Continuous Emission Monitoring System (CEMS)

Working Principle of CEMS

• Sampling Method: Typically uses direct extraction method – a heated probe extracts flue gas to prevent condensation and component loss.
• Pretreatment: Includes dedusting, dehumidification, and cooling to ensure the sample gas is clean, dry, and suitable for analysis.
• Analysis Techniques:
• SO₂, NOx: UV Differential Optical Absorption Spectroscopy (DOAS) or Non-Dispersive Infrared (NDIR);
• Particulate Matter: Laser backscattering or Beta-ray absorption;
• O₂: Electrochemical or paramagnetic sensors;
• Flow, Temperature, Humidity: Measured by Pitot tube, thermocouple, and humidity sensors respectively.

CEMS Process Flow (System Components)

The CEMS consists of four main subsystems:Stack → Sampling Probe → Pretreatment System → Analyzer → Data Logger → IPC → Environmental Platform

Advantages of CEMS

1. High Measurement Accuracy:
• Advanced algorithms (e.g., DOAS + PLS) reduce interference;
• Two-stage condensation and three-stage filtration ensure gas stability.
2. High Reliability & Stability:
• Heated sampling lines prevent clogging;
• Core components are corrosion-resistant and interference-proof, suitable for harsh conditions.
3. Real-Time Capability:
• Response time <30 seconds;
• Real-time data upload with remote monitoring and early warning functions.
4. Modular & Scalable:
• Additional monitoring factors (e.g., CO, HCl) can be added as regulations evolve;
• Compatible with enterprise DCS or environmental agency systems.

Application Areas of CEMS

SO₂, NOx, particulates from coal-fired plants

CO₂, SO₂, dust from sintering, blast furnaces, coke ovens

NOx, particulates from kiln exhaust

Precursors of dioxins, HCl, SO₂, particulates

VOCs, SO₂, NOx, toxic gases

Multi-pollutant co-monitoring

CEMS is a core tool for modern industrial environmental supervision, offering high accuracy, real-time response, and strong stability. It is extensively applied in high-emission sectors such as power, steel, cement, and waste incineration, providing critical data support for carbon accounting, compliance monitoring, and environmental enforcement.

Project Case