Rising film evaporators

The Calandria Evaporator is applied less often today than it was years ago. For most applications, however, the lower equipment costs for other designs has prompted the replacement of ealandria evaporators with rising-film, LTV falling-... 

Figure 10.32. Long-tube evaporators (a) Rising film (b) Falling film...

Several types of evaporators exist.34 The older, more traditional, evaporators are the Roberts and the Kestner, both rising film, tubular evaporators. The Roberts, first introduced in the 1800s, is known as a short tube, natural circulation, vertical tube evaporator. The tubes, inside which the evaporation takes place, are in the range of 1.5 to 3 meters in length. The Kestner evaporator consists of numerous long vertical tubes, 6 to 7.5 meters long, inside a cylindrical shell. In both, the juice to be concentrated is fed to the bottom of the tubes and heated, causing the juice to... 

As the temperature of the miscella exiting the first stage evaporator is low, it is a good heat sink for heat recovery. In various facilities, heat from hot finished oil, heat from steam ejector exhausts, or recovered flash steam is used to preheat the miscella to approximately 75°C in temperature. The preheated, concentrated miscella is then typically heated to 110°C in a steam-heated exchanger prior to entering the second rising film evaporator. 

Long-tube vertical evaporators are normally the cheapest per unit of capacity. When operated in the rising film mode, temperature variation along the... 

In long-tube evaporators, the liquid flows as a thin film on the walls of a long, vertical, heated tube (see Figure 10.32). Both falling film and rising film types are used. They are high-capacity units, suitable for low-viscosity solutions. 

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