HYDRAULIC AND THERMAL STUDY OF A COMPACT HEAT-EXCHANGER REACTOR
Special Symposium - EPIC-1: European Process Intensification Conference - 1
EPIC-1: Intensified Hydrodynamics & Structured Environments (IHSE-3)
Keywords: Intensification - chemical reactor - modelling – optimisation
Since the last 30 years, chemical industries have been more and more constrained. The increasing need of productivity, safety, healthy environment and economic growth have forced all sectors to reconsider their strategies of production widely organised around batch reactor. In fact, in this kind of reactors, mixing and thermal performances (low heat transfer coefficient, disproportion between exchange area and reaction volume) lead to production limitations. In the same time a new concept was growing up: Process Intensification. Process Intensification can be defined as a strategy to enhance mass and energy transfers by the way of compact devices. Such strategy, coupled with transposition from batch to continuous, aims to improve productivity, safety, energy savings, investment costs and storage. In the recent years, Process Intensification allows several novel reaction devices to be developed. One of the most interesting is the heat exchanger reactor. This apparatus, based on the principle of heat exchangers, offers through the use of specific internals a plug-flow hydrodynamic behaviour associated with a great capacity of heat exchange. It also presents a compact structure operating in continuous mode that limits reactive medium hold-up and then improves process safety.
In heat exchanger reactors, the design of internals will condition the performances obtained in terms of hydrodynamics, mixing and heat transfer. In this way, internals constitute one of the key point of the device. In this study, we focus more precisely on a specific kind of internals: stainless steel metallic foams. The choice of this type of insert is based on their great specific surface (between 900 m2/m3 and 2400 m2/m3) and their high thermal efficiency. Moreover these metal foams offer a high porosity (> 95%) that limits pressure drops. The experimental pilot thus consists of two rectangular foams laid out in series and forming a loop of recirculation. This reactive chamber is surrounded by two parallel rectangular channels composing the cooling system.
This work is devoted to the study and characterisation of metallic foams as internals of continuous intensified reactors. In this perspective, hydraulic and thermal behaviour have been studied in detail. Residence time distribution (RTD) experiments have been carried out. The experimental data has been then successfully compared to numerical results provided from both functional analysis and dynamic modelling. In addition, pressure and thermal data are collected using several probes and used to identify the correlations governing pressure drop and heat exchange in the metallic foams. All these results are then used to set up a simulation tool able to determine the optimal operating conditions of a given industrial application performed in an intensified continuous reactor integrating metal foams.
Presented Thursday 20, 09:30 to 09:50, in session EPIC-1: Intensified Hydrodynamics & Structured Environments (IHSE-3).
