Ca3B2O6-modified papermaking white mud for CaCO3/CaO thermochemical energy storage

Abstract

CaCO3/CaO thermochemical energy storage based on concentrated solar power plant is a promising technology because of its high working temperature and energy storage capacity. Papermaking white mud (PWM) from paper mill is a potential CaO-based precursor due to its high content of CaCO3. Herein, a novel Ca3B2O6-modified PWM was synthesized to examine its thermochemical energy storage performance. The influences of the types and dopant amounts of B2O3 precursors on the energy storage capacity of Ca3B2O6-modified PWM were discussed. The stable Ca3B2O6-modified PWM with the mass ratio of CaO to Ca3B2O6 = 88:12 exhibits superior energy storage performance and heat transfer property during CaCO3/CaO cycles. The effective conversion and energy storage capacity of Ca3B2O6-modified PWM are approximately 0.67 and 2129.6 kJ/kg at 31st cycle, respectively, which are 2.48 and 1.76 times as high as those of PWM and pure CaCO3, respectively. The introduction of Ca3B2O6 improves the sintering resistance and thermal conductivity of PWM, resulting in higher cyclic stability and lower decomposition temperature of CaCO3. Ca3B2O6 enhances the basicity and improves the strong basic sites of PWM, which is beneficial for the adsorption of CO2, leading to greater CO2 adsorption capacity. Moreover, Ca3B2O6 increases the oxygen vacancy concentration of PWM, which is conducive to the diffusion of O2– and production of CO32–, further improving energy storage capacity. Hence, Ca3B2O6-modified PWM seems to be a suitable energy storage material for the CaCO3/CaO process.