Application of VOC Online Monitoring Systems in Chemical Plants

With the rapid development of China’s economy, the chemical industry has become an important pillar of the national economy. However, this fast growth has also brought environmental challenges, especially the emission of volatile organic compounds (VOC) exhaust gases. These gases not only pollute the atmosphere but may also pose health risks, such as respiratory diseases and increased cancer risk. In recent years, people’s demand for a high-quality living environment has continued to rise, prompting chemical enterprises to strengthen VOC exhaust gas treatment and monitoring in order to balance economic growth with environmental protection.

In chemical production processes, VOC exhaust gases mainly originate from raw material volatilization, reaction processes, and storage stages. Untreated emissions can spread to surrounding communities, affect air quality, and even cause secondary pollution such as photochemical smog. In response, the national government has introduced a series of policies to regulate and promote VOC control. For example, the “13th Five-Year Plan for Ecological and Environmental Protection” clearly requires improving the VOC emission standard system, strictly enforcing pollutant discharge standards, and promoting total VOC emission control in key regions and industries, aiming for a nationwide reduction of more than 10%. Provinces and cities have also formulated localized policies accordingly, such as strengthening VOC monitoring requirements in industrial parks to ensure enterprises meet emission standards. These measures not only demonstrate the government’s determination to protect the environment but also provide chemical enterprises with a clear path to compliance.

Selection and Challenges of VOC Exhaust Gas Treatment Technologies

At present, the core technologies for VOC exhaust gas treatment are mainly divided into two categories: destruction and recovery. Destruction technologies include combustion, catalytic oxidation, and biodegradation, which convert VOCs into harmless substances such as carbon dioxide and water vapor through chemical reactions. Recovery technologies involve adsorption, absorption, and condensation, using materials or solvents to capture VOCs for resource reuse. The choice of technology depends on the composition, concentration, and treatment requirements of the exhaust gas. For example, high-concentration VOCs are suitable for combustion methods, while low-concentration VOCs are more suitable for adsorption recovery to reduce energy consumption and costs.

However, relying solely on treatment technology is not sufficient to ensure long-term compliance. In actual operations, exhaust gas compositions are complex and variable, and treatment equipment may fail due to improper maintenance, leading to excessive emissions. This makes online monitoring systems essential as the “eyes” of supervision. From a regulatory perspective, installing online monitoring equipment at the end of treatment facilities is an effective solution. It can track pollutant parameters in real time, monitor equipment operating conditions, prevent organized emission outlets from becoming “centralized pollution sources,” and reduce the risk of long-distance pollution diffusion.

Advantages of the Nexisense Series VOC Online Monitoring System

The Nexisense series VOC online monitoring system is designed for fixed pollution sources and provides real-time online monitoring of volatile organic compounds in chemical plant environments. The system integrates gas sampling, filtration, interference elimination, flow control, concentration display, wireless transmission, environmental protection networking, local alarms, and equipment linkage. It adopts standardized, modular, and professional design, supports direct outdoor installation, and features a three-proof structure (waterproof, dustproof, and corrosion-resistant) to ensure stable operation in harsh industrial environments.

The system core uses a PID (Photoionization Detection) VOC gas analyzer, combined with imported dehumidification and dust removal filters, high-performance drying tubes, long-life vacuum sampling pumps, wireless transmission modules, rotameters, 24V power converters, and circuit protection devices. The working process is efficient and streamlined: 220V power is converted to 24V to drive the analyzer, vacuum pump, and wireless module; the vacuum pump actively draws gas, which is dried and filtered before entering the gas chamber for UV lamp ionization detection. The detection results are displayed on the screen in real time and uploaded to environmental protection platforms via 4–20mA, RS485 signals, or wireless HJ 212 protocol.

This design enables faster response, stronger anti-interference capability, higher measurement accuracy, and longer service life. The Nexisense system is suitable not only for monitoring organized and unorganized emissions within enterprises but also for providing data support to environmental protection authorities, helping decision-makers assess regional air quality.

Practical Application Scenarios in Chemical Plants

In chemical plant applications, the Nexisense system is typically installed at exhaust outlets, downstream of treatment equipment, or at plant boundaries. Through active sampling, it captures trace VOC changes and avoids delays associated with passive monitoring. For example, in petrochemical enterprises, the system can monitor benzene series and alkane VOCs to ensure emission concentrations remain below national standards, such as the limits specified in the Integrated Emission Standard of Air Pollutants. When concentrations exceed limits, local audible and visual alarms are triggered immediately, while linked fans, valves, or spray systems respond automatically, such as increasing ventilation or activating backup purification equipment.

In addition, the system supports multi-channel data management. Enterprises can view historical data in real time through dedicated software, generate trend curves, or export Excel reports. This facilitates internal audits and external reporting, helping enterprises pass environmental acceptance inspections. Practical cases show that after introducing the Nexisense system, a large chemical plant reduced VOC emissions by 15% and avoided multiple penalty risks. Wireless networking also enables regulatory authorities to conduct remote supervision, reducing on-site inspection frequency and improving efficiency.

Installation and Maintenance Considerations

When installing the Nexisense system, the layout and prevailing wind direction of the chemical plant should be considered to select monitoring points that cover major emission sources. The modular design simplifies deployment, which can usually be completed within a few days. In terms of maintenance, regular replacement of filters and calibration of sensors are critical to ensure accuracy. Enterprises can also expand the system according to their needs, such as integrating meteorological parameter monitoring (temperature, humidity, wind speed) to further analyze VOC dispersion impacts.

Under the wave of digital transformation, the system also supports integration with Industrial Internet of Things (IIoT) platforms to enable predictive maintenance. Through data analysis, enterprises can identify potential equipment failures in advance, optimize production processes, and reduce operating costs.

Environmental Benefits and Economic Value

Introducing a VOC online monitoring system not only meets environmental protection requirements but also brings multiple benefits. Environmentally, it reduces the impact of VOCs on atmospheric ozone and improves the surrounding ecosystem. Economically, enterprises avoid losses caused by production shutdowns and fines due to excessive emissions. At the same time, real-time data helps optimize exhaust gas treatment processes, saving energy and materials. For example, adjusting catalyst usage based on monitoring feedback can reduce treatment costs by 10%–20%.

In the long term, with the advancement of “dual carbon” goals, the chemical industry will face stricter emission standards. As a reliable tool, the Nexisense system helps enterprises plan ahead and enhance competitiveness.

Frequently Asked Questions (FAQ)

1. What is a VOC online monitoring system?   It is a device that detects volatile organic compound concentrations in real time, used to monitor industrial emissions and ensure compliance.

2. Why do chemical plants need VOC monitoring?   Chemical production easily generates VOC exhaust gases. Monitoring prevents pollution diffusion, protects the environment and public health, and avoids regulatory penalties.

3. How does the Nexisense system work?   It uses a vacuum pump for sampling, filters and dries the gas, detects concentration with a PID analyzer, and uploads data wirelessly.

4. Which data transmission protocols are supported?   It supports 4–20mA, RS485, and HJ 212 protocols for easy integration with environmental protection platforms.

5. How long does system installation take?   Usually completed within a few days, depending on plant size and number of monitoring points.

6. How is the Nexisense system maintained?   By regularly replacing filters, calibrating sensors, and monitoring operating status through software.

7. Can the system link with other equipment?   Yes, it can link with fans, valves, and other devices to enable automatic response when limits are exceeded.

8. What benefits can enterprises gain after introducing the system?   These include emission compliance, cost savings, data analysis support, and environmental improvement.

Conclusion

The application of VOC online monitoring systems in chemical plants is not only a necessary response to national environmental protection policies but also a strategic choice for sustainable enterprise development. Through the Nexisense series products, chemical enterprises can achieve precise monitoring, timely response, and data-driven optimization, ultimately finding a balance between environmental protection and economic benefits. With continuous technological advancement, this field will see more innovation, driving the chemical industry toward greener transformation.