Combined reaction-separation model

Finally, we consider a preliminary approach for the optimal synthesis of reactor-separation systems. Here, we formulate a combined reaction-separation model by postulating a species-dependent residence time distribution. The optimization of this distribution function leads to a separation profile as a function of time along the reactor. The costs for maintaining a separation profile are handled through a separation index, which models the intensity of separation,... 

Fici. l.S. Flow model for combined reaction-separation targeting. 

In this chapter a two a selectivity model is proposed that is based on the premise that the total product distribution from an Fe-low-temperature Fischer-Tropsch (LIFT) process is a combination of two separate product spectrums that are produced on two different surfaces of the catalyst. A carbide surface is proposed for the production of hydrocarbons (including n- and iso-paraffins and internal olefins), and an oxide surface is proposed for the production of light hydrocarbons (including n-paraffins, 1-olefins, and oxygenates) and the water-gas shift (WGS) reaction. This model was tested against a number of Fe-catalyzed FT runs with full selectivity data available and with catalyst age up to 1,000 h. In all cases the experimental observations could be justified in terms of the model proposed. 

This chapter concerns the most important reactive separation processes reactive absorption, reactive distillation, and reactive extraction. These operations combining the separation and reaction steps inside a single column are advantageous as compared to traditional unit operations. The three considered processes are similar and at the same time very different. Therefore, their common modeling basis is discussed and their peculiarities are illustrated with a number of industrially relevant case studies. The theoretical description is supported by the results of laboratory-, pilot-, and industrial-scale experimental investigations. Both steady-state and dynamic issues are treated in addition, the design of column internals is addressed. 

The reaction and separation synthesis approach of Section 5 has been adopted to the problem of activated sludge process design (83). The conventional designs as well as all novel schemes for combined oxidation/denitrification of wastewater are explored. The process is optimized using a novel methodology for optimal reaction/separation network synthesis, supplied with a comprehensive kinetic model (84). The activated sludge process is synthesized using the systematic... 

In rate-based multistage separation models, separate balance equations are written for each distinct phase, and mass and heat transfer resistances are considered according to the two-film theory with explicit calculation of interfacial fluxes and film discretization for non-homogeneous film layer. The film model equations are combined with relevant diffusion and reaction kinetics and account for the specific features of electrolyte solution chemistry, electrolyte thermodynamics, and electroneutrality in the liquid phase. 

Pump and tank model Compressor model Heat exchanger model Cooling-tower model Steam-generation model Furnace model Distillation model Reaction model Separation model Absorption and stripping model Combination of the preceding models... 

The four models used to teach process troubleshooting are the distillation model, the reaction and separation model, the absorption and stripping model, and the combination model. Each model has a complete set of process control instrumentation and equipment arrangements. Various troubleshooting methodologies are applied to these four models. A complete range of troubleshooting scenarios has been developed and is typically included with these models. 

The reactive distillation processes which combine reaction and gas liquid separation are of increasing interest for scientific investigation and industrial application. Nowadays, simulation and design of multi component reactive distillation is carried out using the non equilibrium stage model (NEQ model) due to the limitation of conventional equilibrium stage efficiency calculations for equilibrium model (Lee Dudukovic (1998), Baur al. (2000), Taylor Krishna (1993), and Wesselingh (1997)). So, the NEQ model is developed by numerous authors. But there is a lack of experimental data in order to validate the model. Some input/output measurements are available but they provide little information about the behaviour inside the column. With this in mind, our paper is focus on the NEQ models and experimental validation. 

The following model of the corrosion process can be proposed based on the wealth of data provided by the combined application of SPFM, contact AFM, and IRAS At low RFl, the principal corrosion prodnct, hydrated alnminnm snlfate, is solid. It acts as a diffn-sion barrier between the acid and the alnminnm snbstrate and prevents fnrther corrosion. The phase separation observed between the acid and the salt at low RH strongly snggests that the salt inhibits fnrther corrosion once it precipitates. At high RH, on the other hand, alnminnm snlfate forms a liqnid solntion. Snlfnric acid mixes with this solntion and reaches the nnderlying snbstrate, where fnrther reaction can occnr. The flnid snlfate solntion also wets the snrface better and thns spreads the snlfnric acid. The two processes assist each other, and the corrosion proceeds rapidly once the critical RH of 80-90% is reached. 

After all, even in the first case we deal with the interaction of an electron belonging to the gas particle with all the electrons of the crystal. However, this formulation of the problem already represents a second step in the successive approximations of the surface interaction. It seems that this more or less exact formulation will have to be considered until the theoretical methods are available to describe the behavior both of the polyatomic molecules and the metal crystal separately, starting from the first principles. In other words, a crude model of the metal, as described earlier, constructed without taking into account the chemical reactivity of the surface, would be in this general approach (in the contemporary state of matter) combined with a relatively precise model of the polyatomic molecule (the adequacy of which has been proved in the reactivity calculations of the homogeneous reactions). 

In this chapter, we develop some guidelines regarding choice of reactor and operating conditions for reaction networks of the types introduced in Chapter 5. These involve features of reversible, parallel, and series reactions. We first consider these features separately in turn, and then in some combinations. The necessary aspects of reaction kinetics for these systems are developed in Chapter 5, together with stoichiometric analysis and variables, such as yield and fractional yield or selectivity, describing product distribution. We continue to consider only ideal reactor models and homogeneous or pseudohomogeneous systems. 

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