Agitated falling film

Evaporator, agitated falling-film, s.s. heat surface area, 3-6 m 0.55... 

Costs for forced circulation evaporators, long tube evaporators, and agitated falling-film evaporators are presented in Figs. 15-26 and 15-27. Information on purchased cost of specialized heaters is given in Figs. 15-28 and 15-29, while Figs. 15-30 and 15-31 present costs for process furnaces and direct-fired heaters. 

Cost of agitated falling-film evaporators, complete with motor and drive. 

Agitated falling film usually to concentrate slurry see evaporation. Section 16.11.4.1. 

Related topics are evaporation (Section 16.11.4.1) for gravity and agitated falling films, absorbers (Section 16.11.4.8), and shell-and-tube heat exchangers (Section 16.11.3.3). 

Related topics evaporation Section 4.1 for gravity and agitated falling films. 

T iquid films, whether in the form of natural falling films or in the more advanced form of mechanically agitated films in thin-film apparatus, offer convenient conditions for the solution of many difficult processing problems because of the films favorable surface-to-volume ratio and good heat transfer. This is especially so with an agitated film between heating wall and film. The agitated-film principle has previously found its broadest application in thin-film evaporators. 

The influence of viscosity on the formation and behavior of a mechanically agitated film is based on the theory of the natural falling film along a wall. The mean film thickness 8 of a falling film under laminar conditions is determined according to Nusselt (9) ... 

Figure 2. Comparison between mean film thickness of falling and agitated films in a thin-film apparatus, expressed as a function of peripheral load and viscosity. Curves I, 2, and 3, falling film according to Equation 1 curve 1° and 2°, agitated film in the thin-film apparatus...

Figure 14. Increase of the intrinsic viscosity during the polycondensation reaction of polyester as a function of the residence time. Comparison between free-falling-film reactor (13) and agitated thin-film machine...

Figure 15. Final polycondensation of polyester. Comparison between horizontal rigid film, free-falling film, and agitated thin film in a high viscosity machine (Luwa Filmtruder)...

Following the carbon columns or the demineralizers, the pH of the filtrate is adjusted and the liquor is evaporated. The solids level of the filtrate prior to the evaporators is about 30% dry solids (DS). Typical evaporators are multiple-effect, falling-film evaporators in which the temperature is increased under precisely controlled conditions that prevent formation of unwanted flavors or color in the syrup. As shown in Figure 21.7, the flow is generally countercurrent, i.e. the hottest portion of the evaporation contains the syrup of lowest solids.11 After evaporation, the syrup is pumped to large storage tanks where it is held under agitation and analyzed prior to shipment. 

Discovery Technologies) with a circular arrangement of 12 screw-capped gas-tied glass tubes agitated by magnetic stirring. The second reactor is a commercial pressure batch reactor with a turbine and baffles (Series 4590 from Parr Instruments). The third reactor was the helical falling-film microreactor. 

Packed column, trickle-bed reactor, film reactors (falling film, agitated film, scraped/wiped film), rotating disk (or rotating... 

Rising and falling film especially for heat-sensitive. OK for foaming but not for fouling, crystal formation, or suspended solids. Viscosities <1500 mPa s. Relative to agitated film retention time of 0.5 1 and volume 0.8 1. 

First, the overall mass transfer coefRcient k a of the microreactor was estimated to be 3-8 s [43]. For intensified gas liquid contactors, kj a can reach 3 s while bubble columns and agitated tanks do not exceed 0.2 s Reducing the flow rate and, accordingly, the liquid film thickness is a means of further increasing kj a, which is limited, however, by liquid dry-out at very thin films. Despite such large mass transfer coefficients, gas-liquid microreactors such as the falling film device may still operate between mass transfer and kinetic control regimes, as fundamental simulation studies on the carbon dioxide absorption have demonstrated [44]. Distinct concentration profiles in the liquid, and even gas, phase are predicted. 

Fig. 7.4-5 Combination of a falling film evaporator and an agitated thin-film evaporator...

Agitated thin-film evaporators with a falling, revolving liquid film (Fig. 2-18) are often used in molecular distillation. The film is 0.1-1 mm thick, with a mean residence time ranging from 10 s-10 min and a... 

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