Study on Numerical Simulation of Dynamic Deposition and Shedding Characteristics of Zhundong Coal Ash

doi:10.12096/j.2096-4528.pgt.24220

Abstract

Abstract:

Objectives Power plant boilers often experience severe fouling and slagging issues on the heating surfaces when burning Zhundong coal. Therefore, the deposition and shedding characteristics of Zhundong coal ash on the heating surface were studied. Methods A deposited ash erosion model based on particle adhesion energy is established, and numerical simulations are then conducted to examine the dynamic deposition and shedding processes of Zhundong coal ash on a single tube. Results The model incorporating the coupled erosion mechanisms has a deviation of only 3.3% compared to the experimental results, demonstrating high accuracy. Besides, the shedding rate of the deposited ash increases initially but then levels off. However, within the simulated timeframe, only 25% of the deposited ash can be removed. In addition, the accumulation of deposited ash leads to a gradual increase in the heat transfer loss rate of the heating surface, with the average heat transfer loss rate during a 6-hour period being 1.76 times that of a 1-hour period. Furthermore, the adhesion energy of the deposited ash after 6 hours is 6.11 times that after 1 hour, and the corresponding mass flow rate of air at the soot-blowing outlet needs to be increased by 1.85 times to effectively remove all the deposited ash. Conclusions These findings enhance the understanding of the dynamic deposition and shedding processes of Zhundong coal ash and offer important research data and theoretical support for optimizing soot-blowing operations in industrial applications.

Key words: coal-fired electricity, Zhundong coal, ash deposition, erosion and shedding, average adhesion energy, numerical simulation, alkali metal, soot blowing

CLC Number:

TK 16

Qianxin GUO, Jianbo LI, Hu WANG, Yintang LIANG, Xinjian HAN, Xiongwei RUAN, Xiaofeng LU. Study on Numerical Simulation of Dynamic Deposition and Shedding Characteristics of Zhundong Coal Ash[J]. Power Generation Technology, 2025, 46(4): 829-838.

Figures/Tables 10

Tab. 1 Proximate analysis and ultimate analysis of Zhundong coal and its ash chemical composition

化学成分分析(干燥基)											工业分析					元素分析
w(SiO₂)	w(Al₂O₃)	w(Fe₂O₃)	w(CaO)	w(MgO)	w(TiO₂)	w(SO₃)	w(P₂O₅)	w(K₂O)	w(Na₂O)		$w M a d$	$w V d$	$w F C d$	$w A d$		w(C)	w(H)	w(O)	w(N)	w(S)
11.71	6.69	5.93	32.51	7.56	0.39	27.93	0.09	0.44	4.9		15.6	30.07	64.84	5.09		75.45	3.51	14.69	0.69	0.57

Tab. 1 Proximate analysis and ultimate analysis of Zhundong coal and its ash chemical composition

化学成分分析(干燥基)											工业分析					元素分析
w(SiO₂)	w(Al₂O₃)	w(Fe₂O₃)	w(CaO)	w(MgO)	w(TiO₂)	w(SO₃)	w(P₂O₅)	w(K₂O)	w(Na₂O)		$w M a d$	$w V d$	$w F C d$	$w A d$		w(C)	w(H)	w(O)	w(N)	w(S)
11.71	6.69	5.93	32.51	7.56	0.39	27.93	0.09	0.44	4.9		15.6	30.07	64.84	5.09		75.45	3.51	14.69	0.69	0.57

Tab. 2 Simulation input conditions

参数	数值	来源
烟气温度/K	1 073	实验
探针温度/K	823	实验
入口速度/(m/s)	15	实验
飞灰质量流量/(kg/s)	0.000 24	实验
飞灰密度/(kg/m³)	2 500	文献[28]
沉积灰层孔隙率	0.5	文献[29]
飞灰导热率/[W/(m⋅K)]	1.89	文献[30]

Fig. 1 Comparison between simulated and experimental results of deposited ash thickness and its distribution characteristics

Fig. 2 Morphology of deposited ash with and without erosion model

Fig. 3 Variation patterns of deposited ash mass and shedding amount in heat exchange tube over time

Fig. 4 Variation of average particle size of deposited ash over time

Fig. 5 Variation patterns of surface temperature of deposited ash over time

Fig. 6 Variation of heat flux inside and outside tube over time

Tab. 3 Variation of heat transfer loss rate over time

灰沉积时间/h	传热损耗/kJ	平均传热损耗速率/(kJ/h)
1	7 145.41	7 145.41
2	17 236.44	8 618.22
3	29 597.16	9 865.72
4	43 663.31	10 915.83
5	59 052.21	11 810.44
6	75 547.71	12 591.28

Tab. 4 Average adhesion energy of deposited ash and required mass flow rate for soot blowing

灰沉积时间/h	换热管道沉积灰黏附能/J	吹灰装置出口质量流率/(kg/s)
1	302.39	0.003 9
2	597.01	0.004 9
3	884.62	0.005 6
4	1 201.73	0.006 2
5	1 525.69	0.006 7
6	1 847.79	0.007 2

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