Department of Civil Engineering, Federal University of Viçosa, Campus da Universidade Federal de Viçosa, Viçosa, Minas Gerais 36570-900, Brazil.
Department of Environmental Engineering, Federal University of Lavras (Universidade Federal de Lavras), Campus Universitário, Lavras, Minas Gerais 37200-900, Brazil.
Sci Total Environ. 2021 May 10;768:144480. doi: 10.1016/j.scitotenv.2020.144480. Epub 2021 Jan 5.
Hydrothermal carbonization is a thermochemical treatment whose objective is to convert carbohydrate components of a given biomass into carbon-rich material in an aqueous medium. Biomass of wastewater grown microalgae is among the various potential biomasses for this route. However, operational parameters of hydrothermal carbonization for different types of biomass are still being investigated. In general, larger temperature ranges (180-260 °C) are applied to woody biomasses, which have fibrous and/or ligneous structures and, therefore, are more thermally stable than algae biomass. This study presents the hydrothermal carbonization of microalgae biomass cultivated in an agro-industrial effluent. For this purpose, a Parr reactor was operated at different temperatures (130, 150 and 170 °C) and retention times (10, 30 and 50 min). Results showed improvements in the properties of the hydrochar, mainly energy yield and carbon concentration, after the thermochemical treatment. Energy recovery was improved, as well as hydrophobicity of the carbonized material. It was observed that in the retention time of 10 min, the increase in temperature provided an increase of 7.53% in the yield of solids. On the other hand, in the retention times of 30 and 50 min, when the temperature was increased, the solid yield decreased 6.70% and 0.92%, respectively. Thus, the highest yield of solids (77.72%) and energy (78.21%) was obtained at the temperature of 170 °C and retention time of 10 min. There was a high ash content in the raw biomass (32.99%) and an increase of approximately 3% in the carbonized material, regardless of the applied treatment. With the exception of potassium and sodium, the other macro and micronutrients were concentrated in the hydrochar after thermochemical treatment, indicating the potential of the material for agriculture application, in addition to energy use. Results showed that the retention time was the most significant operational parameter of the process.
水热碳化是一种热化学处理方法，其目的是在水介质中将给定生物质的碳水化合物成分转化为富碳物质。废水生长的微藻生物质就是这种方法的各种潜在生物质之一。然而，不同类型生物质的水热碳化操作参数仍在研究中。一般来说，较大的温度范围（180-260°C）适用于木质生物质，木质生物质具有纤维状和/或木质结构，因此比藻类生物质具有更高的热稳定性。本研究介绍了在农业工业废水中培养的微藻生物质的水热碳化。为此，在不同温度（130、150 和 170°C）和保留时间（10、30 和 50 分钟）下操作 Parr 反应器。结果表明，经过热化学处理后，水热炭的性能得到了改善，主要是能量产率和碳浓度的提高。能量回收得到了改善，碳化材料的疏水性也得到了改善。观察到在保留时间为 10 分钟时，温度升高使固体产率提高了 7.53%。另一方面，在保留时间为 30 和 50 分钟时，温度升高，固体产率分别降低了 6.70%和 0.92%。因此，在 170°C 和 10 分钟保留时间下，获得了最高的固体（77.72%）和能量（78.21%）产率。原始生物质的灰分含量很高（32.99%），碳化材料的灰分含量增加了约 3%，无论应用何种处理方法。除了钾和钠之外，其他宏量和微量元素在热化学处理后都浓缩在水热炭中，这表明该材料除了用于能源利用之外，还有用于农业应用的潜力。结果表明，保留时间是该过程最重要的操作参数。
