Thermochemical Energy Storage Performance Of Modified Papermaking Soda Residue During CaCO₃/CaO Cycles

CaCO3/CaO thermochemical energy storage technology is considered as a great application potential in the third-generation of concentrated solar power generation technology because of its high energy storage density,low energy loss,and low price of raw materials.At present,most of the research uses natural CaO-based materials as energy storage materials.Mining natural CaO-based materials faces problems such as environmental damage and resource waste.As a typical industrial CaO-based solid waste,the main composition of papermaking soda residue is CaCO3,which is a potential CaO-based material and precursor.It is necessary to develop high-performance energy storage materials with papermaking soda residue as precursors,so as to realize the reduction,harmless,and resource utilization of papermaking soda residue.In this paper,the high-performance energy storage materials were prepared by using papermaking soda residue(PSR),organic acid,high-alumina brick,and Ca3B2O6 as CaO-based precursor and additives,respectively.Based on experimental research and microstructure analysis,the energy storage performances of the modified PSR were studied.The strengthening mechanisms of different additives on the energy storage performance of PSR were determined.In order to improve the energy storage performance of PSR,different organic acids were used to modify PSR,The effects of organic acid types on the energy storage performance of PSR in pressurized duel-fixed bed reactor were studied.The influences of carbonation pressure(0.1-1.1 MPa),carbonation/calcination temperatures,and cycle numbers on the energy storage performance of the organic acid modified PSR were discussed.The appropriate energy storage conditions were obtained.The organic acid modification significantly improves the pore structure of PSR,thus improving the energy storage performance.Cmpared with acetic acid and propionic acid modified PSR,citric acid modified PSR exhibits higher energy storage performance.The energy storage performances of the materials are significantly improved with increasing the carbonation pressure.When the carbonation pressure is 1.1 MPa,the effective conversion and energy storage density of the citric acid modified PSR after 30 cycles are about 0.7 and 2210 kJ/kg,respectively,which are 2.56 times those of PSR at 0.1 MPa.Although the energy storage performance of PSR is limited,the citric acid modified PSR shows excellent energy storage performance under pressurized carbonation.From the perspective of resource utilization of PSR,PSR is a potential CaO-based energy storage material.In order to alleviate the attenuation of PSR during the energy storage cycles,it was proposed to use waste high-alumina brick(HAB)as an inert carrier to improve the cyclic stability of PSR.The high-alumina brick modified PSR(HAB-PSR)was prepared by wet mixing method.The effect of the addition of HAB on the energy storage performance of PSR was studied.The influences of carbonation pressure and cycle numbers on the energy storage performance of HAB-PSR were also discussed.The main compositions of HAB-PSR are CaO,Ca12Al14O33,MgO,and Ca2SiO4.When the mass ratio of CaO to HAB is 100:10,HAB-PSR shows the excellent energy storage performance and cyclic stability.After 30 cycles,the effective conversion and energy storage density of HAB10-PSR at 1.1 MPa are about 0.75 and 2394 kJ/kg,respectively,which are 2.78 times those of PSR at 0.1 MPa.The existence of Ca12Al14O33,MgO,and Ca2SiO4 effectively inhibits the growth and agglomeration of CaO grains,enhancing the sintering resistance of PSR.HAB 10-PSR has a good application prospect in CaCO3/CaO energy storage cycles.In order to simultaneously improve the thermal conductivity and energy storage performance of PSR,Ca3B2O6-modified PSR was prepared by using different B2O3 precursors as additives.The effects of the types and doping amount of B2O3 precursors on the energy storage performance of PSR were studied.The carbonation kinetics and thermal conductivity of Ca3B2O6-modified PSR were also discussed.Ca3B2O6-modified PSR is mainly composed of uniformly dispersed CaO,Ca3B2O6,and MgO.The addition of B2O3 precursors significantly improves the cyclic stability and thermal conductivity of PSR.When the mass ratio of CaO to Ca3B2O6 is 88:12,the effective conversion and energy storage density of Ca3B2O6-modified PSR after 30 cycles at 0.1 MPa are approximately 0.67 and 2129.6 kJ/kg,respectively,which are 148%higher than those of PSR.Compared with PSR,Ca3B2O6-modified PSR has higher carbonation/calcination reaction rates,lower CaO regeneration temperature,and stronger sintering resistance.The introduction of Ca3B2O6 enhances the basicity and oxygen vacancy concentration,which is more beneficial for energy storage.The novel Ca3B2O6-modified PSR provides a new idea for the development of high-performance energy storage materials.