2026-10-13T02:52:20Z https://www.scidb.cn/oai

10.57760/sciencedb.39829 2026-06-23T00:25:40Z

2026-06-23 Torrefaction Pretreatment for Upgrading Pyrolysis of Leftover Rice: Mechanisms, Kinetics, and Suppression of NOx Precursors doi:10.57760/sciencedb.39829 en The leftover rice (LR) samples were obtained from the cafeteria at the Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, all from the same batch. The LR was dried at 45 °C until constant weight was achieved and then ground to a particle size below 80 mesh. An aliquot of 2 g of the prepared LR was weighed into a quartz crucible. The crucible was positioned at the top of the reactor. After purging with N2 (300 mL/min for 1 h), the reactor was heated at a constant rate of 10 °C/min to target torrefaction temperatures (200-320°C). Upon reaching the target temperature, the quartz crucible was inserted into the center of the reactor. The sample was torrefied for 40 min. Upon completion of torrefaction, the crucible was removed from the reactor and subsequently cooled under a N2 atmosphere for 10 min, yielding the torrefied sample. The industrial analysis for both raw and torrefied LR adhered to the procedures outlined in the Chinese National Standard GB/T 28731-2012. The elemental composition (C, H, O, N, S, and Cl) of both raw and torrefied LR was determined using an elemental analyzer. The lower heating value (LHV) of raw and torrefied LR was measured using an oxygen bomb calorimeter.In accordance with ICTAC recommendations, Kissinger-Akahira-Sunose (KAS) approach was adopted for kinetic analysis, thereby minimizing potential inaccuracies associated with presumptive reaction models. By circumventing the need to presuppose a specific reaction mechanism, this method enables the determination of activation energy associated with varying conversion levels. Model-free kinetic analyses fall under the category of isoconversional methods, with the KAS method being particularly prevalent in practice. The torrefaction kinetic model was developed using thermogravimetric data obtained under a 40 mL/min flow of high-purity nitrogen (carrier gas). To record the mass loss profiles, samples of approximately 10 mg were subjected to heating up to 400℃ under linear heating program (β=10, 15, and 20 K/min). A 5% O2 atmosphere was employed to assess the influence of trace oxygen, with all other experimental parameters held constant. Least-squares linear regression was utilized to correlate ln(β/T2) with 1/T at identical α values across various heating rates (β). The apparent activation energy (E) was calculated using the slope of the linear regression.Changes in the solid structure of raw and torrefied LR were analyzed using FTIR and NMR. A TG-MS analyzer was employed to carry out thermogravimetric analysis of the samples. The sample (~10 mg) was subjected to heating at 20 K/min under a high-purity nitrogen purge (20 mL/min) until reaching the torrefaction temperature, where it was maintained isothermally for 40 min. The gaseous products from torrefaction were analyzed on-line by MS, following their direct transfer via a heated line from the TGA unit. Analysis via Py-GC/MS was conducted. To analyze the liquid-phase products generated during torrefaction, aliquots of 0.1 mg (±0.01 mg) were heated at 10 °C/ms to the specified temperatures and held for 120 s. To investigate their thermal decomposition, raw and torrefied LR samples were subjected to pyrolysis via thermogravimetric analysis. Using a linear heating program (10 °C/min), ~10 mg samples were heated from 45°C up to 900°C. A flow rate of 20 mL/min was set for the carrier gas, which utilized high-purity N2. To quantitatively evaluate pyrolysis reactivity, the Comprehensive Pyrolysis Index (CPI) was adopted as the measurement indicator. This index comprehensively integrates the maximum weight loss rate, its corresponding temperature, and the pyrolysis temperature range, thereby reflecting both the reaction rate and the width of the active temperature window, and providing an overall measure of pyrolysis reactivity. A higher CPI value indicates a faster and more easily occurring pyrolysis reaction. Due to its reliability in comparing the pyrolysis behaviors of various feedstocks under different pretreatment conditions, CPI has been widely applied in biomass pyrolysis research.To investigate the pyrolysis process, experiments were undertaken using an integrated TG-FTIR-MS system. Under a high-purity N2 atmosphere flowing at 20 mL/min, a ~10 mg sample was heated from room temperature up to 850℃ by applying a constant heating rate of 20 K/min.The pyrolysis oil products were analyzed using Py-GC/MS. A 0.1±0.01 mg sample was held at the target temperature for 120 s after being heated thereto at an ultrafast rate of 10 ℃/ms.  Leftover rice; Torrefaction; Multiscale analysis; Pyrolysis upgrading; Reaction mechanism; NOx precursor suppression Yijian Li Shijie Zhu Junming Liang Kun Zhao Shuang Wang Zengli Zhao Anqing Zheng PUBLIC https://creativecommons.org/licenses/by-nc-sa/4.0/ dataset http://www.doi.org/10.1016/j.seppur.2026.137225 Science Data Bank