CEMS (flue gas online monitoring system) occupies an important position in the chemical fertilizer, cement production, petrochemical, iron and steel metallurgy, thermal power generation, garbage disposal and other industries. Different industries have different flue gas components, but mainly contain SO2, NOx, CO, CO2, etc. Gases such as O2. CEMS is mainly used in power plants and thermal power plants for continuous monitoring and information collection of the concentration of gaseous pollutants and particulate matter. It has ten important environmental protection functions.

1. The working principle of CEMS system

CEMS (Continuous Flue Gas Monitoring System) is used to continuously and automatically monitor the pollutant emission concentration of fixed pollution sources. Install the instrument on the pollution source to measure and monitor the emission concentration and amount of pollutants in real time, and at the same time, transmit the monitored data to the environmental protection monitoring center. The system mainly includes four subsystems, which are gaseous pollutant monitoring system, particulate pollutant monitoring system, flue gas emission parameter measurement system, system control and data acquisition system. Each subsystem has a variety of monitoring and measurement technologies, with different technologies, different working principles and processes. (Take gaseous pollutant monitoring as an example)

2. Detection method of gaseous pollutants

The monitoring and sampling methods of gaseous pollutants include the sampling method and the direct measurement method. Domestic power plants mainly use the direct measurement method. Direct measurement method is divided into point measurement and line measurement. Point measurement is to install the sensor at the end of the probe, the probe is directly inserted into the flue, and the pollutant concentration in the electrochemical or photoelectric sensor is used. Line measurement is to install the sensor and probe directly on the flue or chimney, and then use spectral analysis technology or laser technology to perform long-distance linear online measurement of the measured object.

3. Application of CEMS system in various fields

The CEMS system is widely used, mainly in urban factories. Including chemical plants, cement plants, power plants and other units that generate air pollutants. In petrochemical plants, CEMS systems are mainly installed at the flue gas discharge outlets of sulfur recovery production units, power station boiler flue gas summary discharge outlets, catalytic cracking production unit flue gas discharge outlets, and atmospheric and vacuum production unit flue gas discharge outlets. At these four outlets, real-time monitoring of polluted gases is carried out. In the cement plant, the CEMS system is mainly installed in the flue after the induced draft fan of the rotary kiln at the kiln end to monitor the smoke and dust generated in the cement production process and the gas that will pollute the environment on-line.