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Industrial Pollution - Measuring CO, SO2, NOx, HCL, CH4, CO2, H2O 4/1/2015

In our last article, we discussed about on-line monitoring of Industrial Pollution - on a national level… In this article we will be discussing the smart ways of monitoring pollution due to gas emissions.

On-line monitoring of gas emissions

Few years ago, continuous emission monitoring was considered as a very difficult task for two main reasons:

  • Frequent failure of sampling & conditioning unit of traditional extractive flue gas analysers system.
  • Misalignment, lens contamination problems with In Situ cross duct flue gas analysers.


In 90’s upgradation in design and construction of stack mounted In Situ probe type gas analyser tackled these issues successfully and resulted in demand for this technology in the market for continuous emission monitoring. This probe type Insitu gas analyser eliminated the pitfall of Extractive as well as In Situ cross duct type gas analysers.

The technology

Today gas analyzer manufacturers offer accurate, reliable In Situ flue gas analysers that measure gases by infrared absorption gas filter correlation (GFX) technology. These analyzers are capable of continuously measuring up to seven gases at a time. The measuring probe is mounted on the stack / duct and uses an intrusive stainless steel measurement chamber equipped with sintered diffuser filter to allow flue gas, excluding particulate, into the measurement chamber. The probe incorporates a long measurement cell, into which the gas diffuses through an array of sintered filters.

Infrared beam from transceiver unit passes through the probe measurement chamber and is reflected back to the infrared detector mounted within the transceiver unit through a gold coated mirror. The analyser utilizing an In Situ probe arrangement allows calibration to be verified quickly and easily by the injection of zero and span gases. Fully automated zero calibration using compressed air is possible. This provides long-term accuracy with minimal maintenance.

For online normalization, this type of analyser has a provision of built in measurement of HP, COC, temperature and pressure parameters.

This is a multi-parameter analyzer and can measure upto seven parameters namely CO, SO2, NOx, HCL, CH4, CO2, H2O.

The Benefits :

The technology being Online Insitu type, eliminates the need for Sampling and Conditioning of the gases & the hassles surrounding it, such as condensation, choking, heat tracing issues etc. One can measure upto seven gases like CO,CO2,NO,NO2,SO2,HCL, H2O. The built in CO2, H2O , temperature & pressure measurement can facilitate online normalisation. It is possible to get the data in different units such as ppm, mg/m3, mg/Nm3. The probe is made of stainless steel SS-316 & is rugged.

As the analyzer works on gas diffusion technique, there is no risk of choking of filters & it gives fast response. The analyzer works perfectly even in very dusty application. It can be mounted anywhere after the ESP. The zero calibration is done automatically using plant instrument air. Even the span verification can be done automatically. As it requires a single port, the issue of misalignment never occurs.

Being a field mounted device, it does not require air conditioned panel & hence the power consumption is very low. Such analyzers don’t take lot of time for commissioning as most of the commissioning requirements are taken care in the factory itself. The maintenance required is negligible.


This technology is perhaps the best available one in the available technologies today.

In our next article, we will discuss about smart ways of monitoring water pollution.