CFD Modelling of Chemical Reaction Systems in Jacketed Stirred Tank Reactors

夹套搅拌釜式反应器(STR)的模拟通常假定反应器内完全混合，从而得到均匀的浓度/温度分布和传热流体通过夹套的均匀流动。我们以前在中试规模的STR中对夹套流体和反应器内容物之间的流体力学和共轭换热进行的计算流体力学(CFD)研究表明，完全混合和均匀流动是不现实的假设。本项目的主要目标是通过将反应动力学集成到CFD-传热学模型中，建立适用于精细化工和制药行业相关反应系统的有机合成反应过程模型。有机化合物的化学合成往往是复杂的，涉及多个竞争反应和转化/选择性。产物的分布严重依赖于反应器的流体力学、混合和换热特性，特别是对于大规模的STR。任何不均匀和瞬变的水动力条件都会导致反应条件的时空变化，这可能会产生不希望看到的副产品并降低产率。这些差异很大程度上取决于STR的规模，从实验室到中试工厂到生产规模。最后，在许多情况下，活性成分通过结晶从反应器内容物中分离出来，副产物的存在可能会对晶体的质量产生不利影响。即使是结晶步骤也可能受到容器内普遍存在的任何不均匀和瞬时的流体动力条件以及副产品的存在的不利影响。因此，通过改进实验室、中试工厂和工业反应堆的设计和有效运行，最大限度地减少副产品的形成至关重要。在反应器和结晶过程中发生的物理现象的第一性原理模型的应用可以促进这一点。除了建模外，还将在实验室规模的STR(L 0.5-5)中进行实验，以确定反应动力学并收集过程数据以进行模型验证。这一综合模型将是“建模设计”方法的一个极其强大的工具，它可以准确地预测反应产物分布，促进反应堆设计，扩大和优化操作条件，并通过探索导致热跑道的工艺条件来确定安全操作范围。该模型还可以用于进行计算实验，以最大限度地减少大规模真实实验的数量，这些实验本身就不安全、昂贵和耗时。

Modelling of jacketed stirred tank reactors (STRs) generally assumes perfect mixing within the reactor leading to uniform concentration/temperature distributions and uniform flow of the heat transfer fluid through the jacket. Our previous computational fluid dynamics (CFD) study of hydrodynamics and conjugate heat transfer between the jacket fluid and the reactor contents in a pilot-scale STR revealed that perfect mixing and uniform flow are unrealistic assumptions. The main objective of this project is to develop an organic synthesis reaction process model for relevant reaction systems in the fine chemicals and pharmaceutical industries via integration of reaction kinetics into the CFD-heat transfer model. Chemical synthesis of organic compounds is often complex involving multiple competitive reactions and conversion/selectivity. The product distributions are critically dependent on the hydrodynamics, mixing and heat transfer characteristics of the reactor and particularly for large-scale STRs. Any inhomogeneous and transient hydrodynamic conditions prevailing will result in spatial and temporal variations in reaction conditions which can generate undesired by-products and reduce yield. These variations are quite different depending upon the size of the STRs from laboratory to pilot plant to manufacturing scales. Finally, in many instances, the active ingredients are isolated from the reactor contents via crystallisation and the presence of by-products can adversely affect the quality of crystals. Even the crystallisation steps can be influenced adversely by any inhomogeneous and transient hydrodynamic conditions prevailing within vessel and the presence of by-products. It is therefore of paramount importance to minimise by-products formation through improved design and efficient operation of laboratory, pilot plant and industrial reactors. Application of first principles models of the physical phenomena occurring in the reactor and during the crystallisation can facilitate this. In addition to the modelling, experiments will be carried out in laboratory scale STRs (0.5 - 5 L) to determine reaction kinetics and for collection of process data for model validation. This comprehensive model will be an extremely powerful tool for the "design by modelling" approach, which can predict accurately reaction product distributions and facilitate reactor design, scale up and optimision of operating conditions, and determining a safe operational envelope via exploring process conditions leading to thermal runaways. The model can also be used to conduct computational experiments to minimise the number of real experiments in large scale sizes which are inherently unsafe, costly and time consuming.