Abstract
Plug flow behavior in tubular reactors is often highly desirable in industry, since it can ensure high productivity, good selectivity, and enhanced heat transfer. To achieve this, good radial mixing combined with poor axial mixing is required: these conditions are quite easy to obtain if the flow regime is turbulent, but they are much more challenging to achieve if the flow is laminar. In this work radial mixing and residence time distributions in a side-injected tubular reactor equipped with a series of Sulzer SMX static mixers were investigated using Computational Fluid Dynamics. It was found that even at low values of Reynolds number the reactor can efficiently satisfy the plug flow conditions, and operative diagrams were determined to foresee the reactor behavior.
Highlights
Continuous and discontinuous processes represent the two production modes adopted in the chemical industry
Tubular reactors guarantee a better heat exchange than continuous stirred tank reactors (CSTRs) due to a higher heat transfer area-to-volume ratio. This characteristic allows tubular reactors to operate in more severe reaction conditions and to obtain a larger productivity, keeping the process safe and at a constant quality. This is generally the case when the tubular reactor operates as a plug-flow reactor (PFR)
If the tubular reactor operates with extremely low flow rates, a laminar flow can be attained in the reactor, leading to a wide distribution of reaction times in the reactor and an overall uneven distribution of chemicals
Summary
Continuous and discontinuous processes represent the two production modes adopted in the chemical industry. The fine chemical industry (polymers and pharmaceutical) prefers batch processes for their simplicity and their flexibility as multipurpose systems.[1,2] in the past few years, there is a tendency to shift to continuous processes[3,4] which allow the gain of several advantages over discontinuous systems, such as reduced volumes, higher productivities, automatization with simpler control, and most importantly, constant quality of the produced chemicals.[5,6] Among continuous reactors, tubular reactors guarantee a better heat exchange than continuous stirred tank reactors (CSTRs) due to a higher heat transfer area-to-volume ratio This characteristic allows tubular reactors to operate in more severe reaction conditions and to obtain a larger productivity, keeping the process safe and at a constant quality. These conditions deviate from the desired PFR behavior and can lead to quality and safety issues
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