改进型火电机组烟气直测法碳计量不确定度评定方法

The carbon emission of the power industry accounts for more than 40% of the total carbon emission in China. Accelerating the improvement of the accurate measurement and uncertainty assessment method of carbon emission of thermal power plants plays an important role in the fine supervision of carbon emission of the power industry. Considering that the measuring performance and accuracy of the concentration, flow and other measuring instruments installed on the power plant site may change after long-term operation, using the factory accuracy of the meters to calculate the uncertainty cannot truly reflect the confidence level of the measurement. In this paper, an improved practical method for uncertainty assessment based on the periodic calibration results of the instruments was proposed. The method was used to evaluate the uncertainty of the online monitoring results of carbon emissions for a 660 MW power plant in Hubei Province, the contribution of uncertainty was analyzed, and optimization suggestions were proposed. The results show that the extended relative uncertainty of the carbon measurement results obtained by the direct measurement method is 8.282% (including factor k= 2, confidence level 95%). With the exception of pressure, all other terms are dominated by class B uncertainty. Whether to consider the sensitivity coefficient and the choice of the evaluation method of Class B uncertainty will have a significant impact on the results. The main sources of carbon emission uncertainty are carbon dioxide concentration and flue gas flow measurement. The use of higher precision gas composition and flow measurement instruments, regular maintenance and calibration of measuring instruments, and optimization of measuring point layout in the flue can help reduce the uncertainty.