Co-combustion of oil sludge char and brown coal: characteristics and kinetics

doi:10.11949/0438-1157.20190680

Abstract

Abstract:

The combustion characteristics of sludge coke, lignite and their mixtures at different heating rates were studied by thermogravimetric analysis. Their combustion kinetic parameters were calculated by Kissinger-Akahira-Sunose (KAS)， Flynn-Wall-Ozawa (FWO) and Friedman (FR) methods. The results indicated that the combustion of the oil sludge char was mainly a fixed carbon combustion process, while that of the brown coal was characterized by a process of continuous combustion with a large amount of volatile and little fixed carbon. Compared with the combustion of the oil sludge char, the brown coal had a better combustion performance and its average activation energy was much lower. There was a significant positively synergistic interaction in the co-combustion process of the oil sludge char and the brown coal. When the proportion of brown coal in the blends reached up to 75%, the positively synergistic interaction effect was the strongest. The FR method better reflected the trend of the process, but its generated results were less accurate compared to that from KAS and FWO models. By comparing the theoretical and experimental values of the co-combustion kinetic parameters of the sludge char and the brown coal, it was found that application of thermogravimetric analysis to predict the combustion properties of the mixed fuel exhibited a high reliability, which can thus play an importantly guiding role in the application of the co-combustion technology of the oil sludge char and the brown coal.

Key words: oil sludge char, brown coal, co-combustion characteristic, synergistic interaction, kinetic

摘要：

采用热重分析法研究了不同升温速率下油泥焦、褐煤及其混合物燃烧特性，并利用Kissinger-Akahira-Sunose（KAS）、Flynn-Wall-Ozawa（FWO）和Friedma（FR）等方法计算其燃烧动力学参数。结果表明，油泥焦燃烧主要是固定碳燃烧过程，而褐煤燃烧是挥发分和少量固定碳连续燃烧的过程。褐煤比油泥焦具有更好的燃烧特性，平均活化能更低。油泥焦和褐煤共燃过程中存在明显的协同促进作用，当混合燃料中褐煤占比为75%时协同促进效应达到最强。通过比较KAS、FWO和FR的结果发现，FR法能够更好地体现反应变化的趋势，而KAS法和FWO法的结果具有较高的准确性。通过比较油泥焦和褐煤共燃动力学参数的理论计算值与实验计算值发现，利用热重分析预测混合燃料的燃烧性质具有较高的可靠性，对油泥焦与褐煤共燃技术的应用具有重要的指导作用。

关键词: 油泥焦, 褐煤, 混燃特性, 协同效应, 动力学

CLC Number:

TQ 517.3

Hongyan WEN, Yuming ZHANG, Dexin JI, Guangyi ZHANG. Co-combustion of oil sludge char and brown coal: characteristics and kinetics[J]. CIESC Journal, 2020, 71(2): 755-765.

温宏炎, 张玉明, 纪德馨, 张光义. 油泥焦与褐煤共燃特性及动力学[J]. 化工学报, 2020, 71(2): 755-765.

Figures/Tables 11

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Sample	Proximate analysis/%(mass)				Ultimate analysis/%(mass)					HHVs/ (MJ/kg)
Sample	V_ar	M_ar	A_ar	FC_ar^①	N_d	C_d	H_d	S_d	O_d^①	HHVs/ (MJ/kg)
SC	4.91	1.01	74.40	19.68	0.45	15.96	0.51	0.47	6.95	5.43
25BC75SC	13.87	7.38	58.13	20.62	0.68	26.04	1.17	0.54	8.81	9.07
50BC50SC	19.75	13.63	42.94	23.68	1.02	34.13	1.74	0.61	12.78	13.25
75BC25SC	28.16	19.75	27.16	25.93	1.33	45.21	2.20	0.73	17.10	16.98
BC	33.73	26.09	11.07	29.11	1.78	56.29	3.56	0.95	22.44	21.46

Sample	Proximate analysis/%(mass)				Ultimate analysis/%(mass)					HHVs/ (MJ/kg)
Sample	V_ar	M_ar	A_ar	FC_ar^①	N_d	C_d	H_d	S_d	O_d^①	HHVs/ (MJ/kg)
SC	4.91	1.01	74.40	19.68	0.45	15.96	0.51	0.47	6.95	5.43
25BC75SC	13.87	7.38	58.13	20.62	0.68	26.04	1.17	0.54	8.81	9.07
50BC50SC	19.75	13.63	42.94	23.68	1.02	34.13	1.74	0.61	12.78	13.25
75BC25SC	28.16	19.75	27.16	25.93	1.33	45.21	2.20	0.73	17.10	16.98
BC	33.73	26.09	11.07	29.11	1.78	56.29	3.56	0.95	22.44	21.46

Sample	Component content/%
Sample	Na₂O	MgO	Al₂O₃	SiO₂	SO₃	K₂O	CaO	Fe₂O₃	Others
SC	2.45	3.06	15.50	57.31	3.93	2.59	7.53	5.89	1.74
BC	—	3.94	8.56	12.63	31.65	0.54	34.46	6.52	1.70

Sample	Component content/%
Sample	Na₂O	MgO	Al₂O₃	SiO₂	SO₃	K₂O	CaO	Fe₂O₃	Others
SC	2.45	3.06	15.50	57.31	3.93	2.59	7.53	5.89	1.74
BC	—	3.94	8.56	12.63	31.65	0.54	34.46	6.52	1.70

Sample	β/(℃/min)	T_i/℃	T_max/℃	T_h/℃	K_r×10⁶/(min^-1·℃^-2)	G_b×10⁶/(min^-1·℃^-2)	S×10⁸/(min^-2·℃^-3)
SC	10	426.	497	713	6.43	5.51	0.22
	20	441	515	727	12.03	10.34	0.73
	40	458	534	753	19.26	16.63	1.71
25BC75SC	10	308	412	675	20.45	15.29	1.48
	20	333	447	694	31.02	23.11	4.07
	40	350	469	712	52.41	39.11	13.84
50BC50SC	10	284	378	654	40.92	30.74	4.26
	20	291	380	672	71.21	52.56	14.31
	40	295	409	690	109.63	79.07	42.74
75BC25SC	10	279	372	614	67.70	50.78	9.81
	20	289	385	632	96.38	72.35	27.00
	40	291	396	644	162.49	119.41	95.63
BC	10	306	397	613	64.41	49.63	11.64
	20	316	427	621	87.82	64.99	29.56
	40	331	470	648	155.62	109.59	100.14