采用焦分离方法研究共热解时煤与生物质的相互作用及对焦结构和CO<sub>2</sub>气化反应性的影响

LI Xiao-ming; ZHANG Hong; LIU Meng-jie; ZHI Li-fei; BAI Jin; BAI Zong-qing; LI Wen

采用焦分离方法研究共热解时煤与生物质的相互作用及对焦结构和CO₂气化反应性的影响

李晓明¹,
张红¹,
刘梦杰^{2, 3},
智丽飞¹,
白进^2, ,,
白宗庆²,
李文²

1.
太原科技大学化学与生物工程学院, 山西太原 030024
2.
中国科学院山西煤炭化学研究所煤转化国家重点实验室, 山西太原 030001
3.
中国科学院大学, 北京 100049

基金项目:

Natural Science Foundation of Shanxi Province 201801D121050

Fund Program for the Scientific Activities of Selected Returned Overseas Professionals in Shanxi Province 2017006

Shanxi Scholarship Council of China 2017-086

Natural Science Foundation of China and Xinjiang Province U1703252

详细信息

中图分类号: TQ54
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- 被引次数: 0
出版历程
- 收稿日期: 2020-06-02
- 修回日期: 2020-07-28
- 网络出版日期: 2021-01-23
- 刊出日期: 2020-08-10

Investigation of coal-biomass interaction during co-pyrolysis by char separation and its effect on coal char structure and gasification reactivity with CO₂

1.
School of Chemical and Biological Engineering, Taiyuan University of Science and Technology, Taiyuan 030024, China
2.
State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, China
3.
University of Chinese Academy of Sciences, Beijing 100049, China

Funds:

Natural Science Foundation of Shanxi Province 201801D121050

Fund Program for the Scientific Activities of Selected Returned Overseas Professionals in Shanxi Province 2017006

Shanxi Scholarship Council of China 2017-086

Natural Science Foundation of China and Xinjiang Province U1703252

More Information

Corresponding author: BAI Jin, E-mail: stone@sxicc.ac.cn

摘要

摘要: 煤与生物质的相互作用已被广泛研究。但是，其相互作用机制通常是基于混合焦样的物理化学结构和反应性而提出。在这项工作中，基于不同形状和粒度将无烟煤与生物质共热解后的混合焦分离，然后通过分析分离后煤焦的结构和反应性来揭示煤与生物质相互作用机制。在热解温度为600和900℃条件下，在固定床反应器中制备了混合有不同比例的秸秆（CS）的无烟煤焦样。采用了电感耦合等离子体发射光谱法（ICP-OES）和X射线衍射（XRD）对煤焦的AAEM浓度和微晶结构进行了检测。利用TGA设备分析了分离后的煤焦与CO₂的气化反应性。结果表明，随着掺混比例从0增加到80%，煤焦中活性K和Mg的浓度逐渐增加，并形成更为无序的碳结构。共热解过程中，更多的AAEM种类被混合物中的煤焦通过挥发分-焦相互作用捕获，而不是随生物质挥发分逸出。同时，热解温度的升高引起了K和Na挥发和失活，也导致石墨化度的降低。而且，CS的添加和更低的热解温度均可提高煤焦的气化反应性。此外，在煤焦的碱性指数AI与反应性指数R_0.5之间建立了较好的线性关系（R²=0.9009），表明在煤与生物质共气化过程中，AAEMs对提高煤焦气化反应活性起主导作用。
- 煤与生物质的相互作用 /
- 焦分离 /
- 共热解 /
- 气化反应性 /
- 碱性指数
Abstract: The interaction between coal and biomass has been widely investigated. However, the mechanism is always proposed based on physicochemical structure and reactivity of char mixture. In this work, char mixture after co-pyrolysis of anthracite and biomass was separated based on different shape and size, and then structure and reactivity of the coal char were analyzed to reveal mechanism of coal-biomass interaction. Anthracite char samples with different corn straw (CS) blending ratios were prepared by pyrolysis in a fixed bed reactor at 600 and 900℃. The AAEM concentration and microcrystalline structures of coal char were examined by inductively coupled plasma-optical emission spectrometry (ICP-OES) system and X-ray diffraction (XRD). The gasification reactivity of char sample after separation was analyzed by TGA under CO₂. The results show that concentration of active K and Mg in coal char samples gradually increased and more disordered carbon structure formed as the CS proportion in the blending increased from 0 to 80%. The coal char in the blending captured more AAEM species by volatile-char interactions instead of escaping with volatile from biomass during co-pyrolysis process. Meanwhile, higher pyrolysis temperature led to volatilization and inactivation of K and Na, and also decrease in graphitization degree. Moreover, both addition of CS and low pyrolysis temperature could promote gasification reactivity of coal char sample. Furthermore, a satisfactory linear correlation (R²=0.9009) between alkali index AI and R_0.5 of the char samples was established. This indicated that AAEMs performed the dominate effect to enhance gasification reactivity of coal char during co-gasification of coal and biomass.
- coal-biomass interaction /
- char separation /
- co-pyrolysis /
- gasification reactivity /
- alkali index

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Figure 2 Curve-fitting XRD spectrum for 002 peak of various resulting chars

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Figure 1 XRD patterns of different char samples at a pyrolysis temperature of (a) 600 ℃ and (b) 900 ℃

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Figure 3 Carbon conversion versus reaction time of char samples at a pyrolysis temperature of (a) 600 ℃ and (b) 900 ℃

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Figure 4 Carbon conversion and reaction rate of char samples at a pyrolysis temperature of (a) 600 ℃ and (b) 900 ℃

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Figure 5 (a) Gasification reactivity index and (b) specific reactivity of char samples

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Figure 6 Correlation between R_0.5 and microcrystalline parameters of char samples

(a): R_0.5 and L_{c, a} of all char samples; (b): R_0.5 and N of all char samples; (c): R_0.5 and L_{c, a} of chars where the abnormal sample was removed; (d): R_0.5 and N of chars where the abnormal sample was removed

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Figure 7 Correlation between R_0.5 and AI of char samples

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Table 1 Proximate and ultimate analyses of raw materials

Sample	Proximate analysis w/%				Ultimate analysis w_daf/%				S_{t, d}
Sample	M_ad	A_d	V_daf	FC_d	C	H	O^a	N	S_{t, d}
AC	0.80	25.19	14.00	64.33	89.52	4.02	4.42	1.59	0.34
CS	4.98	5.01	80.58	18.45	48.53	5.64	45.17	0.47	0.19
ad: air dried basis, d: dry-basis, daf: dry ash-free basis, ^a: by difference

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Table 2 Chemical compositions of AC ash and CS ash

Sample	Content w/%
Sample	SiO₂	Al₂O₃	Fe₂O₃	CaO	MgO	SO₃	TiO₂	K₂O	P₂O₅	Na₂O
AC ash	49.11	29.02	12.04	3.91	0.50	2.36	1.91	0.52	0.12	0.51
CS ash	27.01	0.86	0.43	7.95	12.01	7.54	0.05	35.91	5.86	2.39

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Table 3 AAEM concentration in different char samples

Sample	Content w/%
Sample	SiO₂	Al₂O₃	Fe₂O₃	CaO	MgO	TiO₂	SO₃	K₂O	Na₂O	P₂O₅
600AC	50.42	31.19	9.05	3.52	0.43	2.03	2.29	0.46	0.45	0.16
600CS2-AC8	56.62	27.41	3.69	3.59	0.94	1.24	2.21	3.2	0.81	0.29
600CS5-AC5	54.65	25.46	3.66	3.52	1.06	1.14	2.37	7.00	0.82	0.32
600CS8-AC2	54.41	20.92	3.62	3.70	1.78	0.85	2.32	10.93	0.96	0.51
600CS	18.07	0.74	0.64	10.17	15.14	0.03	7.02	39.73	4.59	3.87
900AC	51.67	32.76	8.17	3.04	0.66	2.15	0.49	0.43	0.45	0.18
900CS2-AC8	56.63	28.42	3.96	3.47	1.13	1.28	0.66	3.41	0.74	0.3
900CS5-AC5	54.42	26.38	3.45	3.64	1.66	1.19	1.42	6.88	0.6	0.36
900CS8-AC2	52.45	21.98	2.94	4.16	2.89	0.96	2.5	10.9	0.58	0.64
900CS	26.1	0.81	0.56	10.78	15.62	0.04	4.78	34.08	3.16	4.07

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Table 4 Microcrystalline parameters of studied char samples

Sample	d_{002, P}/nm	L_{C, P}/nm	d_{002, G}/nm	L_{C, G}/nm	X_P	X_G	d_{002, a}/nm	L_{c, a}/nm	N(L_{c, a}/ d_{002, a})
600AC	0.408	2.063	0.347	1.945	24.09	75.91	0.362	1.974	5.453
600CS2-AC8	0.402	2.014	0.348	1.939	24.25	75.75	0.361	1.957	5.421
600CS5-AC5	0.411	2.308	0.351	1.747	12.64	87.36	0.358	1.818	5.078
600CS8-AC2	0.408	1.725	0.351	1.561	13.53	86.47	0.359	1.583	4.409
600CS	0.413	2.020	0.356	1.087	13.77	86.23	0.364	1.215	3.338
900AC	0.397	1.528	0.343	1.732	48.40	51.60	0.369	1.633	4.425
900CS2-AC8	0.399	1.574	0.349	1.562	36.58	63.42	0.367	1.567	4.270
900CS5-AC5	0.400	1.417	0.357	1.351	18.48	81.52	0.365	1.363	3.734
900CS8-AC2	0.391	1.273	0.352	1.253	33.05	66.95	0.365	1.259	3.449
900CS	0.402	1.231	0.356	0.892	28.55	71.45	0.369	0.989	2.680

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