossil fuels will be primary choice in the foreseeable future. As a clean fuel, hydrogen has been recognized for many years. It is urgent to develop sustainable energy systems with producing hydrogen from carbonaceous energy with CO₂ capture. Based on the idea of 'production hydrogen in a single-step and sequestration CO₂ by mineral', the operation condition, multicycle characteristic and the activity improvement of Ca-based CO₂ sorbents used in the process of hydrogen production from carbonaceous energy were studied in this thesis. Furthermore, the effects of different sorbents' regeneration methods and different multicycle characteristic on the hydrogen production systems were analyzed.By the thermodynamics analysis and system simulations of the single-step hydrogen production process, the suitable operating conditions of Ca-based CO₂ absorbents were determined primarily, then the experimental researches on the hydrogen production process were carried out with different kinds of biomass. The calculating and experimental results were consistent and the operating conditions of sorbents were confirmed.On the base of reversible carbonation and calcinations reactions, an atmospheric - pressure fixed bed reactor and a pressurized reactor were used to research the multicycle characteristic of calcined calcium carbonate-CaO, and the effects of temperature, pressure and gas composition on the multicycle conversion ratio were analyzed by SEM and pore analysis, and the reasons of sorbent activity declining were confirmed primarily.The improvement of sorbents' cycle characteristic is developed through different circular routes and additives, and activation research is carried out with water and steam on multicycle sorbent, and the optimal mode of maintaining and enhanced sorbents' cycle characteristic in the process of hydrogen production is determined.The activation experiment about sorbents obtained favourable result, which supplied a convenient and economical process to activate the sorbents, and can be extended to other applications.The system of single-step hydrogen production from carbonaceous energy is designed based on different cycle characteristic of Ca-based CO2 sorbents, and the effects of the cycle characteristic on the production is analyzed. Based on the different sorbent regeneration processes, different hydrogen production systems were designed and simulated, and the effects of absorbent regeneration processes on hydrogen production process is analyzed, and the method of carbon partial conversion( CPC )supplied heat for regeneration is suit to the process of single-step hydrogen production.A new idea of promote the cycle characteristic of Ca-based CO2 sorbents by accreting the sorbents to other carriers and additives is proposed, and the enhancement direct of sorbents' cycle characteristic in the future is also suggested.