RAPIC project: toward a new generation of inexpensive heat exchanger-reactors for process intensification

Process intensification (PI) in chemical production is a major concern of chemical manufacturers. This alternative technology involves transposing syntheses into continuous plug flow reactors with process intensification, leading to a multifunctional heat exchanger-reactor. In this context, the RAPIC R&D project aims to develop an innovative low-cost component (in the 10 kg/hour range). This project deals with the design from the local to the global scale and with testing, from elementary mock-ups to pilot scale. The present paper gives a detailed description of this research project and presents the main results on specification and definition of the reaction channel and the first simple mock-ups

Predicting bulk powder flow dynamics in a continuous mixer operating in transitory regimes

Over recent years there has been increasing interest in continuous powder mixing processes, due mainly to the development of on-line measurement techniques. However, our understanding of these processes remains limited, particularly with regard to their flow and mixing dynamics. In the present work, we study the behaviour of a pilot-scale continuous mixer during transitory regimes, in terms of hold-up weight and outflow changes. We present and discuss experimental results concerning the start-up dynamics of a Gericke GCM 500 mixer, for which a specific experimental protocol has been developed to determine the evolution of the hold-up in the mixer and the real outflow. Empirical relationships are derived so as to link hold-up weight variations with operating conditions. A simple stochastic approach, based on a non-homogeneous Markov chain, is developed to simulate the bulk particle flow and transport in the continuous mixer at a macroscopic level. Although this simple model is only based on the start-up behaviour, it provides a full description of the mixer dynamics in response to strong perturbations on the flow rate or on the rotational speed of the stirring device, such as negative or positive steps. This model is validated experimentally for a wide range of operating conditions, and constitutes a first approach to process control

Modeling and Optimization of Lactic Acid Synthesis by the Alkaline Degradation of Fructose in a Batch Reactor

The present work deals with the determination of the optimal operating conditions of lactic acid synthesis by the alkaline degradation of fructose. It is a complex transformation for which detailed knowledge is not available. It is carried out in a batch or semi-batch reactor. The ‘‘Tendency Modeling’’ approach, which consists of the development of an approximate stoichiometric and kinetic model, has been used. An experimental planning method has been utilized as the database for model development. The application of the experimental planning methodology allows comparison between the experimental and model response. The model is then used in an optimization procedure to compute the optimal process. The optimal control problem is converted into a nonlinear programming problem solved using the sequencial quadratic programming procedure coupled with the golden search method. The strategy developed allows simultaneously optimizing the different variables, which may be constrained. The validity of the methodology is illustrated by the determination of the optimal operating conditions of lactic acid production

Heat exchanger/reactors (HEX reactors): Concepts, technologies: State-of-the-art

Process intensification is a chemical engineering field which has truly emerged in the past few years and is currently rapidly growing. It consists in looking for safer operating conditions, lower waste in terms of costs and energy and higher productivity; and away to reach such objectives is to develop multifunctional devices such as heat exchanger/reactors for instance. This review is focused on the latter and makes a point on heat exchanger/reactors. After a brief presentation of requirements due to transposition from batch to continuous apparatuses, heat exchangers/reactors at industrial or pilot scales and their applications are described

Towards the design of an intensified coagulator

This study compares the hydrodynamics in three millimeter-scale continuous reactor geometries that can be easily used in laboratories and industries – a straight tube, a coiled tube and a Dean-Hex reactor – via numerical simulations and analyses the data in a way that is specifically relevant to coagulation processes, thereby offering insights for engineers to develop new coagulation reactors. A numerical approach based on Lagrangian particle tracking is presented to better understand the impact of the geometry and flow on properties that influence coagulation. The results show that the Dean-Hex meandering geometry provides narrower residence time and shear rate distributions, as well as higher mean average shear rates and Camp number distribution than the other geometries. This is attributed to the generation of transverse flows and radial mixing in the Dean-Hex reactor and suggests that a faster and more homogenous coagulation can be expected

Modelling of ultrafiltration fouling by neural network

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