氨氮在线监测仪电位滴定系统控制策略研究

Study on control strategies of potentiometric titration system of Ammonia nitrogen online monitoring instrument

针对国家环境保护标准(HJ537—2009)中规定氨氮测定的蒸馏-中和滴定法所使用的滴定终点判定方法-混合指示剂法存在变色不敏锐、人眼辨色能力差及难以实现滴定终点自动判定等问题,研究提出一种操作简单、灵敏度高的电位滴定法,以替代传统的指示剂法,提高滴定终点判定的准确性。同时,基于反馈控制和专家控制的基本原理,设计了几种快速滴定的自动控制策略,并对滴定系统进行计算机仿真。结果表明,专家-PID控制策略能使自动电位滴定系统的最大误差小于0.0064 mg/L,滴定时间小于66 s,能实现滴定终点的自动、快速和精准判定。

According to the problems of the titration endpoint determination method-Mixed indicator method used in distillation-neutralization and titration method for determining ammonia nitrogen in the national environmental protection standard （HJ537-2009） is not sensitive to discoloration, the distinguishing ability of human eye is poor and difficult to realize automatic judgment of titration, a method of potentiometrie titration with simple operation and high sensitivity was proposed in order to improve the accuracy of titration endpoint judgment. At the same time, several automatic control strategies of fast titration were designed and the computer simulation of the titration system was carried out based on the principle of feedback control and expert control. The simulation results showed that the maximum titration error of the automatic potentiometrie titration system with Expert-PID control strategy was less than the 0.0064 mg/L, the titration time was less than 66 s, which can realize the automatic, fast and precise judgment of the endpoint of titration.