中低品位高硫铝土矿溶出液晶种分解同步除硫铁的方法及调控机制

Utilization of high-sulfur bauxite with low-median grade is one of important methods to resolve the lackness of bauxite resource in China. But there still exist problems such as excess impurities of sulfur and iron in the alumina product caused by the cocrystallization of Na2[FeS2(OH)2]•2H2O and gibbsite, which dues to lack of regulation of crystallization behavior for Na2[FeS2(OH)2]•2H2O in the sodium aluminate solution containing sulfur. Regarding digestion solution of high-sulfur bauxite in Nanchuan Chongqing as a subject, a method of regulating crystal growth to remove the impurities of sulfur and iron is adopted, and the preparation of Na2[FeS2(OH)2]•2H2O solution and crystal seed is studied. Seeded precipitation process of synthesized and industrial Na2[FeS2(OH)2]•2H2O solution is investigated to reveal the crystallization behavior and rule, and a method of simultaneous removal of sulfur and iron by the seeded precipitation of sodium aluminate solution containing sulfur is established. By controlling the initial supersaturation of the solution and adding the crystal seed, the crystal of Na2[FeS2(OH)2]•2H2O is intensified to precipitation rapidly and fixed-point, and regulation mechanism of crystallization behavior of Na2[FeS2(OH)2]•2H2O is established. The results is a technical support and theory guideline for utilizing the high-sulfur bauxite with low-median grade , which also is helpful to transfer the bauxite resource into economic and social advantage. It is also meaningful for intending the service life of bauxite and ensuring alumina industry to develop continuously, stably, safely and healthily in China.

中低品位高硫铝土矿的利用是缓解我国铝土矿资源供应紧张局面的一项重要措施，但现有生产工艺尚存在羟基硫代铁酸钠共析出而引起的产品硫铁杂质超标等问题，其根源在于未能有效调控含硫铝酸钠溶液中羟基硫代铁酸钠的结晶行为。以重庆南川中低品位高硫铝土矿溶出液为研究对象，采用调控晶体生长以去除硫铁杂质的方法，研究羟基硫代铁酸钠溶液和晶种制备，研究配制羟基硫代铁酸钠溶液加晶种分解过程和工业羟基硫代铁酸钠溶液加晶种分解过程，揭示羟基硫代铁酸钠的结晶行为和规律，建立含硫铝酸钠溶液晶种分解同步除硫铁的方法。通过控制过饱和度和添加晶种，强化羟基硫代铁酸钠晶体快速定点析出，最终建立羟基硫代铁酸钠结晶行为的调控机制。本项目预期研究成果可为利用中低品位高硫铝土矿资源、将地区资源优势转化为经济及社会优势提供技术支撑和理论指导，对延长我国铝土矿资源保障年限，保障我国氧化铝工业持续、稳定、安全及健康发展亦具有重大意义。

中低品位高硫铝土矿综合利用是缓解我国铝土矿供应紧张局面的一项重要措施，但现有生产工艺尚存在羟基硫代铁酸钠共析出而引起的产品硫铁杂质超标问题，其根源在于未能有效调控含硫铝酸钠溶液中羟基硫代铁酸钠结晶行为。本项目以中低品位高硫铝土矿溶出液为研究对象，采用了调控晶体生长以去除硫铁杂质的方法，研究了羟基硫代铁酸钠溶液和晶种制备、配制羟基硫代铁酸钠溶液和工业溶液加晶种分解过程。采用黄铁矿高温高压碱性溶出制备了羟基硫代铁酸钠溶液，较优的制备条件为270℃、2h、苛性碱浓度260g/L、100 r/min、液固比100:1。降温制备了羟基硫代铁酸钠晶种，为墨绿色结晶度不高的混合物，主要由Fe、S、Na、O元素组成。较优的晶种制备条件为60℃、100 r/·min和96小时。硫、铁结晶过程过程表观活化能分别为16.31 kJ/mol和13.26 kJ/mol。对于配制溶液晶种分解过程，可通过优化过程参数缩短成核和晶体长大期以加速晶体析出。较优脱硫条件为24℃、晶种添加量12.5g/L、50ppm聚丙烯酰胺和40min，较优除铁条件为30℃、晶种添加量5g/L、50ppm聚丙烯酰胺和10min，较优的赤泥晶种脱硫条件为60℃、晶种添加量50g/L、100r/min和60min。工业溶液加晶种脱硫的较优条件为60℃、晶桨添加量8mL/L、200r/min和30min，硫和铁去除率达73％和83％，脱硫除铁效果明显；75 °C时硫、铁脱除率亦可达52%和65%。赤泥晶种也具有较好效果，适量添加赤泥晶种，80 min后硫、铁脱除率可达65%和68%。提出了一种中低品位高硫铝土矿溶出液晶种分解同步除硫铁的新方法，通过控制过饱和度和在稀释沉降工序添加晶种，可使硫铁杂质同时快速定点析出，赤泥可作为晶种循环使用，实现了铝酸钠溶液中硫铁结晶行为的工业调控。研究结果可为我国高硫铝土矿资源综合利用提供技术支撑。