Purpose

Biomass slurries, such as those subjected to microwave-assisted alkaline (MAA) pretreatment, will become common substrates for the production of biofuels in the future. While the rheology of acid and ionic liquid pretreated biomass is known, the rheology of alkaline pretreated biomass is not yet reported; hence, the goal of this study was to establish the rheological characteristics of untreated and MAA pretreated sugarcane straw (SC).

Methods

Using rotational rheometry and rheological models, the rheology of SC slurries was assessed as a function of particle size and insoluble solids concentration.

Results

In the range of 5–17% insoluble solids concentration, the slurries were consistently pseudo-plastic (n = 0.33 ± 0.02), possessed yield stress with their flow accurately described by the Casson rheological model (R² = 0.98–0.99). The apparent viscosity and yield stress increased by two orders of magnitude with an increase in insoluble solids concentration. Essentially, MAA pretreated slurries exhibited significantly higher values of apparent viscosity and yield stress than the untreated ones, in the range of 55–80% and 21–63% for particle sizes of < 63 µm (P63) and 90–180 µm (P90), respectively. Pretreated P63 samples exhibited higher apparent viscosity and yield stress than the P90. On the other hand, for untreated samples, P63 samples had a reduced apparent viscosity than P90 samples.

Conclusion

The results of this study definitively reveal that MAA significantly increases the shear rate dependent shear viscosity values along with the yield stress of biomass slurries. This will, therefore, serve as a benchmark for characterizing other MAA pretreated biomass slurries to guide the design of industrial-scale production equipment.

Graphic abstract

中文翻译：

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未经处理和微波辅助预处理的甘蔗秸秆用于生物燃料生产的流变行为研究

目的

生物质浆料，例如经过微波辅助碱（MAA）预处理的浆料，将成为将来生产生物燃料的常用基质。尽管已知酸和离子液体预处理生物质的流变性，但尚未报道碱性预处理生物质的流变性。因此，本研究的目的是建立未经处理和经过MAA预处理的甘蔗秸秆（SC）的流变特性。

方法

使用旋转流变仪和流变学模型，将SC浆料的流变学评估为粒径和不溶性固体浓度的函数。

结果

在5-17％的不溶性固体浓度范围内，浆液始终为假塑性（n = 0.33±0.02），具有屈服应力，其流量由Casson流变模型精确描述（R ²  = 0.98-0.99）。随着不溶固体浓度的增加，表观粘度和屈服应力增加了两个数量级。本质上，MAA预处理浆液的表观粘度和屈服应力值显着高于未处理浆液，对于<63 µm（P63）和90–180 µm（P90）的粒径，其表观粘度和屈服应力值分别在55-80％和21-63％的范围内）， 分别。预处理的P63样品比P90表现出更高的表观粘度和屈服应力。另一方面，对于未经处理的样品，P63样品的表观粘度比P90样品低。

结论

这项研究的结果明确地表明，MAA显着提高了取决于剪切速率的剪切粘度值以及生物质浆料的屈服应力。因此，这将作为表征其他经过MAA预处理的生物质浆料的基准，以指导工业规模生产设备的设计。

图形摘要