Comparison of atmospheric and gas-pressurized oxidative torrefaction of heavy-metal-polluted rice straw
2021
Tan, Mengjiao | Li, Hui | Huang, Zhongliang | Wang, Zhiwei | Xiong, Ruoxuan | Jiang, Shilin | Zhang, Jiachao | Wu, Zijian | Li, Changzhu | Luo, Lin
The oxidative torrefaction of rice straw polluted by heavy metals was carried out in a tube reactor (atmospheric pressure, AP) and an autoclave (gas-pressurized, GP), in order to compare the effects of the torrefaction temperature, carrier gas composition, and reactor type on torrefied products’ properties. Compared with the AP, the GP-torrefied rice straw had a lower solid yield, volatile matter, fixed carbon, hydrogen and oxygen contents, lower overall colour change (ΔE), combustion characteristic factor (SN), but a higher bulk density, higher heating value, ash and carbon content, higher combustion temperatures (Tᵢ and Tf) and fuel ratio. The weight loss, volatile matter, element, higher heating values and combustion characteristics of the AP-torrefied rice straw showed good correlations with its colour parameters, which indicating that it is technically feasible to identification and prediction by the human eye of AP-torrefied RS at the industrial level. However, higher amount of typical heavy metals remained in the GP-torrefied solid products with lower biological availability, indicating that GP torrefaction can be utilized as a low-cost and safe pre-treatment for heavy-metal-polluted rice straw at the industrial scale.
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