摘 要 由于现代工业化的飞速发展,带来了经济的飞速增长的同时也带来了环境污染,对此采用连续烟气检测系统CEMS能更有效的对污染物的排放进行监测,连续烟气检测系统由颗粒物监测、气态污染物监测、烟气排放参数测量等子系统构成，经过抽取式和连续监测,对烟气里的颗粒物的浓度、气态污染物的浓度、烟气的压力、流量、温度、含湿量等参数进行测量，对烟气中各污染物的浓度和排放量进行计算。77644

依据现代连续烟气检测标准的要求,实现烟气流速、温度的实时监测、现场报警设置及其仪器手动校准等方面的功能。本文介绍了连续烟气检测系统的结构组成和工作原理，以及经过气体分析仪对气体分析后，将气体的参数输出为4 ~ 20mA的电流信号分别经过CPU拓展的模块与隔离器中现场平台对数据的处理；系统的状态由气体分析仪输出至CPU中，通过PLC的控制将控制状态输出；处理后的模拟信号与输出状态的数字信号通过Modbus协议与DCS进行通信，将监测数据发送到DCS中进行显示；从而实现对系统运行在线的监控。

该论文有图26幅，表7个，参考文献21篇。

毕业论文关键词：  烟气连续监测系统  Modbus通信协议  环境监测  流速监测  PLC

Design of Continuous Emission Monitoring System based on Modbus communication

Abstract The rapid development of modern industrialization brings not only the high growth of economic, but also the serious environmental pollution。 The Continuous Emission Monitoring System (CEMS) can effectively monitor the emission of pollutants in face of the pollution。 It is composed by granular monitoring subsystem, gaseous pollution monitoring subsystem and gas emission measurement subsystem。 CEMS measures the concentration of particles in the flue gas by extraction and continuous monitoring, and measures the gas pressure, gas flow, gas temperature and the cold quantity parameter of gas。 Then it calculates the concentration and emissions of pollutants in the flue gas。

According to the requirements of the modern CEMS。 The control system includes the functions of alarm setting and manual instruments。 In this paper, the structure and work principle of CEMS are introduced。 And after gas analyzer for gas analysis, the parameters of the gas output for 4 ~ 20mA current signal respectively after expansion CPU module with a separator field platform for data processing; the state of the system by gas analyzer output to the CPU, through the control of the PLC will control the output state; processing of analog signal and output the digital signal through the Modbus protocol and DCS communication。 After that, the monitor data is sent to the DCS and displayed which realized the online monitoring。

Key Words: CEMS  environmental monitoring  temperature monitoring  velocity monitoring   PLC

目 录

摘 要 II

Abstract III

图清单 VI

表清单 VII

1。绪论 1

1。1课题研究的现状及其意义 1

1。1。1 CEMS系统的发展概况 1

1。1。2 PLC的发展概况 2

1。1。3 Modbus协议的概况 3

1。2 课题主要研究内容 3

2。CEMS系统概述 4

2。1 烟气排放连续监测系统（CEMS）的标准组成 4

2。2 烟气排放连续监测系统（CEMS）的测量原理