Polishing Sample Gas with a PD Series Gas Dryer

The ability to accurately measure gas components and concentration is essential in many environmental and industrial process applications to optimize production and meet regulatory requirements. One of the most common sampling techniques in Continuous Emission Monitoring (CEMS) applications is cold/dry extractive sampling.

An analyzer is only as good as its sample!

The cold/dry extractive technique involves extracting the sample gas from the source, transporting the sample gas through a heated umbilical to a sample conditioning system, which includes a thermoelectric cooler, and then to an analyzer for analysis. The function of the sample conditioning system is to prepare the sample to be compatible with the analyzer. This includes removing any particulate, lowering the temperature of the gas, and removing the condensate.

Properly conditioning a sample gas is essential not only to ensure analytical accuracy but also to:

  • Prevent equipment, component, or instrumentation damage or failure
  • Reduce repair and replacement costs
  • Maintain quality of the product yield
  • Minimize fines and legal issues caused by violating environmental regulations

What does it mean to “polish” a sample gas?

The accepted industry standard for the outlet dew point of a thermoelectric cooler is 4°C. This temperature is typically well below the ambient temperature of an environmentally controlled analyzer shed and therefore expected to prevent condensation.

“Polishing” a sample gas refers to further drying the sample gas after the thermoelectric cooler to achieve an even lower dew point. This lower dew point helps to provide greater analytical accuracy and protects the sensors and analyzer from the potentially harmful effects of water.