Steady state countercurrent

Figure 4.25. Steady-state, countercurrent flow heat exchange.

Katto, Y., 1994a, Limiting Conditions of Steady State Countercurrent Annular Flow and the Onset of Flooding, with Reference to the CHF of Boiling in a Bottom-Closed Vertical Tube, Int. J. Multiphase Flow 20 45-61. (3)... 

The program BIOFILT solves the steady-state countercurrent biofiltration operation for MEK removal. The integration is started at the top of the column by assuming a desired concentration in the outlet air. The required column length is determined when the inlet gas concentration exceeds the actual inlet value. 

To develop the performance equation, we combine the rate equation with the material balance. Thus for steady-state countercurrent operations we have for a differential element of volume... 

In this section, the equations are presented for the common types of contactors differential contactors and stage-wise contactors. The equations are developed for the case of steady-state, countercurrent contacting of liquid and gas with negligible heat effects, with a single-component absorption. Some discussion of extensions to other situations follows. 

J. Jelinek and V. Hlavacek, Steady-State Countercurrent Equilibrium Stage Separation with Chemical Reaction by Relaxation Method, Chem. Eng. Sci., 2 79 (1976). 

Figure 3.11 Steady-state countercurrent process, transfer from phase V to L.

A steady-state, countercurrent, staged distillation column is to be used to separate ethanol from water. The feed is a 30 wt % ethanol, 70 wt % water mixture at 40°C. Flow rate of feed is 10,000 kg/h. The column operates at a pressure of 1 kg/cm. The reflux is returned as a saturated liquid. A reflux ratio of L7D = 3.0 is being used. We desire a bottoms composition of Xq = 0.05 (weight fraction ethanol) and a distillate composition of x = 0.80 (weight fraction ethanol). The system has a total condenser and a partial reboiler. Find D, B, Q, and Qr. 

A steady-state countercurrent, staged distillation column is to be used to separate ethanol from water. The feed is a 30 wt % ethanol, 70 wt % water mixture that is a saturated liquid at 1 atm pressure. 

A typical chemical engineering approach to a large-scale separation problem is to try to devise a steady-state, countercurrent system. This has led to methods that are quite different from the scale-up of analytical elution chromatography. First, approaches where the soiid is moved are considered and then methods where the solid does not move but movement is simulated are discussed. Finally, the different systems are compared. In all cases the countercurrent or simulated countercurrent system replaces the column in Figure 14.2-1. The equipment for product and solvent recovery still is required. 

Based on the principle of countercurrent flow presented in Chapter 1.1, steady-state countercurrent flow operations are generally discussed in the following section. 

Two basic approaches can be adopted for using fixed beds to simulate the operation of moving beds. In the first, multiple fixed beds are used in cascade, as shown in Figure 5.12 (and described later in Section 7.7.1) to gain most of the benefit of a continuous steady state countercurrent process. The concept is similar to that used in the pulsed bed. At each switch in the cascade a fully regenerated bed is added to the outlet end of a sequence of beds in series when breakthrough is about to occur. At the same time the... 

Figure 7.17 Profiles for fructose-glucose separation calculated from the steady state countercurrent (cc) model compared with results calculated by numerical simulation at the midpoint of the switch interval for eight (case 1), four (case 2), two (case 3) and one (case 4) columns (source Hidajat et oL 1986).

Jelinek J. and V. Hlavacek, Steady state countercurrent equilibrium stage separation with chemical reaction by relaxation method, Chem. Eng. Commun. 2, 79-85 (1976). 

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