Effects of torrefaction with flue gas on grindability of corn stalk

doi:10.11949/0438-1157.20221270

Abstract

Abstract:

Grindability is one of the issues that must be considered in the large-scale combustion of biomass in existing coal-fired units. Corn stalk was torrefied in a fixed-bed reactor at various conditions. Aiming at biomass single burning and mixed burning with coal, the effects of torrefied atmosphere, temperature on the grindability of fuel were investigated via the mortar grinder, the automatic particle size sieving instrument, the cellulose analyzer, and the Fourier transform infrared spectroscopy. The results showed that compared with torrefaction with nitrogen atmosphere, torrefaction with flue gas atmosphere improved the grindability of corn stalk to be close to that of typical power coal at lower torrefied temperature. This is because the oxidizing components in the flue gas promote the decomposition of cellulose and hemicellulose. When co-grinding, the coal particles showed the role of grinding aid to improve the grindability of corn stalks. The grindability of mixed samples was approximately or even better than that of coal at higher temperatures or flue gas torrefaction condition.

Key words: torrefaction, grindability, corn stalk, dry flue gas, wet flue gas

摘要：

可磨性是生物质在现有燃煤机组规模化燃烧利用中必须考虑的问题之一。本文基于固定床反应器对玉米秆进行烘焙预处理，针对生物质单烧和与煤混烧两种技术路线，利用臼式研磨仪、全自动粒径筛分仪、纤维素分析仪和傅里叶红外光谱，研究了不同烘焙气氛、温度对燃料可磨性的影响。结果表明，相比于氮气，烟气能够在更低的烘焙温度下使玉米秆可磨性提升至接近于典型动力用煤，主要是由于烟气中的氧化性组分促进了纤维素、半纤维素的分解。当共磨时，煤颗粒表现出助磨的作用提升了玉米秆的可磨性，在较高温度或烟气烘焙条件下，混样的可磨性近似甚至优于煤。

关键词: 烘焙, 可磨性, 玉米秆, 干烟气, 湿烟气

CLC Number:

TK 6

Shaozhuang WANG, Dunxi YU, Jiayi LI, Jingkun HAN, Xin YU, Fangqi LIU. Effects of torrefaction with flue gas on grindability of corn stalk[J]. CIESC Journal, 2023, 74(2): 861-870.

王绍壮, 于敦喜, 李佳忆, 韩京昆, 喻鑫, 刘芳琪. 烟气烘焙对玉米秆可磨性的影响规律研究[J]. 化工学报, 2023, 74(2): 861-870.

Figures/Tables 9

Table 1 Proximate analysis， ultimate analysis and calorific value of samples

样品	工业分析/%（质量，ad）				元素分析/%（质量，ad）					HHV/ (MJ·kg^-1)
样品	M	V	A	FC	C	H	N	S	O^①	HHV/ (MJ·kg^-1)
SY煤	9.17	28.60	11.73	50.49	62.73	4.02	1.33	0.23	10.79	23.58
CS	12.06	62.71	7.52	17.71	42.33	5.35	2.02	0.20	30.53	14.37
N₂-240	3.00	60.02	17.85	19.13	43.92	5.04	1.99	0.10	28.11	15.94
N₂-270	2.92	55.61	19.77	21.71	45.84	4.68	2.01	0.09	24.70	16.97
N₂-300	2.87	37.32	24.18	35.16	54.57	4.08	2.32	0.10	11.87	19.86
DFG-240	2.94	53.51	18.13	25.42	48.15	4.69	2.01	0.09	23.99	18.86
DFG-270	2.87	35.83	22.32	38.77	53.35	3.82	2.35	0.11	15.18	19.20
DFG-300	2.80	30.02	25.24	41.94	55.23	3.45	2.51	0.12	10.65	19.70
WFG-240	2.71	52.12	19.72	22.31	48.55	4.48	1.48	0.05	23.02	18.91
WFG-270	2.19	34.31	24.53	38.96	54.42	3.84	1.81	0.07	13.14	20.52
WFG-300	2.10	27.39	28.02	42.49	56.25	3.62	1.87	0.09	8.06	20.86

Fig.1 The van Krevelen diagram of SY coal, raw and torrefied corn stalk

Fig.2 Mass yield and energy yield of torrefied corn stalk

Fig.3 Particle size distribution of separate grinding coal, raw and torrefied corn stalk[(a), (b), (c) and (d), (e), (f) reaction condition was different torrefied atmosphere and temperature]

Fig.4 Particle size distribution of mixed grinding coal, raw and torrefied corn stalk[(a), (b), (c) and (d), (e), (f) reaction condition was different torrefied atmosphere and temperature]

Fig.5 Particle size distribution of mixed grinding coal, raw and torrefied corn stalk in different mixing ratio[(a), (b), (c)(d), (e)(f) reaction condition was different mixing ratio]

Fig.6 R90 and R200 of grinding coal, raw and torrefied corn stalk[(a)(b), (c)(d) reaction condition was R90 and R200 of samples]

Fig.7 Content of three components of raw and torrefied corn stalk

Fig.8 FTIR result of samples under different torrefied condition

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