铁基载氧体辅助无烟煤焦富氧燃烧动力学分析

doi:10.11949/0438-1157.20210849

摘要/Abstract

摘要：

流化床铁基载氧体辅助富氧燃烧下传统石英砂床料被铁基载氧体替代，铁基载氧体扩展了传统床料的“热载体”的功能，另承担了“氧载体”的角色，为调节炉内氧分布与煤燃烧过程匹配提供了新思路。本文在热重实验平台探究了10%O₂/90%CO₂气氛下分析纯Fe₂O₃、赤铁矿及钢渣三种铁基载氧体辅助无烟煤焦燃烧特性及动力学。结果表明，相较于纯无烟煤焦燃烧，铁基载氧体辅助燃烧下无烟煤焦的燃烧特性得到显著改善，其中燃烧速率提高29%以上，燃尽温度降低65℃以上，综合燃烧指数提升2倍以上，活化能与指前因子同步增加且表现出“补偿效应”。三种铁基载氧体中分析纯Fe₂O₃对无烟煤焦燃烧特性的改善略优于赤铁矿和钢渣，钢渣可作为流化床铁基载氧体辅助富氧燃烧的床料替代石英砂。

关键词: 煤燃烧, 铁基载氧体, 反应动力学, 二氧化碳捕集, 热重分析

Abstract:

Iron-based oxygen carrier aided oxy-fuel fluidized bed(FB) combustion replaces the traditional inert bed materials with oxygen carrier. The iron-based oxygen carrier expands the function of the “heat carrier” of the traditional bed material, and also assumes the role of the “oxygen carrier”, providing a new idea for adjusting the oxygen distribution in the furnace to match the coal combustion process. The combustion characteristics and kinetics of anthracite coal char and three types of iron-based oxygen carriers (pure Fe₂O₃, hematite, and steel slag) aided combustion of anthracite coal char were investigated in a thermogravimetric analyzer with the temperature range of 30℃ to 1100℃ at a heating of 10℃/min, 15℃/min and 20℃/min under a 10%O₂/90%CO₂ atmosphere. It is observed that the combustion behavior of anthracite coal char is much improved with the aid of the iron-based oxygen carriers, for instance, the combustion rate increases from 2.84%/min to 3.66%/min, 3.83%/min, 3.72%/min, the burnout temperature decreases from 878℃ to 803℃, 802℃, 810℃, and the comprehensive combustion index increases from 3×10^-8%²/(℃³?min²) to 6.39×10^-8%²/(℃³?min²), 6.21×10^-8%²/(℃³?min²), 6.08×10^-8%²/(℃³?min²) for pure Fe₂O₃, hematite and steel slag aided combustion, respectively. The results of kinetics analysis indicate that there is a compensation effect between the activation energy and the pre-exponential factor for the oxygen carriers aided combustion of anthracite coal char. Among three types of iron-based oxygen carriers, pure Fe₂O₃ is slightly better than hematite and steel slag in improving the combustion characteristics of anthracite coal char. Steel slag can be used as a bed material instead of quartz sand for iron-based oxygen carrier aided oxy-fuel fluidized bed combustion.

Key words: coal combustion, iron-based oxygen carrier, reaction kinetics, CO₂ capture, thermogravimetric analysis

中图分类号:

TQ 534

赵旭, 卜昌盛, 王昕晔, 张鑫, 程晓磊, 王乃继, 朴桂林. 铁基载氧体辅助无烟煤焦富氧燃烧动力学分析[J]. 化工学报, 2022, 73(1): 384-392.

Xu ZHAO, Changsheng BU, Xinye WANG, Xin ZHANG, Xiaolei CHENG, Naiji WANG, Guilin PIAO. Kinetics investigation on iron-based oxygen carrier aided oxy-fuel combustion of anthracite char[J]. CIESC Journal, 2022, 73(1): 384-392.

图/表 14

表1 无烟煤工业分析及元素分析

Table 1 Proximate and ultimate analyses of anthracite coal

含量（工业分析）/%(mass, ad)					含量（元素分析）/%(mass, ad)
M	A	V	FC		C	H	O	N	S
1.12	35.01	9.63	54.24		55.26	2.4	4.16	0.83	1.22

表2 无烟煤灰成分分析

Table 2 Ash analysis of anthracite coal

含量/%(mass)
SiO₂	Al₂O₃	Fe₂O₃	CaO	K₂O	MgO	Na₂O
52.41	32.91	4.5	3.87	1.76	0.53	0.15

表3 三种铁基载氧体的主要化学组成成分

Table 3 Chemical composition of three types of iron-based oxygen carriers

载氧体	含量/%(mass)
载氧体	Fe₂O₃	SiO₂	CaO	MgO	Al₂O₃	MnO	P₂O₅	TiO₂	其他
Fe₂O₃	99.9	―	―	―	―	―	―	―	0.1
赤铁矿	85.92	8.17	0.52	1.34	1.53	―	―	―	2.52
钢渣	27.76	13.51	36.15	9.44	3.78	4.76	1.64	1.18	1.78

图1 三种铁基载氧体的X射线衍射（XRD）谱图

Fig.1 X-Ray diffraction patterns of three types of iron-based oxygen carriers

图2 TG-DTG曲线确定着火温度

Fig.2 Determination of the ignition temperature by TG-DTG curves

图3 15℃/min升温速率下无烟煤焦及三种铁基载氧体辅助燃烧下的TG-DTG-DSC曲线

Fig.3 TG-DTG-DSC curves of anthracite coal char and three types of iron-based oxygen carriers aided combustion at the heating rate of 15℃/min

图4 15℃/min升温速率下无烟煤焦及三种铁基载氧体辅助燃烧下的平均与最大燃烧速率

Fig.4 Average and maximum burning rate of anthracite char and three types of iron-based oxygen carriers aided combustion at the heating rate of 15℃/min

表4 15℃/min升温速率下无烟煤焦及三种铁基载氧体辅助燃烧下的燃烧特性参数

Table 4 Combustion characteristics of anthracite char and three iron-based oxygen carriers aided combustion at the heating rate of 15℃/min

样品	t_i/min	T_i/℃	t_b/min	T_b/℃
AC	39.2	617	56.2	878
AC-F	39.09	616	51.5	803
AC-H	39.26	619	51.4	802
AC-SS	39.24	619	51.9	810

图5 铁基载氧体辅助无烟煤焦富氧燃烧下氧传递机制示意图

Fig.5 Schematic diagram of the mechanism of the oxygen transfer in iron-based oxygen aided oxy-fuel combustion of anthracite coal char

图6 15℃/min升温速率下无烟煤焦及三种铁基载氧体辅助燃烧下的综合燃烧指数

Fig.6 Comprehensive combustion index of anthracite coal char and three types of iron-based oxygen carriers aided combustion at the heating rate of 15℃/min

图7 无烟煤焦及三种铁基载氧体辅助燃烧下KAS法计算动力学参数拟合图

Fig.7 Fitting curves of the KAS method for anthracite char and three types of iron-based oxygen carriers aided combustion

表5 无烟煤焦及三种铁基载氧体辅助燃烧下的反应动力学活化能和指前因子

Table 5 Activation energy and pre-exponential factor of anthracite char and three types of iron-based oxygen carriers aided combustion

转化率α	AC			AC-F			AC-H			AC-SS
转化率α	E/(kJ/mol)	A/min^-1	R²	E/(kJ/mol)	A/min^-1	R²	E/(kJ/mol)	A/min^-1	R²	E/(kJ/mol)	A/min^-1	R²
0.2	82.84	8.45×10³	0.99847	111.77	5.96×10⁵	0.99999	95.07	5.27×10⁴	0.99442	92.90	3.88×10⁴	0.99015
0.3	74.94	1.97×10³	0.99794	100.46	9.14×10⁴	0.99994	89.67	1.86×10⁴	0.99727	91.05	2.23×10⁴	0.99032
0.4	66.11	442.17	0.99817	91.23	2.03×10⁴	0.99988	84.29	7.04×10³	0.99776	86.99	1.00×10⁴	0.98957
0.5	58.24	117.99	0.99811	82.67	5.11×10³	0.99992	78.78	2.70×10³	0.99777	81.88	4.02×10³	0.98765
0.6	51.24	36.56	0.99868	75.44	1.57×10³	0.99993	74.17	1.20×10³	0.99787	77.28	1.76×10³	0.98532
0.7	44.80	12.47	0.99915	69.60	591.09	0.99987	70.69	621.41	0.99831	72.80	792.38	0.98131
0.8	39.31	4.89	0.99962	64.45	244.07	0.99975	67.69	346.58	0.99896	68.32	359.50	0.97437
0.9	34.94	2.25	0.99998	61.29	128.66	0.99905	67.09	260.15	0.99986	64.39	173.31	0.96528
平均值	56.55	1.38×10³	―	82.11	8.94×10⁴	―	78.43	1.04×10⁴	―	79.45	9.79×10³	―

图8 无烟煤焦及三种铁基载氧体辅助燃烧下活化能E与指前因子A间的补偿效应

Fig.8 Fitting curves of compensation effect between the activation energy E and the pre-exponential factor A for anthracite char and three types of iron-based oxygen carriers aided combustion

表6 无烟煤焦及三种铁基载氧体辅助燃烧的补偿因子及线性相关性系数

Table 6 Compensation factors and fitting coefficients for anthracite char and three iron-based oxygen carriers aided combustion

样品	a	b	R²
AC	0.170	5.13	0.999
AC-F	0.166	5.19	0.999
AC-H	0.185	6.68	0.998
AC-SS	0.185	6.81	0.998

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