Chemical reactors batch reactor

For gas-phase reactions this tubular reactor-batch reactor analogy may not be valid since the volmnetric flow rate of the gas, and therefore the gas velocity, can vary along the reactor length as a result of mole number changes accompanying chemical rea-... 

Cascade control, 395-402, 410, 445 Catalytic reactors auctioneering control, 405-7 fluid catalytic cracking, 75-76 regeneration of catalyst, 406 Centra] processing unit, 553-54 Characteristic equation, 285-87 of digital control loop, 623, 628 Characteristic polynomial, 145, 167, 321 of second-order system, 188 Chemical reactors batch (see Batch reactor) catalytic (see Catalytic reactor)... 

Specialties multipurpose chemical plants, batch reactors, etc. 

The analysis in Section 6.2 demonstrated that both the steady-state conversion and the optimum conversion in open chemical reaction systems (continuous-flow reactors) are always lower than the equilibrium conversion in closed chemical systems (batch reactors). 

Many microreactors are at the research level but a few are already commercially available. Microwave-assisted flow processing in microreactors (MAFP) [93] or radiofrequency-heated flow reactors [94,95] are promising alternatives for conventionally heated, multistep production of fine chemicals in batch reactors. Realization of MAFP at an industrial scale requires a proper design of multitubular reactors integrated with microwave heating [96]. 

Run-to-run control is particularly useful to compensate for processes where the controlled variable drifts over time. For example, in a chemical vapor deposition process or in a batch chemical reactor, the reactor walls may become fouled due to byproduct deposition. This slow drift in the reactor chamber condition requires occasional changes to the batch recipe in order to ensure that the controlled variables remain on-target. Eventually, the reactor chamber must be cleaned to remove the wall deposits, effectively causing a step... 

Product Recovery. Comparison of the electrochemical cell to a chemical reactor shows the electrochemical cell to have two general features that impact product recovery. CeU product is usuaUy Uquid, can be aqueous, and is likely to contain electrolyte. In addition, there is a second product from the counter electrode, even if this is only a gas. Electrolyte conservation and purity are usual requirements. Because product separation from the starting material may be difficult, use of reaction to completion is desirable ceUs would be mn batch or plug flow. The water balance over the whole flow sheet needs to be considered, especiaUy for divided ceUs where membranes transport a number of moles of water per Earaday. At the inception of a proposed electroorganic process, the product recovery and refining should be included in the evaluation to determine tme viabUity. Thus early ceU work needs to be carried out with the preferred electrolyte/solvent and conversion. The economic aspects of product recovery strategies have been discussed (89). Some process flow sheets are also available (61). 

Next consider the case that uses randomized blocking to eliminate the effect of some variable whose effect is of no interest, such as the batch-to-batch variation of the catalysts in the chemical reactor example. Suppose there are k treatments and n experiments in each treatment. The results from nk experiments can be arranged as shown in the block design table within each block, the various treatments are applied in a random order. Compute the block average, the treatment average, as well as the grand average as before. 

FIG. 23-23 Batch and continuous polymerizations, (a) Polyethylene in a tiihiilar flow reactor, up to 2 km long hy 6,4 cm ID, (h) Batch process for polystyrene, (c) Batch-continuous process for polystyrene, (d) Suspension (head) process for polyvinylchloride, (e) Emulsion process for polyvinylchloride, (Ray and Laurence, in Lapidus and Amundson, eds, Chemical Reactor Theory Review, Frentice-Hall, 1977. )... 

A factor in addition to the RTD and temperature distribution that affects the molecular weight distribution (MWD) is the nature of the chemical reaciion. If the period during which the molecule is growing is short compared with the residence time in the reactor, the MWD in a batch reactor is broader than in a CSTR. This situation holds for many free radical and ionic polymerization processes where the reaction intermediates are very short hved. In cases where the growth period is the same as the residence time in the reactor, the MWD is narrower in batch than in CSTR. Polymerizations that have no termination step—for instance, polycondensations—are of this type. This topic is treated by Denbigh (J. Applied Chem., 1, 227 [1951]). 

Chemical engineering inherited the definition for the reaction rate from chemical kinetics. The definition is for closed systems, like batch reactors, in which most of the classical kinetic studies were done. Inside a batch reactor little else besides chemical reaction can change the concentration of reactant A. In a closed system, for the reaction of... 

Adequate heat removal facilities are generally important when controlling the progress of exothermic chemical reactions. Common causes of thermal runaway in reactors or storage tanks are shown in Figure 7.4. A runaway reaction is most likely to occur if all the reactants are initially mixed together with any catalyst in a batch reactor where heat is supplied to start the reaction. 

In chemical laboratories, small flasks and beakers are used for liquid phase reactions. Here, a charge of reactants is added and brought to reaction temperature. The reaction may be held at this condition for a predetermined time before the product is discharged. This batch reactor is characterized by the varying extent of reaction and properties of the reaction mixture with time. In contrast to the flasks are large cylindrical tubes used in the petrochemical industry for the cracking of hydrocarbons. This process is continuous with reactants in the tubes and the products obtained from the exit. The extent of reaction and properties, such as composition and temperature, depend on the position along the tube and does not depend on the time. 

From diese various estimates, die total batch cycle time t(, is used in batch reactor design to determine die productivity of die reactor. Batch reactors are used in operations dial are small and when multiproducts are required. Pilot plant trials for sales samples in a new market development are carried out in batch reactors. Use of batch reactors can be seen in pharmaceutical, fine chemicals, biochemical, and dye industries. This is because multi-product, changeable demand often requues a single unit to be used in various production campaigns. However, batch reactors are seldom employed on an industrial scale for gas phase reactions. This is due to die limited quantity produced, aldiough batch reactors can be readily employed for kinetic studies of gas phase reactions. Figure 5-4 illustrates die performance equations for batch reactors. 

Simulation of complex chemical reactions in a batch reactor... 

Thermal runaway reactions are the results of chemical reactions in batch or semi-batch reactors. A thermal runaway commences when the heat generated by a chemical reaction exceeds the heat that can be removed to the surroundings as shown in Figure 12-5. The surplus heat increases the temperature of the reaction mass, which causes the reaction rate to increase, and subsequently accelerates the rate of heat production. Thermal runaway occurs as follows as the temperature rises, the rate of heat loss to the surroundings increases approximately linearly with temperature. However, the rate of reaction, and thus the... 

The coalescence-redispersion (CRD) model was originally proposed by Curl (1963). It is based on imagining a chemical reactor as a number population of droplets that behave as individual batch reactors. These droplets coalesce (mix) in pairs at random, homogenize their concentration and redisperse. The mixing parameter in this model is the average number of collisions that a droplet undergoes. 

Rice, R.W. and Baud, R.E., 1990. The role of micromixing in the scale-up of geometrically similar batch reactors. American Institution of Chemical Engineers Journal, 36, 293-298. 

Wang, Y.-D. and Mann, R., 1992. Partial segregation in stirred batch reactors effect of scale-up on the yield of a pair of competing reactions. Transactions of the Institution of Chemical Engineers, 70, 282-290. 

Leung, J. C., Wnt Sizing for Tempered Vapor Systems, in Safety of Chemical Batch Reactors and Storage Tanks, Benuzzi, A. and Zaldivar,J. M. (ed), 285-298, Kltnver Academic Publishers, Dordrecht, April 1991. 

The design of production plants for the manufacture of the three categories of product varies considerably. Fine chemicals are usually produced in batch reactors, which may also be used for the production of a variety of similar products. Fine chemicals usually have demanding product quality specifications and, consequently, a significant fraction of the production costs are involved in product purification and testing. Intermediate volume chemicals have less rigorous quality specifications than fine chemicals and are usually manufactured in product-specific-plants, either as batch or continuous flow processes. Bulk chemical production plants usually operate continuous flow processes... 

Fletcjjhr. P. The Chemical Engineer. London No 435 (1987) 33. Heat transfer coefficients for stirred batch reactor design. 

To run the residence time distribution experiments under conditions which would simulate the conditions occurring during chemical reaction, solutions of 15 weight percent and 30 percent polystyrene in benzene as well as pure benzene were used as the fluid medium. The polystyrene used in the RTD experiment was prepared in a batch reactor and had a number average degree of polymerization of 320 and a polydispersity index, DI, of 1.17. 

---