硝酸分解磷矿的宏观动力学研究

Macro-kinetics study of decomposing phosphate rock with nitric acid

在间歇反应器中 ,反应温度为 30～ 6 0℃ ,硝酸初始浓度 30～ 5 4 % ,磷矿初始粒径 0 .375～ 1.0 75毫米 ,搅拌强度 4 0 0转 分的条件下研究了硝酸分解磷矿的反应过程机理及宏观动力学。结果表明 ,磷矿分解速率及转化率随着搅拌强度、反应温度、硝酸浓度和颗粒细度的增加而增加 ;氢离子通过液膜的扩散传质是该过程的速率控制步骤。应用固体粒径减小的缩芯模型 ,将上述各影响因素的实验数据回归得到如下的宏观动力学模型 :1- (1-xB) 2 3=8.36 6exp - 6 .198× 10 3RT c1 .31 1AO R- 0 .1 0 91S lnτ活化能Ea=6 .198kJ mol。

Reaction mechanism has been studied in addition with macro kinetics of decomposing phosphate rock with nitric acid in a batch reactor.The reaction temperature was selected from 30 to 60℃,the initial phosphoric acid concentration varied from 30 to 54 wt%,the initial mean particle size 0.375 to 1.075mm,and the stirring speed was 400r/min.The results showed that the rate of decompose and the conversion of phosphate rock increases correspond with the increases in the stirring speed,reaction temperature,initial nitric acid concentration and fineness of the particle.Meanwhile,the rate control step of the decompose process was found to be the diffusion rate of hydrionic ions through the liquid film.By applying the reacted shrinking core model,a kinetic model for the decompose process was fitted to experimental results as follows: 1-(1-X B) 2/3 =8.366EXP-6.198×10 3RTC 1.311 AO R -0.1091 Slnτ The apparent activation energy E α was 6.198kJ/mol,thus the process is a liquid film diffusion controlled process.