Measurement of NH3 Concentrations in Stack Flue Gas Using TDLS8000

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The ammonia (NH3) gas is injected to remove the NOx and thus reduce the NOx concentration in the stack flue gas.

With conventional NH3 analyzers that perform measurements indirectly, NH3 concentrations are obtained through a sampling system. Therefore, there are problems with the maintenance and running costs of the sampling system, and time delays in measurement. The TDLS8000 Laser Analyzer is the solution to all these problems.

Expected Benefits

  • Eliminates the need for sampling and reduces the maintenance and running costs of the sampling system
  • High-speed response, possible to apply measurement results to control the NH3 injection volume, and reduction and optimization of the NH3 injection volume
  • Continuous monitoring, NH3 emission volume monitoring, and environmentally friendly
  • Extends the service life of NOx removal equipment and reduces the ammonium sulfate precipitation of the air heater

Process Overview

The NH3 gas is injected to remove the NOx and thus reduce the NOx concentration in the stack flue gas, as well as to increase the dust collection efficiency of the dust collector (ESP) and prevent erosion. Excess NH3 injection increases the running cost and the residual NH3 amount, resulting in the generation of a foul odor. Therefore, the NH3 concentration in the stack flue gas is measured, controlled, and monitored. 

Example of Boiler Flue Gas, NOx Removal Process (Oil and Gas Fuels)
Example of NOx Removal Process


Solution Details

As compared with conventional NH3 analyzers that perform measurements through a sampling system, the TDLS8000 is able to measure the NH3 concentrations in furnaces directly and thus reduce the maintenance and running costs.

Field Data

Changes in NH3 Injection Volume and Measured Values (Installation Point A / Without NOx Removal Equipment)

Changes in NH3 Injection Volume and Measured Values

The TDLS responds to NH3 injection volume changes at high speed and thus is able to control and monitor the optimum NH3 injection volume.

The TDLS responds to NH3 injection volume

Measurement System

  • TDLS(NH3 analyzer)
  • HMI unit
  • Cable
  • Accessories
    If necessary, please prepare ball valve for process isolation, DC power supply etc.
    And, When P and T are big fluctuation (P; ±5kPa, T; ±10℃), please consider input P, T analog signal or transmitters connection.


  • Please prepare instrument air or N2.
    2 to 20 L/min for optioc.
    5 to 30 L/min for process window


  • Power supply: 24 VDC
  • Purge gas: Instrumentation air or N2, Flow rate: 5 to 50 L/min (depending on the application)
  • Dust concentration (standard): 15 g/Nm3 or less


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