长白松热解特性及热解动力学研究

doi:10.3969/j.issn.1673-5854.2022.06.004

摘要/Abstract

摘要：

为获取长白松的热解特性，预防森林火灾发生，以长白松的树枝、球果、树皮和松针作为研究对象进行热解过程分析，并采用Coats-Redfern法进行热解动力学分析，以球果为研究对象探究各种因素对长白松热解的影响。实验结果表明：4种材料的热解过程均可分为4个阶段，其中主要失重阶段的质量损失率为60%左右。升温速率越大，热解越不充分，并且存在热滞后现象，25℃/min时质量损失率最小（80.34%）；粒径大小对TG、DTG曲线影响较小，粒径越小，内外部受热更均匀，因此0.20 mm粒径的材料质量损失率最大（91.18%）；氮气气氛下主要失重阶段有一个失重峰，而在高纯空气气氛下有两个失重峰，且长白松球果在高纯空气中热解时间更长，热解更充分，促进作用更强，质量损失率为98.14%。热解动力学分析结果显示：4种材料的最佳机理函数为"三维扩散"，活化能最大的是树枝（157.04 kJ/mol），最小的是松针（98.19 kJ/mol），球果的活化能为148.08 kJ/mol，树皮的活化能为115.04 kJ/mol，因此，要格外注意对松针和树皮的防火工作。

关键词: 长白松, 热重分析, 动力学分析

Abstract:

In order to obtain the pyrolysis characteristics of Pinus Sylvestriformis and prevent forest fires, the pyrolysis process was carried out using the branches, cones, bark, and pine needles of P. Syluestriformis. The pyrolysis kinetics analysis was conducted by the Coats-Redfern method, and the influence of various factors on the pyrolysis of P. sylvestriformis was explored using the cones as the research object. Experimental results showed that the pyrolysis process of the four materials could be divided into four stages, where the mass loss rate of the main weightless stage occupied about 60%. The higher heating rate, the less sufficient pyrolysis. There was a thermal hysteresis phenomenon, where the minimum mass loss rate was 80.34% at 25℃/min. Particle size had little influence on TG and DTG curves. The smaller particle size, the more uniform internal and external heating, and the maximum mass loss rate of the materials with a particle size of 0.20 mm was 91.18%. There was a peak of weight loss in the main weight loss stage under nitrogen atmosphere, and two peaks of weight loss under air atmosphere. The pyrolysis time of P. sylvestriformis cones in high pure air was longer, the pyrolysis was more complete, and the promotion effect was stronger, with the weight loss rate of 98.14%. The results of pyrolysis kinetic analysis showed that the optimal mechanism function of the four materials was "three-dimensional diffusion". The branches had the highest activation energy(157.04 kJ/mol), and the lowest value was found in pine needles(98.19 kJ/mol). In addition, the activation energies for the cones and bark were 148.08 and 115.04 kJ/mol, respectively. Therefore, special attention should be paid to the fire prevention of pine needles and bark.

Key words: Pinus sylvestriformis, thermogravimetric analysis, dynamic analysis

中图分类号:

TQ35
TK6

杨跃三, 薛伟, 张华超. 长白松热解特性及热解动力学研究[J]. 生物质化学工程, 2022, 56(6): 24-30.

Yuesan YANG, Wei XUE, Huachao ZHANG. Thermogravimetric Characteristics and Dynamic Analysis of Pinus Sylvestriformis[J]. Biomass Chemical Engineering, 2022, 56(6): 24-30.

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原料 raw material	失水阶段 dehydration stage		微失重阶段 micro weightless stage		主要失重阶段 main weightless stage		炭化阶段 charring stage		总质量损失率/% total mass loss
原料 raw material	温度/℃ temp.	质量损失率/% mass loss rate	温度/℃ temp.	质量损失率/% mass loss rate	温度/℃ temp.	质量损失率/% mass loss rate	温度/℃ temp.	质量损失率/% mass loss rate	总质量损失率/% total mass loss
球果cone	20.0~88.5	7.76	88.5~212.6	3.10	212.6~407.3	60.47	407.3~800.0	11.89	83.22
树皮bark	20.0~99.5	5.70	99.5~204.0	2.97	204.0~446.8	54.69	446.8~800.0	12.27	75.63
树枝trunk	20.0~92.4	5.55	92.4~212.9	1.54	212.9~406.7	66.22	406.7~800.0	10.66	83.97
松针pine needle	20.0~102.7	5.16	102.7~182.8	2.34	182.8~459.0	70.02	459.0~800.0	7.41	84.93

升温速率/ (℃·min^-1) heating rate	失水阶段 dehydration stage		微失重阶段 micro weightless stage		主要失重阶段 main weightless stage		炭化阶段 charring stage		总质量损失率/% total mass loss rate
升温速率/ (℃·min^-1) heating rate	温度/℃ temp.	质量损失率/% mass loss rate	温度/℃ temp.	质量损失率/% mass loss rate	温度/℃ temp.	质量损失率/% mass loss rate	温度/℃ temp.	质量损失率/% mass loss rate	总质量损失率/% total mass loss rate
10	20.0~76.4	8.50	76.4~201.7	4.29	201.7~397.2	63.56	397.2~800.0	14.42	90.77
15	20.0~71.5	7.64	71.5~200.7	3.69	200.7~391.1	58.33	391.1~800.0	14.24	83.89
20	20.0~88.5	7.76	88.5~212.6	3.10	212.6~407.3	60.47	407.3~800.0	11.89	83.22
25	20.0~94.0	8.18	94.0~216.9	2.83	216.9~412.0	58.17	412.0~800.0	11.16	80.34

粒径/mm particle size	失水阶段 dehydration stage		微失重阶段 micro weightless stage		主要失重阶段 main weightless stage		炭化阶段 charring stage		总质量损失率/% total mass loss rate
粒径/mm particle size	温度/℃ temp.	质量损失率/% mass loss rate	温度/℃ temp.	质量损失率/% mass loss rate	温度/℃ temp.	质量损失率/% mass loss rate	温度/℃ temp.	质量损失率/% mass loss rate	总质量损失率/% total mass loss rate
0.45	20.0~90.2	8.23	90.2~218.0	3.18	218.0~403.9	60.26	403.9~800.0	11.87	83.54
0.30	20.0~88.5	7.76	88.5~212.6	3.10	212.6~407.3	60.47	407.3~800.0	11.89	83.22
0.20	20.0~90.6	8.88	90.6~215.1	3.77	215.1~409.2	66.75	409.2~800.0	11.77	91.18

气氛 atmosphere	失水阶段 dehydration stage		微失重阶段 micro weightless stage		主要失重阶段 main weightless stage		炭化阶段 charring stage		总质量损失率/% total mass loss rate
气氛 atmosphere	温度/℃ temp.	质量损失率/% mass loss rate	温度/℃ temp.	质量损失率/% mass loss rate	温度/℃ temp.	质量损失率/% mass loss rate	温度/℃ temp.	质量损失率/% mass loss rate	总质量损失率/% total mass loss rate
空气pure air	20.0~95.4	6.97	95.4~224.3	3.23	224.3~517.8	85.13	517.8~800.0	2.81	98.14
氮气nitrogen	20.0~88.5	7.76	88.5~212.6	3.10	212.6~407.3	60.47	407.3~800.0	11.89	83.22

机理mechanism	G(α)
一维扩散one-dimensional diffusion	α²
二维扩散two-dimensional diffusion	α+(1-α)ln(1-α)
三维扩散three-dimensional diffusion	[1-(1-α)^1/3]²
随机单核成长Random mononuclear growth	-ln(1-α)
n=1/2	α^1/2
n=1/3	α^1/3
相边界反应(圆柱对称收缩) contracting cylinder(cylindrical)	1-(1-α)^1/2
相边界反应(球形对称收缩) contracting cylinder	1-(1-α)^1/3
n=2	1-(1-α)²
n=3	1-(1-α)³