亚熔盐高效提钒铬清洁生产技术产业化应用

Industrialized application of high efficient extraction of vanadium and chromium by sub-molten salt method

在亚熔盐生产线达产达效期间,对钒渣液相氧化、液固分离、钒酸钠结晶、三效蒸发等工序进行了研究。结果表明,在纳微曝气氧化及规模放大效应共同作用下,亚熔盐示范工程可实现较低温度(140~180℃)和较低压力(0.6~1.0 MPa)下钒和铬的高效同步提取,钒和铬的转化率分别为93%和85%;对不同原料来源的钒渣,纳微曝气亚熔盐技术均体现出优异的浸出性能;全自动立式压滤机采用三级逆流洗涤方式,保证了尾渣含水率低于30wt%,钒含量低于0.15wt%,铬含量低于0.05wt%;选用OSLO冷却结晶器进行钒酸钠结晶,钒酸钠结晶率达到61.5%;通过在三效系统蒸汽接口处增设减温减压器,实现循环碱液浓度由试生产初期的45wt%提高至50wt%。利用亚熔盐产线对传统钠化焙烧工艺废水处理过程中产生的钒铬泥进行钒铬浸出,在反应温度175℃、反应压力0.65 MPa、进出料速度0.25 t/h的工作条件下实现了钒铬泥中钒和铬的高效浸出,钒和铬的浸出率分别为93.68%和96.76%。当溶液中铬浓度达到25~30 g/L后,铬酸钠结晶工序可保证将每次液相氧化反应溶出的铬全部结晶析出,铬酸钠的结晶率为17.65%。

In order to ensure the sub-molten salt project to achieve production and efficiency,the processes of liquid phase oxidation of vanadium slag,liquid-solid separation,crystallization of sodium vanadate and three-effect evaporation were systematically studied.The experimental results showed that under the combined action of nano-micro aeration oxidation and scale-up effect,the sub-molten salt demonstration project can achieve the simultaneous extraction of vanadium and chromium at low temperature(140~180℃)and low pressure(0.6~1.0 MPa),the leaching rates of vanadium and chromium were 93%and 85%respectively.Nano-micro-aerated sub-molten salt technology showed excellent leaching performance for vanadium slag from different raw materials.The automatic vertical filter press adopted three-stage counter-current washing mode,which ensured that the water content of tailings was less than 30wt%,the vanadium content was less than 0.15wt%,and the chromium content was less than 0.05wt%.The crystallization rate of sodium vanadate reached 61.5%by using OSLO cooling crystallizer,and the concentration of circulating alkali solution was increased from 45wt%to 50wt%by adding a temperature and pressure reducer at the steam interface of the three-effect evaporation system.In addition,the leaching of vanadium and chromium from vanadium-chromium mud produced during the treatment of wastewater from traditional sodium roasting process was studied by using submerged salt production line.The efficient leaching of vanadium and chromium from vanadium-chromium mud was achieved under the conditions of reaction temperature of 175℃,reaction pressure of 0.65 MPa and feed-in and feed-out speed of 0.25 t/h.The leaching rates of vanadium and chromium were 93.68%and 96.76%.When the concentration of chromium in solution reaches 25~30 g/L,the crystallization process of sodium chromate can ensure that all the chromium dissolved in each liquid phase oxidation reaction was precipitated,and the crystallization rate of sodium chromate was 17.65%.