锯木屑与褐煤共热解生物焦的成浆性能及其流变特性

Preparation and rheological property of the char-water slurry based on co-pyrolysis of sawdust and lignite

模拟外热式直立炭化炉组装热解实验平台对锯木屑、云南褐煤进行热解/共热解提质,采用成浆实验法研究了锯木屑、云南褐煤热解生物焦/半焦及其共热解生物焦的成浆性能。结果表明,热解能显著提高锯木屑、云南褐煤的成浆性能,锯木屑、云南褐煤分别在500℃下热解1.5 h,所得到的生物焦、半焦的成浆浓度分别由热解前的29.21%、54.63%提高至38.57%、60.19%。相同热解条件下,锯木屑与云南褐煤共热解生物焦的成浆性能明显优于锯木屑、云南褐煤分别单独热解混合焦(生物焦与半焦的混合物)的成浆性能。锯木屑浆、生物焦浆、共热解生物焦浆、混合生物焦浆等均从总体上表现为假塑性特性,但当锯木屑含量大于等于50%时,锯木屑与云南褐煤共热解生物焦浆的流变特性与生物焦浆类似,在剪切速率较低的条件下,具有明显的剪切变稠特性,表现出较强的胀塑性。共热解生物焦的成浆性能优于混合生物焦的原因在于云南褐煤和锯木屑在共热解过程中的协同作用整体增强了共热解生物焦的芳构化程度。

An integrated experimental apparatus for pyrolysis /co-pyrolysis was employed to carry out the upgrading process of sawdust,Yunnan lignite,and their blends. The slurry-ability of the upgraded char was investigated. The results show that the slurry-ability of sawdust and Yunnan lignite is significantly improved via pyrolysis process. Bio-char and semi-coke were prepared at 500 ℃ holding 1. 5 h. The solid loadings of the resulting slurry fuels derived from sawdust and lignite were enhanced from 29.21% and 54.63% to 38.57% and60. 19%,respectively. Under the same pyrolysis conditions,the slurry-ability of the char prepared from co-pyrolysis of sawdust and Yunnan lignite is apparently superior to that of the corresponding bio-char /coal char mixture with the same original mass ratio of feedstock. The prepared char-water slurries generally display pseudoplastic behavior,i. e.,the shear press decreases with increasing shear rate. When the mass ratio of sawdust exceeds 50%,the rheological property of char-water slurry tend to be shear thickening,exhibiting strong dilatant behavior at low shear rate,which is similar to the rheological property of biochar-water slurry. The desirable slurry-ability of the char produced from co-pyrolysis could be attributed to the synergistic effect of biomass and coal,which is likely to improve aromaticity of the resulting hybrid char.