TitleCarbonation Kinetics of SrO By CO2 for Solar Thermochemical Energy Storage
Publication TypeThesis
Year of Publication2016
AuthorsBagherisereshki, E
UniversityOregon State University
CityCorvallis, Or.
Thesis TypeMasters Thesis

Given its abundance and accessibility, exploiting solar energy is a powerful approach to reduce dependency on fossil fuels for energy generation. Thermochemical reactions using concentrated solar power at high temperature are an attractive method of energy storage in support of concentrated solar power (CSP). Thermochemical energy storage of on-sun thermal energy is achieved when a reactive system absorbs thermal energy and proceeds with a reversible chemical reaction. In a time of power demand, the reverse reaction is then initiated and energy is released, thus recovering stored chemical energy for use in a power cycle. In this study, strontium-oxide (SrO) carbonation kinetics have been studied by means of thermogravimetric analysis (TGA) and a laboratory scale apparatus including a tube furnace packed with SrO particles dispersed in sand for thermochemical energy storage. In order to better describe the reaction mechanism, the influence of intensive variables such as reaction temperature and CO2 partial pressure were investigated. In both methods, carbonation was performed at several temperatures (900-1150°C) under isothermal conditions. The effect of sample size (25 - 106 µm) and partial pressures of CO2 (0.1-1 bar) has been investigated in TGA. The carbonation reaction progression obtained from TGA can be divided into three stages: an initial induction period; a rapid kinetically-controlled carbonation stage; and finally a sluggish diffusion-controlled regime. The existence of a true induction period must be investigated in an experimental apparatus other than a TGA. The carbonation conversion result from the laboratory scale fixed bed do not indicate the existence of this time period.Time-dependent carbonation conversion after removing the induction period appeared as sigmoid curves. The conversion rates of SrO carbonation were well fitted to Lee's model for the carbonation reaction of calcium oxide by carbon dioxide. The reaction rate constant k as a temperature dependent term presented by Arrhenius equation with activation energy of E[subscript a] = 12.02 kJ.mol1 and the pre-exponential factor of A = 0.323 min1 for TGA.