Uncertainty Evaluation of Stack Flowrate Measurement with S-Type Pitot Tube by Monte Carlo Method

摘要

In order to attempt to mitigate the climate change, efforts to reduce the quantity of carbon emissions by actively seeking CO_2 trading and carefully control the liability of the emission test monitoring system from the industrial factories are a current issue. Therefore, the quality of greenhouse gas (GHG) emissions measurement with a proper uncertainty needs to be firstly considered. Currently, GHG emissions are estimated by a continuous emission measurement (CEM). The U.S Environmental Protection Agency (EPA), has classified the measurement of GHG emissions by the CEM as the highest quality Tier IV with lowest uncertainty level. Relating to accuracy of the CEM, both knowledge of the uncertainty contributions on GHG concentrations and volumetric flow rates are necessary for achieving a credible result. In order to accurately evaluate the uncertainty of the CEM method, flow rate measurements in the stack as well as GHGs concentration measurements by gas analyzer are crucial due to various uncertainty factors. In this study, we concentrate on finding measurand inputs and their uncertainty estimates that affect volumetric flow rates in a heat and power generation plant. Both the law of propagation method and Monte Carlo method (MCM) are used to evaluate the uncertainty of the flow rate measurement in order to minimize the numerical approximation of the partial derivatives of the complex model with respect to the every input. Consequently, the result of MCM is consistent with the result that by the law of propagation of uncertainty. The relative expanded uncertainties at 95% confidence level with coverage factor k=2 are 528.1 m~3 and 527.2 m~3, respectively.