Mixing and chemical reactions

Baldyga, J., Bourne, J.R. and Hearn, S.J., 1997. Interaction between chemical reactions and mixing on different scales. Chemical Engineering Science, 52, 457-466. 

The intra-cell processes are common to all PDF codes, and are treated the same in both Eulerian and Lagrangian PDF codes.8 On the other hand, inter-cell processes are treated differently in Eulerian PDF codes due to the discrete representation of space in terms of x . In PDF codes, fractional time stepping is employed to account for each process separately. Methods for treating chemical reactions and mixing are described in Section 6.9. Thus we will focus here on the treatment of inter-cell processes in Eulerian PDF codes. 

Baldyga )., Bourne J.R., Hearn S.J., Interaction between chemical reactions and mixing on various scales, Chem. Eng. Sci. 52 (1997) 4, p. 457-466... 

In a mixture of ideal gases the sound velocity and consequently the resonant frequencies of a resonator depend on the effective specific heat ratio and the average molecular mass of the mixture. Chemical reaction and mixing processes, for example, are normally accompanied with a change of these properties. Therefore, such dynamic processes can be monitored by a repeated measurement of the shift of one of the eigenfrequencies of the resonator as a function of time. 

The preparation of TPVs involves chemical reactions and mixing of a crosslinldng agent. When TPVs are prepared in a twin-screw mixer, one has to make sure that the crosslinking reaction is complete. The residence time in the twin-screw extruder depends upon several variables, such as ... 

Euleria.n Models. Of the Eulerian models, the box model is the easiest to conceptualize. The atmosphere over the modeling region is envisioned as a well-mixed box, and the evolution of pollutants in the box is calculated following conservation-of-mass principles including emissions, deposition, chemical reactions, and atmospheric mixing. 

An industrial chemical reacdor is a complex device in which heat transfer, mass transfer, diffusion, and friction may occur along with chemical reaction, and it must be safe and controllable. In large vessels, questions of mixing of reactants, flow distribution, residence time distribution, and efficient utilization of the surface of porous catalysts also arise. A particular process can be dominated by one of these factors or by several of them for example, a reactor may on occasion be predominantly a heat exchanger or a mass-transfer device. A successful commercial unit is an economic balance of all these factors. 

The SIMULAR, developed by Hazard Evaluation Laboratory Ltd., is a chemical reactor control and data acquisition system. It can also perform calorimetry measurements and be employed to investigate chemical reaction and unit operations such as mixing, blending, crystallization, and distillation. Ligure 12-24 shows a schematic detail of the SIMULAR, and Ligure 12-25 illustrates the SIMULAR reaction calorimeter with computer controlled solids addition. 

This is another common processing operation, usually for chemical reactions and neutralizations or other mass transfer functions. Pilot plant or research data are.needed to accomplish a proper design or scale-up. Therefore, generalizations can only assist in alerting the designer as to what type of mixing system to expect. 

The unit is operated in the following way The reactants (see Table 5 for mixed acid compn) are introduced thru inlets (4) and (5), mixed with the help of turbine (8) and circulated thru pipe system (1), (3) and (6), chemical reaction and physical exchange being simultaneously effected. They are continuously transported to the separator in the form of an emulsion. ... 

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