烃类蒸汽热裂解动力学模型的现状与对策

Current situation and countermeasures of kinetic models for hydrocarbon pyrolysis

综述了已有烃类蒸汽热裂解动力学模型,指出经验模型、集总模型和分子模型在实际应用时不易外推的原因。自由基机理模型所包含的各基元反应独立于原料、裂解装置以及裂解的工艺条件之外,决定了它具有良好的适应性和外延性,是用于描述烃类热裂解的理想模型。传统的用"假设在反应达到稳态时各自由基产生和消失的速度相等"来研究烃类热裂解自由基反应机理的方法存在较多的任意性和人为因素,造成了计算结果的局限性,影响了烃类热裂解机理的研究。利用分子模拟技术和工艺模型相结合建立适合烃类蒸汽热裂解自由基反应的模拟方法,克服了纯实验研究结果误差大、研究进展缓慢的缺点,可较准确、快速地研究烃类热裂解的自由基反应机理。

Currently,chemical engineers can not build a kinetic model for ethylene pyrolysis accurate- ly. Prediction of model is not accuracy for industrial production. In-depth analysises of establishing the models are carried out. The author points out the limitations of empirical correlation models, lumped kinetic models and molecular level kinetic models. Free radical mechanism is independent of raw mate- rials,cracker and pyrolysis process. It has good adaptability and extension. It is an ideal model for the thermal cracking of hydrocarbons. The traditional method assumes that free-radical rate of appearance is equal to the rate of disappearance in the steady-state. Human factors affect analytical results. It leads to a limitation of the results and the mechanism study of thermal cracking of hydrocarbons. This paper presents a new study method which combines the molecular simulation with the simulation calculation of one-dimensional technology mathematical model. At last, the pyrolysis laws are analyzed by compar- ison of simulation data and experimental data or calculated data. The method can overcome the experi- mental error and the limitations of theoretical research. It can be quickly and quantitative understand- ing of the cracking reaction law by simulation. It can also provide theoretical basis for establishing a general dynamics model of cracking reactions.