CEM India 2017

CEM India - Abstract

Abstract Title: Mistakes and Problems in Gas Sampling and Conditioning
Abstract Type: Oral
Session Choice: Continuous Emission Monitoring
Presenter Name: Mr Jorg Erens
Co-authors:Mr Jörg Lang
Company/Organisation: AGT-PSG GmbH & Co. KG
Country: Germany

Abstract Information :

Irrespective of the current political statements and changes in the US the world understood that reduction of emissions is essential in order to limit the climate change within an acceptable border. The first step to achieve this target is an acceptance and approval of (continuous) emission monitoring systems. But what happens if the monitoring systems itself reduce the emissions compared to the real emission level?

The Components
Subject to the component which is to be measured and monitored a lot of factors of influence consequence into wrong measuring values which can be identified by looking at the different gas sampling and conditioning components:

Gas Sampling Probe:
When taking a gas sample from the process or a stack it is important to ensure a sample temperature above the water vapour resp. acid dew point. Otherwise condensation can happen and water soluble gas components like SO2, NO2, HCL, H2S or NH3 will be washed out uncontrollably. Another example for reduced measuring values is the HF-measurement (Hydrogenfluoride) e.g. in aluminium industry, waste incineration plants or ceramic and glass production. It has to be borne in mind that HF will react with silicates like glass and ceramic. Therefore a ceramic or glassfibre dust filter in the gas sampling probe will cause significant losses of HF.

Sample Gas Transport:
Next to the primary gas sampling also the heated sample line can cause deviations from original conditions of the gas. The often required high temperature of 180°C and above can produce outgassing effects from various sources. Depending which components were used in the production procedure of the heated cable, tubes, insulation and even the jacket material the sample might be falsified with CO or CO2 shares.

Sample Gas Conditioning:
Another known and meanwhile accepted physical problem is the wash out effect of SO2 and NO2 when sample gas is cooled and conditioned for the analyzer (accept for hot gas analysis when cooling is not needed). The transition process from the hot gas phase into the cold gas phase causes condensate which then reacts with the SO2 and NO2. Due to architecture and functional principle of the heat exchanger the wash out ratio can be reduced.

The current solution
These problems demonstrate that there is not only one right solution for gas sampling and conditioning in the sensible field of emission monitoring. The current solution to minimize some of these errors by calibration is just a compromise because in case of changing process conditions (e.g. dew point) errors for the measuring value will occur.
But the compatibility and reproducibility of measuring results is inescapable for the world-wide acceptance of emitting industries and it is our task to supply Perfect Sample Gas.