Faster, More Accurate, Stack-Flow Measurements

Abstract

Exhaust flows from coal-fired electricity-generating-plants are determined by measuring the flue gas velocity at prescribed points in the stack cross section. These velocity measurements are made using EPA-approved differential pressure probes such as the 2-hole S-probe or the 5-hole spherical probe. Measurements using the more accurate 5-hole spherical probes require a time-consuming rotation (or nulling) of the probe to find the yaw angle. We developed a time-saving non nulling technique using a spherical probe that measures all 3 components of velocity and therefore provides better accuracy than an S-probe. We compared the non-nulling and nulling techniques at both high (16 m/s) and low (7 m/s) loads. Their excellent mutual agreement (within 0.3 % of the flow) demonstrates that the non nulling technique accurately measures flue gas flows in a coal-fired stack.