Traceable Flue Gas Flow Rate Measurement Method for Large-Diameter Stacks of Thermal Power Plant

doi:10.12141/j.issn.1000-565X.240571

Abstract

Abstract:

The tracer gas dilution method can address the issue of significant measurement errors in flue gas flow caused by the complex flow field in large-diameter stacks of power plants. The method is traceable and operates on a measurement principle different from the conventional velocity-area method, making it a promising candidate for on-site calibration of flow measurements. To this end, this paper employs numerical simulation to analyze the feasibility and accuracy of the tracer gas dilution method for measuring flue gas flow in power plant stacks. On this basis, it studies the influence of the tracer gas dilution ratio and injection cross-section on measurement results. In addition, different tracer gas sampling schemes were designed to evaluate the stability of the measurements. The results demonstrate that, at a height of approximately 9D (where D is the stack diameter), the tracer gas achieves full mixing with the flue gas; both excessively high and low tracer gas dilution ratios can negatively affect the mixing efficiency; injecting the tracer gas at the flue section can effectively reduce flow measurement errors. Under 80% load rate, when the tracer gas is injected into the stack, the measurement errors vary considerably across different sampling schemes. However, the three-point sampling method demonstrates a stable and accurate performance, with measurement errors of only -3.59%, -0.69%, and -1.05% at the 3D, 8D, and 12D cross-sections, respectively. When the tracer gas is injected into the horizontal flue, the flow measurement errors for all sampling schemes remain within ±10%. Specifically, with three-point sampling, the errors at the 3D, 8D, and 12D cross-sections are 0.98%, -0.52%, and 0.21%, respectively—all within ±1%. These results demonstrate the feasibility and accuracy of the tracer gas dilution method for flue gas flow measurement in large-diameter stacks.

Key words: large-diameter stack, flue gas flow field, flow rate measurement, traceability, tracer gas dilution method

CLC Number:

TM621

LU Zhimin, XIE Zili, LU Weiye, CHEN Xiaoxuan, HUANG Yongru, LIU Zeming, TIAN Xuejun, YAO Shunchun. Traceable Flue Gas Flow Rate Measurement Method for Large-Diameter Stacks of Thermal Power Plant[J]. Journal of South China University of Technology(Natural Science Edition), 2025, 53(9): 138-148.

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示踪剂	安全性	相容性	易测量性（体积分数）	唯一性
H₂	无毒	在热量和氧气作用下具有高度反应活性	200 × 10^-6	否
He	无毒	惰性气体	300 × 10^-6	否
N₂O	有毒	可溶于水	1 × 10^-6	是
CO₂	无毒	可溶于水	5 × 10^-6	是
CO	有毒	易与氧气反应	5 × 10^-6	是
SF₆	无毒	惰性气体	2 × 10^-12	否

方案	稀释比例	示踪剂注入速度/（m·s^-1）	示踪剂稀释后体积分数
1	1∶200万	5.39	0.5 × 10^-6
2	1∶50万	21.55	2.0 × 10^-6
3	1∶10万	107.75	10.0 × 10^-6

负荷率/%	取样方案	烟囱注入时的δ/%			烟道注入时的δ/%
负荷率/%	取样方案	3D截面	8D截面	12D截面	3D截面	8D截面	12D截面
60	单点取样-上	9.03	4.19	-0.94	4.04	-0.51	-0.72
	单点取样-下	-27.10	5.27	2.05	-3.40	1.76	0.80
	单点取样-左	47.97	14.90	3.59	5.46	1.30	0.42
	单点取样-右	-28.09	-8.43	-2.49	-9.46	0.01	-0.86
	单点取样-中心	25.83	-10.65	-4.54	2.63	-1.99	0.14
	3点取样	-2.71	-0.95	-1.21	0.98	-0.27	0.07
80	单点取样-上	3.14	3.40	-3.82	3.16	-1.68	-0.98
	单点取样-下	-27.23	9.32	5.16	-1.32	1.78	1.31
	单点取样-左	49.75	15.57	1.74	7.99	0.54	-0.22
	单点取样-右	-32.02	-4.19	-0.14	-8.68	1.64	-0.37
	单点取样-中心	30.19	-12.20	-3.95	1.20	-1.59	0.33
	3点取样	-3.59	-0.69	-1.05	0.98	-0.52	0.21
100	单点取样-上	5.46	4.34	-3.64	-5.10	-2.41	-0.93
	单点取样-下	-29.37	9.27	4.95	3.24	1.56	1.33
	单点取样-左	52.53	16.22	1.68	9.38	-0.17	-0.67
	单点取样-右	-33.24	-4.79	-0.09	-9.10	2.48	0.17
	单点取样-中心	37.31	-13.00	-4.29	-0.32	-1.24	0.44
	3点取样	-2.99	-0.76	-1.17	-0.85	-0.73	0.27