CEMS (Continuous Emissions Monitoring System) is a system designed for real-time monitoring of pollutants emitted from industrial sources. It is widely used in industries such as power generation, steel, cement, and chemicals to ensure compliance with environmental regulations. Below is a detailed breakdown of CEMS:

‌1. Components of CEMS‌

A CEMS primarily consists of the following subsystems:
‌(1) Sampling System‌

• ‌Probe‌: Extracts gas samples from smokestacks or exhaust ducts.
• ‌Heated Sample Line‌: Prevents sample gas condensation to avoid measurement errors.
• ‌Filter System‌: Removes dust and impurities to ensure sample purity.

‌(2) Analysis System‌

• ‌Gas Analyzer‌: Measures concentrations of SO₂, NOx, CO, CO₂, O₂, etc., using techniques such as UV-DOAS (Differential Optical Absorption Spectroscopy), NDIR (Non-Dispersive Infrared), and CLD (Chemiluminescence Detection).
• ‌Particulate Matter Analyzer‌: Monitors dust emissions via laser scattering, beta-ray attenuation, or electrostatic charge methods.
• ‌Humidity/Temperature/Pressure Sensors‌: Correct measurement data for accuracy.

‌(3) Data Acquisition & Processing System‌

• ‌DAHS (Data Acquisition & Handling System)‌: Collects, stores, processes, and transmits data to regulatory agencies.
• ‌PLC/Industrial PC‌: Controls system operation to ensure data stability and reliability.

‌2. Working Principle of CEMS‌

CEMS operates through the following steps:

1. ‌Sampling‌: Gas is extracted from the emission source via a probe.
2. ‌Pretreatment‌: Samples are heated, filtered, and dehumidified to remove interference.
3. ‌Analysis‌:
   • ‌Gas Analysis‌: Optical, chemical, or physical methods measure pollutant concentrations.
   • ‌Particulate Analysis‌: Laser scattering or beta-ray techniques determine dust levels.
4. ‌Data Processing‌: Data is calculated, corrected, and stored.
5. ‌Data Transmission‌: Results are uploaded to regulatory platforms for compliance verification.

‌3. Common Measurement Methods‌

‌(1) Gas Analysis Techniques‌

• ‌UV-DOAS‌: Measures SO₂ and NOx with high anti-interference capability.
• ‌NDIR‌: Analyzes CO and CO₂ with excellent selectivity.
• ‌CLD‌: High-sensitivity detection of NOx.
• ‌Paramagnetic O₂ Sensors‌: Provide precise oxygen measurements.

‌(2) Particulate Measurement Techniques‌

• ‌Laser Scattering‌: Measures scattered light intensity to determine dust concentration.
• ‌Beta-Ray Attenuation‌: Uses beta-ray absorption for high-dust environments.
• ‌Electrostatic Charge Method‌: Calculates concentration based on particle charge in an electric field.

‌4. Applications of CEMS‌

CEMS is widely adopted in:

• ‌Power Plants‌: Monitors SO₂, NOx, and CO₂ from coal-fired units.
• ‌Steel Industry‌: Tracks emissions from blast furnaces and sintering plants.
• ‌Cement Industry‌: Ensures kiln emissions meet standards.
• ‌Chemical Industry‌: Detects toxic and hazardous gas releases.

‌5. Advantages of CEMS‌

• ‌Real-Time Monitoring‌: Ensures continuous compliance with regulations.
• ‌Automation‌: Minimizes manual intervention and improves accuracy.
• ‌Remote Data Access‌: Enables real-time oversight by regulators.
• ‌High Precision & Stability‌: Advanced sensors and algorithms ensure reliable data.

‌6. Regulatory Requirements‌

• ‌China‌: Follows HJ 75-2017 Technical Specifications for Continuous Emissions Monitoring.
• ‌USA‌: Complies with EPA 40 CFR Part 60/75 under the Clean Air Act.
• ‌EU‌: Mandates CEMS installation under the Industrial Emissions Directive (IED).

‌7. Maintenance of CEMS‌

Regular upkeep ensures accuracy:

• ‌Calibration‌: Use certified gases to verify analyzer performance.
• ‌Probe Cleaning‌: Prevents clogging from dust buildup.
• ‌Flow/Pressure Checks‌: Maintain optimal sampling conditions.
• ‌Software Updates‌: Ensure system stability and troubleshoot issues.

‌8. Future Trends in CEMS‌

• ‌IoT & Cloud Integration‌: Remote cloud-based data management for enhanced oversight.
• ‌AI-Driven Analytics‌: Predictive maintenance and anomaly detection.
• ‌Portable CEMS‌: Compact systems for emergency or small-scale monitoring.

‌Summary‌
CEMS is a critical system for real-time monitoring of industrial emissions, measuring pollutants like SO₂, NOx, CO, CO₂, and particulates to ensure regulatory compliance. Comprising sampling, analysis, and data processing subsystems, it employs advanced technologies (e.g., DOAS, NDIR, laser scattering) and is vital in power, steel, cement, and chemical industries. Future advancements will focus on smart, cloud-connected solutions to meet tightening environmental standards.