磷石膏配料碳热熔融还原硫逸出及熔渣物相分析

Sulfur escape and slag physical phase analysis by carbon thermal reduction melting based on phosphogypsum ingredients

基于配料计算在磷石膏中添加硅、铝、镁等,使其渣系满足矿渣棉生产对酸度系数、氢离子指数、黏度系数的要求。通过热重分析、熔融特性的测定及高温还原焙烧/熔融实验,探究了磷石膏配料在高温还原过程中硫逸出及熔渣的物相结构。结果表明:碳的加入可以促进磷石膏分解,加入量以n(C)/n(S)=0.5为宜;还原剂(石墨、无烟煤、焦炭)及配料的加入均可以降低磷石膏体系的熔融特征温度,CaO-MgO-SiO_(2)-Al2O_(3)四元相图计算表明配料体系在1255.73℃时形成最低共熔点。磷石膏及其配料在高温焙烧过程中的物相演变规律表明,CaS为CaSO_(4)还原过程的中间产物,配料中加入的SiO_(2)可结合更多的CaO促进CaS和CaSO_(4)反应的进行。还原熔融实验表明,n(C)/n(S)对熔渣硫含量及体系脱硫率影响较大。以焦炭为还原剂,磷石膏配料的酸度系数Mk=1.4、pH=4.85、n(C)/n(S)为0.5时,采用刚玉坩埚在1450℃下高温熔融20min后,脱硫率可达99.05%,硫高效逸出的同时形成的熔渣呈非晶态,具有良好的玻璃相结构。

Silicon,aluminum,and magnesium oxides et al.were added to phosphogypsum based on batching calculations to meet the requirements of acidity coefficient,hydrogen ion index and viscosity coefficient for slag wool production.The sulfur escape from phosphogypsum ingredients and the physical phase structure of slags were investigated by thermogravimetric analysis,determination of melting characteristics,and high-temperature reduction roasting and melting experiments.The results showed that the addition of carbon could promote the decomposition of phosphogypsum,and the n(C)/n(S)of 0.5 was favorable to the desulfurization of the system.The reducing agents(graphite,anthracite,coke)and ingredients could decrease the characteristic melting temperatures of phosphogypsum.The CaO-MgO-SiO_(2)-Al_(2)O_(3) quaternary phase diagram showed that the ingredient system formed the lowest eutectic point at 1255.73℃.The phase evolution of phosphogypsum and its ingredients during high-temperature roasting illustrated that CaS was the intermediate product of CaSO_(4) reduction process,and the SiO_(2) in the ingredients combined with more CaO to promote the reaction between CaS and CaSO_(4).The high-temperature reduction melting experiments showed that the amount of carbon had a significant impact on the sulfur content of slag and the desulfurization rate of the system.The phosphogypsum ingredients with Mk=1.4,pH of 4.85,and n(C)/n(S)of 0.5 with coke as a reducing agent were melted in the corundum crucible at 1450℃for 20 min,the desulfurization rate could reach 99.05%,while the slag formed was amorphous with a good glass phase structure.