Batch reactors defined

Batch reactors often are used to develop continuous processes because of their suitabiUty and convenient use in laboratory experimentation. Industrial practice generally favors processing continuously rather than in single batches, because overall investment and operating costs usually are less. Data obtained in batch reactors, except for very rapid reactions, can be well defined and used to predict performance of larger scale, continuous-flow reactors. Almost all batch reactors are well stirred thus, ideally, compositions are uniform throughout and residence times of all contained reactants are constant. 

Peaking and Non-isothermal Polymerizations. Biesenberger a (3) have studied the theory of "thermal ignition" applied to chain addition polymerization and worked out computational and experimental cases for batch styrene polymerization with various catalysts. They define thermal ignition as the condition where the reaction temperature increases rapidly with time and the rate of increase in temperature also increases with time (concave upward curve). Their theory, computations, and experiments were for well stirred batch reactors with constant heat transfer coefficients. Their work is of interest for understanding the boundaries of stability for abnormal situations like catalyst mischarge or control malfunctions. In practice, however, the criterion for stability in low conversion... 

A batch reactor is never a steady-state process operator, unlike a continuous process in which a steady state is defined as the state of a process in which there is no change with time of any condition of the process. This includes the amount and average composition of the material within the process, so that in a continuous process, there can be no accumulation or depletion. Notwithstanding an unsteady-operation where composition changes with... 

As in the case of a batch reactor, the balance equation 2.3-3 or 2.3-4 may appear in various forms with other measures of flow and amounts. For a flow system, the fractional conversion of A (/A), extent of reaction (f), and molarity of A (cA) are defined in terms of Fa rather than nA ... 

Batch production management, 20 704 Batch proportioning methods, 26 249-251 Batch reactions, niobium, 77 136 Batch reactors, 27 332, 353 defined, 3 758t... 

Sequencing batch reactor technology has been developed on a scientific assumption that periodic exposure of microorganisms to defined process... 

The initial volume of 50 mL chosen for the fed-batch reactor imposes relatively low flow rates for the feed stream, as indicated above. However, variations in the concentrations of the substrates in the feed stream are based on variations in the flow rates, and these should be accurate. These considerations lead to a need for accurate changes in a limited range of flow rates. The flow rate of 7 mL/h is in the lowest range of the rates defined by the producer for the peristaltic pumps used, so in the settings defined by the producer, accurate variations could not be obtained. Thus, the peristaltic pumps were operated with tubings of very small diameter. These tubings, of 0.5 mm inner... 

Just as the reaction time t is the natural performance measure for a batch reactor, so are the space-time and space-velocity the proper performance measures of flow reactors. These terms are defined as follows ... 

A batch reactor is defined as a closed spatially uniform system which has concentration parameters that are specified at time zero. It might look as illustrated in Figure 2-4. This requires that the system either be stirred rapidly (the propeller in Fig. 24) or started out spatially uniform so that stirring is not necessary. Composition and temperature are therefore independent of position in the reactor, so that the number of moles of species in the system Nj is a function of time alone. Since the system is closed (no flow in or out), we can write simply that the change in the total number of moles of species j in the reactor is equal to the stoichiometric coefficient Vj multiplied by the rate multiphed by the volume of the reactor. 

For the activity tests an 8-fold batch reactor system (reactor volume 20 ml) with magnetic stirring which allows the measurement of hydrogen uptake at constant hydrogen pressure was used. Analysis of substrates and products was performed offline by GC for determining selectivity values. Activity values were derived from hydrogen up-take within a defined time interval. Hydrogenation of both cinnamic acid and dibenzylether were carried out at 10 bars and 25°C. 

In chemical reaction engineering, an ideal batch reactor is defined as a closed reactor, meaning there is no addition and no removal of any components during the reaction time. The prototype of this reactor is the autoclave, where all reactants are charged into the reactor at the beginning of the operation (Figure 6.3). The reactor is then closed and heated to reaction temperature, the temperature at which the reaction is allowed to complete or at which a catalyst is added. After the reaction is completed, the reactor is cooled and discharged. It is now ready for a new cycle. 

All the thus far formalized steps in defining and performing an experiment are being demonstrated in this example. The process of separating mercury from caustic, as part of the process of extraction in a batch reactor with a mixer, is being tested. 

In order to ensure an adequate quality of products and a safe operation, the monitoring of a batch reactor should include, at least, online measurements of temperature, pressure, and of some composition-related variables. In this context, online measurements may be defined as measurements obtained via instruments strictly connected to the reactor and characterize by response times markedly smaller than the characteristic times of the chemical reaction. In general, this is the case of temperature and pressure, which can be easily measured online by means of reliable, relatively cheap, and poorly intrusive sensors. This allows the introduction of sensor redundancy, a common practice to increase reliability. On the other hand, online... 

Still with reference to the temperature-concentration profile, van Welsenaere and Froment [13] proposed a criterion based on the locus of the temperature maxima that was originally derived for homogeneous tubular reactors but whose validity for batch reactors was also proved. The criterion is discussed here with reference to Fig. 4.8, where the temperature-concentration profiles in a batch reactor are reported for Se = 0.470, 2 = 40, Tro = 7j = 1, and different values of A in the range 0.2-1.16. The maxima of the %(C) curves (continuous lines) define a new curve (dashed line), which has itself a maximum with respect to %. According to the criterion of van Welsenaere and Froment, the latter maximum defines the critical conditions for runaway, i.e., it provides the maximum value of A that allows one to have an easily controlled temperature in the reactor for any given set of the remaining parameters. In Fig. 4.8, the critical point on curve 1 is found at Ac = 0.7. 

Following the Morbidelli and Varma criterion, several other methods have been proposed in recent years in order to characterize the highly sensitive behavior of a batch reactor when it reaches the runaway boundaries. Among the most successful approaches, the evidence of a volume expansion in the phase space of the system has been widely exploited to characterize runaway conditions. For example, Strozzi and Zaldivar [9] defined the sensitivity as a function of the sum of the time-dependent Lyapunov exponents of the system and the runaway boundaries as the conditions that maximize or minimize this Lyapunov sensitivity. This has put the basis for the development of a new class of runaway criteria referred to as divergence-based approaches [5,10,18]. These methods usually identify runaway with the occurrence of a positive divergence of the vector field associated with the mathematical model of the reactor. 

For a plug flow or batch reactor, the yield of component R is defined as... 

The batch reactor is characterized by its volume, Fr, and the holding time, t, that the fluid has spent in the reactor. Flow reactors are usually characterized by reactor volume and space time, r, with the latter defined as the reactor volume divided by the volumetric flow rate of feed to the reactor. The physical significance of r is the time required to process a volume of fluid corresponding to Rr. For catalytic reactions, the space time may be replace by the site time, xp, defined as the number of catalytic sites in the reactor, Sr, divided by the molecular flow rate of feed to the reactor, F. The physical interpretation of rp is the time required to process many molecules equal to the number of active sites in the reactor. 

This review concentrates on MWD in linear polymers. Although it has been approached on a statistical basis in batch reactors, the more usual and general kinetic analysis will also answer all rate questions in the process of defining the MWD. 

Three forms of the reactor operator, R(Y), are shown in Figure 3. These are generally differential operators which operate on each monomer and polymer species to describe the effects of accumulation and the physical processes which move material in and out of the reactor or reactor element. The concentration of a specific species is given by the variable Y. In a simple batch reactor, the reactor operator, RB, is merely defined as the rate of accumulation of a certain species with time per unit volume of reactor—i.e., the rate of change of concentration of the species. 

Analogous to the batch reactor, a fractional conversion of a reactant A can be defined as ... 

Water used in the experiments was doubly distilled and passed through an ion exchange unit. The conductivity was approximately 1 x 10"6 S/m. Simulated HLLW consisted of 21 metal nitrates in an aqueous 1.6 M nitric acid solution as shown in Table 1 and was supplied by EBARA Co. (Tokyo, Japan). Concentrations were verified by AA for Na and Cs with 1000 1 dilution and by ICP for the other elements with 100 1 dilution. Total metal ion concentration was 98,393 ppm. The experimental apparatus consisted of nominal 9.2 cm3 batch reactors (O.D. 12.7 mm, I.D. 8.5 mm) constructed of 316 stainless steel with an internal K-type thermocouple for temperature measurement. Heating of each reactor was accomplished with a 50%NaNO2 + 50% KNO 2 salt bath that was stirred to insure uniform temperature. Temperature in the bath did not vary more than 1 K. The reactors were loaded with the simulated HLLW waste at atmospheric conditions according to an approximate calculated pressure. Each reactor was then immersed in the salt bath for 2 min -24 hours. After a predetermined time, the reactor was removed from the bath and quenched in a 293 K water bath. The reactor was opened and the contents were passed through a 0.1 pm nitro-ceflulose filter while diluting with water. Analysis of the liquid was performed with methods in Table 1. Analysis of filtered solids were carried out with X-ray diffraction with a CuK a beam and Ni filter. Reaction time was defined as the time that the sample spent at the desired temperature. Typical cumulative heat-up and cool-down time was on the order of one minute. Results of this work are reported in terms of recoveries as defined by ... 

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