Batch and Continuous Reactors

In a batch reactor, the reactants are initially charged and, after a certain reaction time, the product(s) are recovered batchwise. In the semi-batch (or fed-batch) reactor, the reactants are fed continuously, and the product(s) are recovered batch-wise. In these batch and semibatch reactors, the concentrations of reactants and products change with time. 

The material balance relationship (i.e., Equation 1.5) holds for any reactant. If the liquid in a reactor is completely stirred and its concentration is uniform, we can apply this equation to the whole reactor. In general, it is applicable to a differential volume element and must be integrated over the whole reactor. 

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In order to be economically viable, a continuous emulsion polymerization process must be able to produce a latex which satisfies application requirements at high rates without frequent disruptions. Since most latex products are developed in batch equipment, the problems associated with converting to continuous systems can be significant. Making such a change requires an understanding of the differences between batch and continuous reactors and how these differences influence product properties and reactor performance. 

The rate of polymerization with styrene-type monomers is directly proportional to the number of particles formed. In batch reactors most of the particles are nucleated early in the reaction and the number formed depends on the emulsifier available to stabilize these small particles. In a CSTR operating at steady-state the rate of nucleation of new particles depends on the concentration of free emulsifier, i.e. the emulsifier not adsorbed on other surfaces. Since the average particle size in a CSTR is larger than the average size at the end of the batch nucleation period, fewer particles are formed in a CSTR than if the same recipe were used in a batch reactor. Since rate is proportional to the number of particles for styrene-type monomers, the rate per unit volume in a CSTR will be less than the interval-two rate in a batch reactor. In fact, the maximum CSTR rate will be about 60 to 70 percent the batch rate for such monomers. Monomers for which the rate is not as strongly dependent on the number of particles will display less of a difference between batch and continuous reactors. Also, continuous reactors with a particle seed in the feed may be capable of higher rates. 

Additions to and withdrawals from the reaction zone. General indications concerning the choice between batch and continuous reactors have been discussed above. Pulsed injections might be... 

Thermomorphic solvent mixtures have been tested for hydroformylation of 1-octene and 1-dodecene to determine the ease of product recovery and catalyst recycling. Using both batch and continuous reactors, we demonstrated the efficacy of a biphasic, thermomorphic, system that had the following advantages ... 

Battelle has developed an efficient process for the thermo-catalytic conversion of succinate into pyrrolidones, especially N-methyl-2-pyrrolidone. The process uses both novel Rh based catalysts and novel aqueous process conditions and results in high selectivities and yields of pyrrolidone compounds. The process also includes novel methodology for enhancing yields by recycling and converting non-useful side products of the catalysis into additional pyrrolidone. The process has been demonstrated in both batch and continuous reactors. Additionally, stability of the unique Rh-based catalyst has been demonstrated. 

Table 4.1 Numerical Values of the Operational Parameters Used in Simulations of Fed-Batch and Continuous Reactors...

In this chapter we consider the performance of isothermal batch and continuous reactors with multiple reactions. Recall that for a single reaction the single differential equation describing the mass balance for batch or PETR was always separable and the algebraic equation for the CSTR was a simple polynomial. In contrast to single-reaction systems, the mathematics of solving for performance rapidly becomes so complex that analytical solutions are not possible. We will first consider simple multiple-reaction systems where analytical solutions are possible. Then we will discuss more complex systems where we can only obtain numerical solutions. 

Bioreactors that use enzymes but not microbial cells could be regarded as fermentors in the broadest sense. Although their modes of operation are similar to those of microbial fermentors, fed-batch operation is seldom practiced for enzyme reactors. The basic equations for batch and continuous reactors for... 

Simulate the change of the substrate and product concentrations for batch and continuous reactors based on the kinetic parameters obtained. Compare one batch run with the simulated results. For this run, take samples every 5 to 10 minutes for 1 to 2 hours. 

Effect of Compositional Nonuniformities on the Unifying Ability of Characteristic Time Ratios to Analyze the Dynamic State of Reactions Figure 11.10, plotting the dimensionless initial reactant concentration as a function of the Damkohler number, Da = ties/tr for both batch and continuous reactors. This analysis assumes a well-mixed reacting system, (a) What will the effects of poor mixing be and how will they influence this analysis (b) What is the maximum allowable striation thickness between the reacting species for the system to be considered well mixed ... 

The methods for both semi-batch and continuous reactors are generally restricted to the 02-aqueous system because of the limitations of the analytical technique for the direct measurement of liquid-phase concentration. Novel agitated vessels for measurement of transient absorption rates are described by Danckwerts and Kennedy (1954), Oishi et al. (1965) and Govindam and Quinn (1964). 

Reaction performance. Supercritical carbon dioxide was used as a reaction media for the enzymatic synthesis of oleyl oleate directly from oleic acid and oleyl alcohol. Reaction was catalyzed by immobilized lipase from Rhizomucor miehei-Ltpozyme IM. Reactions were carried out in the high pressure batch and continuous reactor. 

However, this does not preclude mini emulsion copolymerization in a CSTR for extremely water-insoluble comonomers. In spite of the fact that the copolymer composition in the continuous miniemulsion is less than that predicted using the homogeneous copolymerization reactivity ratios, the miniemulsion copolymer might be more uniform than the macroemulsion copolymer, where the possibility of significant droplet nucleation could lead to two separate homopolymers or, at the very best, copolymers of various composition. Therefore, it is very important to use CSTR data to scale up a continuous miniemulsion copolymerization product to take into account the different particle growth kinetics for batch and continuous reactors. 

We have presented here a general modelling framework for emulsion polymerization reactors which can treat both batch and continuous reactors and includes all previously published models as special cases. Viewing emulsion polymerization through this framework allows one to see the problem in its entirety before proceeding to make simplifying assumptions. 

Recent progress in computer technology and methods for rapid experimental determination of molecular weight distributions (MWD) has encouraged the development of mathematical simulations of polymer synthesis processes in various types of batch and continuous reactors. 

Both batch and continuous reactor operation were studied. The latter was utilized, as although, fine chemicals are usually produced in batch-wise operating slurry reactors, continuous reactors offer several benefits, e.g. minimization of the time between batches, exclusion of catalyst separation and abrasion problems. 

The laws relating optimum operating temperature to medium composition are not well known. This relation was theoretically Investigated for processes whose rates saturate in substrate concentration. The Michaells-Menten reaction mechanism was modified to describe microbial biomass production and metabolite excretion in both batch and continuous reactors. 

Rate Isotherms. Depending on substrate concentration, three thermal sensitivity patterns may be seen in both batch and continuous reactors when the net biomass production rate (as specified by equations (lib) and (15) and Figures 3, 4, and 6) is plotted... 

L. R. (1995) Modeling simultaneous saccharification and fermentation of lignocellulose to ethanol in batch and continuous reactors. Enzyme Microb. TechnoL, 17 (9), 797-803. 

A comparison between continuous and batch equipment is given in Figure 7.34, with defining parameters required by the fed-batch reactor summarized in Table 7.2. These results provide for a convenient point of reference when conversions between batch and continuous reactors are carried out. 

The conventional chemical reactors comprise batch and tank or tubular reactors. The batch reactors are used in small-scale processes while tubular reactors have been preferentially applied in large-scale production. The advantages and drawbacks of batch and continuous reactors are shown in the table below ... 

In this section, some practices in batch and continuous reactors are presented in order to determine the performance in terms of conversion, selectivity, and yield. These examples were conducted in partnership with some Brazilian industries. 

In subsequent treatments, Teramoto et al (25, 26) developed an analysis of both semi-batch and continuous reactor performance which incorporated a quantitative discrimination of the role of film and bulk reaction. The intractability of the non-linear product terms in the diffusion/reaction equations was ultimately avoided by a linearisation method, identical to that proposed by Hikita and Asai (22). In this approach the profiles Co(x) and Cg(x) are replaced by their interfacial values, so t t the diffusion/reaction equations become... 

Culture conditions were optimized in both batch and continuous reactor systems. The kinetics of chitosan production seems to have a slightly better profile in a continuoiis reactor... 

The Fraunhofer Institute ITC operates several batch and continuous reactors for the treatment of solid and liquid waste in a program led by Thomas Hirth ... 

Dub6, M., Soares, Penlidis, A. and Hamielec, A.E. (1997) Mathematical modelling of multicomponent chain-growth pol)mierizations in batch, semi-batch and continuous reactors A review. Ind. Engng Chem. Res., 36, 966-1015. 

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