PM measurement spurs monitor development

Recent epidemiological health studies have implicated PM as one of the critical air pollutants affecting public health. This has lead to stringent world-wide PM regulations and objectives. With this comes the need to better identify and control PM emissions from stationary and other sources.

In the USA, in-stack PM emissions are typically quantified by EPA Methods 5 or 17. These are manual gravimetric reference-type methods that are labour-intensive, slow and subject to uncertainties from filter handling, transport, conditioning and weighing.

TEOM Series 7000 Schematic

Continuous in-stack monitors can provide more detailed information to help characterise stack dynamics. These methods, however, only infer PM mass using indirect techniques based upon opacity, triboelectric, acoustic or beta attenuation approaches. In addition, the current continuous instruments must be mass calibrated using US EPA methods.

To address the situation, Rupprecht & Patashnick (R&P) is developing the TEOM Series 7000 Source Particulate Monitor to provide in-situ, filter-based collection and measurement of stack particulate matter (PM) mass concentration in real-time. It can be used to measure total particulate mass levels or, in conjunction with a cyclone, to measure PM10 or PM2.5 particulate mass levels.

A prototype instrument has already been field-tested at a variety of sites to demonstrate and evaluate performance under real-world conditions and the production model will be launched at ET’99.

The system utilises the patented R&P TEOM technology for high-resolution direct mass readings and may be used to perform Method 17-type tests, as well as short term continuous tests. In addition, because it resolves mass in real time, it provides useful plant process information such as transient particulate mass concentrations during ramped loading, stratification in ducts and control device efficiencies.

Many of the error sources inherent with the US EPA methods can be eliminated utilising the TEOM mass detector, states R&P. These include errors associated with pre- and post- weighing of the filter media such as conditioning, handling and weighing. Because the TEOM mass detector weighs the filter continuously there is no need to pre-weigh filters. For example, a typical test would consist of installing a filter, stabilising the system in the stack, taring and initiating sample collection. The result is directly available at the site, eliminating the need to transport the sample to the lab for conditioning and post-weighing. Inlet losses have also been significantly reduced it is stated and, because the TEOM system is a mass detector, these losses can be quantified immediately on site.

The application of R&P’s proven TEOM inertial weighing technology offers an improved stationary source particulate testing methodology. Variations in aerosol parameters resulting from process ramping show a need for continuous real time mass measurement without dependence on particle size or other particle attributes. Existing continuous monitors all possess such dependencies; however, inertial weighing has a direct physical relationship with mass.

The in-situ TEOM mass detector minimises typical inlet losses found in existing in-situ continuous monitors. Transport losses are minimised due to straight-line isokinetic sampling and there are no losses due to impaction in tubing bends or settling in long horizontal runs.

Applications for this instrument include Method 17 equivalent testing, performing diagnostic studies on control device parameters, and calibration of existing continuous particulate monitors that do not possess a direct relationship with particulate mass.

A further potential use is to calibrate existing continuous monitors that, unlike the TEOM system, do not possess a direct relationship with particulate mass.

R&P equipment is available through UK distributor ETI Group Ltd.

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