Measurement of O2 Concentration in Exhaust Gases from Pulverized Coal-fired Boilers

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In a pulverized coal-fired boiler of a large power plant, an oxygen analyzer is essential for combustion control. Exhaust gases from the pulverized coal boiler contain a large quantity of dust and flow very fast. Oxygen analyzers that employ a sampling method may be subject to wear or clogging, resulting in increased maintenance workload and cost.

A solution to this problem is the ZR22G/ZR802G Zirconia Oxygen Analyzer that has no sampling system and utilizes a long-life sensor. A probe protector is attached to protection it against wear.

Expected Benefits

  • Improves combustion efficiency for pulverized coal-fired boilers 
  • Ensures stable, continuous oxygen measurement 
  • Reduces operating cost 
  • Minimizes the need for equipment replacement

Process Overview

While heavy oil, light oil , kerosene commonly used as a boiler fuel, coal is also used because it is inexpensive and readily available. Unlike oil, coal and gas produce a large quantity of ashes when it is burned, necessitating pulverized coal-fired boilers to be equipped with an ash removal system such as a cyclone. Exhaust gases from these boilers contain a large quantity of dust (10 to 30 g/Nm3) and flow very fast as the result of the large volume of air being blown into the boiler. For oxygen measurement in large ducts, a probe with a long insertion length is used.

Pulverized Boiler

Solution Details

Field Data

Process conditions

Measurement point Economizer outlet
Temperature 300 to 400°C
Flow rate ≤ 30 m/s
Pressure ±1.5 kPa
Dust approx. 15 g/Nm3 or less
Fuel pulverized coal

Measurement system

Detector ZR22G-☐☐☐-S-☐-☐-☐-☐-E-A/CV
Probe protector ZO21R-L-☐☐☐-☐*B
Converter ZR802G-☐-☐-N-N /☐
Flow setting unit ZA8F-☐*C
Pressure regulator G7013XF or G7014XF
Case for calibration gas cylinder E7044KF

Note: the calibration gas cylinder must be purchased locally


Rated voltage 100 to 240 V AC
Rated frequency 50/60 Hz
Power consumption 330 VA (Max. 800 VA)
Instrument air 300 to 700 kPa



  • A probe protector should be attached to the probe for protection against wear or damage. The probe protector should be mounted with the notch of the probe head pointing downstream in the gas flow.
  • It is recommended that the detector be installed with the probe tip pointing downward. As shown in the figure, it may be installed horizontally, too. The probe head tip should not point upstream in the gas flow.


  • Energetyka

    In the mid 1970s, Yokogawa entered the power business with the release of the EBS Electric Control System. Since then, Yokogawa has steadfastly continued with the development of our technologies and capabilities for providing the best services and solutions to our customers worldwide.

    Yokogawa has operated the global power solutions network to play a more active role in the dynamic global power market. This has allowed closer teamwork within Yokogawa, bringing together our global resources and industry know-how. Yokogawa's power industry experts work together to bring each customer the solution that best suits their sophisticated requirements.

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