Kinetic modelling of the pyrolysis of biomass and biomass components

The kinetics of the pyrolysis of lignocellulosic materials was studied with a view of providing simple kinetic models for engineering purposes. Experimental data obtained by means of thermal analysis techniques suggest that the pyrolysis of fine particles (below 1 mm) can be considered to be controlled by pyrolysis kinetics. The rate of pyrolysis of one biomass type can be represented by the sum of the corresponding rates of the main biomass components (cellulose, lignin, hemicellulose). The kinetics of each of these components was simulated by a kinetic scheme capable of predicting the pyrolysis rate and the final weight-loss for a wide range of pyrolysis parameters including various heating conditions.     

废塑料裂解及塑料油精制研究进展

废塑料对环境造成的污染日趋严重,其有效处理成为全球关注的重要问题。对废塑料裂解后产生的废塑料油进一步加工处理得到高附加值化工产品是废塑料资源化利用的有效途径之一。综述目前废塑料裂解制油的发展状况和常用工艺,并比较各种工艺优缺点。介绍所得废塑料油后续精制加工的研究进展,并提出今后的研究方向。     

废塑料制取液体燃料试验研究

利用热解法将废塑料制成高品质液体燃料是资源回收和避免二次污染的重要途径。为此,设计了一套连续给料的鼓泡流化床反应器,对废塑料在鼓泡流化床中热解的关键工艺参数进行了试验研究。通过对试验数据的分析,得到了热解温度对液体产率的影响规律、气体产物的主要成分及其所占份额,并计算了废塑料热解过程的能量收支关系,为废塑料制取液体燃料的工业装置的设计、运行提供了理论及试验依据。     

Flammability of wood plastic composites prepared from plastic waste

The flammability of wood plastic composites manufactured from recycled plastics was investigated by using the cone calorimetry technique. The peak of the heat release rate was 12% to 25% lower compared to references produced from pure polyethylene‐ and polypropylene‐based composites. The total heat capacity and mass loss rate were also smaller for recycled material compared to the references. The stability of the composites was improved due to the presence of various thermally stable compounds, eg, traces of fire retardants, pigments, and other additives and impurities that can be present in recycled material. Incorporation of carbon black into the secondary materials did not reduce the peak of the heat release rate, but the total heat capacity and mass loss rate decreased further.     

橡胶与塑料废弃物用于阻尼材料的新研究

总结了国内外废橡胶和废塑料在制造阻尼材料方面的研究和应用的成果。介绍了废橡胶作为减震降噪的阻尼材料在工程和工业中的研究应用,同时介绍了废胶粉与废塑料共混型阻尼材料、树脂型废胶粉阻尼材料的研究应用,指出废橡胶和废塑料制造阻尼材料用于生产实践,不仅可以起到减震降噪作用,而且能够节约资源,具有显著的环保效益,对于资源的可持续性发展具有重要意义。     

Qualitative and quantitative contaminants assessment in recycled pellets from post-consumer plastic waste by means of spectroscopic and thermal characterization

The complexity of any plastic recycling initiative lies in the heterogeneous nature of the post-consumer commingled plastic waste stream: recycling treatments are challenging without prior reliable sorting. A suitable identification system should be able to recognize different plastics and blends. Nowadays, the main technique used as quality control in plastic waste sorting centers is differential scanning calorimetry, whose result can be purely qualitative or semi-quantitative, since only the crystalline fraction is evaluated. Moreover, the time required for data acquisition is relatively long. Infrared spectroscopy is an alternative, faster technique extensively used in applied research, but not widely utilized in industry. In this work, the cross-use of infrared spectroscopy and calorimetry is tested in a real, practical case: the quality control of recycled pellets (namely composed of polyolefins only), which represent the output of a commingled plastic recycling plant and are used as secondary raw materials for different applications. Appropriate infrared spectroscopy calibration curves were built to allow the quantitative analysis with respect to the most common polymers found in the commingled plastic waste stream; the composition and contaminants in the recycled pellets were thereby determined and tracked through different production batches through the cross-use of the two techniques outlined above.     

废旧地膜的回收与应用

针对超薄型地膜产品生产使用和耐候性差等原因造成使用后不降解或难以回收利用的问题,将农业生产使用后的废旧地膜采用机械或人工方式回收,经过清洗、改性等工艺过程制成颗粒.将回收料与小麦、玉米秸秆粉复合加工制备了复合板材,并对板材的力学性能进行了测试.结果表明,按照10％～50％(质量比,下同)的废旧地膜颗粒添加量制备的复合板...     

稻草和废塑料的热解性能研究

考察了稻草和废塑料在不同温度下单独热解时的气、液相收率,并将它们按不同比例混合,进行了稻草与废塑料的共热解性能实验研究。结果表明,稻草热解过程中添加少量废塑料(塑料与稻草质量比低于4∶10)可以增加气体产物的收率,并且随着废塑料添加比例的增加,热解气中CO2的含量明显下降,CH4与不饱和烃的含量有所增加,这有利于提高热解气中可燃气体的收率,增加经济效益,为实现废塑料的回收增值利用开辟了一条新的途径。     

Kinetic and thermogravimetric analysis of thermal degradation of polychlal fiber/polyester fiber blend

The flammability behavior of a series of polychlal fiber/polyester fiber blends has been investigated in terms of the oxygen index and the thermal degradation characteristics. The thermal degradation behavior of these fiber blends has been studied by a conventional dynamic thermogravimetric technique in a flowing air atmosphere at several heating rates. Quantitative data are presented that pinpoint how the flammability behavior of the blends differs from that of the components. These results indicate that interactions occur between the polychlal and polyester fibers in the blends. © 1993 John Wiley & Sons, Inc.     

Modelling of the pyrolysis of biomass particles. Studies on kinetics,thermal and heat transfer effects

The present work provides a rationally-based model to describe the pyrolysis of a single solid particle of biomass. As the phenomena governing the pyrolysis of a biomass particle are both chemical (primary and secondary reactions) and physical (mainly heat transfer phenomena), the presented model couples heat transport with chemical kinetics. The thermal properties included in the model are considered to be linear functions of temperature and conversion, and have been estimated from literature data or by fitting the model with experimental data. The heat of reaction has been found to be represented by two values: one endothermic, which prevails at low conversions and the other exothermic, which prevails at high conversions. Pyrolysis phenomena have been simulated by a scheme consisting of two parallel reactions and a third reaction for the secondary interactions between charcoal and volatiles. The model predictions are in agreement with experimental data regarding temperature and mass-loss histories of biomass particles over a wide range of pyrolysis conditions.     

PE废塑料溶剂裂解制备聚乙烯蜡

本文以废旧聚乙烯为原料,在溶剂水的作用下进行裂解制备聚乙烯蜡。实验过程中考察了温度、时间及溶剂加入量对产品性能的影响。结果表明:随裂解温度的升高和反应时间的延长都使得反应体系获得了更高的能量,容易使PE大分子发生断链从而得到低分子量PE,从而使产物收率逐渐降低,粘均分子量减少,熔程也随之下降。溶剂加入量对产品性质也有一定影响。当裂解温度为370℃,反应时间60min,溶剂加入量占原料总质量50%时,得到灰白色的聚乙烯蜡,其熔程在104~110℃之间,酸值为0.0143mg·g-1,粘均分子量为3426.4,且具有较高的热稳定性。通过溶剂裂解制得的聚乙烯蜡具有一定的工业应用前景。     

混合废塑料与煤共热解过程中氯的释放动力学研究

通过对混合废塑料与煤共热解的实验数据进行分析计算,推导出热解过程中氯在固(焦炭)、气(煤气)中的分布量与恒温时间、WP加入量之间的关系,建立了焦炭中氯的残留量的表观动力学方程,根据该方程可以计算达到某一残留量要求时,所需的恒温时间。同时也分析了煤气中氯的生成动力学方程,以及以上过程的表观活化能。     

Kinetic modelling of the thermal decomposition of ettringite into metaettringite

Despite recent insights into thermal stability of ettringite and structural changes during decomposition, a lack of knowledge on nucleation and growth mechanisms of metaettringite remained. Therefore, a better understanding of the kinetic modelling of this heterogeneous reaction was proposed. Thanks to an experimental approach allowing to check the validity of kinetic assumptions (rate-determining step, expression of the rate as dα/dt = kf(α)…), a good agreement was found between the calculated and experimental α vs. t and dα/dt vs. t kinetic curves. The reaction area of the region in which the rate-limiting step occurs was also elucidated. Finally, we demonstrated that the rate-limiting step of the growth process follows an Arrhenius law in non-isothermal conditions.     

固定床反应器中生物质/废塑料共热解制备燃料油

通过热重分析不同生物质（木屑和秸秆）单独热解以及与塑料（PP和dcPVC）共热解时的热解行为,研究了生物质与塑料共热解过程中的协同作用。在固定床反应器中考察了塑料的含量对生物质/塑料共热解的影响,最后通过元素分析和GC-MS对所得生物油进行了分析。研究结果表明：生物质和塑料共热解过程中存在明显的协同作用。木屑和PP共热解过程中的协同作用最为显著,当PP含量为80%时,所得生物油的产率最高,明显高于两者单独热解得到的生物油。元素分析和GC-MS分析结果表明：木屑和PP所得生物油的含氢量较高,所得到生物油的热值与石化燃油的相近。     

废塑料热解油中杂质硅、氯的影响及应对策略探讨

废旧塑料化学法回收是应对白色污染,同时实现高值化回收利用的有效方法之一,尤其是利用废塑料热解油进一步生产燃料油或化工产品的技术路线备受关注。但塑料垃圾杂质较多、成份复杂,其中杂质硅、氯对反应器、产物、催化剂或反应本身的影响均不可忽视。本文对塑料热解油中硅、氯杂质的来源、形态、生成机制及催化转化规律进行了分析,并根据杂质可能产生的不利影响提出了有效的应对策略。     

模拟医疗垃圾组分的平衡分析

建立非化学当量平衡模型,根据物料守恒和G ibbs最小自由能原理对模拟医疗垃圾中的典型组分进行热力学平衡分析。考虑温度、压力和过量空气系数对产物的影响,从而预测完全燃烧后的可能产物及其所占百分比。结果表明,产物的生成和体积分数主要受温度和过量空气系数影响,压力的影响次之。要使得热解产物有高热值,应选择尽量小的过量空气系数,过量空气系数越大产物热值保持不变的温度越低。高的温度将促进污染物CO的产生,而加压有利于抑制CO的产生。     

废轮胎(橡胶)热裂解回收利用的新进展

介绍了废轮胎(橡胶)热裂解回收利用所获得的政策支持。分析了废轮胎(橡胶)热裂解工艺水平的提高,如正压改微负压,采用缺氧和无氧技术等。总结了废轮胎(橡胶)在设备方面的改进与提高。     

废轮胎热裂解技术研究现状与进展

结合目前废旧轮胎资源化处理现状及研究成果,本文对热解机理、热解技术进行分析、对比,着重介绍了热解温度、升温速率、物料粒径、催化剂等工艺参数对热解产物产率的影响,分析表明Coast-Redfern积分法所得动力学模型较准确,平均反应活化能为129.5kJ/mol;现有的研究表明,热解温度对产物产率影响最大,气相产物与液相产物产率随温度升高而增加,其中液相产物产率相对较高的热解温度在500～550℃范围内,固相产物品质较高的热解温度在500～650℃范围内。其次对其固、液、气三相产物特性及应用和污染物(S、PAHs)的分布与控制方法做了归纳总结,为废旧轮胎热解技术向工业化发展提供技术依据。     

烟杆废物热解动力学研究

通过热重分析（TGA）方法,采用单步和三平行反应模型分别考察烟杆废物的热解动力学。烟杆废物单步热解的平均活化能为182.4 kJ/mol,最适宜的反应机理函数为14级反应机理f（α）=（1-α）¹⁴。能量补偿效应结果显示烟杆废物的热解可以分为3个阶段α=0~0.32、α=0.32~0.80和α=0.80~1,各阶段的指前因子分别为2.88×10¹⁰、4.33×10¹⁴和9.76×10¹⁶s^-1。单步热解过程中伴有表观活化能的变化以及高级数反应的机理,不能合理地描述烟杆废物的热解机理。采用混合韦伯分布活化能模型考察了三平行反应热解动力学,结果显示：混合韦伯分布活化能模型能很好地拟合烟杆废物热解数据,相关系数R²≥0.997 6;3种伪组分的活化能大小符合E₀（木质素,195.26 kJ/mol）> E₀（纤维素,152.54 kJ/mol）> E₀（半纤维素,121.18 kJ/mol）的顺序;半纤维素的热解机理为一级反应f（α）=1-α,纤维素的热解机理属于成核机理,木质素的机理亦呈现级数反应,级数介于n=3~4之间,木质素的热解机理复杂,可能为多步反应。