五彩湾煤和吐鲁番煤热解动力学模型评估与应用

doi:10.11949/0438-1157.20190441

摘要/Abstract

摘要：

煤热解是煤热加工利用的基础反应，热解动力学模型有助于预测煤在热解过程中挥发分脱除规律，当前文献中已报道了多种热解动力学模型，厘清不同热解模型参数选择的差异，评估不同模型对煤种及热解反应适应性可为热解工艺设计提供参考。采用¹³C NMR核磁共振测量了五彩湾煤和吐鲁番煤的碳化学结构，并使用热重法测量了不同加热速率下的两种低阶煤失重曲线，结合分段式单一速率扫描法、等转化率法和3段式高斯分布活化能模型（3-DAEM）分析热重实验数据。结果表明单一速率扫描法得出的动力学参数难以准确揭示热解反应机理；等转化率法可以较好地得出热解活化能及指前因子分布图；将等转化率方法获得的指前因子赋值给分布活化能模型，可以避免分布活化能模型指前因子选择的盲目性；3-DAEM模型仅需要一条TGA曲线便可获得适用于整个加热速率的动力学参数，其预测结果与实验数据吻合最好，且模拟得出的活化能分布图很好地反映了煤热解三个阶段特征。

关键词: 煤, 热解, 热重分析, 分布活化能, 动力学, 模型

Abstract:

To clarify the differences in parameters selection of different pyrolysis models and evaluate the adaptability of different models to pyrolysis reaction, the segmented single scanning rate method, iso-conversion kinetic method and the 3-stage Gaussian distribution activation energy model (3-DAEM) were applied to analyze the thermogravimetric experimental data of two low-rank coal. The results show that the kinetic parameters obtained by single scanning rate method cannot reveal the pyrolysis reaction mechanism well. The iso-conversion kinetic method can better obtain the activation energy and pre-exponential factor distribution. The data simulated by 3-DAEM fits best with experimental data, and only one TGA curve is needed to obtain the kinetic parameters suitable for the TGA curve at other heating rates. According to the activation energy distribution, coal pyrolysis can be divided into three stages corresponding to the three classes of dominant chemical bonds.

Key words: coal, pyrolysis, thermogravimetry analysis, distributed activation energy, kinetic, model

中图分类号:

TQ 530.2

魏利平,江国栋,古玉宽,滕海鹏. 五彩湾煤和吐鲁番煤热解动力学模型评估与应用[J]. 化工学报, 2019, 70(S2): 275-286.

Liping WEI,Guodong JIANG,Yukuan GU,Haipeng TENG. Evaluation and application of pyrolysis kinetic model of Wucaiwan coal and Tulufan coal[J]. CIESC Journal, 2019, 70(S2): 275-286.

图/表 15

表1 原煤样品的工业分析和元素分析

Table 1 Proximate and ultimate analyses of raw coals

Coal type	Proximate analysis/%				Ultimate analysis/%
Coal type	M_ad	A_ad	V_ad	FC_ad	C_daf	H_daf	O_daf	N_daf	S_daf
WCW	9.97	3.67	27.86	58.5	78.94	3.78	16.26	0.54	0.48
TLF	5.25	11.80	40.69	42.26	78.79	5.81	13.01	2.02	0.37

图1 两种煤样的13C NMR谱图

Fig.1 ?13C?NMR(CP/MAS) spectra of two coal samples

图2 不同升温速率下煤样热解过程TG曲线

Fig.2 TG curves of coal samples during pyrolysis at different heating rates

图3 不同升温速率下煤样热解过程DTG曲线

Fig.3 DTG curves of coal samples during pyrolysis at different heating rates

表2 两种煤样热解特性参数

Table 2 Pyrolysis characteristic values of two coal samples

Coal	$β / (℃ / m i n)$	$T 0 / K$	$T p / K$	$R ∞ / (% / m i n)$	$V f / %$
WCW	10	527.27	722.94	0.78	38.49
	20	542.15	736.09	1.47	37.57
	30	543.20	742.95	2.10	38.01
	50	546.86	777.05	3.74	35.98
TLF	10	457.18	714.67	3.48	41.49
	20	473.42	730.73	6.61	46.65
	30	499.54	734.35	10.01	45.58
	50	518.65	747.02	17.73	45.52

表2 两种煤样热解特性参数

Table 2 Pyrolysis characteristic values of two coal samples

Coal	$β / (℃ / m i n)$	$T 0 / K$	$T p / K$	$R ∞ / (% / m i n)$	$V f / %$
WCW	10	527.27	722.94	0.78	38.49
	20	542.15	736.09	1.47	37.57
	30	543.20	742.95	2.10	38.01
	50	546.86	777.05	3.74	35.98
TLF	10	457.18	714.67	3.48	41.49
	20	473.42	730.73	6.61	46.65
	30	499.54	734.35	10.01	45.58
	50	518.65	747.02	17.73	45.52

图4 不同加热速率下的煤样热解过程α-T?曲线

Fig.4 α-T curves of coal samples during pyrolysis at different heating rates

表3 升温速率为20℃/min时两种煤的热解动力学参数Table 3 Kinetics parameter of coal pyrolysis at heating rate of 20℃/min

Coal	T/K	Method	$E$ /( $k J / m o l$ )	$k$ / $s - 1$	$R 2$
WCW	543—560	C-R	297.0	$1.50 × 1016$	0.87
		Doyle	291.1	$7.91 × 1023$	0.88
		A-B-S-W	14.4	$3.45 × 10 - 3$	0.99
	560—740	C-R	55.0	$2.27 × 10 - 6$	0.99
		Doyle	62.5	142.49	0.99
		A-B-S-W	48.1	3.78	0.98
	>740	C-R	22.3	$2.98 × 10 - 8$	0.99
		Doyle	37.0	3.13	0.99
		A-B-S-W	30.5	0.13	0.76
TLF	473—500	C-R	168.1	$1.06 × 106$	0.78
		Doyle	148.5	$3.41 × 1011$	0.77
		A-B-S-W	13.3	$9.81 × 10 - 4$	0.99
	560—746	C-R	53.4	$1.87 × 10 - 6$	0.95
		Doyle	60.6	108.81	0.96
		A-B-S-W	66.55	1271.17	0.90
	>746	C-R	9.4	$1.98 × 10 - 8$	0.92
		Doyle	23.95	1.21	0.99
		A-B-S-W	18.81	0.25	0.35

表3 升温速率为20℃/min时两种煤的热解动力学参数Table 3 Kinetics parameter of coal pyrolysis at heating rate of 20℃/min

Coal	T/K	Method	$E$ /( $k J / m o l$ )	$k$ / $s - 1$	$R 2$
WCW	543—560	C-R	297.0	$1.50 × 1016$	0.87
		Doyle	291.1	$7.91 × 1023$	0.88
		A-B-S-W	14.4	$3.45 × 10 - 3$	0.99
	560—740	C-R	55.0	$2.27 × 10 - 6$	0.99
		Doyle	62.5	142.49	0.99
		A-B-S-W	48.1	3.78	0.98
	>740	C-R	22.3	$2.98 × 10 - 8$	0.99
		Doyle	37.0	3.13	0.99
		A-B-S-W	30.5	0.13	0.76
TLF	473—500	C-R	168.1	$1.06 × 106$	0.78
		Doyle	148.5	$3.41 × 1011$	0.77
		A-B-S-W	13.3	$9.81 × 10 - 4$	0.99
	560—746	C-R	53.4	$1.87 × 10 - 6$	0.95
		Doyle	60.6	108.81	0.96
		A-B-S-W	66.55	1271.17	0.90
	>746	C-R	9.4	$1.98 × 10 - 8$	0.92
		Doyle	23.95	1.21	0.99
		A-B-S-W	18.81	0.25	0.35

图5 由Doyle方法模拟的数据和实验所得数据的比较

Fig.5 Comparison of data simulated by Doyle method and experimental data

图6 煤样在不同转化率α下lnβ与T-1的曲线-FWO模型

Fig.6 Plots oflnβversusT-1 at various α for FWO model

图7 基于FWO模型的两种煤样热解活化能分布f(E)

Fig.7 Pyrolysis activation energy distributions f(E) based on FWO model for two coals

图8 基于FWO模型的两种煤样热解指前因子分布f(k)

Fig.8 Pyrolysis pre-exponential factor distributions f(k) based on FWO model for two coals

图9 由FWO方法模拟的数据和实验所得数据的比较

Fig.9 Comparison of experimental data and simulated data with FWO method

表4 两种煤样3-DAEM热解动力学参数 (20?K/min)

Table 4 Kinetic parameters of 3-DAEM for pyrolysis of coal samples at heating rate of 20?K/min

Coal	$E 1 / k J / m o l$	$σ 1 / k J / m o l$	$E 2 / k J / m o l$	$σ 2 / k J / m o l$	$E 3 / k J / m o l$	$σ 2 / k J / m o l$	$ω 1$	$ω 2$	n	OF
WCW	279.06	9.90	348.08	74.43	355.20	52.77	0.200	0.334	3.820	0.0005
TLF	176.13	118.51	208.05	3.62	233.95	35.65	0.265	0.365	2.336	0.0008

表4 两种煤样3-DAEM热解动力学参数 (20?K/min)

Table 4 Kinetic parameters of 3-DAEM for pyrolysis of coal samples at heating rate of 20?K/min

Coal	$E 1 / k J / m o l$	$σ 1 / k J / m o l$	$E 2 / k J / m o l$	$σ 2 / k J / m o l$	$E 3 / k J / m o l$	$σ 2 / k J / m o l$	$ω 1$	$ω 2$	n	OF
WCW	279.06	9.90	348.08	74.43	355.20	52.77	0.200	0.334	3.820	0.0005
TLF	176.13	118.51	208.05	3.62	233.95	35.65	0.265	0.365	2.336	0.0008

图10 两种煤样的三高斯活化能分布

Fig.10 Distribution activation energy curves as a function of activation energy for 3-DAEM with Gaussian distribution functions

图11 由3-DAEM模拟不同加热速率下的数据与实验数据比较

Fig.11 Comparison of experimental data and simulated data at various heating rate with 3-DAEM

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