催化裂化提升管反应器数学模拟新方法

催化裂化提升管反应器数学模型基本上都是基于平推流反应器的假设建立起来的,但是由于其内部流动、传热以及反应过程非常复杂、偏离平推流较大,所以在模型的实际应用中必须用装置因数去校正,表现出较强的经验性,为了改变这种状况,本文通过研究分析,提出了对催化裂化提升管反应器进行多维微分模拟的研究方法,从根本上把反应器结构尺寸、物流入口条件,流动特征及传热特征等影响考虑进来,把流动、传热、传质、裂化反应以及湍流脉动作用全部纲入模型中,建立催化裂化提升管反应器的流动反应综合模型,通过对模型的求解,可以得到提升管反应器内催化剂颗粒及油气的速度分布、温度分布以及组分分布,从而揭示工业提升管反应器内的化学工程信息。这些数据对工业提升管反应器的设计、操作优化及新技术的实施都是十分重要的。

A New Mathematical Modeling Approach for Fluid Catalytic Cracking Riser Reactors

Mathematical models for Fluid Catalytic Cracking (FCC) riser reactors were built generally on the basis of assumption of “plug flow” pattern within risers. However, some rectification has to be made by so-called “unit factors” when they were used to commercial FCC units. The models exhibited much more empirical. They shouldn't be so because a basic and complete description on the FCC chemical reaction mechanism are given and model parameters are physically meaningful rather than empirical when established. We believe that the reason that results in this kind of theoretical retrogression is predominantly to model flow patterns of the FCC reactors one-dimensionally because the reality is another case. In addition to the complex catalytic cracking reactions, the flow pattern of oil and catalysts inside reactors is very complicated, which is far away from the ideal “piston flow”. This sort of modeling on the FCC riser reactors did not take the flow and heat transfer pattern into consideration. Therefore, we have carried out some researches to aim at changing the undesired situation. A new mathematical approach was proposed to model the FCC riser reactors, which is called 3-dimensional differential simulation. This approach completely took the riser reactor structures, fluid inlet conditions and the flow patterns as well as heat transfers into consideration. A general flow-reaction model for the FCC riser reactors has been built by integrating gas-solid flow, heat transfer, catalytic cracking reactions and turbulent fluctuation into it. It can be solved with the application of SIMPLE algorithm. Then velocity and temperature distributions of gas-particle two-phase and gaseous component distributions inside the FCC riser reactors can be predicted out to reveal the chemical engineering details of FCC riser reactors. These data are indispensable for the design of the FCC riser reactors and the operation optimization of a commercial FCC riser reactor that is in operation. They also are necessary to the implementation of some new techniques for the FCC riser reactors.