High-Temperature Boiler Flue Gas CO Online Monitoring Solution: Key to Combustion Efficiency and Environmental Compliance

In industrial boilers, thermal power boilers, and kilns, carbon monoxide (CO) is a direct product of incomplete combustion. Excessive CO indicates fuel waste, reduced thermal efficiency, serious safety hazards, and environmental pollution. As a toxic and flammable gas, accumulated CO in flue gas can cause poisoning incidents. In the atmosphere, CO reacts with nitrogen oxides and volatile organic compounds, forming photochemical smog and secondary fine particles, making it a significant precursor of air pollution.

With the continuous tightening of the Emission Standards for Air Pollutants from Boilers (GB 13271-2014) and ultra-low emission policies, CO has become a key parameter in fixed pollution source automatic monitoring systems. Continuous, accurate, and stable monitoring of CO in high-temperature flue gas is essential not only for environmental compliance but also for improving combustion efficiency, reducing energy consumption, and ensuring safe production. The Nexisense SGA-900 series high-temperature boiler CO online monitoring system is a reliable solution designed for these applications.

Importance and Technical Challenges of Boiler Flue Gas CO Monitoring

• Combustion efficiency: High CO levels indicate incomplete combustion, reducing thermal efficiency and increasing fuel costs.

• Safety risks: CO is colorless and odorless, easily causing poisoning if leaked or accumulated.

• Environmental compliance: Many regions have tightened CO emission limits to 100–150 mg/m³, with some requiring below 50 mg/m³.

• Process optimization: Real-time CO data enables dynamic adjustment of air-fuel ratios, optimization of coal and air supply, and reduction of incomplete combustion losses.

Monitoring challenges include:

• High flue gas temperatures (200–800℃)

• High dust concentration (up to several g/m³)

• High water vapor content (10%–20%)

• Coexisting corrosive gases (SO₂, NOx, HCl, etc.)

Traditional sampling methods are prone to clogging, corrosion, or sensor failure under these conditions. Nexisense SGA-900 combines high-temperature sampling, multi-stage pretreatment, and high-reliability analysis to effectively address these challenges.

Core Components and Working Principle of SGA-900 High-Temperature CO Online Monitoring System

• High-temperature sampling probe (up to 800℃)

• High-temperature filter + automatic back-flush device

• Condensation dehumidifier + high-efficiency desiccant

• Vacuum sampling pump + precision flow meter

• Imported high-precision CO analyzer (electrochemical or NDIR infrared)

• Industrial-grade control unit + data acquisition and transmission module

• Stainless steel corrosion-proof housing (IP65+)

  
  

Workflow:

1. High-temperature probe installed at flue sampling point extracts hot gas.

2. Flue gas passes through high-temperature filter to remove large dust particles.

3. Gas enters condensation dehumidifier and drying unit to remove water vapor.

4. Clean sample enters CO analyzer chamber.

5. Sensor converts CO concentration into electrical signal, displaying mg/m³ or ppm in real time.

6. Data transmitted via 4–20mA, RS485 Modbus RTU, or HJ212 protocol to control room/environmental platform.

The system supports automatic zero/span calibration, self-diagnostics, and data retransmission to ensure continuous and reliable monitoring.

High-Temperature Probe: Core Technology for Sampling Hot Flue Gas

• Special alloy material with multi-layer insulation, stable at 800℃

• Customizable probe length (0.5–3 m)

• Built-in high-temperature ceramic or alloy filter element to prevent clogging

• Optional heating or cooling to prevent overheating or condensation

• Quick-install/dismantle structure for easy maintenance

This design positions the sampling point closer to the emission source, reducing concentration loss and response delay from long-distance transmission.

System Integration and Practical Application

• Seamless integration with boiler DCS and combustion control systems

• Real-time CO concentration display and historical trend analysis

• Automatic audible and visual alarm + SMS notification when exceeding limits

• Linkage with combustion optimization: increases secondary air or adjusts coal feed if CO is high

• Switch output control: flue gas discharge allowed only within limits

• Direct data transmission to environmental platform (HJ212 compliant) with automatic daily/monthly reports

Many thermal power plants and industrial boiler users stabilize annual CO levels between 50–100 mg/m³ while improving boiler thermal efficiency by 2–5%, significantly reducing fuel costs.

Installation, Commissioning, and Maintenance

• Sampling point: straight section of flue, 4–6 duct diameters after elbows

• Probe insertion depth: 1/3–1/2 of duct radius

• Pretreatment cabinet installed on accessible platform

• Ensure heating line, cooling water, and back-flush lines are functional

• Check filter and condensate weekly

• Monthly zero/span calibration with standard gas

• Quarterly cleaning of probe and pretreatment piping

• Sensor life: 2–4 years, modular replacement

• Annual system availability: ≥95%

FAQ

1. Why can't standard CO sensors measure 800℃ flue gas directly? High temperature causes sensor decomposition, catalyst deactivation, delayed or permanent failure. SGA-900 uses high-temp probe + multi-stage pretreatment to cool and clean sample gas.

2. How does the system prevent clogging and sensor failure in high dust/humidity? High-temp ceramic filter, automatic back-flush, dual dehumidifier, and desiccant with bypass and automatic cleaning, plus weekly inspections.

3. Electrochemical vs NDIR infrared CO monitoring: which suits boiler flue gas? Electrochemical: fast, low-cost, small-medium boilers; NDIR: high precision, interference resistant, wide range, ideal for large boilers and ultra-low emission projects.

4. How to meet environmental platform data transmission requirements? Built-in HJ212-2017 data collector supports 4G/5G/Ethernet, breakpoint resume, data supplement, alarms, and automated reports.

5. Can SGA-900 optimize combustion automatically? Yes. 4–20mA or Modbus feedback to control system adjusts air-fuel ratio; secondary air increased or coal feed adjusted when CO is high.

6. Maintenance of high-temp probe and common faults? Inspect filters monthly, clean probe quarterly; common faults: filter clog, heating failure—replace filter, check power/temp controller, clean if needed.

7. Can one system monitor multiple boilers? Typically one system per boiler/conduit; multi-boiler shared duct can use multi-probe switching; independent ducts need separate systems.

8. How can CO monitoring reduce fuel consumption? Analyze CO vs load, fuel type, air/coal ratio; optimize combustion, save 2–5% fuel, reduce carbon deposits and maintenance costs.

Conclusion

Online monitoring of boiler flue gas CO ensures environmental compliance, combustion optimization, energy savings, and safety. Nexisense SGA-900, with high-temp sampling, reliable pretreatment, high-precision analysis, and stable data transmission, provides a complete monitoring-to-optimization solution for industrial and thermal power boilers. Deploying a professional CO online monitoring system helps enterprises pass environmental audits, reduce fuel costs, improve combustion efficiency, and enhance equipment reliability. Advanced technology enables efficient and clean combustion as the production norm, making clear skies a daily reality.