牛文娟, 黄金芝, 钟菲, 张诗麟, 孟令凯, 朱彤, 袁巧霞. 不同水热条件对秸秆微波水热碳化产物组成和结构特性影响[J]. 农业工程学报, 2019, 35(10): 205-213. DOI: 10.11975/j.issn.1002-6819.2019.10.026
    引用本文: 牛文娟, 黄金芝, 钟菲, 张诗麟, 孟令凯, 朱彤, 袁巧霞. 不同水热条件对秸秆微波水热碳化产物组成和结构特性影响[J]. 农业工程学报, 2019, 35(10): 205-213. DOI: 10.11975/j.issn.1002-6819.2019.10.026
    Niu Wenjuan, Huang Jinzhi, Zhong Fei, Zhang Shilin, Meng Lingkai, Zhu Tong, Yuan Qiaoxia. Effects of different hydrothermal conditions on compositions and structural characteristics of microwave-assisted hydrothermal carbonization products from crop residues[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2019, 35(10): 205-213. DOI: 10.11975/j.issn.1002-6819.2019.10.026
    Citation: Niu Wenjuan, Huang Jinzhi, Zhong Fei, Zhang Shilin, Meng Lingkai, Zhu Tong, Yuan Qiaoxia. Effects of different hydrothermal conditions on compositions and structural characteristics of microwave-assisted hydrothermal carbonization products from crop residues[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2019, 35(10): 205-213. DOI: 10.11975/j.issn.1002-6819.2019.10.026

    不同水热条件对秸秆微波水热碳化产物组成和结构特性影响

    Effects of different hydrothermal conditions on compositions and structural characteristics of microwave-assisted hydrothermal carbonization products from crop residues

    • 摘要: 为了解秸秆微波水热碳化过程中产物形成机制及其理化结构演变规律,该文采用控制变量法进行了单因素试验设计,研究了水热温度、停留时间、催化剂和原料种类对秸秆微波水热产物组成和结构特性的影响。结果表明,随着水热温度升高和停留时间延长,液相产物的pH值先降低后增加,最低值为3.13,电导率和PO43(-P质量浓度先增加后下降,最大值分别为9.38 mS/cm和308 mg/L,NH4+-N质量浓度增加,260 ℃最大值为155 mg/L,而水热焦的产率、H/C和O/C下降,固定碳、C、高位热值增加。高温和长停留时间使水热焦生成较多纳米碳微球结构,且使其O-H键先增多后减少。高温和K2CO3使水热焦的芳香烃结构和C=O、C-O含氧官能团增强,而长停留时间使其先增强后减弱。高温和长停留时间使水热焦的比表面积、孔体积和孔径均先增加后降低,而K2CO3使水热焦的纳米碳微球和比表面积增加,最大比表面积为10.975 9 m2/g。玉米秆、水稻秆和油菜秆水热焦的纳米碳微球结构最明显,棉花秆水热焦的比表面积和孔体积最大。

       

      Abstract: Abstract: It is important to fully understand the formation mechanism and the physicochemical characteristics evolution of the microwave-assisted hydrothermal products from crop residues, which is also of great significance for high added value utilization of crop residues and quality control of hydrothermal products. The control variable method was used to design the single factor experiment. The effects of hydrothermal temperature, retention time, catalyst and crop residue types on the compositions and structural characteristics of the microwave-assisted hydrothermal products from rice straw, corn stover, rape stalk and cotton stalk were studied. The results showed that with the increase of hydrothermal temperature and retention time, the pH value of the liquid products decreased first and then increased, reaching the lowest value of 3.13, while the electrical conductivity and PO43(-P concentration of the liquid products increased first and then decreased, and the NH4+-N concentration of the liquid products increased and reached the highest concentration of 155 mg/L at 260 ℃. With the increase of hydrothermal temperature and retention time, the yields, H/C and O/C of hydrothermal cokes decreased, while the fixed carbon, C and higher heating value (HHV) of hydrothermal cokes increased. The addition of alkaline catalyst of K2CO3 decreased the C content, HHV value, carbon conversion rate and energy conversion rate of hydrothermal cokes from crop residues, while increased the O/C content of hydrothermal cokes. The carbon conversion rates and energy conversion rates of hydrothermal cokes from crop residue can reach 56.65%-98.13% and 58.22%-92.19%, respectively. With the increase of hydrothermal temperature and retention time, the fragmentation degree in the surface and interior of hydrothermal cokes of the four crop residues were getting more seriously, and the surface and interior of hydrothermal cokes exhibited more nano carbon microsphere structures, while the O-H bond of the hydrothermal cokes of the four crop residues increased first and then decreased. Higher hydrothermal temperature increased the aromatic hydrocarbon structures of C=C, C-H, C-C and active oxygen functional groups of C=O and C-O of hydrothermal cokes, while the aromatic hydrocarbon structures and active oxygen functional groups of hydrothermal cokes increased first and then decreased with the increase of retention time. With the increase of hydrothermal temperature and retention time, the specific surface area, pore volume and pore diameter of hydrothermal cokes from crop residue increased first and then decreased. The addition of alkaline catalyst of K2CO3 increased the aromatic hydrocarbon structures, active oxygen functional groups, specific surface area, pore volume and pore diameter of hydrothermal cokes from crop residue. Comparing the four types of hydrothermal cokes from crop residues, the yields of hydrothermal cokes from cotton stalk and rice straw were higher, and the contents of C, H, volatile matter and the higher heating value of hydrothermal coke from rape stalk were the highest. The nano carbon microsphere structures of hydrothermal cokes from corn stover, rice straw and rape stalk were relatively obvious. Comparing the hydrothermal cokes from the other three types of crop residues, the specific surface area and pore volume of hydrothermal coke from cotton stalk were the largest, while the pore diameter was the smallest.

       

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