PCME - Passionate about Particulate

ProScatter™ is a PCME patented laser forward scatter technique which provides reliable and high accuracy concentration measurement in Incinerator, Power Plant, Cement Stacks and other processes which require high auditing and traceability requirements (eg from EN 14181 and US EPA PS-11). The technique has a high signal to noise ratio even at dust concentrations below 0.1mg/m³ making it suitable for modern industrial plant where emissions are controlled well below the application and minimum detection limit of traditional optical transmission systems.

Core Features of the Technology are:

• Exceptional signal to noise at dust concentrations below 0.1mg/m³ due to the increased signal from capturing a complete cone of light.
• High reliability by having no moving parts in the receiver path and using optical components which do not age with temperature.
• An optical path which can be completely uniquely checked by the automatic insertion of a scattering body ensuring the automatic span check is a true challenge of the instrument’s functionality and contamination condition.

A laser diode light beam is directed through the measurement volume of a probe, positioned in a representative location within the stack. Particles in the stack flow freely through the measurement volume and scatter the laser beam in all directions including a cone of light in the near forward direction. This cone of scattered light is collected and reflected via an inclined mirror and quartz rod to a detector located outside the stack environment. The resulting scatter signal is measured and is proportional to dust concentration for a particular particle size and being in the near forward direction is relatively immune to changes in particle type and refractive index.

A span or contamination check is automatically performed by periodically rotating a scattering material into the laser beam ahead of the measurement volume and comparing the resulting scattered response to a benchmarked level.

• Compared to other forward light scatter probe systems, the ProScatter™ instrument:
  • Has fewer parts which need replacing with time (there are no optical fibres which age with temperature) and has higher reliability by avoiding the need for a moving detector as a contamination check.
  • Performs a span check in the same optical path as when measuring, enabling stray scatter to be reliably detected.
    
    
  • Has a stable optical bench and scattered cone measurement approach which provides reliable long term stable measurement for low dust levels, stack temperatures to 450°C and in probes up to 1.4m in length.
• Provides an alternative solution where stack velocity changes or particle charging by ESPs takes the range of probe electrification technologies outside their application limits.
• Compared to forward scatter cross stack designs, ProScatter™ provides in practice just as good a representative measurement (cross stack scatter has varying response to dust along it’s measurement path) without the errors from misalignment, vibration or near wall measurement sensitivity or the complexity of keeping a double head system clean.
• Compared to Backscatter, Opacity and DynamicOpacity™ systems, the ProScatter™ technique may be used to accurately monitor dust concentrations as low as 0.1mg/m³ (the application and resolution limit of Opacity in a 3m stack in reality is no less than 20mg/m³) and therefore is relevant to the emission limits and performance of the latest filter systems being used in Power and Incineration plant.

PCME ProScatter™ instruments are available with a full range of quality assurance features and options, some of which are unique and patented to PCME Ltd:

• Automatic electronic zero and upscale (span) checks for EN 14181 and US EPA PS-11 compliance, with diffuser simulating scattered signal for true check of instrument’s ability to measure scattered light, rather than just attenuated light.
• ProScatter™ 5-point Filter Audit Unit to perform linearity check with reference ‘scattering bodies’.
• Comms check, to test control unit correctly communicating with and reading dynamic opacity readings from the sensor(s).