神府烟煤以及贵阳贫煤分别与木屑掺烧灰沉积特性研究

胡世豪; 张佳凯; 岑可法; 周昊

神府烟煤以及贵阳贫煤分别与木屑掺烧灰沉积特性研究

浙江大学能源工程学系能源清洁利用国家重点实验室, 浙江杭州 310027

基金项目:

国家杰出青年基金资助 51825605

详细信息

通讯作者:
周昊, Tel:0571-87952598, E-mail:zhouhao@zju.edu.cn

中图分类号: TK6
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出版历程
- 收稿日期: 2020-05-21
- 修回日期: 2020-07-15
- 网络出版日期: 2021-01-23
- 刊出日期: 2020-09-10

Ash deposition characteristics during co-combustion of coal and sawdust

Zhejiang University, Institute for Thermal Power Engineering, State Key Laboratory of Clean Energy Utilization, Hangzhou 310027, China

Funds:

The project was supported by the National Science Fund for Distinguished Young Scholars 51825605

More Information

Corresponding author: ZHOU Hao,Tel: 0571-87952598, E-mail:zhouhao@zju.edu.cn

摘要

摘要: 利用CCD相机和沉积探针组成的在线监测系统，在50 kW下行炉上研究了木屑与神府烟煤以及贵阳贫煤的掺烧灰沉积特性。灰渣沉积过程可分为三个阶段：缓慢增长阶段、快速增长阶段和稳定阶段。烟煤掺烧灰沉积厚度随着木屑掺烧比例的增加而增加，贫煤掺烧灰沉积厚度则随着木屑掺烧比例增加而减小。烟煤中掺烧木屑比例为0、6.7%、15%和22%时，渣层稳定厚度分别为1.37、3.85、11.50、20.56 mm，稳定相对热流密度分别为0.44、0.41、0.30、0.26。贫煤掺烧木屑比例为6.7%、15%和22%时，稳定厚度分别为18.65、10.97和9.78 mm，稳定相对热流密度分别为0.29、0.31、0.33。掺烧木屑之后，灰渣初始层中Ca、K元素显著增加。在相同温度下，随着木屑掺烧比例的增加，灰中熔融相比例增加，因为木屑灰分中含有较多的Na₂O、K₂O等碱金属氧化物，而Al₂O₃、SiO₂等含量较少，降低了灰的熔融温度。
- 生物质 /
- 灰沉积 /
- 热流密度 /
- 在线监测
Abstract: The ash deposition characteristics during co-combustion of coal and sawdust was studied in a 50 kW furnace with an online monitoring system composed of CCD camera and ash deposition probe. The deposition process can be divided into three stages: slow growth stage, rapid and stable stage. The stable thickness of bituminous coal increases with increasing proportion of sawdust, while that of lean coal is opposite. The stable thickness of bituminous coal are 1.37, 3.85, 11.50, 20.56 mm and the stable relative heat flux are 0.44, 0.41, 0.30, 0.26 when blending ratio of sawdust are 0, 6.7%, 15%, 22% respectively. The stable slags thickness of lean coal are 18.65, 10.97, 9.78 mm and the stable relative heat flux densities are 0.29, 0.31, 0.33 when blending ratio of sawdust are 6.7%, 15% and 22%. Ca and K in the initial layer of deposition significantly increases in the co-combustion. The melting fraction calculated by FactSage software shows that at the same tem-perature, the melting fraction of ash increases as the sawdust is increased. Because the wood ash contains more alkali metal oxides such as Na₂O and K₂O, while the content of Al₂O₃ and SiO₂ is less, which lowers the melting temperature of ash.
- biomass /
- slagging /
- heat flux /
- on-line monitoring

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图 1 50 kW下行炉示意图

Figure 1 Schematic diagram 50 kW down-fired furnace

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图 2 在线监测系统原理示意图

Figure 2 Schematic of online monitoring system

(a): CCD camera; (b): deposition probe; (c): close-up of the probe

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图 3 数字图像处理方法；原始图像(左)和边缘图像(右)^[13]

Figure 3 Method of digital image processing; the original image (left) and the edge image (right)

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图 4 烟煤与不同比例的木屑掺混条件下的灰渣生长曲线

Figure 4 Deposition growth curves of bituminous coal with different blending ratios of sawdust

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图 5 贫煤与不同比例的木屑掺混条件下的灰渣生长曲线

Figure 5 Deposition growth curves of lean coal with different blending ratios of sawdust

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图 6 烟煤与不同比例的木屑掺混条件下的相对热流密度变化曲线

Figure 6 Heat flux curves of bituminous coal with different blending ratios of sawdust

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图 7 贫煤与不同比例的木屑掺混条件下的相对热流密度变化曲线

Figure 7 Heat flux curves of lean coal with different blending ratio of sawdust

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图 8 各掺烧工况熔融相比例

Figure 8 Proportion of molten phase

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表 1 烟煤、贫煤与木头的燃料特性

Table 1 Fuel characteristics of bituminous coal, lean coal and sawdust

	Proximate analysis w_ad/%					Ultimate analysis w/%					Ash fusion temperature t/℃
	M	V	FC	A		C	H	N	S	O	DT	ST	HT	FT
SF	8.77	26.96	48.96	15.32		77.94	4.47	1.42	0.34	15.83	1234	1257	1275	1302
GY	1.66	9.00	50.69	38.66		87.23	3.48	1.08	3.23	4.98	1204	1234	1257	1301
Sawdust	6.42	78.21	14.73	0.64		50.40	5.95	0.73	0.04	42.88	1420	>1450	>1450	>1450
	Ash composition w/%												Higher heating value Q/(MJ·kg^-1)
	Na₂O	MgO	Al₂O₃		SiO₂		P₂O₅	SO₃	K₂O	CaO	TiO₂	Fe₂O₃	Higher heating value Q/(MJ·kg^-1)
SF	0.05	1.13	27.95		55.19		0.34	1.06	0.25	6.34	0.78	6.92	22.57
GY	0.15	1.10	26.58		51.66		0.30	1.58	4.31	3.85	1.41	9.07	19.93
Sawdust	0.12	3.22	11.80		40.32		1.57	5.34	2.20	31.35	0.50	3.57	18.07

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表 2 实验工况

Table 2 Operating test parameters

Fuel	SF bituminous coal, GY lean coal, sawdust
Excess air ratio	1.1
Power /kW	50
Velocity of flue gas /(m·s^-1)	~2.0
Furnace temperature t/℃	1200
Oxygen concentration in flue gas /%	4
Thermal oil temperature t/℃	230
Deposition time t/min	120
Case1	SF
Case2	SF+6.7%sawdust
Case3	SF+15%sawdust
Case4	SF+22%sawdust
Case5	GY
Case6	GY+6.7%sawdust
Case7	GY+15%sawdust
Case8	GY+22%sawdust

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表 3 实验结果汇总

Table 3 Test results of different cases

Case	Final stable thickness /mm	Final relative heat flux(q/q₀)
SF	1.37	0.44
SF+6.7%sawdust	3.58	0.41
SF+15%sawdust	11.50	0.30
SF+22%sawdust	20.56	0.26
GY	-	-
GY+6.7%sawdust	18.65	0.29
GY+15%sawdust	10.97	0.31
GY+22%sawdust	9.78	0.33

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表 4 灰渣初始层中的元素分布

Table 4 Elemental composition in the initial layer of deposition

w/%	Na	Mg	Al	Si	P	S	K	Ca	Ti	Fe
SF	1.34	1.77	13.32	47.26	0.82	4.03	2.09	12.05	1.26	16.06
SF+6.7%sawdust	1.35	1.36	11.12	46.80	-	3.79	3.33	13.59	1.01	17.66
SF+15%sawdust	1.12	1.55	11.12	42.78	-	6.77	3.26	21.08	1.39	10.83
SF+22%sawdust	1.60	1.54	12.08	38.11	0.68	5.50	2.12	22.43	0.91	15.02
GY	0.42	0.95	16.61	50.56	0	2.65	1.41	6.99	1.44	18.96
GY+6.7%sawdust	0.33	0.58	15.48	52.30	0.58	2.99	2.23	7.88	1.31	16.32
GY+15%sawdust	0.64	0.80	16.65	51.16	0	2.45	3.71	8.88	0	15.28
GY+22%sawdust	0.56	0.81	17.51	48.52	0.50	2.65	3.93	9.00	2.17	14.35

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表 5 各工况下的灰成分

Table 5 Chemical composition of the ash

w/%	SF	SF+6.7%sawdust	SF+15%sawdust	SF+22%sawdust	GY	GY+6.7%sawdust	GY+15%sawdust	GY+22%sawdust
Na₂O	0.05	0.06	0.06	0.07	0.15	0.15	0.15	0.14
MgO	1.13	1.27	1.44	1.59	1.10	1.24	1.42	1.57
Al₂O₃	27.95	26.87	25.53	24.40	26.58	25.59	24.36	23.33
SiO₂	55.19	54.19	52.96	51.92	51.66	50.90	49.96	49.16
P₂O₅	0.34	0.42	0.52	0.61	0.30	0.38	0.49	0.58
SO₃	1.06	1.34	1.70	2.00	1.58	1.83	2.14	2.41
K₂O	0.25	0.38	0.55	0.68	4.31	4.17	3.99	3.84
CaO	6.34	8.02	10.09	11.84	3.85	5.69	7.97	9.90
TiO₂	0.78	0.76	0.74	0.72	1.41	1.35	1.27	1.21
Fe₂O₃	6.92	6.69	6.42	6.18	9.07	8.70	8.25	7.86

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表 6 灰沉积指数标准^[16]

Table 6 Slagging standard

	Slagging index	Ash deposition tendency
	Slagging index	slight	moderate	serious
1	silicon ratio	＞78.8	66.1-78.8	＜66.1
2	silica-alumina ratio	＜1.87	1.87-2.65	＞2.65
3	acid-base ratio	＜0.2	0.2-0.4	＞0.4
4	iron-calcium ratio	＜0.3 or＞3	0.3-3	≈1

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表 7 各灰沉积指数对比

Table 7 Slagging index of different cases

Case	Silicon ratio	Silica-alumina ratio	Acid-base ratio	Iron-calcium ratio
SF	79.32	1.97	0.18	1.09
	slight	moderate	slight	serious
SF+6.7%sawdust	77.23	2.02	0.20	0.84
	moderate	moderate	slight	moderate
SF+15%sawdust	74.69	2.07	0.23	0.64
	moderate	moderate	moderate	moderate
SF+22%sawdust	72.58	2.13	0.26	0.52
	moderate	moderate	moderate	moderate
GY	78.66	1.94	0.23	2.36
	moderate	moderate	moderate	moderate
GY+6.7%sawdust	76.50	1.99	0.26	1.53
	moderate	moderate	moderate	moderate
GY+15%sawdust	73.91	2.05	0.29	1.03
	moderate	moderate	moderate	serious
GY+22%sawdust	71.78	2.11	0.32	0.79
	moderate	moderate	moderate	moderate

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