Low-temperature pyrolysis (torrefaction) is the first step for combustion. The produced vapors and solids undergo combustion with a different mechanism. Therefore, the composition of the vapors and the functional groups of the produced solids are very important for combustion because they directly influence the diffusion and transfer of oxygen. In this paper, low-temperature pyrolysis of pinewood was studied in a fixed-bed reactor and also by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The effects of temperature, flow rate of nitrogen, and atmosphere were considered to understand the distribution and properties of gas, liquid, and solid products. In situ DRIFTS was used to monitor the evolution of functional group on the solid during low-temperature pyrolysis. The results indicated that temperature was the dominant factor that influenced product formation. Gases released were mainly CO and CO₂, and their yield increased with increasing temperature; noncondensable volatiles contained acetic acids and furans when the temperature was lower than 250 °C, and higher temperatures favored the formation of guaiacols. Characteristic peaks of anhydrides and carboxylic acids showed an irreversible change in the heating and cooling stage, and the change of benzenes can be recovered when cooling to room temperature. This study investigated the evolution of functional groups of biomass during low-temperature pyrolysis, which provided solid feedstock with appropriate chemical structure for combustion.

中文翻译：

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生物质烘焙过程中产生的固体和产物分布的官能团原位演化原理

低温热解（焙干）是燃烧的第一步。产生的蒸气和固体以不同的机理燃烧。因此，蒸气的组成和所产生的固体的官能团对于燃烧非常重要，因为它们直接影响氧的扩散和转移。在本文中，对松木的低温热解进行了固定床反应器研究，并通过原位漫反射红外傅里叶变换光谱法（DRIFTS）进行了研究。考虑温度，氮气流速和气氛的影响，以了解气体，液体和固体产物的分布和性质。原位DRIFTS用于监测低温热解过程中固体上官能团的演变。结果表明，温度是影响产物形成的主要因素。释放的气体主要是一氧化碳和一氧化碳₂，其产率随温度的升高而增加；当温度低于250°C时，不可冷凝的挥发物包含乙酸和呋喃，而较高的温度则有利于愈创木酚的形成。酸酐和羧酸的特征峰在加热和冷却阶段显示出不可逆的变化，冷却至室温时可以回收苯的变化。这项研究调查了低温热解过程中生物质官能团的演变，这为固体原料提供了适合燃烧的化学结构。