CEMS (On-line Flue Gas Monitoring System)It occupies an important position in chemical fertilizer, cement production, petrochemical industry, iron and steel metallurgy, thermal power generation, garbage treatment and other industriesDifferent industry flue gas composition is different,But mainly containsSO2、NOx、CO、CO2、O2and other gases.CEMS is mainly used in power plants and thermal power plants for continuous monitoring and information collection of gaseous pollutants and particulate matter concentrations. It has ten important environmental roles.

1.Working principle of CEMS system

CEMS (Continuous Flue Gas Monitoring System) is used to continuously and automatically monitor the pollutant emission concentration of stationary pollution sources. The instrument is installed on the pollution source to measure and monitor the emission concentration and emission of pollutants in real time. At the same time, the monitoring data is transmitted to the environmental protection monitoring center. The system mainly includes four subsystems, namely, 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 technology, different technology, working principle and process. (Take gaseous pollutant monitoring as an example)

Detection Methods of 2. Gaseous Pollutants

The monitoring and sampling methods of gaseous pollutants include the extraction sampling method and the direct measurement method, and the direct measurement method is mainly used in domestic power plants. 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 inside 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 carry out long-distance linear online measurement of the measured object.

3.Application of CEMS System in Various Fields

The use of CEMS system is very extensive, mainly concentrated in the city's factories. Including chemical plants, cement plants, power plants and other units that produce air pollutants. In the petrochemical plant, the CEMS system is mainly installed at the flue gas discharge port of the sulfur recovery production unit, the flue gas collection discharge port of the power station boiler, the flue gas discharge port of the catalytic cracking production unit and the flue gas discharge port of the atmospheric and vacuum distillation production unit. The contaminated gas is monitored in real time at these four outlets. In the cement plant, the CEMS system is mainly installed in the flue after the induced draft fan of the rotary kiln at the end of the kiln to monitor the smoke and dust generated in the cement production process and the gas that will pollute the environment online.
4.Importance of CEMS System in Thermal Power Generation
    With the rapid development of China's economy and the accelerating process of urbanization, the total demand for industrial electricity and domestic electricity is increasing, that is, more power plants are needed to generate electricity. However, due to the relationship between energy structure in China, traditional thermal power plants still occupy a major position. The big zui problem brought by thermal power plants is serious pollution. China's air quality is deteriorating, especially in the north, coal fuel-based cities, the annual air quality is not up to standard accounted for the vast majority of days. So this problem has reached a point where it must be resolved.The application of CEMS (flue gas online monitoring system) helps to improve this situation to a certain extent.
    However, inIn the monitoring of gaseous pollutants in the CEMS system, the core component is the gas sensor. How to select the sensor determines the quality of the whole project to a large extent. The oxygen content is an important indicator to judge whether the excess air dilutes the flue gas concentration during boiler combustion. Generally, zirconia and electrochemical principles are used. Here, we recommend an oxygen sensor KE-25F3 that is very suitable for CEMS system oxygen content monitoring applications. The sensor has long life, low cost, stable long-term performance, and a threaded interface for easy installation and fixation.

Basic parameters of KE-25F3:

Life Expectancy:5 years

Accuracy:± 1% (full scale)

Temperature range:5-40℃

Relative humidity:10-90% RH (no condensation)

Air pressure range:811hPa-1216hPa

Output characteristics:mV Class Linear Voltage

Advantages of KE-25F3:

Long life, almost unaffectedEffect of CO2, CO, H2S, NOx, H2

Low cost, no preheating, zero power consumption, no external power supply, long-term output stability