Reliability evaluation on SCR denitrification systems in thermal power plants based on FTA

doi:10.3969/j.issn.2097-0706.2024.08.010

Abstract

Abstract:

Making reliability evaluations on selective catalytic reduction（SCR） denitrification systems in thermal power plants is significance for the safe operation of denitrification systems. Based on the classification on failure causes of denitrification systems，a fault tree analysis（FTA） taking abnormal ammonia/nitrogen molar ratio as its main indicator is applied on the evaluation. Then， Boolean algebra is used to analyze the path set of the FTA fault indicator，with a total of 11 minimum cut sets and a total of 5 minimum path sets. Considering the combination modes and propagation paths of impacts of elementary events on top events，an evaluation method for system safety hazards according to confidence degree is proposed. Based on the operational data of a denitrification system in a 300 MW unit boiler，a failure probability analysis was carried out on a specific fault of the reactor，and the conclusion was reached that the relative error between the confidence degree of the minimum cut set K7 and the confidence degree of the reliability evaluation method was only 0.694%. And the relative errors of other 20 fault events were all within 1%. The results show that the proposed evaluation method based on the minimum cut set confidence is accurate and feasible.

Key words: flue gas denitrification, big data analysis, FTA analysis, confidence, electric power big data, SCR

CLC Number:

TK228

WANG Yawen, ZONG Shaoliang, CHENG Zhiyuan, LU Wanpeng. Reliability evaluation on SCR denitrification systems in thermal power plants based on FTA[J]. Integrated Intelligent Energy, 2024, 46(8): 77-85.

Figures/Tables 12

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事件	F（j）	事件	F（j）	事件	F（j）
X1	0.255 6	X6	0.021 3	X11	0.000 1
X2	0.255 6	X7	0.021 3	a1	0.516 0
X3	0.021 3	X8	0.021 3	a2	0.004 7
X4	0.021 3	X9	0.005 6	a3	0.750 0
X5	0.021 3	X10	0.000 1

置信度取值范围	含义	可靠性评价
0.68~1.00	真实	严重安全隐患
0.34~0.67	不太真实	一般安全隐患
0.01~0.33	不真实	小隐患

事件代号	基本事件	测点指标
X3	锅炉负荷过高	锅炉负荷
X4	水解器氨蒸汽出口压力异常	水解器压力
X7	SCR出入口NO_x质量浓度测点不准	SCR出入口NO_x质量浓度
X9	氨蒸汽流量异常	NH₃蒸汽流量
X10	催化剂磨损堵塞	SCR出入口压差
X11	催化剂烧结	SCR出入口烟温

事件代号	基本事件	故障发生概率
X1	思想懈怠	0.21
X2	操作失误	0.55
X3	锅炉负荷过高	0.09
X4	水解器氨蒸汽出口压力异常	0.32
X5	水解器调节阀故障	0.12
X6	燃烧调节不合理	0.66
X7	SCR出入口NO_x质量浓度测点不准	0.77
X8	阀门故障	0.43
X9	氨蒸汽流量异常	0.38
X10	催化剂磨损堵塞	0.23
X11	催化剂烧结	0.46
a1	应急能力差	0.68
a2	催化剂层更换不及时	0.24
a3	设备检修不合格	0.58

隐患事件集合	严重程度
无	严重安全隐患
K₆,K₇	一般安全隐患
K₁,K₂,K₃,K₄,K₅,K₈,K₉,K₁₀,K₁₁	较小隐患