Loccioni Group

Ammonia Slip TDL Analyser



The deNOx process in an industrial plant is the reduction of the NOx concentration in the combustion gas by means of a chemical abatement process. Different technologies have been developed to achieve the NOx concetration reductions: they differ for the part of the process where the deNOx reaction is performed, but they all have in common the use of ammonia or urea use as reagent.

The use of the reagent is one of the main cost in the deNOx process and it also causes a series of potential problems in the plant operations:

  • Corrosion effect
  • Ammonia salt formation
  • Waste of reagent
  • High ammonia concentration in fly ash (coal combustion plants)

By monitoring and controlling the residual ammonia content after the deNOx reaction (ammonia slip) the problems mentioned above can be kept under control and their effects may be minimized.

Measuring principles

  • The NH3 concentration detection is based on the Infrared Absorbance of the NH3 molecule.
  • As Infrared Source a Tunable Diode Laser (TDL) is used to generate a very narrow electromagnetic radiation in the infrared region of the NH3 molecule, around the 1.5µm wavelength.
  • The absorption peak magnitude is directly proportional to the NH3 concentration and to the optical path.

System charateristics

The main characteristic of the ammonia slip monitoring system proposed by Loccioni are the following:

  • Up to 6 meter optical patlength in high dust concentration gas stream (15g/m3)
  • Up to 8 measuring points with a single central unit
  • Possibility to adjust the laser focus to improve immunity to plant mechanical vibrations
  • No need for calibration because of direct absorption quantification technique

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