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NOx Emissions

G4100 NOx/O2 Analyzing Systems

The G4100 NOx/O2 Analyzing Systems are simple and reliable systems used in biomass fired powerplants, providing precise NOx/O2 combustion data to comply with increasingly stringent emission regulations.

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Product information

G4100 NOx/O2 Analyzing System

Reliable monitoring

The G4100 NOx/O2 Analyzing Systems are in-situ gas analyzers that monitor NOx and O2 concentrations directly in exhaust gases. The systems consist of the NOx/O2 analyzer, a sampling board, and either an ejector probe or a diffusion probe with a sensor for the precise monitoring of NOx and O2 levels. They provide reliable data for SCR/combustion optimization as well as data for regulatory environmental reporting requirements, thus helping to ensure environmental compliance. The systems are simple to install and integrate in any industrial environment.

The ejector probe and diffusion probe

The ejector probe on the NOx/O2 analyzer (G4100) drives an ejector, drawing the sample gas into the measuring chamber. This ensures a fast response time. Ejector probes are used in areas with low or negative gas pressure. The diffusion probe (G4130), on the other hand, ensures that the gas is diffused to the measuring chamber. The simple design also ensures minimal maintenance. Even though the response time is not as fast as when using the ejector probe, the diffusion probe is sufficient for most industrial applications.

Simple operation

The G4100 NOx/O2 Analyzing Systems use a zirconium dioxide sensor with multiple diffusion cells. The sensor is small and robust, placed directly in the probe head, and operates reliably in harsh and tough industrial environments. In other words, the systems can be installed on the stack without special protection, only requiring a small filter. The sensor technology allows measurements on wet basis at high temperatures, and it avoids the disadvantages of sample lines, sample systems, and converters. An extra advantage of the G4100 NOx/O2 Analyzing Systems is the interface via touchscreen, making them extremely user-friendly for the personnel.

Constant optimization

Using a G4100 NOx/O2 Analyzing System in combination with an emissions abatement system such as a selective catalytic reduction (SCR) or exhaust gas recirculation system (EGR) will allow constant optimization of fuel combustion, urea injection, and other operating parameters. Real-time emission data provided by a NOx analyzer is crucial for engine and equipment diagnostics.

Low maintenance costs

The simple design of the analyzing systems mean they are cost-effective to install, operate and maintain. A complete system includes an automatic backflushing probe that is connected to the sampling board. Automatic backflushing of the probe head keeps it clean from loose soot and dust. The period between each backflush depends on the actual flue gas and the amount of contamination on the filter.

Service and support

The design of the G4100 NOx/O2 Analyzing Systems ensures low cost of ownership. The systems require occasional cleaning using a soft damp cloth on the touch screen. They have consumable parts that can easily be replaced by the personnel. In the event that assistance is needed regarding replacement of e.g. consumables or retrofit to a new system, Green Instruments provides full service and support to ensure optimal operation throughout the entire product lifetime.


Key features

  • In-situ direct monitoring – fast response
  • Provides data for SCR/combustion optimization
  • Documentation of compliance
  • Simple installation and integration
  • Reliable true wet measurement of NOx and O2 in exhaust gases
  • No sample lines, sample systems or converters
  • Graphic display – interface via touch screen
  • Automatic backflushing for purging filter at probe head
  • Analog outputs
  • Low cost of ownership
  • Global service and support


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