基于双光束光路系统在线监测COD的稳定性研究

Study on stability of on-line double beam optical system for COD determination

针对光度法测定COD的在线监测仪受环境温度影响较大、测定结果稳定性差的问题,对光路和信号采集条件等因素进行验证与探讨,提出优化光纤结构和信号采集、处理方式,以提高系统的稳定性,降低系统受环境温度等因素的影响程度。结果表明,采用特殊结构双光束光纤传导光信号,在信号采集温度为50℃,信号采集时间为1s的条件下,测定结果稳定,受环境温度影响小。根据标准HJ 377-2019要求,对仪器的检出限、示值误差、重复性、低浓度漂移等指标进行测试,其结果均优于仪器测试指标要求,该装置及监测方法可用于水质COD的在线监测。

The on-line monitoring device for COD determination by spectrophotometry is greatly affected by the ambient temperature,and the stability of the determination results is poor.In this study,the factors such as optical path and signal acquisition conditions were verified and discussed.It was proposed to optimize the optical fiber structure and signal acquisition and processing methods,so as to improve the stability of the system and reduce the influence of environmental temperature and other factors.The experimental results showed that,under the condition of signal acquisition temperature of 50℃,and signal acquisition time of 1 second,special structure dual-beam fiber was used to conduct optical signals,the determination results were stable and less affected by the ambient temperature.According to the requirements of standard HJ 377-2019,the detection limit,indication error,repeatability,and low concentration drift of the instrument were tested,all the performance indexes were better than the requirements of instrument test.The on-line monitoring device and the method can be used for online determination of chemical oxygen demand.