Development of a sampling assembly for PM2.5 CEMS

For an extractive type particulate matter continuous emission monitoring system (PM CEMS), the sampling assembly acts as an important interface between the exhaust gas and sensing unit. It serves to transport the aerosol sample and pre-treat it to meet the working conditions required by the sensing unit. To obtain representative samples, the sampling assembly should be designed to minimize the loss of particles. In this study, a conditioner based on a dilution approach was proposed and experimentally validated for use with pipelines for PM CEMS targeting particles less than 2.5 μm in diameter (PM2.5). The results showed that for 3.625 μm particles, the transport efficiency through the conditioner was 98.30% at a dilution ratio of 10. Meanwhile, the conditioner could reduce the sample air temperature to below 50 °C without condensation at flue gas temperatures up to 150 °C and water contents below 10%. Finally, a sampling assembly consisting of the conditioner, a 90° bend sampling probe, and a straight tube was designed to obtain transport efficiency higher than 95%, a stated requirement in this study for particles with a diameter less than 3.625 μm. Overall, this study contributed to designing and verifying a sampling assembly for PM CEMS and provided new strategies for improving monitoring data quality using PM CEMS. •A new concept for a size-selective PM CEMS, based on a dilution-type aerosol conditioner, is introduced.•The design and characteristics of the novel aerosol conditioner are introduced.•A proposal for a potential performance specification for PM2.5 CEMS is given.