Release and transformation characteristics of chlorine, sulfur and AAEMs during cornstalk torrefaction

doi:10.11949/0438-1157.20200628

Abstract

Abstract:

A fixed-bed tube furnace was used to study the release and migration and transformation of chlorine, sulfur, alkali and alkaline earth metals (AAEMs) in corn stalks at different baking temperatures. It was found that the release ratios of chlorine and sulfur, which increased continuously with temperature in the range of 220—300℃, were 10%—40% and 27%—60%, respectively. However, the absolute content of chlorine increased after torrefaction with the decreased ratio of alkali metal chloride and increased ratio of organochlorine (C—Cl). The absolute content of sulfur decreased significantly after torrefaction, meeting the sulfur requirement of commercial biomass pellets. In addition, the proportion of acid-soluble and insoluble Ca and Mg in hydrochloric acid also increased to a certain extent.

Key words: cornstalk, torrefaction, inorganic species, alkali and alkaline earth metallic species, release, migration and transformation

摘要：

利用固定床管式炉研究了玉米秆中氯、硫、碱及碱土金属（AAEMs）在不同烘焙温度下的释放和迁徙转化规律。研究发现氯、硫的释放率随烘焙温度升高呈递增趋势，在220~300℃范围内氯和硫的释放率分别为10%~40%和27%~60%。烘焙后样品中氯的绝对含量相比原样有所增加，并且以碱金属氯化物形式存在的无机氯占比减少，有机氯占比增加；硫的绝对含量显著降低，烘焙后可达到Ⅰ级成型燃料中硫含量要求。AAEMs在烘焙过程中释放率均较低，但赋存形态发生一定变化，主要表现为水溶性AAEMs含量降低，有机结合态AAEMs含量增加，此外盐酸酸溶性和不溶性Ca、Mg的占比也有一定程度增加。

关键词: 玉米秆, 烘焙, 无机组分, 碱及碱土金属, 释放, 迁徙转化

CLC Number:

TK 6

JIANG Hao,ZHU Youjian,LIU Heng,SHAO Jing'ai,CHENG Wei,YANG Peng,WU Guihao,YANG Haiping,CHEN Hanping. Release and transformation characteristics of chlorine, sulfur and AAEMs during cornstalk torrefaction[J]. CIESC Journal, 2020, 71(12): 5785-5792.

蒋好,朱有健,刘恒,邵敬爱,成伟,杨鹏,吴贵豪,杨海平,陈汉平. 秸秆烘焙过程氯、硫释放及AAEMs迁徙转化特性研究[J]. 化工学报, 2020, 71(12): 5785-5792.

Figures/Tables 8

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样品	工业分析^①/%(mass)			元素分析^①/%(mass)					O/C 原子比	H/C 原子比	LHV/ (MJ/kg)	固体产率/%	能量产率/%
样品	灰分	挥发分	固定碳	C	H	O^②	N	S	O/C 原子比	H/C 原子比	LHV/ (MJ/kg)	固体产率/%	能量产率/%
CS	8.69	73.87	17.44	43.06	5.72	41.67	0.74	0.123	0.73	1.58	16.17	—	—
TCS₂₂₀	9.47	71.53	19.00	44.67	5.56	39.16	1.04	0.097	0.66	1.48	16.54	93.02	95.15
TCS₂₆₀	10.55	62.59	26.86	46.86	5.32	36.14	1.05	0.084	0.58	1.35	17.02	79.23	83.39
TCS₃₀₀	11.29	45.45	43.26	55.42	4.61	27.42	1.16	0.098	0.37	0.99	19.08	49.60	58.53

样品	工业分析^①/%(mass)			元素分析^①/%(mass)					O/C 原子比	H/C 原子比	LHV/ (MJ/kg)	固体产率/%	能量产率/%
样品	灰分	挥发分	固定碳	C	H	O^②	N	S	O/C 原子比	H/C 原子比	LHV/ (MJ/kg)	固体产率/%	能量产率/%
CS	8.69	73.87	17.44	43.06	5.72	41.67	0.74	0.123	0.73	1.58	16.17	—	—
TCS₂₂₀	9.47	71.53	19.00	44.67	5.56	39.16	1.04	0.097	0.66	1.48	16.54	93.02	95.15
TCS₂₆₀	10.55	62.59	26.86	46.86	5.32	36.14	1.05	0.084	0.58	1.35	17.02	79.23	83.39
TCS₃₀₀	11.29	45.45	43.26	55.42	4.61	27.42	1.16	0.098	0.37	0.99	19.08	49.60	58.53

氧化物	含量/%(mass)
Na₂O	3.56
MgO	8.09
Al₂O₃	3.23
SiO₂	26.79
P₂O₅	4.57
SO₃	8.61
K₂O	35.96
CaO	8.4
MnO	0.14
Fe₂O₃	0.65

氧化物	含量/%(mass)
Na₂O	3.56
MgO	8.09
Al₂O₃	3.23
SiO₂	26.79
P₂O₅	4.57
SO₃	8.61
K₂O	35.96
CaO	8.4
MnO	0.14
Fe₂O₃	0.65

元素	含量/(mg/g)		释放率/%
元素	玉米秆	300℃烘焙玉米秆	释放率/%
K	14.32	25.77	10.71
Na	0.33	0.58	12.82
Ca	4.29	7.44	13.92
Mg	3.67	6.46	12.79