KNO_(3)介稳区宽度的研究及初级成核动力学计算  

Study on metastable zone width and primary nucleation kinetics for cooling crystallization of KNO_(3)

作　　者：邹洋 陆志艳[1] 胡志林 孙泽 ZOU Yang;LU Zhiyan;HU Zhilin;SUN Ze(School of Resources and Environmental Engineering,East China University of Science and Technology,Shanghai 200237,China;Shanghai Boiler Works Co.,Ltd.,Shanghai 200245,China;Qinghai Minzu University,Xining 810007,China)

机构地区：[1]华东理工大学资源与环境工程学院,上海200237 [2]上海锅炉厂有限公司,上海200245 [3]青海民族大学,青海西宁810007

出　　处：《无机盐工业》2024年第9期67-74,共8页Inorganic Chemicals Industry

基　　金：青海大学盐湖化工大型系列研究设施开放研究项目(2023-DXSSKF-203)。

摘　　要：为研究KNO_(3)在KNO_(3)-NaNO_(3)-H_(2)O中的冷却结晶过程,采用静态平衡法测量293.15~341.38 K下KNO_(3)在该体系中的溶解度,通过Apelblat方程和Van’t Hoff方程得到了溶解度与温度的关系,并计算了KNO_(3)的溶解焓和溶解熵。采用超声波法研究了298.03~332.30 K下NaNO_(3)含量、搅拌速率和冷却速率对KNO_(3)介稳区宽度的影响。实验结果表明,当体系中存在NaNO_(3)时介稳区宽度变窄但影响有限。KNO_(3)介稳区宽度随搅拌速率的增加而变窄,随冷却速率增加而变宽。以KNO_(3)溶解度和溶解焓数据为基础,研究了KNO_(3)的初级成核动力学,采用自洽Nývlt型方程得到成核级数m小于3,KNO_(3)为瞬时成核,且随着饱和温度的升高,成核速率呈先增大后减小的趋势;在经典三维成核理论中,随着饱和温度的升高,成核更容易发生,当饱和温度达到一定程度后,固-液界面能γ趋于稳定。以农用硝酸钾为原料,通过冷却结晶得到高纯度KNO_(3)产品,当饱和KNO_(3)溶液由343.15 K降至298.15 K、搅拌速率为300 r/min、冷却速率为25 K/h时,添加晶种后,溶液中Na^(+)含量仅为0.0011%。For investigating the cooling crystallization process of KNO_(3)in a ternary KNO_(3)-NaNO_(3)-H_(2)O mixture system,the solubility of KNO_(3)was measured by static equilibrium method in the temperature range from 293.15 K to 341.38 K.In order to present the relationship between solubility and temperature,the experimental data was fitted by the Apelblat equation and Van′t Hoff equation,and the dissolution enthalpy and dissolution entropy of KNO_(3)were calculated.Then,the effects of NaNO3 content,stirring rate,and cooling rate on the width of the metastable zone(MSZW)of KNO_(3)in the temperature range from 298.03 K to 332.30 K were analyzed by using an ultrasonic velocity sensor.The results showed that the existence of NaNO3would make the MSZW of KNO_(3)narrow,but the effect was limited,and the MSZW became narrow with the in⁃crease of stirring rate and wide with the increase of cooling rate.Based on the measured solubility and dissolution enthalpy,the primary nucleation kinetics of KNO_(3)were investigated.The nucleation order m obtained using the self⁃consistent Nývlt-like equation was less than 3.Instantaneous nucleation was the dominant nucleation mechanism of KNO_(3),and the nucleation rate showed a tendency to increase firstly and then decrease with increasing saturation temperature.In the classical three⁃dimensional nucleation theory,nucleation was more likely to occur,and when the saturation temperature reached a certain level,the solid⁃liquid interface energyγtended to be stable.Furthermore,the high⁃purity KNO_(3)product was obtained by cooling crystallization with agricultural potassium nitrate as raw material.When the saturated KNO_(3)solution was cooled from 343.15 K to 298.15 K,the stirring rate was 300 r/min,the cooling rate was 25 K/h,and the seed crystal was added,the Na^(+)content in the solution was only 0.0011%.

关 键 词：硝酸钾 硝酸钠 介稳区 成核动力学 工业结晶 

分 类 号：TQ131.13[化学工程—无机化工]