Technology for the higher dust loadings found after unabated combustion processes or after Electrostatic Precipitators


Opacity provides a proven and recognized solution for the higher dust loadings found after unabated combustion processes or after Electrostatic Precipitators in the Power, Steel and Cement Industries.

Core Features of the Technology are:

  • Single pass measurement for simple opacity (color) measurement.
  • Double pass measurement options for Compliance with US EPA PS-1 requirements.
A light source (typically an LED) shines light through the particulate in a stack and the amount of transmitted light is measured by a receiver. In a single pass instrument the receiver is mounted on the opposite side of the stack while in a double pass instrument (UP EPA PS-1 compliant), the light is reflected back to the transceiver by a retro-reflector on the far side of the stack. There are two parameters that Opacity instruments may be designed to measure:

  • First a measurement of the Stack Opacity (stack blackness) according to the simple equation:
    Opacity = 100 (1 – Received Light/ Transmitted Light) %
  • Secondly, a measure of the stack extinction which has a linear relationship with dust concentration for a particular type of dust and dust size:
    Extinction = Natural Log (Received Light/ Transmitted Light)
  • Compared to other Opacity systems, PCME’s PS-1 compliant instrument has lower long term zero drift, meaning that it can be used to monitor dust levels as low as 10mg/m3 in a 5m stack without suffering from zero drift which causes errors when calibrating an instrument.
  • The Opacity and DynamicOpacity measurement algorithms can be combined in certain instruments to provide a more reliable solution for dust measurement than pure opacity system.
PCME’s Double Pass Opacity instruments are available with a range of quality assurance features as required by US EPA PS-1 standards:

  • Automatic Opacity zero check which challenges the full operation of the transceiver by measuring the signal when a mirror is automatically inserted into the beam after the final lens.
  • Automatic span checks, to check ability of the instrument to correctly measure attenuation caused by an optical filter inserted ahead of the zero mirror.
  • Audit filters which may be manually inserted into instrument for zero and linearity checks.