Numerical simulation study on the measurement points arrangement of high-accuracy continuous CO2 emission monitoring system for thermal power plants
Continuous on-line monitoring of high-accuracy CO2 emissions is an important means to measure carbon emissions in China's thermal power sector.In order to improve the measuring point arrangement scheme to improve the measurement accuracy of the existing CO2 on-line monitoring method,this paper takes the original flue of a new unit and an old unit as the simulation object,and uses the numerical simulation method to simulate the flue gas flow field and CO2 concentration field under different loads,different test sections and different distribution modes.The accuracy of the simulation is verified by the field measurement results to improve the arrangement of measuring points in the continuous on-line monitoring of CO2 emissions.The results show that when the flow velocity measuring points of the two units are evenly arranged and the density of measuring points is≥1/m2,the test section does not meet the requirements of GB/T 16157 that the flue monitoring section should be set at≥6 times the diameter of the flue in the downstream direction of the elbow,valve and variable diameter pipe,and≥3 times the diameter of the flue in the upstream direction of the above components.The test results can still accurately reflect the average speed of the section,and the error is less than 2.3%.Increasing the density of measuring points can effectively increase the accuracy of flow velocity measurement.Due to the uniform distribution of CO2 in the cross section,only 1～2 CO2 measuring points can be arranged to meet the requirements of measurement uncertainty,and the test error is less than 0.5%.When the unit load is reduced to 75%and 50%,or the test section moves in the range of 2.5 m along the flow direction,the test error can be controlled within 4%.On this basis,a non-uniform measuring point arrangement method is proposed.With the help of numerical simulation,the test section is divided into several continuous regions according to the flow velocity.With the area of each region as the weight,fewer measuring points are arranged in each region to test the flow velocity of the section.This method only needs 6～9 measuring points on each test section,and the test error is less than 4%.The improved method simplifies the existing on-line monitoring distribution method.
CO2 emissionCEMSmeasurement points arrangementnumerical simulation
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