石煤钒矿酸浸尾渣高温焙烧制备陶粒过程元素硫释放规律

Release of sulfur from roasting the acid leaching tailings of vanadium-bearing stone coal minerals as the raw materials for preparing ceramsite

以石煤钒矿酸浸提钒过程产生的尾渣为原料制备陶粒是实现尾渣资源化的重要途径之一。作为陶粒最主要用途的轻集料对硫含量有严格限制(以SO3计,硫酸盐和硫化物含量≤1.0wt%)。尾渣含硫量通常远高于1.0wt%,故需深入研究尾渣制备陶粒过程元素硫的释放规律。借助热重–红外联用分析了以尾渣为原料制备陶粒过程中的质量、热量变化以及气体释放规律,测试了不同温度焙烧所得样品的硫含量,表征了其物相,并结合热力学计算,讨论了尾渣中硫的释放机理。结果表明,随温度增加,尾渣中的含硫物质逐渐分解并释放出SO_(2)气体,样品的硫含量逐渐降低;1200℃下样品的硫含量可降低至0.44wt%,满足轻集料硫含量要求;尾渣中含有的SiO_(2),Fe_(2)O_(3),Al_(2)O_(3)等组分可促进硫的释放。

The acid leaching tailings of vanadium-bearing stone coal minerals(hereinafter referred to as“tailings”)is the solid waste discharged in the industry of vanadium extraction from stone coal.Using the tailings as raw materials for the preparation of ceramsite is an important way for the resource ultilization of the tailings.Ceramsite can be widely used in many areas,and the main application is to be used as lightweight aggregate in construction industry.Lightweight aggregate has a critical requirement of sulfur content when it is used as building materials.The total contents of sulfate and sulfide,calculated by SO_(3),should be no higher than 1.0wt%.Usually,the sulfur content(calculated by SO_(3))of the tailings is much higher than 1.0wt%,which is much higher than the requirement of lightweight aggregate.So,it is necessary to study the release of sulfur during the preparation of ceramsite using tailings as raw materials.In this work,simultaneous thermogravimetric–Fourier transform infrared spectrometry(TG–FT-IR)analysis were used to investigate the weight loss,the exothermic/endothermic phenomenon,and releasing of gases in the process of roasting the tailings as the raw materials for preparing ceramsite.The sulfur contents of samples prepared by roasting tailings at different temperatures were tested,their crystal phases were characterized,the Gibbs free energies of several reactions were obtained by thermodynamic calculation,and the mechanism of sulfur releasing from tailings was discussed accordingly.The results showed that sulfur-containing substances in the tailings gradually decomposed and SO_(2) was released with temperature increasing.Consequently,the sulfur content of samples gradually decreased with roasting temperature increasing.The sulfur content(0.44wt%)of samples obtained at 1200℃can meet the requirements of lightweight aggregate.Intermediated phases such as wollastonite(CaSiO_(3))might be formed by the reaction of anhydrite and quartz in the tailings,accompanied with the releasing of SO_(2).SiO_(2),Fe_(2)O_(3) and Al_(2)O_(3) in tailings might be helpful for the releasing of sulfur.