A new approach to evaluate the overall heat transfer coefficient of a fluidized bed biomass pyrolyzer

IF 5.8 2区化学 Q1 CHEMISTRY, ANALYTICAL Journal of Analytical and Applied Pyrolysis Pub Date : 2024-10-01 DOI:10.1016/j.jaap.2024.106778

H.T. Lin , A.D.K. Wibowo , T.F. Wang , H.H. Chiu , W.Y. Hsu , A.N. Huang , H.P. Kuo

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Abstract

The heat transfer characteristics of non-pretreated rice husk pyrolysis in a fluidized bed with alumina beads (500 μm - 590 μm) as bed material are studied. Assuming instantaneous heating of biomass to the reaction temperature, the effective overall heat transfer coefficient of the system (UA) is initially calculated based on the compositions of the collected products and reaction temperature. UA ranges from 0.82 to 2.95 W/K. This heat transfer coefficient study allows ad hoc product distributions to be predicted from theoretical bases. The effects of the biomass feeding rate (F) and the bed height (H/D) on UA values are also analyzed. Highest UA and specific heat of the pyrolysis reaction of −3.35 MJ/kg are found at F = 5 g/min and H/D = 1.0, where H/D is the largest and F is the lowest in the range studied. Upon feeding of the low thermal conductivity biomass, UA typically decreases. However, if the bed materials are limited, the fed biomass and its produced char act as an auxiliary heating medium to improve the effective heat transfer coefficient. High UA improves the efficiency of the pyrolysis reaction, but it decreases the bio-oil fraction in the product due to secondary decomposition.

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评估流化床生物质热解器总体传热系数的新方法

研究了以氧化铝珠（500 μm - 590 μm）为床层材料的流化床中未经预处理的稻壳热解的传热特性。假设生物质瞬时加热到反应温度，根据收集的产物成分和反应温度初步计算出系统的有效总传热系数（UA）。UA 在 0.82 到 2.95 W/K 之间。通过对传热系数的研究，可以根据理论基础预测特定的产品分布。此外，还分析了生物质进料速率（F）和床层高度（H/D）对 UA 值的影响。在 F = 5 g/min 和 H/D = 1.0 时，热解反应的最高 UA 和比热为 -3.35 MJ/kg，其中 H/D 在研究范围内最大，F 最低。加入低导热性生物质后，UA 通常会降低。但是，如果床层材料有限，进料生物质及其产生的焦炭可作为辅助加热介质，提高有效传热系数。高 UA 可以提高热解反应的效率，但会因二次分解而降低产品中的生物油部分。

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来源期刊

Journal of Analytical and Applied Pyrolysis 化学-分析化学

CiteScore

9.10

自引率

11.70%

发文量

340

审稿时长

44 days

期刊介绍： The Journal of Analytical and Applied Pyrolysis (JAAP) is devoted to the publication of papers dealing with innovative applications of pyrolysis processes, the characterization of products related to pyrolysis reactions, and investigations of reaction mechanism. To be considered by JAAP, a manuscript should present significant progress in these topics. The novelty must be satisfactorily argued in the cover letter. A manuscript with a cover letter to the editor not addressing the novelty is likely to be rejected without review.