The objective of this thesis is to study the source of errors in stack gas sampling from a stationary source-sampling-analysis system. To identify major parameter, errors due to sampling systems(the temperature, velocity, humidity measurement systems, CEM,…) were classified with 4 factors(the measuring system errors, the system-sensor interaction errors, the system disturbance errors, the conceptual errors), as suggested by Moffat. Because the total error is the Root-Sum-Square of these errors, only relatively big errors have significance. From this analysis, errors due to condensation of water vapor in the sampling line and isokinetic sampling process were identified as important factors.
Condensation of the water vapor in the sampling line results the decrease of the sample gas flow rate and the absorption of the gas to be analyzed. To know the characteristics of gas phase absorption, heat and mass transfer model study and experiment with HCl gas were performed. The model study shows that the water condensation rate is related with the change of the relative humidity. High mass flow rate of the sampling gas with low humidity leads to the low absorption of HCl gas. Experimental results show that major portion of HCl gas is absorbed in general sampling procedure which might cause significant error.
Errors in the isokinetic sampling process are investigated at each step of the process. Isokinetic sampling were carried out with the wet, fluctuating and particulate-containing gas. To calculate the errors due to anisokinetic sampling, Watson's experimental results were used. The errors in Watson's equation caused by the inaccurate assumption of water content were calculated, which were smaller than the errors of anisokinetic sampling. Errors due to anisokinetic sampling were also calculated by Watson's equation, and results show that small particles have less errors. It also suggests that the isokinetic sampling which employs a little faster velocity have less errors. After isokinetic sampling the errors can be calculated from the results. Additionally, if the number of stack gas sampling is more than one, the range of results must be presented.
Among many errors of sampling, errors due to condensation of the water vapor in the sampling line and isokinetic sampling process were identified to be the source of important errors. Based on the heat and mass flow model and the experiment with HCl gas, the characteristics of absorption became known. And errors of isokinetic sampling process were also calculated.