Sequential stirred tank reactors

Different reactor configurations are proposed for the use of immobilized enzymes (Fig. 6.6.3) A) stirred tank reactors B) fixed bed reactors and C) fluidized bed reactors. The selection of the best option depends on the type of support and reaction kinetics. However, very often the activated supports do not present adequate characteristics for the performance of a fixed or fluidized bed reactor and, therefore, the development of stirred tank reactors based on immobilized enzyme or even, sequential stirred tank reactors appear as the more feasible options. 

Case 1 Anaerobic/Aerobic Treatment of Municipal Landfill Leachate in Sequential Two-Stage Up-Flow Anaerobic Sludge Blanket Reactor (UASB)/Aerobic Completely Stirred Tank Reactor (CSTR) Systems... 

Osman, N.A, and Sponza, D.T., Anaerobic/aerobic treatment of municipal landfill leachate in sequential two-stage up-flow anaerobic sludge blanket reactor (UASB)/completely stirred tank reactor (CSTR) system, Proc. Biochem., 40, 895-902, 2005. 

The APP technique, recently introduced [50, 51], uses a continuous stirring tank reactor (CSTR) and relies on the sequential perturbation of an oscillating... 

Continuous Stirred Tank Reactors. (CSTR). The first analysis of continuous reactors for polymerization was by Denbigh (14). He treated the same mechanisms in a CSTR that Gee and Melville (21) had treated in a batch reactor. The problem is simpler in a steady state CSTR since the equation for each dead and live specie is an algebraic rather than a differential equation. These are solved sequentially. The PSSA is not needed. He predicted a narrower molecular weight distribution for a continuous chain polymerization than for the same polymerization carried... 

Continuous Stirred Tank Reactors. Biesenberger (8) solved for the MWD with condensation polymerization in a CSTR, analogous to the treatment Denbigh (14) provided for the other two mechanisms. In this case, the variable residence time distribution leads to an extremely broad MWD with even the maximum weight fraction at the lowest molecular weight (monomer). The dispersion index approaches infinity as the condensation is driven to completion in a stirred tank reactor. A sequential analytical solution of the algebraic equations was obtained with a numerical evaluation of the consecutive equations. 

If the desired product is the first or an early intermediate in a pathway of sequential steps, batch or plug-flow tubular reactors provide better selectivity than do continuous stirred-tank reactors. 

In reactions with parallel steps of different reaction orders or with sequential steps, selectivities depend on the reactor type. Batch and plug-flow tubular reactors give higher selectivities to the product formed by the parallel step of higher order, or to the first product in a step sequence, than do continuous stirred-tank reactors. 

Flush The flush reaction path model is analogous to the perfectly mixed-flow reactor or the continuously stirred tank reactor in chemical engineering (Figure 2.5). Conceptually, the model tracks the chemical evolution of a solid mass through which fresh, unreacted fluid passes through incrementally. In a flush model, the initial conditions include a set of minerals and a fluid that is at equilibrium with the minerals. At each step of reaction progress, an increment of unreacted fluid is added into the system. An equal amount of water mass and the solutes it contains is displaced out of the system. Environmental applications of the flush model can be found in simulations of sequential batch tests. In the experiments, a volume of rock reacts each time with a packet of fresh, unreacted fluids. Additionally, this type of model can also be used to simulate mineral carbonation experiments. 

In reactions with sequential steps, the selectivity to the first intermediate is higher in batch and plug-flow than in continuous stirred-tank reactors, and decreases with progressing conversion in any type of reactor. 

The simultaneous process shown in Figure 1 (a) can be divided into two sequential units, shown in Figure 1 (b), as realized in the Rhone-Poulenc/Ruhrchemie hydroformylation process of propene. The reaction takes place in a continuous stirred tank reactor (CSTR) while the phase separation is carried out in a decanter. 

A free radical reaction involving nitration of decane is carried out in two sequential reactor stages, each of which operates like a continuous stirred-tank reactor (CSTR). Decane and nitrate (as nitric acid) in varying amounts are added to each reactor stage, as shown in Fig. 19.4. The reaction of nitrate with decane is very fast and forms the following products by successive nitration DNO3, D(N03)2, D(N03)3, D(N03)4, and so on. The desired product is DNO3, whereas dinitrate, trinitate, etc., are undesirable products. 

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