Operating diagram countercurrent operation

FIGURE 8 Schematic diagram showing the two basic modes of operating an adsorption separation process (a) cyclic batch two-bed system (b) continuous countercurrent system with adsorbent recirculation. Concentration profiles through the adsorbent bed are indicated. Component A is more strongly adsorbed than B. (Reprinted with permission from Ruthven, D. M. (1984). Principles of Adsorption and Adsorption Processes, copyright John Wiley Sons, New York.)... 

To examine this particular aspect, consider what happens when the ion-exchange treatment of one of the solutions of interest (seawater) is carried out in a two-sectional countercurrent column that is operated at different temperatures, T, and T2 (T2 > T,). A diagram of this column is presented in Fig. 7. 

Figure 7 Schematic diagram of two-sectional countercurrent ion-exchange column operating at different temperatures to provide recovery of waste-free bromine from seawater.

A simplified flow diagram of a concurrent-flow unit operating on vapor feed is shown in Figure 21. Details of the reactor for operation on partially liquid feed are shown in Figures 22 and 23. The latter operation was typical when revamping an existing countercurrent-flow unit, where it was simpler to leave the tar separator in the circuit. For operation on heavy gas oil, the partially-vaporized effluent from the primary furnace was flashed in the tar separator in the usual manner. The vapors were superheated in the secondary furnace and introduced into the reactor via the vapor-inlet nozzle near the top of the reactor, while the tar-separator bottoms were pumped into the reactor through a liquid-injection nozzle. 

The flow diagram for a two-stage (stage 1, stage 2) countercurrent operation is provided in Figure 108. Material balances on the residue for each stage are... 

Figure 108. Flow diagram for 2-stage countercurrent operation.

FIGURE 10.5 Diagram Illustrating the mode of operation of a moving belt filter to obtain phosphoric acid recovery and permitting countercurrent washing of the gypsum filter cake. 

COCURRENT FLOW OPERATION. When the chemical reaction is essentially irreversible and the equilibrium partial pressure of the solute is zero, the number of transfer units for a given separation is the same for countercurrent operation or for cocurrent flow of liquid and gas. Figure 22.24 shows typical operating lines for both cases. In this diagram x is the total solute absorbed and reacted and not the amount of solute present in the original form. For cocurrent operation with the feeds at the top, the gas leaving at the bottom is exposed to rich liquid, which has absorbed a lot of solute, but if jf = 0, the driving force is just y, and Noy is calculated from Eq. (22.50), as for countercurrent flow. 

Figure 8.6 Operating diagram for adiabatic gas-liquid countercurrent contact.

Figure 2.2-9 Flooding point diagram for countercurrent gas-liquid flow [12] after Billet [13]. The lines mark the upper limit of gravity driven countercurrent flow. Under usually operating conditions, 80% of that limit can be used.

Figure 11.5.e-II Operating diagrams for various types of ammonia synthesis reactors, (a) Multitubular reactor with cocurrent flow, (b) Multitubular reactor with countercurrent flow, (c) Multibed adiabatic reactor (from Fodor [122]). 

A countercurrent cascade allows for more complete removal of the solute, and the solvent is reused so less is needed. A schematic diagram of a countercurrent cascade is shown in Figure 13-20. All calculations will assume that the column is isothermal and isobaric and is operating at steady state, hi the usual design problem, the column tenperature and pressure, the flow rates and conpositions of streams F and S, and the desired composition (or percent removal) of solute in the raffinate product are specified. The designer is required to determine the number of equilibrium stages needed for the specified separation and the flow rates and conpositions of the oudet raffinate and extract streams. Thus, the known... 

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