etr unidata

Technology for Continuous Emissions Monitoring – Tribo-Electric

Continuous Emissions Monitoring with Tribo-Electric Technology – the Pros and Cons

Dust monitoring systems employing electro-dynamic and tribo-electric technology use a probe inserted into the stack which measures the electrical charge carried by particles to record their presence. The accuracy and reliability of the dust monitoring instruments is affected by the following:

  • They measure the dust which either hits or is in very close proximity to the probe. As the probe is located on one side of the stack, and anyway covers a very small part of the cross-section, the particulate densities are calculated by extrapolation from a probably non-representative sampling
  • Changes in the characteristics of the gas stream, as for example variations in velocity, undermine the validity of the measurement and the instrument´s calibration
  • They cannot stand high gas stream temperatures (around 500ºC is the upper limit)
  • Humidity creates its own electrical charge, and to avoid the dust monitoring instruments recording this as the presence of more particles, measurement sensitivity has to be sacrificed
  • Humid environments create the risk of electrical shorting
  • Particulate build-up on the probe will change its insulating characteristics and sensitivity
  • Tribo-electric based dust monitoring systems are susceptible to electrical noise (and for this reason, do not work with electrostatic precipitators)
  • Their short-term readings are highly volatile, and to avoid the false alarms this would cause, they require significant dampening, at the expense of sensitivity

ETR-Unidata´s Omicron II and Sigma II use this technology.

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