University of Padova, Department of Industrial Engineering, Via Marzolo 9, 35131 Padova, Italy.
Department of Environmental Engineering, National Advanced School of Public Works, Yaounde, Cameroon.
Waste Manag. 2021 Jul 15;131:341-349. doi: 10.1016/j.wasman.2021.06.017. Epub 2021 Jul 3.
The conversion of timber industry waste to biochar was investigated, based on residues from local tropical hardwoods in Cameroon. Closed and flow reactors, loaded with few grams of the sample and fluxed with different inert gases, were used with the aim of converting these wood residues to a safe and efficient solid fuel that can be exploited by the local community for cooking purposes. The pyrolysis temperature had the highest impact on the process up to approximately 700 °C as biochar yields decreased from 87 to 23.5% while increasing the temperature. A significant concentration of carbon required temperatures greater than 500 °C for the biochar to become a good solid fuel, approaching the heating value of coal. The role of heating rate appeared marginal even in a broad range: 0.1 to 70 °C/min. The dwell time (in the range 0.5 to 5 h) at maximum temperature revealed to be of little influence on the charring which occurred mostly during the first few minutes of the isothermal phase. Thus, actual production time can be <1 h/batch (up to 500 °C at 10 °C/min). Stepwise heating revealed a sequence of devolatilization reactions following their activation energies. Use of CO as inert gas increased the char yield. The inert gas flow rate had two contrasting effects on the biochar yield, in relation to volatile components residence time and the biomass temperature. The reactivity of biochar in combustion suggests a trade-off between heating content and reactivity. Charring in a closed, pressurized reactor produced biochar of low value as fuel, with tars absorbed in the porous solid residue.
研究了以喀麦隆当地热带硬木的残余物为原料，将木材工业废物转化为生物炭的过程。采用封闭和流动反应器，在反应器中装入几克样品，并通入不同的惰性气体，目的是将这些木材残余物转化为安全且高效的固体燃料，供当地社区用于烹饪。热解温度对该过程的影响最大，在约 700°C 时，生物炭产率从 87%降至 23.5%，而温度升高。生物炭要成为一种良好的固体燃料，需要碳的浓度显著增加，其温度需要大于 500°C，接近煤的热值。即使在较宽的范围内（0.1 至 70°C/min），加热速率的作用也显得微不足道。在最高温度下的停留时间（0.5 至 5 小时）对炭化的影响很小，炭化主要发生在恒温阶段的最初几分钟内。因此，实际的生产时间可以 <1 小时/批（以 10°C/min 的速度加热至 500°C）。逐步加热揭示了一系列按其活化能顺序发生的挥发分分解反应。使用 CO 作为惰性气体可提高生物炭的产率。惰性气体流速对生物炭产率有两种相反的影响，与挥发性成分的停留时间和生物质的温度有关。生物炭在燃烧中的反应性表明，加热含量和反应性之间存在权衡。在封闭、加压的反应器中进行炭化会产生低值生物炭作为燃料，焦油被多孔固体残留物吸收。
