Using New Electrodynamic Cross-Correlation Technology for Flow Measurement in Stacks

Abstract
Continuous flow measurement is often performed in industrial stacks to enable emissions to be converted from units of concentration to units of total mass over a given period. This requirement has increasing importance with the advent of emission inventories which industry and regulators are starting to maintain.

The traditional flow measurement techniques for stacks are averaging pitot, ultrasonic transit time and thermal mass, however, all can be rendered unreliable by the presence of high levels of particulate or moisture. In a new technique described as electrodynamic cross-correlation, the measurement is unaffected by moisture or particles. In fact, the technique responds positively to particles, since it is the electrical signature of particles interacting with an electrodynamic sensor which is cross correlated with the signature of a second down stream sensor to determine the transit time of the particles.

This paper describes the operating principle of electrodynamic-correlation instruments, including details of the signal processing. Results from an ECSC (European Coal & Steel Commission) development project test comparing the accuracy of such an instrument against standard pitot methods will be reported. The paper concludes with performance data taken from the operation of the instrument in industrial applications.