Application of Nutech2600 Canister Trigger Sampling System and NCMS6300 Continuous Non-Methane Hydrocarbon Monitoring System in VOC Monitoring in Industrial Parks

Background Introduction

In recent years, the world has made significant progress in combating PM2.5 pollution. However, ozone pollution has become increasingly prominent, leading to a complex pollution scenario dominated by both PM2.5 and ozone. Volatile Organic Compounds (VOCs) are critical precursors in the formation of fine particulate matter (PM2.5) and ozone (O3), drawing increasing attention. Non-methane hydrocarbons (NMHC) refer to the sum of all gaseous organic compounds that respond to flame ionization detectors, excluding methane. NMHC is a comprehensive indicator for monitoring gaseous organic pollutants.

Continuous monitoring systems for NMHC can monitor the concentration of NMHC in ambient air in real-time, assess air quality, help identify and track pollution sources, and provide data support and scientific basis for environmental management and decision-making. These systems are widely used for continuous NMHC monitoring in industrial parks and urban environments.

The online monitoring system for NMHC has the advantage of high temporal resolution, accurately reflecting the concentration changes of NMHC in ambient air and capturing abnormal concentration points. However, it cannot identify the specific species causing the concentration anomalies, making it challenging to determine the reasons and sources of these anomalies. Therefore, we developed the Nutech2600 canister trigger sampling system and NCMS6300 ambient air NMHC continuous monitoring system. When the NCMS6300 system detects high concentrations of NMHC, it immediately triggers the Nutech2600 canister sampling system. The collected samples are then analyzed qualitatively and quantitatively in the laboratory.

Nutech Solution

Nutech’s low-temperature pre-concentration direct method improves the lower detection limit of NMHC, avoiding the negative and zero values often seen in traditional subtraction methods. The system comprises a sample collection unit, analysis unit, data collection and transmission unit, quality control unit, gas supply unit, and other auxiliary equipment. Techniques such as preconcentration, separation, valve switching, and backflushing are used to separate methane from total hydrocarbons, allowing NMHC to peak separately with a detection limit as low as 0.5 ppbC.

Test Results

In a particular industrial park, high concentrations of NMHC were frequently detected at night or early morning. To investigate the cause, a Nutech 2600 canister sampling system was installed in the station, sharing a common sampling line with the NCMS6300 to ensure consistency in sample collection. The figure below shows the variation of NMHC concentration over time, with high concentration points A and B triggering the 2600 canister sampling. Laboratory analysis revealed that point A was dominated by halogenated hydrocarbons and oxygenated VOCs, while point B was mainly alkanes and oxygenated VOCs, indicating different compound compositions.

Further analysis showed that dichloromethane was the dominant species at point A, while n-heptane was dominant at point B. N-heptane mainly originates from diesel vehicle emissions and solvent evaporation, while dichloromethane is commonly used as a solvent in industrial production. Combined with other component analyses, it is speculated that both high concentration points were influenced by solvent evaporation, possibly from different industrial processes. Long-term observation data, meteorological information, and industrial park companies’ information can provide further analysis to determine pollution sources.

Conclusion

The NCMS6300 ambient air NMHC continuous monitoring system, utilizing Nutech’s unique low-temperature pre-concentration direct method technology, directly determines NMHC concentration in ambient air. Combined with the Nutech2600 canister trigger system, it accurately assesses the causes of NMHC high points and infers pollution sources. Long-term, continuous monitoring data accumulation allows for in-depth research and analysis of NMHC emission patterns, influencing factors, and component composition, providing strong support for formulating more scientific and reasonable environmental policies and measures.