Ternary System Without Inerts

We hrst discuss the ternary system without inerts to gain some insights into how changing from a two-product system to a one-product system impacts reactive distillation design. Unlike the quaternary column with distillate and bottoms products, the ternary column without inerts has only one product stream leaving the column. The effects of several design variables are shown to be quite different in the ternary system than those we observed in the quaternary system. 

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. 

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Thus, the column configuration in the one-product ternary system without inerts is quite different than the two-product configuration. Figure 5.1 gives the flowsheet. There are only stripping and reactive sections. 

The ternary system without inerts has a diHerent column structure and requires a different approach for designing the column. There are still two feedstreams and a bottoms stream, but there is no distillate. In addition, the impurity in the bottoms product will be mostly the heavier of the two reactants, component B. This means that the flowrates of the two fresh feedstreams will not be equal. Moreover, the reaction is not equimolar. Two moles of reactants produce 1 mol of product. Thus, there is a decrease in the molar liquid flowrates in the reaction section that is attributable to the nonequimolar reaction. 

In the quaternary system without inerts, the flowrates of both fresh feeds and both produet streams are fixed, and the reflux is changed to drive the purity of one of the products to the desired specification. In the ternary system without inerts and without a distillate stream, the method for converging the column is very different. The flowrate and the composition of product C of the bottoms are fixed. There is no distillate. The flowrates of the two fresh feeds are calculated to provide the amounts needed for the reaction plus that lost in the bottoms. The reflux flowrate is changed to drive the bottoms composition to 98 mol% C. The vapor boilup is changed to control the level in the base. Reflux-drum level is not controlled. 

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... 

Increasing the number of reactive trays Ngx improved energy consumption in the ternary system without inerts. When inerts are present, the same result is observed, as shown in Figure 5.28. Vapor boilup decreases as more reactive trays are added. 

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 ... 

In Chapter 10 we investigated a two-temperature control structure for the quaternary, two-product system. We demonstrated that an internal composition measurement is not required in that system to provide the extremely precise balancing of the stoichiometry of the reaction, that is, feeding exactly the right amount of reactants so that no excess builds up in the column. Will a similar two-temperature control structure be effective in the ternary system without inerts This stracture is shown in Figure 12.14. The two fresh feeds are manipulated to control the temperatures on two trays. 

In the ternary reaction system without inerts, the column has only a bottoms product in which heavy product C is removed and has only stripping and reactive zones. In the ternary reaction system with inerts, the column has both distillate and bottoms streams. Figure 5.10 gives the flowsheet of the reactive column. 

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... 

The most frequently we use the ternary system horizontal projection, on which the most important isotherms are marked. On the Fig. 2.14 the section of this system is presented, on which, apart of earlier discussed two-component compounds, mull-ite, without practical importance for cement chemistry, is shown. However, it is present in siliceous fly ash, but it belongs to inert compounds does not reacting with calcium hydroxide in water. Furthermore two ternary phases are formed in... 

The first three chapters have explored in a fair amount of detail the four-component quaternary system with the reaction A + B C + D. This system has two reactants and two products. In the next two chapters we will study various aspects of two other types of ideal chemical systems. In Chapter 4 we investigated the impact of a number of kinetic and design parameters on the ideal ternary system with the reaction A + B C with and without inerts in the system. In Chapter 5 we study systems with the reaction A4=> B + C in which there is only one reactant but two products. We will illustrate that the chemistry has an important effect on how the many kinetic and design parameters impact the reactive distillation column. 

In Parts I and II we explored the steady-state designs of several ideal hypothetical systems. The following three chapters examine the control of these systems. Chapter 10 considers the four-component quaternary system with the reaction A + B C + D under conditions of neat operation. Chapter 11 looks at control of two-column flowsheets when an excess of one of the reactants is used. Chapter 12 studies the ternary system A + B C, with and without inerts, and the ternary system A B + C. We will illustrate that the chemistry and resulting process structure have important effects on the control structure needed for effective control of reactive distillation columns. 

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