An Evaluation Model for Anisokinetic Sampling of Particle Concentration Measurement with Dusts Emitted from Stacks

Abstract

The investigation for errors due to anisokinetic sampling on particle concentration measurement was conducted with talc and fly-ash particles of sizes in the range of 1-20μm, and also used with several dusts which were emitted from an oil combustion boiler, an alumina kiln and from a glass smelting furnace, respectively. The equation which can be widely applied for Stokes number Sk between 0.1 and 30 was derived from the results. The empirical equation obtained is, C_s/C_o=α(V_o/V_S)+(1-α), where, C_o is the particle concentration in isokinetic sampling, C_s is one in anisokinetic sampling, V_o is the gas velocity in the duct, and V_S is gas suction velocity. Inertia function α in the equation is decided with the values of Sk, V_o/V_S and A_o. Although A_o is a coefficient correlated to Sk and V_o/V_S in a rigorously practical definition, Values of A_o are approximately 1 in fine particles and 0.0625 in coarse ones respectively. It was presumed that a specific thin boundary layer was generated into stream of anisokinetic suction. Thus, it is assumed that the marginal gas velocity in the layer not only increased suddenly, but also decreased according to the values of V_o/V_s.