In this paper, a new approach to the torrefaction process is proposed. The approach consists of obtaining a single torrefied product with an energy value and standardized physicochemical properties in the range of sub-bituminous coal from two types of waste: the cotton stalk and vine pruning. A multifactorial design was used to investigate the effect of temperature, time, and reaction atmosphere on the properties of the torrefied product (char). The process was optimized according to the mass and energy yield and the increase in the higher heating value (HHV). A series of physicochemical, kinetic, and microscopic analyses were carried out on the raw and torrefied biomass to evaluate the combustible properties. Char was obtained with an energy value in the range of sub-bituminous coal and with more uniform fuel properties concerning raw biomass. The optimal torrefaction conditions for cotton stalk were 6% O₂–257.8°C–60 min and 0% O₂–275°C–20 min for vine pruning. The HHV of the cotton stalk and vine pruning increased from 16.88 to 22.21 MJ kg⁻¹ and from 17.01 to 22.43 MJ kg⁻¹, respectively. The char from both residues presented similar O/C and H/C atomic ratios, and its value decreased compared with the raw biomass. Char is hydrophobic and easy to grind. Oxygen concentration played an essential role in reducing the time and temperature of torrefaction.

Graphical abstract

中文翻译：

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通过两种生物质生产具有高能值和标准化特性的焦炭

本文提出了一种新的烘焙工艺方法。该方法包括从两种类型的废物中获得一种具有能量值和在亚烟煤范围内标准化的理化特性的单一焙烤产品：棉花秸秆和葡萄树修剪。使用多因素设计来研究温度，时间和反应气氛对烘焙产品（炭）性能的影响。根据质量和能量产率以及较高发热量（HHV）的增加来优化工艺。对生的和烘焙的生物质进行了一系列的理化，动力学和微观分析，以评估其可燃性。获得的焦炭的能量值在次烟煤范围内，并且与原始生物质有关的燃料性质更均匀。₂ –257.8°C–60分钟，0％O ₂ –275°C–20分钟，用于修剪葡萄树。棉秆和葡萄树修剪的HHV分别从16.88增至22.21 MJ kg ^-1和从17.01增至22.43 MJ kg ^-1。来自两个残基的炭呈现出相似的O / C和H / C原子比，并且其值与原始生物质相比有所下降。炭是疏水的，易于研磨。氧气浓度在减少烘焙的时间和温度方面起着至关重要的作用。

图形概要