Relationship between the structure of macerals of Ordos lignite and its pyrolysis characteristics

doi:10.16085/j.issn.1000-6613.2024-0397

Abstract

Abstract:

The Ordos lignite was separated into vitrinite-rich group (EL-V) and inertinite-rich group (EL-I) by floating-sinking separation method, and the structures and compositions of the raw coal and its maceral were analyzed by industrial analysis, elemental analysis, X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR) and solid state nuclear magnetic resonance (¹³C NMR). The pyrolysis characteristics and the escape pattern of gaseous volatiles of the raw coal and its maceral were investigated by powder-particle fluidized bed and TG-FTIR devices, respectively, to further construct the macromolecular structure models of the raw coal and its maceral and quantum chemical calculations were carried out to recognize the law of chemical bonds breaking. The results showed that the vitrinite-rich group had a higher content of volatiles, contained abundant alkyl side chains, and the largest heat weight loss rate, suggesting that the vitrinite-rich group was more reactive in pyrolysis. Compared with the raw coal and inertinite-rich group, the vitrinite-rich group had higher the pyrolysis gas content and tar contend, and its pyrolysis tar contained more aliphatic hydrocarbons and light aromatic hydrocarbons (TXE). The inertinite-rich group had lower H/C ratio, and higher oxygen content and aromatic ring condensation, and its pyrolysis tar contained higher PAHs and phenolics. In addition, the precipitation behaviors of CO₂, CO, CH₄, aliphatic hydrocarbons and aromatic hydrocarbons were analyzed by TG-FTIR. Based on the breaking of chemical bonds in the macromolecular structure of coal samples and the escape pattern of gaseous volatiles, the possible reaction routes carried out in the coal pyrolysis process were proposed.

Key words: coal, pyrolysis, fluidized bed, macerals, computer simulation

摘要：

采用浮沉分离法将鄂尔多斯褐煤分离成富镜质组（EL-V）和富惰质组（EL-I），通过工业分析、元素分析、X射线衍射光谱（XRD）、傅里叶变换红外光谱（FTIR）和固体核磁（¹³C NMR）分析了原煤及显微组分的结构和组成。采用粉-粒流化床和TG-FTIR装置分别考察了原煤及显微组分的热解特性和气态挥发物的逸出规律，进一步构建原煤及显微组分的大分子结构模型，并进行了量子化学计算，认识了化学键的断裂规律。结果表明，富镜质组的挥发分含量较高，含有丰富的烷基侧链，热失重速率最大，表明镜质组的热解反应性较强。与原煤和惰质组相比，富镜质组热解气体含量和焦油含量较高，且热解焦油含有较多的脂肪烃和轻质芳烃（TXE）。富惰质组的H/C比较低，含氧量和芳环缩合程度较高，所得热解焦油中多环芳烃和酚类物质含量较高。此外，通过TG-FTIR重点分析了CO₂、CO、CH₄、脂肪烃和芳烃的析出行为。根据煤样大分子结构中化学键的断裂和气态挥发物的逸出规律，提出了煤热解过程中可能进行的反应路线。

关键词: 煤, 热解, 流化床, 显微组分, 计算机模拟

CLC Number:

TQ53

WU Qi, BAI Boyang, YIN Yongjie, MA Xiaoxun. Relationship between the structure of macerals of Ordos lignite and its pyrolysis characteristics[J]. Chemical Industry and Engineering Progress, 2024, 43(5): 2370-2385.

吴琪, 白柏杨, 尹永杰, 马晓迅. 鄂尔多斯褐煤显微组分结构与其热解特性间的关系[J]. 化工进展, 2024, 43(5): 2370-2385.

Figures/Tables 22

工业分析（干燥无灰基）

/%（质量分数）

样品	工业分析（干燥无灰基）/%（质量分数）				元素分析（干燥无灰基）/%（质量分数）					原子比
样品	水分	灰分	挥发分	固定碳^①	C	H	N	S	O^①	A_O/C	A_H/C
EL	1.49	7.95	37.27	62.73	70.60	4.19	1.43	0.10	23.69	0.25	0.71
EL-V	2.47	2.11	38.62	61.38	73.77	5.01	1.55	0.15	19.52	0.20	0.81
EL-I	0.78	17.77	31.68	68.32	64.04	3.52	1.22	0.16	31.06	0.36	0.66

样品	2θ/(°)	d₀₀₂/nm	L_c/nm	L_a/nm	f_a
EL	25.80	0.3452	1.21	1.36	0.60
EL-V	25.23	0.3528	1.55	0.98	0.51
EL-I	25.81	0.3450	1.67	1.04	0.63

样品	COOH/C_Ar	R—O—R/C_Ar	Ar—OH/C_Ar	CH₂/CH₃
EL	0.16	0.93	0.29	2.70
EL-V	0.20	1.01	0.17	3.63
EL-I	0.22	1.21	0.41	2.59

化学位移	归属	化学位移	归属
0~17	脂甲基R—CH₃	60~90	环内氧接脂碳
17~22	芳甲基Ar—CH₃	90~126	质子化碳
22~35	亚甲基—CH₂	126~137	桥接芳碳
35~40	次亚甲基—CH	137~148	侧支芳碳
40~50	季碳	148~165	氧取代芳碳
50~60	甲氧基	165~250	羧基（羰基碳）

样品	ƒ_a	ƒ_Al	ƒ $a C$	ƒ $a'$	ƒ $a H$	ƒ $a N$	ƒ $a P$	ƒ $a S$	ƒ $a B$	ƒ $A l *$	ƒ $A l H$	ƒ $A l O$
EL	74.68	25.32	5.35	69.34	46.66	22.68	6.68	5.61	10.39	7.43	17.21	0.67
EL-V	69.10	30.90	5.21	63.88	41.64	22.25	6.40	5.88	9.96	10.23	18.59	2.08
EL-I	75.56	24.44	9.03	66.52	44.52	22.00	6.01	4.65	11.34	11.84	12.60	0.00

样品	ƒ_a	ƒ_Al	ƒ $a C$	ƒ $a'$	ƒ $a H$	ƒ $a N$	ƒ $a P$	ƒ $a S$	ƒ $a B$	ƒ $A l *$	ƒ $A l H$	ƒ $A l O$
EL	74.68	25.32	5.35	69.34	46.66	22.68	6.68	5.61	10.39	7.43	17.21	0.67
EL-V	69.10	30.90	5.21	63.88	41.64	22.25	6.40	5.88	9.96	10.23	18.59	2.08
EL-I	75.56	24.44	9.03	66.52	44.52	22.00	6.01	4.65	11.34	11.84	12.60	0.00

样品	质量损失范围（daf）/%	净失重损失质量（daf）/%	最大热失重峰温度/℃	最大热失重速率/%·min^-1
EL	98.42~72.22	26.21	448.7	-1.02
EL-V	99.21~66.32	32.89	444.1	-1.85
EL-I	98.27~75.56	22.70	452.4	-0.76

样品	分子式	总能量/kcal·mol^-1	元素含量/%				分子量
样品	分子式	总能量/kcal·mol^-1	C	H	O	N	分子量
EL	C₁₄₂H₁₁₂N₂O₃₅	448.37	70.87	4.69	23.27	1.16	2404
EL-V	C₁₄₇H₁₁₆N₂O₃₀	459.48	73.86	4.89	20.08	1.17	2388
EL-I	C₁₄₈H₁₀₀N₂O₅₀	446.52	65.68	3.72	29.56	1.04	2704

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