木本植物叶片热值测试和分析

目的]本研究致力于探讨木本植物叶片的热值分布规律及其与化学组成的内在联系,相应为科学评估其火灾危险性以及能源利用提供基础数据和工程计算方法。方法]选取27种不同科属的木本植物叶样,开展工业分析、元素分析及热值测试。结果]表明,植物叶样的干基高位热值HHVd在17.48~24.01 MJ·kg-1之间变化,平均值为21.16 MJ·kg-1。同科属的植物叶片热值一般较为接近,样品自身灰分含量对干基高位热值的影响可以忽略。分析证实,干基高位热值的变化与样品挥发分和固定碳含量分布密切相关。植物叶片中挥发分和固定碳含量比值随着其化学组成中氧碳摩尔比增加而增大,并且固定碳在可燃组分中的相对含量反映样品木质素含量水平。结论]样品氧碳摩尔比和氢碳摩尔比的增加意味着其木质素含量降低,使得其干基高位热值减小。对于所涉木本植物叶片来说,其干基高位热值可以分别由经验式HHVd=0.189 3VMd+0.369 5FCd和HHVd=0.447 8Cd+1.4072Hd-0.283 7Od准确计算获得,还可以据此迅速确定样品收到基热值。

Heating Value of Woody Plant Foliage and Its Correlations with the Property Parameters

Objective] The present work aims to explore the variation trends of the heating values of woody plant foliage and its relation to the chemical composition. Method] 27 woody plant species belonging to 20 families including coniferous, broadleaf trees and shrubs, were adopted and the measurements were conducted through the proximate analysis, ultimate analysis and the detection of the heating values. Result] Test results of the leaf samples indicate that their higher heating values on air-dried basis (HHV_d) vary in a broad range from 17.48 to 24.01 MJ·kg^-1, with the average value of 21.16 MJ·kg^-1. The values of the HHV_d are very close for the samples from the same family, and the ash content on air-dried basis plays negligible role in altering the magnitudes of the HHV_d for the species studied. Further analysis indicates that the HHV_d closely relies on the content ratio of volatile matter to the fix carbon (VM_d/FC_d). The ratio of VM_d/FC_d increases with the increase in the atomic O/C ratio of the leaf samples, whereas the content ratios of fix carbon to the combustible substances correspond to the levels of the lignin content stored in plant foliage. Conclusion] The increases in the atomic O/C ratio and atomic H/C ratio imply a decrease in the lignin content stored, which lead to a reduction in a higher heating value on air-dried basis. It is found that the higher heating values of these leaf samples on air-dried basis can be precisely determined by the empirical formulas proposed as the following:HHV_d=0.189 3VM_d+0.369 5FC_d and HHV_d=0.447 8C_d+1.407 2H_d-0.283 7O_d, which provide the basis for quick evaluation of the heating values of the leaf samples on the received basis.