生物质连续式水热预处理及固相产物热解特性研究

刘天龙; 李琦; 李中宏; 杨沛艳; 庞新博; 黄鑫; 赵小燕; 曹景沛

doi:10.19906/j.cnki.JFCT.2023082

生物质连续式水热预处理及固相产物热解特性研究

doi: 10.19906/j.cnki.JFCT.2023082

刘天龙^1, ,,
李琦^1,,
李中宏^1,,
杨沛艳^1,,
庞新博¹,
黄鑫^2,,
赵小燕^1,,
曹景沛^1, ,

1.
中国矿业大学江苏省碳资源精细化利用工程研究中心, 江苏徐州 221116
2.
重庆大学低品位能源利用技术及系统教育部重点实验室, 重庆 400044

基金项目: 国家自然科学基金(22108294)，中国博士后科学基金（2021M693412）和江苏省高校优势学科和陕煤-秦岭基础科学研究五年行动计划资助项目资助

详细信息

通讯作者:
E-mail: tianlong.liu@cumt.edu.cn

caojingpei@cumt.edu.cn

中图分类号: TQ35
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- 被引次数: 0
出版历程
- 收稿日期: 2023-12-04
- 修回日期: 2023-12-13
- 录用日期: 2023-12-13
- 网络出版日期: 2024-01-18

Hydrothermal flowthrough pretreatment of biomass and pyrolysis characteristics of residual solid

LIU Tianlong^{1
, ,},
LI Qi^1
,,
LI Zhonghong^1
,,
YANG Peiyan^1
,,
PANG Xinbo¹,
HUANG Xin^2
,,
ZHAO Xiaoyan^1
,,
Cao Jingpei^{1
, ,}

1.
Jiangsu Province Engineering Research Center of Fine Utilization of Carbon Resources, China University of Mining & Technology, Xuzhou 221116, China
2.
Key Laboratory of Low-grade Energy Utilization Technologies & Systems, Chongqing University, Chongqing 400044, China

Funds: The project was supported by the National Natural Science Foundation of China (22108294), the China Postdoctoral Science Foundation (2021M693412), the Priority Academic Program Development of Jiangsu Higher Education Institutions and Shccig-Qinling Program.

摘要

摘要: 生物质复杂的多组分体系和致密交联的化学结构是制约其高值化利用的关键，实现木质纤维组分预分离对生物质分级转化具有重要意义。实验采用连续式水热法预处理稻壳，考察了水热温度和流量对稻壳分解速率以及固相产物化学组成与热解特性的影响。结果表明，稻壳的水热分解符合表面化学反应过程控制的未反应收缩核模型，预处理在180 ℃下能脱除稻壳95%的碱及碱土金属、92%的半纤维素和59%的木质素，极大保留了纤维素组分，这使得稻壳热解产物中以左旋葡聚糖为主的脱水糖的相对含量从9.9%提高至48.2%。
- 稻壳 /
- 水热预处理 /
- 脱水糖 /
- 热解
Abstract: The sophisticated multi-components and densed cross-link chemical structures of lignocellulosic biomass are important bottlenecks restricting its value-added utilization. The pre-fractionation of lignocellulose components is of great significance for the fractional conversion of biomass. The present study subjected rice husk (RH) to hydrothermal treatment in a flowthrough mode and investigated the effects of hydrothermal temperature and water flowrate on the decomposition rate of RH, chemical components of residual solids and their pyrolysis characteristics. It is shown that the decomposition of RH under hydrothermal conditions conformed well to the unreacted shrinking core model with phase boundary reactions rate-controlling. The pretreatment at 180 ℃ removed 95% alkali and alkaline-earth metallic species, 92% hemicellulose and 59% lignin from RH and selectively retained most of the cellulose components. As a result of the pretreatment, the relative content of anhydrosugar (mainly levoglucosan) from pyrolysis of RH at a curie-point temperature of 445 ℃ was increased from 9.9% up to 48.2%.
- rice husk /
- hydrothermal pretreatment /
- anhydrosugar /
- pyrolysis

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图 1 连续式水热预处理装置示意图

Figure 1 Schematic diagram of the experimental setup for hydrothermal flowthrough pretreatment

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图 2 不同水热预处理（a）流量和（b）温度下x_TOC随时间的变化

Figure 2 Temporal changes in x_TOC as a function of (a) flowrate and (b) temperature during hydrothermal pretreatment (x_TOC is determined by the amount of TOC in the liquid divided by that of feedstock)

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图 3 液相产物的（a）单糖收率和（b）每10 min的单糖和低聚糖收率、x_TOC和pH值

Figure 3 Results of (a) overall yield of saccharides of liquid product and (b) changes in yields of mono- and oligo-saccharides, x_TOC and pH values of liquid effluent collected in each 10 min (RH was pretreated at 180 ℃ and 5 mL/min water flow, the liquid product was subjected to hydrolysis for determining the overall yield of saccharides)

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图 4 稻壳水热预处理前后的扫描电子显微镜表征

Figure 4 Scanning electron microscope characterization of (a) RH and (b) treated RH (Conditions for pretreatment: reaction at 180 ℃ for 150 min and 5 mL/min water flow)

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图 5 不同温度下1−(1−x_TOC)^1/3与时间的关系（a）和Arrhenius曲线（b）

Figure 5 Plots of (a) 1−(1−x_TOC)^1/3 against time under different temperatures and (b) lnk against 1/T based on the Arrhenius equation

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图 6 水热预处理温度、时间和流量对固相产物收率的影响

Figure 6 Effects of temperature, time and flowrate on the yield of residual solid during hydrothermal pretreatment (An asterisk represents the yield of residual solid by a batch mode under reaction conditions of 180 ℃ for 1 h and RH/water mass ratio of 1∶40)

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图 7 稻壳及固相产物的热重（TG）和微分热重（DTG）曲线

Figure 7 Thermogravimetric (TG) and differential thermogravimetric (DTG) profiles of RH and residual solids (Pretreatment conditions for a flow mode are 180−190 ℃ for 150 min and 5 mL/min water flow and for a batch mode are 180 ℃ for 60 min and RH/water mass ratio of 1∶40. x represents a mass-based conversion of the sample. DTG profile was deconvoluted into three peaks that were assumed to occur from the pyrolysis of hemicellulose, cellulose, and lignin)

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图 8 稻壳及固相产物的CPy-GC/MS总离子流色谱图

Figure 8 Total ion chromatograms from CPy-GC/MS tests of RH and residual solids

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图 9 稻壳及固相产物热解产物的（a）峰面积和（b）相对含量

Figure 9 Peak area (a) and relative content (b) of products from curie-point pyrolysis of RH and residual solids

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图 11 稻壳及固相产物的碱及碱土金属含量

Figure 11 Contents of alkali and alkaline-earth metallic species in RH and residual solids

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图 10 左旋葡聚糖形成与转化反应路径^[23]

Figure 10 Mechanism of formation and conversion of levoglucosan (adapted from Ref. 23) (LGA, levoglucosan; DGP, 1,4:3,6-dianhydro-β-D-glucopyranose; AGF, 1,6-anhydro-β-D-glucofuranose; and LGO, levoglucosenone)

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图 12 固相产物灰分的XRD谱图

Figure 12 XRD patterns of ash of residual solid (A photograph of ashed sample for XRD analysis is presented in the figure and the solid was prepared under conditions of 180 ℃ for 150 min and 5 mL/min water flow)

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表 1 稻壳及固相产物的工业分析、元素分析和热值

Table 1 Proximate and ultimate analyses and higher heating values of RH and residual solids

Sample^a	Proximate analysis w_dry/%			Ultimate analysis w_daf/%^b				Atomic ratio		HHV^g/ (MJ·kg⁻¹)
Sample^a	A	V^d	FC^e	C	H	N	O^f	H/C	O/C	HHV^g/ (MJ·kg⁻¹)
RH	19.9	60.6	19.5	49.0	6.4	0.5	44.1	1.5483	0.6752	14.3
RH-160	19.0	66.2	14.8	50.2	6.2	0.4	43.3	1.4734	0.6475	14.7
RH-170	16.8	74.7	8.5	51.1	6.0	0.4	42.5	1.3963	0.6239	15.2
RH-180	11.9	78.9	9.2	54.3	5.4	0.3	40.1	1.1767	0.5542	16.6
RH-190	9.0	84.2	6.8	55.2	5.1	0.3	39.5	1.0967	0.5372	17.2
RH-180^c	22.1	65.3	12.6	55.5	5.9	0.4	38.2	1.2689	0.5175	15.9
^a: RH-x samples represent the residual solid, where x is the temperature for hydrothermal pretreatment; ^b: daf is the abbreviation of dry-ash-free; ^c: residual solid prepared by a batch mode under conditions of 180 ℃ for 1 h and 1∶40 mass ratio (RH/water); ^d: volatile matter; ^d: fixed carbon; ^e: calculated by difference; ^f: higher heating value, calculated by Dulong’s formula: Q = 0.3383C+1.442(H−0.125O), where C, H, and O are the contents of carbon, hydrogen, and oxygen, respectively.

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表 2 稻壳及固相产物的化学组成分析

Table 2 Chemical components of RH and residual solids

Pretreatment	Composition w_sample/%					Composition w_RH/%
Pretreatment	ash	hemi.	cel.	lig.	extract.	ash	hemi.	cel.	lig.	extract.
RH	19.9	19.3	31.8	24.2	4.8	19.9	19.3	31.8	24.2	4.8
Flow mode	11.9	3.3	63.5	21.3	<0.1	5.5	1.5	29.4	9.9	<0.1
Batch mode	22.1	7.2	43.2	26.5	1.1	13.8	4.5	27.0	16.5	0.7
Hemi, cel, lig and extract are abbreviations of hemicellulose, cellulose, lignin and extractives, respectively. Pretreatment conditions for a flow mode are 180 ℃ for 150 min and 5 mL/min water flow and for a batch mode are 180 ℃ for 60 min and 1∶40 of RH/water mass ratio.

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表 3 稻壳灰分SiO₂纯度和比表面积分析和对比

Table 3 Results of SiO₂ purity and specific surface area of RH ashes

Sample no.	SiO₂ purity^a /%	Surface area^b /(m²·g⁻¹)	Method	Ref.
1	91.17	−	raw rice husk	this study
2	99.70	216	flow mode, 180 ℃
3	98.91	207	batch mode, 180 ℃
4	99.86	218	3% HCl, room temperature
5	N.A.	164	10% HCl, 100 ℃	[26]
6	96.89	N.A.	water rinsing, room temperature	[27]
7	99.80	N.A.	5% HCl refluxing, 130 ℃
8	99.52	N.A.	ion liquid, room temperature
9	95.77	116	raw rice husk	[28]
10	99.58	218	0.5 mol/L HCl, 60 ℃
11	99.08	208	0.5 mol/L H₂SO₄, 60 ℃
12	91.25	21	raw rice husk	[29]
13	97.94	134	hydrothermo-baric treatment, 300 ℃	[29]
14	99.77	N.A.	5% citric acid, 80 ℃	[30]
^a: by X-ray fluorescence spectrometry; ^b: calculated by the Brunauer-Emmett-Taller method; N.A., not available.

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