硝酸钠废水分段式组合蒸发系统的构建与仿真比选

Construction and simulation comparison of sectional combined evaporation system for sodium nitrate wastewater

硝酸钠废水是一种高沸点升溶液,采用经验图表-吉辛科公式、仿真模拟和杜林直线法则3种方法对比计算硝酸钠废水的沸点升;结合蒸汽压缩机提升二次蒸汽温度的能力,提出分段式组合蒸发工艺,即“MVR+单效”和“MVR+双效”。利用Aspen Plus软件对“MVR+双效”系统进行流程模拟,定量分析了进料温度对MVR系统补充蒸汽量的影响,考察了MVR出料浓度与压缩比对蒸发器有效传热温差、换热面积和压缩机能耗的影响;对传统三效蒸发、“MVR+单效”和“MVR+双效”进行经济性分析。结果表明:MVR蒸发器加热蒸汽量和补充蒸汽量随进料温度升高线性下降,当进料温度大于81.5℃时压缩机的喷淋水量可提供MVR系统所需补充蒸汽量;MVR蒸发部分的最优工况为压缩机压缩比1.9,MVR出口硝酸钠质量分数45%;“MVR+双效”系统年运行成本和年总成本最低。

Sodium nitrate wastewater is a high boiling point rise solution.This study compared and calculated the boiling point rise of sodium nitrate wastewater using three methods,including empirical chart-Gisinko formula,simulation,and Durin’s straight line rule.Combined with the ability of steam compressors to enhance the temperature of secondary steam,the sectional combined evaporation processes,namely“MVR+single-effect”and“MVR+double-effect”,were proposed.Using Aspen Plus software to simulate the process of“MVR+double-effect”system,the effect of feed temperature on the amount of steam replenished in the MVR system was quantitatively analyzed.The effects of MVR discharge con⁃centration and compression ratio on the effective heat transfer temperature difference,heat transfer area,and compressor energy consumption of the evaporator were investigated.Economic analysis was conducted on traditional three effect evaporation,“MVR+single-effect”and“MVR+double-effect”.The results showed that the heating steam volume and supplementary steam volume of the MVR evaporator decreased linearly with the increase of feed temperature.When the feed temperature was greater than 81.5℃,the spray water volume of the compressor could provide the required supplementary steam volume for the MVR system.The optimal working condition for the MVR evaporation section was a compressor compression ratio of 1.9 and MVR discharge concentration of 45%.The“MVR+double-ffect”system had the lowest annual operating cost and annual total cost.