Coal Ash Mineralization And Storage Of CO₂ Synergistically With Heavy Metal Solidification

Fly ash is the main by-product of coal-fired power stations,and about 0.25 kg of fly ash is produced for every 1 kg of standard coal consumed.Occupying farmland to accumulate and store fly ash will not only waste land resources,especially the leaching of harmful metal elements in fly ash will also damage soil quality.On the other hand,in the global CO2 emissions,coal-fired power plants are a long-term,stable,and concentrated source of emissions,accounting for more than 30%of total carbon emissions,In 2020,it is proposed to achieve the "carbon peak"in 2030 and achieve the goal of "carbon neutral" in 2060.CO2 emission reduction is a major demand for my country’s energy development.Therefore,the treatment of CO2 and the harmless treatment of harmful metal elements in fly ash are the inherent requirements for deep emission reduction in coal-fired power plants,Accelerating carbonation of fly ash is a potential way to achieve both emission reductions.While achieving CO2 sequestration by fly ash,it can effectively fix harmful metal elements in the ash through carbonation.The slow conversion in the diffusion control stage is the bottleneck of the technical route.Based on the strong diffusion and permeability of supercritical CO2,and the academic idea that mechanical damage to the sintered fly ash surface can produce more fresh surfaces and pores,this research proposes The method of critical CO2 coupled with mechanical force intensifies the carbonation of fly ash.Through macroscopic experiments,test characterization and theoretical modelings carry out research on the characteristics and kinetics of reaction conditions on the mineralization and storage of fly ash,and the environmental release characteristics and mechanisms of harmful metal elements in fly ash before and after solidification.On this basis,low pressure is revealed And the evolution law of fly ash mineralization and storage in supercritical CO2 environment,to prove the solidification mechanism of carbonation on harmful heavy metals in fly ash,and to obtain efficient CO2 mineralization storage and heavy metal solidification technology optimization parameters.The research results show that the carbonization efficiency of fly ash under CO2 supercritical conditions is generally higher than that under low pressure conditions,and the leaching inhibition effect of harmful heavy metal elements in supercritical conditions is lower than that under low pressure conditions.In this study,the best carbon content of fly ash under the supercritical state of 8MPa is 54.9gCO2/kg ash,the carbonization efficiency is 24.20%,the operating parameters are 100rpm stirring speed,30mL/g liquid-solid ratio,reaction time 5h,40℃;The optimal amount of carbon sequestration under low pressure is 42.3gCO2/kg ash,the carbonization efficiency is 18.65%,the operating parameters are 100rpm stirring speed,30mL/g liquid-solid ratio,reaction time 5h,80℃.In the experimental group modified by mechanical ball milling,the carbonization efficiency is wet ball milling ash>dry ball milling ash>raw ash.At the same time,carbonation has obvious inhibitory effect on the toxic leaching of Pb,Cr and Cd in fly ash,and the leaching inhibition efficiency of Pb,Cr and Cd can reach 48.9%,96.4%,and 87.0%,respectively.