Ternary System With Inerts

The previous section considered the case in which the fiesh feedstreams of both reactants A and B are pure. In most of the real commercial reactive distillation systems, hghter reactant A is fed with other components that are inert in terms of the reaction but have voIatUities that are quite similar to component A. We will assume that fiesh feedstream Fqa is a mixture of reactant A and an inert component I, which is not involved in the reaction. The volatility of I is assumed to be identical to that of A, so both of these components are lighter than the other reactant B and product C. 

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Then we explore the ternary system with inerts present in one of the feedstreams. The reactive distillation column now has two streams leaving the column. One contains product C and the other contains the inerts. 

One of the most important aspects of the design and operation of the ternary system with inerts is to minimize the losses of reactants that can leave with the inerts in the distillate. We will see how reactant losses change as design parameters are varied in the following sections. 

In the quaternary system and in the ternary system without inerts, increasing reactive tray holdup improved reactive column performance in terms of reducing energy consumption. Figure 5.17 demonstrates that the same is true for the ternary system with inerts. However, in addition to the energy benefits, there is also an improvement in yield. Less... 

The final parameter explored in this chapter is the number of trays used in the two separation sections. In Chapter 2 we found that increasing the number of stripping and rectifying trays decreases energy consumption in the quaternary system. In Section 5.1.7 in this chapter we found that there is an optimum number of stripping trays in the ternary system without inerts. What are the effects for the ternary system with inerts ... 

This system is fundamentally a ternary system with inerts. The heavy component is TAME, which leaves the reactive distillation column in the bottoms. 

In this chapter we examine two reactive distillation column systems that are used for the production of real chemical components. The two systems are quite similar and are basically ternary systems with inerts that have characteristics similar to those discussed in Chapter 5 for ideal components. 

The design of two real reactive distillation systems was explored. Both the MTBE and ETBE systems are basically ternary systems with inerts. The control of these two systems will be studied in Chapter 15. 

These results demonstrate that a two-temperature control scheme does not provide effective control of the ternary system with inerts. The two-temperature control structure works for the quaternary system and for the ternary without inerts, but not for the ternary with... 

This system is fundamentally a ternary system with inerts. The methanol fresh feedstream is essentially pure. The hydrocarbon feed comes from an upstream catalytic cracking unit. It is a mixed C5 stream that contains not only the two reactants (2M1B and 2M2B) but also other C5s such as isopentane, n-pentane, 1-pentene, and 2-pentcne. 

The TAME reactive distillation system with a two-column methanol recovery system was successfully simulated in Aspen Dynamics. The system features two recycles (methanol and water) and three feedstreams (C5, methanol, and water). The system is essentially a ternary system with inerts, but the complex vapor-liquid equilibrium results in the formation of azeotropes that result in losses of methanol out of the top of the reactive column with the inerts. Therefore, a methanol recovery system must be included in the plant design and control. 

In Chapter 9 we explored the steady-state designs of both the MTBE and the ETBE reactive distillation columns using Aspen Plus. In this chapter we export the files into Aspen Dynamics as pressure-driven dynamic simulations and then look at dynamics and control. The control structures evaluated on both systems are based on those developed in Chapter 12 for ternary systems with inerts. 

Structure. The control stmcture is shown in Figure 15.5. This stmcture is similar to that used in the ideal ternary system with inerts, which was studied in Chapter 12. It consists of the following loops ... 

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