钾长石-硫酸钙-氧化钙热反应制备可溶性钾机理研究

为了探求钾长石、磷石膏制备硫酸钾的机理,以钾长石、石膏、氧化钙为原料,通过XRD图谱及钾溶出率分析研究了n(钾长石)∶n(CaSO4·2H2O)∶n(CaO)为1∶1∶(2~16)配料的热反应过程.结果表明:最适宜物料配比为1∶1∶10,在此配料体系下,焙烧产物中硅酸钙有CS、C2S和C3S三种,其组成、比例与体系的反应温度有关,硅铝酸钙盐只有C2AS一种,无C3A生成,与文献报告不一致;置换生成K2O的反应有2种途径,当温度低于1100℃时,置换反应发生在KAlSi3O8与CaO之间,超过1100℃时,则KAlSi3O8与CaO和KAlSi2O6与CaO的置换生成反应共存;温度低于1200℃时,置换出的K2O不能结合为硫酸盐,而是以气态的形式逸出;温度高于1200℃时,可溶性钾盐以K2S2O8形式存在,无K2SO4成分.TG-DSC实验结果表明:体系置换反应起始温度约为1000℃,1100℃以后反应激烈进行,与不同温度下XRD图谱分析结果相吻合,高温下体系失重的原因是K2SO4转化为K2S2O8释放出K2O并以气态逸出所致.

Mechanism Study on the Preparation of Soluble Potassium From K-feldspar-CaSO4 -CaO Thermal System

To solve the problem of mechanism of potassium preparation with K-feldspar and phosphogysum, with K-feldspar, calcium sulfate and calcium oxide as raw materials, the thermal response process of system was analyzed under the different molar ratios( n( K-feldspar) ∶ n( Ca SO4·2H2O) ∶ n( Ca O) = 1∶ 1∶( 2 ~ 16)). The experiments show that the most suitable proportion of material is 1∶ 1∶ 10,under the batching system,there are three kinds of calcium silicate in the calcined products,including CS,C2 S and C3 S,and their composition and proportion are associated with the reaction temperature of system. Besides,there is only one form( C2AS) of sialic acid calcium salt,C3 A is nonexistent. These are inconsistent with the reported. There are two different reactions to displace generated K2 O,when the temperature is below 1 100 ℃,the replacement reaction occurs between KAl Si3O8 and Ca O,and when the temperature is higher than 1 100 ℃,Ca O would react with KAl Si3O8 and KAl Si2O6 respectively. Furthermore,when the temperature is below 1 200 ℃,K2 O is not combined with sulfate radical to sulfate,but escaping as gas. When the temperature is higher than 1 200 ℃,soluble potassium exists as K2S2O8,and K2SO4 is unfound. TG-DSC experimental results show that theinitial displacement reaction temperature of the system is about 1 000 ℃,and the reaction goes into overdrive when the temperature is higher than 1 100 ℃. The results are consistent with the XRD analysis of the product which calcined at different temperatures. The cause of system weight loss at high temperature is that K2SO4 is converted into K2S2O8 by releasing gaseous K2 O.