Stirred reactors overview

Analysis of hydrate formation data can be obtained from a tabulation of gas consumption during hydrate formation as a function of time measured in stirred reactors. Formation data thus require either a table (or a plot) of individual experiments. Such a prospect is not viable in this monograph, since the literature hydrate formation data contain a large number of experiments with questionable transferability between apparatuses. Instead an overview of experimental conditions is presented below. The reader is referred to theses and subsequent publications of Englezos (1986), Dholobhai (1989), Skovborg (1993), Bansal (1994), and Turner (2005) for typical data. 

There are four ideal reactors the batch reactor (real counterpart stirred tank reactor), semibatch reactor,1 continuous stirred tank reactor (CSTR), and the plug flow tubular reactor (PFTR) (real counterpart tube reactor). For production applications, there are also numerous other reactors [7-9], An overview of typical and advanced laboratory reactors was given by Kapteijn and Moulijn [6],... 

An overview of dynamic and the stady state analysis for design and modeling of the continuously stirred tank electrochemical reactor has been published [40]. 

A good overview can be found in [Ullmann2]. In the following only the three most important reactor types - the stirred-tank, tubular, and fluidized-bed reactors - are discussed in detail, together with a more recent development, namely the microreactor. 

In Fig. 4.40 a stirred liquid bench-scale calorimeter is displayed. It closely duplicates laboratory reaction setups. The information aboutheat evolved or absorbed is extracted from the temperature difference between the liquid return (Tj) and the reactor (T ). This difference is calibrated with electric heat pulses to match the observed effect at the end of a chemical reaction. In a typical example, 10 W heat input gives a 1.0 K temperature difference between Tj and Tr. The sample sizes may vary from 0.3 to 2.5 liters. The overall sensitivity is about 0.5 W. The calorimeter can be operated between 250 and 475 K. Heat loss corrections must be made for the stirrer and the reflux unit. The block diagram in Fig. 4.40 gives an overview of the data handling. 

Experimental characterization of the mixing quaUty in conventional stirred tank reactors, as well as in micromixers, is an important step for the proper comprehension of the performance of chemical reactors. To identify interactions between mixing and chemical reactions and quantify them, a variety of physical and chemical methods have been developed, whose application to a given mixer may either be easy or may require appropriate adaptations to obtain valuable measurements. The next section gives a brief overview of existing methods. 

Chapter 5 gives an overview of novel green reactors and the application of the CFD technique in modelling of green reactors. This chapter presents detailed discussions on a number of novel reactors, namely, the microreactor, microwave reactor and spinning disc reactor. A brief introduction on CFD and the application of CFD in modelling laminar mixing in a stirred tank reactor is presented. 

The CSTR (continuously stirred tank reactor) with mechanical stirring, typically combining Rushton and marine impellers (see also Figure 1.15) is the standard design for practically all applications. The table gives an overview of all liquid-moving and mbcing options. 

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