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Investigation of heat of biomass pyrolysis and secondary reactions by simultaneous thermogravimetry and differential scanning calorimetry

机译：同时热重分析和差示扫描量热法研究生物质热解和副反应的热量

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摘要

The heat of pyrolysis reactions is of great importance not only for its impact on biomass pyrolysis process but as a fundamental parameter for modelling biomass thermochemical conversion. Previously frequently-used technique that integrates DSC heat flow curves to determine the heat of pyrolysis actually presented the enthalpy change of pyrolysis within a temperature range. This enthalpy change in effect took no account of the sensible heat of the volatiles leaving the crucible before reaching the upper limit of the temperature range. This work was attempted to determine both the heat of biomass pyrolysis as a function of conversion ratios or temperatures and the heat of secondary reactions. To this end, the conventional simultaneous thermogravimetry (TG) and differential scanning calorimetry (DSC) technique was re-examined to investigate thermal behaviour of cellulose, xylan, lignin and four lignocellulosic biomass samples using a TG-DSC analyser. Selected samples around 3.3 mg were thermally decomposed in a crucible either with or without a pierced lid at a heating rate of 10 ℃/min to a maximum temperature of 500 ℃. Specific heat capacities of all the original biomass and char samples were measured through DSC analyses. Temperature-dependent formulas were developed for extrapolating the specific heat of both biomass and char samples at high temperatures. The heat of pyrolysis as a function of conversion ratios was characterised by the derivative of the enthalpy change versus mass changes during pyrolysis. Thus-obtained heat of biomass pyrolysis represented the difference between the enthalpies of formation of the products and reactants at a specific temperature or conversion ratio instead of a temperature range. The results showed that the heat of pyrolysis reactions changed from high endothermic values, via moderately endothermic values and finally rapidly to high exothermic values as the conversion ratios increased. Linear relations were established between the heat of biomass pyrolysis and conversion ratios ranging from 0.2 to 0.8. The heat of secondary reactions was about 80-280 J/g for cellulose and increased with conversion ratios up to 2500-4000 J/g for the lignocellulosic biomass samples.
机译：热解反应的热量不仅对于其对生物质热解过程的影响非常重要，而且作为模拟生物质热化学转化的基本参数也非常重要。以前经常使用的综合DSC热流曲线以确定热解热的技术实际上提出了在一定温度范围内热解的焓变。实际上，这种焓变没有考虑在达到温度范围的上限之前离开坩埚的挥发物的显热。尝试这项工作来确定生物质热解的热与转化率或温度的函数以及副反应的热。为此，使用TG-DSC分析仪重新检查了常规同时热重分析（TG）和差示扫描量热分析（DSC）技术，以研究纤维素，木聚糖，木质素和四个木质纤维素生物质样品的热行为。将选定的约3.3 mg样品在有或没有穿孔盖的坩埚中以10℃/ min的加热速率热分解到最高温度500℃。通过DSC分析测量了所有原始生物质和焦炭样品的比热容。开发了温度相关的公式，用于推断高温下生物质和焦炭样品的比热。热解热作为转化率的函数，其特征在于热解过程中焓变对质量变化的导数。如此获得的生物质热解热代表在特定温度或转化率而不是温度范围下产物和反应物形成焓之间的差异。结果表明，随着转化率的增加，热解反应的热量从较高的吸热值转变为中等的吸热值，最终迅速变为较高的放热值。在生物质热解热与转化率之间的线性关系在0.2至0.8之间建立。对于纤维素，二次反应的热量约为80-280 J / g，对于木质纤维素生物质样品，转化率最高可达2500-4000 J / g。

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  • 来源
    《Fuel》 |2014年第15期|467-476|共10页
  • 作者

    Qun Chen; Ruiming Yang; Bo Zhao; Yan Li; Shujuan Wang; Hongwei Wu; Yuqun Zhuo; Changhe Chen;

  • 作者单位

    Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing 100084, China;

    Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing 100084, China;

    Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing 100084, China;

    Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing 100084, China;

    Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing 100084, China;

    School of Engineering, University of the West of Scotland, Paisley PA1 2BE, United Kingdom;

    Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing 100084, China;

    Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing 100084, China;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    Biomass pyrolysis; Heat of pyrolysis; Secondary reaction; Differential scanning calorimetry; Specific heat capacity;

    机译：生物质热解;热解热;二级反应;差示扫描量热法;比热容;

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