Research on Optimization Method of Precise Ammonia Injection in SCR de-NO x System of Coal-fired Power Plant

doi:10.12096/j.2096-4528.pgt.22129

Abstract

Abstract:

In order to solve the problem of uneven ammonia injection in selective catalytic reduction (SCR) de-NO _x system of coal-fired power plant, a precise ammonia control optimization method was proposed by combining the intelligent feed-forward cascade control technology with the partition control technology. In the intelligent feed-forward process, the improved one-dimensional convolution neural network model with higher prediction accuracy was used to predict the NO _x mass concentration at the inlet of the SCR reactor, which was used as the intelligent feed-forward control signal to realize the fast and accurate control of the NO _x mass concentration under the whole working condition of the unit. In the partition control process, the single sub area and multi-point synchronous sampling measurement technology and equalization control strategy were combined to realize the precise control of ammonia injection in each partition. The proposed optimization method has been applied to several coal-fired power plants. The operation results show that the precise control of ammonia injection amount is realized under the whole working conditions of the unit. The NO _x mass concentration at the outlet section of SCR reactor is uniformly distributed. The ammonia consumption is obviously reduced and the economic benefit is significant.

Key words: coal-fired power plant, SCR de-NO _x, precise ammonia injection, improved one-dimensional convolution neural network, partition control

CLC Number:

TK 09

Zhigang LUO, Chengbing HE, Haoran MENG, Guodong LIU, Peng SHEN, Jun ZHANG, Haoliang ZHANG. Research on Optimization Method of Precise Ammonia Injection in SCR de-NO _x System of Coal-fired Power Plant[J]. Power Generation Technology, 2023, 44(4): 525-533.

Figures/Tables 11

Fig. 1 Schematic diagram of precise ammonia control optimization method

Fig. 2 Structure of ICNN-1D

Tab.1 Structure parameters of ICNN-1D

编号	网络层	卷积核			输出大小	零补
编号	网络层	大小	步长	数目	输出大小	零补
1	输入层	—	—	—	120×1	否
2	卷积层1	8×1	4×1	16	32×16	是
3	池化层1	2×1	2×1	8	16×8	否
4	卷积层2	8×1	2×1	8	8×8	是
5	池化层2	2×1	2×1	4	4×4	否
6	全连接层	8	—	1	8×1	否
7	输出层	1	—	1	1×1	否

Fig. 3 Schematic diagram of partition ammonia injection control

Fig. 4 Single sub area and multi-point synchronous sampling measurement technology

Fig. 5 Equilibrium control principle of partition 1

Fig. 6 NO x mass concentration distribution at SCR outlet section of a 600 MW unit

Fig. 7 NO x mass concentration variation curves at SCR outlet of a 600 MW unit

Tab. 2 Deviation of NO x mass concentration fluctuation at the main outlet

NO _x 质量浓度波动偏差/(mg/m³)	时间占比/%
NO _x 质量浓度波动偏差/(mg/m³)	第1天	第2天	第3天	第4天	第5天	第6天
$> 8$	0.59	1.11	0.65	0.28	0.10	5.99
$> 7$	2.14	1.98	1.80	0.59	0.67	7.45
$> 6$	3.92	4.42	4.22	1.83	2.49	9.88
$> 5$	8.53	9.25	8.51	4.96	7.08	13.88
$< 5$	91.47	90.75	91.49	95.04	92.92	86.12
$< 4$	82.80	82.27	83.74	88.82	85.90	78.39
$< 3$	71.50	68.72	71.55	78.24	73.52	66.95
$< 2$	53.43	51.63	53.12	59.09	56.21	50.65
$< 1$	28.30	26.89	27.58	33.61	32.20	26.50

Tab. 2 Deviation of NO x mass concentration fluctuation at the main outlet

NO _x 质量浓度波动偏差/(mg/m³)	时间占比/%
NO _x 质量浓度波动偏差/(mg/m³)	第1天	第2天	第3天	第4天	第5天	第6天
$> 8$	0.59	1.11	0.65	0.28	0.10	5.99
$> 7$	2.14	1.98	1.80	0.59	0.67	7.45
$> 6$	3.92	4.42	4.22	1.83	2.49	9.88
$> 5$	8.53	9.25	8.51	4.96	7.08	13.88
$< 5$	91.47	90.75	91.49	95.04	92.92	86.12
$< 4$	82.80	82.27	83.74	88.82	85.90	78.39
$< 3$	71.50	68.72	71.55	78.24	73.52	66.95
$< 2$	53.43	51.63	53.12	59.09	56.21	50.65
$< 1$	28.30	26.89	27.58	33.61	32.20	26.50

Fig. 8 Ammonia consumption of a 600 MW unit under different load conditions

Tab. 3 Economic benefit analysis of typical units

参数	装机规模
参数	1×300 MW	1×600 MW	1×1 000 MW
烟气量/(10⁶m³/h)	1.2	2.1	3.0
年利用小时数/h	4 500	4 500	4 500
NO _x 入口质量浓度/(mg/m³)	400	300	250
NO _x 出口质量浓度/(mg/m³)	40	40	40
1 h氨耗量/kg	159.7	201.8	232.8
年氨耗量/t	718.4	908.0	1 047.7
优化后节氨率/%	35%	25%	15%
年节省液氨量/t	251.5	227.0	157.2
液氨单价/(元/t)	3 300	3 300	3 300
烟风系统降低阻力/Pa	1 000	750	750
烟风系统降低电耗/kW	820.1	993.6	1 318.0
综合电价/[元/(kW⋅h)]	0.3	0.3	0.3
节省液氨费用/(万元/a)	83.0	74.9	51.9
节省烟风系统电费/(万元/a)	110.7	134.1	177.9
节省总费用/(万元/a)	193.7	209.0	229.8

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