Size comparisons batch reactor

A useful classification of lands of reaclors is in terms of their concentration distributions. The concentration profiles of certain limiting cases are illustrated in Fig. 7-3 namely, of batch reactors, continuously stirred tanks, and tubular flow reactors. Basic types of flow reactors are illustrated in Fig. 7-4. Many others, employing granular catalysts and for multiphase reactions, are illustratea throughout Sec. 23. The present material deals with the sizes, performances and heat effects of these ideal types. They afford standards of comparison. 

This paper presents the physical mechanism and the structure of a comprehensive dynamic Emulsion Polymerization Model (EPM). EPM combines the theory of coagulative nucleation of homogeneously nucleated precursors with detailed species material and energy balances to calculate the time evolution of the concentration, size, and colloidal characteristics of latex particles, the monomer conversions, the copolymer composition, and molecular weight in an emulsion system. The capabilities of EPM are demonstrated by comparisons of its predictions with experimental data from the literature covering styrene and styrene/methyl methacrylate polymerizations. EPM can successfully simulate continuous and batch reactors over a wide range of initiator and added surfactant concentrations. 

A performance comparison between a BR and a CSTR may be made in terms of the size of vessel required in each case to achieve the same rate of production for the same fractional conversion, with the BR operating isothermally at the same temperature as that in the CSTR. Since both batch reactors and CSTRs are most commonly used for constant-density systems, we restrict attention to this case, and to a reaction represented by... 

Regarding reactor sizes, a comparison of Eqs. 5.4 and 5.19 for a given duty and for s = 0 shows that an element of fluid reacts for the same length of time in the batch and in the plug flow reactor. Thus, the same volume of these reactors is needed to do a given job. Of course, on a long-term production basis we must correct the size requirement estimate to account for the shutdown time between batches. Still, it is easy to relate the performance capabilities of the batch reactor with the plug flow reactor. 

In comparison to the Genus reactor, this system holds the wafer upside down to minimize any particulate on the wafer. Also, since this is a singlewafer machine, a loadlock is provided to ensure that the reaction chamber is never opened to the atmosphere. Attempts to provide this feature on a batch reactor are difficult and expensive, due to the size of the chamber needed. Heating is done in a way similar to the Genus system. High-intensity lamps shine on the back of a chuck to heat it to processing temperature. 

Aside from process comparisons, the main contrast between the systems is that of size, weight, and cost, especially for pressurized systems. Construction of batch reactors for use with ethylene at pressures of 1000 psi (70 atm) and upward has to be massive. The simple construction of the Loop process just pumps and pipework blends itself to use at high pressures. Apart from cost and weight, the small volume of the Loop reactor has obvious safety advantages. Despite these attractions, the Loop reactor system has so far been used successfully only for low-pressure systems such as poly(vinyl acetate) homopolymer for adhesives and copolymers for paint. Large-scale production of ethylene-vinyl acetate copolymers has yet to be demonstrated. 

This nucleation/emulsifier utilization phenomena is one reason why batch kinetics and product characteristics are difficult to extrapolate from batch reactor to continuous stined-tank systems. A comparison of Equations (8.4) and (8.10) illustrates this in a quantitative manner for Smith-Ewart Case 2 kinetics. It should be noted that both formulation and operational variables (such as ) can influence nucleation and polymerization rates differently in the two reactor systems — even for the same kinetic model. One can change some aspects of this potential disadvantage of a CSTR by use of a small particle size seed in the feed stream or by placing a continuous tubular reactor upstream of the CSTR. These techniques can remove the nucleation phenomena tom the CSTR system which can then be used exclusively to grow the seed particles. 

Some variation in the final nanoshell size (100-200 nm) was obtained as a consequence of the particle size distribution of the silica cores (2—4 nm), which was caused by the radial velocity profiles leading to a range of reaction times in the first reaction stage. In spite of this, nanoshells with suitable properties were obtained with good reproducibility. The synthesis was carried out continuously and, in a controlled manner, provided that a fast mixing of the reactants was achieved in each stage. By comparison, the same process carried out in a batch reactor system was considerably more expensive in terms of time, reactants, and more heterogeneous products. 

Almost innumerable instances of such reactions are practiced. Single-batch stirred tanks, CSTR batteries, and tubular flow reactors are all used. Many examples are given in Table 17.1. As already pointed out, the size of equipment for a given purpose depends on its type. A comparison has been made of the production of ethyl acetate from a mixture initially with 23% acid and 46% ethanol these sizes were found for 35% conversion of the acid (Westerterp, 1984, pp. 41-58) ... 

Fig. 1.22. Comparison of size and cost of continuous stirred-tank reactors with a batch or a tubular plug-flow reactor first-order reaction, conversion 0.9 ...

The granulate-filled sandwich structure described in Section II.B permits continuously operated loop systems to be developed as replacements for batch processes. Loop reactors so equipped also exhibit advantages by comparison to conventional fixed-bed reactors better exploitation of the catalytically active component due to smaller granulate size, lower pressure drop, and better gas-liquid mass transfer. 

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