Study On The Fabrication And Properties Of Solid Waste Semi-coke Ash Composite Thermal Storage

A large amount of semi-coke ash is produced annually via metal smelting and other industries.At present,the treatment method of semi-coke ash is still mainly landfilling,but the large amount of alkaline semi-coke ash landfilling will inevitably pollute the local soil and groundwater,damage the local ecological environment,and cause incalculable losses.Energy storage technology plays an important role in achieving the "double carbon" goal.More and more researchers have carried out research on the recycling of solid waste in energy storage and other fields.To make full use of the solid waste semi-coke ash and reduce the damage to the ecological environment and the carbon emissions caused by the accumulation and landfilling of it,this study,firstly,using solid waste semi-coke ash as the skeleton material,pure Na2CO3 and Na NO3 as the PCM,the semi-coke ash/Na2CO3 shape-stable phase change composites,and semi-coke ash/Na NO3 shape-stable phase change composites were fabricated by the cold-compressionhot sintering method.The thermal storage performance,micromorphology,mechanical performance,chemical compatibility and other key performance of each material were characterized and analyzed by differential scanning calorimetry,scanning electron microscopy,constant-speed pressurization method and X-ray diffraction method.It is found that the solid waste semi-coke ash is suitable as the skeleton material of shape-stable phase change composite.The optimum mass ratio of semi-coke ash to Na2CO3 is 5.25:4.75.The thermal energy storage density of this material reaches 961.58 J/g at 100 ~ 900 ℃.After the 200 heating/cooling cycles,it shows good cyclic thermal stability.The optimum mass ratio of semi-coke ash to Na NO3 is5:5.At 100 ~ 380 ℃,the thermal energy storage density of the material reaches 325.91 J/g and the maximum thermal conductivity is 1.004 W/(m?K)as well as the mechanical strength reaches96.98 MPa.After the 4027 heating/cooling cycles,this material shows good cyclic thermal stability.During the experiment,it was found that the main component of semi-coke ash was Ca O.After that,the semi-coke ash is used as Ca O-based adsorbent in post-combustion carbon capture technology to absorb CO2,and mixes N2 and CO2 gases in a certain proportion to simulate industrial flue gas.The influence of gas composition,ventilation time and heating temperature on the carbon capture performance of semi-coke ash was analyzed by using the control variable method,and then the changes in macro morphology,phase,pore structure and micro morphology of semi-coke ash before and after the carbon capture experiment were compared.It is found that the semi-coke ash is suitable for capturing and storing industrial CO2 as Ca Obased adsorbent.In this study,the best conditions for the carbon capture experiment of semicoke ash are: gas component 20 vol.% CO2/80 vol.% N2,ventilation time 40 min,heating temperature 650 ℃.Under the optimal carbon capture conditions,the carbon fixation efficiency of the semi-coke ash reaches 29.27%.After carbon fixation,both the macro and micro morphology of the semi-coke ash have changed,and the obvious diffraction peaks of Ca CO3 has been observed in the phase analysis as well as the specific surface area,pore volume and average pore size of the particles have decreased to a certain extent.Then,using carbon-fixed semi-coke ash as the skeleton material,the carbon-fixed semi-coke ash/Na NO3 shape-stable phase change composites were fabricated by the cold-compression-hot sintering method.Its key performances were characterized and analyzed by the similar methods.It is found that the carbon-fixed semi-coke ash is suitable as the skeleton material of shape-stable phase change composite.The optimum mass ratio of carbon-fixed semi-coke ash to Na NO3 is 5:5.The material has a thermal energy storage density of 288.65 J/g at 100 ~ 380 ℃,and a mechanical strength of 113.75 MPa.After the 500 heating/cooling cycles,this material shows good cyclic thermal stability.In addition,the economic cost and carbon emission of the three shape-stable phase change composites fabricated in this study are significantly low compared with others,and show good commercial application prospect.