Study On Preparation And Growth Behavior Of Calcium Sulfate Whiskers From Sintering Flue Gas Desulfurization Ash

The desulfurization technology of flue gas from iron ore sintering processes also produces a large number of by-products desulfurized ash while achieving SO₂ emission reduction.However,due to the FGD ash contains a large amount of unstable CaSO₃and metal oxide impurities,it is difficult to directly use.At present,there are few technical reports on its effective utilization.Therefore,it is imminent to carry out theoretical and technical research on the utilization of desulphurization ash resources.In this paper,the FGD ash of a steel plant is used as a raw material.In order to solve the key technical problems of CaSO₄ whisker preparation in a one-step process,a systematic study on desulfurization ash efficient removal of impurities and rapid oxidation in the subcritical hydrothermal reaction system,the growth behavior of CaSO₄ whiskers,and the control of process conditions.Use acetic acid to remove impurities from the desulfurized ash,effectively remove CaCO₃ impurities at a mass concentration of 0.4g/g and increase the CaSO₃ content in the ash from 61.61%to81.17%.The effect of hydrothermal conditions on the oxidation rate of calcium sulfite was investigated.The oxidation rate of CaSO₃ was increased to 99.34%at 140?,30minutes,400 r/min,2 MPa and 1:30 of solid-liquid ratio.In order to eliminate the impurity particles and"Siberian Cocklebur"crystals in the original oxidation products,a solution purification step was added during the one-step whisker preparation process.The concentration of the purification agent was 0.6 mmol/g,the temperature was 60?,the purification time was 5 min,and the initial solid-liquid ratio was 1:30,300r/min speed.In this way,the mixing and adhesion of CaCO₃ or other impurities inside and on the surface of the whisker is effectively reduced,the diameter of the whisker is refined,and the aspect ratio increases.After purification and tempering of the oxidized whisker growth environment phase solution,in the same hydrothermal system,CaSO₄ whiskers with an average aspect ratio of 140.8 were prepared at a temperature of 140?,30minutes,and a rotation speed of 100 r/min.The length-to-diameter ratio can reach210?290.In this paper,XRD,SEM-EDS,FTIR and solution Zeta potential were used to analyze the products of the process of preparing CaSO₄ whiskers from desulfurized ash.The influence of the purification concentration of the solution on the crystal structure,unit cell parameters and functional groups of the CaSO₄ whisker was analyzed.The results show that during the growth of the whiskers,the main peak shift and full peak shift of the XRD spectrum of the product are caused by impurities.The solution purification can remove the CO₃^2-occupants in the crystal.The highest electrical performance value and the best system stability.The equilibrium morphology method in material studio software was used to predict the habitual plane of CaSO₄ crystal growth in the subcritical hydrothermal system to be a football type parallel to the c axis;Calculation of the solvation reaction of CaSO₄ solute shows that the solid-liquid ratio is increased,the non-molecular non-bonding force is increased,the crystal growth is hindered,and the crystal hydration tendency is enhanced.By regulation of the reaction system temperature,time,pressure,rotational speed,and the initial solid-liquid ratio,established CaSO₃ subcritical Heterogeneous Oxidation efficient oxidation Slender CaSO₄ whisker growth matched control means.A combined process of hydrothermal efficient oxidation,low-temperature purification of medium solution and dynamic growth of whisker metastable zone was developed,forming a new method of high-pressure hydrothermal reaction semi-dry desulfurization ash one-step preparation of large aspect ratio CaSO₄ whiskers.The high value-added resource utilization of desulfurization ash provides theoretical support.