Yoshimoto Shuhei, Luthfi Numan, Nakano Kanta, Fukushima Takashi, Takisawa Kenji
Graduate School of Bioresources, Mie University, 1577 Kurimamachiyacho, Tsu, Mie, 514-8507, Japan.
Bioresour Bioprocess. 2023 Apr 4;10(1):24. doi: 10.1186/s40643-023-00645-4.
Hydrothermal carbonization (HTC) reacts with biomass in water at a high temperature and pressure to produce hydrochar with a higher heating value (HHV) and lower ash content than dry torrefaction. The high potassium content in biomass can promote thermochemical conversion; however, it lowers the melting temperature of the ash, causing slugging and fouling. Therefore, this study, investigated the effect of potassium on the HTC of sorghum bagasse by comparing the removal of potassium by washing with the addition of KCO. Consequently, the ash content was the highest in the potassium-added hydrochar and was 3.81% at a reaction time of 2 h. Elemental analysis showed that the lower the potassium content, the higher the carbon content, and the hydrochar with potassium removed by water washing at a reaction time of 3 h had the highest carbon content at 68.3%. Fourier transform infrared spectrometer showed dehydration and decarboxylation reactions due to HTC, but no significant differences were observed between the potassium concentrations. The mass yield decreased with increasing potassium content, and was 27.2% for the potassium-added hydrochar after 3 h. This trend was more pronounced with increasing reaction temperature. On the other hand, HHV was not affected by the potassium content. Therefore, the energy yield was similar to the weight yield. Thermal gravimetry and derivative thermal gravimetry (TG-DTG) analysis showed that higher potassium tended to accelerate the decomposition of lignin and decrease the oxidation temperature.
水热碳化（HTC）是在高温高压条件下使生物质与水发生反应，从而产生高热值（HHV）且灰分含量低于干馏的水热炭。生物质中高含量的钾能够促进热化学转化；然而，它会降低灰分的熔化温度，导致结渣和积垢。因此，本研究通过比较水洗除钾与添加碳酸钾对高粱秸秆水热碳化的影响进行了调查。结果表明，添加钾的水热炭灰分含量最高，在反应2小时时为3.81%。元素分析表明，钾含量越低，碳含量越高，在反应3小时时通过水洗除钾的水热炭碳含量最高，为68.3%。傅里叶变换红外光谱仪显示水热碳化导致了脱水和脱羧反应，但不同钾浓度之间未观察到显著差异。质量产率随钾含量增加而降低，添加钾的水热炭在3小时后为27.2%。随着反应温度升高，这种趋势更为明显。另一方面，高热值不受钾含量影响。因此，能量产率与重量产率相似。热重分析和微商热重分析（TG-DTG）表明，较高的钾含量倾向于加速木质素的分解并降低氧化温度。
