Investigation On The Microwave Assisted Leaching Of Calcium In The Stainless Steel Slag By Ammonium Salts And Its Carbonation Process

In recent years,as the production of stainless steel increases,the production and cumulative amount of its by-product stainless steel slag raises.Meanwhile,large amounts of CO₂ are emited during the stainless steel smelting process.Stainless steel slag contains high amount of calcium-containing minerals,which means that it can be used as a potential material to storage and fix CO₂ instead of natural minerals.This paper research the based features and temperature rise characteristic of stainless steel slag under microwave irradiation,base on which the ammonium salt leaching effects of calcium and of impurity ions from stainless steel slag lead by different parameters under microwave irradiation and the influence of calcium carbonate crystallization rate caused by different parameters at the stage of in the process of carbonation is also studied.Moreover,the recycling of leaching medium is preliminary explored at finally.The results show that the main component in the slag is calcium minerals and the phases,such as CaF₂,CaSi₂O₇F₂ and CaAl₂Si₂O₈ in slag,are difficult to react with ammonium chloride.Microwave leaching can promote the the generation and extension of crack in slag particles,and which improve the calcium and magnesium ions leaching rate from slag.The increasement of microwave power,solid-liquid ratio and the initial concentration of NH₄Cl solution can improve the leaching rate of calcium and magnesium ions during the leaching process.The optimization parameters of calcium ions leaching from slag are as follows: the leaching agent is NH₄Cl,the microwave power is 385 W,the solid-liquid ratio is 1:20,initial concentration of leaching agent is 2 mol/L,the initial volume is 400 ml and mechanical mixing speed is 300 rpm.It is beneficial to improve the carbonation rato during the process with the increasing of the CO₂ flow rate,the stirring rate,the concentration of ammonia and the water bath temperature.The carbonate reaction of leaching solution is fast,and the yield rate of calcium are more than 95% in 30 min when suitable amount of ammonia adding.